KINEMATIC COMPENSATION ALGORITHM
GENERAL DESCRIPTION
From system software version C3G 5.11 a new software feature is available, integrated to the system soft
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ware, which improves precision in positioning the robot within the work area. The software compensates ki
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nematic errors due to inaccuracy of the length of the robot levers and errors due to incorrect coupling of the
axes (axis orthogonality) and also flexion errors caused by the weight of mechanical bodies.
NOTES FOR CORRECT USE
Below you will find a series of notes which define some particularities of the new feature and how to use it
correctly.
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To make it possible to activate kinematic error compensation on a robot such as, for example, the
SMART H4 or SMART H1, it is necessary to have the file that identifies the kinematic model. The exten
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sion of this file is .ROB. Each robot has its own specific file, which cannot be used by other robots.
·
With the C3G Plus cell controller it is possible to have a maximum of 4 Arms per system, each of which
has a file which identifies its kinematic model.
·
The files with .ROB extension are saved on floppy disk 1/3 of the system software. We suggest to:
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identify the arm to which the robot to be compensated belongs through the last character in the .ROB file
(particularly for multiarm systems). In this case, to enable the compensation algorithm, all you have to
do is load the .ROB file in the controller ram disk.
· insert the robot serial number in the .ROB file name.
E.g.: File PR103_1.ROB belongs to the robot with serial number 103, Arm 1.
· The possibility exists of personalising the .ROB file name through the system variable
$ARM_DATA[ARM].FL_COMP (maximum 8 characters excluding extension). If the user wants to call the
.ROB file in a particular way, he should set the above-mentioned variable and call the .ROB file in the cor-
responding arm ram disk in the same way. Then, re-start the controller using the CCRW command.
· To check whether dynamic compensation is active, use the controller Execute command with the in-
struction WRITE($A_ALONG1[1]::32::4,NL). The teach pendant or PC video will display a binary num-
ber; counting from the right, bit 23, if set at 1, indicates consent to enable the compensation software,
while bit 22, if set at 1, indicates active compensation. Moreover it is possible to check whether the off
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set has been activated using the “Configure Controller View” command; if the offset is activated “Y” will
be displayed in the last column for “arm”, otherwise “N”.
·
The compensation of kinematic errors acts dynamically during execution of the programme on the final
points of the movement instructions. This means that at each NOMINAL point (point generated with the
CAD system) the compensation algorithm is applied which, in turn, generates a corresponding point called
COMPENSATED, on which the robot is taken in order to improve positioning on the nominal point.
·
The compensation software is functioning only if the robot is out of the singularity areas; therefore it hin
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ders the user from moving the machine to the requested position. However, during the teaching of
points, the programmer must be allowed to move close to the point of singularity in order to look for an
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other point in the surrounds, which is available for the compensation. To this purpose, the command
SET ARM NOSTROKE may be used, which disables the compensation algorithm for 60 seconds. Dur
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ing this lapse of time, the user may reach the point and teach for a new position. In case a longer time is
required as the position to be compensated is rather complex to be reached, the routine COMPS_SET
may be called out from the command menu under the EZ environment in order to disable and enable
the compensation algorithm close to a MOVE instruction. The system command DISPLAY ARM POSI
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TION displays, next to the actual Cartesian position (POS) of the arm and the value of the joints (JNT),
an explicative character concerning the compensation at that point and having the following meaning:
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r : indicates that a movement is in progress or that the compensation has not been per
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formed at the current position;
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N : indicates that the compensation has been performed at the current position and therefore
the displayed position is nominal (ideal);
C3G Plus MAIN OPERATIONS FOR SYSTEM USE
06/0400 5-19
kinematic compensation algorithm
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