WEBVTT 00:00.120 --> 00:06.240 With this lesson, we conclude the creation of the robots digital twin, which will be a fundamental 00:06.240 --> 00:12.000 component throughout the course to continue implementing and testing the remaining functionalities. 00:12.520 --> 00:19.160 In fact, you can also continue using it to test your own ideas and receive a fast feedback that will 00:19.160 --> 00:21.600 help you to accelerate the development. 00:22.240 --> 00:26.440 So back in Visual Studio Code, let's start by creating a new launch file. 00:26.680 --> 00:29.880 So still here within the Arduino board description package. 00:29.880 --> 00:37.480 Within the launch folder, let's create a new launch file called gazebo dot launch dot Pi. 00:37.520 --> 00:38.360 Perfect. 00:38.360 --> 00:39.520 And now as usual. 00:39.520 --> 00:51.440 So as we did also for the display.launch.py file, let's import from the launch package the launch description 00:51.440 --> 00:52.080 class. 00:52.080 --> 01:02.460 And actually the launch file will just contain one function that is the generate It launch description 01:02.460 --> 01:09.620 function, and this function will actually just return an object of type launch description and the 01:09.620 --> 01:10.740 constructor of this class. 01:10.740 --> 01:15.940 So the constructor of the launch description class will just take a list as input. 01:16.100 --> 01:20.220 And now we are going to fill this list here with all the actions. 01:20.220 --> 01:26.020 So with all the nodes that we want to execute with this launch file for the simulation of our robot 01:26.020 --> 01:32.220 in gazebo, we need to start the robot Estate publisher node, which, as we saw in one of the previous 01:32.220 --> 01:38.740 lessons, reads the Urdf model of the robot and publish the Urdf model into a topic. 01:38.740 --> 01:45.340 So into a Ros two topic that then we can use to visualize the robot interface, or also to simulate 01:45.340 --> 01:46.500 it in gazebo. 01:46.940 --> 01:52.780 So instead of rewriting all the instructions for the robot estate publisher node, we can just copy 01:52.780 --> 01:56.020 all of them from the display dot pi. 01:56.340 --> 01:59.000 So here we can copy the model argument. 01:59.000 --> 02:01.720 We can also copy the robot description. 02:01.720 --> 02:04.760 And also here the robot state publisher node. 02:04.960 --> 02:08.440 So let's copy the three of them and let's paste it here. 02:08.760 --> 02:11.720 So in the generate launch description perfect. 02:11.720 --> 02:18.880 We need to import all the missing classes so we can copy also the include statements. 02:20.800 --> 02:21.520 Perfect. 02:21.960 --> 02:25.360 And also as you can see here we are missing to declare this variable. 02:25.360 --> 02:28.280 So the Arduino bot description directory variable. 02:28.680 --> 02:31.760 And let's copy also this variable here. 02:32.440 --> 02:35.880 And let's paste it in our gazebo simulation. 02:35.880 --> 02:40.000 So perfect in our gazebo launch file in this case. 02:40.000 --> 02:47.240 So here when we launch the robot state publisher node, apart from setting the parameter robot description 02:47.240 --> 02:49.760 we can also set an additional parameter. 02:50.240 --> 02:58.070 So here after the robot description let's set the parameter called Use same time. 02:58.350 --> 03:01.990 And now let's set this parameter to true. 03:02.350 --> 03:07.870 And this is due to the fact that now we are starting the robot estate publisher node for the gazebo 03:07.870 --> 03:08.710 simulation. 03:08.710 --> 03:12.710 And so we want to set the user sim time argument to true. 03:12.870 --> 03:14.870 And this is a general parameter. 03:14.870 --> 03:18.950 So the user sim time that is available in any ros2 node. 03:18.990 --> 03:23.550 So basically when you create any ros2 node it will have automatically this parameter here. 03:23.550 --> 03:29.790 So the user sim time that will inform the node whether it is running on a simulation of the robot or 03:29.790 --> 03:33.110 whether the node is running on the real robot. 03:34.150 --> 03:34.790 Perfect. 03:34.990 --> 03:42.710 So after starting the Robot Estate Publisher node, we can also create and set a new environmental variable 03:42.710 --> 03:43.470 in Linux. 03:43.470 --> 03:50.750 So in ubuntu where we are running that will be used by gazebo in order to load and to simulate the Urdf 03:50.750 --> 03:52.750 model of our robot properly. 03:53.190 --> 04:00.170 So to set an environmental variable from a launch file, we can import from the launch actions package. 04:00.170 --> 04:05.050 So from this package here we can import the set environmental variable class. 04:05.210 --> 04:07.530 And now we can create a new instance of this class. 04:07.530 --> 04:09.570 For example let's do it here. 04:09.970 --> 04:12.410 And this is called gazebo. 04:12.410 --> 04:17.770 So let's call this variable gazebo resource path. 04:17.970 --> 04:21.530 And so this is an instance of the set environmental variable. 04:21.730 --> 04:27.650 And now here within the constructor of this class we need to indicate the name of the environmental 04:27.650 --> 04:29.290 variable that we want to set. 04:29.330 --> 04:36.010 And this is the gazebo same resource path. 04:36.170 --> 04:41.890 And basically with this environmental variable we want to communicate to the gazebo simulation where 04:42.010 --> 04:48.370 in the file system it should look for the Urdf model of our robot, and also for all the meshes that 04:48.370 --> 04:50.410 will be used for the simulation. 04:50.850 --> 04:56.190 So actually simply we can say that the value of this variable. 04:56.390 --> 04:57.710 So this is a list. 04:57.710 --> 05:05.550 And for the moment we just want to insert one single value that is the Arduino board description directory. 05:05.550 --> 05:10.790 And so actually we want to tell to gazebo that it has to look within this package here. 05:10.790 --> 05:16.510 So within the Arduino board description package in order to find the meshes of our robot and also the 05:16.550 --> 05:18.470 Urdf model of our robot. 05:18.750 --> 05:24.790 But instead of passing it like this, so instead of passing it as a plain directory, we need to convert 05:24.790 --> 05:26.350 it to a Python path. 05:26.830 --> 05:33.030 So let's import from the path library the path class. 05:33.030 --> 05:38.550 And so we can convert this one here into a Python path. 05:38.830 --> 05:39.590 Perfect. 05:39.590 --> 05:42.550 And to this Python path we can access to its parent. 05:44.270 --> 05:45.030 Perfect. 05:45.870 --> 05:53.210 And let's use the function resolve in order to access to the path of the parent of this directory here. 05:53.370 --> 06:00.010 And finally, let's simply convert all of these into the format that is just a string. 06:00.010 --> 06:05.130 So we are converting the parent of this directory here into a string. 06:05.130 --> 06:10.730 And we are setting this one as an environmental variable in our ubuntu system that then gazebo will 06:10.730 --> 06:11.210 read. 06:11.210 --> 06:13.410 So this one here will be read by gazebo. 06:13.650 --> 06:19.530 And it will be used in order to know the directory of the meshes and the urdf of our robot. 06:20.090 --> 06:22.530 So now we can finally also start gazebo. 06:22.770 --> 06:24.730 And to do so we are going to start. 06:24.730 --> 06:29.050 So we're going to execute another launch file from this launch file. 06:29.050 --> 06:33.690 So basically we're going to nest a launch file in order to do so. 06:33.810 --> 06:36.930 Still from the launch actions package. 06:36.930 --> 06:43.450 So from this one here we need to import another class that is the include launch description. 06:43.450 --> 06:48.910 And so we can use this class here to include a launch file within another launch file. 06:49.270 --> 06:54.910 So let's create here a new variable of this class that is called gazebo. 06:54.950 --> 06:59.230 So with this variable here we're going to start the gazebo simulation. 06:59.710 --> 07:03.070 And this is an instance of the include launch description. 07:03.430 --> 07:07.950 Now here we need to specify the type of the file that we want to launch. 07:08.070 --> 07:12.670 And also we have to specify the directory of the launch file that we want to start. 07:13.150 --> 07:17.390 The other launch file that we want to start is also a Python launch file. 07:17.950 --> 07:19.870 So let's import it. 07:20.990 --> 07:27.590 So from the launch and the launch description sources. 07:27.590 --> 07:33.590 So this one with the final s let's import the Python launch description source. 07:33.870 --> 07:38.310 And now we can use this class here within the include launch description. 07:38.310 --> 07:44.510 In order to declare that the other launch file that we want to execute is also a Python launch file. 07:44.550 --> 07:45.190 Perfect. 07:45.510 --> 07:51.180 And now we can finally insert the directory of these other Python launch file that we want to start. 07:51.180 --> 07:57.220 So again we can use the OS path join. 07:57.380 --> 08:03.140 And the launch file that we want to start is in the Ros gazebo simulation package. 08:03.140 --> 08:06.780 So one of the packages that we have installed at the beginning of the course. 08:07.180 --> 08:11.860 So let's access it with the Get package Share directory function. 08:12.140 --> 08:17.900 And we want to access to the directory of the Ros gazebo simulation package. 08:18.100 --> 08:24.740 And from this package from the launch folder we want to start the launch file that is called. 08:25.060 --> 08:26.460 So let's go here. 08:26.460 --> 08:37.220 So after the Os.path.join we want to start the launch file gazebo sim dot launch dot pi. 08:38.140 --> 08:43.900 And actually here we are missing to insert this one into a vector. 08:45.440 --> 08:45.960 perfect. 08:45.960 --> 08:49.320 So the input of the Python launch description sources class. 08:49.320 --> 08:51.480 So this one here has to be a vector. 08:51.800 --> 08:57.160 And so this one indicates the directory of the launch folder that is within this package here. 08:57.160 --> 09:04.160 And so from the launch folder of this package of the gazebo we want to execute the gazebo SIM. 09:04.200 --> 09:05.400 Don't launch don't pi. 09:05.760 --> 09:07.560 Now we can also configure this node. 09:07.560 --> 09:13.160 So we can configure this launch file with some launch arguments. 09:13.160 --> 09:19.520 And also in this case we need to set a list of launch arguments starting with the argument that is called 09:19.560 --> 09:21.200 gazebo args. 09:21.560 --> 09:24.400 So now we can set all the arguments. 09:24.400 --> 09:28.520 So all the gazebo arguments within a new vector. 09:28.520 --> 09:29.680 So within a new array. 09:30.160 --> 09:35.680 And now here we can insert another string with all the arguments that we want to set to get. 09:36.440 --> 09:37.880 And so we can use a space. 09:38.080 --> 09:41.400 And then we can add the flag minus v four. 09:41.680 --> 09:44.300 And this one indicates the verbosity level. 09:44.340 --> 09:49.700 And so by setting this 1 to 4, we are setting that we want to print the output of this node. 09:49.700 --> 09:56.940 So the output of gazebo in the terminal in order to see its output and eventually inspect any error. 09:57.380 --> 10:04.180 Then let's also use the flag minus r in order to inform that we want to start the simulation immediately. 10:04.340 --> 10:10.620 So as soon as we start the gazebo launch file, we want to start the simulation. 10:10.620 --> 10:13.420 And also we need to specify the name of the word. 10:13.540 --> 10:17.060 So the name of the simulated word in which we want to spawn. 10:17.060 --> 10:19.660 So in which we want to simulate our robot. 10:19.900 --> 10:25.940 And for the moment we are just fine by simulating it within an empty word. 10:25.940 --> 10:29.900 So within a word that has no elements, it has just a ground. 10:29.900 --> 10:31.540 So it has just the ground floor. 10:31.660 --> 10:38.820 And also it has a light source that we can use in order to visualize our robot with this. 10:38.820 --> 10:43.520 So with this instruction here we will start an empty gazebo simulation. 10:43.520 --> 10:49.920 So we will start an empty gazebo environment without any simulated object inside this world. 10:50.040 --> 10:55.280 So in fact, here, as you can see, we are just starting the empty gazebo world. 10:55.280 --> 10:57.720 So a world which has no element in it. 10:58.280 --> 11:02.200 And now, within this empty gazebo world, we want to start. 11:02.200 --> 11:08.640 So we want to simulate our robot using another node that is still available in this package here. 11:08.640 --> 11:11.120 So in the Ros gazebo SIM package. 11:11.880 --> 11:20.640 So we can create a new instance of the node class and let's call it gazebo spawn entity. 11:21.520 --> 11:23.600 And so this is an instance of the node class. 11:23.600 --> 11:28.320 And we want to use this instance in order to start from the package. 11:28.320 --> 11:31.840 That is again the Ros gazebo SIM package. 11:32.200 --> 11:39.460 So from this package here we want to start the executable that is called the create executable. 11:39.820 --> 11:42.420 And also we want to configure this executable. 11:42.460 --> 11:43.300 And so this one. 11:43.300 --> 11:49.500 So this executable here is the one that will spawn our robot model into the gazebo simulation. 11:49.940 --> 11:51.060 So let's configure it. 11:51.060 --> 11:56.900 And let's first set its output to be screen. 11:57.940 --> 12:00.500 So like this in order to visualize. 12:00.500 --> 12:02.620 So here there is a typo it's screen. 12:02.740 --> 12:06.700 In order to visualize the log messages for this node into the terminal. 12:06.980 --> 12:11.180 And then we need to configure it with some arguments. 12:11.620 --> 12:13.740 So this take a list of arguments. 12:14.060 --> 12:22.020 And here so we can start by configuring the flag topic which we can use in order to indicate the name 12:22.020 --> 12:25.620 of the topic where the Urdf model of our robot is being published. 12:25.900 --> 12:32.300 And actually this topic here is the robot description topic. 12:32.300 --> 12:39.800 And in fact so this note here the robot state publisher node which opens so which reads the Urdf model 12:39.800 --> 12:41.760 of our robot will publish it. 12:41.760 --> 12:45.440 So in the topic that is called the robot description topic. 12:45.440 --> 12:47.000 And so now this node here. 12:47.000 --> 12:52.960 So the create node can read the Urdf model of the robot directly from this topic here. 12:52.960 --> 12:55.880 So directly from the robot description topic. 12:56.320 --> 12:58.440 Also let's configure another argument. 12:58.440 --> 13:04.360 So let's use a comma and let's configure the argument that is called name. 13:04.560 --> 13:11.200 And here let's simply set the name of our robot which we have called just Arduino bot. 13:11.240 --> 13:12.000 Perfect. 13:12.000 --> 13:17.040 And so this node here then we will spawn this robot here. 13:17.040 --> 13:18.120 So this description. 13:18.120 --> 13:21.920 So this urdf within this gazebo and the environment. 13:22.440 --> 13:23.000 Perfect. 13:23.000 --> 13:30.360 So now we need to start just one last node that is the gazebo Ros2 bridge. 13:30.520 --> 13:35.430 So this is another instance of the node class and now this node. 13:35.430 --> 13:42.270 So we want to start from the package that is called Ros gazebo bridge. 13:42.710 --> 13:46.030 So from this package we want to start a node that is called. 13:46.070 --> 13:53.550 So the executable is called parameter bridge. 13:53.870 --> 13:54.790 And this node here. 13:54.790 --> 13:59.190 So we can use the parameter bridge node in order to remap. 13:59.190 --> 14:05.950 Namely in order to connect the gazebo messages that are transmitted in the gazebo simulation using the 14:05.990 --> 14:09.550 gazebo transport protocol into Ros two messages. 14:09.550 --> 14:11.630 So we want to create this remap. 14:11.630 --> 14:17.710 We want to create this connection so that other Ros two nodes and other Ros two applications can use. 14:17.710 --> 14:21.670 So can access all the messages that are generated in gazebo. 14:22.310 --> 14:28.590 So in order to do so, in order to define how to do this remap we need to set some arguments. 14:30.070 --> 14:31.950 So again this is a list. 14:32.150 --> 14:34.890 And in this list of arguments we need to specify. 14:34.930 --> 14:38.890 So here let's start by specifying the name of the topic. 14:39.250 --> 14:43.490 So the name of the Ross two topic in which we want to publish some messages. 14:44.330 --> 14:48.810 So let's say that we want to publish a new message in the topic called clock. 14:49.450 --> 14:56.650 And the type of the message that we want to publish is a Ross graph messages. 14:57.290 --> 15:01.330 And from the messages we want to publish a message of type clock. 15:01.650 --> 15:04.930 So here simply we are saying that in this topic here. 15:04.930 --> 15:09.930 So in this Ross two topic called clock, we are going to publish a message of this type. 15:10.210 --> 15:12.130 And actually now we want to specify. 15:12.370 --> 15:14.770 So which is the gazebo information. 15:14.770 --> 15:20.250 So which is the gazebo message that we want to remap into this Ross two message. 15:20.650 --> 15:23.010 So we can use a single parentheses. 15:23.010 --> 15:24.650 So a single squared parentheses. 15:24.890 --> 15:33.630 And here we can specify that the gazebo message that we want to remap is the gazebo Go messages and 15:33.630 --> 15:35.110 the message of type clock. 15:35.470 --> 15:36.110 Perfect. 15:36.310 --> 15:43.910 So with this note here we are converting a gazebo message of this type here that is created and generated 15:43.910 --> 15:45.390 in gazebo simulation. 15:45.390 --> 15:50.190 And we are converting this one into a message of this type here. 15:50.190 --> 15:55.630 So Ros graph messages clock that will be published in this Ros two topic here. 15:56.190 --> 16:02.230 Now with this we have declared all the instructions that we need in order to simulate our modeling gazebo. 16:02.230 --> 16:08.190 So all of these are all the declaration of the instructions that we need now in order to actually start 16:08.190 --> 16:08.990 using them. 16:08.990 --> 16:10.790 We need to declare them here. 16:10.790 --> 16:15.030 So we need to list them in the launch description class constructor. 16:15.030 --> 16:19.870 And so here let's start with the declaration of the model argument. 16:20.230 --> 16:27.390 Then we also have here this one here this environmental variable that is the gazebo resource path. 16:27.750 --> 16:31.650 Then after that we have also the robot estate publisher node. 16:32.850 --> 16:38.810 So the one that reads the Urdf model of our robot and publishes it in the robot description topic. 16:39.370 --> 16:42.490 Then also let's start the gazebo simulation. 16:42.490 --> 16:44.250 So the empty gazebo simulation. 16:44.490 --> 16:52.370 And then within this empty gazebo simulation, let's also spawn our robot using the gazebo spawn empty 16:52.410 --> 16:52.890 node. 16:52.930 --> 16:55.490 And finally, let's also start this node here. 16:55.890 --> 17:02.690 So the gazebo Ros two bridge, which is that will remap this topic here. 17:02.690 --> 17:07.850 So this message from the gazebo simulation to Ros2 a perfect. 17:08.170 --> 17:11.610 So with this one we can also save this launch file here. 17:11.610 --> 17:18.890 And we have completed the creation of this launch file that starts in the order the robot state publisher, 17:18.930 --> 17:20.770 then the empty gazebo simulation. 17:20.770 --> 17:22.170 Then it spawns. 17:22.370 --> 17:26.410 So this one here will spawn our robot in the empty gazebo simulation. 17:26.410 --> 17:31.110 And then we will expose some gazebo messages into Ros two topics. 17:31.630 --> 17:36.190 Now, as we have declared so as we have used some nodes. 17:36.190 --> 17:41.950 So here we can see the create node and also the parameter bridge node from these two packages. 17:41.950 --> 17:48.350 So from the Ros gazebo SIM package and from the Ros gazebo bridge package, we also need to declare 17:48.350 --> 17:51.110 them here in the package dot XML. 17:51.630 --> 17:59.710 So here we need to declare a new execution dependency from the Ros gazebo SIM package. 17:59.990 --> 18:07.310 And then also another execution dependency from the Ros gazebo bridge package. 18:07.550 --> 18:08.070 Perfect. 18:08.070 --> 18:11.710 And so also with this we have completed the package dot XML. 18:11.710 --> 18:15.510 So we have just introduced these two new dependencies. 18:15.510 --> 18:17.110 So we can save also this file. 18:17.110 --> 18:20.830 And finally we can see our launch file works. 18:20.870 --> 18:25.310 And now it starts the gazebo simulation and spawns our robot in it. 18:26.140 --> 18:29.020 So to do so, let's open a new terminal. 18:29.540 --> 18:34.340 Here, let's go to the workspace and let's build it in order to apply the changes. 18:34.580 --> 18:35.300 Here we go. 18:35.660 --> 18:41.220 And then in a new window of the terminal let's source the workspace and then let's launch. 18:41.420 --> 18:49.580 So with Ros2 launch we can start from the Arduino board description package. 18:49.660 --> 18:54.060 So we can start the node that is called gazebo dot launch dot pi. 18:54.220 --> 18:57.540 So we can start this launch file here that we have just created. 18:58.140 --> 18:59.540 So let's press enter. 18:59.860 --> 19:05.580 And as soon as we do so we can see that the simulation of our robot starts in gazebo. 19:05.740 --> 19:09.580 So we can see that automatically the gazebo window is started. 19:09.620 --> 19:14.220 We can also see that our robot is automatically spawned in the gazebo simulation. 19:14.220 --> 19:19.980 And also we can see that it is bending on itself because the control system is not yet started. 19:20.020 --> 19:25.400 And so here we can see that now our robot is perfectly visible in the gazebo simulation. 19:25.400 --> 19:27.680 So we can start using this tool. 19:27.680 --> 19:31.440 So this gazebo simulation in order to develop new applications. 19:31.480 --> 19:38.240 And so also in order to explore new projects and new ideas, and also to get an immediate feedback on 19:38.240 --> 19:39.480 the robot's behavior. 19:40.000 --> 19:48.160 Now, if in your case, as you can see here, you are having a quite small real time factor as I am, 19:48.760 --> 19:55.320 you can just change the physics of the gazebo world so you can click anywhere in the gazebo world, 19:55.560 --> 19:57.320 and then you can go to physics. 19:57.640 --> 20:00.560 So here and then you can increase the step size. 20:00.560 --> 20:07.520 For example from instead of using 0.001 we can just use 0.01. 20:07.520 --> 20:08.840 So let's press enter. 20:08.920 --> 20:10.760 And so this will increase the step size. 20:10.760 --> 20:15.640 And we can see that as we do so we are getting a real time factor that is much better. 20:15.640 --> 20:21.760 And so this will create a simulation that in general will be lighter and also faster to execute.