A method for controlling movement of a movably mounted body (14) of a mechanical system (2, 56, 62). The mechanical system (2, 6, 62) includes a drive unit (4, 64), which is operated by a medium, and also a control valve (20, 22). The movably mounted body (14) is driven by the drive unit (4, 64). A drive movement of the drive unit (4, 64) is controlled with the aid of the control valve (20, 22). In order to avoid or reduce excitation of undesired vibrations in the mechanical system (2, 56, 62), it is proposed that the control valve (20, 22) be actuated using a control signal (u(t)) which comprises a first and also a further switching pulse (S.sub.1, S.sub.3) each having a prespecified pulse duration. The pulse duration of the first switching pulse (S.sub.1) is equal to the pulse duration of the further switching pulse (S.sub.3). A time difference (t.sub.1-3) between the start of the first pulse (S.sub.1) and the start of the further switching pulse (S.sub.3) is matched to a natural period duration of the mechanical system (2, 56, 62).

The hydraulic pressure control device has an idle region, and is provided with a control portion, and a correcting portion which, in cases when the reaction time of the actual pressure to pressure increasing control or pressure decreasing control exceeds a predetermined threshold time, corrects a control current towards the side in which the flow-rate is increased. In cases when a judging portion has judged that the pressure increasing control is in the idle area, the correcting portion applies, as the threshold time, an idle threshold time set to a value different from the threshold time that in cases when the judging portion has not judged that the pressure increasing control is in the idle area. Furthermore, in cases when the reaction time of the actual pressure to the pressure increasing control exceeds the idle threshold time, the correcting portion corrects the control current.

The hydraulic pressure control device has an idle region, and is provided with a control portion, and a correcting portion which, in cases when the reaction time of the actual pressure to pressure increasing control or pressure decreasing control exceeds a predetermined threshold time, corrects a control current towards the side in which the flow-rate is increased. In cases when a judging portion has judged that the pressure increasing control is in the idle area, the correcting portion applies, as the threshold time, an idle threshold time set to a value different from the threshold time that in cases when the judging portion has not judged that the pressure increasing control is in the idle area. Furthermore, in cases when the reaction time of the actual pressure to the pressure increasing control exceeds the idle threshold time, the correcting portion corrects the control current.

A method of operating a fail-fixed hydraulic actuator system is provided. The method includes providing an actuator in an initial position, electromechanically operating a valve assembly to hydraulically drive actuator movement and halting the hydraulic driving of the actuator movement by the valve assembly.

The invention relates to a valve for interruption of a fluid flow along a fluid flow path passing through the valve, the valve includes an inlet adapter, a valve body connected to the inlet adapter, a seal arranged between the inlet adapter and the valve body with a seal opening through the seal for the fluid flowing when the valve is open, a motor control gear unit, and a sealing body with a ball segment-shaped sealing surface element and bearing element arranged on the side of the sealing surface element. The sealing body is mounted within the valve body so as to be rotatable around an axis running substantially perpendicular to the fluid flow path and through the bearing element.

The invention relates to a valve for interruption of a fluid flow along a fluid flow path passing through the valve, the valve includes an inlet adapter, a valve body connected to the inlet adapter, a seal arranged between the inlet adapter and the valve body with a seal opening through the seal for the fluid flowing when the valve is open, a motor control gear unit, and a sealing body with a ball segment-shaped sealing surface element and bearing element arranged on the side of the sealing surface element. The sealing body is mounted within the valve body so as to be rotatable around an axis running substantially perpendicular to the fluid flow path and through the bearing element.

When a fluid is supplied to a first pressure-boosting chamber and/or a second pressure-boosting chamber of a pressure booster, either a first electromagnetic valve unit supplies a fluid discharged from a first pressurizing chamber to a second pressurizing chamber, or a second electromagnetic valve unit supplies a fluid discharged from a third pressurizing chamber to a fourth pressurizing chamber.

In some applications, a piston of a hydraulic actuator may move at high speeds, and large undesired forces may be generated if the piston reaches an end-stop of the hydraulic actuator at a high speed. The undesired forces may, for example, cause mechanical damage in the hydraulic actuator. A controller may receive information indicative of the piston reaching a first position at a first threshold distance from the end-stop, and, in response, may modify a signal to a valve assembly controlling flow of hydraulic fluid to and from the hydraulic actuator. Further, the controller may receive information indicative of the piston reaching a second position at a second threshold distance closer to the end-stop of the hydraulic actuator, and, in response, the controller may further modify the signal to the valve assembly so as to apply a force on the piston in a away from the end-stop.

In some applications, a piston of a hydraulic actuator may move at high speeds, and large undesired forces may be generated if the piston reaches an end-stop of the hydraulic actuator at a high speed. The undesired forces may, for example, cause mechanical damage in the hydraulic actuator. A controller may receive information indicative of the piston reaching a first position at a first threshold distance from the end-stop, and, in response, may modify a signal to a valve assembly controlling flow of hydraulic fluid to and from the hydraulic actuator. Further, the controller may receive information indicative of the piston reaching a second position at a second threshold distance closer to the end-stop of the hydraulic actuator, and, in response, the controller may further modify the signal to the valve assembly so as to apply a force on the piston in a away from the end-stop.

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.