A ball-on-plate system is a mechanical control system for measuring the position of a ball placed on a touch panel and controlling the ball to move to a desired position. This system has been applied to a shelf cart. A hole was made in the center of the top shelf of the cart with a ball-on-plate system installed, allowing objects to be placed on the plate. The cart equipped with this system is named a "level-maintaining shelf cart". When external disturbances act on the cart, the ball- on-plate system ensures that the plate remains level, preventing objects on the plate from sliding or toppling. However, when the cart passes over uneven surfaces or experiences disturbances with acceleration beyond the system's allowable limits, the ball on the touch panel may detach, resulting in an "air ball" state, in which the system cannot measure the position of the ball, leading to instability. To address the air ball state, a compensator consisting of a closed-loop observer and full-state feedback for the ball-on-plate system is designed. A model for the closed-loop observer was created by modeling the ball-on-plate system. Experiments confirmed that the system could maintain stable control even in an air ball state.

In general, rotor inertia has an inversely proportional relationship with proportional gain and bandwidth in a turret speed control system of machine tools; thus, this system has a disadvantage, such as weak disturbance caused by a decrease in the damping ratio and an increase in bandwidth due to low rotor inertia. This paper proposes a damping compensator that is resistance to disturbances in order to improve the above problems. The proposed damping compensator reduces the residual vibration induced in the transient state by using a digital high-pass filter. The experimental results showed that the overshoot was reduced by about 5.5% in the speed response and by about 20% in the torque response in the no-load condition. Under the load condition of 4.8 N.m, the torque response showed that the undershoot was reduced by about 26%.

The need for automated material handling inside the factory has been steadily increasing, especially due to implementation of intelligent manufacturing for better productivity and product quality. Automated material handling devices include logistics robots, automated guided vehicles, industrial robots, collaborative robots, and pick-and-place devices. This study focuses on the development of a low-cost logistics robot that works effectively within a simulated smart factory environment. A nominal PID controller is implemented to guide the robot to follow the line painted on the factory floor. The tracking error information is generated by four down-facing infrared sensors and is fed into the controller. The line-following performance is significantly improved with augmentation of a model-based friction compensator. Optimization of battery power depending on the remaining charge status enhances the reliability. All hardware/software development is supported by the Arduino platform. The step-by-step movement and performance of the logistics robot is verified inside the simulated smart factory environment that includes a robot arm, three conveyors, and two processing stations.