Angular positioning and vibration control of a slewing flexible control by applying smart materials and sliding modes control

Abstract

Flexible links undergoing a slewing motion are widely found in aerospace structures such as satellites and robotic manipulators. In this kind of systems, the lighter the structure the better is its performance and more cost effective is the system. However, the positioning control of flexible structures is challenging because the flexibility may lead the system to vibrate in larger amplitudes, which makes the need of using actuators to control and reduce vibrations. An alternative for those actuators is the use of smart materials, as SMA (Shape Memory Alloys) to control vibrations of such structures. This work will present the angular positioning and vibration control of a flexible link. The angular position control is a torque driven by a DC motor controlled through a sliding modes control method. The system is considered as non-ideal, it means that the vibration of the flexible link accomplishes to the DC motor shaft. SMA actuators are coupled to the flexible link with the objective to reduce the vibration amplitudes and reducing so the settling time of the system. The SMA actuators are controlled through an electric voltage applied to its terminals by applying the Sliding modes control method. The dynamical equations of motion for the system are developed considering a dead zone nonlinearity of the DC motor and a phenomenological model for the SMA. The flexible link is modeled as a continuous structure and just the first vibration mode is analyzed. Numerical simulations results are presented to demonstrate the effectiveness of the sliding modes strategy for the positioning control of the DC motor and for the vibration suppression of the flexible link by using SMA actuators.