Commanding Cartesian Pose through FRI

This is the most basic concept in robotics. Use the kinematics of the robot to obtain the individual joint angles that will take the robot to the desired cartesian point in space, and vice versa.

I am interested in the same question as gman1.

I'd like to control position and orientation of flange of iiwa based on measurement data received on the desktop. (The desktop which is connected to the sunrise controller of iiwa.).

I need to find methods to transmit position and orientation of flange to iiwa.

I have transmitted orientation data to control joints of iiwa via FRI. But controlling the position and orientation of flange is a different task.

If FRI is to be used for controlling position and orientation of the flange, one would have to calculate set of joint angle movements corresponding to change in position an orientation in every time step. These joint angle movements could be transmitted to iiwa via FRI. So calculations should be done before using FRI... I think this has to happen in the desktop computer. Wouldn't this require knowing exact dimensions of arm of iiwa?

This feels like unnecessary complicated, the work that robot usually makes itself has to be done separately in this approach.

Looking forward on any ideas regarding this.

I have started trying also other methods to transmit position orientation (TCP/IP communication and DirectServo)

If I see it right, the only option to move the robot via FRI cartesian, is though a little workaround, by using the transformationProvider.

In this case you send a transformation matrix like :

{ 1, 0, 0, 10},

{ 0, 1, 0, 10},

{ 0, 0, 1, 10}

So the code on the client side would look like:

void TransformationProviderClient::provide()
{
// Change the translational vector of the transformation matrix (all values in mm)
   double x = _transformationMatrix[0][3];
   _transformationMatrix[0][3] = 1;
   double y = _transformationMatrix[1][3];
   _transformationMatrix[1][3] = -400;

   double z = _transformationMatrix[2][3];
   _transformationMatrix[2][3] = 560;

   // Set new transformation matrix for frame with identifier"PBase"
   setTransformation("PBase", _transformationMatrix, getTimestampSec(), getTimestampNanoSec());
}

on the Robot side (not the whole program. just the important sections)

 // Select the frame from the scene graph whose transformation is changed by the client application.
        friConfiguration.registerTransformationProvider("PBase", objectBase);

temp_frame = _lbr.getCurrentCartesianPosition(_lbr.getFlange());
            temp_frame.setAlphaRad(objectBase.getAlphaRad() + temp_frame.getAlphaRad()) ;
            temp_frame.setBetaRad(objectBase.getBetaRad() + temp_frame.getBetaRad()) ;
            temp_frame.setGammaRad(objectBase.getGammaRad() + temp_frame.getGammaRad()) ;
            temp_frame.setX(objectBase.getX());
            temp_frame.setY(objectBase.getY());
            temp_frame.setZ(objectBase.getZ());
            
            _lbr.move(ptp(temp_frame).setJointVelocityRel(0.1));

for me that "solution" is very unpractical. One problem is, that you do not get the current axes values from the robot though the FRI back on the client side.

I would be very happy to get better ideas to make that a little bit more smart.

Thank you SquirrelDance for the idea.

I have been using TCP/IP communication and DirectServo for now.

Quote from PaavoUEF

Thank you SquirrelDance for the idea.

I have been using TCP/IP communication and DirectServo for now.

Hello PaavoUEF,

now I am interested what DirectServo is. Could you please give me a rough idea what is meant by DirectServo? How does is work? Is it a API, too?

I am looking forward to your answer.