Abstract
Since the control of brake pressure has a significant impact on regenerative braking performance of electric vehicles, a novel combined brake pressure control algorithm based on two high-speed on-off valves is developed to improve the precision and timeliness of pressure tracking for the regenerative braking system of electric commercial trucks in this paper. First, a comprehensive mathematical model of the valve control system is built up which is composed of several sub-models and verified by experiments. Second, a PID controller with pulse width modulation (PWM) and a fuzzy controller with cooperative PWM are separately adopted in the proposed combined control algorithm to substitute for the traditional PWM approach. Moreover, through the numerical simulation studies, better control performance is obtained in MATLAB/Simulink on the basis of the built models. Finally, the experimental tests under various typical braking pressure input signals are carried out to verify the simulation results. The comparison between the simulation and experimental results fully demonstrates that the proposed control algorithm is feasible and the dynamic performance of this combined valve control algorithm is considerably improved compared with the conventional PID control algorithm.
Highlights
With the rapid development of various types of electric vehicles to save fossil energy and protect the environment, regenerative braking system (RBS) has been essential for electric vehicles, which could make drive motor work as a generator to recover kinetic energy during the deceleration process [1]–[5]
Because the control performance of this system is crucial for the whole blending braking performance, studying practical, effective and accurate method for pneumatic braking pressure
Control is of great importance for the regenerative braking system of electric commercial trucks [6]
Summary
With the rapid development of various types of electric vehicles to save fossil energy and protect the environment, regenerative braking system (RBS) has been essential for electric vehicles, which could make drive motor work as a generator to recover kinetic energy during the deceleration process [1]–[5]. Lv et al [6], [10] presented a pressuredifferent-limiting modulation control method for regenerative braking system and obtained a linear hydraulic pressure control performance between coil current and pressure difference across the tested valves. Where mis the transient mass airflow in the air chamber, Cd is the non-dimensional discharge coefficient of the valve, Av is the effective cross-sectional area of inlet/outlet orifice, p1 is the pressure of upstream, p2 is the pressure of downstream, K is the adiabatic index, R0 is the ideal gas constant and T is the temperature of upstream. CONTROL ALGORITHM DESIGN Conventional PID control method with PWM is widely used in the valve control systems Using this method cannot achieve good performances in accurate pressure control as the hysteresis of high-speed on-off valves and nonlinearity characteristic of airflow. Ds De Ds where Dm is the duty ratio of controller output, Dd is upper limit of dead zone, Ds is lower limit of saturation zone and De is modified duty ratio of effective zone
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