JPS62140104A - Robot control system - Google Patents

Abstract

PURPOSE:To prevent the generation of excessive power and to ensure the smooth control operation of a robot by obtaining the controlled variable from the deviation between the present position and a designated position and comparing the controlled variable with the set maximum controlled variable so that the controlled variable is kept under the maximum controlled variable. CONSTITUTION:If the controlled variable ua of a controlled variable generating part 4 is positive and exceeds the maximum controlled variable umax, the output u1 of a multiplexer 72 reaches the variable umax. While the output u2 of a multiplexer 75 also reaches the variable umax. When the controlled variable ua is positive and less than the variable umax, the output u1 of the multiplexer 72 is equal to the variable ua. Then the output u2 of the multiplexer 75 is also equal to the variable ua since the variable ua is positive and larger than the minimum controlled variable umin. Both max. and min. controlled variables umax and umin can be set optionally by a CPU 6 according to the working contents and the type of an object. This prevents an excessive torque produced by a motor 1 even though the steady deviation is produced and the controlled variable ua is increased.

Description

[Detailed Description of the Invention] [Table of Contents] Overview Industrial Application Fields Prior Art Problems to be Solved by the Invention Means for Solving the Problems (Fig. 1) Working Examples fat - Description of Examples ( Figure 2) Description of other embodiments Effects of the invention [Summary] In a robot control system that performs work on an object by controlling the drive source of the robot by position feedback,
A control unit that obtains a controlled variable based on the deviation between the current position and the commanded position, compares the controlled variable with a set maximum controlled variable, and outputs a control JTj M that limits the controlled variable so that it does not exceed the set maximum controlled variable. This is to prevent excessive force from being applied to the object due to steady-state deviation.

[Industrial application field]

The present invention relates to a control method for a robot that performs work on an object using position feedback control, and particularly to a control method for a robot that allows the robot to easily work even under external restraint conditions.

In recent years, many attempts have been made to automate various tasks using robots.

Generally, a robot has a large number of joints and arms, and each joint is provided with a driving actuator to control the position of the arm.

In such a robot, the hand at the end of the arm picks up an object and commands it! The mainstream is a pink-and-place operation in which the object is brought to a position, and such a simple operation can be easily realized using position feedbank control.

On the other hand, as robots become more widespread, robots are required to perform more complex tasks, such as the one shown in Figure 3.
It is required to open and close the door DR using the hand HD at the tip of the arm 3.

In such work, since the door DR, which is an object, rotates around its axis, the robot is constrained by the object. Such operations include opening and closing drawers, pressing push buttons, etc., and the robot is subject to various constraint conditions while working on the object to be worked on.

[Conventional technology]

Position control is widely used as a control method for such robots, and a conventional control method will be explained with reference to FIG.

An arm 3 is driven by a motor 1 serving as an actuator, and a position θ of the motor 1 (or arm 3) is detected by a position detector 2. The detected current position device θ is input to the control amount generator 4, and the command position θ from the CPU 6 is
. The adder 40 takes the positional deviation Δθ with respect to the control amount U,
is calculated.

To calculate the control amount U, for example, the position deviation Δθ is input to the integrator 4.
1 and multiplied by the feedback gain f in the multiplier 43, the deviation amount obtained by multiplying the positional deviation Δθ by the feedback gain f2 in the multiplier 44, and the positional deviation Δθ
The estimated angular velocity ω is obtained from the model 42 of the controlled object,
The angular velocity amount multiplied by the feedback gain f in the multiplier 45 is added by the adders 46 and 47, and obtained.

This control amount U is input to the power amplifier 5, and the power amplifier 5 drives the motor 1 by passing a current im proportional to the control amount U through the motor 1.

However, there may be other ways to find it.

In such a position control system, a control amount U is obtained based on the positional deviation Δθ, and the motor 1 is subjected to position feedback control.

(Problems to be Solved by the Invention) However, in such a position control system, it is difficult to smoothly perform work that is subject to the constraint conditions from the aforementioned object.

However, it is nearly impossible for the robot to completely know the state of the object at all times. For example, when opening and closing the door DR mentioned above, as shown in Figure 5, the door DR is connected to the solid line MT in the figure.
Even though the movement trajectory is constrained as shown in FIG.
It is extremely difficult to issue commands that completely match the above.

Even if such a situation occurs, in pick-and-place operations where the object is not subject to equivalent restraints, there will be no hindrance to the equivalent work, but if the object is restrained, a steady deviation, which is a steady positional deviation, will occur. It will always occur.

When there is such a steady-state deviation, in the position control system,
Since the control jB N u is determined so as to eliminate this deviation, the current flowing through the motor 1 increases. Particularly in recent years, in the case where the arm 3 is driven by the motor 1 via a speed reducer, the required current becomes large.

This situation is particularly noticeable when the integral amount of the positional deviation Δθ is fed back, but it may occur even when the integral amount is not fed back.

When there is a steady deviation due to such external constraints,
The deviation will not disappear unless the object or robot is deformed.

Therefore, under external restraint conditions, an excessive force is applied to the object or robot, making it difficult to operate smoothly, and in some cases, the object or robot may be destroyed, or the motor or robot may be damaged due to excessive current. There was also the problem that the power amplifier could be damaged.

SUMMARY OF THE INVENTION An object of the present invention is to provide a control method for a robot that can smoothly and easily perform work under restraint conditions by controlling the position of the object without knowing the state of the object.

[Means for solving problems]

FIG. 1 is a diagram explaining the principle of the present invention.

In the figure, the same parts as those shown in Figure 4 are indicated by the same symbols, and 7 is a control symbol. ! Bit selection section, CPU6
The maximum control amount u is set from the control amount generator 4, and the maximum control amount u is set from the control amount generating section 4. 31Il quantity u, and the maximum limit i11 quantity U set,
A control i1u that does not exceed the maximum control amount U is output to the power amplifier 5.

Incidentally, C0NT is a control section, which is composed of a CPU 6, a control amount generation section 4, and a control amount selection section 7. The function of the selection unit 7 may be configured to be executed by the CPU 6.

[Effect]

In the present invention, since the maximum control amount is limited by the control amount selection section 7, it is possible to prevent the output control amount from becoming large and excessive current flowing through the motor when there is a steady-state deviation.

Therefore, when working under restrained conditions, it is possible to prevent positional control that would generate excessive force on the robot even if the state of the object is not completely known, and this makes work under restrained conditions easier. can be executed.

It is known that the power amplifier 5 itself has an overcurrent protection function to limit the current to the motor 1, but depending on the target object and work content, even a current that does not reach this current limit value may be excessive. It often becomes a powerful force,
Even if the current limiting function of the power amplifier 5 is used, generation of excessive force under restraint conditions cannot be prevented.

〔Example〕

fat - Description of Embodiment FIG. 2 is a block diagram of an embodiment of the present invention, showing details of the control amount selection section 7 of FIG.

In the figure, 70 is a first buffer, which has a maximum control i1u that is more positive than the CPU 6. 8 is set, 7D is a first comparator, which compares the maximum control amount u,,X of the first buffer 70 and the control amount from the control amount generation section 4, The output u1 of the multiplexer of is U,
When ≦U□8, U,=u, ,u, , , When <u, u,'''u,ll is controlled. 72 is a first multiplexer, and a first buffer 70 Maximum side of ?il
73 is a second buffer which inputs the l quantities u,, , 74 is a second comparator;
The negative maximum side of the second buffer 73? Bfuat+t and the output U of the first multiplexer 72 are compared, and the output u2 of the second multiplexer, which will be described later, is determined as u1≧umkn.
When uz -ul, tl+ <u+*in, 75 is the second multiplexer that controls the maximum negative side of the second buffer 73. l
1uat, 1 and the output ul of the first multiplexer 72
is input, and selects and outputs u*tR or U as the output u2 according to the comparison result of the second comparator 74. 76 is a D/A (digital/analog) converter, and the second multiplexer 75 outputs u*tR or U as the output u2. It converts the output u2 into an analog control amount U and supplies it to the power amplifier 5.

To explain the operation of the configuration of the embodiment shown in FIG.
If the controlled amount U, is positive and exceeds Ull, then the first
The output U of the multiplexer 72 becomes u-ax.・u
lllmX is greater than Ul, the force 1, etc., the output u2 of the second multiplexer 75 becomes u7.8. Further, if the control amount U is positive and is less than or equal to 8, the output of the first multiplexer 72 is 1. lI becomes U, and since U, is positive, U, is greater than u, 7, so the output U, of the second multiplexer 75 becomes U.

On the other hand, the control amount U1 is negative and the negative maximum control amount U1. .

If the following (that is, if u a <u aia), the output u1 of the first multiplexer 72 becomes U, and the output u8 of the second multiplexer 75 becomes ul,11.

Further, if the control amount U is negative and is greater than or equal to u,i, the output u of the first multiplexer 72 becomes U, and the output u8 of the second multiplexer 75 becomes U.

Therefore, the control amount u2 to be output is u, 11≦U,≦u
, llx for ul, and ua1 for ul>ullam
1+1 and u,<u,1. Deu, 1. Thus, the controlled amount U is the positive maximum controlled amount U, 1. and the negative maximum control amount ua1
m.

The maximum control amounts u, 1, u, i can be arbitrarily set by the CPU 6 depending on the work content and the type of target object. Even if 2nlua becomes large, generation of excessive torque from motor l can be prevented.

Therefore, the robot does not apply excessive force to the object, preventing destruction of the object or the robot, and enables smooth position control operation even if there is a steady deviation.

In other words, in position feedback control, the torque generated by the motor 1 is controlled to follow the external constraint conditions so that excessive force is not generated, and the state of the object under the external constraint conditions is not known. Also, generation of excessive force can be prevented.

This makes it possible to smoothly open and close doors and drawers, fit objects together, and work under the constraints of button press rings.

(bl Description of other embodiments In the above embodiment, the maximum control amount is set from the CPU 6 before starting the work, but the CPU 6 monitors the position of the robot from the current position θ, and when approaching the target object. The maximum control amount may be set to be large when the robot approaches the robot, and the maximum control amount may be set to be small after the robot approaches the robot, so that there is no substantial restriction on mu control while the robot is moving in space.

Also, the positive and negative maximum control amount is used as the maximum control amount, but is it possible to use the positive minimum control amount instead of the negative maximum control amount? I I may be used as a cent, and a positive or negative minimum control amount may be added to limit the control amount to the minimum value. In this case, the robot will be able to exert a constant minimum force even if there is no steady-state deviation. It can be applied to objects, and may be preferable depending on the work content.

Furthermore, since the control amount selection section 7 is a comparison selection operation, it can be realized by the software of the CPU 6, and the control amount selection section 7 itself may be configured by the CPU, and the control amount generation section 4 can also be implemented by the CPU.
It may be realized by the PU 6 or the CPU of the control amount selection unit 7,
Various configurations can be used depending on the required processing speed and cost.

In the above-mentioned embodiment, the control amount selection unit 7 is composed of digital elements, but ua, uaax, usia, u I
,u! may be treated as an analog quantity and constructed using analog elements.

Although the present invention has been described above using examples, the present invention can be modified in various ways according to the gist of the present invention, and these are not excluded from the present invention.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to smoothly perform work on a robot in a restrained state by preventing the generation of excessive force, and this can be achieved with a stable position control system. It also has this effect.

Furthermore, when a force less than the maximum control amount is being generated, the same operation as a normal position servo system can be performed, so that high-speed movement equivalent to that of the conventional system is possible when moving in the air.

Furthermore, it is possible to easily introduce force control into a position control system, and it is easy to implement, and it also has the effect that an existing position control type robot can be easily provided with a force control function.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of the principle of the present invention, Fig. 2 is a configuration diagram of an embodiment of the present invention, Fig. 3 is an explanatory diagram of work under external restraint conditions, Fig. 4 is an explanatory diagram of the prior art, and Fig. 5 is an explanatory diagram of the prior art. The figure is an explanatory diagram of problems in the prior art. In the figure, 1--Motor (drive source), 3--Arm, C0NT--Control section, 4--Controlled amount generation section, 5--Amplifier, 7-- Control amount selection section.

Claims (1)

[Claims] A robot control method in which a drive source of a robot is controlled by position feedback to cause the robot to perform work on an object, the control amount being determined based on the deviation between the current position of the robot and a commanded position, a control section that compares the control amount with a set maximum control amount and outputs a control amount that is limited so that the control amount does not exceed the maximum control amount; A robot control method characterized by having an amplifier that drives a robot.