Abstract
The paper presents a simplified 3D-model for active vibration control of rotating machines with active machine foot mounts on soft foundations, considering static and moment unbalance. After the model is mathematical described in the time domain, it is transferred into the Fourier domain, where the frequencies response functions regarding bearing housing vibrations, foundation vibrations and actuator forces are derived. Afterwards, the mathematical coherences are described in the Laplace domain and a worst case procedure is presented to analyze the vibration stability. For special controller structures in combination with certain feedback strategies, a calculation method is shown, where the controller parameters can be directly implemented into the stiffness matrix, damping matrix and mass matrix. Additionally a numerical example is presented, where the vibration stability and the frequency response functions are analyzed.
Highlights
In praxis, large rotating machines are often fixed directly on soft foundations. e.g. elastic steel frame foundations, which sometimes lead to problems regarding vibrations, caused by resonances and instability [1]-[7]
After the model is mathematical described in the time domain, it is transferred into the Fourier domain, where the frequencies response functions regarding bearing housing vibrations, foundation vibrations and actuator forces are derived
The active vibration system includes active machine foot mounts—actuators, which are put between the machine feet and the foundation, acting only in vertical direction—vibration sensors, which are mounted at each machine foot, detecting the vertical vibrations, and a separate controller for each actuator (Figure 1)
Summary
Large rotating machines are often fixed directly on soft foundations. e.g. elastic steel frame foundations, which sometimes lead to problems regarding vibrations, caused by resonances and instability [1]-[7]. The active vibration system includes active machine foot mounts—actuators, which are put between the machine feet and the foundation, acting only in vertical direction—vibration sensors, which are mounted at each machine foot, detecting the vertical vibrations, and a separate controller for each actuator (Figure 1). This concept was basically investigated in [21], but only for induction motors and it was only based on a plane 2D-model. The damping coefficients are here dependent on the whirling angular frequency, whereas in [22] the damping coefficients have been considered constant as a simplification
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