robotics: manipulators arm

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James Patrick 2020-2-13

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评论： James Patrick 2020-2-13

hello!!!!

I'm trying to modalise kinematics and dynamics of a scarat 4- DOF (RRPR) with one joint prismatics using toolboxes of Peter Corke.

I don't know how to obtaint dynamics equations with MATLAB and simulate the kinematics.

Thsese are my 2 codes that I have wrote .

the first code this is the error

Error using sym/subsindex (line 769)

Invalid indexing or function definition. When defining a function, ensure that the arguments are symbolic variables and

the body of the function is a SYM expression. When indexing, the input must be numeric, logical, or ':'.

Error in sym/subsref (line 814)

R_tilde = builtin('subsref',L_tilde,Idx);

the second code this the error

Error using tb_optparse (line 303)

unknown options: mask

Error in SerialLink/fkine (line 59)

opt = tb_optparse(opt, varargin);

the first it is to draw et flower and the second is for dynamics

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Answer 1

Walter Roberson 2020-2-13

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在 MATLAB Online 中打开

A_02 = simplify( A_01(q1)*A_12(q2));

That returns an array, not a function handle or symbolic function.

A_03 = simplify(A_02(q2)*A_23(d3));

With A_02 being an array, q2 is attempting to index it.

A_02 involves two variables, so I cannot predict which variable you want q2 to substitute for (function handle case.)

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Walter Roberson 2020-2-13

编辑：Walter Roberson 2020-2-13

在 MATLAB Online 中打开

You have

q1.num(:,1) = atan2(s1,c1);

q1 is a symbolic variable, not a structure. You cannot create a field named num for a symbolic variable.

Symbolic variables are "objects" that do have some internal properties, but nothing that can be set by the user.

In particular, this is not Python, and you cannot set the "numeric value" of the symbolic variable to anything.

I would suggest

q1_num(:,i) = atan2(s1,c1);

and likewise for the other variables you try to set .num of -- after all, in a number of other places in the code you are already using _ instead of .

Do watch out that in that particular statement you should be indexing with (:,i) instead of (:,1)

Later you will run into the problem,

prismatic joint 3 has no qlim parameter set, set it or specify 'workspace' plot option

referring to the call

plot(Scarat,[q1_num(1,i),q2_num(1,i),d3_num(1,i),q4_num(1,i)])

When I investigate, I find that Scarat.qlim is a 4 x 2 array in which the third row (corresponding to the prismatic joint) is -inf inf . I also find that the internal routines set the qlim entry to -inf inf in the case of any joint that is not a revolute joint.

If you were to set a qlim for

L(3) = Link([0,0,0,0,1]);

then it looks like it would be copied. So you need to either set qlim there, or else you need to pass the 'workspace' option to plot(Scarat) giving the x and y and z limits of the workspace.

James Patrick 2020-2-13

Exemple Scarat.m

Thank's ...

I have arrange the code like you have told me but the the simulation give me a new error . this is it:

Index exceeds matrix dimensions.

Error in SerialLink/plot>create_robot (line 469)

d = norm( d(4:6)-d(1:3) ) / 72;

Error in SerialLink/plot (line 252)

handle = create_robot(robot, opt);

this is the new code. I think that the error is in the plot

James Patrick 2020-2-13

Thank's for your help it is good now!!!!

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