ACCEL program instruction
Syntax
ACCEL (profile) acceleration, deceleration
Function
Set acceleration and deceleration for robot
motions. Optionally, specify a defined acceleration profile.
Usage Considerations
The ACCEL instruction can be executed by any
program task as long as the robot selected by the task is not attached by any
other task. The instruction applies to the robot selected by the task.
If the V+ system is not configured to
control a robot, executing the ACCEL instruction causes the error *Robot not
attached to this program*.
Before an acceleration/deceleration profile
can be used, it must be defined for the selected robot (profile 0 is always
defined). (The robot configuration is edited using the SPEC utility, see Instructions for
Adept Utility Programs.)
Parameters
| profile |
Optional integer specifying
the acceleration profile to use. Acceptable values are 0 to 8 (depending
on the number of defined profiles). The default is the last specified
profile (see Details for the number of the start-up profile). If a
profile is specified that has not been defined, profile 0 is used.
|
| acceleration |
Optional real value, variable,
or expression considered as a percentage of the maximum possible
acceleration. |
| deceleration |
Optional real value, variable, or expression considered
as a percentage of the maximum possible deceleration. The value should normally be in the range of 1 to 100
(upper limits greater than 100 may be established by the robot
manufacturer). If an out-of-range value is specified, the nearest
extreme value will be used. If a parameter is omitted, its current setting remains
in effect. |
Details
If profile 0 is used, a square wave
acceleration profile is generated at the beginning and end of the motion.
If a profile is specified, that profile is
invoked for subsequent robot motions. Defined profiles set the maximum rate of
change of the acceleration and deceleration. The values set with this
instruction define the maximum acceleration and deceleration magnitudes that
are achieved.
When the V+ system is initialized, the
profile, acceleration, and deceleration values are set to initial values,
which can be defined by the SPEC utility program. As delivered by Adept, the
initially selected profile may be either 0 or 1 depending on the type of
robot. The settings are not affected when program execution starts or stops,
or when a ZERO command is processed.
Normally, the robot manufacturer sets the
100% acceleration and deceleration values to rates that can be achieved with
typical payloads and robot link inertias. However, because the actual
attainable accelerations vary greatly as a function of the end-effector,
payload, and the initial and final locations of a motion, accelerations
greater than 100% may be permitted for your robot. The limits for the maximum
values are defined by the robot manufacturer and vary from one type of robot
to the next. If you specify a higher acceleration than is permitted, the limit
established by the robot manufacturer is utilized.
You can use the functions ACCEL(3) and
ACCEL(4) to determine the maximum allowable acceleration and deceleration
settings.
For a given motion, the maximum attainable
acceleration may actually be less than what you have requested. This occurs
when a profile with a nonzero acceleration ramp time is used and there is
insufficient time to ramp up to the maximum acceleration. That is, for a given
jerk, a specific time must elapse before the acceleration can be changed from
zero to the specified maximum value. If the maximum acceleration cannot be
achieved, the trapezoidal profile is reduced to a triangular shape. This
occurs under two circumstances:
-
The motion is too short. In this case,
the change in position is achieved before the maximum acceleration can be
achieved.
-
The maximum motion speed is too low. In
this case, the maximum speed is achieved before the maximum acceleration.
In both of these situations, raising the
maximum acceleration and deceleration values does not affect the time for the
motion.
Hint: If you increase the maximum
acceleration and deceleration values but the motion time does not change, try
the following: increase the program speed, switch to an acceleration profile
that allows faster acceleration ramp times, or switch to acceleration profile
0, which specifies a square-wave acceleration profile.
NOTE: This type of acceleration limiting
cannot occur with acceleration profile 0 because a square-wave acceleration
instantaneously changes acceleration values without ramping.
Examples
Set the default acceleration time to 50% of
normal and the deceleration time to 30% of normal:
ACCEL 50, 30
Change the deceleration time to 60% of
normal; leave acceleration alone:
ACCEL ,60
Reduce the acceleration and deceleration to
one half of their current settings:
ACCEL ACCEL(1)/2, ACCEL(2)/2
Invoke defined profile #2 and set the acceleration magnitude
to 80% of the defined rate:
ACCEL (2) 80
Related Keywords
ACCEL real-valued function
DURATION program instruction
PAYLOAD program instruction
SCALE.ACCEL system switch
SELECT program instruction
SELECT real-valued function
SPEED monitor command
SPEED program instruction
