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Adjustment of setting of equipment.
1. Introduction
ATV32 is only available in open loop configuration. It means that it is not possible to know
the actual position by reading an internal register which contains the position coming from an
encoder. It is then not possible to control an ATV32 in position mode.
But it is possible to execute simple positioning movements in open loop. If the speed loop is
set correctly then the drive is able to follow the speed reference accurately. If the RUN order
is removed at the right time it is possible to stop at a desired position, especially when using
synchronous motors.
The following curves show a basic point-to-point movement:
Output
frequency
Target
frequency
Acceleration
ramp
Deceleration
ramp
Time
Position
Target
position
Time
RUN
order
RUN order
must be given
during this time
Time
The target is to calculate the RUN order duration.
This duration depends on the acceleration/deceleration ramps, on the target frequency and
on the target distance.

Target velocity unit is Hz

Acceleration/deceleration unit is Hz/s (and NOT seconds from 0 Hz to FRS)

Target position unit is pole pair (20 pole pairs correspond to 10 turns with a 1500
rpm motor)
2. First case: Trapeze
 Target frequency is 10 Hz
 Acceleration/deceleration ramp is 25 Hz/s
(corresponds to ACC = DEC = 2 s with FRS = 50 Hz)
 Target position is 20 pole pairs (corresponds to 10 turns with a 1500 rpm
motor)
Output
frequency
Rectangle
10 Hz
25 Hz/s
25 Hz/s
Right
triangle
t2
t1
Time
Left
triangle
Position
20 pole
pairs
p1
Time
t1 = target frequency / acceleration = 10 Hz / 25 Hz/s = 0.4 s
p1 = area of the left triangle = t1 * target frequency / 2 = target frequency ² / (2* acceleration)
= (10 Hz) ² / (2*25 Hz/s) = 2 pole pairs
Trapeze area = target position = left triangle area + rectangle area + right triangle area
Because acceleration = deceleration, triangles have the same area.
It gives: target position = 2 * triangle area + rectangle area = 2 * p1 + (t2-t1) * target
frequency
i.e. target position = 2* target frequency ² / (2* acceleration) + (t2-t1)* target frequency
i.e. target position = target frequency ² / acceleration + (t2- (target frequency / acceleration)) *
target frequency
i.e. target position = target frequency *t2
Then t2 = target position / target frequency = 20 pole pairs / 10 Hz = 2 seconds.
Conclusion: If the RUN order is given during 2 seconds then the obtained distance will be 20
pole pairs, which corresponds to 10 turns.
3. Second case: Triangle
Same inputs but acceleration is now 5 Hz/s (10 s with FRS = 50 Hz)
t1 = 10 Hz / 5 Hz/s = 2 s
p1 = (10 Hz) ² / (2 * 5 Hz/s) = 10 pole pairs: half of the distance is reached at the end of the
acceleration ramp
t2 = 20 pole pairs / 10 Hz = 2 seconds: this gives the following profile:
Output
frequency
10 Hz
5 Hz /s
5 Hz /s
t1 = t2 = 2 s
Time
This is the limit case where deceleration starts when target frequency is reached. The
particular value of acceleration is called ACCmin:
target frequency = ACCmin * t1 = ACCmin * t2
i.e. target frequency = ACCmin * target position / target frequency
i.e. ACCmin = target frequency² / target position
If now acceleration ramp is smaller than ACCmin (5 Hz/s), then it will not be possible to
reach the target frequency. V1 value is then smaller than 10 Hz:
Output
frequency
V1
3 Hz /s
3 Hz /s
t3
target position = left triangle + right triangle
i.e. target position = (V1 * t3 / 2) + (V1 * t3 / 2) = V1 * t3
i.e. t3 = target position / V1
i.e. t3 = target position / (t3 * acceleration)
i.e. t3² = target position / acceleration
i.e. t3 = square root( target position / acceleration )
Here t3 = square root ( 20 / 3 ) = 2.58 seconds
Time
The previous calculations can be summarized as following:
Acceleration >
target frequency²
/
target position ?
NO
YES
Trapeze profile:
Trun = target position
/
target frequency
Triangle profile:
Trun = square root
(target position
/
acceleration)
One major issue is: how to calculate the square root in ATVlogic?
No “square root” (or sqrt) block does exist, but there is a way to determine the square root in
a recursive way.
If the following calculation is executed several times (yprevious is the previous result):
y = ( (x / yprevious) + yprevious) / 2
then it will give sqrt(x).
Example with x = 6084. At the beginning yprevious = 1:
x
6084
6084
6084
6084
6084
6084
6084
6084
6084
yprevious
1
3042
1522
762
384
199
114
83
78
It is OK: 78 * 78 = 6084
It works for x between 1 and 32766.
y
3042
1522
762
384
199
114
83
78
78
4. ATVlogic implementation of
square root
B01
B03
1
B02
1
x
B05
41
B04
1
Sqrt(x)
It is very important that the function blocks are executed in the right order:
B00 then B01, etc…, then B05.
Execution order can be modified using “Device -> ATV Logic -> Edition -> Set view execution
order”:
ATV Logic implementation of Trun calculation (in AUX)
The target of this diagram is to calculate the value of TRUN.
M03 is FRS
M02 is the frequency target (in Hz)
ACC (in seconds) and DEC must have the same value. This program only reads ACC.
M04 is the target distance (in pole pairs)
“TRUN” is then fed to the PRE task:
RUN order pulse generation (in PRE)
The attached project file also contains a state machine to manage a forward-reverse
sequence.
LI3 is used to start the sequence. The motor is stopped during 3 seconds then the direction
is reversed.
5. ATVlogic monitoring function
In the toolbar the following button is used to display the current values on the diagram:
For example it is possible to check the behaviour of the square root function:
ATVlogic monitoring function
It is OK: Square root(240) = 15.
The values are not refreshed continuously: pressing this button only reads the values once.
6. Program limitations

It is not possible to have target distance larger than acceleration (in Hz/s). This
creates an overflow:
Because 32761 * 20 / 16 = 40951 and because ATVlogic is programmed with signed 16 bits
integers, then 40951 is limited to 32761.

This also creates precision problems:
Here ACC = 9 s
FRS = 150 Hz
ATVlogic calculates ACC = 16 Hz/s, but in reality the float value is 16.6667 Hz/s.