Hello! I try to create a simple model with a closed loop. It contains 3 main and 2 auxiliary links and 3 revolute and 1 prismatic joints. I want to control the motion of my model by changing the value for prismatic joint. Thus I added two dummy objects. But my model doesn't move when I launch simulation. Please investigate my model and point what I did wrong. Thanks in advance!
https://drive.google.com/file/d/1SMpvVF ... drive_link
Failed to model closed loop
Re: Failed to model closed loop
Your construction looks good. There are a few details:
- Make sure that the auxiliary shapes are non-respondable (e.g. the very small cubes), otherwise you'll have contact points/friction where none is expected
- When running with Bullet or ODE, make sure to properly adjust inertias and masses, as they require often specific constraints with those engines (i.e. design considerations 7&8)
- Currently all joints are free, and you can't easily test your mechanism. Set one of those joints to position control and adjust its position via sim.setJointTargetPosition to test if the mechanism behaves as expected. Adjust the force/torque of that joint upwards
Re: Failed to model closed loop
Thank you for help!
I checked again my model according to your suggestions and could resolve the issue. Specifically, I set control mode for prismatic joint to 'Position' and adjusted max force = 5 N, max velocity = 1 m/s, max acceleration = 0.001 m/s^2 and max jerk = 1 m/s^3. Also I limited motion of prismatic joint to the range [0.0, 0.08]. I've update my model.
I checked again my model according to your suggestions and could resolve the issue. Specifically, I set control mode for prismatic joint to 'Position' and adjusted max force = 5 N, max velocity = 1 m/s, max acceleration = 0.001 m/s^2 and max jerk = 1 m/s^3. Also I limited motion of prismatic joint to the range [0.0, 0.08]. I've update my model.
Re: Failed to model closed loop
Hello, everyone!
Now I try to implement closed loop from the simple model above to my real scene and meet the following behavior. I want the hydraulic cylinder (HC) to move the silage pipe (SP) up and down. SP is long and is supposed to be equipped with additional equipment at the end. When there is no equipment added the movement is ok, but when I added a small (for beginning) part (on the videos this part is called just a 'Cylinder') HC couldn't move SP up and down. I guess that the issue is in wrong settings for engine. When I randomly adjust HC engine parameters the behavior also changes. But could you please point me the correct way to adjust its (or another) parameters? Also maybe it's possible to disable any dynamics for the entire construction, because I, actually, need FK and IK for this construction. This could be even more preferebly, because I do not have deep understanding of robotics and really need just to calculate kinematics. But when I made all links not dynamic and set all joints in kinematic mode the constructions absolutely broke or did nothing. And I also can't to insert dymmies in 'dynamic, overlap constraint' to model closed loop.
https://drive.google.com/file/d/13EYcwm ... drive_link
https://drive.google.com/file/d/1bE9_nz ... drive_link
Now I try to implement closed loop from the simple model above to my real scene and meet the following behavior. I want the hydraulic cylinder (HC) to move the silage pipe (SP) up and down. SP is long and is supposed to be equipped with additional equipment at the end. When there is no equipment added the movement is ok, but when I added a small (for beginning) part (on the videos this part is called just a 'Cylinder') HC couldn't move SP up and down. I guess that the issue is in wrong settings for engine. When I randomly adjust HC engine parameters the behavior also changes. But could you please point me the correct way to adjust its (or another) parameters? Also maybe it's possible to disable any dynamics for the entire construction, because I, actually, need FK and IK for this construction. This could be even more preferebly, because I do not have deep understanding of robotics and really need just to calculate kinematics. But when I made all links not dynamic and set all joints in kinematic mode the constructions absolutely broke or did nothing. And I also can't to insert dymmies in 'dynamic, overlap constraint' to model closed loop.
https://drive.google.com/file/d/13EYcwm ... drive_link
https://drive.google.com/file/d/1bE9_nz ... drive_link