Abstract Based on the investigation and analysis of the situation in full mechanized coal mining face at home and abroad, the electro- hydraulic control system for hydraulic support is put forward, designed and realized。 It adopted intrinsically safe circuit design technology and field bus technology to connect all control units to the host computer。 Each control unit of the control system is equipped with one hydraulic support。 Certain control unit(s) controlled by either the other control units or the host computer can operate adjacent support, distant support or a group of supports。 Host computer in an explosion-proof housing also has the functions of real-time monitoring, remote control, fault diagnosis and upload data etc。 The result of industrial experiment up to three months shows that the system works reliably and meets the design requirements。73857

Keywords:Hydraulic Support, Electro-hydraulic Control System, Host Computer;

1。 Introduction

Electro-hydraulic control system for hydraulic supports is the core of full mechanized coal mining face。 And it can implement automatic control of production equipments and improve the production efficiency, working conditions and safety of coal mining face。 The system based on network detects the position of the shearer and hydraulic supports automatically to achieve automatic control。 Besides, it has the ability to monitor states of other equipments, to implement the communications between ground and underground computers and to complete the remote control。 Compared with other industrial electro-hydraulic control systems, it has special characteristics, such as high pressure, anti-burning explosion-proof, dust-proof, anti-corrosion, anti-vibration and anti-electromagnetic interference。

Since the mid-1970's people abroad have started to study electro-hydraulic control system for hydraulic supports, launched the product after nearly a decade and perfected gradually the system after the 1990's。 At present, many countries already have had mature products with different characteristics in the promotion stage, such as Germany, the United States, United Kingdom, Poland, Japan, France, and Russia etc。

At present, the control method of hydraulic supports made in China is mainly manual, which is equivalent to the control level of developed countries in the 1970’s。 The electro-hydraulic control system equipped with hydraulic supports is manufactured in foreign countries, especially in Germany。 The outstanding companies which  have already come into home market are DBT (its HQ is Bucyrus in the USA), Marco, EEP and TIEFENBACH in Germany and JOY in America。 We have not achieved the target of industrialization and indigenization of the system, although our government has invested much in technical research of the electro-hydraulic control system for hydraulic supports from the 1990’s。 In order to improve the level of mining equipments, strengthen the international competition and break through the international technical monopoly, it is urgent to research and produce autonomously electro-hydraulic control system for hydraulic supports。

2。 Structure of the electro-hydraulic control system

Through the structure analysis of the electro-hydraulic control systems for hydraulic supports made by the EEP Company and Marco Company in Germany, combined with the actual application, block diagram of the self- designed electro-hydraulic control system is put forward and shown in Fig。 1。

Fig。 1。 Block diagram of hydraulic supports electro-hydraulic control system

Electro-hydraulic control system for hydraulic supports mainly contains the control units, host computer and the intrinsically safe network。 The support control unit includes the controller, sensors, electromagnetic pilot valves and main control valves。 The control unit connects each other by the main cable。 The controller adopts RS422 communication in accordance with self-definitional frame format。 However, the overall adopts CAN bus communication in accordance with the standard extend frame format。 The host computer monitors all controllers through the CAN bus network。 The intrinsically safe network connects all the control units and host computer by signal isolators。 The controller uses the pressure sensor, the position sensor and the displacement sensor to detect the working state of hydraulic supports and takes advantage of CAN bus network to transfer information to the host computer, then the host computer makes decision to implement the automatic control of hydraulic supports。