GB2574596A - Prosthetic device - Google Patents

Abstract

A prosthetic device 300 comprising means for engaging a wearer, at least a palm section carrying at least one digit operated by at least one actuator and a sensor means 302, 306 mounted to the palm section of the device and arranged to provide sensor signals 312 representing objects in the vicinity of the device. The device 300 further comprises control means coupled to the sensor means 302 and 306 and to at least one actuator and configured to drive the at least one actuator in response to sensor signals. The control means may be coupled to receive myoelectric signals from the wearer and configured to drive the actuator. The control means may be configured to identify objects by comparing sensor signals with data stored in a memory. The control means can be arranged to alter the type of grip in response to at least one identified object. The sensor means 302 and 306 may comprise a camera, infra-red, LIDAR, sonar or radar sensor.

Description

PROSTHETIC DEVICE

The present invention relates to a prosthetic device comprising or including a prosthetic hand or partial prosthetic hand, which includes at least one controllable actuator for controlling at least one digit.

BACKGROUND

Prosthetic hands are known to be worn by amputees and those who were born without a hand.

One type of prosthetic hand replaces the wearer’s entire hand and attaches to the wearer’s forearm. It may even be part of a larger prosthetic device that attaches to the upper arm or even the shoulder.

Another type of prosthetic hand is designed for those who are missing one or more digits but whose hand includes a palm. These generally fit around the wearer’s palm (using a “socket”) and include up to five digits, depending upon what the wearer requires.

Prosthetic hands are generally driven by myoelectric signals derived from the wearer. These are small electrical signals derived from the wearer’s muscles in known manner. In use the wearer’s muscles learn which signals to provide in order to drive the prosthetic device.

One drawback with existing prosthetic hands is that they lack functionality and do not move naturally. For example, a human hand approaching an object will adapt its position and/or mode of gripping before arriving at the object. The effect is one of a functional and smooth adaptation to the requirements of gripping the object. Unfortunately, a prosthetic hand, when compared to a human hand, seems jerky and uncoordinated.

Another drawback is that the strength of grip provided by a prosthetic hand, in other words the force applied by the at least one actuator, is very difficult to control. The wearer may therefore crack an egg unintentionally or squash a piece of cake by applying too much force. Conversely, a hard object or a ball may be gripped too weakly and dropped.

It is an object of the present invention to ameliorate at least some of the above drawbacks.

According to the present invention there is provided a prosthetic device comprising means for engaging a wearer, at least a palm section carrying at least one digit operated by at least one actuator, sensor means mounted to the palm section of the device and arranged to provide sensor signals representing objects in the vicinity of the device, control means coupled to the sensor means and to the at least one actuator, the control means being configured to drive the at least one actuator in response to the sensor signals.

By providing a sensor on the palm of the prosthetic device, the controller responsible for driving the at least one actuator can determine the wearer’s intention and/or anticipate an interaction with an object. This permits the controller to drive the at least one actuator in a manner appropriate to the task.

Preferred features of the invention are set out in the dependent claims.

BRIEF DESCRIPTION OF THE FIGURES

The present invention will now be described, by way of example, with reference to the following figures, in which:

Figures 1 to 16 illustrate a prosthetic hand to which the present invention may be applied, in particular:

Figure 1 is a first cross-sectional view of a digit in a first, raised, position;

Figure 2 is a cross-sectional view of the digit of figure 1 but in a second, lowered, position;

Figure 3 is an exploded view of the digit shown in figures 1 and 2;

Figure 4 is an isometric view of the digit of the above-mentioned figures;

Figure 5 is a partially disassembled arrangement of the above-referenced digit;

Figures 6 to 8 are front isometric views of the digit referred to above showing various rotational positions thereof;

Figures 9 to 16 illustrate a full prosthetic hand incorporating elements of the present invention and showing a plurality of different positions of the one or more digits provided thereon;

Figure 17 shows a first view of another prosthetic hand to which the present invention may be applied;

Figure 18 shows another view of the hand illustrated in Figure 17;

Figure 19 shows a front view of the sensor range around the hand;

Figure 20 shows a side view of the sensor range around the hand;

Figure 21 shows the hand approaching a medium-sized ball;

Figure 22 shows the hand holding the medium-sized ball;

Figure 23 shows the hand approaching a small-sized ball;

Figure 24 shows the hand holding the small-sized ball;

Figure 25 shows the hand approaching a large-sized ball;

Figure 26 shows the hand adjusting its grip in response to detecting the large-sized ball;

Figure 27 shows the hand holding the large-sized ball;

Figure 28 shows the hand approaching a computer mouse;

Figure 29 shows the hand having moved the operation mode of the thumb in anticipation of gripping the computer mouse;

Figure 30 shows the hand gripping the computer mouse;

Figure 31 shows the hand approaching an anticipated collision with an object;

Figure 32 shows the hand adopting a protective fist position;

Figure 33 shows a block schematic diagram of sensors, actuators and control circuitry; and

Figure 34 shows an alternative prosthetic device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention incorporate at least one sensor located in or on the palm of the prosthetic hand. The sensor may, for example, comprise an optical camera, a thermal camera, a LIDAR, SONAR or low-powered RADAR sensor. In certain embodiments (discussed further below), more than one type of sensor may be employed.

The output of the sensor is interpreted by a control system coupled to the sensor and to one or more actuators in order to control the prosthetic device. The control system is arranged to identify an object, or class of objects and provide drive signals to the actuator(s) as appropriate. For example, the control system is arranged to control at least the force applied by the actuator(s) in order to apply an appropriate grip. A gentle grip will be applied to delicate items so that they are not crushed while a stronger grip will be applied to more resilient, heavier items. The control system will be described in more detail below.

Figures 1 to 16 show a prosthetic device to which the present invention may be applied. While the described device is a sophisticated prosthetic hand, the present invention is equally applicable to other types of prosthetic hand with conventional actuators.

Referring now to the drawings in general but with particular reference to figures 1 to 5, a prosthetic device 10 may include one or more thumbs and/or fingers referred to herein generally as digits 14, each of which is mounted on a base portion 12 which, in turn, is mounted onto an anchor 30. The anchor 30 may comprise the main body or palm of a prosthetic hand or may comprise a sleeve or cover to be placed over a portion of the user’s natural hand if portions thereof are present. Such may be the case where the patient has lost one or more digits but not an entire hand. The one or more digits 14 are each provided with an actuation mechanism or motor 40, 80 for creating one or other or both of pivotal and I or rotational movement of the digit in question 12. These mechanisms 40, 80 may be provided as separate units, as shown herein, or may be combined as one unit if so desired and each are described in more detail later herein. The digits 14 are each provided with a proximal end 14a closest to the anchor 30 and a distal end 14b remote therefrom. The proximal end 14a is pivotally connected to the base portion 12 by means of a pivot shown generally at 16 and also described in more detail alter herein. One or more of the one or more digits may have a base portion 12 which is connected to the anchor 30 by means of a rotational mount in the form of, for example, a bearing shown generally at 60 which facilitates the base portion 12 and the digit 14 rotating about a second axis X2. Again, this feature is described in more detail later herein. It will be appreciated that the arrangement of mounting the digit 14 to a base portion 12 which is, in turn, connected to an anchor 30 which forms part of the main body of a prosthetic hand may be used with or without the further feature of the base portion (and hence the digit) being rotatable about the second longitudinal axis X2. It will also be appreciated that the rotational aspect may be incorporated into prosthetic digits without the specific actuator arrangement as shown in this particular document but that a significant advantage may be gained by incorporating the two in one product.

Referring now more particularly to figure 3 which is an exploded view of the digit 14 of figures 1 and 2, it will be seen that the digit has a longitudinal axis X and is mounted at a proximal end 14a to the base 12 by means of a pivot 16 operational around a third axis Y which is generally perpendicular to axis X and which may comprise a first portion 16a forming, for example, an aperture on the base 12 and a second portion 16b on the proximal end 14a of the digit 14 itself, in the particular arrangement of the drawings, said base portion 12 includes first and second sides 12a, 12b projecting therefrom in a common direction D and being spaced apart from each other by an amount S and wherein each side 12a, 12b includes a first portion of the pivot connection 16a and wherein said digit 14 includes a first side 14d and a second side 14e and wherein said first side 14d includes a first portion 16b1 of the pivot connection 16b and said second side 14b of the digit 14 includes a second portion 16b2 of the pivot connection 16b and wherein each of said second portions 16b1, 16b2 of the pivot connection 16b extend into respective first portions 16a of the pivot connection 16 when assembled. The digit 14 further includes a linear actuator 40 contained therein and having a first portion 40a secured to the elongate digit 14 for movement therewith and a second portion 40b remote therefrom and axially movable relative thereto, as shown by arrow A in figure 3.

The second portion 40b of said linear actuator 40 may include one or more transfer pivot pins 40d, 40e extending outward therefrom whilst said base portion 12 may include one or more apertures 32a, 32b for receiving said one or more transfer pivot pins 40d, 40e. The apertures 32a, 32b are radially displaced by an amount R relative to the pivot connection 16 such as to allow for pivotal movement of said digit 14 about said pivot connection 16 upon axial translation of said second portion 40b of the linear actuator 40. In essence, the second end of the actuator 40a, pushes against apertures 32a, 32b and as the other end of the linear actuator 40 is connected to the digit 14 this will cause the digit 14 to pivot about the pivot connection 16 and axis X. This movement will cause the digit 14 to replicate the opening and closing of the digit and control of the linear actuator may be initiated in accordance with a desired control sequence or instruction as and when desired from a controller shown schematically at 100.

As can be seen more clearly in some of the later drawings, the proximal end 14a of the digit(s) 14 are located such that the first side and second sides 14d, 14e of said digit are contained between said first and second sides 12a, 12b of said base portion 12.

As mentioned above, each of said first and second sides 12a, 12b include respective apertures 32a, 32b for receiving respective second portions 40d, 40b of the pivot 16. The first and second portions 14d, 14e of the digit 14 are each provided with a respective slot 20a, 20b at their respective proximal ends 14a extending along said longitudinal axis X of said digit 14 and these slots 20a, 20b receive respective transfer pivot pins 40d, 40e of actuator 40 therethrough such as to allow the linear actuator 40 to be connected to the anchor 30. The slots 20a, 20b extend for a sufficient length as to allow for the full and free movement of the linear actuator as and when desired. Movement of transfer pivot pins 40d, 40e will cause the digit 14 to pivot about pivot connection 16 as will be described in more detail later herein.

The base portion 12 may, in one embodiment, also include a second longitudinal axis X2 extending between said proximal side 12a and said distal side 12b and a bearing 60 may be provided between the base portion 12 and said anchor portion 30 such that said base portion 12 is mounted to said anchor portion 30 via said bearing 40 and rotatable about said second longitudinal axis X2 as and when required. The bearing 60 may comprise a hollow bearing include an internal aperture 62 for allowing the passage of portions of a rotational actuator or electrical or operational supply cabling to be provided therethrough.

This capability is new to prosthetic digits and may be used to provide the user with a higher degree of motion and possibly a greater degree of feedback than has been previously known in the field of prosthetic digits. The device 10 may also include a rotation actuator 80 for causing rotational movement of the digit 14 within said bearing 60 about said second longitudinal axis X2. Such a rotational actuator 80 may be housed within the digit itself 14 or may be mounted remotely therefrom, although advantages of compactness and controllability will be present if the rotational actuator is mounted within the digit itself 14. Whilst there are a number of rotational actuator arrangements that could be used, it has been found that an arrangement in which the rotational actuator 80 is housed within the digit and anchored relative thereto will allow for the use of a torque tube 82 extending therefrom which can be connected at a first end 82a to the rotational actuator 80 and at a second end to the anchor 30. The anchor 30 is comprised of two parts, a rotation housing 30a wherein the base portion 12 pivots around axis X2, and a housing 30b wherein the torque tube proximal end 82b is connected. The torque tube 82 is connected at its first end 82a to the rotation actuator 80, and at its second end 82b to the housing 30b at point 30c. Housing 30b and the rotation housing 30a are both connected to the palm of the hand 200. The torque tube 82 may extend through bearing 60 or may pass around it if space permits. The torque tube may also be hollow and include a first opening 82a thereinto for receiving any electrical wiring or connections thereinto and a second opening 82b for allowing any such electrical wiring or connections to be routed out of the torque tube 82. The first and second openings 82a, 82b may be on the first and second ends 82a. Preferably the torque tube is sufficiently flexible so as to allow for the desired degree of movement of the digit 14 but is sufficiently resistant to rotation as to ensure the desired rotational movement is transmitted. Such an arrangement would allow for the transmission of rotational torque from the rotational actuator 80 through the torque tube 82 to the anchor 30 at which point it is reacted and this will cause the base portion 20 and digit 14 to rotate about axis X2. Again, the rotational actuator 80 may be operably connected to a controller shown schematically at 100 and may be operated by said controller as and when desired.

The above design provides a prosthetic device 10 with one or more digits 14 which can, if desired, have compound movement in the sense that they can each move about two axes, one of which replicates the normal bending of a human digit and one of which replicates the rotational movement which is normally associated with a thumb but which could be used on the fingers of a prosthetic device. It also provides a prosthetic device which is able to be relatively compact and may allow for the production of smaller prosthetic devices than has been known until now.

The above arrangement may be added to in a number of ways. For example, the digit 14 may be provided with a first load sensor 510 (which may be a microprocessor) for sensing external resistance to pivotal movement of said one or more digits 14. Such a sensor may be used to 5 provide feedback on the strength of grip being applied to an object. The arrangement may also include a second load sensor (520) for sensing external resistance to rotational movement of said one or more digits (14). Again, this may be used to provide feedback on the strength of any grip being asserted by the digit. Still further, the digit may be provided with an overload mechanism in the form of spring-loading of the mechanisms arranged such as to provide a degree of resilient resistance to motion which would accommodate any overload through resilient motion. In the example of the rotational arrangement using a torque tube 82, the resilience to rotational motion could be incorporated by way of the torque tube itself being a spring or having resilient properties. In the example of the linear actuator 40, the resilience may be built into the mechanism by which the movable second portion 40b is connected to the static first portion 40a which, again, may include resilient members or spring arrangements.

In a preferred embodiment the torque tube 82 allows the electrical cables from actuators 40 and 80 to pass through it, thus allowing a smooth and minimally moving path.

Thus far we have described a single digit arrangement 14 forming one or other of a thumb or finger of a prosthetic device. It will, however, be appreciated that a partial or complete prosthetic hand may be assembled from or including the above-described components. A partial hand may comprise one or more digits whilst an entire hand would comprise all the digits in the form of both fingers and thumbs. It will be appreciated that aspects of the present invention may be provided on the thumb and I or the fingers of a prosthetic device and that further actuation mechanisms may be provided in addition to those described herein.

Rotational movement of the digit 14 is shown in figures 6 to 8 whilst the opening and closing of a full prosthetic hand is shown in figures 9 to 16. From these figures it will be appreciated that a full or partial prosthetic hand may be provided simply by attaching one or more of the abovementioned digits 14 onto a socket portion or glove portion for fitting over the hand of a patient requiring less than a full prosthetic replacement of digits or a palm portion of a prosthetic device where a full set of digits is required. For convenience each of the glove portion and palm portion will be referred to hereafter as a palm portion and provided with a single reference number 200. Those skilled in the art will, however, appreciate that the digit and the following may be applied to either the glove or full palm arrangement. In each of the arrangements of figures 9 to 16 the base portion 12 of each of the one or more digits 14 is connected to the anchor 30 as described above but now each anchor 30 is, itself, mounted onto the glove I palm 200 in a pattern designed to replicate a full hand or replace missing digits if a partial replacement is desired. Each digit is as described above but it will be appreciated that one may dispense with the rotational element of the digit 14 when the invention is applied to the fingers as fingers may not need to have rotational movement capability. The thumb may also be provided without rotational capability, but this is not a preferred arrangement of the present invention.

The controller 100 is connected to each of the linear and I or rotational actuators 40, 80 in each digit 14 to cause the supply of current thereto in the manner required to control the digit. Such control is already well known in relation to simple opening and closing of the digit but is not known for rotational control. Control of the digits 14 may be undertaken in any one of a number of ways but generally requires the input of control signals to open and close the digits 14 in accordance with a pre-determined movement profile or in response to an individual tailored request for movement when, for example, the hand is required to provide a certain grip profile. Figures 9 to 16 illustrate that the present invention is able to replicate the full degree of movement of the human hand including the ability to have the thumb rotate as it moves towards the fingers of the hand on the other side of the palm. Such compound movement of the thumb and possibly also one or more of the fingers will mean that the present prosthetic hand is able to provide grip patterns that have not been previously available to a patient.

Figure 17 shows a view of a prosthetic hand 300 to which suitable sensors 302, 304, 306 have been mounted. The manner in which the sensors may be mounted, and protected from damage, will be familiar to the skilled person. While three sensors are shown, there may be a single sensor, two sensors or more than three sensors. The hand is shown in “key grip” mode to provide a clear view of the palm-mounted sensors.

Figure 18 shows an alternative view of the prosthetic hand 300 from the thumb side, showing the palm-mounted sensors 302, 304, 306. Although the left hand is shown, the present invention is equally applicable to the right hand.

Figure 19 shows the range 308 of the sensors relative to a front view of the hand and Figure 20 shows the range 310 of the sensors relative to a side view of the hand. The overall sensed volume is thus approximately spherical. If the range of the sensors is too great, then the processing load on the system will be increased. If the range is too small then there will be insufficient time after the sensors detect an object to prepare the prosthetic hand to grip or otherwise interact with the object.

In some embodiments, the range of the sensor(s) is deliberately greater in order to determine the location of the wearer, for example, to determine whether they are in a familiar situation such as their home or workplace.

Figure 21 shows a prosthetic hand 300 in the vicinity of an object, in this case a medium sized ball 320. This embodiment of the hand comprises two sensors 302, 306. Shown at 312 are the paths of exemplary sensing signals travelling from/to the palm-mounted sensors. The nature of the object (i.e. ball 320) is identified by the control system in response to the signals received by the at least one sensor. Furthermore, the control system (not shown, to be described further below) has detected that the wearer is moving the prosthetic hand towards the ball (for example by comparing consecutive image samples) and interprets this to mean that the wearer intends to pick up the ball.

Consequently, the control system provides appropriate drive signals to the actuator(s) in the prosthetic hand to place the hand in all-fingers-gripping mode with the thumb in the opposable position. Once the control system determines that the ball is sufficiently close, it provides the necessary drive signals to the actuators to bring the fingers and thumb together to grip the ball. While this control of the actuators may be performed solely in response to the output of the at least one sensor, it may also be based upon current feedback from the actuators as will be described further below.

Figure 22 shows the prosthetic hand gripping the ball 320. Once the object is in the hand, the control system may continue to use the camera or other sensor (for example to respond to the object slipping from the hand). Alternatively, the control system may use current feedback from the actuator(s) as described further below. As a further alternative, both of these inputs can be utilised.

Figures 23 and 24 illustrate a similar scenario to that shown in Figures 21 and 22 but where a different object, in this case a small ball 322, is to be picked up by the prosthetic hand. As shown in Figure 23, the two sensors 302, 306 arranged on or in the palm of the hand detect the object and the control system interprets that the wearer’s intention is to pick it up, as before. However, the object 322 is too small to be picked up by the hand in all-fingers-gripping mode so the control system drives the actuators as appropriate to place the hand in a tripod-grip using only the thumb, the index and middle fingers. Figure 24 shows the hand gripping the small ball 322. Again, feedback may be provided to the control system by the sensor(s) and/or by current feedback from the actuators to ensure that the object is properly gripped.

Figures 25, 26 and 27 illustrate a further scenario in which a larger object, in this case a large ball 324 is to be picked up. Figure 25 shows the sensor or sensors in the palm of the hand detecting the object. The control system interprets that the wearer’s intention is to pick it up, as before, and determines that the object is large. Consequently, as shown in Figure 26, the control system places the hand into the fully-open position as it approaches the ball. Figure 27 shows the hand gripping the ball. Again, feedback may be provided to the control system by the sensor(s) and/or by current feedback from the actuators.

Figure 28 shows the prosthetic hand approaching a computer mouse. The control system, in response the output from the sensor(s), determines that the object is a computer mouse and that the wearer intends to grip the mouse. The control system moves the thumb of the hand to the non-opposing position as shown in Figure 29 and the control system controls the hand to both grip the mouse and place the index finger of the prosthetic hand over the mouse button. This is shown in Figure 30. The second finger of the hand may also be placed over the “right click” button of the mouse or a scroll wheel (not shown).

There are many further examples of objects that can be recognised by the control system to permit an appropriate grip mode to be selected. These include a coffee cup, a glass, a plate, cutlery, a pen, a remote control, keys, the steering wheel of a car and so on. In addition to identifying specific items, the control system may be configured to identify generic (classes of) items.

Figures 31 and 32 illustrate an optional feature that is designed to protect the prosthetic hand if the control system detects that a collision with an object is imminent. Figure 31 shows an object 328 moving towards the hand which the control system determines may cause damage thereto. The control system is configured to quickly close the hand (to the fist-mode) in order to protect the hand from the anticipated collision (Figure 32).

In addition to selecting the grip mode (such as all-fingers-gripping, tripod-grip or mouse grip) of the hand as appropriate to an object, embodiments of the present invention are further arranged to control the force applied by the digit or digits of the hand. It is known to determine the force being applied by a prosthetic hand by measuring the current drawn by the actuators. In one case, a given current is drawn as an actuator moves its digit through free space and this current will rise to a higher value when a firm grip is being applied to an object. When the control unit identifies an object and determines that the wearer intends to pick it up, the control unit selects and applies an appropriate drive current. For example, when the control system identifies that the wearer is going to pick up an egg, a lower drive current is chosen as compared with that required to pick up a heavier but more resilient object such as a coffee cup. This drive current is preferably 8 continuously controllable up to the limit for a given actuator (of course, in a digital system it will be controlled in finite steps).

A single sensor according to an embodiment of the invention may comprise a camera whose output is interpreted by the control system according to known machine vision principles. The camera may, for example, be an optical camera or a thermal imaging camera. A single sensor may also comprise a LIDAR (Light Detection And Ranging) sensor which is scanned across the volume in front of the palm of the prosthetic hand. Alternatively, LIDAR may be provided using a single transmitter and multiple receivers arranged in a suitable pattern to image the required volume. Multiple transmitters may also be used and/or the role of transmitters and receivers can be reversed as part of a sequence to image the volume. Appropriate arrangements will be apparent to those skilled in the art of machine vision. As an alternative to LIDAR, infra-red, SONAR or low power radar may be used.

Techniques to interpret the environment in which these sensors are deployed are likewise known to those familiar with machine vision.

Further embodiments of the present invention may incorporate different types of sensors mounted to the palm of the prosthetic device. For example, a camera may be combined with LIDAR (Light Detection And Ranging), sonar or radar system in order to improve the depth perception provided by the sensors. Any and all combinations of the disclosed sensors are envisaged.

In addition, further sensors (be they cameras, LIDAR or others) may be deployed around the prosthetic hand, other than on or in the palm. For example, a sensor on the back of the hand may allow improved control over the approach of the hand to an object and/or enhanced detection of impending collisions. This sensor or these sensors may be selected from the same set of sensors as the palm-mounted sensor(s).

In addition, the thermal imaging camera(s) can detect a potentially damaging hot object in the vicinity of the hand. The hand can move to protect itself from the heat.

Figure 33 shows a block schematic diagram of a control system 400 according to an embodiment of the present invention. While many features are shown, most embodiments of the invention will only be provided with a subset of them. The control system may be mounted in any convenient location, although typically it will be convenient to mount it together with the batteries that drive the prosthetic hand. The control system circuitry may also be distributed to some extent. For example, it may be convenient to mount some control circuitry on a small circuit board close to each actuator while the remainder is mounted together with the batteries.

The system has a controller 402 coupled to a memory 404, to one or more sensors 406, 408 and to the actuator or actuators of the prosthetic hand. Five actuators 412, 414, 416, 418 and 420 are shown that correspond to the five digits of the prosthetic hand but any number from one upwards may be provided. In some embodiments there may be more than one actuator per digit. The controller 402 may be a microprocessor, ASIC or other digital control device. The memory 404 may be integral with the controller in some circumstances. The actuators are provided with current sensing functionality and each provide a current-sensing signal 432, 434, 436, 438 and 440 to the controller 402.

Several sensors are shown. Firstly, an optical camera 406 which is mounted to the palm of the prosthetic hand is supplemented by three LIDAR sensors 422, 424 and 426 also mounted to the palm of the hand. The three LIDAR sensors are illustrated as a transmitter 422 and two receivers 424, 426 but further transmitters and receivers could be provided and/or the role of the transmitter and receivers could be reversed in sequence. Alternatively, a single sensor could be used for both transmission and reception of light by providing scanning functionality and either transmitting and receiving at different times or by implementing a chirped LIDAR system using a frequencymodulated transmit signal. The ability to sense a three-dimensional volume could also be provided with more than one sensor arranged in an array.

Further, a second camera 408 (provided on the back of the hand) is also connected to the controller.

The controller is connected to a sensor 410 for myoelectric signals from the wearer, obtained in a conventional manner.

In some embodiments the controller is provided with a microphone to detect speech from the wearer and the relevant functionality to recognise that speech and take action in response. One application of this is to allow the prosthetic hand to write what the wearer says.

The controller is arranged to interpret the signals received from the camera and/or other sensing arrangements to identify objects in the vicinity of the prosthetic hand. While many techniques are available in the field of machine vision, the illustrated embodiment uses a look-up technique by comparing the received signals with signatures pre-stored in the memory 404. Assuming that there is a match, an object or class of objects has been identified. The controller will also determine whether the hand is moving towards the object, for example by comparing sensor signals over time. Once the controller has identified an object and confirmed that the user wants to pick it up or otherwise interact with it, the controller retrieves one or more parameters from the memory. This may be the same memory that stores the signature, a separate memory or separate part of the memory. The parameters retrieved may include grip type (e.g. tripod grip) and grip strength or more specific parameters (such as current) for each actuator on the hand.

These parameters are then used by the controller, in conjunction with the myoelectric signals 110 to interact with the object as illustrated, for example, in Figures 21 to 30 or to protect the hand as shown in Figure 31 and 32. The controller provides the appropriate drive signals to the one or more actuators in known manner. Ongoing signals from the sensor(s) may be interpreted to ensure that the object is held or gripped properly (e.g. is not slipping from grip).

Preferably, the controller 402 is also responsive to the current feedback signals 412, 414, 416, 418, 420 from the actuator(s). These are then used by the controller to ensure that the grip strength is appropriate for the object or class of objects (i.e. the current feedback signals may be compared with parameters retrieved from the memory). If the actual current feedback is higher or lower than that indicated by the appropriate parameter then the controller will adjust the drive to the relevant actuator(s). For example, if the identified object is a coffee cup being picked up by the handle, then a high grip strength will be required. If the object is identified as a piece of cake then a low grip strength will be required.

The controller is preferably configured to continue to monitor the object once it has been gripped using the sensor(s) and/or the current feedback. If the object appears to be slipping then the controller may increase the grip strength to prevent it from falling.

A water sensor 430 may optionally be provided on the prosthetic hand to protect the hand from damage. For example, the controller may be arranged to switch off the hand in response to water detection.

The LIDAR sensors could be replaced with sonar or low power radar sensors. The number and arrangement of sensors, the implementation of scanning and so on would be similar to that described for LIDAR.

It may be desired to switch off the sensor operation in some circumstances, such as when the wearer is simply walking somewhere (to save battery power), in which case an appropriate switch or button may be provided on the prosthetic device to activate/de-activate this functionality, or the wearer can switch off the sensor operation through myoelectric control

The control system may also be networked in known manner such that it receives software updates and/or data relating to new objects or classes of objects. Such networking may be wireless in which case updates could occur at any time or may be wired, allowing software updating to be performed while the batteries of the prosthetic device are being charged.

The control system may further be arranged to learn the grip mode and/or grip strength to be applied to various objects in order not to damage or drop them. A wearer may, for example, frequently use a tool or a piece of kitchen equipment that is not pre-programmed into the control system. The control system simply adds this piece of equipment to its memory together with appropriate grip mode and grip strength. It may, of course, require some iterations to learn to recognise the object from different perspectives and also to apply an appropriate grip strength. The parameters stored in the memory can be updated in accordance with feedback. Likewise the parameters stored in respect of objects that are already pre-programmed can be updated using this technique (for example, the wearer has a heavier coffee cup than has been pre-programmed). Those skilled in the art of machine learning can readily implement such a learning system.

In certain embodiments, the sensor(s) may be arranged to have a greater range than shown in Figures 19 and 20 in order to identify not only the object to be picked up or operated, but also to identify the wider environment of the wearer. Most people spend a large proportion of their time in a relatively small number of environments, such as work and home. Upon detecting that the wearer is in their home, for example, the grip mode and/or grip strength controlled by the control system can be adapted according to known parameters. For example, the grip strength required to turn a particular door knob can be pre-programmed into the control system.

In addition, the control system may be arranged to recognise the wearer’s other hand and to effect control of the prosthetic hand to interact therewith.

The controller of the prosthetic hand may be pre-programmed with particular movements such as a signature of a user. This might be triggered by the controller recognising the word “signature” on a form. Indeed further, the hand can be programmed to write, through voice recognition. A number of handwriting fonts can be provided and chosen by the wearer.

The controller may be arranged, in response to detecting that there are no objects in the vicinity of the hand, to perform a particular sequence of movements.

Figure 34 shows an alternative prosthetic device 350 for a wearer that has at least the palm of 5 their hand. While four fingers and a thumb are provided on the illustrated device, one or more digits may be provided according to the wearer’s requirements. The sensor or sensors are mounted on or to this device as shown in Figure 17.

io The principles of operation for this alternative embodiment are the same as for the first embodiment.

Claims (25)

1. A prosthetic device (300) comprising means (350) for engaging a wearer, at least a palm section carrying at least one digit operated by at least one actuator (412, 414, 416, 418, 420), sensor means (302, 304, 306) mounted to the palm section of the device and arranged to provide sensor signals (312) representing objects in the vicinity of the device, control means (402) coupled to the sensor means and to the at least one actuator, the control means being configured to drive the at least one actuator in response to the sensor signals.

2. A prosthetic device as claimed in claim 1, wherein the control means (402) is further coupled (410) to receive myoelectric signals from the wearer and configured to drive the at least one actuator in response to the myoelectric signals.

3. A prosthetic device as claimed in claim 1 or claim 2, wherein the control means (402) is configured to identify objects by comparing the sensor signals with data stored in a memory (404).

4. A prosthetic device as claimed in claim 1, claim 2 or claim 3, wherein the control means (402) is configured to operate the at least one actuator to move the at least one digit as the prosthetic device approaches an object.

5. A prosthetic device as claimed in any one of claims 1 to 4, wherein the control means (402) is configured to operate the at least one actuator to control an applied force in response to the sensor signals.

6. A prosthetic device as claimed in any one of claims 1 to 5, wherein the control means (402) is arranged to alter the type of grip in response to at least one identified object.

7. A prosthetic device as claimed in any one of claims 1 to 6, wherein the sensor means (302, 304, 306) comprises at least one camera.

8. A prosthetic device as claimed in claim 7, wherein the at least one camera is a thermographic camera.

9. A prosthetic device as claimed in any one of claims 1 to 8, wherein the sensor means (302, 304, 306) comprises at least one infra-red sensor.

10. A prosthetic device as claimed in any one of claims 1 to 9, wherein the sensor means (302, 304, 306) comprises at least one LIDAR sensor.

11. A prosthetic device as claimed in any one of claims 1 to 10, wherein the sensor means (302, 304, 306) comprises at least one sonar sensor.

12. A prosthetic device as claimed in any one of claims 1 to 11, wherein the sensor means (302, 304, 306) comprises at least one radar sensor.

13. A prosthetic device as claimed in any one of claims 1 to 12, wherein the prosthetic device further comprises at least one further sensor (408) mounted elsewhere on the device than the palm section and wherein the control means (402) is configured to control the at least one actuator in response to an output from the at least one further sensor.

14. A prosthetic device as claimed in claim 13, wherein the at least one further sensor (408) is mounted to the back of the device.

15. A prosthetic device as claimed in any one of claims 1 to 14, wherein the control means (402) are configured to control the at least one actuator to cause the hand to perform a preprogrammed sequence of movements.

16. A prosthetic device as claimed in claim 15, wherein the pre-programmed sequence of movements comprise the wearer’s signature.

17. A prosthetic device as claimed in any one of claims 1 to 16 wherein the control means (402) are configured to identify the wearer’s other hand from the sensor signals and control the at least one actuator to cause the prosthetic device to interact with that other hand.

18. A prosthetic device as claimed in any one of claims 1 to 17, wherein the control means (402) are configured, in response to no objects being detected in the vicinity of the prosthetic device, to control the at least one actuator to perform a pre-programmed sequence of movements.

19. A prosthetic device as claimed in any one of claims 1 to 18, wherein the control means are configured, in response to an imminent collision between the prosthetic device and another object (328), to curl the at least one digit to protect the prosthetic device.

20. A prosthetic device as claimed in any one of claims 1 to 19, further comprising means (430) for detecting water, wherein the control device (402) is configured to deactivate the prosthetic device in response to detection of water.

21. A prosthetic device as claimed in any one of claims 1 to 20, wherein the control means (402) are configured to detect if an object is slipping from grip and to control the at least one actuator to apply greater force in response to such detection.

22. A prosthetic device as claimed in any one of claims 1 to 21, wherein the control means (402) is configured to identify whether the wearer is in a familiar environment and to effect control of the at least one actuator in response to that identification.

23. A prosthetic device as claimed in any one of claims 1 to 22, further comprising means for enabling and disabling the sensor means in response to wearer instructions.

24. A prosthetic device as claimed in any one of claims 1 to 23, wherein the palm section of the device is arranged to enclose the palm of the wearer.

25. A prosthetic device as claimed in any one of the claims 1 to 24, further comprising voice recognition means, wherein the controller is configured to control the at least one actuator to write what the wearer is saying.