Comparative performance analysis of drives for induction motors

The asynchronous polyphase induction motor has been the motor of choice in industrial settings for about the past half century because power electronics can be used to control its output behavior. Before that, the dc motor was widely used because of its easy speed and torque controllability. The two main reasons why this might be are its ruggedness and low cost. The induction motor is a rugged machine because it is brushless and has fewer internal parts that need maintenance or replacement. This makes it low cost in comparison to other motors, such as the dc motor. Because of these facts, the induction motor and drive system have been gaining market share in industry and even in alternative applications such as hybrid electric vehicles and electric vehicles. The subject of this thesis is to ascertain various control algorithms’ advantages and disadvantages and give recommendations for their use under certain conditions and in distinct applications. Four drives will be compared as fairly as possible by comparing their parameter sensitivities, dynamic responses, and steady-state errors. Different switching techniques are used to show that the motor drive is separate from the switching scheme; changing the switching scheme produces entirely different responses for each motor drive.

Bidirectional cargo transport by microtubule-based molecular motors

We have reconstituted a simple in vitro system using only mammalian dynein and mammalian kinesin attached to a single cargo. These cargoes undergo saltatory motion typically seen in vivo, indicating that the motors engage in a tug-of-war. When the complex hits a barrier, the cargo often reverses direction. In some cases, it tries several up-and-back motions, during which time the dynein likely pulls the cargo onto a different protofilament, and is sometimes able to bypass the blockage. This explains why eliminating kinesin or dynein stops motion in both directions in vivo. We also find that mammalian dynein, but not kinesin, often takes backwards steps when under backward force. However, yeast dynein coupled with mammalian kinesin does not display these attributes, as expected.