WEBVTT 00:00.260 --> 00:07.220 In this lesson, we will create our first launch file to start visualizing the RDF model of the robot 00:07.220 --> 00:08.120 in RVs. 00:08.630 --> 00:14.900 The output will be very similar to the previous laboratory lesson, but this time we will be using just 00:14.900 --> 00:18.920 one terminal and just one command to start the launch file. 00:19.710 --> 00:20.910 To create a launch file. 00:20.910 --> 00:22.890 Let's open Visual Studio code. 00:22.890 --> 00:29.250 And so in the Arduino board description folder, where we have already created the Urdf model for our 00:29.250 --> 00:34.470 robot, let's create a new folder called Launch. 00:34.710 --> 00:37.950 And here let's create a new file called 00:38.610 --> 00:43.680 display.launch.py. 00:44.370 --> 00:51.690 As I mentioned in the theoretical lessons launch file in Ros two is a python file in which we can define 00:51.690 --> 00:54.270 a list of instructions to be executed. 00:54.570 --> 00:57.750 This list is called launch description. 00:57.750 --> 01:00.180 So let's start importing this class. 01:00.180 --> 01:11.100 So from the launch library, let's import the launch description class and then we need to define a 01:11.100 --> 01:11.910 new function. 01:11.910 --> 01:17.730 So let's call this one generate launch 01:19.620 --> 01:20.790 description. 01:21.300 --> 01:24.780 And this is executed when we launch the launch file. 01:24.780 --> 01:31.830 So when we start this file and here we need to define all the components that needs to be started and 01:31.830 --> 01:36.510 it will return a launch description object with all these components. 01:36.510 --> 01:46.040 So let's return a launch description object that contains a list of all the applications. 01:46.040 --> 01:52.260 So of all the nodes that we want to start over the action in general that we want to start with this 01:52.260 --> 01:53.070 launch file. 01:54.060 --> 01:56.520 As we did in the previous laboratory lesson. 01:56.520 --> 01:59.740 Let's start by executing the first node. 01:59.760 --> 02:06.420 So the robot estate publisher node, which is the one that reads the RDF model of the robot and publish 02:06.420 --> 02:10.170 it within our Ros2 topic to start a node. 02:10.200 --> 02:23.720 Let's import from the launch Ros library and from the actions module, let's import the node class and 02:23.730 --> 02:26.590 now we can use it to create a new instance of this node. 02:26.610 --> 02:31.380 So a new variable called Robot State. 02:34.380 --> 02:39.120 Publisher, for instance, that is an object of the node class. 02:39.150 --> 02:44.820 And here in the constructor of the Node class, we need to specify the package that contains the node 02:44.820 --> 02:46.240 that we want to start. 02:46.260 --> 02:58.200 So the package is the robot state publisher and the next we also need to specify the name of the node 02:58.230 --> 02:59.760 that we want to start. 03:00.060 --> 03:09.150 So let's start the X code table that has the same name of the package. 03:09.150 --> 03:15.510 So also this one is called Robot State Publisher. 03:15.510 --> 03:19.680 And the next we also need to configure this node with some parameters. 03:19.680 --> 03:25.260 So specifically, we need to indicate where the Urdf model of our robot is located. 03:25.350 --> 03:37.470 So let's set the parameters and let's set specifically the robot description parameter. 03:37.470 --> 03:43.710 And to this one we need to assign the directory where in our PC is the robot description? 03:43.710 --> 03:52.770 For the moment, let's store this one in a variable that we are going to call robot Description. 03:52.770 --> 03:56.760 So now we need to assign a value to this variable here. 03:56.880 --> 04:03.360 And to create this variable we need to declare an argument for this launch file which can be changed 04:03.360 --> 04:05.070 when the launch file is started. 04:05.070 --> 04:11.370 So for example, you can use in the future this same launch file to visualize also other urdf model 04:11.370 --> 04:14.610 of other robot that you might create in the future. 04:15.350 --> 04:17.990 To declare an argument for a launch file. 04:17.990 --> 04:30.170 Let's import from the launch library and from the actions module, the declare launch argument class. 04:30.170 --> 04:33.550 And now let's use this one to declare a launch argument. 04:33.560 --> 04:42.140 Let's call, for example, this one model arc as an instance of the declare launch argument, and this 04:42.140 --> 04:48.200 one will contain the name and the directory of the Urdf model that we want to visualize in our case. 04:48.680 --> 04:53.120 So the name let's call this one model. 04:53.120 --> 04:55.250 So this is the name of the argument. 04:55.250 --> 04:56.510 And by default. 04:56.510 --> 05:03.200 So if this argument is not set by the user who started this launch file, we want to visualize the urdf 05:03.200 --> 05:04.730 model of our robot. 05:04.730 --> 05:07.130 So the Arduino but Urdf sacrum. 05:07.430 --> 05:10.160 And so here let's set a default value. 05:11.970 --> 05:15.270 And as we want to indicate, a path to our directory. 05:15.270 --> 05:24.300 So to the directory where the Urdf model is stored, let's import the OS library from Pi for Python 05:24.540 --> 05:29.370 and let's use the OS path. 05:31.210 --> 05:35.530 Join function and also let's import. 05:36.730 --> 05:43.330 So here from the amend index python. 05:43.480 --> 05:53.440 So from the packages module, let's import the function, get package share directory and so we can 05:53.440 --> 05:57.520 use this function here for example within the join function. 05:57.520 --> 05:58.660 So let's use it. 05:58.660 --> 06:08.260 Get package share directory to obtain the full path, the full directory to the Arduino bot description 06:08.260 --> 06:13.510 package so that we don't have to rewrite all the path to this directory. 06:13.630 --> 06:17.620 So let's format this a little bit better. 06:22.260 --> 06:25.920 Okay so that it is easier to read for this package. 06:25.920 --> 06:27.330 So within the Arduino. 06:27.540 --> 06:32.820 Description package, we want them to open the Urdf folder. 06:32.820 --> 06:42.330 And then within this folder we want to open the Arduino bot dot Urdf dot acro file. 06:43.230 --> 06:45.330 Let's also add a description. 06:45.330 --> 06:49.920 So after the default value here, let's add a. 06:50.880 --> 07:04.560 Description and is just says absolute path to the robot urdf file so that every person that uses this 07:04.560 --> 07:08.760 launch file knows what the model argument does. 07:09.960 --> 07:14.070 Now we can finally create the robot description variable. 07:14.070 --> 07:18.370 So the one that we needed within the robot state publisher node. 07:18.390 --> 07:22.200 So let's instantiate this variable before using it. 07:23.300 --> 07:27.500 And this will contain the configuration parameter for the node. 07:27.830 --> 07:32.390 Also, to declare a variable of this type, we need to import another class. 07:32.420 --> 07:35.520 This time still from the Ros launch. 07:35.540 --> 07:40.040 So from launch Ros. 07:40.160 --> 07:43.520 This time from the parameter description. 07:43.730 --> 07:47.900 Let's import the parameter value. 07:48.290 --> 07:54.020 And now we can create the robot description as an instance of the parameter value class. 07:54.760 --> 08:01.540 Anyway, this parameter cannot simply contain the path to the robot's urdf model because we didn't use 08:01.570 --> 08:04.350 pure Urdf convention for its creation. 08:04.360 --> 08:06.100 Instead we used. 08:06.640 --> 08:08.430 So we use the exact format. 08:08.440 --> 08:15.220 So before using it, before taking this parameter and loading with the robot state publisher, we first 08:15.220 --> 08:22.720 need to convert our model into plain urdf format and we can do this by running a command. 08:22.750 --> 08:28.830 So in order to run a command from a launch file, we need to import another class. 08:28.840 --> 08:40.660 So from launch dot substitutions, let's import the command class and now let's use this one within 08:40.660 --> 08:44.740 the parameter to execute a certain command. 08:44.980 --> 08:48.430 And this command says Sacrow. 08:50.170 --> 08:55.120 And so it is responsible for converting the model to the Urdf. 08:55.120 --> 08:58.840 And also we need to pass the path to our model. 08:58.840 --> 09:01.990 So the path which we defined in the model argument. 09:01.990 --> 09:03.070 So here. 09:04.280 --> 09:11.210 Since the launch file arguments can be set while the file is started, we use another class from the 09:11.210 --> 09:13.280 launch substitutions modules. 09:13.280 --> 09:21.410 So from this one that is called launch configuration and we use this one to read the content of the 09:21.410 --> 09:24.950 modal argument when the launch file is started. 09:25.160 --> 09:27.860 So here sakoura. 09:29.580 --> 09:30.870 And then comma. 09:31.530 --> 09:40.470 And then we read the content of the modal argument that basically contains the full directory to the 09:40.530 --> 09:42.310 urdf modal of our robot. 09:42.330 --> 09:50.460 Basically what we are saying here is that the robot description will be the full plain urdf modal. 09:50.670 --> 09:56.190 And here we are going to take this full urdf model by converting. 09:56.190 --> 10:03.030 So using the command acro, by converting what we encounter at the modal path. 10:03.030 --> 10:05.760 So that by default was this one. 10:05.760 --> 10:08.280 So was the exact model of our robot. 10:08.900 --> 10:12.020 Now let's move on by launching another node. 10:12.020 --> 10:19.910 So if we remember, we also needed to launch the joint state publisher node that offered those sliders 10:19.910 --> 10:22.040 that allowed us to move the robot. 10:22.310 --> 10:25.670 So let's create a new variable joint. 10:27.770 --> 10:32.480 State publisher going. 10:32.780 --> 10:36.170 And this is a new instance of the Node class. 10:36.170 --> 10:49.640 And this time we want to start the node from the package joint state publisher and the executable. 10:52.470 --> 10:56.790 That we want to start is also called Joint State Publisher. 10:57.270 --> 10:59.820 This is Joint state publisher. 11:00.000 --> 11:04.570 We also denote is called Joint State Publisher. 11:05.550 --> 11:08.250 And then we just need to start one last note. 11:08.280 --> 11:09.870 That is Rvhs. 11:10.050 --> 11:15.600 So let's call this one Arv's node. 11:16.050 --> 11:17.790 And so this is our node. 11:18.210 --> 11:19.980 And from the package. 11:22.210 --> 11:25.150 That is called RV two. 11:25.570 --> 11:28.360 Let's start the executable. 11:28.900 --> 11:32.170 That is also called RV two. 11:33.680 --> 11:35.060 And let's name it. 11:35.540 --> 11:39.170 So let's assign a name that is RV to. 11:39.800 --> 11:44.090 We also want to see the output of this node in the terminal. 11:44.090 --> 11:48.320 So with any log message that this node may run. 11:48.530 --> 11:50.900 And so we set the output. 11:53.060 --> 11:59.510 Here, a comma and then output to the screen. 12:00.500 --> 12:08.330 If you remember by default when we start this, it shows the default graphical interface every time 12:08.330 --> 12:10.850 without any visualization or plugins. 12:11.330 --> 12:17.330 Anyway, we can make it load at different configuration at startup and for example, we can load the 12:17.330 --> 12:23.870 one that we have created and we have stored in the RV's folder and that already contains, for example, 12:23.870 --> 12:28.490 the visualization of the Urdf model of the robot and with its meshes. 12:28.910 --> 12:38.810 To do so, we need to pass some arguments, so arguments and let's pass a vector and here let's use 12:38.810 --> 12:46.130 the flag minus D to pass the directory of the RVs configuration that we want to visualize. 12:46.340 --> 12:57.290 And in order to take the directory, we can use again the path join function from the library of Python. 12:57.290 --> 13:04.500 And here again we can use the get package shared directory to get access to the full directory of the 13:05.130 --> 13:09.990 Arduino bot description package. 13:09.990 --> 13:22.590 And then within this one let's access to the Arviz folder and then we want to use the display dot RV. 13:22.610 --> 13:26.640 So we want to load this one by default when we start arviz. 13:27.520 --> 13:34.150 With this, we have created a variable, an object for each instruction that we want to start. 13:34.150 --> 13:36.580 So here we have declared an argument. 13:36.610 --> 13:39.250 Here we have started three nodes. 13:40.200 --> 13:46.470 Now we can pass these variables so these instructions to the launch description file, so to this one 13:46.470 --> 13:51.420 so that they can effectively be started when we execute the launch file. 13:51.900 --> 13:57.210 Let's start with the instruction that defines the argument of the launch file. 13:57.210 --> 13:58.920 So the model argument. 13:59.040 --> 14:07.470 Then let's launch the robot state publisher, then the joint state publisher, and then let's execute 14:07.470 --> 14:08.060 args. 14:09.230 --> 14:12.680 With these, we have finished and now we can save. 14:12.680 --> 14:20.010 And we only need to install the launch folder which we created in this lesson inside the Cmakelists.txt 14:20.060 --> 14:20.370 file. 14:20.390 --> 14:22.410 So let's open this file. 14:22.430 --> 14:29.930 Here we have already installed the meshes and the urdf folder, so let's install also the launch folder 14:30.080 --> 14:36.980 and the RV's folder which contains the configuration that RVs has to display by default. 14:37.550 --> 14:43.670 Furthermore, to ensure that the launch file that we just created is started without any issue and that 14:43.670 --> 14:48.140 all the packages that are needed to start the launch file are available. 14:48.140 --> 14:56.600 We need to declare some dependencies in the package dot XML and so we need to declare an execution dependency 14:56.600 --> 15:07.550 from the robot state publisher package which we used in our launch file and also another one from the 15:07.550 --> 15:13.320 joint state publisher Gooey package. 15:13.340 --> 15:22.520 Then also another one from our vs Chu and finally another one. 15:22.520 --> 15:28.700 So another execution dependency from the Ros two launch library. 15:29.710 --> 15:31.270 With this, we have finished. 15:31.270 --> 15:33.970 And now we can finally execute this launch file. 15:34.510 --> 15:41.170 So let's open a new terminal and let's go to the workspace and let's build it. 15:41.530 --> 15:48.430 In order to install the new file and the new folders, when this is done, we can finally open a new 15:48.430 --> 15:49.670 window of the terminal. 15:49.690 --> 15:52.240 As always, let's source the workspace. 15:54.670 --> 16:02.380 And now we can start the launch file with the command Ros to launch, followed by the name of the package 16:02.380 --> 16:08.680 which contains the launch file that we want to start, which is the Arduino bot description, followed 16:08.680 --> 16:10.960 by the name of the launch file itself. 16:10.960 --> 16:17.230 So if we press tab twice, we can see that we have the display dot launch available. 16:17.440 --> 16:19.330 So let's start this file. 16:19.960 --> 16:26.320 As we press enter, we can see that there is an error, an error in the directory. 16:26.350 --> 16:31.480 Since here there is no space between the command and the directory. 16:31.720 --> 16:33.970 So let's go back in Visual Studio code. 16:34.670 --> 16:37.460 And here we need to add a space. 16:37.700 --> 16:39.410 So let's save again. 16:40.250 --> 16:42.350 Let's build again the workspace. 16:44.280 --> 16:46.710 And now we can launch the file again. 16:47.610 --> 16:51.060 As we do so, we can see that just with one command. 16:51.060 --> 16:58.710 So just with the command Ros to launch, basically we have reproduced and we have the same result as 16:58.710 --> 16:59.970 the previous lesson. 16:59.970 --> 17:07.980 And so now we have again the Urdf model of our robot that is perfectly displayed and perfectly moving 17:07.980 --> 17:09.150 in the terminal. 17:11.030 --> 17:16.880 Now we are going to use this additional tool, the launch files, in the subsequent lesson of the course 17:16.880 --> 17:21.950 to start more complex application with more features with extremely ease.