kinematics model of hybrid robot

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Mohamed Magdy
Posts: 10
Joined: 02 Sep 2019, 18:32

kinematics model of hybrid robot

Post by Mohamed Magdy » 06 Sep 2019, 19:44

hey
I am building an IK kinematics model of hybrid (3 Dof parallel +2 Dof serial ) robot , I built the model then set up the IK system, add and moved the dummy, and link them.But when I start the simulation ,i see some strange configurations.
I have some questions
1-how to motion planing in task space considering the time ?
3-why the last Ik group do not work well ?
Last edited by Mohamed Magdy on 18 Sep 2019, 22:22, edited 1 time in total.

coppelia
Site Admin
Posts: 7272
Joined: 14 Dec 2012, 00:25

Re: kinematics model of hybrid robot

Post by coppelia » 09 Sep 2019, 06:38

Hello,

you have a mechanism that contains loops. The best way to handle IK in that situation would be to first create a mechanism with a single branche, like a serial manipulator. Create an IK group with an IK ement for that. Then, add a branch for the first loop (i.e. closing on the robot base). For that, create an IK element that is solved in the same IK group. The tip of your IK element will try to close the loop by following the target fixed on the base of the robot. Do the same for the second loop. It is important that the two loop IKs are defined with an IK base on the base of the robot.
Then your IK should work fine, also without damping.

Cheers

Mohamed Magdy
Posts: 10
Joined: 02 Sep 2019, 18:32

Re: kinematics model of hybrid robot

Post by Mohamed Magdy » 09 Sep 2019, 11:34

Hey admin
thanks so much for your response.
I'm newbie to v rep and little confused . Do you mean like that

1-but the serial part isn't moving (orientation )now and interfering the path , that means if a real part was there, a collision will occur and the serial part which has two revolute joints is not used ?

2-path and motion planing are not in calculation modules where can I find them?
Last edited by Mohamed Magdy on 18 Sep 2019, 22:23, edited 1 time in total.

Mohamed Magdy
Posts: 10
Joined: 02 Sep 2019, 18:32

Re: kinematics model of hybrid robot

Post by Mohamed Magdy » 13 Sep 2019, 04:31

Greetings
I really need an answer
thanks in advance

coppelia
Site Admin
Posts: 7272
Joined: 14 Dec 2012, 00:25

Re: kinematics model of hybrid robot

Post by coppelia » 13 Sep 2019, 12:13

Have a look at the ik_fk_simple_examples folder, that illustrates several IK/FK problems in a simple way. That will help you understand. You can also have a look at the model Models/robots/non-mobile/ABB IRB 360.ttm (but that models is a bit more complex because it allows for IK and FK operations.

Cheers

Mohamed Magdy
Posts: 10
Joined: 02 Sep 2019, 18:32

Re: kinematics model of hybrid robot

Post by Mohamed Magdy » 13 Sep 2019, 17:02

Greetings
thank you so much ,the examples were good basics .
I tried to correct my model as you said

also this IK :https://drive.google.com/open?id=1up1ja ... zPy3sTPVbV

-I have analytical equations of kinematics of the hybrid robot ,how can I import them into the v rep ?
I also checked the External Kinematics page
-what should i do if i want a joint to remain in specific position or angle during following a path ?
I want the spindle angle to be always normal to the path and anf if it was changed , returns itself to that normal angle .
thanks in advance
Last edited by Mohamed Magdy on 18 Sep 2019, 22:23, edited 2 times in total.

Mohamed Magdy
Posts: 10
Joined: 02 Sep 2019, 18:32

Re: kinematics model of hybrid robot

Post by Mohamed Magdy » 16 Sep 2019, 01:21

Hello sir,
I know that you're doing your best to help us but I'll appreciate if you reply to my question as soon as you could..
I'm sorry if I bothering you but I really need your help..
thanks in advance..

coppelia
Site Admin
Posts: 7272
Joined: 14 Dec 2012, 00:25

Re: kinematics model of hybrid robot

Post by coppelia » 18 Sep 2019, 05:59

You can't import the analytical equations into V-REP.

If you want a joint to maintain a specific angle, then you have to (temporarily) exclude it from IK resolution. You would do this by changing the joint mode.

Cheers

Mohamed Magdy
Posts: 10
Joined: 02 Sep 2019, 18:32

Re: kinematics model of hybrid robot

Post by Mohamed Magdy » 18 Sep 2019, 14:03

hello

the spindle itself now is maintaining a specific angle but when the platform (parallel structure )moves ,the serial part is orienting in space .
I tried first to remove alpha beta _gamma constraints in IK module ,but the problem still occurs,also changed the joints mode but seems not working .I want to make the tool(drill bit) always normal to the path and if platform made orientation , the serial part correct its orientation to be perpendicular again

cheers

coppelia
Site Admin
Posts: 7272
Joined: 14 Dec 2012, 00:25

Re: kinematics model of hybrid robot

Post by coppelia » 19 Sep 2019, 08:29

It is very difficult to guess what you are doing or what you are doing wrong.

If you need your end-effector to maintain a specific orientation, then exclude the joints that are responsible for that orientation from the IK calculation.
You can also introduce auxiliary joints to help IK resolution to reach a specific position/orientation.

Cheers

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