Fluid management in surgical procedures. At least some of the example embodiments are methods including: pumping surgical fluid through a tube to a surgical site by a fluid controller operating in a first mode, the first mode comprising a first relationship of fluid flow and pressure drop across the tube and cannula, and the first mode comprising a first set of proportional, integral, and differential (PID) parameters; and then pumping surgical fluid through the tube to the surgical site with the fluid controller operating in a second mode, the second mode comprising a second relationship of fluid flow and pressure drop across the tube and cannula, the second relationship different than the first relationship, and the second mode comprising a second set of PID parameters used, the second set of PID parameters different than the first set of PID parameters.

The performance of a solenoid drive liquid pump can be very dependent on the magnitude and stability of an input voltage, with non-ideal input power resulting in loss of efficiency and potential damage to the pump. Pulse width of drive signals provided to the pump, which cause solenoids to alternately energize to move liquid through the pump, may be adjusted in duration in order to compensate for non-ideal input voltage. A drive control module of the pump gathers voltage information, determines an improved pulse width based upon that voltage information, and then provides drive signals based upon the improved pulse width. Operating in this manner, a pump can operate at or near peak efficiency despite both significant variances in input voltage and non-sinusoidal input voltage, and without customized components or adapters.

A method for operating a linear compressor is provided. The method includes estimating an acceleration of the motor of the linear compressor using at least a robust integral of the sign of the error feedback. A position of the motor of the linear compressor when the motor of the linear compressor is at the bottom dead center point is also determined based at least in part on a measured current to the motor of the linear compressor and an estimated acceleration of the motor. The position of the motor of the linear compressor when the motor of the linear compressor is at a top dead center point is calculated based at least in part on the position of the motor of the linear compressor when the motor of the linear compressor is at the bottom dead center point and a stroke length of the motor of the linear compressor.

A control method and a system for controlling the piston of a resonant linear compressor including at least one electronic control unit, the electronic control unit including at least one observing electronic circuit and at least one control circuit associated to each other. The observing electronic circuit is configured for: measuring at least one electric magnitude of the electric motor; estimating at least one set of electric parameters and at least one set of mechanical parameters of the resonant linear compressor; and estimating and providing at least one control parameter of the system for the control circuit based on the measured electric magnitude measured and on the estimated set of electric and mechanical parameters. The control circuit is configured for actuating the electric motor from the at least one control parameter.

Methods and systems for monitoring a variable-speed pump system to detect a blockage condition. A value indicative of pump performance is sensed and a pump load coefficient is calculated. The value of the pump load coefficient does not change substantially due to changes in pump speed and is indicative of a blockage of a drain in a liquid holding tank. A blockage of the drain is detected based at least in part on the calculated pump load coefficient and the operation of the pump is adjusted based on the detected blockage.

A well pumping system can include an actuator that reciprocably displaces a rod string, a continuous position sensor that continuously detects a position of a member of the actuator, and a control system that modifies reciprocal displacement of the rod string by the actuator, in response to an output of the continuous position sensor. A well pumping method can include reciprocably displacing a rod string, continuously detecting a velocity profile with a continuous position sensor, and modifying the velocity profile while the rod string reciprocably displaces, in response to an output of the continuous position sensor.

A control method and a system for controlling the piston of a resonant linear compressor including at least one electronic control unit, the electronic control unit including at least one observing electronic circuit and at least one control circuit associated to each other. The observing electronic circuit is configured for: measuring at least one electric magnitude of the electric motor; estimating at least one set of electric parameters and at least one set of mechanical parameters of the resonant linear compressor; and estimating and providing at least one control parameter of the system for the control circuit based on the measured electric magnitude measured and on the estimated set of electric and mechanical parameters. The control circuit is configured for actuating the electric motor from the at least one control parameter.

A method for controlling a microfluidic pump having a pump body defining a cavity, and an actuator arranged to generate pressure oscillations of a fluid contained within the cavity in order to cause fluid flow through an inlet and an outlet of the cavity, the method comprising: oscillating the actuator at a first frequency and determining an indication of a peak velocity of the a peak velocity of the actuator at said first frequency; oscillating the actuator at a second frequency and determining an indication of a peak velocity of the actuator at said second frequency; and adjusting the frequency of oscillation of the actuator to said first or second frequency for which the lowest peak velocity of the actuator was determined.