JPH02185380A - Power feedback method for master/slave manipulator - Google Patents

Abstract

PURPOSE:To constrain an unstable phenomenon accompanied by the power feedback of a master slave manipulator by feeding back the power effected on the handling body by a slave manipulator to the driving power of a master manipulator via a phase lead element. CONSTITUTION:A human and master interaction block 11 shows the dynamic process that the position of a master is decided by operating the master by human. Now, the position of the master is equal to the position of a human hand and yet it is equal to the positional target Xr of a slave. A slave and work interaction block 12 shows the dynamic process of the interaction by the contact of the slave controlled so as to be coincident with this positional target Xr and the body becoming the operation object. The action force Fe generated by this interaction is multiplied by a power feedback ratio Kf by a power feedback ratio block 13 and after leading the phase by a phase leading block 14 it is fed back as a master motor generating force Fn.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for controlling a remote control device, and particularly to a method for controlling a remote control device.

The present invention relates to a force feedback method suitable for master/slave manipulators.

[Conventional technology]

The conventional device is based on Eiji Nakano's "Introduction to Robotics" (19
As discussed on pages 74 to 77 of 1988, a system is adopted in which the acting force of a slave manipulator (hereinafter referred to as slave) is directly fed back to a master manipulator (hereinafter referred to as master). In addition, a constant called the force feedback ratio is 1
It is also common to return by multiplying by Generally, the larger K is, the more acute the sense of force transmitted to the operator becomes, so a value of 1 is required for delicate operations and handling of fragile objects.

[Problem to be solved by the invention]

In the above-mentioned conventional technology, the following unstable phenomenon has been known empirically.

(1) Oscillation is likely to occur when the force feedback ratio Kn is increased.

(2) Oscillation is likely to occur when it comes into contact with an object with large rigidity (signal Kc will be used hereinafter).

The purpose of the present invention is to suppress this oscillation and to enable use with a force feedback ratio Kn and a contact stiffness Kc larger than those of the prior art.

[Means to solve the problem]

The above objective is achieved by feeding back the slave's acting force through the phase advance element.

[Function] Since the phase lead element has the effect of improving phase lag, which is one of the conditions that cause the unstable phenomenon of the 5 system, stable operation can be realized even under conditions where conventional oscillations occur.

〔Example〕

The present invention will be explained in detail below. FIG. 1 shows a block diagram of an embodiment of the invention. The human-mask interaction block 11 represents a dynamic process in which the position of the mask is determined by a human manipulating the mask. Here, the position of the mask is equal to the position of the human hand, which is also equal to the slave position 'Rx r, and the slave-work interaction block 12 uses this position axr
This figure shows the dynamic process of interaction between the slave, which is controlled so as to match the target object, and the object to be manipulated (hereinafter referred to as the workpiece). The acting force Fc generated by this interaction is multiplied by the force feedback ratio by 1 (force feedback ratio block 13), and the phase is further advanced by the phase advance block 14 before being fed back as the master motor generated force Fn.

The principle of the present invention will be explained in more detail using FIG. FIG. 2 is a more specific representation of the block diagram of FIG. 1 assuming a master/slave manipulator with -degree of freedom. It becomes more complicated for a manipulator with many degrees of freedom, and the force Fc is generally expressed by a three-dimensional vector (force in three directions and torque in three directions), but the principle of the present invention is as shown in Fig. 2. It can be fully understood by a simple example. Furthermore, in a system in which independent control is performed for each joint axis, the same ellipse as in FIG. 2 is obtained even with multiple degrees of freedom.

First, the human-mask interaction block 21 will be explained. As a model of the human hand, we use the natural position [x a spring, , and the damping coefficient Bh.

If the actual position is xr, the force generated by one human hand Fh
is, Fh=Kn (xd xr) BhSXr −・
(x). Here, S represents a Laplace operator.

On the other hand, since the master motor generates a force Fl in the opposite direction to Fh, this difference acts on the inertia M of the mask, so the position xr is expressed as. The above is the content shown in the human-mask interaction block 21. Formula (1).

From (2) we obtain the following relationship.

(3) Next, looking at the slave-work interaction block 22, there are the following two types of forces that act on the inertia M of the slave. The first is the force exerted by the slave motor, which is generated to cause position 11x to follow position target Xr. Here, taking proportional/derivative control as an example, position deviation
-X r and velocity X are each 1. We are giving negative feedback twice as much. The second force is a reaction of the acting force Fc on the workpiece, and is expressed as Kcx, where Kc is the stiffness of the workpiece. Expressing the above in the form of a transfer function, we finally have the force feedback block 23. Looking at block 24, the following equation is obtained.

S+α a Here, α and a are constants that determine the action of the phase advance element, and the phase advances between the angular frequencies a to αa[rad/sl.

The characteristics of the system represented in the block diagram of Fig. 2 are expressed by the equation (3
), (4), and (5) to calculate the roots (eigenvalues of the system) of the characteristic equation. First, for comparison with the present invention, the characteristics of the conventional method will be first determined. In the conventional method, the phase lead block 24 can be considered to have a unit gain;
Other constants that can be calculated with α = 1 are - For example, M, = 1 [kgl, K11 = 300 [
N/m, Bh = 35 [Ns/m1M = 10[k
gl, Kt=10'[N/m]+Kz=2000[
It was set as Ns/ml. FIGS. 3 and 4 show the results of this calculation. First, looking at Figure 3, here the stiffness of the workpiece is fixed at 10' [N/m], the force feedback ratio Kg is set from O to 1 in 0.1 increments, and the positions of the four roots of the system are is plotted on the complex plane. As shown in the figure, in the conventional method, when , becomes large, two roots move to the positive side (right half plane) of the real part, making it unstable at eKt=o-3. In Figure 4, Kz is fixed to 1,
Rigidity Kc from 0 to 104 [N/m] by 10' [N/m]
The position of the root is plotted in the same way with the setting in increments. In this case, as Kc increases, the second root moves toward the right half. It is unstable at Kc=3×103 [N/m]. What is shown in FIGS. 3 and 4 is in good agreement with the properties of the empirically known unstable phenomenon described above.

Now, FIG. 5 shows a similar analysis of the characteristics of the present invention.

Figure 6 was obtained. Here, the phase lead constant is a=6
0 [rad/s], (E: 100. As is clear from the comparison with Figures 3 and 4, the unstable roots have moved to the stable side (left half).

For K, it is stable up to 0.7, for Kc it is 7X10”[N/
m ] has been shown to be stable.

This stabilizing effect is also noticeable in the transient response simulation waveform. Figure 7 shows Kc=lO'[N/ml
, shows the transient response of the conventional method when *=0.2, and although it is stable, it is largely undulating. On the other hand, FIG. 8 shows the one of the present invention, and a remarkable stabilizing effect is observed.

To summarize the above explanation, by serially coupling the mask-human interaction block and the slave-work interaction block, the condition that the phase of the slave position @X with respect to the mask position 1j Then, since 5 times the contact force Kcx is returned as it is,
When either K or 1 becomes large, the loop gain exceeds 1 and oscillates. Therefore, the present invention improves the phase lag by using a phase advance element, and is configured to prevent instability even if the loop gain exceeds 1.

Therefore, instead of directly feeding back the contact force F c (= Kc It is also effective to feed back the estimated value of Fc obtained by inversely calculating the dynamic equation from the change in the value of Fc through the phase advance element of the present invention.

〔Effect of the invention〕

According to the present invention, by improving the phase lag of the system, it is possible to move the eigenvalue to the stable side, and therefore it is possible to suppress the unstable phenomenon accompanying force feedback of the master/slave manipulator.

[Brief explanation of the drawing]

Figures 1 and 2 are block diagrams of an embodiment of the present invention, and Figure 3 is a block diagram of an embodiment of the present invention.
4 shows the root locus of the conventional example, FIGS. 5 and 6 show the root locus of the present invention, FIG. 7 shows the transient response of the conventional example, and FIG. 8 shows the root locus of the present invention. FIG. 3 is a diagram showing the transient response of the invention. 11...Human-mask interaction block, 12...
Input rape work interaction block, 13... force feedback ratio block, 14... phase advance block. Figure 2 Figure re+11 Figure 6 Figure 3 eal Figure Lime (s) Figure 8 0.2 time (s)

Claims (1)

[Claims] 1. In a master/slave manipulator composed of a master manipulator and a slave manipulator, the force exerted on the object handled by the slave manipulator is returned to the driving force of the master manipulator via a phase advance element. A force feedback method for a master/slave manipulator, characterized by the following. 2. In the master-slave manipulator, the contact force of the slave manipulator, which is obtained by back calculating the dynamic equation from the force generated by the actuator of the slave manipulator, the drive current value, or the time change in position, is applied via the phase advance element. A force feedback method for a master/slave manipulator, characterized in that the force is returned to the driving force of the master manipulator.