CROSS-REFERENCES TO RELATED APPLICATIONS

[0001] This application claims priority to Indian provisional patent application no. 201941043480 entitled A Multimodal 3-Degrees Of Freedom Haptic Device filed on 25.10.2019.

HELD OF THE INVENTION

[0002] The disclosure relates generally to a haptic device and in particular, to a grasper that may reproduce various haptic sensations such as stiffness, texture, shape, and shear from a virtual or remote environment in three degrees of freedom.

DESCRIPTION OF THE RELATED ART

[0003] Haptics is the sense of touch, which is the combination of two forces, namely kinesthetic and tactile forces. A haptic feedback interface helps humans to interact with remote or virtual environments, and consequently, a bidirectional feature of these interfaces became indispensable to feel the environments convincingly. The continued developments of these existing bidirectional interfaces lead to multi-fold applications such as military, space and underwater explorations, medical, rehabilitation and entertainment. Many of the haptic devices reported in the literature render either kinesthetic or tactile feedback, wherein the kinesthetic feedback is associated with shape, weight, and rigidity, and the tactile feedback is related to the surface (texture and smoothness), and shear of the object. However, the nonexistence of either one of the feedback to the user makes the whole experience unrealistic.

[0004] Demonstrating a cluster of tactile effects in one haptic device is possible only by increasing the bulkiness and mechanical complexity of the system. Many of the existing devices focus on illustrating the different combinations of tactile effects like slip contact, skin stretch, vibrations, shape, and texture but do not provide stiffness (an essential haptic modality). Most of the proposed devices by researchers can render either stiffness with the shape or only texture but not both. These interfaces are also limited in their resolution and workspace. In addition, due to the lack of appropriate combination of haptic feedback modalities, none of these devices could offer an impression of feeling the natural environment. Realizing stiffness, along with texture and shape, remains a challenge. The analysis of haptic modalities determines that rendering of stiffness combined with texture and shape can provide better haptic fidelity for the user. This is because of the dominating nature of perceptual cues of material properties other than geometric properties. Attempts have been made in the literature to equip haptic devices with a vibrotactile display. Such a vibrotactile display through vibration offers the user, the perceptual cues of roughness and texture of an object.

[0005] However, when the variation of the texture of the said object changes rapidly, intense vibrations from the actuator may subjugate the feel of a real object. Haptic devices, especially tool-based end-effectors, which consist of only one contact point, provide reduced overall haptic fidelity and perception. In order to offer a higher haptic fidelity, workspace and human adaptability, researchers have developed multi fingered haptic interfaces. These interfaces enhance the perception and grasping power dramatically through multiple contact point interactions, and thus overlaying path for various applications like rehabilitation, telesurgery, training, and gaming, which involves grasping, exploration, and manipulation.

[0006] The patent CN108845512A discloses a kind of large texture tactile sense reproduction force compensating system that includes a tactile sense reproduction terminal that has an interaction plate and force feedback gloves. The patent US7249951B2 describes a method and apparatus for providing an interface mechanism for a computer simulation. The US patent application US20190334426A1 relates to vector haptic feedback by perceptual combination of cues from mechanically isolated actuators. An apparatus and method for 3 degrees of freedom (3DOF) tactile feedback is disclosed in the patent US9030306B2. The US patent US8216212B2 discloses a system that provides haptic feedback to the handle of a tool

[0007] Disclosed herein is a haptic device that may provide feedback in 3 degrees of freedom.

SUMMARY OF THE INVENTION

[0008] In various embodiments, the invention is a haptic device. The device includes a texture module having an array of textures configured to display one or more tactile sensations based on a contact force, the array of textures having fine to coarse textures. In various embodiments, one or more actuators are placed under the texture module and are configured to simulate vibrations or shape or both based on a selected texture and geometric shape. A position control module configured to realize shape, shear and texture of a virtual environment is included. The device further includes an impedance control module configured to provide stiffness of the virtual environment that is a function of the contact force. In various embodiments, the device generates a feedback that has stiffness, texture, shear or shape or a combination thereof.

[0009] In one embodiment, the contact force is from a single source. In various embodiments, the texture module includes at least one spherical segment having the array of textures and configured to move relative to a user’s finger for displaying one or more tactile sensations. In various embodiments, the spherical segment is a truncated spherical segment. In one embodiment, the device has a texture module having a first roller, a second roller and a belt having the array of textures and configured to connect the first roller and the second roller. In various embodiments, the array of textures in the belt are placed horizontal along the width of the belt. In various embodiments, the belt is discretized into small zones along the length, each zone having a texture. In various embodiments, one or more actuators placed under the texture module are vibro-actuators. [0010] In various embodiments, the position control module has a gimbal arrangement having a first motor configured to actuate in a pitch degree of freedom (DoF) and a second motor configured to actuate in a roll DoF and a third motor configured to control the position of the spherical segment with respect to the contact force. In various embodiments, the impedance control module includes a linear guide connected to the third motor and a four-bar mechanism having a flexure configured to convert the rotary motion of the third motor to linear motion and to provide stiffness to the spherical segment as a translational DoF.

[0011] In various embodiments, the contact force is through multiple contacts. The device has a first grasper segment and a second grasper segment each having a finger access provision configured to contact the array of textures by one or more user’s fingers. In various embodiments, the texture module includes a drum that has a first and a second semicircular cylindrical portion placed closer and a gap between the first and the second semicircular cylindrical portions. The array of textures is placed along the surface of the first and the second semicircular cylindrical portions. In various embodiments, the first grasper segment is configured to envelop the first semicircular cylindrical portion, and the second grasper segment is configured to envelop the second semicircular cylindrical portion. The set up may be used to exert a force on the array of textures on the surface of the first and the second semicircular cylindrical portions based on the user’s finger movement.

[0012] In various embodiments, the position control module includes a circular arm assembly connected to the first and the second grasper segments and is configured to allow the grasper segments to traverse the drum circumferentially. The module also includes a linear guide carrying the circular arm assembly, the drum and the first and the second grasper segments and configured to produce longitudinal DoF. In various embodiments, the impedance control module includes a linear actuator connected to the drum, a flexural beam suspension configured to allow the first and the second semicircular cylindrical portions of the drum to move laterally. The module also includes a cam connected to the linear actuator and a follower connected to the flexural beam suspension and configured to convert the longitudinal movement of the linear guide to lateral motion of the semicircular cylindrical portions. In various embodiments, the cam is wedge shaped. The device having the first and the second grasper segments are connected to the circular arm assembly through a prismatic joint that allows the segments to move laterally inwards and a rotary motor configured to drive the circular arm assembly.

[0013] In various embodiments, the texture module includes a first crowned roller, a second crowned roller, a drive roller driven by an encapsulated motor and a belt comprising the array of textures and connecting the first, the second crowned rollers and the drive roller. In various embodiments, the first grasper segment and the second grasper segment each having a finger access provision are configured to be placed on either side of the belt and contact the array of textures by one or more user’s fingers. The position control module may include a circular arm assembly connected to the first grasper segment and the second grasper segment and configured to allow the grasper segments to move laterally and circumferentially. A rotary motor may be configured to drive the circular arm assembly.

[0014] In various embodiments, the impedance control module includes a four-bar module having crowned rollers and a linear motor configured to convert the longitudinal movement of the shaft of the linear motor to lateral movement. In various embodiments, the four-bar module is configured to control the center distance between the crowned rollers. In various embodiments, the device is configured to operate in a tangible mode and a wearable mode. In various embodiments, the device is configured to switch between the impedance control and the position control. [0015] In various embodiments, a grasper is disclosed. The grasper includes a first grasper segment and a second grasper segment having a finger access provision and configured to be placed on either sides of a texture module and to exert a force on an array of textures by one or more user’s fingers. The position control module is configured to realize a shape, shear and texture of a virtual environment and an impedance control module configured to provide stiffness of the virtual environment that is a function of the user’s finger movement, wherein the device generates an action based on stiffness, texture, shear or shape or a combination thereof.

[0016] In various embodiments, the texture module comprises a drum having first and second semicircular cylindrical portions placed closer and having a gap therebetween. In various embodiments, the array of textures is placed along the surface of the first and the second semicircular cylindrical portions. The grasper may include one or more additional grasper elements. In various embodiments, one or more actuators are placed under the texture module and are configured to simulate vibrations or shape or both based on a selected texture and geometric shape. In various embodiments wherein the position control module comprises a circular arm assembly connected to the first and the second grasper segments and configured to allow the grasper segments to traverse the drum circumferentially. The module also includes a linear guide carrying the circular arm assembly, the drum and the first and the second grasper segments and configured to produce longitudinal DoF.

[0017] In various embodiments, the impedance control module includes a linear actuator connected to the drum. A flexural beam suspension is configured to allow the first and the second semicircular cylindrical portions of the drum to move laterally. A cam is connected to the linear actuator and a follower connected to the flexural beam suspension and is configured to convert the longitudinal movement of the linear guide to lateral motion of the semicircular cylindrical portions. In various embodiments, the cam is wedge shaped. In various embodiments, the first and the second grasper segments are connected to the circular arm assembly through a prismatic joint that allows the segments to move laterally inwards. In various embodiments, the texture module includes a first crowned roller, a second crowned roller, a drive roller and a belt comprising the array of textures and connecting the first, the second crowned rollers and the drive roller. In various embodiments, the impedance control module includes a four-bar module having the crowned rollers and a linear motor and is configured to convert the longitudinal movement of the linear motor to lateral movement and a rotary motor configured to drive the circular arm assembly circumferentially around the textured belt.

[0018] In various embodiments, the four-bar module is configured to control the center distance between the crowned rollers. In one embodiment, a remote surgical system incorporating the device is disclosed. The device provides feedback to the system based on the finger movements of a surgeon holding the device. A hand-held game controller incorporating the devices disclosed. The device provides a feedback to the game controller based on the user’s finger movements.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The invention has other advantages and features which will be more readily apparent from the following detailed description of the invention and the appended claims, when taken in conjunction with the accompanying drawings, in which:

[0020] FIG. 1A illustrates a complete model of the 3-Degree of Freedom (DoF) haptic device.

[0021] FIG. IB illustrates a kinematic model of the 3-DoF haptic device.

[0022] FIG. 1C illustrates a semi-compliant four-link mechanism for providing stiffness.

[0023] FIG. 2A illustrates the belt having the array of textures along the length of the belt.

[0024] FIG. 2B illustrates the belt having the array of textures discretized. [0025] FIG. 3A illustrates the complete model of texture split drum haptic grasper.

[0026] FIG. 3B illustrates the flexure beam suspension mechanism.

[0027] FIG. 3C illustrates the wedge shaped cam and the follower connected to the flexure beam suspension.

[0028] FIG. 4A illustrates the complete model of texture belt haptic grasper.

[0029] FIG. 4B illustrates the crowned belt tension adjustment roller mechanism.

[0030] FIG. 4C illustrates the belt curve to render the cylindrical surface.

[0031] FIG. 4D illustrates the belt tension regulation mechanism in the grasper.

[0032] FIG. 5 illustrates the block diagram of the hybrid control methodology. [0033] FIG. 6A illustrates the shape profiles in x-y direction.

[0034] FIG. 6B illustrates the shape profiles in y-z direction.

[0035] FIG. 7 illustrates the shear stress profiles for four different objects.

[0036] FIG. 8 illustrates the stiffness profile for four different objects.

[0037] Referring to the drawings, like numbers indicate like parts throughout the views.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0038] While the invention has been disclosed with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the invention. In addition, many modifications may be made to adapt to a particular situation or material to the teachings of the invention without departing from its scope.

[0039] Throughout the specification and claims, the following terms take the meanings explicitly associated herein unless the context clearly dictates otherwise. The meaning of "a", "an", and "the" include plural references. The meaning of "in" includes "in" and "on." Referring to the drawings, like numbers indicate like parts throughout the views. Additionally, a reference to the singular includes a reference to the plural unless otherwise stated or inconsistent with the disclosure herein.

[0040] The invention discloses a device that may render an appropriate combination of haptic modalities representing a remote/virtual environment. In various embodiments, the invention provides multi-contact tactile sensations by the use of multiple textures attached to a carrier using one or more design principles. The device in its various embodiments has three degrees of freedom, out of which two degrees of freedom provide the tactile and shear sensations, through the use of multiple textures attached to a carrier. A vibro-actuator placed beneath the textures recreates the surface texture of an environment to be simulated by varying frequency, amplitude, envelope and duration and also increases the number of textures that may be simulated using the invention. The combinatory movement of all three degrees of freedom renders the stiffness, shape and, shear of an environment. The invention, in addition to providing multi-contact sensations, also feature grasping and manipulation capabilities and may be used as an input device in various applications.

[0041] The invention In various embodiments, is a haptic device 100 that may render a combination of haptic modalities representing a remote/virtual environment· The haptic device 100 as shown in FIG. 1A includes a texture module, a position control module and an impedance control module. In various embodiments, the texture module includes an array of textures 105 that is configured to display one or more tactile sensations based on a contact force that may be exerted by the touch of a user on the array of textures 105. The array of textures 105 are actual textures and represent fine to coarse textures. The textures in various embodiments may be provided by any kind of material having surface roughness such as using polymer, mineral, or metallic or other materials. In various embodiments, the textures may be produced by aggregation, molding, machining or knurling. The scale of surface roughness may range from micron- size asperities to mm sized features that provide actual feel of a texture. In some embodiments the textures may be pasted in replaceable form as and when needed. In alternative embodiments the textures may be provided magnetic backing that allows the user to slap on the textures on the carrier. This increases the modularity i.e. allows many more textures that can rendered by the device.

[0042] In various embodiments, one or more actuators 103 are placed under the texture module and are configured to simulate vibrations or shape or vibration and shape based on the texture and geometric shape of remote/virtual environment. In various embodiments, a position control module is configured to realize shape, shear and texture of a virtual environment. The device also includes an impedance control module that is configured to provide stiffness of the virtual environment that is a function of the contact force. In various embodiments, the device 100 generates a feedback that may reproduce various haptic sensations such as stiffness, texture, shape, and shear of a virtual or remote environment in three degrees of freedom.

[0043] In one embodiment, the contact force is from a single source. The contact force is a finger touch of a user. In various embodiments, the device 100 as shown in FIG. 1A includes at least one spherical segment 101. The texture module of the device includes the spherical segment 101 having the array of textures 105 placed over it and is configured to move relative to a user’s finger that is in contact with the texture. In various embodiments, the device displays one or more tactile sensations in a reachable workspace 106 that envelopes of the device as illustrated in FIG. 1A.

[0044] The kinematic model of the device is illustrated in FIG. IB. In various embodiments, the spherical segment 101 is a truncated spherical segment. In various embodiments, the texture module 150 as shown in FIG. 2A and 151 in FIG. 2B includes a first roller 152, a second roller 154 and a belt 156 having the array of textures 105 configured to connect the first roller 152 and the second roller 154. In one embodiment, the array of textures 105 in the belt 156 are placed horizontal along the width of the belt as shown in FIG. 2A. This provides textures of very long length, but only fewer textures are possible with this design. In another embodiment, the belt 156 as shown in FIG. 2B is discretized into small zones along the length, each zone having a texture. This enables many textures of smaller lengths. In this type, switching between textures becomes time consuming, when the textures are placed at the extreme ends of the belt since the belt has to physically wind from one side to the other to reach the other extreme. In addition, providing stiffness to the texture with this kind of implementation becomes challenging.

[0045] In various embodiments, one or more actuators 103 are placed under the texture module. This arrangement helps to recreate a variety of variants of the affixed textures by varying the frequency, amplitude, duration, and envelope of the vibrating actuator. In various embodiments, the actuators are vibro-actuators. In various embodiments, the position control module includes a gimbal arrangement 110 that includes a first motor 112 configured to actuate in a pitch degree of freedom (DoF), a second motor 114 configured to actuate in a roll DoF, and a third motor 122 configured to control the position of the spherical segment 101 with respect to the contact force. The roll and pitch DoF of the embodiment moves the spherical segment 101 equipped with an array of textures relative to a user’s finger for displaying different tactile sensations. The gimbal arrangement 110 is designed to decouple the pitch and roll DoF. The motors are joint limited to protect the spherical assembly from interfering with other components in the system.

[0046] In various embodiments, the impedance control module as shown in FIG. 1C includes a linear guide 120 connected to the third motor 122 and a four-bar mechanism 130 comprising a flexure 131 configured to convert the rotary motion of the third motor 122 to linear motion and to provide stiffness to the spherical segment 101 as a translational DoF. The third DoF enables realizing the stiffness of an object using the third motor. By varying the impedance of the third motor, different stiffness may be obtained, as and when the user exerts a force on the spherical segment. Using the same third motor, vibrations and shape may also be simulated to get the feel of diverse textures and geometric shapes. In various embodiments, the device is backlash-free due to the use of compliant flexure with a minimal number of moving components. In various embodiments, the four-bar mechanism is semi-compliant. The four-bar mechanism along with the flexure 131 in tension, may overcome the limitations of flexures when they are loaded in compression. Because of the way the flexure 131 is positioned in the four-bar assembly, any force that the motor/user exerts on the spherical segment appears as a tensile load on the flexure. Utilizing the flexure 131 on the four-bar assembly also has the added advantage of a backlash-free mechanism with a minimal number of moving components and eliminates the need for lubrication. In various embodiments, arranging different textures on a spherical segment enables rapid switching between textures as and when needed since the spherical segment may be moved (roll and pitch) quite fast.

[0047] In various embodiments, the contact force is through multiple contacts. This may be done to visualize thin, long axisymmetric virtual objects. The device as shown in FIG. 3A includes a first grasper segment 172 and a second grasper segment 174 each having a finger access provision 176 configured to contact the array of textures 105 by two or more of the user’s fingers. In operation the grasper segments 172 and 174 are configured to not come in contact with the textures. The user’s finger tips are configured to contact the textures via the finger access provisions 176. In one embodiment, the texture module includes a drum 168 that includes a first 166 and a second 164 semicircular cylindrical portions placed closer to each other and a gap 162 there between the first 166 and the second 164 semicircular cylindrical portions. This may be referred to as a split drum configuration. The gap 162 allows the segments to move laterally inside when grasped by the user. This gap 162 is critical to the functioning of the device and is kept as minimum as possible in the range of 1mm to 5mm because the gap presents distortion and affects the way the user perceives a cylindrical object. In various embodiments, the gap 162 between the split drums is optimized to have a broad grasp displacement and minimal distortion of the circularity of the virtual object.

[0048] In various embodiments, the array of textures 105 is placed along the surface of the first 166 and the second 164 semicircular cylindrical portions. The first grasper segment 172 is configured to envelop the first semicircular cylindrical portion 166 and the second grasper segment 174 is configured to envelop the second semicircular cylindrical portion 164. In various embodiments, a force is exerted on the array of textures 105 on the surface of the first 166 and the second 164 semicircular cylindrical portions using user’s finger movements on the array of textures. In various embodiments, the position control module includes a circular arm assembly 180 and a linear guide 178. The circular arm assembly 180 is connected to the first and the second grasper segments 172, 174 and is configured to allow the grasper segments to traverse the drum 168 circumferentially. In various embodiments, the linear guide 178 carries the circular arm assembly 180, the drum 168 and the first and the second grasper segments 172, 174, configured to produce longitudinal DoF and enables the user to explore different textures along the length and circumference of the drum 168.

[0049] In various embodiments, the impedance control module as illustrated in FIG. 3B includes a linear actuator 182 connected to the drum 168. A flexural beam suspension 184 is configured to allow the first and the second semicircular cylindrical portions 166, 164 of the drum to move laterally. The split drum mounted on the flexural beam suspension is configured for backlash-free operation. The beam suspension 184 due to its compliance provides the natural return of the segments of the split drum to their neutral position, once the grasping force is removed. In various embodiments, a cam 186 is connected to the linear actuator 182 and a follower is connected to the flexural beam suspension 184 and is configured to convert the longitudinal movement of the shaft of the linear actuator 182 to lateral motion of the semicircular cylindrical portions 164, 166. In various embodiments, the cam 186 as shown in the FIG. 3C is wedge shaped. In various embodiments, the first and the second grasper segments 172, 174 are connected to the circular arm assembly 180 through a prismatic joint that allows the segments to move laterally inwards. In various embodiments, the grasper is spring- loaded to make it return to its neutral position when grasping force is removed. A light spring loading of the grasper segments is vital to prevent the inner surface of the grasper segments from rubbing against the textures of the split drum. To reduce the friction between the cam interfaces, a bearing liner may be used. Therefore, using impedance control, the stiffness felt by the user at the grasper may be modulated by the linear actuator.

[0050] In various embodiments, the texture module may include a first crowned roller 192, a second crowned roller 192, a drive roller 194 driven by an encapsulated motor and a belt 196 that has the array of textures 105 connecting the first, the second crowned rollers 192 and the drive roller 194 as shown in FIG. 4A. In various embodiments, the first grasper segment 172 and the second grasper segment 174 each having a finger access provision 176 and are configured to be placed on either sides of the belt 196 and contact the array of textures by two or more user’s fingers. In various embodiments, the position control module includes a circular arm assembly 180 connected to the first grasper segment 172 and the second grasper segment 174 and configured to allow the grasper segments 172, 174 to move laterally and circumferentially and a rotary motor 190 configured to drive the circular arm assembly

180.

[0051] In various embodiments, the impedance control module includes a four-bar module 198 as illustrated in FIG. 4B, that includes the crowned rollers 192 and a linear motor and is configured to convert the longitudinal movement of the shaft of the linear motor 182 to lateral movement. In various embodiments, the four-bar module 198 is configured to control the center distance between the crowned rollers 192. This may modulate the grasping stiffness felt by the user. The crowned rollers 192 enable the belt surfaces to curve to match the circular travel of the grasper segments as shown in FIG. 4C. The tension regulation mechanism in the grasper is illustrated. in FIG. 4D. The advantage of using an inextensible belt over a split drum is that the crowned belt alleviates the circular distortion presented by the split drum that better matches the circular travel of the grasper during use and hence provide an undistorted feel of the object being manipulated. In one embodiment, the device is configured to operate in a tangible mode, where the base of the device is stationary. In another embodiment, the device is configured to operate in a wearable mode. In the wearable mode, the user may carry the device on their arm while interacting with remote/virtual environment through which perception, grasping, and manipulation are achieved. In various embodiments, the device is configured to switch between the impedance control and the position control.

[0052] In various embodiments, the invention is a grasper that may be incorporated in system that may render multiple textures of a remote environment. The grasper provides feedback to the system based on the finger movements of a surgeon holding the device. In various embodiments, the grasper has three degrees of freedom grasp pinch, linear translation, and rotary motion. The grasper as shown in FIG. 3A includes a first grasper segment 172 and a second grasper segment 174. A finger access provision 176 is provided on each grasper. The first grasper segment 172 and the second grasper segment 174 are configured to be placed on either side of a texture module. In various embodiments, a user may exert force on an array of textures 196 present in the texture module, using the user’s fingers through the finger access provision. In various embodiments, the texture module 150 in the grasper includes a split drum 168 that has a gap 162 between a first 166 and second 164 semicircular cylindrical portions.

[0053] In various embodiments, the array of textures 105 is placed along the surface of the first 166 and the second 164 semicircular cylindrical portions. In various embodiments, the grasper may include one or more additional grasper elements. In various embodiments, one or more actuators 103 are placed under the texture module and are configured to simulate vibrations or shape or both based on a selected texture and geometric shape. In various embodiments, the grasper includes a position control module that is configured to realize a shape, shear and texture of a virtual environment. In various embodiments, the grasper further includes an impedance control module configured to provide stiffness of the virtual environment that is a function of the user’s finger movement. In various embodiments, the device generates an action based on stiffness, texture, shear or shape or a combination thereof. In various embodiments, the grasper may be utilized in a remote surgical system.

[0054] In various embodiments, the invention is a grasper that may be incorporated in a system where the remote environment has a uniform texture. The grasper may provide a feedback to the game controller based on the user’s finger movements. The grasper as shown in FIG. 4A includes a first grasper segment 172 and a second grasper segment 174. A finger access provision 176 is provided on each grasper. In various embodiments, the texture module may include a first crowned roller 192, a second crowned roller 192, a drive roller 194 driven by an encapsulated motor and a belt 196 that has the array of textures 105 connecting the first, the second crowned rollers 192 and the drive roller 194. In various embodiments, the first grasper segment 172 and the second grasper segment 174 each having a finger access provision 176 and are configured to be placed on either sides of the belt 196 and contact the array of textures by one or more user’s fingers. In various embodiments, the position control module includes a circular arm assembly 180 connected to the first grasper segment 172 and the second grasper segment 174 and configured to allow the grasper segments 172, 174 to move laterally and circumferentially and a rotary motor 190 configured to drive the circular arm assembly 180. In various embodiments, the impedance control module includes a four-bar module 198 that includes the crowned rollers 192 and a linear motor and is configured to convert the longitudinal movement of the shaft of the linear motor 182 to lateral movement that aid in varying the center distance between the crowned rollers.

[0055] In various embodiments, the four-bar module is configured to control distance between the crowned rollers 192. This may modulate the grasping stiffness felt by the user. The crowned rollers 192 enable the belt surfaces to curve to match the circular travel of the grasper segments. The grasper may be applicable in a hand-held game controller. In various embodiments, a hybrid control methodology as depicted in FIG. 5 is implemented by combining the position and impedance control to provide high- fidelity haptic sensations to the user. In one embodiment, when the user moves his finger without changing the vertical displacement of the haptic interface, position control is applied. Consequently, shape, shear and texture of the virtual environment are realized. In another embodiment, when the user probes the haptic interface radially, impedance control is applied, and therefore, a force is generated, providing stiffness of the virtual environment. A PD (proportional-Derivative) position controller is used for shape and shear rendering and an impedance controller for stiffness rendering.

[0056] The advantages of the device include enhancing the perception, manipulation and grasping abilities of the haptic device through multi-contact interactions. The device provides realistic tactile sensations to the user by utilizing actual substrate surfaces having different textures rather than simulating such textures using just vibrations or other mechanical means. This mode of rendering tactile sensations is preferable over emulation by vibration or tactile arrays, because of the additional dimension to the tactile sensation. The haptic device may find application in assisting surgeons in medical robotics, rehabilitation, training, gaming, space exploration, underwater robotics, virtual reality.

[0057] Examples

[0058] Example 1: Rendering of a Virtual Environment Using Single Contact and Multi-contact Interactions

[0059] The haptic device having a spherical platform was constructed. The user was allowed to interact with the spherical platform of the haptic device to sense the environment with the objective of feeling the shape and shear profile (reference trajectory) of the remote/virtual environment. A reference shape trajectory (sum of sinusoidal) of a virtual environment was provided, and by tracking the motion of the user, the shape was accordingly represented by the coordinated movements of the three actuators. FIG. 6A & FIG. 6B is the reference and rendered shape trajectories in x-y and y-z directions, respectively. The results demonstrate the efficacy of the haptic device in rendering shape. Reference shear profile for four diverse objects were assumed with varying textures and fractional derivative order a approximately corresponding to human tissues (especially for a>1). FIG. 7 displays the reference and rendered shear stress profiles, and results demonstrate the effectiveness of the haptic device in generating shear. The textures were rapidly switched and modulated using the vibro actuator in accordance with the environment’s surface properties. When the user varies position (probing radially) of the haptic device, the variable becomes an input for the virtual/remote environment, and corresponding desired force was generated. A force sensor underneath the haptic device measured force experienced by the user and this data was sent to the controller, thus changing the control torque accordingly. The implemented impedance controller modifies the perceived impedance of the user in accordance with the stiffness characteristics (desired impedance) of the remote/virtual environment. Four different objects with stiffness constants ( kl , k2, k3 and k4) were considered, and the rendered stiffness profiles are shown in FIG. 8. The results demonstrate the accuracy of the haptic device with impedance controller in providing stiffness along with texture. In conclusion, the haptic device may render multiple imperative modalities to experience the environments as it is.

[0060] When the user operates the haptic grasper while interacting with the environment, two modes of operation were allowed, namely tangible mode and wearable mode. In tangible mode, the remote/virtual object is considered as passive, the user perceives the general shape, shear, stiffness, and texture. In wearable mode, the user can grasp, and manipulate the dynamically varying physical properties of the remote/virtual environment, where stiffness, local shape and texture are rendered. The shape and stiffness in both modes are rendered through flexural beam suspension and crowned tension adjustment rollers in the second and third embodiments, respectively. The back and forth motion of the graspers of the second and third embodiments allow the user to manipulate a remote/virtual object and provide shear sensation. Hence, the invention may find use as an input device for teleoperation, medical and rehabilitation applications, space applications, gaming etc.

[0061] Although the detailed description contains many specifics, these should not be construed as limiting the scope of the invention but merely as illustrating different examples and aspects of the invention. It should be appreciated that the scope of the invention includes other embodiments not discussed herein. Various other modifications, changes, and variations, which will be apparent to those skilled in the art may be made in the arrangement, operation and details of the system and method of the present invention disclosed herein without departing from the spirit and scope of the invention as described here. In addition, many modifications may be made to adapt to a particular situation or material to the teachings of the invention without departing from its scope as delineated in the appended claims.