JPH02284887A - Control method for multi-freedom degree joint - Google Patents

Abstract

PURPOSE:To improve position controllability by providing an electrode in both ends of each artificial rubber muscle, using a difference of internal resistance, between both the artificial rubber muscles with extension and contraction opposite to each other in each freedom degree, serving as a sensor signal and using a signal, in which this sensor signal is added by aligning the polarity in accordance with a driving direc tion of each joint, serving as a position feedback signal. CONSTITUTION:An actuator uses a plurality of artificial rubber muscles A to H while connecting their pressure fluid action part to the same pressure fluid source through each pressure control valve 8a to 8d. Here this pressure fluid uses conductive fluid. Each artificial rubber muscle A to H provides in its both ends an electrode detecting internal resistance of the pressure fluid by a change of length in each artificial rubber muscle A to H, and a difference of internal resistance, between both the artificial rubber muscles with extension and contraction opposite to each other in each freedom degree, serves as a sensor signal. A signal, adding each sensor signal by aligning the polarity in accordance with a driving direction of each joint, serves as a position feedback signal, and by comparing this signal with a command signal to the control valves 8a to 8d, a position is controlled.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a joint device used in a robot manipulator, etc., and in particular, the actuator includes McKibben muscles (rubber artificial muscles).
This paper relates to a method for controlling multi-degree-of-freedom joints using

[Conventional technology]

Figure 1 shows an example of a multi-degree-of-freedom joint using multiple McKibben muscles. As each McKibben muscle expands and contracts, the second arm 2 swings in the east-west and north-south directions relative to the first arm 1. It also rotates from side to side. The first and second arms 1.2 of this multi-degree-of-freedom joint are connected to the intermediate member 3 via a spherical joint 4 provided on the intermediate member 3 so as to be able to bend and rotate freely. Support members 5 and 6 are fixed to both arms 1 and 2 at positions equidistant from the intermediate member 3, and two McKibben muscles are formed between each of the support members 5 and 6 and the intermediate member 3. connected.

That is, 2 parts are attached to the south end of the support member 5 on the first arm 1 side.
The end of the main McKibben muscle ASB is connected to the north end, and the ends of the two McKibben muscles C and D are connected to the north end. The other ends of one of the two McKibben bars ASB are connected to the east-west positions on the south side of the intermediate member 3, and the other ends of the other two McKibben bars CSD are connected to the north east-west positions of the intermediate member 3. It is.

Furthermore, the ends of two McKibben muscles ESF are connected to the east end of the support member 6 on the second arm 2 side, and the ends of two McKibben muscles GSH are connected to the west end. The other ends of the two McKibben lines E and F are located north and south on the east side of the intermediate member 3, and the other ends of the other two McKibben lines G and H are located north and south on the west side of the intermediate member 3. connected to each location.

Each of the McKibben muscles described above becomes thicker and shorter in length as the internal pressure increases, and becomes thinner and longer in length as the internal pressure decreases.

Among the above-mentioned McKibben muscles, two McKibben muscles are connected via the intermediate member 3, that is, (A
, E), (BSG) (C.

F) and (DSH) are each connected to the same hydraulic pressure source in pairs, and by controlling the hydraulic pressure within the McKibben muscles of each pair, they extend and contract in synchronization. .

By selectively expanding and contracting the four pairs of McKibben muscles, the second arm 2 swings in the east-west and north-south directions with respect to the first arm 1, and also rotates in the left-right direction.

In the multi-degree-of-freedom joints described above, it was impossible to mount an angle (position) detector compactly, so position feedback could not be performed, and only the internal pressure of each McKibben muscle was fed back to each McKibben muscle. The supply liquid pressure was controlled.

[Problem to be solved by the invention]

In the conventional control method described above, it was not possible to accurately control the expansion and contraction of each McKibben muscle, and the position controllability was poor.

The present invention has been developed based on the above-mentioned problems, and it is possible to provide position feedback without an external sensor, thereby improving position controllability, reducing cost, and making it more compact. The present invention aims to provide a control method for a multi-degree-of-freedom joint that can compensate for disturbances caused by acting temperature changes and improve the reproducibility of a position sensor.

[Means and operations for solving the problem] In order to achieve the above object, the present invention uses a plurality of McKibben muscles as an actuator, and connects the same pressure fluid acting portion of each McKibben muscle through a pressure control valve. connected to a pressure fluid source,
Furthermore, in multi-degree-of-freedom joints that use conductive fluid as the pressure fluid, electrodes are installed at both ends of each McKibben muscle to detect the internal resistance of the pressure fluid due to changes in the length of each McKibben muscle, and The difference in the internal resistance of both McKibben muscles, which stretch and contract in opposition to each other, is used as a sensor signal, and the polarity of each sensor signal is adjusted and added according to the drive direction of each joint, and the resultant sum is used as a position feedback signal. and the command signals sent to each pressure control valve.

〔Example〕

An embodiment of the present invention will be described with reference to FIGS. 2 to 4 for the multi-degree-of-freedom joint shown in FIG.

FIG. 2 schematically shows a McKibben stripe. Both ends of the McKibben stripe serve as electrodes, and these electrodes come into contact with the liquid inside. Conductive fluid is now used as the pressure fluid that acts on the McKibben muscles. Therefore, both mtM of the McKibben muscle are electrically connected via the internal pressure fluid, but the internal resistance R due to the pressure fluid at this time changes depending on the length of the McKibben muscle. A fixed resistor 8 having a resistance value Ro is connected to one electrode of each McKibben muscle, and +bV is applied to both ends of the resistor 8, respectively.

bv is being applied. At this time, the voltage i at the terminal 7 provided between the Matsukiben strip and the fixed resistor 8 becomes, and the change in internal resistance between the electrodes of the McKibben strip is extracted by the voltage i at the terminal 7. ing.

FIG. 3 shows an example of the control system according to the present invention for the multi-degree-of-freedom joint shown in FIG. 1, and shows each pair of McKibben muscles (C,
F), (ASE), (B.

G), (D, H) are each pressure control valve 8.
They are connected to the same pressure liquid source 9 via a, 8b, 8c, and 8d. The control section of each of the pressure control valves 8a to 8d includes neutral pressure setting devices 9a, 9b, 9c, 9ds pressure cuff feed back comparators 10a, 10b, 10c, 10.
d.

Position feedback comparators 11a and llb.

] 1c and lid are connected to the pressure liquid source 9 in order from the downstream side, and addition circuits 12a, 12b, 12c,
A controller 13a for east-west direction, a controller 13b for north-south direction, and a controller 13C for left-right rotation are connected via 12d. Each of the controllers 13a to 13c is controlled by a lever of a joystick lever assembly @14 shown in FIG.

Each of the pressure feedback comparators 108 to 10d is provided with a pressure sensor 16a, 16b for detecting the pressure of each pair of Matsukiben muscles.

Pressure signals are input from 16c and 16d. Also, position feedback comparators 11a to lid
A change signal in the internal resistance of each pair of McKibben muscles is input to each of the McKibben muscles.

The present invention will be explained in detail below.

(1) Oscillation in the east-west direction (Yaw) Operate the joystick lever 15 in the east or west direction. When the joystick lever I5 is now operated in the east direction, the east-west direction controller 13a is controlled in the east direction, and the east-west direction control signal v1 corresponding to the control amount is inputted to each control circuit. , the pressure control valves 88 to 8d are operated so that (A, E), and (CSF) located on the east side are shortened, and (BSG) and (DSH) located on the west side are extended.

When the joystick lever 15 is operated in the west direction, the operation is opposite to the above.

(2) Swinging in the north-south direction (Pitch) When the joystick lever 15 is operated in the south direction, the control signal V2 of the north-south direction controller 13b at this time causes the McKibben curve (A, , E) located on the south side, (B, G) are shortened,
Each of the pressure control valves 8a to 8d is operated so that the McKibben muscles (CSF) and (D, H) located on the north side extend and move.

When the joystick lever 15 is operated northward, the operation is the opposite.

(3) Left-right rotation (Roll) When the joystick lever 15 is rotated to the right, the control signal V3 of the left-right rotation controller 13c at this time causes McKibben muscles (C, F), (BSG) on the upstream side of the rotation direction.
) stretches, and the downstream McKibben muscle (ASE), (D
, H) are operated to shorten the pressure control valves 8a to 8d.

When the joystick lever 15 is operated to the left, the operation is opposite to this.

In each of the above operations, pressure feedback is provided to each pressure feedback comparator 10a to 10d, and position feedback is provided to each position feedback comparator 11a to 11d.
feedback will be provided to each.

Next, the position feedback signal will be explained.

First, the difference in voltage signals due to changes in internal resistance of both McKibben muscles that stretch and contract in each degree of freedom is used as a sensor signal.

That is, the sensor signal in this example is (1) east-west direction (Y aw ) (voltage signals of McKibben lines C, F, A, and E located on the east) - (McKibben line B located on the west).

G, D, H voltage signals) - Y (2) North-south direction (Pitch) (Voltage signals of McKibben muscles C, F, D, H located in the north) - (McKibben muscles A located in the south.

E, , B, G voltage signals) - p (3) Lateral rotation (Ro l l) (Voltage signals of McKibben muscles C, F, B, G located on the left) - (McKibben muscles AE located on the right) , D, H voltage signals) -R. Then, the voltage signal of each McKibben muscle mentioned above is A1-
The above calculation formulas when expressed by Hl are as follows.

(1)' East-west direction (Y a w) (Ci+F i+Ai+Ei)-(Bi+Gi+Di+
Hi)-Y (2)' North-south direction (Pitch) (Ci+Fi+Di+Hi)-(Ai+Ei+Bi+G
i)-P (3)'Left-right rotation (Ro l 1) (Ci+Fi+
Bi+Gi) −(Ai+Ei+D i +Hi
) -R Next, position feedback will be explained.

A position feedback signal is obtained by adding the sensor signals (YSP, R) from each degree of freedom with their polarities adjusted according to the driving direction of each joint. In this example, it is as follows.

(1) Since the McKibben muscle CSF is located to the east, north, and left, its position feedback signal S1 is S + −Y +
P + R −3(Ci+Fi)−(Ai+Ei) (Bi+Gi)−(Di+Hi) (2) Since McKibben muscle ASE is located to the east, south, and right, its position feedback signal S, is 52−y+ (−
1) P+ (-1) R=-(Ci+Fi)+3 (Ai
+Ei) (B i+Gi) - (Di+Hi) (3) Since McKibben muscles B and G are located to the west, south, and left, their position feedback signal S3 is S3- (-1)
Y+ (-1)P+R=-(Ci+F i)-(A
i+Ei)+3 (Bi+Gi)-(Di+H1)(
4) McKibben Line, H is located to the west, north, and right, so
The position feedback signal s4 is S4 = (1)y
+p ten (-1) R=-(Ci+Fi)-(Ai+Ei
) (Bi+Gi)-3(Di+Hi), and each signal S1, S2, s3, s4 is input to each position feedback comparator 11a to lid.

Note that since the sensor signal is the voltage difference due to the change in internal resistance of the McKibben muscle, which stretches and contracts in opposition to each other, it may be subtracted from either of them. Therefore, each of the above calculation formulas can be rewritten as follows.

That is, the sensor signal is (1)′ east-west direction (Y aw ) (Bi+Gi+Di+Hi) −(Ci+Fi×Ai+
Ei) 暉Y (2)'North-south direction (Pitch) (Ai+Ei+Bi+Gi) -(Ci+F i+
D i +Hi) -P (3)' Left-right rotation (Ro l 1) (Ai+Ei+
Di+Hi)-(Ci+Fi+Bi+Gi)-R If the subtraction method of the sensor signal is reversed as described above, the position feedback signal will be as follows.

(1) The position feedback signal S'1 of the McKibben muscle CSF is S/1 - 3 (Ci + Fi) + (Ai + Ei) +
(B t+Gi) + (Di+Hi) (2)' The position feedback signal S/2 of McKibben muscles A and H is S' 2- (Ci+Fi)-3(Ai+Ei)+ (
Bi+GE) +(Di+Hi)(3)'The position feedback signal S'3 of McKibben muscle BSG is S'3- (Ci+Fi)+(Ai+Ei)-3(
B i + G i) + (D i +Hi) (4)' McKibben line, the position feedback signal S/4 of H is S' 4- (Ci + Fi) + (Ai + Ei) + (
Bi+Gi)+3 (Di+Hi) As mentioned above, each McKibben muscle is expanded and contracted for each bear that operates the same way, and the first
The second arm 2 rotates relative to the arm 1 in east-west directions, north-south directions, and left-right directions. The motion of each pair of McKibben muscles at this time is feedback-operated by a pressure feedback signal from a pressure sensor and a position feedback signal based on the internal resistance of each pair of McKibben muscles.

〔Effect of the invention〕

According to the present invention, the position of the McKibben muscle of each bear can be fed back without an external sensor, thereby improving position controllability and achieving low cost and compactness. Furthermore, by using the difference in voltage signals due to changes in the internal resistance of both McKibben muscles, which expand and contract in each degree of freedom, as the sensor signal for the position feedback signal, it is possible to compensate for disturbances caused by temperature changes in the working pressure fluid. It is also possible to improve position controllability.

[Brief explanation of drawings]

Figure 1 is a perspective view showing an example of a multi-degree-of-freedom joint, Figure 2 is a schematic diagram showing changes in the internal resistance of the McKibben muscle, Figure 3 is a block diagram showing the control system, and Figure 4 shows the joystick lever. FIG. A to H are McKibben muscles, 1.2 is an arm, 3 is an intermediate member, 8a to 8d are pressure control valves, and lla to lid are position feedback comparators. Patent applicant Director of the Institute of Industrial Technology Figure 2 Figure 4

Claims (1)

[Claims] A plurality of McKibben muscles A to H are used as actuators, and the pressure fluid acting portions of each of these McKibben muscles A to H are connected to the same pressure fluid source via pressure control valves 8a to 8d, respectively, and the pressure fluid is In a multi-degree-of-freedom joint using conductive fluid, electrodes are provided at both ends of each McKibben muscle A to H to detect the internal resistance of the pressure fluid due to changes in the length of each McKibben muscle A to H. The difference in the internal resistance of both McKibben muscles, which stretch and contract in opposition to each other, is used as a sensor signal, and the polarity of each sensor signal is adjusted and added according to the drive direction of each joint, and the resultant sum is used as a position feedback signal. A method for controlling a multi-degree-of-freedom joint, characterized in that the information is compared with a command signal sent to each of the pressure control valves 8a to 8d.