JPH01210279A - Master slave manipulator - Google Patents

Abstract

PURPOSE:To increase the amplification rate of force so as to improve controllability of a robot by installing a frequency characteristics conversion means for giving on eof signals transmitted from a locking force detecting means a frequency characteristic different from the frequency characteristic to be given to the other signal relating to differential drive on the master side. CONSTITUTION:A third motor unit 3 comprising a torque detecting unit 21a, a speed reduction unit 22a, a DC motor 23a and a torque control driver 24a relates to the differential drive of a second joint and torque on one side detected by the torque detecting unit 21a passes through a strain amplifier 28a enclosing a low pass filter 29a acting as a frequency characteristics conversion means and is fed in an A/D converter 27. In the similar way, torque on the other side detected by a torque detecting unit 21b passes through a strain amplifier 28b enclosing a low pass filter 29b and is inputted into the A/D converter 27. In this case, the amplification rates of torque given to motor units 3, 4 are increased by delicately changing the frequency characteristics of transmission signals by means of the low pass filters 29a, 29b.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a master-slave manipulator using a differential drive system on the master side.

(Prior Art) Conventionally, a method using a master-slave manipulator has been known as a method for realizing work by remote control in places that are dangerous for humans. Master-slave manipulators have multiple degrees of freedom in their arms in order to achieve movements equivalent to those of humans, and are controlled by a force-feedback type bilateral system to control the movements of the master side. In other words, it is possible to accurately transmit human steering movements to the slave side.

One of the driving methods for such a manipulator is 2.
There is a differential drive system that provides two degrees of freedom to one joint by coordinating the rotation speed and rotation direction of two motors. When this method is used, the capacity of the motor to achieve the same torque at the joint is only half that required for one motor, compared to the case of a one-motor method with one degree of freedom. Additionally, since the two motors are always being driven regardless of whether one or two degrees of freedom are required, they have advantages such as better drive efficiency compared to a one-motor system with one degree of freedom. .

By the way, in the master/slave manipulator, a force control method is adopted in which the operating force detected on the master side is amplified and used as a command for the master side drive system. However, in this control method, there is a correlation between the force control amplification factor and the attitude of the arm, and if a certain amplification factor and a certain attitude are achieved simultaneously, a resonance phenomenon will occur in the master arm. This is due to the characteristics of the drive system, particularly the relationship between changes in the input/output phase difference and changes in the natural frequency due to the posture of the arm.

Therefore, in the master/slave manipulator, in order to suppress the resonance phenomenon to a level that does not cause discomfort to the operator, regardless of the arm posture, force control is applied so that the drive system remains stable at the time of the largest resonance. The amplification factor has been determined. Therefore, the amplification factor of the force control on the master side could not be made sufficiently large, and the operability of the master arm could not be improved, so that the master/slave manipulator as a whole was not able to fully demonstrate its capabilities.

(Problem to be solved by the invention) As described above, in the conventional master/slave manipulator, the amplification factor of force control is determined in response to the resonance phenomenon of the master arm so that the drive system is stable at the time of the largest resonance. As a result, the operability of the master arm was not improved, and the master/slave manipulator as a whole was not able to fully demonstrate its capabilities.

The present invention solves a serious problem, and is designed to provide a differential drive system master system that is sufficiently stable even when the force control amplification factor is set to a larger value than ever before. The purpose is to provide a slave manipulator.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention provides a master side that uses a differential drive system for joint drive, and force information acting on the joints on the master side. In a master/slave manipulator consisting of a slave side driven by
One signal was given a frequency characteristic different from that of the other signal.

=−− °−1 (Function) By using the above control method, there is a slight difference in transmission time between the signals from the two force detection means related to the differential drive, so it is necessary to superimpose them. Conventionally, the amplitude of the joint signal is not amplified, and the master arm remains sufficiently stable during resonance. Therefore, the force amplification factor can be made larger than before, and the overall performance of the master/slave manipulator is improved.

(Example) Below, implementation of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a front cross-sectional view showing the internal structure of a master arm of a master-slave manipulator used in carrying out the present invention, and FIG. 2 is a side cross-sectional view of the master arm. This master arm is a so-called distributed drive type in which the drive means (unit) for driving each joint is arranged or near the joint.
First motor unit 1. The second motor unit 2 includes a first joint 11, a third motor unit 3. The fourth motor unit 4 has a second joint 12, a fifth motor unit 5. The sixth motor unit 6 is involved in driving the third joint 13, and each joint 11, 12, 13 has two degrees of freedom. In addition, this master arm has a second joint 12. A differential drive system is used for the third joint 13, for example, the second joint 1
For any movement of the motor 2, it is necessary that the third motor unit 3 and the fourth motor unit 4 be adjusted. In addition, a robot finger 7 is provided at the tip of the arm, and this is either driven by a motor unit (not shown), or this part is not particularly driven in this embodiment.

Next, Table 1 shows how the resonance phenomenon occurs due to changes in the posture of the master arm. However, in this example, the experiment was conducted focusing only on the second joint 12.

3 is a block diagram showing the drive system of the second joint 12. Torque detection section 21a, which is force detection means;
Reducer 22a, DC motor 23a.

The third motor unit 3 consisting of the torque control driver 24a is involved in differential drive of the second joint 12, and is connected to the torque detection section 21.
The torque T3 detected at point a passes through a distortion amplifier 28a containing a low-pass filter 29a, which is a frequency characteristic conversion means, and is taken into the A/D converter 27. Similarly, the torque detecting section 21b, which is a force detecting means, the reducer 22b, D
The fourth motor unit 4, which includes a C motor 23b and a torque control driver 24b, is also involved in the differential drive of the second joint 12.
The torque T4 detected by the torque detection section 21b is input to the A/D converter 27 through a distortion amplifier 28b having a built-in low-pass filter 29b, which is a frequency characteristic conversion means. The torque signals input to these A/D converters 27 are processed by the CPU (Central Processing).
g Unit) 2B, passes through the D/A converter 25, and is again sent to the torque control drivers 24a, 2
4b, and the motor units 3 and 4 are given an operation commensurate with the torques T3 and T4. The manipulator of this embodiment is equipped with a unitary servo mechanism.

In the drive system configured as above (now, the second joint 12
When an external force signal is transmitted, torque acts on the drive means 30a, 30b as shown in the following equation.

Here, T is the tilt torque of the second joint 12.

Bch T is the rotational torque of the second joint 12, r is the reduction ratio oll It is.

The torque 7.31T4 thus decelerated and distributed is detected by the torque detection units 11a and 11b using strain gauges, sent to the distortion amplifiers 18a and 18b, voltage transformed, and digitalized by the A/D converter 27. After being converted, it is taken into the CPU 26. At this time, the distortion amplifier 18
Low-pass filters 29a and 29 built in a and 18b
b gives a subtle change to the frequency characteristics of the transmitted signal. Fourth
The figure is a graph showing this change in frequency characteristics. The broken line ■ indicates a state in which the cutoff frequency is set high in the low-pass filter 29a, for example, and the high frequency region is not cut that much, and the low-pass filter is used only for its original noise-eliminating function. On the other hand, a solid line (2) indicates a state where the cutoff frequency is lowered in the low-pass filter 29b, for example, and the high frequency region is significantly cut off compared to the line (2). When the frequency is changed in this way, the torque detection 21a,
Since the signals of 21b both had characteristics like the line ■,
The peak value of the joint signal was amplified twice as shown by the broken line ■, but in the present invention, the lines ■ and ■ have different signal characteristics, so they are shown as a solid line. Line ■
As shown in (9)r^, the force value is not amplified very much, and therefore, in order to make the peak value of line (2) coincide with the peak value of line (2), it is possible to increase the force amplification factor.

Table 2 shows the experimental results in this example. In this embodiment, the cutoff frequencies of the low-pass filters 29a and 29b are a combination of 10 Hz and 100 Hz.

Table 2 This makes it possible to eliminate resonance phenomena.

Next, FIG. 5 shows another graph of the characteristics of the lines ``■'' and ``■'' shown in FIG. 4. Originally, it is desirable for signal transmission to have no delay time, and the ideal pulse waveform is as shown by the dotted line.However, in reality, in order to cancel the noise contained in the signal,
) The high frequency range is cut, and by doing so, the waveform becomes slightly smoother as shown by lines ■ and lines ■. In this experiment, the low-pass filter 29a.

The cut-off frequency of 29b is set to 10 Hz and 100 Hz, but when the cut-off frequency is lowered, that is, when the high frequency region is largely cut off, the time to reach a constant strain voltage is delayed as shown by the line (■). Therefore, the present invention, which attempts to reduce the amplitude at resonance by changing the frequency characteristics, is nothing but giving a difference to the delay time of the transmitted signal.

As mentioned above, in this example, the cutoff frequency is 10Hz.
, 10 CIHz, but it goes without saying that other frequency combinations are also possible. Similarly, the force amplification factor can be made larger than before, and the master/slave manipulator has good operability. will be realized. A similar effect can also be achieved with a manipulator equipped with a pirate servo mechanism.

Further, in this embodiment, the experiment was conducted focusing only on the second joint 12, but of course the present invention may be applied to all the differential drive joints of the arm, and by doing so, the operability of the manipulator is further improved. do.

In addition, in the present invention, by changing the cutoff frequency of the low-pass filter built into the distortion amplifier, the frequency characteristics change, resulting in a difference in the delay time of the transmitted signal, and the CPU
(For example, in one force detection means, the output signal is obtained by averaging the current signal and the previous signal input.) The same effect can be achieved by using a program that does this.

[Effects of the Invention] As described above, according to the present invention, the force amplification factor can be made larger than before by a simple method of varying the frequency characteristics of the force detection means related to differential drive. Realizes a master/slave manipulator with good operability.

[Brief explanation of the drawing]

1 and 2 are a front sectional view and a side sectional view showing the internal structure of the master arm of the master slave manipulator used in the present invention, and FIG. 3 is a block diagram showing the drive system of the present invention, Figures 4 and 5 show the effects of the present invention at different frequencies.
This is a graph considered from the perspective of signal transmission time. 1.2, 3, 4, 5.6...Motor unit (drive means) 11.12.13...Joints 21a, 21'b...Torque detection section (force detection means) 29
a, 29b...Low pass filter (frequency characteristic conversion means)

Claims (1)

[Scope of Claims] A master-slave manipulator consisting of a master side that uses a differential drive system for joint drive and a slave side that is driven by force information acting on the joints of the master side, wherein the differential drive system on the master side A master/slave manipulator characterized in that one of the signals from the force detection means related to driving is passed through a frequency characteristic conversion means that gives a frequency characteristic different from that of the other signal.