Adaptive hybrid suppression control of space free-flying robots with flexible appendages

Abstract

SUMMARYControl of rigid–flexible multi-body systems in space, during cooperative manipulation tasks, is studied in this paper. During such tasks, flexible members such as solar panels may vibrate. These vibrations in turn can lead to oscillatory disturbing forces on other subsystems, and consequently may produce significant errors in the position of operating end-effectors of cooperative arms. Therefore, to design and implement efficient model-based controllers for such complicated nonlinear systems, deriving an accurate dynamics model is required. On the other hand, due to practical limitations and real-time implementation, such models should demand fairly low computational complexity. In this paper, a precise dynamics model is derived by virtually partitioning the system into two rigid and flexible portions. These two portions will be assembled together to generate a proper model for controller design. Then, an adaptive hybrid suppression control (AHSC) algorithm is developed based on an appropriate variation rule of a virtual damping parameter. Finally, as a practical case study a space free-flying robot (SFFR) with flexible appendages is considered to move an object along a desired path through accurate force exertion by several cooperative end-effectors. This system includes a main rigid body equipped with thrusters, two solar panels, and two cooperative manipulators. The system also includes a third and fourth arm that act as a communication antenna and a photo capturing camera, respectively. The maneuver is deliberately planned such that flexible modes of solar panels get stimulated due to arms motion, while obtained results reveal the merits of proposed controller as will be discussed.

Cooperative Manipulation

“…Such a paradigm is aimed at enforcing an equivalent impedance relationship both at the manipulator end-effectors and at the grasped object level. The MIC approach has been recently extended to the cooperative manipulation of flexible objects in Zarafshan et al (2016).…”

Dynamics and robust control of a space manipulator with flexible appendages for on-orbit servicing

“…Solutions minimizing flexible appendages coupling with the SMS through optimized trajectories [19] or using coupling factors in the control strategy [20], nonlinear Model Predictive Control minimizing disturbances form manipulator motions [21] have been adopted. Active control of vibrations disturbances, such as the use of piezoelectric actuators placed on the flexible elements [22] or joint variable stiffness control actuators [23], has shown limitations for actual missions. This can be illustrated with capture scenarios when target presents flexible appendages for instance.…”

“…For instance, a manipulator's end-effector trajectory optimization can include vibration suppression objectives while capturing a defined target [27] or an input disturbance torque can be included to improve control performances for an OOS operation [28]. The Newton-Euler approaches are mostly used to obtain the dynamics for a combination of rigid and flexible bodies system [29,30] but Lagrangian methods which are well suited to control design can also be adopted [31].…”

Robust fuzzy sliding mode control and vibration suppression of free-floating flexible-link and flexible-joints space manipulator with external interference and uncertain parameter

“…The flexible link has lightweight, less inertia, low energy consumption, sizeable working place, and high work efficiency. But, it may deform and vibrate [27,28,29]. The flexible joint, caused by the harmonic drive gears, can reduce the damage caused by a collision when the manipulator grabs the target object and can compensate for the torque.…”