JP2005103739A - Vibration suppressing control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device for suppressing vibration of a low rigidity machine whose vibration frequency is changed depending on conditions. <P>SOLUTION: Movement amounts of a first shaft and a second shaft calculated in a motion command decoding means 31 are respectively output to a first movement command calculation means 32 of the first shaft and a second movement command calculation means 33 of the second shaft. The first movement command calculation means 32 and the second movement command calculation means 33 are respectively constituted of a controller 3 for outputting a movement command to a first servo driver 1 and a second servo driver 2. A vibration frequency calculation means 34 of the controller 3 sequentially calculates vibration frequencies of the first shaft based on the second movement command calculation means 33, and outputs the vibration frequencies to a vibration suppressing means 11 of the firs servo driver 1. Therefore, vibration damping effect is always provided, even in a machine whose vibration frequency is changed depending on conditions. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a vibration suppressing device for a low-rigidity machine.

Conventionally, there is, for example, Patent Document 1 as a method for suppressing vibration of a low-rigidity machine.
The prior art will be described with reference to FIG. As shown in FIG. 5, the machine is composed of a first axis composed of a first servo driver and a first motor, and a second axis composed of a second servo driver and a second motor. In the operation of this machine, the arm extends and contracts by the second axis, and the arm moves back and forth by the first axis. The arm is vibrated by the front and back of the arm, and the vibration frequency of the arm tip changes due to the expansion and contraction of the arm. Since this vibration is absorbed by the mechanism between the motor from the arm tip, the servo driver that obtains the feedback signal via the motor cannot detect the vibration. However, in this machine, since the arm tip works, vibration of the arm tip becomes a problem. In this case, as shown in FIG. 4, it is necessary to use the vibration suppression control set for the vibration frequency in a certain arm state in the first servo driver that drives the first axis.
Further, the prior art disclosed in Patent Document 1 discloses a method for issuing a command that is difficult to generate arm vibration, instead of a normal trapezoidal command or a triangular wave command. In FIG. 7, the top is a speed command signal, and the acceleration is maximized at 75% of the acceleration time. Further, the acceleration of deceleration is maximized at a time of 25% of the deceleration time. That is, in the acceleration time from the start of acceleration of the arm, that is, starting to the end of acceleration, that is, reaching the predetermined speed, the acceleration peak is reached when 75% or about 75% of the acceleration time has elapsed from the acceleration start time. Command to the arm drive means so that Further, in the deceleration time from the start of deceleration of the arm to the end of deceleration, that is, the stop, a negative acceleration peak occurs at the time when 25% or about 25% of the deceleration time has elapsed from the deceleration start time. As described above, a deceleration command is issued to the arm driving means.
In the machine as shown in FIG. 5, for example, when the arm extends from 1000 mm to 1500 mm, the vibration frequency changes about 20 times from 20 Hz to 11 Hz. The conventional vibration suppression control by the servo driver damps vibration with respect to a set specific frequency. The allowable deviation of the vibration frequency is only about 10% to 20%.

JP 2000-79583 A

However, since the conventional vibration suppression control considers vibration suppression only for the state with the largest amplitude, a vibration suppression effect is always obtained for a machine whose vibration frequency changes as shown in FIG. I can't.
Further, even with a method of obtaining a vibration suppression effect by modifying a command as in Patent Document 1, it is not always possible to obtain a vibration suppression effect for a machine whose vibration frequency changes as shown in FIG.
The present invention has been made to solve the above-described problem. In the prior art, the vibration suppression control setting executed only by the servo driver is linked with the controller to change the vibration frequency of the machine. The aim is always to obtain a vibration control effect.

According to the first aspect of the present invention, the first motor for driving the first shaft, the first position control means for controlling the first motor by feeding back the position signal of the first encoder attached to the first motor, and vibration suppression A first servo driver comprising a control means, a second motor for driving the second shaft, and a second position control means for controlling the second motor by feeding back a position signal of a second encoder attached to the second motor. The movement amounts of the first axis and the second axis calculated by the second servo driver and the motion command decoding means are output to the first movement command calculation means and the second movement command calculation means, respectively, and the first movement command output means, The second movement command output means is composed of a controller that outputs a movement command to the first servo driver and the second servo driver, respectively, and the controller is based on the output of the second movement command means. The vibration frequency of the first axis is sequentially calculated and output to the vibration suppression means of the first servo driver, so that a damping effect can always be obtained even for a machine whose vibration frequency changes depending on the state. .
According to a second aspect of the present invention, in the vibration suppression control device according to the first aspect, the vibration suppression control means of the first aspect is moved from the first servo driver to the controller, and the vibration frequency suppression means of the controller is provided on the second axis. Since the vibration frequency parameter of the first axis is calculated on the basis of the movement command and set in the vibration suppression control means, a vibration damping effect can always be obtained even for a machine whose vibration frequency changes depending on the state.
According to a third aspect of the present invention, in the vibration suppression control apparatus according to the first aspect, the vibration frequency calculation means of the first aspect is moved from the controller to the first servo driver, and the position information of the second axis is transmitted by the communication means. 1 is transmitted to the frequency calculation means of the servo driver, and the vibration frequency calculation means calculates the vibration frequency of the first axis based on the position information of the second axis, and sequentially sets it as the vibration frequency parameter in the vibration suppression control means. Since it is configured, a damping effect can always be obtained even for a machine whose vibration frequency changes depending on the state.
According to a fourth aspect of the present invention, there is provided the vibration suppression control apparatus according to the first aspect, wherein a plurality of output contacts provided in the second servo driver and a plurality of input contacts provided in the first servo driver are connected to each other. Outputs ON / OFF information based on the position information of the second axis, and the first servo driver specifies the position information of the second axis of the second servo driver between the contacts based on the ON / OFF information. According to the positional information, the vibration frequency of the first axis is calculated, and is sequentially set as the vibration frequency parameter of the vibration suppressing means, so that a vibration suppression effect can be always obtained even for a machine whose vibration frequency changes depending on the state. Can do.
According to the fifth aspect of the present invention, in the vibration suppression control apparatus according to the first aspect, since the vibration frequency calculation is performed as a function, a vibration damping effect is always obtained even for a machine whose vibration frequency changes depending on the state. be able to.
According to the sixth aspect of the present invention, in the vibration suppression control apparatus according to the fifth aspect, since the function is constituted by an approximate expression, a damping effect can always be obtained even for a machine whose vibration frequency changes depending on the state.
According to a seventh aspect of the present invention, in the vibration suppression control apparatus according to the sixth aspect, when the approximate expression is the maximum degree 2 and the error is large, the error is adjusted by applying a correction coefficient to each coefficient of the approximate expression. Since it comprised in this way, the damping effect can always be acquired also with respect to the machine from which a vibration frequency changes with states.

  The present invention has an effect that a vibration suppression effect can always be obtained even for a machine whose vibration frequency changes by linking the setting of vibration suppression control with a controller.

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

FIG. 1 is a configuration diagram of the first embodiment. In FIG. 1, 1 is a first servo driver, 2 is a second servo driver, 3 is a controller, 4 is a first motor, 5 is a second motor, 6 is a first encoder, and 7 is a second encoder. Further, 31 is a motion command decoding calculation means, 32 is a first movement command calculation means, and 33 is a second movement command calculation means. Further, 11 is a vibration suppression control means, 12 is a first position control means, and 22 is a second position control means. Next, the operation will be described.
The first movement command calculation means 32 for the first axis and the second movement command calculation means 33 for the second axis of the controller are based on the movement amounts to the first axis and the second axis calculated by the motion command decoding means 31. A movement command to the first servo driver and the second servo driver is output.
Here, in the robot arm shown in FIG. 5, it is known that the frequency of vibration in the first axis direction varies with the arm length, and the arm length is uniquely determined by the position of the second axis. In response, vibration frequency calculation means 34 for outputting the vibration frequency of the arm is newly added in the motion controller. The vibration frequency parameter value output by the vibration frequency calculation means 34 is input to the vibration suppression control means 11 of the first servo driver. When the controller and the first servo driver are connected by data transmission means such as serial communication, the vibration frequency can be easily set in the vibration suppression control means 11 by a normal parameter transmission method using serial communication. Further, when the moving distance is transmitted by the pulse train signal, it can be realized by driving the external contact signal of the servo driver from the controller separately from the signal transmission path and changing the vibration frequency parameter in the servo. The vibration frequency calculation means 11 creates a table by measuring in advance the relationship between the movement amount of the second axis and the vibration frequency of the arm, for example, and subtracts the memory table from the input movement amount of the second axis to obtain the frequency. Is configured to output. Based on the movement command of the second axis output from the motion command decoding means 31 to the movement command calculation means 33, the vibration frequency calculation means 34 sets the vibration frequency in the first axis direction as the vibration frequency parameter of the vibration suppression control means 11. Therefore, even if the arm length changes, the vibration suppression control means 11 always operates optimally, so that the vibration of the arm in the axis 1 direction can always be suppressed.

  Next, a second embodiment of the present invention will be described. Example 2 is shown in FIG. The difference from FIG. 1 is that, in FIG. 1, the vibration suppression control 11 configured in the first servo driver is realized by a controller. Based on the movement command of the second axis output from the motion command decoding means 31 to the movement command calculation means 33 in the controller, the vibration frequency calculation means 34 converts the vibration frequency in the first axis direction to the vibration frequency of the vibration suppression control means 11. Since it is set as a parameter, even if the arm length changes, the vibration suppression control means 11 can always perform the optimum operation, so that it is possible to always suppress the vibration of the arm in the first axis direction. Further, since the vibration suppression control means 11 is configured in the controller, it is not necessary to transmit the vibration frequency parameter to the first axis, and the first servo driver may be a normal servo driver similar to the second servo driver. effective.

  Next, a third embodiment of the present invention will be described. Example 3 is shown in FIG. The difference from FIG. 1 is that, in FIG. 1, the vibration frequency calculation means 34 configured in the controller is realized in the first servo driver, and the position information of the second servo driver is communicated to the first servo driver. 41 is transmitted. In the first servo driver, the position information of the second axis transmitted by the communication means 41 is input to the vibration frequency calculating means 34 to calculate the vibration frequency of the first axis, and the vibration frequency calculating means 11 Set sequentially as vibration frequency parameters. The communication means 41 can be realized by serial communication or can be transmitted by a parallel signal. Also, the output contact of the second servo driver and the input contact of the first servo driver are connected, and contact ON / OFF information according to the position information of the second axis in the second servo driver is output. The first servo driver can restore the position information of the second axis in the second servo driver from the ON / OFF information. According to the restored position information, the vibration frequency of the first axis can be calculated and sequentially set as the vibration frequency parameter of the vibration frequency calculation means 11.

Next, a fourth embodiment of the present invention will be described. In the first to third embodiments of the present invention, the number of data to be acquired by an actual machine in order to create the table of the vibration frequency calculation means 11 is large, and the amount of work increases. In order to reduce this amount of work, in the fourth embodiment, the vibration frequency calculation means 11 is configured by function calculation. In all of the first to third embodiments, since the vibration frequency calculation means 34 is used, all the other frequency calculation methods described below apply to the configuration of the control system of the first to third embodiments. The configuration of the first embodiment will be described as a representative.
Create machine models for the first and second axes as follows. Consider the mechanical system shown in Fig. 5. At this time, the arm length changes due to the movement of the second axis, and the tip of the arm vibrates due to the movement of the first axis. At this time, a mechanical model in which the vibration of the arm tip is modeled is as shown in FIG. Using this machine model, a function equation for calculating the vibration frequency of the first axis is created from the movement command for the second axis. At this time, the vibration frequency of the arm can be calculated from Equation (1).

f = (1 / 2π) √ (3EI / Ml ³ ) (1)
here,
f Vibration frequency of arm E Young's modulus of arm (determined from material)
I Sectional moment of inertia (determined from the sectional shape of the arm)
M Total mass converted to the arm tip l The arm length M can be obtained from equation (2) by the Rayleigh method.
M = m + 33 m _b / 140 (2)
From equations (1) and (2), the vibration frequency of the arm can be obtained by equation (3).
f = (1 / 2π) √ (3EI / (m + 33m b / 140) l 3) ··· (3)

In the mechanical system of FIG. 5, a change in the arm length l can be considered as a cause of the change in the vibration frequency. Considering the arm length l ₀ in the initial state and only the arm length changes .DELTA.l, the vibration frequency of the arm length can be determined by formula (4) or (5).
f = (1 / 2π) √ (3EI / ((m + 33 m _b / 140) (l ₀ + Δl) ³ )) (4)
f = (1 / 2π) √ (3EI / (m + 33m b / 140) l 3)
× √ (l ³ / (l + Δl) ³ )
= F ₀ √ (1 / (1+ (Δl / l)) ³ ) (5)
Here, the following system is assumed.
Fundamental frequency
_{f 0 = (1 / 2π)} √ (3EI / (m + 33m b / 140) l 3) ··· (6)
Basic arm length l
Young's modulus E = 206 × 10 ⁹ (Pa)
Second moment of inertia of arm cross section I = 3.50 × 10 ⁷ (m ⁴ )
Basic mass of arm tip m = 5 (kg)
Mass of arm m _b = 30 (kg)

For the first axis, parameters necessary for vibration suppression control are output from the vibration frequency of the first axis calculated by a function equation created in addition to the normal movement command. That is, as in the first to third embodiments, the vibration frequency calculation means 34 vibrates the vibration frequency in the first axis direction based on the movement command of the shaft 2 output from the motion command decoding means 31 to the movement command calculation means 33. It is set as a vibration frequency parameter of the suppression control means 11.
According to the second embodiment of the present invention in which the vibration frequency calculation means 11 is configured using the function equation (3), the parameters of the function equation are determined only by data of several actual machines, and the vibration frequency can be calculated. Compared to the first embodiment, there is an effect that less data is acquired by an actual machine and less labor is required.

In the fifth embodiment, when an analytically derived function is complicated, a load is imposed on the function calculation in the controller, such as an increase in calculation time and an increase in register capacity in the CPU. In this case, the calculation burden can be reduced by creating an approximate expression of a function expression as follows.
When √ (1 / (l + Δl) ³ ) in Equation (5) for obtaining the vibration frequency is expanded by Macrolin's, Equation (7) is obtained.
f = f ₀ (1− (3Δl / 2l) + (15Δl ² / 8l ² ) − (35Δl ³ / 16l ³ ) + ..)
... (7)
At this time, it is assumed that the arm length varies between 0.5 and 1.5 (m), and the basic arm length l is set so that the error of the equation (7) with respect to the equation (5) with respect to the equation (5) is minimized. Is selected, the error is minimized when l = 1 (m). Expressions (8), (9), and (10) are obtained by approximating Expression (5) with a first to third order expression.

First order approximation
f = f ₀ (1-3Δl / 2l) (8)
Second order approximation f = f ₀ (1- (3Δl / 2l) + (15Δl ² / 8l ² )) (9)

Third order approximation f = f ₀ (1− (3Δl / 2l) + (15Δl ² / 8l ² ) − (35Δl ³ / 16l ³ ))
... (10)

  According to the configuration of FIG. 2 relating to the second embodiment of the invention, as in the first to third embodiments, the vibration frequency calculating means 34 based on the movement command of the shaft 2 output to the movement command calculating means 33 by the motion command decoding means 31. Sets the vibration frequency in the first axis direction as the vibration frequency parameter of the vibration suppression control means 11, so that even if the arm length changes, the vibration suppression control means 11 can always perform the optimum operation. In addition to being able to suppress vibration in one axis direction, the controller performs vibration suppression control calculation, so the burden of calculation of the servo driver can be reduced.

If the order of the approximate expression in Example 5 is as low as 2 or less, the calculation burden becomes small, but the error from the original function expression becomes large. In the sixth embodiment, this problem can be solved by adjusting the error by multiplying each coefficient of the approximate expression by a correction coefficient.
When the correction coefficient β is applied to Equations (7) and (8) so as to reduce the error, the following equation is obtained.

First order approximation f = βf ₀ (1-3Δl / 2l) (11)
Second order approximation f = f ₀ (1−β × (3Δl / 2l) + (15Δl ² / 8l ² )) (12)
At this time, the correction coefficient may be a value that takes into account the parameter fluctuation range. For example, when l fluctuates from 0.5 to 1.5 (m), the maximum error becomes smaller as follows when the value of the correction coefficient is as follows.
In case of first order approximation, β = 1.3, 54 [%] → 40 [%]
In case of quadratic approximation, if β = 1.25, 32 [%] → 15 [%]
According to the sixth embodiment, since the function can be calculated with the first and second order approximate expressions, the square root operation is not necessary as compared with the case where the function expression obtained by the usual means is used as it is. The load is greatly reduced.

  The present invention was made in response to the market demand that the throughput must be improved while the rigidity of the arm decreases as the robot becomes smaller and lighter, and the vibration frequency of the arm tip changes depending on the posture. Even so, it tried to operate at high speed while suppressing vibration. Therefore, it can be applied not only to robots but also to all low-rigidity machines.

The figure which showed the 1st Example of this invention The figure which showed the 2nd Example of this invention The figure which showed the 3rd Example of this invention Figure showing a conventional example Conceptual diagram of an example mechanical system Model diagram of arm part of illustrated mechanical system Command signal of conventional example

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st servo driver 2 2nd servo driver 3 Controller 4 1st motor 5 2nd motor 6 1st encoder 7 2nd encoder 11 Vibration suppression control means 12, 22 Position control means 31 Motion command decoding means 32, 33 Movement command calculation Means 34 Vibration frequency calculation means

Claims (7)

A first motor comprising a first motor for driving the first shaft, a first position control means for feeding back a position signal of a first encoder attached to the first motor and controlling the first motor, and a vibration suppression control means. A servo driver,
A second servo driver comprising a second motor for driving the second shaft, and second position control means for feeding back a position signal of a second encoder attached to the second motor and controlling the second motor;
The movement amounts of the first axis and the second axis calculated by the motion command decoding unit are output to the first movement command calculation unit and the second movement command calculation unit, respectively, and the first movement command output unit and the second movement are output. The command output means includes a controller that outputs a movement command to each of the first servo driver and the second servo driver,
The controller is configured to sequentially calculate a vibration frequency of the first axis by a vibration frequency calculation unit based on an output of the second movement command unit, and output the vibration frequency to the vibration suppression unit of the first servo driver. Suppression control device.   The vibration suppression control means is moved from the first servo driver to the controller, and the vibration frequency suppression means of the controller calculates a vibration frequency parameter of the first axis based on a movement command of the second axis, and the vibration The vibration suppression control device according to claim 1, wherein the vibration suppression control device is set in a suppression control means.   The vibration frequency calculation means is moved from the controller to the first servo driver, and position information of the second axis is transmitted to the frequency calculation means of the first servo driver by communication means, and the vibration frequency calculation means is the first 2. The vibration suppression control apparatus according to claim 1, wherein a vibration frequency of the first axis is calculated based on position information of two axes, and is sequentially set as a vibration frequency parameter in the vibration suppression control means.   A plurality of output contacts provided on the second servo driver are connected to a plurality of input contacts provided on the first servo driver, and the output contacts output ON / OFF information based on position information of the second axis, The first servo driver specifies the position information of the second axis of the second servo driver as the range between the contacts from the ON / OFF information, calculates the vibration frequency of the first axis according to the specified position information, The vibration suppression control apparatus according to claim 1, wherein the vibration frequency parameter of the vibration suppression unit is sequentially set.   4. The vibration suppression control device according to claim 1, wherein the vibration frequency calculation is performed as a function.   The vibration suppression control apparatus according to claim 5, wherein the function is configured by an approximate expression.   The vibration suppression control apparatus according to claim 6, wherein the approximation formula is set to a maximum degree of 2 and the error is adjusted by applying a correction coefficient to each coefficient of the approximation formula when the error is large.

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