| 摘要 |
PROBLEM TO BE SOLVED: To accurately detect a speed by generating a double higher harmonic based on an exclusive disjunction of speed pulses in two phases and correcting dispersion of its pulse width. SOLUTION: From two speed sensors 3 installed to a rotary shaft in an induction motor 2, two phase speed signals in an A phase and a B phase are inputted to an inverter controller 1. The speed signal 4 is formed into a complete rectangular wave 6 by pulse shaping by means of an interface circuit 5, and at the same time, its voltage level is changed for generating a double higher harmonic 7. A counter circuit 8, which is operated on the basis of a clock 10 from a clock oscillator 9, stores a counter value to a register 11 every time when both edges of the double higher harmonic 7 are detected, and then, clears the counter value. Similarly, the counter circuit 12 measures a pulse width of a high/low level in the A/B phase so as to output a counter value 13. A counter correction circuit 14 finds an error of a pulse width in each of the A phase and the B phase from dispersion of the pulse width of the double higher harmonic 7 stored in the register 11 so as to output a counter correction value 15. |
