Optimal Design Methodology Of The Electro-mechanical Transmission System For Hybrid Tracked Vehicles

Tracked vehicles have been widely used in industry,agriculture and military.Hybrid tracked vehicles have higher output power,better fuel economy and lower emissions compared to the conventional internal combustion engine(ICE)vehicles.Electro-mechanical transmission is an important type of powertrain for hybrid tracked vehicles.Nowadays,the research of electro-mechanical powertrain for hybrid tracked vehicles has several problems,such as insufficient analysis of few topologies,poor optimality and slow calculation of energy management strategy,and inefficient parameter sizing with low accuracy.To overcome these issues,the optimal design of electro-mechanical powertrain for hybrid tracked vehicles is proposed.To improve the comprehensive performance and the energy efficiency,the multi-mode hybrid tracked vehicles with two output shafts using multiple planetary gears are employed.Two outputs are coupled with power elements through planetary gears.Two outputs can help the vehicle realize straight driving and turning without any additional steering mechanism which increases the compactness of the drivetrain layout.Compared to other power-split hybrid tracked vehicles,the new design has omitted the steering shaft which can reduce the complexity of the design structure and increase the compactness.The design also ensures high efficiency under different working conditions.To systematically explore all the possible designs of multi-mode hybrid powertrain with planetary gears,an automated modelling method and rapid screening method are proposed.By decomposing the dynamic equations,the characteristic matrix which has a one-to-one correspondence with topologies can be obtained rapidly.By considering about the operating conditions,basic requirements and overall performance of tracked vehicles,the screening of a large number of topology candidates can be realized which reduces the computational load for large-scale optimization.To solve the problem of optimal design of hybrid tracked vehicles,a topology-control-size-integrated collaborative optimization approach is presented.A novel near-optimal energy management strategy,Efficiency-based Evaluation Real-time Control Strategy(EERCS),is proposed to calculate near-optimal control rules for design candidates rapidly.EERCS can maximize the normalized power efficiency considering the SOC balance and smooth mode shift.With the help of EERCS,the optimal design together with its parameters is computed using a progressive rule-based iterative optimization method.By sensitivity analysis,uniform design and chaos-enhanced method,efficient and accurate optimization can be realized.In order to verify the effectiveness of the proposed optimal design method,the theoretical derivation of the design method and performance simulation of topology designs are implemented.The simulation results show that the proposed optimal design method is suitable for the complex electro-mechanical powertrain design of tracked vehicles.The hardware-in-loop experiments are also conducted to evaluate the performance of the final optimal design under different typical cycles.Results of the experiments show that the optimized design has improved drivability and fuel economy compared to the current series hybrid benchmark which results in high application value.