This thesis carries out two basic studies for the flux function and the global observability of IPMSMs, leading to, respectively, two lightweight sensorless algorithms. First, we show that the flux function almost always gives a one-to-one correspondence between the rotor angle and flux, implying that the familiar IPMSM flux equations admit a unique position solution. This result eliminates the need for the arctan/atan2 function, leading to a simple flux estimation-based algorithm. Second, we show that the pair (speed, position) of IPMSMs is not globally observable, and the number of all indistinguishable pairs is at most four, an invariant independent of motor parameters and coincides with the number of the solutions of the two fundamental IPMSM equations. This result, which caps the worst-case scenario sensorless IPMSMs can behave, follows as a corollary by characterizing the observability condition involving infinitely many equations as a special limited form of the injectivity nature of finitely many polynomials. This bigger problem is approached through algebraic methodologies. The FOC scheme causes the “collapse” of at most two indistinguishable pairs and joins forces with the knowledge of motor/generator mode to turn the sensorless task “observable”, leading to another simple algorithm. / Thesis / Doctor of Philosophy (PhD)

<p>The VAWT project at Uppsala University has successfully managed to develop a vertical axis wind turbine (VAWT). The VAWT has many benefits compared to the Horizontal axis wind turbines (HAWT) which are the most common wind turbine design today. One of the many advantages with the VAWT is that it allows the generator to be located on the ground level. That reduces the required tower strength. The wind turbine is not self starting, i.e. the turbine needs a certain speed before the wind can force the turbine to revolve. The wind turbine is therefore in need of special start procedure. During the start, power electronics is used to operate the generator as a motor. Today Hall latches are located in the air gap of the generator which provides the signals that govern the power electronics. However, there is a demand to have a start that does not require Hall latches. Such controller would increase the reliability of the starter system. The design of the wind turbine could be even more simplified. Hence, the diploma work treats a programmed microcontroller to control the start-up without using any sensors at all. A hub motor was obtained for laboratory work, a driver and an inverter were constructed to drive the motor using a microcontroller. The finished start-up program has the ability to start the hub motor both sensorless and using Hall sensors. The microcontroller controls the motor by measuring the phase voltages of the motor. This information is used to decide which phases of the motor the electric current should go through. The current to the motor is limited using pulse width modulation strategy (PWM). Current limitation is necessary to protect the power electronics and limit the torque during the start. The result of start-ups using both Hall sensor and sensorless showed that the two start strategies are able to accelerate the rotor at the same rate. However, the start-ups using Hall sensors reached a higher top speed than the sensorless starts. However, the wind turbine is not in need of a higher speed than what the sensorless start was able to reach. Thus, the sensorless start is considered to be as good as the start using Hall sensors.</p>

The VAWT project at Uppsala University has successfully managed to develop a vertical axis wind turbine (VAWT). The VAWT has many benefits compared to the Horizontal axis wind turbines (HAWT) which are the most common wind turbine design today. One of the many advantages with the VAWT is that it allows the generator to be located on the ground level. That reduces the required tower strength. The wind turbine is not self starting, i.e. the turbine needs a certain speed before the wind can force the turbine to revolve. The wind turbine is therefore in need of special start procedure. During the start, power electronics is used to operate the generator as a motor. Today Hall latches are located in the air gap of the generator which provides the signals that govern the power electronics. However, there is a demand to have a start that does not require Hall latches. Such controller would increase the reliability of the starter system. The design of the wind turbine could be even more simplified. Hence, the diploma work treats a programmed microcontroller to control the start-up without using any sensors at all. A hub motor was obtained for laboratory work, a driver and an inverter were constructed to drive the motor using a microcontroller. The finished start-up program has the ability to start the hub motor both sensorless and using Hall sensors. The microcontroller controls the motor by measuring the phase voltages of the motor. This information is used to decide which phases of the motor the electric current should go through. The current to the motor is limited using pulse width modulation strategy (PWM). Current limitation is necessary to protect the power electronics and limit the torque during the start. The result of start-ups using both Hall sensor and sensorless showed that the two start strategies are able to accelerate the rotor at the same rate. However, the start-ups using Hall sensors reached a higher top speed than the sensorless starts. However, the wind turbine is not in need of a higher speed than what the sensorless start was able to reach. Thus, the sensorless start is considered to be as good as the start using Hall sensors.

Sensorless control of the synchronous reluctance motor has been a topic of research for more than a decade, producing several successful methods to accomplish this goal. However, a technique that has been overlooked is the full-order nonlinear observer, which is essentially a software model of the motor driven by measurements from the actual motor. Presented in this thesis is the design, implementation, and experimental testing of a full-order observer-based sensorless control technique which requires only the phase current and voltage measurements that are typically available in standard three-phase inverters. A technique is also presented for calculating a table of observer feedback gains parameterized only by the steady-state motor speed. This allows a gain-scheduling observer to be implemented which, as shown using experiments, improves the transient response of the observer over a wide speed range. The sensorless controller consists of a full-order nonlinear observer coupled with an input-output linearization speed controller. The resulting controller was implemented in Simulink and executed on a dSPACE DS1103 real-time DSP board using the Real-Time Workshop extension to Simulink. A custom built three-phase IGBT inverter was used to interface the DSP to a 100 watt synchronous reluctance motor for laboratory testing. The resulting sensorless controller was able to successfully track a varying speed reference from 150 rpm to 1800 rpm with a tracking error under 5% for most of the speed range. At the lowest speeds, the tracking error begins to increase but the observer remains stable down to 150 rpm.

Switched reluctance motor (SRM) is an attractive candidate for many industrial and domestic applications such as electric vehicles and home appliances. Rotor position detection is of significant importance for SRM control. However, external position sensors like absolute encoders and magnetic sensors reduce the reliability of SRM drive system in hash environments and increase the cost. Therefore, position sensorless control becomes a promising technique for SRM. In this thesis, a new position sensorless control method for SRM is proposed to estimate rotor position and speed. Sliding mode observer is adopted at high speed and pulse injection method is adopted at low speed. Both of the two methods are adopted with a motion model based on the third order phase locked loop to improve the dynamic tracking performance. The analysis method of the proposed position sensorless method is also presented. Both simulation and experiment results are presented to verify the proposed sensorless control method. The simulation results show that the proposed method can precisely estimate rotor position and speed with short response time. Experimental results further demonstrate the reliability and effectiveness of the proposed positon sensorless control method. / Thesis / Master of Applied Science (MASc)

No description available.

The TI TMS320LF2407A DSP is used as the control kernel in this thesis, proposing a method of sensorless control for the brushless DC motor. With six-step pulse-width modulation, the information of the back electromagnetic signals can be detected and is used to estimate the rotor position instead of the Hall sensors. To strengthen the system and reduce the power consumption, we propose the idea of close loop framework, including speed feedback and current feedback. Then, the phase-change signal is set as no delayed, 15 degree delayed, and 30 degree delayed and compare the results each other. Finally, setting up experimental framework, to verify the superiority of sensorless drivers with close-loop framework, and choosing better phase-change degree to improve system and efficiency.

This thesis presents a unified nonlinear optimization based speed and position estimation method in position sensorless control of interior permanent magnet synchronous motor (IPMSM) drives at wide speed range including standstill. The existing electromotive force (EMF) based sensorless methods are suitable for medium and high speed operation, but they can't be applied at low speed and standstill condition due to the reduced EMF values. The conventional saliency tracking based sensorless methods usually employ the continuous voltage or current injection at low speed including standstill condition. However, these methods degrade at high speed by introducing higher loss and torque ripples caused by the injection. Additionally, the initial rotor position needs to be detected at the machine startup to avoid the reverse rotation and to guarantee the delivery of the expected torque. Therefore, different position estimation techniques need to be combined in the controller at wide speed range, which increases the control system complexity. Hence, a unified nonlinear optimization based speed and position estimation method is proposed. At startup and standstill conditions, three steps are employed for initial position estimation. Step I employs pulse voltage injection in the stationary reference frame and a cost function which contains the knowledge of initial rotor position. The rotor position can be estimated by minimizing the cost function with injected voltage and induced current. Since the estimation results in Step I have an ambiguity of 180 degree, a generalized approach to magnetic polarity detection which exploits asymmetries in machine specific differential inductance profiles is employed as Step II. In order to improve the estimation accuracy, continuous sinusoidal voltage is injected in estimated rotor reference frame in Step III. A modified cost function is minimized based on the injected voltage and resulting current. At running state, cost functions which employ both speed and position as decision variables are proposed and utilized for estimation. The speed and position estimation can be delivered by minimizing the proposed cost functions based on the measurements of the stator voltage and current. Since only one position estimator exists in the drive system, the speed and position estimation is unified at wide speed range. The feasibility of the proposed estimation algorithms is validated with the prototype 5 KW IPMSM drives test bench. In order to benchmark the proposed estimation method, the performance of the proposed method was compared with existing sensorless control methods on the same prototype IPMSM drives test bench. Under the same test conditions, the proposed method outperforms with improved transient performance and steady state accuracy. Moreover, the proposed method is capable of delivering estimation with different voltage injection types and involving the nonlinear motor parameters, which makes this method more flexible in practice. Additionally, the capability of estimating speed and position with low sampling frequency also makes the application of the proposed method promising in high power AC motor drive systems. / Thesis / Doctor of Philosophy (PhD)

No description available.

This thesis focuses on compact brushless DC fan motor, drive circuit structure of motor is proposed, several functions such as output low current limit circuit and low rotation speed limit are added in order to increase robustness of drive circuit. Besides, speed feedback controller is used to solve several problems such as high frequency full speed exciting noise and high power dissipation which occurs in open loop rotation speed control circuit.With regard to BLDC fan motors generally use Hall sensor to detect rotor position, this research proposes sensorless control technology for the purpose of reducing circuit cost and motor size.