WO2023277798A2

WO2023277798A2 - Robotic hand

Info

Publication number: WO2023277798A2
Application number: PCT/SG2022/050401
Authority: WO
Inventors: Haoyong Yu; Lufeng PAN
Original assignee: National University of Singapore
Current assignee: National University of Singapore
Priority date: 2021-06-30
Filing date: 2022-06-10
Publication date: 2023-01-05
Anticipated expiration: 2023-12-30
Also published as: CN117396313A; WO2023277798A3

Abstract

An anthropomorphic robotic hand comprising: a plurality of fingers; a thumb; a body, the fingers and thumb extending from the body; one or more differential assemblies each controlling flexion and/or extension of two of the fingers, each differential assembly comprising: a differential mechanism attached, in use, to a motor via a tendon; and a further tendon extending through the differential mechanism to the two fingers; and a thumb tendon extending, in use, from a thumb motor to a carpometacarpal joint of the thumb, the thumb tendon being actuated by the thumb motor to control adduction and/or abduction of the thumb.

Description

Robotic Hand

Technical Field

The present invention relates, in general terms, to a robotic hand, more particularly relates to an anthropomorphic robotic hand.

Background

Due to the complexity system and heavy cost, the applications of a full-actuated robotic hand are limited although it can do very complicated tasks. To reduce overall size and cost of robotic hands, under-actuation mechanisms are widely used, which refer to mechanisms having fewer actuators than degrees-of- freedom. Under-actuated robotic hands are much lighter, easier to control, and economical than their fully-actuated counterparts, but lack relative dexterity.

Prior under-actuated robotic hands can be classified as adaptive devices and fixed-motion coupled devices according to their moving behaviour. In fixed- motion coupled devices, motions are coupled between joints under one actuator. Usually the motion of one joint will results in a proportional motion of other coupled joints. In this way, if contact occurs to block the motion of one joint, all coupled joints are thereby fixed.

In adaptive devices, motion of the distal digit can continue after the proximal digit contacts the object. Said adaptive mechanism allows the fingers to passively adapt to the outline of object. Under-actuated robotic hands need to be designed to be more adaptive, compliant, and anthropomorphic to broaden their applications to unstructured environments which approximate those of human daily life. However, existing under-actuated robotic hands do not incorporate all the criteria mentioned above, but only some of them.

It would be desirable to overcome all or at least one of the above-described problems. Summary

Disclosed herein is an anthropomorphic robotic hand comprising: a plurality of fingers; a thumb; a body, the fingers and thumb extending from the body; one or more differential assemblies each controlling flexion and/or extension of two of the fingers, each differential assembly comprising: a differential mechanism attached, in use, to a motor via a tendon; and a further tendon extending through the differential mechanism to the two fingers; and a thumb tendon extending, in use, from a thumb motor to a carpometacarpal joint of the thumb, the thumb tendon being actuated by the thumb motor to control adduction and/or abduction of the thumb.

In some embodiments, the plurality of fingers comprises four fingers and the robotic hand comprises two said differential assemblies each controlling a re spectively different two fingers.

In some embodiments, the robotic hand further comprises a tendon extending from an interphalangeal joint, through a metacarpal phalangeal joint of the thumb, in use to a motor, the tendon being actuated to control extension and/or flexion of the thumb.

In some embodiments, each of the fingers and thumb comprises multiple joints, each joint comprising a biasing member to bias the respective joint in an ex tended condition.

In some embodiments, the further tendon of each differential assembly has two opposite ends connected to a fingertip of respectfully different ones of the two fingers.

In some embodiments, each differential mechanism is configured to balance forces on the respective two fingers. In some embodiments, the robotic hand comprises a palm portion, the differ ential mechanism of each differential assembly being disposed in the palm por tion.

Disclosed herein is also an anthropomorphic lower arm assembly comprising: a forearm; a robotic hand mentioned above; and a wrist connecting the forearm to the robotic hand.

In some embodiments, the lower arm assembly comprises the motor for each differential assembly, the motor for controlling adduction and/or abduction of the thumb, and the motor for controlling flexion and/or extension of the thumb, disposed within the forearm.

In some embodiments, the motor for each differential assembly controls both flexion and extension of the fingers, the motor for controlling adduction and/or abduction of the thumb control both adduction and abduction, and the motor for controlling flexion and/or extension of the thumb controls flexion and exten sion of the thumb.

In some embodiments, the motor for each differential assembly pulls the differ ential mechanism towards the respective motor to reduce a distance between the motor and differential mechanism, thereby to cause flexion of the fingers.

In some embodiments, the lower arm assembly further comprises a linear motor disposed in the forearm, for controlling rotation of the wrist.

Brief description of the drawings

Embodiments of the present invention will now be described, by way of non limiting example, with reference to the drawings in which:

Figure 1 shows an anthropomorphic robotic hand in plan form from the dorsal side; Figure 2 shows a forearm from back side without the dorsal cover;

Figure 3 is a cross section of the forearm from the medial side;

Figure 4 is an exploded isometric view of the forearm;

Figure 5 is an isometric view of wrist flexion when the linear motor is actuated;

Figure 6 shows the tendon routing in the hand from the dorsal side;

Figure 7 is an isometric view of thumb flexion when servo is actuated;

Figure 8 is an isometric view of thumb adduction when servo is actuated;

Figure 9 is an isometric view of index finger and middle finger flexion when servo is actuated;

Figure 10 is an isometric view of ring finger and little finger flexion when servo is actuated;

Figure 11 is an isometric view of the adaptive motion of index finger and middle finger;

Figure 12 is an isometric view of the adaptive motion of ring finger and little finger;

Figure 13 is a top view of the differential mechanism;

Figure 14 is an exploded isometric view of the differential mechanism;

Figure 15 is an exploded isometric view of the palm;

Figure 16 shows the differential mechanism restricted on the track of the front half of palm from the dorsal side; Figure 17 is an isometric view of the assemble between thumb and the front half of palm;

Figure 18 is an isometric view of the assemble between fingers and the back half of palm;

Figure 19 is a side view of the finger;

Figure 20 is a cross section of the finger from the medial side;

Figure 21 is an exploded isometric view of the finger;

Figure 22 is an isometric view of the hand in a clutch position;

Figure 23 is an isometric view of the hand in a pinch position; and

Figure 24 is an isometric view of the hand in a side pinch position.

Detailed description

The present invention relates to an anthropomorphic robotic hand, which enables motions to imitate human hands to grasp daily items. This invention is a type of mechatronic end effector which can be mounted on robotic manipulator for object grasping or used as a prosthetic hand attached to an amputee. Said end effector can be commonly mounted on a robotic arm and can usually perform a single task on an object (such as a sucking disc, gripper, welding machine, etc.). Grippers/manipulators are a universal type of end effector to grasp or manipulate objects. Compared with the traditional grippers/manipulators on robotic arms, the proposed robotic hand can also be used in an environment with a complicated structure. The proposed anthropomorphic grippers can also be used as end effectors which tend to work in unstructured environments such as a hotel, restaurant, and residence. In the present disclosure, anthropomorphic grippers are also called robotic hands due to their humanoid appearance and motion. The proposed robotic hands can be used for grasping. Compared with the fixed- motion coupled graspers, the proposed adaptive robotic hands can grasp more varied objects and grasp them more stably. Indeed, most of the objects in human daily life have complex shape, variable dimensions, and may be fragile, deformable, and flexible with irregular surface conditions, which require the dexterity, versatility, and power of the robotic hand used to grasp those objects. The additional criteria of size and mass are also important to be able to make end effectors portable using a robot arm. Finally, instrumentation of end effectors with sensors helps ensure effectiveness and safety for the grasping operation and for the user. Proposed under-actuated robotic hands as described herein can incorporate all the criteria mentioned above. In addition, unlike most existing under-actuated robotic hands that omit sensors to simplify the systems so as to decrease the sizes and costs, the proposed invention has embedded sensors, thus has the capability to grasp various objects.

The proposed anthropomorphic robotic hand refers to a manipulator whose number of fingers, degrees of freedom, shape, and function are close to those of a human hand. It can operate objects flexibly and finely. Said anthropomorphic robotic hand is suitable as a high-performance prosthesis or used in flexible assembly and other industrial scenarios. It can also replace personnel to work in hazardous environments such as pollution, positioning and radiation. It can be used by service robots with high versatility, and are key components of bionic or humanoid robots. The anthropomorphic robotic hand is characterized by the small hand size and the large number of joints, which requires the transmission of large forces in a small space, and often requires that each joint can be independently controlled to achieve higher flexibility.

The beneficial effects of the present invention are as follows. The proposed anthropomorphic robotic hand draws insights from the anatomical structure of a human hand. The anthropomorphic robotic hand is very suitable for the smooth operation of complex shaped objects, easy to produce, disassemble and maintain, and is very suitable for high-end prosthetics or as a high-performance versatile robot dexterous hand or end-effector device. The anthropomorphic robotic hand can be equipped with flexible or rigid shell, flexible jacket or bionic skin that can be waterproof, dustproof and prevent chemical erosion, and can shield or weaken ionizing radiation. It can replace personnel to work in dangerous environments with pollution, contamination and radiation.

In addition, an aim of some embodiments of the present invention is to provide an under-actuated robotic hand that is adaptive, dextrous, light weight, economical, anthropomorphic in size and appearance, and have force sensors embedded in each digit to grasp various and fragile daily necessities. In accordance with an embodiment of the present application, there is provided an anthropomorphic robotic hand that consisted of one palm, four fingers and one thumb arranged like human hand.

In some embodiments, the thumb can be adducted as a natural human thumb and can be flexed to make contact with the fingers to provide both "pinch" and "clutch" postures of grasp. It will be appreciated that the thumb is able to adduct/abduct and flex/extend independently to provide both "pinch" and "side pinch" postures of grasp. It is a further object of the invention that the fingers can be individually compliant to external forces exerted in such a manner as to flex the fingers. In the present invention, such compliance will not cause the hand or fingers to malfunction in any manner. It is a further object of some embodiments of the invention that the fingers can adaptively grasp objects. This adaptively allows one or all fingers to fully close onto an object regardless of the position of the other fingers. It will be appreciated that this adaptive ability of the fingers is a passive action of the function of the hand.

Figure 1 shows an example anthropomorphic robotic hand (100). The robotic hand 100 comprises: a plurality of fingers (2, 3, 4 and 5); a thumb (6); a body (1), the fingers (2, 3, 4 and 5) and thumb 6 extending from the body (1); one or more differential assemblies (shown in Figure 6) each controlling flexion and/or extension of two of the fingers (2, 3, 4 and 5) , each differential assembly comprising: a differential mechanism (15 shown in Figure 6) attached, in use, to a motor via a tendon (246 or 248 shown in Figure 6); and a further tendon (250 or 252 shown in Figure 6) extending through the differential mechanism (15) to the two fingers; and a thumb tendon (242 shown in Figure 6) extending, in use, from a thumb motor to a carpometacarpal joint of the thumb (6), the thumb tendon (242) being actuated by the thumb motor to control adduction and/or abduction of the thumb (6).

As shown in Figure 1, the hand 100 is made up of seven distinct parts. In particular, the body (1) forms palm of the hand 100. The palm (1) provides for the attachment of the wrist (7), thumb (6) and fingers. In some embodiments for example in Figure 1, the plurality of fingers comprises four fingers, i.e., index finger (2), middle finger (3), ring finger (4) and little finger (5). The palm (1) comprises the differential mechanism that allows the adaptive motion between index finger (2), middle finger (3), ring finger (4), and little finger (5). Each finger (2, 3, 4 or 5) is attached to the palm (1), and has three joints allowing flexion and extension. The thumb (6) is also attached to the palm (1). Said thumb (6) also has three joints, one of which represents the metacarpal joint and allows the thumb adduction and abduction, and the other two joints allow the thumb flexion and extension. It will be appreciated that the above two types of motions (i.e., flexion/extension and adduction/abduction) are independent.

The present invention also relates to an anthropomorphic lower arm assembly (102) comprising: a forearm (8); a robotic hand (100) mentioned above; and a wrist (7) connecting the forearm (8) to the robotic hand (100).

In one example, the wrist (7) is a rotational joint that connects with palm (1) and forearm (8). The forearm (8) contains the actuation system of present invention as seen in Figure 2, Figure 3 and Figure 4. In some embodiments, the lower arm assembly (102) may further comprise a linear motor disposed in the forearm (8), for controlling rotation of the wrist (7). In particular, Figure 2 shows the forearm (8) from back side without the dorsal cover (10). Figure 3 is a cross section of the forearm (8) from the medial side. The main body of forearm (8) comprises shell (9) and dorsal cover (10) which are fixed by a screw (15) (which is illustrated in Figure 6). As shown in Figures 2 and 3, the bases of servos (12) are fixed in shell (9) by screws (13) to ensure they cannot move in the forearm (8). The bottom of the forearm (8) may have four threaded holes (not shown) that can be mounted on the robot.

Figure 4 is an exploded isometric view of the forearm (8), and it shows the overall assembly of the forearm (8). There is one linear motor (11) and four servos (12) inside the forearm (8). As shown in Figure 4, the base of linear motor (11) is fixed in shell (9) by a screw (13) and a nut (14).

In some embodiments, wrist (7), which is controlled by linear motor (11), can rotate relative to the forearm (8). Figure 5 is an isometric view of wrist flexion when the linear motor (11) (not shown in Figure 5) is actuated. In particular, the head of linear motor (11) is configured to connect the link of wrist (7) to control the rotation motion of wrist (7). The lower arm assembly (102) further comprises a linear motor disposed in the forearm, for controlling rotation of the wrist.

Figure 6 shows the tendon routing in the hand (100) from the dorsal side. The wheel of servos (12) tethered with tendons (242, 244, 246, 248, 250 and 252) to control the motion of thumb (6) and fingers (2, 3, 4 and 5). In the present disclosure, the actuation systems are mounted within the forearm (8) and extend into fingers (2, 3, 4, 5) or thumb (6) by tendons (242, 244, 246, 248, 250 and 252). The tendons thus allow the fingers (2, 3, 4, 5) to flex/extend, and allow the thumb (6) to adduct/abduct and/or flex/extend.

In the present disclosure, the actuation systems comprise the actuator (see 121) used to control flexion/extension of the thumb (6), the actuator (see 122) used to control adduction/abduction of the thumb (6), the actuator (see 123) used to control flexion/extension of the index finger (2) and middle finger (3), and the actuator (see 124) to control flexion/extension of the ring finger (4) and little finger (5). It will be appreciated that the actuation systems allow the hand (100) to perform passive (e.g. biasing fingers in a closed or curled condition rather than an open condition) and adaptive grasping.

Tendon (242) passes through the distal interphalangeal joint (602) and metacarpophalangeal joint (604) of the thumb (6) and tethered with servo (121). In some embodiments, tendon (242) extends from the interphalangeal joint (602), through the metacarpal phalangeal joint (604) of the thumb (6). In particular, one end of tendon (242) is attached within the distal end of the thumb (6). Said tendon (242) passes through the distal two joints (i.e., interphalangeal joint 602 and metacarpal phalangeal joint 604), then passes into the palm (1), and finally passes into the forearm (8) to be attached to the actuator (121). As a result, pulling the tendon can cause the thumb to flex. In use to a motor, the tendon (242) is actuated to control extension and/or flexion of the thumb (6). In one example, servo (121) is used to control the flexion/extension motion of the thumb (6) as seen in Figure 7, which is an isometric view of thumb flexion when servo (121) is actuated.

In some embodiments, the lower arm assembly (102) comprises the motor for each differential assembly (15), the motor (which may be installed with servo 121) can be used for controlling flexion and/or extension of the thumb (6). The main function of the each differential assembly (15) is to allow the tendons (246, 248, 250 and 252) that pass through each differential assembly (15) not to slip off even when the tendons (246, 248, 250 and 252) loose. It will be appreciated that said motor for controlling flexion and/or extension of the thumb (6) can also control both adduction and abduction. Said motor may be disposed within the forearm (8). Tendon (242) allows said thumb (6) to be adducted as a natural human thumb and can be flexed to make contact with the fingers to provide both "pinch" and "clutch" postures of grasp. It will be appreciated that the thumb (6) is able to flex/extend independently to provide both "pinch" and "side pinch" postures of grasp.

Tendon (244) passes through the carpometacarpal joint (606) of the thumb (6) and tethered with servo (122). As a result, servo (122) controls the adduction/abduction motion of the thumb (6) as seen in Figure 8, which is an isometric view of thumb adduction when servo (122) is actuated. In particular, one end of tendon (244) is attached within the distal end of the carpometacarpal joint (606) of thumb (6). Said tendon (244) passes through the carpometacarpal joint (606), then passes into the palm (1), and finally passes into the forearm (8) to be attached to actuator (122). As a result, pulling tendon (244) can cause the thumb (244) to adduct.

In some embodiments, the lower arm assembly (102) comprises the motor for each differential assembly (15). The motor (which may be installed with servo 122) can be used for controlling adduction/abduction of the thumb (6). It will be appreciated that said motor for controlling adduction and/or abduction of the thumb (6) can also control both adduction and abduction. Said motor may also be disposed within the forearm (8). Tendon (244) allows said thumb (6) to be adducted as a natural human thumb and can be adducted to make contact with the fingers to provide both "pinch" and "clutch" postures of grasp. The thumb (6) is able to abduct/adduct independently to provide both "pinch" and "side pinch" postures of grasp.

In the present invention, the robotic hand (100) comprises two said differential assemblies (15) each controlling a respectively different two fingers.

In particular, tendon (246) is tethered with the servo (123) and the differential mechanism (15) of index finger (2) and middle finger (3). In some embodiments, the motor (which may be installed with servo 123) for each differential assembly pulls the differential mechanism (15) towards the respective motor to reduce a distance between the motor and differential mechanism (15), thereby to cause flexion of the fingers (2) and (3). As a result, servo (123) controls the flexion/extension motion of the index finger (2) and middle finger (3) as seen in Figure 9, which is an isometric view of index finger (2) and middle finger (3) flexion when servo (123) is actuated.

In particular, one end of tendon (250) is attached within the distal end of the index finger (2). Said tendon (250) passes through the differential mechanism (15) which is in the palm (1), then passes back through the middle finger (3). In some embodiments, tendon (250) has two opposite ends connected to a fingertip of respectfully different ones of the index finger (2) and middle finger (3). Tendon (250) ends at the distal end of the middle finger (3). One end of tendon (246) is attached within the bottom of the differential mechanism (15), and passes into the forearm (8) to be attached to actuator (123). As a result, pulling tendon (246) causes the index finger (2) and middle finger (3) to flex, and can achieve adaptive grasping between the index finger (2) and middle finger (3). As will be discussed later, tendons (252) and (248) can apply the same method to cause the ring finger (4) and little finger (5) to flex and achieve adaptive grasping between the ring finger (4) and little finger (5).

The lower arm assembly (102) comprises the motor for each differential assembly (15). The motor (which may be installed with servo 123) can be used for controlling flexion or extension of index finger (2) and middle finger (3). It will be appreciated that said motor can also be used for control both flexion and extension of ring finger (4) and little finger (5). Said motor may be disposed within the forearm (8). An object of some embodiments of the invention is that the index finger (2) and middle finger (3) can be individually compliant to external forces exerted in such a manner as to flex the fingers. Such compliance will not cause the index finger (2) and middle finger (3) to malfunction in any manner.

Tendon (248) is tethered with the servo (124) and the differential mechanism (15) of ring finger (4) and little finger (5). In some embodiments, the motor (which may be installed with servo 124) for each differential assembly pulls the differential mechanism (15) towards the respective motor to reduce a distance between the motor and differential mechanism (15), thereby to cause flexion of the fingers (4) and (5). Servo (124) controls the flexion/extension motion of the ring finger (4) and little finger (5) as seen in Figure 10, which is an isometric view of ring finger (4) and little finger (5) flexion when servo (124) is actuated.

In some embodiments, the lower arm assembly (102) comprises the motor for each differential assembly (15), the motor (which may be installed with servo 124) can be used for controlling flexion and/or extension of ring finger (4) and little finger (5). It will be appreciated that said motor can be used for controlling both flexion and extension of ring finger (4) and little finger (5). In some cases, the index finger (4) and middle finger (5) can be individually compliant to external forces exerted in such a manner as to flex the fingers. It will be appreciated that such compliance will not cause the ring finger (4) and little finger (5) to malfunction in any manner.

In particular, one end of tendon (252) is attached within the distal end of the ring finger (4). Said tendon (252) passes through the differential mechanism (15) which is in the palm (1), then passes back through the little finger (5). In some embodiments, tendon (252) has two opposite ends connected to a fingertip of respectfully different ones of the ring finger (4) and little finger (5). Tendon (252) ends at the distal end of the ring finger (4). One end of tendon (248) is attached within the bottom of the differential mechanism (15), and passes into the forearm (8) to be attached to actuator (124). As a result, pulling tendon (246) causes the index finger (2) and middle finger (3) to flex, and can achieve adaptive grasp between the ring finger (4) and little finger (5).

In some embodiments, each differential mechanism is configured to balance forces on the respective two fingers. In particular, tendon (250) connects the index finger (2) and middle finger (3) through the differential mechanism (15), which can balance the force on index finger (2) and middle finger (3) and achieve adaptive grasping between index finger (2) and middle finger (3) as can be seen in Figure 11, which is an isometric view of the adaptive motion of index finger and middle finger.

As shown in Figure 11, when a force (1101) is applied on middle finger, the index finger (2) will keep moving under the influence of the differential mecha nism (15). The index finger (2) and middle finger (3) can therefore adaptively grasp objects. This ability to adaptively grasp allows the index finger (2) and middle finger (3) to fully close onto an object regardless of the position of the other fingers.

Tendon (252) connects the ring finger (4) and little finger (5) through the differential mechanism (15), which can balance the force on ring finger (4) and little finger (5) and achieve adaptive grasping between ring finger (4) and little finger (5) as seen in Figure 12, which is an isometric view of the adaptive motion of ring finger (4) and little finger (5). As shown in Figure 12, when a force (1201) is applied on ring finger (4), the little finger (5) will keep moving under the influence of the differential mechanism. In some embodiments, tendon (252) has two opposite ends connected to a fingertip of respectively different ones of ring finger (4) and little finger (5). The ring finger (4) and little finger (5) can thus adaptively grasp objects. This adaptively allows the ring finger (4) and little finger (5) to fully close onto an object regardless of the position of the other fingers.

Figure 13 and Figure 14 are a top view and an exploded isometric view of the differential mechanism (15), respectively. The differential mechanism (15) is made up of a pulley (25), a pulley shell (26), a pulley cover (27) and a screw (13). The pulley (25) is a wheel on an axel or shaft that is designed to support movement and change of direction of a cable, or transfer of power between the cables. In particular, the pulley (25), the pulley shell (26), and the pulley cover (27) are fixed by screw (13). Tendon (250) and tendon (252) may be routed around the pulley (25) and tethered with two fingers (i.e., index finger (2) and middle finger (3), or ring finger (4) and little finger (5)) of each end. The pulley shell (26) will prevent tendon (250) and tendon (252) falling off the pulley (25) when it is slack. There are holes (1401) on the bottom of the pulley shell (26) and pulley cover (27), which can be used to tether tendon (246) and tendon (248). There is a chute on the back of the pulley shell (26), which is engaged with the pulley track in the palm (1), thereby defining the direction of movement of the differential mechanism (15).

As mentioned before, the robotic hand (100) comprises the palm portion (1). In some embodiments, a base section forming the major frame can represent the palm portion (1). It will be appreciated that the differential mechanism (15) of each differential assembly can be disposed in the palm portion (1). Other com ponents of the robotic hand (100) may be mounted onto or into the palm (1). In particular, the robotic hand has mounting points intended for the purpose of mounted on other robotic devices. The differential mechanism (15) of each differential assembly can be positioned in the palm (1). In some embodiments, the palm (1) is made up of front half (28) and back half (29), which are fixed by screws (13) as can be seen in Figure 15, which is an exploded isometric view of the palm. As mentioned before, the differential mechanism (15) is engaged with the pulley track in the palm (1), thereby defining the direction of movement of the differential mechanism (15).

Figure 16 shows the differential mechanism (15) restricted on the track of the front half (28) of palm (1) from the dorsal side. In particular, the pulley tracks (1601 and 1602) are arranged in the front half (28). The differential mechanisms (15) can move in the palm (1) along the pulley tracks (1601, 1602).

Figure 17 is an isometric view of the assembly between thumb (6) and the front half (28) of palm (1). In one embodiment, the front half (28) provides for the attachment of the thumb (6) by screws (13).

Figure 18 is an isometric view of the assembly between fingers and the back half of palm. In one embodiment, the back half (29) provides for the attachment of the fingers (2, 3, 4, 5) by screws (not shown in Figure 18).

Figure 19 is a side view of a finger (2, 3, 4 or 5). Figure 20 is a cross section of a finger (2, 3, 4 or 5) from the medial side. Figure 21 is an exploded isometric view of each finger. As can be seen in Figures 19, 20 and 21, each finger (2, 3, 4 or 5) is made up of four parts, which corresponds to the distal phalange (16), the medial phalange (17), the proximal phalange (18) and the distal end of the metacarpal (19) of the human fingers respectively. Each phalange is made up of a plurality of digit bodies (20), force sensors (21) and digit covers (22). The phalanges (16, 17, 18) and metacarpal (19) are connected with each other by the snap-fit joint and two torsion springs (23).

In the present disclosure, each of the fingers (2, 3, 4 and 5) and thumb (6) comprises multiple joints. Each joint comprising a biasing member to bias the respective joint in an extended condition. In one embodiment, the torsion springs (23) can work as the biasing members to bias the respective joint in said extended condition. It will be appreciated that torsion springs (23) provide resilience force to return the finger (2, 3, 4 or 5) back to its rest condition, as shown in Figure 21. As shown in Figures 19, 20 and 21, metacarpal (19) pro vides attachment between fingers (2, 3, 4, 5) and the palm (1). As shown in Figures 19 and 20, tendon (24) passes through the holes on digit covers (22) of every phalange and transfers actuation force to every joint on the finger. The fingers (2, 3, 4, and 5) contain force sensors in every digit. In some embodi ments, the force sensors (21) are embedded in every digit body (20) and are covered by digit cover (22). The cables of the force sensors (20) pass through the fingers inside, and are also embedded inside fingers (2, 3, 4, 5).

Figure 22, Figure 23 and Figure 24 are isometric views of the hand 100 in a clutch position, in a pinch position, and in a side pinch position, respectively. When servo (121), servo (122), servo (123), and servo (124) are actuated (see Figure 6), the "clutch" posture can be achieved to grasp heavy objects, as shown in Figure 22. When servo (121), servo (122), and servo (123) are actuated, the "pinch" posture can be achieved to grasp tiny objects, as can be seen in Figure 23. When servo (121), servo (123), and servo (124) are actuated, the "side pinch" posture can be achieved to grasp flake objects, as shown in Figure 24. It will be appreciated that in the present disclosure, servers (121, 122, 123, and 124) connect a power source external to the hand (100).

It will be appreciated that many further modifications and permutations of various aspects of the described embodiments are possible. Accordingly, the described aspects are intended to embrace all such alterations, modifications, and variations that fall within the spirit and scope of the appended claims.

Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavor to which this specification relates.

Claims

Claims:

1. An anthropomorphic robotic hand comprising: a plurality of fingers; a thumb; a body, the fingers and thumb extending from the body; one or more differential assemblies each controlling flexion and/or extension of two of the fingers, each differential assembly comprising: a differential mechanism attached, in use, to a motor via a tendon; and a further tendon extending through the differential mechanism to the two fingers; and a thumb tendon extending, in use, from a thumb motor to a carpometacarpal joint of the thumb, the thumb tendon being actuated by the thumb motor to control adduction and/or abduction of the thumb.

2. A robotic hand according to claim 1, wherein the plurality of fingers com prises four fingers and the robotic hand comprises two said differential as semblies each controlling a respectively different two fingers.

3. A robotic hand according to claim 1 or 2, further comprising a tendon ex tending from an interphalangeal joint, through a metacarpal phalangeal joint of the thumb, in use to a motor, the tendon being actuated to control exten sion and/or flexion of the thumb.

4. A robotic hand according to any one of claims 1 to 3, wherein each of the fingers and thumb comprises multiple joints, each joint comprising a biasing member to bias the respective joint in an extended condition.

5. A robotic hand according to any one of claims 1 to 4, wherein the further tendon of each differential assembly has two opposite ends connected to a fingertip of respectfully different ones of the two fingers.

6. A robotic hand according to any one of claims 1 to 5, wherein each differen tial mechanism is configured to balance forces on the respective two fingers.

7. A robotic hand according to any one of claims 1 to 6, comprising a palm portion, the differential mechanism of each differential assembly being dis posed in the palm portion.

8. An anthropomorphic lower arm assembly comprising: a forearm; a robotic hand according to any one of claims 1 to 7; and a wrist connecting the forearm to the robotic hand.

9. A lower arm assembly according to claim 8, comprising the motor for each differential assembly, the motor for controlling adduction and/or abduction of the thumb, and the motor for controlling flexion and/or extension of the thumb, disposed within the forearm.

10. A lower arm assembly according to claim 9, wherein the motor for each dif ferential assembly controls both flexion and extension of the fingers, the motor for controlling adduction and/or abduction of the thumb control both adduction and abduction, and the motor for controlling flexion and/or exten sion of the thumb controls flexion and extension of the thumb.

11. A lower arm assembly according to claim 9 or 10, wherein the motor for each differential assembly pulls the differential mechanism towards the respective motor to reduce a distance between the motor and differential mechanism, thereby to cause flexion of the fingers.

12. A lower arm assembly according to any one of claims 8 to 11, further com prising a linear motor disposed in the forearm, for controlling rotation of the wrist.