A milling machine may have a frame, a milling drum attached to the frame, and ground engaging tracks that support the frame and propel the milling machine in a forward or rearward direction. The milling machine may have height adjustable actuators connecting the frame to the tracks. Each actuator may have a cylinder attached to the frame, a piston slidably disposed within the cylinder, and a rod connected at a first end to the piston and connected to a track at a second end. The milling machine may have a tank storing hydraulic fluid and a fluid conduit connecting the tank to the cylinder. The milling machine may have a control valve selectively controlling a flow rate of the hydraulic fluid in the fluid conduit. The milling machine may also have a controller that determines a height of the frame relative to the ground surface based on the flow rate.

The present disclosure relates to variable recruitment actuator systems and related methods. In one embodiment, a variable recruitment actuator system may include a high-pressure fluid connection and a plurality of actuators. A variable recruitment actuator mechanism may selectively recruit a subset of the plurality of actuators based on a position of the variable recruitment actuator mechanism by selectively placing the subset of the plurality of actuators in fluid communication with the high-pressure fluid connection. A control system to control the position of the variable recruitment actuator mechanism may operate based on an input from a user.

A vehicle control surface, such as an aircraft horizontal stabilizer, is hydraulically controlled using solenoid operated valves (SOVs) controlling directional control valves and/or rate control valves with small numbers of ports, e.g. a four port three position directional control value and/or a four port two position rate control valve.

The invention relates to a hydraulic positioning device for an agricultural implement, wherein preferably a uniform movement of several hydraulic cylinders is achieved by using a progressive distributor.

A compressed air provision device (2) for aerating a first pressure chamber (10) of a pneumatic actuator in order to actuate an actuator element (11) of the pneumatic actuator (3) in accordance with an actuation specification, in particular a position, movement, pressure and/or force specification. The compressed air provision device (2) is configured to calculate an aeration period (bd) and to aerate the first pressure chamber (10) in accordance with the calculated aeration period (bd) in order to bring about actuation of the actuator element (11) in accordance with the actuation specification.

A hydraulic stage includes a hydraulic element located between and sealing a first and second chamber, wherein the first chamber comprises at least one aperture through which fluid is arranged to flow into or out of the first chamber; and at least one piezoelectric element which is positioned adjacent to the at least one aperture and is arranged to deform in response to an applied potential difference such that it blocks or obstructs the at least one aperture to a varying degree according to the level of deformation, so as to control fluid flow into or out of the first chamber. The level of deformation of the piezoelectric element thus reduces or increases an effective size of the inlet or outlet aperture to which it is adjacent, restricting or permitting an increase in fluid flow accordingly.

The present disclosure relates to variable recruitment actuator systems and related methods. In one embodiment, a variable recruitment actuator system may include a high-pressure fluid connection and a plurality of actuators. A variable recruitment actuator mechanism may selectively recruit a subset of the plurality of actuators based on a position of the variable recruitment actuator mechanism by selectively placing the subset of the plurality of actuators in fluid communication with the high-pressure fluid connection. A control system to control the position of the variable recruitment actuator mechanism may operate based on an input from a user.

The disclosure relates to a method for operating a hydraulic drive which comprises a hydraulic consumer with a positionable piston in a cylinder which is connected to a tank at one connection via a pump of variable rotational speed and at another connection via a proportional valve, wherein a position of the piston is controlled using a model-based control in which a rotational speed of the pump is used as a manipulated variable and in which a position of the proportional valve is preset.

An actuation pressure to actuate one or more hydraulic actuators may be determined based on a load on the one or more hydraulic actuators of a robotic device. Based on the determined actuation pressure, a pressure rail from among a set of pressure rails at respective pressures may be selected. One or more valves may connect the selected pressure rail to a metering valve. The hydraulic drive system may operate in a discrete mode in which the metering valve opens such that hydraulic fluid flows from the selected pressure rail through the metering valve to the one or more hydraulic actuators at approximately the supply pressure. Responsive to a control state of the robotic device, the hydraulic drive system may operate in a continuous mode in which the metering valve throttles the hydraulic fluid such that the supply pressure is reduced to the determined actuation pressure.

One object is to calculate the position of a rod of a linear actuator with a high precision. The linear actuator includes a rod capable of moving in an axial direction relative to a housing. The rod is moved by rotation of an output shaft of a motor. A position sensor for sensing the relative position of the rod relative to a preset reference position is provided in the housing. A rotation sensor for sensing the rotation angle of the output shaft of the motor is provided in the vicinity of the motor. The linear actuator includes a position calculating unit for calculating the position of the rod based on a position sensing value of the position sensor and a rotation angle sensing value of the rotation sensor.