Building a Cell

Download and Install

The first step is to download a free trial of Verbotics Weld. Cell Editor is included in the installer of Verbotics Weld 1.0 or greater. Once you have downloaded the installer, follow the installation prompts to install the software on your computer.

In addition to the software, a number of robot and asset presets are available. These presets can be used in Cell Editor to add predefined robots to the cell. Presets can be downloaded within the Preset Library (including the examples used in this tutorial) or additional external .vbpreset files can be added to Cell Editor. To add these additional presets to Cell Editor, navigate to the local Preset Library using the address found within the Edit > Preferences > Search Paths > Robot Presets field.

Cell Editor Format

The underlying format that Verbotics Weld (and Cell Editor) uses is the Unified Robotics Description Format. URDF is an effective method for representing a robot and its world, including all static colliders and links on the robot itself. One important concept of URDF is its use of links and joints.

Most of these details are hidden from you when using Cell Editor. However, it is nevertheless good to understand the fundamentals.

Links are parts of the world that can hold collision and visual models. They do not define position and orientation alone.

Joints are the parent to links and control the positioning of links.

Therefore, when moving a link, what you are actually doing is moving the origin of the parent joint. One useful way to think of links and joints in URDF is to think of joints as transforms and links as connections between them. To learn more about URDF visit Cell Editor Detailed References

Create a Work Cell

Once downloaded, a new work cell can be created. A work cell is a representation of the world defined about the robot, including accurate spatial information and parameters that are used for both simulation and planning.

Step 1: Create a new work cell

Press New on the ribbon interface to create a new cell. Let’s call it “ABB_World”

Creation of a new Cell

Cell Editor has now created a new empty workcell for you. Notice the manipulator in the center of the screen. A a basic cell tree has been added by default to this cell, including a single Joint and Link

Note

The underlying format that Verbotics (and Cell Editor) uses is the URDF. URDF is an effective method for representing a robot and its world, including all static colliders and links on the robot itself. One important concept of URDF is its use of Links and Joints.

Most of these details are hidden from you when using Cell Editor. However, it is nevertheless good to understand the fundamentals.

Links are parts of the world that can hold collision and visual models. They do not define position and orientation alone.

Links are positioned by their parent Joint.

Therefore, when moving a Link, what you are actually doing is moving the origin of the parent joint. One useful way to think of Links and Joints in URDF is to think of Joints as transforms and links as connections between them.

Step 2: Place the Positioner

While Robots can always be created manually, many common manufactured models have already been modelled and can be imported directly into the workcell. One such robot is the ABB IRB 2600id Manipulator, which can be placed on the IRBT 2005 positioner.

1. Right click, then delete the base_joint. This will delete all children, thereby also deleting base_link

2. Select the world

3. Click ‘Import Robot’ to import a robot, then select the IRBT 2005 under positioners. Click Import to confirm.

4. When prompted whether you would like to set as the default positioner, select Yes

Step 1 Delete the base_joint

Step 3 import the positioner

Step 3: Place the manipulator onto the positioner

Now that a positioner has been created, we can import a robot and place it onto the positioner track. To do this, we need to traverse down the tree to find the irbt2005_mount_link, then import the manipulator onto this link.

1. In the 3D view, select the carriage of the irbt 2005 positioner to select the link in the URDF widget.

2. Expand the carriage link fully, by right clicking irbt2005_carriage_link and selecting Fully Expand

3. Click the irbt2005_mount_link at the bottom of the joint/link tree to select it.

4. Click ‘Import Robot’ and select the IRB 2600ID under manipulators. Click the Import button.

5. When prompted, set the robot as the default manipulator

Step 3 Select the mount link

Note

The robot we have imported already has a torch attached. Normally, Robots will be packaged with no torch included, and they can be imported from the torches section of the preset menu.

Step 4: Add a station

In order to perform welds in our cell, we will need somewhere for parts to be placed. For this, we can import and use a station.

1. Select the world and press ‘Import Robot’

2. Import the IRBP L station. When prompted, set as the default station.

3. Using the Transform Widget in Transform mode, apply the following transformation in local space.

x	4500 mm
y	1700 mm
Yaw	180.0°

Step 3 Apply a transformation to the imported station

Step 5: Disable collisions

One of the important steps for developing a cell is allowing some collisions that result from valid robot states. In most instances, we would like collisions to be detected when we plan welds (such as between the nozzle and the station). However, sometimes links can collide most or all of the time, even when the cell is in a completely valid state. Cell Editor can automatically detect which links collide the majority of the time and disable collisions between them, meaning planning is unaffected by degenerate link collisions.

1. Let’s check where our manipulator can move. Click Show Reachability under Analyze in the ribbon. Currently, no points are reachable, so the display is unaffected.

2. To fix our reachability problem, click Analyze Collision under the Analyze tab in the ribbon.

3. Set the % Samples colliding to disable to 70%, then hit Go.

4. Many links are displayed, alongside the link they collided with and the proportion of samples where a collision ocurred (expressed as a percentage).

   • For more information about collision analysis, read the reference page

5. Click Ok to apply the collision analysis. Collisions that were selected in the dialog will be disabled

At this point you will notice that the Show Reachability option has enabled the visibility of a point cloud. This point cloud indicates possible positions for the robot to reach.

Note

Sometimes, a certain link may collide for a large proportion of the samples (~50%), but this behaviour may be intentional. Take great care in ensuring that the results from the Analyze Collisions dialog reflect what you are trying to achieve with the cell.

Step 6: Configure the Model

Every cell that can be used with Verbotics Weld has a Model attached. The Model provides metadata about the Cell, some necessary for planning when used with Weld.

1. Click the ‘Configure Model’ button under the Cell submenu of the ribbon.

   • Cell Editor has automatically filled a number of fields on the General page. These correspond to the positioner, station and manipulator and were set when the parts were import and set as Default.

2. Under the ‘Collisions’ tab, tick the following Invalid Configurations

   • 4 - forward down right

   • 5 - backward up left

   • 6 - backward up right

   • 7 - backward down left

3. Using the search field and the add/remove buttons, add the following links to the Additionally Padded Links

   • irb2600id_link_5

   • irb2600id_link_6

   • torch_link

   • nozzle_link

4. Hit the ‘Ok’ button to confirm the model changes

Results of the model configuration

Step 7: Test the cell in Verbotics Weld

Once the Cell is configured for basic planning operations, it can be opened in Verbotics Weld and tested in a Weld Planning environment. Below is an outline of the process of testing a workcell for planning ability. For more detailed instructions, consult the full Weld walkthrough.

1. Click the ‘Open in Weld’ button to open the cell in Verbotics Weld. If you have not saved the project, you will be prompted to do so.

2. Import one of the sample parts available from our website. Click ‘Import Part’ and navigate to the part to open it.

3. Click ‘Identify Welds’ to identify welds on the imported part. Click ‘Create * welds…’ to create the welds identified in the dialog.

4. Add some default Weld Settings to the identified welds.

5. Attempt to plan the welds. The welds should successfully plan, and robot simulation should show no abnormalities.