Vehicle Speed Estimation Under Wheel Slip and Pitching
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Solution Overview
Problem
Existing vehicle speed estimation methods in a slip state suffer from inaccuracies due to deviations between detected longitudinal acceleration and actual vehicle acceleration, particularly during pitching, which affects the precision of vehicle control systems.
Innovation Solution
A vehicle control device that includes a wheel speed acquisition unit, an acceleration acquisition unit, a calculation unit, and a slip determination unit, which calculates an estimated vehicle speed by executing a limit process on detected acceleration and switches modes of this process based on slip state determinations to improve accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If vehicle speed is estimated based on longitudinal acceleration sensor detection results, then the estimation can be obtained, but the calculation accuracy deteriorates in slip state due to pitching deviation
Solution Approach 1:
The patent dynamically switches between two different limit process modes (first mode and second mode) based on the detected slip state. When the vehicle is in a slip state, it switches to the second mode which applies different acceleration limiting logic, thereby adapting the estimation algorithm to current vehicle conditions and improving accuracy despite pitching deviations
Solution Approach 2:
The patent changes the processing parameters (limit process mode) based on the slip state determination. By detecting whether the vehicle is in a slip state and switching between different acceleration limiting strategies, the system adjusts its parameters to maintain accurate vehicle speed estimation under varying road conditions
2Device complexity
If a fixed limit process is applied to acceleration detection, then the processing is simple, but the vehicle speed estimation accuracy deteriorates when switching between grip and slip states
Solution Approach 1:
The patent implements a dynamic limit process that automatically switches between first and second modes based on real-time slip state detection. This dynamic adaptation allows the system to maintain simple processing within each mode while achieving high accuracy across varying conditions by selecting the appropriate mode for current vehicle state
3Speed
If acceleration sensor detection is used directly without limit process, then the response is fast, but the vehicle speed estimation accuracy deteriorates due to pitching influence
Solution Approach 1:
The patent applies preliminary anti-action by pre-establishing two different limit process modes that are specifically designed to counteract pitching influences. When slip state is detected, the second mode is activated which applies acceleration limiting logic that compensates for pitching effects, thereby preventing accuracy degradation before it occurs
Data Source
AI summary
A vehicle control device includes a wheel speed acquisition unit which acquires wheel speeds of wheels of a vehicle based on detection results of wheel speed sensors, an acceleration acquisition unit which acquires an acceleration in a longitudinal direction of the vehicle based on a detection result of an acceleration sensor, a calculation unit which calculates a first vehicle speed based on the wheel speeds of the wheels, an estimation unit which calculates a second vehicle speed estimated based on the first vehicle speed and the detected acceleration, and a slip determination unit which determines whether the vehicle is in a slip state. The estimation unit calculates the second vehicle speed by executing a limit process on the detected acceleration, and switches a mode of the limit process when it is determined that the vehicle is in the slip state during acceleration or deceleration of the vehicle.