Sky Power, a leading manufacturer of 2-stroke combustion and Wankel engines for UAS, has introduced a novel engine construction kit for unmanned aerial vehicles (UAVs) in order to enable more efficient and performance-optimized engines. Using this construction kit, propulsion units can be ideally tuned to the customer’s desired performance parameters and application area. The kit was introduced at the 2018 AUVSI Xponential trade show.
“We’re seeing ever stronger demand for application-oriented solutions,” commented Karl Schudt, managing director of Sky Power GmbH. “That’s why we considered how we could best serve this demand, since each customer favours his own solution. In the past, UAS manufacturers were just interested in getting their flight systems into the air. That’s why propulsion units were often relegated to a subordinate role. This has changed permanently in recent years. Today, UAS have got to fly efficiently and be tuned exactly to their application area.” Out of this came the first engine construction kit for UAS systems from Sky Power with which customer- and application-specific propulsion solutions can be quickly visualized and implemented.
The engine construction kit consists of widely different components. At the centre is the basic engine, which can be equipped with both a carburetor and the new injection from Sky Power. To this is added as desired an exhaust, silencer, and the new ECU and ignition. The engine can furthermore be provided with an e-drive or generator, which uses a converter to generate electrical energy for batteries and super capacitors.
Super capacitors can be charged and discharged very fast. They can withstand a lot more switching cycles than rechargeables, so they lend themselves as substitutes for the latter whenever severe switching stress is required. Super capacitors’ application area stretches from provision of the weakest currents for data retention in static memories (SRAM) up into the power-electronics range, for instance as the store of electrical energy in the KERS system in Formula-1 racing cars. This is also exactly the property required in UAS propulsion units when they’re used as a hybrid system or to feed in energy to enhance the engine’s short-term performance.
All 3W-International engines can be equipped with this e-drive supercap system. The engine can therefore be used as a pure power generator for electrical motors, but also as a combined system in which electrical and combustion energy can be used in combination. Pure usage from combustion energy is likewise possible. The customer’s performance parameters and application area determine the engine’s usage type. “At the trade fair, we’ll show visitors which modular components are necessary for an electrical emergency system, for direct engine use, for a range extender, and for hybrid applications,” explained Schudt. The hybrid application is being accorded a lot of attention at Sky Power because the demand for such propulsion solutions continues to intensify. “Hybrid drive units are going to be the propulsion source for unmanned systems in the future.”
The engine construction kit necessitates the propulsion manufacturer’s early involvement in the customer’s project. Not only must the right components be sought out, but they must also be tuned to one another. Thus for instance, the silencer must be orientated towards the basic engine’s cylinder volume in order to prevent a performance-diminishing backing up of exhaust gases. The e-drive must be selected based upon the desired electrical power and the ECU must be calibrated to the propeller used, the desired flight performance, and the flight surroundings. The same applies to the use of carburetors or injection. In addition, the customer requirement decides the use. For instance, cost-optimized carburetors make sense for target drones, whereas a carburetor must be discouraged in the case of performance-optimized engines.
“Many details must be clarified with the customer before initial engine assembly. So we’ve got to maintain tight information exchange with the customer. After all, he’s getting an individualized product that has to conform with defined parameters. That’s why we’ve invested in additional in-house test systems in order to demonstrate the engine performance that the customer wants,” Schudt continued.