JPH0152156B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Technical Field of the Invention The present invention relates to a force applying device, particularly when gripping an object to be manipulated in an article processing device such as an industrial robot for assembling precision machinery.
The present invention relates to a force applying device that can apply a minute force to an article.

(B) Conventional technology and problems As the so-called F/A (Factory Automation) and FMS (Flexible Manufacturing System) progress, robots are increasingly being introduced into production processes. on the other hand,
For example, semiconductor processes that require fine work, assembly of magnetic heads for peripheral equipment, or soft foods.
Automation of materials inspection, etc. is lagging far behind. This is due to the fact that, although it is thought that automation will be promoted by highly intelligent robots, there are currently no robots that can control minute forces on the order of grams, for example. In other words, automation of micro work that handles micro parts, etc.
This has been difficult to achieve because there are no robots capable of micro-force control.

For example, in the conventional method, when controlling the gripping force, a pressure sensor is provided at the gripping portion of the fingers, and the gripping force is controlled by the width of the fingers. In this case, it is necessary to switch between the position control mode and the force control mode in accordance with the work timing, and not only is the timing of switching difficult, but the difference in gain between the position control mode and the force control mode at the time of switching is Since it is affected by the moving speed of the fingers during gripping and is not constant, vibrations and collisions will occur when it comes into contact with the gripped object. Therefore, it is nearly impossible to control the gripping force within a small range. Furthermore, two control circuits and two sensors are required for position control and force control, resulting in high costs.

(C) Object and Structure of the Invention The present invention aims to solve the above-mentioned problems, and even with the specified gripping force, when gripping an object to be manipulated or pushing the object, there is a slight impact on the object. The object of the present invention is to provide a force applying device that is capable of applying a force. Therefore, the force applying device of the present invention is a force applying device that receives a force applying command to an article and applies the commanded force to the article,
A movable part that applies a force to an article has a force generating means supported by an elastic body whose other end is fixed to a base, and a force generating means configured to cancel the reaction force of the elastic body generated when the elastic body is displaced. and a reaction force canceling means for driving the force generating means.

The movable part of the force generating means that applies force to the article is supported by an elastic body, and when the force is applied to the article, the reaction force of the elastic body is generated due to the displacement of the elastic body. Since the force generating means is driven so that the reaction force is canceled by the reaction force canceling means,
For example, the spring constant of a spring used as an elastic body acts as if it had become extremely small, and the influence of position errors is almost eliminated.
It becomes possible to apply a minute force to the object to be manipulated.

(D) Embodiment of the Invention FIG. 1 is a sectional view of a robot hand showing an embodiment of the present invention, and FIG. 2 is a control block diagram of the embodiment shown in FIG.

In the figure, 1 is a robot arm, 2 is a hand base, 3-1 and 3-2 are a pair of fingers, 4 is a parallel spring, 5 is a strain gauge, 6 is a voice coil motor, 7 is a permanent magnet, and 8 9 is a coil, 9 is a yoke, 10 is a stopper, and 11 is an object to be gripped.

The finger parts 3-1 and 3-2 are formed to face the hand base 2 attached to the robot arm 1, and
In particular, the finger portion 3-1 is formed of a rigid body, and the other finger portion 3-1 is made of a rigid body.
-2 is formed such that its tip portion is supported by a pair of parallel springs 4. The parallel spring 4 exerts a restoring force against relative displacement of the tip portion of the finger portion 3-2 in the illustrated direction. parallel spring 4
A strain gauge 5 is attached to the inside of each of the fingers, and the strain gauge 5 makes it possible to detect the displacement of the tip of the finger 3-2 relative to the hand base 2 from the deflection of the parallel spring 4. .

The voice coil motor 6 is a yoke 9 to which a permanent magnet 7 is attached, and consists of a portion fixed to the hand base 2 and a coil 8 portion attached to the tip of the finger portion 3-2. By applying and controlling current to the coil 8, the fingers can be opened and closed in the directions shown. As a result, the object to be gripped 11 is gripped or released.
Note that the parallel spring 4 made up of two plate-shaped spring bodies has low rigidity only in the moving direction and relatively high rigidity in other directions, so the present invention is not limited to this. However, it is suitable as a movement guide in one direction using a spring.

In the robot hand shown in FIG. 1, the gripping force is not controlled by the opening width of the hand, but by controlling the force generated by the voice coil motor 6, that is, by controlling the current supplied. That is, a sensor for detecting displacement, such as the strain gauge 5, is used as a sensor, and control is performed as follows.

In the control of this embodiment, in particular, the signal from the strain gauge 5, which is a displacement sensor, is fed back positively so as to cancel the spring force of the parallel spring 4, and the gripping force command value is determined by the force generated by the voice coil motor 6. I am trying to calculate it from.

Here, the generated force is as follows: Generated force=Bli However, B: air gap magnetic flux density of the voice coil motor l: number of windings of the voice coil motor i: energizing current of the voice coil motor. Regarding this generated force, unlike in the case of a rotary motor, the air gap magnetic flux density B of the voice coil motor 6 is constant within the operating range, and the generated force has high linearity with respect to the current, so the calculated value and the actual value are well matched. Match.

A control block diagram of the robot hand shown in FIG. 1 is shown in FIG. The current, speed, and displacement are each fed back. Note that in the following description, parameters are defined as follows.

e: Voltage between terminals of voice coil motor R: Resistance between terminals of voice coil motor i: Current between terminals of voice coil motor L: Inductance between terminals of voice coil motor B: Air gap magnetic flux density of voice coil motor l: Voice coil motor Number of coil turns M: Mass of moving part D: Viscous damping coefficient k: Spring constant of parallel spring x: Displacement of parallel spring O _c : Open loop gain of operational amplifier I _c : Feedback gain of current V _c : Speed of Feedback gain P _c : Displacement feedback gain S: Laplace operator R(S): Gripping command X(S): Displacement F(S): Gripping force Here, the characteristics of the voice coil motor 6 are as follows: e=Ri+Ldi/dt+Blx 〓 ……(1) Bli＝Mx¨＋Dx〓＋kx ……(2)

In Fig. 2, the transfer function from the gripping command R(S) to the displacement X(S) of the ^parallel spring is found as follows: _c O
_c +RM+LD)S ² +((I _c D/Bl+V _c )O _c +Bl +kL+RD/Bl)S+(kI _c /Bl−P _c )O _c +kR/Bl
}...(3) becomes. Therefore, the steady-state value of X(S) when R(S) changes stepwise is: lim ^a → ⁰ SX(S) = 1/(kIc/Bl−P _c )O _c +kR/Bl...
(4) becomes. That is, this control system is expressed by the above equation (4) and has a steady position error.
Here, since O _c is generally a very large value of 80 db to 100 db, the steady position error is almost zero. This is not preferable for controlling the robot hand. If the width of the object to be held is not accurately known, the voice coil motor 6 will act as a spring with a spring constant expressed by equation (4) in the low frequency band due to an error in the width indication, and a large force will be generated. As a result, it becomes impossible to control the gripping force.

Therefore, in this embodiment, a method is adopted in which the gain of the position error is made as low as possible within the range in which the control system is stable, and the generated force due to the position error is suppressed.
That is, as is clear from equation (4), since the displacement is fed back positively (the sign of P _c is negative), the above method can be realized. From equation (4), P _c may be adjusted so that P _c k /Bl (R / O _c + I _c ) ... (5). In this state, as is clear from equation (3) above, it appears as if the spring constant of the parallel spring of the finger has become extremely small. Therefore, the restoring force by the spring becomes very small with respect to positional errors. In experiments, we were able to reduce the spring constant to an apparent 0.1 [g/mm]. As a result, when the opening/closing stroke of the hand is ±2 [mm], the maximum force generated on the gripped object is ±2 [mm].
This is a very small value of 0.2 [g].

If only the gripping force component is input as R(S) in this state, the robot hand can grip the object with a force error within ±0.2 [g] regardless of the width of the object. In addition, if a gripping command with the opposite sign is given to the gripping command, the stopper can be moved with a constant force.
0 and becomes open.

As explained above, the robot hand of this embodiment can freely grasp the object 11 with a force ranging from a minute force to a large force, without affecting the width of the object 11, with a simple gripping force command. can.
In addition, the sensor is only a displacement sensor such as the strain gauge 5, and the structure is simple, so
Low cost. Note that by controlling the gripping force using the signal from the displacement sensor, it is also possible to measure the width of the gripped object regardless of whether it is soft or hard.

By configuring the robot hand shown in FIG. 1, particularly the voice coil motor 6, as shown in FIG. 3, the robot hand can be made smaller and lighter. FIG. 3 shows an exploded perspective view of an embodiment of the article processing apparatus according to the present invention.

In the figure, numerals 2 to 5 correspond to those in FIG. 1, and 7-
1 and 7-2 are permanent magnets, which correspond to the permanent magnet 7 shown in FIG. 1, and 8' is a coil,
Corresponding to the coil 8 shown in FIG. 1, 9-1, 9
-2 is a yoke corresponding to the yoke 9 shown in FIG. 1, 14 is a terminal, 15 is a bobbin, 16 is a spacer, and 17 and 18 are screw holes.

If a cylindrical voice coil motor 6 as shown in FIG. 1 is used as the actuator for opening and closing the finger parts 3-1 and 3-2, the voice coil motor 6 must be installed in the opening and closing direction of the hand. It won't happen. Therefore, in this case, the hand should be small/
Difficult to reduce weight. Therefore, as shown in FIG. 3, a flat coil 8' and a permanent magnet 7-1,
7-2 is attached to the side of the hand using a voice coil motor.

Yoke 9-1 with permanent magnet 7-1 attached
The spacer 16 made of a non-magnetic material such as aluminum, and the yoke 9-2 to which the permanent magnet 7-2 is attached are screwed into the screw hole 18 of the hand base 2. On the other hand, the flat coil 8' formed on the bobbin 15 is fixed to the tip side of the finger portion 3-2, which is moved by the parallel spring 4 for opening and closing. As a result, when the terminal 14 is energized, the action of the coil 8' and the magnetic circuit causes the finger portion 3-2 to
The tip of the handle receives force in the direction of opening and closing the hand. Note that voice coil motors as shown in FIG. 3 may be used on both sides of the hand.

By realizing the voice coil motor using a flat coil as described above, space is saved and the hand can be made smaller and lighter.

Incidentally, conventionally, it has been customary to use plastic such as resin as the bobbin of a general voice coil motor. However, when plastic or the like is used as the bobbin, there are problems such as low thermal conductivity and softening due to heat generated by the coil. Therefore,
In order to solve this drawback, the bobbin 15 shown in FIG.
is made of aluminum. Aluminum material is lightweight, has high thermal conductivity, and is also highly rigid. Furthermore, since aluminum material has high electrical conductivity, it has the advantage of inducing large eddy currents when moving in a magnetic field. The induction of this eddy current serves to increase the viscous damping coefficient of the voice coil motor. Therefore, the stability of the control system can be improved. However, it is necessary to ensure sufficient insulation between the coil 8' and the bobbin 15. Therefore,
If the bobbin 15 is anodized, the coil 8'
Good insulation can be obtained without affecting the number of turns.

As a result of the above, a bobbin that is lightweight, has high rigidity, high thermal conductivity, and high damping can be realized at low cost. Note that the color of the alumite is preferably black. The bobbin 15, which has been treated with black alumite, has a groove formed to match the outer shape of the coil in order to prevent the coil from being scratched.

FIG. 4 shows a diagram for explaining an embodiment of attachment of the magnet plate shown in FIG. 3. In the figure, symbols 7-1 or 7-2 and 9-1 or 9-2
corresponds to FIG. 3, and 19 represents a magnet fixing plate.

In the voice coil motor of the robot hand shown in Figure 3, permanent magnets 7-
For example, rare earth cobalt magnets are used as the magnets 1 and 7-2. This magnet has a high holding power, so
Rather than magnetizing the magnetic circuit after assembling it, a magnetized one is generally installed. In this case, if an attempt is made to arrange the magnets as shown in FIG. 3, the magnets will attract or repel each other, and a great deal of time will be wasted in assembling and adhering the magnets.

Therefore, as shown in FIG. 4, for example, by using a magnet fixing plate 19, the permanent magnets 7-1, 7
-2 is made easy to locate. That is, the magnet fixing plate 19 is provided with square holes that are slightly larger than the outer dimensions of the permanent magnets 7-1 and 7-2, and by fitting the permanent magnets 7-1 and 7-2 into these holes, the yoke 9 The magnet position is determined on the -1 and 9-2 planes. The magnet fixing plate 19 may be made of any non-magnetic material. Also,
The thickness of the magnet fixing plate 19 should be approximately the same as the thickness of the magnet, taking into account protrusion due to attraction/repulsion of the magnet.
A little thinner is better.

By using the magnet fixing plate 19 as described above, the permanent magnets 7-1 and 7-2 can be easily positioned, and not only can they be manufactured in a short time, but also can be connected to the permanent magnets 7-1 and 7-2. Adhesion treatment with irons 9-1 and 9-2 is also unnecessary, making it possible to significantly reduce costs.

The above-mentioned robot hand as shown in FIG. 1 or 3 has a relatively simple structure when the object to be manipulated, that is, the object to be grasped, is of a substantially constant size, so that it can be operated with minimal force. Extremely useful as a controllable gripper. However, the opening/closing span of the hand is limited to about 4 mm, for example, depending on the length of the parallel spring 4, and if the size of the grasped object changes, the robot hand must be replaced accordingly. Is required.

FIG. 5 is a perspective view of an embodiment of a robot hand improved in this respect, and FIG. 6 is a control block diagram of the embodiment shown in FIG. In the figure, 3-1 and 3-2
1 is a finger portion corresponding to FIG. 1, 22 is a voice coil portion of the voice coil motor, 23 is a magnetic circuit portion of the voice coil motor, 24 is a DC motor, 25 is an angle encoder, 26 is a feed screw, and 28 is a gripping force control. 29 represents a constant current amplifier.

In this embodiment, in order to be able to grip an object with a specified gripping force without being affected by the width of the object to be gripped, a pair of finger portions 3-1 and 3-3 are provided as shown in FIG. -2 is divided into left and right. The feed screw 26 is passed below the finger portions 3-1 and 3-2, and the finger portion 3-1 of the feed screw 26
The side is, for example, a left-hand thread, and the finger portion 3-2 side is a right-hand thread. By cutting the screw in the opposite direction in this way, if the feed screw 26 rotates,
The finger portion 3-1 and the finger portion 3-2 move in opposite directions and have variable spans. Feed screw 26
is directly connected to a relatively small DC motor 24, and the rotation of the DC motor 24 provides the force for moving the fingers. The DC motor 24 is provided with an angle encoder 25, and by knowing the rotation angle of the DC motor 24 with the angle encoder 25, span control of the hand becomes possible.

The upper tip portion of the finger portion 3-2 is supported by a parallel spring as described in FIGS. 1 and 3, and includes a voice coil portion 22 attached to the upper portion of the finger portion 3-2. A voice coil motor constituted by a magnetic circuit section 23 attached to the lower part of the finger section 3-2 applies force in the opening/closing direction of the finger section. Note that the internal configuration of the voice coil motor is similar to that explained in FIG. 3, so a detailed explanation will be omitted.

In FIG. 6, the gripping force control unit 28 performs the same control as that shown in FIG. 24, and the detected value by the angle encoder 25 is fed back. That is, the voice coil motor is used to control the gripping force, and the DC motor 24 is used to control the gripping width, so that accurate gripping force can always be controlled regardless of the width of the gripped object.

If there is no voice coil motor and the gripping force is controlled only by a DC motor that performs span control, there will be a dead zone in the control system due to friction in moving parts such as the DC motor and the feed screw. For example, force control of less than several grams is nearly impossible.
In this embodiment, it is of course impossible to eliminate the span error due to the dead zone, but
Since the voice coil motor performs gripping force control as described above, force control that is not affected by span displacement is possible within a certain range; for example, if the span error is within ±2 [mm]. , accurate gripping force can be controlled.

In other words, if the width of the gripped object is, for example, ±2 [mm]
The robot hand of this embodiment can grip an object with accurate gripping force if the gripping force is applied with an accuracy within the range of 1. In particular, since there is no friction in the support system of the voice coil motor, highly accurate force control that is unaffected by disturbances caused by frictional force can be easily achieved.

The robot explained in the illustrated embodiment in FIG.
In the hand, the grip force control by the voice coil motor and the span control by the DC motor 24 are performed completely independently. In conjunction with these controls, for example, if the control of the DC motor 24 can be controlled based on the signal from the displacement sensor provided on the spring body portion of the finger portion 3-2, micro-force control with even more accuracy and quick response can be achieved. It is thought that this will become possible.

FIG. 7 is a perspective view of another embodiment of the present invention, FIG. 8 is a schematic diagram for explaining the embodiment shown in FIG. 7, and FIGS. A block diagram of the control system, Fig. 11 is a front view of an embodiment of the robot hand excluding the voice coil motor, Fig. 12 is a right side view of the robot hand shown in Fig. 11, and Fig. 13 is a view shown in Fig. 11. 14 is a front view of an embodiment in which a voice coil motor is attached to the robot hand shown in FIG. 11, and FIG. 15 is a right side view of the robot hand shown in FIG. Figure 16 is a diagram for explaining the shape of one embodiment of the finger part of the robot hand.
FIGS. 17 and 18 are diagrams for explaining the structure of an embodiment of the nut portion of the screw feeding mechanism.

In FIGS. 7 to 18, reference numerals 3-1,
3-2, 4, 5 correspond to Figure 1, 22 to 2
4 corresponds to FIG. 5, 30 is a stopper, 31 is a base, 32 is a bearing, 40 is a protrusion, 41 is a side plate, 45 is an elastic body, 46 is a nut, and 47 is a screw part in a finger part.

As can be seen from FIG. 7, etc., the robot hand of this embodiment has a similar external appearance to the robot hand of the embodiment illustrated in FIG. Finger part 3-
1 and 3-2 are provided separately, and a right-handed screw and a left-handed screw are mounted on a feed screw 26 that is carved corresponding to each finger portion 3-1, 3-2. The left and right fingers open and close as the DC motor 24, which is directly connected to the feed screw 26, rotates. A parallel spring 4 is attached to the finger portion 3-2.
A square hole is provided so that the spring surface can be configured with a strain gauge 5 as a displacement sensor. In such a configuration, the voice coil motor mounted on the finger portion 3-2 operates as the main motor, and the DC motor 24 that rotates the feed screw 26 operates as a slave. That is, when the object cannot be gripped only by the displacement of the voice coil motor, the DC motor 24 rotates to achieve the required span, thereby controlling the span to a predetermined value. Although it is not impossible to control the force with this span control alone, normally a moving mechanism such as the feed screw 26 has large friction, so there is a dead zone in the control system, and as mentioned above, it is difficult to control the force on the gram order. . That is, in order to control a force that is less than the frictional force of the moving mechanism, a sophisticated control method must be used, and a large amount of time is required for control design and adjustment.

The robot hand according to the present invention has a so-called voice coil motor that uses a parallel spring 4 as a support mechanism to apply a gripping force to the finger part 3-2, and a DC motor 24 that drives a feed screw 26 that has high friction and can be stably controlled. By adopting a hybrid actuate mechanism, micro-force control can be performed very easily. The voice coil motor has a voice coil section 22 and a magnetic circuit section 23, and has the same structure as the voice coil motor described above in FIG. 3 and the like.

Next, the micro-force control mechanism of this embodiment will be explained through the control method of the hybrid actuate mechanism. Note that the parameters used in FIGS. 9 and 10 and the following explanation are as follows.

U ₁ (S): Input to DC motor U ₂ (S): Input to voice coil motor S: Laplace operator _On , O _c : Open loop gain of logic operation element _On , D _c : Viscous damping coefficient B: Air gap magnetic flux density of voice coil motor l: Length of winding of voice coil motor L _c : Inductance of voice coil motor R _c : Resistance between terminals of voice coil motor I _c : Current feedback constant of voice coil motor V _c : Speed feedback constant of the voice coil motor P _c : Position feedback constant of the voice coil motor M _c : Mass of the moving part of the voice coil motor k : Spring constant of the parallel spring in the finger part x _c : Displacement of the parallel spring in the finger part K _n : DC motor induced voltage constant L _n : DC motor inductance R _n : DC motor terminal resistance I _n : DC motor current feedback constant V _n : DC motor speed feedback constant P _n : DC motor position feedback constant M _n : Load mass of the DC motor _minus mass of the moving part of the voice _coil motor In the example robot hand, the eighth
A strain gauge 5 attached to the parallel spring 4 shown in the figure detects the amount of displacement of the parallel spring portion. 9th
As can be seen from the block diagram of the force control system shown in the figure, in this control system, the displacement signal from the strain gauge 5 attached to the parallel spring 4 is fed back positively to the voice coil motor, and the DC motor 24
In this case, the same parallel spring displacement and speed signals as the voice coil motor are fed back negatively. That is, the present invention is characterized in that the amount of feed by the feed screw 26 and the gripping force by the fingers 3-1, 3-2 are controlled only by the amount of displacement of the parallel spring 4 without detecting the displacement of the feed screw 26. The amount of positive feedback by the displacement signal to the voice coil motor is determined in the same manner as the example explained in FIG. 2.

In such a control system, the required gripping force U ₂ (S) is applied to the voice coil motor, and the required gripping force U ₁ is applied to the DC motor.
(S) and U ₁ (S) = 0. In the voice coil motor, for example, a stopper 30 directly connected to the voice coil 22' schematically shown in FIG. is displaced inward with a constant force until it hits the stator. Then, the DC motor 24 rotates so that the displacement _xc of the parallel spring 4 becomes zero. However, as is clear from FIG. 9, no matter how much the DC motor 24 rotates, the displacement _xc of the parallel spring 4 cannot be made zero. (However, this does not apply when the acceleration generated by the DC motor 24 is extremely large.) Therefore, the DC motor 24 continues to rotate, the fingers move inward, and the span becomes the width of the object to be grasped. When the object is gripped, it hits the object to be gripped.

Then, before the hand movement system grasps the object, M _c x¨ + (M _n + M _c ) x¨ _n = −D _n x〓 _n + K _n I _n −F _r ……(6) M _c (x¨ _n +x¨ _c = −kx _c −D _c x〓 _c +BlI _c ……(7) L _n I〓 _n = −R _n I _n +E _n −K _n x〓 _n ……(8) L _c I〓 _c = −R _c I _c +E _c −Blx〓 _c ...(9) However, from the moment of contact with the object to be grasped,
It will look like this:

M _n x¨ _c = −kx _c +BlI _c +K _n I _n −F _r −(D _n +D _c )x〓 _c
…(10) L _n I〓 _n =−R _n I _n +E _n −K _n x〓 _c …(11) L _c I〓 _c =−R _c I _c +E _c −Blx〓 _c …(12 ) If the contact point is set to an initial value (time t=0), the control system becomes as shown in FIG. The transfer function of this control system can be expressed as follows. Here, it is assumed that the open loop gain of the operational amplifier is _n = _c ≒∞.

K _n /I _n U ₁ (S) + K _c /I _c U ₂ (S) = {M _n S ² + (K _n /I _n
V _n +K _c /I _c V _c )S + K _n /I _n P _n -K _c /I _c P _c +k}X(S) + F _r (S) ...(13) Also, U ₁ (S) = 0 Therefore, the target input U ₂ (S), friction force F _r (S) and output X (S)
The following relationship holds true between them.

X(S)=K _c /I _c・1/M _n S ² + (K _n /I _n V _n +K _c /I _c V _c
)S+K _n /I _n P _n -K _c /I _c P _c +k・U ₂ (S) -1/M _n S ² + (K _n /I _n V _n +K _c /I _c V _c )S+K _n / I _n P _n
−K _c /I _c P _c +k·F _r (S) (14) The following is clear from this equation (14).

This control system is observable and controllable.

(However, in the range of K _n /I _n P _n -K _c /I _c P _c +k>0) A steady position error occurs with respect to the step input.

The presence of friction causes steady-state position errors.

Two actuators can be controlled as one hybrid motor.

That is, the characteristics of equation (14) represent the same characteristics as in the case of a single DC motor that does not use a voice coil motor, and no improvement is seen in terms of position control. However, the relationship between the grip force F(S) generated by the fingers and the input is F(S) = K _c /I _c U ₂ (S) - K _c /I _c (V _c S - P _c + I _{c / K c k )} If the feedback constant V _c of the speed being controlled is set to zero, F(S) can be controlled regardless of displacement and without time delay or steady-state error. In other words, accurate gripping force control at the same time as contact,
This is possible regardless of the steady-state position error of the DC motor 24. Furthermore, even if V _c is set to zero, the damping of the system does not become zero due to the viscosity control (very small value) of the voice coil motor, and the system remains stable.

In order to establish the above equation (16), the linearity of the displacement of the sensor that detects the spring constant k is a problem.
has a structure in which the rigidity can be weakened in only one direction, and even the strain gauge 5 can accurately detect the spring constant k without being affected by torsion or the like.

As described above, the robot hand of this embodiment is independent of disturbances such as friction, and moreover, it is possible to accurately control from a minute force to a large force. In addition, even if there is a slight error, the object to be gripped is always gripped in a posture where the displacement of the spring is almost zero, so for example, the feed screw 26 and the final screw part of the finger part do not get twisted, and the life of the screw is long. The durability of the moving mechanism is also excellent.

Furthermore, as is clear from the above equations (14) and (16), the response time of the robot hand is determined by the position feedback constant P _n of the DC motor. Generally, as P _n becomes larger, the control system becomes unstable;
It becomes an oscillating state. At this time, the frictional force acts to dampen this oscillation. In this force control system, position errors due to friction do not affect the gripping force as described above, so the frictional force of the system can be increased.
By appropriately increasing the frictional force of the system, the rapid response of the system can be improved. In particular, if a feed screw mechanism is used as the movement mechanism, the movement by the screw has relatively large friction, so it is useful for improving the rapid response of the system.

The front view, side view, etc. of the robot hand shown in FIG. 7 are as shown in FIGS. 11 to 15. Here, FIGS. 11 to 13 show the voice coil motor with the voice coil motor removed, and FIGS. 14 and 15 show the voice coil motor attached. In particular, finger portion 3-
2 is provided with a protrusion 40 as shown in FIGS. 11 and 14. This protrusion 40
When the hand is moved open by the feed screw 26, it finally comes into contact with a side plate 41 fixed to the base 31.

In conventional robot hands, the hand is generally opened using a displacement command. However, if the hand is opened using a displacement command, distortion occurs due to a displacement error, which is not preferable. In this embodiment, a protrusion 40 serving as a stopper is provided on the outside of the finger 3-2 on which the voice coil motor is mounted, so that the hand can be opened by force control. It's getting old. That is, the opening control is performed using the same control as when the hand is closed. In the block diagrams of the force control system in Figures 9 and 10, when opening the hand, a signal with the opposite sign to that when closing the hand is sent to _U2.
Give as (S). Then, due to the outward displacement of the finger portion 3-2 by the parallel spring 4, this displacement signal is transmitted to the control system of the DC motor 24, and the hand is moved to the open side by the movement mechanism of the feed screw 26. Then, the protrusion 40 contacts the side plate 41. When the protrusion 40 comes into contact with the side plate 41 and is pressed with a predetermined force, the displacement of the parallel spring 4 returns to its original state and the movement of the finger stops. In this way, since the opening and closing of the hand can be controlled by force control, there is no strain on the moving mechanism or the like.

Using the same control principle, the object to be manipulated can be gripped by a so-called internal grip. That is, for example, the tip of the finger part is connected to the finger part 3 shown in FIG.
-1', 3-2'. From the closed state of the hand, for example, when gripping a tubular object 11' as shown in FIG _.
When (S) is applied to the control system, the object to be gripped 11' is gripped from the inside as shown in FIG. 16B. Of course,
The shape of the tip of the finger portion is not limited to that shown in FIG. 16, and various changes can be made.

By the way, as mentioned above, in the robot hand of this embodiment, it is better that the moving mechanism using the DC motor has an appropriate amount of friction. Therefore, the feed screw 26 is suitable, but it is even better to use the following method. As shown in FIG. 17 and FIG. 18, which is a partial sectional view thereof, the nut portion of the feed screw 26 is attached to the final screw portion 4 of the finger portion.
A so-called backlashless structure is employed in which elastic bodies 45, 45', such as rubber plates, are sandwiched between 7, 47' and nuts 46, 46'. By doing this, the nut 46 and the closing screw part 47 of the finger part receive force in the direction of the arrow shown in FIG. sticking is prevented. Further, it is also possible to adjust the friction force to a predetermined value.

FIG. 19 shows another embodiment of the present invention, and FIG. 20 shows an example of a circuit used in the embodiment shown in FIG.

In the figure, symbols 3-1, 3-2, 22, 23, 2
4 and 26 correspond to FIG. 7, 50 is an angle encoder, 51 is a signal cable, 52 is a power supply, 53 is an operational amplifier, 54 is an analog-to-digital converter,
55 is a counter, 56 is a processor (CPU), 5
7 and 58 represent input/output ports.

In the aforementioned robot hand shown in FIG. 7, the object can be grasped even if the width of the object is unknown. On the other hand, there are many cases in which the controller of the robot needs to detect the width of the object gripped by the robot hand. Therefore, as shown in FIG. 19, an angle encoder 50 is attached to one end of the shaft rotated by the DC motor 24 for span control, and a circuit for detecting the width, as shown in FIG. 20, for example, is provided. In addition,
The other parts are the same as the example described in FIG. 7 and subsequent figures, so detailed explanation will be omitted.

In Fig. 20, the amount of displacement due to the parallel spring is
It is detected by the strain gauge 5, amplified by the operational amplifier 53, and converted into a digital quantity by the analog-to-digital converter 54. This value can be passed on to processor 56 via input/output port 57. On the other hand, angle encoder 5
The output of 0 causes the counter 55 to increase or decrease through the signal cable 51, and the processor 56 can continue to receive the counter value corresponding to the amount of rotation angle from the input/output port 58.

The width of the object to be held is measured as follows. First, in order to detect the zero point, close the hand without grasping anything. At that time, counter 5
5, and the value related to the displacement due to the output of the strain gauge 5 is stored and set as an initial value.
Next, the object to be gripped, which is the object of width measurement, is gripped with a minute force using the control method described above, and the value of the counter 55 at that time and the offset amount from the initial displacement value of the strain gauge 5 are calculated. are multiplied by a conversion value determined in advance through experiments, etc., and then added together. By doing this, the robot of this example
Since the hand can grip an object with a very small force, it is possible to easily measure the width of even a soft object, for example.

(E) Effects of the Invention As explained above, according to the present invention, it becomes possible to apply a minute force to an article. For example, it becomes possible to grip an object to be manipulated with any arbitrary minute force on the order of grams. Moreover, even if the width of the gripped object is not constant, the object can be gripped with a predetermined and stable force. Therefore, for example, when handling minute parts such as magnetic heads and IC chips used in information processing equipment,
It will now be possible to widely introduce robots in fields that have traditionally been difficult to automate.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a robot hand showing the configuration of an embodiment of the present invention, FIG. 2 is a control block diagram of the embodiment shown in FIG. 1, and FIG. 3 is an embodiment of the robot hand according to the present invention. Exploded perspective view, Figure 4 is the 3rd
FIG. 5 is a perspective view of another embodiment of the robot hand according to the present invention; FIG. 6 is a control block diagram of the illustrated embodiment; FIG. The figure is a perspective view of another embodiment of the present invention, FIG. 8 is a schematic diagram for explaining the embodiment illustrated in FIG. 7, and FIGS. 9 and 10 are force control systems for the embodiment illustrated in FIG. 7. Block diagram, No. 11
The figure is a front view of an embodiment of the robot hand excluding the voice coil motor, Figure 12 is a right side view of the robot hand shown in Figure 11, and Figure 13 is a sectional view taken along the line A-A' in Figure 11. , Figure 14 is the first
Figure 1 is a front view of an embodiment in which a voice coil motor is attached to the robot hand shown in Figure 1.
A right side view of the illustrated robot hand, FIG. 16 is a diagram for explaining the shape of one embodiment of the finger portion of the robot hand, and FIGS. 17 and 18 are configurations of one embodiment of the nut portion of the screw feeding mechanism. FIG. 19 is a diagram showing another embodiment of the present invention,
FIG. 20 shows an example of a circuit used in the embodiment shown in FIG. In the figure, 3-1 and 3-2 are finger parts, 4 is a parallel spring, 5 is a strain gauge, 6 is a voice coil motor, 8 is a coil, 22 is a voice coil part, 23
24 is a magnetic circuit, 24 is a DC motor, 26 is a feed screw, 40 is a projection, 45 is an elastic body, and 50 is an angle encoder.

Claims (1)

[Scope of Claims] 1. A force applying device that receives a command to apply force to an article and applies the commanded force to the article, comprising an elastic body having one end fixed to a base, and the other end of the elastic body. a movable part attached to the article for applying the force to the article; a stator attached to the base; and a movable part attached to the movable part; a drive for moving the movable element relative to the stator; means, a detection means for detecting a reaction force generated by the displacement of the elastic body, and receiving the force application command and reaction force information from the detection means, canceling the reaction force and applying the commanded force to the article. A force applying device comprising: a control means for controlling the driving means so as to apply force to the force. 2 The base receives a movement command, and the elastic body
The force applying device according to claim 1, wherein the force applying device is a moving mechanism that moves the movable part and the drive means. 3. The force applying device according to claim 1 or 2, wherein the reaction force detection means is a displacement detection means for detecting displacement of the elastic body. 4. The force applying device according to claim 2, wherein the moving mechanism is configured to be driven based on a displacement signal from the displacement detecting means. 5. A patent characterized in that the control means receives a positive feedback of a displacement signal from the displacement detection means, and the moving mechanism uses the sum of the displacement signal and speed signal from the displacement detection means as a negative input signal. A force applying device according to claim 4. 6. The force applying device according to any one of claims 1 to 5, wherein the driving means is a voice coil motor. 7. The force applying device according to claim 6, wherein the voice coil motor includes at least a pair of magnet plates and a flat coil. 8. The force applying device according to claim 6 or 7, wherein the bobbin of the voice coil motor is made of an alumite-treated aluminum material. 9. A patent characterized in that the magnet plate of the voice coil motor is positioned at a fixed position by providing a hole of the size of the magnet plate in a non-magnetic plate and inserting the magnet plate into the hole of the non-magnetic plate. Claim No. 7
The force applying device according to item 8 or item 8. 10. The force applying device according to any one of claims 1 to 9, wherein the elastic body is a parallel leaf spring. 11 A force applying device that receives a command to apply force to an article and applies the commanded force to the article, which comprises an elastic body whose one end is fixed to a base, and a device that is attached to the other end of the elastic body and applies the commanded force to the article. a DC motor including a movable part for applying force to an article, a stator attached to the base and a mover attached to the movable part, and a reaction force for detecting a reaction force generated by displacement of the elastic body. A force applying device comprising: a detection unit; and a control unit that receives the force application command and the reaction force information and controls the DC motor so as to cancel the reaction force and apply the commanded force to the article. .