Left Ventricular Assist Devices (LVADs) are an emerging treatment for the thousands of patients suffering from end-stage heart disease. These "artificial hearts" are implanted and cooperate with the natural heart in pumping blood. The current (second generation) pumps are rotary pumps that use the blood itself as a lubricant in fluid film bearings. This project is directed at the 3rd generation of pumps being developed in commercial research laboratories which employ feedback-controlled magnetically-levitated pump impellers. Magnetic levitation eliminates mechanical wear and shear-induced damage to the blood (red blood cells, platelets, and leucocytes). Motivated by the benefits of magnetic levitation, the first magnetically-levitated pump was implanted in an animal trial by members of this project at the University of Pittsburgh in 1998. The technology was enabled by feedback control, advances in magnetic materials and systematic optimization of the controlled plant. However, the small size, short time constants, nonlinearity, instability, and quasi-periodic disturbances from the natural heart pose an awesome challenge to those of us who promise patients that this engineered system will sustain their lives. The essential trade-off in the levitation controller design is power consumption versus robust stability. Moreover, interactions of actuator, power electronics, and control design offer opportunities for significant power savings. This work is directed at efficiency gains associated with improvements of control response to quasi-periodic pressure disturbances from the natural heart, and optimization of PWM waveforms driving the electromagnetic actuators. We believe that the extension of concepts from optimization, nonlinear internal models, nonlinear learning control, and attention to representative patient blood pressure waveforms will lead to a robust low-power levitation controller for maglev LVADs. The consequences of a successful project will be safe controllers for medical use and a significant reduction in portable battery weight.
The intellectual merits of this project are the interdisciplinary collaboration amongst power and control researchers, cardiac surgeons, and bioengineers; the innovative extension of nonlinear control theory to quasiperiodic disturbance rejection; and the experimental apparatus we propose for developing drive waveforms and communicating our ideas to the medical and engineering communities.
The broader impacts will include improving the lives of thousands of heart disease patents, the training of PhD students bridging control theory and biomedicine; the publication of well cited papers; the development of a apparatus; exhibiting our experimental work at conferences; and the continuation of the PI's robotics program involving 180 K-12 students from underrepresented groups.
