Control systems and feedback assemblies for hydraulic axial displacement machines, such as pumps and motors. The control systems and feedback assemblies can have enhanced adjustability. An angle sensor for sensing the angular position of a pivot arm can have a housing, and the housing can be angularly adjustable about the pivot axis relative to the pivot arm.

A hydraulic pump includes a cylinder block, a plurality of pistons, a swash plate, a first pressing unit, and a second pressing unit. The cylinder block has a plurality of cylinder bores and is disposed so as to be rotatable. Each of the plurality of pistons is retained in associated one of the cylinder bores so as to be movable. The swash plate is configured for controlling the amount of movement of the plurality of pistons in accordance with the size of the tilt angle. The first pressing unit is configured for pressing the swash plate in such a direction as to reduce the tilt angle of the swash plate. The second pressing unit is configured for pressing the swash plate in such a direction as to increase the tilt angle of the swash plate by a pressure supplied from the outside of the hydraulic pump.

A method for evacuating a process space by initially evacuating the process space to a pressure limit value using two compressors operated in parallel, and on reaching or undershooting the pressure limit value, the process space is subsequently evacuated using the two compressors operated in series.

A method for evacuating a process space by initially evacuating the process space to a pressure limit value using two compressors operated in parallel, and on reaching or undershooting the pressure limit value, the process space is subsequently evacuated using the two compressors operated in series.

A system and method for independent control of simultaneous fracturing for multiple wellbores is disclosed. In certain embodiments, a first clean pumping unit and a first dirty pumping unit are fluidically coupled to a first wellbore, wherein the first clean pumping unit pumps a first fluid to the first wellbore and the second clean pumping unit pumps a second fluid to the first wellbore. In certain embodiments, a second clean pumping unit and a second dirty pumping unit are fluidically coupled to a second wellbore, wherein the second clean pumping unit pumps the first fluid to the second wellbore and the second dirty pumping unit pumps. In certain embodiments, a controller controls a pumping rate of at least one of the first clean pumping unit and the first dirty pumping unit based on a desired parameter of a combined fluid pumped to the first wellbore.

A system and method for independent control of simultaneous fracturing for multiple wellbores is disclosed. In certain embodiments, a first clean pumping unit and a first dirty pumping unit are fluidically coupled to a first wellbore, wherein the first clean pumping unit pumps a first fluid to the first wellbore and the second clean pumping unit pumps a second fluid to the first wellbore. In certain embodiments, a second clean pumping unit and a second dirty pumping unit are fluidically coupled to a second wellbore, wherein the second clean pumping unit pumps the first fluid to the second wellbore and the second dirty pumping unit pumps. In certain embodiments, a controller controls a pumping rate of at least one of the first clean pumping unit and the first dirty pumping unit based on a desired parameter of a combined fluid pumped to the first wellbore.

A system and method for pumping fluid. The system includes a sequence of two or more positive-displacement sub-systems each having a respective one-way inlet. A respective one-way flow path links each adjacent two of the sub-systems. A one-way outlet from a last of the sub-systems is provided. The system is capable of a mode of operation in which at least some of the sub-systems are substantially in phase with respect to each other to cause the system to draw fluid from more than one of the one-way inlets; and another other mode of operation in which at least some of the sub-systems are substantially in antiphase with respect to each other to increment a pressure of the fluid as the fluid moves along the sequence.

A variable positive displacement pump actuator system for a variable positive displacement pump can include a supply line configured to provide a supply pressure, a main pump line configured to provide a pump pressure greater than the supply pressure from the variable positive displacement pump, and at least one electro-hydraulic servo valve (EHSV) in fluid communication with the supply line and the main pump line to receive the supply pressure and the pump pressure. The at least one electro-hydraulic servo valve can be configured to output a first regulated pressure and a second regulated pressure. The system can include a first control line in fluid communication with at least one of the at least one EHSV to receive the first controlled pressure, a second control line in fluid communication with at least one of the at least one EHSV to receive the second controlled pressure, a first hydraulic actuator configured to connect to and/or otherwise actuate a lever arm of the variable positive displacement pump, the first hydraulic actuator in fluid communication with the first control line and the supply line to receive the first control pressure and the supply pressure to control a position of the first hydraulic actuator, and a second hydraulic actuator configured to connect to and/or otherwise actuate the lever arm of the variable positive displacement pump, the second hydraulic actuator in fluid communication with the second control line and the supply line to receive the second control pressure and the supply pressure to control a position of the second hydraulic actuator.

A pump system contains a pair of pumps each of which contains a vibration actuator vibrated by electromagnetic drive and can discharge fluid due to drive of the vibration actuator. The pump system has a vibration suppression mode in which the pair of the pumps are driven so that vibration of the vibration actuators of the pair of pumps is cancelled each other and a vibration generation mode in which the pair of the pumps are driven so that the vibration of the vibration actuators of the pair of pumps is superimposed with each other.

A pump system contains a pair of pumps each of which contains a vibration actuator vibrated by electromagnetic drive and can discharge fluid due to drive of the vibration actuator. The pump system has a vibration suppression mode in which the pair of the pumps are driven so that vibration of the vibration actuators of the pair of pumps is cancelled each other and a vibration generation mode in which the pair of the pumps are driven so that the vibration of the vibration actuators of the pair of pumps is superimposed with each other.