Vehicle Lateral Velocity Estimation Using Gravity Compensation
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Solution Overview
Problem
Current vehicle stability control systems lack a robust and accurate method for estimating vehicle lateral velocity, particularly on low friction surfaces and banked roads, leading to reduced responsiveness and increased difficulty in controlling the vehicle during large side-slip angles.
Innovation Solution
A system and method that calculates vehicle lateral velocity by defining relationships between front and rear axle lateral forces and side-slip angles using measurements of yaw-rate, longitudinal speed, lateral acceleration, and steering angle, incorporating a nonlinear tire model and kinematic observer to estimate surface coefficient of friction and compensate for tire non-linearity and suspension effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If standard stability control systems use lateral acceleration sensors to estimate lateral velocity, then the system can detect vehicle instability, but the estimation becomes inaccurate on banked roads due to gravity bias effects
Solution Approach 1:
The patent introduces a gravity compensation mechanism that acts as an intermediary between the lateral acceleration sensor and the lateral velocity estimator. By measuring roll angle and calculating the gravity component along the vehicle body, the system subtracts this bias from the raw lateral acceleration signal, thereby eliminating the harmful effect of banked roads on estimation accuracy
Solution Approach 2:
The patent changes the parameter being measured by compensating for gravity effects. Instead of using raw lateral acceleration, the system transforms it into a gravity-compensated lateral acceleration by subtracting the gravity component (g*sin(roll_angle)), thereby adapting the measurement to account for banked road conditions
2Reliability
If the vehicle operates on low friction surfaces with large side-slip angles, then the vehicle may experience reduced responsiveness and difficulty in control, but standard systems lack the accurate lateral velocity estimation needed to detect and stabilize these conditions
Solution Approach 1:
The patent implements a feedback mechanism where the estimated lateral velocity and side-slip angle continuously inform the stability control system. The estimator uses sensor inputs (yaw rate, lateral acceleration, steering angle, wheel speeds) to compute lateral velocity, which then feeds back to the stability controller to adjust braking and steering interventions, creating a closed-loop system that adapts to low friction conditions
Solution Approach 2:
The patent employs a dynamic estimation approach that adapts to changing vehicle conditions. The lateral velocity estimator continuously updates its calculations based on current sensor readings and vehicle state, allowing the system to respond dynamically to varying friction conditions and large side-slip angles rather than relying on static assumptions
3Adaptability or versatility
If production stability control systems rely only on yaw-rate, lateral acceleration, steering wheel angle, and wheel speed sensor measurements, then the system uses available sensors, but the lateral velocity estimation lacks robustness and accuracy
Solution Approach 1:
The patent makes the existing sensor system multi-functional by using the same sensors (yaw rate, lateral acceleration, steering angle, wheel speeds) for both basic stability control and advanced lateral velocity estimation. The system processes these universal inputs through enhanced algorithms that also compensate for gravity effects and adapt to varying friction conditions, thereby extracting more information from the same hardware
Data Source
AI summary
A system and method for estimating vehicle lateral velocity that defines a relationship between front and rear axle lateral forces and front and rear axle side-slip angles. The method includes providing measurements of vehicle yaw-rate, lateral acceleration, longitudinal speed, and steering angle. The method also includes using these measurements to provide a measurement of the front and rear axle forces. The method calculates a front axle lateral velocity and a rear axle lateral velocity, and calculates a front axle side-slip angle based on the rear axle lateral velocity and a rear axle side-slip angle based on the front axle lateral velocity. The method then estimates front and rear axle forces, and selects a virtual lateral velocity that minimizes an error between the estimated and measured lateral axle forces. The method then provides an estimated vehicle lateral velocity using the selected virtual lateral velocity.