Swee King Phang

Design and mathematical modeling of a 4-standard-propeller (4SP) quadrotor

The recent development of small yet sophisticated sensors has led to the development of smaller unmanned aerial vehicles, especially in the form of quadrotor. When it is limited by the availability of the reverse propellers, the conventional quadrotor will no longer be realizable, and thus introducing the 4-standard-propeller (4SP) quadrotor design. This paper presents a comprehensive nonlinear modeling of a 4SP quadrotor, and the guidelines to design it. The advantages of constructing such aircraft and its detailed working principle are first highlighted. A nonlinear mathematical model is then derived based on the first-principles approach. The model parameters are finally identified and verified through actual flight tests.

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.

Systematic Design and Implementation of a Micro Unmanned Quadrotor System

This paper presents a guideline to systematically design and construct a micro quadrotor unmanned aerial vehicle (UAV), capable of autonomous flight. The designed micro UAV has a gross weight of less than 40g including power supply sufficient for an 8-min flight. The design is divided into three parts. First, investigation is made on the structural design of a conventional quadrotor. The quadrotor frame is then carefully designed to avoid any potential structural natural frequencies within the range of rotors operating speeds, based on simulation results obtained from MSC Nastran. Second, avionic system of the aircraft will be discussed in detail, mainly focusing on the design of printed circuit boards which include sensors, microprocessors and four electronic speed controllers, specially catered for micro quadrotor design. Last, a mathematical model for the micro quadrotor is derived based on Newton–Euler formalism, followed by methods of identifying the parameters. The flight test results are later described, analyzed and illustrated in this paper.

Autonomous Mini-UAV for indoor flight with embedded on-board vision processing as navigation system

This paper describes the development of an Unmanned Aerial Vehicle (UAV) with the aid of a vision processing system for indoor navigation. A co-axial radio-controlled (RC) helicopter is upgraded with a customized on-board avionics system which include two Gumstix Linux computer systems as the on-board processors. A camera module is used to capture real time video during the flight to perform real time image processing. High level control commands are sent to the avionics system such that the UAV could perform simple indoor navigation by tracking the colored tracks on the ground. Important data such as attitude, velocity and acceleration of the UAV, together with the real time video will be feedback to the ground station via communication links for giving commands and monitoring purposes. Flight tests have been carried out to verify the results of the vision processing system and to ensure the robustness of the controller in the UAV.

Platform design and mathematical modeling of an ultralight quadrotor micro aerial vehicle

In this paper, a micro quadrotor aircraft with approximately 40 g gross weight and 8 min flight endurance is developed. System development of this micro aerial vehicle is discussed in terms of the design of the mechanical structure and electrical systems. Mechanical structure is designed based on the proposed weight budget, propulsion system efficiency as well as results of structural analysis. Mechanical parts are designed and analyzed with 3D simulation software then 3D printed. Development of the electrical systems includes integration of processor, inertia measurement unit, and communications with commercial off-the-shelf electronics. Finally, a mathematical model of the quadrotor is derived based on the quadrotor X-configuration working principle. Parameters involved are further identified with experimental setups or simulations. The controller is first simulated with software simulator and then tuned with real flight tests.

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 Helicopter for Vertical Replenishment

This paper presents an intelligent and robust guidance, navigation and control solution for a rotary-wing UAV to carry out an autonomous cargo transportation mission between two moving platforms. Different from the conventional GPS/INS-only navigation scheme, this solution also integrates sophisticated Lidar and vision systems capable of precisely locating cargo loading and unloading positions. Besides, another complementary GPS/INS system is set up on the moving platforms with communication to the unmanned helicopter so that the controlled UAV is able to follow the dynamic platforms with good tracking performance. The whole system has been successfully implemented, and with its superb performance the Unmanned Systems Research Group from the National University of Singapore won the first place in the final round of the rotary-wing category competition of the 2nd AVIC Cup — International UAV Innovation Grand Prix 2013.

DESIGN AND CONSTRUCTION METHODOLOGY OF AN INDOOR UAV SYSTEM WITH EMBEDDED VISION

This paper describes the design and construction of an autonomous indoor coaxial rotorcraft system with onboard vision processing capability. A radio-controlled (RC) helicopter was modified and upgraded with essential avionics and processing elements for autonomous flight. This paper shows that in an indoor environment, where GPS signals are unavailable, vision-based navigation system can be used as a substitution. An embedded vision system that is compact and light enough to be carried by indoor UAVs is integrated into the control loop. The system has been successfully tested and the UAV was able to follow a painted track on the ground autonomously.

Search and Rescue Using Multiple Drones in Post-Disaster Situation

We present the development and application of multiple autonomous aerial vehicles in urban search and rescue missions. The missions are designed by the 2014 International Micro Aerial Vehicle Competition, held in Delft, the Netherlands, August 2014. Different mission tasks are identified for search and rescue missions, such as aerial photography, low altitude flight in urban environment, indoor navigation and rooftop landing. These tasks are all of paramount importance for rescuers in a disaster-hit place. We have designed a team of micro aerial vehicles with specific configurations to meet the mission requirements. A range of key technologies have been developed, including robust controller design, real-time map stitching, indoor navigation and roof-top perching. The proposed solutions are successfully demonstrated in the competition.