Hydraulic System Control Design Of Free Piston Engine

With the rapid development of national economy and the acceleration of theindustrialization process, the demand for power machinery in all sectors of society isshowing a more diversified trend. In the past decades, the conventional internal combustionengine with reciprocating piston have achieved great development due to its reasonablestructure, high reliability and fuel efficiency which have make it the main power plant intransportation, engineering machinery, marine and other industries. Free piston engineappeared almost simultaneously with the traditional internal combustion engine, but waslimited to the level of industrial technology and control technology of that time, it has notbeen considerably developed in a long period of time. In recent years, due to the fact thattraditional power machinery consumes a lot of non-renewable energy, causing growingenvironmental pollution and energy depletion, free piston engine which is simple-structuredand has a higher energy efficiency starts to regain people’s attention, setting off adevelopment boom.In this paper, a hydraulic control system for free piston engine is designed anddescribed. Firstly, in view of the special characteristics of free piston engine, taking intoaccount the changes in the position randomness and flexibility of the piston, a program tomonitor and control the position of the piston is proposed, which uses both high-speed lineardisplacement sensor and trigger sensors as a combination to control piston position, thusensuring the reliability and flexibility of the piston position control.Secondly, according to the hydraulic system control requirements, the electroniccontrol unit, sensor and actuator are selected. According to actual control conditions,hydraulic control system hardware circuit is designed and produced, including the clockproduction unit, power supply, reset circuit, and memory expansion circuit. Analog anddigital signal acquisition module, power module, communication module are speciallydesigned. Using an integrated development environment provided by Keil, controllingprogram is developed and debugged based on the principle of modular programming.Various functional modules are written and debugged separately, greatly shorten the development cycle and maintenance costs.Lastly, experiments are conducted on the free piston engine in order to verify theavailability of the control system. The results show that the system can work properly andstably, and almost realizes the anticipant controlling goal. Specially, the signal acquisitionmodule and power amplifier module can meet the requirements of high speed and heavyload. The piston assembly can reciprocate properly according to the predeterminedcontrolling program. With enough oil pressure and flow, the engine can work well under thecontrol of the system.