An active mass damper utilizing rotating masses to damp the vibrations of an oscillator with two translational degrees of freedom in a horizontal plane and one rotational degree of freedom about a vertical axis is presented along with a corresponding closed-loop control algorithm. The damper consists of two masses rotating about a single vertical axis, powered by two actuators. In a preferred mode of operation, these masses rotate with a nearly constant and equal angular velocity in opposite directions, thus producing a harmonic control force in a single horizontal direction. By varying the relative angular position of the rotating masses, this control force can be directed in an arbitrary direction and used to damp the translational motion. In previous research, a control algorithm was derived for this purpose. The rotational degree of freedom can additionally be controlled by producing a moment by imposing angular accelerations on the rotating masses. In this paper, the previous control algorithm is augmented such that the rotational degree of freedom is additionally controlled. The augmented control algorithm is verified with help of numerical simulations.

© Springer International Publishing AG 2018. A novel active mass damper, the twin rotor damper (TRD), was presented in previous research, including control algorithms for monofrequent vibrations. In this paper, the steady-state damping performance is evaluated by applying a harmonic excitation force to a single degree of freedom (SDOF) oscillator with and without the action of the damping device. Using the velocity of the SDOF oscillator as feedback, adequate steady-state damping performance can be achieved with the TRD by setting the control force of the TRD in antiphase to the velocity of the SDOF oscillator. An analytic solution describing the steady-state damping performance is derived. The analytic solution allows for the comparison with a dynamic vibration absorber (DVA) of comparable size (stroke) and control mass. The analytic comparison shows that the TRD achieves greatly better damping performance than the DVA.

CIU triaxial tests are conducted on very pure kaolinite and illite clay powders using two different pore fluids to study differences in shear parameters. First, the two materials are characterized in-depth. Special attention was paid to sample preparation in order to generate high-quality samples. The evaluation of the test data reveals an increase in friction angle for both materials when using a 1M KCl solution as compared to demineralized water. Kaolinite shows a lower friction angle for the same pore fluid than illite. Future work will further investigate different salt concentrations and different salt types.