KAS T-Bot Motion Control

Introduction

This application note details using the KAS PxMM multi-axis controller to control a 2 axis T-Bot mechanism. A T-Bot performs 2 axis control through a  mechanism (a single belt with fixed pulleys that drives both axes). The T-Bot creates full motion within a 2-dimensional envelope. A KAS project file and a printable DOCX file are attached at the bottom of this article.

The application was created by first starting out with the following template:

Code was then added and removed as needed to create the 2 axis T-Bot control.

Key Code That Was Added

Setup MCS Coordinate system (added to the Main Program Step 6)

The T-Bot mechanism utilizes the MCS (Machine Coordinate System) as opposed to the ACS (Axis Coordinate System) that KAS usually employs. The MC_Kin_Ref Structure (see KAS help) defines the T-Bot robotic system transform and the Function  MC_SetKinTra (see KAS help) initiates it:

Relative and Absolute Motion

A relative and absolute move were also added to the Man Program. Note the Coordinate System input is set to 1 for the MC_COORDINATE_SYSTEM_MC. Here is the Function Block for the Relative Move:

Homing the T-Bot

The program TBot_Homing was added to home the T-Bot. Homing consisted of moving to a hard stop (end of travel), first the X-axis (horizontal), then the Y-axis (vertical). Prior to homing, the max current of the X and Y axis was limited to maintain T-Bot mechanical integrity. The end of travel was sensed by the position error exceeding a preset value. After both axis physical limits are sensed an offset of 2 inches is made on each axis. At the end of homing the max currents are reset.

Motion Sequence (using Absolute and Circular interpolation)

A new program Tbot_MoveSequence was added that sequences motion through linear and circular interpolation moves. 

Sample of the Linear interpolation move

The circular interpolation move makes a complete circle:

Control Panel

The Control Panel was modified to operate the T-Bot. The sequence to start motion is:

1. Wait for “ECAT Up” LED to turn on after project starts running
2. Click on “Group Enable”
3. Click on “Set Tbot Kin Transform” button. “At completion, the MCS Coord Set” LED will turn on
4. Click on “Home Tbot (Move to Hard Stop)”. At completion, the “Home Hard Stop Method” LED will turn on
5. Click on “Start Motion Sequence” button or ether the “Start Absolute Move” button or “Start Relative Move” button to make one move per the Position/Distance inputs. After changing these inputs click the Yellow Set buttons for the new parameters to take effect.

Remote IO Control

An AKT-DNH-000 8 remote Input module and AKT-DT-000 8 remote output module were added to exercise the T-Bot demo from Remote IO. 

1. AKT-DNH-000 8 remote input module
   
   • b_GroupEnableIO – Enables drives and sets up T-Bot Kinetic transform
   • b_HomeHardStopIO – Home axis and moves to start position
   • b_StartSequenceIO -  Execute Motion Sequence (will repeat sequence when this input remains high
2. AKT-DT-000 8 remote output module
   
   • b_StartSequenceIO – indicates when ECAT network is up and drives are ready to be enabled

Operation Video

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