Position Sensors for Industrial Applications Based on Electromagnetic Encoders

Abstract

Optical and magnetic linear/rotary encoders are well-known systems traditionally used in industry for the accurate measurement of linear/angular displacements and velocities. Recently, a different approach for the implementation of linear/rotary encoders has been proposed. Such an approach uses electromagnetic signals, and the working principle of these electromagnetic encoders is very similar to the one of optical encoders, i.e., pulse counting. Specifically, a transmission line based structure fed by a harmonic signal tuned to a certain frequency, the stator, is perturbed by encoder motion. Such encoder consists in a linear or circular chain (or chains) of inclusions (metallic, dielectric, or apertures) on a dielectric substrate, rigid or flexible, and made of different materials, including plastics, organic materials, rubber, etc. The harmonic signal is amplitude modulated by the encoder chain, and the envelope function contains the information relative to the position and velocity. The paper mainly focuses on linear encoders based on metallic and dielectric inclusions. Moreover, it is shown that synchronous electromagnetic encoders, able to provide the quasi-absolute position (plus the velocity and direction of motion in some cases), can be implemented. Several prototype examples are reviewed in the paper, including encoders implemented by means of additive process, such as 3D printed and screen-printed encoders.

Design Optimization of PCB-Based Rotary-Inductive Position Sensors

“…The linearity error is of crucial importance since it defines the variation of the response of the sensor from the ideal curve. The ideal case is the one wherein the response of the sensor depends linearly on the position of the target as predicted in (1). As far as the IPS sensors are concerned, the linearity error basically depends on the difference between the ideal induced voltage and the actual signal picked up by RXs.…”

“…Optical encoders are able to perform precise and high resolution position measurements [1]. Indeed, displacement measurements by means of optical interferometer can reach sub-nanometer or picometer accuracy [2].…”

A novel linear displacement sensor based on double-threshold decoding algorithm

“…When the substrate slides on another substrate, the linear displacement is measured to 20 mm with a resolution of approximately 126 nm. Paredes et al (2021) proposed an electromagnetic linear encoder made from metal and electrolyte. Chen et al (2019) proposed a high-speed and low-noise complementary metal–oxide–semiconductor (CMOS) optical linear encoder, and built a CMOS circuit to eliminate common mode noise.…”

A Second Harmonic Wave Angle Sensor with a Collimated Beam of Femtosecond Laser

“…Various studies are still being carried out to improve the performance of angle sensors, even though many types of angle sensors have been established and commercialized with various measurement methods and models for specific measurement purposes [3][4][5][6]. Research on the conventional angle sensor, such as inductive angle positioning sensors [7,8], autocollimators [9,10], and rotary encoders [11,12], is no exception. The angle-sensing technology is still being challenged to meet the need for current trends in technology that lead to the manufacturing of high complexity products, yet shrinking in dimensions.…”