{"action":"created","issue":{"url":"https://api.github.com/repos/dartsim/dart/issues/1108","repository_url":"https://api.github.com/repos/dartsim/dart","labels_url":"https://api.github.com/repos/dartsim/dart/issues/1108/labels{/name}","comments_url":"https://api.github.com/repos/dartsim/dart/issues/1108/comments","events_url":"https://api.github.com/repos/dartsim/dart/issues/1108/events","html_url":"https://github.com/dartsim/dart/issues/1108","id":356584606,"node_id":"MDU6SXNzdWUzNTY1ODQ2MDY=","number":1108,"title":"velocity profile discontinuity in non-impact situation","user":{"login":"junhyeokahn","id":23005104,"node_id":"MDQ6VXNlcjIzMDA1MTA0","avatar_url":"https://avatars2.githubusercontent.com/u/23005104?v=4","gravatar_id":"","url":"https://api.github.com/users/junhyeokahn","html_url":"https://github.com/junhyeokahn","followers_url":"https://api.github.com/users/junhyeokahn/followers","following_url":"https://api.github.com/users/junhyeokahn/following{/other_user}","gists_url":"https://api.github.com/users/junhyeokahn/gists{/gist_id}","starred_url":"https://api.github.com/users/junhyeokahn/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/junhyeokahn/subscriptions","organizations_url":"https://api.github.com/users/junhyeokahn/orgs","repos_url":"https://api.github.com/users/junhyeokahn/repos","events_url":"https://api.github.com/users/junhyeokahn/events{/privacy}","received_events_url":"https://api.github.com/users/junhyeokahn/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"assignees":[],"milestone":null,"comments":8,"created_at":"2018-09-03T19:12:04Z","updated_at":"2018-09-21T04:06:59Z","closed_at":null,"author_association":"NONE","body":"Hello,\r\nI have observed velocity jump when the contact exists, which prevent me to use high gains at velocity.\r\nFor example, in the example of ```osgAtlasSimbicon```, the figure below is the graph of num_time_step vs joint velocity at 31st joint of Atlas.\r\n<img width=\"556\" alt=\"screen shot 2018-09-03 at 2 01 30 pm\" src=\"https://user-images.githubusercontent.com/23005104/44999390-7fd3db00-af82-11e8-9a69-88fdb2d6669a.png\">\r\n<img width=\"556\" alt=\"screen shot 2018-09-03 at 2 02 01 pm\" src=\"https://user-images.githubusercontent.com/23005104/44999395-82cecb80-af82-11e8-9774-085ad0a81813.png\">\r\n\r\nIt is natural having velocity jump during the impact event.\r\nHowever, there seems to be a velocity discontinuity even in non-impact situation.\r\nProbably I am asking this because I do not understand how the simulation works behind the scene."},"comment":{"url":"https://api.github.com/repos/dartsim/dart/issues/comments/423407188","html_url":"https://github.com/dartsim/dart/issues/1108#issuecomment-423407188","issue_url":"https://api.github.com/repos/dartsim/dart/issues/1108","id":423407188,"node_id":"MDEyOklzc3VlQ29tbWVudDQyMzQwNzE4OA==","user":{"login":"jslee02","id":4038467,"node_id":"MDQ6VXNlcjQwMzg0Njc=","avatar_url":"https://avatars3.githubusercontent.com/u/4038467?v=4","gravatar_id":"","url":"https://api.github.com/users/jslee02","html_url":"https://github.com/jslee02","followers_url":"https://api.github.com/users/jslee02/followers","following_url":"https://api.github.com/users/jslee02/following{/other_user}","gists_url":"https://api.github.com/users/jslee02/gists{/gist_id}","starred_url":"https://api.github.com/users/jslee02/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/jslee02/subscriptions","organizations_url":"https://api.github.com/users/jslee02/orgs","repos_url":"https://api.github.com/users/jslee02/repos","events_url":"https://api.github.com/users/jslee02/events{/privacy}","received_events_url":"https://api.github.com/users/jslee02/received_events","type":"User","site_admin":false},"created_at":"2018-09-21T04:06:59Z","updated_at":"2018-09-21T04:06:59Z","author_association":"MEMBER","body":"I had the same impression, but it now seems to make sense to me. Although the velocity jump visually large, those jumps only happens one or several times with some interval. I think the impact (its integration) is negligible. Assuming your timestep is 1e-3, the integration of the jump part (vel - avg_vel_around_the_jump) in the position profile would be the slope change of -2-e3 (= -2 * 1e-3). If you zoom in the position graph further, I guess you would see the non-smoothness."}}
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