Vehicle Speed Estimation With CAN Delay Compensation
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Solution Overview
Problem
Conventional vehicle body speed estimation methods for electric vehicles do not adequately consider the delay time caused by CAN communication and sensor detection, leading to inadequate utilization of the high torque response of electric motors for improved starting performance.
Innovation Solution
A vehicle control device that includes a delay correction amount calculation unit to estimate the increase or decrease in vehicle body speed during the delay time, an error correction unit to correct past estimated speeds based on communication delays, and a vehicle body speed calculation unit to accurately calculate the current speed by adding the delay correction amount to the corrected past speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If wheel speed is acquired through CAN communication, then the vehicle body speed estimation can be performed, but the delay time of CAN communication and sensor detection causes the estimated speed to be inaccurate
Solution Approach 1:
The patent applies preliminary action by calculating the delay correction amount in advance based on the relationship between wheel speed and vehicle body speed. The system pre-calculates what the speed increase or decrease would be during the delay period, allowing the controller to compensate for the delay when the wheel speed data arrives. This enables the system to predict and correct for the time loss before it affects the control decision.
Solution Approach 2:
The patent implements feedback by using the calculated delay correction amount to adjust the estimated vehicle body speed. The system continuously monitors wheel speed, calculates the corresponding delay correction, and feeds this correction back to improve the accuracy of the vehicle body speed estimation. This closed-loop approach ensures that the estimated speed accurately reflects the actual vehicle state despite communication delays.
2Device complexity
If conventional estimation methods are used without delay correction, then the calculation process is simple, but the vehicle body speed estimation does not account for communication and sensor delays
Solution Approach 1:
The patent applies preliminary action by pre-calculating the delay correction amount based on the relationship between wheel speed and vehicle body speed. Instead of implementing complex real-time delay compensation algorithms, the system pre-determines the correction value that represents the speed increase or decrease during the delay period. This approach maintains calculation simplicity while improving estimation accuracy.
Solution Approach 2:
The patent applies parameter changes by introducing a delay correction amount parameter that adjusts the estimated vehicle body speed. The system modifies the speed estimation by adding or subtracting this correction parameter, which is calculated based on the wheel speed and the known delay characteristics. This parameter-based approach simplifies the correction process while maintaining accuracy.
Data Source
AI summary
An electronic control unit (ECU) 10 includes: a delay correction amount calculation unit 120 that calculates, as a delay correction amount α, an estimated increase or decrease in vehicle body speed during a delay time occurring when a wheel speed ωw is acquired through a wheel speed sensor and controller area network (CAN) communication, the calculation being based on one of a front-rear acceleration X of an electric vehicle 1 and an estimated vehicle body speed V; an error correction unit 130 that calculates a corrected past estimated vehicle body speed Vp′, obtained by correcting a past estimated vehicle body speed Vp, based on an error ΔV between the past estimated vehicle body speed Vp and a CAN vehicle body speed Vs, the past estimated vehicle body speed being the estimated vehicle body speed V calculated earlier by the delay time, the CAN vehicle body speed being based on the wheel speed ωw acquired through CAN communication; and a vehicle body speed calculation unit 140 that calculates the current estimated vehicle body speed V by adding the delay correction amount α and the corrected past estimated vehicle body speed Vp′.