Visual encoder: robust and precise measurement method of rotation angle via high-speed RGB vision

Abstract

In this paper, a new measurement method of the rotation angle of a rotor, which is named the 'visual encoder,' was proposed. This method is based on the principles of the vision-based method and the optical encoder, and realized by using a high-speed vision system. The visual encoder shows advantageous features such as non-contact, high-resolution and robustness against the free motion and the fluctuation of the rotation axis. A high resolution method to increase the measurement resolution was also suggested. The accuracy and the robustness of the visual encoder were confirmed through the experimental verifications, and the operation was possible at 6,000 rpm even under the fluctuation of rotation axis.

Instantaneous Rotational Speed Measurement Using Image Correlation and Periodicity Determination Algorithms

“…With rapid advances in imaging sensors and image processing algorithms in recent years, imaging based techniques provide a promising alternative to rotational speed measurement [13][14][15][16][17][18][19][20][21]. The imaging technique is potentially suitable for applications in a hostile environment because of its sensing principle.…”

“…For the image series of a moving object, the intensity variation of pixels is the reflection of the motion of the object [23]. Existing speed measurement systems based on the imaging principle are normally implemented by exploiting the intensity distribution difference between two consecutive frames with the aid of camera calibration techniques [13][14][15][16][17][18]. An instantaneous rotational speed measurement system using a high-speed camera and a well-designed varying-density fringe pattern was proposed by Zhong et al [13,14].…”

“…The imaged fringe pattern intensity changed due to the rotation of the shaft, from which the instantaneous rotational speed was obtained. Kim et al [15] used a high-speed camera with a switching colour pattern on the rotating shaft for rotational speed measurement. Li et al [17] proposed a vision-based method to measure the rotational angle using a calibration pattern with a spot array.…”

Structural dynamic response analysis using deviations from idealized edge profiles in high-speed video

“…7 The emergence of high-speed imaging sensors has increased the sampling frame rate of cameras considerably, providing more advantage in structural high frequency information observation than common commercial cameras. [8][9][10][11] Noises from frame interpolation are technically avoided from the source benefiting from a relatively high sampling rate, and subtle motion details can be recorded in a high-speed video file.…”

Rotational speed measurement using a low-cost imaging device and image processing algorithms

“…In recent years vision-based approaches have been deployed to measure rotational speed in recognition of their advantages of non-contact measurement and simple system structure [9][10][11][12][13][14]. A rotational speed measurement system using a high-speed camera and a double-sine-varying-density fringe pattern was proposed by Zhong et al [9].…”