Electric Shift-by-Wire Motor Control for Noise Reduction
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Solution Overview
Problem
The electric shift-by-wire (SBW) system experiences impact and noise issues due to the rotational driving of an electric motor, which complicates achieving low vibration and silence, despite efforts to reduce these factors.
Innovation Solution
A method of controlling the electric motor in the SBW system involves determining the current and target stages, performing motor OFF control when they are identical, and implementing reverse driving duty control based on the difference between the current and target positions, with specific duty and period settings adjusted according to motor speed, to reduce impact and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the motor is rotatably driven to perform gear shifting, then the gear shifting function is achieved, but impact and noise occur during the motor control process
Solution Approach 1:
The patent applies periodic action by using PWM (Pulse Width Modulation) control to periodically switch the motor power supply between ON and OFF states. This periodic switching allows the motor to achieve smooth position control while reducing impact and noise, as the motor does not continuously run but rather in controlled pulses that accumulate to achieve the desired rotational displacement for gear shifting.
Solution Approach 2:
The patent changes the control parameters by transitioning from conventional position control to PWM duty cycle control. By adjusting the duty cycle ratio (the proportion of ON time within each PWM period), the motor speed and torque are dynamically controlled, enabling smooth acceleration and deceleration that reduces impact and noise while maintaining the gear shifting function.
2Object-generated harmful factors
If PWM control is applied to reduce impact and noise, then vibration characteristics improve, but switching time increases due to repeated ON/OFF cycling
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing optimal PWM duty cycle values and switching timing in lookup tables based on the motor's current position and target position. This allows the controller to quickly retrieve and apply pre-optimized control parameters without real-time computation delays, reducing the overall switching time while maintaining the vibration-reducing benefits of PWM control.
3Object-generated harmful factors
If the motor is controlled to hold position at 90% of target position, then impact and noise are reduced, but heat generation increases due to prolonged motor operation
Solution Approach 1:
The patent applies partial action by using PWM control with duty cycles less than 100%, where the motor operates intermittently rather than continuously. The motor is activated only for the necessary duration and intensity to achieve the target position, avoiding prolonged operation and excessive heat generation while still reducing impact and noise through controlled, periodic activation rather than continuous holding.
Data Source
AI summary
Disclosed herein is a motor control strategy of an electric shift-by-wire (SBW) system and is a method of performing PWM waveform simulation control in order to solve an impact/noise occurrence problem in a motor control process. A method of controlling the electric motor of an electric SBW system includes determining whether a current stage and a target stage are identical, rotating the motor in the direction of the target stage when the current stage and the target stage are not identical, performing motor OFF control when the current stage and the target stage are identical, performing reverse driving duty control when a difference between the current position and target position of the motor is less than a first setting value, and stopping the motor when the difference between the current position and target position of the motor is less than a second setting value.