<p>For non-deconstructive generator inspection, robots which can crawl in a gap of a rotor and a stator have been developed.Since the robot should be enough thin to crawl in the gap, the inspection devices also need to be compact. Percussion is amethod to detect the stator wedge looseness. Since echo vibration excited by striking the target is analyzed in this method,the device requires two functions: a striking function and a sensing function. Basically, two devices such as a hammer anda microphone are utilized to achieve the functions. In this paper, a percussion device with the force control technique andthe inspection method to detect the stator wedge looseness are proposed. Since the proposed device can not only controlthe striking force but also sense the reaction force by itself, it is expected that the device can be compact. Moreover, in theproposed method, inner stator slot model parameters are estimated by analyzing the gain characteristics of the proposeddevice. Then, the amount of the stator wedge looseness is evaluated based on the model parameters. The validity of theproposed percussion device and the inspection method are evaluated through the experiments.</p>