Electric Power Steering Mode Switching Fade Control
Solution Overview
Problem
Conventional electric power steering systems face challenges in smoothly switching between torque control and position/speed control, leading to unintentional self-steer due to torque variations during mode switching, which existing gradual-change methods fail to fully mitigate.
Innovation Solution
An electric power steering apparatus that includes a torque sensor and motor control unit, capable of switching between torque and position/speed control systems based on a predetermined trigger, with fade processing that gradually changes steering angle command values, assist torque levels, and steering angle speeds sensitive to steering torque, using fade gain signals and an external disturbance observer to compensate for inertia and friction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional gradual-change methods are used to switch between torque control and position/speed control, then switching smoothness is improved, but torque variations during mode transition still cause unintentional self-steer
Solution Approach 1:
The system performs preliminary actions by gradually fading the torque control gain and position/speed control gain before complete mode switching occurs. This preliminary fading process prepares the control system for smooth transition by progressively adjusting the influence of each control mode, preventing sudden torque changes that would cause self-steer.
Solution Approach 2:
The invention changes control parameters dynamically during mode transition by adjusting the torque control gain and position/speed control gain as fading factors. These parameter changes are implemented continuously during the transition period, allowing the system to maintain stability while switching between control modes without causing unwanted steering movements.
2Stability of the object's composition
If fade processing is applied to gradually change control values during mode switching, then control continuity is improved, but torque variations still occur that can cause self-steer
Solution Approach 1:
The system employs feedback mechanisms to monitor the actual steering torque and control state during mode transitions. Based on this feedback, the control gains are dynamically adjusted to compensate for torque variations, ensuring that the fade processing maintains control continuity without generating harmful self-steer torque fluctuations.
Solution Approach 2:
The invention applies counteracting control strategies during fade processing by balancing the torque control and position/speed control influences. The fading factors are designed to counterweight the torque variations that occur during transition, ensuring that the net torque remains stable and prevents self-steer while maintaining control continuity.
Data Source
AI summary
An electric power steering apparatus includes a function to switch a control system of the motor between a torque control system of a torque system to control a motor output torque and a position and speed control system of a steering angle system to control a steering angle of a steering in accordance with an ON/OFF of a post-diagnosis automatic steering command being a judgment result of an automatic steering execution judging section; and a characteristic calculating section to calculate a fade gain signal F1 that applies a first fade characteristic of the torque system, a fade gain signal F2 that applies a second fade characteristic of the steering angle system, and a fade gain signal F3 that applies a third fade characteristic of the steering angle speed, sensitive to the steering torque.