HCTL-1101 Datasheet, PDF (28/40 Pages) AVAGO TECHNOLOGIES LIMITED – General Purpose Control ICs Position and Velocity Control Low Power CMOS

The parameters of Ring, X, Y, and Max Advance must be
positive numbers (00H to 7FH). Additionally, the following
equation must be satisfied:
In order to utilize the greatest flexibility of the Commuta-
tor, it must be realized that the Commutator works on a
circular ring counter principle, whose range is defined by
the Ring register (R18H). This means that for a ring of 96
counts and a needed offset of 10 counts, numerically the
Offset register can be programmed as 0AH (10D) or AAH
(-86D), the latter satisfying Equation 8.
If bit #2 in the Status register is set to allow the commuta-
tor to count in full counts, a higher resolution codewheel
may be chosen for precise motor control without violating
the commutator constraints equation (Equation 8).
Example:
Suppose you want to commutate a 3-phase 15 deg/step
Variable Reluctance Motor attached to a 192 count en-
coder.
1. Select 3-phase and quadrature mode for commutator
by writing 0 to R07H.
2. With a 3-phase 15 degree/step Variable Reluctance
motor the torque cycle repeats every 45 degrees or 8
times/revolution.
3. Ring register
= (4)(192) counts/revolution
= 8/revolution
= 96 quadrature counts
= 1 commutation cycle
4 By measuring the motor torque curve in both directions,
it is determined that an offset of 3 mechanical degrees
and a phase overlap of 2 mechanical degrees is
needed.
Figure 11. Phase Advance vs. Motor Velocity.
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