Vehicle Stability Control Using Motor Speed Signals
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Solution Overview
Problem
Electronic stability control systems in electric vehicles face limitations due to inaccurate or low-resolution wheel speed sensor data, particularly at low vehicle speeds, leading to underperformance in traction and stability control functions.
Innovation Solution
Using electric motor speed signals from the vehicle communication bus to replace wheel speed sensor signals in certain conditions, especially at low speeds, to provide more accurate and timely information for improved traction control, parking maneuvers, and off-road stability functions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If wheel speed sensor signals are used for stability control, then the system can detect wheel speed, but the measurement precision deteriorates at low vehicle speeds
Solution Approach 1:
The electric motor speed sensor serves dual purposes: it provides speed information for both powertrain control and stability control functions. By utilizing the same sensor for multiple functions, the patent eliminates the need for separate wheel speed sensing at low speeds, thereby improving measurement precision without adding complexity.
Solution Approach 2:
The electric motor speed sensor acts as an intermediary source of speed information that bridges the gap when traditional wheel speed sensors fail to provide adequate resolution at low speeds. This intermediary source provides the necessary measurement precision for stability control during low-speed operations.
2Measurement precision
If wheel speed sensor signals are used, then the system can provide speed information, but the resolution is insufficient at low speeds
Solution Approach 1:
The electric motor speed sensor, already present for powertrain control, is utilized for stability control functions as well. This multi-functional use provides high-resolution speed signals for reliability-critical stability control without requiring additional dedicated sensors.
Solution Approach 2:
The patent changes the source of speed signal parameters from wheel speed sensors to electric motor speed sensors. This parameter change provides higher resolution data, particularly in the low-speed range, thereby improving the reliability of stability control systems.
3Measurement precision
If traditional wheel speed sensors are used, then the system can detect wheel rotation, but accuracy is lost when wheels lose traction
Solution Approach 1:
The electric motor speed sensor serves as an intermediary measurement source that is not directly affected by wheel-road traction conditions. Since it measures motor shaft rotation rather than wheel rotation, it provides accurate speed information even when wheels are slipping or spinning.
Solution Approach 2:
The patent uses the electric motor speed sensor signal as a copy or alternative representation of vehicle speed that is more reliable under slip conditions. This copied signal from the motor shaft provides accurate speed information without being contaminated by wheel slip effects.
Data Source
AI summary
A vehicle control system includes a powertrain electronic control unit and an electronic stability control unit that is connected to the powertrain electronic control unit via a vehicle communication bus. The vehicle powertrain includes a wheel, a wheel speed sensor that is configured to detect a speed of the wheel, an electric motor that is configured to drive the wheel, and an electric motor speed sensor that is configured to detect the speed of the electric motor. If the vehicle is not traveling at low speeds (for example, less than 2 kilometers per hour), the electronic stability control unit controls the vehicle based on an output of the wheel speed sensor. However, if the vehicle is traveling at low speeds, the electronic stability control unit controls the vehicle based on an output of the electric motor speed sensor.