Search

A number of manufacturing challenges exist in creating a robust permanent-magnet synchronous motor (PMSM) design to meet critical requirements for cogging torque and torque ripple in specific applications. In addition, reduction of the back electromotive force (BEMF) harmonics that lead to torque ripple is also required during design. Due to manufacturing tolerances, maintaining capability with these requirements is very difficult, particularly for mass production of units. A design of experiments (DOE) that combines manufacturing tolerances with assembly process variations is proposed here to address the sensitivity of cogging torque and harmonics. The limits for the parts and the process variations are extracted from an actual production environment. The DOE is laid out according to one of the robust engineering matrices chosen from Taguchi's method. The DOE results are then utilized to set the tolerance limits for manufacturing the rotor magnets and to set the allowance for the rotor assembly process variations. The method helps to limit the cogging torque and harmonics within predefined bands, thereby producing a robust motor. This paper also investigates the capability of maintaining the tolerances of magnets for a surface-mounted PMSM. The analysis is done using a finite-element method and verified with experimental results.

Aerosols are the primary source of chemical elements transported by rainwater, which are removed from the atmosphere by rainout or by washout. Atmospheric aerosols (sea salt, crustal dust, and biogenic aerosols) have been found as the major sources of dissolved species in river water. Dissolved components from rainwater come from those originating from sea salt aerosols; from those originating from terrestrial aerosols (soil dust, biological emissions); and from those originating from anthropogenic sources (industry, agriculture, burning of fossil fuels, etc.). Along with the geological characterization of the watershed, meteorological parameters are critically important in evaluating rainfall effects. Keywords: rainout; washout; sea salt aerosols; terrestrial aerosols; rainwater chemistry; strontium isotope

Precise isolation and resolution of scan chain defects are more critical than ever due to increased reliance on scan-based design to achieve desired test content. At the same time, its diagnosis is becoming more difficult as product design increases in complexity alongside shrinking fabrication processes. In this paper, we present a new scan chain diagnosis procedure that is centered on Load Pass Unload Fail/Load Fail Unload Pass (LPUF/LFUP) and Scan Shift Logic State Mapping (SSLSM) techniques to isolate both stuck-at and timing scan chain faults without the design overhead and defect assumptions of previously proposed methods. More importantly, this procedure is extended to analyze scan chain with multiple defects, which is becoming a more frequent occurrence as process scales down in size.