Johan Meyer

Brushless DC motor characterisation and selection for a fixed wing UAV

The aim of the paper is to present a method for evaluating brushless DC motors (BLDC) for fixed wing Unmanned Aerial Vehicles (UAVs). Selection of a BLDC motor, which operates in its efficient region for a UAV platforms specifications, will affect the endurance capabilities of the UAV platform. A four-constant model is presented as a means of modelling and predicting the characteristics of BLDC motors. Further, physical testing of each motor is performed on a constructed motor test bench. Validation of the models results is compared to physical testing. The methods presented provide a means of accurately characterising a given BLDC motor. This data can be used to design the additional components used in the UAVs propulsion system.

Design considerations for a low altitude long endurance solar powered unmanned aerial vehicle

This paper presents design considerations for a low altitude long endurance solar powered unmanned aerial vehicle (LALE UAV). The considerations addressed include the determination of the available solar power, the design of the UAV wing for long endurance flights and the determination of the electrical power and energy balance of the UAV. Using these considerations, a solar powered UAV was designed and long endurance flight simulated Based on the simulation results it is in principle possible to design and build a solar powered LALE UAV.

Small fuel cell powering an unmanned aerial vehicle

This paper presents the design of a power plant in the form of a 100 W hydrogen fuel cell to provide sufficient power to maintain steady, level flight for a small scale fixed wing unmanned aerial vehicle (UAV). The size of the fuel size is smaller than any other fuel cell previously used for this type of application. What makes this aircraft unique is the small fuel cell, which will be integrated into the UAV to achieve the objective of sustaining flight using only 100 W of power. Performances of the fuel cell and aircraft are evaluated using data from laboratory and flight tests.

Design and implementation of an autonomous hybrid vehicle

This paper outlines the design strategy for the University of Johannesburgs (UJs) hybrid vehicle entry into the South African Solar Challenge (SASC) 2010. The SASC is a biennial event focused on alternative energies and showcasing various automotive technologies. The SASC is broken up into different classes; UJ entered in the Greenfleet Technology class. This paper presents the design principles and strategies used to implement a working prototype vehicle which is hybrid (propelled by multiple energy sources) and autonomous (able to operate without human assistance).

Vibration Disturbance Localization Using a Serial Array of Identical Low-Finesse Fiber Fabry-Perot Interferometers

An optical fiber sensor system for localization of a vibrational disturbance along the fiber is presented. The sensor system is based on a serial array of identical Fabry-Perot interferometers, formed directly in the single mode SMF-28e fiber by pairs of fiber Bragg gratings with reflectivity of 0.04% each. Interferometers were interrogated by an intensity modulated distributed feedback diode laser. We present a signal processing algorithm for localization of a disturbed interferometer and experimental results for a serial array of 14 in-fiber interferometers. Simple sensor configuration and the use of low-frequency components make it potentially inexpensive and suitable for applications where continuous monitoring for appearance of vibrations is required.

A critique on previous work in vision aided navigation

This paper presents a critique on previous work in the field of vision aided navigation, particularly in the fusion of visual and inertial sensors for navigation. Several improvements and updates are proposed for the existent systems. GPS receivers have allowed for accurate navigation for many vehicles and robotic platforms. GPS based navigation can, however, prove to be impractical in applications where there is no GPS reception such as underground, indoors or in some urban areas. This pertains, in particular, to many robotic applications where position must be known in global coordinates or relative to a reference point. An inertial navigation system (INS) can be used to calculate ones relative navigation state via dead-reckoning calculations. The downfall of a low-cost INS is the errors associated with the system. While these errors are initially small, integration causes large drift errors over time. To combat this problem, cameras can be used to estimate the errors present in the INS readings. These results can then be used to correct the navigation state output from the INS. While the motion estimations from the cameras are not error-free, this method is made highly effective because of the complementary nature of the errors from the cameras and INS. Several improvements are proposed for this method; algorithmically, in updates to its hardware, and with the introduction of graphics processors to improve computational performance. The overall system performance, individual steps, algorithms, and results are compared to results from similar works to those of the proposed improvements. It is shown that the accuracy, responsiveness and overall performance of the system can potentially be greatly improved.

Critical design parameters for a low altitude long endurance solar powered UAV

The paper presented provides theoretical findings of the critical solar UAV parameters required for prolonged flight. The parameters being, battery energy density, wing surface area, total UAV weight and solar surface area. The findings are based on two individual models, a solar and an aerodynamic model, which are combined to form a solar powered UAV model.

Design Considerations for Long Endurance Unmanned Aerial Vehicles

The arena of Unmanned Aerial Vehicles (UAVs) has for many years been dominated by the defence industries. The reason for this can be attributed to the complexity and cost of designing, constructing and operating of these vehicles. An additional contributing factor is the legislative issues around operating an unmanned aircraft in civilian airspace. However in resent years advances in micro-electronics especially Micro Electronic Mechanical Systems (MEMS) and advanced composite manufacturing techniques have placed the design and construction of UAVs in the domain of the commercial civilian users. A number of commercial UAV applications have emerged where the legislative requirements for operating of a UAV in segregated airspace can be met. UAVs are extremely well suited for the dull, dirty and dangerous tasks encountered in performing surveying and surveillance applications. For these tasks the primary design considerations in the design of the UAV would be the propulsion system, the guidance and control system and the payload system.

Fibre Bragg gratings in polymer optical fibre at 980 nm

We describe the production of Bragg gratings at 980 nm in two types of single mode polymer optical fibres. The first type is based on PMMA (polymethylmethacrylate) with a core of PMMA-PS copolymer with less than 5% PS (polystyrene). The second type is based on PMMA with the addition of PBzMA (polybenzylmethacrylate) and PEMA (polyethylmethacrylate) in the core. The success rate of inscribing gratings in the first and second type was 30 and 100%, respectively. The reflectivity varied from grating to grating. The disappearance of the gratings after a certain period of time is subject to further investigation.

A Sustainable Model for Problem Based Learning in a South African School

South Africa is currently facing an education dilemma with high numbers of youth unemployment and a growing specialized skills shortage in Science, Technology, Engineering and Mathematics (STEM). STEM problem based learning events, hosted by government and the corporate sector, has shown to improve science and technology literacy and to encourage the youth to pursue tertiary education in the field of science. Unfortunately, schools face a range of challenges which restricts them from participating in these learning methods, depriving learners of the advantages offered by problem based learning. This paper presents a model for the sustainable provision of STEM problem based learning opportunities in South African schools. The presented model is based on a two-team mentoring model which makes problem based learning sustainable in a South African school environments. The Shell Eco Marathon is in its third year, and the students that have passed through the program will now be progressing to university. The impact of this program, therefore, will be become evident by the success of the students’ studies in the near future.Copyright