Research On Control Strategy And Test Technology Of Electromechanical Combined Braking For Electiric Drive Tracked Vehicle

Due to high transmission efficiency,strong maneuverability and economical fuel consump-tion,electric drive tracked vehicles have become a research hotspot in the fields of agriculture,construction and military industry.Electric drive tracked vehicles are developing in the direction of high speed and high power.Good braking performance is the key to ensure flexible and safe driving.The electromechanical combined brake(ECB)system can not only reduce the friction loss of the mechanical brake,prolong its service life,but also recover the regenerative braking energy and improve the energy economy.At present,domestic researches on electromechanical combined brake control strategy and test technology of electric drive tracked vehicles ars rela-tively rare.Based on a project called "Comprehensive Performance Testing System of Electromechani-cal Compound Drive System",this paper focus on system modeling,braking torque steady-state and dynamic allocation control strategy,braking stability control and energy economy perfor-mance,as well as bench test technology of ECB for tracked vehicle.The detailed research contents of the full text are as follows:(1)Modeling the ECB system of electric drive tracked vehicle.The ECB system is mainly composed of mechanical hydraulic brake subsystems and electric brake subsystems including two motors,a battery and a brake resistor.The time-varying hysteresis effect of the mechanical hy-draulic brake system is analyzed by bench test.A first-order inertia plus hysteresis transfer func-tion model of the mechanical brake system is established by system identification method.The method of suppressing the response divergence of time-varying hysteresis system by Smith pre-dictive control is proposed.The motor system is modeled by look-up table method.,and the external characteristic curve and efficiency characteristic curve of the motor are obtained through motor performance bench test.By system identification method,the transfer function of the motor is obtained,thus the dynamic response model of the motor braking is established.The mathemat-ical model and simulation model of battery pack and DC-DC power converter are established by theoretical deduction.Finally,a complete model of the electromechanical combined braking sys-tem of the electric drive tracked vehicle is established by integrating the two subsystem models.(2)Aiming at how to recover the braking energy as much as possible under the premise of ensuring total braking performance,the paper designs the steady-state and dynamic allocation control strategy of the combined braking torque.According to the respective characteristics of the two braking subsystems,a steady-state braking torque distribution method based on fuzzy control strategy is proposed,which takes vehicle speed,braking strength and battery SOC status as input and electric braking moment distribution coefficient as output.The effectiveness of the strategy is verified by simulation analysis under typical braking conditions.As for the braking irregularity caused by the asynchronism of dynamic response between time-varying hysteretic mechanical braking system and electric braking system,a 2 DOFs control strategy based on feedforward-feedback is proposed for dynamic coordinated braking torque allocation.The effectiveness of the strategy is verified by comparing the simulation results with and without dynamic coordination control strategy.(3)Braking stability and energy economy of the combined braking system are studied.In view of the deviation phenomenon during the braking process caused by the random unbalanced disturbance of the double-side driving wheel,the internal and external factors affecting the stabil-ity of the electromechanical combined braking are analyzed,and the total braking system model of the vehicle is established.Based on the model,a fuzzy PI-based bias-coupled double-side brake synchronization control strategy is proposed.The simulation results with and without dual-side brake synchronization control verify the effectiveness and robustness of the control strategy.In addition,in order to comprehensively analyze the specific contribution of electromechanical com-bined braking to the energy economy of the whole vehicle,the electromechanical combined brak-ing strategy is integrated into the vehicle energy management strategy,and the vehicle simulation model including the engine-generator set is established.Fuel performance of the vehicle with and without electromechanical combined braking is simulated and compared under the actual driving conditions in which the braking process and driving process coexist.The results show that the ECB can effectively improve the energy economy of the vehicle.(4)Test technology of ECB for electric drive tracked vehicles is also studied in the paper.In order to satisfy the inertial load emulation requirements,the dynamic load simulation technology of the test bench is deeply studied.The road resistance and equivalent rotary inertia of the electric drive tracked vehicle are derived.Dynamometer is used to simulate the road surface resistance load and inertia load at the same time.The speed tracking method with feedforward compensation is proposed to control the dynamometer to make the dynamic load emulation possible.Based on the analysis of the dynamic characteristics and control strategy of the load emulation platform,an overall platform simulation model including the drive system and the load emulation system is established.(5)The hardware-in-loop real-time simulation platform and load emulation platform are built.The system composition and control principle of dynamic load emulation platform,as well as Dspace hardware-in-loop real-time simulation platform are elaborated.The effectiveness and ro-bustness of the speed tracking algorithm with feedforward compensator are verified by the load emulation platform,and the accuracy of the overall platform simulation model is also validated.Relying on the hardware-in-loop real-time simulation platform,the effectiveness of braking torque dynamic allocation control strategy and the two-side brake synchronization control strategy,as well as the economy of energy consumption,are fully validated.