Motor Stopping Precision via Torque Management
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Solution Overview
Problem
Existing shift range control devices face challenges in accurately stopping a motor at a target position due to rough resolution of rotation angle detectors, leading to increased energization requirements and potential overshooting or undershooting during motor reversal.
Innovation Solution
A shift range control device incorporating an angle calculation unit and a drive control unit that calculates the motor angle based on rotation position signals and employs fixed phase energization control to stop the rotor, maintaining a state where brake torque exceeds acceleration torque, and reduces motor current based on their difference to ensure precise stopping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If fixed phase energization control is used to stop the rotor, then the motor can be stopped at the target position, but the rotor vibrates with respect to the stop position due to uneven torque (brake torque larger than acceleration torque)
Solution Approach 1:
The patent applies periodic action by switching between different energization phases in a cyclic manner. When vibration is detected, the system alternates between the original energization phase and an adjacent phase, creating a periodic torque variation that counteracts the vibration and achieves smoother stopping at the target position.
Solution Approach 2:
The patent changes the energization phase parameter dynamically based on vibration detection. When rotor vibration is detected during fixed phase energization control, the system switches to alternate phase energization, changing the torque characteristics to reduce vibration while maintaining stopping precision.
2Use of energy by moving object
If motor current is reduced based on torque difference, then energy consumption is optimized, but stopping accuracy may be compromised
Solution Approach 1:
The patent employs feedback control by continuously monitoring rotor position and vibration during the stopping process. Based on this feedback, the system dynamically adjusts the energization phase and current, ensuring that energy is reduced only when it does not compromise stopping accuracy, thus optimizing both energy consumption and stopping precision.
3Device complexity
If rotation angle sensor with rough resolution is used, then device complexity is reduced, but motor reversal control becomes inaccurate leading to overshooting or undershooting
Solution Approach 1:
The patent introduces an intermediary computational approach by calculating motor angle through integration of rotation speed over time, rather than relying directly on the rough resolution sensor. This intermediary calculation method provides smoother and more accurate angle information for control purposes, reducing overshooting and undershooting during motor reversal.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The device effectively stops the motor at the target position by managing torque dynamics, reducing the risk of overshooting or undershooting and optimizing energy consumption.
Implementation Method 1
a drive control unit that drives the motor so that a motor angle becomes a target angle according to a target shift range
Implementation Method 2
an angle calculation unit that calculates a motor angle based on a signal from a rotation angle sensor that detects a rotation position of the motor
Data Source
AI summary
A shift range control device switches a shift range by controlling drive of a motor. An angle calculation unit calculates a motor angle based on a signal from a rotation angle sensor that detects a rotation position of the motor. A drive control unit drives the motor so that the motor angle becomes a target angle according to the target shift range, and stops a rotor by a fixed phase energization, when the motor angle reaches a target angle. When the rotor vibrates with respect to stop position, the drive control unit maintains a state in which a brake torque, which is the torque generated when moving away from center of vibration, is larger than an acceleration torque, which is the torque generated when moving toward the center of vibration, and reduces the current that energizes the motor based on a difference between the brake torque and the acceleration torque.