The aerial robot presented here for the first time was based on a quadrotor structure, which is capable of unique morphing performances based on an actuated elastic mechanism. Like birds, which are able to negotiate narrow apertures despite their relatively large wingspan, our Quad-Morphing robot was able to pass through a narrow gap at a high forward speed of 2.5 m.s− 1 by swiftly folding up the structure supporting its propellers. A control strategy was developed to deal with the loss of controllability on the roll axis resulting from the folding process, while keeping the robot stable until it has crossed the gap. In addition, a complete recovery procedure was also implemented to stabilize the robot after the unfolding process. A new metric was also used to quantify the gain in terms of the gap-crossing ability in comparison with that observed with classical quadrotors with rigid bodies. The performances of these morphing robots are presented, and experiments performed with a real flying robot passing through a small aperture by reducing its wingspan by 48% are described and discussed.

The new open-source quadrotor platform called X4-MaG presented here was developed for academic and research applications. X4-MaG is a small, low-cost open quadrotor of only 307-grammes which offers two levels of controllers providing a manual mode and an automatic mode thanks to powerful Linux-based controller embedded onboard. The experiments presented here show the reliability of the open hardware and software embedded onboard the quadrotor. To estimate the robot s attitude, a quaternion-based complementary filter requiring very few computational resources was developed and implemented on an 8-bit Arduino board. It was also established that the stabilization feedback system based on quaternions tracks the attitude setpoints with precision up to twice greater than a classical cascaded PI controller. The controllers and estimators were designed in the Matlab/Simulink environment and directly implemented onboard the tiny Linux-based autopilot board using a custom made toolbox (RT-MaG toolbox). The autopilot was tested in the brand-new Marseilles Flying Arena with various 3-D flight trajectories and found to be highly accurate with errors of only 0.7cm in hover and less than 3.2cm at 1.2m.s-1. The X4-MaG quadrotor was able to reach speeds greater than 2m.s-1 and reject attitude disturbances of 20' within 0.8s. Acronyms X4-MaG: X4 quadrotor developed in Marseille and Grenoble: an open hardware and software platform. RT-MaG: Real-Time Marseille and Grenoble toolbox. COM: Computer-On-Module. 2. THE LINUX-BASED X4-MAG QUADROTOR Matlab/Simulink was often used in ground station because it allows users to test and design new control algorithms very easily. [16] used Matlab/Simulink, a Vicon motion capture system and a custom-made RF module for steering a quadrotor vehicle along a trajectory. But the control algorithms are not executed onboard. Programming the X4-MaG quadrotor via Matlab/Simulink was achieved by means of our new open-source toolbox ([13]) which enable to run Simulink model in real-time on Linux based Computer-On-Module (more information are given in section 2.3. At the hardware level, the quadrotor X4-MaG is composed entirely of low cost off-the-shelf components. Its light weight (307g) and its small frame made of a printed circuit board (PCB) make it highly resistant and robust to crashes. At the software level, the robot is equipped with two different controllers which trigger a rescue mode in case of failure of the main controller. In addition, the high level controller (the main controller) is based on the Gumstix Overo, a powerful low consumption Computer-On-Module providing the robot with huge computational resources at no cost to the payload and the endurance of the quadrotor. Since the Gumstix COM is fully supported by our new opensource Matlab/Simulink toolbox RT-MaG (see the website [13]), the robot is directly piloted via 90 X4-MaG: A Low-Cost Open-Source Micro-Quadrotor and Its Linux-Based Controller International Journal of Micro Air Vehicles