Regeneration And Compound Braking Characteristics Of Battery Hydraulic Hybrid Railway Engineering Vehicles

As an indispensable equipment in the process of railway construction,operation and maintenance,railway engineering vehicles have been used more and more widely.Because of the special working environment of metro tunnels,the exhaust emission and noise of diesel railway engineering vehicles not only cause great potential safety hazards and injury to engineers,but also cause serious environmental pollution.Battery railway engineering vehicle has the characteristics of no emission and low noise,which can effectively solve this problem,but it also has some shortcomings such as high current impact during regenerative braking,low energy recovery efficiency,low energy utilization rate and poor stability of downhill speed that is difficult to be adjusted.Hydraulic hybrid technology which is based on the characteristics of high-power density of hydraulic system shows unique advantages in improving the dynamic characteristics of vehicles,energy conversation and environmental protection performance.In order to improve the shortcomings of the battery railway engineering vehicle,an electro-hydraulic hybrid system is proposed in this paper.The system parameters,performance of hydraulic regenerative braking,combined simulation analysis of composite braking characteristics and downhill speed control strategy are studied.Firstly,according to the structure and characteristics of the battery railway engineering vehicle,the structure and configuration scheme of the electro-hydraulic hybrid system are determined,and the hydraulic regenerative braking circuit is designed.According to the main technical parameters and driving conditions of the battery railway engineering vehicle,the main parameters of the drive system and accumulator are calculated.Secondly,based on the designed electro-hydraulic hybrid system,a mathematical model of hydraulic regenerative braking and energy recovery efficiency is established to preliminarily evaluate the performance of hydraulic regenerative braking.The hydraulic regenerative braking model is built in AMESim.The parameters of the hydraulic system of the railway engineering vehicle are simulated under the conditions of braking and uniform downhill speed.The feasibility and validity of the hydraulic regenerative braking and the correctness of the simulation model are verified by the test platform.Then,under the condition of ensuring the braking performance,the characteristics of the hydraulic and friction compound braking are simulated and analyzed through AMESim and MATLAB/Simulink.As the speed decreases,the braking torque can be increased by controlling the displacement of the variable pump/motor.The friction braking force should be moderately reduced to increase hydraulic regenerative braking torque,under the condition of ensuring the braking performance,and friction braking wear is reduced,the energy recovery rate is improved.The excess volume of accumulator is not conducive to increasing regenerative braking torque and will reduce the energy recovery efficiency.The relatively higher pre-charged pressure of accumulator could increase the total energy recovery rate,but the hydraulic energy recovery is reduced.Finally,in order to improve the energy efficiency and speed stability in the downhill process of the battery railway engineering vehicle,a control strategy of maintaining the vehicle downhill speed stability by hydraulic regeneration/friction-free braking is proposed.In order to ensure that the excess energy of rail engineering vehicle in the downhill process is maximize recovered,accumulator is preferred to recover energy.The combined simulation analysis of velocity characteristics is carried out by MATLAB/Simulink and AMESim,and the feasibility and effectiveness of the strategy are verified by experiments.