A hand-held power tool has a tool holder for holding a tool along a working axis. A hammer mechanism has a striker that is moved periodically at an impact rate along the working axis between a turning point in the proximity of the tool and a turning point remote from the tool. A drive control of the hammer mechanism sets the impact rate to a set point value. A vibration absorber has an oscillator that moves along the working axis about a resting position and one or multiple springs that drive the oscillator back into the resting position. A first sensor is used to determine a phase of the motion of the striker. A sensor is used to determine a first phase of a compression point of the hammer mechanism. Another sensor is used to determine a second phase of a turning point in the proximity of the tool, of the hammer mechanism. A damping controller adapts the set point value in such a way that a phase difference between the first phase and the second phase is less than a threshold value.

The present invention relates to a damper unit for damping oscillations of a tower structure when secured thereto, the damper unit comprising a damper unit structure adapted for attachment to the tower structure, a pendulum structure, a suspension arrangement for suspending the pendulum structure from the damper unit structure such that the pendulum structure is allowed to displace from a neutral position for the pendulum structure, the suspension arrangement comprising one or more wires for suspending the pendulum structure, a sensor adapted for measuring oscillations of the tower structure, and tuning means configured for adjusting the natural frequency of the suspended pendulum structure in response to measured oscillations of the tower structure. The present invention further relates to an associated method.

A device for damping vibrations in a structure including a first (or inner) element rotatably mounted around a rotational axis and a second (or outer) element rotatably mounted around said rotational axis. A radius (R1) of a circle portion delimitating the first element with respect to the rotational axis, being smaller than a radius (r2) of a circle portion delimitating the second element with respect to the rotational axis.

Apparatus and methods to reduce unwanted motion in precision instruments are described. An active vibration-isolation system may include a feedback loop that senses motion of an intermediate mass. In noisy environments, where the feedback loop would otherwise fail or provide inadequate isolation, feedforward control can be implemented to sense floor vibrations and reduce motion of the intermediate mass that would otherwise be induced by the floor vibrations. The feedforward control can reduce motion of the intermediate mass to a level that allows the feedback loop to operate satisfactorily.

Methods of attenuating vibration transfer to a body of a vehicle using a dynamic mass of the vehicle via minimizing a particular angular frequency of a wheel. One method includes receiving vehicle information over a time interval and determining, based on the vehicle information, an instantaneous angular velocity that corresponds to a particular angular frequency of the wheel. This method includes generating a gain-and-phase-compensated actuator drive command to counteract a vibration that occurs at the particular angular frequency of the wheel, which is based on the instantaneous angular velocity, and communicating the gain-and-phase-compensated actuator drive command to a hydraulic mount assembly that supports the dynamic mass. This method includes actuating an actuator of the hydraulic mount assembly in response to the gain-and-phase-compensated actuator drive command in order to minimize the vibration transfer to the body due to the vibration that occurs at the particular angular frequency of the wheel.

An agricultural machine, the machine comprising: a distributor boom; a sensor for detecting a vibration of the distributor boom; an electronic control device in communication with the sensor; and a mobile mass coupled to the distributor boom and associated with an actuator, the electronic control device, upon detection of a vibration in the distributor boom, configured to actuate the actuator to relocate the mobile mass in the direction of the vibration to be damped with respect to the distributor boom.

Apparatus and methods to reduce unwanted motion in precision instruments are described. An active vibration-isolation system may include a feedback loop that senses motion of an intermediate mass. In noisy environments, where the feedback loop would otherwise fail or provide inadequate isolation, feedforward control can be implemented to sense floor vibrations and reduce motion of the intermediate mass that would otherwise be induced by the floor vibrations. The feedforward control can reduce motion of the intermediate mass to a level that allows the feedback loop to operate satisfactorily.

The present invention provides a semi-active vibration absorption and energy dissipation control system for restraining vortex-induced vibration of bridges. It has the advantages and characteristics that: (1) springs are horizontally placed at the bottom of a beam, and lengths are not limited, so that the frequency requirement of a low-frequency target can be satisfied; (2) different target frequencies can be realized through different combinations of a plurality of springs connected in series and in parallel, so that multi-order vortex-induced vibration control needs are satisfied; (3) the springs made of fiber reinforced nylon materials are adopted, and are notched, so that a frequency implementation range can be greatly widened; (4) the material and the form of a mass body are not limited, and a water bag can be used, which has low cost and is convenient for disassembly, assembly and mass adjustment.

This disclosure relates to an active inerter damper configured to be disposed on or in a building structure. The active inerter damper includes a base, a lead screw, a rotational mass block, a driving device and a controller. The lead screw is movably disposed above the base along an axial direction. The rotational mass block is engaged with the lead screw so as to be rotatable with respect to the base. The driving device is connected to the lead screw. The controller is electrically connected to the driving device, and the controller is configured to activate the driving device to move the lead screw along the axial direction so as to rotate the rotational mass block via the lead screw.

A resonator having a support and a seismic mass. Movement means include a first electromagnetic assembly comprising a first electric coil that is not electrically powered. An actuator is connected to a processor unit, the processor unit electrically powering the actuator with adjustable electrical power. A resilient member is interposed between said seismic mass and said support.