Abstract: A method of phase angle control including the steps of generating a first periodic function having a first amplitude and generating a second periodic function having a second amplitude, which second periodic function is phase shifted relative to the first periodic function by a first phase angle. The method further includes generating a first positive feedback periodic function and generating a second positive feedback periodic function which is phase shifted relative to the first positive feedback periodic function by a second phase angle. In addition, the method includes generating a first control function, a first weighting function, a second weighting function, and linearly combining the product of the first positive feedback periodic function and the first weighting function with the product of the second positive feedback periodic function and the second weighting function to generate a second control function.

Abstract: An orbital fluid pumping mechanism (37) having an outer tube (12) and an inner member (14) positioned substantially concentrically within the outer tube. Helical lobes (18, 22) form sealed pumping chambers to move the fluid.