https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1065&context=usafresearch

A review of space robotics technologies for on-orbit servicing

Considering gravity change from ground alignment to space applications, a fuzzy proportional-integral-differential (PID) control strategy is proposed to make the space manipulator track the desired trajectories in different gravity environments The fuzzy PID controller is developed by combining the fuzzy approach with the PID control method, and the parameters of the PID controller can be adjusted on line based on the ability of the fuzzy controller Simulations using the dynamic model of the space manipulator have shown the effectiveness of the algorithm in the trajectory tracking problem Compared with the results of conventional PID control, the control performance of the fuzzy PID is more effective for manipulator trajectory control

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Fuzzy PID Control of Space Manipulator for Both Ground Alignment and Space Applications

Abstract This paper addresses fixed-time trajectory tracking for a dual-arm free-floating space robot (FFSR) with the large initial errors and bounded uncertainty. A wrist-based trajectory planning method is improved by fixed-time stability to fast eliminate the error caused by singularity. Then, a novel low-chattering and global-nonsingular fixed-time terminal sliding mode control strategy is studied by state approaching angle and switching sliding mode; the practical fixed-reachable Lyapunov stability analysis is presented for a mechanical control system. In the end, the proposed trajectory planning method and controller are combined to improve the tracking accuracy of end-effector to the nanoscale. Simulation results validate the effectiveness of the proposed methodologies.

Trajectory planning and low-chattering fixed-time nonsingular terminal sliding mode control for a dual-arm free-floating space robot

Risk analysis and management of submerged floating tunnel and its application

: Space robotics has been considered one of the most promising approaches for on-orbit services (OOS) such as docking, berthing, refueling, repairing, upgrading, transporting, rescuing, and orbit cleanup. Many enabling techniques have been developed recently and several technology demonstration missions have been completed. Several manned servicing missions were also successfully accomplished but unmanned real servicing missions have not been done yet. All of the accomplished unmanned technology demonstration missions were designed to service perfectly known and cooperative targets only. Servicing a non-cooperative satellite in orbit by a robotic system is still an untested mission facing many technical challenges. One of the largest challenges would be how to ensure the servicing spacecraft and the robot to safely and reliably dock with or capture the target satellite and stabilizing it for subsequent servicing, especially if the serviced target is unknown regarding its motion and kinematics/dynamics properties. Obviously, further research and development of the enabling technologies are needed. To facilitate such further research and development, this paper provides a literature review of the recently developed technologies related to the kinematics, dynamics, control and verification of space robotic systems for manned and unmanned on-orbit servicing missions.

A Review of Robotics Technologies for On-Orbit Services

In this paper, the kinematics and dynamics of free-floating space robot system with dual-arms are analyzed, and it is shown that the Jacobian matrix and the dynamic equations of the system are nonlinearly dependent on inertial parameters. In order to overcome the above problems, the system is modeled as under-actuated robot system, and the idea of augmentation approach is adopted. It is demonstrate that the dynamic equations of the system can be linearly dependent on a group of inertial parameters. Based on the results, a robust variable structure control scheme for free-floating space robot system with dual-arms with uncertain inertial parameters to track the desired trajectory in joint space is proposed, and a planar space robot system with dual arms is simulated to verify the proposed control scheme. The advantage of the control scheme proposed is that it requires neither measuring the position, velocity and acceleration of the floating base with respect to the orbit nor controlling the position and attitude angle of the floating base. In addition to this advantage, it is computationally simple, because we choose to make the controller robust to the uncertain inertial parameters rather than explicitly estimating them online.

Robust Variable Structure Control for Free-floating Space Robot System with Dual-Arms in Joints Space

In this paper, the kinematics and dynamics of free-flying dual-arm space robot systems are analyzed. By use the method of multibody dynamics, the dynamics equations and Jacobi relationship of dual-arm space robot systems are established. Based on the results, the control problem for dual-arm space robot to track the desired trajectory in workspace is discussed. Because of the high structure complexity and the parameter uncertainly of dual-arm space robot systems, the scheme of variable structure control with better robustness to uncertainty and disturbance is proposed. The advantages of the control scheme proposed are that it need not to control the position of the base. To show the feasibility of the proposed control scheme, a simulation study of dual-arm space robot systems is presented.

Dynamic and Variable Structure Control for Dual-arm Space Robot to Track Desired Trajectory in Workspace

The robust control and active vibration suppression of a free-floating space flexible manipulator with an attitude-controlled base are studied. Combined the momentum conservation of the system, the dynamic equations are developed by using the Lagrangian method and assumed mode method. It is verified that the dynamic equations can be linearly dependent on a group of inertial parameters. Based on the results and under the assumption of two-time scale, a singular perturbation model of the space flexible manipulator system is obtained, then the controller can be designed separately to track desired trajectory and to suppress vibration. The fast subsystem controller will damp out the vibration of the flexible link using an optimal Linear Quadratic Regulator (LQR) method. The slow subsystem robust controller dominates the trajectory tracking of coordinated motion with uncertain system parameters. The numerical simulation is carried out, which confirms that the proposed controller is feasible and effective.

Robust control and active vibration control of space flexible manipulator by singular perturbation approach

In this paper, we propose a closed-loop attitude controller for a free-floating space robot with initial angular momentum, and the planar two-link space robot have two revolute joints. We process a kinematic analyse to the robot system and obtain a nonholonomic system with 3-state and 2-input. Then we choose a coordinate transformation, and convert the nonholonomic system into the time-state control form. We also use the exact linearization algorithm of a 1-input state equation to linearize the time-state control form. The attitude controller can be designed conveniently on the basis of the time-state control form. And the numerical simulation is carried out in this paper.

Chen Li

Papers

Robust Variable Structure Control for Free-floating Space Robot System with Dual-Arms in Joints Space

Dynamic and Variable Structure Control for Dual-arm Space Robot to Track Desired Trajectory in Workspace

Robust control and active vibration control of space flexible manipulator by singular perturbation approach

Attitude Control of a Space Robot with Initial Angular Momentum Using Time-State Control Form

Fuzzy Adaptive Control for Grasped Objects by Closed-chain Space Manipulator Based on Integral Sliding-mode