| Budget Amount *help |
¥4,030,000 (Direct Cost: ¥3,100,000、Indirect Cost: ¥930,000)
Fiscal Year 2012: ¥4,030,000 (Direct Cost: ¥3,100,000、Indirect Cost: ¥930,000)
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| Research Abstract |
Flywheel energy storage system (FESS) works by accelerating flywheel to high speed rotation andmaintaining the energy in the system as kinetic energy. The energy is converted back by slowing downthe flywheel. A typical system consists of a rotor suspended by bearings inside a vacuum chamber to reduce friction, connected to a combined electric motor/generator. Active magnetic bearings (AMBs) arenecessary to improve total energy efficiency. In conventional mechanical bearings, viscous damping isdirectly proportional to speed, and at high speed, too much energy would be lost. From this background,we have been focusing on the use of AMB in FESS due to the significant advantages such as contactlessand frictionless bearings at high speed rotation. Usually, magnetic bearings are mostly used only insystems with immovable environment. Here on the contrary, we developed a vehicle with flywheel usingmagnetic bearing and gimbal mechanism as energy storage system. Flywheel-power assistedcars(mostly
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mechanical, or with mechanical bearings) have been developed since long time ago and inongoing researchs in effort to make flywheel systems smaller, lighter, cheaper and have greater capacity.Proposed flywheel systems would eliminate the disadvantages of existing battery systems such as low power density, long charge times, heavy weight, short lifetimes, and lead pollution. The weakness isdifficulty to store energy for a long time in flywheel. And, high speed rotation implies that the safetyconcerned with burst failures should be guaranteed. From this consideration, carbon fiber reinforcedpolymer (CFRP) is chosen as the material for the flywheel, since it is lighter and yet stronger than steel.In vehicle applications, flywheels also act as gyroscopic body, since the angular momentum is typically of a similar order of magnitude as the forces acting on the moving vehicle. This property may be detrimentalto the handling characteristics. Besides, this property could be utilized to improve stability in curves.Conversely, the effect can be almost completely removed by mounting the flywheel within anappropriately applied set of gimbals, where the angular momentum is conserved without affecting thevehicles. We achieved good performance of flywheel supported by zero-bias AMBs by means ofcontrollers which significantly compensate gyroscopic effects. The flywheel can rotate up to 300Hzwithout any gyroscopic effect. We mounted FESS on an electric vehicle (EV) and designed electricpower converter to charge/discharge the energy. We developed and implemented new algorithm tocompensate gyroscopic effect while EV is turning. This report describes experimental results includingmaneuverability and overall energy efficiency, including the results of outdoor field experiments such asfeasibility test of steer-by-wire system, implementation of input shaping to reduce vibration andgyroscopic effects, simple adaptive control method for flywheel attitude control, and the efficiencymeasurement of the energy conversion system. Less
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