DISCUSSION AND PRACTICAL ASPECTS ON CONTROL ALLOCATION FOR A MULTI-ROTOR HELICOPTER

This paper presents practical methods to improve the flight performance of an unmanned multi-rotor helicopter by using an efficient control allocation strategy. The flying vehicle considered is an hexacopter. It is indeed particularly suited for long missions and for carrying a significant payload such as all the sensors needed in the context of cartography, photogrammetry, inspection, surveillance and transportation. Moreover, a stable flight is often required for precise data recording during the mission. Therefore, a high performance flight control system is required to operate the UAV. However, the flight performance of a multi-rotor vehicle is tightly dependent on the control allocation strategy that is used to map the virtual control vector v = [T, L, M, N ]T composed of the thrust and the torques in roll, pitch and yaw, respectively, to the propellers' speed. This paper shows that a control allocation strategy based on the classical approach of pseudo-inverse matrix only exploits a limited range of the vehicle capabilities to generate thrust and moments. Thus, in this paper, a novel approach is presented, which is based on a weighted pseudo-inverse matrix method capable of exploiting a much larger domain in v. The proposed control allocation algorithm is designed with explicit laws for fast operation and low computational load, suitable for a small microcontroller with limited floating-point operation capability

Nonlinear actuator fault detection for small-scale UASs

This paper presents a recursive strategy for online detection of actuator faults on a unmanned aerial system (UAS) subjected to accidental actuator faults. The proposed detection algorithm aims to provide a UAS with the capability of identifying and determining characteristics of actuator faults, offering necessary flight information for the design of fault-tolerant mechanism to compensate for the resultant side-effect when faults occur. The proposed fault detection strategy consists of a bank of unscented Kalman filters (UKFs) with each one detecting a specific type of actuator faults and estimating corresponding velocity and attitude information. Performance of the proposed method is evaluated using a typical nonlinear UAS model and it is demonstrated in simulations that our method is able to detect representative faults with a sufficient accuracy and acceptable time delay, and can be applied to the design of fault-tolerant flight control systems of UASs

From Topology to Quasi-Topology. The Complexity of the Notional Domain

This article examines a fundamental metalinguistic construction of the theory of enunciative operations: the notional domain. In particular, we try to explain some elementary topological concepts on which this construction is based and we try to show the key role they play in the description of some basic linguistic operations

Robust fault-tolerant tracking control for a near-space vehicle using a sliding mode approach

In this study, a flight fault-tolerant control scheme based on an adaptive sliding mode technique is proposed. First, a control allocation of a near-space vehicle (NSV) attitude dynamics is analysed, and actuator fault modelling is introduced. Then, a modified sliding model tracking control approach, using a continuous strategy of integral sliding mode control, is designed to improve the position tracking precision. This scheme can solve the chattering problem without loss of robustness and control accuracy. Actuator fault and unmeasurable external disturbances are compensated for by an integral action term. To verify the effectiveness of the proposed control scheme, a numerical simulation is performed for an NSV attitude system, which is a non-linear aircraft model with six degrees of freedom. Simulation results demonstrate that the closed-loop system has good performance in spite of the actuator fault and system disturbances.B Jiang, Y Xu, P Shi and Z Ga

Design and implementation of a leader-follower cooperative control system for unmanned helicopters

10.1007/s11768-010-9188-6Journal of Control Theory and Applications8161-6