{"action":"created","issue":{"url":"https://api.github.com/repos/RobotLocomotion/drake/issues/12401","repository_url":"https://api.github.com/repos/RobotLocomotion/drake","labels_url":"https://api.github.com/repos/RobotLocomotion/drake/issues/12401/labels{/name}","comments_url":"https://api.github.com/repos/RobotLocomotion/drake/issues/12401/comments","events_url":"https://api.github.com/repos/RobotLocomotion/drake/issues/12401/events","html_url":"https://github.com/RobotLocomotion/drake/issues/12401","id":528264928,"node_id":"MDU6SXNzdWU1MjgyNjQ5Mjg=","number":12401,"title":"mbp: For quadrotor-modeling workflows, would be nice to have 2DOF floating base coordinates and \"thruster\" actuators","user":{"login":"EricCousineau-TRI","id":26719449,"node_id":"MDQ6VXNlcjI2NzE5NDQ5","avatar_url":"https://avatars1.githubusercontent.com/u/26719449?v=4","gravatar_id":"","url":"https://api.github.com/users/EricCousineau-TRI","html_url":"https://github.com/EricCousineau-TRI","followers_url":"https://api.github.com/users/EricCousineau-TRI/followers","following_url":"https://api.github.com/users/EricCousineau-TRI/following{/other_user}","gists_url":"https://api.github.com/users/EricCousineau-TRI/gists{/gist_id}","starred_url":"https://api.github.com/users/EricCousineau-TRI/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/EricCousineau-TRI/subscriptions","organizations_url":"https://api.github.com/users/EricCousineau-TRI/orgs","repos_url":"https://api.github.com/users/EricCousineau-TRI/repos","events_url":"https://api.github.com/users/EricCousineau-TRI/events{/privacy}","received_events_url":"https://api.github.com/users/EricCousineau-TRI/received_events","type":"User","site_admin":false},"labels":[{"id":351649295,"node_id":"MDU6TGFiZWwzNTE2NDkyOTU=","url":"https://api.github.com/repos/RobotLocomotion/drake/labels/team:%20dynamics","name":"team: dynamics","color":"0052cc","default":false,"description":null}],"state":"open","locked":false,"assignee":null,"assignees":[],"milestone":null,"comments":2,"created_at":"2019-11-25T18:37:34Z","updated_at":"2019-11-25T19:45:18Z","closed_at":null,"author_association":"CONTRIBUTOR","body":"(My attempt to transcribe a Slack convo with @mposa, regarding [today's Drake Developers meeting](https://docs.google.com/document/d/15iNBw_2O3TGbThHr6wlJNKctHSY5bEvt1rLhl5obZao/edit#heading=h.w1yphvs70spa))\r\n\r\nMichael's students are modeling a 2D quadrotor, and have found it to be not necessarily straightforward to model a 2D floating base with quadrotor thruster actuators.\r\n\r\nSince we only have 3D floating base mobilizers at present, they could not leverage our current floating base setup. Instead, they added two prismatic joints (x, y) and one revolute joint (z), and (I believe) with made-up links in between those virtual joints.\r\n\r\nTo model thrusters, they made those virtual joints actuated, and then mapped their model inputs (thrust) to the virtual joint inputs with a mapping done by another system block.\r\nFor this workflow, it would be more ideal to have something that could more explicitly and directly model thrusters.\r\n\r\nFrom the meeting, one possible workflow for actuation was to add a `SpatialForce` input, connected via `MultibodyPlant::get_applied_spatial_force_input_port()`, and still do the mapping there. However, this does not address the planar floating base DOF problem.\r\n\r\n@sherm1 Can I ask who would possibly be able to work this into their queue? (I won't be, at least for the remainder of this quarter.)\r\n\r\n@rcory Can I ask how y'all model the planar floating block for your dexterous manipulation example?"},"comment":{"url":"https://api.github.com/repos/RobotLocomotion/drake/issues/comments/558311184","html_url":"https://github.com/RobotLocomotion/drake/issues/12401#issuecomment-558311184","issue_url":"https://api.github.com/repos/RobotLocomotion/drake/issues/12401","id":558311184,"node_id":"MDEyOklzc3VlQ29tbWVudDU1ODMxMTE4NA==","user":{"login":"sherm1","id":4088016,"node_id":"MDQ6VXNlcjQwODgwMTY=","avatar_url":"https://avatars1.githubusercontent.com/u/4088016?v=4","gravatar_id":"","url":"https://api.github.com/users/sherm1","html_url":"https://github.com/sherm1","followers_url":"https://api.github.com/users/sherm1/followers","following_url":"https://api.github.com/users/sherm1/following{/other_user}","gists_url":"https://api.github.com/users/sherm1/gists{/gist_id}","starred_url":"https://api.github.com/users/sherm1/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/sherm1/subscriptions","organizations_url":"https://api.github.com/users/sherm1/orgs","repos_url":"https://api.github.com/users/sherm1/repos","events_url":"https://api.github.com/users/sherm1/events{/privacy}","received_events_url":"https://api.github.com/users/sherm1/received_events","type":"User","site_admin":false},"created_at":"2019-11-25T19:45:18Z","updated_at":"2019-11-25T19:45:18Z","author_association":"MEMBER","body":"Filed issue #12404 to track requests for additional joint types."}}
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