BACKGROUND

[001] Mechanical grippers may be used to hold an object upon which an operation is to be performed. The mechanical gripper may comprise finger-like elements. Mechanical grippers may be useful in situations where gripping using a human hand is undesirable or impractical, for example, in areas that would be hazardous to a human.

BRIEF DESCRIPTION OF THE DRAWINGS

[002] Examples are further described hereinafter with reference to the accompanying drawings, in which:

Fig. 1A is a line drawing of a mechanical gripper with a mesh contact surface according to one example of the principles described herein.

Fig. 1B is a line drawing of a mechanical gripper with a mesh contact surface according to one example of the principles described herein.

Fig. 1C is a line drawing of a mechanical gripper with a mesh contact surface holding an object according to one example of the principles described herein.

Fig. 2 is a schematic drawing of a mechanical gripper with a mesh contact surface according to one example of the principles described herein.

Fig. 3 is a schematic drawing of a mechanical gripper with a mesh contact surface arranged to match the configuration of the fingers in a human hand according to one example of the principles described herein.

Fig. 4A is a line drawing of a digit of the mechanical gripper according to one example of the principles described herein.

Fig. 4B is an exploded view of the digit of Fig. 4A.

Fig. 5 is a schematic drawing of a digit of a mechanical gripper at different stages of its actuation by an actuator according to one example of the principles described herein.

Fig. 6 is a schematic drawing of a mechanical gripper without a mesh contact surface according to one example of the principles described herein.

Fig. 7 is a schematic drawing of a mesh contact surface according to one example of the principles described herein.

Fig. 8 is a schematic drawing of a mechanical gripper with a mesh element disposed between two of the three digits according to one example of the principles described herein. Fig. 9 is a schematic drawing of a mechanical gripper with a mesh contact surface according to another example of the principles described herein.

Fig. 10 is a schematic drawing of a mechanical gripper with a mesh contact surface arranged to match the configuration of a human hand according to one example of the principles described herein.

Fig. 11 is a block diagram of a method according to one example of the principles described herein.

Fig. 12 is a block diagram of an example method for controlling the rigidity of a mesh contact surface according to one example of the principles described here.

Fig. 13 is a block diagram of an example method for controlling a motor according to one example of the principles described herein.

DETAILED DESCRIPTION

[003] The human hand is an efficient tool for gripping objects to be worked on. However, it may be desirable to provide a mechanical gripper, for example in order to automate a process or to operate in an area that is hazardous to humans. Mechanical grippers may provide other benefits, such as improved strength, resilience, stamina, etc. when compared with human hand. However, use of mechanical grippers can be cumbersome and they may not be appropriate for all gripping tasks. The use of mechanical grippers may also present challenges when gripping delicate objects or objects with certain geometries.

[004] An example of a process or operation in which a mechanical gripper according to the present disclosure may be used is in cleaning a 3D printed object according to some 3D printing processes. This can be very labour intensive but is crucial in finishing 3D printed parts. In certain 3D printing processes, after an object has been printed, powdered build material or support powder may adhere to or remain on the surface of the object. In order to complete the production of the object, this material should be removed. The material may be removed, for example, by using a liquid jet (e.g. a water) or gas jet (e.g. an air jet), or by scraping. The implements for applying the cleaning process (such as a jet nozzle or scraping element are referred to herein as cleaning implements). Inhalation of airborne power by humans should be avoided, and it might be desirable to clean the object in a low-oxygen environment to reduce the risk of an explosion. This may lead to the printed object being handled by a human operator with cumbersome thick gloves, using a vacuum cabinet or other processing chamber, whilst simultaneously using an air jet to remove all the excess residual powder. The gloves may obscure the user’s view of the object and obstruct the air jet, leading to the object being put down and picked up multiple times, which may cause damage to the 3D printed object.

[005] Further, automation of the cleaning process may lead to improved efficiency. Because of these factors, the use of a mechanical griper to hold and manipulate an object during cleaning may be beneficial. 3D printed components may have a variety of different shapes and dimensions, and so a mechanical gripper for use in the cleaning process that is suitable for gripping a variety of objects would allow for production and handling of a greater variety of 3D printed objects. Further, manipulating the object to perform the cleaning can be challenging, since the gripper may obscure parts of the object to be cleaned, or may obstruct the positioning of the cleaning implements. Additional manipulations of the object, such as changing a grip to expose different portions of the surface of the object may increase the risk of damaging delicate parts of the object and may lead to increased time to complete the cleaning operation. In some cleaning operations, the degree of cleaning to remove the adhered material may vary between instances of producing identical products. In such cases a closed-loop system may be appropriate, in which the progress of the cleaning is determined (e.g. using sensors such as cameras or direct observation by a human) and the cleaning process modified based on the determination (e.g. applying additional cleaning to a portion that is determined to still have material adhered to it after an initial cleaning process is applied to that portion). In some cases, the mechanical gripper may obscure the sensing process (e.g. by blocking the view of the camera or human operator), complicating the implementation of a closed-loop control system.

[006] In the field of robotics and prosthetics, it is intuitive to create mechanical manipulators that mimic physical properties of the human hand, such as digits having a solid surface, articulated wrists, etc. In this disclosure, a mechanical hand is described that may have nonhuman physical properties. The non-human physical properties may provide improved performance for tasks in which materials or signals are to flow to or from the object while it is being manipulated.

[007] A mechanical gripper according to some disclosed examples may enable grip and control of the pose of an object. Mechanical grippers according to some disclosed examples do not obstruct, or do not substantially obstruct, flows around the object or between the object and its surroundings. In one application, for example, the mechanical gripper enables an object to be positioned and oriented without obstructing a cleaning jet directed at the object’s surface, such that a surface in contact with the gripper may be cleaned by the jet without readjusting the grip of the mechanical gripper on the object.

[008] Fig. 1A is a line drawing of a mechanical gripper according to some examples of the principles described herein. A mechanical gripper 100 may comprise a digit 110 and a mesh contact surface 120. The mesh contact surface 120 for contacting an object to be held by the gripper. Movement of the digit may also cause movement of the mesh contact surface, such that the mesh contact surface is controllable by movement of the digit. The mesh contact surface may be connected to, linked to or supported by the digit 110. For example, a spacer 115 may be provided between the digit 110 and the contact surface 120. In this way, movement of the mesh contact surface may be controllable by movement of the digit. The digit 110 may be attached to a base 130. The mesh contact surface 120 may be attached to the base via the digit 110. The mesh contact surface may act like a pad of a finger for contacting gripped objects.

[009] Fig. 1A shows a gripper with a single digit 110. A single digit 110 may be sufficient to grip an object in some situations. For example, the digit 110 may be arranged to encircle or wrap around the object to allow the object to be gripped, or the object may have a shape suitable for holding by a single digit, for example by hooking the digit 110 in a hole or recess in the object. In other examples additional elements may be provided to assist in gripping or holding the object. For example, one or more additional digits may be provided and/or a support member, such as a plate, may be provided such that the digit 110 may urge the object towards the support member to grip the object between the digit 110 and support member.

[0010] The mechanical gripper 100 may comprise a spacer 115 disposed between the mesh contact surface 120 and the structural elements of the digit 110. The spacer 115 may retain the mesh contact surface 120 apart from the digit 110, such that any motion of the mesh contact surface 210 conforms with movement of the digit, e.g. due to actuation of the digit 110. In some examples the spacer 115 may be rigid or may be made of a resilient material, such as rubber, or be made from the same material as the mesh contact surface 120 or from another mesh-like material. The spacer 115 may be integrally formed with the digit 110 and/or the mesh contact surface 120. The spacer 115 may maintain a constant separation between the digit 110 and the mesh contact surface 120. In some examples, a linkage may be provided between the digit 110 and mesh contact surface 120, instead of, or in addition to, spacer 115. Such that the mesh contact surface 120 is supported by the digit 110 via the linkage. The linkage may provide a controllable separation between the digit 110 and the mesh contact surface 120. For example, the linkage may include a cam such that rotation of the cam varies a separation distance between the digit 110 and the mesh contact surface 120, or a distance between first and second connection points, where the first connection point is a location of a connection between the linkage and the digit 110 and the second connection point is a location of a connection between the linkage and the mesh contact surface 120. In some examples the linkage may be elasticated.

[0011] The digit may be supported or disposed on a base 130. The base may be any structure suitable for mounting the digit. For example, the base may be part of a robotic arm, an articulated wrist, etc.

[0012] Fig. 1B is a line drawing of a mechanical gripper with a mesh contact surface 120 according to one example of the principles described herein. The mechanical gripper 100 may comprise a digit 110, mesh 125 including mesh contact surface 120 and a base 130. The mesh 125 may be supported by, affixed to, or attached to the digit directly without a spacer or linkage, as discussed with reference to Fig. 1A. In the example of Fig. 1B the mesh 125 and/or digit 110 are shaped such that part of the mesh 125 is held away from or spaced apart from the digit, where the part includes a portion of the mesh to be in contact with a gripped object (l.e. the mesh contact surface 120).

[0013] Fig. 1C. Illustrates a gripper with more than one digit 110; three are shown in the particular example of Fig. 1C. In the example of Fig. 1C each of the digits 110 has the same structure, having the same number of jointed sections, the same dimensions, and each comprising a mesh contact surface 120. However, in some examples the digits 110 may be different in one or more particulars, e.g. some may omit the mesh contact surface 120, and/or may have different sizes or sections, the digits may be solid structures or created with wires, as described in more detail below. Each of the digits may be attached to base 130.

[0014] In some examples disclosed herein, the mechanical gripper may be adapted to hold onto an object 140. The mechanical gripper 100 may hold the object 140 during an operation involving the object. The mesh contact surface 120 is such that the object 140 is substantially unobstructed, for the purposes of the operation, by the mesh contact surface 120 when the mesh contact surface 120 is in contact with the object 140. As such, the mechanical gripper 100 enables, for example, gases, fluids, particles and/or signals (as appropriate for the relevant operation) to flow through the mesh contact surface 120 to and/or from the object 140. The mesh may include gaps, holes or voids, and the gas, fluid, particles, signals, etc. may pass through the gaps, holes or voids.

[0015] Mechanical grippers 100, as described above in relation to Fig. 1, may be used in cleaning 3D printed objects. The mesh contact surface 110 may allow for improved cleaning of the object while it is being gripped. For example, the mesh contact surface may be such that the mesh does not obscure (or substantially does not obscure) the surface of the object for the purposes of the cleaning operation. Where a gas or liquid jet is used in the cleaning process the properties of the mesh (such as dimensions of strands forming the mesh and holes between the strands) may allow the jet to pass through holes or voids in the mesh to clean the surface. The holes or voids may be large enough to allow matter removed from the surface (such as excess powder) to pass through them. Where the cleaning method involves scraping the surface of the object, the holes or voids in the mesh may allow sufficient contact between the surface of the object and a scraping implement to remove unwanted matter adhered to the surface. The cleaning may alternatively or additionally include brushing and/or vacuuming and/or blowing operations through the holes or voids in the mesh.

[0016] In some cases of 3D printed plastics, the printed objects achieve rigidity very quickly and so cleaning may be performed with abrasive blasting (e.g. sandblasting) techniques, which use an air jet with abrasive particles (e.g. sand particles) in the air flow to increase the frictional force of the air jet stream and chip away at the support structures or residual powders from the printing process. Also, abrasive blasting may be used as a sculpting technique to etch away at a surface with the air jet and abrasive particles to create an object.

[0017] In the case of metallic additive manufacture, printed objects are often very fragile and have to undergo a fusing / sintering process to make the metal much more robust before it can be considered the final structure of the object, air jets may be used to remove the excess powders. The mesh contact surface may provide for a simplified or improved process by allowing the air jets to pass though the holes or voids of the mesh.

[0018] Cleaning is an example of an operation which may be performed on the object held by a gripper as described in relation to Fig. 1. However, the gripper of Fig. 1 may be used to hold an object in many other operations, such as: painting, coating, dipping, spraying, polishing, deposition (e.g. vapor deposition, sputter deposition, electrostatic deposition), electroplating, applying a jet (e.g. a gas, liquid or particle jet,) inspection or observation, viewing, measuring, scanning (e.g. surface scanning, optical code detection, etc.), ultrasound analysis, applying electromagnetic waves, millimeter wave analysis, x-ray analysis, curing (e.g. UV curing), vapor smoothing, abrasive blasting and construction/production, e.g. additive manufacture and/or engraving. In some examples more than one of these processes/operations may be applied to the object. For example, optical inspection may be used during a cleaning process, followed by dipping the cleaned object in a treatment bath and curing the treatment. In each of these stages the process/operation may be applied though holes/voids in the mesh contact surface.

[0019] In some examples, the gripper may be used in a painting or coating operation. In this case, a painting or coating implement, such as a paint/coating jet nozzle, brush or roller, may apply paint or other coating to the surface of the object through the holes or voids in the mesh contact surface 130. The paint or coating may be applied over the mesh (such that the paint or coating is also applied to the mesh of the mesh contact surface 130 as well as the surface of the object). In some examples the properties of the mesh contact surface may be such that the paint or coating may cover the object even where strands of the mesh are in contact the surface of the object. For example, the paint or coating may flow or soak between the mesh contact surface 130 and the surface of the object. In some examples the dimensions of the mesh may be such that surface tension of the paint or coating causes portions of the object in contact with strands of the mesh to be covered by the paint/coating when the gripper releases the object after painting/coating.

[0020] In some examples, the gripper may be used in a dipping process. The object may be held by the gripper and dipped in a liquid, such as a liquid surface treatment. The liquid may be stored in a bath or vat, for example, that the griper may enter at an upper portion of the bath or vat. The liquid may come into contact with the surface of the object by passing or flowing through holes or voids in the mesh contact surface. In some examples the properties of the mesh contact surface may be such that the liquid may cover the object even where strands of the mesh are in contact the surface of the object. For example, the liquid may flow or soak between the mesh contact surface 130 and the surface of the object. In some examples the dimensions of the mesh may be such that surface tension of the liquid causes portions of the object in contact with strands of the mesh to be covered by the paint/coating when the gripper releases the object after painting/coating.

[0021] In some examples, the gripper may hold an object during observation, measurement or inspection of the object. In some examples the mesh contact surface does not, or substantially does not, obscure the object for the purposes of the observation, measurement or inspection. For example, the object may be visually inspected by a user or an automated system, e.g. using cameras or direct observation. The object may be visible through gaps and voids of the mesh contact surface. A laser may be used to measure the surface of the object through the gaps or voids in the mesh. In other examples other forms of radiation may be used to analyze the object and/or its surface. For example, infrared radiation. In some examples, ultrasound may be used to measure properties of the object, with the ultrasound being applied and/or detected via holes or voids in the mesh contact surface. In some examples, the ultrasound may partially pass though strands of the mesh (e.g. where an ultrasound transducer is partially in contact with the surface of the object and partially in contact with a strand of the mesh). In some such cases, the effect of the mesh strand may be negligible for the purposes of the analysis being conducted, e.g. due to a low portion of the transducer’s active area being in contact with the strand. In some examples a camera may be used to observe the surface of the object and image processing performed to remove the mesh contact surface from the image, e.g. by approximating portions of the object surface obscured by the mesh contact surface and replacing portions of the image corresponding to the mesh with the approximated portions of the object surface in a processed image. In some examples, images of portions of the object around the obscured portion (captured by the same or a different camera) may be used to extrapolate the appearance of the obscured portion of the object.

[0022] In some examples the gripper may be used in a production process, for example involving etching and/or additive manufacture applied to the object. In some examples, the etching and or additive manufacture may be performed through holes or voids in the mesh contact surface. In some examples, an individual digit (and the corresponding mesh contact surface) may be lifted away from the object to allow material to be added or etched. In this case. The use of mesh contact surfaces may aid in monitoring the process, e.g. by maintaining a good visibility of the object through the mesh contact surface. In some examples, an additive manufacturing process may be performed over the mesh, such that the object is formed over portions of the mesh contact surface. In this case, the mesh contact surface may be cut to remove the object from the gripper. The use of the gripper in additive manufacturing and/or etching, for example, may allow improved access to the object for the implements operating on the object, as the object may be moved and rotated by the gripper to allow access to different portions of the surface and/or allow access from different directions and angles.

[0023] In some examples the object to be held may emit light, e.g. for use as a light source. The use of a mesh contact surface reduces obstruction of the light by the gripper. In other examples the object to be held may be a camera device. In such cases, obstruction of the field of view of the camera may be reduced by the use of mesh contact surfaces. Where the mesh is visible to the camera (e.g. the mesh is visible in an image captured by the camera), image processing may be performed to remove the mesh from the final image.

[0024] Grippers according to some examples have contact surfaces that do not substantially obstruct the object for the purposes of certain operations. Accordingly, the options for sensing and/or acting on the object may be greatly extended. The gripper may thus allow more effective or efficient operations to be performed or may allow use of a mechanical gripper for applications that otherwise would not be amenable to carrying out with a mechanical gripper.

[0025] The properties of a mesh suitable for use as a mesh contact surface may depend on the particular process to be carried out on the object to be held. For example, in fluid deposition, suitable filament geometries may be determined by the surface tension of the fluid, such that regions in contact with filaments of the mesh self-heal when the mesh is no longer in contact with the surface. In powder removal applications, filament geometries may depend on the powder grain sizes and the angles of incidence of any cleaning jets. Powder grains that are obstructed by the filament may be shielded from the cleaning jets. In some examples, the obstructed grains, i.e. stacks of grains that are hidden behind a filament, are not stable if the stack height is greater than the width of the filament. Accordingly, for a mesh having fine enough filaments the obstruction due to the filaments will be negligible. In the case of etching, a fine enough mesh would have negligible effect on a multi-angle blast/laser-etch or on additive masking followed by liquid etching.

[0026] In some examples the object may be coated or immersed in a fluid during the operation. The fluid and the material of the mesh may be matched with each other, such that the effect of the mesh on the operation is reduced or eliminated. For example, where the operation includes visually observing or inspecting the object (or other processes involving the passage of electromagnetic radiation through the mesh), the fluid and material of the mesh may have matching optical indices (e.g. the same or similar optical indices). Accordingly, the visibility of the mesh may be reduced, and the effect of the mesh on the process (e.g. inspection) may be reduced. In some examples the mesh may become effectively invisible. Similarly, in processes involving the passage of sound waves (e.g. ultrasound) the use of matched fluid and mesh material may reduce the effect or detectability of the mesh. [0027] The force of friction between two objects in contact may be approximated by the equation R£mL/, where F is the force of friction, m is the coefficient of friction, and N is the normal force. Accordingly, the contact force of friction does not depend on the contact area. As such, the force of friction between an object and a mesh contact surface is substantially the same as the force of friction between an object and a solid (non-mesh-like) contact surface, assuming the same normal force and coefficient of friction. In other words, the level of grip for a mechanical gripper on an object is proportional to the amount of force being applied to the object by the gripper (the normal force), not the area over which the force is applied (the pressure). In other words, the level of grip on an object for a mesh contact surface, versus a large padded gripper with no voids in the surface, as is used in the field of robotics and prosthetics, is the same - if the force being applied to the object by the gripper is the same and the coefficient of friction between the two is the same.

[0028] Fig. 2 is a schematic drawing of a mechanical gripper 200 with a mesh contact surface 220. The digits 210 in this example may be flexible or jointed digits. The mesh contact surface 220 is shown with voids. An operation to be carried out involving an object which is held by the mechanical gripper may be carried out through the voids in the mesh contact surface. The digits of Fig. 2 have a wireframe construction. For example, the digit may be an articulated digit comprising a framework of wires connected by hinges.

[0029] Wireframe digits may have spaces, voids or gaps between the wires forming the digit. Accordingly, the digit itself is less likely to obstruct a process or obscure an object being held. Accordingly, in some examples the process is to be applied through gaps in the wireframe of the digit as well as (or instead of) through holes or voids in the mesh contact surface.

[0030] Thus, having a mesh contact surface may reduce or eliminate readjustment of a grip on the object during cleaning or other processing, since the airflow for cleaning (for example) can travel through the voids in the mesh and reach the object unobstructed. This also applies to a water jet or other such fluids which may be used to clean or perform an operation on the object. Such processes may be aided by the physical manipulation of the object through controlling the position and/or orientation of the gripper or the ability to view the object’s orientation through the mesh of the gripper. Observing portions of the object through the mesh contact surface may simplify or improve determination of the orientation of the object. For example, by allowing detection of fiducials or structural elements that would otherwise be obscured by the gripper. This may lead to improved or more efficient processing of the object. For example, a 3D printed object may have intricate crevices where residual 3D printing powder may be particularly prone to becoming trapped. These crevices may be known to a user or automated system, but locating these portions may depend on precise knowledge or determination of the orientation of the object in order to expose those parts to the air jet to remove the residual 3D printing powder. [0031] Forming the elements of the digit from cut metal (e.g. cut from sheets of steel) allows for a simple construction. However, using a wireframe construction for the digit, as shown in Figure 2, may reduce obstruction by the gripper relative to a construction of cut sheet metal.

[0032] In some examples, jointed portions of the digits may have relative dimensions similar to the relative dimensions of the bones (phalanges and/or metacarpals) of a human hand. In some examples the digits may have dimensions similar to the typical dimensions of human fingers.

[0033] The digits and/or the gripper of Fig. 2 may be mounted on a base, mechanical wrist, mechanical arm, etc. In some examples the base, etc. may be solid, In some examples the digits hold the object to be held sufficiently far away from the base that the base does not (or substantially does not) obstruct or interfere with the process or operation to be performed on the object.

[0034] Fig. 3 is a schematic drawing of a five-digit mechanical gripper 300 with a mesh contact surface 320 arranged to match the configuration of the fingers in a human hand, e.g. having four finger-like digits and a thumb-like digit. By providing a mechanical hand that mimics the function and control of a human hand, it is possible for a human operator to provide control in an intuitive manner, e.g. using a glove controller, which detects movements of the fingers of the user’s hand and translates these to corresponding movements of the digits of the gripper. As shown in, for example, Figs. 1 and 2, and in alternative examples, the digits might have dimensions or arrangements that do not mimic human fingers or hands and may, for example, be exaggerated or adapted to better suit the needs of the operation to be performed on the object to be held by the mechanical gripper 300.

[0035] Fig. 4A is a line drawing of a digit of a mechanical gripper according to some examples. In some examples, the digit is an articulated digit comprising a framework of wires connected by hinges 410. The digit may comprise at least one phalanx section. In some examples, the digit comprises an upper phalanx section 420 (dashed line), upper-middle phalanx section 430 (long dashed line), lower-middle phalanx section 440 (long dash dot line) and lower phalanx section 450 (long dash dot dot line). The phalanges are movable relative to each other and are connected by hinges 410 and control wires 460. The articulation of a phalanx section articulates the next adjacent phalanx section in a distal direction by way of control wires 460, as shown and described in more detail with regard to Fig. 5 below. Here, proximal refers to a lower part of the digit 110 (e.g. toward a base 130 or element on which the digit is mounted), while distal refers to an upper end of the digit (e.g. away from the base 130 or toward the tip or free end of the digit 110).

[0036] Figure 4B shows an exploded view of the digit of Fig. 4A, with each of the phalanx sections shown individually. Dashed lines show connections between the elements in the assembled digit 100. Each of the phalanx sections may be rigid, such that elements within a phalanx section are fixed with respect to other elements in the same phalanx section.

[0037] In this example, lower phalanx section 450 may be fixed or attached to an anchor, such as base 130, and so may be considered to be fixed when considering flexing of the digit 110 (although movement of the base may cause movement of the lower phalanx section 450). The lower phalanx section has an upper control section 457 for rotatably connecting to middle control wire 460b.

[0038] Lower-middle phalanx section 440 has one or more lower mounting portions 442, shown as hinges in Figs. 4A and 4B to rotatably mount the lower-middle phalanx section 440 on the lower phalanx section 450 at one or more upper mounting portions 458 of the lower phalanx section 450. The upper mounting portions 458 are shown in Figs. 4A and 4B as portions of the wire frame of the lower phalanx section to which the hinges of the lower mounting portions 442 are attached. The lower mounting portions 442 of the lower-middle phalanx section 440 and the upper mounting portions 458 of the lower phalanx section 450 allow relative rotational motion between the lower phalanx section 450 and the lower-middle phalanx section 440 in a flex/extend direction of the digit.

[0039] Lower-middle phalanx section 440 has a lower control portion 445 to rotatably attach to a lower control wire 460a. A pulling or pushing of the control wire causes a corresponding push or pull on the lower control portion 445, which in turn causes rotation of the lower-middle phalanx section about the upper mounting portions 458 of the lower phalanx section 450 (or equivalently, rotation about the lower mounting portions 442 of the lower-middle phalanx section 440). An actuator may be used to push and/or pull the lower control wire 460a to control flexing and extension of the digit 110. For example, a linear actuator or a motor that produces circular motion may be used.

[0040] The lower-middle phalanx section 440 has one or more upper mounting portions 448 for mounting the upper-middle phalanx section 430. The lower-middle phalanx section 440 also includes an upper control portion 447 for rotatably connecting to an upper control wire 460c, the other end of which is attached to the upper phalanx section 410.

[0041] Upper-middle phalanx section 430 has one or more lower mounting portions 432, shown as hinges in Figs. 4A and 4B to rotatably mount the upper-middle phalanx section 430 on the one or more upper mounting portions 448 of the lower-middle phalanx section 440. Figs. 4A and 4B show the lower mounting portions 432 of the upper-middle phalanx section 430 as hinges and show the upper mounting portions 448 of the lower-middle phalanx section 440 as portions of the wire frame of the lower-middle phalanx section 440 to which the hinges of the lower mounting portions 432 of the upper-middle phalanx section 430 are attached. The lower mounting portions 432 of the upper-middle phalanx section 430 and the upper mounting portions 448 of the lower-middle phalanx section 440 allow relative rotational motion between the lower-middle phalanx section 440 and the upper-middle phalanx section 430 in a flex/extend direction of the digit.

[0042] Upper-middle phalanx section 430 has a lower control portion 435 to rotatably attach to middle control wire 460b. Middle control wire is also attached to the upper control portion 457 of the lower phalanx section 450. Rotation of the lower-middle phalanx section 440 due to pushing or pulling of the lower control wire 460a causes arcuate motion of the lower mounting portions 432 of the upper-middle phalanx section 430, centered on the lower mounting portions 442 of the lower-middle phalanx section 440. Control wire 460b causes control portion 435 to move in an arc centered on the upper control portion 457 of the lower phalanx section 450. This leads to relative rotation between the upper-middle phalanx section 430 and the lower-middle phalanx section 440. This relative rotation leads to flexing or extending of the upper-middle 430, lower- middle 440 and lower 450 phalanx sections.

[0043] The upper-middle phalanx section 430 has one or more upper mounting portions 438 for mounting the upper phalanx section 420. The upper-middle phalanx section 430 of Figs. 4A and 4B does not have an upper control portion as there are no phalanx sections beyond the upper phalanx section. However, if a further phalanx section was attached to the upper phalanx section, the upper-middle phalanx section 430 may include an upper control portion for connection to a lower control portion of that further phalanx section by an additional control wire.

[0044] Upper phalanx section 420 has one or more lower mounting portions 422, shown as hinges in Figs. 4A and 4B to rotatably mount the upper phalanx section 420 on the one or more upper mounting portions 438 of the upper-middle phalanx section 430. Figs. 4A and 4B show the lower mounting portions 422 of the upper phalanx section 420 as hinges and show the upper mounting portions 438 of the upper-middle phalanx section 430 as portions of the wire frame of the upper-middle phalanx section 430 to which the hinges of the lower mounting portions 422 of the upper phalanx section 420 are attached. The lower mounting portions 422 of the upper phalanx section 420 and the upper mounting portions 438 of the upper-middle phalanx section 430 allow relative rotational motion between the upper-middle phalanx section 430 and the upper phalanx section 420 in a flex/extend direction of the digit.

[0045] Upper phalanx section 420 has a lower control portion 425 to rotatably attached to upper control wire 460c. Upper control wire is also attached to the upper control portion 447 of the lower-middle phalanx section 440. Rotation of the upper-middle phalanx section 430 with respect to the lower-middle phalanx section 440 (e.g. due to pushing or pulling of the lower control wire 460a) causes arcuate motion of the lower mounting portions 422 of the upper phalanx section 420, centered on the lower mounting portions 432 of the upper-middle phalanx section 430. Upper control wire 460c causes control portion 425 of the upper phalanx section 420 to move in an arc centered on the upper control portion 447 of the lower-middle phalanx section 440. This leads to relative rotation between the upper phalanx section 420 and the upper-middle phalanx section 430. This relative rotation leads to flexing or extending of the upper 420, upper-middle 430 and lower-middle 440 phalanx sections.

[0046] The upper phalanx section 420 of Figs. 4A and 4B does not have upper mounting portions, as there are no phalanx sections beyond the upper phalanx section 420. However, if a further phalanx section was attached to the upper phalanx section 420, the upper phalanx section 420 may include one or more upper mounting portions for mounting that further phalanx section. Similarly, the upper phalanx section 420 of Figs. 4A and 4B does not have an upper control portion as there are no phalanx sections beyond the upper phalanx section. However, if two further phalanx sections were attached to the upper phalanx section 420, the upper phalanx section 420 may include an upper control portion for connection to a lower control portion of the second of the further phalanx sections by an additional control wire.

[0047] Where a wireframe digit has N phalanx sections where N is greater than 3, the first phalanx section may be a lower phalanx section that has upper mounting portions for mounting a second phalanx section and an upper control portion for connection to a third phalanx section via a second control wire. The nth phalanx section (n=2...N-2) may have a lower mounting section for mounting the nth phalanx section on the n-1th phalanx section. The nth phalanx section may also have a lower control portion for connection to an n-1th control wire. The nth phalanx section may also have an upper mounting portion for mounting an n+1th phalanx section. The nth phalanx section may have an upper control portion for connection to an n+2th phalanx section via an n+1th control wire. The N-1th phalanx section may have upper and lower mounting portions for mounting Nth and N-2th phalanx sections, respectively. The N-1th phalanx section may also have a lower control portion for connection to an N-2th control wire. The Nth phalanx section may have lower mounting portions for mounting the Nth phalanx section on the N-1th phalanx section. The Nth phalanx section may also have a lower control portion for connection to an N-1th control wire. In this arrangement, the first control wire may be connected to an actuator to cause flexing and/or extension of the digit.

[0048] According to the arrangement of Figs. 4A and 4B, rigid linkages (control wires 460) may be used, such that the digit positions (i.e. degree of flex/extension) are uniquely determined by the relative positions of the lower control wire 460a and the anchor point(s) of the lower phalanx section 440. Where the lower phalanx section is fixed (or fixedly mounted on a base) the flexing of the digit may be completely controlled by pushing and/or pulling the lower control wire 460a.

[0049] The use of rigid control wires allows the lower control wire to directly control flexing and extension of the digit. Where a non-rigid cable or string is used to control the digit, pushing forces cannot be transmitted along the cable. In such cases, a spring or elasticated member may be provided to urge the digit toward a particular state (e.g. extended) and the cable may pull the digit into a different state (e.g. flexed) by pulling against the resistance provided by the spring. To return to the original state, the pull on the cable may be released or relaxed and the spring may cause the digit to return to the original state (e.g. extended). Using a rigid control wire may allow for greater control of the digit, since the digit is directly controlled during both flexing and extending. In addition, the rigid control wire does not pull against a spring (or similar element), which may lead to increased performance and/or efficiency. In some examples according to the arrangement of Figs. 4A and 4B flexing and extension of a whole digit may me controlled by actuation of a single control wire 460a.

[0050] In some examples, a pair of non-rigid cables or strings may be provided to control each digit, with a first cable for flexing the digit and a second cable for extending the digit. The use of a single rigid control wire to control both flexing and extension may lead to a simpler and/or more reliable construction.

[0051] Figs. 4A and 4B provide a particular example of a wireframe digit. However, other structures and control arrangements may be used.

[0052] In some examples, the mesh contact surface may be separable from the digit. In some examples the mesh contact surface may fit over one or more digits like a sock or glove. This may provide a simple mechanism for replacing mesh contact surfaces and/or provide a simple construction or attachment mechanism for the mesh contact surfaces.

[0053] Fig. 5 is a schematic drawing of a digit 510 of a mechanical gripper, e.g. the mechanical gripper of Figs. 4A and 4B, at different stages of its actuation (a) - (d) by an actuator 520. In the example of Fig. 5 the actuator produces rotational motion. As shown, the actuator 520 may be located external to the digit. For example, the actuator 520 may be located in base 130, or in a wrist or elbow of a mechanical arm to which the gripper 100 is mounted. Locating the actuator 520 external to the digit 510 may reduce obstruction of the object, e.g. compared with an actuator 520 located in the digit 510, since the actuator 520 is then likely to be located further away from the object to be held by the gripper 110. This may allow for a process or operation to be performed on the object more efficiently or conveniently. Further, in some examples locating the actuator 520 external to the digit may reduce the risk of damage to the actuator 520 when applying a process or operation to the object. For example, subjecting an actuator 520 to abrasive blasting or dipping in liquids may damage the actuator 520. The actuator 520 may control the flexing and extension of the digit. In some examples, the range of motion for the digit 510 of the mechanical gripper may match or mimic the range of motion of the motion of a human finger, but may differ in other examples. In some examples, the actuator 520 may be connected to a lower control wire 460a of the digit at a first fixing point 530, such that the first fixing point 530 is moved along a circular arc in response to actuation of the actuator. The lower phalanx section 450 may be anchored with respect to the actuator at a second fixing point 540. In the example of Fig. 5 the second fixing point is on the axis of the actuator 520, but other anchor/fixing points are possible. In some examples, the second fixing point 540 may also be moveable relative to the actuator 520, e.g. by actuation of a second actuator. This may provide additional control over the position and flexing of the digit 510. Actuation of the digit is caused by the rotational actuation of the actuator 520 such that the first fixing point 530 is moved with respect to the second fixing point 540 (in the example of Fig. 5, the first fixing point 530 travels radially around the second fixing point 540) causing the lower control wire 460a to flex or extend the digit 510 based on the rotation of the actuator 520. As described in relation to Fig. 4B, the phalanges may be connected by control wires 460, so the force applied to the lower control wire 460a by the rotation of actuator 520 is transferred along the digit 510 and actuates all phalanges at once, as shown in stages (a) - (d) of Fig. 5. In other examples a control mechanism may be used which enable finer control of each phalanx section, e.g. individually or in groups of two or more.

[0054] In some examples of the arrangements of Figs. 4A, 4B and 5, in which the second fixing point 540 is on an axis of the actuator and a radius of the arc followed by the first fixing point 530 is equal to the length of the linkage between the lower control portion 445 and the lower mounting portion(s) 442, the angle of rotation of the lower middle phalanx section 440 may be arranged to be equal to the angle of rotation of the actuator. By increasing or decreasing the radius of the arc relative to the length of the linkage the rotation of the lower-middle phalanx section 440 may be exaggerated or suppressed relative to the rotation of the actuator.

[0055] At stage (a) full actuation (flex) of the digit 510 is shown, as the actuator 520 begins to rotate as shown in stage (b), the fixing point 530 travels radially around the second fixing point 540 and the digit 510 begins to unflex/extend and continues to do so through stage (c) until stage (d) when the digit 510 is fully unflexed/extended. In alternative examples, the actuator 520 may be a linear actuator. The controlling of the actuation as described above allows for the control of the grip of an object to be held by the mechanical gripper, as the degree of bending (flexing) of the digit 510 is based on the rotation of the actuator 520. The use of rigid control wires that can transmit pushing and pulling forces allows for a directly controlled unflexing/extension (e.g. without relying on a spring) in addition to a directly controlled flex/bend of the digit. This may provide improved control or adjustment of grip.

[0056] The examples of Figs. 4A, 4B and 5 included rigid control wires 460 between the actuator 520 and the digit 510 of the mechanical gripper 500 to provide the actuating motion of the digit and hence the gripping force on the object. However, mechanical grippers according to other examples may use a tendon-like method of actuating the digits, e.g. having a control cable attached to the upper phalanx section of the digit that is run through the digit and pulled to flex/bend the digit to provide a gripping force on an object to be held. The pull on the control wire may then be released and the digit returned to its original position by a spring mechanism. The control cable may not transmit a pushing force, and so such solutions rely on the force of the spring to return the digit to its original position. A system using rigid control wires 460, e.g. as in Figs. 4A, 4B and 5 may provide more control of the flexing/extending and, in some cases, a simplified construction.

[0057] In some examples, a resistance to the rotation of the actuator 520 may be sensed. The sensed resistance may be used to determine a force applied to the object by the digit 510 and/or to control the digit 510. In this way the actuation (e.g. flexing) of the digit 510 can be stopped (e.g. by controlling the actuator 520 to prevent further actuation) when the sensed resistance to movement of the actuator 520 reaches a threshold. This arrangement may allow precise control of the force applied by the actuation of the digit 510, and hence the level of grip on the object, by controlling the actuator’s 520 rotational displacement. This arrangement may reduce the risk of damaging an object that is being gripped by monitoring and/or limiting the force that the gripper applies to the object. In some examples, the force applied to the object may be monitored and adjusted in a closed-loop system. In some examples an angle of rotation of the actuator may be sensed, and the force derived from the angle of rotation.

[0058] In some examples, the monitoring and/or control may be performed directly based on the sensed resistance to rotation and/or sensed angle of rotation, without determining a value for the applied force.

[0059] In an alternative example, an image feed of a camera disposed behind the meshes of the digit 510 can be analyzed to detect a distortion of the mesh contact surface (e.g. by detecting shapes of one or more filaments of the mesh and the deviation from their unloaded shapes) due to contact with an object to be held. The degree of the distortion of the mesh contact surface may be linked in a known way (e.g. by calibration) to the force being applied by the mesh contact surface to the surface of the object. Determination of the force applied may allow improved control of the digit/gripper, e.g. by allowing the force applied to the object to be monitored, and possibly limited. The determination of the force may be used in a closed-loop control of the digit/gripper.

[0060] In an alternative example, the distortion of the mesh contact surface may be detected by using capacitive sensing. For example, the mesh contact surface may be formed of first and second sets of conductive wires. The wires of the first set may be substantially parallel with each other and the wires of the second set may be substantially parallel with each other and substantially perpendicular to the wires of the first set. The first and second sets of wires may be separated by a dielectric material. Other structures are possible; for example, the wires may deviate from being parallel and perpendicular to each other.

[0061] Determining an applied force, or a parameter indicative of force, based on resistance to rotation of a motor, angle of rotation of a motor, or distortion of a mesh contact surface 130 (e.g. based on optical observation or capacitive sensing) may provide an accurate indication of the force.

[0062] Determining a force applied to the object (or determining a parameter indicative of the force) may allow haptic feedback to be supplied to a user. In examples using a glove controller to control the gripper, haptic feedback regarding the force applied to the object may be provided intuitively by applying pressure to the user’s hand within the glove.

[0063] Fig. 6 is a schematic drawing of a mechanical gripper 600 without a mesh contact surface. The wires shown are, in some examples, the structural and control elements of the digits of the mechanical gripper (e.g. as shown in Figs. 4A, 4B and 5) which support a mesh contact surface, either directly connected to the wires or via a spacer or linkage. However, in some examples, the mesh contact surface may be omitted, such that the wires of mechanical gripper 600 form the contact surfaces for an object to be held. For some processes and objects, the mesh surface may not be needed, for example where the object can be held without damage by the digit in the absence of a mesh contact surface, and the process can operate though voids in the digits.

[0064] Fig. 7 is a schematic drawing of mesh contact surfaces 700 according to some examples of the principles described herein, suitable for use with the gripper of Fig. 6. The mesh contact surfaces 700 provide a wide contact area and grip to an object to be held without obscuring, or without substantially obscuring, the object to be gripped. In some examples, the mesh contact surfaces 700 are less rigid than the structural elements of a mechanical gripper, such as those in Fig. 6 or the wires forming the phalanges of Figs. 4A and 4B. This may allow the mesh contact surface to conform (to some degree) with the surface of the object to be gripped. This may, in turn provide improved grip and/or reduce the risk of damage to the object. In some examples, the mesh contact surfaces 700 may be flexible to conform to the surface of the object being gripped.

[0065] In some examples, the mechanical gripper further comprises a rigidity control element, the rigidity control element is adapted to controllably apply a condition to the mesh contact surface 700. The rigidity of the mesh contact surface 700 may be variable in response to the applied condition. Examples of applying a condition include applying one or more of an electric current, heating and/or cooling (to vary a temperature), an electric field, a magnetic field, or exposure to electromagnetic radiation etc. In some examples, the rigidity of the mesh contact surfaces 700 may be controlled (e.g. by applying or ceasing to apply a condition) such that the mesh contact surfaces 700 become more flexible (e.g. flexible enough to conform to the surface of, or prominent features of, the object to be held). In some examples, the rigidity may be further controlled such they the mesh contact surfaces 700 are made more rigid (e.g. by ceasing to apply or by applying a condition), to ‘lock in’ the gripped object due to the previously conformed shape of the mesh to the object surface features.

[0066] In some examples, filaments of the mesh may be formed from resistive wires coated in a thermoplastic material (such as Nylon 6). A current may be passed though the wires to heat the plastic coating and thereby reduce its stiffness. In the case of Nylon 6, which is a hard material at 50 degrees C (i.e. at its glass transition temperature), there is a rapid drop in stiffness (decreasing modulus of elasticity) as it heats up from 50 degrees C to 100 degrees C. The current may be turned off to allow the plastic to cool (or active cooling could be applied, e.g. using a fan to produce a flow of cool air) and return to a less flexible state. This may “lock” the mesh into a shape that conforms to an object being held. In some examples, a flow of warm air may be used instead of, or in addition to, an electric current to increase the temperature of the thermoplastic material.

[0067] In some examples, UV curing may be used to set a material of the mesh (or a coating on the mesh) in order to increase the rigidity of the mesh contact surface.

[0068] In some examples the mesh contact surface may be in a first state or a second state, with the rigidity of the mesh contact surface being higher in the second state than the rigidity of the mesh contact surface in the first state. The mesh contact surface may be controllably changed between the first state and the second state (e.g. by applying a condition such as a current). In some examples the mesh contact surface is naturally in the first or second state and may transition to the other of the first or second state in response to application of the condition. In some examples a condition (e.g. heating) may be applied to place the mesh contact surface in the first state and another condition (e.g. cooling) may be applied to place the mesh in the second state. In some examples the transition from the first state to the second state may be reversible. In other examples the transition may be irreversible. In some examples a transition between from the first to the second state (or vice versa) caused by application of a condition may be reversed by ceasing application of the condition. In other examples, following a transition to a state by application of the condition, the mesh contact surface will remain in that state when the application is ceased.

[0069] The voids in the mesh contact surfaces 700 may allow additional peripherals or implements to be utilized in a mechanical gripper which are to access to the surface of the object.

[0070] Fig. 8 is a schematic drawing of an example mechanical gripper 800 having a plurality of digits 810 in which the mesh contact surface includes a mesh element 850 disposed between two or more of the digits 810. The mesh contact surface may include one or more mesh contact pads 820 on one or more of the digits 810. In the example of Fig. 8, each digit 810 has mesh contact pads 820 disposed along each digit. In other examples, some or all of the digits 810 have no mesh contact pads 820. In some examples the mesh element 850 is the mesh contact surface. The mesh element 850 may allow the object to be gripped more reliably and/or reduce the risk of the object slipping from the grip of the gripper, and possibly being damaged. Operations and/or processing involving the object may be performed though holes or voids in the mesh element 850. In some examples, the mesh element 850 does not substantially obstruct the object for the purposes of an operation or process involving the object.

[0071] The mesh element 850 and the mesh contact pads 820 may be supported by structural elements 830 of the digits 810 (e.g. by attachment to the wire frame of the digits, as illustrated in Fig. 8). In some examples the mesh element 850 may form a web or webbing between two or more digits. The mesh element 850 may be flexible or elasticated, such that it does not substantially restrict the movement of the digits 810 when they are actuated. In some examples the mesh element 850 may include or be made from ferrule cable mesh.

[0072] In some examples, the rigidity and/or elasticity of the mesh element 850 may be variable, in a similar manner to the mesh contact surfaces 700 of Fig. 7. The rigidity may be controlled by varying properties such as an electric current, a temperature, an electric field, a magnetic field, or exposure to electromagnetic radiation etc. In a further example, the mesh element 850 may be less rigid than the rigidity of the structural elements 830 of the mechanical gripper 800 and the same or less rigid than the mesh contact pads 820.

[0073] In mesh-like structures there is often a relationship between stiffness and elasticity. Ferrule cable mesh may allow significant extension or contraction of the mesh, even where the individual filaments do not stretch, as the extension and contraction is achieved via bending of the filaments. If the mesh element 850 is formed using ferrule cable mesh that has a controllable stiffness (e.g. by forming the ferrule cable mesh of conductive wire coated in thermoplastic material, as described above) the elasticity of the mesh element 850 may be controlled by controlling the stiffness of the ferrule cable mesh.

[0074] Fig. 9 is a schematic drawing of an example mechanical gripper 900 according another example of the examples described herein. In some examples, the mechanical gripper 900 comprises at least one digit 910, a mesh contact surface 920, a sensor 925, structural elements 930, sensor mounting element 935, and a processing section 945. In some examples, the sensor may be a camera, an electromagnetic radiation sensor, a distortion sensor, a force sensor, a sonic sensor or the like. In examples the processing section 945 is to: control the gripper 900 based on a detected signal of the sensor 925; and/or control an operation involving an object to be held by the gripper 900; and/or determine a force applied by the mesh contact surface 920 to the object based on the detected signal of the sensor 925.

[0075] In some examples, a feed of the sensor 925 can be analyzed to detect a distortion of the mesh contact surface due to contact with an object to be held. The degree of distortion of the mesh contact surface may be indicative of the force being applied by the mesh contact surface to the surface of the object. Accordingly, the processing section 945 may determine the force applied to the object, or some measure indicative of the force, based on the detected distortion of the mesh.

[0076] In some examples, the sensor 925 may be disposed behind the mesh contact surface 920 (i.e. with the mesh contact surface 920 between the sensor 925 and the location in which an object to be gripped contacts the mesh contact surface 920). This arrangement may provide improved sensor data (e.g. due to the angle and proximity that may be achieved). In some examples, determination of distortion of the mesh contact surface may be improved by locating the sensor 920 behind the mesh contact surface 920.

[0077] The holes or voids in the mesh contact surface 920 may allow the sensor to operate without being obstructed by the digit. In some examples, the sensor may be mounted on the structural elements 930 by sensor mounting element 935. In other examples, the sensor may be located within the digit 910 of a solid digit, e.g. within a recess in the digit, and unexposed to the environment, such that the sensor 925 is protected from, and not exposed to, any process that is being applied to an object held by the gripper. In some examples, there may be a window which seals the recess in the digit to protect the sensor, the window may be made of a material that does not obstruct the sensor (e.g. a transparent material, wherein the sensor is a camera). In some examples, the window may be a hole, such that the sensor is exposed in the direction of the object by the hole; however, the sensor 925 may still be protected from and not exposed to processes that are applied to an object held by the gripper.

[0078] Processing section 945 may be, or include, at least one of a rigidity control element, a processor, communication electronics, volatile memory (e.g. DRAM), non-volatile memory (e.g. ROM), flash memory, a graphics processor or CPU, a chipset, an antenna, a display, a digital signal processor, a crypto processor, a chipset and a mass storage device (e.g. a hard disk drive (HDD), compact disk (CD), digital versatile disk (DVD), and the like).

[0079] Fig 10 is an example of a mechanical gripper that mimics the structure of a human handlike mechanical gripper. In some examples the gripper may have four finger-like digits and one thumb-like digit. The gripper may have human-like maneuverability in the joints of the digits and/or may have a base with maneuverability that mimics a human wrist. In some examples, the relative proportions etc. of the elements of the gripper may reflect relative dimensions of similar elements of a human hand. The use of a gripper with human hand-like properties may allow for more intuitive control by a human user. In some examples, a gripper may be controlled using a control glove that may be worn on the hand of a human user and detects movement of the user’s fingers and/or hand, such that these movements may be reproduced in a mechanical gripper. Grippers with hand-like properties may be suitable for control using a control glove. [0080] Fig. 11 describes a method 1100 according to one or more examples. In use, a mechanical gripper 100 may execute a method 1100 for gripping an object. The method 1100 comprises block 1110, controlling a mechanical gripper to grip an object. For example, the mechanical gripper may be controlled, manipulated or operated to pick up and orient an object. The method 1100 also comprises block 1120, carrying out an operation involving the object, wherein a portion of the mechanical gripper that is in contact with a surface of the object comprises a mesh. The operation carried out on the object may be any of cleaning, painting, coating, dipping, spraying, polishing, deposition (e.g. vapor deposition, sputter deposition, electrostatic deposition), electroplating, applying a jet (e.g. a gas, liquid or particle jet), inspection or observation, viewing, measuring, scanning (e.g. surface scanning, optical code detection, etc.), ultrasound analysis, applying electromagnetic waves, millimeter wave analysis, x-ray analysis, curing, vapor smoothing, abrasive blasting and construction/production, e.g. additive manufacture and/or engraving. In some examples more than one of these processes/operations may be applied to the object. For example, optical inspection may be used during a cleaning process, followed by dipping the cleaned object in a treatment bath and curing the treatment. In each of these stages the process/operation may be applied though holes/voids in the mesh contact surface.

[0081] In some examples, the operation carried out on the object may be done through the holes or voids in the mesh contact surface 130. The paint or coating may be applied over the mesh (such that the paint or coating is also applied to the mesh of the mesh contact surface 130 as well as the surface of the object). In some examples the properties of the mesh contact surface may be such that the paint or coating may cover the object even where strands of the mesh are in contact the surface of the object. For example, the paint or coating may flow or soak between the mesh contact surface 130 and the surface of the object. In some examples the dimensions of the mesh may be such that surface tension of the paint or coating causes portions of the object in contact with strands of the mesh to be covered by the paint/coating when the gripper releases the object after painting/coating.

[0082] In some examples, the gripper may be used in a dipping process. The object may be held by the gripper and dipped in a liquid, such as a liquid surface treatment. The liquid may be stored in a bath or vat, for example, that the griper may enter at an upper portion. The liquid may come into contact with the surface of the object by passing or flowing through holes or voids in the mesh contact surface. In some examples the properties of the mesh contact surface may be such that the liquid may cover the object even where strands of the mesh are in contact the surface of the object. For example, the liquid may flow or soak between the mesh contact surface 130 and the surface of the object. In some examples the dimensions of the mesh may be such that surface tension of the causes portions of the object in contact with strands of the mesh to be covered by the paint/coating when the gripper releases the object after painting/coating.

[0083] Fig. 12 illustrates a method 1200 according to some examples. For example, a mechanical gripper 100 may execute a method 1200 for gripping an object. At block 1210 the mesh contact surface 130 is in a first state. The first state may be associated with a particular rigidity of the mesh contact surface 130. In some examples the first state is the normal state of the mesh contact surface 130, in other examples a condition may be applied to the mesh contact surface to place the mesh contact surface in the first state. At 1220 the gripper is controlled to grip an object while the mesh contact surface is in the first state. In some examples the gripper may grip the object and the mesh contact surface 130 may be placed in the first state while the object is held by the gripper. The rigidity of the mesh contact surface 130 in the first state may be such that the mesh contact surface 130 conforms to the surface of the object.

[0084] At block 1230, the rigidity of the mesh contact surface 130 may be controlled to increase the rigidity of the mesh contact surface 130. In some examples, a rigidity control element may be used to control the rigidity of the mesh contact surface 130. The rigidity control element may be adapted to controllably apply, or cease applying, a condition to the mesh contact surface 130. The rigidity of the mesh contact surface 130 may be variable in response to the applied condition. Examples of the condition include an electric current, a temperature, an electric field, a magnetic field, or exposure to electromagnetic radiation etc. In some examples, the rigidity of the mesh contact surfaces 130 may be controlled such that they are made to be flexible enough, in the first state, to conform to the surface of, or prominent features of, the object to be held. In an additional example, the rigidity may be further controlled such they the mesh contact surfaces 700 are made more rigid (e.g. in a second state), to ‘lock in’ the grip on the object due to the previously conformed shape of the mesh to the object surface features. This may provide improved grip on the object. The controlling may further comprise increasing the rigidity of the mesh contact surface area from the first state to a second state.

[0085] Fig. 13 shows a method 1300 according to some examples. At block 1310, a digit of the gripper is articulated by performing a first articulation. The first articulating may comprise controlling a motor to cause circular motion, in a first direction, of an anchor point of a control wire, the circular motion to pull the control wire. This may cause the digit to flex, for example. The method may also include, at 1320, a second articulation of the digit. The second articulation of the digit may comprise doing the reverse of the first articulation, by controlling a motor to cause circulation motion in a second direction opposite the first direction of the anchor, the circular motion to push the control wire. This may cause the opposite articulation in the digit compared with the first articulation. For example, the digit may extend. The method 1300 may provide accurate control of the digit in both the first and second articulations (e.g. flexing and extending).

[0086] In some examples a processing system for processing an object may include a gripping element to grip the object during processing, the gripping element having a gripping surface to contact a surface of the object during gripping; a processing element to carry out an operation involving the object, wherein the gripping surface is composed of strands that define holes in the gripping surface, the holes and strands such that the gripping surface does not obstruct the object for the purpose of the process. The gripping element of the processing system may be any of one the examples discussed herein comprising a mechanical gripper. The gripping surface of the processing system may be any one of the examples discussed herein comprising a mesh contact surface. The operation of the processing system may be any one of painting, coating, dipping, spraying, polishing, deposition (e.g. vapor deposition, sputter deposition, electrostatic deposition), electroplating, applying a jet (e.g. a gas, liquid or particle jet,) inspection or observation, viewing, measuring, scanning (e.g. surface scanning, optical code detection, etc.), ultrasound analysis, applying electromagnetic waves, millimeter wave analysis, x-ray analysis, curing, vapor smoothing, abrasive blasting and construction/production, e.g. additive manufacture and/or engraving. The processing element may be a tool for applying the operation (e.g. a fluid jet nozzle, laser scanner, etc.) In some examples more than one of these processes/operations may be applied to the object at any given time.

[0087] In a non-medical example application, after a 3D printed object or part has been printed, the part may undergo a series of operations or processes to finish the part. In one example, the operation to be carried out on the part may be vapor smoothing. Vapor smoothing involves a 3D printed part being held in an enclosed container with a solvent, such as acetone, wherein the part is in contact with the solvent in vapor form. The solvent reacts with the 3D printed part to smooth off the surfaces of the 3D printed part. During vapor smoothing the 3D printed part should be constantly monitored to allow a user to address any ‘drooping’ of the part as the surfaces react with the solvent. The examples discussed herein allow for the part to be monitored through voids of the mesh contact surface while being supported by the gripper during the smoothing process while allowing a user to avoid potentially hazardous contact with the solvent.

[0088] In a non-medical example application, to quantify the properties of an object, the operation or process carried out on an object may involve surface profiling. Surface profiling may include, for example, quantifying the roughness of a surface. The surface profiling may be carried out with non-contact or optical sensors, laser ranging or white light interferometry. The object may be visible to the sensors through gaps and voids of a mesh contact surface of a mechanical gripper, according to any of the examples disclosed herein, to carry out the surface profiling. In such examples, the effect of the mesh strand may be negligible for the purposes of the analysis being conducted.

[0089] In a non-medical example application, identification of an object may be performed though an identifier, such as a bar code or matrix bar code. Scanning for an identifier may be performed through the voids and holes of the mesh of the mechanical grippers to identify the object. Identifier scanning applications may include product tracking, item identification, time tracking, life cycle stage management, and supply chain management. In some examples, identifier codes may comprise codewords that use an error correction algorithm (e.g. the Reed- Solomon error correction algorithm with four error correction levels). Thus, in some examples, portions of the code that are not visible due to the mesh contact surface may be recovered through error correction. In some examples the information elements in the code may be larger than a strand thickness of the mesh contact surface, such that the strands do not prevent reading the information elements.

[0090] In cleaning applications, the surfaces of the object being held (e.g. by a user or a gripper) may not be fully exposed to the cleaning process as a result of being held. For example, the hand or gripper may partially obscure the object. This may lead to the grip on the object being adjusted repeatedly until all parts have been exposed sequentially. Examples of the grippers described herein may eliminate or reduce the degree to which the object is obscured by the gripper. According to some examples, the gripper may be turned to expose any part of the object to a processing element (e.g. a sensor such as a camera or a cleaning jet), without adjusting the grip to expose parts that were previously obscured. This may reduce cleaning times and/or the risk of damage to the object by additional handling. Some examples allow for processing elements to be deployed within or behind the mesh of the gripper, as the mesh contact surfaces do not obstruct the surfaces that are being sensed or acted upon.

[0091] A number of examples of non-medical applications have been described, and the described methods may be used in various non-medical processes. However, examples of the gripper described above may also find application in medical processes. For example, a gripper as described above may be useful in medical methods that are performed at a location remote from a medical professional controlling the gripper. The gripper may provide improved visibility of the medical process, as the mesh elements reduce the obstruction of sensing elements (such as cameras). In some examples, processes such as washing or suction may be performed through the mesh of the contact surfaces. For the avoidance of doubt, producing components for use in a medical procedure is not considered to be medical process for the purposes of the current description.

[0092] Throughout the description and claims of this specification, the words “comprise” and “contain” and variations of them mean “including but not limited to”, and they are not intended to (and do not) exclude other components or integers. Throughout the description and claims of this specification, the singular encompasses the plural unless the context demands otherwise. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context demands otherwise.

[0093] Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect or example are to be understood to be applicable to any other aspect or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the stages of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or stages are mutually exclusive. Examples are not restricted to the details of any foregoing examples. The Examples may extend to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the stages of any method or process so disclosed.

[0094] The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.