Adaptive control of space-based robot manipulators (original) (raw)
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ROBUST REACTION CONTROL OF SPACE MANIPULATORS
The minimization of the dynamic disturbances transferred to the base spacecraft by a redundant manipulator during operations is an important issue in space robotic missions, because it leads to reduced energy consumption of the Attitude Control System and, therefore, to an increased system operating life. The use of redundant manipulators makes it possible to perform the required tasks and in the meantime minimize the reactions transferred to the base spacecraft and possibly other additional performance criteria, which can be used to increase the robustness of the solution. A robust solution should at least take into account the joint limits, the joint velocity and acceleration limits, and the avoidance of algorithmic and dynamic singularities. The method proposed in this paper consists in using the recently developed least squares reaction control solution, which can take into account the joint acceleration limits in the real-time solution, and modifying it in order to take into account the joint and the joint velocity limits. The method is based on the concept that it is possible to impose joint and joint velocity limits indirectly, by computing the related joint acceleration limits, which are the ones that are used in the solution algorithm. In this way a robust solution is obtained, which attains a twofold objective: from one side the physical limits of the manipulator joints are taken into accounts, and from the other side the method can be used to avoid manipulator dynamic and algorithmic singularities, thanks to the imposed change of the history in the joint space. The proposed robust reaction control method has been validated by means of software simulations, which helped to demonstrate the proposed concepts and to evaluate their pros and cons.
Adaptive control of free-floating space manipulators
SMC 2000 Conference Proceedings. 2000 IEEE International Conference on Systems, Man and Cybernetics. 'Cybernetics Evolving to Systems, Humans, Organizations, and their Complex Interactions' (Cat. No.00CH37166), 2000
In this paper, adaptive control of free-floating space manipulators is considered. The dynamics based on the momentum conservation law for the free-floating space manipulator has non-linear parameterization properties. Therefore, the adaptive control based on a linear parameterization model cannot be used in this dynamics. In this paper, the dynamics of the free-floating space manipulator system are derived using the Dynamically Equivalent Model (DEM) approach. The DEM is a fixed-base manipulator system and allows us to linearly parameterize the dynamic equations. Using this linearly parameterized dynamic equation, an adaptive control method is developed to control the system in joint space. Parameter identification and torque calculations are done using the DEM dynamics. Simulations show that the tracking errors of the manipulator joints to a given desired trajectory become zero when the calculated torques act on the joints of the space manipulator system.
Multiple Model Adaptive Control in Uncertain Dynamic Model of Space Manipulator
—In this paper, Multiple Model Adaptive Control approach is utilized in an uncertain dynamic model of free floating space manipulator. Uncertainty issue in the Space manipulator is a significant concern that must be resolved by an efficient control approach. The uncertainty challenge triggers problematic outcomes when uncertainty bound is large. Therefore, multiple model adaptive control approach is exerted in the dynamic model of space manipulator that switches over manifold controllers to handle the uncertainty issue. In order to subside switching deficiency an aggregation of weighted control signals, as the main control law, is used in the model. Simulation results show desirable outcomes.
Trajectory tracking control of flexible-joint space manipulators
Canadian Aeronautics and Space Journal, 2012
Operational problems with robots in space relate to several factors. One of the most important factors is the elastic vibrations in the joints. In this paper, control strategies for endpoint tracking of a 12.6 m)12.6 m trajectory by a two-link space robotic manipulator are reviewed. Initially, a manipulator with rigid joints is actuated using a transpose jacobian control law and a model reference adaptive control system that adapts, in real-time, the control gains in response to errors between the actual system outputs and the ideal system outputs defined by a reference model. The rigid-joint dynamics model was pursued further to study a manipulator with flexible joints modeled with linear-and nonlinear-joint stiffness models. Then, the two rigid-joint control schemes were modified using the singular perturbation-based theory and applied for the control of both linear and nonlinear flexible-joint robot models. Finally, the rigid and flexible control systems described in this paper were evaluated in numerical simulations. Simulation results suggested that greatly improved tracking accuracy can be achieved by applying the adaptive control strategies.
Journal of Dynamic Systems, Measurement, and Control, 2018
In this study, a continuous robust-adaptive operational space controller that ensures asymptotic end-effector tracking, despite the uncertainties in robot dynamics and on the velocity level kinematics of the robot, is proposed. Specifically, a smooth robust controller is applied to compensate the parametric uncertainties related to the robot dynamics while an adaptive update algorithm is used to deal with the kinematic uncertainties. Rather than formulating the tracking problem in the joint space, as most of the previous works on the field have done, the controller formulation is presented in the operational space of the robot where the actual task is performed. Additionally, the robust part of the proposed controller is continuous ensuring the asymptotic tracking and relatively smooth controller effort. The stability of the overall system and boundedness of the closed loop signals are ensured via Lyapunov based arguments. Experimental results are presented to illustrate the feasibi...
Strategies for Control of Space Robots: A Review and Research Agenda
Modelling and control of space robots is not an easy task to perform, because the equations of motion that govern phenomenon are highly nonlinear. Furthermore, unlike fixed base manipulators a freefloating space robot exhibits non-holonomic behavior as a result of the non-integrability of the angular momentum conservation law. In recent days space robots are extensively used to play a significant role in space applications like, scheduled servicing of satellites and spacecrafts including refuelling tasks, inspection of remote sites or verification of structures, retrieval of tumbling tools or astronauts, and assembly or welding of space structures. In a large number of these applications, the manipulator endeffector is required to interact with the environment. Due to the interaction between the endeffector and the environment, the interaction torques act on the endeffector which gets transmitted through links to the base of the vehicle and the orientation of the vehicle changes. He...
Modelling and control of space robots is not an easy task to perform, because the equations of motion that govern phenomenon are highly nonlinear. Furthermore, unlike fixed base manipulators a freefloating space robot exhibits non-holonomic behavior as a result of the non-integrability of the angular momentum conservation law. In recent days space robots are extensively used to play a significant role in space applications like, scheduled servicing of satellites and spacecrafts including refuelling tasks, inspection of remote sites or verification of structures, retrieval of tumbling tools or astronauts, and assembly or welding of space structures. In a large number of these applications, the manipulator endeffector is required to interact with the environment. Due to the interaction between the endeffector and the environment, the interaction torques act on the endeffector which gets transmitted through links to the base of the vehicle and the orientation of the vehicle changes. Hence, precise control of the manipulator's trajectory, attitude and impedance are critically important. This paper addressed the current state-oftheart in key areas of the space robotics by reviewing recently available literatures particularly on free flying and free floating space robots which help in summarizing various research outcomes in a structured manner.
Robust Trajectory Tracking Control of Space Manipulators in Extended Task Space
Pomiary Automatyka Robotyka
This study provides a new class of controllers for freeflying space manipulators subject to unknown undesirable disturbing forces exerted on the end-effector. Based on suitably defined taskspace non-singular terminal sliding manifold and the Lyapunov stability theory, we derive a class of estimated extended transposed Jacobian controllers which seem to be effective in counteracting the unstructured disturbing forces. The numerical computations which are carried out for a space manipulator consisting of a spacecraft propelled by eight thrusters and holonomic manipulator of three revolute kinematic pairs, illustrate the performance of the proposed controller.