An internal power angle control strategy for high-speed sensorless brushless DC motors

High-speed Brushless DC Motors(BLDCMs)usually adopt a sensorless control strategy and operate in three-phase six-state drive mode.However,the sampling errors of the rotor position and the driving method increase the Internal Power Angle(IPA),resulting in a decrease in the efficiency of the system.Conventional IPA reduction strategies are either sensitive to motor parameters,or ignore diode freewheeling during the commutation process,or require additional current sensors.In this paper,a new strategy to reduce the IPA is proposed.Firstly,a Zero-Crossing Point(ZCP)detection method for the back-EMF without filter is proposed to reduce the sampling errors of the rotor position.Secondly,the relationship between the non-energized terminal voltage and the ZCP of the corresponding back-EMF is analyzed.The non-energized terminal voltage that has completed the diode freewheeling is divided into two triangles by half of the bus voltage.When the IPA is suppressed,the areas of the two triangles are equal.Thirdly,an advanced angle for reducing the IPA is obtained through a PI regulator which can eliminate the deviation between the two areas.Finally,both a simulation model and an experimental circuit are built to verify the proposed control strategy.

Pricing Power of China's Cocoon and Silk Products in International Market:An Empirical Analysis Based on International Market Power

Do China＇s silk products only have advantage in number but no pricing power in international market？ In this paper, we used the residual demand elasticity model to estimate the international market power of China＇s silk products. The empirical results revealed that China＇s raw material products such as natural silk products and semi-finished products such as satin products had certain market power in the main export markets, but the finished silk products such as woman＇s blouse or shirts and shawls had no market power in the target markets including USA and Germany. The scale economy from resource endowment and great market share are the base of the international market power of natural silk products. The advantage from industry agglomeration and great market share are the source of the international market power of satin products. Technical bottlenecks and inefficiency in brand building are the cause of unobvious international market power of China＇s finished silk products, and the competition from Italy and France has increased the difficulty to enhance market power. In order to consolidate and improve the international market power of China＇s silk products, it is suggested to stabilize the production scale and strengthen industrial base, to speed up the resources integration and optimize the industrial distribution, to strengthen science and technology innovation and adjust product structure, to speed up the brand construction and enhance the influence of brand, and to enlarge the scale of organization and achieve scale economies.

The Sixth International Conference on Fluid Power Transmission and Control(ICFP'2005)

Date: April 12-15, 2005 Venue: Zhejiang University, Hangzhou, P. R. China Organized by Institute of Mechatronic Control Engineering, Zhejiang University

The 3rd International Symposium on High Power Laser Science and Engineering

9 to 12,April,2018 Suzhou,China International Symposium series on High Power Laser Science and Engineering,aiming at bringing together worldwide scientists and engineers working on high power laser and physics,is held every two years since 2014.On behalf of the 3rd International Symposium on High Power Laser Science and Engineering(HPLSE2018),