Geng Lu

Robust LQR Attitude Control of a 3-DOF Laboratory Helicopter for Aggressive Maneuvers

Robust attitude control problem for a three-degree-of-freedom (3-DOF) laboratory helicopter is investigated. The helicopter dynamics involves nonlinearity, uncertainties, and strong interaxis coupling. A robust controller is proposed with three parts: a nominal feedforward controller, a nominal linear quadratic regulation (LQR) controller, and a robust compensator. The LQR controller is applied to deal with a nominal linear error system derived by the feedforward control strategy and linearized approximation, while the robust compensator is designed to restrain the effects of uncertainties, nonlinear properties, and external disturbances. It is shown that the attitude tracking error of the closed-loop system can be guaranteed to converge to any given small neighborhood of the origin in a finite time. Experimental results on the 3-DOF laboratory helicopter demonstrate the effectiveness of the proposed control strategy.

Formation Control for High-Order Linear Time-Invariant Multiagent Systems With Time Delays

Formation control problems for high-order linear time-invariant multiagent systems with time delays are investigated. First, a general time-varying formation control protocol is proposed. Then, based on consensus approaches, necessary and sufficient conditions for multiagent systems to achieve a given time-varying formation are presented. An explicit expression of the time-varying formation reference function is also given. It is shown that the motion modes of the formation reference can be specified. Furthermore, necessary and sufficient conditions for formation feasibility are proposed. An approach to expand the feasible formation set and an algorithm to design the protocol for multiagent systems to achieve time-varying formations are provided, respectively. Finally, numerical simulations are presented to demonstrate theoretical results.

Robust Tracking Control of a Quadrotor Helicopter

In this paper, a robust tracking control method for automatic take-off, trajectory tracking, and landing of a quadrotor helicopter is presented. The designed controller includes two parts: a position controller and an attitude controller. The position controller is designed by the static feedback control method to track the desired trajectory of the altitude and produce the desired angles for pitch and roll angles. By combining the proportional-derivative (PD) control method and the robust compensating technique, the attitude controller is designed to track the desired pitch and roll angles and stabilize the yaw angle. It is proven that the attitude tracking error of each channel can converge to the given neighborhood of the origin ultimately. Experimental results demonstrate the effectiveness of the designed control method.

Robust attitude tracking control of small-scale unmanned helicopter

Robust attitude control problem for small-scale unmanned helicopters is investigated to improve attitude control performances of roll and pitch channels under both small and large amplitude manoeuvre flight conditions. The model of the roll or pitch angular dynamics is regarded as a nominal single-input single-output linear system with equivalent disturbances which contain nonlinear uncertainties, coupling-effects, parameter perturbations, and external disturbances. Based on the signal compensation method, a robust controller is designed with two parts: a proportional-derivative controller and a robust compensator. The designed controller is linear and time-invariant, so it can be easily realised. The robust properties of the closed-loop system are proven. According to the ADS-33E-PRF military rotorcraft standard, the controller can achieve top control performances. Experimental results demonstrate the effectiveness of the proposed control strategy.

Output containment control for swarm systems with general linear dynamics: A dynamic output feedback approach ☆

Abstract Output containment control problems for high-order linear time-invariant swarm systems under directed interaction topologies are investigated using a dynamic output feedback approach. Firstly, to propel the outputs of followers to converge to the convex hull formed by the outputs of leaders, a dynamic output containment protocol is presented. Then necessary and sufficient conditions for swarm systems to achieve output containment are proposed. To ensure the scalability of the criteria, a sufficient condition which only includes two linear matrix inequality constraints independent of the number of agents is further presented. Moreover, an approach independent of the number of agents is proposed to determine the gain matrices in the dynamic output containment protocols. Finally, numerical simulations are presented to demonstrate theoretical results.

Time-varying output formation control for high-order linear time-invariant swarm systems

Formation control of swarm systems has gained considerable attention from scientific communities due to its potential applications in various areas. In practical applications, the dynamics of each agent may be of high order and only the outputs of all agents are required to achieve time-varying formations. Therefore, this paper focuses on time-varying output formation control problems for high-order linear time-invariant swarm systems with directed interaction topologies. A general output formation protocol is proposed based on the relative outputs of neighboring agents. Necessary and sufficient conditions for swarm systems to achieve time-varying output formations are presented using a consensus based approach. An explicit expression of the output formation reference function is given. For a swarm system, whether or not a desired output formation is feasible is a crucial problem. Based on partial stability theory, necessary and sufficient conditions for output formation feasibility are derived. Approaches to expand the feasible time-varying output formation set and an algorithm to design the protocol for swarm systems to achieve time-varying output formation are presented respectively. Finally, theoretical results are demonstrated by numerical simulations.

Robust output tracking control of a laboratory helicopter for automatic landing

Robust output tracking control problem of a lab helicopter for automatic landing in high seas is dealt with. The motion of the helicopter is required to synchronize with that of an oscillating platform, e.g., the deck of a vessel. A robust linear time-invariant output controller consisting of a nominal controller and a robust compensator is proposed. The robust compensator is introduced to restrain the influences of uncertainties. It is shown that robust stability and robust tracking property can be achieved. Experimental results demonstrate the effectiveness of the designed control approach.

Output Containment Control for High-Order Linear Time-Invariant Swarm Systems

Output containment control problems for high-order linear time-invariant swarm systems are investigated. Firstly, output containment protocols are presented for leaders and followers respectively to make sure that the output dynamics property of leaders can be improved and the outputs of followers can converge to the convex hull formed by the outputs of leaders. Then output containment problems for swarm systems are transformed into stability problems, and sufficient conditions for swarm systems to achieve output containment are proposed. Moreover, an approach to determine the gain matrix in the output containment protocol is given, which has less calculation complexity. Finally, numerical simulations are presented to demonstrate theoretical results.

Aggressive Attitude Control of Unmanned Rotor Helicopters Using a Robust Controller

In this paper a robust controller is proposed for unmanned helicopters. The mathematical model of the helicopter is a multi-input, multi-output (MIMO) system with nonlinearities, parameter uncertainties, coupling effects, and external disturbances. A novel robust controller, which includes a nominal controller and a robust compensator, is proposed for obtaining robust attitude tracking performance in pitch and roll channels, respectively. The nominal controller is designed to achieve desired tracking performance for the nominal model, and the robust compensator design is based on robust signal compensation technology for restraining the effects of external disturbances, parameter uncertainties, nonlinearities and couplings. The proposed controller is linear, time invariant, and easy to implement. The robust property of the system is analyzed. It is proved that robust attitude tracking performance can be achieved. Experiments were carried out on a prototype unmanned helicopter THeli260, which included simulation evaluation and flight test under aggressive maneuvers. The results of the experiment exhibit advanced performance of the robust controller.

HArCo: Hierarchical Fiducial Markers for Pose Estimation in Helicopter Landing Tasks

A reliable pose estimation is crucial in the landing tasks of helicopters. This paper mainly focuses on presenting a smooth and reliable pose estimation method during helicopter landing using Augmented Reality (AR) markers. Based on the proposed hierarchical fiducial marker system called Hierarchical Augmented Reality Code (HArCo), pose estimation can be performed within a much longer range. The design of the system, generation of the marker dictionary and the application in helicopter landing are thoroughly described in this paper. The performance of the pose estimation algorithm based on HArCo is tested in a landing task. As pose information is accessible throughout the landing procedure, a safe auto-landing based on HArCo can also be conducted.