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This paper focuses on the adaptive control of robot manipulators with closed architecture and parametric uncertainty. We propose a new class of adaptive controllers via exploiting the potential as applying the forwardstepping approach and the input–output properties of an inverted form of the dynamics of robots with closed architecture. The condition that ensures the stability and convergence of the closed-loop system becomes rather moderate due to the new design and analysis, and the result presented further enhances the connection between nonlinear control theory and most industrial/commercial robotic applications. [ABSTRACT FROM AUTHOR]

This brief investigates the image-space regulation problem for visually servoed robotic systems by considering the uncertainties in the camera model and the manipulator kinematics and dynamics. By exploiting the depth-related passivity of the overall system kinematics, we first propose an adaptive dynamic controller that avoids the image-space velocity measurement by introducing a filter. In addition, we further show how to utilize the passivity property to design an adaptive kinematic control scheme, which simplifies the controller structure of the visually servoed robotic systems with the assumption that the low-level control loop can guarantee the square-integrability and boundedness of the joint velocity tracking error. We prove that both the proposed adaptive controllers can ensure the asymptotic convergence of the image-space position error. The results from a numerical simulation and extensive experimental studies illustrate the performance of the proposed adaptive image-space regulation control schemes. [ABSTRACT FROM AUTHOR]

This paper investigates adaptive zero reaction motion control for free-floating space manipulators with uncertain kinematics and dynamics. The challenge in deriving the adaptive reaction null-space (RNS)-based control scheme is that it is difficult to obtain a linear expression, which is the basis of the adaptive control. The main contribution of this paper is that we skillfully obtain such a linear expression, based on which, an adaptive version of the RNS-based controller (referred to as the adaptive zero reaction motion controller in the sequel) is developed at the velocity level, taking into account both the kinematic and dynamic uncertainties. It is shown that the proposed controller achieves both the spacecraft attitude regulation and end-effector trajectory tracking. The performance of the proposed adaptive controller is shown by numerical simulations with a planar three-degree-of-freedom space manipulator. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the visual tracking problem for robotic systems without image-space velocity measurement, simultaneously taking into account the uncertainties of the camera model and the manipulator kinematics and dynamics. We propose a new image-space observer that exploits the image-space velocity information contained in the unknown kinematics, upon which, we design an adaptive controller without using the image-space velocity signal where the adaptations of the depth-rate-independent kinematic parameter and depth parameter are driven by both the image-space tracking errors and observation errors. The major superiority of the proposed observer-based adaptive controller lies in its simplicity and the separation of the handling of multiple uncertainties in visually servoed robotic systems, thus avoiding the overparametrization problem of the existing work. Using Lyapunov analysis, we demonstrate that the image-space tracking errors converge to zero asymptotically. The performance of the proposed adaptive control scheme is illustrated by a numerical simulation. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the flocking problem for multiple uncertain mechanical systems interacting on directed topologies. We propose an integral-sliding adaptive control to realise the objective of flocking, which gives rise to a cascade closed-loop system, and also propose a new notion – iBIBO (integral-bounded-input bounded-output) stability to characterise a new input–output property of a special class of dynamical systems, which is then used for the stability analysis of the closed-loop system. With the proposed iBIBO analysis tool and Lyapunov-like approach, we show that the proposed adaptive controller ensures the position and velocity consensus of the mechanical systems if and only if the damping is greater than certain lower bound for a given stiffness, and that the velocities of the mechanical systems converge to the weighted average of their initial values and the positions of the mechanical systems converge to the initial-states-dependent ramp trajectory. The performance of the proposed adaptive control scheme is shown by numerical simulation results. [ABSTRACT FROM PUBLISHER]

In this paper, we present a tutorial on passivity based attitude control that has been investigated over the past two decades. Both regulation control and adaptive tracking control for the attitude motion of rigid bodies are discussed under a unified passivity framework. Our attention is mainly confined to the attitude control schemes that are based on the passivity notion. Output feedback attitude control, attitude synchronization, and some open problems are also discussed. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the problem of task-space synchronisation of multiple robotic agents in the presence of uncertain kinematics and dynamics. Our control objective is to realise synchronisation without the measurements of task-space velocity. The communication topology is assumed to be directed graphs containing a spanning tree. A decentralised task-space observer with kinematic parameter updating is proposed to avoid the reliance of task-space velocity. Based on the observer, we propose the distributed adaptive synchronisation controller for two cases: (1) the leaderless consensus case and (2) the leader-follower case, where all the followers track the convex hull spanned by the virtual leaders and for each follower, it is required that there exists at least one leader that has a directed path to the follower. The asymptotic synchronisation is proved with Lyapunov analysis and input–output stability analysis tools. Simulations with multiple robotic agents are performed to show the effectiveness of the proposed schemes. [ABSTRACT FROM PUBLISHER]

Abstract: This paper is devoted to the investigation of adaptive inverse dynamics for free-floating space manipulators (FFSMs) suffering from parameter uncertainties/variations. To overcome the nonlinear parametric problem of the dynamics of FFSMs, we introduce a new regressor matrix called the generalized dynamic regressor. Based on this regressor, and with Lyapunov stability analysis tools, we obtain a new parameter adaptation law and show that the closed-loop system is stable, and that the joint tracking errors converge asymptotically to zero. Simulation results are provided to illustrate the performance of the proposed adaptive algorithm. Furthermore, we conduct a comparative study between adaptive inverse dynamics, prediction error based adaptation, and passivity based adaptation. [Copyright &y& Elsevier]

Abstract: It has been about two decades since the first globally convergent adaptive tracking controller was derived for robots with dynamic uncertainties. However, not until recently has the problem of concurrent adaptation to both the kinematic and dynamic uncertainties found its solution. This adaptive controller belongs to passivity-based control. Though passivity-based controllers have many attractive properties, in general, they are not able to guarantee the uniform performance of the robot over the entire workspace. Even in the ideal case of perfect knowledge of the manipulator parameters, the closed-loop system remains nonlinear and coupled. Thus the closed-loop tracking performance is difficult to quantify, while the inverse dynamics controllers can overcome these deficiencies. Therefore, in this work, we will develop a new adaptive Jacobian tracking controller based on the inverse manipulator dynamics. Using the Lyapunov approach, we have proved that the end-effector motion tracking errors converge asymptotically to zero. Simulation results are presented to show the performance of the proposed controller. [Copyright &y& Elsevier]

Abstract: Most research so far on trajectory tracking of free-floating space manipulators has assumed that the kinematics of the space manipulator is exactly known. However, when a space manipulator picks up different tools of unknown lengths or unknown gripping points, its kinematics and dynamics change and are difficult to derive exactly. Thus, in this paper, we have proposed a passivity based adaptive Jacobian controller for free-floating space manipulators. The proposed controller consists of a transposed Jacobian feedback and a dynamic compensation term, and the parameter adaptation laws are derived by Lyapunov-like stability analysis tools. It is shown that the end-effector motion tracking errors converge asymptotically. To avoid using spacecraft acceleration, we define a new reference velocity, which is called spacecraft reference velocity. In addition, we have also conducted passivity interpretation of the proposed controller to obtain some physical insight into its properties. Simulation results are presented to show the performance of the proposed controller. [Copyright &y& Elsevier]

Most research so far on force/position tracking control of robots has assumed that the kinematics and dynamics are exactly known. In this work, we deal with force/position tracking under uncertainties arising from robot kinematics, dynamics, surface stiffness and position with an emphasis on uncertain kinematics. A robot with uncertain kinematics and dynamics in contact with a compliant surface is considered. A new adaptive Jacobian controller has been designed to cope with the uncertain robot kinematics, dynamics, environmental stiffness and position. It is shown that the controller can achieve force and position tracking via Lyapunov stability analysis. Simulation results demonstrate the performance of the controller. [ABSTRACT FROM AUTHOR]

This paper investigates bilateral control of teleoperators with nonlinearity and uncertainty and with arbitrary bounded unknown time-varying delay. We propose two new approaches for teleoperators: a composite approach and a direct approach, and both the approaches are shown to be capable of guaranteeing the stability and infinite manipulability of teleoperators with degree one independent of the time-varying delay. The distinctive point lies in the introduction of a direct channel between the external input sources (from either the human operator or environment) and consensus equilibrium increment of the teleoperator, guided by the design paradigm for ensuring the infinite manipulability. It is demonstrated that the composite approach improves the performance of the teleoperator, and that the direct approach yields separation between the controlled dynamics of the teleoperator and the objective of achieving synchronization and infinite manipulability of the teleoperator. We also propose a hybrid bilateral controller for a typical application context. The application scenarios of the proposed approaches are further demonstrated by extensive simulation results. [ABSTRACT FROM AUTHOR]