JPS62210515A - Digital servo system controller - Google Patents

Abstract

PURPOSE:To provide a stable control capability less in speed variance by using a value obtained by correcting a measured speed with its correction value to perform the control operation processing. CONSTITUTION:A control logic part 12 reads in a position signal PN from a position detecting means 121 at intervals of a certain sampling time and obtains a speed VN in a speed detecting means 122 by operation and obtains a speed variation DELTAVN with the operation of a speed changing means 123 by operation. A discriminating means 124 discriminates whether a condition is satisfied or not; and it if is not satisfied, the absolute value of a correction value MN is reduced to update the value MN. The correction value MN and the speed VN are used to obtain a speed VN' used for servo processing by the operation of an adding means 127, and a deviation EN between a speed command RN and the speed VN' is obtained by operation in a deviation detecting means 128, thus generating the operation signal of a servo motor.

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a digital servo system control device in which position and speed are controlled by a microprocessor, and particularly to a digital servo system control device suitable for obtaining stable speed control performance.

[Conventional technology]

Position servo systems using servo motors, which are normally used for various automatic machines, robots, and other FA-related equipment, use a pulse encoder and speed generator directly connected to the servo motor shaft to obtain a single position and speed feedback signal. , to control the position and speed of the servo motor. However, due to the rapid progress of microprocessors in recent years. With the progress of digitalization of control algorithms, a method has been developed to remove the speed generator and obtain the speed signal from a pulse encoder that provides a digital position signal, with the aim of improving the performance and lowering the cost of the control system. They tend to be adopted. One such method is described, for example, on pages 277 to 284 of the Journal of the Institute of Electrical Engineers of Japan, Vol. 101, No. 12, published in December 1980. [Problems to be Solved by the Invention] When controlling the speed of a servo motor using the digital servo system as described above, there are the following problems. In other words, regarding speed detection, the servo motor speed can only be measured in a certain rotation speed unit in relation to the motor rotation speed, the number of pulses generated by the pulse encoder per motor rotation, and the sampling time. The detected speed of the motor includes a quantization error. Further, as a control problem, there is a problem in that the quantization error in the speed measurement described above directly appears as a control deviation and causes speed fluctuations and acceleration fluctuations on the controlled side. SUMMARY OF THE INVENTION An object of the present invention is to provide a digital servo system control device that eliminates the above-mentioned problems and provides stable control performance with little speed fluctuation. [Means for Solving the Problems] The above-mentioned object of the present invention is to digitally detect and feed back the operating position of the driven body at regular sampling times, and to detect and feed back the operating position of the driven body according to the control logic determined in the control logic section. In a digital servo system that forms an operation signal for a driven object and supplies it to a power converter to control the operating position and speed of the driven object by its power output, the control logic section is configured to control the position at the Nth sampling. A speed detection means for determining the speed signal difference (VN=Ps-PN-1) between the signal PN and the position signal PN-1 at the previous (N-1)th sampling, and the Nth position signal obtained from the speed detection means. The amount of speed change between the speed signal VN at the time of sampling and the speed signal VN-1 at the previous (N-1)th sampling (ΔVII=VN
-Vw-z) and speed change detection means for determining ΔVN×
A determining means for checking whether the conditions ΔVN-L<O and ΔVN≠0 are satisfied or not, and if the conditions are satisfied, 1ΔVN l
> I MN l and ΔVNXMN 0, the real number MN
correction amount setting means for setting the value of MN; and correction amount updating means for updating the value of MN by reducing it by a predetermined calculation method that monotonically decreases the absolute value of MN when the value is not established; and speed detection using the MN. Correction value VN' of the speed signal from the means
(=VN+MN), and performs a predetermined control logic operation on the correction value VN' as a speed feedback signal of the control logic section, and outputs it as an operation signal for the driven body. Ru. [Operation] Since the control device of the present invention operates at every fixed sampling time Ts, hereinafter, the current sampling time will be referred to as the N-th sampling time, and will be indicated with a subscript N. The previous sampling time is N-1, and the next sampling time is Time points are indicated with subscripts such as N+1. First, at the Nth sampling point, the determining means determines that ΔV
It is determined whether the conditions of NXΔVN-1<O and ΔVN≠0 are satisfied. If the above judgment holds true,
The correction amount setting means sets a correction amount MN that satisfies the above conditions. Next, in the addition means, V N '=V is determined by MN from the correction amount setting means and the speed VN from the speed detection means.
s + M n is found. Here, l ΔVN'
l = l VN' -VN-11= l VN0M
N VN-1l = 1ΔVN+MNl < lΔVN1 , and when ΔV s > O, 0<ΔVN'<ΔVN When ΔVN<O, ΔV N <ΔVN'<0 holds true, so V s ' is always a change in VN. This means that the value is determined as a value that changes by an amount smaller than the amount of change ΔVN in VN in the direction of ΔVN. Therefore, the VN found here is better than when the control deviation is found using the measured VN.
When the control deviation is determined using N', the amount of variation is smaller when compared to the control deviation at the previous sampling time. That is, fluctuations in power supplied to the servo motor are reduced. This apparently means that the control is performed by lowering the control gain. Therefore, if the above-mentioned speed fluctuation requirements are satisfied at each sampling point, the above-mentioned control operation is repeated, so
An apparently low control gain can be obtained, and stable speed control performance can be obtained. Next, if the above requirements are not met, the absolute value of MN is reduced by the action of the correction amount updating means. As a result, the absolute value of the correction amount MN becomes smaller, so the value of VN' (=VN+MN) obtained by the adding means becomes a value close to VN. If this condition continues for several samples, MN'qO becomes MN'qO, and therefore VN' ``FVN.In other words, the influence of correction by MN suddenly disappears, so the apparent control gain recovers to the set control gain, and the load Control performance that follows fluctuations and set value fluctuations without continuous windows can be obtained. [Example] Examples of the present invention will be described below with reference to the drawings. Fig. 1 shows an example of the control device of the present invention. This figure shows the configuration of a digital servo system equipped with a digital servo system, and in this figure, 1 is a digital control section and 2 is a driven section.
1, and this command value and the position count value of the pulse counting unit 24 taken in via the sampler 13 that operates at fixed time intervals Ta, execute control logic and generate a drive control signal for the motor 22. It consists of a sampler 13 that samples the signals output from the logic section 12 and the control logic section 12 at fixed time intervals Ta, and a zero-order hold element 14 that holds the sampled values of the sampler 13. Here, if the digital control unit 1 is composed of logical operation elements such as a microcomputer, the sampler 13 and the zero-order hold 14 can be easily realized by the internal timer function and signal input/output control function of the microcomputer. Ru. The driven part 2 is driven by a motor in this example. The driven unit 2 includes a power conversion unit 21 that converts a drive signal from the digital control unit 1 into a drive power signal for a motor 22, a servo motor 22 driven by the drive power signal supplied from the power conversion unit 21, and a servo motor. A pulse encoder 23 that is directly connected to the output shaft of the motor 22 and used to detect the rotation angle of the motor z2, and a pulse counter 24 that detects the signal of the pulse encoder 23, discriminates the rotation direction of the motor 22, and measures the number of pulses. It has become. An example of the configuration of the control logic section 12 described above will be explained using FIG. 2. In this FIG. 2, 121 is a position detection means, 122 is a speed detection means, 128 is a deviation detection means, 12
9 is a control calculation means, 123 is a speed change detection means, 124
125 is a determination means, 125 is a correction amount setting means, 126 is a correction amount updating means, and 127 is an addition means, which are element means provided to realize the present invention. Next, the operation of an example of the control device of the present invention described above will be explained. The input signals to the control logic unit 21 are the speed command value RN generated by the command generation unit 11 and the counted value of the position signal of the pulse counting unit 24 that measures the rotational position of the servo motor. The control logic unit 12 reads a position signal by the position detecting means 121 at every fixed sampling time, and sets it as PN. Since Ppi is the count value of the pulse signal, it is naturally an integer value. Next, by the operation of the speed detection means 122, the difference between the currently input position PN and the previously input position flPs-t, that is, the speed VN, is calculated by calculating VN=P-s-Ps-1. Naturally, it is an integer value. Subsequently, the speed change detection means 123 operates to calculate the difference between the currently obtained speed VN and the previously obtained speed VN-1, that is, the speed change amount ΔVN, by calculating ΔVN=VN-VN-t. As a result, the determining means 124 operates, and the ΔVN
Using ΔVN-t obtained last time, it is determined whether the conditions ΔVN≠0 and ΔVNXΔVN-1<O hold. If the condition is met, the next predetermined condition |
MN that satisfies ΔVN | > | MN | and ΔVN
Set as the correction amount of N. If the above-mentioned determination condition is not satisfied, the absolute value of MN is decreased and the value of MN is updated by a method that will be described later. Subsequently, the addition means 127 operates and uses the MN obtained by updating or setting the MN and the speed vN obtained by the speed detection means 122 to calculate the IK 'b physical IC speed vN' to VN' It is determined by calculating =VN+MH. Finally, the deviation detection means 128 operates and detects the deviation EN, which is the difference between the speed command RN and the V N ', as EN=RN-V N
' is calculated by the calculation. Based on the erroneous deviation EN, the control calculation means 129 generates an operation signal for the servo motor 22 shown in FIG. 1 according to a predetermined control logic, and sends it to the power converter 21. By the above operation, the discrimination means 1
In the case where the discrimination condition is satisfied by the discrimination in 24,
Compared to the case where the control deviation EN is determined using the detected speed VN and the control calculation process is performed. Since the control deviation EN is determined and the control calculation process is performed using VN', which assumes that there has been a speed change less than or equal to the detected speed change amount ΔVN, the operation signal due to the quantization error of the detected speed VN is A drastic change in speed is suppressed, and therefore the servo motor is stably operated at a substantially constant speed. Further, if the discrimination condition is not satisfied as determined by the discrimination means 124, the absolute value of MN is reduced at each sampling time point, so the value of MN is corrected. Good control performance can also be obtained without loss of coordination. Next, an example of a method in which the correction amount is monotonically decreased at each sampling time point in the correction amount updating means 126 will be described below. MN (5) k+1→k MN/-4MN However, it is assumed that k≧0 and that it is initialized at the same time as MN by the correction amount updating means. Next, the present invention is substantially easy to implement using a microcomputer. Therefore, 2 correction amount setting means 12
The value of MN set in 5 is Mn=-8GN (ΔVN)
= 0.5atΔV>OO, 5atΔv<0 FIG. 3 shows a processing flowchart when the correction method of the correction amount updating means 126 is changed from MN/2 to MN. In FIG. 3, operations corresponding to the elements in FIG. 2 are given the same reference numerals. Also, please refer to 130 in Figure 3, PM
, VN, and ΔVN are reset to PM-1m VN-1eΔVN-1, and a situation in preparation for the next calculation is added to make the operating situation in FIG. In addition, although it is assumed that only the control deviation EN is used in the control calculation of 129, V N '
Others may be used, but they are omitted here as they are not essential. In addition, if there is no need to use V N ', t27 and 128 in FIG. 3 are the same, and EN
=Rs-VN-MN can also be used. Since the actual explanation of FIG. 3 is the same as the operation of FIG. 2 described above, the explanation thereof will be omitted. Next, another embodiment of the present invention is shown in FIG. 4. In this embodiment, the essential difference from the embodiment shown in FIG.
The update process for 126 MNs is executed regardless of the condition determination in 4.
Two points are that the setting value of MW of 25 is increased by the amount reduced by 126. The substantial operation is similar to the embodiment shown in FIG. Next, still another embodiment of the present invention is shown in FIG. In the embodiment shown in FIG. 5, the method of setting 125 MNs is changed from the embodiment shown in FIG. That is, a new MN is obtained by adding -8GN (ΔVN) to the already set MW. In this way,
If condition 124 is satisfied for each sampling period, the past history can be included in the MN setting value,
Allows for more fine-grained control. The above explanation uses a servo motor control directly connected to a servo motor shaft as a position detection element, but the present invention measures the position with a digital value and detects the speed based on the difference in position signals between each sample time. It is applicable to all types of position and velocity servo control systems that involve quantization errors in velocity detection. An example of the results of operation according to the present invention is shown in FIG. Comparing this operation result with the conventional operation result shown in Fig. 7, the detected speed fluctuates in the same way), but due to the action of the present invention, the fluctuation of the control deviation is suppressed to a minimum, and as a result, it becomes stable. It can be seen that speed control performance is obtained. Good results have also been obtained in that the amount of speed fluctuation is significantly reduced. As described above, according to the embodiments of the present invention, in a digital servo control system with quantization errors in speed detection,
The amount of speed change is determined by calculation, and when the amount of speed change satisfies certain conditions, the amount of correction is set so that the amount of speed change is less than the measured amount of speed change, and the measured speed is corrected accordingly. By performing control arithmetic processing using the value corrected by the amount, the apparent control gain is reduced and quantization errors during speed detection are removed, and when the speed change does not satisfy a certain condition. Since the absolute value of the correction amount set for each sample time point is reduced, the influence of the correction amount can be eliminated in the operating region where the quantization error does not affect. Therefore, a high-response, high-performance servo system that can be operated with a high control gain set in the control system can be obtained. Also. According to the servo control method of the present invention, the correction calculation function of the present invention operates even when accelerating from a stopped state, and in this case,
Since the set control gain is apparently increased, the start-up during acceleration is improved, but the effect of the correction disappears around the end of acceleration, so the effect of reaching the set speed smoothly at the end of acceleration can be obtained. Conversely, when decelerating from constant speed operation, the correction calculation function of the present invention works, lowering the brushing control gain at the beginning of deceleration, smoothly transitioning from constant speed operation to deceleration operation, and ending deceleration. By this time, the apparent control gain becomes the set control gain for the same reason as above, so a sharp control response can be obtained at the end of deceleration, which has the excellent effect of making it easier to switch from speed control to position control. can get. [Effects of the Invention] According to the present invention, it is possible to provide a digital servo system that provides stable control performance with little speed fluctuation.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a digital servo system equipped with an example of the control device of the present invention, FIG. 2 is a diagram showing the configuration of a control logic section that constitutes the device of the present invention, and FIG. 3 is its operation. 4 and 5 are processing flowcharts of other examples, FIG. 6 is a characteristic diagram showing the operating performance of the digital servo control system according to the present invention, and FIG. 7 is a characteristic diagram of the conventional digital servo control system. It is a characteristic diagram showing driving performance. DESCRIPTION OF SYMBOLS 1... Digital control part, 2... Driven part, 11.
... Command generating section, 12... Control logic section, 22... Motor, 23... Pulse encoder, 24... Pulse counting section. 2nd item 12,...control logic section '' Fig. 3

Claims (1)

[Claims] 1. The operating position of the driven object is digitally detected and fed back at regular sampling times, and an operation signal for the driven object is formed in accordance with the control logic determined in the control logic section. In a digital servo system that supplies the power to a power converter and controls the operating position and speed of the driven body by the power output, the control logic unit outputs the position signal P_N at the Nth sampling and the previous ( N-1) Difference between the speed signal and the position signal P_N_-_1 at the time of sampling (V_N
-P_N-P_N_-_1);
The amount of speed change (ΔV_N=V_
speed change detection means for determining N-V_N_-_1), and Δ
A determining means for checking whether the conditions of V_N×V_N_-_1≦0 and ΔV_N≠0 are met or not, and if the conditions are met, |
The value of M_N is reduced by a correction amount setting means that sets a real number M_N such that ΔV_N | and an addition means for calculating a correction value V_N'=(V_N+M_N) of the speed signal from the speed detection means using the M_N, and the correction value V_N' is used as the speed feedback of the control logic section. A control device for a digital servo control system, characterized in that it executes a control logical operation determined as a signal and outputs it as an operation signal for a driven body. 2. The correction amount setting means determines |ΔV at the time of using M_N in the addition means, based on the establishment from the determination means.
A real number M_N that satisfies the relationship _N | 2. The digital servo system control device according to claim 1, wherein the value of M_N is updated by decreasing the value of M_N. 3. The correction amount setting means determines |ΔV at the time of using M_N in the addition means, based on the establishment from the determination means.
Set a real number α_N that satisfies the conditions of _N|>|α_N| and ΔV_N×α_N<0, and set M
2. The control device for a digital servo control system according to claim 1, wherein in addition to _N, a new M_N=M_N+α_N is set. 4. The correction amount setting means determines that the real value set to M_N is |M at the time of calculating the correction value V_N' of the speed signal V_N
A digital servo system control device according to any one of claims 1 to 3, characterized in that it is predetermined and set such that _N|<1. 5. The correction amount updating means executes the calculation M_N×α→M_N where (0<α<1) in order to monotonically decrease the absolute value of M_N. Described in any of Section 3. Digital servo system control device. 6. The digital servo system control device according to claim 5, wherein the remainder α in the correction amount updating means is set to α=1/2n, where n is a natural number.