Experimental Investigation of Linear Encoder’s Subdivisional Errors under Different Scanning Speeds

Abstract

Optical encoders are widely used in applications requiring precise displacement measurement and fluent motion control. To reach high positioning accuracy and repeatability, and to create a more stable speed-control loop, essential attention must be directed to the subdivisional error (SDE) of the used encoder. This error influences the interpolation process and restricts the ability to achieve a high resolution. The SDE could be caused by various factors, such as the particular design of the reading head and the optical scanning principle, quality of the measuring scale, any kind of relative orientation changes between the optical components caused by mechanical vibrations or deformations, or scanning speed. If the distorted analog signals are not corrected before interpolation, it is very important to know the limitations of the used encoder. The methodology described in this paper could be used to determine the magnitude of an SDE and its trend. This method is based on a constant-speed test and does not require high-accuracy reference. The performed experimental investigation of the standard optical linear encoder SDE under different scanning speeds revealed the linear relationship between the tested encoder’s traversing velocity and the error value. A more detailed investigation of the obtained results was done on the basis of fast Fourier transformation (FFT) to understand the physical nature of the SDE, and to consider how to improve the performance of the encoder.

Methods for Reducing Subdivision Error within One Signal Period of Single-Field Scanning Absolute Linear Encoder

“…The position error over the linear encoder’s entire measuring range can be determined by laser interferometer [ 17 , 18 ]. The SDE of the linear encoder can be measured by the constant-speed approach [ 31 ], which we adopted in our experiments. The experimental setup, shown in Figure 10 , was placed in a temperature- and humidity-controlled room.…”

Special Issue on IWPMA (International Workshop on Piezoelectric Materials and Applications in Actuators) 2019

“…These advances make it possible to meet current industrial requirements, involving innovations such as underwater actuation for robot propulsion using a dual rotor mechanism ( [5]) or a micro-aerial vehicles with ultrasonic motor-driven flapping wings ( [6]). Combined with precise metrological methods, for instance optical positioning ( [7]), these advances open up new application fields.…”

Investigation of the Portal-Type Machine Tool Gear-Belt Gearbox

“…The problem of sensor manufacturing errors and the influence of these errors on the measured motion parameters is widely studied by specialists in various fields of technology [17,18]. A large number of investigations are to the development of methods and algorithms for processing encoder measuring signals and error compensation for the most accurate measurement of the technical systems elements movement parameters [17,[19][20][21]. The presence of distortion of the encoder scale necessitates the use of algorithms for correcting the measured position, but this problem is not considered in this paper.…”