Cerin's profile - activity

In a composite model, is it possible to make one part of a model static while make other parts dynamic?

I'd like to position a platform in a static position a few meters in the air, while allowing actuators attached below it to move, simulating the platform being mounted to a ceiling. I tried making the platform model static, while making the actuator models dynamic, but Gazebo seems to interpret the entire model as static if even one part is static.

What's the easiest way to programmatically manipulate a legged model? Through the excellent "build a robot" tutorial, I was able to build a simple four-legged platform. How would I manipulating the limbs to test different gaits?

I've read through some of the other tutorials, and I'm a little confused on how to proceed. Do I write a model plugin, or connect it to ROS...or both?

I'm not trying to do anything fancy. I just want to be able to write a simple program to extend/retract/rotate legs in different sequences.

Are there any keyboard shortcuts for quickly switching the camera view to +/- X/Y/Z. There are times when I want to view a model orthogonally from the top down along the Z-axis, and it can literally take minutes of scrolling, and even then it doesn't seem completely possible with the mouse.

Also, is there any way to make a glyph show up indicating the origination of the axis?

What are the rules by which Gazebo interprets joint poses? They seem completely different from links.

I have a two simple "bars", representing parts of a leg, each rotated by 45 degrees to form a "knee" at their intersection:

<link name="upper">
    <pose>-.01 .035 .1 0 0 0.785398</pose>
    <inertial>
        <pose>0 0 -0.5 0 0 0</pose>
        <inertia>
            <ixx>0.01</ixx>
            <ixy>0</ixy>
            <ixz>0</ixz>
            <iyy>0.01</iyy>
            <iyz>0</iyz>
            <izz>0.01</izz>
        </inertia>
        <mass>10.0</mass>
    </inertial>
    <collision name="collision">
        <geometry>
            <box>
                <size>0.04 0.005 0.003</size>
            </box>
        </geometry>
    </collision>
    <visual name="visual">
        <geometry>
            <box>
                <size>0.04 0.005 0.003</size>
            </box>
        </geometry>
        <material>
            <script>Gazebo/Purple</script>
        </material>
    </visual>
</link>
<link name="middle">
    <pose>0 0 .097 0 0 -0.785398</pose>
    <inertial>
        <pose>0 0 -0.5 0 0 0</pose>
        <inertia>
            <ixx>0.01</ixx>
            <ixy>0</ixy>
            <ixz>0</ixz>
            <iyy>0.01</iyy>
            <iyz>0</iyz>
            <izz>0.01</izz>
        </inertia>
        <mass>10.0</mass>
    </inertial>
    <collision name="collision">
        <geometry>
            <box>
                <size>0.07 0.005 0.003</size>
            </box>
        </geometry>
    </collision>
    <visual name="visual">
        <geometry>
            <box>
                <size>0.07 0.005 0.003</size>
            </box>
        </geometry>
        <material>
            <script>Gazebo/Blue</script>
        </material>
    </visual>
</link>

I want to attach a revolute joint at the intersection, representing the knee joint. So I thought the joint's pose would be identical to the point at the end of the bar. This point is calculated as the half the length of the bar, minus an inset, rotated about the origin by 45 degrees, which is the x/y coordinate of (-0.0229809703886, 0.0229809703886).

This gives me a joint with a pose like:

<joint name="upper_middle_joint" type="revolute">
    <pose>-0.0229809703886 0.0229809703886 0 0 0 0</pose>
    <child>middle</child>
    <parent>upper</parent>
    <axis>
        <limit>
            <lower>-0.4</lower>
            <upper>0.4</upper>
        </limit>
        <xyz>0 0 1</xyz>
    </axis>
</joint>

However, when I view this in Gazebo, it looks like:

![joint misalignment](http://i.imgur.com/rwkXhUz.png)

Instead of posing the joint up along the y-axis by 0.023 and over along the negative x-axis by 0.023, it appears to have moved the joint up along the y-axis by 0.04 and nothing along the x-axis.

What am I doing wrong?

How do you edit a pre-existing model in Gazebo?

I created a very simple model in SDF following a tutorial, and now I'm trying to follow this tutorial on how to edit an existing model in the GUI model editor. However, the tutorial's instructions doesn't match Gazebo 4.

I can insert my model onto the stage, but then it says to "Right click on the model you just inserted and select Edit Model", yet the right-click menu shows no such option.

If I click Edit->Model Editor, I get the model editing screen, but it doesn't seem to let me actually edit the model I just inserted. Does model editing not work in Gazebo 4 or am I doing something wrong?

Is there some way to decrease the size of the joint arrows? I'm modelling parts that are less than a cm, and the arrows seem to render about 5 cm in diameter, causing them to blot out my model.

I'm trying to follow this tutorial to build a myrobot_gazebo package for Indigo with Gazebo 5.

I create my package with:

catkin_create_pkg myrobot_gazebo gazebo_msgs gazebo_plugins gazebo_ros gazebo_ros_control myrobot_description

then, when I try to update my dependencies with:

rosdep update
rosdep install --from-paths . --ignore-src --rosdistro indigo

I get the error:

Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 ros-indigo-gazebo-ros-control : Depends: gazebo2 but it is not going to be installed
                                 Depends: libsdformat1 but it is not going to be installed
                                 Depends: ros-indigo-gazebo-ros but it is not going to be installed
E: Unable to correct problems, you have held broken packages.
ERROR: the following rosdeps failed to install
  apt: command [sudo -H apt-get install ros-indigo-gazebo-ros-control] failed

I also tried building my package with the explicit gazebo5 dependencies with:

catkin_create_pkg cheetahbot_gazebo gazebo5_msgs gazebo5_plugins gazebo5_ros gazebo5_ros_control cheetahbot_description

but that results in a similar error, with rosdep being unable to locate "gazebo5roscontrol".

I'm assuming this is because I'm using Indigo, which is built for the old Gazebo 2, while I'm using Gazebo 5. How do I fix this?

I saw this page in the Gazebo tutorials that make a brief mention to this problem:

I need to use gazebo4/gazebo5 and ROS Indigo, what can I do?

Warning!: Using this option, you won't be able to use any ROS Indigo package related to Gazebo from ROS deb repository. The way to go is to build them from source. Thanks to catkin workspaces this is quite easy to do.

If you need some features only present in version 4.x or 5.x of Gazebo, there is a way of installing gazebo4 or gazebo5 and ROS Indigo. Please follow the instructions about how to use ROS with gazebo4 package or gazebo5 which are in this same docuement.

However, I can't find any clear instructions about how to use ROS with gazebo5 in that document. They mention installing the ros-indigo-gazebo5-ros-pkgs package, but I already have that installed.

A similar question, "how to use Gazebo 3.* with Indigo is mentioned, and it links to here, but that's just a landing page and there are no instructions on how to make it work with Indigo.

I'm trying to model a simple quadruped robot, and the legs contain four segments. Since the legs are identical, instead of duplicating the leg SDF inside the main model SDF file, is there some way I can model the leg once in a separate SDF file and "include" it four times in the SDF file for the "complete" robot?

Is there any way to rotate the camera around a model by dragging the mouse, especially when editing a model?

I can't find any documentation for Gazebo's mouse and keyboard shortcuts, and playing around with the mouse, I've found I can only pan the view by clicking the dragging, and zooming the view with the mouse scroll bar. I can't find any way to "orbit" around a point, which is a common feature in most CAD systems. Is this possible in Gazebo?

Also, most annoyingly, if I double-click any object, the view immediately switches to a high-up perspective that doesn't let me see any detail, and since I can't rotate the view at all, the only way I can fix it is by going to View->Reset Camera. Why does double clicking a model screw up the camera view?

When the gui is running, how do you find the x/y/z/r/p/y of the current camera pose? It seems to be the only thing not listed in the left-hand panel.