AMCI SMD17K, User Manual

Page: 39 / 98

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
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39
REFERENCE 3
C
ALCULATING
M
OVE
P
ROFILES
The equations in this reference use a unit of measure of steps/second/second (steps/second
2
) for acceleration
and deceleration. However, when programming the SMD17K, all acceleration and deceleration values must
be programmed in the unit of measure of steps/second/millisecond.

To convert from steps/second
2
to steps/second/millisecond, divide the value by 1000. This must be done
when converting from a value used in the equations to a value programmed into the SMD17K.

To convert from steps/second/millisecond to steps/second
2
, multiply the value by 1000. This must be
done when converting from the value programmed into the SMD17K to the value used in the equations.
Constant Acceleration Equations
When you choose to use constant accelerations, the speed of the move will increase linearly towards the Pro-
grammed Speed. This is the fastest form of acceleration, resulting in the fastest move between two points at
its programmed speed. For the smoothest transition from the starting speed, the starting speed should be equal
to the square root of the acceleration in steps/sec
2
. For example, if the choose acceleration is 20,000 steps/
sec
2
, the smoothest transition occurs when the starting speed is 141. (141
2

20,000)
Figure R3.1 Constant Acceleration Curves
Variable Definitions
The following variables are used in these equations:

V
S
= Configured Starting Speed of the move

V
P
= Programmed Speed of the move

a = Acceleration value. Must be in the units of steps/second
2

d
= Deceleration value. Must be in the units of steps/second
2

T
A
or T
D
= Time needed to complete the acceleration or

deceleration phase of the move

D
A
or D
D
= Number of Steps needed to complete the acceleration

or deceleration phase of the move
This reference was added for customers that must program very precise profiles.
Understanding this section is not necessary before programming the SMD17K
and therefore can be considered optional. Two different approaches are presented
here. The constant acceleration example takes given parameters and calculates
the resulting profile. The variable acceleration example starts with a desired
speed profile and calculates the required parameters.
SPEED
AC
C
E
L
E
R
A
TIO
N
TIME TIME
t t
Programmed
Speed
SP
E
E
D
TIME
Ta