Research On The Control Strategy Of Parallel Hybrid Loader

With the constant, fast, stable growth of Chinese economy, loaders, as one oftypical construction machinery, usher in an unprecedented development opportunity.However, because of high fuel consumption and bad emissions, it has greatsignificance researching on high efficient, energy saving and environment protectingloader, as the non-renewable resource--petroleum is consuming up. The application ofhybrid technology in the car is successful, which provides a new thinking for theenergy saving research of construction machinery, especially to loaders. Many foreignconstruction machinery manufacturers have carried out more in-depth research on thehybrid loaders, and domestic construction machinery manufacturer have alsoresearched the related subject with the cooperation of the universities. However, theoverall level is still lagging behind, especially the research on parameters matchingand energy management control strategies of the hybrid system also need to carry outlot of research work.In this dissertation, parameters matching and energy management strategies ofthe parallel hybrid system are studied through theory and simulation. As the prototypeof a ZL50loader, the control strategy of the parallel hybrid loader is designed withStochastic Dynamic Programming (SDP). The problem of energy management of thehybrid system is put forward based on dynamic programming. Load torque demandscan be seen as a Markov random process, SDP can develop an appropriate controlstrategy under different working conditions quickly by online calculating the matrixof change probability of the torque demands. State space and the control variables arereasonably optimized, which significantly improve the computational efficiency of thecontrol strategy. And the solving algorithm of the stochastic dynamic programming isstudied in this thesis.The simulation model of the parallel hybrid loader is built in theMATLAB/Simulink simulation environment, based on which the control effect of Multi-Work-Point Control (MWPC), Instantaneous Optimization Control (IOC) andSDP are studied respectively. The simulation results showed that the hybrid loaderwith these three strategies can achieve high rate of fuel saving compared with thetraditional loaders. Especially, SDP can effectively improve the working conditionand the fuel efficiency of the engine, and the SOC value of the super capacitor arefluctuation in a small range, which ensuring the hybrid system can always operate atefficient state in the entire process.