1. Creating a Robot

Cell Editor Walkthrough

This tutorial is part 1 of a 5-part walkthrough on creating your first cell in the verbotics cell editor. It acts as an introductory guide to cell editor, and it is recommended you complete all 5 walkthrough videos before viewing the proceeding tutorials.

In this tutorial we will show you how to create your very first cell in the verbotics cell editor, and follow a step-by-step guide how to add a usable robot to this cell.

Prerequisites and Resources

This walkthrough uses a robot model files which can be downloaded here.

It also uses the datasheet which can be downloaded below: Robot Datasheet.

Video Tutorial

Timestamps:

Step by Step Guide

Introduction

This 5-part walkthrough takes you through creating a cell from scratch for use in Verbotics Weld. This first part will explore the initial creation of the cell and the process of adding a robot into this cell.

Step 1: Creating a New Cell

Create a new cell using either the new button in the ribbon menu, or by selecting new from the file drop-down menu. A new window will load showing a blank cell.

Creating the Robot’s Kinematics

Creating the robot’s kinematics can be done either manually or using the create robot tool. Instead of manually creating the individual joints and links, this tutorial will use the create robot tool, so navigate and select the tool from the ribbon menu to load its dialogue.

Create Robot Tool

The dialogue is split into 4 sections:

The left shows a standard kinematic diagram to visualise variables with their associated links
The top right dialogue is for naming the robot and applying a prefix to each generated link and joint
The middle right dialogue, labelled Kinematic Structure, is for inputting the lengths of the different links making up the robot
The bottom right dialogue, labelled Joints, is for inputting each joints range of motion, and velocity

Leave the name and prefix as the default values, and move onto the kinematic structure. Using the diagram we’ve provided below, match the diagrams values to the standard diagram shown in create robot and input their values into the appropriate section.

Standard	Robot Diagram

The final values should be:

Joint	Length
d1	445mm
a1	150mm
a2	700mm
a3	115mm
d4	795mm
d6	85mm

Next, using the tables provided below, fill out the minimum, maximum and velocity values for each joint:

Ranges	Velocity

Note

Each axis corresponds with each joint, e.g. axis 1 is equivalent to joint 1, axis 2 is equivalent to joint 2, etc.

Once completed, click okay and Cell Editor will generate the links and joints, and add them into your cell.

Examining the Kinematic Structure

If you navigate to the URDF tree located on the right, you can expand the world_link to see the branch of joints and links making up the robots kinematics. Additionally, if you enable visability of kinematics in the tool bar, you’ll be able to see the visual representation of these joints and links in the viewer.

Robot Kinematic Structure in Viewer

Step 2: Importing the Robot’s Model

Next you’ll apply a visible model to the robot, navigate to the STEP button located in the ribbon menu. This will open the Import STEP Model dialogue, which allows you to open and import STEP files into cell editor.

Click browse and navigate to the directory containing the STEP files of the robot you downloaded. Select all the files then click Open.

Uncheck all of the options available in the dialogue before clicking import.

Import STEP Model Dialogue

The each step file will be loaded into verbotics as mesh bodies under the Imported branch of the urdf tree.

Now, you’ll need to go through each of these meshes and drag-and-drop each mesh onto the link shown in their name. For example, CABLES_LINK1a, CABLES_LINK1b and LINK1_CAD will each need to be dragged and dropped into link 1. These can also be moved by holding ctrl and selecting all 3 meshes, then changing the parent in the properties tab.

When you do this, you may be presented with the following dialogue referring to retaining the global position of the rearranged meshes:

Retain Global Position Dialogue

While rearranging the cell elements won’t immediately change their position, this dialogue box will ask you to confirm whether the moved elements should remain in their current global position, or if they should shift to change their position to match the destinations origin.

By clicking yes or yes to all the current, or all current items, will remain at their current global position. Inversely, selecting no will shift the elements position. As our kinematics was generated at the world origin, and the imported mesh was placed at the world origin, our mesh should already be in the correct position, so go ahead and select yes to all.

Once all meshes have been positioned inside their associated links, navigate to the jogging pane and use the sliders to ensure that the mesh of each joint moves as expected.

Robot with Visual Bodies

Step 3: Preparing and Checking Collisions

Creating Collision Bodies

Next is to add collision bodies to the robot. First ensure that collision bodies are visible. In the toolbar locate the button represented by view collisions button .

If this button is greyed out it means the collision bodies have been set to be visible.

There are 2 methods to creating collision bodies. The first is to manually add each collision body using the “add body” button in the toolbar. The second, is using the create bounds function to automatically create bounds for each mesh.

For this tutorial, use the create bounds function. Set the selection type to be bodies, then select the entire robot in the viewer. Now, right click and select create bounds. The window that loads allows us to rapidly generate collision bodies of any shape to be fit to our cell.

Creating Collision Bounds

First set the shape to be “mesh”. For the quality, it’s important that this is set to the lowest acceptable setting. While sometimes when working with very precise projects this may need to be accurate, it’s better to select lower quality generation if possible as this creates meshes with less vertices and hence results in better performance when using your cell in verbotics weld.

Note

In the Cell collisions tutorial, we’ll explore why it’s better to create the collisions for different cell components joint by joint rather than all at once. And how to create optimal and effective collision bodies for your cells.

The create bounds function updates the viewer to preview the collision bounds that would be generated by the current parameters. Click create to confirm these bounds and add them to the cell.

Checking and Disabling Collisions

The next step is to ensure that collisions are disabled between connected joints on the robot. This can be done quickly by using the analyse collisions function located in the ribbon menu.

The collision analyser collects a number of samples and recommends disabling collisions between joints over a specified threshold, as connected links should collide enough to surpass the set threshold.

By default, the analyse collisions window will have it’s threshold parameter set to 20%. Leaving this as is, click Go to start the function.

Analyse Collisions Function

Upon completion, a list of collisions will be identified, which each identified collision specifying whether disabling the collision is necessary. In the list generated for this cell, all collisions should be recommended to be disabled. Click okay to confirm disabling all these collisions. Select one of these links, you should find in properties that multiple links with disabled collisions have been specified.

Note

You may not want all collisions disabled, especially between the robot and positioners in future tutorials. If you disable all collisions without first ensuring that these components are either connected or impossible to collide, programs you generate may allow the robot to crash into itself if these parts are in fact able to collide.

Step 4: Finalising the Cell

The final step to completing the robot is to inform Cell Editor of the joints making up the robot, and identifying key links.

Open the model configuration menu by clicking the model button in the ribbon menu. Now, select robot from the side menu and click Add Robot.

Robot Model Configuration

You should find 2 items are required, a group for the manipulator and a link for the robot flange. Type flange into the flange dialogue box, then select the flange link from the drop down box.

Next, a group containing the robots joints is required. Since this is not yet made, return to the main window and click the create group button .

Name this group robot. Next, navigate to the properties tab, and using the search bar located at the bottom, search for each joint making up the robot and click add to add the joint to the group.

Now return to model and select the group in the manipulator dialogue box.

You’ve now successfully created your first robot in cell editor. Save the cell for use in part 2 of the walkthrough, where the next stage is to add tools to the robot.