NOVA electronics Inc.
MCX514 -
26
－
26
－
■
Triangle Form Prevention of S-curve Acceleration / Deceleration Driving
S-curve acceleration / deceleration driving also has the triangle form prevention function for keeping a speed curve smooth.
In fixed pulse driving of S-curve acceleration/deceleration where acceleration and deceleration are symmetrical, when the number
of output pulses does not reach the number of pulses required for accelerating to a drive speed or when decelerating stop is
performed during S-curve acceleration, the triangle form prevention function works in both cases and keeps a speed curve smooth.
＜
The Prevention of Triangle Driving Profile in Fixed Pulse Driving
＞
In fixed pulse driving of S-curve acceleration/deceleration where acceleration and deceleration are symmetrical, when the number
of output pulses does not reach the number of pulses required for accelerating to a drive speed, the following method is applied to
keep a speed curve smooth.
Fig. 2.2-9 The Rule of 1/12 of S-curve Acceleration / Deceleration
If the initial speed is "0" and the acceleration is increased up to the time "t" at a constant jerk "a", in the section of acceleration
increasing, the speed "v(t)" in the time "t" can be expressed as follows.
2
at
v(t)
=
a:
coefficient related to speed
Therefore, the total number of pulses “p(t)” utilized during the time from “0” to “t” is the integral of the speed “v(t)” from the time
“0” to “t”.
3
at
3
1
p(t)
×
=
This value indicates 1/3 of at
２
×
t (the number of pulses of one square on the figure) regardless of the value of the jerk.
In fixed pulse driving, the acceleration is increased from the time “0” to “t” at a specified jerk, and is decreased from the time “t”
at the same jerk. When the acceleration reaches 0, and if the deceleration is also increased / decreased at the same jerk, the number
of pulses that were utilized in fixed pulse driving is expressed, as shown in Fig. 2.2-9, as follows.
4
3
1
3
2
1
1
3
2
3
1
=
+
+
+
+
+
squares on the figure
Therefore, the number of pulses (1/3 of a square) that were utilized during the time from “0” to “t” in acceleration increasing
section is 1/12 of pulses that were utilized in all fixed pulse driving.
For this reason, in S-curve acceleration / deceleration fixed pulse driving, when the number of output pulses during acceleration is
more than 1/12 of total output pulses, MCX514 will stop increasing acceleration and start to decrease the acceleration value with
the speed curve as shown in Fig. 2.2-9.
［
Rule of 1/12
］
This method makes an ideal curve when the initial speed is 0, however the initial speed cannot be 0, so the pulses from 0 on the
figure to the initial speed will be excess and will be output at the peak of the speed.
