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Multi-Phase-Shift Control of a Power Converter
Get PDFMulti-phase-shift control of a power converter is provided. The power converter includes a dual-active-bridge (DAB) converter having a transformer, a first H-bridge coupled to the primary winding of the transformer, and a second H-bridge coupled to the secondary winding of the transformer. The DAB converter is operable to generate two-level and three-level voltage waveforms on the primary winding and on the secondary winding to yield a system which ensures zero-voltage switching and unity power factor over a wide range of input and output voltage levels and power throughputs. In a multi-phase shift (MPS) mode of operation, the DAB converter changes from a two-level voltage in at least one of the windings to a three-level voltage in both windings in response to the instantaneous load being below a predetermined level, resulting in more performance of the DAB converter in light load conditions
Vibration Analysis of Healthy Skin: Toward a Noninvasive Skin Diagnosis Methodology
Get PDFSeveral noninvasive imaging techniques have been developed to monitor the health of skin and enhance the diagnosis of skin diseases. Among them, skin elastography is a popular technique used to measure the elasticity of the skin. A change in the elasticity of the skin can influence its natural frequencies and mode shapes. We propose a technique to use the resonant frequencies and mode shapes of the skin to monitor its health. Our study demonstrates how the resonant frequencies and mode shapes of skin can be obtained using numerical and experimental analysis. In our study, natural frequencies and mode shapes are obtained via two methods: (1) finite element analysis: an eigensolution is performed on a finite element model of normal skin, including stratum corneum, epidermis, dermis, and subcutaneous layers and (2) digital image correlation (DIC): several in-vivo measurements have been performed using DIC. The experimental results show a correlation between the DIC and FE results suggesting a noninvasive method to obtain vibration properties of the skin. This method can be further examined to be eventually used as a method to differentiate healthy skin from diseased skin. Prevention, early diagnosis, and treatment are critical in helping to reduce the incidence, morbidity, and mortality associated with skin cancer; thus, making the current study significant and important in the field of skin biomechanics
Proof of Concept: VR Rehabilitation Game for People with Shoulder Disorders
No full textShoulder pain is very common in adult population (16%–26%) and it has several impacts on the Activities of Daily Living (ADLs). In this context, an effective rehabilitation is needed to assist the patients to regain autonomy and improve ADLs. An alternative approach to monotonous traditional rehabilitation can be offered by Virtual Reality (VR) technology and video game console systems. In this paper, we present a proof of concept of a computer game for shoulder rehabilitation. The system consists in a VR application developed with the Unity game engine, and it is currently controlled via mouse interactions; however, the software application has been designed for the Nintendo Wii Remote MotionPlus as the main game controller, but this tool will be integrated in the next development phase. Our goal is to develop a rehabilitation game: suitable to be used both at home and at a hospital, highly motivating for the patient, and requiring low-cost technology (e.g. a consumer-grade tracking system). The game has been tested preliminary with three healthy subjects who agreed that the application is engaging, motivating and intuitive
Effects of Control-Display Mapping and Spatially Dependent Gain on Supported Free-Hand Gesture Pointing Performance
No full textWhile gesture controls will be important as future computing input modalities, they are limited by reduced performance and increase ergonomic risk. Performance of pointing in free-hand gestural controls is affected by control-display (CD) parameters such as gain and mapping, but specific CD function parameters that yield optimal performance are unclear. This paper describes an experiment that examines the effect of altering CD gain in different movement directions (‘spatially dependent gain’, SDG) for different CD mappings on their performance in armrest-supported pointing tasks. Thirteen participants were given a series of circular Fitts’ tasks with different fixed CD gain and mapping settings. The SDG was used to warp the Fitts’ circle in the participants’ physical motor-space in order to take advantage of inherent motor performance differences. Additionally, the placement of the movement controller was also studied. The results show that mapping is the most significant factor; vertical mapping produced throughput results that were approximately 0.5 bits/s greater on average than the other mappings. Vertical mapping is also where CD gain shows the most effect. Lower gain settings produce results that are 0.14 bits/s faster than higher gain when the user is in vertical mapping. No significant differences were found in pointing performance between SDG conditions. These preliminary results suggest that participants adapt easily to motor-space warping and that further study of non-fixed gain functions (e.g. pointer acceleration functions) is necessary in order to maximize free-hand performance
