Steering System Supporting Torque Compensation
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Solution Overview
Problem
Current steering systems face challenges in effectively managing nonlinear control paths and varying counterforces due to factors like wheel friction, vehicle speed, and steering system inertia, leading to compromised performance across different operating points.
Innovation Solution
A method that determines a supporting torque based on target and actual rack positions, vehicle speed, rack speed, and torsion bar torque, which is introduced into the steering gear to enhance controller performance by pre-controlling counterforces and compensating for inertia and friction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a compromise controller design is used for all operating points, then the controller can be designed more simply, but the performance at specific operating points deteriorates
Solution Approach 1:
The patent applies preliminary action by calculating and compensating for counterforces in advance based on predicted rack position and vehicle speed. The counterforce compensation value is determined before the actual steering action occurs, allowing the controller to pre-adjust for known forces like friction and inertia. This resolves the contradiction by maintaining simple controller architecture while achieving high performance through predictive compensation.
Solution Approach 2:
The patent changes parameters by dynamically adjusting the counterforce compensation based on operating conditions such as vehicle speed, rack position, and rack acceleration. The supporting torque is modified as a function of these varying parameters, allowing the controller to adapt to different operating points without requiring complex redesign. This maintains design simplicity while optimizing performance across all conditions.
2Reliability
If the controller tries to compensate for all varying counterforces, then the performance improves, but the controller design becomes more complex
Solution Approach 1:
The patent segments the counterforce compensation into distinct components: friction compensation based on rack speed, inertia compensation based on rack acceleration, and spring compensation based on rack position. Each component is calculated separately and then summed to form the total supporting torque. This segmentation allows the controller to handle complex varying forces through multiple simple, manageable calculations rather than one complex unified controller design.
3Reliability
If friction compensation is added to the controller, then steering performance improves, but the computational load and control complexity increase
Solution Approach 1:
The patent replaces complex mechanical friction compensation mechanisms with a computational approach. Instead of using mechanical devices to physically compensate for friction, the system calculates a friction compensation value based on rack speed and vehicle speed, then adds this as a torque component. This substitution of mechanical complexity with computational simplicity resolves the contradiction by achieving friction compensation through straightforward mathematical calculations rather than complex mechanical control systems.
Data Source
AI summary
A method for operating a steering system of a motor vehicle includes ascertaining a first torque depending on a target steering rack position and depending on the actual steering rack position, ascertaining a second torque depending on a vehicle speed, ascertaining a supporting torque depending on the first and the second torques, and introducing the supporting torque into a steering gear of the steering system.