JP3164574B2 - Servo motor controller - Google Patents

Description

Description: BACKGROUND OF THE INVENTION [Field of the Invention] The present invention relates to a servo motor control for controlling a drive current value supplied to a servo motor in accordance with an external command value.

[Prior art] In a conventional servo motor control device of this kind, for example, PW
As a device for performing M control, a torque command value and a feedback value are compared, a deviation value is substituted into a preset function, a PWM command value is obtained, and a three-phase AC having a magnitude corresponding to the obtained PWM command value is obtained. There is a control device that supplies the servo motor to the servo motor by PWM control. For example, a device described in Japanese Patent Application Laid-Open No. 63-14891 (control method of a torque control device) is a PWM control device.
By setting the function for calculating the command value in consideration of the resistance value and the inductance value of the armature coil of the servomotor, the responsiveness of a control system formed between the servomotor and the servomotor is improved.

[Problems to be Solved by the Invention] However, in the above-described configuration, even if the function of obtaining the PWM command value or the feedback gain of the current is improved to improve the responsiveness, it is possible to cope with the characteristic change of each servo motor. However, there is a problem that there is a limit to improvement in responsiveness. This is because even if the current of the magnitude corresponding to the calculated PWM command value is applied even if the characteristics of the servo motor change with the change of the operation state and the value of energy loss etc.
This is because a driving force required for the servomotor is not generated. If the driving force required for the servomotor is no longer generated, not only will the improvement in responsiveness be hindered, but also the output torque of the servomotor will be macroscopically constant, but will be accompanied by fluctuations microscopically. Becomes As a result, when the servomotor is used as a tool drive source of the processing apparatus, there is a problem that a processing surface becomes uneven when performing extremely precise processing.

The servo motor control device of the present invention solves the above problems,
The purpose is to improve the responsiveness.

Configuration of the Invention The configuration of the present invention that achieves the above object will be described below.

[Means for Solving the Problems] A servo motor control device according to the present invention includes a drive current value calculation unit that calculates a drive current value to be supplied to a servo motor based on an external command value. A servo motor control device that drives the servo motor using the drive current value calculated by the means; a power supply state detection unit that detects an operation state such as a command value and a drive speed of the servo motor; Correlation storage means for storing how the energy loss of the servo motor connected to the servo motor control device changes in response to a change in the operating state detected by the means, and detected by the operating state detecting means. The energy loss generated in the servomotor based on the operating state and the change in the energy loss stored in the correlation storage means. Correction amount calculating means for calculating a current value correction amount for compensating the estimated energy loss, and the drive current value calculating means based on the current value correction amount calculated by the correction amount calculating means. And a driving current correcting means for correcting the driving current value calculated by the following.

[Operation] In the servo motor control device of the present invention having the above configuration, when a command value is given from the outside, the energy loss corresponding to the operating state detected by the operating state detecting means is stored in the correlation storage means. Correlation (indicating how the value of energy loss changes with changes in operating conditions)
The correction amount calculation means estimates the current value from among the above, and further obtains a current value correction amount for compensating the estimated energy loss.
The correlation stored in the correlation storage means is set by examining, in advance, an energy loss that occurs in accordance with the operating state of a specific connected servomotor itself by an experiment or the like. Then, the drive current correction means corrects the drive current value calculated by the drive current value calculation means using the current value correction amount for compensating for the energy loss. Therefore, even if the characteristics of the connected servomotor change due to the change in the operation state and the value such as the energy loss changes,
In the configuration of the present invention, the driving force of the servo motor is controlled so as to approach the command value in the operation state at that time.

Note that the command value corresponds to, for example, a torque command value, but the command value can be one factor representing the operating state so that the torque command value substantially indicates the value of the torque of the servomotor. Therefore, the command value may be considered as the operating state. In such a case, the correlation stored in the correlation storage means is a relationship between the operation state including the command value and the energy loss generated in response to the operation state of the specific servo motor to be connected.

〔Example〕

In order to further clarify the configuration and operation of the present invention described above, a preferred embodiment of the servo motor control device of the present invention will be described below. FIG. 1 is a block diagram showing a control system of a servo motor control device as one embodiment of the present invention, and FIG. 2 is a configuration diagram of the control device.

As shown in FIG. 2, this control device is constituted by a digital circuit centered on a microcomputer C as shown in the figure in consideration of simplification of the configuration and versatility. That is, a CPU 1 that executes logical operations, a ROM 3 that nonvolatilely stores various control programs executed by the CPU 1 and a data table used in the programs, and a RAM 5 that temporarily stores information and assists the operations of the CPU 1. And an input / output port 7 for exchanging information with these logic circuits and other devices as main components.

Other devices of the control device include a PWM that outputs a PWM signal according to a PWM command value output from the input / output port 7.
A circuit 9, a power amplifier 11 composed of a power transistor, and a control circuit 13 for driving the power amplifier 11 based on a PWM signal from the PWM circuit 9 are provided. The PWM command value output from the input / output port 7 is calculated by a logic circuit centered on the CPU 1, and the power amplifier 11 and the control circuit 13 apply the three-phase alternating current PWM controlled according to the PWM command value to the servo motor M. Supply.

The control device of the embodiment employs a feedback control method to stably control the servomotor M with higher accuracy. The information of the servo motor M that is fed back is the output of the current detection coil 15 for detecting the magnitude of the current supplied to the servo motor M and the output of the encoder 17 for detecting the rotational position of the rotary shaft of the servo motor M.

In the device configured as above, the RO of the control device
M stores in advance a program of the positioning control and a data table that defines the correlation between the current command value and the PWM command value. The positioning control program of the embodiment constitutes the following control system by execution. As shown in FIG.
, A feedback loop of speed control centered on the speed amplifier 21 as its minor loop, and a feedback loop of torque control centered on the torque amplifier 23 as its minor loop. When the command data is input from the host system 25, the torque is controlled with reference to the data in the data table storage unit 27 to transfer the control target such as a tool to the position command value indicated by the command data, and the control target is set to the target. Position in position.

On the other hand, the data table is stored in the data table storage unit described above.
In the embodiment, a data table (corresponding to the correlation storage means of the present invention) indicating a change in the value of the energy loss generated in the connected servomotor itself in accordance with the change in the operating state. ) And a data table indicating the amount of correction of the PWM command value required to compensate for the energy loss, corresponding to the value of the energy loss. FIG. 3 is a graph showing an example of these data tables. In addition, each data table is used to measure the energy loss generated by changing the operating state of the specific servo motor itself to be connected, and to compensate for the energy loss.
The correction amount of the command value is obtained and obtained by an experiment while changing the value of the energy loss. The measurement and the experiment were performed under the condition that the feedback control was not performed.

In the data table, 2 represents the value of the energy loss due to the friction loss and the iron loss that change with the rotation speed as a variable.
The two tables are shown in the graphs of FIGS. 3 (A) and (B). The friction loss occurs between the rotating shaft and the bearing of the housing. Iron loss is caused by leakage magnetic flux or the like in an iron core around which an armature coil is wound. Both energy loss values tend to increase with increasing rotational speed.

As a third data table, a table showing the value of energy loss due to copper loss changing with the PWM command value as a variable is shown in the graph of FIG. 3 (C). Copper loss is mainly caused by heat loss. The loss value tends to increase as the PWM command value increases.

As a fourth data table, a table showing the energy loss as a difference between the cumulative value of the input energy and the cumulative value of the output energy, which varies with the operation duration as a variable, is shown in the graph of FIG. The operation continuation time is related to the temperature rise of the servo motor, etc., and the energy loss using this as a variable is caused by a change in the characteristics of the components, for example, a change in the resistance of the armature coil or a change in the amplification factor of the power amplifier. I do. Energy loss values tend to increase with increasing operating duration.

FIG. 3E is a graph showing a correction amount of the PWM designated value for compensating the above four types of energy loss.
Experimental results are set so that the correction amount of the PWM command value increases as the energy loss increases. The sum of the above four types of energy loss values corresponds to the energy loss in this graph. The correction amount is an amount added to the PWM command value.

Each data table described above is slightly different depending on the actual dimensions of the members constituting each servo motor even if the servo motors are of the same model.

The servo motor control device according to the embodiment configured as described above controls the servo motor as follows. As shown in FIG. 2, when a position command value is input from the host system 25, in a position control feedback loop, the position command value and the position detection value from the encoder 17 are compared, and the deviation value is compared with the position. Input to the amplifier 19, a process of calculating a speed command value necessary for the position detection value to follow the position command value is performed at intervals of several milliseconds.

In the feedback loop of the speed control, a value obtained by multiplying a speed detection value obtained by differentiating the position detection value of the encoder 17 by the differentiation factor S with the speed command value thus calculated and further applying a gain β2 to the speed command value, The deviation is input to the speed amplifier 21, and a process of calculating a torque command value necessary for the speed detection value to follow the speed command value is performed at intervals of several hundred microseconds.

Further, in a torque control feedback loop, a gain β3 is applied to a current detection value obtained by digitally converting a detection signal of the current detection coil 15 via the A / D converter 29 with respect to the torque command value calculated by the speed amplifier 21. The obtained values are matched, the deviation value is input to the torque amplifier 23, and the PWM command value is determined at intervals of several tens of microseconds by referring to the data in the storage unit 27 of the data table defining the above-described correlation. .

In this torque control feedback loop PWM
An example of the processing routine for obtaining the command value is shown in the flowchart of FIG. By starting the process, first, the torque command value
Four values of Otrq, current feedback value Ftrq, rotation speed detection value N, and operation continuation time H are read (step 100). As the rotation speed detection value N, a feedback value of the speed control loop is used. The operation continuation time H is obtained by a soft timer or the like which is repeated at predetermined intervals from the start of operation of the servo motor M.

Next, among the read values, a deviation value D between the torque command value Otrq and the current feedback value Ftrq is determined, and the deviation value D is substituted into a predetermined function f (x) to obtain a PWM provisional command value PrO.
The arithmetic processing for obtaining pwm (step 110) is performed. The function f (x) for substituting the deviation value D includes a proportional term, an integral term, and the like, and is a known function. The processing of step 110 corresponds to the drive current value calculation means of the present invention.

Next, the thus obtained values indicating the three operating states of the detected rotational speed N, the PWM provisional command value PrOpwm, and the operation continuation time H are compared with the data tables shown in FIGS. 3 (A) to 3 (D). Then, a process for obtaining four types of energy loss in this operating state is performed. From the detected rotational speed N, two energy loss values EL1 and EL2 due to friction loss and iron loss are specified with reference to the graphs of FIGS. 3A and 3B (step 120). From the PWM temporary command value PrOpwm, referring to the graph of FIG. 3 (C), the energy loss value EL due to copper loss
3 is specified (step 130). From the operation continuation time H,
The energy loss value EL4 between the input and output energy is specified with reference to the graph of FIG. 3 (D) (step 140).

When the four energy loss values EL1, EL2, EL3, EL4 are obtained in this way, these are summed, and the total energy loss value is calculated.
The correction amount CV of the PWM temporary command value PrOpwm is specified from ELamt with reference to the graph of FIG. 3 (E) (step 150).

Finally, the correction amount CV is added to the PWM provisional command value PrOpwm, and the PWM
A calculation process (step 160) for obtaining the command value OPpwm is performed. The processing in step 160 corresponds to the drive current correcting means of the present invention.

By the processing shown in the above flowchart, the PWM4 command value OPpwm obtained as a value that can compensate for the energy loss in the operating state at that time is output from the input / output port 7 to the PWM circuit 9. The PWM circuit 9 generates a PWM signal in accordance with the PWM command value, and the control circuit 13 drives the power amplifier 11 based on the PWM signal. Supply as current.

As described above, according to the servo motor control device, the PWM command value Otrq is obtained from the deviation value D between the torque command value Otrq output from the speed amplifier 21 and the feedback value Ftrq.
When calculating Ppwm, the PWM command value O which can refer to the data table and can compensate for the energy loss that varies depending on the operating state
Since Ppwm is obtained, the servo motor M
Even if the characteristics of the above change, the three-phase alternating current can be controlled so as to correspond well to the torque command value Otrq, and an excellent effect that response can be improved can be achieved. For example, when calculating the PWM command value, energy loss values that focus on factors such as friction loss, iron loss, and copper loss are used, but these factors are slightly different depending on the connected servo motor. And determines the main energy loss that occurs in the servo motor.
The command value can compensate the energy loss well.
Therefore, the torque of the servo motor M is macroscopically and microscopically constant. When the servo motor is used as a tool drive source of the processing apparatus, the possibility of unevenness on the processing surface when performing extremely precise processing as in the related art is eliminated.

Further, in the embodiment, a PWM temporary command value is calculated from a deviation value between the torque designation value Otrq and its feedback value Ftrq, and a correction amount specified according to an operation state is added to the calculated PWM temporary command value to obtain a PWM command value. Since the value is obtained, the data to be stored as the correlation only needs to be the data of the energy loss that changes according to the change of the operating state and the data of the correction amount for compensating the energy loss. There is an advantage that it may be small.

Furthermore, since the characteristic change due to the temperature rise of the servomotor is estimated and compensated for by the operation continuation time H, it is not necessary to newly add a temperature sensor, so that there is an effect that the device configuration is simplified.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments at all, and it is needless to say that the present invention can be implemented in various modes without departing from the gist of the present invention. For example, the correlation referred to when calculating the drive current value does not indicate the correction amount of the drive current but may indicate the value of the drive current value itself. As the energy loss, in addition to the energy loss described in the embodiment, other factors such as windage may be considered. Alternatively, a temperature sensor may be attached to the servomotor, and a data table indicating the energy loss value corresponding to the temperature may be set in advance.

Effect of the Invention As described in detail above, according to the servo motor control device of the present invention, the correlation between the energy loss and the operating state (shows how the value of the energy loss changes according to the change in the operating state). Are stored in the correlation storage means in advance, and the correction amount calculating means estimates the energy loss expected according to the operating state detected by the operating state detecting means, and further compensates for this energy loss. Is calculated. Since the drive current correction means corrects the drive current value calculated by the drive current value calculation means using the current value correction amount, even if the operation state changes and the characteristics of the servomotor change, the torque command The three-phase alternating current can be controlled so as to correspond to the value well, and an excellent effect that response is improved is achieved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a control system of a servomotor control device as one embodiment of the present invention.

FIG. 2 is a configuration diagram of a control device.

3 (A), (B), (C), (D), and (E) are graphs each showing a stored correlation.

FIG. 4 is a flowchart showing an example of a PWM command value calculation process in a torque amplifier 1. CPU 3. ROM 5. RAM 9. PWM circuit 11 Power amplifier 13. Control circuit 27 Data table storage M: Servo motor

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-213503 (JP, A)

Claims (1)

(57) [Claims] And a drive current value calculating means for calculating a drive current value to be supplied to the servomotor based on an external command value, wherein the drive current value is calculated using the drive current value calculated by the drive current value calculation means. A servo motor control device that drives a motor; an operating state detecting unit that detects an operating state such as a command value and a driving speed of the servo motor; A correlation storage means for storing how the energy loss of the servomotor connected to the servomotor control device changes; an operation state detected by the operation state detection means; and the energy stored in the correlation storage means. Estimating an energy loss occurring in the servomotor based on a change in the loss, and compensating for the estimated energy loss. A correction amount calculating means for calculating a current value correction amount at the current value correction amount calculated by the correction amount calculating means,
A drive current correction unit that corrects the drive current value calculated by the drive current value calculation unit.