Development of an electrodynamic actuator for an automatic modal impulse hammer

In Experimental Dynamic Substructuring, automatic modal impulse hammers have been shown to be a very useful tool. The Automatic Modal Impulse Hammer AMimpact (described in an earlier publication (Maierhofer et al, Development of a low cost automatic modal hammer for applications in substructuring. In: Conference proceedings of the society for experimental mechanics series. Springer International Publishing, June 2019, pp 77–86. https://doi.org/10.1007/978-3-030-12184-6_9)) developed at the Chair of Applied Mechanics (TUM) uses an electromagnetic actuator with the principle of reluctance forces. This has some disadvantages regarding the power density, and therefore makes it difficult to render the automatic hammer compact. Also, the force is very nonlinear with respect to the position of the piston. This results in quite some effort in positioning the impulse hammer at the right distance from the object. This contribution shows the process of developing a new electromagnetic actuator in combination with a permanent magnet. The physical principle is now based on the Lorentz forces. The goal is to find a configuration with minimal packaging and a sufficiently adjustable impulse peak. Using a modern 3D-FEM approach, the multiphysical system is simulated and optimized. A special control strategy is developed to overcome the disadvantage of unknown distance to the structure. Therefore, a hall sensor is used to monitor the actual position of the hammer. The system is built, then experimentally tested on an academic benchmark system. Furthermore, test series were carried out to prove repeatability.