Power Steering Control System Dynamic Sensor Smoothing
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Solution Overview
Problem
Existing power steering systems suffer from errors and lag in steering angle sensors, leading to inconsistent or intermittent driving of the power steering actuator, which negatively affects the steering feel and driving experience.
Innovation Solution
A method of controlling power steering assist by determining the rate of movement of the steering input and vehicle speed, and adjusting the electric power steering assist actuator accordingly, using a higher number of sensor outputs at lower speeds and rates of movement to improve accuracy and reduce error.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a standard steering angle sensor is used, then the system is simple and cost-effective, but the measurement precision and reliability deteriorate due to errors and lag in sensor signals
Solution Approach 1:
The system dynamically adjusts the smoothing parameter based on operating conditions (vehicle speed and steering rate). When vehicle speed is low and steering rate is low, a higher smoothing parameter is applied to filter sensor errors more aggressively. When vehicle speed or steering rate increases, the smoothing parameter decreases to maintain responsiveness. This dynamic adaptation resolves the contradiction by making the control system complexity variable rather than fixed.
Solution Approach 2:
The patent changes the smoothing parameter (a control parameter) based on operating conditions to optimize measurement precision. By adjusting this parameter, the system can tolerate sensor errors better under certain conditions while maintaining responsiveness under others, effectively resolving the contradiction between precision and complexity without hardware changes.
2Measurement precision
If sensor outputs are processed with high smoothing at all times, then measurement precision improves, but the response speed deteriorates causing lag in steering assist response
Solution Approach 1:
The smoothing parameter is dynamically adjusted based on real-time operating conditions. At low vehicle speeds and low steering rates, high smoothing is applied to improve precision. At high vehicle speeds or high steering rates, the smoothing parameter is reduced to maintain fast response. This dynamic behavior resolves the contradiction between precision and response speed.
Solution Approach 2:
The system changes the smoothing parameter value based on operating conditions. When vehicle speed exceeds a threshold or steering rate exceeds a threshold, the smoothing parameter is reduced, allowing faster response. This parameter adaptation resolves the trade-off between precision and response speed.
3Speed
If the control system uses a fixed short processing period, then response speed is maintained, but measurement precision deteriorates due to insufficient data sampling
Solution Approach 1:
The processing period (number of sensor outputs used) is dynamically adjusted based on operating conditions. When vehicle speed is low and steering rate is low, the system uses more sensor outputs (longer processing period) to improve measurement precision through better averaging. When vehicle speed or steering rate increases, the processing period is shortened to maintain response speed. This resolves the contradiction between speed and precision.
4Stability of the object's composition
If the power steering actuator is driven continuously, then steering assist smoothness improves, but energy consumption increases
Solution Approach 1:
The steering assist is provided continuously but its magnitude is dynamically adjusted based on operating conditions. The control system calculates the desired steering assist as a function of vehicle speed, steering rate, and steering angle, applying appropriate smoothing to ensure smoothness. This dynamic control provides continuous smooth assist while optimizing energy consumption by adjusting assist levels to actual needs rather than maintaining constant high assist.
Data Source
AI summary
In at least some implementations, a method of controlling assist in a power steering system, includes determining a rate of movement of a steering input over a period of time, determining a rate of vehicle speed over the period of time, and controlling an electric power steering assist actuator as a function of one or both of the rate of movement of the steering input and the rate of vehicle speed. The rate of movement of the steering input is determined using a higher number of output signals from a steering angle sensor when one or both of the rate of vehicle speed is lower and the rate of movement of the steering input is lower, than when one or both of the rate of vehicle speed is greater and the rate of movement of the steering input is greater.