AWD Vehicle Speed Estimation During Wheel Slip Events
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Solution Overview
Problem
All-wheel-drive electrified vehicles face challenges in accurately calculating vehicle speed, especially during wheel slip events, due to the complexity of managing road grade and wheel acceleration, which affects traction control and stability.
Innovation Solution
A vehicle speed estimation algorithm that integrates measured longitudinal acceleration and wheel speed data, using flags to switch between different calculation methods, compensates for road grade and corrects accelerometer measurements to provide accurate vehicle speed estimates, enabling precise control of traction systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If vehicle speed is calculated using wheel speed data during wheel slip events, then speed calculation simplicity is improved, but measurement precision deteriorates due to inaccurate wheel speed readings
Solution Approach 1:
The patent introduces accelerometer data as an intermediary measurement source to compensate for wheel speed inaccuracies during slip events. The controller fuses wheel speed data with accelerometer data to calculate vehicle speed, using the accelerometer as a mediator that provides reliable acceleration measurements even when wheels are slipping, thereby maintaining measurement precision without excessive complexity
Solution Approach 2:
The patent creates a universal speed calculation system that can operate under multiple conditions (normal driving and wheel slip) by integrating multiple measurement sources. The controller automatically selects or fuses between wheel speed-based calculation and accelerometer-based calculation, making the system universally applicable across different operating conditions while maintaining both simplicity and precision
2Measurement precision
If accelerometer data is used to calculate vehicle speed, then measurement precision is improved, but device complexity increases due to additional sensors and processing
Solution Approach 1:
The patent applies partial action by using accelerometer data selectively rather than continuously. The controller determines whether wheel slip is occurring and only then incorporates accelerometer data into the speed calculation. During normal operation, the simpler wheel speed-based calculation is used, adding complexity only when necessary to maintain precision during slip events
Solution Approach 2:
The patent implements a dynamic calculation system that adapts its methodology based on operating conditions. The controller dynamically switches between or fuses different calculation approaches (wheel speed-based vs. accelerometer-based) depending on whether wheel slip is detected, making the system complexity variable rather than fixed, thereby reducing overall complexity while maintaining precision when needed
3Ease of operation
If wheel slip control is implemented using speed threshold comparison, then ease of operation is improved, but reliability deteriorates during extreme slip conditions
Solution Approach 1:
The patent implements feedback by continuously monitoring the difference between calculated vehicle speed and wheel speed, using this feedback to detect wheel slip conditions and adjust control actions. The controller calculates wheel slip as the difference between these speeds and uses this feedback signal to determine when intervention is needed, maintaining reliability through continuous adaptive feedback rather than fixed thresholds
Solution Approach 2:
The patent changes the control parameter from simple speed threshold comparison to a more robust parameter based on the difference between vehicle speed and wheel speed. By using the calculated vehicle speed (which incorporates accelerometer data during slip) as a reference, the control system adapts its parameters dynamically, maintaining reliability under extreme conditions while keeping operation simple through automated parameter adjustment
Data Source
AI summary
A vehicle includes an all-wheel-drive powertrain having an electric machine configured to power wheels. A controller is programmed to output a first calculated vehicle speed derived from integrating a measured longitudinal acceleration of the vehicle and output a second calculated vehicle speed based on the measured longitudinal acceleration and a speed of one of the wheels. The controller is further programmed to, responsive to a flag being present, command a speed to the electric machine that is based on the first vehicle speed to reduce wheel slip, and responsive to a flag not being present, command a speed to the electric machine that is based on the second vehicle speed to reduce wheel slip.