Safeguards

Forum discussion the 6-axis articulated Adept Viper s1700 robot

Safeguards

Postby ToddR » Tue May 12, 2009 6:35 pm

In addition to being cautious of motions through singularities (Info here: http://www1.adept.com/main/ke/data/procedures/singularity/singularity.pdf) the user should also exercised caution when assigning acceleration and speed values for all moves, especially straight line motion.

In a straight line motion there is only one possible combination of motor positions for each servo set point. In many cases of straight line motion a single motor has to do the most work and there is no option to defer some of the work to another motor. It will be obvious that you are trying to push a joint too hard if the motion is unsteady. You may receive a *Soft Envelope Error* or *Hard Envelope Error* if the robot's tool flange strays to far from it's commanded position at any time during the move. In the case of a soft envelope error the motion will be stopped and program operation will be terminated. In the case of a hard envelope error the robot will be stopped and power will be disabled.

It is also possible that before an envelope error can stop the robot a motor amp fault can occur. This error can be dangerous as it will stop the current motion and enable the robot's brakes, but the robot is likely to continue moving for a short time (~80ms) before the brakes begin to engage. During this time the robot may be moving in an unexpected or undesired direction, potentially toward a collision with either objects in your work cell or the floor.

For this reason it is extremely important to ensure that the moves you program are not too aggressive for the robot to handle:

-The robot's ability will vary based on the supplied voltage. Be sure that the voltage supplied to the robot falls within the specifications found in your user's guide.
-Make use of the parameter SPEED.LIMIT described in the link above on singularities. SPEED.LIMIT places a limit on the percentage of maximum joint speed any joint is allowed to attempt. For example, if PARAMETER SPEED.LIMIT is set to 120 then if at any point in a straight line move any one joint reaches 120% of its maximum rated RPM the motion will be stopped. While this stop may be abrupt, it is favorable to potentially dropping or damaging the robot by attempting moves.
-It is not recommended that you set SPEED.LIMIT higher than 120.
-Using an acceleration profile of zero for straight line moves is not recommended with this robot.
ToddR
 

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