Electric Power Steering Current Control for Noise and Response
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Solution Overview
Problem
Electric power steering devices experience noise and vibration due to noise in control signals, particularly in steering holding states, and the implementation of noise reduction filters complicates control responsiveness.
Innovation Solution
An electric power steering device with a motor, current command value calculation, current control, and gain setting units that adjust gain based on rotational velocity to suppress noise influence while maintaining control responsiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a noise reduction filter is installed in the feedback control device, then noise influence is suppressed, but control responsiveness deteriorates and filter characteristic switching becomes complex
Solution Approach 1:
The patent applies dynamics by making the gain parameter adjustable based on operating conditions. The gain is set to a first value during steering holding states (low rotational velocity) to suppress noise, and to a second value during regular steering (high rotational velocity) to maintain responsiveness. This dynamic adjustment resolves the contradiction by adapting the noise suppression level to the current operational state rather than using a fixed filter characteristic.
Solution Approach 2:
The patent changes the gain parameter of the feedback control device based on rotational velocity. When rotational velocity is below a threshold (steering holding state), the gain is set to a first value for noise suppression. When rotational velocity exceeds the threshold (regular steering), the gain is set to a second value for responsive control. This parameter change approach eliminates the need for complex filter characteristic switching while achieving both noise suppression and responsiveness.
2Object-affected harmful factors
If filter characteristic switching is performed between regular steering and steering holding state, then noise suppression is achieved, but device complexity increases
Solution Approach 1:
Instead of switching between different filter characteristics, the patent simplifies the approach by changing only the gain parameter based on rotational velocity. This single parameter adjustment achieves noise suppression during steering holding states while maintaining simple control structure, avoiding the complexity of multiple filter characteristic switching mechanisms.
Solution Approach 2:
The patent extracts the essential noise suppression function from complex filter switching and implements it through a simple gain adjustment mechanism. By separating the noise suppression function from complex filter management and implementing it through rotational velocity-based gain setting, the system achieves noise suppression without increasing control complexity.
Data Source
AI summary
An electric power steering device including: a motor configured to generate a steering assist force; a current command value calculation unit configured to calculate a current command value to control driving current of the motor; a current control unit configured to output a first voltage command value, based on current deviation of a measured value of the driving current to the current command value; a first gain setting unit configured to set a first gain depending on rotational velocity of the motor; a disturbance voltage suppression unit configured to calculate a third voltage command value by adding output from a first delay element to a second voltage command value obtained by limiting the first voltage command value by the first gain and input the third voltage command value to the first delay element; and a driving circuit configured to drive the motor, based on the third voltage command value.