Linear Vibration Motor Control via Back-EMF Detection
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Solution Overview
Problem
Conventional linear vibration motors face challenges in efficiently detecting and controlling the amplitude, velocity, and acceleration of a reciprocating vibrator due to a short non-energization period, which affects cost-effectiveness and circuit size, and existing solutions either shorten or lengthen this period inadequately, leading to inefficiencies in current supply timing.
Innovation Solution
A method for controlling a linear vibration motor that includes a non-energization period greater than 1/4 cycle, during which electromotive voltage is detected to accurately determine displacement, velocity, or acceleration, allowing for optimal pulsed DC current supply timing and PWM control to efficiently operate the motor, while also using a microcomputer for accurate oscillation control and voltage feedback to maintain constant amplitude.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the non-energization period is lengthened to sufficiently detect amplitude displacement, velocity and acceleration, then measurement accuracy is improved, but current supply timing becomes too late to efficiently supply electric current
Solution Approach 1:
The patent applies periodic action by dividing the operation cycle into distinct periodic phases: an energization period for efficient current supply and a non-energization period for detection. By setting the non-energization period to greater than 1/4 cycle, the system ensures sufficient detection time while maintaining periodic efficiency in current supply timing
Solution Approach 2:
The patent changes the parameter of non-energization period duration to greater than 1/4 cycle, which optimizes the balance between detection accuracy and current supply efficiency. This parameter adjustment allows the system to detect vibration characteristics accurately while maintaining efficient periodic current supply
2Productivity
If the non-energization period is shortened to efficiently supply electric current, then current supply efficiency is improved, but detection time becomes insufficient
Solution Approach 1:
The system uses periodic action with a specifically designed cycle where the non-energization period exceeds 1/4 cycle. This periodic structure ensures that despite the relatively long detection phase, current supply efficiency is maintained through optimized timing in the subsequent energization period
Solution Approach 2:
The patent applies preliminary action by performing detection during the non-energization period before the next energization period begins. This allows the system to complete necessary measurements in advance, ensuring accurate detection without compromising subsequent current supply efficiency
3Measurement precision
If highly accurate external oscillation is used to detect vibration characteristics within a short period, then detection accuracy is improved, but cost and circuit size increase
Solution Approach 1:
The patent applies self-service by using the motor's own back electromotive force during the non-energization period as the detection signal source. This eliminates the need for external oscillation sources and complex control circuits, reducing both cost and circuit size while maintaining detection accuracy
Solution Approach 2:
The back electromotive force acts as an intermediary that provides detection information without requiring external oscillation equipment. By utilizing this naturally occurring electrical signal during the non-energization period, the system achieves accurate vibration characteristic detection with simplified circuitry
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
This approach enables cost-effective and efficient operation by extending detection periods, improving accuracy, and ensuring timely energization, reducing measurement errors, and maintaining consistent vibration amplitude despite battery voltage variations, thus enhancing motor control and energy efficiency.
Implementation Method 1
detecting an electromotive voltage induced in the winding as the vibrator makes vibrating movement within the non-energization period
Data Source
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AI summary
A linear vibration motor includes a stator formed of an electromagnet with a winding, a vibrator provided with a permanent magnet and a control unit for controlling a driving current supplied to the winding of the electromagnet. The linear vibration motor is configured to reciprocate the vibrator relative to the stator. A method for controlling operation of the linear vibration motor includes: providing a non-energization period during which no driving current flows through the winding of the electromagnet, the non-energization period being equal to greater than a 1/4 cycle; detecting an electromotive voltage induced in the winding as the vibrator makes vibrating movement within the non-energization period; detecting the displacement, velocity or acceleration of the vibrator based on the electromotive voltage thus detected; and controlling the driving current supplied to the winding based on the displacement, velocity or acceleration of the vibrator thus detected.