Experimental research into the influence of photodectector types on characteristics of optical mini-sticks of unified human-machine interfaces

Abstract

The article provides the results of the experimental research into the influence of different types of photo detectors of digital optical mini-sticks on their transformation function – the useful mini-stick signal as a function of the mini-stick control lever deviation value. The set problem was solved using experimental research methods. Circuits with a photodiode (PIN photodiode PD15– 21B/TR8 manufactured by Everlight company) and circuits with a phototransistor (phototransistor KP­ 2012P3C manufactured by Kingbright company) were studied. An automated test bench was used for the research. The test bench allows setting the mini-stick rotation angle and the value of mini-stick lever deviation from the central position to the left or to the right. The influence on mini-sticks was set by the test bench software. Based on the test results the test bench software plotted a ray path diagram. The mini-stick signal quality was assessed in terms of resolution, accuracy, non-linearity and hysteresis. The following results were obtained in the research. The mini-stick using a photo transistor as a photo detector ensures the output signal amplitude and resolution which exceed those of mini-stick with a photodiode by factor of 3.5 to 4. It allows using mini-sticks with a phototransistor for high-pre-cision control of complex robotic systems, manipulators and aircraft, and for designing joysticks and unified human-machine interfaces on their basis. The indices of precision, non-linearity and hystere-sis of both mini-stick types are comparable and meet the basic requirements applied to control devices. Thus, mini-sticks based on phototransistors can be regarded as the best in terms of the signal quality. Taking into consideration the circuitry, overall dimensions and the cost of hardware components which are identical for both photo detectors, mini-sticks based on phototransistors shall be considered to be more advanced switching devices.