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A46E_EETimesEuro_2_375x10_875_A45.qxd 10/17/1 DC-3 Series Advanced wheel hub drive DC-1 Series passes extensive driving tests HiQP Series By Christoph Hammerschmidt Besides high design freedom and low-wear characteristics, wheel-integrated DC-DC electric drives offer a high potential to improve safety and driving dynamics of electric vehicles. However, they pose high challenges to drive design and manufacturing - in particular with respect to the safety assessment and to the specific measures for CONVERTERS series deployment. A research consortium led by Fraunhofer IFAM now succeeded in proving the safety of such drives even in the case of malfunctions. The consortium tested two wheel hub drives, mounted at the rear axle of a NEW!! Fraunhofer-developed demo vehicle under various difficult road surface conditions. The wheel hub drive generated a torque of up to 900 Nm per wheel. Tests included HIGH INPUT VOLTAGES dynamic turning manoeuvres on wet surface, directional stability on slick, icy roads as well as during heavy braking - and all of them in combination with various system UP TO 900 VDC. malfunctions which have been controlled selectively by the scientists. Subject to the test were innovative concepts of drive monitoring and error handling of fault-tolerant drive technologies under the aspect of operational safety. DC-1 Series • 120-370 VDC input voltage range • 5-300 VDC regulated isolated outputs • Up to 300 watts output power • 4.5” X 2.5” X 0.50” encapsulated package • DC-3 Series • 300-900 VDC input voltage range • 3.3 -300 VDC regulated isolated outputs • Up to 50 watts, single and dual outputs • Thru hole and terminal strip models • HiQP Series • 125-475 VDC input voltage range • 24-200 VDC regulated isolated outputs • Up to 50 watts output power • 2.50” X 1.55” X 0.50” encapsulated package ALL MODELS AVAILABLE WITH EXPANDED OPERATING TEMPERATURES SELECTED MILITARY SCREENING CUSTOM DESIGNS For full characteristics of these and the entire PICO product line, see PICO’s Full line catalog at www.picoelectronics.com PICOELECTRONICS, Inc. Pico Representatives Germany ELBV/Electronische Bauelemente Vertrieb E-mail: info@elbv.de Phone: 0049 89 4602852 Fax: 0049 89 46205442 England Ginsbury Electronics Ltd. E-mail: rbennett@ginsbury.co.uk Phone: 0044 1634 298900 Fax: 0044 1634 290904 In a first phase, the project partners collected and analysed data on possible effects of errors. By means of measurements on test rigs and numerical simulations, they determined the brake torque during short circuits in the coils as well as during failures of sensors and other components. Based on this knowledge they could develop specific hardware and software concepts for failure management. In this context, they developed a novel error recognition method that enables localising any errors reliably. Failures of the current sensor and the angle sensors can be detected safely through a comparison of values obtained though measurements and through modelbased calculation. In the case of an error, the model data are used. Handling of complications like short circuits in the windings or converters is based on a fault-tolerant design of the entire drive system. Towards this end, the electric motor consists of multiple redundant subsystems, enabling designers to isolate any errors and to compensate brake torque resulting from a failure, guaranteeing safely stopping the vehicle and even continue operation in emergency mode. The test proved that in particularly during rides at the physical limits under difficult road and weather conditions the implementation of the project results led to significant safety improvements. At any operational situation the formation of improper brake torques could be avoided. Even during fast turns and wet or even slippery road conditions, the vehicle remained controllable. First assessments as to the economics of the concepts showed that the safety measures can be integrated into electric drives without added cost, which makes it possible to transfer the results into series vehicle production. The project consortium included Fraunhofer IFAM and the institute for drive systems and power electronics of the Hannover university. It was funded in part by the German federal ministry for economy and energy. www.electronics-eetimes.com Electronic Engineering Times Europe December 2014 45


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