Suchergebnisse

The world's commercial unmanned aerial vehicle (UAV) industry has witnessed unprecedented boom in recent years. Delighted with an ample supply of this excellent high-tech product, global consumers are paying more attention on UAVs. Civilian UAVs now vastly outnumber military ones, with the estimate of over a million sold by 2016. An UAV has various degrees of autonomy as enabled by the use and precise control of motors. Traditional Direct Current (DC) motors are replaced by permanent magnet synchronous motors (PMSM) associated with the new power electronic inverters. Because of a PMSM's higher power density than a DC motor, it reduces the rotor losses, thus improving its efficiency. The other improvement comes from the advanced control methods. The simple drive system based on a DC motor with open-loop control is outdated. High frequency switches in power electronic inverters offer an opportunity to change motor input voltage values and frequencies faster than ever before. Vector control approaches are employed with closed-loop feedback control, which brings high precision and good dynamics. Integrated inverter-motor drive systems are in progress. This thesis focuses on how to control PMSM installed in the UVAs with a high performance of dynamic response and fewer speed ripples. Field Oriented Control (FOC) is one type of vector controls to control a PMSM in a quadrotor. FOC of PMSM and Pulse Width Modulation (PWM) are introduced. The simulation results of FOC of PMSM with third-harmonic injection PWM and traditional FOC are compared. This comparison proves that FOC of PMSM with third-harmonic injection provides a better dynamic response for a quadrotor's movement in vertical direction. In addition, since PWM is helpful to reduce the speed ripples, PMSM has a better steady-state response during operations.

Virtual healthcare information technologies (HIT) are being adopted during the Covid-19 pandemic. We propose that even after Covid-19, virtual HIT can still have great potentials to address the challenges brought by the aging population on healthcare systems. The key questions are (1) what kinds of virtual HIT will be useful for seniors and (2) how these HIT will affect senior citizens' health-related quality of life (HRQL)? Centered on the concept of HRQL and grounded on task-technology fit (TTF) theory, this paper builds a framework of useful virtual HIT in the context of long-term care for seniors. The framework proposes senior citizens' human characteristics (i.e. restricted mobility, deteriorated working memory and attention, and social isolation) will influence their health-related tasks (task adaptability, autonomy, and interdependence). A set of virtual healthcare systems can be designed to fit seniors' tasks. These HIT will increase seniors' HRQL through increased task-technology fit (i.e. quality of healthcare, timeliness of healthcare, and relationships with seniors). This framework can serve as a base for researchers and practitioners in their endeavor to design more suitable HIT for seniors.