This study presents the development of a modular knee exoskeleton system that supports the knee joints of hemiplegic patients. The device is designed to realize the polycentric motion of real human knees using a four-bar linkage and to minimize its total weight. In order to determine the user's intention, force-sensitive resistors (FSRs) in the user's insole, a torque sensor on the robot knee joint, and an encoder in the motor are used. The control algorithm is based on a finite state machine (FSM), where the force control, position control and virtual damping control are applied in each state. The proposed hardware design and algorithm are verified by performing experiments on the standing walking and sitting motion controls while wearing the knee exoskeleton.

This study introduces a two-wheeled self-balancing mobile robot based on a control moment gyroscope module. Two-wheeled mobile robots are able to achieve better mobility and rotation in small spaces and to move faster than legged robots such as humanoid type robots. For this reason, the two-wheeled mobile robot is generally used as a mobile robot platform. However, to maintain its balance, the two-wheeled robot needs to use movements of its two wheels. When an unexpected disturbance affects the robot, the robot maintains its balance with movements of the wheels and tilting of the body. If the disturbance exceeds the response capability of the robot, the robot will lose its stability. At the same time, the safety of the robot may be put at risk by movements to maintain balance. To address these issues, a robot was designed with a control moment gyroscope module to improve balance while minimizing movement. When a disturbance is applied to the robot, the disturbance is estimated by a disturbance observer and the control moment gyroscope controller compensates the disturbance. Using the control moment gyroscope module, the robot can maintain balance with just small movements of its wheels. Improved performance and stability were verified with experiments and simulations.

Legged robots can move on various grounds via walking; however, they have difficulty in moving fast. To overcome this limitation, some legged robots have been studying dynamic motions such as jumping and running. In this article, we present a strategy for generating an optimal jumping motion for legged robots in real time. For convenience, we divided the proposed jumping trajectory into vertical and horizontal directions. The vertical motion trajectory ensures a continuous center of mass position, speed, and acceleration, as well as minimizes the maximum torque and maximum speed of the joints; we generated it via a nonlinear optimal process. Besides, for the horizontal motion, we proposed a novel model predictive control using a height varying inverted pendulum model. In the proposed method, the zero moment point is placed in the support polygon for stable jumping; also, the robot does not slip on the ground and takes off at a desired velocity. We verified the jumping motion using RoK-3, a biped robot developed for the experiment.

With the recent advancements in delivery service robots, the necessity for stair climbing in indoor and outdoor environments has increased. However, stairs are challenging obstacles for robots to overcome. Most studies in the field of delivery robots have focused on traversing even terrains, such as roads and aisles. However, delivery service robots should be capable of climbing stairs in both indoor and outdoor environments. The main purpose of this study is to develop MOBINN, a mobile balancing robot that is capable of climbing stairs for delivery services. MOBINN has novel flexible wheels that can adapt to the shape of the stairs and reduce the torque needed for climbing them. Due to the advantages of flexible wheels, MOBINN can climb stairs without needing an additional degree of freedom. The head structure is designed to reduce damage to delivery packages as the robot maintains a horizontal orientation when climbing stairs. The design also includes an linear quadratic regulator (LQR)-based motion controller and observer for stair climbing. This study experimentally verified that the novel flexible wheels lowered the required torque and enabled stable stair climbing.