Research On Coordinated Control Of Power-split Hybrid Electric Vehicle Based On Time Delay Prediction And Interference Compensation

Hybrid electric vehicle(HEV)has two power source systems: engine and motor.By rationally designing its energy management strategy,fuel consumption and exhaust pollutant emissions could be effectively reduced,and fuel savings of 15% to 50% can be achieved.Among them,the power-split HEV can not only decouple the engine torque and speed through the planetary power-split device,but also has the function of electronic continuously variable transmission.That is,it is an electromechanical composite transmission system structure with great development potential,and also the HEV configuration that experts and scholars are vying to explore.The coordinated control among multiple power sources is an inevitable control problem in the mode switching process of power-split HEV,which will seriously affect the dynamic performance and driving comfort of the vehicle.In order to improve the mode switching quality of HEV and maintain the stable transmission of multiple powers,a power-split HEV with double planetary gears is taken as the research object in this paper,and the coupling characteristics of time-varying delay and external disturbances in the typical mode switching process is deeply analyzed.Furthermore,based on the Markov chain time delay prediction model,an improved extended state observer with time delay is designed.Aiming at the dual effects of system delay and external interference,the multi-module integration design of the coordination controller is used to realize the high-efficiency stability and interference suppression of the vehicle mode transition,which provides a new idea for the optimization design of the power-split HEV controller,and lays a solid foundation.First of all,the speed and torque characteristics,power split characteristics and transmission efficiency characteristics of the dual planetary power coupling structure are analyzed.Combined with the working state of each power source,the principle and mode switching relationship of eight working modes of the power-split HEV are revealed.Based on the forward modeling theory,a transient mode switching simulation model of HEV is built,including the dynamic model of key components,the driver model,the torque distribution model of each mode,the driving resistance torque model and other submodels,which lays the theoretical foundation for the subsequent design of multiple power sources control strategy.Then,the exploration of typical mode switching behavior of power-split HEV and the design of coordinated control strategy for time delay compensation are completed.According to the characteristics of HEV multi-mode operation and mode switching,the coordinated control problem of multi-power sources,which is easy to deteriorate the vehicle dynamic performances during transient mode switching process,is described.The basic motor compensation coordinated control strategy is designed primarily,and the deterioration law of HEV time-varying delay on the coordinated control effect of basic motor compensation is revealed emphatically.Thus the key time lag factors are extracted,and the time lag compensation coordinated control strategy composed of BP-Smith adaptive compensation module,torque limit module and basic motor compensation module is designed.The research results show that,compared to the traditional Smith predictive control and the BP-Smith adaptive compensation control strategy,the time-delay compensation coordinated control strategy significantly reduces the mode switching jerk and the target vehicle speed tracking error further,accelerates the speed of jerk convergence to zero,and the speed of the engine speed adjusted to the economic speed.And then,it is clearly pointed out that the engine torque interference composed of engine inertia torque,gas pressure fluctuation torque,modeling error,etc.and the equivalent output load interference caused by vehicle driving condition changes are the key factors that directly affect the HEV mode switching responses.In order to accurately estimate the above-mentioned two kinds of disturbances and accelerate the rapid convergence of the observer error system,an improved extended state observer is designed with reference to the deviation control principle to realize online estimation,and a coordinated control strategy for disturbance compensation is proposed based on this.The simulation analyzes the estimation accuracy of the improved extended state observer and the correctness of the disturbance compensation torque redistribution algorithm under different disturbances,which demonstrates the effective suppression of the strategy against the key interference and its excellent adaptability under a wide range of road conditions.Finally,the mode switching response characteristics of HEV under the coupling effect of system time delay and interference are studied,and the influence laws of time delay and disturbance alone are compared and analyzed,revealing the fact that the coexistence of system time delay and disturbance will seriously deteriorate the vehicle dynamics and ride comfort.Two unconventional extended state observers fused with Markov chain time delay prediction models are constructed to accurately estimate the system interference under the influence of time delay,and the main tools for interference observation in this paper are compared and optimized in terms of practicability,reachable bandwidth and observation accuracy.Aiming at the deterioration of HEV performance caused by the coexistence of time delay and interference,a compound HEV switching control strategy including a time delay prediction module,a BP-Smith estimation control module and an interference compensation module is proposed,so that the whole vehicle can effectively maintain system mode switching stability under the influence of random time delay and external interference,reflecting its superior anti-interference ability.In addition,a power coupling prototype bench test and a hardware-in-the-loop test platform based on the D2 P rapid control prototype and NI real-time simulator are built,and the HIL test research of the above-mentioned power-split HEV coordinated control strategies,as well as the model verification are carried out.The experimental results verify the feasibility,effectiveness and practicability of the HEV coordinated control strategy proposed in this paper.