Four-Wheel Independent Steering Load Compensation for Stable Tracking
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Solution Overview
Problem
Existing four-wheel independent steering systems in vehicles lack compensation for external load and friction, leading to limited control performance and instability, especially in autonomous driving scenarios, and require additional components to handle sensor failures.
Innovation Solution
A four-wheel independent steering apparatus with a load estimator and processor that estimates and compensates for external load and friction, using a load estimator and processor to calculate and apply compensation values based on sensor inputs, even in the absence of current sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a typical PID controller is used without compensation functions, then the device complexity is reduced, but the control performance and stability deteriorate due to inability to compensate for external load and friction
Solution Approach 1:
The patent merges the PID controller with a load compensator into a single integrated controller unit. The load compensator calculates compensation values based on vehicle dynamics parameters (lateral acceleration, steering angle, etc.) and adds these to the PID control output, combining multiple control functions in one device to improve reliability without proportionally increasing complexity
Solution Approach 2:
The controller is designed to perform multiple functions: basic PID position control, load compensation based on vehicle dynamics, and friction compensation. This multi-functional approach allows a single controller to handle various control requirements, improving control performance while managing device complexity through unified architecture
2Reliability
If additional compensation functions are added to the controller, then the control performance improves, but the device complexity increases
Solution Approach 1:
The load compensator pre-calculates compensation values based on expected load conditions using vehicle dynamics models. By preparing compensation values in advance based on predicted load scenarios, the system improves control performance without requiring complex real-time calculations, thus managing device complexity
Solution Approach 2:
The patent introduces an intermediary load compensator module that sits between the PID controller and the steering actuator. This intermediary calculates and adds compensation values to the PID output, separating the compensation function from the core PID logic and making the overall system more manageable while improving control performance
3Device complexity
If current sensors are removed or fail, then the device complexity and cost are reduced, but the ability to perform continuous position control deteriorates
Solution Approach 1:
The load compensator uses readily available sensor data from the vehicle's existing sensor system (accelerometers, steering angle sensors, etc.) to calculate load compensation values. By utilizing existing sensors for multiple purposes, the system maintains position control capability without requiring additional current sensors, thus reducing complexity while preserving control continuity
Solution Approach 2:
The patent changes the control parameters from direct current measurement to indirect load estimation using vehicle dynamics parameters. By estimating load based on lateral acceleration, steering angle, and other available parameters rather than directly measuring current, the system maintains control functionality without requiring current sensors
Data Source
AI summary
Disclosed herein is a four-wheel independent steering apparatus. The apparatus includes a load estimator configured to receive, from a sensor disposed in a steering system, a value corresponding to a sensing by the sensor, and calculate an amount of load based on the value received from the sensor. The apparatus also includes a processor configured to receive, from an autonomous driving controller that is an upper-level controller, a steering angle reference, calculate an output value for allowing an actual steering angle to track the steering angle reference, based on the steering angle reference, the value from the sensor, and the amount of the load from the load estimator, and output the output value to the steering system.