1 00:00:06,420 --> 00:00:11,743 Now we are going to learn about the very lightweight simulator turtlesim 2 00:00:11,743 --> 00:00:17,715 it provide all the basic functionalities of ros2 that a bigginer needs to learn 3 00:00:17,715 --> 00:00:19,716 so open up your terminal 4 00:00:28,740 --> 00:00:33,300 in order to install the turtlesim you first need to update 5 00:00:42,000 --> 00:00:56,520 so now you can install this package using sudo apt install ROS its distro foxy and turtlesim 6 00:00:58,980 --> 00:01:09,480 so this is the command to download or to install a package in ros base workspace first 7 00:01:09,480 --> 00:01:17,880 we type sudo apt install and then the ros distro if its foxy then we will write foxy if 8 00:01:17,880 --> 00:01:22,432 it's humble then we will write humble and then the pakage name so 9 00:01:22,533 --> 00:01:43,560 let's give it a try it is installed and now we can find out the executable files in this package ros2 package executable turtlesim 10 00:01:46,140 --> 00:01:51,420 so it has given us a list of the Node that we can utilize 11 00:01:52,320 --> 00:02:01,380 so let first write ros2 run turtlesim 12 00:02:04,620 --> 00:02:14,280 Node so a window appears so this is the first simulator that we utilize to learn the basic 13 00:02:14,280 --> 00:02:22,980 ros Concepts we can move our Turtle around play with the several parameters and services 14 00:02:24,420 --> 00:02:34,800 so open another terminal and we are going to control it ros2 run 15 00:02:37,140 --> 00:02:43,860 turtlesim turtle underscore 16 00:02:44,460 --> 00:02:51,780 teleop keys okay so it has created a Node that can move the turtle around so you can 17 00:02:52,380 --> 00:03:01,080 press forward backward key right to rotate it to right left to rotate it to left right and left 18 00:03:02,220 --> 00:03:09,240 so you can play with it as it moves it draws a line it's pretty fun to play with it 19 00:03:09,240 --> 00:03:11,530 and you can also choose these letters to 20 00:03:11,530 --> 00:03:19,800 rotate to absolute orientation so let's press G 21 00:03:22,440 --> 00:03:31,560 G and P C and D you can play with it and F to cancel the rotation 22 00:03:32,940 --> 00:03:41,640 so if I press like G and then suddenly I press F it will stop right there 23 00:03:41,640 --> 00:03:52,680 To quit this node we can press Q and we are going to see the Node list ros2 Node list so we currently 24 00:03:52,680 --> 00:04:03,060 have one node that is turtlesim and we can also see the topics ros2 topic list so these are 25 00:04:03,060 --> 00:04:11,220 the topic currently I know you do not understand the topic and nodes and services parameters but 26 00:04:11,220 --> 00:04:19,920 you will learn them in the next lectures uh you just get an idea and ros2 service 27 00:04:22,260 --> 00:04:37,380 list and these are a bunch of services that this node contains and ros2 action list so it 28 00:04:37,380 --> 00:04:45,600 has also an action now we will install the rqt.rqt is a tool that will allow you to monitor 29 00:04:45,600 --> 00:04:53,460 subscribe or publish onto a topic and it will even allow you to call services to install this tool 30 00:04:53,460 --> 00:05:03,960 we will just copy this command and paste it here enter your password to just update the system and now 31 00:05:22,020 --> 00:05:28,020 so now the tool is installed we can type rqt and 32 00:05:33,060 --> 00:05:40,980 appeared so it is showing me the topics we can monitor them and the message type of 33 00:05:40,980 --> 00:05:48,840 the topic and the value So currently we are not monitoring any of the topic. Let's 34 00:05:49,500 --> 00:05:55,620 click here so this command velocity topic has several values in it currently 35 00:05:55,620 --> 00:05:59,880 there is no data being published on this topic I will just open another terminal 36 00:06:01,260 --> 00:06:13,740 Okay ros2 run turtlesim turtle_teleop_key yes 37 00:06:18,660 --> 00:06:21,960 drag it down and move the turtle around 38 00:06:26,280 --> 00:06:30,720 so here you can see it get the data and the frequency 39 00:06:31,920 --> 00:06:38,760 this is how you can monitor the topic on rqt now no data is being published on 40 00:06:38,760 --> 00:06:46,020 this topic so it is giving us no frequency but if I move the robot around it will give us 41 00:06:46,020 --> 00:06:57,720 some value of frequency it also shows the X and linear X and rotational z that we give it using 42 00:06:57,720 --> 00:07:04,620 the tally operation let's just uncheck this topic and let's check the pose of the turtle 43 00:07:06,480 --> 00:07:12,900 move the turtle around it is giving us the value of the pose of the turtle in the 44 00:07:12,900 --> 00:07:20,520 turtlesim window this is the frequency more than 62 and the value of x and the theta 45 00:07:21,120 --> 00:07:28,320 let's just play a little bit more so you can see it is changing it's pose 46 00:07:30,420 --> 00:07:37,860 as I move it around in the window so now we will try to call some services and check the topic and 47 00:07:37,860 --> 00:07:48,780 go to the plugin and select service caller so here we have the service caller okay here 48 00:07:48,780 --> 00:07:55,980 it is the service that is clear we have a list of other services that we can utilize but let's just 49 00:07:56,640 --> 00:08:04,140 select clear and call so it has finished all the lines that were on on the window 50 00:08:05,160 --> 00:08:07,080 that's again move it around 51 00:08:08,580 --> 00:08:17,640 and we will see the line select the service reset and call so it will just reset our window 52 00:08:20,460 --> 00:08:26,280 turtle one set pen here are a bunch of arguments that it needs to know 53 00:08:26,280 --> 00:08:36,540 and we will like set it to 255 give it any random value less than 255 54 00:08:38,280 --> 00:08:44,340 this is RGB value and width let's increase it to four 55 00:08:46,500 --> 00:08:54,420 and call so the service is called and yeah here you can see the difference 56 00:08:58,860 --> 00:09:07,740 so now let's call another service that is spawn I will I selected the service spawn and it is asking 57 00:09:08,520 --> 00:09:16,620 what is the value of X Y theta and the name of our new turtle that will be spawn in 58 00:09:16,620 --> 00:09:29,820 the window let's say two and four and the name call here is our the second turtle 59 00:09:31,260 --> 00:09:38,040 but if I try to move I can only move one turtle that was turtle one 60 00:09:40,260 --> 00:09:48,240 I cannot move to Turtle 2 with this teleop now let's check the topics 61 00:09:51,000 --> 00:09:54,840 now we have turtle one and turtle two topics 62 00:09:56,220 --> 00:10:05,040 and we can also see some extra services that are related to Turtle 2 and turtle one so here 63 00:10:05,040 --> 00:10:14,640 is the command to move the second Turtle as well okay this is the command to move so ros2 run 64 00:10:15,540 --> 00:10:25,020 Turtle Sim turtle_teleop_key -- or dash dash 65 00:10:26,880 --> 00:10:34,980 Ros minus args these keyword will let the ros know that the user 66 00:10:34,980 --> 00:10:40,980 want to specify an argument and what is the argument the argument is the remap 67 00:10:43,260 --> 00:10:46,380 and remap what I want to remap turtle 68 00:10:49,860 --> 00:10:54,540 1 CMD vel 69 00:10:57,000 --> 00:10:58,800 to turtle 70 00:11:01,560 --> 00:11:02,280 2 71 00:11:04,740 --> 00:11:14,520 CMD underscore vel so why am I doing this the default topic for this node is turtle one 72 00:11:14,520 --> 00:11:21,540 slash CMD vel but we have another turtle that has Turtle 2 cmd vel 73 00:11:21,540 --> 00:11:27,000 topic so I will just hit enter and try to move and here you can see 74 00:11:28,140 --> 00:11:32,340 the turtle 2 is also moving and we can also move turtle one as well 75 00:11:34,920 --> 00:11:38,040 that must be a very exciting experience for you 76 00:11:38,040 --> 00:11:44,340 so you have learned to use the turtlesim you have monitored a topic on rqt 77 00:11:44,340 --> 00:11:50,880 and you also called several Services related to turtlesim so that was it