4. Adding a Positioner

Cell Editor Walkthrough

This tutorial is part 4 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’ll be creating a robot positioner to be used in tangent with our robot as a manipulator.

Prerequisites and Resources

This walkthrough requires you to download a positioner model file, which is available here.

Additionally, this walkthrough continues on from part 3’s cell, if you lost or didn’t save that cell, download the example cell here to continue on with this tutorial.

Video Tutorial

Timestamps:

• 0:00 Start
• 0:15 Introduction
• 0:58 Step 1: Adding the Positioners Model
• 6:06 Step 2: Preparing Carriage Motion
• 8:20 Step 3: Preparing Collisions
• 10:59 Step 4: Finalising the Positioner

Step by Step Guide

Introduction

This 5-part walkthrough takes you through creating a cell from scratch for use in Verbotics Weld. This fourth part will explore the creation and model configuration of a workpiece position.

Step 1: Adding the Positioners Model

Start off by first adding the robot positioner’s model to your cell. Open the STEP file importer and navigate to the 4m_Robot_Positioner STEP file, then go ahead and import the model into your cell.

Once the model loads, adjust the positioners translation and rotation. For this, make sure to place the positioner perpendicular to the workstation. To make this easier, go ahead and disable visibility for the robot as you’ll be moving this later anyway.

Robot Positioner Model

Next, you’ll need to set-up the positioners kinematics and motion. If you expand the links and joints under imported, you’ll find our positioner is made up of 5 different joints, with 2 end joints, 2 modular joints and 1 carriage joint.

For the positioner today, you’ll be simplifying this down into a base joint and a carriage joint.

Select the 4 joints starting with “stand”, then right click and select child bodies. Now right click once more and merge all of these bodies. Make sure to right click on one of the selected bodies when you do this.

Move this merged mesh into the “unsaved” link, making sure to retain all global positions. Then delete the 4 empty joints.

The last joint is the carriage, once again right click on the joint, click select child bodies, then merge the carriages meshes. Go ahead and move this new mesh into the carriage link, and remove the extra joints.

With the positioner simplified down, rename our joints and links, then finally place the positioner in your cell’s main branch.

Robot Positioner Joints and Links

Step 2: Preparing the Carriage Motion

The next step is add motion capabilities and limits to the positioner’s carriage, which means you need to go ahead and change the carriage joints type.

In the previous walkthrough video, you added motion to the workstation by setting several of its joints to be the revolute type. However, as the positioners carriage travels along a straight line instead of rotating, you’ll instead be using the prismatic type .

Set the carriage joint to be prismatic. You’ll see upon doing this, the axis and limits options appear.

Prismatic Joint Properties

Start with the axis. With the carriage joint still selected, use the viewer to determine which axis lines up with the positioner.

You should find this to be the x-axis, represented by the red arrow, as such set the axis to x in properties.

First, you need to make sure the carriage is starting in the correct position. Using the diagrams in the data-sheet (diagrams shown below), notice the carriage is starting too close to the end of the positioner, as such shift it along the x axis 50mm.

Robot Positioner Diagram

Next you’ll need to specify the limits, which you’ll be able to find in the data sheet you can download from this tutorial’s webpage. The data sheet states the following: For a single carriage on the positioner: Distance = 0.8m + 1m per module.

As such, this means the travel distance for our positioner is 2.8m.

Since the carriage has its home on the positive end of the positioner, set the maximum range to 0mm and the minimum range to -2800mm.

Step 3: Preparing Collisions

Select the joints that make up the positioner and open the create bounds function. For the positioner, use the box shape with a 5mm margin, leaving the quality as approximate.

Collision Boxes Generated

Note

When generating collision bounds, your results won’t look identical to the ones shown above. However, as long as the bounds cover the visual bodies making up each joint appropriately, then the collision bodies you generate will be acceptable.

Once these are created, re-enable vision of the remainder of the cell. Before you can analyse the newly added collisions, the cell needs to arranged with the robot placed on the positioner.

This can be done by dragging and dropping the “robot_base_joint” onto the carriage positioner link. This will prompt you with the “retain global position” dialogue. For this case, make sure to select no.

The robot may require some adjustment to be positioned correctly, however once complete your cell should look similar to what is shown below:

Robot Placed on Robot Positioner

Once the robot is positioned correctly, open analyse collisions from the ribbon menu to start preparing the collisions:

1. Ensure that Start from scratch is disabled

2. Run the function

3. Check the collisions detected between links and make sure only links connected or adjacent to the positioner have their collisions disabled

4. Click OK to save and apply the results to your cell

Step 4: Finalising the Positioner

For the positioner to be recognised and used in verbotics, you need to update the model configuration to include the positioner.

To start, create a new joint group containing all of the positioners joints and give the group an appropriate name. Once that’s done, open the model configuration menu.

Navigate to the robot created in part 1, here you should notice an empty box labelled positioner. In that box, search and select the joint group containing the positioner which you created a moment ago.

After this, you can exit the model configuration by clicking Save.

Once that’s done, your robot positioner is all ready to be used in verbotics. Make sure to complete the fifth and final part of the cell editor walkthrough to have the cell ready to use in verbotics weld.