Unmanned Systems Technology 001 | UAV Factory Penguin C | Real-time operating systems | Hirth S1218 two-stroke twin | Base stations | ASV C-Enduro | Composites | Datacomms

57 speed, ultimately stalling the blades to avoid overspeed. The normal operating speed – a function of the wind speed and the load imposed by its electrical machine – is about 1500 rpm. The turbine is hung down from the centre of the surrounding hoop by a carbon fibre tube, produced by ASV. Its output current travels through a cable running inside that tube and then through one side of the hoop to a stock controller mounted on the hull, which Hyperdrive modified to meet its requirements and which provides a dc output, with current and voltage variable. That output normally goes into the dc supply on the vessel, where it is apportioned between the drive motors and the battery. However, if the battery is in danger of becoming overcharged, it can be diverted to resistors in an aluminium rear corner of the right-hand side of the (otherwise composite) hull, so that the excess energy in effect simply heats the surrounding seawater. The solar panels It should not be surprising that ASV conceived the C-Enduro using solar power from the outset, as its head of design Rafael Coelho has a background in solar-powered electric craft. A native of Brazil, as a student at the Universidade Federal de Rio de Janeiro he travelled to the Netherlands to participate in the World Cup for solar-powered boats, and was subsequently involved in the development of a Brazilian solar boat competition before moving to the UK to progress his career. The conventional solar panels specified by ASV represent in essence the largest area it is feasible to cover within the constraints of the vessel’s size. Each of the 12 panels measures 1 m x 0.5 m and generates up to 50 W, hence in total a peak of 1.2 kW of electrical power is available, sunlight permitting. The panels are wired in series and, as is normal, an MPPT (maximum power point tracking) charge controller interfaces between them and the dc supply. The MPPT links up the panels according to how the sun is falling on the total surface area, and controls the current to ensure that the cells are operating at their most efficient point. A commercial off-the-shelf MPPT is used, which monitors panel output and stops excess current input to the dc supply. It will simply stop drawing current from the panels in that event, so there is no need to shed excess current from the system. If necessary, the panels can quite happily sit there in bright sunshine not producing electricity. In case of a system fault there is the option of cutting off the supply from the solar panels via circuit breakers under the control of the CAN ECU, but normally they are left switched on all the time. The diesel engine “One of the biggest challenges with the C-Enduro’s propulsion system was not the battery, or the e-machines or the control system, it was the combustion engine powering the generator,” Hyperdrive’s managing director Stephen Irish says. “This had to be a diesel engine in view of certain vessel launching regulations – essentially there is less fire risk than with a petrol engine – so the challenge was to find a lightweight solution.” Irish notes that the key to any such range-extender type engine, given a low power requirement (in this case about 4 kW at the crankshaft), is power density – in effect the ratio of output to the weight of the combined unit. In this respect, conceptually a two-stroke petrol engine wins out here, with a four-stroke spark ignition unit ahead of a compression ignition unit since its structural integrity requirement is less. A diesel engine it had to be though. “Low-power diesel engines are widely found in canal narrrowboats, but they aren’t designed for low weight,” remarks Irish. “It seemed at first that all existing units were too heavy.” Unmanned Systems Technology | November 2014 Hyperdrive Innovation (www.hyperdriveinnovation.com ) specialises in low-carbon vehicle technology, primarily powertrain and mostly electric and hybrid. Its strengths include energy storage and battery technologies, power management and systems integration. Primarily it undertakes projects on behalf of clients but has also successfully deployed its own product range in automotive, industrial and marine applications. Core Hyperdrive products include its own battery pack, battery management system, range extender, and data logging and telemetry system, all of which have been developed and are built in-house. The logging system can interrogate an entire vehicle. Hyperdrive also has its own engine control unit that acts as the vehicle controller for hybrid and electric vehicles that it too develops in-house. Hyperdrive Innovation The engine had to be a diesel in view of launching regulations, so the challenge was to find a lightweight one