Communication between C++ and Java

[ahundt]

We will serialize one line of the path format, then send it from C++ to Java:
http://www.coppeliarobotics.com/helpFiles/en/pathImportExport.htm

Serialization will be done with a shared flatbuffer data type:
https://github.com/google/flatbuffers

A message passing system, Zeromq, will be used to pass the serialized message from C++ to Java:
http://zeromq.org/

Java will feed the point to the robot initially using smartservo.

FRI can potentially be used later to overlay and adjust the motion.

Question: where to handle transform from optical tracker to robot base frame?

• Will be implemented by @athundt and @astrick3

C++

@athundt will take the lead on this

• Install zeromq
• Install google flatbuffers
• Implement messaging functions for path step then full path

Java

@astrick3 can you take the lead on this part?

• We should try to use a package manager for Java such as maven.
  • Tried this but it did not work, skipping.
• Install zeromq
• Install google flatbuffers
• Implement ZeroMQ "DEALER" communication.

Testing

• Communication with C++ plugin over zeromq+flatbuffers

[ahundt]

Commit df67234 creates the initial path flatbuffer file.

[ahundt]

I created a few azmq issues during this process to help me learn and debug azmq:

• Crash on high rate send 68
• Match asio support for futures and coroutines 67
• small example of send and receive over loopback not working 63

[ahundt]

I ran a test using the instructions with Java in a VM and C++ running in OS X. There was no communication between the two. I took a look and the Java implementation appears to use a pub/sub system rather than a zeromq dealer system.

[ahundt]

It looks like we need to add a motion overlay for FRI command control to work. Here is the Java from Kuka's sample application.

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.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 LBRJointSineOverlay 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 = "127.0.0.1";
    }

    @Override
    public void run()
    {
        // configure and start FRI session
        FRIConfiguration friConfiguration = FRIConfiguration.createRemoteConfiguration(_lbr, _hostName);
        friConfiguration.setSendPeriodMilliSec(4);
        FRISession friSession = new FRISession(friConfiguration);
        FRIJointOverlay jointOverlay = new FRIJointOverlay(friSession);

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

        }

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

        // async move with overlay ...
        _lbr.moveAsync(ptp(Math.toRadians(-90), .0, .0, Math.toRadians(90), .0, Math.toRadians(-90), .0)
                .setJointVelocityRel(0.2)
                .addMotionOverlay(jointOverlay)
                .setBlendingRel(0.1)
                );

        // ... blending into sync move with overlay
        _lbr.move(ptp(Math.toRadians(90), .0, .0, Math.toRadians(90), .0, Math.toRadians(-90), .0)
                .setJointVelocityRel(0.2)
                .addMotionOverlay(jointOverlay)
                );

        // done
        friSession.close();
    }

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

}