Inverse Kinematic with fixed joint

Hey Guys,

I want to do the inverse Kinematics for my 6DOF-Robot. So far it works, but how can i set a revolute joint fixed for 8degrees for the inverse calculation? I don't want that the ik is using this joint. It just should stay at 8°.

Do I have to use the generalizedinversekinematics to set these constraints, or is there some other fix?

Thanks a lot, best greets from Germany!

Marius

My Code for Joint1 wich should stay in the ik calculation at 8. With the positionlimits of [8,8] brings me an error.

link1 = robotics.RigidBody('L1');

jnt1 = robotics.Joint('incline','revolute');

jnt1.PositionLimits = deg2rad( [-8, 8]);

setFixedTransform(jnt1, [eye(3),[0;0;0];[0 0 0 1]]);

jnt1.JointAxis = [0 1 0];

link1.Joint = jnt1;

addBody(loader, link1, 'base');

[Sara Boznik]

Maybe you can use

while jnt1.PositionLimits <8

and so you stop it.

[Marius Wesolowski]

Thanks Sara for your hint.

But then it calculates from 0 to 8 right?

I fust want to fix it at 8.

Ohh i see there is a Mistake in my code it should be [8,8] for positionLimits.

When i run it with [8,8] there is a mistake (see below). So i did it with 7.999 but its not that what i want..

Error using validateConfiguration

Expected input to be non-NaN.

Error in robotics.manip.internal.RigidBodyTree/validateConfiguration (line 1130)

validateattributes(qi, {'double'}, {'nonempty', 'nonnan', 'finite', 'real', ...

Error in robotics.manip.internal.RigidBodyTree/getTransform (line 648)

qvec = obj.validateConfiguration(Q);

Error in rigidBodyTree/getTransform (line 471)

T = obj.TreeInternal.getTransform(varargin{:});

Error in LoaderZXYRPY (line 128)

Tik = getTransform(loader, configSol,'L9')

[Sara Boznik]

So you want also 8?

Then just write

while jnt1.PositionLimits <=8

Because while takes so long as conndition is complished.

[Sara Boznik]

oh now i see, you need only for 8, then delete <

[Marius Wesolowski]

Yeah for yout understanding it's right, only for 8, practically it isn't a joint it's just a steel between some joints with a angle of 8. So i want to write it for calculation as a fixed joint with the value of 8.

So thanks i will try to include the while function.