Abstract
This paper presents, for the first time, an absolute linear electromagnetic encoder consisting of a rubber belt with two chains of screen-printed metallic inclusions (rectangular patches). The position, velocity, and direction of the belt (the moving part) is determined by detecting the inclusions when they cross the stator (the static part). The stator is a microstrip line loaded with three complementary split ring resonators (CSRRs), resonant elements exhibiting a resonance frequency perturbed by the presence of inclusions on top of them (contactless). The line is fed by three harmonic signals tuned to the resonance frequencies of the CSRRs. Such signals are generated by a voltage-controlled oscillator (VCO) managed by a microcontroller. The sensed data are retrieved from the pulses contained in the envelope functions of the respective amplitude modulated (AM) signals (caused by the belt motion) generated at the output port of the line. One of the signals provides the absolute belt position, determined by one of the chains, the encoded one. The information relative to the velocity and motion direction is contained in the other AM signals generated by the motion of the other chain, periodic, and thereby, uncoded. The spatial resolution of the system, a figure of merit, is 4 mm. Special emphasis is devoted to the printing process of the belt inclusions.
Highlights
Motion control is today present in a wide variety of industrial scenarios, such as robotics, the automotive and aeronautics industry, the textile industry, logistics, the food industry, mechatronics, space, and medical instrumentation, to cite some examples
The encoder presented in this paper is implemented by screen-printing chains of rectangular patch inclusions on a rubber belt, a commercial elevator belt
Concerning the encoder system presented in [8], it was the precursor of the one proposed in this paper, but we have demonstrated for the first time system its functionality by including the necessary elements for retrieving the signals containing the relevant information, i.e., the voltage-controlled oscillator (VCO), the microcontroller, and the associated circuitry
Summary
Motion control is today present in a wide variety of industrial scenarios, such as robotics, the automotive and aeronautics industry, the textile industry, logistics, the food industry, mechatronics, space, and medical instrumentation, to cite some examples. We investigate the possibility of using the moving target as the encoder, provided it is made of a dielectric material, in particular, rubber This is of interest, since many industrial and logistic systems utilize belts made of rubber (e.g., conveyor belts, elevator belts, etc.). There are sensors based on coupling modulation [13–17] and frequency variation [18], where a resonant (movable) element is displaced over a transmission line based structure (typically, the resonator in motion is displaced in a plane parallel to the one of the lines, but there are realizations, where the resonator displaces vertically [17,19]) These systems offer a very limited input dynamic range, as compared to linear electromagnetic encoders, where such dynamic range is potentially unlimited. The system proposed in this paper cannot compete against optical encoders and Hall effect sensors in terms of resolution, but, in many applications, the resolutions demonstrated in this paper suffice, in particular in industrial scenarios (elevators, conveyor systems, etc.)
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