A PC-controlled electromagnetic impactor (PCC-EMI) is developed that can be used for broad band excitation of rotating structures from a stationary system. Begin, magnitude and position of the force impact exerted to the moving structure are automatically and precisely controlled by a personal computer through a new electronic circuit device. Bouncing effects of the hammer tip are electronically suppressed and an impact can be aimed to any desired point on the rotating structure with high accuracy and high repeatability. Experiments are carried out to test the positioning and repeatability capabilities of the system. Common frequency response functions are measured for a rotating disk and natural bending frequencies are experimentally determined in terms of the speed of rotation of the disk.