Jinqiang Cui

A Comprehensive UAV Indoor Navigation System Based on Vision Optical Flow and Laser FastSLAM

Abstract This paper presents a comprehensive control, navigation, localization and mapping solution for an indoor quadrotor unmanned aerial vehicle (UAV) system. Three main sensors are used onboard the quadrotor platform, namely an inertial measurement unit, a downward-looking camera and a scanning laser range finder. With this setup, the UAV is able to estimate its own velocity and position robustly, while flying along the internal walls of a room without collisions. After one complete flight, with the collected data the historic UAV path and the indoor environment can be well estimated. The autonomous navigation part of the system does not require any remote sensory information or off-line computational power, while the mapping is done off-line. Complete flight tests have been carried out to verify fidelity and performance the navigation solution.

Development of an Unmanned Coaxial Rotorcraft for the DARPA UAVForge Challenge

In this paper, we present a comprehensive design for a fully functional unmanned rotorcraft system: GremLion. GremLion is a new smallscale unmanned aerial vehicle (UAV) concept using two contra-rotating rotors and one cyclic swash-plate. It can fit within a rucksack and be easily carried by a single person. GremLion is developed with all necessary avionics and a ground control station. It has been employed to participate in the 2012 UAVForge competition. The proposed design of GremLion consists of hardware construction, software development, dynamics modeling and flight control design, as well as mission algorithm investigation. A novel computer-aided technique is presented to optimize the hardware construction of GremLion to realize robust and efficient flight behavior. Based on the above hardware platform, a real-time flight control software and a ground control station (GCS) software have been developed to achieve the onboard processing capability and the ground monitoring capability respectively. A GremLion mathematical model has been derived for hover and near hover flight conditions and identified from experimental data collected in flight tests. We have combined H1 technique, a robust and perfect tracking (RPT) approach, and custom-defined flight scheduling to design a comprehensive nonlinear flight control law for GremLion and successfully realized the automatic control which includes take-off, hovering, and a variety of essential flight motions. In addition, advanced mission algorithms have been presented in the paper, including obstacle detection and avoidance, as well as target following. Both ground and flight experiments of the complete system have been conducted including autonomous hovering, waypoint flight, etc. The test results have been presented in this paper to verify the proposed design methodology.

A mono-camera and scanning laser range finder based UAV indoor navigation system

This paper presents a comprehensive control and navigation scheme for an indoor UAV system. In addition to the inertial measurement unit commonly used onboard of most UAVs, the testbed quadrotor platform is also equipped with a mono-camera looking downwards and a laser range finder capable of scanning a level plane. With this setup, the UAV is able to estimate its own velocity and position robustly, while flying along the internal walls of a room without collision. The whole system does not require any remote sensory information or off-line computational power. All algorithms are self-sustained and running onboard in real time. Complete flight tests have been carried out to verify the solution.

Nonlinear modeling of a miniature fixed-pitch coaxial UAV

This paper presents the work that has been done to derive an accurate nonlinear model for a miniature fixed-pitch coaxial helicopter. Starting from the Newton-Euler rigid body dynamic equations, forces and torques generated at various parts of the UAV have been identified and formulated. The physical meanings behind the model are clearly explained, and the methods of identifying all the important model parameters are also provided. The full model is verified by comparing simulation results and actual flight tests with the NUS FeiLion coaxial UAV. The agreement between the two is promising.

Development of an unmanned tail-sitter with reconfigurable wings: U-Lion

In this paper, we present the development of a reconfigurable hybrid unmanned aerial vehicle (UAV): U-Lion. U-Lion is a small-scale UAV that is capable of vertical takeoff and landing (VTOL) and fixed-wing flight modes through its unique mechanical design. Mainly built with carbon fiber and Expanded PolyOlefin (EPO) foam, U-Lion is equipped with an array of electronic avionic components which enable stable control of the UAV both in VTOL and Cruise modes. It was employed by the National University of Singapore (NUS) Unmanned System Research Group to participate in the 2013 UAV Grand Prix (UAVGP) competition held in Beijing, China. Its design adopts a reconfigurable wing and a tailsitter structure, which combines the advantages of a fixed-wing plane and a rotor helicopter effectively. U-Lion could transit from vertical takeoff to a hovering stage before flying in cruise mode to realize efficient long duration flight. The propulsion of U-Lion comes from a self-fabricated contra-rotating motor fixed on a gimbal mechanism which can change the direction of the motor for the required thrust. This thrust-vectored propulsion system primarily provides control in the VTOL mode but also enhances flight capabilities in the cruise mode. The detailed design and implementation procedure have been presented in this paper along with our Computational Fluid Dynamics (CFD) simulation results, real flight tests and competition performance.

Vision-based autonomous flocking of UAVs in unknown forest environment

This paper studies tandem flocking of a team of unmanned aerial vehicles (UAVs) equipped with limited range sensors exploring an obstacle-rich GPS-denied environment such as a forest or urban canyon. There is no communication between UAVs and the follower can only estimate its leaders relative position by its on-board camera. A vision-based leader-follower flocking strategy is proposed to achieve this kind of flocking in unknown cluttered environments. The leader UAV explores its way to reach a given goal position and the follower UAV follows its corresponding leader UAV via on-board camera and avoid obstacles at the same time. The simulation of a team of six UAVs demonstrates the effectiveness of our proposed flocking strategy in a forest environment.

Development of an Unconventional Unmanned Coaxial Rotorcraft: GremLion

In this paper, we present an unmanned system design methodology for a fully functional unmanned rotorcraft system: GremLion, developed with all necessary avionics and a ground control station. It has been employed to participate in the 2012 UAVForge competition. The proposed design methodology consists of hardware construction, software development, dynamic modeling and flight control, as well as mission algorithms. The test results have been presented in this paper to verify the proposed design methodology.