A servo system composed of hydraulic components (what is a servo system?) is called a hydraulic servo system. Hydraulic servo systems have advantages such as easy implementation of linear motion speed, displacement, and force control; high driving force, torque, and power; small size and light weight; good acceleration performance; fast response speed; high control precision; and easy-to-ensure stability (classification of servo systems). So, what exactly is a hydraulic servo system ? This article summarizes the basic knowledge of hydraulic servo systems through research and compilation.
Operating characteristics of a hydraulic servo system (working principle of a servo system)
(1) The hydraulic servo system is a position tracking system.
(2) The hydraulic servo system is a force amplification system.
(3) The hydraulic servo system is a negative feedback system.
(4) The hydraulic servo system is an error system.
Classification of hydraulic servo systems
In summary, the working principle of a hydraulic servo system is based on feedback control of fluid power. That is, it uses a feedback connection to obtain a deviation signal, and then uses this deviation signal to control the energy input to the system, causing the system to change in the direction of reducing the deviation, thereby ensuring that the actual output of the system matches the desired value.
Working principle diagram of hydraulic servo system
Working characteristics of hydraulic servo systems:
(1) A feedback connection exists between the system's output and input, thus forming a closed-loop control system. The feedback medium can be mechanical, electrical, pneumatic, hydraulic, or a combination thereof.
(2) The main feedback of the system is negative feedback, that is, the feedback signal is opposite to the input signal. The difference signal obtained by comparing the two controls the hydraulic energy. The energy input to the hydraulic component moves it in the direction of reducing the deviation, that is, the deviation is used to reduce the deviation.
(3) The power of the input signal of the system is very small, while the output power of the system can be very large. Therefore, it is a power amplifier device. The energy required for power amplification is supplied by hydraulic energy, and the control of the energy supply is automatically performed according to the deviation of the servo system.
Composition of hydraulic servo system
A hydraulic servo system consists of the following basic components:
Input element – A component that applies a given value to the input of the system. This component can be mechanical, electrical, hydraulic, or a combination thereof.
Feedback measurement element – An element that measures the output of a system and converts it into a feedback signal. Various types of sensors are commonly used as feedback measurement elements.
Comparison element – An element that compares the input signal with the feedback signal to obtain the error signal.
Amplification and energy conversion components—components that amplify error signals and convert signals of various forms into high-power hydraulic energy. Electrical servo amplifiers and electro-hydraulic servo valves are examples of this type of component.
Actuators are components that apply hydraulic energy to the controlled object to produce regulating actions, such as hydraulic cylinders or hydraulic motors.
Controlled objects—various types of production equipment, such as machine workbenches, tool holders, etc.
Based on the output physical quantity, servo systems can be categorized as position, velocity, and force servo systems.
Classified by signal: mechanical-hydraulic, electro-hydraulic, and pneumatic-hydraulic servo systems.
Based on components: valve control system and pump control system.
Principle of hydraulic servo system
In hydraulic servo systems, control signals can take the form of organic-hydraulic servo systems, electro-hydraulic servo systems, and pneumatic-hydraulic servo systems. In organic-hydraulic servo systems, the setpoint, feedback, and comparison stages utilize mechanical components, commonly found in aircraft control systems, automotive steering systems, hydraulic copying machine tools, and construction machinery. However, friction, backlash, and inertia in the feedback mechanism can adversely affect system accuracy. In electro-hydraulic servo systems, error signal detection, correction, and initial amplification employ electrical and electronic components or computers, forming analog servo systems, digital servo systems, or hybrid digital-analog servo systems. Electro-hydraulic servo systems offer advantages such as high control precision, high response speed, flexible signal processing, and wide applicability, and can be used to construct servo systems for position, speed, and force.
