Sunday, 23 February 2014

Robbie's arm moving

Here is a video of Robbie moving his arm to random points selected in RVIZ I have cut out the planning stages they can last up to 10 seconds for complex solutions.
Robbie can drive to a selected point
move his arm to a selected point
that leaves grasping  then the butler is online
"Robbie get me a beer"

Tuesday, 18 February 2014

ROS Movit

At last I have ROS Moveit working, after writing the action servers it all came together. The simulation mode is great for testing learning to use it will be a challenge. I did have one problem that cause me a headache for a while. The simulator worked but when it came to using a real robot it failed the problem was you have to modify the demo launch file not just use move group launch. The demo launch file you remove static transformation and the robot state  publishers.
I still need to tune the joint angles and reduce the error in movement to the required angle. Its very interesting to watch Robbie move his arm and avoid obstacle's  in his way.
The next challenge is to recognize a object and pick it up move it. That will require a Kinect but Robbie’s kinect is too low to be of use. So I stuck one in his head a Asus camera would be better as it's smaller but the jinect was only $30 against $300 for the Asus. It makes him look strange once every thing is working we will have to do a redesign not just on the head but also the arms.

Friday, 14 February 2014

Elbow Mod update ver 3

After a some testing I found the version 2 of the elbow mod to be lacking
when power was removed to joint sagged when power was applied the joint would snap into position after a few day trying to control the joint the plastic started to fail. The arm was tearing it self to pieces the solution would be motor breaking and velocity control. Another idea is to use a worm screw gearbox but the original Inmoov gearbox is not suitable but the  Hector   robot has a gearbox that would work with some modification I had some parts laying around from a previous idea
they wern't of good quality and  I didn't have enough filament to reprint or the bearings required so i made some PLA bushes. Not wanting to use a motor and controller I opted for the standard servo with feed back. The good news is it works
and I have nearly 160 degrees of rotation the servo handles the load fine but the feedback is a little jittery later I will change the servo with a motor and the feedback will be solved. the elbow pivot is a little high. I want to do some testing with the complete arm before i reprint the parts. What i really need to know is if the arm can reach and pick up objects for a table. The original hand is very limited
so I replaced the hand with a claw, the arm now has 6 DOF  and a gripper all with feedback and controlled through action servers. Of course that brings in it's own problems as the joints have to get to there goal with a high degree of accuracy before moving on to the next goal.