Absolute Shaft Encoder Research Articles

A self-powered absolute shaft encoder based on triboelectric nanogenerator

A rotary encoder is an important element for measuring the rotational motion in various mechanical systems. This paper proposes a self-powered absolute shaft encoder (SPASE) based on a triboelectric nanogenerator that enables absolute angle measurement and stable signal detection without additional circuits for signal processing by utilizing a voltage pumping method. SPASE was designed by separating the measurement function and the triboelectric power generation function and modularizing the parts that perform each function. A SPASE prototype with a size of ϕ42 mm × 50 mm was manufactured. It was experimentally confirmed that, in this prototype, a voltage of 182.7 V can be generated in the pumping module and that stable angle measurement with a resolution of 12° can be successfully conducted over a wide speed range from 40 to 2000 rpm in the sensing module. Furthermore, SPASE exhibits great applicability and flexibility as a self-powered absolute angle sensor because the pumping and sensing modules are separated and each module can be independently operated as needed. SPASE is expected to be used in various fields that require rotation monitoring without any external power sources.

Design of an Absolute Shaft Encoder Using Optically Modulated Binary Code

In order to avoid the fabrication of coding pattern over a shaft coupled disk of the binary coded absolute encoder, a new design concept has been presented in this paper. The proposed prototype can encode the binary information by optical modulation principle. Instead of lithographic fabrication, here the pattern code bits are implemented optically through a plurality of infra-red (IR) light emitting diodes (LED). Each LED transmits a bit of information as modulated optical signal and modulation is served by the principle of serial infra red control protocol. During the rotation of an object, a window position of the shaft coupled disk determines which bits’ information will be transmitted. Now, an IR detector of the receiver unit decodes this code by demodulating the transmitted signal. Finally, the absolute position of the object is evaluated from this code by searching a look-up table data. Thus, the receiver unit of the proposed encoder can sense the position of an object remotely without using any additional wireless device. Also, the sensing heads may not be damaged by the rotating disk vibration. The prototype has been tested by using De-Bruijn coding pattern and obtained promising results. Also, the proposed method is equally valid for any binary or gray pattern code.

Fuel level measurement system based on absolute shaft encoder

In this article a new type of absolute shaft encoder is presented for the measurement of fuel level in a tank. This measurement technique is based on the principle of sensing the float arm displacement with respect to the fuel level. Here, the mechanical displacement is detected by an absolute shaft encoder and each position is represented by variant intensity of lights. Furthermore, the variation of light intensity is converted into voltage level by using a signal processing circuit (SPC) and calibrated with measured fuel level. Experimentally, it is observed that the developed prototype is able to measure the fuel level up to the range of 30cm within the accuracy of ±1% FSO.

A Simple Approach to Design a Binary Coded Absolute Shaft Encoder

In this paper, an optical type absolute shaft encoder coding pattern is presented. Compared with the conventional binary or gray code pattern resolution ( ${2}^{n}$ ), the proposed code exhibits two times more resolution ( $2^{n^{2}}$ ). Even, to represent high density positional information of rotating object, it is required very less number of tracks. This pattern sequence is based on $n$ -by-2 matrices of binary codes where consecutive two columns of each code represented as high–low order bits. To retrieve the encoded position from these coding patterns, an extra pulse track was added at the outside of coded tracks. Moreover, it was used for providing a synchronized clock pulse into a simple photodetector-based sequential logic circuitry; it is the decoding unit of this encoder. Thus, depending on these synchronized pulses, the proposed encoder is able to provide error free positional information for a high-speed rotating object. Eventually, in order to prove this concept, a prototype is designed and tested, where a satisfactory performance was achieved.

RTK GPS mapping of transplanted row crops

This study demonstrated the feasibility of using a real-time kinematic (RTK) global positioning system (GPS) to automatically map the location of transplanted row crops. A positive-placement vegetable crop transplanter retrofitted with an RTK GPS receiver, plant, inclination, and odometry sensors, and an on-board real-time data logger were used for transplant mapping in the field during planting. Sensing the location where each plant was placed in the soil using an absolute shaft encoder mounted on the planting wheel proved to be more robust and accurate than using an infrared light beam sensor to detect the stem location of each plant immediately after planting. Field test results showed that the mean error between the plant map locations predicted by the planting data and the surveyed locations after planting was 2 cm, with 95% of the predicted plant locations being within 5.1 cm of their actual locations. Along-track errors were greater than transverse-track errors indicating that some improvement in plant map accuracy might be obtained by characterization of dynamic planting effects on final plant location. Overall, the system was capable of automatically producing a centimeter-level accuracy plant map suitable for use in precision plant care tasks such as intra-row weed control.

System for measuring the size of high-current density solid electron beams

A measurement system is described for determining the size of a high-current density solid electron beam from a Pierce-type electron gun. The apparatus incorporates ten graphite apertures and two graphite tubes mounted at 30/spl deg/ intervals on an off-axis drum that is rotated by a stepper motor. The graphite apertures are used to make localized beam-edge current-interception measurements at ten discrete locations at 1-cm intervals along the length of the beam. The graphite tubes can be used either to produce an integrated edge-current profile over an 11.4-cm length of the beam, or to measure the net current outside of two specific diameters centered on the beam axis. The active aperture or tube and its position with respect to the beam axis are determined by the orientation of the drum, which is read out using an absolute shaft encoder. This permits the position of each aperture or tube to be determined to an accuracy of 60 /spl mu/m.

Use of a `look-up' table improves the accuracy of a low-cost resolver-based absolute shaft encoder

The accuracy of a low-cost, resolver-based 14-bit absolute encoder has been improved significantly from about 10 to about 2 arcmin (the resolution limit) by the use of a `look-up' table. The methodology adopted for generating this table and incorporating it into the drive-system software of our four-element -ray telescope array is described.