mc1451a-e ETC-unknow, mc1451a-e Datasheet - Page 19

• Manufacturer Part Number: mc1451a-e
• Description: Advanced Brushless Motor Control Chipset
• Manufacturer: ETC-unknow

The profile mode may be programmed independently for each axis. For
example axis #1 may be in trapezoidal point to point mode while axis
#2 is in S-curve point to point.
Generally, the axis should be at rest when switching profile modes.
Under certain conditions however, switching into certain profile modes
"on-the-fly" is allowed. See specific profile descriptions for details.
S-curve Point to Point
The following table summarizes the host specified profile parameters
for the S-curve point to point profile mode:
Profile
Parameter
Destination
Position
Maximum
Velocity
Max. Accel.
Jerk
* uses 1/2 16 scaling. Chipset expects a 32 bit number which
has been scaled by a factor of 65,536 from units of
counts/sample time. For example to specify a velocity of 2.75
counts/sample time, 2.75 is multiplied by 65,536 and the
result is sent to the chipset as a 32 bit integer (180,224 dec.
or 2c000 hex.).
** uses 1/2 16 scaling. Chipset expects a 16 bit number which
has been scaled by a factor of 65,536 from units of
counts/sample time 2 . For example to specify an acceleration
of .175 counts/sample time 2 , .175 is multiplied by 65,536 and
the result is sent to the chipset as a 16 bit integer (11,469
dec. or 2ccd hex).
*** uses 1/2 32 scaling. Chipset expects a 32 bit number which
has been scaled by a factor of 4,294,967,296 (2 32) from units
of counts/sample time 3 . For example to specify a jerk value of
.0075 counts/sample time 3 , .0075 is multiplied by
4,294,967,296 and the result is sent to the chipset as a 32 bit
integer (32,212,256 dec. or 1eb8520 hex).
Representation & Range
signed 32 bits
-1,073,741,824 to 1,073,741,823
unsigned 32 bits* (1/2 16 scaling)
0 to 1,073,741,823
unsigned 16 bits ** (1/2 16 scaling)
0 to 32,767
unsigned 32 bits *** (1/2 32 scaling)
0 to 2,147,483,647
Units
counts
counts/smpl
counts/smpl 2
counts/smpl 3
19
Use the following figure showing a typical S-curve velocity vs. time
graph for reference in reading the next section:
The S-curve profile drives the axis at the specified jerk until the
maximum acceleration is reached. (phase I). it will then drive the axis at
jerk = 0 (constant acceleration) through phase II. It will then drive the
axis at the negative of the specified jerk though phase III, such that the
axis reaches the specified maximum velocity with acceleration = 0. This
completes the acceleration phase. At the end of the acceleration phase
of the move, the velocity will be constant, and the acceleration will be 0.
At the appropriate time, the profile will then decelerate (phases V, VI
and VII) symmetrically to the acceleration phase such that it arrives at
the destination position with acceleration and velocity = 0.
There are several conditions where the actual velocity graph of an S-
curve motion will not contain all of the segments shown in the above
figure. For example, if the max. acceleration is not reached before the
"half-way" point to the max. velocity, then the actual velocity profile will
not contain a phase II or a phase VI segment (they will have a duration
of 0 servo loops). Such a profile is shown below:
Another such condition is if the position is specified such that max.
velocity is not reached. In this case there will be no phase IV, and there
may also be no phase II and VI, depending on where the profile is
"truncated".
While the S-curve profile is in motion, the user is not allowed to
change any of the profile parameters. The axis must be at rest
before a new set of profile parameters can be executed. If
parameters are changed during motion then a 'command error'
Phase
Phase
I.
I.
Phase
Phase
II.
III.
S-curve that doesn't reach max. acceleration
Phase
III.
S-curve profile
Phase
Phase
IV.
IV.
Phase
V.
Phase
Phase
V.
VI.
Phase
Phase
VII.
VII.