Fuzziy Digital Filter for Robotic Manipulator Operation

In this article it is described the operation principle of a robotic manipulator ARMino device and the connection diagram of its electrical components. The device includes: An Arduino Mega control board, four servos, four potentiometers, a prototyping board, a computer. Turning the shafts on the potentiometer adjusts the position of the servo spindles. When the voltage on the potentiometer’s pin changes, the voltage at the analog inputs of the microcontroller changes. Then, in the microcontroller, the voltage is scaled to the value of the servo rotation angle. After that, the joints of the robotic manipulator are rotated. During the operation of the ARMino robotiс arm, a contact bounce problem appeared, significantly reducing the accuracy of positioning and the smooth movement of the ARMino joints. To solve this problem, a digital filter was developed. This article describes the digital filter working algorithm, which consists of four steps. One of the steps consists on finding the digital filter coefficients, which regulate the signal voltage level transmitted to the servo motors, and its transition process time which forms the signal edge. The main problem developing a digital filter is that the standard procedure of finding the digital filter coefficients, the coefficients are given by a recommended range of values, which complicates choosing from this range, a single value and transmitting it to the servos. To solve this problem, a fuzzy digital filter was developed, the algorithm of which consists of six steps. The first step determines the input variables degree of truth. The second step is to calculate the degrees of truth of the fuzzy rules preconditions. The third step is to calculate the degrees of truth of the fuzzy rules conclusions by using the process of finding the maximum values. The fourth step is the defuzzification stage in which a precise value of the fuzzy digital filter coefficient is calculated. The fifth step is the output voltage transmitted to the servos. In the sixth step, the output voltage in the microcontroller is converted to the angle value and the servo is given the command to rotate. This article presents numerical simulation of the fuzzy digital filter algorithm, using as an example the servo responsible of the ARMino base rotation. Experimental studies on the functioning of the fuzzy digital filter have been carried out, confirming the expediency of its use. The graphics of the transition process of the robotic manipulator base movement without and with the use of a digital filter are given.

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