JP3018445B2 - Tuning control characteristics of industrial systems - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a control characteristic tuning method for an industrial system that controls the operation of a machine by a servo mechanism.

[Prior art] Usually, when controlling the operation of a machine by a servo mechanism,
As shown in FIG. 3, the control unit 4 compares the output value of the plant (the machine in which the servo motor is incorporated) 2 with the command value to determine the operation amount of the servo motor (hereinafter abbreviated as “motor”). Calculate and drive the motor.

FIG. 4 is a block diagram of such an industrial system.

The industrial system includes a controller 1 and a plant 2, and a feedback path includes a position detector 14 and a differential element.
It is configured with 15.

The controller 1 includes a command specifying unit 3 and a control unit 4. The control unit 4 includes a position control unit 5, a speed and current control unit 6.

The position control unit 5 includes a subtractor 7, an integrator 8, and a proportional controller 9. The subtractor 7 controls the position command output from the command setting unit 3 in the form of the number of pulses per unit time (pps). Pp corresponding to the specified speed
s is output, and a position command is output in the form of pps so that the total number of pulses (integrated value of pps) output so far corresponds to the current position. An integrator 8 is needed for that. ) Is subtracted from the speed feedback to obtain the error signal ε.
Generate The integrator 8 (transfer function 1 / s) integrates the post-combination signal ε, and uses the difference between the position set value (integrated value of position command) and the detected position value (integrated value of speed feedback) as a position deviation signal ε _P. Output. Proportional controller 9 (proportional gain K _P) amplifies the position error signal, and outputs it as a speed command e _V. The speed and current control unit 6 includes a subtracter 10, a speed control unit 11, and a current loop 12. Subtractor 10 of the speed feedback, generates a deviation with respect to the speed command e _V, and output as a speed deviation signal epsilon _V. Speed control unit 11 and the proportional element of the proportional gain K _V, made in integral element of the integration time T _I, and outputs a current command e _I in response to the speed deviation signal epsilon _V (in the Figure 4, the proportional gain K _V , the integral element gain K _V / (T _I s),
Feedback proportional gain 1, integral element gain 1 / (T _I s), forward proportional gain K _V ). Current loop 12 in the proportional control system, having a proportional gain K _I, and outputs the manipulated variable y in response to the current command e _I. The plant 2 inputs the manipulated variable y,
Run a machine (not shown). In FIG. 4, the operation of the plant 2 includes an element for generating a torque from the manipulated variable y.
13 ₁ and are represented by elements 13 ₂ to generate a speed from the torque. The transfer function of the element 13 ₁ transfer function is element 13 ₂ is K _T is H (s). When the plant 2 is a single motor, H (s) = (Js) ^-1 . Here, J is the moment of inertia of the motor.

The position detector 14 detects position information (hereinafter abbreviated as position) of the plant 2 to be controlled as a pulse number. The differentiating element 15 receives the output of the position detector 14 and outputs velocity (pps) feedback.

The transfer function G ₁ of the speed loop of the industrial system is expressed by the following equation.

Where K is a comprehensive proportional gain of the speed loop, and _{K = K V K I K T} (2). When the control object is a single motor, the transfer function {G ⁰ ₁ ▼} of the speed loop is expressed by a secondary system as in the following equation.

Here, K _J = K / J.

Furthermore the transfer function G ₃ of the position loop is expressed by the following equation.

As is clear from the equations (1) to (4), in the industrial system of FIG. 4, the plant characteristic H (s) can be expressed at least approximately by a mathematical expression, and its coefficient can be accurately grasped. In this case, each gain of the control unit can be determined so that optimal control can be obtained. However, when the characteristics of the plant can be approximately expressed but the coefficients cannot be accurately grasped, each gain of the control unit is adjusted as follows.

First, the gain of each loop constituting the control unit 4 is set to 0, and the gain of the current loop is gradually increased from 0. Then, at the frequency resonating with the plant, an oscillation phenomenon appears in the current output value. At this time, the gain of the current loop is set lower than the value of the gain at which the oscillation expression appears. Similarly, the gains of the speed loop and the position loop are set. The gain set as described above is used as each gain of the control unit 4.

[Problem to be Solved by the Invention] In the method for tuning the control characteristics of an industrial system, when the plant is an industrial robot or an NC device that drives an actuator by a motor, the operation safety during oscillation is increased. May not be guaranteed and may damage the system. In addition, since the output of the control target is observed with human intervention, there is a problem in that the gain varies, and uniform operation of the system cannot be guaranteed.

An object of the present invention is to provide a method for tuning the control characteristics of an industrial system, which can obtain desired control characteristics without variation without causing the industrial system to oscillate.

[Means for Solving the Problems] A first method for tuning control characteristics of an industrial system according to the present invention includes a servo mechanism including at least a current loop and a speed loop, and controls the operation of a machine connected to a servo motor. An industrial system to be controlled, which has a tuning mode such as a normal operation mode, and operates in a control operation according to a set control characteristic in the normal operation mode, and controls a control characteristic of the industrial system in the tuning mode. A method for automatically adjusting an industrial system, wherein a transfer function of an output speed with respect to an input torque of a servo motor connected to a machine is converted into a primary system type (J _e s) ^-1 and said current is adjusted. The loop is configured as a proportional control method or a control method that can be approximated to a proportional control, and the speed loop is provided with an integral gain and a subsequent By the total proportional gain connected to the I_P control system, the output speed of the servo motor is fed back to the input side of the integral gain, and the feedback signal is branched and the feedback signal is fed through the feedback proportional gain. Returning to the input side of the overall proportional gain, the speed loop is configured as a secondary system having a natural angular frequency and a damping constant. In the tuning mode, the natural angular frequency ω _n and the damping which describe the control characteristics of the speed loop are set. A constant ζ is set to a desired value, a speed loop having its natural angular frequency ω _n and a damping constant ζ is set as a reference speed loop, and a feedback proportional gain of the speed loop is set to 1, and the integration time was adjusted to 2ζ / ω _n, has the step of adjusting the overall proportional gain 2ζω _n J _e.

A second method for tuning control characteristics of an industrial system according to the present invention includes a servo mechanism including a current loop, a speed loop, and a position loop, and controls the operation of a machine connected to a servomotor in response to a position command. An industrial system having a normal operation mode and a tuning mode.In the normal operation mode, the operation is performed by a control operation according to a set control characteristic, and in the tuning mode, the control characteristic of the industrial system is automatically adjusted. A method for tuning an industrial system, comprising: converting a transfer function of an output speed with respect to an input torque of a servo motor connected to a machine into a primary system type (J _e s) ^-1 ; A proportional control method, a control method that can be approximated to a proportional control, and the speed loop is connected to an integral gain and a subsequent stage in a forward direction. The overall proportional gain by being configured to I_P control scheme, the feedback of the output speed of the servo motor to the input side of the integral gain,
Further, the feedback signal is branched and returned to the input side of the total proportional gain via the feedback proportional gain to configure the speed loop into a secondary system having a natural angular frequency and a damping constant. Setting the natural angular frequency ω _n and the damping constant ζ that describe the control characteristics of the speed loop to desired values, and setting the speed loop having the natural angular frequency ω _n and the damping constant と_し as a reference speed loop, The feedback loop gain of the velocity loop is set to 1, the proportional gain of the position loop is set to 0, and the angular frequency ω is sufficiently smaller than the natural angular frequency ω _n of the reference speed loop.
_o and a first tuning speed command having a constant amplitude A are input to the speed loop, and the amplitude of the speed output by the controlled object in response to the first tuning speed command is observed and is changed to the first speed command. and amplitude a _1, the equal angular frequency to the natural angular frequency omega _n amplitude a
Is input to the speed loop, and the amplitude of the speed output by the control target in response to the second tuning speed command is observed, and this is referred to as the second amplitude.
A ₂ and the ratio A ₂ / A ₁ of the second amplitude A ₂ to the _first amplitude A ₁ is 1 /
There is a step of adjusting the overall proportional gain of the speed loop so as to be equal to (2ζ) [Operation] The transfer function of the output speed with respect to the input torque of the motor incorporated in the plant is (J _e s) ^-1. And the current loop is configured by the proportional control method, and the speed loop is I_P
Since the control system is used, the transfer function of the velocity loop is a quadratic system in which K _Je = K / J _e is substituted for K _J in equation (3). Therefore, That is, By adjusting the integration constant T _I and the overall proportional gain K so as to satisfy the following condition, the speed loop can be provided with desired control characteristics.

The effective moment of inertia J _e of the motor connected to a plant can be determined by the method described in engagement mow Sho 61-244286 Patent Publication filed by the present applicant (see below).

Overall proportional gain K, without define the effective moment of inertia J _e, can be adjusted as follows.

Now, the frequency response of the reference speed loop is And Equation (9) is obtained when ω = 0 G _M (0) = 1 (10) When ω = ω _n become. Therefore, when a speed command having a constant amplitude A and a speed command having an angular frequency sufficiently smaller than the natural angular frequency ω _n of the reference speed loop is input to the speed loop, the amplitude A ₁ of the speed output is measured. sets the same amplitude a has a specific angle speed of the amplitude a ₂ to be output when the input speed command with equal angular frequency to the frequency omega _n the speed loop, a ₂ is a ₁
By adjusting the overall proportional gain K so as to be 1/2 of the above, K satisfying the expression (1) can be obtained. Usually, the factor of the total proportional gain K is “adjusted by adjusting the proportional gain K _V of the speed loop.

Example Next, an example of the present invention will be described.

In the tuning of the control characteristics of the industrial system of the present invention, when the norm speed loop is determined, the integration time T _I from equation (8) is determined immediately. However, in addition to the coefficients は and ω _n of the reference speed loop,
It depends on the effective inertia moment J _e of the motor. Therefore, in the second embodiment, a method of determining the effective moment of inertia J _e to determine the total proportional gain K is disclosed. In the second embodiment, the total proportional gain K is determined without explicitly defining the effective inertia moment J _e. Disclose a method for determining

 First, a first embodiment will be described.

The effective moment of inertia J _e, in the case of rotating by connecting the motor to the machine, by converting the effect of machine has on the rotation of the motor to change the moment of inertia of the motor, which when the load inertia J _x , The sum of the motor inertia moment J and the load inertia moment J _x , that is,
It is a quantity defined by J _e = J + J _x . Load moment of inertia
If J _x is described as J _x = J _x using the conversion ratio x to the inertia moment J of the motor, J _e = (1 + x) J. The motor connected to the machine, the transfer function of outputting the speed as an input torque becomes (J _e s) ^-1, it becomes the primary system format.

Above, the values from the definition J _e of the effective moment of inertia J _e is determined as follows.

After step inputting a predetermined speed command to the speed loop,
The speed of the motor after a predetermined time has elapsed is measured for the motor alone and when the machine is connected to the motor, and the speed for the motor alone is indicated by _{ｏ o} , and the speed when the machine is connected to the motor is indicated by υ _{Let x} be J _e = (υ _o / υ _x )
J (see JP-A-61-244286).

Natural frequency omega _n of the thus effective moment of inertia J _e and norms velocity loop obtained, overall percentage gain K is determined from the equation (7) using the attenuation constant zeta.

Next, a second embodiment will be described. FIG. 1 is a block diagram of one embodiment of an industrial system to which the second tuning method of the present invention is applied.

The industrial system according to the present embodiment can perform operations in two modes, a normal operation mode and a tuning mode. In the normal operation mode, the same operation as that of the industrial system shown in FIG. 4 is performed, and in the tuning mode, the tuning according to the present invention is performed. Therefore, the industrial system of the present embodiment includes the same components as those of the industrial system of FIG. 4 and components added for performing tuning. In FIG. 1, the same components as those of the industrial system in FIG. 4 are given the same numbers.

The industrial system comprises a controller 1A, a plant 2, a position detector 14, and a differential element 15. Among them, the plant 2, the position detector 14, and the differential element 15 are the same as the corresponding elements in FIG.

The controller 1A includes a command setting unit 3A, a control unit 4A, a tuning command setting unit 3B, and a state observation unit 16. The control unit 4A is the same as the control unit 4 in FIG. 4 except that an input terminal of a tuning command is provided in an input unit of the speed control unit 11.

In the tuning mode, the state observation unit 16
, Ie, the speed feedback of the motor 13, and detects the amplitude of the speed feedback generated in response to the tuning command, and outputs the detected value to the command setting unit 3A as a tuning signal. The command setting section 3A
In the normal operation mode, the position command is transmitted to the position control unit 5 of the control unit 4A.
When the tuning mode signal is input in the tuning mode, the tuning command setting unit 3B
Outputs the tuning command signal and changes the control parameters (proportional gain and integration time) of the control unit 4A. Upon receiving the tuning command signal, tuning command setting section 3B outputs a tuning command having a predetermined amplitude and a designated frequency to speed control section 11 of control section 4A.

Next, the operation of this embodiment will be described. FIG. 2 is a block diagram showing the operation of the industrial system of the present embodiment.

As described above, the industrial system of this embodiment operates in the normal operation mode in the same manner as the industrial system shown in FIG.

In the tuning mode, the operator first sets the natural frequency ω _n and damping constant の of the reference speed loop in the tuning command setting unit 3B. In this embodiment, ζ = 1 is set. The command setting unit 3A sets the proportional gain K _P of the position control unit 5 to 0 and sets the integration time T _I of the speed control unit 11 to 2 / ω _n (see Equation 8) as initial parameters. Other proportional gains are set to values that allow normal operation when the motor is installed in an industrial robot or NC device.

Here, the command setting unit 3A sets the position command value to 0, and supplies a tuning command signal to the tuning command setting unit 3B. The tuning command setting unit 3B gives the speed control unit 11 a sine wave having a frequency of 0.1 Hz to 1 Hz and an amplitude A as a low frequency speed command. A state monitoring unit 16 detects the peak value of the motor speed output from the plant 2 in response to the low frequency velocity command, to the values as A _1. When the peak value A ₁ is detected, the low frequency peak detection signal is supplied to the command setting section 3A as tuning time signal. Command setting section 3A transmits this signal to tuning command setting section 3B. Tuning command setting unit 3B has received the low-frequency peak detection signal, an angular frequency equal to the natural angular frequency omega _n norms velocity loop, the amplitude has on the speed control unit 11 of the speed command of the sine wave A. State observing unit 16 detects the peak value of the motor speed to be output in response to the speed command of the angular frequency omega _n, this value and A _2. If A ₂ is a half of A _1, speed loop will be matched to the norms velocity loop. If A ₂
Is larger than A _1/2 , the command setting unit 3A
Proportional gain K _V is reduced, A ₂ and increasing the proportional gain K _V smaller adjusts the proportional gain K _V so that the half of A _1.

In the above process, when adjusting the proportional gain K _V, the command setting unit 3A state observing unit 16 by tuning during signal
The adjustment was commanded, a command setting unit changes the proportional gain K _V in. When the adjustment of the proportional gain K _V is completed,
The state observation unit 16 is commanded by the tuning signal.
3A instructs the end of the adjustment, and the command setting unit 3A instructs the tuning command setting unit 3B to stop outputting the tuning command by the tuning command signal.

When the adjustment of the speed loop is completed, the adjustment of the position loop is performed next.

The position loop is a tertiary system when the position control unit 5 is a proportional control system, and a quaternary system when the position control unit 5 is an I_P control system. In any case, the operator sets the reference position loop, and the command setting unit 3A controls the position loop proportional gain K _P and the position control unit 5 to control the I_P control so that the position loop matches the reference position loop. In the case of the method, the integration time is determined.

If the position controller 5 is proportional control system, the transfer function of the speed loop when the G _V, transmission of the position loop function G _P
Is Given as G _V, by using the transfer function control parameters are adjusted, it can be matched easily position loop norms position loop.

Finally, the adjustment of the speed loop is carried out as follows, practically a compromise between the first and second embodiments.

(A) The conversion ratio x is determined in advance for various machines to be connected to the motor.

(B) The motor is disconnected from the machine, that is, the motor alone is controlled, and the proportional gain _KVO of the speed loop is determined by the method of the second embodiment.

(C) The proportional gain K _V1 when the motor is connected to the machine having the conversion ratio x is determined as K _VO (1 + x).

Through the above processing, the speed loop in which the motor is connected to the machine can be made to match the reference speed loop.

(D) In the case of performing the adjustment with higher precision, the proportional gain K _v1 obtained in (c) is set as the initial setting value and the second
The proportional gain is readjusted by the method of the embodiment.

The command setting unit calculates the estimation error of the effective inertia moment J _e from the ratio between the initial setting value K _V1 of the proportional gain and the readjustment value K _V2 (see Equation 7), and obtains an accurate effective inertia moment or conversion ratio x. Can be grasped.

In the above embodiment, the control method of the current loop is the proportional control method. However, if the current loop can be approximated to the proportional control even if an integral element or the like is added to the current loop, It has been experimentally known that there is no practical problem if the closed-loop transfer function can be approximated to a second-order system.

〔The invention's effect〕

As described above, the present invention has the following effects by configuring the speed loop as a secondary system and automatically adjusting the proportional gain and the integration time so that the secondary system matches the reference speed loop.

(1) The control characteristics can be adjusted without causing the oscillation of the industrial system. As a result, even if the safety of the operation at the time of the oscillation is not guaranteed, the desired adjustment can be performed without fear of damaging the system. Can be.

(2) Since automatic adjustment can be performed without human intervention, uniform adjustment without variation can be performed.

(3) Using the high-precision effective moment of inertia value obtained by the adjustment, it is possible to set the desired control parameters for each industrial robot or NC device in which the motor is incorporated, with simple calculations. .

[Brief description of the drawings]

FIG. 1 is a block diagram of one embodiment of an industrial system to which the second tuning method of the present invention is applied, FIG. 2 is a block diagram showing the operation of the industrial system of the embodiment of FIG. 1, and FIG. FIG. 1 is a block diagram schematically showing the configuration of a conventional industrial system, and FIG. 4 is a block diagram of the industrial system shown in FIG. 1,1A: Controller, 2: Plant, 3,3A: Command setting unit, 3B: Tuning command setting unit, 4, 4A: Control unit, 5: Position control unit: 6, 6A Speed and current controller, 7, 10, 11 ... subtractor, 8 ... integrator, 9 ... proportional controller, 11 ... speed controller, 12 ... current loop, 13 ... motor, 14 ... Position detector, 15: Differential element, 16: State observation unit.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G05B 11/36 501 G05B 11/36 503 G05B 13/02 H02P 5/00

Claims (2)

(57) [Claims] An industrial system including a servo mechanism having at least a current loop and a speed loop for controlling the operation of a machine connected to a servo motor, the system having a normal operation mode and a tuning mode, and having a normal operation mode and a tuning mode. In the tuning mode, the controller operates in the control operation according to the set control characteristics, and in the tuning mode, automatically adjusts the control characteristics of the industrial system. by converting the transfer function of the output speed to the primary system of the type (J _e s) ^-1 with respect to the input torque, configured to control system can be approximated to the current loop proportional control method or the proportional control and the speed loop Is configured in an I_P control system with an integral gain and a subsequent The speed is fed back to the input side of the integral gain, and the feedback signal is branched and returned to the input side of the total proportional gain via the feedback proportional gain, so that the speed loop is adjusted to a natural angular frequency and a damping constant. In the tuning mode, the natural angular frequency ω _n and the damping constant 記述 す_る that describe the control characteristics of the speed loop are set to desired values, and the natural angular frequency ω _n and the damping constant ζ and the norm speed loop speed loop with bets, by setting the feedback proportional gain of the speed loop to 1, to adjust the integration time of the speed loop 2ζ / ω _n, adjust the overall proportional gain 2ζω _n J _e A method for tuning the control characteristics of an industrial system, comprising the steps of: 2. An industrial system for controlling the operation of a machine connected to a servomotor in response to a position command, the system including a servo mechanism comprising a current loop, a speed loop, and a position loop. In the tuning mode of the industrial system, which operates in a control operation in accordance with the set control characteristics in the normal operation mode and automatically adjusts the control characteristics of the industrial system in the tuning mode, by converting the transfer function of the output speed to form (J _e s) ^-1 of the primary system to the input torque of the servo motor connected, the current loop proportional control system or a control system which can be approximated to the proportional control, And the speed loop is formed into an I_P control system by an integral gain and a subsequent proportional gain connected in a forward direction. The output speed of the servo motor is fed back to the input side of the integral gain, and the feedback signal is branched and returned to the input side of the total proportional gain via the feedback proportional gain, whereby the speed loop is controlled. In the tuning mode, the natural angle frequency ω _n and the damping constant 、 that describe the control characteristics of the speed loop are set to desired values, and the natural angle is set in the tuning mode. A speed loop having a frequency ω _n and a damping constant ζ is set as a reference speed loop, a feedback proportional gain of the speed loop is set to 1, a proportional gain of a position loop is set to 0, and a natural angular frequency ω of the reference speed loop is set. angular frequency ω _o sufficiently smaller than _n
And a first tuning speed command having a constant amplitude A is input to the speed loop, and the amplitude of the speed output by the control target in response to the first tuning speed command is observed. and a _1, wherein the second tuning-speed command with the natural angular frequency omega _n equal angular frequency of the amplitude a and input to the velocity loop, the control target is output in response to the second tuning speed command Observe the amplitude of the velocity and change it to the second amplitude A ₂
And the ratio A ₂ / A ₁ of the second amplitude A ₂ to the _first amplitude A ₁ is 1 / (2
A method for tuning control characteristics of an industrial system, comprising a step of adjusting a total proportional gain of a speed loop so as to be equal to ζ).