A damper for a semiconductor metrology or inspection system includes a pair of parallel plates with a fluid with a variable viscosity retained between plates. At least one wire is disposed between the plates, which may include one or more sets of lands and grooves. In some implementations, both plates include intermeshed lands and grooves. A controller is configured to provide a current to the at least one wire in order to adjust an electromagnetic field or a current through the fluid. The fluid may be a magnetorheological fluid or an electrorheological fluid in which the viscosity of the fluid is variable based on the electromagnetic field or current through the fluid. The controller varies the current applied to the wire to adjust the viscosity of the fluid to alter the damping of the semiconductor metrology or inspection system based on movement of the stage.

An active composite variable damping rotational control device includes a variable damping module and a power module. The variable damping module includes a magnetorheological fluid tank and a rotational inertia wheel. The rotational inertia wheel is arranged in the magnetorheological fluid tank fully filled with magneorheological fluid. The power module includes a device tubular cavity, a driver, an encoder and a speed changer. The driver is fixed on the inner wall of the device tubular cavity. The driver, the encoder and the speed changer are coaxial. A driving shaft of the driver passes through the speed changer and extends into the magnetorheological fluid tank to be fixed perpendicularly at the center of the rotational inertia wheel. The control effect of the present invention may not be greatly affected by the change of a structural form and the change of an external load.

An aircraft comprises an aircraft component, a sensor, and a multiple frequency vibration absorber (absorber). The sensor is operable to detect a frequency of a vibration of the aircraft component. The absorber is coupled to the aircraft component and configured to absorb the vibration. The absorber comprises a beam element, a fluidic flexible matrix composite (FFMC) tube, a valve, and a controller. The beam element is attached to the aircraft component. The fluidic flexible matrix composite (FFMC) tube is coupled to the beam element and is operable to absorb the vibration based on a stiffness of the FFMC tube. The valve is fluidically coupled to the FFMC tube and is to control the stiffness of the FFMC tube based on regulating a flow of a liquid through the FFMC tube. The controller can actively control absorption of the vibration via the FFMC tube based on opening and/or closing the valve.

In some examples, an oscillatory pumping system comprises: one or more active piston, a fluid, and two motors. The one or more active piston is disposed in a channel fluidically coupling two fluid chambers. The passive piston has a frequency response operable to counteract a vibratory displacement. The fluid is disposed in the channel and the two fluid chambers. The two motors couple to the one or more active piston. The two motors are operable to selectively change the frequency response of the passive piston based on oscillating the one or more active piston.

In one embodiment, a centrifugal force generating device comprises a first hydraulic rotor, a second hydraulic rotor, and one or more hydraulic control valves. The first hydraulic rotor comprises a first mass and is configured to rotationally drive the first mass around a first axis of rotation using a first flow of hydraulic fluid through the first hydraulic rotor. The second hydraulic rotor comprises a second mass and is configured to rotationally drive the second mass around a second axis of rotation using a second flow of hydraulic fluid through the second hydraulic rotor. The one or more hydraulic control valves are configured to control the first flow of hydraulic fluid through the first hydraulic rotor and the second flow of hydraulic fluid through the second hydraulic rotor.

Embodiments relate to dynamic stroking seats for vertical take-off and landing (VTOL) aircraft. Seat ballast tanks are attached to aircraft seats. The seats are sprung by a fixed or variable load energy absorption system. The weight of a user is determined and assigned to a corresponding seat of the user. Based on the weight of the user, the fluid level in the ballast tank is monitored and adjusted to achieve a target weight range.

An industrial truck is described, the industrial truck comprising a chassis, a mast arranged on the chassis in an upright position, a load-carrying apparatus, which is configured for receiving a load that is to be transported, a support structure that supports the load-carrying apparatus on the mast and can be moved, together with the load-carrying apparatus, upwards and downwards on the mast, and comprising a device for reducing vibrations, wherein the device for reducing vibrations has at least one additional mass body, which is supported by the mast or the components connected thereto and is not constantly rigidly coupled to the mast or the support structure or the load-carrying apparatus, but is movably mounted by a bearing arrangement such that it is movable relative to the mast in response to mast vibrations, in particular to mast vibrations having horizontal vibration components, in order to counteract mast vibrations.

A tunable mass-damping apparatus may include a housing having an interior surface, an interior volume containing a fluid, and an axis. The housing may be configured to be coupled to a wind tunnel model. The apparatus may further include a mass configured to move back and forth in the interior volume along the axis. The mass may be configured to make an airtight seal with the interior surface of the housing, thereby dividing the interior volume into an upper chamber and a lower chamber. The apparatus may include a passage fluidly connecting the upper chamber and the lower chamber and a spring configured to exert a position-dependent force upon the mass. The spring may be characterized by a variable spring constant chosen based on a variable natural frequency of a support structure of the wind tunnel model. The variable spring constant may be established with a nickel-titanium alloy spring heated to at least one calibrated temperature that corresponds to a predetermined spring constant.

The invention relates to a new type of tuned mass damper which is suitable in particular for damping oscillations of a low frequency, and can thus be used preferably as a construction damper when building or siting high, narrow structures, such as wind-turbine towers. The invention relates in particular to a pendulum oscillation damper having a first pendulum, to which the mass is attached, and a second pendulum, which is formed by a spring-like support device of a different design and is operated using a gas-air volume such that, with the aid thereof, the frequency of the oscillation system can be adapted and adjusted.

In one embodiment, a centrifugal force generating device comprises a first hydraulic rotor, a second hydraulic rotor, and one or more hydraulic control valves. The first hydraulic rotor comprises a first mass and is configured to rotationally drive the first mass around a first axis of rotation using a first flow of hydraulic fluid through the first hydraulic rotor. The second hydraulic rotor comprises a second mass and is configured to rotationally drive the second mass around a second axis of rotation using a second flow of hydraulic fluid through the second hydraulic rotor. The one or more hydraulic control valves are configured to control the first flow of hydraulic fluid through the first hydraulic rotor and the second flow of hydraulic fluid through the second hydraulic rotor.