Předpokládaná doba čtení: 4 minuta
Overview of Hydraulic Control System
The hydraulic control system is based on the motor to provide power, hydraulic oil as the working medium, the use of a hydraulic pump to convert mechanical energy into pressure energy, to promote the hydraulic oil, through the functional body to control a variety of valves to change the flow of hydraulic oil, to promote the hydraulic cylinder to make different strokes, different directions of action, to complete a variety of equipment different action needs. It is compared with simple mechanical transmission, electrical transmission, and pneumatic transmission, has a large power transfer, small structure, fast response, and other characteristics.
The Advantages of The Hydraulic System
1. Hydraulic components of the power to weight ratio and torque inertia ratio are large;
2. Smooth work, fast response, small impact, can be directly under load or start;
3. Easy to realize complex movements, centralized operation or remote control;
4. Easy to achieve infinitely variable speed control.
PLC System Design
1. Selection of PLC
PLC chip integrated CPU, RAM, ROM, and input and output circuits, PLC is mainly used for logic conversion between input and output, logic signal flow can be expressed as input – CPU logic conversion – output, the output signal for various control of equipment, in fact, PLC only plays the role of the intermediate converter. To achieve centralized management of control system data, the site data is transmitted remotely, using a PLC serial communication module.
2. The Working Principle of PLC Control
The PLC system mainly controls the start and stop of the solenoid-operated reversing valve by compiling the program to achieve the free entry and exit of the hydraulic cylinder according to the process requirements. In the selection of PLC, the first step is to analyze the hydraulic system movement process, design functions and input devices (push button switches, travel switches, sensors, etc.) and output devices (hydraulic reversing valve solenoid coil, contactor coil, indicator) role, clear input, output signal correspondence, and quantity, choose the PLC with which to adapt.
3. PLC Program Design
- Execution mode: the automatic mode can complete the reciprocating movement of the piston rod in a predetermined way. The piston rod is required to be able to return after a pre-determined time after reaching an endpoint. This requires that the two coils of the solenoid-operated reversing valve must be sucked in or released in turn at certain intervals, a process that can be carried out by the internal PLC program. If the control mode needs to be switched, this can be done using. The changeover control button on the HMI of the host computer or an external switch can be used to force the changeover. The manual mode allows the control of the solenoid valves one by one. To be able to control the operation of the system in a simple way when accuracy is not required or for simple tests. The manual method can be used to control the operation of the system simply.
- Execution process: the process of executing the PLC program is divided into three stages, namely the input sampling stage, the program execution stage, and the output refresh stage.
- PLC control system of anti-interference design: although PLC has a strong anti-interference ability, if the environment is too harsh, electromagnetic interference is particularly strong or PLC installation and use of improper methods, it is still possible to bring the safety and reliability of the PLC control system. Therefore, in the design of the PLC control system, but also need to pay attention to the system’s anti-interference design, mainly from three aspects to consider: to take measures against power interference to reduce power interference caused by the PLC control system failure, to take a reasonable grounding method, can avoid the harm of voltage shock; take measures against I/O interference, and to reduce the damage to components.