Problem with prismatic joint (RRP)

[jakub.wie...@gmail.com]

Hello! 

I have been using Robotic toolbox to make a visualization of a RRP robot (| . -)  and it doesn't work properly. Here is my code:

l1 = 1;

l2=1.5;

L1 = Link ([0 l1 0 pi/2],'standard');

L1.isrevolute

L1.qlim =  pi/180*[-180 180];

L2 = Link ([0 0 0 pi/2,0,pi/2],'standard');

L2.qlim =  pi/180*[-180 180];

L3 = Link ([0 1 0 0 1 l2], 'standard');

L3.qlim = [0 1]

bot = SerialLink([L1 L2 L3], 'name', 'robot')

bot.plot([0 0 0],'workspace', [-3 3 -3 3 -3 3])
bot.teach

Here is my DH table

The problem is that the last coordinate system is created not at the right place as shown in the picture (in the end-effector) but in second (revolute) joint, where the 2nd coordinate system is mounted). Moreover, the last coordinate system is even not created at all. There is also another problem, that while changing the last variable (q3) something strange shows up - it looks as if it was an 'extra link'? It's shown in the picture: 

I would be grateful for any help with that problem.

Jacob

[Erik van Oene]

Hi Jacob,

For me this code works when plotting a sllightly positive q3:

>> bot.plot([0 0 0.1],'workspace', [-3 3 -3 3 -3 3])

When trying to plot the zero configuration the following error is trown:
Error using SerialLink/animate (line 95)
Prismatic length must be > 0

Error in SerialLink/plot (line 300)
    robot.animate(qq);

Even if i change the L3.lim to a negative value it gives this error.

Further the model works correctly for me (using Version 9.10.0)

Erik

Op dinsdag 13 januari 2015 10:21:56 UTC+1 schreef jakub.wie...@gmail.com:

[Peter.I.corke]

Suggest you remove the code that does that test, in retrospect not useful, but a value of exactly zero causes a problem with Matlab hgtransforms used in plot

Peter.

Sent from my iPhone

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[itzel25...@gmail.com]

Hi, I try  with the same code  in version 10 and for the prismatic  joint and give me 3 errors.

Error using RTBPlot.plot_options (line 755)

Prismatic joint(s) present: requires the 'workspace' option

Error in SerialLink/plot (line 212)

    opt = RTBPlot.plot_options(robot, varargin);

Error in ejemploInternet (line 15)

bot.plot([0 0 0.1],'workspace', [-3 3 -3 3 -3 3])

I want to buil prismatic joints, but this not work,   please help.

[Erik van Oene]

Checkout this message  (a few posts ago):

Possible bug in RTB10 - SerialLink plotoption and workspace

Op donderdag 12 oktober 2017 20:33:01 UTC+2 schreef itzel25...@gmail.com:

[namrat...@gmail.com]

L(1)=Link([0 1 0 0 0])

L(2)=Link([0 1 0 0 1])

Rrobot=SerialLink(L)

W=[-5 5 -5 5 -5 5]

Rrobot.plot([1 2],'workspace',W,)

Warning: floor tiles too small, making them 3.000000 x bigger - change the size or disable them

Error using text
X, Y, and Z must be the same length

Error in SerialLink/plot>create_robot (line 346)
        text(b(1), b(2)-s, bz, [' ' robot.name], 'FontAngle', 'italic', 'FontWeight', 'bold')

Error in SerialLink/plot (line 251)
        handle = create_robot(robot, opt);

I made the changes as you suggested, But I am still facing problem with prismatic joints! Can you please suggest a solution for this? 

[Peter Corke]

I get an error but a different one to you.  Can you do a clf before the plot and see if that gives a different outcome

[mahd...@gmail.com]

Hello!!

I have been trying to build RRPR robot using robotics toolbox but I have a problem when I define the prismatic Link

[Peter Corke]

without a code example and description of the "problem" nobody will be able to help you.