The objective of this paper is to demonstrate the effect of active damping on regenerative chatter instability for a turning operation. Two approaches are used for this purpose. In the first approach, the traditional stability analysis technique in [1] and other works is adopted and a correlation between the chip shape (which is dependent on the spindle speed) and the system damping is presented. It is shown that different spindle speeds cause changes in the system damping, resulting in different levels of stability limits at different spindle speeds. A second approach involves plotting of the root locus of the system poles with increasing axial width of cut. This study presents a different perspective to the problem. It is shown that the low and high stability regions of the stability lobe diagram are due to different relative positions of the poles and zeros of the system. Active damping is proposed as a strategy to enhance the stability limits of the system. The effect of active damping is 2 studied by the two approaches, mentioned above, both showing that active damping can successfully enhance the stability limits,particularly in the low stability regions.

The motivation of the work is twofold: (a) understand the physics behind regenerative chatter and the influence of structural damping and (b) demonstrate an active damping technique based on collocated actuator/sensor pairs. A numerical stability analysis is performed using the root locus method and it is shown that, along with the structural poles, eigenvalues due to the delay parameter may contribute to instability. Since experimental demonstration of chatter in real machines is difficult, an alternative way of demonstration via a mechatronic simulator is presented, using the 'hardware-in-the-loop' concept. The mathematical model of the regenerative cutting process in turning is simulated in a computer and this is interfaced to a beam, representing the structural dynamics of the machine, via a displacement sensor and force actuator. In this way, a hardware and a software loop are combined. In a second step, an additional control loop is added, consisting of an accelerometer sensor and a collocated inertial actuator. Numerical and experimental stability lobe diagrams are compared, with and without active damping.

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The aim of this work is to present active vibration control of stiffened plates. A stiffened plate finite element with piezoelectric effects is formulated. The characteristic feature of the stiffener is that it can have any shape in plan and need not pass through the nodal lines of the finite element mesh. The coupling between the direct and the converse piezoelectric effects is neglected for simplicity. A velocity feedback algorithm is employed in the active control. Numerical examples for vibration control of isotropic and orthotropic stiffened plates have been presented.