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Point-Wise Vibration Pattern Production via a Sparse Actuator Array for Surface Tactile Feedback

Xiaosa Li, Runze Zhao, Chengyue Lu, Xiao Xiao, Wenbo Ding

TL;DR

This study tackles producing precise, point-wise tactile vibration on handheld devices using only five sparse actuators. It builds a linear time-invariant model of a five-actuator tactile board, identifies 160 Hz as the optimal drive frequency, and uses simulated annealing to optimize actuator phases for focused energy at target locations. The approach converts actuator-driven patterns into energy-distribution images via RMS; it then decouples and reconstructs patterns to closely match single-point targets with SSIM around 0.9. The work enables embedding high-quality haptic feedback into common devices with minimal actuator count, expanding interactive capabilities in consumer electronics.

Abstract

Surface vibration tactile feedback is capable of conveying various semantic information to humans via the handheld electronic devices, like smartphone, touch panel,and game controller. However, covering the whole device contacting surface with dense actuator arrangement can affect its normal use, how to produce desired vibration patterns at any contact point with only several sparse actuators deployed on the handled device surface remains a significant challenge. In this work, we develop a tactile feedback board with only five actuators in the size of a smartphone, and achieve the precise vibration pattern production that can focus at any desired position all over the board. Specifically, we investigate the vibration characteristics of single passive coil actuator, and construct its vibration pattern model at any position on the feedback board surface. Optimal phase and amplitude modulation, found with the simulated annealing algorithm, is employed with five actuators in a sparse array. And all actuators' vibration patterns are superimposed linearly to synthetically generate different onboard vibration energy distribution for tactile sensing. Experiments demonstrated that for point-wise vibration pattern production on our tactile board achieved an average level of about 0.9 in the Structural Similarity Index Measure (SSIM) evaluation, when compared to the ideal single-point-focused target vibration pattern. The sparse actuator array can be easily embedded into usual handheld electronic devices, which shows a good significant implication for enriching their haptic interaction functionalities.

Point-Wise Vibration Pattern Production via a Sparse Actuator Array for Surface Tactile Feedback

TL;DR

This study tackles producing precise, point-wise tactile vibration on handheld devices using only five sparse actuators. It builds a linear time-invariant model of a five-actuator tactile board, identifies 160 Hz as the optimal drive frequency, and uses simulated annealing to optimize actuator phases for focused energy at target locations. The approach converts actuator-driven patterns into energy-distribution images via RMS; it then decouples and reconstructs patterns to closely match single-point targets with SSIM around 0.9. The work enables embedding high-quality haptic feedback into common devices with minimal actuator count, expanding interactive capabilities in consumer electronics.

Abstract

Surface vibration tactile feedback is capable of conveying various semantic information to humans via the handheld electronic devices, like smartphone, touch panel,and game controller. However, covering the whole device contacting surface with dense actuator arrangement can affect its normal use, how to produce desired vibration patterns at any contact point with only several sparse actuators deployed on the handled device surface remains a significant challenge. In this work, we develop a tactile feedback board with only five actuators in the size of a smartphone, and achieve the precise vibration pattern production that can focus at any desired position all over the board. Specifically, we investigate the vibration characteristics of single passive coil actuator, and construct its vibration pattern model at any position on the feedback board surface. Optimal phase and amplitude modulation, found with the simulated annealing algorithm, is employed with five actuators in a sparse array. And all actuators' vibration patterns are superimposed linearly to synthetically generate different onboard vibration energy distribution for tactile sensing. Experiments demonstrated that for point-wise vibration pattern production on our tactile board achieved an average level of about 0.9 in the Structural Similarity Index Measure (SSIM) evaluation, when compared to the ideal single-point-focused target vibration pattern. The sparse actuator array can be easily embedded into usual handheld electronic devices, which shows a good significant implication for enriching their haptic interaction functionalities.
Paper Structure (8 sections, 7 equations, 5 figures, 1 algorithm)

This paper contains 8 sections, 7 equations, 5 figures, 1 algorithm.

Table of Contents

  1. Introduction
  2. Coil Actuator Specification
  3. Vibration Board Modeling
  4. Vibration Pattern of Single Actuator
  5. Homogeneity and Superposition of Multiple Patterns
  6. Vibration Pattern Decoupling
  7. Experiments and Results
  8. Conclusion

Figures (5)

  • Figure 1: Point-wise vibration pattern feedback superimposed by the sparse actuator array on the top feedback board, with the bottom circuit board for actuator voltage driving.
  • Figure 2: Specification of single coil actuator. (A) Flip-latch structure for actuator. (B) Resonance energy variation for vibration drive sine wave in the sweep frequency. (C) Time-domain vibration response in the acceleration form on the feedback board, for sine, triangle, square, and ramp wave driving in the sweep frequency, respectively.
  • Figure 3: Modeling of the vibration feedback board system. (A) Vibration pattern generation for single actuator. (B) The linearity between the onboard vibration amplitude and the actuator driving strength. (C) Superposition of vibration pattern form different actuators. (D) Transfer the vibration patterns in single period to the energy distribution image, for satisfying the human tactile perception ability.
  • Figure 4: The global optimal amplitude spectrum searching in all phases for each actuator, based on the vibration superposition model and the simulated annealing algorithm.
  • Figure 5: Effect of point-wise vibration pattern generation on the tactile feedback board. (A) Comparison between composite vibration energy pattern and target pattern for different target feedback points. (B) Raw vibration patterns from five actuators are superimposed as the optimal energy distribution image closet to the target pattern. (C) SSIM value promotion of vibration energy distribution during the simulated annealing search process.