Differential Torque Control Using Drive Speed Backup Signals
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Solution Overview
Problem
When wheel speed sensors fail, it is challenging to obtain an appropriate differential rotation speed, making it difficult to prevent burn-in of the differential device.
Innovation Solution
A vehicle control device that includes a drive source, a differential device, a speed sensor for the drive source, wheel speed sensors for the wheels, and a control device. In case of a wheel speed sensor failure, the control device sets an index value by multiplying the drive source's rotation speed by a predetermined coefficient and controls the torque output based on this index value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wheel speed sensors are used to measure differential rotation speed, then burn-in prevention is effective, but the system becomes vulnerable to sensor failures
Solution Approach 1:
The drive source rotation speed sensor acts as an intermediary to provide alternative rotation speed data when wheel speed sensors fail. The control device uses the drive source rotation speed as a substitute measurement to calculate the differential rotation speed, ensuring continuous burn-in prevention capability even when the primary wheel speed sensors are unavailable.
Solution Approach 2:
The system dynamically changes the measurement parameter from wheel rotation speed (when sensors are functional) to drive source rotation speed (when sensors fail). This parameter substitution allows the control device to maintain the differential rotation speed calculation and burn-in prevention function under varying operational conditions and sensor availability.
2Measurement precision
If wheel speed sensor failure occurs, then measurement accuracy is lost, but the system can switch to using drive source rotation speed
Solution Approach 1:
The control device is pre-configured with the capability to use drive source rotation speed as a backup measurement source. When wheel speed sensor failure is detected, the system immediately switches to using the drive source rotation speed sensor data, which was already available and functional, to maintain accurate differential rotation speed measurement without interruption.
3Device complexity
If the system uses only wheel speed sensors, then the structure is simpler, but the system cannot operate reliably when sensors fail
Solution Approach 1:
The drive source rotation speed sensor serves multiple functions: it primarily monitors drive source speed for general vehicle control, and secondarily provides differential rotation speed measurement data when wheel speed sensors are operational. When wheel speed sensors fail, it automatically assumes the additional function of enabling burn-in prevention, demonstrating multi-functionality that enhances system reliability without adding dedicated components.
Data Source
AI summary
A vehicle control device includes a drive source mounted on a vehicle, a differential device configured to distribute a driving force generated by the drive source to a right drive wheel and a left drive wheel, a speed sensor configured to detect a rotation speed of the drive source, a pair of wheel speed sensors configured to detect rotation speeds of the right drive wheel and the left drive wheel, and a control device configured to set an index value having a value obtained by multiplying the rotation speed of the drive source by a predetermined coefficient in a case that at least one of the pair of wheel speed sensors fails, and to control torque output from the drive source based on the index value.