The proportional controller is a control device that performs linear regulation based on the deviation signal. Its control law is that the input deviation is proportional to the output quantity, and it has the characteristics of fast response but with static deviation. When the system is stable, the controller output is zero, but the actual value of the controlled object still deviates from the set value. It needs to be compensated by adjusting the proportional degree to change the amplification coefficient [3].
The proportional controller consists of a proportional control amplifier and a proportional electromagnet. The proportional electromagnet, as an electrical-mechanical conversion device, can convert current signals into displacement or thrust, and has the characteristics of simple structure and convenient maintenance [1]. The control amplifier provides specific performance currents for the electromagnet, supporting open-loop or closed-loop regulation.
Modern intelligent proportional controllers adopt an integrated design to achieve integrated packaging of sensors, amplifiers, and valve bodies, and are equipped with digital chips to support multi-functional control. Through optimized structural design, such as the optimization of the displacement rotor and drive shaft structure of the three-rotor proportional controller, the volume and weight are reduced by approximately 38% and 50% respectively, while maintaining high control accuracy [2] [4]. The intelligent controller can compound control parameters such as displacement and speed through software algorithms and integrate real-time communication functions [2]. Working principle
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The proportional control amplifier and the proportional electromagnet constitute the proportional control system, which is simply referred to as the proportional controller. The performance of this system directly affects the overall performance of the proportional valve. Even if individual components such as the proportional control amplifier and the proportional electromagnet meet the design requirements, the resulting system may not meet the system’s requirements. The reason for this is the parameter matching issues between different units in the system. By testing the comprehensive performance of the proportional control system and adjusting the corresponding parameters using the adjustable parts of the system’s units, the system can achieve optimal matching. This is the purpose of designing this system.
The electro-hydraulic proportional valve is a type of valve that continuously and proportionally controls parameters such as the pressure and flow of the oil based on the input electrical signal. It not only can achieve complex control functions but also has advantages such as anti-pollution, low cost, and fast response. It has been increasingly widely applied in hydraulic control engineering.
The proportional control amplifier is an electronic device used to provide specific performance currents for the proportional electromagnet and to perform open-loop or closed-loop regulation of the electro-hydraulic proportional valve or electro-hydraulic proportional control system. It is an important component of the electro-hydraulic proportional control element or system.
The proportional electromagnet, as the electro-mechanical conversion device of the electro-hydraulic proportional control element, functions to convert the current signal supplied by the proportional control amplifier into or displacement. The proportional electromagnet has a large thrust, a simple structure, low requirements for oil quality, is easy to maintain, and has a low cost. It is the most widely used electro-mechanical conversion device in electro-hydraulic proportional control technology. The characteristics and working reliability of the proportional electromagnet have a very important impact on the electro-hydraulic proportional control system and components, and is one of the key components in electro-hydraulic proportional control technology [1]. Application
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The proportional controller is the core component of the electro-hydraulic proportional control system. Modern electro-hydraulic proportional controllers integrate digital functions such as proportional amplifiers, intelligent controllers, and fieldbus interfaces. To achieve an integrated design with the proportional valve, the proportional controller should be miniaturized and have high energy efficiency. Currently, there is a significant gap in the design of proportional controllers in China compared to that of foreign countries. Particularly, the lack of high energy efficiency design is notable. The energy consumption of domestic proportional controllers is relatively high.
Characteristics of intelligent proportional controllers:
(1) Miniaturization and integration design. Due to the miniaturization of sensors and electronic components, components such as sensors, measurement amplifiers, control amplifiers, and valves have been integrated into one. Major hydraulic companies around the world have embedded electronic circuits in valves or pumps in their new developed proportional control systems, reducing wires and connectors, and overall, it is more concise and has lower requirements for users, with higher system reliability.
(2) Digitalization and intelligence. Using digital chips and microprocessors, various control functions that were previously implemented by hardware are realized through software. It is flexible, convenient to use, and has low cost. Intelligent nodes with communication functions can communicate with other nodes or central controllers in real time. Each hydraulic component of each node can complete the functions of collecting, processing, and storing certain signals according to its own special requirements, and the central control station can complete on-site control, monitor the entire system, and perform fault diagnosis.
(3) Multifunctionality. For example, when an electro-hydraulic proportional valve controls an actuator or pump, it can simultaneously control displacement, speed, acceleration, force, or pressure. This depends on the system using different sensors, feedback quantities, and control algorithms, or on the switching of electronic circuits. [2]