A pump includes a cylinder, a piston and a controller. The cylinder has first and second ends and includes first and second inlet-outlet ports, each of the first and second inlet-outlet ports is configured to alternately intake a fluid to the cylinder and output the fluid from the cylinder. The piston is configured to be moved within the cylinder between the first and second ends by alternately reversing a direction of movement of the piston, so as to pump the fluid through the first and second inlet-outlet ports. The controller is configured to control the movement of the piston within the cylinder, including: (a) choosing between first and second operational modes, (b) in the first operational mode, controlling the piston to oscillate over a predefined interval that does not exceed a predefined distance from the first end or from the second end, and (c) in the second operational mode, controlling the piston to move at a selected speed between the first end and the second end.

A displacement control valve improved in the function of discharging a liquid refrigerant in a control chamber at startup achieves a reduction in startup time and an improvement in operating efficiency during control of a variable displacement compressor simultaneously. An opening area between a third valve section and a third valve seat surface in a control area to control the flow rate or pressure in a working control chamber is set smaller than an area of an auxiliary communicating passage, thereby reducing the minimum area of a Pc-Ps flow path in the control area.

A method for operating a linear compressor includes substituting a first observed velocity, a bounded integral of the first observed velocity, an estimated clearance, an estimated discharge pressure, and an estimated suction pressure into the mechanical dynamic model for the motor, calculating an observed acceleration for the piston with the mechanical dynamic model for the motor, calculating a second observed velocity for the piston by integrating the observed acceleration for the piston, calculating an observed position of the piston by integrating the second observed velocity for the piston, and updating an estimated clearance, an estimated discharge pressure, and an estimated suction pressure based upon an error between the first and second observed velocities and an error between the bounded integral of the first observed velocity and the observed position.

A method of operating a pump can include advancing a stepper motor one or more additional steps in a first direction after detecting a first change in a limit sensor state corresponding to a piston reaching an end of its travel in a first direction. After advancing the stepper motor the additional step or steps in the first direction, the stepper motor can be reversed and advanced in a second direction until a second change in the limit sensor state is detected. The stepper motor can then be advanced in the second direction a predetermined number of steps associated with a full travel of the piston.

A method of operating a pump can include advancing a stepper motor one or more additional steps in a first direction after detecting a first change in a limit sensor state corresponding to a piston reaching an end of its travel in a first direction. After advancing the stepper motor the additional step or steps in the first direction, the stepper motor can be reversed and advanced in a second direction until a second change in the limit sensor state is detected. The stepper motor can then be advanced in the second direction a predetermined number of steps associated with a full travel of the piston.

A fluid dispenser with a fluid pump for dispensing fluid on movement of an actuator, and an air pump for delivering a stream of air through at least one sound generator on movement of the actuator. The sound generator produces at least two sounds as the actuator is moved from a first position to a second position, with each sound produced in a different time period during a cycle of operation, or differing from the other sound in respect of one or more detectable sound characteristics, such as duration, frequency, temporal alignment, amplitude, and/or timbre. The time period of each sound is a function of the relative location of the actuator between the first and second positions.

A linear compressor and methods of operation, for example, to control extension of the linear compressor, are provided herein. A method may include supplying a time varying voltage to a motor of the linear compressor, determining an uneven fatigue condition at the linear compressor, and applying a limiting force at the motor in a negative axial direction in response to the determining step.

A fluid dispenser with a fluid pump for dispensing fluid on movement of an actuator, and an air pump for delivering a stream of air through at least one sound generator on movement of the actuator. The sound generator produces at least two sounds as the actuator is moved from a first position to a second position, with each sound produced in a different time period during a cycle of operation, or differing from the other sound in respect of one or more detectable sound characteristics, such as duration, frequency, temporal alignment, amplitude, and/or timbre. The time period of each sound is a function of the relative location of the actuator between the first and second positions.

A method for operating a construction-material and/or viscous-material pump for conveying construction material and/or viscous material has the steps of: a) determining a required value of a power or of a size of the motor system, corresponding to the power, for moving the conveying piston, b) setting, on the basis of the required value, a speed value of the motor system in such a manner that a power and/or speed reserve value between an operating point, wherein the operating point is defined by the required value of the power or of the size and the speed value, and a characteristic curve of the motor system, wherein the characteristic curve is defined by maximum values of the power or of the size and speed values, wherein maximum values are different for different speed values at least in sections, is greater than or equal to a reserve limit value.

Controllability of a linear motor or a compressor is improved. There is provided a linear motor system that includes: an armature having magnetic poles and winding wires; a mover having a permanent magnet; and a power conversion unit that outputs AC power to the winding wires, in which the mover and the armature are relatively movable, and the mover or the armature is connected to an elastic body. The linear motor system further includes: a position detection unit that detects and outputs the position of the mover with respect to the armature, a position estimation, or a current detection unit that outputs the value of current flowing through the winding wires; and a control unit that controls the output of the power conversion unit on the basis of the output of the position detection unit, the output of the position estimation unit, or the output of the current detection unit. In the case where a signal having a frequency substantially the same as the frequency of the AC power is applied to the output of the position detection unit, to the output of the position estimation unit, or to the output of the current detection unit, the control unit changes the frequency of the AC power, and in the case where a signal having a frequency substantially larger than the frequency of the AC power is applied, the control unit keeps the frequency of the AC power substantially the same.