KUKA FRI program using JAVA

Question

I am trying to establish the FRI connection for KUKA LBR iiwa. I know how to configure the FRI connection as there are example programs available in the Sunrise.Workbench.

A sample code is given below. My question is 'how to pass' the joint torque values (or joint position or wrench) to the controller using 'torqueOverlay' as mentioned in the code below. Since I could not find any documentation on this, it was quite difficult to figure out. Any sample code with explanation or any clues would be more than helpful.

JAVA code:

package com.kuka.connectivity.fri.example;

import static com.kuka.roboticsAPI.motionModel.BasicMotions.ptp;

import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;

import com.kuka.connectivity.fri.ClientCommandMode;
import com.kuka.connectivity.fri.FRIConfiguration;
import com.kuka.connectivity.fri.FRIJointOverlay;
import com.kuka.connectivity.fri.FRISession;
import com.kuka.roboticsAPI.applicationModel.RoboticsAPIApplication;
import com.kuka.roboticsAPI.controllerModel.Controller;
import com.kuka.roboticsAPI.deviceModel.LBR;
import com.kuka.roboticsAPI.motionModel.PositionHold;
import com.kuka.roboticsAPI.motionModel.controlModeModel.JointImpedanceControlMode;

/**
 * Moves the LBR in a start position, creates an FRI-Session and executes a
 * PositionHold motion with FRI overlay. During this motion joint angles and
 * joint torques can be additionally commanded via FRI.
 */
public class LBRTorqueSineOverlay extends RoboticsAPIApplication
{
    private Controller _lbrController;
    private LBR _lbr;
    private String _clientName;

    @Override
    public void initialize()
    {
        _lbrController = (Controller) getContext().getControllers().toArray()[0];
        _lbr = (LBR) _lbrController.getDevices().toArray()[0];
        // **********************************************************************
        // *** change next line to the FRIClient's IP address                 ***
        // **********************************************************************
        _clientName = "127.0.0.1";
    }

    @Override
    public void run()
    {
        // configure and start FRI session
        FRIConfiguration friConfiguration = FRIConfiguration.createRemoteConfiguration(_lbr, _clientName);
        // for torque mode, there has to be a command value at least all 5ms
        friConfiguration.setSendPeriodMilliSec(5);
        friConfiguration.setReceiveMultiplier(1);

        getLogger().info("Creating FRI connection to " + friConfiguration.getHostName());
        getLogger().info("SendPeriod: " + friConfiguration.getSendPeriodMilliSec() + "ms |"
                + " ReceiveMultiplier: " + friConfiguration.getReceiveMultiplier());

        FRISession friSession = new FRISession(friConfiguration);
        FRIJointOverlay torqueOverlay = new FRIJointOverlay(friSession, ClientCommandMode.TORQUE);

        // wait until FRI session is ready to switch to command mode
        try
        {
            friSession.await(10, TimeUnit.SECONDS);
        }
        catch (final TimeoutException e)
        {
            getLogger().error(e.getLocalizedMessage());
            friSession.close();
            return;
        }

        getLogger().info("FRI connection established.");

        // move to start pose
        _lbr.move(ptp(Math.toRadians(90), Math.toRadians(-60), .0, Math.toRadians(60), .0, Math.toRadians(-60), .0));

        // start PositionHold with overlay
        JointImpedanceControlMode ctrMode = new JointImpedanceControlMode(200, 200, 200, 200, 200, 200, 200);
        PositionHold posHold = new PositionHold(ctrMode, 20, TimeUnit.SECONDS);

        _lbr.move(posHold.addMotionOverlay(torqueOverlay));

        // done
        friSession.close();
    }

    /**
     * main.
     * 
     * @param args
     *            args
     */
    public static void main(final String[] args)
    {
        final LBRTorqueSineOverlay app = new LBRTorqueSineOverlay();
        app.runApplication();
    }

}

Answer 1

Currently FRI can only be controlled in C++.

Java is also necessary to initialize the FRI interface. The C++ code if found in a file called FRI-Client-SDK_Cpp.zip which is included in the kuka connectivity suite. You need to go in the menus to the software components and check the box that enables FRI (fast robot interface). Look in the docs for how to enable/disable software components. Enabling the FRI component will dump this zip file into a folder within your sunrise project for you.

You may just want to try using the grl library itself because it provides an easier to use FRI wrapper. It isn't 100% perfect but is has run successfully for the FRI position motion case. Please note that some manual patching of FRI-Client-SDK_Cpp.zip is necessary to build the grl kuka drivers because distribution of the zip file itself isn't yet allowed. Disclaimer: I'm the author of grl.

Here is grl Java code for starting FRI

Source that calls HoldPosition then drives via FRI exclusively:

package grl.friCommunication;

import static com.kuka.roboticsAPI.motionModel.BasicMotions.ptp;

import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;

import com.kuka.connectivity.fri.FRIConfiguration;
import com.kuka.connectivity.fri.FRIJointOverlay;
import com.kuka.connectivity.fri.FRISession;
import com.kuka.roboticsAPI.applicationModel.RoboticsAPIApplication;
import com.kuka.roboticsAPI.controllerModel.Controller;
import com.kuka.roboticsAPI.deviceModel.LBR;

/**
 * Creates a FRI Session.
 */
public class FRI_Command extends RoboticsAPIApplication
{
    private Controller _lbrController;
    private LBR _lbr;
    private String _hostName;

    @Override
    public void initialize()
    {
        _lbrController = (Controller) getContext().getControllers().toArray()[0];
        _lbr = (LBR) _lbrController.getDevices().toArray()[0];
        // **********************************************************************
        // *** change next line to the FRIClient's IP address                 ***
        // **********************************************************************
        _hostName =  "192.170.10.100";
    }

    @Override
    public void run()
    {
        // configure and start FRI session
        FRIConfiguration friConfiguration = FRIConfiguration.createRemoteConfiguration(_lbr, _hostName);
        friConfiguration.setSendPeriodMilliSec(10);
        FRISession friSession = new FRISession(friConfiguration);
        FRIJointOverlay motionOverlay = new FRIJointOverlay(friSession);


        // wait until FRI session is ready to switch to command mode
        try
        {
            friSession.await(10, TimeUnit.SECONDS);
        }
        catch (final TimeoutException e)
        {
            return;
        }

        // move to start pose
        _lbr.move(ptp(Math.toRadians(90), .0, .0, Math.toRadians(90), .0, Math.toRadians(90), .0));

         for(int i = 0; i < 100; i++) {
             // async move with overlay ...
             _lbr.moveAsync(ptp(Math.toRadians(90), .0, .0, Math.toRadians(90), .0, Math.toRadians(90), .0)
                     //.setJointVelocityRel(0.0)
                     .addMotionOverlay(motionOverlay)
                     .setBlendingRel(0.0)
                     );

             // ... blending into sync move with overlay
             _lbr.moveAsync(ptp(Math.toRadians(90), .0, .0, Math.toRadians(90), .0, Math.toRadians(-90), .0)
                     //.setJointVelocityRel(0.0)
                     .addMotionOverlay(motionOverlay)
                     .setBlendingRel(0.0)
                     );
         }

        _lbr.move(ptp(Math.toRadians(90), .0, .0, Math.toRadians(90), .0, Math.toRadians(-90), .0)
                .addMotionOverlay(motionOverlay)
                );
        // done
        friSession.close();
    }

    /**
     * main.
     * 
     * @param args
     *            args
     */
    public static void main(final String[] args)
    {
        final FRI_Command app = new FRI_Command();
        app.runApplication();
    }

}

FRI code is available https://github.com/ahundt/grl. Disclosure: I'm the author of grl.