Frequency-Modulated Piezoelectric Haptic Display

Boyuan Liang Lingfeng Sun Masayoshi Tomizuka
MSC Lab, University of California, Berkeley
In Submission
arXiv

Project Summary

Motivation: Existing haptic displays usually has small pixels but bulky on-skin driver circuits, making wearability and scalability hard.

Approach: Frequency-modulated (FM) haptic display. Haptic pixels use higher frequency instead of larger deformation to represent stronger haptic sense. All pixels share the same power sinusoidal wave source.

Results: Experiments show that this FM mechanism can effectively render haptic patterns, revealing a path towards wearable large-scale haptic glove.

Shared Source Frequency Modulation

Second research result visualization

Overview of the SSFM structure.
Upper Left: Schematic of a single pixel, powered by the shared base signal and gated by an analog switch.
Upper Right: Temporal relation among the base waveform, the analog switch action, and the converted waveform. To produce a nominal frequency of 200/n Hz, the switch is opened for n-1 base periods and then closed again for one period.
Lower Left: Spectra of the converted waveform for selected pixel intensities n=1,2,4,10,20,50.
Lower Right: Example of how dynamic haptic patterns are generated by SSFM, where darker shading denotes a higher nominal frequency.

Second research result visualization

Implementation of the proof-of-concept prototype.
Upper left: Top view of the assembled display.
Upper middle: Close-up of the display surface.
Upper right: Snapshot of a human-participant experiment.
Lower left: Exploded view of the prototype. The piezoelectric actuators are mounted on photo-cured resin holders, with aluminum support frames beneath to limit deflection of the holders under hand pressure.
Lower right: Schematic of the electrical connections. The ESP32 microcontroller sets the state of each analog switch channel over a high-speed SPI link, while the host PC streams haptic display frames to the ESP32 over a serial connection.

Experiment Results

Volunteer tests conducted with 11 participants, 8 male and 3 female. Results show that this frequency-modulated (FM) design can effectively deliver haptic patterns.

First research result visualization

Experiment 1: identification of vibration position along the index finger. Each block corresponds to one stimulated pixel, outlined in blue, and its entries give the distribution of reported positions.

Second research result visualization

Experiment 2: discrimination of vibration intensity. Participants reported which of two successive vibrations had the higher nominal frequency.

Third research result visualization

Experiment 3: multi-finger vibration perception. Participants reported which two fingers were stimulated, denoted index (I), middle (M), ring (R), and little (P).

Fourth research result visualization

Experiment 4: perception of linear motion patterns among the up, down, left, and right directions.

Fifth research result visualization

Experiment 5: perception of rotational motion speed among 16, 32, and 64 mm/s

Sixth research result visualization

Experiment 6: perception of linear motion patterns among the four diagonal directions.

Future Work

Second research result visualization

Based on the theoretical foundation of this work, our immediate next step is building a haptic glove with large pixel sizes. On the left is a rendering of the wearable haptic device on one finger.

BibTeX

@article{liang2026frequency,
        title={Frequency-Modulated Piezoelectric Haptic Display},
        author={Boyuan Liang and Lingfeng Sun and Masayoshi Tomizuka},
        journal={arXiv},
        year={2026}
      }