PNIPU: Touch screen responsive to touch sound

2023: Presentation of the touch screen responding to the touch sound

Perm Polytechnic scientists have developed a touch screen that responds to the sound of touch. The university announced this on November 8, 2023.

source = PNIPU

Conventional control panels with buttons do not work well in an aggressive environment, dust and moisture penetrate into the slots. At the same time, the buttons often break. Touch screens have become the main input interface for mobile phones, tablets, general purpose PCs and terminals. However, they are generally made of brittle materials and have many limitations (must be flat and uniform). Because of this, devices become less versatile and reliable. It would be convenient to have a touchscreen made of durable metal or plastic. Perm Polytechnic scientists have developed a touch screen that detects the touch point by sound. Sound waves propagate along the surface, and from the propagation time of the wave it is possible to accurately determine the location of the touch. At the same time, the surface can be of any shape and size, made of any material, and the buttons are simply drawn. The system is durable, vandal resistant and accurate.

source = PNIPU

When the user touches the screen, a shock wave forms, which propagates through the touch panel. Microphones located in its interior register sound vibrations, sound comes to different microphones in due time. Then their readings are transmitted to the microcontroller and processed there - the relative time delay and signal strength are calculated, from which you can calculate the distance and location of the user's touch, - explained Alexey Kozin, assistant of the Department of Automation and Telemechanics at Perm Polytechnic.

During the study, scientists simulated a sensory acoustic device. The mathematical model determines the propagation of sound in solids and its localization, taking into account the time delay and volume.

Polytechnics created a model in a software complex in the form of a hollow metal structure (20 cm wide, 30 cm long, 10 cm high), three microphones are attached to the inside of the walls. When modeling, the scientists used an echo-free medium and a single touch in the center. Signal strengths and peak wave values were determined. To test the possibility of implementing the system in practice, scientists conducted an experiment for which an aluminum box was used. The coordinates of the microphones and the touch fully correspond to the model, the approximate duration of the touch is 85 ms, and its peak value occurred at a time of 900 μs. As a result, microphone No. 3 (closest to touch) registered the sound wave first, and microphone No. 1 - the last. The time delay between the third and second microphone is 109.4, and between the third and first microphone is 201.6.

The acoustic sensor is very cheap and allows you to make a screen from any material - from a piece of metal and even from a wooden board. Vibration test showed high noise immunity of our sensor. It turned out that the most in demand is the use of our touch screen in mine equipment, where high dust content of air leads to very fast wear of devices, "said Anna Yakubchik, graduate student of the Department of Information Technologies and Automated Systems at PNIPU.

The obtained results of the experiment correspond to all calculated and computer values. The system developed by scientists allows you to accurately determine the place of contact of the user with the touch screen through sound waves following the touch. The technology is durable, vandal-resistant and weather-free. Therefore, its use on sensor devices in outdoor and unfavorable environments is effective and promising.