Electric Motor Control System for Wheel Slip Management
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Solution Overview
Problem
Existing motor vehicle control systems for electric propulsion motors experience oscillations in wheel speed during braking and acceleration, leading to increased noise, vibration, and harshness (NVH) and poor deceleration, due to the reliance on torque control alone which fails to effectively manage slip on varying road surfaces.
Innovation Solution
A control system that switches between torque control and speed control modes based on wheel slip, with the torque control mode generating a predetermined drive torque and the speed control mode enforcing a predetermined rotation speed of the electric propulsion motor, independent of rotor position, to manage slip and prevent excessive wheel slip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If torque control is used to manage wheel slip, then the control system can maintain simplicity and respond quickly to slip conditions, but oscillations in wheel speed occur leading to increased NVH and poor deceleration performance
Solution Approach 1:
The control system dynamically switches between torque control mode and speed control mode based on detected wheel slip conditions. When slip is detected, the system transitions from torque control to speed control, enabling adaptive response that maintains both quick reaction capability and wheel speed stability across varying operating conditions.
2Stability of the object's composition
If speed control mode is implemented to reduce oscillations and improve stability, then wheel speed stability improves and NVH reduces, but the control system complexity increases due to mode switching logic
Solution Approach 1:
The control system changes the control parameter from torque to speed based on operating conditions. A slip detection mechanism triggers a parameter change in the control algorithm, switching from torque control to speed control. This parameter-based switching approach manages complexity by using a clear threshold-based decision criterion rather than complex multi-variable control logic.
3Use of energy by moving object
If torque control is used during braking, then the electric machine can provide regenerative braking torque, but excessive wheel slip occurs on varying road surfaces leading to loss of traction
Solution Approach 1:
The control system uses feedback from wheel speed sensors to detect slip conditions during braking. When slip is detected, the system provides feedback that triggers a mode transition from torque control to speed control, ensuring reliable traction control while maintaining regenerative braking capability through the feedback-driven adaptive response.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces unwanted oscillations in wheel speed, enhances traction control, and quickly corrects loss of traction during acceleration, providing improved vehicle stability and smoother operation by directly controlling commutation speed to maintain desired wheel speeds.
Implementation Method 1
Modern (brushless) motors, and in particular synchronous motors such as switched reluctance motors and permanent magnet DC motors, are controlled by power electronics with commutation controlled in response to an estimate of the angular position of the motor
Implementation Method 2
the commutation controller aligns the stator (or rotor—some machines are organised with the fixed field in the stator, others have the constant field (or permanent magnet) in the rotor) magnetic field in relation to the magnetic field on the rotor (stator). The magnitude and (mis)alignment of the fields generates torque in the motor
Data Source
AI summary
A motor vehicle control system (210C, 220) for controlling an electric propulsion motor (230) to drive a wheel (290) of the vehicle (200), the control system (210C, 220) being configured to operate in one of a first mode and a second mode in dependence at least in part on an amount of slip experienced by at least one driven wheel (290), in the first mode the control system (210C, 220) being configured to cause the at least one electric propulsion motor (230) to generate a predetermined amount of drive torque, in the second mode the control system (210C, 220) being configured to cause the at least one electric propulsion motor (230) to rotate at a predetermined speed, wherein the control system (210C, 220) is configured to operate in the first mode if the amount of slip experienced by the at least one driven wheel (290) is below a predetermined slip amount and to operate in the second mode if the amount of slip experienced by the at least one driven wheel (290) exceeds the predetermined slip amount.