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We propose a position sensorless control scheme for a four-switch, three-phase brushless DC motor drive, based on the zero crossing point detection of phase back-EMF voltages using newly defined error functions （EFs）. The commutation instants are 30° after detected zero crossing points of the EFs. Developed EFs have greater magnitude rather than phase or line voltages so that the sensorless control can work at a lower speed range. Moreover, EFs have smooth transitions around zero voltage level that reduces the commutation errors. EFs are derived from the filtered terminal voltages Vao and Vbo of two low-pass filters, which are used to eliminate high frequency noises for calculation of the average terminal voltages. The feasibility of the proposed sensorless control is demonstrated by simulation and experimental results. 相似文献
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John Spandorfer Tanya Puklus Victoria Rose Mithaq Vahedi Lauren Collins Carolyn Giordano Richard Schmidt Chris Braster 《Anatomical sciences education》2014,7(2):144-152
Peer assessment has been shown to be an effective tool to promote professionalism in medical students. Peer assessment may be particularly useful in anatomy dissection laboratory as the required close collaboration and long hours of anatomy laboratory provide students insights into their peers' work habits and interpersonal skills. The objective of this study was to quantitatively and qualitatively analyze the use of a validated peer assessment tool in Gross Anatomy. Students in a first year medical school class evaluated three members of their dissection group using an online survey tool. The mid‐course and end‐of‐course evaluation included open‐ended comments, as well as a five‐point scale that measured three work habits, two interpersonal attributes and one overall score. All 267 students completed the assignment. The overall score and four of the five other assessed categories showed significant improvement from the mid‐ to end‐of‐course evaluations. Quantitative and qualitative data also revealed significant improvement among the students who received the lowest mid‐course assessments. Seventy‐six percent of the class agreed with the statement: “Based on the feedback I received, I made a change in how I worked with or taught my peers.” The use of this peer assessment tool used by students in anatomy was associated with improvements in work habits and interpersonal attributes, particularly by the cohort of students who received the lowest mid‐course feedback. Peer assessment offers students an opportunity to improve their interpersonal skills and work habits. Anat Sci Educ 7: 144–152. © 2013 American Association of Anatomists. 相似文献
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