WEBVTT 00:00.110 --> 00:06.140 Let's experiment with an already existing package that provides you with a simplified 2D simulation 00:06.140 --> 00:07.220 of a robot. 00:07.250 --> 00:09.800 This package is named Turtle SIM. 00:09.800 --> 00:14.960 This will be a good opportunity to apply what you've learned with the Ros two tools in this section, 00:14.960 --> 00:19.460 and we will often come back to Turtle SIM during the course, and at the end of the course, you will 00:19.460 --> 00:23.120 do a complete project based on that simplified robot. 00:23.120 --> 00:24.860 So let's start it right away. 00:24.860 --> 00:25.760 How to start. 00:25.760 --> 00:29.210 You open a terminal and you do Ros two run. 00:29.240 --> 00:32.600 Because anytime we're going to start a node we do Ros to run. 00:32.600 --> 00:38.990 So in which package the node is the package is named turtle SIM. 00:39.020 --> 00:40.790 And you can also use auto completion. 00:40.790 --> 00:42.200 It should be found. 00:42.200 --> 00:48.920 And then the executable is named turtle SIM node like that. 00:48.920 --> 00:52.790 So Rosrun turtle sim turtle sim node. 00:52.790 --> 00:54.530 If you get an error here. 00:54.530 --> 01:01.310 If it's turtle sim not found, then you can install it with sudo apt install and then ros dash. 01:01.310 --> 01:07.510 I'm going to write distro for distribution, but you replace it with your current Ross distribution 01:07.510 --> 01:10.360 and then dash turtle sim. 01:10.390 --> 01:16.750 You see, it's very easy to install a package, but it should already be here when we installed Ross 01:16.750 --> 01:18.280 two in the installation section. 01:18.280 --> 01:23.560 That's part of the desktop install for Ross two, so you should not have any problem. 01:23.560 --> 01:25.210 So let's press enter. 01:25.450 --> 01:27.460 And you see we have a new window. 01:27.460 --> 01:31.030 So I'm going to put that on the side here. 01:32.530 --> 01:32.980 All right. 01:32.980 --> 01:33.610 Like this. 01:33.610 --> 01:38.860 So as you can see a node for now we've only started nodes that print stuff in the terminal. 01:38.860 --> 01:43.810 But a node can also be uh it can also have a graphical view. 01:43.990 --> 01:44.320 All right. 01:44.350 --> 01:50.290 So this node will spawn a turtle here you see in this small window. 01:50.290 --> 01:54.010 And you see we also have some logs about spawning a turtle etc.. 01:54.040 --> 01:58.210 Now in a second terminal I'm going to start another node. 01:58.210 --> 02:01.750 And this node will be able to control that turtle. 02:01.750 --> 02:04.080 So let's do Ros2 run. 02:04.080 --> 02:08.610 And that's going to also be the total SIM package. 02:08.820 --> 02:14.910 But then turtle is going to be turtle Teleop key. 02:14.940 --> 02:15.300 Okay. 02:15.330 --> 02:23.790 So once again auto completion restaurant turtle sim turtle Teleop key I press enter and you see this 02:23.790 --> 02:25.980 node is going to read from the keyboard. 02:26.100 --> 02:28.530 So we can use the arrow keys to move the turtle. 02:28.530 --> 02:32.700 So make sure that you select this terminal okay not any other terminal. 02:32.700 --> 02:34.710 Make sure you select this terminal. 02:34.710 --> 02:36.780 And then let's press on the arrow keys. 02:36.780 --> 02:42.240 And you can see the turtle here is moving as I press on the keys. 02:43.650 --> 02:49.560 So it seems that this node is actually communicating with that node. 02:49.590 --> 02:51.990 How well we are going to find out. 02:52.020 --> 02:54.180 Let's run our cut graph. 02:54.450 --> 02:57.270 So I run it on a third terminal. 03:00.120 --> 03:00.660 Okay. 03:00.660 --> 03:09.950 If needed you can click on this to refresh and you can also change to nodes only or nodes topics. 03:09.980 --> 03:10.400 All right. 03:10.400 --> 03:12.470 You can have different views here. 03:12.470 --> 03:14.540 And let's go to nodes only. 03:14.570 --> 03:15.830 But it's going to be the same. 03:15.830 --> 03:19.280 And so you can see that we have our turtle sim. 03:19.400 --> 03:22.670 That's the node we have started here on that terminal. 03:22.670 --> 03:24.110 And then we have the teleop. 03:24.140 --> 03:24.560 Turtle. 03:24.560 --> 03:26.270 That's the node we have started here. 03:26.270 --> 03:29.270 And you can see they are communicating between each other. 03:29.270 --> 03:37.670 So the Teleop Turtle key is sending here some messages to the turtle SIM with this turtle one Cmdvel. 03:37.730 --> 03:38.780 So what is that. 03:38.780 --> 03:40.010 This is a topic. 03:40.220 --> 03:44.060 So that's a good transition with the next section that's going to be focused on topics. 03:44.060 --> 03:47.540 You will understand everything about the topics. 03:47.570 --> 03:47.870 All right. 03:47.900 --> 03:53.660 So what we can guess for now is that this terminal here will start a node that reads from the keyboard 03:53.690 --> 03:59.780 and then sends a command to that node here, which is going to output the command and give it to the 03:59.780 --> 04:01.070 turtle on the screen. 04:01.070 --> 04:01.550 Great. 04:01.580 --> 04:07.780 Now let's for example let's stop that node and let's run it again. 04:07.780 --> 04:09.760 And this time I'm going to use. 04:09.880 --> 04:18.160 So let's put it like that I'm going to use dash dash Ross args and then dash R to remap the node. 04:18.820 --> 04:22.030 And let's name it my total. 04:22.030 --> 04:25.360 So I want to rename the node I press enter. 04:25.900 --> 04:28.180 So we have the total SIM here. 04:28.180 --> 04:30.400 Again different total but doesn't matter. 04:30.400 --> 04:34.390 And then I can refresh the view and you see that. 04:34.390 --> 04:37.630 So here the view has switched okay. 04:37.660 --> 04:39.220 The sides have switched. 04:39.220 --> 04:41.860 But you see we still have the top total node here. 04:41.860 --> 04:43.360 And then we have my total. 04:43.360 --> 04:44.620 So you can rename the node. 04:44.620 --> 04:49.600 And as you can see as we rename the node we also see this on our graph. 04:49.840 --> 04:53.740 All right so we have discovered the basics of this total SIM node. 04:53.740 --> 04:58.390 We are going to come back to this quite often in this course including in the final project. 04:58.390 --> 05:04.180 And before we start to look at topics in the next section, let's practice a bit more with what you've 05:04.180 --> 05:06.160 learned so far in this section.