A Design Method of Traveling Wave Rotary Ultrasonic Motors Driving Circuit under High Voltage Using Single-Sided Hertzian Contact Forced Oscillator Model.

Traveling wave rotary ultrasonic motors (TRUMs) are widely used in various industrial processes due to their attractive features, such as compact structure, high accuracy, and fast response. However, the major limiting factors of the operational performance of TRUMs under high-voltage excitation are the nonlinear behavior caused by the nonlinearities of the piezoelectric materials and the friction between the stator and rotor of the motor. In this study, a nonlinear dynamics model and an identification method are presented to directly design the driver circuit for suppressing the nonlinear behavior under high voltage excitation. Firstly, by studying the time-frequency characteristics of the isolated electrode voltage, a single-sided Hertzian contact forced oscillator model of TRUMs is established, involving the nonlinearities of the piezoelectric material and friction. Secondly, a harmonic balance nonlinear identification is proposed in the time domain for TRUMs. The influence of the voltage and preload on the nonlinear phenomena is discussed. Lastly, a novel driver circuit is proposed to suppress the nonlinearities using feedback from the isolated electrode. Experiments showed that the total harmonic distortion decreased by 89.4% under 500 Vpp. The proposed drive circuit design method is used to find a high excitation voltage and preload to achieve greater motor output power.

Comparisons between main and ratoon crops in resource use efficiencies, environmental impacts, and economic profits of rice ratooning system in central China.

Rice production in China is constrained by excessive water consumption, labor shortage, large environmental footprint, and low economic profit. Rice ratooning is a promising practice to increase famers' profit with higher resource use efficiency and less environmental impact compared with other rice cropping systems. However, there is limited information on the differences in energy use efficiency, water and labor productivity, environmental footprint, and economic return between main crop (MC) and ratoon crop (RC) in this cropping system. This study was conducted to compare the system performance between the two crops of ratoon rice using on-farm survey data. Average grain yield was 8.40 and 4.55 t ha-1 for MC and RC, respectively. Although RC produced 45.9% lower grain yield, it had 57.3% less total energy input and 71.0% lower total production cost than MC, which resulted in a significantly higher energy use efficiency, net energy ratio, net economic return and benefit-to-cost ratio. Lower total energy input and production cost of RC was mainly attributed to the reduction in fertilizer application and labor input, respectively compared with MC. In addition, both labor and water productivity of RC was significantly higher than those of MC. Furthermore, the global warming potential (GWP) and yield-scaled GWP of RC was 59.3% and 23.4% lower than those of MC, respectively, due to lower agronomic inputs and GHGs emissions. Overall, our results suggested that RC had higher resource use efficiency, better economic performance, and less environment impact compared with MC.