WEBVTT 00:00.050 --> 00:03.140 This is the step two for this final project. 00:03.140 --> 00:09.470 And in this step we are going to spawn some turtles on the turtle sim window here. 00:09.470 --> 00:13.250 And actually the first step and the second step are completely independent. 00:13.280 --> 00:16.130 Okay, you could have done the first step second. 00:16.130 --> 00:18.560 And this step first okay. 00:18.590 --> 00:24.470 Because for now the well the turtle controller and the turtle spawner that we will create are not communicating 00:24.470 --> 00:25.250 with each other. 00:25.250 --> 00:26.870 That's going to be for the step number three. 00:26.870 --> 00:29.300 So I'm going to I'm going to stop that. 00:29.300 --> 00:35.810 I'm going to I'm going to start the turtle sim again okay. 00:35.840 --> 00:40.460 And let's first see what we want to do here. 00:40.940 --> 00:44.090 So we want to spawn some turtles okay. 00:44.120 --> 00:50.660 There's going to be a node called turtle spawner responsible for spawning a turtle every x amount of 00:50.660 --> 00:51.020 time. 00:51.020 --> 00:54.980 And then this master turtle will have to catch them one by one. 00:54.980 --> 00:58.730 This time if we look at the services Ros2 service list. 00:58.820 --> 01:01.160 So we've done that previously in this course. 01:01.170 --> 01:04.410 And you see we have a spawn service. 01:04.410 --> 01:13.380 So we're going to use this spawn service to service type with uh spawn. 01:14.910 --> 01:25.500 You see we have the type Ros2 service uh, not service interface show okay. 01:25.500 --> 01:32.850 And we see so what do we need to send as a request x coordinate y coordinate the theta. 01:32.850 --> 01:37.500 So the orientation and an optional name here we're going to use the name. 01:37.500 --> 01:39.240 And then what we receive the name. 01:39.240 --> 01:42.510 So if you didn't provide the name you receive the generated name. 01:42.510 --> 01:45.750 Or if you provided the name you receive the same thing. 01:45.750 --> 01:53.370 Let's just test it from the terminal Ros2 service call with spawn. 01:53.400 --> 01:57.990 And then the type is turtle sim service spawn. 01:58.530 --> 02:11.510 And what I'm going to provide x, let's say 3.4 y 4.5 and then theta. 02:11.690 --> 02:13.610 Well let's give. 02:13.610 --> 02:15.200 So that's going to be in radians. 02:15.230 --> 02:17.750 So for example in radians you have 3.14. 02:17.960 --> 02:18.950 That's pi. 02:19.130 --> 02:24.440 So the total should be not facing the right side but the left side okay. 02:24.470 --> 02:29.330 Because that's pi that's 180 degrees and name. 02:30.410 --> 02:32.180 And let's use quote like that. 02:32.210 --> 02:34.400 ABC for testing. 02:35.060 --> 02:41.270 And you see we have a new total with the x 3.4 y is 4.5. 02:41.300 --> 02:43.730 Theta is 3.14. 02:43.850 --> 02:45.980 So it's facing left. 02:46.610 --> 02:52.040 And you see we have the name ABC and we get the name ABC as the response. 02:52.070 --> 02:52.460 All right. 02:52.460 --> 02:55.190 So that's the service we need to use in our node. 02:55.220 --> 02:59.450 So it's a good thing to first try it and test it from the terminal if you can. 02:59.480 --> 03:03.290 Now let's uh well where will we create our node? 03:03.290 --> 03:05.030 We will need to create a new file. 03:05.060 --> 03:07.670 Let's go to our package. 03:08.510 --> 03:09.440 Turtle. 03:12.590 --> 03:12.980 Turtle. 03:12.980 --> 03:14.420 SIM, catch them all. 03:15.170 --> 03:17.750 Turtle SIM, catch them all again. 03:18.500 --> 03:22.370 And let's create a turtle 03:23.450 --> 03:26.720 spawner.py. 03:27.260 --> 03:27.950 Okay. 03:28.310 --> 03:30.950 Also let's make it executable. 03:31.790 --> 03:33.890 Turtle spawner. 03:33.920 --> 03:34.880 All right. 03:34.880 --> 03:37.820 And then we can open VSCode. 03:37.850 --> 03:40.130 I don't need that one anymore. 03:40.280 --> 03:41.150 Turtle spawner. 03:41.180 --> 03:48.890 Let's take the well the node OOP template from here. 03:49.880 --> 03:53.360 And it's going to go there. 03:54.830 --> 04:02.630 Turtle spawner node here as well. 04:02.640 --> 04:06.750 and let's name it Turtle Spawner. 04:08.340 --> 04:10.560 Okay, I don't need that. 04:10.560 --> 04:12.780 And as well. 04:12.810 --> 04:13.290 Okay. 04:13.320 --> 04:15.150 And so what do we want to do in this code. 04:15.150 --> 04:20.820 Well we are going to create a service client so we can interact with the service server. 04:20.820 --> 04:22.710 We have just seen the spawn service. 04:22.710 --> 04:26.730 And we are simply going to call this every x amount of time. 04:26.730 --> 04:29.070 So for example every second every two seconds. 04:29.070 --> 04:31.950 And so let's start by creating a service client. 04:31.950 --> 04:34.680 We will first import the interface. 04:34.680 --> 04:36.510 What was the interface. 04:36.930 --> 04:38.370 We go back here. 04:38.370 --> 04:41.850 It's turtle sim srv spawn. 04:42.120 --> 04:51.450 So from turtle sim turtle sim dot srv import spawn. 04:51.450 --> 04:56.700 And we've already added turtle sim to the package dot XML, so no need to do that again. 04:56.700 --> 05:07.960 And here I'm going to do self dot spawn client Is self create client spawn. 05:08.380 --> 05:10.120 What is the name? 05:10.150 --> 05:13.180 The exact name slash spawn. 05:14.260 --> 05:17.170 So I'm going to use that exact name here. 05:17.170 --> 05:26.680 And then well let's just create a function called spawn service for example. 05:27.970 --> 05:36.040 Um we're going to give it the turtle name and then x y and theta coordinates okay. 05:36.070 --> 05:38.170 That's what we need for the service. 05:38.170 --> 05:44.530 And before we think about the logic of when we're going to call this service, let's just write the 05:44.530 --> 05:48.010 code to call it and to get the response in a callback. 05:48.010 --> 05:54.940 So for that you could open one node where we've done it before, for example the add to ins client. 05:55.390 --> 05:56.290 Okay. 05:56.290 --> 05:59.470 And we're just gonna get inspiration from that. 05:59.470 --> 06:01.540 So first we can wait. 06:02.710 --> 06:14.210 Let's do a do a weight while not self dot spawn client wait for service with let's say one second that's 06:14.210 --> 06:17.750 going to be self logger. 06:18.410 --> 06:28.640 Actually self get logger one waiting for spawn service. 06:28.880 --> 06:36.020 When we know that the service has been found, then we can create a request. 06:36.650 --> 06:47.360 So let's create a request which is going to be a spawn dot request object request. 06:47.750 --> 06:57.170 In this request we have a text field which is going to be the x from the parameters here. 06:57.380 --> 07:05.310 Then we have request dot y and then we have request Dot theta. 07:07.260 --> 07:11.490 And then we have request dot name. 07:12.450 --> 07:12.780 Okay. 07:12.810 --> 07:15.240 So we actually here have name it. 07:16.140 --> 07:16.980 Turtle name. 07:17.310 --> 07:17.580 Okay. 07:17.610 --> 07:18.570 We create a request. 07:18.570 --> 07:24.270 And then we need to send the request to the service with call async. 07:24.270 --> 07:39.090 So we do we're going to save it as a future self dot spawn client dot call async and we send the request. 07:39.660 --> 07:42.300 After that we can register a callback. 07:42.570 --> 07:44.430 Let's create a callback first. 07:44.430 --> 07:50.100 So callback call spawn service for example. 07:51.360 --> 07:54.960 So we're going to receive a future. 07:54.960 --> 07:58.170 And we're going to pass the request as well. 07:58.200 --> 08:04.810 So then we can later we can check the information that we have for x, y and theta. 08:04.810 --> 08:06.310 And what do we do here? 08:06.310 --> 08:14.140 For now, what we just do response is equal to future dot result. 08:14.290 --> 08:20.140 And in this response we have one thing in this response we have you see a name. 08:20.140 --> 08:22.480 So we have name one thing to know. 08:22.480 --> 08:27.670 And that's something you can test on your own, is that if you try to spawn a turtle, for example, 08:27.670 --> 08:32.650 that has a name that already exists, then it's going to return a empty string. 08:32.680 --> 08:38.350 Okay, so if there is an error while creating the turtle while it's spawning, a new turtle is going 08:38.350 --> 08:39.610 to return an empty string. 08:39.610 --> 08:43.540 And that's how you can know that no turtle was spawned. 08:43.540 --> 08:46.060 If you get a name, then there is a new turtle. 08:46.060 --> 08:53.230 So we're just going to do an if response dot and we don't have any auto completion, maybe we can add 08:53.230 --> 08:54.130 response. 08:54.130 --> 08:59.050 It's going to be a spawn dot response okay. 08:59.080 --> 09:07.650 So this is optional but makes the code a bit better if response dot Instancename is an empty string. 09:07.740 --> 09:10.590 Actually is not an empty string. 09:11.160 --> 09:15.510 Then we are going to do self dot get logger. 09:15.510 --> 09:16.800 For now we just print. 09:17.490 --> 09:32.670 We can say new alive turtle and plus response dot name which is a string. 09:32.700 --> 09:42.090 Okay, so after we get the response from the server, we print the name of the turtle if it succeeded. 09:42.120 --> 09:42.480 All right. 09:42.480 --> 09:47.490 So now I need to do a future dot add done callback. 09:47.700 --> 09:50.070 And if you remember here. 09:50.070 --> 09:52.140 So I'm going to provide the callback. 09:52.140 --> 10:00.300 But if I want to also provide an extra argument I need to use the partial function from the func tools. 10:00.300 --> 10:08.070 So I'm going to do from func tools import partial. 10:08.670 --> 10:11.460 And I will do here. 10:11.490 --> 10:17.520 So the partial is just to check directly here. 10:17.550 --> 10:23.430 Partial and then self callback call spawn service. 10:23.430 --> 10:26.010 And then we need to put request. 10:26.040 --> 10:29.310 That's the field is equal to request. 10:29.610 --> 10:32.220 We don't use it now but we're going to use it later. 10:34.500 --> 10:34.830 All right. 10:34.830 --> 10:37.200 So this is well nothing special. 10:37.200 --> 10:38.820 This is something we've already done. 10:38.820 --> 10:43.590 And you can just basically kind of almost copy paste from the previous code that we've done. 10:43.590 --> 10:46.830 And then before we go further, let's actually test this code. 10:46.830 --> 10:52.380 So let's test that that function here called spawn service is correctly working. 10:52.380 --> 10:54.330 How can we make a quick test. 10:54.330 --> 10:58.350 Well you just here you see you create the node okay. 10:58.380 --> 10:59.490 You create the client. 10:59.520 --> 11:04.770 Then you can directly send a request and you're going to get the response when the node is spinning. 11:04.770 --> 11:11.050 So here we could do node dot call spawn service with. 11:11.080 --> 11:13.000 So we need to provide a name. 11:13.000 --> 11:18.100 Let's do test and then a coordinate x. 11:18.250 --> 11:26.590 Let's do 3.0 coordinate y 3.0 theta is going to be 0.0 okay. 11:26.590 --> 11:27.460 Let's save. 11:27.460 --> 11:31.090 And then we need to create an executable for that. 11:31.090 --> 11:35.980 So I'm adding a comma here the executable. 11:35.980 --> 11:39.760 Let's name it spawner or turtle spawner as you want. 11:39.760 --> 11:41.920 And it's going to be turtle sim. 11:43.180 --> 11:49.360 Catch them all dot turtle spawner. 11:50.290 --> 11:53.320 And we want to execute the main function. 11:53.320 --> 11:54.760 Let's save that. 11:54.760 --> 11:59.980 Make sure you saved all the files and let's build click on build. 11:59.980 --> 12:05.740 So even if we use Simulink install as you know already, we need to build again because we have a new 12:05.740 --> 12:16.820 You file so packages select turtle sim, catch them all and we can use SIM link install. 12:16.820 --> 12:19.760 That's going to apply to the existing files. 12:19.760 --> 12:22.220 So the ones that we are going to build right now. 12:23.300 --> 12:26.000 So what do we need to test this. 12:26.000 --> 12:28.760 We need to start the turtle sim. 12:28.760 --> 12:34.550 So Rosrun turtle sim and turtle sim node. 12:34.550 --> 12:41.090 In fact for every test we do, that's going to be the first thing anyway we need to launch for our application. 12:43.580 --> 12:58.130 And here I'm going to source the terminal because we have the new node Ros to run my no turtle sim catch 12:59.360 --> 13:00.650 them all. 13:00.920 --> 13:03.320 And this time it's going to be the spawner. 13:03.860 --> 13:05.480 Let's see what we get. 13:05.900 --> 13:11.850 And you see that we are spawning a new turtle here on the coordinate three, three and zero for the 13:11.850 --> 13:12.840 orientation. 13:12.840 --> 13:17.490 And we have a log new turtle test. 13:17.520 --> 13:19.200 So that's the name of the turtle. 13:19.200 --> 13:23.610 And you can see spawning turtle test here with x, y and theta. 13:23.610 --> 13:25.620 So it's correctly working. 13:27.510 --> 13:29.040 Now let's go back to the code. 13:29.340 --> 13:33.990 So you see it's best to try to test stuff as soon as you can. 13:34.140 --> 13:34.410 Okay. 13:34.440 --> 13:36.420 You add a small functionality and you test. 13:36.420 --> 13:39.300 That's going to be much easier for you to develop ros2 applications. 13:39.300 --> 13:42.240 And now the question is, well, we're not going to do this. 13:42.240 --> 13:43.470 I'm going to remove. 13:43.500 --> 13:45.780 We're not going to spawn turtles like that. 13:45.780 --> 13:50.340 We want to spawn a turtle every, let's say every two seconds. 13:50.340 --> 13:51.810 So how do we do this. 13:51.840 --> 13:56.910 Well, as I told you previously, in this course you can just call this and you can call the service 13:56.910 --> 13:58.980 from anywhere you want. 13:59.010 --> 13:59.250 Okay. 13:59.280 --> 14:01.110 It could be from any callback you want. 14:01.140 --> 14:03.030 So we can create a timer. 14:03.060 --> 14:08.080 And so I'm going to create a timer here self dot Spawn. 14:08.590 --> 14:16.000 Turtle timer is equal to self dot create timer. 14:16.030 --> 14:18.760 Let's say two seconds to start. 14:18.760 --> 14:22.570 And then what I'm going to do is I'm not going to call this directly. 14:22.570 --> 14:24.460 I'm going to create an intermediate function. 14:24.460 --> 14:25.480 You will see why. 14:25.510 --> 14:31.390 So spawn new turtle with self. 14:32.680 --> 14:37.960 And I'm going to put that here self dot spawn new turtle. 14:37.960 --> 14:43.660 So this method is going to be called every two seconds when the node is spinning. 14:43.660 --> 14:45.460 Now why do I do this. 14:45.460 --> 14:51.670 Because we need to call that with a different name every time and also with different coordinates. 14:51.670 --> 14:57.520 So in this function I'm going to compute different names and coordinates which I'm going to choose at 14:57.520 --> 14:58.120 random. 14:58.120 --> 15:01.510 And then I'm going to call that function here okay. 15:01.540 --> 15:03.400 So let's start with the name. 15:03.400 --> 15:05.740 We're going to choose a name and to choose a name. 15:05.740 --> 15:08.180 Well we need the name that's different every time. 15:08.180 --> 15:12.710 So we first need a string, let's say turtle, my turtle, whatever we want. 15:12.740 --> 15:15.080 And then we could just add one. 15:15.080 --> 15:17.480 So let's say turtle one, turtle two, turtle three. 15:17.510 --> 15:19.430 There's going to be easier to do. 15:19.430 --> 15:31.220 And I'm going to add here self dot turtle name prefix is equal to turtle by default okay. 15:31.250 --> 15:34.730 So later on we will add this as a parameter. 15:34.730 --> 15:37.010 So basically we're going to start the name with turtle. 15:37.040 --> 15:40.250 But I just create a attribute in the class for that. 15:40.250 --> 15:45.950 So self dot turtle name prefix. 15:46.370 --> 15:50.000 Plus I will need here a number okay. 15:50.030 --> 15:55.010 So I'm going to also create here a turtle counter. 15:56.060 --> 16:00.530 Let's initialize to well let's initialize to zero. 16:01.370 --> 16:05.510 And then the first thing we do is we just do plus one for example. 16:05.540 --> 16:10.980 So self dot turtle hotel counter plus equals one. 16:10.980 --> 16:15.030 So in this case it's going to start at one and then two and three etc.. 16:15.030 --> 16:17.340 And I'm going to add this. 16:17.340 --> 16:24.210 So I need to cast it as a string because that's an integer self total counter okay. 16:24.240 --> 16:27.180 So every time we just create a different name. 16:27.180 --> 16:33.060 So you see here it's going to be turtle one and then turtle two, turtle three etc.. 16:33.060 --> 16:34.590 So that's it for the name. 16:34.590 --> 16:38.250 Now we need an x and a y and a theta coordinate. 16:38.250 --> 16:40.740 And how are we going to choose that. 16:40.740 --> 16:43.530 Well I'm going to just choose a value at random. 16:43.530 --> 16:50.520 And for that we can include the Python module here import random. 16:50.520 --> 16:57.510 And then I can do random dot uniform between let's say 0.0. 16:57.510 --> 17:02.370 And then let's say that the max value is 11.0 okay. 17:02.400 --> 17:08.370 So that's going to simply return a random value a random float value between 0 and 11. 17:08.950 --> 17:16.150 Let's do the same for y random dot uniform 0.0 11.0. 17:16.150 --> 17:22.570 And then theta is going to be random dot uniform. 17:22.570 --> 17:26.380 So we don't really need to provide an orientation. 17:26.380 --> 17:31.300 Because the only thing that really matters in the end is the position of the target total. 17:31.300 --> 17:33.280 But let's just make things complete. 17:33.280 --> 17:35.200 And let's add also an orientation. 17:35.200 --> 17:39.490 So it's going to be between zero and basically two times pi. 17:39.520 --> 17:41.740 So we have a complete circle. 17:41.740 --> 17:43.450 So we have 360 degrees. 17:43.450 --> 17:46.000 And I'm just going to provide the exact value. 17:46.000 --> 17:50.770 So I will import the math module. 17:50.770 --> 17:55.660 And I will do two times math dot pi. 17:55.690 --> 17:56.230 All right. 17:56.230 --> 17:59.800 So with this I have a different name every time. 17:59.800 --> 18:02.590 And I have a random coordinates. 18:02.590 --> 18:12.200 And then I can do self dot call spawn service with the name first and then x y theta. 18:12.410 --> 18:12.830 All right. 18:12.830 --> 18:14.870 And that should be it for the code. 18:14.870 --> 18:19.610 So to recap quickly in the constructor where we create some variables. 18:19.610 --> 18:27.290 Here we create a service client and we create a timer that's going to call this method here every two 18:27.290 --> 18:27.800 seconds. 18:27.800 --> 18:33.410 So we create a different name every time we create random coordinates. 18:33.410 --> 18:36.110 And then we call the service. 18:36.110 --> 18:40.160 So we create the request we call asynchronously the service. 18:40.160 --> 18:44.390 We add a callback and we get the response in that callback. 18:44.390 --> 18:46.520 So we should be able to test that. 18:46.550 --> 18:47.750 Let's go back to the terminal. 18:47.750 --> 18:50.000 And we have already used Simulink install. 18:50.000 --> 18:54.410 So let's run the total sim here. 18:54.440 --> 18:59.750 Let's start the spawner and let's see what we get. 19:01.790 --> 19:02.030 Okay. 19:02.030 --> 19:08.300 You can see the first time we have an error because we are trying to create turtle one which already 19:08.300 --> 19:08.750 exists. 19:08.750 --> 19:10.200 So that's not really a problem here. 19:10.200 --> 19:11.340 And then turtle two. 19:11.370 --> 19:12.060 Turtle three. 19:12.060 --> 19:14.010 You can see we have a new log every time. 19:14.010 --> 19:16.260 And we have a new turtle on the screen. 19:16.470 --> 19:16.980 All right. 19:17.010 --> 19:19.320 Once every two seconds. 19:19.320 --> 19:24.720 That is basically here you can see generated with random coordinates. 19:24.720 --> 19:28.710 So it's correctly working and I can stop the turtle spawner. 19:29.010 --> 19:35.010 And so the thing you can see at the beginning we got an error because turtle one is the turtle here 19:35.040 --> 19:36.000 is called the well. 19:36.000 --> 19:40.830 It's the main the first turtle that I will call maybe the master turtle that's going to have to catch 19:40.830 --> 19:41.910 the other turtles. 19:41.910 --> 19:46.590 So you could decide if you want to just increase the counter. 19:46.590 --> 19:50.790 So not start at one here, but start at two. 19:50.820 --> 19:52.140 It doesn't really matter here. 19:52.170 --> 19:52.590 Okay. 19:52.620 --> 19:56.460 If we have the prefix turtle we're just going to skip the first one. 19:56.520 --> 19:57.690 It's not really a problem. 19:57.690 --> 20:01.830 And then you see we have turtle two, turtle three, turtle four etc.. 20:01.860 --> 20:08.970 Now the next part of the challenge is how to actually control the main turtle so that we catch the different 20:09.000 --> 20:10.650 turtles that we have spawned.