# Help with DMU Kinematics please

#### luss

##### New member
Can you help me with this robot I made, what joints should I put and where?

#### luss

##### New member
I put active and passive joint where I thought they should be but it didnt work so anyone know exactly how it should go?

#### MrCATIA

##### Super Moderator
That's a nice looking assembly you've made. It's also a complex series of mechanisms, each having an input and motion. A little too complex for learning how to use CATIA Kinematics.

I suggest you start with something much simpler - a 4-bar linkage, or a piston/crankshaft would be good.

There's a good Kinematics tutorial in the CATIA Help documentation. http://catiadoc.free.fr/online/CATIAfr_C2/kinugCATIAfrs.htm

There are also a lot of videos on YouTube where you can learn how to make a mechanism and how to make joints.

Learn how to make some simple mechanisms first, and then come back and we'll take a look at your robot.

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#### luss

##### New member
I understood it on simpler assemblies and then I failed to do it on this robot, I tried 100+ times and it didnt work, the main problem is it at the end when i have one joint left and first it says i need to add some joints for the mechanism to work and then i put it on and it says that the mechanism is over constrained or this joint isnt needed.

#### MrCATIA

##### Super Moderator
Good - you understand how CATIA Kinematics works making a mechanism with 1 DOF and 1 input command to simulate the motion.

Your robot is a combination of several mechanisms (maybe 5?) each with an input command and each moving independently of the other mechanisms. Please see my image below

Do you agree with these motions? Did I miss any?

It seems you are adding Assembly Constraints to this product, and then converting the constraints into Kinematic Joints. Are you familiar with defining all the Joints yourself with the DMU Kinematics workbench?

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#### luss

##### New member
Yes those are the motions and yes I know how to define all the joints