1 00:00:00,870 --> 00:00:06,090 In the last lecture, we created a simple robot model simulation and controlled it over Ros using the 2 00:00:06,090 --> 00:00:07,640 ignition parameter bridge. 3 00:00:07,650 --> 00:00:13,710 So let's configure our package so that we can create a launch file to easily launch our simulation and 4 00:00:13,710 --> 00:00:16,620 any related nodes such as our parameter bridge. 5 00:00:18,230 --> 00:00:25,670 First things first, let's configure our smokeless text file to utilize the ignition simulation by calling 6 00:00:25,670 --> 00:00:31,760 the install command on the world and models directory so that when you make launch files you can easily 7 00:00:31,760 --> 00:00:32,660 reference them. 8 00:00:32,870 --> 00:00:38,660 So we should make sure to reference the ROS package that allows us to run ignition gazebo and our parameter 9 00:00:38,660 --> 00:00:41,960 bridge, which is Ros Ignition gazebo. 10 00:00:44,480 --> 00:00:48,200 Then you should also be sure to include it in your package, that XML file. 11 00:00:57,940 --> 00:01:03,280 Then back to my C make list text file right below where I install my launch directory to the share folder. 12 00:01:03,310 --> 00:01:09,700 I can make this a bit more compact, copy it and include it for my world and models directory. 13 00:01:19,110 --> 00:01:26,940 Now, if I go ahead and save these files and rebuild my project with Culkin, build Simulink install. 14 00:01:31,720 --> 00:01:32,020 All right. 15 00:01:32,020 --> 00:01:33,220 Let's go ahead and build. 16 00:01:34,490 --> 00:01:39,020 So now when I go into our install folder in our workspace directory. 17 00:01:40,640 --> 00:01:45,500 Then into package, then share, and then into our package name again. 18 00:01:45,500 --> 00:01:51,560 We eventually see the Models and Worlds folder, which has our linked files, which we're going to be 19 00:01:51,560 --> 00:01:53,420 using for our simulation. 20 00:01:54,230 --> 00:02:00,350 So let's go ahead and create a launch file to start up our simulation and the ignition bridge so we 21 00:02:00,350 --> 00:02:03,320 can send commands over Ros to control our robot. 22 00:02:03,770 --> 00:02:10,400 So I'll make a new launch file in my launch folder called Simulation Dot launch dot pie. 23 00:02:11,270 --> 00:02:16,250 I'll include some of the standard imports, such as our launch description node and execute process 24 00:02:16,250 --> 00:02:18,200 objects, which we've used before. 25 00:02:23,110 --> 00:02:28,900 Then we will include a couple of imports which will help us resolve our paths to things such as our 26 00:02:28,900 --> 00:02:29,890 world files. 27 00:02:39,090 --> 00:02:45,060 So now I'll grab the path of the ignition Ross package so I can use it to launch our simulation. 28 00:02:45,060 --> 00:02:49,860 So I want to grab the share directory so I can grab reference files such as the launch files. 29 00:02:54,730 --> 00:02:56,110 Then I will do the same thing. 30 00:02:56,110 --> 00:02:58,750 But grab the share directory of our package. 31 00:03:06,260 --> 00:03:10,190 And then I will create one more variable to get the location of the world file. 32 00:03:17,440 --> 00:03:20,800 Now, keep in mind that this path object in itself is not a string. 33 00:03:20,800 --> 00:03:26,890 So if we want it to be just that full path, we have to call the dot as POSIX function. 34 00:03:28,290 --> 00:03:32,310 And this will return the string representation of that particular path for us. 35 00:03:32,340 --> 00:03:37,710 Now let's go ahead and define our Generate Launch description call, which we define our launch description 36 00:03:37,710 --> 00:03:38,370 list in. 37 00:03:42,340 --> 00:03:45,060 So the first thing I want to do is launch the simulation. 38 00:03:45,070 --> 00:03:49,990 We could use the execute process object to run the same command we ran in terminal to start our ignition 39 00:03:49,990 --> 00:03:50,730 gazebo. 40 00:03:50,740 --> 00:03:55,510 But it's worth noting there is an existing launch file to allow us to do that from the ROS Gazebo SIM 41 00:03:55,510 --> 00:03:56,320 package. 42 00:03:56,320 --> 00:04:00,460 So I'll import a few more things which will allow us to reference another launch file. 43 00:04:06,450 --> 00:04:09,150 Then I can reference the launch file like so. 44 00:04:42,730 --> 00:04:44,620 And oops, I actually made a mistake here. 45 00:04:44,620 --> 00:04:48,460 This is actually g z underscore sim dot launch by. 46 00:04:49,000 --> 00:04:49,490 All right. 47 00:04:49,510 --> 00:04:54,910 Basically what we did is reference a Python launch description which finds the ignition gazebo launch 48 00:04:54,910 --> 00:05:00,880 file from the corresponding package and passes in extra arguments such as passing the simulation world 49 00:05:00,880 --> 00:05:06,880 file path and the dash r flag, which tells the simulation to run on startup a.k.a not be paused. 50 00:05:07,030 --> 00:05:12,100 Now I'll eventually go with the execute process command instead, but it is worth showing as this is 51 00:05:12,100 --> 00:05:17,200 a recommended way to start your launch file by ignition and you can find more example launch files for 52 00:05:17,200 --> 00:05:19,150 ignition at the following link. 53 00:05:20,100 --> 00:05:24,540 Now that we've launched our simulation, let's create a node object, which will be our ignition parameter 54 00:05:24,540 --> 00:05:29,680 bridge so we can convert the command velocity topic from ignition over to ROS two. 55 00:05:29,700 --> 00:05:32,670 This is just like the terminal command we ran in the last lecture. 56 00:06:02,960 --> 00:06:07,700 Now, there are two ways which you can remap the topic, either by passing in the Ross arguments like 57 00:06:07,700 --> 00:06:14,060 we did in Terminal with the dash R flag and then passing in the the original topic name to the converted 58 00:06:14,060 --> 00:06:15,410 topic name like this. 59 00:06:15,890 --> 00:06:21,260 Or alternatively you can utilize the node objects remapping argument to do the same thing in a easier 60 00:06:21,260 --> 00:06:22,850 to read tuple format. 61 00:06:22,870 --> 00:06:26,360 So just go ahead and comment this out and try the remapping key. 62 00:06:38,300 --> 00:06:43,580 So again, either format is acceptable, either US arguments with the dash r flag or re mappings, but 63 00:06:43,580 --> 00:06:48,860 I find re mappings to be much more readable, especially if you end up remapping multiple topics. 64 00:06:48,860 --> 00:06:52,070 Simply just keep adding tuples to the list. 65 00:06:52,100 --> 00:06:54,460 Now there is one more thing we have to do. 66 00:06:54,470 --> 00:06:59,060 If you remember from the last lecture, we needed to set an environment variable so that Ignition gazebo 67 00:06:59,090 --> 00:07:02,990 knew where to look for our models we included in our world PSD file. 68 00:07:02,990 --> 00:07:07,640 So I'll go ahead and import the functionality to allow us to set environment variables. 69 00:07:15,440 --> 00:07:20,660 If you remember, we configured our models folder to get included into our shared directory so we can 70 00:07:20,660 --> 00:07:23,690 go ahead and find it just like we did with our world file. 71 00:07:30,540 --> 00:07:35,010 Then I need to add it to the beginning of my launch description so that it gets applied before we launch 72 00:07:35,010 --> 00:07:35,970 our simulation. 73 00:07:36,000 --> 00:07:41,100 This will take in the name of the environment variable, which is ignition gazebo, resource path, 74 00:07:41,100 --> 00:07:44,190 and a value which will be our model's path variable. 75 00:07:47,580 --> 00:07:52,140 Oh, and it seems I made a mistake here where I'm forgetting a comma, just causing some errors here. 76 00:07:52,140 --> 00:07:53,280 So let's try this again. 77 00:07:53,610 --> 00:07:54,170 There we go. 78 00:07:54,180 --> 00:07:55,860 Now, my autocomplete is working properly. 79 00:08:06,000 --> 00:08:06,480 Great. 80 00:08:06,480 --> 00:08:07,940 This just about covers it. 81 00:08:07,950 --> 00:08:11,940 Let's save the file and compile our workspace. 82 00:08:14,390 --> 00:08:14,660 All right. 83 00:08:14,660 --> 00:08:16,130 So that's gone ahead and compiled. 84 00:08:17,310 --> 00:08:21,630 Now let's open up a terminal and I'll go ahead and source it and launch our new launch file. 85 00:08:26,220 --> 00:08:27,300 And oops, we got one more. 86 00:08:27,660 --> 00:08:28,850 Path is not horrible. 87 00:08:28,860 --> 00:08:30,570 I must have missed one somewhere here. 88 00:08:30,570 --> 00:08:32,580 So here we created our launch file path. 89 00:08:32,580 --> 00:08:35,340 I forgot to convert this back to a string. 90 00:08:36,090 --> 00:08:41,220 All right, let's try Save that since I use some link install, that should take change effect immediately. 91 00:08:41,280 --> 00:08:42,570 Let's try this one more time. 92 00:08:43,710 --> 00:08:48,570 Oh, and it seems I made one more typo here where I was supposed to include the actual world file, 93 00:08:48,570 --> 00:08:50,760 not just stop at the world's directory. 94 00:08:50,760 --> 00:08:55,380 So the file we are interested in running is our wheeled model world. 95 00:08:55,770 --> 00:08:56,100 All right. 96 00:08:56,100 --> 00:08:57,050 Hopefully no more typos. 97 00:08:57,060 --> 00:08:58,560 Let's try this one more time. 98 00:08:59,430 --> 00:09:00,420 Control C out of this. 99 00:09:00,600 --> 00:09:01,500 Clear the screen. 100 00:09:03,210 --> 00:09:04,050 And there we go. 101 00:09:04,050 --> 00:09:08,280 Now we see our simulation opening with our corresponding world. 102 00:09:09,320 --> 00:09:14,300 And now we can also go ahead and open up a second terminal tab and double check to see if the topic 103 00:09:14,300 --> 00:09:16,340 is being remapped into ROS. 104 00:09:16,490 --> 00:09:17,540 And it's not. 105 00:09:18,680 --> 00:09:23,660 Well, and it seems I made one more typo down here where I was defining the topic message type. 106 00:09:23,660 --> 00:09:25,640 So I misspelled geometry. 107 00:09:25,730 --> 00:09:27,140 So geometry. 108 00:09:27,140 --> 00:09:27,670 So there we go. 109 00:09:27,680 --> 00:09:29,510 I just swapped a few letters. 110 00:09:29,630 --> 00:09:34,430 So we're taking the modeled wheel model command velocity topic and we're taking the geometry. 111 00:09:34,430 --> 00:09:38,930 Underscore messages, message twist from ignition messages twist. 112 00:09:39,290 --> 00:09:41,060 All right, try this one more time. 113 00:09:47,130 --> 00:09:49,770 So our simulation starts up like it did before. 114 00:09:52,110 --> 00:09:54,900 And now we see this command veil topic. 115 00:09:55,290 --> 00:10:00,240 So we could also go ahead and open up a visualization program like RCT to publish the values to our 116 00:10:00,240 --> 00:10:02,220 robot like we've done in the previous lecture. 117 00:10:04,600 --> 00:10:06,910 So here I already have it set up from last time. 118 00:10:08,490 --> 00:10:13,100 So we'll just set this to, say 0.5 and start publishing. 119 00:10:13,110 --> 00:10:18,840 And now if I head over to our simulation, we see that our robot is indeed moving. 120 00:10:20,900 --> 00:10:21,230 All right. 121 00:10:21,230 --> 00:10:24,890 So this seems to be in working order, but let's go back to our launch file so I can show you another 122 00:10:24,890 --> 00:10:30,480 nifty feature you will commonly see when working with simulation launch files, which are event handlers. 123 00:10:30,500 --> 00:10:36,260 You see, if we start this simulation and the user were to close the simulation window, the launch 124 00:10:36,260 --> 00:10:38,480 file in the background would still be running. 125 00:10:39,260 --> 00:10:44,650 So in order to stop this, we actually have to hit control C to stop things such as the parameter bridge. 126 00:10:44,660 --> 00:10:50,780 To avoid this, we can instead set up an event handler to listen for a shutdown of the simulation and 127 00:10:50,780 --> 00:10:53,780 stop the rest of the nodes and processes in the launch file. 128 00:10:53,780 --> 00:10:57,320 So I'll go ahead and import some things which will help us with that. 129 00:11:09,850 --> 00:11:13,150 And to use it, I can add it to our launch description like so. 130 00:11:22,200 --> 00:11:27,930 So basically here I'm calling the unprocessed exit handler to detect when the simulation has been closed. 131 00:11:27,930 --> 00:11:32,340 And then we will emit a shutdown event for our entire ROS launch instance. 132 00:11:32,460 --> 00:11:38,160 Now, I need to define this simulation target action variable, which you can do by taking that action 133 00:11:38,160 --> 00:11:42,600 out of your launch description and instead assigning it to a variable. 134 00:11:43,600 --> 00:11:48,000 So essentially what we would normally do is take this include launch description object. 135 00:11:48,010 --> 00:11:49,720 We'll just cut it out like this. 136 00:11:51,320 --> 00:11:59,210 And then right above the definition, I can simply say simulation is equal to and paste it in like so. 137 00:11:59,580 --> 00:12:01,160 I'll fix the tabbing a little bit. 138 00:12:03,000 --> 00:12:08,400 And then now to add it back to our launch description, all we would have to do is type in the variable 139 00:12:08,400 --> 00:12:09,420 simulation. 140 00:12:11,560 --> 00:12:18,820 So this format does the same exact thing as what we had earlier in the sense that it's taking this value 141 00:12:18,820 --> 00:12:21,700 and pulling it into our launch description. 142 00:12:21,820 --> 00:12:27,340 But now we have this nice variable which we can reference for our target action in the Register event 143 00:12:27,340 --> 00:12:28,030 handler. 144 00:12:28,480 --> 00:12:30,850 Now the only problem is referencing a launch description. 145 00:12:30,850 --> 00:12:36,830 File object does not give the functionality of referencing something like a node or executable process. 146 00:12:36,850 --> 00:12:43,990 So if we were to save this launch file and rerun the simulation, I get an error saying caught exception 147 00:12:43,990 --> 00:12:48,100 in launch since the target action is not an execute local or callable instance. 148 00:12:48,100 --> 00:12:50,920 So this is why I prefer to use the execute process. 149 00:12:50,920 --> 00:12:55,930 Call within the launch file to launch the simulation just like we did in terminal, which in my opinion 150 00:12:55,930 --> 00:12:57,520 looks a lot cleaner and easier to understand. 151 00:12:57,520 --> 00:13:03,580 But I wanted to go over this functionality of how you can include external launch descriptions from 152 00:13:03,580 --> 00:13:04,810 other packages. 153 00:13:05,600 --> 00:13:08,030 So for now, I'm just going to comment this form out. 154 00:13:09,620 --> 00:13:14,960 And I'll just say here, you can't use with event handlers. 155 00:13:17,860 --> 00:13:22,810 And so now we'll redefine our simulation variable and instead call execute process with the command 156 00:13:22,810 --> 00:13:24,100 we used to run in terminal. 157 00:13:34,360 --> 00:13:34,720 All right. 158 00:13:34,720 --> 00:13:38,950 So again, we still have our simulation within our launch description, which it's referencing from 159 00:13:38,950 --> 00:13:39,730 this variable. 160 00:13:39,730 --> 00:13:44,890 And all we've done is changed it from this include launch description, format to execute process. 161 00:13:44,890 --> 00:13:51,130 So now if I go ahead and save this file and rerun our launch file, I'm going to screen. 162 00:13:54,750 --> 00:13:58,830 We see this launches as it did before and as we've been doing throughout this section. 163 00:13:58,830 --> 00:14:06,210 But now if I go ahead and close the simulation, we see this will start closing out our parameter bridge 164 00:14:06,210 --> 00:14:08,540 and other instances within the launch file. 165 00:14:08,550 --> 00:14:12,960 So that's gone ahead and closed automatically since it detected we closed the simulation, which is 166 00:14:12,960 --> 00:14:18,810 pretty handy if all that launch file is doing is working with that gazebo simulation instance. 167 00:14:20,140 --> 00:14:25,340 So that just about covers utilizing these launch files for our simulation instances. 168 00:14:25,360 --> 00:14:30,430 So two things I want to mention before we end off this lecture is that you can reference multiple ignition 169 00:14:30,430 --> 00:14:34,630 to ROS topic conversions within our ignition bridge node. 170 00:14:34,630 --> 00:14:40,510 So all you have to do is keep adding the topics which you want to transfer over from ignition to ROS 171 00:14:40,510 --> 00:14:41,020 two. 172 00:14:41,020 --> 00:14:45,070 And then the second thing I wanted to mention is if you want to learn more about event handlers such 173 00:14:45,070 --> 00:14:50,230 as the one I've used here, you can check out the following raw materials page for more information. 174 00:14:52,320 --> 00:14:52,850 All right. 175 00:14:52,860 --> 00:14:54,420 That wraps up this lecture. 176 00:14:54,420 --> 00:14:59,460 These last couple of lectures were mainly to help give you a baseline on how to incorporate simulation 177 00:14:59,460 --> 00:15:03,210 usage with ignition gazebo into your RA package. 178 00:15:03,330 --> 00:15:08,520 So in the next lecture, we will wrap this section up with a project to combine everything we've learned 179 00:15:08,520 --> 00:15:15,960 about ignition gazebo, PSD files, creating models using plug ins, Ros Topic Bridging launch file 180 00:15:15,960 --> 00:15:20,700 incorporation, all within a realistic robotics simulation project. 181 00:15:20,700 --> 00:15:22,080 So I'll see you there.