Technical Field

The technical field relates to tactile sensor comprising a support supporting a first conducting face opposite facing a second conducting face. The sensor is of the restive type and for sensing pressure. The technical field relates to the sensor, arrangements of sensors and methods of producing such sensors.

Background Art

Tactile sensors are generally known. Typically the sensors are of piezoelectric type. Alternative and improved tactile sensors are required as are alternative and improved methods of production of tactile sensors.

US 2017/0031491 Al describes a tactile sensor with a first conducting face flat upper electrode and a second opposing conductive face of a lower electrode, including conductive portions on or in protruding recoverable deformable thereby having different. The electrode conductive faces move relative to each other by applied pressure force.

WO 2017/091151 Al describes a tactile sensor with a first conductive face upper electrode that is micro-structured with pyramidal arrays thereby having a conductive face with a first topology and facing a lower flat electrode, thereby having a second face with different topology. The faces are arranged to move relatively to each other by an applied pressure force.

WO 2017/091151 Al also describes a method of producing a tactile sensor in where a support and second layer with a conductive second face with a second topology is provided. WO 2018/144772 discloses a pressure sensor that includes a first electrode layer and a second electrode layer including multiple conductive micro-structures and a dielectric layer between the first and second electrode layer.

US 2020/0018656 disclose a tactile sensor capable of detecting a shear force based on pressure sensitive elements. WO 2020/087027 also discloses a tactile sensor of capacitive type capable of detecting shear forces.

Of general interest is US 2013/0275057, which discloses a grid of wires to reconstruct a continuous position of force on a surface from interpolation based on data signals received from the grid of wires. Likewise, WO 2018/7232326 discloses a grid arrangement for sensing shear load from an object.

Despite the before cited documents, there is a need for a tactile sensor of an alternative type and with an improved dynamic range and that is simple and easy produce.

Summary of Invention

An objective of the invention is achieved by a tactile sensor comprising a support supporting a first conducting face opposite facing a second conducting face. The first and second faces arranged to move relatively to each other by an (externally) applied pressure force. At least one of the first or second faces has a topology different from the topology of the opposite face.

Thereby providing a conductance or resistance between the first and second face as a function of an externally applied pressure force. The conductance or resistance is obtained between the first and second face and may be e.g. by appropriately arranged wires. The tactile sensor has a proved adjustable design regarding dynamic range and characteristics and will thus enable or improve sensing of an object in respect of the following types of sensing.

Sensing of contact events such as making contact, braking contact, or sliding may be improved or enabled. Sensing of forces and torques such as normal force, shear force, normal torque may be improved or enabled. Sensing of the local geometry of an object’s contact point, surface curvature, or edges may be improved or enabled. Sensing of material properties such as compliance, texture, or friction may be improved.

Thus, tactile sensing requires a great plurality of sensing characteristics and thus not one layout or configuration may suit all types optimally. The outlined construction of a tactile sensor allows for at the same time to improve sensing more types of the above types of sensing at the same time or during the same sensing event.

As for the arrangement of a first conducting face facing an opposite second conducting face, the faces are arranged to move relatively to each other by a pressure force. The faces may be provided on layers as will be disclosed and the pressure force may be applied to an accessible external surface. The external surface may of a kind suitable for an end effector of a robot.

At least one of the faces has a surface topology as a result of a grating with a pattern. That is a face with a geometrical shape different from the pattern i.e. geometrical shape of the opposite face. Thereby providing a conductance or resistance between the first and second face as a function of applied pressure force.

This allows the technical design and achievement of the sensor regarding dynamic range and sensitivity. The dynamic range may be increased whilst the sensitivity is maintained at a measurable, in terms of S/N-ratio, acceptable level. Likewise, increased sensitivity may be achieved in a certain force range.

As such the disclosed tactile sensor is a force detection device. The device may be of the resistive type of pressure sensor.

The support may be a rectangular housing with two walls in opposite sides which provides a supporting structure for other parts and electrical layout which a person skilled in the art will be able to arrange according to design requirements.

One face may be achieved by a layer or a conductive structure with patterned structure and dimensions with known resistivity which is fixed on the bottom of inner area of housing. The pattern may be periodic.

In an aspect a thin flexible foil with a spring effect in case of an applied normal force on the surface may be fixed on the top of the two walls of the support or housing. The flexible foil may cover the support or housing while it keeps a gap due to wall thickness in the absence of applied force.

A conductive face may be formed by a conductive layer from a semi-hard material e.g. rubber with known resistivity placed on the central back of the flexible layer facing towards the opposite pattern, e.g. the periodic structure, while still preserve a gap, i.e. disconnected, with the patterned face, e.g. the periodic structure, in the absence of applied force. There may be a non-conductive touch pad or contact face formed by a semi-hard rubber with known thickness of larger than the gap size between the two conductive faces or two conductive layers, an; which has a smaller x-y size than the inner area of the housing and is place in the central part of flexible layer facing upward.

There is provided for an electrical layout to the device. Such layout may include an input electrical channel for the purpose of feeding an input voltage which activate the detection as soon as there is contact between the two conductive faces or two conductive layers. Correspondingly, there is an output channel for the purpose of reading out the output signal in order to estimate the contact resistance between the two conductive faces or two conductive layers.

Such construction will provide that the conductive parts will contact each other in case of an applied force that is detected and can be estimated upon touch. As such the sensor is a tactile sensor.

In an aspect there is a force detection device where the amount of an applied force can be interpreted from the output signal of the device based on a sensory output from at least one tactile sensor, at least one tactile sensor array or matrix.

Typically one of the faces as a result of the corresponding layer, e.g. the second face of the second layer, is of a flexible material such as an elastomer or composite, which may have a shape memory effect with respect to deformation during compression and recovery. A further advantage of the outlined tactile sensor arrangement is to improve sensitivity capabilities despite the shape memory effects. A given shape memory may simplistically be characterized by a cycle and as such dynamically cycle between a first shape and a second shape. By forming the first or second face with different topologies accommodates such first and second shapes. Thus, a first topology may ensure optimal sensitivity to a first memory caused shape and a second topology may ensure optimal sensitivity to a second memory caused shape. The first and second topology may be in the grating or spatially separated as outlined.

In one configuration the second layer and face may be the flexible layer and with a planar topology as a first memory shape. The second memory shape may reflect topology first topology of the first face, complementary. The topology of the direct opposing face may then advantageously have different topologies. As an example the combination of an edged and rounded topology.

In an aspect at least one face has a topology comprising a form chosen among an ellipsoid form factor, a triangular form factor; a square form factor, a trapezoid form factor, a sinusoidal form factor; a free form factor or combinations thereof.

The forms result in distinct and different sensor characteristics which may be used according to special requirements. One special requirement could be to mitigate the shape memory effect.

In an aspect, at least one face has a topology extending in a normal direction and having asymmetrical faces in the transverse direction. Thereby improving sensitivity to a force applied with a tangential component. As an example, a first layer is applied on a planar base with the normal direction perpendicular to the planar base. A first face made with a topology with a sawtooth form factor has an asymmetry that will increase the extent of the face in one transverse direction relative to the opposite transverse direction and thus provide a larger contact area when the face of the second layer experiences a tangential force in that one transverse direction. Thus, sensitivity to e.g. shear forces, torques is improved when the tactile sensor is arranged to provide indication of e.g. slippage.

In an aspect the least one tactile sensor has the first conducting face formed by a first conductive layer chosen among an moldable material filled with conductive fillers. The material may be adhesive or both moldable as well as adhesive. The material is hardened or in a final state of hardening after being molded or adhered. In an aspect a conductive material or filler can be chosen among: silver particles, silver nanowire, gold particles, graphite particles, carbon black particle, carbon nanotube, carbon nanofiber, or variants thereof. A person skilled in the art may select conductive fillers such as cobber, aluminum or alike.

The electrically conductive material may be a single or two component epoxy resin filled with conductive particles with a paste-like viscosity before curing. Curing can happen either in room temperature, by exposure to heat or exposure to a light source.

Final cured material should be electrically conductive in the thickness range 0.1- lmm. It should have a known homogeneous volume resistivity <1 ohm -cm and a shore hardness A >70. Safe operating temperature range should include -10 °C to + 100 °C. The advantage of using epoxy resin is having adhesion properties to a wide group material while it does not adhesive effect to silicon therefore a silicon mold can be used to form the structured patterns when the material is in the process of curing.

The advantage of using silver is having high electrical conductivity and the concentration of silver defines the level of conductivity.

The conductive material may be a two-part silver epoxy (commercially available from e.g. Chemtronics) with 1:1 mixing ratio, which can be cured in the room temperature or by exposure to heat. The volume resistivity of final cured material is less than 0.001 ohm-cm and the shore A hardness is > 70. The safe operating temperature is -91 °C to +100 °C.

The advantage of using this combination of epoxy and silver particles is that it follows the required physical properties for hardness, resistivity and safe temperature operating range. It has conductive structural adhesion while a silicon mold can be used for creating patterned structure and removed easily after curing the material. The curing time can be reduced by increasing the heat exposure.

In an aspect of the second face, the second conducting face may be formed by a second conductive layer chosen among electrically conductive polymer composites.

The second layer may be an elastomer. The base polymer may be a silicon elastomer. In an aspect a conductive filler can be chosen among carbon black, carbon nanofiber, graphite, silver nanowire, silver particles or variants thereof. A person skilled in the art may select conductive fillers such as cobber, aluminum or alike, The electrically conductive polymer composite should have a volume resistivity in the range of 1 to 10 ohm-cm along the surface. The uniform thickness of the material should be 0.1 to 2 mm. Safe operating temperature range should include - 10 °C to +100 °C. The tensile strength of the material should be > 0.3 MPa and the shore A hardness should be in the range of 10-75 (depending on the performance range of sensor) to prevent the permanent deformation. The material should have elongation of > 50 % to have a safe range of temporary deformation before the breakage under a tensile load. It should have a durability of >10000 times of use.

The advantage of having high shore hardness is to increase the dynamic range of the sensor. And the advantage of having low shore hardness is to have more elasticity of the material less memory effect when releasing the applied force.

The electrically conductive polymer composite can be a silicon base polymer filled with graphite. Such graphite could be as commercially provided (e.g. from Holland Shielding) and with thickness of 1 mm and volume resistance of 1.8 ohm-cm. Safe operating temperature range is -50 °C to +160 °C. The tensile strength of is -0.34 MPa and the shore A hardness is 71 with elongation of >50%.

The above mentioned values and ranges merely serves as a starting point and a person skilled in the art will appreciate that the values are approximate. Some adjustments or variations may provide similar effects and may well be explored according to specifics of implementation.

In an aspect at least one face comprises multiple and different topologies. In an aspect, multiple tactile sensors arranged in a matrix or an array of such.

Thus, a matrix of tactile sensors or an array of tactile sensors may be provided. Each sensor may be a tactile sensor as disclosed. Using a matrix of sensors allows or improves for detection of torque.

An array or matrix arrangement allows for detection of contact and braking contact including localization of contact or the object. Local geometry of an object may also be determined including contact point, object curvature as well as edge detection.

An array or matrix may be realized so that a single base is used. Certain parts of an array or matrix may be configured with one type of topologies whereas other parts of an array or matrix may be configured with another type of topologies.

In example there may be a first array or a first part of an array comprising a first type of topology of e.g. the first face, which type may be a triangular shape. There may be a second array or a second part of an array comprising a second type of topology of e.g. the first face, which type may be a rounded shape.

In example, and likewise to the different topologies of an array, there may be a first matrix or a first part of a matrix with one topology and a second matrix or second part of a matrix with another topology.

Furthermore, forces and torques inducing normal forces, shear forces and normal torque may be determined with a larger dynamic range, signal to noise. A further advantage is that the tactile sensor as disclosed may be made or formed according to a shape or geometry of fingers or contact areas of an end effector of a grasper or gripper unit.

An array of tactile sensors may be formed by configuring the tactile sensors with a common ground. Likewise, a matrix of tactile sensors may be formed by configuring the tactile sensors with a common ground.

In an aspect the support configured with a hole. That is the support and the tactile sensor has a through hole. One or more tactile sensors may be arranged in the vicinity of the hole. Two tactile sensors may be provided substantially on each side of the hole. The sensors may be arranged about 180 degrees apart. Three tactile sensors may be provided around the hole. The sensors may be arranged about 120 degrees apart.

In example, a tactile sensor matrix may be made on a base, which may be a common base, forming part of a support.

In an aspect the tactile sensor may comprise a further sensor type. The further sensor type may be configured to detect presence or slippage of an object. The further sensor type may be of an optical type.

In an aspect the hole may be provided with a further sensor or alternatively the further sensor may replace the hole, i.e. be located where the hole is. In an aspect there is a tactile sensor arrangement comprising an arrangement of multiple tactile sensors e.g. three tactile sensors, tactile sensor arrays, or tactile matrices; alternatively. The tactile sensors may be equally distributed around a centre, a line or a path of interest. That is the sensors may optionally extend spatially along a line or arc capable of tactile sensing defined by e.g. an end effector. Thereby providing “360-degrees” sensing.

The advantage is to have at least one active taxel in the contact area where the end effector is in contact with an object. Moreover, it introduces the possibility to have the distribution of the force on the whole surface of the end effector and edge detection of the object.

There may be a further sensor in the centre area. In the shown embodiment there is a hole in the centre region. The hole provides space for a further sensory output. The arrangement allows for the tactile sensor arrangement to be placed on an end effector with existing sensor. The tactile sensor arrangement may be fitted with a further sensor, which could be an optical sensor configured to detect distance, slippage, or rotation of an object.

The advantage is to combine the information about both static and dynamic applied forces to have a better control of grasping process with an end effector.

An objective is achieved by a method of producing a tactile sensor. The method of producing a tactile sensor may comprise acts as follows. There is an act of providing a support. The support may have a base and walls that are non-conductive. There may be provided and second layer of conductive material and with a conductive second face with a second topology.

There is an act of applying a conductive form-able material on the provided support. The material may be form-able paste like or liquid material. The material may be an epoxy type of paste that is conducive or a composite of a form-able and curable material and a conductive material e.g. conductive metallic and particulate type.

There is an act of forming a first conductive face of the form-able material. The forming may be performed by molding a conductive paste or liquid material provided. This may be performed with a mold having a complementary topology to the desired first topology. The first topology that is different from the second topology of the second face provided or to be provided.

There is an act of arranging the second conductive face of the second conductive layer opposite to the first conductive face

Thereby providing a tactile sensor with great freedom of design and improved dynamic range and sensory characteristics.

The method may be applied to produce a single tactile sensor with improved dynamic range due to a flexibility and increased design flexibility in a contact area between two conductive faces as a function of the faces being forced together. The method may be applied to produce a single tactile sensor with different spatial sensory characteristics. The method may be applied to produce an array or matrix of tactile sensors

Not shown, the method may involve a further act of connecting at least one first wire to the first conducting face and connecting at least one second wire to the second face. Wiring may be performed with great flexibility using the exemplified method of production e.g. the wires may be embedded in the paste in-situ.

In particular the method of producing may be so that the act of forming a first conductive face involves forming at least two different topologies, each different from the second topology of corresponding second face.

Thus a tactile sensor may be manufactured by a process comprising acts as outlined.

Brief Description of Drawings

Embodiments of the invention will be described in the figures, whereon:

Fig. 1 illustrates principles of a tactile sensor;

Fig. 2 illustrates layers forming a tactile sensor;

Fig. 3 illustrates a tactile sensor (singlet), an array of tactile sensors, and a matrix of tactile sensors;

Fig. 4 illustrates topologies of conductive faces of a tactile sensor;

Fig. 5 illustrates asymmetric aspects of a conductive face as exemplified with a sawtooth form factor;

Fig. 6 illustrates dynamic responses of different topologies of a conductive face of a tactile sensor; Fig. 7 illustrates arrangements of topologies of conductive faces;

Fig. 8 illustrates array of tactile sensors;

Fig. 9 illustrates aspects of tactile sensor outputs including object slippage;

Fig. 10 illustrates a tactile sensor arrangements configured to accommodate a further sensor; and

Fig. 11 illustrates a method of producing a tactile sensor.

Description of Embodiments

Figure 1A shows a tactile sensor 10 comprising a support 20 (not shown) supporting a first conducting face 51 opposite facing a second conducting face 52. Generally, there is a face 50 that is conductive. The face 50 is of a material or layer 40. The first face 51 may be of a first layer 41. The second face 52 may be of a second layer 42.

At least one of the faces 51,52 has a topology 60A different from the topology 60B of the opposite face 52,51. In the embodiment, the first face 51 has a first topology 61 formed 60A with a triangular shape; and the second face 52 has a second topology 62 formed 60B with a planar shape that is different from the triangular shape.

The respective first and second faces 51,52 supported e.g. in a wall and arranged to move relatively to each other by an applied pressure force 5. The force 5 may be applied externally to a suitable external face of the second layer 42. The arrangement and the characteristics of the second layer 42 and the arrangement of the second face 42 towards the first face 41 and the characteristics of the first layer 41 allows the applied force 5 to deform at least one of the layers 41, 41 and the form of the faces 51, 52 so that the contact 70 between the conductive faces 51, 52 becomes a function of the applied force 5. The lower part of figure 1A illustrates how a contact area 72 is formed as a function of the deformation of substantially the second layer 42 when pressed against a more rigid first layer 41. Wires 30 (not shown) are easily applied to the respective conductive faces 51, 52 and the tactile output is provided as a function of the conductivity or resistivity between.

Figure 2 illustrates element of an assembly of a tactile sensor 10. Figure 2A shows different elements forming some parts of the tactile sensor 10. From the top: there is an element as a fourth layer 44 forming touching surface 54. There is a flexible connection layer as a third layer 43. There is a conductive layer forming the second layer 42 with a substantially planar second face 52. There is a grating or pattern forming the first conductive layer 41 with the first topology 51. There is a base 22 forming part of a support 20. Figure 2B further shows a touch pad with the touching surface 54 to be connected to with the conductive second face 52, which is arranged opposite the first conductive face 51 supported by the support 20 comprising the base 22 element and wall 24 elements.

Figure 2C shows a tactile sensor 10 assembled according to the elements of figures 2A and 2B. Variations, alternatives, or combinations of the elements may be realized according to the herein disclosed features.

Figure 3 illustrates 3A a tactile sensor 10 as a taxel 11, 3B an array (2D) of tactile sensors 12, and 3C a matrix of tactile sensors 13. For illustrative purposes, the sensor layout comprises a support 20 with a base 22 and wall elements 24. The base 22 support a first layer 41 with a first conducting face 51 with a first topology 61. The walls 24 supports a third layer 43 that is a flexible layer to which a second layer 42 with a second conductive face 52 is attached and arranged so that the second face 52 faces the first face 51 that is essentially comprises repetitions of triangles. The second face 52 has a second topology 62 that is essentially planar in this embodiment. On the third layer 43, there is a fourth layer 44 arranged to receive a force on a touch surface 54 (touch face) and transfer the force to the second layer 42 via the third layer 43.

In the shown embodiment, the first and second faces 51, 52 are arranged not to be in contact when no force is applied to the sensor.

Figure 3B an array of tactile sensors 12, each tactile sensor 101, 1011, ..., lOi essentially with reference to figure 3A, and arranged with respective contact surfaces 541, 5411, ... 54i so that each tactile sensor lOi functionally is separated allowing for the layout or spatial design of the touch surfaces 54 allows for edge or shape detection of an object.

Figure 3C illustrates a matrix of tactile sensors 13 were with a dimension I, II, ...i, .... and a dimension a, b, c, .... The illustrated matrix comprises e.g. a single tactile sensor 10, which single sensor extends from bottom towards the top. The sensor 10 may have first and second faces extending as graphically indicated. Wires may be placed along the extend and thus the long sensor may provide a single output on a spatial output according to the wiring.

The illustrated matrix 13 comprises e.g. an array 12III of sensors, which are here three distinct tactile sensors 10111a, 10111b, 10111c. It is noted that sensors a, b, and c could be configured so that some or all are identical.

Figure 4 illustrates different topologies 60 of a face 50 (not shown). Different forms are shown in A, B, C, D, and E. Generally, the shown forms are repetitive patterns 65 characteristic by a periodicity 66 and an amplitude 67. In general, first topology 61 and second topology 62 may have similar patterns 65, but with different periodicity 66A or different amplitude 67A. A face 60 may have a spatially varying periodicity 66 or varying amplitude 67.

4A illustrates a topology 60 of a face 50 e.g. with reference to figure 1, where the topology 60A has a rounded form factor such as an ellipsoid or sinusoidal form factor. The rounded form has a spatial periodicity 66A and an amplitude 67A.

In the case where the opposite face is planar the and the material of the opposite layer is soft, then the resistivity will tend to decrease proportionally to the contact area 72 between two opposite layers. The form factor may be suitable for force detection in a wider dynamic range 82 depending on the form factor’s characterization.

4B illustrates a topology 60 of a face 50 e.g. with reference to figure 1, where the topology 60B has a linear (with a slope) form factor such as a trapezoid or triangular form factor. The rounded form has a spatial periodicity 66B and an amplitude 67B.

In the case where the opposite face is planar the and the material of the opposite layer is soft, then the resistivity will tend to decrease proportionally to the contact area 72 between two opposite layers. The form factor may be suitable for a smaller dynamic range 82 and higher force detection resolution depending on the form factor’s characterization. 4C illustrates a topology 60 of a face 50 e.g. with reference to figure 1, where the topology 60C has a flat form factor such as a square form factor. The rounded form has a spatial periodicity 66C and an amplitude 67C.

In the case where the opposite face is planar the and the material of the opposite layer is soft, then the resistivity will tend to be binary i.e. ON/OFF like characteristics.

The resistivity will decrease suddenly in the event of contact 70 between two opposite layers and the output signal will be at its maximum level. The form factor may be suitable for using the sensor as a switch to identify the presence or absence of a touch.

4D illustrates a topology 60 of a face 50 e.g. with reference to figure 1, where the topology 60D has a combination of form factors with a rounded form factor closest to the intended opposite face transitioning into a linear form factor e.g. a triangle form factor at the bottom. The combined form has a spatial periodicity 66D and an amplitude 67D.

In the case where the opposite face is planar the and the material of the opposite layer is soft, then the resistivity will tend to decrease proportionally to the contact area 72 between two opposite layers. The form factor may be suitable for the combination of having a wide dynamic range 82 and increasing the force detection resolution at high forces.

4E illustrates a topology 60 of a face 50 e.g. with reference to figure 1, where the topology 60E has a combination of form factors with a linear form factor e.g. a triangle form factor to the intended opposite face transitioning into a rounded form factor e.g. a circular form factor at the bottom. The combined form has a spatial periodicity 66E and an amplitude 67E.

In the case where the opposite face is planar the and the material of the opposite layer is soft, then the resistivity will tend to decrease proportionally to the contact 70 area between two opposite layers. The form factor may be suitable for the combination of having a wide dynamic range 82 and increasing the force detection resolution at low applied forces 5.

Figure 5 illustrates an embodiment of a first layer 41 forming a first face 51 with asymmetric faces.

Figure 5 A shows a first face 51 with a topology 60 extending in a normal direction (see arrow) from a base 20 and having asymmetrical faces in the transverse direction (see arrow). The first face 51 is characterized by a periodicity 66 and an amplitude 67. The form factor is a saw-tooth type resulting in an asymmetry that provides a larger face in one transverse direction (here as seen from the right) compared to a smaller face in the opposite transverse direction (here as seen from the left). The pattern in this case has a first tangential extent 55 (towards the right) compared to a second tangential extent 56 (towards the left).

As seen in figures 5B and 5C an applied force 5 with a force component in the transverse direction will result in the second layer 42 to make contact as indicated and there will essentially be a first tangential contact area 75 and a second tangential contact area 76, that are different. Thus, the skewing of a topology by having different first and second tangential extents will generally introduce asymmetric face will allow to detect transverse force in an improved way.

Figure 6 illustrates the response 80 and dynamic range 82 of tactile sensors 10 (not shown) with a first face 51 with a first topology 61 in two cases. One first face 51A with a round topology 61A and another first face 51B with a sharp topology 61B. The faces 51 are provided by applying a generating the pattern by molding a conductive paste on a base 22.

For both cases there is a groove distance 68 of about 1.35 mm, which groove distance greatly improves signal growth (slope) and results in a faster response say compared to a groove distance 68 (not shown) of 0.5 mm and even better compared 0.35 mm.

The round topology 61A increases the dynamic range 82 of the sensor output, which may be advantageous with respect to detecting shapes of as well as slippage. The sharp topology has a comparatively flatter slope, but a relatively high (instant) onset, which may be advantageous with respect to e.g. contact type of sensing.

Figure 7 illustrates embodiments of a base 22 and a first conductive layer 41 with a first conductive face 51 with a first topology 61.

Figure 7A shows a trapezoid type of topology 61AI and 61AII. Each topology may have distinct characteristics of the grating such as the periodicity, amplitude 67A, slope and plateau of each trapezoid as the general characteristic 69A of a generic type, and the groove distance 68AI. 1

Figure 7B shows ellipsoid type of topology 61BI and 61BII. Each topology may have distinct characteristics of the grating such as the periodicity, amplitude 67B, a- and b- values characterizing an ellipse as the general characteristic 69B of the generic ellipse-type, and the groove distance 68BI.

Figure 7C illustrates combinations of topology types. In view of figures 7A and 7B, the illustrated embodiment combines trapezoid type of topology 61A and ellipsoid type of topology 61B, which as an example has the same periodicity and the same groove distance, but with varying amplitudes 67A, 67B.

In one embodiment, one stretch comprises a grating with a trapezoid type topology 61A and a stretch that comprises a grating with an ellipsoid type topology 61B, where the ellipsoid amplitude 67B is larger than the trapezoid amplitude 67A. In another embodiment a base comprises repetitions of trapezoid-ellipsoids topologies 61A, 61B with respective amplitudes 67A, 67B.

Figure 8 exemplifies arrangements forming tactile sensors 10 or tactile sensor arrays 12. Generally, there is a base 22 supporting a first conductive layer 21.

There are walls 24 supporting a third layer 43, which supports a second conductive layer 42 arranged opposite the first conductive layer 41. The third layer 43 further supports an external fourth layer 44 arranged to contact an object and transmit a pressure force to move the second conductive face with a second topology 62 and contact the first conductive face with a first topology 61 so as to change the resistivity as a function of the applied pressure force. For illustrative purposes the second topology 62 of the second face is substantially planar. Embodiments in figures 7A and 7C have those features specifics as follows. Figure 8A exemplifies substantially identical tactile sensors 10 arranged as a tactile sensor array 12. The first topology 61 of the first face is essentially a triangular type. There is substantially a one-to-one correspondence between a touching surface 54 and the grating forming the first conductive face 51.

The resistivity between two opposite layers will tend to decrease proportionally to the contact area 72 between them for each taxel 11. The advantage is to have the ability of force distribution identification on a tactile sensor array 12 and possible edge detection by comparing each taxel’s output. This configuration works as long as the size of object 1 is not the same or smaller than the dead spaces between touch surfaces 54 or there is at least one contact 20 position in one of the touch surfaces 54.

Figure 8B exemplifies basically the same configuration shown in figure 8A, but with different - here alternating - first topologies exemplified by sharp or triangular topologies 61A and round or ellipsoid topologies 61B.

The resistivity between two opposite layers will tend to decrease proportionally to the contact area 72 between them for each taxel 11 which depends on its form factor. The advantage is to have different sensitivity of force detection in each specific position of a tactile sensor array 12 which can be used for an object with not uniform geometry. This configuration works as long as the size of object 1 is not the same or smaller than the dead spaces between touch surfaces 54 or there is at least one contact 70 position in one of the touch surfaces 54. Figure 8C exemplifies spatially separated sets of first faces 51 of triangular gratings as topologies 61. There is a single touching surface 54 covering or communicating with the separated sets of first faces 51.

The resistivity between two opposite layers will tend to decrease proportionally to the contact area 72 between them for each taxel 11. The advantage is to have the ability of force distribution identification on a tactile sensor array 12 and possible edge detection by comparing each taxel’s output. This configuration works regardless of the size of object and where the contact 70 position is.

Figure 8D exemplifies basically the same configuration shown in figure 7B, but with different - here alternating - first topologies exemplified by sharp or triangular topologies 61A and round or ellipsoid topologies 61B of the spatially distributed sets of first faces 51.

There is a single touching surface 54 covering or communicating with the separated sets of first faces 51. The resistivity between two opposite layers will tend to decrease proportionally to the contact area 72 between them for each taxel 11 which depends on its form factor. The advantage is to have different sensitivity of force detection in each specific position of a tactile sensor array 12 which can be used for an object with not uniform geometry. This configuration works regardless of the size of object and where the contact 70 position is.

Figure 9A and 9B illustrates tactile sensors arranged on an end effector 2 moving and providing a force 5 on an object 1 though contact 70. As a result of the object 1, there is a sensory output 18 from each tactile sensor 10 forming a sensory output distribution 19. A sensory output distribution 19 can have different characteristics indicative of the type of contract with the object 1. The sensory output distribution 19 may be indicative of a shape of the object (19i), by the surface of the object (19ii), and an edge of the object (19iii) just to exemplify a few.

Figure 9C illustrates an increase of applied force 5 to an object 1 in contact 70 with a tactile sensor 10 arranged on an end effector 2. As a result of the increase of applied force 5 between the object 1 and the tactile sensor 10 arranged on an end effector 2, the sensory output 18 from the tactile sensor 10 is changing.

Figure 9D illustrates a situation sensory output distribution 19 where the object 1 is under influence of a force. The sensory output distribution profile may be indicative of force and thus indicative of if the object is securely held or if there is a risk of slippage. The temporal change of the sensory output distribution may be indicative of an actual slippage of the object.

Figure 10 illustrates a tactile sensor arrangement 15 comprising an arrangement of three tactile sensors 10ABC (tactile sensor arrays 12ABC, or tactile matrices 13ABC; alternatively). The tactile sensors are substantially equally distributed around a center. The sensors may optionally extend spatially along a line or arc capable of tactile sensing. Thereby providing “360-degrees” sensing and being able to detect gives the advantage of having at least one active taxel 11 in the contact area 72 where the end effector 2 is in contact 70 with an object 1. Moreover, it introduces the possibility to have the distribution of the force on the whole surface of the end effector 2 and edge detection of the object 1. There may be a further sensor in the center area. In the shown embodiment there is a hole in the center region. The hole provides space for a further sensory output. The arrangement allows for the tactile sensor arrangement 15 to be placed on an end effector with existing sensor.

The support 20 with a through hole 26 is illustrated with a void prepared for the tactile sensor 10 (array 12, or matrix 13) as well as a wire path 35.

Figure 10B illustrates the tactile sensor arrangement of figure 10A fitted with a further sensor 90 which could be an optical sensor 92 configured to detect distance, slippage, or rotation of an object.

Figure 11 illustrates a method of producing 900 a tactile sensor 10 (not shown). The method comprising acts as will be exemplified.

There is an act of providing 190 a support. The support may have a base and walls that are non-conductive. There may be provided and second layer of conductive material and with a conductive second face with a second topology.

There is an act of applying 1200 a conductive form-able material on the provided support. The material may be form-able paste like or liquid material. The material may be an epoxy type of paste that is conducive or a composite of a form-able and curable material and a conductive material e.g. conductive metallic and particulate type. 1

There is an act of forming 1300 a first conductive face 51 of the form-able material. The forming may be performed by molding a conductive paste or liquid material provided. This may be performed with a mold having a complementary topology to the desired first topology. The first topology that is different from the second topology of the second face provided or to be provided. Forming may be performed by a grating process by pressing, stamping or alike.

There is an act of arranging 1400 the second conductive face 52 of the second conductive layer opposite to the first conductive face.

Thereby providing a tactile sensor with great freedom of design and improved dynamic range and sensory characteristics.

The method may be applied to produce a single tactile sensor with improved dynamic range due to a flexibility and increased design flexibility in a contact area between two conductive faces as a function of the faces being forced together.

The method may be applied to produce a single tactile sensor with different spatial sensory characteristics. The method may be applied to produce an array or matrix of tactile sensors.

Not shown, the method may involve a further act of connecting 1500 (not shown) at least one first wire to the first conducting face and connecting at least one second wire to the second face. Wiring may be performed with great flexibility using the exemplified method of production e.g. the wires may be embedded in the paste in-situ. In particular the method of producing may be so that the act of forming a first conductive face involves forming at least two different topologies, each different from the second topology of corresponding second face.

Thus, a tactile sensor 10 (as exemplified in the previous figures, but not limited hereto) may be manufactured by a process comprising acts as outlined.

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