{"action":"created","issue":{"url":"https://api.github.com/repos/RobotLocomotion/drake/issues/8601","repository_url":"https://api.github.com/repos/RobotLocomotion/drake","labels_url":"https://api.github.com/repos/RobotLocomotion/drake/issues/8601/labels{/name}","comments_url":"https://api.github.com/repos/RobotLocomotion/drake/issues/8601/comments","events_url":"https://api.github.com/repos/RobotLocomotion/drake/issues/8601/events","html_url":"https://github.com/RobotLocomotion/drake/pull/8601","id":314457687,"number":8601,"title":"Adds compass gait example","user":{"login":"RussTedrake","id":6442292,"avatar_url":"https://avatars2.githubusercontent.com/u/6442292?v=4","gravatar_id":"","url":"https://api.github.com/users/RussTedrake","html_url":"https://github.com/RussTedrake","followers_url":"https://api.github.com/users/RussTedrake/followers","following_url":"https://api.github.com/users/RussTedrake/following{/other_user}","gists_url":"https://api.github.com/users/RussTedrake/gists{/gist_id}","starred_url":"https://api.github.com/users/RussTedrake/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/RussTedrake/subscriptions","organizations_url":"https://api.github.com/users/RussTedrake/orgs","repos_url":"https://api.github.com/users/RussTedrake/repos","events_url":"https://api.github.com/users/RussTedrake/events{/privacy}","received_events_url":"https://api.github.com/users/RussTedrake/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":{"login":"edrumwri","id":2224335,"avatar_url":"https://avatars0.githubusercontent.com/u/2224335?v=4","gravatar_id":"","url":"https://api.github.com/users/edrumwri","html_url":"https://github.com/edrumwri","followers_url":"https://api.github.com/users/edrumwri/followers","following_url":"https://api.github.com/users/edrumwri/following{/other_user}","gists_url":"https://api.github.com/users/edrumwri/gists{/gist_id}","starred_url":"https://api.github.com/users/edrumwri/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/edrumwri/subscriptions","organizations_url":"https://api.github.com/users/edrumwri/orgs","repos_url":"https://api.github.com/users/edrumwri/repos","events_url":"https://api.github.com/users/edrumwri/events{/privacy}","received_events_url":"https://api.github.com/users/edrumwri/received_events","type":"User","site_admin":false},"assignees":[{"login":"edrumwri","id":2224335,"avatar_url":"https://avatars0.githubusercontent.com/u/2224335?v=4","gravatar_id":"","url":"https://api.github.com/users/edrumwri","html_url":"https://github.com/edrumwri","followers_url":"https://api.github.com/users/edrumwri/followers","following_url":"https://api.github.com/users/edrumwri/following{/other_user}","gists_url":"https://api.github.com/users/edrumwri/gists{/gist_id}","starred_url":"https://api.github.com/users/edrumwri/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/edrumwri/subscriptions","organizations_url":"https://api.github.com/users/edrumwri/orgs","repos_url":"https://api.github.com/users/edrumwri/repos","events_url":"https://api.github.com/users/edrumwri/events{/privacy}","received_events_url":"https://api.github.com/users/edrumwri/received_events","type":"User","site_admin":false}],"milestone":null,"comments":17,"created_at":"2018-04-15T22:19:24Z","updated_at":"2018-04-18T23:00:37Z","closed_at":null,"author_association":"CONTRIBUTOR","pull_request":{"url":"https://api.github.com/repos/RobotLocomotion/drake/pulls/8601","html_url":"https://github.com/RobotLocomotion/drake/pull/8601","diff_url":"https://github.com/RobotLocomotion/drake/pull/8601.diff","patch_url":"https://github.com/RobotLocomotion/drake/pull/8601.patch"},"body":"Note: contains #8600 (so the examples will run), but you can safely skip over that commit in your review.  I will handle the curation before merging.\n\n<!-- Reviewable:start -->\n---\nThis change is [<img src=\"https://reviewable.io/review_button.svg\" height=\"34\" align=\"absmiddle\" alt=\"Reviewable\"/>](https://reviewable.io/reviews/robotlocomotion/drake/8601)\n<!-- Reviewable:end -->\n"},"comment":{"url":"https://api.github.com/repos/RobotLocomotion/drake/issues/comments/382555651","html_url":"https://github.com/RobotLocomotion/drake/pull/8601#issuecomment-382555651","issue_url":"https://api.github.com/repos/RobotLocomotion/drake/issues/8601","id":382555651,"user":{"login":"RussTedrake","id":6442292,"avatar_url":"https://avatars2.githubusercontent.com/u/6442292?v=4","gravatar_id":"","url":"https://api.github.com/users/RussTedrake","html_url":"https://github.com/RussTedrake","followers_url":"https://api.github.com/users/RussTedrake/followers","following_url":"https://api.github.com/users/RussTedrake/following{/other_user}","gists_url":"https://api.github.com/users/RussTedrake/gists{/gist_id}","starred_url":"https://api.github.com/users/RussTedrake/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/RussTedrake/subscriptions","organizations_url":"https://api.github.com/users/RussTedrake/orgs","repos_url":"https://api.github.com/users/RussTedrake/repos","events_url":"https://api.github.com/users/RussTedrake/events{/privacy}","received_events_url":"https://api.github.com/users/RussTedrake/received_events","type":"User","site_admin":false},"created_at":"2018-04-18T23:00:37Z","updated_at":"2018-04-18T23:00:37Z","author_association":"CONTRIBUTOR","body":"\n\n\n\nReview status: 7 of 11 files reviewed at latest revision, 5 unresolved discussions.\n\n---\n\n*[a discussion](https://beta.reviewable.io/reviews/robotlocomotion/drake/8601#-LADgKA5CcVj6rB-fsME:-LAPyAWYA0sZbsBqd-W4:biaxmpy) (no related file):*\n<details><summary><i>Previously, sherm1 (Michael Sherman) wrote…</i></summary><blockquote>\n\nThat's easy if you have constraints that can be enabled and disabled via a boolean in the state! This would be a prescribed motion constraint theta=0. Without those it could still be approximated with a stiff joint force (torsional spring-damper element) that looks at a bool state variable to see if it is active.\n</blockquote></details>\n\nagreed.  the trick will be that if you turn on / off constraints like that, then you would want to also write the impact dynamics (the derivation i did for the compass gait will extend naturally, and give you the impact dynamics, too.)  \n\ni believe that you might be able to get away with the compliant contact model at the knees with no \"sticking\".  McGeer's walkers actually had suction cups at the knees (because they required force to keep the knee straight), but I *think* it's possible that this model will only require one-sided torques at the knee during stance around the stable limit cycle.\n\nBe warned, however, that the basin of attraction of that limit cycle is very small.  Especially if you want to use physically reasonable masses at the links.  There was a reason why McGeer had big curved feet!\n\n---\n\n\n*Comments from [Reviewable](https://beta.reviewable.io/reviews/robotlocomotion/drake/8601)*\n<!-- Sent from Reviewable.io -->\n"}}
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