In this paper we present the design and control of a novel six degrees-of-freedom aerial vehicle. Based on a static force and torque analysis for generic actuator configurations, we derive an eight-rotor configuration that maximizes the vehicle's agility in any direction. The proposed vehicle design possesses full force and torque authority in all three dimensions. A control strategy that allows for exploiting the vehicle's decoupled translational and rotational dynamics is introduced. A prototype of the proposed vehicle design is built using reversible motor-propeller actuators and capable of flying at any orientation. Preliminary experimental results demonstrate the feasibility of the novel design and the capabilities of the vehicle.

Design, modeling and control of an omni-directional aerial vehicle

We present FAST-Hex, a novel UAV concept which is able to smoothly change its configuration from underactuated to fully actuated by using only one additional motor that tilts all propellers at the same time. FAST-Hex can adapt to the task at hand by finely tuning its configuration from the efficient (but underactuated) flight (typical of coplanar multi-rotor platforms) to the full-pose-tracking (but less efficient) flight, which is attainable by non-coplanar multi-rotors. We also introduce a novel full-pose geometric controller for generic multi-rotors (not only the FAST-Hex) that outperforms classical inverse dynamics approaches. The controller receives as input any reference pose in ℝ3×SO(3) (3D position + 3D orientation). Exact tracking is achieved if the reference pose is feasible with respect to the propeller spinning rate saturations. In case of unfeasibility a new feasible desired trajectory is generated online giving priority to the positional part. The new controller is tested with the FAST-Hex but can be used for many other multi-rotor platforms: underactuated, slightly fully-actuated and completely fully-actuated.

https://hal.archives-ouvertes.fr/hal-01348538/document

Modeling and control of FAST-Hex: A fully-actuated by synchronized-tilting hexarotor

Robust stability and performance analysis based on integral quadratic constraints

In this paper, the problem of designing a control law in case of rotor failure in quadrotor vehicles is addressed. First, a nonlinear mathematical model for a quadrotor vehicle is derived, which includes translational and rotational dynamics. Then a robust feedback linearization controller is developed, which sacrifices the controllability of the yaw state due to rotor failure to linearize the closed-loop system around a working point, where roll and pitch angles are zero and the angular speed around the vertical axis is a nonzero constant. An H∞ loop shaping technique is adopted to achieve regulation of these variables around the chosen working point. Finally, an outer loop is proposed for achieving control of the linear displacement under the assumption of small angles approximation for the pitch and roll angles. The proposed control strategy allows the vehicle to use the remaining three functional rotors to enter a constant angular speed around its vertical axis, granting stability and representing an ...

Flight control of a quadrotor vehicle subsequent to a rotor failure

This paper proposes a fully distributed control protocol that achieves time-varying group formation tracking for linear multiagent systems connected via a directed graph. The group formation tracking often leads to sub-formations especially when the leaders are placed far apart or they have separate control inputs. In the proposed approach, the followers are distributed into several subgroups and each subgroup attains the predefined subformation along with encompassing the leaders. Each subgroup can be assigned multiple leaders, contrary to the single-leader case considered in most existing literature, which makes the current problem nontrivial. When multiple leaders exist in a subgroup, the subformation attained by that subgroup keeps tracking a convex combination of the states of the leaders. A distributed adaptive control protocol has been introduced in this paper which uses only relative state information and, thus, avoids direct computation of the graph Laplacian matrix. Due to the virtue of this, the proposed scheme remains effective even when some of the agents get disconnected from the network due to sudden communication failure. An algorithm is provided to outline the steps to design the control law to attain time-varying group formation tracking with multiple leaders. Toward the end, a case study on multitarget surveillance operation is taken up to show an important application of the proposed adaptive control technique.

/pdf/distributed-adaptive-time-varying-group-formation-tracking-25j6l5l2wz.pdf

Distributed Adaptive Time-Varying Group Formation Tracking for Multiagent Systems With Multiple Leaders on Directed Graphs

A new class of nonplanar multirotor rotary vehicle is introduced that has the capability of independent control of both thrust and torque vectors in three dimensions. The vehicle configuration is based around the use of six thrust producing rotors arranged in pairs on three separate reference planes. Variable thrust can be provided via fixedpitch/variable-speed rotors or variable-pitch/fixed-speed rotors. The orientation of rotor reference planes affects the orthogonality of force and torque control, and it is shown how maneuverability can be traded with propulsive efficiency. The static mapping between force and torque control outputs and rotor inputs is derived from rotor geometry and a simple rotor aerodynamic model that does not include interference between rotors or fuselage drag and does not explicitly include induced-velocity effects. Controllers are synthesized for both position and attitude control, with acceptable stability demonstrated via Lyapunov analysis. Vehicle closed-loop dynamic response is investigated in simulation, and controller performance is shown to meet design requirements in the presence of unmodeled rotor inertia effects. Experimental results on a static test rig confirm that the simplified rotor aerodynamic modeling used for control synthesis is adequate for symmetric flight conditions around hover. A free flying prototype has been flight-tested in hover, showing that practical vehicles are possible, accepting the fact that increased control capability comes at the expense of reduced payload and duration, compared with a conventional helicopter.

Kinematic analysis and control design for a nonplanar multirotor vehicle

https://personalpages.manchester.ac.uk/staff/Alexander.Lanzon/publications/open_pdf_files/SCL-14_Carrasco-MayaGonzalez-Lanzon-Heath.pdf

LMI searches for anticausal and noncausal rational Zames–Falb multipliers

Given a linear time-invariant plant, the search of a suitable multiplier over the class of Zames-Falb multiplier is a challenging problem which has been studied for several decades. Recently, a new linear matrix inequality search has been proposed over rational and causal Zames-Falb multipliers. This paper analyzes the conservatism of the restriction to causality on the multipliers and presents a complementary search for rational and anticausal multipliers.

LMI search for rational anticausal Zames-Falb multipliers

Absolute stability of bilateral teleoperation has been investigated under the assumption that both human and environment behave as passive systems. This robust design is required since human and environment must be considered as unknown systems at the design stage. If this approach is widely used in the literature, it leads to conservative conditions. Recently, teleoperation has been described in the integral quadratic constraint (IQC) framework, which provides powerful tools to develop less conservative description of both, human and environment. In this initial work, we consider that the environment can be described by a memoryless, monotone, and bounded nonlinearity. Then, Zames-Falb multipliers can be introduced to relax the conservatism of current state-of-the-art stability conditions. The usefulness of our result is shown in a 2-channel position-force teleoperation; where the well known lack of passivity of a PD-F controller is corrected by the use of Zames-Falb multipliers.

Martin Maya-Gonzalez

Papers

Kinematic analysis and control design for a nonplanar multirotor vehicle

LMI searches for anticausal and noncausal rational Zames–Falb multipliers

LMI search for rational anticausal Zames-Falb multipliers

Teleoperation with memoryless, monotone, and bounded environments: A Zames-Falb multiplier approach