Vehicle Rolling Direction Estimation Using Unsigned Wheel Speed
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Solution Overview
Problem
Automatically started vehicles face challenges when stopped on hills, as they may roll due to grade, leading to unintended movement during engine restart, and existing systems rely on direction-specific wheel speed sensors, increasing costs.
Innovation Solution
A method that estimates rolling direction and road grade using unsigned wheel speed sensors and vehicle longitudinal acceleration, adjusting actuators to mitigate movement by correlating sensor data and applying kinematic equations to adjust engine torque and brakes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direction-specific wheel speed sensors are used to determine rolling direction, then measurement precision is improved, but device complexity and system cost increase
Solution Approach 1:
The patent introduces an intermediary computational approach by using unsigned wheel speed sensors combined with longitudinal acceleration data from other sensors to infer rolling direction. Instead of directly measuring signed wheel speed, the system processes unsigned speed data through correlation analysis with acceleration signals to determine direction, thereby avoiding the need for expensive direction-specific sensors while maintaining adequate measurement precision
Solution Approach 2:
The patent replaces the mechanical/sensor-based solution (direction-specific wheel speed sensors) with a computational approach that processes data from existing unsigned sensors. By substituting direct physical measurement with signal processing and correlation analysis, the system achieves rolling direction detection without requiring specialized hardware, thus reducing device complexity and cost
2Stability of the object's composition
If vehicle brakes are applied to prevent rolling on hills, then vehicle stability is improved, but engine starting reliability deteriorates due to engine stop conditions
Solution Approach 1:
The patent applies preliminary action by determining the rolling direction and road grade before the engine start event occurs. The controller uses unsigned wheel speed sensors and longitudinal acceleration to predict the vehicle's rolling tendency, then pre-adjusts engine torque or transmission settings to counteract gravitational forces before the driver releases the brake, thereby preventing unintended movement without requiring brake application during startup
Solution Approach 2:
The patent implements feedback by continuously monitoring unsigned wheel speed and longitudinal acceleration to determine rolling direction and road grade. This feedback information is used to dynamically adjust engine torque or transmission settings in real-time, creating a closed-loop control system that automatically compensates for gravitational forces on hills, ensuring both vehicle stability and reliable engine starting
3Stability of the object's composition
If engine torque is increased to counteract gravitational forces on hills, then vehicle stability is improved, but unnecessary engine torque is produced when not needed
Solution Approach 1:
The patent applies partial action by adjusting engine torque only to the extent necessary to counteract the calculated gravitational forces on hills. Rather than always applying maximum compensating torque, the system calculates the specific torque needed based on road grade and rolling direction, applying only the partial amount required to prevent rolling, thereby avoiding unnecessary energy consumption while maintaining vehicle stability
Data Source
AI summary
Systems and methods for determining vehicle rolling direction and road grade are disclosed. In one example, a vehicle rolling direction is determined from a correlation coefficient. The vehicle rolling direction is applied to a kinematic equation to determine road grade.