Hi, I've made the sdf for a delta arm using points from CAD. It loads correctly and the joints should be placed perfectly but when I start the simulation it moves about erratically.
The sdf file is here https://pastebin.com/YWgYFPXw . The top three joints are revolute. The middle three and bottom three are universal (The axi are shown in the first image)
The starting position: 
Then after starting simulation and waiting for the robot to come to rest it ends up like this:
I assume this is from improper joint alignment so I tried making the middle three joints ball joints to remove alignment problems there. This did not work, the ball joints acted as fixed joints.
Has anyone managed to get delta arm simulation right? Do you have ideas for me to try?
