Optoelectronic-Based Pose Sensing for a Hand Rehabilitation Exoskeleton Continuous Structure

Abstract

Hand exoskeleton pose monitoring is of great importance in the rehabilitation training of stroke patients to ensure precise robotic trajectory control and provide a patient recovery assessment mechanism. In this paper, a low-cost pose sensor unit based on the principle of photoelectric reflection is proposed to measure the pose of a multi-segment continuous structure in a hand rehabilitation exoskeleton. The sensor unit consists of five photosensitive elements that measure the rotation angle of an arrangement of adjacent segments, each integrated with a sensing element, to estimate the actuator's motion. An accurate device with a user-friendly interface is then designed for calibration of the sensing elements. The experimental results indicate that the sensitivity exceeds 0.047 V/° for the sensing elements, and hysteresis and repeatability errors are less than 1.1% and 1.8%, respectively. A comparison between the proposed sensor output and the results benchmarked by a VICON motion capture system demonstrates that the sensor can measure the bending angle of the multi-segment structure with a mean error of 3.23 degrees.

A method for patient gait real-time monitoring based on powered exoskeleton and digital twin

“…In addition to the conventional motor built-in encoder, many uncommon sensors have also been studied and verified. Optoelectronic-based pose sensors can be used for pose measurement [11], triboelectric bidirectional sensors for DOF rotations detection [12]. Based on these sensors, a support vector machine (SVM) and neural network [13] are used to help enhance the sensing ability of exoskeletons, which will be discussed in detail in 2.3.…”

“…This is a mature and classical method, focused on by a lot of researchers and companies [21]. Furthermore, there are also many other kinds of mechanical sensors used, such as strain gauge, optoelectronic-based pose sensor (mentioned above) [11], etc.…”

A Review of Hand Function Rehabilitation Systems Based on Hand Motion Recognition Devices and Artificial Intelligence

“…The sensor is small, simple, sensitive, safe, and low-cost, and can be easily integrated into the exoskeleton of the hand without affecting actuation. In a later study, the team also proposed a low-cost micro-hand posture sensor based on photoelectric technology that can be integrated into the hand exoskeleton [ 52 ], which measures the posture of multi-segment continuous structures in the hand rehabilitation exoskeleton. The sensor has low energy consumption, low noise, high sensitivity, and good real-time performance.…”

Miniature Optical Joint Measurement Sensor for Robotic Application Using Curvature-Based Reflecting Surfaces

“…Many alternative optical based sensors have also been proposed. For example [4] shows the use of optoelectronic sensors to measure pose in the exoskeleton of a robotic hand actuator. Optoelectronic sensors comprise of a Light Emitting Diode (LED) that emits infrared light and a Phototransistor (PT) to collect reflected light.…”