Electrovibration is a type of surface haptics that can modulate lateral forces acting between a fingertip and a touch surface. Electrovibration is fast, consumes little power, and does not involve the use of any mechanical actuators. However, it suffers from problems such as nonuniform perceived intensity due to varying environmental impedances, as well as possible electric shock, which have to be solved for commercialization. In this paper, a current feedback method is proposed to provide uniform intensity of electrovibration, regardless of the varying environmental impedances. The proposed method can also prevent electric shock. To show the effectiveness of the proposed method, a hardware prototype was developed and a user study was conducted. The user study result shows that the proposed current control method can provide significantly more uniform perceived intensity of electrovibration as compared with the conventional voltage control method.

This paper presents three methods of input voltage signals that allow low voltage operation of an electrovibration display while preserving the perceptual feel and strength of electrovibration stimuli. The first method uses the amplitude modulation of a high-frequency carrier-signal. The second method uses a dc-offset, and the third method uses a combination of the two methods. The performance of the three methods was evaluated by a physical experiment that measured and analyzed static (dc-component) and dynamic (vibratory component) friction forces and two subsequent psychophysical studies. The physical experiment showed that only the dc -offset method enabled a statistically significant increase in the static friction force between the fingertip and the surface of the electrovibration display. The static friction increase was closely related to the root mean square of input voltage level. In contrast, all of the three methods increased the dynamic friction force significantly, which was deemed to be related to the high frequency effect validated in the previous literature. The first psychophysical study showed that the three proposed methods can significantly reduce the peak-to-peak (p-p) amplitude of an input voltage signal while generating perceptually equally strong electrovibrations to that produced by the conventional method. Using lower p-p voltage has the merits of a simpler electrical circuit and less electromagnetic noise, saving the overall system cost. Further, the perceived intensity of electrovibration was more correlated to the dynamic friction force than the static friction force. The second psychophysical study was a discrimination experiment, and it demonstrated that all the three proposed methods and the conventional method can provide perceptually similar stimuli despite their different signal forms and voltage amplitudes. Our experimental investigation allowed us to conclude that the dc-offset method is the best way to lower the driving voltage of an electrovibration display while providing perceptually equivalent electrovibrations.

It is important to operate devices with control panels and touch screens assisted by haptic feedback in mobile environments such as driving automobiles and electric power wheelchairs. A lot of consideration is needed to give accurate haptic feedback, especially, presenting clear touch feedback to the elderly and people with reduced sensation is a very critical issue from healthcare and safety perspectives. In this study, we aimed to identify the perceptual characteristics for the frequency and direction of haptic vibration on the touch screen with vehicle-driving vibration and to propose an efficient haptic system based on these characteristics. As a result, we demonstrated that the detection threshold shift decreased at frequencies above 210 Hz due to the contact pressure during active touch, but the detection threshold shift increased at below 210 Hz. We found that the detection thresholds were 0.30–0.45 gpeak with similar sensitivity in the 80–270 Hz range. The haptic system implemented by reflecting the experimental results achieved characteristics suitable for use scenarios in automobiles. Ultimately, it could provide practical guidelines for the development of touch screens to give accurate touch feedback in the real-world environment.

Many recent games, such as racing and flight games, open their game telemetry data to users by storing them in the local memory. Such telemetry data can provide useful information for haptic rendering, and this advantage has been exploited by the industry. This approach applies to any applications that export telemetry data in run time. The haptic rendering module operates as a separate process that accesses the telemetry data in parallel with the application. It is simple, efficient, and modular while retaining the application intact. We examine the approach's viability for user experience improvement by developing three telemetry-based haptic rendering algorithms for car racing games. They express the car engine response, collisions with external objects, and the road surface texture, respectively. Building a haptics-enabled driving platform, we conducted a user study comparing gaming experiences between our telemetry-based algorithms and conventional sound-to-tactile conversion algorithms. The results showed that the telemetry-based effects elicited better experiences than the sound-based effects.