Zachary T. Dydek

Adaptive Control of Quadrotor UAVs: A Design Trade Study With Flight Evaluations

This brief describes the application of direct and indirect model reference adaptive control to a lightweight low-cost quadrotor unmanned aerial vehicle platform. A baseline trajectory tracking controller is augmented by an adaptive controller. The approach is validated using simulations and flight tested in an indoor test facility. The adaptive controller is found to offer increased robustness to parametric uncertainties. In particular, it is found to be effective in mitigating the effects of a loss-of-thrust anomaly, which may occur due to component failure or physical damage. The design of the adaptive controller is presented, followed by a comparison of flight test results using the existing linear and augmented adaptive controllers.

Adaptive Control of Quadrotor UAVs in the Presence of Actuator Uncertainties

This paper describes the application of model reference adaptive control on a light-weight, low-cost quadrotor UAV platform. An adaptive controller was designed to augment an existing linear controller that provides autonomy and waypoint following. The design of the adaptive controller is driven by Lyapunov stability arguments and has a proof of stability grounded in a nonlinear framework. The approach was validated using flight testing inside an indoor test facility. The adaptive controller was found to offer increased robustness to parametric uncertainties. In particular, it was found to be effective in mitigating the effects of a loss of thrust anomaly, which may occur due to component failure or physical damage. The design of the adaptive controller is presented, followed by a comparison of flight test results using the existing linear and augmented adaptive controllers.

Theoretically Verifiable Stability Margins for an Adaptive Controller

†† † ‡ § This paper seeks to provide the beginnings of a theoretically motivated V&V technique for adaptive controllers in the context of controlling uncertain flight vehicle dynamics. Using a Reduced Linear Asymptotic System (RLAS), which characterizes the asymptotic behavior of an adaptive system, a systematic approach is proposed for deriving the stability margins of an adaptive flight control system (AFCS). Robustness properties of the AFCS in the presence of input disturbances and unmodeled dynamics along with robustness margins are derived. Methods for tuning the free adaptive system parameters such as Γ are presented, which may be needed to satisfy the desired performance criteria. Making use of the fact that the RLAS is a linear time invariant system, optimization procedures based on output feedback and Linear Matrix Inequalities are proposed for tuning such free parameters. The approach is validated using simulations of a nonlinear 6 DoF aircraft model with actuator constraints.

Adaptive control and the NASA X-15 program: A concise history, lessons learned, and a provably correct design

The NASA X-15 research airplane was one of the earliest aircraft to feature an adaptive control scheme, making its first flight in 1959. The program is largely considered a success, the one exception being the fatal accident that occurred on November 15, 1967. The circumstances which led to the anomalous behavior of the X-15 during that flight are reproduced using a fully nonlinear six-degree-of-freedom aircraft model and a detailed model of the original MH-96 adaptive controller. Using the lessons learned from the X-15 program as well as decades of work in the field of stable adaptive control, a provably correct (PC) adaptive controller is designed for the X-15. When subjected to the same conditions that caused the original MH-96 adaptive controller to fail, the PC adaptive controller is able to recover and complete the maneuver successfully.

Composite adaptive posicast control for a class of LTI plants with known delay

Many potential applications of adaptive control, such as adaptive flight control systems, require that the controller have high performance, stability guarantees, and robustness to time delays. These requirements typically lead to engineering trade-offs, such as a trade-off between performance and robustness. In this paper, a new Composite Adaptive Posicast Control (CAPC) framework is proposed for linear time-invariant (LTI) plants with input-matched parametric uncertainties and known delay. The CAPC architecture uses a combination of several modifications to the typical direct model reference adaptive control (MRAC). The described approach is a nonlinear controller design that explicitly accounts for known time delay. The stability of the overall closed-loop system can be guaranteed using nonlinear analysis tools. The benefits of the CAPC approach are explored using a simulation of the longitudinal dynamics of a fixed-wing aircraft. Comparison studies are presented for 80 ms and 250 ms time delay cases.

Combined/Composite Adaptive Control of a Quadrotor UAV in the Presence of Actuator Uncertainty

Many potential applications of adaptive control, such as adaptive flight control systems, require that the controller have high performance, stability guarantees, and robustness to time delays. These requirements typically lead to engineering trade-os, such as a trade-o between performance and robustness. In this paper, we examine a combined/composite model reference adaptive control (CMRAC) approach that can be used to achieve higher performance as well as higher levels of robustness. The CMRAC design is validated with flight tests of a light-weight, low-cost quadrotor UAV platform inside an indoor test facility. The combined/composite adaptive controller was found to oer increased robustness to parametric uncertainties. The design of the combined/composite adaptive controller is presented, followed by a comparison with the existing linear controller and a direct adaptive controller.

A robust environment for simulation and testing of adaptive control for mini-UAVs

A simulation environment is developed to assist in the design, development, and validation of complex controllers with applications to mini-UAVs, such as the four-rotor DraganFly RC helicopter (quadrotor). The simulation system is modular and includes interfaces which allow for substitution of software subsystems with hardware components. This approach enables a smooth transition from the design and simulation phases to the implementation phase. The benefits of the proposed simulation environment are examined through the application of model reference adaptive control to a quadrotor UAV in the presence of actuator uncertainties and nonlinearities.

High performance adaptive control in the presence of time delays

Many potential applications of adaptive control, such as adaptive flight control systems, require that the controller have high performance, stability guarantees, and robustness to time delays. These requirements typically lead to engineering trade-offs, such as a trade-off between performance and robustness. In this paper, we examine several modifications to the typical direct model reference adaptive control (MRAC) approach which can be used to achieve higher performance as well as higher levels of robustness. A new Time Delay Resistant (TDR) adaptive control framework is proposed using a combination of several modifications to MRAC. The various modifications to MRAC, as well as the TDR adaptive controller are applied to the control of longitudinal dynamics of an aerial vehicle in simulation.

Time delay resistant adaptive control of mini-UAVs

Abstract Many potential applications of adaptive control, such as adaptive flight control systems, require that the controller have high performance, stability guarantees, and robustness to time delays. These requirements typically lead to engineering trade-offs, such as a tradeoff between performance and robustness. In this paper, a new Time Delay Resistant (TDR) adaptive control framework is proposed using a combination of several modifications to the typical direct model reference adaptive control (MRAC) approach. The benefits of the TDR approach are explored with a simulation of the longitudinal dynamics of a fixed-wing aircraft. Flight tests of a 4 rotor mini-UAV were also performed using a subset of the TDR adaptive control features.