Servo control system

2024-07-05 10:29:57

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“ The servo control system is an operating system that can automatically control the mechanical movement of the test device according to the predetermined requirements. [2] In many cases, the servo system refers specifically to the feedback control system in which the controlled quantity (the output of the system) is the mechanical displacement or displacement velocity and acceleration, and its function is to make the output mechanical displacement (or rotation angle) accurately track the input di ”

Basic Definition

The servo control system is an operating system that can automatically control the mechanical movement of the test device according to the predetermined requirements. In many cases, the servo system specifically refers to the feedback control system in which the controlled quantity (the output of the system) is the mechanical displacement or displacement velocity and acceleration, and its function is to make the output mechanical displacement (or rotation angle) accurately track the input displacement (or rotation angle). The structural composition of the servo system is not in principle different from other forms of feedback control systems.

Key indicators

The main indicators to measure the performance of the servo control system are system accuracy, stability, response characteristics and working frequency, especially in terms of frequency bandwidth and accuracy.

The frequency band width is referred to as the bandwidth, which is defined by the frequency response characteristics of the system and reflects the fastness of the tracking of the servo system. The higher the bandwidth, the better the speed. The bandwidth of the servo system is mainly limited by the inertia of the control object and the actuator. The greater the inertia, the narrower the bandwidth. The bandwidth of the general servo system is less than 15 Hz, and the bandwidth of the servo system of large equipment is less than 1~2 Hz. Since the 70s of the 20th century, due to the development of torque motor and high-sensitivity speed measuring machine, the servo system has realized direct drive, eliminated or reduced nonlinear factors such as tooth backlash and elastic deformation, and made the bandwidth reach 50 Hz, and successfully applied in long-range missiles, artificial satellites, precision commanders and other places. The accuracy of the servo system is mainly determined by the accuracy of the measuring element used. Therefore, high-precision measuring elements such as precision potentiometers, self-leveling machines and resolvers must be used in servo systems. In addition, additional measures can be taken to improve the accuracy of the system, such as connecting the measuring axis of the measuring cell (such as a self-leveling machine) to the rotating shaft through a reducer, so that the rotating angle of the rotating shaft is magnified to improve the relative measurement accuracy. Servos with this scheme are called precision and rough measurement systems or dual-channel systems. The angle measurement line meshed by the reducer and the rotating shaft is weighed into the fine reading channel, and the angle measurement line directly taken from the rotating shaft is called the coarse reading channel.

Structural composition

There are many types of mechatronics servo control systems, but from the perspective of automatic control theory, the servo control system generally includes five parts: controller, controlled object, execution link, detection link, and comparison link.

Comparison link

The comparison link is to compare the input command signal with the feedback signal of the system to obtain the deviation signal between the output and the input, which is usually implemented by a special circuit or computer.

controller

The controller is usually a computer or PID control circuit, and its main task is to transform the deviation signal output of the comparison element to control the actuator to act as required.

Execution link

The function of the execution link is to convert the input various forms of energy into mechanical energy according to the requirements of the control signal to drive the controlled object to work. The actuators in the mechatronics system generally refer to various motors or hydraulic, pneumatic servo mechanisms, etc.

Accused object

Mechanical parameters include displacement, velocity, acceleration, force, and moment for the plant.

Testing

The detection link refers to the device that can measure the output and convert it into the dimensions required for the comparison link, which generally includes sensors and conversion circuits.

Author： Guangzhou Servode Electric Co., Ltd.