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Motor Axis and Master Axis Tabs
The Absolute Position view allows the user to configure the necessary parameters for both the Motor Axis (this is the axis being
controlled by the EZMotion), and the Master Axis (if applicable). If the encoder selected for use on either the Motor Axis or Master
Axis are not of the absolute type, then the setup parameters on that tab will be grayed-out and cannot be modified. The following
descriptions of the Absolute Position Setup parameters are duplicated for both the Motor Axis and Master Axis.
Absolute Position Setup
Absolute Position Auto-Calculate Enable
This check box is used to enable or disable the automatic calculation of the position for EZMotion, based on a defined absolute
home position, on power-up.
If this check box is selected, EZMotion will only read the position from the absolute feedback device on power-up, and then set the
position feedback equal to that value. However, EZMotion will NOT take into account any previously defined home position. This is
how EZMotion worked in and prior to A8 firmware (previous to the release of this feature). If you have already achieved the desired
absolute position calculations by creating a user program, and you wish to continue using that method (instead of this new method),
leave the check box clear. If clear, the Absolute Position Mode parameters will remain unavailable.
If the check box is selected, EZMotion will internally calculate the correct feedback position of the machine in user units based on a
previously defined home position and the position feedback from the absolute feedback device. The previous sentence is valid only
if the system has been previously homed (either using a homing routine or the DefineHome function). The Application Type radio
buttons are then used to determine the method used for calculating the position feedback on power-up or after a warm-start (see
below).
Absolute Position Mode
One-Sided Mode
One-Sided Mode implies that once the absolute home position has been defined, the user wishes to utilize the full multi-turn
resolution of the encoder in ONE DIRECTION from the home point. Using the example of a 12-bit multi-turn absolute encoder, the
motor could then travel 4096 revs in the positive direction without experiencing any problems due to absolute rollover.
NOTE
In One-Sided mode, if the motor moves in the negative direction from the home position, EZMotion cannot detect this condition,
and therefore the absolute position would be incorrectly calculated on the next power up.
EXAMPLE: The user homes the motor to a sensor. When the sensor activates, the motor is at the machine home position PM = 0
revs (where PM is the Position feedback of the Machine). When the motor is at the home position of 0 revs, the absolute encoder
reads PA = 1375 revs (where PA is the Position feedback of the Absolute Encoder). In this example, 1375 is just a randomly chosen
number for demonstration purposes. Therefore, EZMotion now uses this relationship of PM and PA at the home position to calculate
the machine position (PM) on power up.
Position Feedback of Machine when at Home = PMH = 0
Position Feedback of Absolute Encoder when at Home = PAH = 1375
If the motor then moves 1000 revs in the positive direction, PM will be PMH + 1000 or PM = 1000, and PA is PAH + 1000 or PA =
2375. If the machine is powered-down and then back up, EZMotion would read the position from the absolute encoder PA, subtract
the position of the absolute encoder at the home position PAH, and then add the position feedback of the machine at the home
position PMH, to get PM.
Calculation #1: Used when P
P
= P
- P
M
A
AH
= 2375 - 1375 + 0
= 1000 revs
If the motor then moves an additional 2000 revs in the positive direction, P
1000) or P
= 3000. P
M
the absolute encoder rev counter will reach 4096 and rollover to 0. Therefore, we will never get a value of 4375 on the absolute
encoder. In this case, the absolute encoder would read P
defined the application type to use One-Sided Mode, EZMotion can interpret this position from the absolute encoder to properly
calculate the correct machine position. If the machine was powered-down, and then back up, the P
Calculation #2: Used when P
P
= (Maximum Encoder Multi-Turn Resolution - P
M
= (4096 - 1375) + 279 + 0
= 3000 revs
3000 revs is exactly the result that we wanted! Notice that even though P
the correct position since the user has defined that the application is running in One-Sided Mode.
If the motor moves an additional 2000 revs in the positive direction, P
or P
= 5000. P
would be P
M
A
as P
= 6375 - 4096 = 2279. Notice that when P
A
is as follows:
P
= P
- P
M
A
AH
80
> P
A
AH
+ P
MH
would be P
+ 3000 or P
A
AH
A
< P
A
AH
+ 5000 or P
= 6375. Again, since the 12-bit encoder cannot exceed 4096, we need to recalculate P
AH
A
= 2279, we should use Calculation #1 above since 2279 > 1375. Therefore, our P
A
+ P
MH
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will be P
M
= 4375. However, we know that since this is a 12-bit multi-turn absolute encoder,
= 4375 - rollover position = 4375 - 4096 = 279 revs. Since the user has
A
) + P
+ P
AH
A
MH
rolled over when it reached 4096, we can still calculate
A
will be P
M
MH
+ 3000 (because we had already moved
MH
would be calculated as follows:
M
+ 5000 (because we already moved 3000 before)
EZMotion User/Programming Guide
A
M
Revision: A8
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