The Design Of Energy Management Strategy For Electric-driving Swing System In Hybrid Excavator

The slewing mechanism of hydraulic excavator costs lot of time in a typical working cycle.It has the characteristic of frequently starting and braking with excessive instantaneous power demands,which is hard for the engine to stabilize the working points into a high efficient area in the energy supplying process.Such feature will result in a low utilization of crude oil,a poor performance of exhausting emissions and a lot of waste of natural resources.Applying the hybrid technology with appropriate energy management strategy to the excavator slewing mechanism can effectively improve the engine fuel efficiency and economy.Firstly,the background and significance of the research is introduced in this paper,and the current research situation of the slewing mechanism in hybrid excavator is briefly summarized.On this basis,the current energy management strategies for the slewing mechanism of the hybrid excavator are summarized,too.Then,the powertrain structure and motion characteristic of the electric－driving swing system are analyzed respectively on the hybrid excavator.On this basis,an energy management strategy,consisting of the strategy of electric-driving swing system power flow optimal distribution and the strategy of swing motor dynamic power demands optimization,is proposed to improve the engine f-uel efficiency and solve the problem of D.C bus voltage pumping with motor braking.The corresponding design scheme is given.To solve the power flow distribution problem of the electric-driving swing system in the designed energy management strategy,an engine optimal fuel consumption strategy is proposed with finite control set model predictive control.Using the instantaneous power supplying capability of supercapacitor with a real-time power flow distribution,the engine’s working points are regulated indirectly so that the power requires of the swing motor can be accessed with an efficient engine operation.To solve the dynamic power demands optimization of the swing PMSM in swing system,a strategy of electromagnetic torque current optimization is designed with PSO algorithm.By optimizing the iq reference in the FOC of PMSM,the motor has a better dynamic performance within the same control requirements.Within such optimization,the D.C bus voltage fluctuation in the PMSM dynamic process is weaken by limiting it’s excessive power.A reasonable speed curve for the PMSM is also programmed to provide a more stable load power requirements for the engine optimal fuel consumption strategy.Finally,a 20t hybrid excavator for scientific research and its electric－driving swing system are introduced.The design of the vehicle control system,including the energy management strategy and the lower power control system,is given.The software and hardware design processes are introduced respectively.The experiment results verify the validity and feasibility of the designed energy management strategy.