Experimental tests of a flywheel inertial actuator

This paper presents the results of experimental tests carried out on a new inertial actuator that can be used to implement a velocity feedback loop to reduce the flexural vibration of flexible structures. Classical inertial actuators used in vibration control systems incorporate coil-magnet linear motors, with the magnet suspended on soft springs and the coil attached to the base. With this configuration there are two aspects that limit the effectiveness of the feedback vibration control system. Firstly, the inherent dynamics of the springs-magnet system limits the stability, and thus control performance of the feedback loop. Secondly, when exposed to shocks, the actuator suffers undesired stroke saturation effects, which may also lead to instability of the feedback loop. The inertial actuator presented in this paper includes an additional flywheel element that increases the inertia of the proof mass without increasing the weight of the suspended mass. As a result, the fundamental natural frequency of the actuator could be lowered without increasing the static displacement of the suspended mass. This improves the stability of the feedback loop, both by increasing the feedback gain margin and by improving the robustness to shocks. This paper presents the measured frequency responses functions that characterise the electro-mechanical response of a flywheel actuator prototype, which are contrasted with simulations obtained from a simplified lumped parameter model. The experimental results agree well with the simulation results and confirm that the new flywheel actuator can be effectively used to implement a more robust velocity feedback loop.