Drive Wheel Torque Control Using Road Friction Estimation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional methods for estimating road surface friction coefficient fail to detect minor slips, leading to a low frequency of estimation and suboptimal drive control due to the varying relationship between slip ratio and road surface conditions.
Innovation Solution
A control device that estimates the maximum friction coefficient of a drive wheel using a coefficient estimation unit, calculates a torque upper limit with a limit calculation unit, and sets a target torque to avoid exceeding this limit using a target-setting unit, thereby enabling optimal acceleration and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the road surface friction coefficient is estimated only when large slip occurs, then the estimation can be performed with simple calculation, but the estimation frequency becomes very low and cannot detect minor slips
Solution Approach 1:
The system performs preliminary action by estimating the road surface friction coefficient during normal driving conditions before large slip occurs. The coefficient estimation unit continuously monitors drive wheel acceleration and torque to proactively determine the friction coefficient, enabling the control system to have advance knowledge of road conditions and prevent slip rather than merely reacting to it.
2Reliability
If the maximum friction coefficient is accurately estimated, then optimal drive control can be executed to achieve best acceleration and stability, but the control system complexity increases
Solution Approach 1:
The system implements feedback by continuously monitoring actual drive wheel acceleration and comparing it with the calculated torque to detect slip conditions. The coefficient estimation unit uses this feedback information to continuously update the road surface friction coefficient estimation, which then feeds back to the control system to adjust torque application and maintain optimal traction without excessive complexity.
Solution Approach 2:
The patent replaces complex mechanical slip detection mechanisms with an electronic calculation system. Instead of using mechanical sensors or complex physical detection devices, the system uses the coefficient estimation unit to calculate the friction coefficient based on readily available torque and acceleration data, substituting mechanical complexity with computational simplicity.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
An EVC 10 includes: a coefficient estimation unit 105 that estimates a maximum friction coefficient of a drive wheel with respect to a front road surface when a mobile body causes the drive wheel to rotate and travels on the road surface; a limit calculation unit 102 that calculates a torque upper limit for driving the drive wheel according to the estimated maximum friction coefficient; and a target-setting unit 103 that sets a target torque to drive the drive wheel so as not to exceed the torque upper limit.