JPH01170386A - Controller for motor - Google Patents

Abstract

PURPOSE:To accurately control a motor by varying a PWM signal to a driving circuit in response to the voltage of a power source. CONSTITUTION:A processor 4 compares a motor speed signal R1 with a speed command signal R2 to calculate a difference, and calculates a control signal R3 to obtain a PWM signal so that the difference should become zero. Further, the signal R3 is corrected by the power source voltage input at that time, and a correction control signal R'3 is output to a PWM signal generator 6. The generator 6 drives first - fourth power MOSFETs 71-74 by the PWM signal on the basis of the signal R'3 from a processor 4. Thus, even if the voltage of the power source is varied, the rotating speed of the motor can be accurately controlled.

Description

[Detailed description of the invention] [Industrial application field] The present invention is applicable to robots, NC machine tools, and VTRs.

The present invention relates to a motor control device used in general machines that require highly accurate speed control or position control, such as office processing equipment such as CDs.

[Conventional technology]

Various types of motor control devices that require highly accurate control are known, and examples thereof will be described with reference to FIG.

In FIG. 2, motor 1 is a DC servo motor,
The rotational speed is detected as a pulse number by an encoder 2, the pulse number is counted by a counter 3, and the result is inputted to a processor 4 as a motor speed signal R1, and a speed command signal R2 is also inputted to this processor 4.

The processor 4 calculates the difference between the speed command signal R2 and the motor speed signal R1 based on the calculation command from the ROM 5,
A control signal R3 that should make the difference zero is calculated and output to the PWM signal generator 6.

On the other hand, the motor 1 is connected to the first to fourth power MOSFETs 7
1,72.73.74 to the power supply 8, the first
~Fourth P'7-M08 FETs 71 to 74 are driven at appropriate timing by a PwM signal from a PWM signal generator 6, thereby controlling the rotation speed of the motor 1. 9 is a capacitor.

Since this is the case, the control signal R3 from the processor 4
is input to the PWM signal generator 6, the first to fourth power MO8FETs 7. ~74 at an appropriate timing with a PWM signal to control the rotation speed of motor 1 using speed command signal R2.
The control is performed so that the difference between the motor speed signal R1 and the motor speed signal R1 becomes zero.

[Problem that the invention seeks to solve]

With such a control device, the voltage of the power source 8 may fluctuate for some reason. For example, if the power source 8 is a battery, the voltage decreases over time.

On the other hand, when considering the current IM flowing through the motor 1, ignoring the internal resistance of the motor 1, the current IM becomes Vt/L. However, V
is the voltage across both ends (voltage of the power supply), L is the inductance, and t is the switching time.

Therefore, in the conventional motor control device that outputs a PWM signal in order to make the difference between the motor speed signal R1 and the speed command signal R2 zero, as described above, when the power supply voltage changes, the current to the motor 1 changes. has changed,
The motor will not rotate at the desired speed and it will take time for control to take effect.

SUMMARY OF THE INVENTION An object of the present invention is to provide a motor control device that can more accurately control the motor rotation speed even when the power supply voltage fluctuates.

[Means and actions for solving the problem] P is connected to the power source 8.
A motor 1 connected via a drive circuit driven by a WM signal, a means for detecting the rotation speed of the motor 1 and outputting a motor speed signal R1, and a difference between this motor speed signal R1 and a command speed signal R2. means for calculating a control signal R3 that sets the value to zero; means for detecting the power supply voltage; means for correcting the control signal R3 based on the power supply voltage; and means for calculating the control signal R3 based on the control signal R/3. and a means for outputting a PWM signal to the reference voltage. This allows the motor 1 to be accurately controlled by passing a current of the same value as the current.

〔Example〕

Embodiments of the present invention will be described below with reference to FIG. Note that members that are the same as those in the prior art have the same reference numerals.

The voltage of the power source 8 is detected by connecting both ends of the power source 8 through the first and second resistors 10.11, and the detected voltage is converted into a digital signal by the A-D converter 12 and input to the processor 4.

As in the past, the processor 4 compares and calculates the difference between the motor speed signal R1 and the speed command signal R2, and generates a control signal R3 to obtain a P W M signal to set the difference to zero.
After calculating, the control signal R3 is corrected based on the power supply voltage input at that time, and a corrected control signal R'3 is output to the PWM signal generator 6.

Correcting the control signal R3 means changing the duty ratio of the PWM signal due to fluctuations in the power supply voltage.

That is, from the above-mentioned equation of IM vt/L, the power supply voltage V
is 9710 times the reference value vo, the switching time t
When the reference time of is set to to, the correction is made so that it is multiplied by 1079 times.

In addition, in the above embodiment, the DC servo motor is
Although we have described the case where the motor is driven by an H-bridge using four SFETs, it can be applied to any type of motor as long as it is controlled by the PWM method. Position control may also be performed in a similar manner.

〔Effect of the invention〕

Even if the power supply voltage fluctuates, PWM is applied to the drive circuit accordingly.
Since the signal changes and provides accurate control current, motor 1
can be controlled precisely.

[Brief explanation of the drawing]

FIG. 1 is a diagrammatic configuration explanatory diagram showing an embodiment of the present invention, and FIG.
The figure is an explanatory diagram of a conventional example. 1 is a motor, 2 is a pulse encoder, 4 is a processor,
6 is a PWM signal generator, 8 is a power supply. Applicant Komatsu Manufacturing Co., Ltd. Representative Patent Attorney Masaaki Yonehara

Claims (1)

[Claims] 1. A motor 1 connected to a power source 8 via a drive circuit driven by a PWM signal, a means for detecting the rotation speed of the motor 1 and outputting a motor speed signal R_1, and means for calculating a control signal R_3 for driving the motor so that the difference between the motor speed signal R_1 and the command speed signal R_2 is zero; a means for detecting the power supply voltage; and a means for detecting the power supply voltage; A motor control device comprising means for correcting the signal R_3 and means for outputting a PWM signal to the drive circuit based on the corrected control signal R'_3. 2. The motor control device according to claim 1, wherein the control signal R_3 is corrected by changing the decoupling ratio of the PWM signal due to fluctuations in the power supply voltage.