Torque Coordination Control of an Electro-Hydraulic Composite Brake System During Mode Switching Based on Braking Intention

Abstract

The electro-hydraulic composite braking system of a pure electric vehicle can select different braking modes according to braking conditions. However, the differences in dynamic response characteristics between the motor braking system (MBS) and hydraulic braking system (HBS) cause total braking torque to fluctuate significantly during mode switching, resulting in jerking of the vehicle and affecting ride comfort. In this paper, torque coordination control during mode switching is studied for a four-wheel-drive pure electric vehicle with a dual motor. After the dynamic analysis of braking, a braking force distribution control strategy is developed based on the I-curve, and the boundary conditions of mode switching are determined. A novel combined pressure control algorithm, which contains a PID (proportional-integral-derivative) and fuzzy controller, is used to control the brake pressure of each wheel cylinder, to realize precise control of the hydraulic brake torque. Then, a novel torque coordination control strategy is proposed based on brake pedal stroke and its change rate, to modify the target hydraulic braking torque and reflect the driver’s braking intention. Meanwhile, motor braking torque is used to compensate for the insufficient braking torque caused by HBS, so as to realize a smooth transition between the braking modes. Simulation results show that the proposed coordination control strategy can effectively reduce torque fluctuation and vehicle jerk during mode switching.

The Eco-Driving Considering Coordinated Control Strategy for the Intelligent Electric Vehicles

“…The dynamic response characteristics of in-wheel motors and hydraulic response characteristics need to be compensated in different braking stage and regenerative braking energy should be recycled to the maximum extent [33,34]. The braking torque of the lower-level distribution controller is used to compensate for the insufficient braking torque to realize a smooth transition between the braking modes [35]. Key parameters in the braking force distribution strategy, such as the optimal distribution coefficients, need to be achieved by the genetic algorithm and weight coefficients can be used to achieve a dynamic distribution [36].…”

“…Taken above performance indicators into consideration, constraints in NMPC can be expressed as follows. (35) Supposing ah,lon keeps the same in p steps and IEV's states from k th to (k+p) th step time can be predicted as follows.…”

Structure design and coordinated control of electromagnetic and frictional braking system based on a hub motor

“…Thus, many researchers adopt this method that assumptions and ignoring some influencing factors braking system are related to its structural parameters when researching this aspect. [28][29][30] Figure 5 shows the dimension parameters of the electromagnetic system in the integrated braking system. The eddy current braking torque can be expressed as:…”

Research on Composite Braking Mode Switching Strategy Based on Fuzzy Algorithm

“…The upper controller identifies the driver's braking intention, and the lower controller adopts the method of electronic control brake compensation to reduce the composite braking. Yang et al [11] controlled the brake pressure of each wheel cylinder through a novel combined pressure control algorithm, which significantly improved the problem of vehicle brake switching mode jitter.…”