HCTL-1101 Datasheet, PDF (24/40 Pages) AVAGO TECHNOLOGIES LIMITED – General Purpose Control ICs Position and Velocity Control Low Power CMOS

Synchronizing Multiple Axes
Synchronizing multiple axes with HCTL-1101s can be
achieved by using the SYNC pin as explained in the Pin
Discussion section. Some users may not only want to syn-
chronize several HCTL-1101s but also follow custom pro-
files for each axis. To do this, the user may need to write a
new command position or command velocity during each
sample time for the duration of the profile. In this case,
data written to the HCTL-1101 has to be coordinated with
the Sample Timer. This is so that only one command posi-
tion or velocity is received during any one sample period,
and that it is written at the proper time within a sample
period.
At the beginning of each sample period, the HCTL-1101 is
performing calculations and executions. New command
positions and velocities should not be written to the HCTL-
1101 during this time. If they are, the calculations may be
thrown off and cause unpredictable control.
The user can read the Sample Timer Register to avoid writ-
ing too early during a sample period. Since the Sample
Timer Register continuously counts down from its pro-
grammed value, the user can check if enough time has
passed in the sample period to insure the completion of
the internal calculations. The length of time needed by the
HCTL-1101 to do its calculations is given by the Minimum
Limits of R0FH (Sample Timer Register) as shown in Table
4. For Position Control Mode, the user should wait for the
Sample Timer to count down 07H from its programmed
value before writing the next command position or veloc-
ity. If the programmed sample timer value is 39H, wait un-
til the Sample Timer Register reads 32H. Writing between
32H and 00H will make the command information avail-
able for the next sample period.
Commutator
Status Register
Commutator Ring
X Register
Y Phase Overlap
Offset
Max. Phase Advance
Velocity Timer
(R07H)
(R18H)
(R1AH)
(R1BH)
(R1CH)
(R1FH)
(R19H)
The Commutator is a digital state machine that is config-
ured by the user to properly select the phase sequence for
electronic commutation of multiphase motors. The Com-
mutator is designed to work with 2, 3, and 4-phase motors
of various winding configurations and with various en-
coder counts. Along with providing the correct phase en-
able sequence, the Commutator provides programmable
phase overlap, phase advance, and phase offset.
Phase overlap is used for better torque ripple control.
It can also be used to generate unique state sequences
which can be further decoded externally to drive more
complex amplifiers and motors. Phase advance allows the
user to compensate for the frequency characteristics of
the motor/amplifier combination. By advancing the phas-
es enable command (in position), the delay in reaction of
the motor/amplifier combination can be offset and higher
performance can be achieved.
Phase offset is used to adjust the alignment of the com-
mutator output with the motor torque curves. By correctly
aligning the HCTL-1101’s commutator output with the
motor’s torque curves, maximum motor output torque
can be achieved.
The inputs to the Commutator are the three encoder sig-
nals, Channel A, Channel B, and INDEX and the configura-
tion data stored in registers.
The Commutator uses both channels and the INDEX pulse
of an incremental encoder. The INDEX pulse of the encod-
er must be physically aligned to a known torque curve lo-
cation because it is used as the reference point of the rotor
position with respect to the Commutator phase enables.
The INDEX pulse should be permanently aligned during
motor encoder assembly to the last motor phase. This is
done by energizing the last phase of the motor during
assembly and permanently attaching the encoder code-
wheel to the motor shaft such that the INDEX pulse is ac-
tive as shown in Figures 7 and 8. Fine tuning of alignment
for commutation purposes is done electronically by the
Offset register (R1CH) once the complete control system
is set up.
24