| Modern tracked vehicles play an important role in the Army's mobile combat platform,which are high-performance,high-compact and high-power integrated devices.The Electro-Mechanical Transmission(EMT)system can meet the special requirements of the heavy-duty and off-road vehicles for the wide speed range and driving power.Therefore,the EMT has become a hot spot of research on tracked vehicle transmission.In this paper,a new double side motors coupling drive transmission scheme is taken as the research object.The kinematics and efficiency of this new power coupling mechanism are analyzed based on the graph theory.The simulation model of series hybrid electric tracked vehicle is established with the corresponding energy management strategy developed.Then,the system efficiency is analyzed under typical working conditions.Last but not least,with the optimal system efficiency as the goal,the transmission system and control strategy parameters are optimized using the genetic algorithm.Firstly,the kinematics and efficiency of this new power coupling mechanism are analyzed based on the graph theory.The equations of the mechanical efficiency have been constructed by graph theory and the methodology of fundamental circuits for gear trains.Further,the theoretical analysis model of transmission efficiency for tracked vehicle is established to predict total power loss of the planetary gear sets including the losses of meshing teeth,gearings and churning,which realizes the automatic analyses of the kinematics and efficiency of coupling mechanism.Secondly,the simulation model of series hybrid electric tracked vehicle is established with the corresponding energy management strategy developed.The numerical models for key components of double side motors coupling drive transmission are established.Then,the backward-facing simulation model of series hybrid electric tracked vehicle is built.The driving modes are divided according to the driving characteristic of tracked vehicles.For the purpose of fuel economy and low emissions,a power flowing control strategy is proposed based on engine optimal fuel consumption curve,which can also reduce the energy losses of power battery.Thirdly,the efficiency of the system under typical operating conditions is analyzed comprehensively.The external force and torque,the track traction or braking force and the torque of double side motors are analyzed in different turning radius.According to the principle of power balance,the torque and power demand of double side motors under different turning radius are analyzed,which is different from the existing dual motor independent drive system.The efficiency of the system and key components under straight and turning conditions is analyzed.Meanwhile,the working states and efficiency characteristics of key components are compared,which indicates the direction of system parameter optimization.Finally,with the optimal system efficiency as objective function,the transmission system and control strategy parameters are optimized using the genetic algorithm.The optimization model of hybrid tracked vehicle control strategy is established.The efficiency of the power coupling mechanism,motor and power battery and the change trend of battery SOC are analyzed with the optimized results,which verifies the rationality and validity of optimization.In pivot turning,the meshing efficiency of coupling mechanism is increased;in the small radius turning of 0.5B,the meshing efficiency and the motor efficiency are both increased.For the straight driving condition,the motor efficiency and discharge efficiency of power battery are both increased,and the fluctuation of SOC is also reduced.The simulation results validate the reasonableness and effectiveness of the optimized parameters. |
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