Research On Piston Motion Control Of An Opposed-Piston Free-Piston Engine Generator

Free-piston engine generator(FPEG),as an energy conversion device,has attracted the attention of researchers with its advantages of variable compression ratio,variable fuel and high thermal efficiency.At present,the free piston reciprocating motion control is still a challenge that restricts its development.Based on years of research by the research group,this paper takes an opposed-piston FPEG as the research object,and conducted simulation and test research on the free piston reciprocating motion control,including the following aspects:(1)The working process of FPEG was analyzed.The thermodynamic model and kinetic model of FPEG were established.The simulation model of FPEG was established in Matlab/Simulink and Magnet,and the model was verified by the prototype.(2)Based on the simulation model,the dynamic characteristics of the free piston reciprocating motion were simulated and analyzed.Including: the influence of mover performance difference on the free piston synchronous motion;the influence of stroke generation current on the free piston reciprocating motion;the influence of cyclic combustion variations on the position of inner turning center(ITC).(3)Based on the simulation analysis of dynamic characteristics,a master-slave control scheme was designed,and a synchronous control strategy based on position following and an ITC control strategy based on artificial neural networks were proposed.The control strategies were simulated and analyzed.The results show: Under working conditions with cyclic combustion variations,the ITC control accuracy is within ±0.2mm.(4)Based on the proposed master-slave control scheme,the software and hardware architecture of the electronic controller was designed,and the prototype test bench was built.In the non-combustion conditions,the start-up process,shut-down process and stable operation process of the prototype were studied through tests.The results show: the prototype can be successfully started and run stably at a frequency of 50Hz;the opposed-piston can move synchronously and the position deviation of ITC is less than 0.1mm;the control accuracy of ITC in stable operation process is within ±0.1mm.