L1 Adaptive Output Feedback Controller Research Articles

Design and Implementation of an L1 Adaptive Proportional Output Feedback Controller

A new approach for output feedback L1 adaptive control based on a proportional adaptation law is presented. The effectiveness of this design is assessed in simulation and validated through real-time testing on an airfoil pitch control wind tunnel experimental rig. Experimental evaluation of the robustness of the controllers, assessed by introducing various disturbances into the control signals, shows that the adaptive control has a better performance compared to PID control, particularly in scenarios with reduced control effectiveness and time-varying disturbances. The experimental results demonstrate the efficacy of the proposed method in practical applications.

L1 adaptive output-feedback fault-tolerant control for uncertain nonlinear systems subject to unmodeled actuator dynamics and faults

This paper develops a L1 adaptive output-feedback fault-tolerant controller for uncertain nonlinear systems in the presence of unmodeled actuator dynamics and actuator faults. The proposed controller consists of the output predictor, adaptive laws, and the control law. The output predictor is a dynamic system expressed as a linear system with adaptive parameters which mean the matched uncertainties and the unmatched uncertainties. Piecewise-constant adaptive laws are designed to update the adaptive parameters so that the estimation error is driven to zero at each integration time step. The control law with low-pass filters is introduced to compensate for the performance degradation because of system uncertainties, unmodeled actuator dynamics and faults, and to guarantee the uniform boundedness of the input and output signals of the system. Two simulation examples verify the effectiveness of the proposed controller.

L 1 adaptive output feedback control for underactuated MIMO systems

Abstract This paper addresses the problem of output feedback control for underactuated (non-square) MIMO systems with unknown input gain and matched uncertainties. The L1 adaptive output feedback control architecture in this paper includes a state predictor, an error observer, adaptation laws, and a low-pass filter. It is shown that the proposed control strategy guarantees that the error signals of the closed-loop system are semi-globally bounded. Simulation results are presented to validate the theoretical claims.

A Collaborated Multi-controller Strategy by Using L1 Adaptive Augmentation Control for Power-generation Systems with Uncertainties

For dealing with uncertain operation circumstances, a collaborated multi-controller strategy of the cascade architecture with a L1 adaptive augmentation controller and a conventional baseline controller is introduced to power-generation systems. For its arbitrarily close, fast, and robust tracking performance, the L1 adaptive output feedback controller is designed as the augmentation controller in the inner-loop to keep the nominal dynamics of the system in the overall operation scope. The robust PID controller and offset-free linear MPC controller are recommended as the available outer-loop baseline controllers to follow control commands. The closed-loop stability of the cascade control system is ensured. The simulation experiments on a benchmark nonlinear boiler-turbine generation model verify the greatly improved adaptation and robustness of the augmentation control system in the presence of unknown uncertainties. Additionally, it is easy to upgrade a conventional control system to this cascade one in practice because the add-in L1 adaptive augmentation controller influence little on the augmented system setup.DOI: http://dx.doi.org/10.5755/j01.itc.44.3.8846

Missile two-loop acceleration autopilot design based on 𝓛1adaptive output feedback control

This article documents the design of a novel two-loop acceleration autopilot based on L1 adaptive output feedback control for tail-controlled missiles. The inner loop is an adaptive angle-of-attack tracking loop and the outer loop is the traditional PI controller for error compensation. A systematic low-pass filter design procedure is provided for minimum phase system and is applied to the inner loop design while the parameters of the outer loop are obtained from the multi-objective optimization problem. The effectiveness of the proposed autopilot is verified through numerical simulations under various conditions.

Coordinated Path Following of Multiple UAVs for Time-Critical Missions in the Presence of Time-Varying Communication Topologies

We address the problem of steering multiple unmanned air vehicles (UAVs) along given paths (path-following) under strict temporal coordination constraints requiring, for example, that the vehicles arrive at their final destinations at exactly the same time. Path-following relies on a nonlinear Lyapunov based control strategy derived at the kinematic level with the augmentation of existing autopilots with ℒ1 adaptive output feedback control laws to obtain inner-outer loop control structures with guaranteed performance. Multiple vehicle time-critical coordination is achieved by enforcing temporal constraints on the speed profiles of the vehicles along their paths in response to information exchanged over a dynamic communication network. We consider that each vehicle transmits its coordination state to only a subset of the other vehicles, as determined by the communications topology adopted. We address explicitly the case where the communication graph that captures the underlying communication network topology may be disconnected during some interval of time (or may even fail to be connected at any instant of time) and provide conditions under which the closed-loop system is stable. Flight test results obtained at Camp Roberts, CA in 2008 and hardware-in-the-loop (HITL) simulations demonstrate the benefits of the algorithms developed.