Stepping Motor Drive Controller Torque Control
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Solution Overview
Problem
Stepping motors in vehicle instruments generate pulsation during sweeping operations, causing discomfort to drivers due to excessive torque and resonance, leading to smoothness degradation and pointer overshooting.
Innovation Solution
A drive controller that controls a stepping motor to perform a sweeping operation by accelerating to a predetermined speed with a rated torque signal and then rotating at a constant speed using a decreased torque signal lower than the rated torque, specifically during the constant-speed period of the sweeping operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a motor is driven with the same torque as that at the time of performing a normal operation during the constant-speed period of the sweeping operation, then the acceleration and resistance against vibration requirements are satisfied, but the smoothness is degraded due to excessive torque and pulsation is generated in the pointer operation
Solution Approach 1:
The patent applies dynamic torque control by switching between two torque levels based on the operational phase. During acceleration period, rated torque is applied to satisfy acceleration requirements. During constant-speed period, torque is reduced to a level that prevents pulsation while maintaining vibration resistance. This dynamic adjustment of torque characteristics resolves the contradiction between needing high torque for acceleration/vibration resistance and low torque for smooth operation.
2Productivity
If a motor is driven at a speed near its vibration resonance point (resonance frequency) in the constant-speed period, then the sweeping operation can be completed efficiently, but the pulsation tends to be more remarkable causing driver discomfort
Solution Approach 1:
The patent changes the torque parameter during the constant-speed period to a level that avoids exciting vibration resonance. By reducing torque from the rated level to a decreased torque level, the system operates efficiently at resonance frequency without amplifying pulsation. This parameter change allows the pointer to complete the sweeping operation efficiently while minimizing harmful pulsation effects.
3Manufacturing precision
If rated torque is applied during the constant-speed period of sweeping operation, then the pointer acceleration and vibration resistance are satisfied, but the pointer overshoots for the instructed electric angle and pulsation is generated
Solution Approach 1:
The patent segments the sweeping operation into two distinct phases with different torque characteristics: acceleration period with rated torque and constant-speed period with decreased torque. This segmentation allows the system to achieve precise positioning during acceleration while maintaining stability during constant-speed operation, preventing both overshooting and pulsation generation.
Data Source
AI summary
A drive controller of an instrument controls a stepping motor to rotate a pointer of the instrument attached to a rotation shaft of the stepping motor, the pointer rotatable between a zero scale position and a maximum scale position. The drive controller controls the stepping motor to perform a sweeping operation in which the pointer is swung from the zero scale position to the maximum scale position and returned back to the zero scale position, wherein the drive controller controls the stepping motor, during the sweeping operation, to accelerate to a predetermined speed by outputting a rated torque signal to the stepping motor and controls the stepping motor to rotate at the predetermined speed by outputting a decreased torque signal to the stepping motor, the decreased torque signal being lower than the rated torque signal.