Vibration Motor Control via Current Feedback and Pulse Width Adjustment
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Solution Overview
Problem
Existing vibration motor control systems fail to effectively manage current increases due to temperature changes and load variations, leading to inefficiencies and system shutdowns, as they cannot distinguish between current and voltage changes, causing unstable operation and ineffective current flow.
Innovation Solution
A method and driver for a vibration motor that control frequency and pulse width based on real-time current detection, using a microcomputer to adjust the drive signal and pulse width to prevent current exceeding the supply limit, ensuring stable operation and maximum power output within the limited supply amount.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the pulse width is narrowed to prevent noise and unnecessary energy supply when battery voltage is high, then energy saving is improved, but the system cannot detect actual motor current consumption leading to inability to handle current increases from temperature or load changes
Solution Approach 1:
The patent implements current detection feedback by measuring the voltage drop across a series resistor to obtain actual motor current consumption information. This feedback mechanism allows the control system to adjust the pulse width dynamically based on real current status, preventing both unnecessary energy supply when current is low and ensuring reliable operation when current increases due to temperature or load changes.
2Productivity
If pulse width control and velocity control are implemented simultaneously in the first frequency domain, then both current limitation and velocity adjustment are achieved, but stable driving cannot be conducted due to mixed operations
Solution Approach 1:
The patent implements dynamic control by sequentially adjusting pulse width and frequency based on detected current levels. When current exceeds the threshold, the system first narrows the pulse width to reduce current consumption, then adjusts frequency to control velocity. This dynamic, staged approach separates the control operations in time while achieving both current limitation and velocity control, ensuring stable driving.
3Speed
If the frequency is decreased to increase motor velocity, then velocity control is improved, but the frequency may exceed resonance frequency causing the motor to stop
Solution Approach 1:
The patent uses current detection as feedback to monitor motor operating status. By detecting changes in current consumption patterns, the system can identify when frequency approaches dangerous levels near resonance. This feedback allows the control algorithm to adjust frequency changes more conservatively, preventing the motor from stopping while still achieving velocity control through coordinated pulse width and frequency adjustments.
4Reliability
If current control is implemented to prevent exceeding supply limits, then current management is improved, but circuit efficiency degrades due to ineffective current flowing in the capacity component side
Solution Approach 1:
The patent implements dynamic pulse width adjustment based on detected current levels. Instead of continuously limiting current to the maximum allowable value, the system adjusts the pulse width proportionally to the actual current consumption and load requirements. This dynamic approach ensures current never exceeds supply limits while minimizing unnecessary current reduction, thereby maintaining higher circuit efficiency compared to static current limiting methods.
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 solution allows for stable and efficient operation of the vibration motor by preventing current overload, maintaining system performance and preventing battery voltage drops, even under varying load conditions.
Implementation Method 1
an AC signal is supplied to an electromechanical energy conversion element, and vibrational waves are generated in an ultrasonic vibrator
Implementation Method 2
relatively moves a movable body contacting the ultrasonic vibrator by a frictional force
Data Source
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AI summary
Provided is a method of controlling a vibration motor, in which there are provided: a unit that generates a drive signal for generating elliptic motion; a unit that switches the drive signal with a voltage from a power supply, and changes a pulse width of the drive signal; a unit that detects a current flowing in an electromechanical energy conversion element through the switching unit; a unit that detects a position and a velocity of an object to be driven; and a control unit that controls the respective units, and sets the velocity of the object to be driven. The control unit controls a frequency and the pulse width of the drive signal so as to exercise a maximum output characteristic with respect to a target velocity within a range in which the current detected by the current detection unit does not exceed a given limit value.