Steering Wheel Oscillation Compensation via Variable-Frequency Observer
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Solution Overview
Problem
Existing methods for compensating steering wheel rotary oscillations in vehicles often impair steering feel by incorrectly damping desired road feedback, and require additional sensors and complex calculations, making them inefficient and potentially unsafe.
Innovation Solution
A method using a variable-frequency disturbance observer to calculate a compensation torque based on torsion bar torque, which is fed back to maintain compensation even when the disturbance is no longer detectable, preventing re-emergence of oscillations and ensuring full or substantial compensation without affecting steering feel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If high-frequency components of steering torque are damped to reduce steering wheel rotary oscillations, then steering wheel oscillations are reduced, but desired road feedback is incorrectly detected as disturbance and eliminated, impairing steering feel and safety
Solution Approach 1:
The invention applies local quality by selectively damping only the harmful high-frequency oscillation components within the steering torque signal while preserving the lower-frequency road feedback information. The disturbance variable calculator identifies and isolates specific frequency ranges corresponding to rotary oscillations, applying damping compensation only to those targeted frequencies rather than uniformly damping all high-frequency components, thus maintaining steering feel and road information while reducing harmful oscillations.
Solution Approach 2:
The invention implements feedback by continuously monitoring the steering torque signal, calculating a disturbance variable that represents the harmful oscillation components, and applying real-time compensation through the torque actuator. The system measures the actual steering torque, processes it through the disturbance variable calculator, and adjusts the compensation dynamically based on the detected oscillation levels, creating a closed-loop control system that maintains steering feel while suppressing unwanted oscillations.
2Measurement precision
If additional torque sensors and complex autocorrelation calculations are used to detect and compensate steering wheel rotary oscillations, then compensation accuracy is improved, but device complexity and calculation time increase
Solution Approach 1:
The invention applies self-service by utilizing the existing torque sensor already present in the electric power steering system to detect both the steering torque and the rotary oscillation components. The system processes the torque signal through the disturbance variable calculator, which uses efficient algorithms to identify oscillation patterns without requiring additional sensors. This approach achieves accurate oscillation detection while avoiding the need for extra hardware and minimizing calculation overhead.
Solution Approach 2:
The invention replaces complex mechanical measurement systems with an electronic signal processing approach. Instead of using additional torque sensors or mechanical vibration sensors, the system substitutes the existing torque sensor signal with a digital processing chain that calculates the disturbance variable through efficient algorithms, replacing what would otherwise require complex mechanical measurement and analysis systems.
3Ease of operation
If rotor angular velocity is used as measurement variable for compensation, then measurement simplicity is improved, but measurement accuracy deteriorates, particularly at low power levels on the rack
Solution Approach 1:
The invention introduces an intermediary approach by using the torque sensor signal as an intermediate measurement that correlates with the oscillation conditions. Rather than directly measuring rotor angular velocity, the system uses the torque signal processed through the disturbance variable calculator as an intermediary indicator of oscillation, which provides more accurate and reliable measurement across the full operating range, particularly at low power levels where direct angular velocity measurement becomes unreliable.
Data Source
AI summary
A torque actuator is regulated so as to permit an activation of the torque actuator such that steering wheel rotary oscillations that occur can be compensated. For this purpose, in one embodiment, a torsion bar torque is detected. A compensation torque is determined as a function of the detected torsion bar torque by means of a variable-frequency disturbance variable and state variable calculator. The compensation torque or a signal corresponding to the compensation torque is then taken into consideration during activation of the torque actuator.