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Using mates in Assembly Motion 2008 0.1?

Question asked by Jay Mackey on Dec 5, 2007
Latest reply on Dec 14, 2007 by Jay Mackey

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Maybe there is a better way, but I would like to use a mate that isset to 'position only' to get a complex assembly (six-axis robotwith complex 4-bar linkage, with complex end-effector) in to aposition, and then either set a keyframe while the mate dialog isstill open (ideal solution), or be able to OK the mate dialog andthen keyframe the position. Unfortunately, SW08 does notallow keyframing while the mate dialog is active, and itimmediately returns the assembly back to the position of the activekeyframe as soon as the mate dialog is closed.

My current method is to define a 'Current Robot Position' made upof three mates that fully define the current robot pose (by tying afeature on the end-effector to a feature on the workpiece). Setting it up (or editing it to get the robot to a new pose)forces the robot to the new position. Then I can suppressthose mates so that the robot assembly positions are keyframed andtherefore become motion drivers, instead of keyframing the mates,which results in the robot component motions being driven by themates, which are meant to be temporary. This is basically avariation on the 'position-only mates' scheme outlined above.

The other option is creating a set of mates for every single robotpose, probably about 40 positions, and then keyframing thesuppression of all but one set of mates at a time.

I'm asking if there are other advanced techniques. One optionthat has occurred to me would be making a 3D path through all 40positions. This would only be used to guide the 'tool-tip'through its motions, I would still have to manually move or mate upthe end-effector to take care of it's orientation. I'm noteven going to try it because it sound like more work than mycurrent scheme.

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Jay Mackey Dec 6, 2007 7:33 PM
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I figured out that with my robot assembly, I want to keyframe thetool plate on the 6th axis, and maybe the forearm on the 4th axissometimes to ensure the 'wrist' is oriented in a certain directionsince it is possible to have the end-effector in the same positionsometimes with the wrist either up or down, so you need to keyframewhen it wants to go opposite of what you want.

I can use a set of three mates that can be unsuppressed and editedto get the robot into each position relative to a very non-uniformworkpiece. The mates move the tool tip relative to theworkpiece. I keyframe the robot toolplate to which theend-effector is mounted, and then suppress the 'positioning' mates,and delete the keypoints they generated. (A good question iswhy, when Auto-key generation is off, do changes to mates cause akeypoint to be generated??)

The biggest issue I have at the moment is that playback insolidworks is useless in this case. I assume that my assemblyis just too big, with a moderately complex kinematic chain whichhas to be solved, and that it is a bad case of frame-drop. Isthere any way to force it to not drop frames? It is moreimportant to see the flow of motion than to have atemporally-accurate playback that drops all but the first, 1middle, and the last frame in a 2 second 60-frame playback! Ihave to save an AVI to see what my changes have done, and then Ican see it step through the frames slowly as it records todisk.
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- Gerald Davis @ Jay Mackey on Dec 7, 2007 12:59 AM
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  Jay -
  One of the good things with Assembly Motion (aka Animator) is the ability to control angle mates and distance mates at keyframes.
  
  I'd be tempted to design your animation sequence using those instead of trying to suppress/unsuppress coincident mates. You may need to use the coincident mates to determine what the target angles are.
  
  I like your suggestions, though. If you send in and enhancement request, let us know about it so we can pile on and perhaps elevate the suggestion into the next release.
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  - Jay Mackey @ Gerald Davis on Dec 7, 2007 2:13 PM
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    In reference to playback, I did find that I can 'scrub' thetimeline, click and drag on the 'timebar' and move it up and downthe time line to get a smooth 'playback' of the animation. This saves having to render out an AVI every time I want tocheck my edits.
    
    I'm using concentric and distance mates. The workpiece hasholes, and the end-effector performs a drilling and a rivetingoperation with two different, parallel tools. So there aretwo 'tool-tips'. I need to move the drill to concentric tothe hole, but at an 'approach' position, about 400mm away, thenmove to the actual position, and finally, use a distance mate onthe drill slide cylinder to extend it down to drill. Afterthe drill is retracted, I just reverse the robot motion back upaway from the piece, and then do the whole concentric and distancemate using the same hole and the rivet tool-tip. Again,there is an approach position, and the final position. Thedepart position is just a copy of the approach position keypoint. I could get away with just using the concentric mate, andthen manually move the end-effector into the desired positions, butit would look a little sloppy due to random slight variations incomponent orientations if I don't control the rotation of theend-effector about it's long axis relative to the work-piece. There are seven points to drill and rivet, so that means thatthere are over 40 points to keyframe in the entire robot cycle whenyou take into consideration the approach, final, depart, andintermediate points along the path of the robot.
    
    A lot of the trouble I had that prompted me to post here was that Ididn't understand what conflicts can arise if you keyframe too manycomponent positions. At least the red timeline gave me ahint, but I couldn't find what the red timeline actually means inthe help. I was originally selecting the entire robot andkeyframing it, but that meant that it effectively can't move at allin between keypoints.
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    - Gerald Davis @ Jay Mackey on Dec 7, 2007 8:34 PM
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      Jay -
      The attached animation was done by using key frames to change angle mates. The screen capture shows some of the the key points.
      
      I found the 6 axis assembly in 3D content central.
      
      This kind of animation would be easier to produce if the angle mates didn't ever flip. Sadly, they do so it pays to save your work often and experiment a little bit dragging key points around to get the mates to flip back.
      
      I recommend the struggle with controlling angle mates (and distance mates) in animations because it gives you precise control over the positioning and sequencing. Dragging things into position to create key points isn't always easy.
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      - Jay Mackey @ Gerald Davis on Dec 14, 2007 6:10 PM
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        Thanks, Gerald,
        
        Here's what I've figured out over the last three weeks of trying to animate a robot:
        
        Using angle mates to animate a six-axis robot, where you have three tool-tips on the end-effector that need to be precisely aligned and positioned with features on a workpiece just isn't remotely feasible. I program real robots, and moving individual joints to get a tool-tip into position on a work piece would drive a person insane. Instead, you can jog the robot in a coordinate system based on the tool-plate at the sixth axis, or even better, create a custom coordinate system oriented on the actual tip of the custom end-effector you are using.
        
        The equivalent in SW would be to create an 'animation guide' component that acts as a custom coordinate system. Then mate your tool tip(s) to this guide. Since I have three different 'tips' or positions (a Machine Vision Camera, a drill, and a fastener feeder), I've set up three sets of mates and have suppressed them. (During the animation, the Animation Guide component is hidden.) If you only have one tool-tip, then you could forego the guide component and just position the tool tip itself to the workpiece feature(s).
        
        Then I can set up multiple sets of mates between the guide and features on the workpiece, or I can just edit one set of mates to get the guide into each position.
        
        NONE of the above mates are used in the animation (i.e., keyed). They are ONLY used to position the tool tips. If they were used to keyframe position, the robot would jump instantaneously from pose to pose. Instead, the position of only one component is keyframed. This component then drives the position of every other component that is mated to it. In this case, the best choice is the tool-plate on the sixth axis of the robot.
        
        The procedure is thus: set the mates of the guide to the first feature and unsuppress them. Select the mates of the first tool-tip and unsuppress them. (Put the mates in a folder, and unsuppress all of them at once by just unsuppressing the folder itself.) The robot assembly will then be driven to the first position. Key the driving component (the tool-plate in my case, since it is the last component with an unmated degree of freedom in the kinematic chain of the robot arm, not counting the positioning mates I just turned on.) Now, if necessary, you can key distance or angle mates on actuators in the end-effector. To go to the next tool-tip position, select a new position on the timeline, suppress the mates for the first tool-tip, and unsuppress the mates to the second tool-tip. The robot will be driven to the new position that is still relative to the Animation Guide component that is still mated to the workpiece feature. Again, keyframe the tool-plate position. Animate any end-effector actuator mates, such as cylinders, etc. Repeat for a third tool-tip, if necessary, etc.
        
        Now unsuppress all of the positioning mates, including the animation guide's mates. Unsuppress new mates that move the guide to the next feature on the workpiece (or just edit the one set of positioning mates to accomplish the same thing). The Animation Guide component is moved to a new hole position (or whatever feature you are working on), and now a set of tool-tip positioning mates can be unsuppressed to move the robot to a new pose.
        
        Remember, none of these positioning mates should be keyframed!!!!! Unfortunately, SW automatically adds keypoints each time you unsuppress and suppress these mates, even when the 'auto' keyframing button is off. Also, unfortunately, it can be a huge hassle to deal with these keypoints. You may have to leave them in place until you have finished all keyframing at a given position. But once you have the tool-plate keyframed, you should be able to delete the positioning-mate keypoints. In the end, you end up with just one component driving all robot movement, which makes it MUCH easier to change the timeline!!!! (i.e. change the pacing at one sequence by dragging keypoints up or down the timeline.)
        
        Also note that since in this case we are likely to have the same exact sequence of motion occuring on the end-effector (cylinders extending and retracting, etc.), and all these key-framed mates are relative to the base of the end-effector, you can copy and paste these keypoints to each place on the timeline that you need theme for how ever many positions you have on the workpiece. Of course, if the robot does 'different' actions at each different spot on the workpiece, then you probably won't be able to copy and paste any keypoints.
        
        In the end, you only have one component whose position drives the entire robot pose from pose to pose, letting SW solve the joint-angles of the robot arm. If the pose to pose change is drastic, you may have to key a few intermediate poses, or else the robot may achieve the correct end-effector position with a pose that is incorrect. This happens with four-axis or six-axis robots in the real world as well, since there are situations where two different poses can achieve the same end-effector position (i.e., elbow pointing left, or elbow pointing right, wrist bent up, or wrist bent down, etc.). This would be especially true in SW if you don't use a joint-angle mate with min/max limits, but instead allow the joint to spin freely through the full 360 degrees times an infinite number of turns.
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Using mates in Assembly Motion 2008 0.1?

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