Suwoong Lee

A method of vertical and horizontal force estimation by using air-filled material and camera for soft physical human-robot interaction: fundamental experiments

A method of vertical and horizontal force estimation for soft physical human–robot interaction by using an air-filled material and a camera was proposed in this study. First, we considered hypotheses for vertical and horizontal force applied to the air-filled material. Second, the prototype of air-filled material and vision-based force-sensing device (AVFSD) was constructed. Based on the result of preliminary experiments, the relationships between force, pneumatic pressure, and contact surface displacement were formulated. The vertical and horizontal force could be estimated using the AVFSD with percentage errors of 3.6 and 5.8%, respectively, and the hypotheses were verified through the experiments. Graphical Abstract

Operation of forearm support-type lift assist system (FOLAS) by using pneumatic pressure in air cushions

The objective of this study is to develop an operation method of forearm-support type lift assist system (FOLAS)using pneumatic pressure in air cushions. The FOLAS has air cushions, which work as a buffer between the machine and the user’s forearm, and the user’s operating intention can be indirectly detected by measuring the variation of the pneumatic pressure inside the air cushions. Force control to compensate the weight of a lifted object was adopted for the vertical operation of the FOLAS on the assumption that force applied to an air cushion has proportional relationship to pneumatic pressure in the air cushion. Position control using overlap length between movable cushion and fixed cushion was adopted for the horizontal operation, and the overlap length was estimated by the pneumatic pressure ratio in the air cushions. Independence between the vertical and horizontal operation manners that commonly utilize pneumatic pressure in the movable cushion was verified through basic experiments. An experiment for the operational performance showed that the FOLAS could be operated according to the operator’s intention. In an experiment for a lifting motion, the FOLAS could move continuously supporting the operator’s forearm and reduce the muscle activation of elbow muscle. Graphical Abstract

Vision-based fluid-type tactile sensor for measurements on biological tissues

Hardness, dimensions, and location of biological tissues are important parameters for electronic palpation protocols with standardized performance. This study presents a novel fluid-type tactile sensor able to measure size and depth of heterogeneous substances in elastic bodies. The new sensor is very simple and can be easily fabricated. It consists of an image sensor, LED lights, and a touchpad filled with translucent water. The intensity field of the light traveling in the touchpad is analyzed to estimate the touchpad shape which conforms to the shape of an object in contact. The use of the new sensor for measuring size and depth of heterogeneous substances inside elastic bodies as well as hardness of elastic bodies is illustrated. Results obtained for breast cancer dummies demonstrate the effectiveness of the proposed approach.

Seat posture stabilizing function for an electric wheelchair based on controlled pendulum mechanism

The purpose of this study is to develop a seat posture stabilizing function for an electric wheelchair without actuators. The non-actuator seat posture stabilizing function uses instruments that can stabilize the posture of a passenger seat, including controlled pendulum mechanism, brake, and posture angle detector. When applying the novel seat posture stabilizing function to personal mobility means, we found that the seat posture stabilizer could maintain the stability of seat against 15° of both uphill and downhill slopes. In addition, for the implementation of the non-actuator seat posture stabilizing function, we plan to suggest a design guideline for installation on a hinge position using Nx dynamic motion S/W.

Driver drowsiness detection via PPG biosignals by using multimodal head support

Drowsy driving can lead to accidents. Therefore, finding methods by which drowsy driving can be prevented is essential. This paper proposes a method of detecting drowsy driving that utilizes the Low Frequency (LF), High Frequency (HF), and LF/HF values of photoplethysmography (PPG) signals measured on fingers and earlobes. In experiments conducted, of 20 subjects, drowsiness was identified in 14 through PPG signals from their fingers. Further, of those 14 drowsy drivers, PPG signals from the earlobes of eight were also used to determine whether they were drowsy while driving.