Abstract: An electric powered vehicle includes a traction motor powered from a source of switched DC power. The motor includes a tachometer for measuring the rotational velocity of the motor and for providing a tachometer signal indicative thereof. A low pass filter low pass filters the tachometer signal and produces a reference tachometer signal. A summing circuit combines the tachometer signal and the reference tachometer signal to produce a deviation signal. The deviation signal is provided to a signal processing circuit which includes a comparator and a reference value generator. The comparator compares the output of the summing circuit to a reference value provided by the reference value generator and produces a binary changing signal as a function of the comparison.