Vibrations are usually caused by continuous disturbances with large amplitudes. Different from other control methods, disturbance rejection control is a potential method, which considers the unknown disturbances in the control design. To remedy the shortcomings of the existing disturbance rejection control in the vibration reduction of structures especially under high-frequency periodic disturbances, this paper aims to improve the control ability of the current disturbance rejection control for the vibration suppression of smart structures under any unknown periodic disturbances with high-order frequency or random disturbances varying fast. Afterwards, the refined disturbance rejection control is compared with the previously designed disturbance rejection control with proportional–integral observer and disturbance rejection control with generalized proportional–integral observer on both theoretical and numerical levels.
This paper presents the development of a soft rehabilitation robot to conduct Continuous Passive Motion (CPM) for hand rehabilitation. The main contribution of this work is the implementation of a McKibben actuator as an artificial muscle due to its proven advantages: simple structure, light weight, and high power-to-weight ratio. The development worked successfully when tested on a healthy subject, where the flexion and extension of the finger were controlled with an antagonistic pair of actuators. However, there is a limitation of the McKibben actuator regarding its length-dependency. In this research, the concept of a pulley system was proposed to overcome this limitation. Although there is a friction factor that reduces the contracting displacement by at least 15% of the original displacement, a pulley is still a potential solution as it can reduce the installation space of the actuator from 40 to 15cm while still producing sufficient force for the finger motion. Throughout this research, it was found that the pattern of the flexor pulley system is affecting the system’s efficiency in terms of motion assistance.
Cutting force in broaching process is essential information for quality controlling, troubleshooting and tool life prediction, yet existing technical bottleneck in prediction and acquirement in internal spline holes broaching process. Based on the mechanics of orthogonal metal cutting, a numerical model of the cutting force in internal spline broaching is constructed by Johnson-Cook material constitutive and failure model taking friction on both rake face and flank face into consideration, and is used to numerically estimate the cutting forces. A measurement apparatus is developed and real-time cutting force is monitored, which contains the effects of structural vibration and can be divided into static cutting force and dynamic cutting force. Wavelet transform filtering method is therefore employed to separate the static component from dynamic component. Calculated value of the cutting force by numerical model is in good agreement with the static cutting force by experimental measuring. The model and measurement method are feasible in intelligent manufacturing where internal broaching process is used.
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