Vehicle State Estimation with Slip-Adaptive Velocity Fusion
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Solution Overview
Problem
Existing vehicle state estimation devices face decreased accuracy over time due to numerical integration errors in estimating vehicle velocity and attitude angle, particularly when wheels are in a sliding state.
Innovation Solution
A vehicle state estimation device that uses inertial measurement sensors for acceleration and angular velocity, and wheel speed sensors to differentiate between steady-state and transient vehicle states, adjusting estimation methods based on wheel sliding conditions to enhance accuracy without requiring mass or friction coefficient values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If numerical integration is used to estimate vehicle state continuously, then the estimation can be maintained over time, but the estimation accuracy decreases with lapse of time due to integration errors
Solution Approach 1:
The patent implements periodic correction of the numerically integrated vehicle state using wheel speed sensor measurements at predetermined time intervals. This periodic action resets and corrects accumulation errors, allowing long-duration estimation while maintaining accuracy by regularly synchronizing with external reference measurements.
Solution Approach 2:
The patent uses wheel speed sensor measurements as feedback to correct the numerically integrated vehicle state. The feedback mechanism compares the integrated state with actual sensor measurements and adjusts the estimation accordingly, preventing error accumulation and maintaining long-term accuracy.
2Device complexity
If wheel speed is used to estimate vehicle velocity, then the estimation is simple and direct, but the accuracy deteriorates when the wheel is in a sliding state
Solution Approach 1:
The patent dynamically switches between different velocity estimation methods based on sliding detection. When sliding is detected, the system transitions from using wheel speed to using numerically integrated acceleration, and adjusts the coupling between wheel angle and vehicle attitude accordingly. This dynamic adaptation maintains simplicity while improving accuracy under varying conditions.
Solution Approach 2:
The patent changes the estimation parameters (velocity calculation method and attitude coupling) based on the detected sliding state. This parameter change allows the system to adapt to different road conditions, using the appropriate method for each state to maintain both simplicity and accuracy.
3Measurement precision
If the vehicle state is estimated using equation of motion with mass and friction coefficient, then the theoretical accuracy can be high, but the estimation becomes dependent on vehicle usage and road surface conditions
Solution Approach 1:
The patent extracts and removes the dependencies on mass and friction coefficient from the velocity and attitude estimation process. By using wheel speed and angular velocity measurements directly, rather than forces requiring these parameters, the system achieves high accuracy while being independent of vehicle loading and road surface conditions.
Data Source
AI summary
A vehicle state estimation device for a vehicle provided with an inertial measurement sensor and a wheel speed sensor includes: a vehicle state estimation unit that estimates a vehicle state including a vehicle velocity based on an acceleration and an angular velocity acquired by the inertial measurement sensor and a wheel speed acquired by the wheel speed sensor; and a determination unit that determines whether a wheel is slipping. The estimation unit estimates a steady-state vehicle velocity based on the wheel speed and calculates a transient vehicle velocity by time integration based on the acceleration and the angular velocity. When the wheel is slipping, the estimation unit decides an estimated value of the vehicle velocity to be close to the transient vehicle velocity, and when the wheel is not slipping, the estimation unit decides the estimated value of the vehicle velocity to be close to the steady-state vehicle velocity.