Electric Power Steering Torque Compensation
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Solution Overview
Problem
Existing lane keeping travel control devices face challenges in maintaining performance under disturbance torque, as they often cancel out driver-intended steering torque, making it difficult for drivers to intervene during automatic steering.
Innovation Solution
An electric power steering system that includes a motor, rotational angle detection, current detection, steering torque estimation, and compensation units to differentiate and adjust torque components, allowing for prioritization between system control and driver input, thereby enhancing cooperation between the two.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If disturbance torque is fed back to suppress lane keeping performance degradation, then lane keeping performance is improved, but driver intervention becomes difficult because steering torque is canceled out
Solution Approach 1:
The disturbance torque is segmented into two distinct components: high-frequency component (driver input) and low-frequency component (actual disturbance). By separating these components, the system can apply different feedback gains to each, allowing disturbance compensation while preserving driver intervention capability.
Solution Approach 2:
Different feedback gains are applied to different frequency components of the disturbance torque. The high-frequency component receives a smaller feedback gain to preserve driver input, while the low-frequency component receives a larger feedback gain to effectively compensate for actual disturbances. This local differentiation resolves the contradiction between lane keeping performance and driver intervention.
2Ease of operation
If high frequency component feedback gain is reduced to enable driver intervention, then driver intervention becomes easier, but disturbance torque compensation effectiveness is reduced
Solution Approach 1:
The disturbance torque is segmented into high-frequency and low-frequency components. This segmentation allows the system to apply different feedback strategies to each component, ensuring that driver intervention is facilitated while disturbance compensation remains effective through targeted low-frequency feedback.
Solution Approach 2:
The feedback gain is differentiated by frequency component: smaller gain for high-frequency (driver input) and larger gain for low-frequency (disturbance). This local quality differentiation ensures that each component is handled appropriately, resolving the contradiction between ease of operation and reliability.
3Reliability
If system priority is increased to improve lane keeping performance, then lane keeping performance is improved, but driver input responsiveness is reduced
Solution Approach 1:
The feedback gain is made dynamic by applying different gains to different frequency components. The system dynamically adjusts the level of compensation based on the frequency characteristics of the input torque, allowing high system priority for disturbances while maintaining driver input responsiveness through reduced high-frequency feedback gain.
Solution Approach 2:
Different priority levels are applied locally to different frequency components: high priority for low-frequency disturbances and low priority for high-frequency driver inputs. This resolves the contradiction by allowing the system to be responsive to both system performance requirements and driver input requirements simultaneously.
Data Source
AI summary
An electric power steering system includes an electric motor, a rotational angle detection unit, a current detection circuit, a steering torque detection unit, a target torque setting unit, a current command value setting unit, and a current control unit. The target torque setting unit includes a basic target torque setting unit, a first compensation value computation unit, a second compensation value computation unit, and a correction unit. The basic target torque setting unit sets basic target torque for the electric motor. The first compensation value computation unit sets a first compensation value based on steering torque. The second compensation value computation unit computes a second compensation value which is an estimated value of disturbance torque other than the steering torque. The correction unit corrects the basic target torque.