Bowden-cable Angle Sensor (BoA Sensor) & BoA Sensor based Motion Tracking Smart Work Suit

This research proposes a new and low-cost bend sensor that can measure a wide range of accumulated bend angles with large curvatures. The proposed bend sensor utilizes a Bowden-cable, which consists of a coil sheath and an inner wire. Displacement changes of the Bowden-cable’s inner wire, when the shape of the sheath changes, have been considered to be a position error in previous studies. However, this study takes advantage of this position error to detect the bend angle of the sheath. The bend angle of the sensor can be calculated from the displacement measurement of the sensing wire using a Hall-effect sensor or a potentiometer. Simulations and experiments have shown that the accumulated bend angle of the sensor is linearly related to the sensor signal, with an R-square value up to 0.9969 and a root mean square error of 2% of the full sensing range. The bend sensor is not affected by a bend curvature of up to 80.0 m-1, unlike previous bend sensors.

In the next study, a motion-tracking smart work suit is presented to monitor the movements of workers using the BoA sensor mechanism. Activity data of workers can be used to manage their safety and working processes. To date, the adoption of motion measuring systems in industrial sites has been limited, due to cost and noisy environments. In this study, a motion-tracking smart work suit is presented to monitor the movements of workers. This system comprises modular joint-angle sensors that utilize a BoASensor mechanism, a conventional work suit with added sensor sleeves, and a monitoring device. The modularized joint-angle sensor can be easily attached or detached onto or from the normal work suit, improving its usability and washability. This suit could experience relative motion and deformation between the body, degrading sensor robustness, unlike conventional motion sensing suits. The screw sensor routing method is proposed to minimize the coordination effect between the sensor and skeletal system during body movements. Various postures recorded with the suit exhibited root mean square errors lower than 7.75% from the elbow range of motion (150°) compared with the inertial-measurement-unit- (IMU)-based motion tracker. It was determined that there exists statistical significance between the proposed screw-routing method and the IMU in precision, thereby demonstrating sensing robustness with various upper limb motions. Additionally, the linearity analysis revealed that screw-routing has the highest linear behavior. The proposed work suit is expected to be utilized in preventing industrial accidents at various sites, owing to its low production cost and high accessibility.

Keywords: #Low-cost, #Bend-sensor, #Motion Sensing, #Smart suit

• Useok Jeong and Kyu-Jin Cho, "A Novel Low-Cost, Large Curvature Bend Sensor Based on a Bowden-Cable," Sensors, Vol.16, No.7: 961, Jun. 2016.

• Jewoo Lee, Kyu-Jin Cho, and Useok Jeong, "Motion Tracking Smart Work Suit With a Modular Joint Angle Sensor Using Screw Routing," IEEE Robotics and Automation Letters, vol. 7, no. 4, 2022.

• Patent: Bending Sensor, 10-1856310