Vehicle Speed Detection Switching for Braking Control
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Solution Overview
Problem
In vehicles equipped with a driving motor, the generation of frictional braking force during rotation of the output shaft leads to erroneous vehicle speed detection due to torsion in the driving force transmission path, causing inaccuracies in vehicle speed calculation.
Innovation Solution
The braking and driving force control system uses output shaft side vehicle speed when only load braking is applied and switches to wheel-side vehicle speed when frictional braking is generated, allowing for accurate control of braking and driving forces by utilizing the wheel-side vehicle speed, which is less affected by torsion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If frictional braking force is generated during rotation of the output shaft, then braking control can be performed, but torsion is generated in the driving force transmission path causing erroneous vehicle speed detection
Solution Approach 1:
The patent segments the vehicle speed detection system into two independent paths: one based on output shaft rotation speed and another based on wheel rotation speed. By separating these detection paths, the system can select the appropriate speed signal depending on the braking mode, preventing torsion in the driving force transmission path from affecting speed detection accuracy.
Solution Approach 2:
The patent changes the parameter used for vehicle speed detection based on the braking mode. When frictional braking is detected, the system switches from using output shaft rotation speed to using wheel rotation speed. This parameter switching resolves the contradiction by selecting the appropriate measurement source that is not affected by torsion under different operating conditions.
2Device complexity
If vehicle speed is calculated from output shaft rotation speed, then speed detection is simplified, but torsion during frictional braking causes erroneous detection
Solution Approach 1:
The patent implements a multi-functional speed detection system that can operate in different modes. The wheel speed sensor serves both as a backup detection method and as the primary method during frictional braking, while the output shaft speed sensor serves as the primary method during regenerative braking. This universality allows the system to maintain simplicity while ensuring accuracy under various conditions.
Solution Approach 2:
The patent introduces dynamic switching between different speed detection methods based on the braking mode. The control unit dynamically selects whether to use output shaft rotation speed or wheel rotation speed for vehicle speed calculation, depending on whether frictional braking or regenerative braking is being applied. This dynamic adaptation resolves the contradiction by optimizing the detection method for each operating condition.
Data Source
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AI summary
A braking-driving force control system is provided in which erroneous vehicle speed detection may be avoided even when a frictional braking power is generated during rotation of an output shaft coupled to an electric driving motor as driving source. When only regenerative braking force is being generated as braking force while the vehicle is traveling, the braking force and the driving force are controlled based on an output shaft side vehicle speed calculated from the rotational state of an output shaft of a driving source, and when the frictional braking power is being generated while the vehicle is traveling, the braking force and the driving force will be controlled based on a wheel side vehicle speed representing the vehicle speed calculated from the rotational state of the vehicle wheel.