MToolTCPCalib - 4 Axis robot?

JacquesTheAutomater

Good day,

I have used the ABB RAPID function MToolTCPCalib in the past to teach the TCP offset of a calibration pin tool with a 6 axis robot. 
However attempting to repeat the same with a virtual IRB 660 4 axis robot I keep getting the error below, regardless of actual passed joint targets:

40801: Calculation error

Description

Task: MAINTASK

Cannot calculate the tool frame. 

Program Ref. /Teach/rCalculateAndDisplayTCP/MToolTCPCalib/87

Causes

It is not possible to calculate the tool frame with the selected approach points.

Actions

Select new approach points as accurate as possible. 

Does anyone know if it is actually possible to use MToolTCPCalib  to get the x,y,z TCP offset of a tool with a 4 axis robot?
 
Thanks in advance, 

xerim

Are you sure you are assigning the points as jointtargets and not robtargets? 

JacquesTheAutomater

Hi xerim,

Thanks for the feedback, yes indeed MToolTCPCalibis being passed 4 joint targets:

MToolTCPCalib jp1,jp2,jp3,jp4,tCalPin,nMaxErr,nMeanErr;

where jp1 - jp4 are joint targets:

TASK VAR jointtarget jp1:=[[157.47,-16.2178,36.1094,0,0,85.735],[9E+09,9E+09,9E+09,9E+09,9E+09,9E+09]];

TASK VAR jointtarget jp2:=[[146.052,4.97363,38.7396,0,0,-206.682],[9E+09,9E+09,9E+09,9E+09,9E+09,9E+09]];

TASK VAR jointtarget jp3:=[[152.539,-25.0653,32.5315,0,0,-299.196],[9E+09,9E+09,9E+09,9E+09,9E+09,9E+09]];

TASK VAR jointtarget jp4:=[[132.324,-34.0644,27.6696,0,0,-27.4108],[9E+09,9E+09,9E+09,9E+09,9E+09,9E+09]];

xerim

According to the technical reference manual, there are a list of conditions that must be fulfilled before using the instruction MToolTCPCalib. See below

innebandy

The orientation of 4 targets should be different each other as the picture attached. Otherwise, you will get the error because the calculation result is infinite. And of course this is the limitation of 4 axis robot.

JacquesTheAutomater

Thanks innebandy, so it seems that a difference in orientation via rotation around world z axis alone is not enough, and MToolTCPCalib therefore does not work on 4 axis robots.

innebandy

You’ve got a point there.