Andreas Hermann's profile - activity

Just to see, if I get this right: I will NOT be able to have a hardware_interface for my device A and another hardware_interface for my device B and have them controlled in sync by one single trajectory controller? So I have to aggregate ALL different drivers (CANOpen, Serial, ...) in one interface?

Hi everyone!

we implemented a ros_control HW-Interface for our robot arm and added the joint_limits_interface. Now, if I use a position_controllers/JointPositionController to move the arm, the angles and velocities seem to be limited correctly, but acceleration limits are completely ignored. Do I miss something?

By looking into the code of joint_limits_interface.h I assume, that there is no acceleration limiter when using a postion controller? Am I right? Only in velocity control?

If so, a little hint in the (otherwise great) documentation would be nice (:

Thanks, Andreas

I answer my own question, showing my solution how to pipe message data via Qt SIGNALS and SLOTS, which hopefully helps others. So after initializing the plugin, I subscibe to a toppic with a custom message type, and in the message callback I just emit a SIGNAL carrying the whole message. In the according SLOT I then update the UI Widgets with the message data. I had to use the most basic PyQt_PyObject as data format to transfer my custom message type.

def __init__(self, context):
    foo()
    bar()
    and_so_on()

    self.sub = rospy.Subscriber('monitoring_result', MyMessageType, self.monitoringCallback,  queue_size=1)
    self.connect(self, SIGNAL("changeUI(PyQt_PyObject)"), self.monitoringSlot)

def monitoringCallback(self, data):
    self.emit(SIGNAL("changeUI(PyQt_PyObject)"), data)

def monitoringSlot(self, data):
    self._widget.lcdGoalID.display(data.current_trajectory + 1)
    self._widget.progressBar.setValue(data.max_num_collisions)
    self._widget.progressBar.setRange(0, data.coll_threshold)

    p = self._widget.palette()
    self._widget.setAutoFillBackground(True);
    if data.severe_collision:
        p.setColor(self._widget.backgroundRole(), Qt.red)
    else:
        p.setColor(self._widget.backgroundRole(), Qt.green)
    self._widget.setPalette(p)

Hi everyone,

while writing a RQT plugin I had a hard time to figure out, how to connect a rospy callback to a PyQt SLOT in order to update the UI in a correct way.

The ROS WIKI only tells you, that one should not directly modify Widgets in a callback, due to Thread-Safety but lacks an example... So I propose to add a link to an example plugin in the Wiki which shows how to connect a ROS callback to a qt SLOT and update widgets (unfortunately I don't know one).

Can someone point out a good plugin code as an example?

Thanks, Andreas