Linear Vibration Motor Drive Circuit for Faster Haptic Startup
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Solution Overview
Problem
Existing drive control circuits for linear vibration motors face challenges in minimizing rise time and achieving high response rates, which are critical for haptics applications where rapid feedback is essential.
Innovation Solution
A drive control circuit that generates a drive signal with alternating positive and negative currents, featuring adjustable nonconducting periods and PWM signal duty ratios to optimize the conducting periods, allowing for adaptive control of the drive signal's cycle width and phase to match the eigen frequency of the motor, thereby reducing rise time and enhancing response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the nonconducting period width is set to be shorter before the first conducting period compared to steady operation, then the rise time is reduced and response speed is improved, but the control complexity increases
Solution Approach 1:
The drive control circuit dynamically adjusts the nonconducting period width based on the operational state. During drive start, the nonconducting period width is set to a first value (shorter), and during steady operation, it is set to a second value (longer). This dynamic adjustment optimizes both rise time and response speed without requiring permanent structural complexity
Solution Approach 2:
The control circuit changes the parameter of nonconducting period width according to different operational phases. By setting different width values for drive start and steady operation, the system achieves optimized performance at each stage while managing control complexity through parameter variation rather than structural change
2Speed
If the duty ratio of PWM signal is increased during drive start compared to steady operation, then the rise time is reduced, but energy consumption increases
Solution Approach 1:
The drive control circuit employs periodic PWM signals with varying duty ratios at different operational stages. During drive start, a higher duty ratio is applied to accelerate the vibrator quickly. During steady operation, the duty ratio is reduced to maintain vibration while consuming less energy. This periodic modulation with stage-dependent parameters resolves the contradiction between fast rise time and energy efficiency
Solution Approach 2:
The control circuit applies a high duty ratio PWM signal preliminarily during the drive start phase to achieve rapid acceleration and minimal rise time. Once the vibrator reaches steady operation, the duty ratio is reduced. This preliminary high-energy action is only applied when necessary, minimizing overall energy consumption while achieving fast response
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 proposed solution effectively minimizes the rise time and maintains high response rates, ensuring efficient vibration performance and adaptability to variations in motor frequency, thus improving the overall haptic feedback experience.
Implementation Method 1
a linear vibration motor, having a stator and a vibrator at least one of which is constituted by an electromagnet, which vibrates the vibrator relative to the stator by supplying a drive current to a coil of the electromagnet
Data Source
AI summary
A drive signal generating unit generates a drive signal used to alternately deliver a positive current and a negative current to a coil. The drive signal is such that nonconducting periods are set before and after a positive current conducting period and the nonconducting periods are set before and after a negative current conducting period. A driver unit generates the drive current in response to the drive signal generated by the drive signal generating unit and then supplies the drive current to the coil. The drive signal generating unit sets the width of a nonconducting period such that, after the drive start of the linear vibration motor, the width of a nonconducting period to be set before at least the first conducting period of the drive signal is shorter than the width of a nonconducting period to be set before each conducting period during steady operation of the linear vibration motor.