A rotational speed control apparatus for an engine is provided. The engine configured to drive a compressor that compresses a cooling medium for air conditioning. The rotational speed control apparatus includes electronic control unit. The electronic control unit is configured to: (a) correct a torque of the engine through feedback in accordance with a deviation between a rotational speed during idle operation and a target rotational speed; (b) (i) calculate a load torque of the compressor, and (ii) correct the calculated load torque through feedback in accordance with a deviation between the rotational speed of the engine and the target rotational speed and correct a required value of the torque of the engine in accordance with the corrected load torque, in a predetermined period from a start of a changeover between a driven state of the compressor and a stopped state of the compressor.

A control device for a power machine includes a target circuit pressure specifying unit configured to specify a target circuit pressure of the hydrostatic continuously variable transmission, a measurement value acquisition unit configured to acquire an actual circuit pressure of the hydrostatic continuously variable transmission, a brake torque determination unit configured to determine a brake torque based on the target circuit pressure and the actual circuit pressure, and a pump control unit configured to control the hydraulic pump based on the brake torque. The brake torque is a torque consumed by the hydraulic pump.

Methods and apparatus to determine parameters of a pumping unit for use with wells are disclosed. An example apparatus includes a housing and a processor positioned in the housing. The processor is to determine a first load on a polished rod of a pumping unit, to estimate a first torque of a motor of the pumping unit, and determine a first torque factor for the pumping unit. The processor is to, based on the first load, the first torque, and the first torque factor, determine a phase angle of a counterbalance of the pumping unit or a moment of the counterbalance.

A method and system for determining the pump fillage of a sucker rod pumping system using torque feedback when pumping wellbore fluids from the particular well on which the sucker rod pumping system is installed. During the pump stroke, a microprocessor samples torque of the pump's mechanical system at an associated horsehead position at regular intervals and once the stroke is completed the raw torque samples and associated horsehead positions are placed in an array, the array of raw torque samples and horsehead positions can be filtered by the microprocessor into a second filtered array and then converted by the microprocessor into a rotatum array (derivative of torque with respect to time) of one or both of the raw or filtered arrays and stored as a rotatum array. The down stroke portion of the rotatum array is then analyzed by the microprocessor to determine the horsehead position when the piston of the down hole pump encounters wellbore fluid in the well (pump fillage). The microprocessor, based on the determined pump fillage, adjusts the speed of the pumping system to maintain an optimal pump fillage determined to be the most economical for the particular well on which the sucker rod pumping system is installed.

The invention relates to an electronic control device (13) for a refrigerant compressor, comprising at least: a drive unit (18); and a compression mechanism (5) which is actively connected to the drive unit (18), with at least one piston (9) which is driven by a crankshaft (6) and moves back and forth between a lower and an upper dead point in a cylinder of a cylinder block (8), in which the electronic control device (13) is designed to detect, control and/or regulate the rotational speed () of the drive unit (18) and to at least approximately detect the piston position, and in which the electronic control device (13) is designed to drive the compression mechanism (5) by means of the drive unit (18) in such a way that at least one drive angle segment () and at least one transit angle segment () is provided for the duration of a regulating time interval (t) comprising more than one crankshaft rotation, for a plurality of crankshaft rotations, preferably for each crankshaft rotation of the regulating time interval (t), and the compression mechanism (5) is subject to a positive operating torque (Bm) during the at least one drive angle segment (), and to a smaller positive operating torque (Bmv) compared to the positive operating torque (Bm) or to no positive operating torque (Bm) during the at least one transit angle segment ().

The invention relates to a method and to an apparatus for vibration compensation in a piston compressor, the piston compressor of which is driven by means of a crankshaft by a three-phase motor controlled by a frequency converter, wherein the current position the crankshaft of the piston compressor is determined, and based on this the frequency converter, a torque (M.sub.M) for the three-phase motor is predetermined, which torque follows the load torque (M.sub.L) of the piston compressor in order to reduce the vibration stimulation of the entire piston compressor.

A hydraulic pressure control device comprising: a hydraulic sensor provided between a hydraulic pump and a load; a speed command arithmetic unit configured to output a speed command value Vc based on a difference between a hydraulic pressure detection value Pd from the hydraulic sensor and a hydraulic pressure command value Pc; a torque command value arithmetic unit configured to calculate a torque command value Tc based on a difference between a speed detection value Vd of a motor and the speed command value Vc; a current controller configured to control current of the motor based on the torque command value Tc; and a hydraulic pressure abnormality detector configured to detect whether a hydraulic circuit has abnormality based on the speed command value Vc and an operating condition of the load of the hydraulic circuit commanded from an upper-level control device.

An electric oil pump device includes an electric oil pump driven by a motor and a microcomputer that adjusts a control parameter of feedback control related to a motor current value or a motor rotation speed based on an oil temperature estimated based on a relationship between at least one of a hydraulic pressure, the motor current value, or a torque of the electric oil pump and at least one of an oil discharge amount or the motor rotation speed of the electric oil pump.

Presented herein are systems and methods for attenuating flow ripple generated by a hydraulic pump. In certain aspects, a method and system for operating a hydraulic positive displacement pump according to a stabilized command profile are disclosed, such that flow ripple generated by operation of the pump according to the stabilized command profile is attenuated as compared to operation of the pump according to a corresponding nominal command profile. In other aspects, a pressure-balanced active buffer is disclosed that allow for at least partially cancelling flow ripple in a hydraulic circuit comprising a pump. In another aspect, a method for generating ripple maps for a pump is disclosed. Such ripple maps may be used, for example, to determine the stabilized command profile used to operate the pump, or may be used by the pressure-balanced active buffer to counteract ripple in the hydraulic circuit.

A method of operating a compressor includes obtaining a harmonic series representation of speed variation as the rotor rotates through each revolution. The method includes regulating an electric motor to compensate for or cancel out the periodic speed variation. Specifically, the method includes calculating an electromagnetic torque using a torque control input model based on the speed error and the harmonic series representation of the speed error. The operation of the electric motor is then adjusted such that the electromagnetic torque applied by the motor cancels out the speed variation such that noise and vibrations are minimized.