JPH07271445A - Servocontroller - Google Patents

Abstract

PURPOSE:To improve the accuracy of control to a servo driving system by automatically correcting offset. CONSTITUTION:The current signals of U- and V-phases detected by a current sensor 7 are respectively inputted to an offset detecting regulator 9 composed of an operational amplifier 8 and a variable resistor VR1 and an offset adjuster 11 composed of an operational amplifier 10 and a variable resistor VR2, and the offset of a driving command signal is detected. The detected offset is converted to an analog/digital converter 12 and corresponding to the torque command value calculated by a CPU 3 in the period of 32ms, it is inputted to a preservation buffer and updated when both motor speed and a motor current are '0'. Then, corresponding to the torque command value arithmetically processed in the arithmetic period of 1ms, the updated offset amount is added from the preservation buffer and corrected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a servo control device for controlling a servo drive system such as an industrial robot.

[0002]

2. Description of the Related Art Offsets generated in various control signals output to a servo drive system of an industrial robot or the like are eliminated by an operator operating a knob of an offset adjuster at the start of normal operation. Was there.

[0003]

However, there is a risk that the offset amount may not be adjusted accurately due to the influence of vibration of the industrial robot or due to artificial work. In particular,
If the industrial robot is stopped for a long time during operation, offset may occur again. Further, an offset occurs and fluctuates due to changes in work environment factors such as temperature and the like, and deterioration over time of electronic control elements and the like. Therefore, the offset of the drive command signal cannot be completely eliminated only by the adjustment at the start-up of the operation. Further, there is a problem in that it is impossible and unrealistic to constantly perform the offset adjustment in terms of work efficiency.
The present invention has been made to solve the above problems,
An object of the present invention is to provide a servo control device capable of automatically correcting an offset and improving control accuracy for a servo drive system.

[0004]

A servo controller according to the present invention as set forth in claim 1 for achieving the above-mentioned object is shown in FIG.
As shown in (a), the servo drive system 10 to be controlled is
Offset updating means 101 for detecting the offset of the control signal output to 0 and updating the offset.
And a correction unit 102 that corrects the control signal based on the updated offset, and the servo drive system 100 stops the detection and update of the offset by the offset update unit 101 at a predetermined cycle. The feature is that it is performed in the state.

Further, as shown in FIG. 1B, the servo control device of the present invention for attaining the object is a target position for the AC servo motor 2 to be controlled and the AC servo. Arithmetic processing means 201 for inputting the current position of the motor 2 to calculate a control signal, conversion processing means 202 for converting the control signal into a drive command signal for the AC servomotor 2, and output from the conversion processing means 202. The offset updating unit 203 includes an offset updating unit 203 that detects an offset of the drive command signal that has been updated and updates the offset, and a correction unit 204 that corrects the control signal based on the updated offset. Detection and update of the offset are performed at a predetermined cycle and when the AC servomotor 2 is stopped. And it features.

[0006]

In the servo control device according to the first aspect of the present invention, when the offset updating means 101 has a predetermined cycle and the servo drive system 100 is in a stopped state, it is output to the servo drive system 100. The offset of the control signal is detected and sequentially updated, and the correction means 102 corrects the control signal based on the updated offset. Therefore,
There is an effect that the offset of the control signal with respect to the servo drive system, which fluctuates due to artificial adjustment or a temporal factor, can be automatically eliminated, and the control accuracy can be improved.

The servo controller according to claim 2 is
When the offset updating means 203 has a predetermined cycle and the AC servomotor 2 is in a stopped state, the offset of the drive command signal output to the servomotor 2 is detected and sequentially updated to the updated offset. Based on the correction means 204, the control signal is corrected. Therefore, the offset is automatically canceled each time the AC servomotor 2 is stopped, and the offset is updated at a predetermined cycle even if the stop time is long, and the operation can be restarted in the state where the offset is always canceled. Therefore, by using the AC servomotor 2 as a servo control device for an industrial robot using the drive source as a drive source, there is an effect that control can be performed with high accuracy.

[0008]

Embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 2 is a block diagram showing an outline of control of an 8-pole AC servo motor (hereinafter simply referred to as a motor) 2 by the servo control device 1 of the present invention. A central processing unit (hereinafter referred to as CPU) 3 inputs a target position and a current position of the motor 2 and performs a position control process and a speed control process at a calculation cycle of 1 ms according to a predetermined processing program.
A torque command value, which is a control signal for, is calculated. The target position is input by dividing the position command signal pattern created every 32 ms in units of 1 ms. Further, the rotation angle of the motor 2 detected by the encoder 4 is captured and input to the CPU 3 as the current position (θ). Since the torque of the motor 2 is proportional to the current, the torque command value calculated by the CPU 3 is expressed as a current command value.

The CPU 3 also performs a sine conversion process on the torque command value calculated as the current command value. Then, while performing sine conversion, each (2π / 3)
Is provided to generate U-phase, V-phase, and W-phase drive command signals. The drive command signal for each phase is input to the gate array 5, and the current control process is performed for each phase. After the current control process, the drive command signals of each phase are switched by the power element 6 and the motor 2 is energized.

U phase and V detected by the current sensor 7
The phase current signals are the operational amplifier 8 and the variable resistor VR, respectively.
1 is input to the offset detection adjuster 9 and the operational amplifier 10 and the offset detection adjuster 11 including the variable resistor VR2, and the offset of the drive command signal is detected.
The detected offset is converted into a digital amount by an analog / digital converter (hereinafter referred to as A / D converter) 12,
When the motor speed and the motor current are both 0 according to the torque command value calculated by the CPU 3 in a cycle of 32 ms, they are input to the save buffer and updated. And 1m
For the torque command value calculated in the calculation cycle of s,
The offset amount updated from the storage buffer is added and corrected. The offset detection adjusters 9 and 11 have a variable resistance V
The offset can be manually canceled by operating R1 and VR2.

FIG. 3 is a flow chart showing an outline of the offset updating process executed by the CPU 3. This offset updating process is performed at a cycle of 32 ms. First, in step 301, it is determined whether or not the motor speed is 0. Then, in step 302, it is determined whether or not the motor current is zero. If it is determined that the motor 2 in which the motor speed and the motor current are both 0 is stopped, step 303.
Then, the detection value of the current sensor 7 is input to the A / D converter 12 via the offset detection adjusters 9 and 11, and the offset amount converted into the digital amount is stored in the storage buffer and updated.

FIG. 4 is a flow chart showing an outline of a torque command value calculation process executed by the CPU 3. This arithmetic processing is performed at a cycle of 1 ms. First, step 4
At 01, the target position and the current position are input to perform position control. Subsequently, in step 402, speed control is performed to calculate a torque command value (current command value) which is a control signal for the motor 2. Then, in step 403, the updated offset amount is read from the storage buffer and added to the calculated torque command value to correct it. Servo control device 1 having the above configuration
Since the offset is detected when the motor 2 is in a stopped state where the influence of vibration or the like is small, the offset update process can be accurately performed.

FIG. 5 is a perspective view of a 6-axis industrial robot 30. This industrial robot 30 has 6 axes X _{1 to} X ₆ each.
The above-mentioned motor 2 is used as a drive source of the above, and the servo control device 1 described in the above embodiment is mounted.
Therefore, there is an advantage that the control can be performed with high accuracy because the control can be performed by the drive command signal in which the offset is automatically canceled.

[Brief description of drawings]

FIG. 1 is a diagram corresponding to a complaint.

FIG. 2 is a block diagram showing an outline of control of a motor of a servo control device according to the present invention.

FIG. 3 is a flowchart showing an outline of offset update processing executed by a CPU.

FIG. 4 is a flowchart showing an outline of a torque command value calculation process executed by a CPU.

FIG. 5 is a perspective view of a 6-axis industrial robot.

[Explanation of symbols]

1 Servo Control Device 2 Motor 3 CPU 4 Encoder 7 Current Sensor 9, 11 Offset Detection Adjuster 12 Analog / Digital Converter 100 Servo Drive System 101, 203, Steps 301-303 Offset Update Means 102, 204, Step 403 Correction Means 201 Arithmetic processing means 202 Conversion processing means

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication location G05B 21/02 A 7531-3H (72) Inventor Yoshino Okano 1-1 chome Showa-cho, Kariya city, Aichi prefecture Within Nippon Denso Co., Ltd.

Claims (2)

[Claims] 1. An offset updating means for detecting an offset of a control signal output to a servo drive system to be controlled and updating the offset, and correcting the control signal based on the updated offset. The servo control device is configured to detect and update the offset by the offset updating means at a predetermined cycle and when the servo drive system is in a stopped state. 2. A calculation processing means for calculating a control signal by inputting a target position for an AC servomotor to be controlled and a current position of the AC servomotor, and a drive command signal for the control signal for the AC servomotor. Conversion processing means for converting into the following, an offset of the drive command signal output from the conversion processing means, and an offset updating means for updating the offset, and the control signal is corrected based on the updated offset. A servo control device comprising a correction means, wherein the offset update means detects and updates the offset at a predetermined cycle and when the AC servomotor is in a stopped state.