Wheel Hub Motor Torque Distribution for Energy-Saving Stability Control
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Solution Overview
Problem
Existing electric vehicles with wheel hub motors face challenges in achieving energy-saving control while maintaining handling stability and safety, particularly under urban driving conditions with frequent acceleration, deceleration, and turning.
Innovation Solution
A hierarchical control system and method for torque distribution in hub motor-driven electric vehicles, utilizing a motor efficiency map-based drive torque distribution control and tire slip rate-based drive torque distribution control, along with a fuzzy control module and sequence quadratic programming, to optimize torque distribution and improve vehicle stability and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If wheel hub motors are used to drive electric vehicles, then transmission efficiency is improved and vehicle structure is simplified, but unsprung weight increases which deteriorates handling stability
Solution Approach 1:
The control system is divided into two layers: upper layer for energy-saving control and lower layer for stability control. This segmentation allows independent optimization of each function while maintaining overall system performance, resolving the contradiction between transmission efficiency and handling stability.
Solution Approach 2:
The system dynamically adjusts torque distribution parameters based on operating conditions, using motor efficiency maps to optimize energy consumption while maintaining handling stability through adaptive control of torque allocation to different wheels.
2Loss of energy
If motor efficiency map-based torque distribution control is implemented, then energy-saving effects are achieved, but control system complexity increases
Solution Approach 1:
The control strategy is segmented into upper-layer energy-saving control using efficiency maps and lower-layer stability control, allowing each layer to focus on its specific function and reducing overall system complexity through modular design.
Solution Approach 2:
A torque distribution controller acts as an intermediary between the driver's torque demand and the actual motor torque output, using efficiency maps to optimize energy consumption while maintaining simple motor control architecture.
3Loss of energy
If hierarchical control system is used for torque distribution, then both energy-saving and handling stability are improved, but system complexity increases
Solution Approach 1:
The hierarchical control system is segmented into distinct upper and lower layers with clear functional boundaries, allowing independent development and testing of each layer while reducing the perceived complexity through modular architecture.
Solution Approach 2:
The lower-layer torque distribution controller serves multiple functions: it maintains handling stability through differential torque control and simultaneously implements energy-saving strategies from the upper layer, reducing the need for additional dedicated components.
Data Source
AI summary
A hierarchical control system for torque distribution of hub motor-driven electric vehicles constructs a hierarchical controller with upper and lower layers. An upper layer torque distribution controller's drive torque distribution control strategy is determined through a fuzzy control module. A lower layer torque distribution controller receives the torque, yaw velocity, and side-slip angle from the upper layer torque distribution controller and performs drive torque distribution control based on the motor efficiency map or tire slip rate by using the torque, yaw velocity, side-slip angle and actual values of vehicle feedback to obtain a generalized torque output to a wheel hub motor model for calculating to obtain a target torque and inputting it into a 7-degree-of-freedom vehicle model. The 7-degree-of-freedom vehicle model feeds back vehicle states to the upper layer torque distribution controller to form a closed-loop control, achieving energy-saving control and improving handling stability and safety.