Traction Motor Wheel Speed Estimation for Low-Speed Sensing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Electric vehicles face performance issues due to limited resolution in wheel speed sensing, particularly at low vehicle speeds, which can negatively impact systems relying on accurate wheel speed data.
Innovation Solution
An apparatus and method for wheel speed estimation using an electronic control unit that calculates an estimated wheel speed based on motor speed and mechanical dynamic models of the electrical powertrain, including a gearbox and drive axle, allowing synchronization with sensed wheel speed and providing redundancy for faulty sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If wheel speed sensors are used to sense wheel speed, then wheel speed information can be obtained for vehicle control systems, but the resolution is limited at low vehicle speeds which negatively impacts system performance
Solution Approach 1:
The patent introduces an intermediary estimation system that uses motor speed (from encoder) and mechanical dynamic models as mediators to derive wheel speed information. Instead of relying directly on wheel speed sensors which have limited resolution at low speeds, the system uses the motor encoder signal as an intermediary that provides higher resolution data, combined with a mechanical model of the drivetrain (including gearbox and drive axle) to calculate estimated wheel speed. This intermediary approach bypasses the limitation of direct wheel speed sensing.
Solution Approach 2:
The patent replaces the mechanical wheel speed sensing system with an electronic estimation system. Instead of using mechanical sensors mounted on the wheel hub or axle that suffer from resolution limitations, the system substitutes a computational approach using motor encoder data and mechanical dynamic models. This substitution transforms the problem from a mechanical measurement limitation to an electronic computation solution that can provide higher resolution wheel speed information.
2Adaptability or versatility
If rotational speed sensors are installed at various places in the electric drive system, then speed information can be obtained for multiple control functions, but the complexity of the sensing system increases
Solution Approach 1:
The patent makes the motor encoder serve multiple functions. Primarily, the motor encoder provides motor speed feedback for motor control. Secondarily, it serves as the primary sensor for estimating wheel speed for various vehicle control systems (traction control, stability control, braking systems, etc.). This multi-functionality eliminates the need for separate wheel speed sensors, reducing system complexity while maintaining versatile speed sensing coverage across all required control functions.
Solution Approach 2:
The system uses the existing motor encoder (which is already part of the electric motor assembly) to serve the additional function of wheel speed estimation. The motor encoder is essentially 'self-servicing' by providing dual-purpose data: motor control feedback and wheel speed estimation input. This self-service approach eliminates the need for additional dedicated wheel speed sensors, reducing overall system complexity while maintaining comprehensive speed sensing capability.
Data Source
AI summary
Method and apparatus for wheel speed estimation include an electrical powertrain having an electric motor providing a motor speed, a wheel, and a mechanical coupling between the motor and the wheel, and an electronic control unit calculating an estimated wheel speed based on the motor speed and mechanical dynamic models of the electrical powertrain.