Non-cooperative Target Satellite Research Articles

AN OPTIMAL GRASP PLANNER FOR SPACE ROBOTS USING CLAMPED B-SPLIE

Space manipulator is one of the key technologies to carry out on-orbit servicing and maintenance missions in the future. Until now, it is still a vast challenging mission to capture a non-cooperative target satellite by using a space robot, especially when the motion of the target satellite is tumbling. How to design a feasible and optimal grasping strategy is very important for the successfully capturing of non-cooperative target. Based on the concept of the Clamped B Spline, this paper investigates an optimal grasp planner for a kinematically redundant space manipulator to capture an arbitrarily rotating target, such as space debris, dysfunctional satellites, etc. The kinematics and dynamics of the space robotic system and non-cooperative target in pre- and post-capture phases are firstly introduced as the foundation for designing the grasp planner. With consideration of the kineto-statics duality of the non-cooperative target captured by a space robot, the concept of the force manipulability ellipsoid was derived and employed as an optimization index in the following grasp planning strategy design. Subsequently, the space robotic optimal grasping time and the target's terminal motion states are determined with consideration of the robotic capability map, the target motion prediction and the grasping direction of the space robotic end-effector. Furthermore, the joint trajectories are parameterized with time normalization using the clamped B-spline curves. The grasp planner of the space robot is then transformed as a multi-constraint, multi-objective nonlinear optimization issue with consideration of the space robotic joint angle, velocity, collision avoidance and end-effector's grasping cone limits, and solved by a constrained particle swarm optimization algorithm with adaptive inertia parameters. The designed grasp planning strategy is applied to a seven degree-of-freedom kinematically redundant manipulator mounted on a free-floating spacecraft base, and the successful capturing of a tumbling target satellite in space is realized. Simulation results are presented and demonstrated the feasibility and effectiveness of the proposed method.

On Orbit Capture and Control of Space Manipulator Based on Magneto Rheological

With the rapid development of space technology, the performance and technology of spacecraft is in the continuous improvement. The key technology for the non-cooperative target satellite on-orbit capture and control becomes very important. For the question of on orbit capturing a non-cooperative target, a method based on Magneto Rheological (MR) damper is proposed. There are many successful applications of MR damper in ground-base and aviation systems. However, the application of this device on a space manipulator has not been addressed yet. In this paper, A 6DOFs space robot is built in Maplesim, and analyses the kinematic and dynamic model, and the component of MR damper is also created, after simulation, the results shows that the angular velocities of joints and base has been smoothly dampen. Although the control algorithm is simple, it’s very valuable to use the MR damper in capture non-cooperative target.

Receding horizon guidance and control using sequential convex programming for spacecraft 6-DOF close proximity

This paper presents a receding horizon implementation of sequential convex programming for the spacecraft six-degree-of-freedom close proximity to a non-cooperative target satellite. With linearized relative translational dynamics and newly derived discrete rotational equations in terms of modified Rodrigues parameters, nonlinear system dynamics of the original optimal guidance and control problem for proximity are converted into convex ones for sequentially planning. The nonconvex constraint on field-of-view of the visual sensor pointing with coupled attitude and relative position is then approximately relaxed as a convex standard second-order cone, and concave spherical and ellipsoidal obstacle regions respectively around the target's body and solar arrays are convexified by affine constraints in terms of tangent planes. The original nonlinear optimal guidance and control problem is accordingly transformed into a series of second-order cone programming sub-problems via iteratively successive convexification with the trust region constraints, and sequentially solved using disciplined convex programming method. A close-loop guidance and control using the proposed sequential convex programming scheme is then demonstrated by means of receding horizon to robustly drive the spacecraft maneuvering close to the target. Numerical simulations and results reveal that the proposed method provides rapid and reliable guidance and control performance for six-degree-of-freedom close proximity and shows the potential for on-board implementations in real-time applications.

A parametric analysis of a controlled deployable space manipulator for capturing a non-cooperative flexible satellite

In the near future robotic systems will be playing an increasingly important role in space applications such as repairing, refueling, re-orbiting spacecraft and cleaning up the increasing amount of space debris. Space Manipulator Systems (SMSs) are robotic systems made of a bus (which has its own actuators such as thrusters and reaction wheels) equipped with one or more deployable arms. The present paper focuses on the issue of maintaining a stable first contact between the arms terminal parts (i.e. the end-effectors) and a non-cooperative target satellite, before the actual grasp is performed. The selected approach is a modified version of the Impedance Control algorithm in which the end-effector is controlled in order to make it behave like a mass-spring-damper system regardless of the reaction motion of the base, so to absorb the impact energy. The effects of non-modeled dynamics in control determination such as the structural flexibility of the manipulator and the target satellite are considered as well, and their impact on control effectiveness is analyzed. The performance of the proposed control architecture and a parametric analysis are studied by means of a co-simulation involving the MSC Adams multibody code (for describing the dynamics of the space robot and target) together with Simulink (for the determination of the control actions). The results show that the first contact phase of the grasping operation of a large satellite requires careful tuning of the control gains and a proper selection of the end-effector dimensions; otherwise, the large geometric and inertia characteristics of the target could lead to a failure with serious consequences. Both successful and underperforming cases are presented and commented in the paper.

A Non-Cooperative Satellite Feature Point Selection Method for Vision-Based Navigation System.

The number of feature points on the surface of a non-cooperative target satellite used for monocular vision-based relative navigation affects the onboard computational load. A feature point selection method called the quasi-optimal method is proposed to select a subset of feature points with a good geometric distribution. This method, with the assumption that all of the feature points are in a plane and have the same variance, is based on the fact that the scattered feature points can provide higher accuracy than that of them grouped together. The cost is defined as a function of the angle between two unit vectors from the projection center to feature points. The redundancy of a feature point is calculated by summing all costs associated with it. Firstly, the feature point with the most redundant information is removed. Then, redundancies are calculated again with the second feature point removed. The procedures above are repeated until the desired number of feature points is reached. Dilution of precision (DOP) represents the mapping relation between the observation variance and the estimated variance. In this paper, the DOP concept is used in a vision-based navigation system to verify the performance of the quasi-optimal method. Simulation results demonstrate the feasibility of calculating the relative position and attitude by using a subset of feature points with a good geometric distribution. It also shows that the feature points selected by the quasi-optimal method can provide a high accuracy with low computation time.

Detumbling strategy and coordination control of kinematically redundant space robot after capturing a tumbling target

This paper focuses on the motion planning to detumble and control of a space robot to capture a non-cooperative target satellite. The objective is to construct a detumbling strategy for the target and a coordination control scheme for the space robotic system in post-capture phase. First, the dynamics of the kinematically redundant space robot after grasping the target is presented, which lays the foundation for the coordination controller design. Subsequently, optimal detumbling strategy for the post-capture phase is proposed based on the quartic B $$\acute{\text{ e }}$$ zier curves and adaptive particle swarm optimization algorithm subject to the specific constraints. Both detumbling time and control torques were taken into account for the generation of the optimal detumbling strategy. Furthermore, a coordination control scheme is designed to track the designed reference path while regulating the attitude of the chaser to a desired value. The space robot successfully dumps the initial velocity of the tumbling satellite and controls the base attitude synchronously. Simulation results are presented for detumbling a target with rotational motion using a seven degree-of-freedom redundant space manipulator, which demonstrates the feasibility and effectiveness of the proposed method.

Performance Analysis and Gains Tuning Procedure for a Controlled Space Manipulator Used for Non-cooperative Target Capture Operations

In the near future robotic systems will be playing an increasingly important role in space applications such as repairing, refuelling, re-orbiting spacecraft and cleaning up the increasing amount of space debris. Space Manipulator Systems (SMSs) are robotic systems made of a bus (which has its own actuators such as thrusters and reaction wheels) equipped with one or more deployable arms. The present paper focuses on the issue of maintaining a stable first contact between the arms terminal parts (i.e. the end-effectors) and a non-cooperative target satellite, before the actual grasp is accomplished. The selected approach is a modified version of the Impedance Control algorithm, in which the end-effector is commanded in order to make it behave like a mass-spring-damper system regardless of the reaction motion of the base, so to absorb the impact energy. A very important aspect in the analysis of the control performance is the evaluation of the field of applicability of the controller itself. In the present work the influence of this issue on the effectiveness of the proposed control architecture will be analysed, together with the control gains tuning which allows for a robust achievement of the mission requirements. Several numerical results will be presented and discussed.

Safe path planning for free-floating space robot to approach noncooperative spacecraft

In order to eliminate plume impingement on the target satellite, a free-floating space robot (also known as a chaser), which has the advantage of executing on-orbit service, is always used. This paper develops a path planning method for a safe rendezvous of chaser with a noncooperative target satellite in orbital coordinates. Safety principles for rendezvous in terminal approaching phase are proposed. Grasp points on the target satellite are analyzed and classified into two categories, and a moving ellipse trajectory is adopted to approach a rotating and uncontrolled target satellite. This method guarantees that the chaser can successfully escape if unexpected error occurs or capture fails. The simulation results show that, with this novel autonomous rendezvous method, the chaser can approach the noncooperative target satellite along the designated trajectory in any quadrant of the orbital plane.

Development and hardware-in-the-loop test of a guidance, navigation and control system for on-orbit servicing

The rendezvous phase is one of the most important phases in future orbital servicing missions. To ensure a safe approach to a non-cooperative target satellite, a guidance, navigation and control system which uses measurements from optical sensors like cameras was designed and developed. During ground-based rendezvous, stability problems induced by delayed position measurements can be compensated by using a specially adapted navigation filter. Within the VIBANASS (VIsion BAsed NAvigation Sensor System) test campaign, hardware-in-the-loop tests on the terrestrial, robotic based facility EPOS 2.0 were performed to test and verify the developed guidance, navigation and control algorithms using real sensor measurements. We could demonstrate several safe rendezvous test cases in a closed loop mode integrating the VIBANASS camera system and the developed guidance, navigation and control system to a dynamic rendezvous simulation.

On Grasping a Tumbling Debris Object with a Free-Flying Robot

The grasping and stabilization of a tumbling, non-cooperative target satellite by means of a free-flying robot is a challenging control problem, which has been addressed in increasing degree of complexity since 20 years. A novel method for computing robot trajectories for grasping a tumbling target is presented. The problem is solved as a motion planning problem with nonlinear optimization. The resulting solution includes a first maneuver of the Servicer satellite which carries the robot arm, taking account of typical satellite control inputs. An analysis of the characteristics of the motion of a grasping point on a tumbling body is used to motivate this grasping method, which is argued to be useful for grasping targets of larger size.