Torque-Assist Motor Control for Steering Vibration Reduction
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Solution Overview
Problem
In vehicle steering systems with electric power assist, amplifying current gain to increase frequency response often results in noise amplification, leading to vibrations in the steering handwheel, particularly at low speeds.
Innovation Solution
A system and method that dynamically adjust integral and proportional gain factors based on motor speed to control a torque-assist motor, using a motor speed calculation module, gain calculation module, error calculation module, and controller to calculate a quadrature axis voltage, which affects the electrical current applied to the motor, thereby reducing noise amplification at low speeds and increasing frequency response at higher speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If current gain is increased to achieve increased frequency response, then bandwidth is improved, but handwheel vibration is amplified at low speeds
Solution Approach 1:
The patent applies dynamics by making the gain factors variable rather than fixed. The proportional and integral gain factors are dynamically adjusted based on motor speed, allowing the system to achieve high frequency response at higher speeds while reducing gain at low speeds to minimize handwheel vibration. This is implemented through the gain calculation module that computes speed-dependent gain factors.
Solution Approach 2:
The patent changes the parameters of the control system by adjusting the proportional and integral gain factors based on motor speed. Instead of using fixed gain values, the system modifies these parameters dynamically according to operating conditions, thereby optimizing frequency response while reducing harmful vibrations at different speed ranges.
2Speed
If proportional and integral gain factors are adjusted to increase bandwidth, then frequency response is improved, but noise in feedback signal is amplified
Solution Approach 1:
The system dynamically adjusts the gain factors based on motor speed, making the noise filtering adaptive. At low speeds where noise is more problematic, the reduced gain naturally attenuates noise amplification. At higher speeds, the increased gain improves frequency response without excessive noise issues, resolving the contradiction between bandwidth and noise.
Solution Approach 2:
The patent changes the control parameters (proportional and integral gain factors) as a function of motor speed. This parameter variation allows the system to optimize the trade-off between noise amplification and frequency response across different operating conditions, achieving high bandwidth when needed while minimizing noise at low speeds.
Data Source
AI summary
A method for controlling operation of a torque-assist motor includes determining a rotational position of the torque-assist motor and producing a motor speed signal that is indicative of a rotational speed of the motor. One or more gain factors are produced based on the rotational speed of the torque-assist motor. An electrical current applied to the torque-assist motor is detected, and a current error is calculated based on a commanded electrical current and the electrical current applied to the torque-assist motor. A quadrature axis voltage is calculated based on the current error and the one or more gain factors. An inverter is driven with a direct voltage signal that is phased with the rotational position of the torque-assist motor so as to produce the electrical current applied to the torque-assist motor. The electrical current exhibits a characteristic that is affected by the quadrature axis voltage.