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An adaptive fuzzy backstepping optimal control method is developed for modular robot manipulators (MRMs) via value iteration (VI). This paper adopts joint torque feedback (JTF) technique to construct subsystem dynamics model, and the state space description is deduced. According to fusion function which contains the error in joint angular velocity and position, the cost function is established. The integral reinforcement learning (IRL) is integrated into the VI algorithm, which solves the optimal tracking control issue without system drift dynamics. For purpose of improving the control effect, the optimal tracking control issue of manipulator can be reconsidered as the optimal compensation issue which adopting the local dynamics information. Then the uncertainty in the model can be compensated by an adaptive fuzzy backstepping compensation controller which is constructed by fuzzy logic system (FLS) and backstepping control method. The optimal compensation control strategy is adopted to deal with the interconnected dynamic coupling (IDC), which contains global information about each joint. Based on the VI algorithm and adaptive dynamic programming (ADP) method, an effective solution of Hamiltonian-Jacobi-Bellman (HJB) equation is presented. According to Lyapunov theorem, the trajectory tracking error is uniformly ultimately bounded (UUB) by using the adaptive fuzzy backstepping optimal control method. Finally, the effectiveness of the proposed method is verified by experiments. [ABSTRACT FROM AUTHOR]

Major challenges of controlling physical human–robot interaction (pHRI)-oriented modular robot manipulator (MRM) include performance optimization and solving the coupling effect between the human and the robot as well as MRM subsystems. In this paper, a cooperative game-based decentralized optimal control approach is developed for MRMs with pHRI. The joint torque feedback (JTF) technique is utilized to form the MRM dynamic model, then, the major objective of optimal control with pHRI is transformed into approximating Pareto equilibrium by adopting cooperative game governed between the human and the MRM that are regarded as players with different tasks and optimization criteria in interaction process. On the basis of adaptive dynamic programming (ADP) algorithm, the decentralized approximate optimal control strategy with pHRI is developed by a critic neural network (NN)-based cooperative game manner for solving the coupled Hamilton–Jacobian–Bellman (HJB) equation. The position tracking error under pHRI is verified to be ultimately uniformly bounded (UUB). Experiment results have been presented, which exhibit the superiority of the proposed method. [ABSTRACT FROM AUTHOR]

This paper proposes a decentralized variable impedance control method of modular robot manipulators (MRM) with physical human-robot interaction (pHRI) using Gaussian process-based motion intention estimation. The dynamic model of MRM subsystem is established by using joint torque feedback (JTF) technique. Human limb dynamic model is regarded as mechanical impedance model, and human motion intention is estimated online based on Gaussian process. A variable impedance control method is proposed to make the MRM comply with human motion intention in the process of pHRI. A decentralized sliding mode control strategy is designed to achieve high performance position tracking and compensate the uncertainty of the controller. Based on Lyapunov theory, the uniform ultimately bounded of tracking error of each joint is proved. Finally, the effectiveness of the proposed control method under pHRI is verified by experiments. The experimental results show that the proposed method reduces the position tracking error by ∼ 10% and the interaction force by ∼ 20% compared with the existing control methods. [ABSTRACT FROM AUTHOR]

For the problem of dynamic contact force tracking control under physical human-robot interaction (pHRI), we propose a dual closed-loop adaptive decentralized control framework. The dynamic model of modular robot manipulator (MRM) subsystem is established based on joint torque feedback (JTF) technology. On the basis of fully analyzing the model uncertainty, the method based on decomposition is used to dynamically compensate the model uncertainty. Using Lyapunov theory, the uniform and ultimate boundedness (UUB) of dynamic contact force tracking error and MRM position tracking error in pHRI process are confirmed. A neural network (NN) observer is designed to dynamically compensate the uncertainty of controller. Finally, the effectiveness of this method is verified by experiments. [ABSTRACT FROM AUTHOR]

This paper develops a data-driven multiplayer mixed-zero-sum game control approach of modular robot manipulators (MRMs) with uncertain disturbance via adaptive dynamic programming (ADP). The dynamic model of MRMs is formulated via joint torque feedback. We deem n modules and uncertain disturbance as players in the game theory structure. The uncertainties in the MRM system such as joint friction and interconnected dynamic couplings (IDCs), we employ data-driven model based on recurrent neural networks (RNNs) to built. According to ADP, the Hamilton-Jacobi (HJ) equation can be solved by using critic neural networks and derivate the optimal control law. The closed-loop robotic system is proved to be asymptotic stable via mixed-zero-sum game control. Experiments are conducted to verify the effectiveness. [ABSTRACT FROM AUTHOR]

A critic-observer decentralized force/position approximate optimal control method is presented to address the joint trajectory and contacted force tracking problem of modular and reconfigurable manipulators (MRMs) with uncertain environmental constraints. The dynamic model of the MRM systems is formulated as an integration of joint subsystems via extensive state observer (ESO) associated with the effect of interconnected dynamic coupling (IDC). A radial basis function neural network (RBF-NN) is developed to deal with the IDC effects among the independent joint subsystems. Based on adaptive dynamic programming (ADP) approach and policy iteration (PI) algorithm, the Hamilton–Jacobi–Bellman (HJB) equation is approximately solved by establishing critic NN structure and then the approximated optimal control policy can be derived. The closed-loop manipulator system is proved to be asymptotic stable by using the Lyapunov theory. Finally, simulation results are provided to demonstrate the effectiveness and advantages of the proposed control method. [ABSTRACT FROM AUTHOR]