Abstract: A volume sensor is described for automating an extracorporeal system used for the recovery and concentration of salvaged blood. The system includes a disposable plastic reservoir in which blood is collected from the surgical site and stored for processing. Volume is sensed in one embodiment by a strain gage device which is sensitive to vertical forces. In another embodiment volume is sensed by measuring the transit time of an ultrasonic pulse-echo signal generated by piezoelectric transducer.

Abstract: Apparatus for controlling torque and torque ripple in a variable reluctance motor uses a generated torque waveform for each phase of the number of phases associated with the motor and corresponds to an electrical current having a predetermined constant magnitude. The generated torque waveforms are utilized to provide a table of values representative of the electrical current magnitude at each of a number of sensed rotor angular positions. The values correspond to the torque produced by the motor when excited by an electric current having that value and the location of the value in a memory device are defined by the sensed angular position of the rotor and a desired torque command signal. Depending on the torque to be produced by the motor and the rotor position, the motor is excited with the value of current selected for one or a combination of phases to cause the motor to develop a desired torque which has a substantially flat and ripple-free response characteristic.