PROBLEM TO BE SOLVED: To obtain a contact-force measuring apparatus by which a contact force can be measured with good accuracy, by a method wherein an impulse response function is computed on the basis of a frequency response function between the vibration of a current collector and the contact force, which is found by using an equivalent model, and the impulse response function and the vibration of the current collector are superposed and integrated.
SOLUTION: By a computation or a vibration test by using an equivalent model, a frequency response function between the vibration of a current collector (a pantograph) and the contact force of the current collector with a feeder (a trolley wire) is found by a frequency-response-function computing part 25. On the basis of the frequency response function, an impulse response function is computed by an impulse- response-function computing and processing part 26 so as to be stored in an impulse- response-function storage part 27. Then, the vibration of the pantograph is measured by a sensor (a strain gage, a displacement meter, an accelerometer or the like), and it is converted into a digital signal so as to be stored in a vibration-waveform storage part 24. A superposing and integrating circuit 28 computes the contact force of the pantograph with the trolley wire on the basis of outputs from both storage parts 24, 27, and it is converted into an analog signal so as to be outputted. As a result, it is possible to observe the contact force of the pantograph with the trolley wire.