EPS Motor Controller Dead Band Compensation for Noise Reduction
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Solution Overview
Problem
Existing motor control systems for electric power steering face issues with motor operation noise due to noise sensitivity in current detection and parameter variations, particularly when using feedforward control techniques, which also lead to increased torque command value noise sensitivity and complications from non-linear elements like dead bands in the drive system.
Innovation Solution
A motor control system that incorporates a current control block, a motor control circuit, a dead band compensation block, and an adder to calculate and apply a compensation value at the zero-crossing point of the motor current, reducing noise sensitivity and operation noise by integrating feedforward control with observer-based parameter correction and dead band compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If feedback control is used for motor current control, then control accuracy is improved, but motor operation noise is generated due to noise in current detector
Solution Approach 1:
The patent introduces a dead band compensation block as an intermediary component between the current control block and the PWM generator. This block processes the reference voltage through dead band compensation calculation, acting as a mediator that eliminates the harmful non-linear effects while preserving the control accuracy. The intermediary block converts the reference voltage to a compensated reference voltage that accounts for dead band effects, thereby preventing motor operation noise without sacrificing control precision.
2Object-generated harmful factors
If feedforward control technique is used to suppress motor operation noise, then noise is reduced, but motor output torque varies due to parameter variations
Solution Approach 1:
The patent combines feedforward dead band compensation with feedback control mechanisms. The dead band compensation block operates in a feedback loop where the reference voltage is continuously adjusted based on the actual motor current and the compensated reference voltage. This feedback mechanism ensures that parameter variations are compensated in real-time, maintaining motor output torque stability while preserving the noise suppression benefits of feedforward control.
Solution Approach 2:
The patent dynamically adjusts the dead band compensation value based on operating conditions. The dead band compensation block calculates compensation values that vary with the reference voltage and motor current, effectively adapting to parameter variations in the motor and drive circuit. This parameter change approach maintains torque stability across different operating points while suppressing motor operation noise.
3Object-generated harmful factors
If existing feedforward technique is used, then motor operation noise is suppressed, but parameter variables increase and controller complexity increases
Solution Approach 1:
The patent segments the control system into distinct functional blocks: current control block, dead band compensation block, and PWM generator. Each block performs a specific function, with the dead band compensation block being a dedicated component that handles only dead band compensation. This segmentation allows for modular implementation that reduces overall controller complexity while maintaining effective noise suppression.
Solution Approach 2:
The patent extracts the dead band compensation function as a separate, dedicated block from the overall control system. By taking out the dead band compensation calculation as an independent functional unit, the system avoids the complexity of integrating multiple compensation functions into a single complex controller. This extraction simplifies the controller architecture while maintaining effective noise suppression.
Data Source
AI summary
A technique for reducing an operation noise even when a high-pass filter is used for controlling a motor is provided. A controller is used in a motor control system for driving a motor used for position control by using a drive circuit and an inverter. The controller includes a current control block for receiving a motor current and outputting a reference voltage, a motor control circuit for outputting a signal indicating a duty ratio from the reference voltage output from the current control block, a dead band compensation block for calculating a compensation value of a non-linear element of a drive system, and an adder. The dead band compensation block outputs a duty value corresponding to the dead band at a timing at which the motor current crosses zero. The adder adds the duty value to a signal indicating the duty ratio and outputs the signal.