Development of collision avoidance system for useful UAV applications using image sensors with laser transmitter

The main goal of this study is to demonstrate the approach of achieving collision avoidance on Quadrotor Unmanned Aerial Vehicle (QUAV) using image sensors with colour-based tracking method. A pair of high definition (HD) stereo cameras were chosen as the stereo vision sensor to obtain depth data from flat object surfaces. Laser transmitter was utilized to project high contrast tracking spot for depth calculation using common triangulation. Stereo vision algorithm was developed to acquire the distance from tracked point to QUAV and the control algorithm was designed to manipulate QUAV's response based on depth calculated. Attitude and position controller were designed using the non-linear model with the help of Optitrack motion tracking system. A number of collision avoidance flight tests were carried out to validate the performance of the stereo vision and control algorithm based on image sensors. In the results, the UAV was able to hover with fairly good accuracy in both static and dynamic collision avoidance for short range collision avoidance. Collision avoidance performance of the UAV was better with obstacle of dull surfaces in comparison to shiny surfaces. The minimum collision avoidance distance achievable was 0.4 m. The approach was suitable to be applied in short range collision avoidance

Quadrotor UAV indoor localization using embedded stereo camera

Localization of Small-Size Unmanned Air Vehicles (UAVs) such as the Quadrotors in Global Positioning System (GPS)-denied environment such as indoors has been done using various techniques. Most of the experiment indoors that requires localization of UAVs, used cameras or ultrasonic sensors installed indoor or applied indoor environment modification such as patching (Infra Red) IR and visual markers. While these systems have high accuracy for the UAV localization, they are expensive and have less practicality in real situations. In this paper a system consisting of a stereo camera embedded on a quadrotor UAV (QUAV) for indoor localization was proposed. The optical flow data from the stereo camera then are fused with attitude and acceleration data from our sensors to get better estimation of the quadrotor location. The quadrotor altitude is estimated using Scale Invariant Feature Transform (SIFT) Feature Stereo Matching in addition to the one computed using optical flow. To avoid latency due to computational time, image processing and the quadrotor control are processed threads and core allocation. The performance of our QUAV altitude estimation is better compared to single-camera embedded QUAVs due to the stereo camera triangulation, where it leads to better estimation of the x-y position using optical flow when fused together

Relative position-based collision avoidance system for swarming UAVs using multi-sensor fusion

This paper presents the development of a quadrotor unmanned aerial vehicle (UAV) that is capable of quad-directional collision avoidance with obstacles in swarming applications through the implementation of relative position based cascaded PID position and velocity controllers. A collision avoidance algorithm that decides evasive manoeuvres in two dimensional flight by the means of net error calculation was developed. Sensor fusion of ultrasonic (US) and infrared (IR) sensors was performed to obtain a reliable relative position data of obstacles which is then fed into collision avoidance controller (CAC) for generating necessary response in terms of attitude commands. Flight tests performed proved the capability of UAV to avoid collisions with the obstacles and dummy non-flying UAVs that existed at a closer distance in its four primary directions of detections during flight successfully

Performance measure of satellite flying in coplanar and non-coplanar formation

In order to fulfill specific mission objective demand, spacecraft performance can be further optimized by means of various methods or configurations. Like for instance, selection of orbit type and inclination with a periodically repeated ground track will ensure the high efficiency of ground target coverage be accomplished throughout the whole duration of mission. Unfortunately, a single monoli thic satellite most often unable to accommodate the requirement solicitated by many multi background users. So, to deal with the issue, an alternative solution would be to operate a swarm of satellites flying in synchronized formation. In this paper, three satellites flying in co-planar and non-coplanar formation were simulated. Here, the resulting model of two deputy satellites operating in the same orbital plane but different phase angle moved along the orbit path while both still maintaining constant relative distance with the non-coplanar chief spacecraft throughout the whole orbit period were presented. The use of unique projected circular orbit (PCO) formation arrangement allows the assessment of some important performance measure parameters like average overlapping coverage area and optimum swath width coverage distance. For the determination of area on the surface of the Earth overlapped by three satellites, the analys is was done using the multiple boundary overlap condition. Parametric studies were conducted involving different formation distance and formation height to observe pattern variation of average total overlapping area and maximum coverage distance. Preliminary result showed that at a specific Earth central angle, the total overlapped area decreased substantially with the increased distance in formation. Height factor does not have significant influence in the total overlapped area variation due to constraint imposed on satellites operating in Low Earth Orbit (LEO) altitude regime. Results were tabulated using 3-dimensional graphs to study the relationships exist between multiple variables. Finally, conclusions were made based on our findings with regards to the performance of positioning satellites in such configuration

Development of unmanned aerial vehicle (UAV) based high altitude balloon (HAB) platform for active aerosol sampling

The knowledge on the abundance and diversity of the minute particles or aerosols in the earth's stratosphere is still in its infancy as aerosol sampling at high-altitude still possess a lot of challenges. Thus far, high-altitude aerosol sampling has been conducted mostly using manned flights, which requires enormous financial and logistical resources. There had been researches for the utilisation of high altitude balloon (HAB) for active and passive aerosol samplings within the stratosphere. However, the gathered samples in the payload were either brought down by controlling the balloon air pressure or were just dropped with a parachute to slow the descend speed in order to reduce the impact upon landing. In most cases, the drop location of the sample are unfavorable such as in the middle of the sea, dense foliage, etc. Hence a system that can actively sample aerosols at high-altitude and improve the delivery method in terms of quality and reliability using unmanned aerial vehicle (UAV) is designed and tested in this study

Implementation of extended high-gain observer in low-cost optitrack motion tracking system for UAV control

The objective of this paper is to present the implementation procedure and experimental results of using Extended High-Gain Observer (EHGO) in estimating the states from low-cost Optitrack camera that is being used as the motion tracking in the Unmanned Aaerial Vehicle (UAV) system. Owing to the low-cost sensor, the signal produced is noisy which requires filters to produce a good signal. The standard procedure to obtain differentiated signal is complex. Therefore, this paper proposed an alternative method using EHGO. The theory of EHGO is presented, and the steps taken to transform EHGO algorithm from continuous to digital form are described. Validation is performed in open-loop and closed-loop flight test to analyze the performance. The results show that EHGO able to estimate the velocity state at the same performance quality as the standard procedure using Kalman filter. Nonetheless, the advantage of EHGO is due to its simple algorithm hence minimal parameters to tune

Application of sliding mode control with extended high gain observer to stabilize the underactuated quadrotor system

This work proposes an output feedback controller for stabilization of the quadrotor underactuated system in the presence of time varying disturbances and model uncertainties. The proposed control is an improvement to the sliding mode control (SMC). An extended high-gain observer (EHGO) when combined with sliding mode control (SMC) able to give feasible performance beyond the performance of the standard sliding mode. It is able to bring the state trajectories of the closed-loop system close to the target system with a smaller ultimate bound of error and smaller control magnitude. The proposed method is illustrated by simulation

Comparative computational study of double rotating cylinder embedded on Selig S1223 aerofoil and flat plate for high altitude platform

The high-altitude platform was built as an alternative approach to address the weakness of the terrestrial and satellite communication networks. It can be an aircraft or balloon positioned 20 to 50 km above the earth’s atmosphere. The use of the Magnus effect was not noticeable in the production of the high-altitude platform, while past research study has denoted its aerodynamic performance in generating greater lift and stall angle delay, which would be beneficial in creating such a flying device. This research delineates the proposed designs using the computational fluid dynamics approach utilizing ANSYS WORKBENCH 2019 software. The embedment of the rotating cylinder onto the design would best portray the use of the Magnus effect in generating higher lift coefficients with probable delay in stall angle. Hereby, the design of embedding rotating cylinder onto Selig S1223 aerofoil and the flat plate is proposed to test their aerodynamic performances for high altitude platform purposes. Here, Fluent fluid flow analysis was simulated for 500 RPM and 1000 RPM momentum injection with free stream velocities from 5 m/s to 30 m/s for different angles of attack of 0 to 20 degrees. The analysis has resulted in a greater impact on its lift coefficient and stall angle delay of about 39% and 53% enhancement for modified aerofoil while showing 128% and 204% betterment for modified flat plate than their respective unmodified model. Therefore, it is perceived that the CyFlaP has better stability yet is simplistic in a design suitable for HAP application

Introduction of current pollination techniques and factors affecting pollination effectiveness by Elaeidobius kamerunicus in oil palm plantations on regional and global scale: a review

Oil palm (Elaeis guineensis) is considered as the most efficient and economic vegetable oil and has the capacity to fulfil the growing global need for oil consumption. The literature on oil palm pollination and its well-known pollinator Elaeidobius kamerunicus (EK), which performs natural pollination, is reviewed in consideration of extrinsic and intrinsic factors related with pollination effectiveness and palm oil production. The state of the oil palm and pollinators’ interaction is demonstrated by illustrating the phenology and behaviour of the inflorescences. In addition, the effectiveness of weevils as a pollinator mostly differs within different localities, seasonal and climate changes. Nevertheless, oil palm pollination can be determined by studying the phenology changes of the plant's flowers changes during anthesis. This paper discusses the oil palm phenology studies related with weevils and the major factors that influence their performance as well as the application of recent pollination practices in oil palm plantations

Conceptual exploration for airborne wind energy system for electricity generation in Pulau Perhentian Kecil, Malaysia – MBSE approach

Renewable energy plant research such as wind energy has been on the rise for the past few decades. The objective of this paper is to do a conceptual exploration of the new type of wind harvesting system known as Airborne Wind Energy System (AWES) to be used in Pulau Perhentian Kecil using Model-Based Systems Engineering Approach (MBSE) where the final selection is chosen using TOPSIS method. There are several types of concept designs to choose from based on their unique mode of operation. The candidate concept designs are from Ampyx Power B.V, Magenn Power, Makani and Altaeros Energies. From the TOPSIS analysis, Ampyx Power B.V has been selected due to its highest fulfilment of the requirements. This exploration into several potential AWES may help solve the deficiency of the current systems and advantageously utilise the suitable geographical factors of Pulau Perhentian Kecil