Abstract
Simultaneous determination of linear and angular positions of rotating objects is a challenging task for traditional sensor applications and a very limited set of solutions is available. The paper presents a novel approach of replacing a set of traditional linear and rotational sensors by a small set of image sensors. While the camera’s angle of view can be a limiting factor in the tracking of multiple objects, the presented approach allows for a network of image sensors to extend the covered area. Furthermore, rich image data allows for the application of different data processing algorithms to effectively and accurately determine the object’s position. The proposed solution thus provides a set of smart visual encoders emulated by an image sensor or a network of image sensors for more demanding spatially distributed tasks. As a proof of concept, we present the results of the experiment in the target application, where a MP image sensor was used to obtain sub-degree angular resolution at 600 rpm and thus exceeding the design parameters and requirements. The solution allows for a compact, cost-effective, and robust integration into the final product.
Highlights
Linear and rotary position sensors are an essential part of different actuation systems and there are numerous variations of the proposed solutions, and several real-world implementations
Linear and rotary position sensors can not be combined directly to measure the linear and rotary position of an object—while shaft rotation sensors are regarded as COTS (Common Off-The-Shelf) components, most types require the shaft to have no or very limited linear play [1,2]
The underlying concept is in replacing physical sensors with a set of image-based ones, smart sensors rendered by the image processing, and data fusion algorithms
Summary
Linear and rotary position sensors are an essential part of different actuation systems and there are numerous variations of the proposed solutions, and several real-world implementations. The most common implementations of the angular absolute encoders code the angular position with binary values, defined by different sequences of features on the rotating component. The resolution of such sensors is usually limited by the spacing of the features. The prevailing data encoding approach of binary-features based solutions is in the use of single-distance codes, in reference to the Hamming distance of 1 between adjacent codes This results in well defined angular positions that are mostly immune to switching delays of the sensing parts (historically, the encoders were mechanical devices, where individual signal contacts were subjected to bouncing and other switching anomalies). The performance of the system is evaluated and presented in the final part of the paper
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