The design and implementation of speed control driver, which is applied to two-phase brushless DC fan motor is presented in this thesis. In addition, motor coils current limiter, output-stage Snubber circuit, and lock detection and auto-restart circuit are added to the driver for the sake of increasing stability and robustness. Because of high frequency energizing noise and dispensable power consumption problems generated by open-loop fixed frequency PWM speed control approach, several closed-loop speed control methods with speed estimation signal feedback are adopted for improvement. Furthermore, this thesis proposes a sensorless driving control strategy to eliminate Hall sensor in rotor position detection, and similarly has closed-loop speed control methods to achieve the goal of driver cost reduction, size decrease, and good control performance.

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The DSP is used as the control kernel in this thesis, proposing a method of sensorless and variable speed driving with current feedback for the DC compressor. By detecting the back electromotive force signals directly, the information of rotor position can be obtained, the commutation process and the speed estimation can also be achieved. Combining the current feedback method, the sinusoidal commutation with sensorless control makes the motor lower speed ripple and higher rotating efficiency. The results show that the sinusoidal commutation approach has the advantages of higher efficiency and less speed ripple as compared to the approaches of traditional-step commutation and six-step with current feedback by experimental setting.

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Exoskeletons are getting popular day by day due to their abilities in helping people. Exoskeletons can be used to help people gain motor senses through rehabilitation. It can also help healthy people to augment their abilities. These exoskeletons need to be strong yet light, so that the human body can support the exoskeleton, while the exoskeleton can support the activity that is being performed. This calls for under-actuated systems, which help in avoiding unnecessary mass due to additional actuators, while providing the same movement capabilities. This thesis describes in detail about two such under-actuated upper body exoskeletons which can be used for lifting loads. The design of such exoskeletons and novel control techniques for comfortable usage is discussed in detail. / Master of Science / Exoskeletons are assistive devices which can help people in several ways. An exoskeleton can help people who are affected with stroke by enabling them to walk through rehabilitation and physiotherapy. It can also help people to perform beyond their capacity in terms of physical activities. This could be to lift more load than possible, run faster than usual. This thesis describes the design and working two such exoskeletons which can be attached to the upper body. These exoskeletons can be used by people to lift loads which would require a lot of effort and muscle activity. The addition of these exoskeletons potentially reduce the muscle activity on the user and helps avoiding injuries in long term. Such exoskeletons have to be light weight so that they do not defeat the purpose of reducing muscle activity. This problem is solved by using under-actuated systems, because a significant mass of the exoskeleton is taken by the actuators such as the motors. Using under-actuated systems help in lowering the mass of the exoskeleton, while still being able to perform the same kinds of motion. This thesis also talks about how these exoskeletons can be controlled such that the load is being lifted with minimal efforts, and being aware of the loads it is lifting to provide the correct amount of torque, above or below which can lead to the motor shooting up or down causing muscular discomfort and injuries in the arm.

Rotor position estimation of switched reluctance machines (SRMs) is the main focus of this work. Rotor position sensors are a crucial component of optimal motor controls. Fail-safe operation and system cost reduction have been extensively researched and implemented in industry and academia. Position sensorless control on switched reluctance machines introduces a new challenge due to high nonlinearity under different operating conditions. A comprehensive review of SRM analytical modeling is presented, detailing each technique's main advantages and drawbacks. A least square-based analytical model (LSA) is proposed, which provides a simpler implementation and improved performance when compared to the methods commonly used in the literature. A literature review of rotor position sensor technology, position sensor fail modes, and position sensorless control is presented, providing a good roadmap of potential development and current limitations of the current technology. A wide speed range sensorless control is usually required when considering fail-safe techniques, fail detection methods, and low-cost applications. A unified nonlinear optimization-based sensorless control is proposed in this thesis, where a single method is used for startup, low and high speeds, with reduced memory allocation where a look-up table is not required, optimal transient response due to the elimination of a phase-locked-loop (PLL), and robustness against parameter variation. The method is validated at a wide speed range and torque conditions, thus showing the performance against conventional methods. / Thesis / Doctor of Philosophy (PhD)

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No description available.

Brushlesss dc (BLDC) motors and their drives are penetrating the market of home appliances, HVAC industry, and automotive applications in recent years because of their high efficiency, silent operation, compact form, reliability, and low maintenance. Traditionally, BLDC motors are commutated in six-step pattern with commutation controlled by position sensors. To reduce cost and complexity of the drive system, sensorless drive is preferred. The existing sensorless control scheme with the conventional back EMF sensing based on motor neutral voltage for BLDC has certain drawbacks, which limit its applications. In this thesis, a novel back EMF sensing scheme, direct back EMF detection, for sensorless BLDC drives is presented. For this scheme, the motor neutral voltage is not needed to measure the back EMFs. The true back EMF of the floating motor winding can be detected during off time of PWM because the terminal voltage of the motor is directly proportional to the phase back EMF during this interval. Also, the back EMF voltage is referenced to ground without any common mode noise. Therefore, this back EMF sensing method is immune to switching noise and common mode voltage. As a result, there are no attenuation and filtering necessary for the back EMFs sensing. This unique back EMF sensing method has superior performance to existing methods which rely on neutral voltage information, providing much wider motor speed range at low cost. Based on the fundamental concept of the direct Back EMF detection, improved circuitry for low speed /low voltage and high voltage applications are also proposed in the thesis, which will further expand the applications of the sensorless BLDC motor drives. Starting the motor is critical and sometime difficult for a BLDC sensorless system. A practical start-up tuning procedure for the sensorless system with the help of a dc tachometer is described in the thesis. This procedure has the maximum acceleration performance during the start-up and can be used for all different type applications. An advanced mixed-signal microcontroller is developed so that the EMF sensing scheme is embedded in this low cost 8-bit microcontroller. This device is truly SOC (system-on-chip) product, with high-throughput Micro core, precision-analog circuit, in-system programmable memory and motor control peripherals integrated on a single die. A microcontroller-based sensorless BLDC drive system has been developed as well, which is suitable for various applications, including hard disk drive, fans, pumps, blowers, and home appliances, etc. / Master of Science

O objetivo deste trabalho é desenvolver a simulação de um sistema de controle de velocidade para compressores herméticos domésticos utilizando motores brushless DC controlados por uma estratégia do tipo sensorless. O ponto central é o desenvolvimento da simulação global de controle a partir de um modelo adequado do motor BLDC com base no programa Matlab/Simulink. São abordadas algumas estratégias de controle sensorless além de alguns métodos de partida para este tipo de máquina. As estratégias de controle e partida propostas para o trabalho são analisadas detalhadamente e simuladas através do Matlab em ambiente Simulink utilizando as ferramentas do power system blockset (PSB). Os resultados destas simulações são apresentados e discutidos no final deste trabalho. / The aim of this work is to develop the simulation of a speed control system for household hermetic compressors using brushless DC motors controlled by a sensorless strategy. The main point of the work is the development of the control global simulation from a suitable BLDC motor model based on Matlab/Simulink program. Some sensorless control strategies and even some starting methods for this type of machine are approached. The control and starting strategies proposed for this work are analyzed in detail and simulated by Matlab in Simulink program using power system blockset (PSB) tools. The simulation results are presented and discussed at the end of this work.