{"action":"created","issue":{"url":"https://api.github.com/repos/kriswiner/MPU-9250/issues/12","labels_url":"https://api.github.com/repos/kriswiner/MPU-9250/issues/12/labels{/name}","comments_url":"https://api.github.com/repos/kriswiner/MPU-9250/issues/12/comments","events_url":"https://api.github.com/repos/kriswiner/MPU-9250/issues/12/events","html_url":"https://github.com/kriswiner/MPU-9250/issues/12","id":81288220,"number":12,"title":"Yaw Pitch and Roll Estimation","user":{"login":"akhilmohan4487","id":5743851,"avatar_url":"https://avatars.githubusercontent.com/u/5743851?v=3","gravatar_id":"","url":"https://api.github.com/users/akhilmohan4487","html_url":"https://github.com/akhilmohan4487","followers_url":"https://api.github.com/users/akhilmohan4487/followers","following_url":"https://api.github.com/users/akhilmohan4487/following{/other_user}","gists_url":"https://api.github.com/users/akhilmohan4487/gists{/gist_id}","starred_url":"https://api.github.com/users/akhilmohan4487/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/akhilmohan4487/subscriptions","organizations_url":"https://api.github.com/users/akhilmohan4487/orgs","repos_url":"https://api.github.com/users/akhilmohan4487/repos","events_url":"https://api.github.com/users/akhilmohan4487/events{/privacy}","received_events_url":"https://api.github.com/users/akhilmohan4487/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"milestone":null,"comments":8,"created_at":"2015-05-27T05:38:06Z","updated_at":"2015-05-30T18:48:41Z","closed_at":null,"body":"Hello Kris,\r\n\r\nI am back with more questions.\r\n\r\n1. In the MPU9250 algo you have derived the Euler angles from quaternion representing orinatation of sensor wrt NED frame. How did you decided you pick one rotation sequences (Tait Bryan, Euler angle) and what is the basis of selection.Depending on the selection you have different set of Y,P and R values and out of which one is correct for one case. I have read a bit on this and discussed with few of my friends,but did not understood the matter well.\r\n2. What is sensor to segment calibration and can you give me a simple example to understand this?\r\n3. The system calculates accelero/gyro biases and magneto hard iron biases. How do I verify whether this is enough ?\r\n\r\nI know I have asked too many theoretical questions, but hope at least you would be able to provide some materials or the path through which I have to look .\r\n\r\nThanks and Regards,\r\nAkhil."},"comment":{"url":"https://api.github.com/repos/kriswiner/MPU-9250/issues/comments/107074980","html_url":"https://github.com/kriswiner/MPU-9250/issues/12#issuecomment-107074980","issue_url":"https://api.github.com/repos/kriswiner/MPU-9250/issues/12","id":107074980,"user":{"login":"kriswiner","id":6698410,"avatar_url":"https://avatars.githubusercontent.com/u/6698410?v=3","gravatar_id":"","url":"https://api.github.com/users/kriswiner","html_url":"https://github.com/kriswiner","followers_url":"https://api.github.com/users/kriswiner/followers","following_url":"https://api.github.com/users/kriswiner/following{/other_user}","gists_url":"https://api.github.com/users/kriswiner/gists{/gist_id}","starred_url":"https://api.github.com/users/kriswiner/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/kriswiner/subscriptions","organizations_url":"https://api.github.com/users/kriswiner/orgs","repos_url":"https://api.github.com/users/kriswiner/repos","events_url":"https://api.github.com/users/kriswiner/events{/privacy}","received_events_url":"https://api.github.com/users/kriswiner/received_events","type":"User","site_admin":false},"created_at":"2015-05-30T18:48:41Z","updated_at":"2015-05-30T18:48:41Z","body":"Hi Akhil,\n\nAll I know is that Euler angles are rather easily derived from the\nquaternions. So if you have the quaternions in each of the two coordinate\nframes, you should be able to derive the respective Euler angles.\n\nI prefer to work in the lab frame where everything is oriented relative to\nan absolute and fixed reference frame.\n\nKris\n\n-----Original Message-----\nFrom: Akhil Mohan [mailto:notifications@github.com] \nSent: May 30, 2015 11:26 AM\nTo: kriswiner/MPU-9250\nCc: Kris Winer\nSubject: Re: [MPU-9250] Yaw Pitch and Roll Estimation (#12)\n\nHello,\nI was reading ISB recommendation on JCS (joint co-ordinate system) for\nfingers and ended up in real confusion esp in this para,\n\"Rotations are described using Euler angles. For a clearer interpretation of\nthese angles it is suggested that the coordinate systems of the proximal and\ndistal body segments are initially aligned to each other by the introduction\nof 'anatomical' orientations of these coordinate systems. The rotations of\nthe distal coordinate system should then be described with respect to the\nproximal coordinate system. If both coordinate systems are aligned, the\nfirst rotation will be around one of the\ncommon axes, the second rotation around the (rotated) axis of the moving\ncoordinate systems, and the third rotation again around one of the rotated\naxes of the moving coordinate system. This last axis is preferably aligned\nwith the longitudinal axis of the moving segment.\"\nWhat I understood is,\n1. The qSG derived from Madgwick have to change in to qBG (quaternion which\ndescribes orientation of body in the global frame). For this, we should know\nhow the IMU sensor coordinaes in body co-ordinate frame (qSB). For an\ninitial pose this is known and will be constant in an experiment.\nso qBG = qSG X q'SB where ' is the conjugate\n\n1.\tDid not understand how to derive the Euler angle sequence for\ncalculating joint angles\n\nDo you have any idea in this area ?\n\nThanks and Regards,\nAkhil.\n\n-\nReply to this email directly or view it on GitHub\n<https://github.com/kriswiner/MPU-9250/issues/12#issuecomment-107074049> .\n<https://github.com/notifications/beacon/AGY1qu0fi513PkHSytnAQH7bLyjnVGFAks5\noOfgdgaJpZM4ErXP_.gif> \n\n\n"}}