Four control modes of servo drive

Feedback compensation open loop control

The accuracy of open-loop system is low, because the step error , start stop error and mechanical system error of servo driver will directly affect the positioning accuracy. This system has the advantages of both open-loop and closed-loop, that is, it has the stability of open-loop and the accuracy of closed-loop. The system will not vibrate because of the resonance frequency, crawling and malfunction of the machine tool. Feedback compensation open loop control does not need clearance compensation and pitch compensation.

Closed loop control

Because the accuracy of open-loop control can not meet the requirements of machine tools, in order to improve the control accuracy of servo driver, the best way is to use closed-loop control. That is to say, there are not only the predecessor control channel, but also the feedback channel of the detection output. the deviation signal is obtained by comparing the command signal with the feedback signal, forming a closed-loop control system with deviation control.

Semi closed loop control

For the closed-loop control system, reasonable design can achieve reliable stability and high accuracy, but the direct measurement of the position signal of the worktable needs to use the position detection device with high installation and maintenance requirements, such as grating, magnetic ruler or linear inductosyn. The equivalent feedback signal of position output can be obtained indirectly by measuring the angular displacement of drive shaft or lead screw. Because the error caused by this part of the transmission can not be compensated by the closed-loop system, which does not include the transmission chain from the rotating shaft to the worktable, the error caused by this part of the transmission can not be compensated automatically by the closed-loop system, the closed-loop control system composed of equivalent feedback signal is called semi closed-loop servo driver, and this control mode is called semi closed-loop control mode.

Feedback compensation semi closed loop control

The principle of compensation of the servo driver is the same as that of the open-loop compensation system. Two independent measurement systems composed of resolver and inductosyn work in amplitude discrimination mode. The disadvantage of the system is high cost. It needs two sets of detection system. The advantage is that it is easier to adjust than the full closed-loop system and has good stability. It is suitable for the feed drive of high-precision large-scale CNC machine tools.

Recent related posts

03/12/2021

Four control modes of servo drive

1.Feedback compensation open loop control. The accuracy of open-loop system is low, because the step error , start stop error and mechanical system error of servo driver will directly affect the positioning accuracy. This system has the advantages of both open-loop and closed-loop, that is, it has the stability of open-loop and the accuracy of closed-loop.

03/10/2021

The main circuit fuse fusing is a common fault of SCR servo driver. The causes of fuse fusing are as follows

The "phase sequence" of power incoming line is incorrect. Due to the synchronization problem between the trigger pulse and the main circuit of SCR servo driver, there are strict requirements on the "phase sequence" of the input power supply. If the "phase sequence" is not correct, connecting the power supply may immediately cause the fuse of the main circuit of the driver to blow.

03/10/2021

Common faults

The motor of servo driver is unstable, and the speed is fast and slow. The main reasons for this kind of fault are as follows: 1.The servo driver parameters are not adjusted properly, and the regulator does not reach the best working state.

03/09/2021

Servo driver related parameter setting method

Position feedforward gain: set the feedforward gain of the positioning loop. The larger the set value is, the smaller the position delay isand the larger the feedforward gain of the position loop is, the high-speed response of the control system will rise, but the position of the system is unstable and prone to oscillation. When high response characteristics are not required, this parameter is usually set to 0, indicating the range of 0 ~ 100%.

03/07/2021

AC servo driver wiring precautions

For signal line and encoder input line, please use shielded wire. Wiring length: the length of signal line from NC to AC servo driver is less than 3m, and the length of input line from AC driver to encoder is less than 20m. The ground wire should be thick wire as far as possible. According to the third grounding standard (grounding resistance < 100 Ω), one point grounding method should be adopted to connect the ground wire. If the motor and the machine tool are insulated, the motor should be grounded.

03/05/2021

Precautions for use and installation

Ambient temperature of servo driver. 1) Operating temperature: - 10 ℃ ~ + 40 ℃; (2) storage temperature: - 25 ℃ ~ + 65 ℃; (3) ambient humidity: 5% ~ 90%, no condensation; (4) vibration / shock: vibration is 0.5g (4.9M / S2), shock is 2G (19.6m / S2).

03/05/2021

What is servo drive?

As one of the importanttechnologies of CNC machine tools, industrial robots and other industrial machinery control, servo drive technology is widely concerned at home and abroad. In the last decade of the 20th century, the development of microprocessor (especially DSP), power electronics, network technology and control technology havelaid a good foundation for the further development of servo drive technology.

03/04/2021

Advantages of servo motor

Precision: the closed-loop control of position, speed and torque, and the problem of out of step of stepping motor is solved; Speed: high speed performance, general rated speed can reach 2000 ~ 3000 rpm;

03/04/2021

What is servo motor brake

Servo motor brake, also known as holding brake, is a component of power release. Generally, the servo motor with brake is integrated with the motor. Generally, DC24 V power supply is used. It is mainly used to lock the rotor shaft of servo motor after power off.

03/03/2021

The key detection items of servo motor and common problems in servo motor detection

1).Servo motor detection -- cogging torque: Cogging torque is an inherent phenomenon of permanent magnet motor, which can make the motor torque fluctuate and produce vibration and noise. We measure the change of motor torque in a rotation cycle on a special test bench and analyze the distribution of cogging torque.