The tower crane is widely used in construction and transportation engineering. To improve working efficiency and safety, input shaping methods have been applied. Input shaping is a method of reducing residual vibration of flexible systems by convolving a sequence of impulses with unit step command. However, input shaping is based on the linear system theory in which its control performances are degraded, in case of nonlinearity and unmatched dynamics of the control systems. In this paper, a new optimal reference input shape design method based on minimizing cost function is suggested and applied, to a simple cart-pendulum system which is a simplified model of tower cranes. Since pendulum dynamics is nonlinear, analytic solution does not exist. To overcome this problem, in this paper, a machine learning approach is suggested to find optimal reference input shape for the cart position control. The feasibility of the proposed design method is verified through some simulation examples by using MatLab.

An elevating drone station is very useful when lifting and lowering the battery charging station for safe installation, maintenance, and energy efficiency of a drone operation. When drone station modules rise above the average roof level of neighboring structures they may receive a strong wind force; thus, understanding the physical phenomena of both the structures and fluid is important to understand the structure"s reaction to the wind force. However, most studies in the field of drone stations did not perform a structural safety evaluation under wind loadings. Therefore, in this paper, we carried out a fluid-structure interaction analysis to verify the design of the lifting-and-lowering-type drone station.

The lifting-and-lowering type drone station is very useful when lifting and lowering the battery charging station for safe installation, maintenance, and energy efficiency of drone operation. Therefore, understanding the coupling motion between cable and pulley is important for evaluating characteristics like safety and dynamic stability of the lifting-and-lowering type drone station. Although multibody dynamics (MBD) is widely used for numerically analyzing the dynamic behavior of interconnected bodies, attempts to analyze the coupling motion between cable and pulley have been made only recently, within the last decade. Therefore, this paper attempts to develop the MBD model for the lifting-and-lowering type drone station, including cables, pulleys, and winches using MotionSolve (Altair). The results of the winch torque obtained analytically and numerically were compared to verify the effectiveness of the proposed MBD model.

The purpose of this study was to compare ankle joint loads (Linear and Angular Impulses) while descending the stairs and ramp. Ten young male subjects participated in this study. Stairs and ramp of identical slope (30 degrees) were custom-made to include force plates in the middle of pathways. Subjects descended the stairs and ramp at a comfortable speed and posture. The stance period was divided into three phases, weight acceptance (WA), single limb stance, and pre-swing. Three-directional impulses and their sum were derived from the reaction forces and moments at the ankle joint. Differences in impulse sums (Both Linear and Angular) between stairs and ramp were significant only in the early (WA) phase, whereas those of stairs were greater than the ramp. All subjects adopted forefoot strike strategy for the stairs and 80% of the subjects adopted rearfoot strike strategy for the ramp. An increase in the GRF and moment arm of the GRF at the ankle joint in case of forefoot strike may have contributed to the increase in the linear and angular impulse in the early phase of stair descent compared to ramp descent. The results are in agreement with the preference of ramp in the elderly.