View Full Version : Robotic Arm
04-04-2003, 01:38 PM
As you can see I am new to this forum site so apologies at the start for waffling on my behalf.
I am trying to model and animate a robotic arm for a project. I have been banging my head now for several days and it suddenly dawned on me that a forum may be my salvation.
See piccy for an idea of what is involved.
I have been struggling with bones and Inverse IK. Basically the main body is sorted as it only moves on two axis, y and z.
The "hand" at the end though has been trying its best to test the jedi calm. Any advice or help will be much appreciated.
Back to banging my head off the monitor for the moment.
Forgot to mention I am using Max 4.
04-04-2003, 02:36 PM
i understand you're frustrated but i still don't get what exactly are you trying to do?
if you could be more specific maybe we can suggest some tips.
04-04-2003, 03:02 PM
thanks for replying.
The actual robotic arm is to be used in a packing process where it suctions products up with the hand and then deposits them on pallets. The hand can spin a full 180 clockwise and anti clockwise. The hand also has grippers on it which can pick up empty pallets.
The basic function of the arm is to bend up and down on the z axis with forward and backward motion on the y axis. I have managed to conquer this with a simple bone structure, 3 bones and a HI Solver to create a link. The main arms of the robot being bottom and top repectively are linked to the corresponding bones.
The arm is then controlled by a pointer helper I have created which has the ik chain linked to it. See piccy for ref.
The bit which is puzzling me is the "hand" at the end of thearm. It has to stay perpendicular to the ground at all times as shown in the picture. But I cannot work out how to attach a futher bone to create the fluid motion. I have created a pointer helper which allows me to rotate the "hand" by eye whenever the arm moves but it is not accurate.
Also on the actual "hand" are two grips which move into a retracted position or extended to grip objects. I have managed to get a similar bone setup for controlling the basic functions but then I ma stuck. I cannot get this system to link to the main hand when it is moving up and down without breaking my ik chain. I can go into more detail but I fink this reply is looking big already.
Thanks again mate for replying...
04-04-2003, 03:08 PM
wee bit more info..........
Ideally I am trying to set up a system of controls to allow the arm to bend backwards and forwards, up down, with the hand always rotating to face perpendicular to the ground plane. Then being able to control the opening or closing of the grips.
Everything is a separate mesh at present. The control arms and grips on the hand are a bastch as when the main arm moves down the bones, ik chain and relevant mesh is left behind doing wonderful useless movement. I cannot work out how to link this separate system to the main movements of the arm.
Plus eventually the whole baby has to spin 360' on its base pad.
04-04-2003, 03:26 PM
well it sounds to me like you got the arm part down in terms of control
so you wanted to have the hand parallel with the ground no matter where the arm is - well for this i recomend that you attach it to with a position contraint. that would maintain its orientation no matter how you move its parent. whether its parallel or perpindicular to the ground would depend on the orientation you wanted and also you can always rotate it.
you second issue about the fingers opening and closing, if this operation were gonna be used a lot in an animation, what i would do is set it up and wire to a slider that way all you'd have to do is animate the slider. essentially this is just wiring the rotation of an object to slider controls.
05-04-2003, 10:29 AM
thanks for the advice. It is Saturday morning here now and after the effects of beer from last night I shall get down to fixing the problems.
When you mean wiring the controls of the fingers for opening and closing will that assist in keeping them "stuck" to the side of the hand when it moves down? This is the one bit that has been really messing with me.
Can you attach an IK chain and bones to the mesh and then attach all of that to the hand without breaking the links so that the movement still keeps its integrity whilst following the movement of the hand?
Thanks again man.
05-04-2003, 03:48 PM
well the only reason i mentioned wiring is that if you do an operation over and over again its easier to put in on a slider. but you don't really need to do that, no reason to wire if you're ok with just manually rotating a control to open and close the fingers.
as for what the second part of your reply, what do you mean by attaching, you mean linking? cuz attaching and linking are two very different things.
what i would do is set up my model in a neutral position. create bones for it and and then set up my rig in terms of any constraints and ik and dummies. there's a great tutorial on the 3dtotal front page by my good friend mike rickard. he talks about rigging the legs of a character. i think that one would help you a lot with this project of yours.
05-04-2003, 05:40 PM
I really appreciate your time here to help out my confused brain.
I have given the wiring a bash and yup, it is making life a whole lot easir than before. Took me a whiley but got there in the end.
This is a whole new ball game for me as I am used to architectural visualisation than creating this type of model.
Sorry about my misuse of words. When I mean attaching I actually meant linking. At present my bone system and IK chain for the grips are linked to a separate pointer helper to allow me to move the grip back and forwards. What I am failing to do is then link this entire system back onto the hand so that when the hand moves the bones etc go with it. They are just floating in space at present and I cannot work out how to link them to the hand without breaking either the IK chain or the actual bone connections.
I am going to go through the tutorial you have mentioned and hopefully I can get a better understanding than jumping in at the deep end.
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