How to run pbvs or ibvs

[Abdulrahman Alshanoon]

Hi all

I reading chapter 15 I want to run the example pbvs and ibvs but I getting some errors 

cam=CentralCamera('name','Camera','default'); 
P=mkgrid(2,0.5,'T',transl(0,0,3)); 
Tc0=transl(1,1,-3)*trotz(0.6); 
TcStar_t=transl(0,0,1); 

Tc_t_est = cam.estpose(P, p);

Tdelta = TcStar_t * inv(Tc_t_est);

I get this error :

Struct contents reference from a non-struct array object.

Error in  *  (line 225)

            n = obj1.dim;

or

when I try 

Tdelta = Tc_t_est * inv(TcStar_t)

I got this error

Error using  *  (line 254)

LHS should be matrix with 3 rows

Any solutions please ??!!

[Peter Corke]

Please see my reply to your other post.   I think you are using the old syntax (textbook edition1 from 2011) with the newest version of the toolbox (2017).

peter

[abdulrah...@gmail.com]

Thanks for help Dr Peter 

I have the following issue, I am using RTB 10.2, vision 4.1 and your 2017 book, I tried with Matlab R2016a, R2016b, and R2018a. I don't know what should I do? 

>> cam = CentralCamera('default');           

principal point not specified, setting it to centre of image plane

>> P = mkgrid( 2, 0.5, 'pose', SE3(0,0,3) );   

Undefined function or variable 'cam'.

Error in  *  (line 254)

ibvs = IBVS(cam, 'pose0', T_C0, 'pstar', pd);                    assert(numrows(a) == n-1, 'RTB:RTBPose:badops', 'LHS should be matrix

with %d rows', n-1);

Error in mkgrid (line 72)

        p = SE3.check(opt.pose) * p;

[Peter Corke]

There's something wrong with the code you cut and pasted.  Those two lines run fine, but the command that fails is not given.  mkgrid() cannot give that error message.

peter

[abdulrah...@gmail.com]

Thanks again for prompt reply 

I solved my issue by removing the path of RTB10.2, and run the file 10.2Robotics Toolbox for MATLAB.mltbx. For vision 4.1, I just added the whole folder to the path. Then I run the following IBVS code, it works fine with me:-

cam = CentralCamera('default');           % defining the camera with known parameters

P = mkgrid( 2, 0.5, 'pose', SE3(0,0,3) );  % target four points in image plane

pd = bsxfun(@plus, 200*[-1 -1 1 1; -1 1 1 -1], cam.pp'); % the desired features target position is centered on the %principle points and implicitly have the square target fronto-parallel to the camera.

T_C0 = SE3(1,1,-3)*SE3.Rz(0.6);              % initial camera position in the world coordinates

p = cam.plot(P, 'pose', T_C0)                   % initial camera pose in pixel coordinates

e = pd - p;  % image plane error bet. The desired camera position and initial camera position

J = cam.visjac_p( p, 1 ); % image Jacobian 8 × 6 matrix, since p has four feature points

lambda = 0.125; % gain value

v = lambda * pinv(J) * e(:); % control law determines the required translational and angular velocity of the camera

%T_C = T_C0 .* delta2tr(v); % the updated motion of the camera toward the goal

ibvs = IBVS(cam, 'pose0', T_C0, 'pstar', pd);

ibvs.run();

ibvs.plot_p(); % plot the path of the feature points on the image plane

ibvs.plot_vel(); % Cartesian velocity

ibvs.plot_camera(); % Cartesian position

ibvs.plot_jcond(); % condition number of the image Jacobian 

Thanks sir