WO2017033885A1

WO2017033885A1 - Motor-driven hand

Info

Publication number: WO2017033885A1
Application number: PCT/JP2016/074365
Authority: WO
Inventors: 浩史横井; 鶴松叶; 銀来姜; 壮一郎森下; 辰太郎迫田
Original assignee: 国立大学法人電気通信大学
Priority date: 2015-08-24
Filing date: 2016-08-22
Publication date: 2017-03-02
Also published as: JPWO2017033885A1

Abstract

Provided is a compact motor-driven hand that has sufficient pinch force and achieves natural motion. The motor-driven hand is provided with: a palm part; a finger part which is rotatably connected to the palm part by means of a joint rotational shaft; a motor which drives the finger part; a first wire part which has one end wound around an output shaft of the motor and which has the other end connected to a first working point of the finger part; and a second wire part which has one end wound around the output shaft of the motor and which has the other end fixed to a second working point of the finger part. The first wire part is connected to the first working point so that the distance between the first wire part and the joint rotational shaft increases when the motor is rotated in a first direction. The second wire part is connected to the second working point so that tension increases when the motor is rotated in a second direction opposite to the first direction.

Description

Motor driven hand

The present invention relates to a motor-driven hand applied to an artificial prosthesis, a robot hand or the like.

Using a servo motor for radio control (referred to as “RC servo motor”) for an electric hand is an effective method for realizing controllability and responsiveness of the joint angle. As a driving method of the electric hand, a direct-acting driving method and a driving method using a winding mechanism are known. The direct drive system is a system in which the rotation shaft of the joint portion is rotated from the motor main shaft through a gear or a belt. This method can only generate torque proportional to the rotation angle of the motor spindle, and the gear ratio cannot be changed freely. The drive system using the winding mechanism moves the finger using a wire pulling mechanism such as a winch. It is a method. This method can realize a more natural movement as compared with the direct-acting driving method. A robot hand has been proposed in which a plurality of phalanx parts separated from each other are connected with wires, and a plurality of adjacent fingers are moved in conjunction with each other, and a driving force is concentrated on one finger from a plurality of driving parts. (For example, refer to Patent Document 1).

However, in the conventional winding mechanism, the tow wire gets entangled with the motor spindle and causes problems such as biting the wire. For this reason, the motor is limited to a single-rotation type motor, and the problem of insufficient torque occurs. If a plurality of motors are used to supplement the driving force, the apparatus becomes large.

In recent years, myoelectric prostheses that use surface myoelectric potentials generated in muscles as a control signal in response to commands from the brain have attracted attention. In the case of myoelectric prosthetic hands, it is faster to learn from children, but it is necessary to change prosthetic hands as they grow up. Therefore, a motor drive mechanism that is inexpensive, small, and has high followability is further desired.

JP 2011-245575 A

In any drive system, the motor size is restricted if the electric hand is downsized. A small RC servo motor is inexpensive and easily available, but its output is limited and it is difficult to obtain sufficient finger joint torque. Even when the electric hand is downsized, the strength of the pinch force and natural movement are still required.

Therefore, an object is to provide a small motor-driven hand having sufficient pinch force and natural movement.

In order to solve the above problems, the motor-driven hand is
Palm (51),
A finger part (53) rotatably connected to the palm part by a joint rotation axis (21);
A motor (11) for driving the fingers;
A first wire portion having one end wound around a pulley (17) fixed to the output shaft (13) of the motor and the other end connected to a first action point (19A) of the finger portion; ,
A second wire portion having one end wrapped around the pulley and the other end connected to a second operating point (19B) of the finger;
Have
The first wire portion is connected to the first action point so that a distance between the first wire portion and the joint rotation axis is increased when the motor rotates in a first direction;
The second wire portion is connected to the second action point so that a tension increases when the motor rotates in a second direction opposite to the first direction.

The above configuration realizes a small motor-driven hand with sufficient pinch force and natural movement.

It is the schematic of the motor drive hand of 1st Embodiment. It is a figure which shows the modification of 1st Embodiment. It is the schematic of the motor drive hand of 2nd Embodiment. It is a structural example of the guide coil lever used with the motor drive hand of FIG. It is a figure which shows the state which the hand of the motor drive hand of FIG. 3 closed. It is a figure which shows the modification of 2nd Embodiment. It is the schematic of the motor drive hand of 3rd Embodiment. It is a figure explaining operation | movement of the automatic adjustment tensioner used with the motor drive hand of FIG. It is a figure explaining operation | movement of the automatic adjustment tensioner used with the motor drive hand of FIG. It is the schematic of the motor drive hand of 4th Embodiment. It is a figure which shows an example of the motor current detection circuit used by embodiment. It is a figure which shows the example of the feedback control by motor current detection. It is a figure which shows the effect of the booster mechanism of the motor drive hand of embodiment. It is a mimetic diagram when rotating a MP joint with a motor drive hand of composition of an embodiment. It is a figure which shows the relationship between angle (theta) 3 of FIG. 14, and pinch force. It is the schematic of the motor drive hand of 5th Embodiment. It is the schematic of the chain wheel used in FIG. It is a figure which shows the modification of a pulley. It is a figure which shows the pulling direction of the wire at the time of pulley rotation.

In the embodiment, in the motor-driven hand, (1) a booster mechanism that obtains a large torque with a small general-purpose motor, and (2) a configuration in which the gear ratio between the motor output shaft and the rotation shaft to be driven is variable are realized. . By the booster mechanism (1), a small electric hand having a sufficient pinch force can be realized at low cost. The variable speed ratio variable configuration (2) enables more natural and stable movement.

A specific configuration will be described below with reference to the drawings.
<First Embodiment>
FIG. 1 is a schematic view of a motor-driven hand 1A according to the first embodiment. 1A is a side view seen from the thumb side when the palm of the motor-driven hand is front, and FIG. 1B is a cross-sectional view taken along line AA ′ of FIG. In the first embodiment, a small general-purpose servo motor and a wire winding mechanism are used to increase the torque by changing the distance between the rotating shaft to be driven and the wire, thereby improving the pinch force of the motor driving hand 1A. . Although the details will be described later, since the gear ratio between the output shaft of the motor and the rotation shaft to be driven becomes variable, for example, as the hand of the motor drive hand 1A closes in order to grasp an object, the movement becomes slower. Can be.

The motor drive hand 1 A includes a motor 12 that drives the thumb 52 and a motor 11 that drives the index finger 53. The

motors

11 and 12 are both small general-purpose RC servomotors. The driving force of the motor 11 is transmitted to the index finger 53 by a wire. The driving force of the motor 12 is transmitted to the thumb 52 via a pole (crank arm) 18 having one end fixed to the main shaft of the motor 12.

The five fingers including the thumb 52 and the index finger 53 are connected to the palm 51. Of these, the index finger 53 and the four fingers (not shown), the middle finger, the ring finger, and the little finger, are connected in common to the palm 51 through a metacarpophalangeal (MP) joint rotation shaft 21 at the base of the finger so as to move integrally. ing. It is good also as a structure which arrange | positions the potentiometer 23 coaxial with MP joint rotating shaft 21 inside the motor drive hand 1A, and detects the rotation angle of MP joint rotating shaft 21. FIG.

A bearing 14 and a pulley 17 are disposed coaxially with the output shaft 13 of the motor 11, and a wire A and a wire B are wound around the pulley 17. The pulley 17 is fixed to the output shaft 13 of the motor 11 and rotates around the central axis C. As the motor 11 rotates, the wire A and the wire B are wound and unwound on the pulley 17. A cylinder housing 15 for guiding the wires may be provided so that the wires A and B do not come off the pulley 17.

One end of the wire A arranged on the palm side is fixed to the action point 19A of the index finger 53, and the other end is wound around the pulley 17 in a clockwise direction. As a feature of FIG. 1, the wire A has an action point 19A so that the distance R between the wire A and the MP joint rotation shaft 21 increases as the motor-driven hand 1A moves in the direction of closing the hand and grasping an object. It is connected to the. In the example of FIG. 1, the action point 19A is set in the vicinity of the second joint 53P that hits the middle of the index finger 53, but an appropriate force that can transmit the force from the motor 11 to the index finger 53 and move it effectively. A point can be selected as the point of action 19A. The action point 19A is preferably located on the palm side with respect to a straight line connecting the center of the output shaft 13 and the center of the MP joint rotation shaft 21.

One end of the wire B arranged on the back side (back side) of the hand is fixed to the action point 19B near the back side of the second joint 53P of the index finger 53, and the other end is wound around the pulley 17 in the counterclockwise direction. It has been. The wire B is connected to the action point 19B so that the rotational force of the motor 11 is effectively transmitted to the index finger 53 and the tension of the wire B is appropriately maintained while the motor drive hand 1A is operating. The action point 19 B is preferably located on the back side of the hand with respect to a straight line connecting the center of the output shaft 13 and the center of the MP joint rotation shaft 21.

The wire A and the wire B may be two independent wires or may be wound around the pulley 17 so as not to idle one wire (see FIG. 1B), and one end may be the wire A and the other end may be the wire B. . That is, regardless of the number of wires, a portion corresponding to wire A having one end fixed to the action point 19A and the other end wound around the pulley 17, and one end fixed to the action point 19B and the other end wound around the pulley 17. It is sufficient if there is a portion corresponding to the attached wire B.

In the conventional winding mechanism, the rotation of the motor 11 is transmitted to the MP joint rotation shaft 21 by directly winding one end side of the wires A and B around the MP joint rotation shaft 21. In such a conventional winding mechanism, the output level of the motor must be increased in order to increase the torque, but the output of the small general-purpose RC servo motor has a limit.

On the other hand, in the configuration of FIG. 1, one end side of the wire A moves to the action point 19A of the index finger 53 so that as the index finger 53 closes, the wire A passes through a position away from the MP joint rotation shaft 21 in the palm direction. It is connected. When the output shaft 13 of the motor 11 rotates clockwise in FIG. 1A, the wire A is wound around the pulley 17 and the index finger 53 is pulled downward in the figure. In accordance with the movement of the index finger 53 closing, the action point 19A also moves downward in the figure. As a result, the moment increases because the wire A moves away from the MP joint rotation shaft 21. Further, the rotation of the MP joint rotation shaft 21 causes the middle finger, the ring finger, and the little finger (not shown) to move in the same direction in conjunction with the index finger 53. At this time, the wire B is unwound from the pulley 17.

If the output level of the motor 11 is constant, the distance (moment arm) R from the axis of the MP joint rotation shaft 21 to the wire A is greater than the distance from the axis of the output shaft 13 of the motor 11 to the wire A. The torque increases. That is, a greater effect can be obtained with a small force.

In FIG. 1, as the hand is closed, the action point 19A moves downward in the figure, and the wire A moves away from the MP joint rotation shaft 21 and the moment arm R becomes larger. As compared with, torque, that is, pinch force can be increased.

The closer the index finger 53 is to the thumb 52, the greater the distance R between the MP joint rotation shaft 21 and the wire A and the greater the torque. Torque is maximized when the thumb 52 touches the tip of the index finger 53.

The output of the motor 11 is represented by the product of torque and angular velocity. When the motor output is constant, when the torque increases, the angular velocity of the MP joint rotation shaft 21 decreases and the reduction ratio increases. That is, the moving speed of the index finger 53 becomes slower as the index finger 53 moves in the direction of pinching and the pinch force increases. This action is closer to the movement of the human hand and is advantageous when pinching small and fragile things with care and sufficient pinch force.

When releasing the finger, the output shaft 13 of the motor 11 rotates counterclockwise. The wire B is wound around the pulley 17 and the index finger 53 moves upward in the drawing. The MP joint rotation shaft 21 also rotates counterclockwise, and the four fingers commonly connected to the palm 51 move in a direction away from the thumb 52. At this time, the wire A is unwound from the pulley 17, but the wire A passes through a position away from the MP joint rotation shaft 21, so that the entanglement with the MP joint rotation shaft 21 does not occur.

Note that the rotation of the motor 11 may be feedback controlled in accordance with the rotation angle of the MP joint rotation shaft 21 detected by the potentiometer 23.

1 can increase torque while using a small general-purpose motor, so that even a small myoelectric prosthetic hand for children can have a sufficient pinch force. In addition, since a general-purpose motor and a simple mechanism are used, the cost for producing a prosthetic hand can be greatly reduced. Moreover, the entanglement of the wire can be suppressed and the output shaft 13 of the motor 11 can be rotated one or more times. Although an example has been shown in which the index finger 53 and four fingers of middle finger, ring finger, and little finger (not shown) are commonly connected to the palm 51 by the MP joint rotation shaft 21, the four fingers may be configured to move apart. . In that case, the above mechanism may be provided for each of the four fingers.

FIG. 2 is a modification of FIG. In FIG. 2, three wires A, B, and C and a spring structure 20 are used. The spring structure 20 absorbs the tension of the wire when the MP joint rotation shaft 21 rotates to reduce the resistance. As shown in FIG. 2B, the spring structure 20 includes a pair of washers (or spring washers) 36 and 37 and a compression spring 31 fixed between the

washers

36 and 37.

1, one end of the wire A is connected to the palm-side action point 19A in the vicinity of the second joint 53P of the index finger 53, and the other end is wound clockwise around the pulley 17 (see FIG. 1B). It has been. One end of the wire B is wound around the pulley 17 counterclockwise, and the other end is fixed to the washer 37 of the spring structure 20. One end of the wire C is connected to the washer 36 of the spring structure 20, and the other end is fixed to the acting point 19 B on the back side in the vicinity of the second joint 53 P of the index finger 53. Since the wire B and the wire C are inserted and guided through the compression spring 31, the compression spring 31 may be referred to as a “guide coil”. The wire A and the wire B may be two independent wires or may be wound around the pulley 17 so as not to idle one wire (see FIG. 1B), and one end may be the wire A and the other end may be the wire B. This is the same as FIG. That is, it is only necessary to have a portion corresponding to the wire A and a portion corresponding to the wire B regardless of the number of wires.

As in the case of closing the hand, the distance R (moment arm) between the wire A and the MP joint rotation shaft 21 increases as the index finger 53 bends toward the lower side of the figure, as in FIG. In the example of FIG. 2, the wires B and C are connected to the spring structure 20 to adjust the lengths of the wires B and C to maintain the tension. Thereby, winding and unwinding of the wire B can be performed smoothly. Further, by providing the spring structure 20, the compression spring 31 contracts when tension is generated in the wire, and the compression spring 31 extends when the tension of the wire is released. Biting into the pulley 17 can be prevented.

Although FIG. 2 shows an example in which the spring structure 20 is provided on the wire B side, the spring structure 20 may be on the wire A side, or may be on both the wire B side and the wire A side. Although a structure using a compression spring and a washer is shown as the spring structure 20, a structure in which the wire B and the wire C are connected to both ends of the tension spring may be used.
Second Embodiment
FIG. 3 is a schematic view of a motor-driven hand 1C according to the second embodiment. The same components as those in FIG. 1 are denoted by the same reference numerals, and redundant description is omitted.

The motor drive hand 1 C has a wire A, a wire B, a wire C, and a guide coil lever 30. The guide coil lever 30 has a function of adjusting the distance R between the wire C and the MP joint rotation shaft 21, that is, the moment arm, while adjusting the lengths of the wires A and C. The guide coil lever 30 realizes a torque-sensitive boosting mechanism, and the angular velocity of the MP joint rotation shaft 21 can be changed more effectively.

The guide coil lever 30 is fixed to the palm 51, and the wire A and the wire C are guided into the compression spring 31 of the guide coil lever 30. One end of the wire A is inserted into the compression spring 31 and fixed to the washer 37 (see FIG. 4) of the spring structure 20, and the other end is wound around the pulley 17 (see FIG. 1B) clockwise. Yes. One end of the wire C is inserted into the compression spring 31 and connected to the washer 36 (see FIG. 4) of the spring structure 20, and the other end is connected to the action point 19 A of the index finger 53. Similar to the first embodiment, the wire C is connected to the action point 19A so as to pass through a position away from the MP joint rotation shaft 21. One end of the wire B is fixed to an action point 19B on the back side near the second joint 53P of the index finger 53, and the other end is wound around the pulley 17 in a counterclockwise direction. The wire A and the wire B may be two independent wires or may be wound around the pulley 17 so as not to idle one wire (see FIG. 1B), and one end may be the wire A and the other end may be the wire B. . That is, it is only necessary to have a portion corresponding to the wire A and a portion corresponding to the wire B regardless of the number of wires.

FIG. 4 shows a configuration example of the guide coil lever 30. The guide coil lever 30 includes a spring structure 20, a cross link 35 connected to the spring structure 20, and a base 38 that supports the cross link 35. The guide coil lever 30 is fixed to the palm 51 by a base 38.

The spring structure 20 has a pair of

washers

36 and 37 and a compression spring 31 fixed at both ends to the

washers

36 and 37, as in FIG. One end of one link 35 a of the cross link 35 is fixed to a washer 36, and the other end is slidably held in a groove 39 of the base 38. One end of the other link 35b is fixed to the washer 37, and the other end is slidably held in the groove 39 of the base 38.

When the motor 11 rotates in the clockwise direction and the index finger 53 moves in the direction of gripping the object, the wire A is pulled toward the motor 11 and wound around the pulley 17. Even if the wire A is wound around the pulley 17, the length of the wire C is not changed, so that the compression spring 31 contracts due to the tension of the wire A and the wire C that are pulled together. As contraction of the compression spring 31, the distal end of the link 35a and the link 35b is slid toward each other in the groove 39, the base 38 and the link 35a (or link 35b) gradually increases the angle theta from the initial angle theta ₁ formed by Become. As a result, the wire C is further away from the MP joint rotation shaft 21 and the moment arm R is increased.

FIG. 5 shows a state in which the hand is closed by the motor-driven hand 1C. In the state of FIG. 5 in which the index finger 53 is closest to the thumb 52, the torque is maximized and the pinch force is maximized. In this case, the angle formed by the base 38 and the link 35a of the guide coils lever 30 (or links 35b), the maximum angle theta _2, and the height of the cross link 35 is the highest. The wire C is farthest from the MP joint rotation axis 21 and the moment arm R is maximum. The wire B is pulled in a direction to be unwound from the pulley 17 (or the output shaft 13 of the motor 11).

When the motor 11 rotates counterclockwise and moves in the direction of opening the hand, the tension of the wire C is reduced and the wire A is unwound from the pulley 17. The compression spring 31 of the guide coil lever 30 extends to the original length, and the link 35 a and the link 35 b slide in a direction away from each other in the groove 39. The angle formed by the base 38 and the link 35a (or the link 35b) returns to the original initial angle θ ₁ (see FIG. 4), and the motor drive hand 1C returns to the state shown in FIG. The wire B is wound around the pulley 17 to increase the tension.

In the configuration of the second embodiment, it is possible to increase the torque by increasing the moment arm more effectively than in the first embodiment, and the gear ratio can be made variable efficiently. Instead of the cross link 35 of the guide coil lever 30, any member that can expand and contract, such as a pantograph or a bellows, may be used.

FIG. 6 shows a motor-driven hand 1D as a modification of the second embodiment. 6A shows a state in which the hand is opened, and FIG. 6B shows a state in which the hand is closed.

The motor-driven hand 1D has two

guide coil levers

30A and 30B that are commonly supported by the base 38. The guide coil lever 30A and the guide coil lever 30B have the same configuration as described with reference to FIGS.

In the modification shown in FIG. 6, in addition to the wires A to C, the wire D is used. One end of the wire B is wound counterclockwise around the pulley 17 or the output shaft 13 of the motor 11, and the other end is fixed to the end (washer) on the index finger 53 side of the guide coil lever 30B. One end of the wire D is fixed to the end (washer) of the guide coil lever 30B on the motor 11 side, and the other end is connected to the action point 19B of the index finger 53. Both the wire B and the wire D are inserted through the compression spring 31 and guided.

In the state where the hand of FIG. 6 (A) is opened, the height is lowest when the guide coil lever 30A is folded. In the guide coil lever 30B, the cross link 35B rises slightly due to the tension between the wire D and the wire B, and the moment arm R 'is increased.

6B, the compression spring 31 of the guide coil lever 30A is contracted by the tension of the wire A and the wire C, and the cross link 35A is raised. The wire B is unwound to reduce the tension, the cross link 35B of the guide coil lever 30B is folded to the lowest position, and the moment arm R 'is reduced.

With the configuration of FIG. 6, the length of the wire is adjusted on both sides of the index finger 53, and a more effective variable speed ratio booster mechanism is realized in both the opening and closing operations of the finger.
<Third Embodiment>
FIG. 7 is a schematic view of a motor-driven hand 1E according to the third embodiment. 7A is a side view seen from the thumb side when the palm of the motor-driven hand is the front, and FIG. 7B is a cross-sectional view taken along the line AA ′ in FIG. 7A. In the third embodiment, the self-aligning tensioner 40 is used to realize a quick movement at the start of the hand opening / closing operation and a stable wire tension. The same components as those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted.

The self-aligning tensioner 40 includes a housing 45 and a guide coil 41 and a guide coil 42 each having one end fixed to the housing 45. The housing 45 surrounds the output shaft 13 of the motor 11 and is in contact with the pulley 17 in a frictionable state.

The guide coils 41 and 42 are formed of compression springs, the wire A is inserted through the guide coil 41, one end of which is wound around the pulley 17 in the clockwise direction, and the other end is connected to the action point 19A of the index finger 53. . The wire B is inserted through the guide coil 42, one end of which is wound around the pulley 17 counterclockwise, and the other end is connected to the action point 19 B of the index finger 53. The wire A and the wire B may be two independent wires or may be wound around the pulley 17 so as not to idle one wire (see FIG. 1B), and one end may be the wire A and the other end may be the wire B. . That is, it is only necessary to have a portion corresponding to the wire A and a portion corresponding to the wire B regardless of the number of wires. The pulley 17 is fixed to the output shaft 13 of the motor 11, and the rotational force of the motor 11 is transmitted from the pulley 17 to the action points 19 A and 19 B of the index finger via the wires A and B.

The guide coil 41 is fixed starting from the intersection of the tangent drawn from the point of action 19A of the index finger 53 to the pulley 17 and the outer periphery of the housing 45 or the vicinity thereof. The guide coil 42 is fixed starting from the intersection of the tangent drawn from the point of action 19B of the index finger 53 to the pulley 17 and the outer periphery of the housing 45 or the vicinity thereof. The direction in which the guide coil 41 and the guide coil 42 extend is in a plane parallel to the rotation surface of the housing 45.

The self-aligning tensioner 40 uses the frictional force between the housing 45 and the pulley 17 to generate an acting force in the normal direction of the wire A and the wire B, thereby reducing the reduction ratio and the wire. Stabilize traction of A and B. However, almost no force is generated in the longitudinal direction of the wires A and B, and the operation of the four fingers including the index finger 53 is not limited.

8 and 9 are diagrams for explaining the operation of the self-aligning tensioner 40. FIG. FIG. 8A shows an initial state. In this state, the motor 11 is not rotating.

In FIG. 8B, when the motor 11 starts rotating and grasping, the tension of the wires A and B is still small (the load is hardly applied), and the housing 45 rotates together with the pulley 17. At this time, the guide coils 41 and 42 transmit the power of the motor 11 in the normal direction of the wire A with almost no deformation. When the motor 11 further rotates, the tension of the wire A increases due to the force in the normal direction of the wire A, and the traction force increases. The housing 45 rotates clockwise together with the output shaft 13 of the motor 11 by a static frictional force with the pulley 17. In this state, since the turning radius r is larger than the radius of the pulley 17 for the wire A, the reduction ratio is considerably small. At this time, since the rotation radius r is large and the winding speed of the wire A is high, even if the wire A is slack, it is possible to quickly remove the slack without biting into the pulley 17.

In FIG. 8C, the guide coils 41 and 42 are bent by the interaction between the wire A and the guide coil 41 and the interaction between the wire B and the guide coil 42 during the gripping operation, and the turning radius for the wire A is increased. Becomes smaller. In other words, the moment arm as seen from the output shaft 13 of the motor 11 gradually decreases, and the reduction ratio gradually increases. The housing 45 rotates in the clockwise direction together with the pulley 17 until just before the rotation of the motor 11 overcomes the static frictional force.

In FIG. 9 (A), the tension of the wire A is further increased at the end of the grasping operation. Then, the rotation of the motor 11 overcomes the static frictional force between the housing 45 and the pulley 17, the housing 45 and the pulley 17 are idle, and the housing 45 returns to its original position. In this state, the turning radius for the wire A is the radius of the pulley 17. Further, the wire B which is not tensioned is loosened.

9B, when the opening operation is started, the tension of the wire B is small, and the housing 45 rotates together with the pulley 17 counterclockwise. In this state, since the turning radius r for the wire B is large and the winding speed of the wire B is fast, the slack of the wire B is quickly absorbed.

Whether the housing 45 is interlocked with the rotation of the motor 11 is determined by the magnitude relationship between the frictional force between the pulley 17 and the tension applied to the wire A and the wire B. That is, the housing 45 rotates in the clockwise direction and the counterclockwise direction within a certain angle range according to the rotation direction of the motor 11.

In the first embodiment and the second embodiment, in the state immediately before gripping an object, that is, in the state corresponding to FIG. 9A, the torque is maximized to increase the pinch force, and the reduction ratio is increased to 4 The finger movement was controlled gently.

On the other hand, in the third embodiment, a speed reduction with respect to the target object is realized by reducing the reduction ratio in a state corresponding to FIG. Thereby, a more natural operation can be realized.
<Fourth embodiment>
FIG. 10 is a schematic view of a motor-driven hand 1F according to the fourth embodiment. In the fourth embodiment, the

guide coil levers

30A and 30B of the second embodiment and the self-aligning tensioner 40 of the third embodiment are used in combination.

FIG. 10A shows a state where the hand is open, and FIG. 10B shows a state where the hand is closed. While the gripping operation is started and the object is approached, that is, when the operation is performed with a relatively weak torque, the self-aligning tensioner 40 works effectively to realize a quick movement. At the same time, the lengths of the wire A and the wire B are adjusted by the compression springs 31 of the

guide coil levers

30A and 30B to prevent the wire A and the wire B from being entangled.

As shown in FIG. 10B, when sufficient rotational torque is required immediately before the object is pinched, the moment arm of the

guide coil levers

30A and 30B with respect to the MP joint rotation shaft 21 is enlarged and four fingers are moved. Reduce speed and move carefully.

This configuration realizes a motor-driven hand 1F having a sufficient pinch force and natural operation. Even when the guide coil lever 30B is omitted, the same effect can be obtained.

In the fourth embodiment, an example in which the second embodiment and the third embodiment are combined is shown as an example, but it is needless to say that the first to third embodiments can be arbitrarily combined.
<Prevention of overload>
FIG. 11 shows an example of a control configuration for preventing overload. A motor current detection circuit 60 is connected to the motor drive hand 1F. The motor current detection circuit 60 includes a motor controller 61 and a current sensor 62. The rotation angle of the MP joint rotation shaft 21 is detected by the potentiometer 23, and the detection result is supplied to the motor controller 61. The motor controller 61 controls the motor 11 based on the detected rotation angle so that the rotation angle of the MP joint rotation shaft 21 does not exceed a predetermined value. Further, the current sensor 62 may be connected to the motor 11 and the motor 11 may be controlled so that the current value of the motor 11 does not exceed a certain value based on the current detection result.

FIG. 12 shows an example of overload prevention control by the motor controller 61. The horizontal axis represents time, and the vertical axis represents the current flowing through the motor 11. In the operation start period A, the current value suddenly rises from zero, and the index finger 53 starts to move toward the thumb 52.

* In section B where the operation starts and approaches the object, the current output is made constant in the first half. Since the size of the target is unknown, the motor 11 moves toward the command value until the four fingers and the thumb come into contact with each other. The torque at this stage may not be so large. In the embodiment using the self-aligning tensioner 40, the movement of the four fingers in this section is expedited.

Thereafter, when the index finger 53 approaches the vicinity of the target object, the current value gradually increases. In the embodiment, the moment arm with respect to the MP joint rotation shaft 21 is large at this time, and a sufficient pinch force is ensured. However, a more accurate pinch operation may be realized by combining current control. The movement of the four fingers in this section is slow, and the operation moves to carefully grasping the object.

In the section C where the target object is grasped, the current value is controlled so as not to exceed a certain value. An excessive load is prevented from being applied to the motor 11, and the object is held with a constant force.

In addition, it may replace with the control which detects the electric current of the motor 11, and may detect and control the change of the length of the compression spring 31 of the guide coil lever 30.

FIG. 13 is a diagram showing the effect of the boost mechanism of the motor-driven hand according to the embodiment in comparison with the conventional configuration. FIG. 13A shows the pinch force in the configuration of the first embodiment, and FIG. 13B shows the pinch force in the conventional linear motion drive system. The same general-purpose RC servo motor was used, and the current value of the maximum output of the servo motor was measured using a pinch meter. From the measurement results, it can be seen that the configuration of Embodiment 1 can achieve a pinch force that is twice or more that of the direct drive system.

Since the configuration of the second embodiment can increase the moment arm more effectively than the first embodiment, it is predicted that the pinch force can be further increased under the same conditions. Further, by using at least one of the guide coil lever 30 and the self-aligning tensioner 40, a more natural movement is realized in the motor-driven hand.

FIG. 14 is a diagram for explaining the mechanism of the boost mechanism of the motor-driven hand having the configuration of the first embodiment. In FIG. 14, the point O is the rotation center of the output shaft 13 of the motor 11, the point C is the action point 19 A, and the point M is the rotation center of the MP joint rotation shaft 21. The T point is the tip of the index finger 52, and a pinch force is generated at the T point by the rotation of the motor 11. Y is a vertical base line, and θ3 is an angle formed by the MO line and the vertical base line Y. As θ3 decreases, the normal distance between point M and the wire increases, and the moment arm length increases. This corresponds to a case where the index finger 53 moves in a direction approaching the thumb 52. When θ3 increases, the normal distance between point M and the wire decreases, and the moment arm length decreases. This corresponds to a case where the index finger 53 moves in a direction away from the thumb 52.

FIG. 15 plots the pinch force as a function of θ3. The horizontal axis is the angle θ3, and the vertical axis is the magnitude of the pinch force. In this simulation, the motor drive voltage is 5 V, the distance between MCs is 26 mm, and the distance between MTs is 70 mm. θ3 and the pinch force are correlated, and as the value of θ3 decreases, the moment arm length increases and the pinch force increases. From FIG. 15, it is confirmed that the angle θ3 is one of the machine elements that influence the maximum pinch force of the motor-driven hand. Further, θ3 can be set in a range of at least 70 ° to 110 ° with a motor-driven hand.
<Fifth Embodiment>
FIG. 16 is a schematic view of a motor-driven hand 1G according to the fifth embodiment. In the fifth embodiment, the torque increasing operation of the first to fourth embodiments or the operation of the booster mechanism is further stabilized. In the first to fourth embodiments, by using at least one of the spring structure 20, the guide coil lever 30 (30A and / or 30B), and the self-aligning tensioner 40, the angular velocity of the MP joint rotation shaft 21 can be effectively reduced. It is changing. However, due to secular change, at least a part of the wires A, B, C, and D may be deteriorated, and bending and slipping may occur. Therefore, the ball chain 65 is used for at least a part of the wires A to D. The ball chain 65 is made of a light and strong material such as stainless steel, aluminum, carbon, and duralumin. The diameter of each ball of the ball chain 65 can be appropriately selected according to the size of the motor-driven hand 1G and required characteristics.

As an example, a stainless steel ball chain 65 having a ball diameter of 2.0 to 2.5 mm is used. One end side of the ball chain 65 is fixed to the action point 19A of the index finger 53 of the motor-driven hand 1G, and the other end is fixed to the action point 19B opposite to the action point 19A of the index finger 53.

The chain wheel 80 is used for the pulley fitted to the output shaft 13 of the motor 11 so that the motor 11 can pull the ball chain 65 and rotate the four fingers including the index finger.

FIG. 17 shows a configuration example of the chain wheel 80. FIG. 17A is an external view of the chain wheel 80, and FIG. 17B shows a gear shape formed on the chain wheel 80. The chain wheel 80 is designed to suit the size and characteristics of the ball chain 65. For example, the dynamic torque τ of the motor 11 when the input voltage is 5 V is 529 N · mm. When the magnitude of the force pulling the ball chain 65 fixed to the action point 19A is F and the length of the normal to the action line of the pulling force F (moment arm) is r, the dynamic torque τ is
τ = r × F × sin 90 °
It is expressed. In order to increase the force for pulling the ball chain 65 with a constant motor drive voltage, the length r of the normal from the center of the MP joint rotation shaft 21 to the ball chain 65 is decreased. When the ball diameter of the ball chain 65 is 2.3 mm, the diameter of the output shaft 13 of the motor 11, the size of the motor driving hand 1G (including the distance from the MP joint rotating shaft 21 to the tip of the index finger 53), the action point 19A From the conditions such as the position, the minimum value of the moment arm r is about 5.2 mm. That is, the maximum value of the pulling force F is 101.7N. If the yield strength of the ball chain 65 is 51N to 59N, as shown in FIG. 17 (A), the hole 82 is formed in two stages in the pulley 82 of the chain wheel 80, and the ball chain 65 is used in a double manner. Is desirable. Thereby, the pulling force F can be dispersed to prevent the ball chain 65 from being broken.

When the yield strength of the ball chain 65 is equal to or greater than the maximum value of the tensile force F, the hole 81 formed on the outer periphery of the chain wheel 80 may be formed in one step. On the contrary, when the yield strength of the ball chain 65 is smaller than the tensile force F, the pulley 82 may be provided with three or more steps (triple) holes 81.

The diameter of the hole 81 of the chain wheel 80 is set according to the ball diameter of the ball chain 65 to be used. In the example of FIG. 17, for example, twelve holes 81 are formed per step along the outer periphery of the pulley body 62 having a diameter of about 10 mm. The cross-sectional shape of the hole 81 may take any shape such as a semicircular shape (hemispherical groove), a V shape (conical groove), or a U shape (a combination of a cylindrical groove and a hemispherical groove). By engaging each ball of the ball chain 65 with the hole 81 of the pulley 82, slipping and bending can be reduced, and the operation of the motor-driven hand 1G can be stabilized.

The design specifications in FIG. 17 are merely examples, and can be appropriately changed according to the age, body shape, etc. of the wearer of the motor-driven hand 1G. 16 and 17 may be combined with at least one of the guide coil lever 30 and the self-aligning tensioner 40. As described above, the human finger moves quickly when the resistance is low, and generates a large force when the resistance is high. By using the guide coil lever 30, the moment arm length between the MP joint rotation shaft 21 and the ball chain 65 is adjusted to enable an operation closer to a human finger. Further, by using the self-aligning tensioner 40, it is possible to quickly absorb the deflection of the chain wheel 80 and the ball chain 65 when performing an operation of grasping and releasing an object.
<Modified example of pulley>
18 and 19 are diagrams showing a modification of the pulley used in the first to fifth embodiments. The pulley 70 includes a first cylinder 71 and a second cylinder 72 having different diameters. The other end of the wire A, one end of which is fixed to the action point 19A (see FIG. 1 and the like), is fixed and wound around the first cylinder 71 having a small diameter. The other end of the wire B, one end of which is fixed to the action point 19B (see FIG. 1, etc.), is fixed and wound around the second cylinder 72 having a large diameter. The winding directions of the wire A and the wire B are opposite to each other.

The first cylinder 71 having a small diameter has a smaller winding amount per unit time than the second cylinder 72, and moves the index finger 53 of the motor-driven hand slowly. The second cylinder 72 has a larger winding amount per unit time than the first cylinder, and moves the index finger 53 of the motor-driven hand faster.

18 and 19, when the pulley 70 rotates in the direction of the arrow R together with the output shaft 13, the wire A is wound in the direction of the arrow A, and the index finger 53 moves in a direction approaching the thumb 52. At this time, the wire B is unwound in the direction of the arrow B. As the index finger 53 approaches the thumb 52, the normal length R (see FIG. 1) from the MP joint rotation shaft 21 to the force action line, or the moment arm increases, and the rotation of the first cylinder 71 becomes dominant. . Thereby, the movement of the index finger 53 becomes slow. When the index finger 53 moves away from the thumb 52, the pulley 70 rotates in the direction opposite to the arrow R. As the moment arm becomes smaller, the finger moves faster and the rotation of the second cylinder 72 becomes dominant.

18 and 19 may be combined with at least one of the spring structure 20, the guide coil lever 30, and the self-aligning tensioner 40. By using the spring structure 20, the bending of the wire can be reduced. By using the guide coil lever 30, the size of the moment arm can be effectively changed. By combining with the self-aligning tensioner 40, the slack of the wire can be absorbed and the tension can be maintained appropriately. Further, a hole 81 as in the fifth embodiment may be formed in each of the first cylinder 71 and the second cylinder 72, and the ball chain 61 may be used for at least one of the wire A and the wire B. As a result, the opening / closing operation of the motor-driven hand becomes more stable.

The motor-driven hands 1A to 1G described in the embodiment and any combination thereof are applied to a myoelectric prosthetic hand and a robot hand, and are particularly expected to be applied to a myoelectric prosthetic hand and a small robot hand for children.

This application is based on Patent Application No. 2015-165296 filed with the Japan Patent Office on August 24, 2015, and includes all the contents thereof.

1A to 1G

Motor drive hand

11, 12 Motor 13 Output shaft 14

Bearing

17, 70

Pulley

19A, 19B Action point 21 MP joint rotation shaft 30 Guide coil lever (wire adjustment unit)
31 Compression springs 36, 37 Washers 35 Cross links (expandable members)
40 Self-aligning

tensioner

41, 42 Guide coil 45 Housing 51 Palm part 52 Thumb (finger part)
53 Index finger (finger)
65 Ball chain 71 First cylinder 72 Second cylinder 80 Chain wheel 81 Hole 82 Pulley body

Claims

The palm,
A finger part rotatably connected to the palm part by a joint rotation axis;
A motor for driving the fingers;
A first wire portion having one end wound around a pulley fixed to the output shaft of the motor and the other end connected to a first action point of the finger;
A second wire portion having one end wrapped around the pulley and the other end connected to a second action point of the finger;
Have
The first wire portion is connected to the first action point so that a distance between the first wire portion and the joint rotation axis is increased when the motor rotates in a first direction;
The motor is characterized in that the second wire portion is connected to the second action point so that a tension increases when the motor rotates in a second direction opposite to the first direction. Driving hand.
A spring structure for relaxing loosening of the wire is provided between the pulley and the first action point, or at least one of the pulley and the second action point;
The motor-driven hand according to claim 1.
A booster mechanism disposed between the pulley and the first operating point;
The first wire portion has one end wound around the pulley and the other end connected to one end of the boost mechanism, and one end connected to the other end of the boost mechanism. A second portion connected and connected at the other end to the first operating point,
The motor-driven hand according to claim 1.
The boost mechanism is
A compression spring for guiding the first wire portion;
Elastic members connected to both ends of the compression spring;
A base that is fixed to the palm and supports the elastic member;
Have
The distance between the first wire portion and the joint rotation shaft is changed by changing the height of the expansion / contraction member according to the movement of the finger portion due to the rotation of the motor. The motor-driven hand described.
The elastic member is a cross link or a pantograph,
The motor-driven hand according to claim 4, wherein the cross link or the pantograph is slidably supported in a groove formed in the base.
An aligning tensioner which is rotatably installed with respect to the pulley and has a first guide coil and a second guide coil;
Further comprising
The first wire portion is guided by the first guide coil and wound around the pulley, and the second wire portion is guided by the second guide coil and wound around the pulley. The motor-driven hand according to any one of claims 1 to 5, wherein:
The aligning tensioner has a housing disposed coaxially with the pulley,
One end of the first guide coil and one end of the second guide coil are each fixed to the housing,
7. The housing according to claim 6, wherein the housing is installed so as to follow the rotation of the pulley by a predetermined frictional force, and can rotate freely with respect to the pulley when a force larger than the frictional force is applied. Motor driven hand.
At least a portion of the first wire portion and the second wire portion is a ball chain;
A hole having a size corresponding to the ball diameter of the ball chain is formed on the outer periphery of the pulley.
The motor-driven hand according to claim 1, wherein the ball chain is engaged with the hole.
The pulley has a first cylinder having a first diameter and a second cylinder having a second diameter larger than the first diameter;
The motor-driven hand according to any one of claims 1 to 8, wherein the first wire portion is wound around the first cylinder, and the second wire portion is wound around the second cylinder.
The motor-driven hand according to claim 9, wherein winding directions of the first wire portion and the second wire portion are opposite to each other.