Hello Unfortunately I do not think that I can help you, but I am having a similar problem.
I am have been trying to use the IMU sensor, (I have added a few missing player interface related files), but in my case the acceleration is allways zero. Anyway I was not able to figure out why so I made some minor additions to the gazebo code and differentiated the linear velocity between each timestep. This way the reported acceleration will be the actual velocity derivative. The problem is that I wont get g=-9.81 in my output. This is OK in my ground robot case as I usually just remove the gravity component anyway. For flying robots I do not not know if this is Ok. I tried adding an additional "artificial" gravity vector (rotated into the curent body coordinate system) but realised that when the robot was moving along the Z-axis (very rarely), I would get double acceleration. -9.81 as well as the actual velocity derivative (-9.81 when free falling). I the end I removed the artificial gravity vector, as I actual have no real use for it. It is probably possible to solve this in some smart way but I have not had time to try and figure one out. I am using a fairly recent Gazebo svn version and player 3.0.2 /Peter On 03/28/2011 05:26 PM, Neostek wrote: > Hello everyone, > i'm using Gazebo to simulate a PD controller on a quadrotor UAV. > The control evalueates the force and torque to apply to the quadrotor and > then i use the methods > dBodyAddRelForce(body_id, 0, 0, thrust) and dBodyAddRelTorque(body_id, > roll_torque, pitch_torque, 0). > Now i would like to get information about position, velocity and > acceleration of the quadrotor. > To do so, i use the methods: > body->GetPosition() > body->GetLinearVel() > body->GetLinearAccel() > and the last one appears to give practically nonsense results (gravity > acceleration depending on the mass for instance...). > Browsing into the code i found out that GetLinearAccel() simply does > return this->GetForce() / this->GetMass(); > That is " F = m*a " as it should be. > Anyway the controller works and the quadrotor get still on the target point, > but the acceleration i get on the z axis is positive (e.g. = 19.6) even > though the quadrotor is not varying its height. > I really have no point...please help me! :) > Thanks in advance. > > Marco > > > For the sake of completeness i'm using the following software version: > Gazebo - 0.9.0 > Player - 2.1.3 ------------------------------------------------------------------------------ Enable your software for Intel(R) Active Management Technology to meet the growing manageability and security demands of your customers. Businesses are taking advantage of Intel(R) vPro (TM) technology - will your software be a part of the solution? Download the Intel(R) Manageability Checker today! http://p.sf.net/sfu/intel-dev2devmar _______________________________________________ Playerstage-gazebo mailing list Playerstage-gazebo@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/playerstage-gazebo
