JPH05274040A - Digital control system - Google Patents

Abstract

PURPOSE:To perform smooth positioning even in the area of a low speed by calculating respective integral values of a position detection value and a position estimated value by a state observer to compare them with each other and correcting the state variable in the state observer by the error signal. CONSTITUTION:A state observer 120 estimates the speed and the position by a controlled variable and a manipulated variable obtained by control operation or the state variable and calculates the integral value of a position detection value P and that of a position estimated value Pest and compares them with each other by comparing parts 121, 122, and 123 and corrects the state variable in the state observer 120 itself by error signals. The state observer 120 multiplies estimated movement distance errors Xest and err by a proper constant to correct the acceleration, the speed, and the position in the state observer 120 itself. The position estimated value Pest is fed back as a position signal, and thereby, an influence of quantization is reduced because the value smaller than the actual encoder resolving power is fed back, and smooth positioning is performed by operation of signals of small units.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positioning control device for a motor or the like, and uses an encoder that outputs discrete data as a position detector. In a positioning control device equipped with a digital control system that arithmetically controls various data with a microprocessor, a state observer in particular estimates state variables such as speed and position, and a smooth operation is performed by feeding back these estimated signals. Regarding the control method to be performed. 2. Description of the Related Art Generally, a general positioning control device simply uses a position command value and a position detection value obtained by counting output pulses of an encoder attached to an actuator.
The position deviation is calculated, and the positioning is performed based on the actuator speed command value proportional to the position deviation. FIG. 3 is a block diagram showing an example of the configuration of a conventional positioning control device. In FIG. 3, 305 is a motor, 306 is a response characteristic inside, 307 is a force constant, and s in the formula is a differential operator. Reference numeral 308 indicates a load weight to be driven by the motor. The count value of the output pulse of the encoder is used as the position signal.
321 is a differentiator. The operation will be briefly described below with reference to the drawings. First, the position command input unit 301 from the outside
The difference between the position command value Pref and the position detection value P input to
The position deviation Perr calculated by the comparison unit 310 is obtained. The position controller 302 receives the position deviation and generates a speed command Vref. The time difference of the position detection value P is obtained in the differentiator 321. Using this as the speed Vest, the difference from the speed command is calculated in the comparison unit 311 to obtain the speed deviation Verr. The speed controller 303 receives the speed deviation Verr as an input and generates a current command Iref. The comparison unit 312 calculates the difference between the detected current I and the current command Iref to obtain the current deviation Ierr. Based on this current deviation signal Ierr, the current controller 304 drives the motor 3
05 is controlled to output a desired torque, and finally the position deviation P is controlled to 0. FIG. 4 is a block diagram showing an example of another structure of a conventional positioning control device, which is provided with a state observer 420. In the figure, 405 is a motor, 406 inside is a response characteristic, and 407 is a force constant. Reference numeral 408 indicates the load weight to be driven by the motor. Also, 42
Reference numerals 7 and 428 represent the estimated value of the force constant and the estimated value of the loaded weight, respectively. As described above, the operation will be briefly described with reference to the drawings. First, the position command input unit 401 from the outside
The difference between the position command value Pref and the position detection value P input to
The position deviation Perr calculated by the comparison unit 410 is obtained. The position controller 402 receives the position deviation and generates a speed command Vref. The difference between the speed Vest estimated by the state observer 420 and the speed command Vref is
The speed deviation Verr is calculated by the comparison unit 411. The speed controller 403 receives the speed deviation Verr as an input and generates a current command Iref. The comparator 412 calculates the difference between the detected current I and the current command Iref to obtain the current deviation Ierr. Based on the current deviation signal Ierr, the current controller 404 controls the motor so that the motor outputs a desired torque, and finally the position deviation P is controlled to be zero. [0007] The speed estimation method is different between the control method typified by FIG. 3 and the control method typified by FIG. 4, and attention is paid to the speed feedback signal. The control system shown in FIG. 3 has a larger quantization error rate than the control system shown in FIG. Therefore, in the speed control system, that is, in the stages of the speed control system after 302 and 402, the control system in which the speed is estimated using the state observer operates more smoothly. To explain this, in the control method as represented by FIG. 3 in which the time difference between the position detection values is fed back as the speed, particularly in the low speed region where the output pulse of the encoder cannot be obtained for a long time. Since the quantization error determined by the resolution of the encoder and the sampling period occurs in the feedback signal Vest, smooth control may not be possible depending on the degree of the quantization error. Although it is possible to reduce the influence of the quantization error by adding a low-pass filter for signal smoothing after the differentiator 321 in FIG. 3, it has a drawback that the response of the control system is deteriorated. ..
On the other hand, in the control method using the state observer typified by FIG. 4, even in the low speed region where the output pulse of the encoder cannot be obtained for a long time, the speed estimated value calculated from the detected current I is used. Smooth control is performed. In a general positioning control apparatus, a method is adopted in which a position signal is also fed back to form a position control system and an acceleration / deceleration operation is controlled by an input position command signal from the outside. According to this method, in both the configurations of FIG. 3 and FIG. 4, the position feedback signal contains a quantization error determined by the resolution of the encoder. Further, in the method of estimating the velocity by configuring the state observer using a microprocessor or the like as represented by FIG. 4, when the detector includes some steady detection error. , The velocity estimate can be used, but the position estimate cannot be used. Therefore, when performing position feedback, there is no other method than feeding back the actual position detection value, and depending on the extent to which the quantization error determined by the encoder resolution is included in the position feedback signal, smooth control is still possible in the low speed region. Sometimes you can't. The main reason why the estimated position value cannot be used is, for example, as shown in FIG. 5, when a detection error ε occurs in the detected current I which is the input of the state observer 420, the estimated speed value Vest is Vest = ( ε / s) · [s / {s (s + K2) + K1}] × (Kfest / Mest), and the steady value of Vest is lim (s · Vest) = 0s → 0 using the theorem of the final value, and Vest Will steadily approach the true value, but the estimated position value Pest will be Pest = (ε / s) · [1 / {s (s + K2) + K1}] × (Kfest / Mest), Similarly, the steady-state value is lim (s · Pest) = (ε · Kfest) / (K1 · Mest) s → 0, and Pest is constantly (ε · Kfest) / (K1
・ It can be understood from the fact that the error of (Mest) comes to exist. As shown in FIG. 1, a state observer for using a position estimation value is used to estimate an estimated acceleration using a difference between an integrated value of a position and an integrated value of an estimated position. By configuring the estimated velocity and the estimated position to be corrected, Pest can be prevented from containing a steady error. This is shown as follows using the same method as described above. That is, when the detection error ε occurs, the estimated speed value Ves
t becomes Vest = (ε / s) · [s ² / {s (s (s + K3) + K2) + K1}] × (Kfest / Mest), and if the final value theorem is used, the steady value of Vest is lim (s · Vest) = 0 s → 0 Therefore, Vest constantly approaches the true value. Further, the position estimation value Pest is Pest = (ε / s) · [s / {s (s (s + K3) + K2) + K1}] × (Kfest / Mest), and its steady value is similarly lim (s · Pest ) = 0 s → 0 Therefore, Pest also constantly approaches the true value. Further, the estimated value Xest of the moving distance is Xest = (ε / s) · [1 / {s (s (s + K3) + K2) + K1}] × (Kfest / Mest), and the steady value is similarly lim (s Xest) = (ε · Kfest) / (K1 · Mest) s → 0 Xest is constantly (ε · Kfest) / (K1 · Mest)
) Error occurs, but the influence of the detection error does not appear on Vest and Pest. By feeding back the estimated position value Pest as a position signal, a value less than the actual encoder resolution is fed back, and the influence of quantization can be reduced. Therefore, it is possible to perform smoother control than the conventional control system. Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a control system in the positioning control device of the present invention. 101 is a position command input unit, 105 is a motor, 108 is a motor 105
Is a load driven by, and 120 is a state observer. Further, FIG. 2 shows a flowchart in the case where a software method is used as a means for realizing the present invention.
The operation will be described below with reference to the flowchart. First,
The input position command value Pref and the position detection value P are fetched at regular intervals (processes 201 and 202), and the moving distance X is processed 2
Calculate according to the formula of 03. Next, the estimated moving distance error X
est and err are calculated according to the formula of process 204. Based on this estimated movement distance error Xest, err, processing 205 to 20
The estimated acceleration Aest, the estimated velocity Vest, and the estimated position Pest are calculated by the equations shown in FIG. These parts are respectively the comparison parts 121, 122, 122 in the block diagram of FIG.
It corresponds to the signal immediately after 123. K1, K2, and K3 are gains of the state observer, and are set so that the poles of the state observer have a Butterworth pattern on the complex plane, for example. In this way, by multiplying the estimated moving distance error by an appropriate constant and correcting the acceleration, velocity, and position in the state observing device, it is possible to constantly bring the velocity and position estimation results closer to the true values. it can. The value of the estimated moving distance Xest required in the process 204 is finally calculated according to the formula of the process 208. As described above, since the calculation is performed with a signal of a finer unit than that of a control system which feeds back a position detection value and its time difference as a speed, a smooth positioning operation can be performed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a positioning control system of the present invention. FIG. 2 is a flowchart showing a positioning control method of the present invention. FIG. 3 is a block diagram showing an example of a conventional positioning control method. FIG. 4 is a block diagram showing another example of a conventional positioning control method. 5 is a diagram showing a case where an error is input to the positioning control system of FIG. [Explanation of reference numerals] 102, 302, 402 Position controller 103, 303, 403 Speed controller 104, 304, 404 Current controller 105, 305, 405 Motor 108, 308, 408 Load 120, 420 State observer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location G05B 11/36 501 B 7740-3H 503 A 7740-3H

Claims (1)

Claim: What is claimed is: 1. An actuator for driving a controlled object, an encoder for detecting the position of the actuator, and means for performing a control operation based on a count value of output pulses of the encoder and a position command given from the outside. And a positioning control equipped with a state observer that estimates the speed and position by the function of the count value of the output pulse of the encoder, which is the controlled amount, the operation amount obtained by the control calculation, or the state variable inside the detected actuator. In the device, the state observer calculates and compares the integrated value of the position detection value and the integrated value of the position estimated value, and the state signal in the state observer is corrected by the error signal. method.