Problem with ikine().

[Za]

Hello. I am trying to build a simple 2DOF robot and I keep getting the same error:

Error using SerialLink/ikine (line 164)

Number of robot DOF must be >= the same number of 1s in the mask matrix

Error in zac (line 10)

q = R.ikine(T, [0 0], [1 1 0 0 0 0])

I don't know what else to try. I have tried changing the mask matrix and it didn't help. I tried different examples with 3 or 4 Links and it still didn't work.

L(1) = Link([0, 0, 256, 0]);

L(2) = Link([0, 0, 123, 0]);

R = SerialLink(L)

R.plot([0.4, 0.3]);

R.teach()

T = transl(0.4, 0.5, 0.6);

q = R.ikine(T, [0 0], [1 1 0 0 0 0])

 

[Peter Corke]

This has come up a few times recently, you are not using the function as per the documentation.  The syntax is:

q = R.ikine(T, [0 0], 'mask', [1 1 0 0 0 0])

Why do you think the 'mask' option is not required?  If you are using the first edition of RVC book then please use RTB9.10 not RTB10.

Peter

[Za]

Thank you. I see now that I read the documentation poorly. All the examples I came across were written without 'mask' and it didn't occur to me that whoever wrote them was using older version of RTB. In the future I will read the documentation more thoroughly. Thank you again. 

[Satyendra kumar]

Dear Peter Sir,

I am working with 2R,3R inverse kinematics problem.

I am facing this problem.

 

 

log

Warning: ikine: rejected-step limit 100

exceeded (pose 1), final err 0.224109 

> In SerialLink/ikine (line 244)

  In threedof>invbutton_Callback (line 281)

  In gui_mainfcn (line 95)

  In threedof (line 42)

  In @(hObject,eventdata)threedof('invbutton_Callback',hObject,eventdata,guidata(hObject)) 

Warning: failed to converge: try a

different initial value of joint

coordinates 

> In SerialLink/ikine (line 273)

  In threedof>invbutton_Callback (line 281)

  In gui_mainfcn (line 95)

  In threedof (line 42)

  In @(hObject,eventdata)threedof('invbutton_Callback',hObject,eventdata,guidata(hObject)) 

 

Here is my button callback for 3R robot

 

px = str2double(handles.edit4.String);

py = str2double(handles.edit5.String);

pz = str2double(handles.edit6.String);

 

L1_1 = 020; L2_2 = 050;L3_3 = 040;

L(1) = Link([0 ;L1_1 ; 0; pi/2]);

L(2) = Link([0 ; 0 ;L2_2 ; 0]);

L(3) = Link([0 ; 0 ;L3_3 ; 0]);

 

Robot = SerialLink(L);

Robot.name  = '3DOFRobot';

 

T = [1 0 0 px;

      0 1 0 py; 

      0 0 1 pz ;

      0 0 0 1];

 

Q0 = [0 -pi/2 pi/2];

QF = Robot.ikine(T, Q0, 'mask',[1 1 1 0 0 0]) * 180/pi;

 

I faced same problem for 2R also.

 

q = Robot.ikine(T, [0 0], 'mask', [1 1 0 0 0 0])

 

My work setup

8.5.0.197613 (R2015a)

Robotics Toolbox for MATLAB (release 10.2)

Shall i switch to RTB9.10.

[Peter Corke]

Inverse kinematics for under actuated arms is tricky.  Have a look at the FAQ or talk to your professor.