JPS63106805A - Hybrid control device for position and force for direct movement multi-freedom robot - Google Patents

Abstract

PURPOSE:To attain a force control of a robot in an advancing direction by setting the restoring force restored to a designated path and a viscous force returned to a designated speed in response to a deviation when an external force is eliminated and a robot is restored to the designated path and the designated speed. CONSTITUTION:A deviation between an object position R(s) and a position C(s) of an end effector of a robot is taken and the deviation is used for an input to a controller of a transfer function G(s) expressed in equation I, where (k) is a spring constant (the spring force is active as a restoration force), (m) is a mass constant, C is a viscous constant, kv, N, Km represent constants being values of the hardware and Km/S(1+ TmS) is a transfer function of a motor. In using a controller having the transfer function G(s) above, a force proportional to the deviation between the object position R(s) and the end effector position C(s) is exerted as a restoration force restoring the robot to the object position and in exerting an external force F(s) to the robot, the robot is operated in the direction and a force proportional to the speed of the robot is exerted as the viscous force in the opposite direction. Thus, the force control is applied in a direction in parallel with the advancing direction and also in the advancing direction at the same time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a control device for industrial robots, automatic machines, etc., and particularly to a hybrid control device for position and force of a rectangular multi-degree-of-freedom robot.

[Conventional technology]

Figure 4 shows an example of a straight-shaped multi-degree-of-freedom robot. The multi-degree-of-freedom robot includes an end effector (robot hand) 8, a force sensor 2 for detecting an external force applied to the end effector 8, and a mouth.

It is provided with position sensors 9 such as rotary encoders arranged at various locations on the bot drive unit to detect the position of the end effector 8. The control device 7 of the robot 1 receives a force feedback signal/signal F from the force sensor 2 and position feedback from the position sensor 9 in order to control the end effect 8 .

A speed command value is generated from the signal X and the target position (given as a target trajectory), and this is output to the robot 1.

The conventional position and force hybrid control method is

As shown in Fig. 5, if the target position is given by a straight line 11, s in one direction, for example, the one parallel to the direction of travel.

Position control is performed only in the X direction, and force control is performed only in a direction perpendicular to this direction, for example, in the X direction.

It has become.

In addition, as something related to the conventional hybrid control of position and force, there is a transaction of the.

Transactions
of the A SMF) June 1981 issue, 30
Volume 3-2, pages 123-133.

[Problem that the invention seeks to solve]

The above-mentioned prior art does not control both force and position simultaneously in any direction. In other words, as shown in Figure 1 and Figure 5, if you apply force 14 for a certain period of time to the end effect whose X-direction component becomes force 13, the locus of the end effect will become as shown by the broken line 12, and the force -Control only works in the X direction. More precise control.

In this case, as shown in FIG. 6, when a force 14 is applied to the end effect 1, as shown by a locus 12'.

It is necessary to perform force control not only in the X direction but also in the X direction.

There is. However, in the past, such matters were not considered.

No consideration was given.

The purpose of the present invention is only in the direction parallel to the direction of travel.

The object of the present invention is to provide a hybrid position and force control device that simultaneously controls force in the traveling direction as well as in the traveling direction. ′ [Means for solving the problem] The above purpose is to provide a rectangular multi-degree-of-freedom robot that is equipped with a means for detecting position and a means for detecting external force. If the robot's motion deviates from the specified path and specified speed, there will be a means to return to the original specified path and specified speed after the external force is removed, and a means to control the restoring force and viscous force of the robot when an external force is applied. means for setting the size as a parameter on software; and the specified speed.

Reduce the steady-state deviation when the magnitude of the degree is constant.

This can be achieved by having the means.

[Effect]

When the external force is removed and the robot returns to the specified path and speed, the restoring force and specification when returning to the specified path.

The magnitude of the viscous force when returning to speed is set according to the deviation, so force control in the direction of robot movement.

is also possible.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to FIGS. 1 to 3.

FIG. 1 shows a hybrid according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a control device. In FIG. 1, the target position R (sl) and the robot end effector position Cf
sl, and convert this deviation into a transfer function () (81
' is used as an input to the control device. Here, k is the spring constant (the spring force acts as a restoring force), m is the mass 1 constant, C is the viscosity constant, and kV * N r Kin is the hard value.

A constant is indicated and is also written within a block in the figure.

Km/8 (1+Tm8) is the motor transfer function.

We use a controller g with such a transfer function G(sl).

And the bias between the target position Yahana end effector position #q,)!
.

A force proportional to the difference attempts to return the robot to the target position.

Acts as a restoring force. In addition, external force Fist is applied to the robot.
.

When added, the robot moves in that direction. moreover,.

A force proportional to the robot's speed is in the opposite direction.

Acts as viscous force.

, 4.

Here, if the target position moves at a constant speed vr.

In other words, the steady deviation (in this case, the steady speed deviation) when the ramp input (R (sl=vr/S2)) is applied is:
.

It can be found using equation (1) from the final value theorem.

The above first embodiment is an example of one human input signal and one output signal, but this can be multi-dimensional, for example two-dimensional (6th example shown in the figure).
To extend it, do the following:

The parallel direction to the direction of travel shown in Figure 6 is the X axis, and the perpendicular direction is the y axis.
When used as an axis, job) is displayed in pect as follows.

be done.

Similarly, Qsl and Ffsl are also displayed as two-dimensional vectors.

In addition, each story is shown in swatches in Figure 1.

Continuous functions and constants are extended to a diagonal matrix representation as follows.

When expanded in this way, the steady-state deviation of the fi1 formula is X.

This appears only in the axial direction, that is, in the direction of travel.

Because it is moving at an almost constant speed in this direction.

Due to the influence of viscous resistance C (>0).

In the equation (1) representing the constant deviation, only k and C can be changed as parameters on the software. vy is the target value of moving speed and cannot be changed, and kr+Km and N are hard values and cannot be changed.

Also, it is clear from equation (1) that if C is made smaller or k is made larger, the steady-state deviation becomes smaller, but
C. has been determined to be optimal for the physical work the robot is required to perform, and it is not appropriate to change it.

It's not painful.

FIG. 2 is a block diagram of a control device according to a second embodiment of the present invention in which compensation is added to further reduce the steady-state deviation. In this embodiment, in addition to the configuration of the first embodiment, compensation as shown by the two-dot chain line is added. When this compensation is equivalently transformed, the compensation (1 + drill s (
Same as inserting 1 + Megumi s)).

k C etc.

In such a control system, there is the same R (sl=v r/s") as described above.

When the pump input is applied (that is, the target position is V, the velocity becomes V).

), the steady-state deviation at that time is shown by equation (9).

, 7.

Therefore, according to equation (9), when C,=, high reputation °゛°°°顛 ゛, button 5PXsl = 0...
The steady deviation becomes a tower in theory.

In reality, the value of equation 01 is determined experimentally. By setting this value, the steady-state deviation can be significantly reduced, although it may not become zero, and as a result, even if the target position is moved on the curve, the robot's end effect and effect will deviate from the curve. quantity is significantly reduced. l...Next, a multi-degree-of-freedom robot equipped with such a control system.

The actual operation of the machine will be explained with reference to FIG.

In this embodiment, it is applied to a robot for deburring.

There is.

The purpose of removing paris is to remove the unevenness of the surface due to paris.

To be more precise, it means cutting away the convex parts and making the surface flat.

That is.

In reality, it is unevenness due to Paris as shown by curve 42.

When flattening the surface, the movement trajectory 44 of the target position is shown.

It doesn't have to be a strict straight line, just a dotted line.

As shown, even if there is some waviness, the whole thing.

It is good if it becomes flat. However, as shown in curve 42, even fairly large concavities and convexities can be processed during machining.

It is required to follow the pattern appropriately without cutting, to sharpen large protrusions, and to reduce small protrusions to make the uneven surface smooth.・The deburring robot is a robot equipped with a rotary cutting tool 8 as the end effector 8 of the robot l as shown in FIG. Remove the paris by rotating it counterclockwise and moving it in the X direction as shown.

Ru.

In Figure 3, the target position moves from a1 to a and then to a8.

According to this, byte 8 moves from b1 to b and then b.

represents the state. The direction parallel to the direction of travel is the X-axis, and the direction perpendicular to the direction is the y-axis, as shown in fig.

The symbol is a vector quantity representing force.

First, the balance of force when bite 8 is in bl.

think of. In this control method, the deviation i from the target value.

A restoring force (spring force) proportional to the amount acts toward the town.

The X component of this restoring force is fkx,1, and the X component is f
ky is 1. Also, a force (viscosity) proportional to the moving speed.

The force (force) acts in the opposite direction to the velocity (in this case, it is moving in the positive direction of the X axis). This is fax 1. .

The resultant force of these fkx,1, fky,1 and fCX,1 is f3,1, which is f82. and the reaction force to bite 8 ・gr, 1 are balanced. In addition, the rotational force of the cutting tool 8 (torque) and the torque gi due to friction,
In balance.

There is. Note that here it is assumed to be a steady state, and the velocity in the X-axis direction is minute and the viscous force is small, so it is not taken into account.

Considering the y-axis direction, the y-coordinates of point b1 and point b1 are the same (that is, the distance between the straight line 44 and the point and the 1u line 44 and 5 points is the same), so the spring in the y-axis direction power, fky,
1 and.

fly, 5 have the same size. The y coordinate of the 8 points is .

Since point b is larger than point b1, the spring force in the y-axis direction.

’kY+2 is larger than fky, 1 or fky, 3.

Also, points b1 and 7 move at a constant speed in the X-axis direction.

Therefore, the viscous force in the X-axis direction, fcx,1, f
CX, 2.

are equal.

Also, when there is a large gap in the direction of travel like point 53, the speed of point 53 in the X-axis direction decreases.

Target point a moves at the same speed as before, so deviation a3+')
3 is getting bigger. At this time, the X components of point b1 and point 8 are the same.

Since the
I hear it.

In this way, when point b comes above a high paris (that is, when the X component of point b becomes large), the force of pressing against the paris increases, and more paris are removed. On the other hand, when you come to "lower Paris", you get less Paris.

I will take it.

Also, when there is a large Paris in the direction of travel, move forward.

A large force acts in the direction of the line, and it acts as if it takes a lot of pressure.

As described above, in this control method, simply ■.

As long as you give a straight line trajectory like , you can calculate the position and force.

Hybrid control suitable for the size of Paris.

The surface can be flattened by deburring.

Ru.

, 11° As explained above, according to each of the above embodiments, the force.

The hybrid control of position and position becomes the function of the mouth. Furthermore, in the case of the second embodiment (in this case, it was expanded to two dimensions).

Consider the case. Also, considering the case where the direction of travel is not necessarily parallel to the Can multiply. In general, since the direction of travel is not constant, a special calculation is required to know the direction of travel each time compensation is applied, but in this method, 1.1 vector R15l is used, so 1 indicates the direction of travel.

A secondary effect is that the above calculation time can be reduced.

〔Effect of the invention〕

According to the present invention, not only the direction parallel to the traveling direction but also the
At the same time, force control can also be performed in the direction of travel.

Hybrid control of position and force is possible.

[Brief explanation of the drawing]

FIG. 1 shows a hybrid according to a first embodiment of the present invention. The block diagram of the control device, FIG. 2 is the 12th block diagram of the present invention.
．． A block diagram of a hybrid control device according to the second embodiment, FIG. 3 is an explanatory diagram of the operation when the present invention is applied to a deburring robot, and FIG. 4 is a diagram of a multi-degree-of-freedom robot. FIG. 5 is an explanatory diagram of the conventional control system, and FIG. 6 is an explanatory diagram of the problems faced by the present invention. 1...Robot 2...Force sensor 8...
End effector 9... position t sensor k... spring constant C... viscosity constant m... mass constant

Claims (1)

[Claims] 1. In a linear motion multi-degree-of-freedom robot equipped with a means for detecting a position and a means for detecting an external force, when an external force is applied to the robot, the robot moves along a specified path in accordance with the external force.
If the robot deviates from the specified speed, there is a means to return to the original specified path and specified speed after the external force is removed, and a means to set the magnitude of the robot's restoring force and viscous force as parameters on the software when external force is applied. A hybrid position and force control device for a linear-acting multi-degree-of-freedom robot, comprising means for reducing a steady-state deviation when the specified speed is constant.