Belal H. Sababha

MICRORAPTOR: A LOW-COST AUTONOMOUS QUADROTOR SYSTEM

This paper describes Microraptor, a complete low-cost autonomous quadrotor system designed for surveillance and reconnaissance applications. The Microraptor ground station is custom-made and features a graphical user interface that presents and allows the manipulation of various flight parameters. The aerial vehicle is a 4-rotor vertical takeoff and landing (VTOL) vehicle that features the advantages of traditional helicopters with significant reduction in mechanical complexity. The vehicle frame is a handmade magnesium and carbon fiber structure. The onboard avionics system is a custom dual processor design capable of autonomous path navigation and data exchange with the ground station. The vehicle is outfitted with a video and still-photo system that provides real-time images to the system operator through the GUI. The system is being developed at Oakland University by a team of multidisciplinary undergraduate and graduate engineering students. Microraptor placed 5th at the 2008 Association for Unmanned Vehicle Systems International (AUVSI) Unmanned Aerial Systems (UAS) Competition and is set to compete again in June of 2009.Copyright

Rapid Prototyping of Quadrotor Controllers using MATLAB RTW and dsPICs

This paper presents a rapid prototyping approach to attitude control algorithms of a quadrotor aerial vehicle. The MATLAB’s Simulink Real Time Workshop (RTW) is used to implement closed loop PID control algorithms for vehicle roll, pitch, and yaw stabilization. The graphical environment of Simulink allows developers to easily implement and tune complex control algorithms. Moreover, RTW automatically generates executable C code for Microchip dsPIC embedded processors. The performance of several control loops is evaluated experimentally.

A PV solar tracking system: Design, implementation and algorithm evaluation

Electrical energy is considered to be the soul of modern civilization. Traditional electrical energy generation approaches which usually rely on oil and its derivatives, produce different kinds of pollution in addition to being expensive to implement and maintain. And most important, they are exhaustible on the long run. Jordan is a country with very limited natural resources and the energy bill exhausts a large amount of its GDP. Solar energy is a promising renewable energy resource that could solve many of the countrys problems if well utilized specially that the majority of days in Jordan are sunny. One method to utilize harvested solar energy is through using tracking algorithms. In this research, a PV solar tracking test-bed is designed and implemented. The test-bed is used to evaluate different solar tracking algorithms. Then we propose a modified tracking algorithm that was able to increase the harvested energy by 4% on sunny days and 10% on cloudy and rainy days when compared to other evaluated algorithms.

A real-time gracefully degrading avionics system for unmanned aerial vehicles

Graceful degradation is an approach for developing dependable safety-critical embedded applications, where redundant active or standby resources are used to cope with faults through system reconfiguration at run-time. Compared to traditional hardware and software redundancy, it is a promising technique that may achieve dependability with a significant reduction in cost, size, weight, and power requirements. Checkpointing protocols, which are necessary components of degrading systems, support task migration through state preservation. They allow real-time embedded systems to recover from any failure by restarting from the last well-defined and consistent state, thus preserving the progress of computations that have been achieved. This paper demonstrates and applies the graceful degradation concept to achieve fault tolerance in an unmanned aerial vehicle (UAV) real-time embedded system. A checkpointing protocol is used to reserve the state of the avionics of the UAV system. Faults were injected during run-time causing one of the systems stability critical control tasks to fail. The system was able successfully to recover by restarting the affected critical task(s) on a different processor with last valid consistent state(s). This paper presents the architecture, fault injection scheme, and the results of the tests performed, which demonstrate the viability of graceful degradation in our tested UAV.

Vision-based sensing of UAV attitude and altitude from downward in-flight images

Autonomous unmanned aerial vehicles (UAVs) often carry video cameras as part of their payload. Outdoor video captured by such cameras can be used to estimate the attitude and altitude of the UAV by detecting the location of the horizon in the video frames. This paper presents a video frame processing algorithm for estimating the pitch and roll of a UAV, as well as its altitude. The frames are obtained from a downward pointing video camera equipped with a fisheye lens. These open-loop estimates can serve as redundant data used to implement graceful-degradation in the event that the main closed-loop control sensors fail, or for fault-tolerance purposes to augment inertial sensors for increased accuracy. The estimated values had a mean error of ±0.7 angular degrees for roll and ±0.9 angular degrees for pitch, while the altitude estimation from the video had a mean error of ±0.9 meters. The results are presented and compared to actual attitude and altitude values obtained from a traditional inertial measurement unit and, in the case of altitude comparison, an absolute air pressure sensor. The algorithm was developed on a personal computer to work at 10 frames per second and uses only simple image processing functions that can be deployed using open source libraries on lightweight computing boards capable of image processing.

A compact portable object tracking system

Computer vision and object tracking are becoming increasingly more important with a wide variety of applications in our daily life. Most of the available tracking systems are not compact enough to be mounted on small ground or aerial robots. Also, most of these systems are relatively expensive. The tracking system presented in this work is a compact low cost system which makes it suitable for weight sensitive applications. The proposed system is a commercial off the shelf android-based mobile device that is mounted on a pan/tilt gimbal. The system utilizes the camera and the processor of the mobile device to capture and process video frames. The tracking algorithm is a newly modified algorithm that combines three well known algorithms: SURF, CAMShift, Lucas-Kanade. Each of these algorithms is deployed at a different stage of the tracking process which yields a reliable real-time tracking system. The newly modified tracking algorithm was developed using OpenCV within an Android environment. An indoor lab experimental test showed that the system was able to track a (3cm × 5cm) object moving at a speed of 133cm/sec and placed 50 cm away from the system.

Evaluation of Communication Induced Checkpointing in Resource Constrained Embedded Systems

Reconfiguration-Based Fault-Tolerance is one approach for developing dependable safety-critical embedded applications. This approach, compared to traditional hardware and software redundancy, is a promising technique that may achieve the required dependability with a significant reduction in cost in terms of size, weight, price, and power consumption. Reconfiguration necessitates using proper checkpointing protocols to support state reservation and task migration. One of the most common approaches is to use Communication Induced Checkpointing (CIC) protocols, which are well developed and understood for large parallel and information systems, but not much has been done for resource limited embedded systems. This paper implements four common CIC protocols in a resource constrained distributed embedded system with a Controller Area Network (CAN) backbone. An example feedback control system implementation is used for a case study. The four implemented protocols are described and performances are contrasted. The paper compares the protocols in terms of network bandwidth consumptions, CPU usages, checkpointing times, and checkpoint sizes in additional to the traditional measures of forced to local checkpoint rations and total number of checkpoints.Copyright

On the analysis of road surface conditions using embedded smartphone sensors

Road conditions play a critical role in ensuring traffic safety and reducing traffic jams and congestions. Ensuring healthy conditions require constant monitoring to detect and predict potential road deterioration. This work proposes a low-cost solution that takes advantage of sensory capabilities of smartphones. By recording Gyro rotation sensor data, we show that abnormalities can be detected by calculating the second moment of sensor data. Our work is validated by drive tests that show results are consistent and repeatable. The work also proposed a dynamic time warping technique to measure similarity between drive results and to obtain accurate representation of multiple drives data.

A Statistical Approach to Estimating Driving Events by a Smartphone

The ability of a smartphone to provide motion sensing information enables a low-cost, portable tool to analyze and understand vehicle driving events. Fuel economy, Driving Safety, and better estimation of driving cost can be analyzed based not only on distance and time of travel but also on the nature of driving. This work studies sensors data collected during a field drive test and proposes a new approach to classifying driving events. The new approach is based on the statistics of sensors data collected. It is shown that by using the mean and variance of the sensors data, it will be possible to distinguish different driving events. This enables estimating cost of travel to include, in addition to distance and time of travel, the number of events that adds to fuel consumption and vehicle wear and tear.

A rotor-tilt-free tricopter UAV: design, modelling, and stability control

This paper presents an unconventional tri-rotor unmanned aerial vehicle (UAV) design that only employs three brushless motors with three fixed pitch propellers for propulsion and flight control. No additional mechanics for dynamically tilting motor(s), found on existing tricopters, are used. The dynamic model of the proposed system is developed. Then a control strategy to control the stability and manoeuvring of the UAV is presented. The control strategy is achieved by only manipulating the rotational speeds of the propellers at each rotor. Two of the rotors rotate in the same direction while the third rotates in the opposite direction. The control methodology is novel compared to other systems that require either coaxial rotors or an extra servo motor to control the yaw of the UAV. Results show that the proposed design achieved stable flight with minimal position-attitude cross control effect. The fixed nature of the rotors in the proposed design, reduced mechanical requirements and cost compared to existing vehicles of its type.