Temperature invariant and high precision absolute rotary encoder using photocells on visible light spectrum
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ORIGINAL RESEARCH
Temperature invariant and high precision absolute rotary encoder using photocells on visible light spectrum Vanita Jain1
•
Nalin Luthra1 • Gopal Chaudhary1
Received: 1 November 2019 / Accepted: 8 June 2020 Ó Bharati Vidyapeeth’s Institute of Computer Applications and Management 2020
Abstract This paper introduces temperature invariant absolute rotatory encoder using photocells on the visible light spectrum. A multivariate function is proposed to remove error arising on photocells through temperature variance and a small change in light intensity. Multiple experiments are conducted in the controlled environment to prove proposed multivariate function. Encoder introduced in this paper is more scalable than grey code encoder available in the market. Dynamic auto calibration is also proposed to make encoders more reliable with time. Keywords Absolute rotary encoder Grey code Dynamic auto calibration Temperature invariant
1 Introduction Absolute angular position measuring system is very important in robotics and automation industries [1]. With the advancement in the automation industry, we require more precise and accurate data processing to enhance performance of robots. There are two types of encoders incremental (relative) and absolute [2]. Incremental encoders begin counting from zero each time the encoder powers up. Incremental encoders generate output signals (pulses) when the motor rotates. These types of encoders are usually used to determine the speed and relative angular position of the shaft [3]. Absolute encoders provide the absolute angular position of the shaft. They do not lose & Vanita Jain [email protected] 1
Bharati Vidyapeeth’s College of Engineering, New Delhi, India
track of positioning even if the change in position takes place after the system is turned off [4]. There are three types of rotary encoders technologies namely conductive, magnetic and optical. Conductive encoders [5, 6] are capable of detecting angular position while in being contact with the disk. This disk provides resistance due to which change in voltage takes place which is detected by the controller to find the angular position. This disk can also be considered as a potentiometer where as resistance of potentiometer depends upon on temperature. Magnetic encoders are divided into two types, off-axis and on axis. These types of encoders work on laws of electromagnetic induction [7]. These types of encoders are better than traditional optical encoders in harsh environment [8]. Optical encoders are the most common encoders used in industry today. They are available in incremental and absolute forms [2]. Optical absolute encoders, use the opaque disk (code disk) that has one or more circular tracks, with arrangements of identical slits. Some slits obstruct light whereas others allow light to pass. When the shaft rotates, the light is incident on photo sensors in a periodic manner. This enables us to compute the angular position of the system. There are two types of absolute encoding code
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