Electric Power Steering Assist Control for Vibration Suppression
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Solution Overview
Problem
Conventional electric power steering systems face challenges in achieving both excellent steering characteristics and effective suppression of reverse input vibration, particularly at high levels, as increasing torque derivative control to reduce vibration leads to poor steering characteristics, and existing normative models often interfere with each other, making it difficult to simultaneously optimize both factors.
Innovation Solution
An electric power steering apparatus with a control unit that calculates a first assist component based on steering torque and a compensation component, and a second assist component through rotation angle feedback control, using an ideal model that separates the assist components to avoid interference and adjust for vehicle characteristics, while also incorporating road information compensation to maintain necessary feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If torque derivative control level is increased to suppress reverse input vibration, then reverse input vibration suppression is improved, but steering characteristic deteriorates
Solution Approach 1:
The assist force is divided into two separate components: a basic component that ensures excellent steering characteristics, and a torque derivative control component that suppresses reverse input vibration. By segmenting the control into distinct parts with different functions, the system can optimize each component independently and combine them to achieve both goals simultaneously.
Solution Approach 2:
Different control strategies are applied to different aspects of the steering system. The basic component provides optimal steering feel across all operating conditions, while the torque derivative control component specifically targets reverse input vibration suppression. This local differentiation allows each component to excel at its specific function without compromising the other.
2Object-affected harmful factors
If two normative models are used to suppress reverse input vibration, then vibration suppression is improved, but model interference occurs making it difficult to optimize both factors
Solution Approach 1:
The torque derivative control component is extracted from the complex two-model normative system. Instead of using two interacting normative models that cause interference, the invention isolates the vibration suppression function into a separate torque derivative control mechanism that operates independently from the basic assist component, thereby eliminating model interference while maintaining vibration suppression effectiveness.
Data Source
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AI summary
An assisting command value calculating unit (23) calculates a first assisting factor (Ta1*) on the basis of the value of a torque differential control volume (Tdt*) added to a basic assist control volume (Tas*) based on a steering torque (Th) value, while increasing or decreasing, on the basis of an assisting gradient (Rag), the torque differential control volume (Tdt*) based on a torque differential value (dTh). Additionally, the assisting command value calculating unit (23) is provided with a pinion angle F/B control unit (40). The pinion angle F/B control unit (40) calculates a pinion angle command value, capable of being converted to a steering angle of the steering wheel, on the basis of the steering torque (Th) and the first assisting factor (Ta1*), and executes rotational angle feedback control. The assisting command value calculating unit (23) calculates an assisting command value (Ta*) on the basis of the value of a second assisting factor (Ta2*), calculated by the pinion angle F/B control unit (40), added to the first assisting factor (Ta1*).