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Magnetic losses under triangular symmetric and asymmetric induction waveforms have been measured over a broad range of frequencies and predicted starting from standard results obtained with sinusoidal induction. Non-oriented Fe-Si and Fe-Co sheets, nanocrystalline Finemet-type ribbons, and Mn-Zn ferrites have been investigated up to f = 1 MHz and duty cycles ranging between 0.5 and 0.1. The intrinsic shortcomings of the popular approach to loss calculation of inductive components in power electronics, based on the empirical Steinmetz equation and its numerous modified versions, are overcome by generalized application of the Statistical Theory of Losses and the related concept of loss separation. While showing that this concept applies both to ferrites and metallic alloys and extracting the hysteresis (quasi-static), excess, and classical loss components, we relate in a simple way the magnetic energy losses under symmetric triangular induction (square wave voltage) and sinusoidal induction. The loss behavior under asymmetric triangular induction is retrieved from the symmetric one, by averaging the energy losses pertaining to the two different semi-periods. Good comparison with the experimentally measured energy loss versus frequency behavior is demonstrated in all materials.

Epidermal electronics (e-skin) emerging in recent years offer the opportunity to noninvasively and wearably extract biosignals from human bodies. The conventional processes of e-skin based on standard microelectronic fabrication processes and a variety of transfer printing methods, nevertheless, unquestionably constrains the size of the devices, posing a serious challenge to collecting signals via skin, the largest organ in the human body. Herein we propose a multichannel noninvasive human–machine interface (HMI) using stretchable surface electromyography (sEMG) patches to realize a robot hand mimicking human gestures. Time-efficient processes are first developed to manufacture µm thick large-scale stretchable devices. With micron thickness, the stretchable µm thick sEMG patches show excellent conformability with human skin and consequently comparable electrical performance with conventional gel electrodes. Combined with the large-scale size, the multichannel noninvasive HMI via stretchable µm thick sEMG patches successfully manipulates the robot hand with eight different gestures, whose precision is as high as conventional gel electrodes array.

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Abstract:As one of the main parasitic parameters in permanent magnet (PM) synchronous machines (PMSMs), cogging torque is the main component of the torque ripple, which has always been the handicap in the high-performance, low-speed drive systems. Over the last two decades, various methods have been proposed to decrease the cogging torque in both radial-flux and axial-flux PMSMs. Among these methods, stator slot skewing, stator tooth notching, PM skewing, PM shifting, and pole pairing are extensively investigated. However, little work has been done on reducing the cogging torque of the claw pole machine (CPM), whose cogging torque cannot be ignored. In this paper, the general methods that have been used to reduce the cogging torque in radial-flux and axial-flux PMSMs are developed and verified in a CPM with a soft magnetic composite (SMC) core. The 3-D finite element method (FEM) is used to calculate the cogging torque and PM flux linkage per turn. By comparing different cogging torque reduction technologies, it can be found that the magnet step skewing and unequal claw pole width are very suitable for CPM.

By using global ring winding, the torque coefficient of the transverse flux machine (TFM) is proportional to its number of pole pairs, and thus the TFM possesses high torque density ability when compared with other electrical machines. As a special kind of TFM, the claw pole machine (CPM) can have more torque due to its special claw pole teeth. The manufacturing of CPM or TFM with silicon steels was very difficult in the past, and is a handicap for the progress of this kind of machine. Thanks to the advent of soft magnetic composite (SMC) materials, the manufacturing process of CPM has become more and more simple. More attention has been paid to this kind of technology, and some mass production CPMs with SMC cores have appeared. However, there are few works that discuss the key design issues for this kind of machine. In this paper, a small CPM with SMC is used as as a research benchmark. Various design methods that can be adopted to improve its performance have been studied, including unequal stator claw pole teeth, a skewing magnet design, consequent pole design, and etc. The 3D finite element method (FEM) is used for the machine analysis, and it is verified by the experimental results of a CPM with SMC cores.

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