Simple position controller for the bebop parrot
Hi all,
so for testing I wrote a simple program to control the Parrot Bebop with a simple position controller. It is only a P Controller so far. I am having trouble with sending commands to the bebop using geometry/Twist messages on the /bebop/cmd_vel topic which is subscribed by the bebop_autonomy driver. I get the global position from ORB_SLAM. The problem is that the bebop is firstly flying to the goal as expected but then ignores the new messages and still flies straight for a while. It seems like it is lagging behind the control commands. I publish the commands with 30Hz and no buffer. Is there a limit of frequency at which I can send commands to the bebop? My messages that i publish are also kind of small. Is there a minimum value I have to publish for the bebop to react to that value? The following is a little snippet of the /bebop/cmd_vel topic which shows the velocity in forward(backward direction ( I cut out everything else ) :
x: 0.00170661452601
x: 0.00139718720513
x: 0.00102911312076
x: 0.000721920479964
x: 0.000403190302238
x: 0.000121841902687
x: -0.000146641207167
x: -0.000424717322279
x: -0.000707121894496
x: -0.000975525184413
As you can see the velocity is getting smaller the closer it gets to the goal and in the last message the velocity gets negative which means that the bebop has already reached and overshooted it a bit. It still flies forward and the values are getting more negative. Which means that my controller reacts and sends commands to the bebop but the bebop ignores them. The same happens for linear.y but does not occur for linear.z and angular.z. Up and down and angular are really straightforward and working fie so far. I also checked rqt_graph and there was nothing else publishing to /bebop/cmd_vel. My tfs are also alright so far and publishing at 33Hz. I am still using bebop_driver v0.4.1 for convenience reasons.
So can somebody help me? Maybe there is already a position controller which I can have a look at?
Greetings and thank you,
Michael
