Three-chip schematic block diagram and composed position servo system

The generation of tach voltage (T AC HO) is explained as follows. Among the output signals of the photoelectric encoder
, FTA and FTB are two orthogonal sinusoidal signals, and FTF is
a signal with one pulse per revolution. FTA and FTB are amplified by amplifiers N and N to produce V^^
and VAB, which are differentiated by an external RC network. There is a phase shift between the signals VMA and VhdB and the original signal,
and the amplitude is proportional to the motor speed. They are sent to the input terminals of the two multipliers respectively.
The other input terminals of the two multipliers are v^o and V AC, respectively, which are composed of V-s and V. *
Obtained after passing through the comparator. The two multiplier outputs are in operational amplifier N.
The speed measurement signal T AC HO is obtained by summing , completing the function of the F/V converter. Figure 2-14 shows
the waveforms at each point during forward and reverse rotation.
  L290 also sends three square pulse signals of ST
A, STB and STF to the MCU. STA and STB are used for position tracking, and STF is used for system initialization to determine
the origin of the absolute position.