A method of operating a compressor includes obtaining a mechanical angle and an angular speed of a rotor, determining an amplitude of a fundamental harmonic of a periodic load torque exerted on the rotor based at least in part on the mechanical angle and a harmonic series representation of the periodic load torque, obtaining a speed error by subtracting the angular speed from a reference angular speed, determining a DC component of the periodic load torque based at least in part on a speed error and a closed loop feedback control algorithm, calculating an electromagnetic torque using the DC component of the periodic load torque and the amplitude of the fundamental harmonic of the periodic load torque, and operating the electric motor to generate the calculated electromagnetic torque on the rotor.

A pump having a fluid driver disposed within the interior volume of the pump and to a method of delivering fluid from an inlet of the pump to an outlet of the pump using the fluid driver. The fluid driver includes a variable-speed and/or a variable torque prime mover and a fluid displacement assembly. The pump can be used in a fluid pumping system to provide fluid to an actuator that is operated by the fluid. At least one of a speed and a torque of the pump is controlled so as to adjust at least one of a flow and a pressure in the fluid pumping system to a desired set point, without the aid of another flow control device.

A method for controlling a gear pump by a control device to compensate a tooth engagement-induced volume flow pulsation to reduce noise emissions. The method includes acquiring a gear angle and an actual speed of the gear pump; keeping a relationship between a respective modulation angle and an amplitude of a pilot control torque of the gear pump to compensate the volume flow pulsation to an actual speed; modulating the pilot control torque on the basis of the acquired gear angle, a predetermined correction angle, the modulation angle, a number of teeth of the gear pump and the amplitude; and driving the gear pump with a drive torque overlaid with the modulated pilot control torque. The modulation angle is calculated using a PT element with the actual speed as the input variable.

An apparatus includes a torque adjustment circuit to receive a torque setpoint and a torque feedback signal corresponding to a differential torque between a pair of meshing gear teeth of a first gear and a second gear. The torque adjustment circuit is further configured to output a torque adjustment signal corresponding to a difference between the torque setpoint and the torque feedback signal. The apparatus also includes a motion control circuit to provide a first speed demand signal to a first motor that drives the first gear and a second demand signal to a second motor that drives the second gear, and dynamically synchronize torque between the pair of meshing gear teeth such that the differential torque between the pair of meshing gear teeth is within a predetermined range by adjusting at least one of the first speed demand signal or the second speed demand signal.