Haptic Waveform Ramp-Down for Audible Noise Reduction
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Solution Overview
Problem
Conventional haptic actuators, such as linear resonant actuators, generate audible noises during operation, which detract from the user experience by causing abrupt changes in mechanical motion and acceleration, leading to undesirable noise generation when entering a high impedance state.
Innovation Solution
The introduction of a ramp down portion in the voltage waveform cycle, dividing it into a drive portion, a ramp down portion, and a high impedance portion, allows for a smooth transition into the high impedance state, reducing or eliminating noise by gradually reducing the voltage and current before disabling the haptic driver, thereby minimizing mechanical disturbances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the haptic driver is abruptly disabled when entering high impedance state, then the response time is fast, but audible noise is generated due to abrupt changes in mechanical motion and acceleration
Solution Approach 1:
The patent applies preliminary action by introducing a ramp down portion before the haptic driver is fully disabled. During this ramp down portion, the voltage waveform gradually reduces the voltage and current from the end drive voltage to the end ramp down voltage, preparing the system for the upcoming high impedance state transition and preventing abrupt mechanical motion changes that cause noise.
Solution Approach 2:
The patent applies dynamics by making the voltage waveform time-varying during the transition period. The ramp down portion creates a dynamic transition where the voltage magnitude changes continuously from the drive portion level to the end ramp down voltage level, allowing the mechanical system to adapt smoothly to the upcoming high impedance state rather than experiencing abrupt changes.
2Force
If the voltage waveform is maintained at high level continuously, then the haptic feedback strength is strong, but mechanical disturbances and noise generation increase when transitioning to high impedance state
Solution Approach 1:
The patent applies preliminary action by reducing the voltage waveform magnitude during the ramp down portion before transitioning to high impedance state. This preliminary reduction of voltage and current minimizes the energy stored in the haptic actuator, thereby reducing mechanical disturbances when the driver is subsequently disabled.
Solution Approach 2:
The patent applies parameter changes by modifying the voltage waveform parameters during the ramp down portion. The voltage magnitude transitions from the end drive voltage to the end ramp down voltage, and the dv/dt rate changes from the drive portion to the ramp down portion, creating a smoother transition that reduces mechanical disturbances.
3Device complexity
If the voltage waveform transitions abruptly to high impedance state, then the control simplicity is maintained, but audible noise and mechanical motion instability occur
Solution Approach 1:
The patent applies segmentation by dividing the voltage waveform into distinct portions: drive portion, ramp down portion, and high impedance portion. This segmentation allows each portion to have optimized characteristics - the drive portion provides strong haptic feedback, the ramp down portion provides smooth transition, and the high impedance portion provides quiet operation - while maintaining overall control structure.
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 significantly reduces or eliminates audible noise by smoothly transitioning into the high impedance state, maintaining mechanical motion stability and enhancing the overall haptic feedback experience.
Implementation Method 1
a haptic controller configured to compose a voltage waveform at a resonant frequency of a haptic actuator
Implementation Method 2
a haptic driver configured to drive the haptic actuator with the voltage waveform
Data Source
AI summary
Innovative techniques to design and generate haptics waveforms are proposed. The proposed techniques reduce or eliminate audible noises being generated by a haptic actuator during operation. A haptic controller may compose a voltage waveform at a resonant frequency of the haptic actuator and generate a corresponding control signal. Instead of suddenly entering a high impedance state from a driving state, the voltage waveform may include a ramp down portion in which the voltage ramps down continuously but quickly so that the current flowing within the actuator is brought down before entering the high impedance state. In this way, audible noises may be reduced or even eliminated.