Electric Power Steering PID Control Initial Value Calculation
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Solution Overview
Problem
Conventional electric power steering (EPS) systems using PID control loops often generate large outputs upon initiation, leading to undesired movements and requiring blending factors that can cause non-smooth transitions and increased complexity, along with additional tuning efforts.
Innovation Solution
A method for controlling a steering angle that computes an error signal, a feedforward term, and a feedback term, and uses an integral control term with an initial value calculated based on these terms to generate a control output signal for the motor, eliminating the need for blending factors and reducing tuning complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional PID control loops are used, then the system can provide basic steering control, but large outputs are generated upon initiation causing undesired movements
Solution Approach 1:
The patent applies preliminary action by calculating and setting an initial value for the integral control term before the control loop begins operation. This initial value is computed based on the difference between target and actual steering angles, allowing the system to start with a pre-adjusted integral component that prevents large initial outputs and undesired movements from occurring when the control loop is first initiated.
2Object-generated harmful factors
If blending factors are used to reduce large initial outputs, then the harmful effects are minimized, but the transition becomes non-smooth and control stabilization is delayed
Solution Approach 1:
Instead of using blending factors that gradually increase control output over time, the patent applies preliminary action by pre-calculating the appropriate initial integral term value before control begins. This allows the system to immediately start with the correct control level without gradual transitions, achieving both harm reduction and fast stabilization simultaneously.
3Object-generated harmful factors
If blending factors are used to manage initial control output, then large outputs are reduced, but additional tuning and system complexity increase
Solution Approach 1:
The patent eliminates the need for blending factors and their associated tuning by applying preliminary action - calculating the appropriate initial integral term value before control begins. This single pre-computation step replaces the entire blending factor mechanism, reducing system complexity while still preventing large initial outputs.
Solution Approach 2:
The patent applies the taking out principle by removing the blending factor component entirely from the control system. By extracting this unnecessary element and replacing it with a simple initial value calculation, the system achieves the same harm reduction effect with significantly reduced complexity and no additional tuning requirements.
Data Source
AI summary
Technical solutions described herein include a method of controlling, in an electric power steering system, a steering angle according to a target steering angle by computing an initial value of an integral control term in a proportional integral derivative (PID) control loop used to calculate a control output signal, such as a motor torque command. The initial value of the integral control term is computed as a negative of the initial value of the feedforward term minus the initial value of the feedback term. The initial value of the integral control term corresponds to an initial value of a control output. Accordingly, the technical solutions described herein facilitate handling non-zero initial condition in Electric Power Steering angle control.