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2016-09-06 12:11:43 -0500 asked a question Why do I get a ClassNotFoundException exception when executing a modified version of a simple rosjava publisher?

execute the Talker. Hello. The ClassNotFoundException exception is raised by RosRun in its main method at line 56. The name of the missing class is correct and it is precisely the same as the original version of the Talker. The class compiles succesfully both by using gradle and catkin_make.

I don't use Eclipse and I am forbidden from using it.

The command I'm using to execute the publisher is: ./[NAME OF THE SCRIPT LOCATED IN /build/install/[PACKAGE NAME]] [FULL NAME OF JAVA CLASS OF THE PUBLISHER]

So, why would rosjava not find a class because I add some lines of codes to it?

2016-08-11 11:42:01 -0500 answered a question Setting GPS waypoints in tum_simulator

I've done precisely that a few months ago. I managed to create a separate controller that publishes appropriate velocity commands to the topic and reads the position. So you would have to create a closed loop. As far as I know there are no libraries for autonomous flight compatible with tum_simulator.

2016-08-10 10:42:06 -0500 answered a question Adding an external jar in Rosjava

Turns out that the package.xml file is not influencing my build at all apparently (maybe it's caused by my use of gradle to compile) and the one I had to edit was the build.gradle file by adding an appropriate reference directly to the jar. The following links to gradle's documentation. It explains clearly how to create a dependency.

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2016-08-06 10:22:56 -0500 commented answer ROSJAVA : Implementing geometry_msgs.Vector3

This links now leads to a missing page. Where could I find the new documentation?

2016-08-06 10:17:30 -0500 commented answer Creating composite rosjava messages without a Node

I think I'm facing a similar situation, however I'm not sure of that. Do you happen to know somewhere I could examine some examples? I had some trouble finding a complete reference (mostly because of similar names from ROS and documentation from previous versions of rosjava clogging up my searches).

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2016-08-05 19:28:43 -0500 commented question Adding an external jar in Rosjava

Okay, I made some progress and was able to add external libraries through the build.gradle file which details the dependencies that gradle is going to link (if you like me use gradle to compile the package, I'm editing the question to specify that I'm using gradle).

2016-08-05 19:22:57 -0500 commented question How to create a waypoint in a simulation generated with the tum_simulator package

@Trinto I didn't implement so far collision detection or avoidance as this implies adding sensors or a more complex control system interpreting position and velocity changes but I'm working on it. For details on what caused my difficulties in getting the drone's position check my answer below.

2016-08-05 19:21:36 -0500 answered a question How to create a waypoint in a simulation generated with the tum_simulator package

Sorry for not updating, I solved my problem. Turns out that the standard tum_simulator is not compatible with Indigo. I would suggest you to check this repository instead if you're using Indigo (and possibly more recent versions). I was able with some tweaking to create a naif controller that applies a velocity proportional to the distance up to a certain distance where the drone hovers near the point, I'm not yet satisfied with this implementation but that goes beyond the scope of this question.

2016-08-04 15:35:06 -0500 commented answer How to use an external library with a rosjava

Excuse me what is the "target/" directory in this case?

2016-08-04 15:35:05 -0500 asked a question Adding an external jar in Rosjava

I need to add an external jar in Rosjava. I noticed several references to a file manifest.xml in other questions that my package (catkin generated) does not have. I noticed that there's a package.xml file that allows me to add dependencies but I don't need to only add the dependency, I need to add the jar to make the project compile (using gradle, I didn't look into other compiling methods so far). Adding it to /usr/lib/java (the location I normally use for java projects does not seem to work at all. I've wasted a few days for this rather trivial matter and I'm quite perplexed about what I'm supposed to do. Thanks for your help.

P.s.: I managed to add the external libraries so far by editing the build.gradle file and adding the opportune dependencies as stated in gradle's documentation. Initially I faced difficulties because nothing pointed me at the documentation in the first place so I struggled to find it (and I have to say that it's rather well written). So I'm adding the link below. I'm still facing some problems with rosjava_geometry msgs but I'm confident this difficulty can be solved in a short time and will edit the question and possibly add an answer as soon as I'm able to work a bit on my project. At the moment the situation is that I lack appropriate documentation of the rosjava messages, examples of how to use them in my project and a precise idea of how the package.xml file role in all that (it seems slightly different than the package's manifest of ROS).

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2015-10-17 16:03:18 -0500 asked a question How to create a waypoint in a simulation generated with the tum_simulator package

The tum_simulator package allows to simulate a ardrone in gazebo. I want to create a control package allowing me to set waypoints in this simulation and see the drone moving between them. Possibly also implementing collision avoidance. However I'm facing some difficulties in understanding what's the best approach to this problem. According to the roswiki page ( ) tum_simulator offers the position (published in the /navdata topic). However the /ardrone/navdata topic is of type ardrone_autonomy/Navdata which is:

 std_msgs/Header header
  uint32 seq
  time stamp
  string frame_id
float32 batteryPercent
uint32 state
int32 magX
int32 magY
int32 magZ
int32 pressure
int32 temp
float32 wind_speed
float32 wind_angle
float32 wind_comp_angle
float32 rotX
float32 rotY
float32 rotZ
int32 altd
float32 vx
float32 vy
float32 vz
float32 ax
float32 ay
float32 az
uint8 motor1
uint8 motor2
uint8 motor3
uint8 motor4
uint32 tags_count
uint32[] tags_type
uint32[] tags_xc
uint32[] tags_yc
uint32[] tags_width
uint32[] tags_height
float32[] tags_orientation
float32[] tags_distance
float32 tm

I can't find the position of the drone. Without it I would have to implement my own odometry evaluation. Am I missing something? Did I somehow install the wrong package or is the wiki page wrong? Do you know if a control package for this simulator is already implemented?