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Mobile robots are widely used in many applications, such as transportation, military domain, searching, guidance, rescue, hazard detection, and carpet cleaning. Because mobile robots usually carry limited power sources, such as batteries, energy saving is an important concern. In particular, differential wheeled mobile robots that have two independently movable wheels are popular because of relatively low mechanical complexity to achieve three-dimensional motion on a ground. This article presents a new wheeled device with a redundant drive system which consists of three independently movable actuators and two planetary gears to connect the actuators to two wheels. The proposed system is able to continue its motion safely when one of the motors breaks down for some causes and also able to operate over a longer period of time due to energy saving consumption property. Experimental results show that the proposed method is effective in saving energy approximately by 20.45% for linear motion and 13.05% for circular motion compared to a conventional one.

DieleCtriC loss in a piezoelectriC CeramiC transducer is concerned with the vibration, and inCreases remarkably under the high-power operation even in a so-Called hard PZT. When ordinary hard WI ceramics is used over the vibrational velocity of about 0.25 (mIs), the theletriC loss becomes larger than the mechaniCal vibration loss. In the paper, a new advanCed measurement method for obtaining simultaneously both the mechanical loss and the dielectric loss of the piezoeleCtriC ceramic transduCer under high-power operation is described. At the resonance frequency, the dielectric loss and the mechanical vibration loss can be separately and simultaneously measured. In the study, some experimental results have been obtained and evaluated with respect to the accuracy. These results are very useful for the precise design of the piezoelectric power devices.

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