# Path planning with industrial robots with tracking

• posted

Hi robots,
I have folowing problem: Industrial manipulaator moves between point
1(start point)
and point 2 (end point) in 3D.End point is not fix (part on the
conveyor).How to calculate
trajectory between point 1 and point 2 ?Does somebody has on-line
algorithm for C
or C++ or PLC program?
Best regards
Leo
• posted
Can't you just predict where end point is going to be and move the manipulator there? A more complicated way is to have a formula the moves the manipulator as a function of the converyor position and then use the chain rule to adjust for the conveyor speeds.
Why not get a motion controller that can do this.
Peter Nachtwey
• posted
What you wrote is not path planning. I need function p(t9 (t is time and p is distance from beginnig point). Every 1msec I write this position to servo controller and servo controller changes speed, acceleration etc. It means this p(t) is not known at the start of the moving (because endpoint is not fix). If endpoint is fix, I have solution.
Best regards
Leo
• posted
Sure it is. It predicts where the point 2 is will be and goes there.
That is wasteful. The motion controller better be able to change the motion profile smoothly on-the-fly to do that.
I think what you are asking for is a superimposed move. In this case you tell the motion controller to move the maniplutor to the current point 2. You said you can do that. At the same time you add the motion of point to the motion of the manipilator. You are adding two motion profiles together. When the first motion profile is done the manipulator will be at point 2 where ever that is on the converyor. Simple. The downside of this technique is that the manipulator will mimick all the uneven motion from the conveyor.
Peter Nachtwey
• posted
TRhere is only one motion profile.
• posted
OK, It is not clear what you mean. How can ONE motion profile move between point 1 and point 2 when point 2 can be in more that one place dpending on the conveyor speed? Some part of the target generator must take into account the motion of point 2 on the manipulator. If you aren't going to put the effort into explaining the problem then you aren't going to get the answers you need.en
Peter Nachtwey
• posted
e motion profile.
OK, Peter. I have algorithm if point 1 is fix and point 2 is fix. It means, I have coordinate for point 1(X1,Y1,Z1) and I have coordinate for point 2 (X2,Y2,Z2). Now, I know distance between between this two points and I can calculate trajectory between points P1 and P2 as function of time:P(t) (as input values are max.velocity,max.acceleration,max.jerk...).Next, every 1 msec I write new value in servo drives( if I have 3 drives, then I have to calculate move for every drive):P(t1)P(t2)......P(tn) =2EP(t1) is pont(X1,Y1,Z1) and point P(tn) is P(X2,Y2,Z2). My problem is:Which algorith can I use if point P(X2,Y2,Z2)is not fix, but I know every moment what is coordinate of this point. Regards
Leo
• posted
one motion profile.
Leo, I don't think you have understood what I am saying about super- imposed moves. The two motion profiles are run concurrently, not sequentially. That is pvaj(t)=3Dpvaj1(t)+pvaj2(t). pvaj is my term for position, velocity, acceleration and jerk. pvaj1(t) is the motion profile to point 2 at time 0. pvaj2(t) is derived from the actual motion of the conveyor. Every millisecond the pvaj1(t) and pvaj2(t) are calculated and summed yield pvaj(t). pvaj(t) is the target that the manipulator will follow. Note, is is often hard to estimate the acceleration and jerk from the conveyor with out the use of an Kalman filter or observer.
Peter Nachtwey

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