Under-actuated prosthetic hand based on continuum transmission mechanism
Technical Field
The invention relates to the technical field of medical instruments, in particular to a medical prosthetic hand system.
Background
Due to accidents, industrial injuries, diseases and the like, a large number of amputation patients are generated in the world, most of the amputation patients are hand amputation patients, and the amputation patients cannot independently complete daily life requirements, so that the quality of life is obviously reduced. In order to improve the quality of life of the hand amputated disabled people, related companies and research institutes have developed various artificial limbs, including single-degree-of-freedom artificial limbs and multi-degree-of-freedom artificial limbs having a humanoid shape, which are widely used.
The single-degree-of-freedom artificial hand can complete limited gripping actions through simple finger opening and closing, has single function and poor practicability, does not have human-like appearance, is not harmonious with a human body after being worn, and is easy to be rejected by a patient; the multi-degree-of-freedom artificial hand has the appearance of a hand, is easy to accept by a patient, has better flexibility due to the number of joints close to that of the hand, and can realize various actions, but the multi-degree-of-freedom artificial hand has a complex structure and high cost due to the use of more hinges, connecting rods or other traditional transmission modes, and is not widely applied at present.
Disclosure of Invention
In view of the above-mentioned drawbacks of the prior art, the present invention aims to: the output of the artificial hand with multiple degrees of freedom is controlled by adopting less input; meanwhile, the use of a hinge, a connecting rod and other kinematic pairs with complex structures is avoided, so that the weight of the artificial hand is reduced, and the cost is reduced.
In order to achieve the purpose, the invention provides a novel underactuated prosthetic hand, which adopts fewer motors as drive input, and particularly designs a flexible transmission mechanism, wherein the drive input and the drive output form a continuous body which is integrally connected with each other and can continuously change elastic deformation, and under the condition of proper drive input, the continuous body mechanism can output more (more than the number of the drive input) motion output through the integral continuous deformation. The motion outputs generated by the transmission of the continuum mechanism are different, but have reasonable mathematical relationship with each other. The rotation of each joint of the artificial hand is realized by using each path of motion output, so that the artificial hand imitating the human shape realizes flexible and coordinated motion. Because the mechanism does not use the traditional rigid kinematic pair such as the hinge, the connecting rod and the like, the return difference of the system is eliminated. A large number of elastic alloy wires are used as driving and transmitting elements, so that the artificial hand has strong self-adaptive capacity, and meanwhile, the weight of the artificial hand is obviously reduced. The system adopts less driving input, realizes more motion output, and has simple structure and obviously reduced cost. Meanwhile, all paths of motion are coordinated with each other, so that all joints of the fingers have a coordinated motion relation, and the artificial hand can complete more coordinated motion which is more similar to that of a human hand.
The technical scheme of the invention is as follows:
the invention mainly comprises three parts, including a motor driving unit, a continuum transmission mechanism and a self-adaptive prosthetic hand with a human-simulated appearance, and the parts are explained in detail below. A motor drive unit: the motor driving unit consists of two similar parts and is fixed on the same base. Wherein each part comprises a motor fixed on the base plate, and an output gear fixed on the output shaft of the motor. Meanwhile, two racks are arranged on two sides of the output gear and are respectively connected to the substrate through linear guide rails, the racks are meshed with the middle gear, and when the gear rotates, the two racks respectively move towards different directions. Each rack is respectively fixed with an elastic alloy wire, when the motor rotates, the elastic alloy wires can do linear push-pull motion, and two elastic alloy wires driven by the same motor have opposite motion directions but the same motion distance. The two motors are arranged side by side to drive four elastic alloy wires, and the elastic alloy wires penetrate through the fixed metal tubes to be connected to the continuum mechanism and serve as motion input of the continuum mechanism. Continuum transmission for motion coordination: the mechanism is used for realizing the under-actuated motion of the prosthetic hand, and converting the independent motion input of the two pairs of elastic alloy wires into the motion output of the six elastic alloy wires which are mutually coordinated. The mechanism consists of a base, a spacing disc, a locking disc, a spring and an elastic alloy wire. Through holes are arranged at the same positions on the base and the spacing disc and are respectively used for the driving wire and the driven wire to pass through, then all the elastic alloy wires are locked and fixed by the locking disc, and springs are arranged among the fingers of the base, the spacing disc and the locking disc and penetrate through the elastic alloy wires to keep the spacing among the discs. In the initial state, the continuum structure is rectilinear in shape. When the two-way driving input pushes and pulls the four driving wires, the continuum mechanism forms arc-shaped bending, the output wires also form corresponding shapes passively, and the lengths of the extension and the shortening of the output wires are different because the output wires are fixed at different positions on the locking disc. The output wires are used for driving each joint of the artificial hand, so that the fingers can be bent to different degrees. An adaptive prosthetic hand with a humanoid appearance: the artificial hand is constructed according to the size of the hand, has the appearance and the size similar to those of the hand, and can realize the movement similar to the hand. Mainly comprises a palm and five fingers, wherein the five fingers are respectively fixed at corresponding positions on the palm. Similar to human hand, the thumb has four degrees of freedom and is driven by two elastic alloy wires, one of which is fixed on the tip of the thumb and extends to the outside after passing through the second knuckle and the third knuckle of the thumb so as to realize the bending of the thumb. And the other elastic alloy wire is fixed on the fourth knuckle, passes through the thumb fixing base and the palm and extends out of the prosthetic hand to realize the side swing of the thumb. The index, middle, ring and little fingers are somewhat different in size but have the same structural form, all with three degrees of freedom, depending on the characteristics of the human hand. Each finger is driven by an elastic metal wire, one end of the metal wire is fixed on the fingertip, and the other end of the metal wire passes through the second knuckle, the third knuckle, the finger base and the palm and then extends out of the artificial hand. The elastic alloy wire is pushed or pulled outside, and the corresponding finger can be tightened or unfolded. In order to realize the motion function similar to that of human hand closely, torsion springs are arranged among the joints, so that the joints of the fingers keep the unfolding state.
The whole working principle of the invention is that when the program control motor rotates at different angles, a pair of elastic alloy wires driven by the same motor are pushed and pulled back and forth in opposite directions and at equal distances through the transmission of the gear and the rack. Two pairs of elastic alloy wires extend to the continuum mechanism as the drive input to the continuum transmission mechanism. The continuous body is bent into an arc shape in a certain direction due to the push-pull movement of the two pairs of driving elastic alloys, and the driven wire which is fixed on the locking disc and is parallel to the driving wire is passively bent into a corresponding shape, so that the driven wire also generates push-pull movement. The six driven wires extend out of the continuous body and are used for driving five fingers of the humanoid artificial hand, so that each finger of the artificial hand is bent or unfolded, and the function of grabbing or operating an object is realized.
An under-actuated prosthetic hand based on a continuum transmission mechanism comprises a motor driving unit, a continuum transmission mechanism and a manipulator, wherein the continuum transmission mechanism comprises a fixing plate, a plurality of fixing pipes, a plurality of guide pipes, a base, a plurality of driven wires, a spacing disc and a locking disc, one ends of the fixing pipes and the guide pipes are connected to the base, the other ends of the fixing pipes are connected to the fixing plate, one ends of the driven wires are fixed on the locking disc, and the other ends of the driven wires sequentially penetrate through the spacing disc, the base, the guide pipes and the fixing plate and are finally connected to fingers of the manipulator; the motor driving unit comprises a motor, an output mechanism and a plurality of driving wires, wherein one end of each driving wire is fixed on the output mechanism, and the other end of each driving wire sequentially penetrates through the fixing plate, the fixing pipe, the base and the spacing disc and is fastened on the locking disc; the manipulator comprises a palm and five fingers, each finger is provided with a plurality of knuckles, and two adjacent knuckles are rotatably connected; the rotation of the motor driving unit can be converted into linear motion of the driving wire through the output mechanism, and the linear motion of the driving wire can drive the continuum transmission mechanism to deform, so that the driven wire with one end fixed with the locking disc of the continuum transmission mechanism moves, and accordingly, each finger of the manipulator is driven to complete corresponding action.
Preferably, the output mechanism comprises a base plate, output gears, racks, guide rails and sliding grooves, the output gears are fixedly connected to an output shaft of the motor, the two racks are meshed with two sides of each output gear in parallel, each rack is fixed on the guide rail, the size of each guide rail is matched with that of the corresponding sliding groove fixed on the base plate and can slide along the corresponding sliding groove, and the driving wires are fixedly connected with the racks.
Preferably, the motor drive unit comprises two motors and two output gears, the two motors driving the four drive wires via the two output gears and the rack.
Preferably, the base, the fixed plate, the spacer disc and the locking disc are provided with small holes for the driving and driven wires to pass through, the distribution of the small holes being set according to the motion of the manipulator to be achieved.
Preferably, the fixed tube is arranged between the fixed plate and a corresponding small hole on the base for the driving wire to pass through, one end of the guide tube is fixed on the small hole of the base, and the other end of the guide tube passes through the fixed plate and extends to the manipulator.
Preferably, a plurality of driving wires and/or driven wires passing between the adjacent base, spacer disc and locking disc are sleeved with springs so that a certain distance is maintained between the base, spacer disc and locking disc.
Preferably, the five fingers comprise a thumb, the thumb comprises a fingertip, a second knuckle, a third knuckle, a fourth knuckle and a fixed base, the fixed base is fixed on the palm of the hand through screws, a driven wire of the continuum transmission mechanism penetrates through the fourth knuckle, the third knuckle and the second knuckle of the thumb and is fixed on the fingertip of the thumb, and the pushing and pulling movement of the driven wire can realize the bending or stretching of the thumb; and the other driven wire of the continuous body transmission mechanism penetrates through the palm and the fixed base and is fixed on the fourth knuckle of the thumb, and the outward expansion or the inward contraction of the thumb can be realized by the push-pull movement of the driven wire.
Preferably, the five fingers comprise an index finger, a middle finger, a ring finger and a little finger, the index finger, the middle finger, the ring finger and the little finger have similar structures, each finger comprises a fingertip, a second knuckle, a third knuckle and a finger base, the finger bases are fixed on the palm of the hand through screws, four driven wires of the continuum transmission mechanism respectively penetrate through the palm and the finger bases, the third knuckles and the second knuckles of the corresponding fingers and are fixed on the fingertips of the corresponding fingers, and the push-pull movement of each driven wire can respectively realize the bending or stretching of the index finger, the middle finger, the ring finger and the little finger.
Preferably, two adjacent knuckles are connected through a rotating pin to form a rotatable joint, and a torsion spring is arranged at the joint, so that the fingers can keep an unfolded and straightened state when the fingers are not pulled by the driven wire to move.
Preferably, the driving wire and the driven wire are made of high elastic nitinol wires, the fixing tube is made of a metal material, and the guide tube is made of a teflon material.
Drawings
FIG. 1 is a schematic perspective view of an under-actuated prosthetic hand based on a continuum transmission mechanism according to the present invention;
FIG. 2 is a schematic perspective view of a motor drive unit of the prosthetic hand of FIG. 1;
FIG. 3A is a schematic illustration of the continuum transmission mechanism of the prosthetic hand of FIG. 1;
FIG. 3B is a schematic view of the continuum segment of the continuum transmission mechanism of FIG. 3A being curved in a direction to form an arc;
FIG. 4A is a schematic view of a manipulator of the prosthetic hand of FIG. 1;
FIG. 4B is a diagram illustrating a thumb configuration of the manipulator of FIG. 4A; and
fig. 4C is a schematic diagram of the index finger structure of the manipulator in fig. 4A.
Detailed Description
The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings so that the objects, features and advantages of the invention can be more clearly understood. It should be understood that the embodiments shown in the drawings are not intended to limit the scope of the present invention, but are merely intended to illustrate the spirit of the technical solution of the present invention.
Fig. 1 is a schematic perspective view of an under-actuated prosthetic hand based on a continuum transmission mechanism. It should be noted that the prosthetic hand structure shown in fig. 1 is only for convenience in describing the structure and operation principles of the present invention and should not be construed as limiting the present invention. In addition, it should be noted that although not shown in FIG. 1, the prosthetic hand of the present invention also includes an outer shell that is shaped similarly to a human hand. As shown in fig. 1, the continuous body transmission mechanism-based under-actuated prosthetic hand of the present invention includes a motor driving unit 100, a continuous body transmission mechanism 200, a manipulator 300 and a base 400, wherein the motor driving unit 100, the continuous body transmission mechanism 200 and the manipulator 300 are all fixed on the base 400, and the motor driving unit 100 drives the continuous body transmission mechanism 200 to deform, so that the continuous body transmission mechanism 200 transmits an output to the manipulator 300 to control the manipulator to perform different actions.
Fig. 2 shows a perspective view of the motor drive unit 100 of the prosthetic hand. As shown in fig. 2, the motor driving unit 100 includes two similar portions 101 and 102 fixed on the same substrate 1, wherein the first motor driving portion 101 includes a motor 2, an output gear 3, and two racks 4 and 5. The motor 2 is fixed on the base plate 1, the output gear 3 is fixedly connected to the output shaft of the motor 2, two racks 4, 5 are meshed with both sides of the output gear 3 in parallel, each rack, for example, the rack 4, is fixed on the guide rail 7 through an adapter plate 6, or the racks can be integrated with the guide rail. The size of the guide rail 7 is matched with the size of a sliding groove 8 fixed on the substrate 1 and can slide along the sliding groove 8, so that the rotation of the output gear 3 can drive the two racks to respectively move along different directions, but the movement distances are the same. The racks 4 and 5 are respectively fixed with driving wires 9 and 10, and are pressed by fixed pressing blocks 11 and 12. When the motor 2 rotates, the driving wires 9 and 10 do linear push-pull motion.
The second motor driving part 102 has a similar structure to the first motor driving part 101, and will not be described in detail. Two drive wires 13, 14 are also fixedly connected to the two racks of the second motor drive section 102. When two motors arranged side by side drive respective output gears to rotate, the two pairs of racks and respective guide rails slide along a straight line in the sliding groove, so that the corresponding two pairs of driving wires 9, 10, 13 and 14 are driven to do straight line push-pull motion. A pair of driving wires driven by the same motor has the same movement speed and opposite movement directions. The other end of each drive wire is connected to the continuum drive mechanism 200 such that the push-pull motion of each drive wire can cause the continuum drive mechanism to bend into a different shape, as will be further described below.
Preferably, the drive wires 9, 10, 13, 14 are made of high elasticity nitinol wires.
Fig. 3A is a schematic diagram of a continuum transmission mechanism 200 of a prosthetic hand. As shown in fig. 3A, the continuum transmission mechanism 200 includes a fixed plate 36, fixed tubes 15, 16, 17, 18, guide tube 23, base 19, driven wires 24, 25, 26, 27, 28, 29, spacer discs 20, and locking discs 22. Wherein one end of the driven wire is fixed on the locking disc 22, and the other end passes through the spacing disc 20, the base 19, the guide tube 23 and the fixing plate 36 in sequence and finally is connected to the manipulator 300.
Specifically, in the continuum transmission mechanism 200, the base 19 and the fixed plate 36 are fixed on the base 400, and the base 19, the fixed plate 36, the spacing plate 20 and the locking plate 22 are provided with small holes for passing the driving wire and the driven wire, and the distribution of the small holes is set according to the motion of the robot to be achieved. Two spacer disks 20 are shown, however it will be appreciated that the number of spacer disks may vary depending on the actual requirements. The fixed tube is arranged between the fixed plate and the corresponding small hole on the base for the drive wire to pass through, and the two pairs of drive wires 9, 10, 13, 14 from the motor drive unit pass through the fixed plate 36 and are respectively guided to the base 19 by the fixed tubes 15, 16, 17, 18, then pass through the base 19 and the spacing disc 20 in sequence, and finally are fixed on the locking disc 22.
A spring 21 is provided over the drive wire between adjacent base 19, spacer 20 and lock 22 discs to maintain the discs at a distance. One end of the guide tube is fixed on a small hole of the base, the other end of the guide tube penetrates through the fixed plate and extends to the manipulator, one ends of the six driven wires 24, 25, 26, 27, 28 and 29 are all fastened on the locking disc 22, the other ends of the six driven wires penetrate through the spacing disc 20 and the base 19 in sequence and are guided to the fixed plate 36 through the six guide tubes 23, and the guide tubes penetrate through the fixed plate 36 and then are connected with the manipulator.
Preferably, the driven wires 24, 25, 26, 27, 28, 29 are made of high elasticity nitinol wires, the fixed tube is made of a metallic material, and the guide tube is made of a teflon material. Hereinafter, for convenience of description, a structure formed by the driving wire and the driven wire portion and the spacer, the spring and the locking plate at the rear side of the base 19 will be referred to as a continuum 38.
The continuum 38 initially assumes a flat position. When the motor drives the two pairs of driving wires to do push-pull movement, the positions of the driving wires in the continuum 38 are different, and the movement of the driving wires drives the continuum 38 to do bending movement, so that the driven wires with one ends fastened on the locking disc do corresponding stretching movement. Fig. 3B shows a schematic view of the continuous body 38 bent downward to form an arc, six driven wires are respectively fixed at different positions on the locking disc, and the stretching motions of the different driven wires along with the bending motion of the continuous body are different, so that the six driven wires extending to the manipulator can drive each finger to perform different motions. Different driving wire outputs can be obtained by changing the rotating direction or speed of the motor, so that different continuous body bending motions are obtained, and the manipulator is controlled to be in different postures by the driven wire.
Fig. 4A shows a schematic view of a robot 300. As shown in fig. 4, the manipulator 300 has a shape and a joint structure similar to a human hand, and the manipulator 300 includes a palm 30, a thumb 31, an index finger 32, a middle finger 33, a ring finger 34 and a small finger 35, each finger has a plurality of knuckles, adjacent two knuckles can rotate mutually, the base of the finger is fixed at a proper position of the palm, and six driven wires 24, 25, 26, 27, 28, 29 with the tail ends fixed on the locking disc 22 of the continuum transmission mechanism penetrate through the guide tube 23 to enter the palm and are connected with each finger, which will be described in detail later.
FIG. 4B shows the structure of the thumb and its connection to the palm; figure 4C shows the structure of the separated index finger. As shown in fig. 4B, the thumb includes a fingertip 41, a second knuckle 42, a third knuckle 43, a fourth knuckle 44 and a fixed base 45, the fixed base 45 is fixed on the palm by a screw 46, and the connection between the fourth knuckle and the fixed base, between the third knuckle and the fourth knuckle, between the second knuckle and the third knuckle and between the fingertip and the second knuckle is made by a rotation pin, thereby having a rotatable joint. The thumb is controlled by two driven wires 24, 25, wherein the driven wire 24 is fixed on the fingertip 41 of the thumb and extends to the outside through the second knuckle 42, the third knuckle 43 and the fourth knuckle 44 of the thumb, and the driven wire 24 is pushed and pulled to realize the bending or stretching of the thumb 31; the driven wire 25 is fixed on the fourth knuckle 44 and extends out of the prosthetic hand through the fixed base 45 and the palm, and the abduction or adduction of the thumb 31 is achieved by pushing and pulling the driven wire 25.
The index finger 32, middle finger 33, ring finger 34 and small finger 35 are of different lengths but of similar construction and are driven by elastic alloy wires 26, 27, 28, 29 respectively. Taking the index finger as an example, as shown in fig. 4C, the index finger 32 comprises a fingertip 47, a second knuckle 48, a third knuckle 49, and an index base 50, wherein the index base 50 is fixed on the palm of the hand by a screw 46, and the third knuckle and the index base, the second knuckle and the third knuckle, and the fingertip and the second knuckle are connected by a rotation pin, so that the joints can rotate. The index finger is controlled by the driven wire 26, the driven wire 26 is fixed on the tip 47 of the index finger and extends to the outside through the second knuckle 48, the third knuckle 49 and the index base 50 of the index finger, and the bending or stretching of the index finger 32 can be realized by pushing and pulling the driven wire 26.
Since the driven wires 24, 26, 27, 28, 29 control three joints of the thumb, index finger, middle finger, ring finger and little finger, respectively, the fingers can adapt to the shape of the contacted object under the action of external force. In addition, each joint is provided with a torsion spring 37 which can keep the fingers in an unfolded and straightened state when the driven wire is not pushed or pulled.
According to the underactuated prosthetic hand based on the continuum transmission mechanism, when the program control motor rotates at different angles, the pair of driving wires driven by the same motor are pushed and pulled back and forth in opposite directions and at equal distances through gear and rack transmission. Two pairs of drive wires extend to the continuum transmission as drive inputs to the continuum transmission. The push-pull motion of the two pairs of driving wires causes the continuum to bend into an arc shape in a certain direction, and the driven wires fixed on the locking disc bend along with the arc shape, so that the driven wires also generate the push-pull motion. The six driven wires extend out of the continuous body and are used for driving five fingers of the humanoid artificial hand to bend or unfold each finger of the artificial hand, so that the function of grabbing or operating an object is realized.
While the preferred embodiments of the present invention have been illustrated and described in detail, it should be understood that various changes and modifications of the invention can be effected therein by those skilled in the art after reading the above teachings of the invention. Such equivalents are intended to fall within the scope of the claims appended hereto.