Collisions

Collisions are implemented into a cell using collision bodies and are used to determine when 2 links are overlapping, and hence identifying a collision.

Verbotics uses detected collisions when planning to determine valid motion plans. Effective collision bodies are therefore essential to ensuring safe and efficient welding programs for physical robotic welding cells.

Collision Identified with Collision Checker Tool

Collision bodies prevent the creation of motion plans where 2 links drive into one-another, and can further be used to influence the regions where a robot should operate.

Collisions between links can be disabled by adding links into the Links with Collisions Disabled property of a selected link.

Collision Tools

There are a variety of tools available to use in relation to creating, disabling and testing collisions. Below is an overview of each tool, however for an in-depth guide on adding collisions to a workcell, visit our Optimised Cell Collisions tutorial.

Create Bounds

Generating Platter Collision Body with Create Bounds

The create bounds tool can be accessed from the context menu after selecting any number of joints or bodies and right-clicking.

The tool creates collision bodies around the selected cell elements according to a series of options available to adjust in the tool.

Separately/Merged: Select whether collision bodies should be generated for each selected cell element individually, or to generate a single collision to cover all of the selected cell elements.

Shape: Select the shape of the collision bodies to be generated. Depending on the selected shape, a section of additional parameters will appear at the bottom of the dialog.

Margin: The distance between the selected elements and the generated collision bodies.

Box Additional Options:

• Orient to minimise volume: Rotates the collision body to reduce the size of the generated collision body while still retaining the set margin.

• Decompose into (up to): Breaks the collision box into a set number of collision boxes to better cover the selected bodies.

Cylinder Additional Options:

• Generate cylindrical torch geometry: Breaks the cylinder into a series of smaller cylinders following the spine of the selected body. Intended to be used to generate collision bodies along the path of the torch.

• Max Error: The maximum amount of error allowed to occur between the generated collision bodies and the selected bodies. Default: 1000mm^3

• Depth: The detail of the generated collision for the torch geometry. A higher value for detail means smaller and more frequent collision bodies generated to better follow the path of the torch.

• Nozzle Mode: If enabled, generated collision bodies will be aligned with the z-axis of nozzle origin, instead of around the selected bodies.

Mesh Additional Options:

• Decompose and Optimise: Breaks the generated mesh down into a number of smaller meshes, then optimises these meshes until they meet the selected quality setting:

• Quality: The complexity and number of meshes to be generated when decomposing a collision mesh. There are 4 presets available to select from, as well as a custom option. Each option adjusts the following values:

  • Max Count: The number of hulls to be generated. Lower values will result in better performance, but lower detail meshes.

  • Detail: The resolution of the generated meshes.

  • Minimum Error: The amount of error allowed to occur before finishing optimisation.

  • Max Vertices: The maximum number of vertices per convex hull. Lower values will result in better performance, but lower detail meshes.

  • Shrink Wrap: Shrinks the surface of the generated collision mesh to better conform to the selected bodies. This is done by moving the mesh vertices to the closest viable position out from the surface mesh.

Примечание

Shrink wrapping a collision may result in areas of the selected body not being encompassed by the generated collision body if margin is set too low.

Collision Checker

A widget located on the right side of the application. When enabled, this tool indicates whether the current state of the cell is valid, and if any links are colliding.

Clicking on either the Valid? or Colliding? labels will open a dialog listing pairs of links colliding with each other. Each listed pair will have a Disable button on the right, clicking this will disable collisions between the 2 links.

Collision Checker Tool

Analyse Collisions

The analyse collisions tool is located in the ribbon menu, but can also be opened from Tools->Analyse Collision. This tool generates a number of sample states for the current cell, then indicates how often different links collided across the generated samples.

This tool is intended for identifying collisions in a cell that need disabling.

The « Go» button at the bottom of the tool will start the analyser. Once finished, a list of results will be displayed on the right of the dialog.

Analyse Collision Tool

Settings

Number of Samples: The number of samples to generate while analysing collisions.

Samples colliding to disable: A percentage threshold used to determine when 2 colliding links should have their collisions disabled. Any 2 links that collide in this percentage of samples or more will be recommended to have their collisions disabled.

Start from scratch: Re-enables all collisions between links, regardless of previously disabled links, before running the analyser.

Disable links fixed to each other: Forcefully enabled, this option recommends all links that are fixed to each other to be disabled.

Disable adjacent links: Links that are connected by a joint will be recommended to have their collisions disabled.