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A novel actor–critic–identifier architecture for approximate optimal control of uncertain nonlinear systems ✩ Keywords: Learning control Adaptive control Optimal control Approximate dynamic programming Actor–critic–identifier a b s t r a c t An online adaptive reinforcement learning-based solution is developed for the infinite-horizon optimal control(More)
—A continuous controller is developed for a robot that moves in free space, undergoes a collision with a viscoelastic environment , and then regulates the new coupled dynamic system to a desired setpoint. Since the model for the viscoelastic surface contains uncertainties that do not satisfy the linear-in-the-parameters assumption, the model is approximated(More)
—The problem of prescribing, reducing, or controlling the interaction forces between a robot and the environment during a noncontact-to-contact transition is intriguing because large interaction forces can damage both the robot and/or the environment or lead to degraded performance or instabilities. In this paper, we consider a two-link planar robotic arm(More)
Adaptive critic (AC) based controllers are typically discrete and/or yield a uniformly ultimately bounded stability result because of the presence of disturbances and unknown approximation errors. A continuous-time AC controller is developed that yields asymptotic tracking of a class of uncertain nonlinear systems with bounded disturbances. The proposed(More)
Keywords: Time-varying systems Optimal control Adaptive control Tracking applications Actor–critic a b s t r a c t Adaptive dynamic programming has been investigated and used as a method to approximately solve optimal regulation problems. However, the extension of this technique to optimal tracking problems for continuous-time nonlinear systems has remained(More)
Controlling a nonlinear system with actuator delay is a challenging problem because of the need to develop some form of prediction of the nonlinear dynamics. Developing a predictor-based controller for an uncertain system is especially challenging. In this paper, tracking controllers are developed for an Euler–Lagrange system with time-delayed actuation,(More)
—A continuous robust adaptive control method is designed for a class of uncertain nonlinear systems with unknown constant time-delays in the states. Specifically, a robust adaptive control method and a delay-free gradient-based desired compensation adaptation law (DCAL) are utilized to compensate for unknown time-delays, linearly parameterizable(More)
—An approximate online solution is developed for a two-player zero-sum game subject to continuous-time nonlinear uncertain dynamics and an infinite horizon quadratic cost. A novel actor-critic-identifier (ACI) structure is used to implement the Policy Iteration (PI) algorithm, wherein a robust dynamic neural network (DNN) is used to asymptotically identify(More)
—With the motivation of using more information to update the parameter estimates to achieve improved tracking performance, composite adaptation that uses both the system tracking errors and a prediction error containing parametric information to drive the update laws, has become widespread in adaptive control literature. However, despite its obvious(More)