JPH06170769A - Damping control method - Google Patents

Abstract

PURPOSE:To suppress the generation of vibration when a robot arm is brought into a stop in a case of a robot arm being driven through a series of accelera tion operation and deceleration operation continued from the acceleration opera tion. CONSTITUTION:The natural vibration period and the coefficient of damping of a robot arm are measured at steps S1 and S2. A speed pattern according to which the robot arm is driven by a desired distance is determined at a step S3. A time difference between torque peaks of acceleration and deceleration of a driven system to drive the robot arm according to the speed pattern is determined at a step S4. A speed pattern is corrected at steps S5, S6, and S7 so that the time difference between torque peaks obtained at the step S4 is adjusted to a value being an integral number times as large as the natural vibration period of the robot arm. A speed pattern is corrected at steps S8 and S9 so that maximum torque during deceleration is adjusted to a value obtained by multiplying by a damping amount of maximum torque during acceleration.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration control method,
In particular, the present invention relates to a vibration damping control method suitable for suppressing residual vibration during positioning of a robot arm used in an automatic assembly machine or the like.

[0002]

2. Description of the Related Art FIG. 7 is a schematic configuration diagram of a control system of a general robot. In the figure, reference numeral 5 is a finger portion for handling a work piece (not shown), 4 is a robot arm for attaching the finger portion 5 to its tip and rotating and moving it up and down, 3 is a servo for rotating and raising and lowering the robot arm 4. A motor 2 is a servo amplifier for driving the servo motor 3, and 1 is a controller for driving the servo motor 3 via the servo amplifier 2 to control the robot arm 4.

In the configuration as described above, the operation will now be described by exemplifying the rotational driving of the robot arm 4.
The timing chart will be described.

Now, the robot arm 4 is moved from the position a to the position c.
Shall be driven to. In that case, the controller 1 gives the servo motor 3 a speed command as shown in FIG. 8B so that the robot arm 4 changes its position as shown in FIG. 8A.

In this case, ideally, the robot arm 4 together with the finger portion 5 accelerates from time t1 to time t2, has a constant speed from time t2 to time t4, and decelerates from time t4 to time t5. Position a while changing its speed
Change the rotation position from to position c.

On the other hand, similarly, when the robot arm 4 is driven from the position a to the position b, the controller 1 causes the robot arm 4 to change the position with respect to the servo motor 3 as shown in FIG. 8 (D). , A speed command as shown in FIG.

In this case, ideally, the robot arm 4 together with the finger portion 5 accelerates from time t1 to time t3 and decelerates from time t3 to time t5. Change the rotation position up to.

However, in actuality, inertial force or the like acts on the robot arm 4 and the finger portion 5 driven by the servo motor 3, and therefore, in each case of acceleration, acceleration termination, deceleration, and deceleration termination. Vibration is generated in the robot arm 4 and the finger portion 5. As a result, FIG.
As shown in (F), vibration occurs due to acceleration / deceleration in the finger portion 5 at the tip of the robot arm 4, and there is a problem that the vibration does not stop even when positioning is stopped at positions b and c.

As described above, in the robot or the like, the movable parts such as the robot arm 4 and the finger parts 5 which are driven in response to the operation command from the controller 1 vibrate at the time of acceleration / deceleration, at the time of starting or stopping the motion. This is due to the inertial force and rigidity of the movable part, and becomes more remarkable as the operating speed, acceleration, and deceleration are increased in order to increase the speed.
This vibration is a particular problem when positioning is stopped, and the next operation cannot be started until the vibration is stopped. For this reason, the operating time becomes long, which causes a substantial decrease in operating speed.

Researches for suppressing the vibration at the time of positioning such a robot have been widely performed in the form of damping control. For example, JP-A-63-314606 and JP-A-6-314606
The device shown in No. 3-314607 is one example, but in each case, the signal of the acceleration sensor attached to the tip of the robot arm is fed back as a disturbance torque after the vibration occurs at the tip of the robot arm, and the acceleration is measured. It is intended to suppress vibration by controlling it.

Since the conventional damping control method for the robot or the like is performed by the feedback control as described above, the damping is started after the vibration actually occurs.
Even if the time from vibration generation to vibration convergence can be shortened, it cannot be reduced to zero. Further, since the control information for converging the vibration is captured from the vibrating state, the vibration damping control cannot be performed unless the vibration occurs, and it cannot be said that the vibration damping is complete. Moreover, in order to follow the vibration and suppress it, a CPU capable of high-speed calculation is required, and the vibration control system becomes expensive and complicated.

On the other hand, as shown in the block diagram of FIG. 9, a configuration in which a CPU 11 and a memory 12 are provided in a controller 1 is disclosed in Japanese Patent Application Nos. 4-263714 and 4-264385 by the present applicant. Proposed.

This is the speed at which the natural vibration of the drive target consisting of the robot arm 4 having the finger portion 5 at the tip and the servo motor 3 is measured in advance, and the CPU 11 and the memory 12 in the controller 1 drive the drive target. A pattern is obtained in advance, and a time difference t1 between torque peaks of acceleration and deceleration of the drive system by the servo amplifier 2 and the servo motor 3 is obtained corresponding to this speed pattern, and the time difference t1 of the torque peak is the natural vibration cycle of the drive target. By correcting the speed pattern so that it becomes an integral multiple of, it is intended to suppress the residual vibration of the drive target including the servo motor 3, the robot arm 4, and the finger portion 5 after the end of the operation.

However, in this case, as shown in the timing chart of FIG. 10, the current of the servomotor 3, that is, the torque changes as shown in FIG. 10B with respect to the speed pattern shown in FIG. To do. If the robot arm 4 is controlled by correcting the speed pattern so that the torque peak time difference t1 in this case is an integral multiple of the natural vibration period, the residual vibration of the robot arm 4 can be suppressed. However, since the peak value of the amplitude of the robot arm is not necessarily the same during acceleration and deceleration, vibration is not completely suppressed, and the acceleration at the tip of the robot arm 4 is as shown in FIG. Even if it changes and the residual vibration can be suppressed to some extent, it cannot be completely converged. In other words, when vibration occurs at the tip of the robot arm during acceleration,
As shown in 0 (C), the peak value of this vibration is a. As shown in the timing chart of FIG. 11, this vibration is attenuated while the robot arm is moving, and its amplitude is reduced to B during deceleration. If the amount of attenuation per vibration is α and the number of vibrations is n, then B / A = nα (1) Here, nα will be described below as an attenuation amount during deceleration with respect to acceleration. It is the damping rate of vibration at the tip of the robot arm, and α <1. In the vibration suppression of the torque peak time difference t1 at the time of acceleration and deceleration of the robot arm, that is, only the phase difference, the suppression effect is too strong against the vibration that occurs during acceleration and is about to be damped during deceleration. That is, when the same torque as during acceleration is applied during deceleration, the tip acceleration of the robot arm during deceleration overshoots to the deceleration side, as indicated by the arrow in FIG. as a result,
After deceleration, residual vibration will be generated.

[0015]

Since the conventional damping control method is constructed as described above, residual vibration can be suppressed to some extent by manipulating the time difference between acceleration and deceleration, that is, the phase difference. However, there is a problem that the robot arm 4 cannot be completely converged after the robot arm 4 is stopped. That is, when the vibration generated during acceleration is attenuated during deceleration, the same amplitude as during acceleration is attempted to be generated during deceleration, so that there are cases where vibration cannot be completely suppressed. This is exactly the same when trying to cancel out the vibration generated at the start of acceleration with the vibration generated at the end of acceleration, and in some cases it may not be possible to completely suppress vibration by a method that focuses only on the time of the vibration cycle. It was

The object of the present invention is to solve the above-mentioned problems of the prior art, and in particular, when the robot arm is moved by an acceleration operation and a deceleration operation subsequent thereto, vibrations due to positioning of the tip of the robot arm or the like are generated. Learn in advance,
By adding a condition to cancel the vibration to the control command of the robot arm and correcting the speed control curve, the vibration generated when the robot arm decelerates due to the vibration generated when the robot arm accelerates is canceled, and when the robot arm stops. It is to obtain a damping control method capable of suppressing the occurrence of residual vibration.

[0017]

In order to achieve the above object, the present invention provides, as a damping control method, a first step of measuring a natural vibration period and a damping ratio of a driven object, and a moving distance of the driven object. A second step of obtaining a velocity pattern according to
A third step of obtaining the time difference between the respective peaks of acceleration and deceleration of the drive system corresponding to the speed pattern, and based on the speed pattern as it is when the time difference between the peaks is close to an integral multiple of the natural vibration cycle of the driving target. Then, if the time difference of the peak is different from an integer multiple of the natural vibration period of the drive target, based on the speed pattern corrected so that this becomes an integer multiple,
A fourth step of driving a drive target by modifying a speed pattern so that the maximum torque during deceleration is a value obtained by multiplying the attenuation amount of the maximum torque during acceleration is provided. is there.

[0018]

In the above means, the damping control method according to the present invention measures the natural vibration period and the damping rate of the driven object in the first step, and in the second step, the speed corresponding to the moving distance of the driven object. The pattern is obtained, and in the third step, the time difference between the respective peaks of acceleration and deceleration of the drive system that drives the driven object is obtained corresponding to the speed pattern. In the fourth step, the peak obtained in the third step is obtained. When the time difference of is close to an integral multiple of the natural vibration period of the drive target, it is based on the speed pattern as it is, and when the time difference of the peak is different from the integer multiple of the natural vibration period of the drive target, it is modified to be an integer multiple. Based on the speed pattern, the speed pattern is corrected so that the maximum torque during deceleration becomes a value obtained by multiplying the attenuation amount of the maximum torque during acceleration, and the drive target is driven.

[0019]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a flowchart of a vibration damping control method according to an embodiment of the present invention.

As shown in the figure, step S1 and step S2 are set as preparatory steps, and the following steps S3 to S10 are set as control when actually operating the robot arm. It is what is done.

Next, the damping control method of the embodiment will be described based on the timing charts of FIGS. 2, 3, 4, 5, and 6.

In step S1, the vibration of the movable portion such as the robot arm and the finger portion of the robot, that is, the natural frequency f of the tip portion of the robot is measured. This is done by actually vibrating the robot arm and measuring it. As a result, as shown in the timing chart of FIG. 2, it is possible to measure changes in the natural frequency f (natural vibration period λ) and the amplitude associated with the vibration of the robot arm.

In the next step S2, the free vibration cycle of the movable part, that is, the natural vibration cycle λ and the damping rate α are calculated based on the measurement result in step S1, that is, the state of the vibration operation shown in the timing chart of FIG. To do. By the way, the calculation of the natural vibration period λ is performed by obtaining the reciprocal of the natural frequency f.

Through the operations described above, the preliminary preparation is completed.

When actually moving the robot arm, the control after step S3 is performed. First, step S3
Then, the speed pattern of the movement of the robot arm is calculated based on the input conditions such as the moving distance of the robot arm tip, the maximum speed, and the maximum acceleration. This speed pattern is obtained, for example, in the form shown in the timing chart of FIG.

In the next step S4, the time difference t between the torque peaks during acceleration and deceleration of the servomotor for driving the robot arm is calculated. This torque peak time difference t is obtained from the time interval between the torque peaks of the servo motors during acceleration and deceleration, as shown in the timing chart of FIG.

In the next step S5, the torque peak time difference t is surplus calculated with the natural vibration period λ. This is done by dividing the torque peak time difference t by the natural vibration period λ.

In step S5, the division result n and the remainder ta are obtained. In step S6, it is determined whether the remainder ta is close to "0" or "λ". Here, when the remainder ta is not close to “0” or “λ”, the process proceeds to step S7 so that t3 = (n + 1) λ (2), that is, the torque peak time difference t becomes t3. The speed pattern is corrected and the process proceeds to step S8. By the way, n is an integer of 1, 2, 3, ... As a result, the speed pattern is corrected as shown in FIG. 4 (A), and the torque peak time difference t is also corrected to the time difference t3 as shown in FIG. 4 (B).

On the other hand, if the remainder ta is close to "0" or "λ" in the determination in step S6, then t3 = t ... (3) and the process directly proceeds to step S8.

In step S8, the amount of attenuation is obtained from the vibration waveform measured in step S1 and the time difference t3. This is calculated by B / A = nα (4) By the way, FIG. 5 is a timing chart showing how the vibration of the tip portion of the robot arm is damped.
Since the amplitude B is measured as the amplitude after the time difference t3 has elapsed with respect to the amplitude A of the vibration at a specific time,
The amount of attenuation (B / A) can be obtained by taking the ratio of both.

Next, in step S9, the speed pattern is modified so that the maximum torque during deceleration is equal to the attenuation amount of the maximum torque during acceleration. As a result, as shown in FIG. 6A, it is possible to obtain a speed pattern shown by a solid line in contrast to the conventional speed pattern shown by a dotted line.

Then, for a speed pattern as shown in FIG. 6A, a necessary servo motor current, that is, torque is calculated. This is the maximum torque value Tmax during acceleration.
On the other hand, during deceleration, the setting is such that Tr = nα · Tmax (5), and the torque pattern is as shown in FIG. 6 (B).
As shown in.

Based on the above settings, step S
10, the robot arm is driven. as a result,
As shown in FIG. 6 (C), the acceleration at the tip of the robot arm is almost completely converged at the point of deceleration after the end of acceleration, and the residual vibration after the robot arm is stopped can be completely suppressed. .

Now, the above-mentioned operation will be described in more detail by returning to the principle.

First, in steps S1 and S2, the robot arm is operated to obtain the natural frequency f of the robot arm, the natural vibration period λ, and the damping rate α of vibration acceleration.

Next, in step S3, when the moving distance, the maximum speed, the maximum acceleration, etc. are input, the speed pattern corresponding to them is obtained, and the time difference t between the acceleration torque and the deceleration torque is obtained. Further, since the damping rate α of the vibration generated by the acceleration or deceleration is obtained, it is considered that the condition of the expression (5) should be satisfied in order to suppress the residual vibration after the deceleration.

When the deceleration torque is reduced in accordance with the damping rate α during deceleration, as shown in the deceleration speed pattern of FIG. 12, in the quadratic curve portion, the straight line portion, the quadratic curve portion and the following speed change, This is dealt with by decreasing the ratio x% of the quadratic curve. In other words, this is dealt with by reducing the slope of the change in speed. As a result, the torque during deceleration is shown in Fig. 6.
As shown in (B), it is set lower corresponding to the attenuation rate α.

As a result, the vibration remaining at the tip of the robot arm immediately after deceleration and stop can be completely suppressed.

That is, steps S3 to S10
By performing the above control, the residual vibration when the robot arm is stopped is effectively suppressed, and the work of handling the workpiece by the finger portion provided at the tip of the robot arm can be immediately started.

As a result of the above control, when the tip of the robot arm is moved by a specific distance, residual vibration when the robot arm is stopped can be effectively suppressed, so that positioning can be performed quickly and robot control can be performed. Can be speeded up.

Further, since it is not the feedback control,
It is not necessary to incorporate an expensive sensor or speed up the control system, and the system can be configured at low cost.

Further, unlike the configuration in which the vibration is generated and then detected and suppressed, the control is performed so as not to generate the vibration from the beginning, so that the vibration suppression effect is high and the efficient operation can be achieved from the viewpoint of energy saving. it can.

In the above embodiment, the structure in which the speed pattern is corrected in real time is illustrated, but the speed pattern in all the motion patterns may be obtained in advance and the speed pattern may be determined by referring to the table. Good.

In the above embodiment, the driving of the robot arm has been described as an example, but the present invention can be similarly applied to other controlled objects and the same effects can be obtained. . Further, it goes without saying that the same can be applied to the case where the controlled object is not only the rotational movement but also the linear movement.

[0046]

As described above, according to the vibration suppression control method of the present invention, the natural frequency and the damping rate of the vibration of the driven object such as the robot arm are measured in advance to suppress the natural vibration. Since the velocity pattern is calculated in consideration of the damping of the amplitude and the robot arm is moved based on this, it is possible to speed up the driving of the robot arm and suppress the residual vibration when it stops. The effect is that the can be configured easily and at low cost.

[Brief description of drawings]

FIG. 1 is a flowchart of a vibration suppression control method according to an embodiment of the present invention.

FIG. 2 is a timing chart showing a vibration attenuation pattern of a robot arm.

FIG. 3 is a timing chart of speed and torque based on an initially calculated speed pattern.

FIG. 4 is a timing chart of speed and torque based on a corrected speed pattern.

FIG. 5 is a timing chart showing a state of attenuation of a vibration waveform corresponding to time.

FIG. 6 is a timing chart of speed and torque based on a final speed pattern.

FIG. 7 is a block diagram of a control system of a known robot.

8 is a timing chart explaining the operation in the configuration of FIG.

FIG. 9 is a block diagram of a control system of a robot that realizes a conventional damping control method.

FIG. 10 is a timing chart illustrating a vibration suppression control method based on torque peak time difference correction.

FIG. 11 is a timing chart for explaining vibration that occurs only by acceleration vibration.

FIG. 12 is a timing chart of a speed pattern during deceleration.

[Explanation of symbols]

 1 Controller 2 Servo Amplifier 3 Servo Motor 4 Robot Arm 5 Fingers 11 CPU 12 Internal Memory

Claims (1)

[Claims] 1. A first step of measuring a natural vibration period and a damping rate of a driven object, a second step of obtaining a speed pattern according to a moving distance of the driven object, and a driving operation corresponding to the speed pattern. The third process for obtaining the time difference between the peaks of acceleration and deceleration of the system, and if the time difference of the peaks is close to an integral multiple of the natural oscillation period of the drive target, the peak time difference is based on the speed pattern as it is. If it is different from an integer multiple of the natural vibration period of, the speed pattern is adjusted so that it becomes an integer multiple, and the speed pattern is adjusted so that the maximum torque during deceleration becomes the value obtained by multiplying the attenuation amount of the maximum torque during acceleration. And a fourth step of correcting the driving target to drive the driving target, the damping control method.