Redundant EPS Steering Control to Cut ECU Delay and Vibration
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Solution Overview
Problem
Existing steering systems in autonomous vehicles face instability and reduced steering feel due to communication delays and potential failures in the Electronic Control Units (ECUs) of the EPS steering apparatus, particularly in redundancy structures, leading to risks and vibrations.
Innovation Solution
A redundant ECU system with first and second controllers that calculate and manage target currents based on steering torque, speed, and angle information, ensuring stable steering by distributing current control tasks and minimizing communication delays through limit current management and excess current handling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a redundant ECU system with main ECU and sub ECU is used to guarantee fail-safe steering control, then steering reliability is improved, but communication delay occurs in the current command transmission process
Solution Approach 1:
The patent segments the current control into two parts: a first current command from the main ECU and a second current command from the sub ECU. These segmented current commands are then synthesized to form the total current command for the steering motor. This segmentation allows parallel processing of current calculations, eliminating the need for sequential communication and thus reducing communication delay while maintaining redundancy for reliability.
Solution Approach 2:
The patent implements preliminary action by having both the main ECU and sub ECU calculate their respective current commands simultaneously and independently before synthesis. The sub ECU pre-calculates its current command based on steering torque, vehicle speed, and steering angle information without waiting for the main ECU's command, thereby eliminating communication delay while ensuring both controllers are ready to contribute to steering control.
2Reliability
If the sub ECU drives the steering motor with current according to current command from main ECU, then redundancy is guaranteed, but steering feel in on-center area is reduced and vibration occurs
Solution Approach 1:
The patent applies dynamics by making the control configuration adaptive rather than fixed. The system dynamically switches between different operational modes: when both ECUs are normal, it operates in dual-controller mode with simultaneous current calculation; when one ECU fails, it automatically switches to single-controller mode. This dynamic adaptation ensures optimal steering feel in normal conditions while maintaining redundancy benefits, and prevents vibration by avoiding the problematic half-current command transmission mode.
3Reliability
If the main ECU supplies current corresponding to 1/2 of target current and sub ECU supplies remaining 1/2, then redundancy is achieved, but steering stability is compromised due to communication delay
Solution Approach 1:
The patent implements feedback by having the main ECU synthesize the first current command and the second current command from the sub ECU to generate the total current command for the steering motor. This feedback mechanism ensures that both current commands are properly integrated and coordinated, maintaining steering stability. The synthesis process acts as a feedback loop that adjusts and harmonizes the contributions from both ECUs, preventing the instability that would result from simple parallel operation with communication delays.
Data Source
AI summary
The present disclosure provides an apparatus for controlling steering, including a torque sensor for generating steering torque information by detecting a steering torque of a vehicle, a vehicle speed sensor for generating traveling speed information by detecting a driving speed of the vehicle, a steering angle sensor for generating steering angle information by detecting a steering angle of the vehicle, first and second controllers that are communicatively connected to the sensor, vehicle speed sensor and steering angle sensor, and a steering motor which is controlled by at least one of the first and second controllers, wherein the first or second controller calculates target currents including a plurality of control currents based on at least one of steering torque information, traveling speed information and steering angle information, and controls the steering motor according to the size of the target currents or the types of the plurality of control currents.