Optimization And Control Of An Electromechanical Dual-speed Transmission

Suffering from global warming,air pollution,and energy crisis in recent years,more and more countries and regions have introduced policies to support the development of new energy vehicles and encouraged alternative fuel vehicle programs.Particularly,pure electric vehicle technology has attracted great attention due to its advantages in terms of zero emission,high efficiency,and low noise.Therefore,the electrification and intelligentization of passenger cars and commercial vehicles are increasingly popular.However,the off-road dump trucks,which account for a large percentage of CO2 emission and petroleum consumption,are still equipped with traditional powertrain system.To address these problems,this thesis has proposed a novel two-speed transmission for pure electric dump trucks that allow higher cruising mileage,larger battery capacity and less operational cost.As a result,electric dump trucks are expected to get popularized in mining areas.The main contents of this thesis are as follows:To begin with,this thesis has proposed a two-speed transmission scheme with dual planetary gear sets and a novel electromechanical clutch actuator.Furthermore,a kinematics model of the transmission has been established based on the analysis of the power flow for each gear.Beyond that,a dynamic model of the transmission has been made following the principle of the Lagrange kinetic equation.Besides,the thesis has analyzed working mechanism and self-locking condition of the novel clutch actuator and established the dynamic model of the novel clutch actuator.Secondly,on the basis of the dynamic model of transmission and energy consumption model of dump trucks,this thesis has designed a two-parameter shifting schedule for electric dump trucks with the illustration of their operation features.To improve their economic and dynamic performance,the research has adopted random mutation particle swarm optimization algorithm to improve the gear ratios of two-speed transmission.Additionally,the thesis has examined the energy-saving mechanism of the transmission and the impact on battery life enhancement with the optimization and simulation results.Thirdly,to improve the two-speed transmission shift quality,some observers has been established in this thesis to estimate the state variables during the shifting process.At the same time,a clutch disengagement strategy has been proposed based on the shaft torque estimation that can reduce drive shaft oscillation effectively.Moreover,the illustration of shifting process as well as the begin and end constrains have contributed to obtain the motor speed adjustment curve.After that,depending on the state estimation,an H∞ robust controller has been synthesized to control and track the motor speed during the shifting process.This has verified the tracking performance without/with external disturbance.In the end,to achieve seamless shifting,a novel integrated dual-motor transmission scheme has been presented.Considering the transmission structure and operation features of mining vehicles,this thesis has designed a real-time mode switching and power distribution strategy.Optimal economic performance has been realized through the throttle,driving model of the current velocity and the distribution relationship of motor power.The rationality and real-time performance have been verified by hardware-in-the-loop experiments.Furthermore,based on the energy management strategy,the parameter optimization has been made to improve the economic performance of pure electric vehicles,thereby prolonging battery life.Meanwhile,seamless shifting has been realized by taking a torque compensation strategy with the coordination of two motors during shifting process.This has improved the comfort for both driving and riding.