Large optical mirrors for space applications require accurate surface evaluation between successive corrective machining steps. Without proper compensation for self-weight, gravitational deformation can affect the measured surface figure and thereby reduce the reliability of the machining process. In this study, an air-cylinder-based gravity compensation device was developed to maintain the target support loads for large optical mirrors. A proportional–integral–derivative (PID) controller with load-cell feedback was implemented, and the initial gains obtained using the Ziegler–Nichols method were retuned on the basis of the measured system response. Single-axis experiments showed that the retuned controller met the specified performance requirements for overshoot, settling time, and steady-state error, even when applied to air cylinders with different spring reaction forces. The validated control method was then applied, via a sequential multi-channel control scheme, to a five-axis gravity compensation system to assess its applicability to multi-point gravity compensation. The experimental results confirmed stable convergence to the target support loads and effective load regulation at steady state, demonstrating that the proposed system is suitable for the multi-point gravity compensation of large optical mirrors.

Carrying heavy objects in agricultural and industrial sites is the most basic labor, which requires a lot of energy. Many equipment such as crane, chain block, elevator, and forklift truck has been developed to reduce human power. Nevertheless, many tasks require human labor. In addition, rapid aging is increasing musculoskeletal diseases in industrial workers. Consequently, various muscle auxiliary wear robots and devices are being developed. In this study; a passive upper limbs exoskeleton (H-Frame) was developed to help carry over 20 kg of weight in industrial and agricultural sites. For the functional test of the developed H-Frame, tests were carried out for 20, 30, and 40 kg of each box. To measure the objective and numerical data of the H-Frame, various sensor values such as EMG (Electromyography), harness compression force sensor, and load cell value of side support and rope were measured. EMG and metabolic experiments were also performed on 8 subjects before and after wearing the device. The average value of the upper extremity muscle showed a 44% reduction effect after wearing. The device helped the wearer when carrying heavy objects. It could help prevent musculoskeletal diseases in industrial and agricultural fields.