WEBVTT 00:00.560 --> 00:05.390 To create the XML model of the robot following the Urdf format. 00:05.420 --> 00:11.000 Let's start by creating a new Ros two package inside our Arduino bot workspace. 00:11.510 --> 00:15.560 So let's go within the workspace and within the source folder. 00:15.560 --> 00:22.880 And here we have already created the Arduino bot Pi examples package and the Arduino bot CP examples 00:22.880 --> 00:23.570 package. 00:23.660 --> 00:33.020 So to add a new package to this folder, let's use again the command Ros2 package create followed by 00:33.020 --> 00:36.500 the build type that we want to use for creating this package. 00:36.500 --> 00:42.740 And since we won't be including any Python or Cplusplus code in this package, let's use the default 00:42.740 --> 00:44.270 Ros to build type. 00:44.630 --> 00:49.700 So as build type, let's use the amend cmake. 00:49.730 --> 00:51.770 That is the default one for Ros two. 00:52.100 --> 00:58.520 And then we also need to assign a name to this package which we can call Arduino bot. 00:59.840 --> 01:05.210 This option and let's press enter to create also this package here. 01:05.210 --> 01:10.400 So in the Arduino bot description package, we are going to include all the components related to the 01:10.400 --> 01:17.150 Urdf model of our robot and we are not going to develop a so to insert any cplusplus or Python code 01:17.180 --> 01:20.180 within this package, but only XML files. 01:20.750 --> 01:25.430 So let's go back to the workspace now and let's build it again. 01:27.040 --> 01:31.270 So that also the new package, as we can see here, is compiled. 01:31.270 --> 01:33.220 And now it's available in Ros two. 01:35.140 --> 01:40.360 Now let's move on to the fun part in which we are going to develop the urdf model of our robot. 01:40.480 --> 01:46.420 So in the Arduino bot description package that we have just created, let's create a new folder. 01:46.420 --> 01:54.220 So this one called Urdf, and this folder will contain the XML file with the robots model. 01:54.220 --> 01:56.800 So the robot's link and the robot's joint. 01:56.950 --> 01:59.740 And so let's create a new file within this folder. 01:59.740 --> 02:06.490 And this is called Arduino bot dot Urdf dot Acro. 02:06.730 --> 02:14.110 And as you can see, this is not a regular urdf file, but this is a acro file and this is a format. 02:14.110 --> 02:22.270 So the acro format extends the urdf format and allows us to do more advanced things with our robots 02:22.420 --> 02:23.500 XML tags. 02:24.120 --> 02:30.060 Then before starting implementing the model of our robot still within the Arduino board description 02:30.060 --> 02:32.310 package, let's create another folder. 02:32.310 --> 02:35.760 And this one is called Meshes. 02:36.060 --> 02:40.770 So let's create this folder and this will contain the 3D models. 02:40.770 --> 02:46.860 So the 3D CAD of our robot, which we are going to use for the visualization and the simulation of our 02:46.860 --> 02:47.490 robot. 02:47.880 --> 02:51.540 So let's download the attached archive to this lesson. 02:51.540 --> 03:00.630 So the file Arduino board meshes and let's extract its content and then let's copy all the content. 03:00.630 --> 03:09.150 So all the STL files that are in this folder, let's copy this one and let's paste them within the Arduino 03:09.150 --> 03:15.210 bot workspace, the source folder and within the Arduino board description and within the meshes folder 03:15.210 --> 03:16.680 that we have just created. 03:16.680 --> 03:20.880 So let's paste all the 3D models of the robot within this folder. 03:20.880 --> 03:22.680 So within the meshes folder. 03:23.100 --> 03:31.330 Now back in our model, so back in the Arduino board dot Urdf file, let's start by declaring that this 03:31.330 --> 03:32.980 is an XML model. 03:33.130 --> 03:41.920 So let's declare that this is an XML model and also let's say which version of XML we are using. 03:41.920 --> 03:46.690 So the version is the 1.0. 03:47.460 --> 03:53.400 As we learned in the theoretical lessons, when we create a new RDF model of a robot, we need to use 03:53.400 --> 03:58.260 the tag robot, which then contains all the other components of the robot. 03:58.710 --> 04:06.210 An XML tag can be seen as a container in which we can nest other containers, so in which you can declare 04:06.210 --> 04:11.730 other properties related to the tag itself, or also in which you can insert other components of the 04:11.730 --> 04:18.990 robot attack starts with the angular bracket and then followed by the name of the tag that in this case 04:18.990 --> 04:20.730 is robot. 04:20.730 --> 04:24.630 And then it's still closed by another angular bracket. 04:24.630 --> 04:31.080 And now, as we can see, thanks to the XML extension for Visual Studio code that we installed in one 04:31.080 --> 04:34.650 of the first lessons, the tag is also automatically closed. 04:34.650 --> 04:36.390 And so we can see that here. 04:36.390 --> 04:37.860 This one is our container. 04:37.860 --> 04:44.670 So the robot container and this is the opening tag and this is the closing tag of our container that 04:44.670 --> 04:48.820 was automatically inserted by the visual Studio code extension. 04:49.730 --> 04:51.350 Now between these two tags. 04:51.350 --> 04:56.520 So between the opening and the closing tags, we are going to insert all the components of the robot. 04:56.540 --> 05:04.100 So let's start by giving the robot a name and let's call it Arduino bot. 05:04.100 --> 05:11.210 And then since this is a sacral model, so since we are using the sacral format and not plain urdf, 05:11.240 --> 05:17.890 we also need to indicate where the definition of this format is located with the command x, m, l, 05:17.990 --> 05:21.470 n s and then sacral. 05:22.460 --> 05:35.300 And this is in the http ww w ross.org and then in the wiki and then sacral. 05:36.220 --> 05:40.150 Let's start by adding the very first link to our robot. 05:40.450 --> 05:46.830 So let's use a tag link which we can close in the same line by using the forward slash. 05:46.840 --> 05:50.590 So this tag link will be opened and closed within the same line. 05:50.920 --> 05:54.240 And let's call this one word. 05:54.550 --> 05:59.860 Since we are not going to assign any other properties to this link, we can directly close this link 05:59.860 --> 06:01.150 within the same line. 06:01.150 --> 06:04.120 So that's why we use the forward slash. 06:04.390 --> 06:11.110 Actually, this first link of the model doesn't belong to the robot yet, but will only serve to anchor 06:11.110 --> 06:14.110 the manipulator to the word reference frame. 06:14.500 --> 06:20.710 This link then is the parent of all the other links that compose the robot, and we will also be the 06:20.710 --> 06:24.400 interface link between the robot and the external world. 06:24.790 --> 06:26.890 Now let's add another link. 06:26.890 --> 06:29.650 That is the very first link of the robot. 06:29.740 --> 06:36.130 Now we can open and close this link in two separate lines since we are going to insert some attributes 06:36.230 --> 06:37.250 to this link. 06:37.490 --> 06:44.000 And so let's name this link, this time the base link. 06:44.270 --> 06:50.780 And now we can associate a mesh with this link that defines how we want this component to be rendered. 06:50.780 --> 06:52.400 So to be visualized. 06:52.610 --> 06:56.000 In order to do so, we can use the tag visual. 06:56.000 --> 07:03.410 So within the tag link we can use the tag visual and then within this tag we can use a geometry. 07:03.410 --> 07:04.940 So we want to display a geometry. 07:04.940 --> 07:09.260 And this geometry is defined within a mesh. 07:10.460 --> 07:22.370 And the mesh that we want to render for the base link is in the package Arduino but description and 07:22.370 --> 07:24.880 within the meshes folder. 07:24.890 --> 07:31.730 So within this folder here that we created and in which we inserted all the STL file of our robot. 07:31.880 --> 07:38.170 For this first link, we want to display the basement dot STL file. 07:38.980 --> 07:46.420 Now since this file, this mesh is quite large, let's scale its resolution equally in all the directions. 07:46.450 --> 07:49.300 Using the property scale. 07:49.360 --> 07:57.010 And so let's set it to 0.010.01 and 0.01 in all direction. 07:57.490 --> 08:00.940 Then we also need to specify the origin of this mesh. 08:00.940 --> 08:04.810 So the origin of this mesh with respect to the base link. 08:04.810 --> 08:11.530 So where this mesh is located and how this mesh is oriented with the respect of the base link. 08:11.770 --> 08:16.960 So still within the visual tag, let's use another tag that is called origin. 08:17.140 --> 08:23.680 And this origin tag has two properties that are r.p that defines the orientation. 08:23.770 --> 08:28.780 And then there is X, Y, Z that instead defines the position. 08:29.590 --> 08:35.800 As I mentioned, these values express the placement and the orientation of the mesh relative to the 08:35.800 --> 08:36.730 link It belongs. 08:36.730 --> 08:38.680 So in this case to the base link. 08:38.800 --> 08:42.220 And these values depend on how the mesh was generated. 08:42.220 --> 08:48.790 And typically they are obtained by trying different values and also observing how the mesh moves relative 08:48.790 --> 08:51.970 to the link until we are satisfied about the result. 08:52.000 --> 08:59.620 For the moment, let's set all of this to zero and then we are going to visualize this model with these 08:59.620 --> 09:04.270 values set to zero and we are going to see if the mesh renders properly. 09:04.270 --> 09:10.540 So if the mesh renders in the proper position and orientation that we desire in order to simulate and 09:10.540 --> 09:12.070 visualize them correctly. 09:12.740 --> 09:18.170 But before doing so, but before starting visualizing our robot, let's connect. 09:18.170 --> 09:23.180 So let's add a joint that connects the two links that we have just created. 09:23.330 --> 09:29.060 So this is done with a tag joint and let's give it a name. 09:30.110 --> 09:37.400 So the name of the joint is the virtual joint, as this is not a proper joint. 09:37.400 --> 09:44.360 So as this joint doesn't belong properly to the robot, but just serve to attach the robot to the world. 09:44.360 --> 09:48.740 So to attach the first link of the robot that is the base link to the world. 09:49.040 --> 09:51.410 So the parent of this joint. 09:54.160 --> 09:56.590 Is the link named. 09:58.360 --> 10:02.140 World and the child of this joint. 10:02.140 --> 10:09.190 So of this connection is the link that we called base link. 10:09.730 --> 10:11.830 This connection is fixed. 10:11.830 --> 10:17.020 So basically the base link cannot move with the respect to the world. 10:17.140 --> 10:22.630 And so we can set the type of this joint to be fixed. 10:22.630 --> 10:24.550 And so this means that the base link. 10:24.580 --> 10:29.920 Cannot move, cannot rotate or translate with respect to the frame world. 10:30.340 --> 10:31.910 Also, we need to indicate. 10:31.930 --> 10:38.530 How these two links are connected to each other so their relative position and orientation again. 10:39.520 --> 10:41.230 With the tag origin. 10:41.230 --> 10:45.670 And in this case, let's set the r p so the orientation to zero. 10:45.790 --> 10:49.180 And this means that the base link and the world link. 10:49.210 --> 10:50.590 Are oriented the same way. 10:50.800 --> 10:55.360 And also let's set the X, y, z property to zero. 10:55.360 --> 10:59.330 And this means that also these two links have the same center. 10:59.330 --> 11:05.930 So the base link is exactly oriented and positioned the same as the world frame. 11:06.750 --> 11:09.690 This two despite having the same name. 11:09.690 --> 11:13.890 So the origin tag here, they have a completely different meaning. 11:14.040 --> 11:18.720 In fact, as I said, this one is needed in order to attach. 11:18.720 --> 11:25.050 So in order to express the transformation matrix between the base link and the word link. 11:25.050 --> 11:27.360 So between these two reference frames. 11:27.360 --> 11:32.130 And so we can see that here the transformation matrix is zero among these two links. 11:32.130 --> 11:38.070 Instead, these are their tag origin is useful in order to render properly the mesh. 11:38.070 --> 11:46.200 So in order to set the orientation and the position of this mesh so of the basements with respect to 11:46.200 --> 11:47.280 the base link. 11:47.280 --> 11:51.270 And so this is just used for visualization and simulation. 11:52.150 --> 11:58.120 And now let's already visualize our robot in order to see the two links that we have created and how 11:58.120 --> 11:59.650 they are connected to each other. 11:59.650 --> 12:05.740 And also in order to customize these variables here, in order to render properly the RDF model. 12:05.740 --> 12:07.330 And so these mesh here. 12:07.570 --> 12:15.400 To do so, we first need to install the meshes folder and also the Urdf folder. 12:15.400 --> 12:21.040 So we need to install these two folder in Ros two so that they are recognized within our package. 12:21.810 --> 12:22.170 To do. 12:22.170 --> 12:25.650 So let's go to the Cmakelists.txt file. 12:25.650 --> 12:32.670 And here let's delete all the commented rows in order to have a more readable file. 12:34.020 --> 12:34.770 Okay. 12:34.770 --> 12:46.860 And now here, let's add an install instruction and we want to install the directory that is called. 12:48.940 --> 12:53.190 Meshes and also the directory that is called Urdf. 12:53.200 --> 12:59.290 So we want to install basically this folder and also this folder so that when we do the build of our 12:59.290 --> 13:06.430 package, these two folders are recognized by Ros2 and so we can use its content and we want to install 13:06.430 --> 13:07.060 this one. 13:07.060 --> 13:15.670 So the destination is the shared folder and within the shared folder we want to install in the sub folder 13:15.670 --> 13:17.440 that has the same name of the package. 13:17.440 --> 13:27.910 So Arduino bot description and we can access to this folder by using also the variable project project 13:29.350 --> 13:29.590 name. 13:29.920 --> 13:34.180 So basically this will contain the string arduino bot description. 13:34.970 --> 13:38.910 Now let's save this file and let's build our workspace. 13:38.930 --> 13:42.140 In order to start visualizing our urdf model. 13:42.440 --> 13:49.100 So in our new terminal, let's go to the workspace and let's start by building it. 13:50.060 --> 13:54.530 Now the build is complete so we can open a new window of the terminal. 13:55.150 --> 13:57.930 And here we can start by sourcing the workspace. 13:57.940 --> 14:00.790 So the file setup dot bash. 14:00.940 --> 14:07.180 And now in order to display our Urdf model, we are going to use a library that is available in Ros 14:07.180 --> 14:09.940 two and that is called Urdf tutorial. 14:09.970 --> 14:12.430 So let's start by installing this library. 14:12.640 --> 14:19.000 So with apt get install and then we want to install the package. 14:19.030 --> 14:22.150 Then the Ross version that in my case is. 14:23.560 --> 14:25.630 And then also the name of the package. 14:25.630 --> 14:29.620 That is the Urdf tutorial package. 14:29.620 --> 14:33.130 So let's press enter to install this package. 14:33.130 --> 14:38.680 And then now, as you can see in my case, I already have it, so I can already start using it. 14:39.280 --> 14:41.620 Now to display our Erdf model. 14:41.620 --> 14:48.100 So the Erdf model of our robot in RVs, we need to execute a command that we haven't encountered so 14:48.100 --> 14:52.780 far and also some files, some Ros, two files that we haven't encountered so far. 14:52.780 --> 14:58.090 So don't worry if you don't know these command yet, it will be clear in the following lessons. 14:58.240 --> 15:05.710 So the command that we are going to use to visualize our Erdf model is Ros two launch, and then from 15:05.710 --> 15:13.810 the Erdf tutorial package that we have just created, let's start the display dot launch. 15:13.900 --> 15:20.020 And then to this one we need to pass the full directory of our Erdf model that we want to visualize. 15:20.020 --> 15:27.580 So in my case this is in the OLM and then in the Workspace Arduino Bot workspace in the source folder, 15:27.850 --> 15:37.090 then in the Arduino bot description in the Erdf folder, and I want to render the Arduino bot Erdf exact. 15:37.870 --> 15:45.350 So let's press enter and this will open the visualization of the robot model. 15:45.350 --> 15:50.770 So here we can see that we have our robot model and also we can see the frames. 15:50.780 --> 15:56.690 So we can already see the base link and the word that are basically here. 15:56.720 --> 16:01.910 Those are overlapped and so we can see just one, but there are two actually. 16:02.590 --> 16:06.700 Now we can see that, for example, the mesh is not rendered properly. 16:06.700 --> 16:13.510 And with this I mean that the center so the reference frame base link is not properly centered with 16:13.510 --> 16:14.320 the base. 16:14.320 --> 16:20.890 And so we need to change a little bit our model of the robot and specifically we need to modify this 16:20.890 --> 16:21.460 one here. 16:21.460 --> 16:25.450 So this tag here in order to match the mesh of the robot. 16:25.450 --> 16:28.570 So this one that is the base of the robot with this frame. 16:28.570 --> 16:36.310 So with the center of this frame, I have already tested some values and the ones that are working are 16:37.090 --> 16:38.830 -0.5. 16:38.830 --> 16:48.130 So let's translate along the x axis, about -0.5 and also about -0.5 along the Y axis. 16:48.130 --> 16:50.350 So let's save this again. 16:50.650 --> 16:53.860 And now let's interrupt the visualization. 16:54.790 --> 17:00.190 Let's build again the workspace and let's restart the visualization. 17:00.460 --> 17:05.300 And now we can see that the mesh is perfectly centered. 17:05.300 --> 17:09.620 So this is the meaning of changing this parameter here. 17:09.620 --> 17:11.180 So the origin here. 17:11.420 --> 17:16.580 And so this will change the position of the mesh relative to the link it belongs to. 17:16.910 --> 17:23.480 Now let's close the visualization and let's continue adding new links and new joints to the robot. 17:23.870 --> 17:29.090 So let's start by adding a new link and let's call this one. 17:29.090 --> 17:33.500 So the name of this link is the base plate. 17:34.100 --> 17:37.160 And also to this one, let's attach a mesh. 17:37.580 --> 17:46.310 So again, let's use the visual tag and within it let's use the geometry tag. 17:46.310 --> 17:50.360 And within this geometry tag we want to visualize a mesh. 17:51.200 --> 17:56.870 And this time the mesh that we want to visualize is still in the package. 17:59.150 --> 18:04.190 Arduino But description within the Meshes folder. 18:04.190 --> 18:09.080 And now we want to visualize the mesh that is called base plates. 18:09.470 --> 18:21.080 So this one base plate dot STL, and also in this case, let's scale it so by 0.01 in all the directions 18:21.080 --> 18:23.300 since this mesh is quite large. 18:23.690 --> 18:30.380 Also let's specify the origin of this mesh by adding the tag origin within the tag visual. 18:30.380 --> 18:35.870 And so we need to specify the orientation of the mesh so r pi and its translation. 18:35.870 --> 18:37.640 So x, y, z. 18:37.640 --> 18:44.360 And this is specify how the mesh is positioned and oriented with respect to the base plate. 18:44.360 --> 18:50.960 So this frame here, let's set the Pi to zero and instead the x, y, z. 18:50.960 --> 19:01.490 I tried several values and the ones that are working better are -0.39 -0.39 and -0.56. 19:01.490 --> 19:08.600 So these are the values that render the base plates in the correct position of the robot. 19:09.110 --> 19:11.480 Now let's continue by adding a new joint. 19:11.990 --> 19:15.800 So let's add a new joint and let's call this one. 19:16.130 --> 19:23.840 So the name of this joint is joint one and this connects the parent link. 19:24.080 --> 19:27.620 So the link that is the previous one. 19:27.620 --> 19:28.880 So the base link. 19:30.300 --> 19:32.230 To the new one that we have created. 19:32.250 --> 19:40.350 So the child in this case the child link, is the one that we have just created, and that is called 19:40.350 --> 19:41.640 base plate. 19:42.730 --> 19:44.920 Now if for this connection. 19:44.920 --> 19:50.530 So for this link, we used the type fixed as we did for the previous joint. 19:50.560 --> 19:56.890 This means that we are implementing a static connection between the base link and the base plate, and 19:56.890 --> 20:03.250 this means that the base plate cannot move, cannot rotate or translate with respect to the base link. 20:03.400 --> 20:07.120 But this is not the case, in fact, for our robot. 20:07.150 --> 20:10.810 The base plate is the rotating base of the robot. 20:10.810 --> 20:15.700 So the first joint that is already actuated by a motors for our robot. 20:15.850 --> 20:22.960 So in order to implement this, let's set the type of this connection to be revolute. 20:22.960 --> 20:29.530 And this means that the base plate can rotate with the respect to the base link so to its parent. 20:30.300 --> 20:36.360 And now since we are using a movable joint, so a joint that can rotate, let's also indicate which 20:36.360 --> 20:38.100 is the rotation axis. 20:38.550 --> 20:46.580 So here let's set the property axis and this as X, y, z. 20:46.590 --> 20:51.450 So we need to set the X, y, z, and we need to set which is the rotation axis. 20:51.450 --> 20:54.420 And in this case it is the Z axis. 20:54.420 --> 20:58.770 So let's indicate this one by setting 001. 20:58.770 --> 21:05.850 And so this indicates that the rotation axis that the base plate can use for rotate along the base link 21:05.880 --> 21:07.410 is the Z axis. 21:08.360 --> 21:12.140 Finally, we also need to indicate the origin of this connection. 21:13.430 --> 21:19.190 And so we need to indicate which is the transformation matrix that connects these two frames. 21:19.190 --> 21:24.410 So the transformation matrix that connects the base link to the base plate. 21:24.710 --> 21:34.910 So let's set the properties R, P and the property X, Y, Z, and these express the rotation and these 21:34.910 --> 21:37.160 instead express the orientation. 21:37.870 --> 21:44.290 Now we can take these values from the CAD model of our robot, and here we can see that the base plate 21:44.320 --> 21:52.600 link is oriented the same way as the base link, so we can set the Rpy property to zero since they are 21:52.600 --> 21:53.800 oriented the same way. 21:53.950 --> 22:02.180 Also still from the CAD model, we can see that the base plate is translated along the Z axis by three 22:02.180 --> 22:02.890 centimeters. 22:03.070 --> 22:10.240 And so let's set the X, y, z to be zero zero and 0.307. 22:11.050 --> 22:14.950 Now since this joint one here, it's a movable joint. 22:14.950 --> 22:20.150 So a joint that allows the rotation of the two links that are connected between each other. 22:20.170 --> 22:24.220 We need also to specify which are the limits of this rotation. 22:24.220 --> 22:27.250 And this is done with the tag limit. 22:27.700 --> 22:31.660 So here we need to specify the minimum and the maximum angle. 22:31.660 --> 22:37.900 So the lower angle of rotation and the upper angle of rotation. 22:37.900 --> 22:41.020 And also we need to specify the maximum force. 22:41.320 --> 22:47.500 So the maximum effort and also the maximum velocity. 22:48.400 --> 22:54.250 Now since we are going to use the same actuators, so the same motors for all the movable joints of 22:54.250 --> 22:58.920 our robotic arm, basically their mechanical and kinematic limits will be the same. 22:58.930 --> 23:05.320 And so in order to avoid hard coding all these values for each joint of our Erdf model, we can use 23:05.320 --> 23:12.340 one of the amazing features provided by the Acro format, which is the ability to create some variables 23:12.340 --> 23:19.180 also known as properties in the Acro format that function the same way as the variables in any other 23:19.180 --> 23:20.500 programming language. 23:20.770 --> 23:23.370 So we can start by defining a new property. 23:23.380 --> 23:26.380 Let's go at the beginning of our robot tag. 23:26.470 --> 23:29.980 And so let's create a new variable, a new Sakura 23:32.350 --> 23:45.940 property, and for example, let's name this one Pi, and this will contain the value 3.14 159. 23:45.940 --> 23:48.440 So it will contain this number here. 23:48.440 --> 23:55.190 And so from now on in the urdf model of our robot, whenever we want to use this value here, instead 23:55.190 --> 23:59.810 of retyping all these value here, we can just use the variable pi. 24:00.720 --> 24:01.700 Now the same way. 24:01.710 --> 24:05.220 Let's create other two properties, so other two variables. 24:05.220 --> 24:09.330 So let's copy this one and let's paste it two more times. 24:09.510 --> 24:12.360 And these are the effort. 24:13.500 --> 24:25.650 And the velocity and let's set them respectively to 30.0 and to 10.0. 24:26.010 --> 24:32.550 Now we can start using these properties to set the limits So the rotation, the effort and the velocity 24:32.550 --> 24:34.380 limits for the joint one. 24:34.620 --> 24:36.750 So let's set that the joint one. 24:36.750 --> 24:42.240 So the minimum angle that the joint one can reach is -90 degrees. 24:42.240 --> 24:47.910 So minus in radians is pi divided by two. 24:48.770 --> 24:53.150 And also the maximum angle that it can reach is plus 90 degrees. 24:53.150 --> 24:58.610 So in radians it is pi divided by two. 24:58.640 --> 25:02.540 So this is the way in which we can use exact property. 25:02.570 --> 25:05.120 So a variable in the exact model. 25:06.440 --> 25:09.470 Also, let's do the same for the effort. 25:10.010 --> 25:13.960 So here, let's use the effort variable. 25:13.970 --> 25:20.780 And here for the velocity, let's use the velocity variable. 25:22.250 --> 25:27.080 Now we can save this model and let's visualize it one more time. 25:27.080 --> 25:29.450 So let's open again the terminal. 25:29.930 --> 25:37.040 Let's build our workspace and let's use the same mysterious command we have been using so far in order 25:37.040 --> 25:38.600 to visualize our robot. 25:38.900 --> 25:43.040 And so now we can see that it is composed of two meshes. 25:43.340 --> 25:47.990 So there are two links here that are the world and the base link. 25:47.990 --> 25:52.250 And then we have another frame here, and this is the base plate. 25:52.250 --> 25:55.130 And these two links are attached to each other. 25:55.130 --> 26:02.330 And also we can see that by using this slider that was also automatically launched, we can also move 26:02.510 --> 26:03.980 the base plate. 26:03.980 --> 26:09.980 And so we can rotate actually the base plate with the respect to the base link, we can see how the 26:09.980 --> 26:12.530 base plate frame is rotating. 26:12.530 --> 26:18.560 So this frame here is rotating with the previous one that instead is fixed. 26:18.950 --> 26:21.110 So this is the rotation. 26:21.110 --> 26:24.390 And also we can see the limits of this rotation. 26:24.390 --> 26:31.860 So it goes from 1.57, so 90 degrees to -1.57 radians. 26:31.860 --> 26:33.780 So -90 degrees.