Ahmed H. Mitwalli

Learn More
Digital control is rare in the area of power converters due mainly to cost considerations. As operating requirements of power supplies become more stringent, however, their control poses difficult problems better dealt with using digital rather than analog control. With the falling prices of microcontrollers and the increase in their processing power,(More)
—This paper describes a power electronic system that, among other possibilities, can be used to charge electric vehicle batteries. A large-signal linear multirate digital controller for the charging current permits the charger to track and deliver a desired current trajectory for a wide range of loads. This controller simultaneously ensures that the charger(More)
This paper describes a power electronic system that, among other possibilities, can be used to charge electric vehicle batteries. A large-signal linear, multirate digital controller for the charging current permits the charger to track and deliver a desired current trajectory for a wide range of loads. This controller simultaneously ensures that the charger(More)
Polymer gels that exhibit a change in volume in response to a small change in an environmental parameter such as temperature have been fabricated and studied for several decades. We have developed gels that change volume in response to an applied alternating magnetic field. These gels could serve as actuators in servomechanisms. This paper presents(More)
Properly fabricated polymer gels exhibit a n abrupt change in volume in response to a small change in a n environmental parameter such as temperature. We have developed gels that change volume i n response to a n applied alternating magnetic field, and we are working to apply these gels as actua-tors. This paper describes power electronic circuits suitable(More)
In a regulation application, a power supply is typically tasked with maintaining a fixed1 voltage or current in the face of possible disturbances. In a tnzcking application, on the other hand, a controller works to cause an average output voltage or current to follow a desired reference waveform as a function of time or some other variable. This paper(More)
This paper describes a sensor employing a gel formed from an interpene-trating polymer network of poly(vinyl alcohol) and a copolymer of N-isopropylacrylamide and acrylic acid. This gel exhibits a continuous volume-phase transition that is strongly dependent on the presence of polyvalent metal ions in the gel solvent. A sensor apparatus has been constructed(More)
  • John Mburu Gachora, Martin F. Schlecht, Frederic R.Morgenthaler, David Otten, Beth McDonald, Vivian Mizuno +6 others
  • 2006
In this thesis, a four-phase switchmode dc-dc converter has been designed. The converter uses a two stage topology whose advantages over the single stage topology have been outlined. Paralleling of converters as a means for better perfomance has been investigated. Specifically effects of interleaving on output voltage ripple has been discussed. The choice(More)
This paper describes an adaptive digital controller for a unity power factor ac-dc converter. The controller is A hardware design is presented and analyzed, foilowed by the software implementation of the control (algorithm. Issues in digital control of power converters, such as quantization effects and fixed-point representation of system parameters, are(More)