# Tag Info

6

Please see this bug ticket: https://code.ros.org/trac/ros/ticket/3691 I filed this bug report (with patch to fix) 13 months ago and am pretty disappointed in the ROS team that they have not put this in trunk.

6

You can follow the example code here and simply add a second subscription like so: import rospy from std_msgs.msg import String def callback1(data): rospy.loginfo("Callback1 heard %s",data.data) def callback2(data): rospy.loginfo("Callback2 heard %s",data.data) def listener(): rospy.init_node('node_name') rospy.Subscriber("chatter1", ...

4

It's really easy. env = openravepy.Environment() env.StopSimulation() env.Load('_ArmFileName'_.xml') #Whatever .xml file you're using robot = env.GetRobots()[0] manip = robot.SetActiveManipulator('left_arm') #whatever arm you're using robot.SetDOFValues(joint_values, manip.GetArmIndices()) env.CheckCollision(robot) where joint_values is the an array of the ...

4

This has been merged as of six weeks ago: https://github.com/ros/ros_comm/commit/8a1f92fc0c888099fe47005f609883601b7d8d72#diff-1

4

I suspect that your Arduino is reseting, by the fact that the stall current of the motor by the product sheet is $800mA$, and you are using the USB power, then Arduino regulator, to supply the motor. As you are using the USB/Serial converter to make the connection to the Raspberry Pi, when it resets, it can be creating a new "virtual" serial port on the ...

4

There are a couple libraries for doing what you want to to, the first is pyMAVlink and the second is dronekit-python it is going to be easiest to use dronekit as it handles a lot of the lower level stuff like processing incoming packets and connecting over your preferred interface for you automatically. I assume you want to load waypoints from a file and ...

4

If you make a career of robotics, you will come in contact with a lot of languages, a lot of libraries, and a lot of systems. The more you know about the fundamentals, the easier it will be to adjust to something new. Likewise, if you focus your learning on whatever project or context is relevant to you at any given moment, it's more likely to stick with ...

3

You can use both! ROS nodes can be written in python. I'm doing a similar project and the reusability of ros code is a nice thing to have in mind. ROS also have many things already implemented (even that you want to build everything from scratch). The message types of ROS will also provide an easier to integrate application, for future projects and ...

3

If you understand how relative pose estimation works in theory, it should be quite trivial to translate it into OpenCV code. First, you can pick any feature detection/description approach you like (say SIFT and brute force matching) and obtain a list of matches. But here, you need to be absolutely sure there is overlap between the images: because without ...

2

I hope you have already done Armature creation. If not you need to do that first. Components in MORSE are either robots, sensors or actuators. Robots are mainly containers for sensors and actuators. Assuming you already have an initial simulation environment called mysim, you can create a new sensor with: \$ morse add sensor <name> mysim or, for ...

2

2

Setting up the software to extract new custom sensor data via MAVLink seems to be harder than it should be. Step one is to make the quadcopter send off the data. First, you need to define a new MAVLink message type using XML in mavlink/message_definitions. You can just make up a new unused integer for the message_id. Second, you generate the message ...

2

If you are just starting out with quadcopters, it might be better if you buy an off-the-shelf quadcopter first. Then hack it for your needs while learning the ropes. (i.e. you wouldn't build a car, bike, computer, etc. from scratch if you've never taken one apart, hacked it, and completely understand what every piece is for. so why do this with a robot?) ...

2

It looks like openinterface.py itself is not easily found anymore, but you can probably use instead pyrobot, which is based on openinterface.py. Pyrobot is an interface for Roomba and Create 1, not Create 2, but it should be easy to adapt it to work with the Create 2. The default baud rate needs to be changed from 57600 to 115200, and there are a few ...

2

The VisiLibity implementation appears to have python bindings.

2

I'm having a hard time following your code, partly because I don't know Python but I think mostly because I'm not sure I understand your variables. That said, I think I do understand your problem. An approach I would take to solve this would be to "warp" the data before evaluation, then make your decisions, then "de-warp" the output. For example, consider ...

2

This is how I do it: # return True if in collision, False if no collision # pass in joint angles q to test configuration other than current def inCollision(q=None): with env: if q == None: return env.CheckCollision(robot) or robot.CheckSelfCollision() else: initq = robot.GetDOFValues() robot....

2

The answer Specifically, the arguments to this jacobian are the state of the robot. The reason It is the jacobian of the measurement function with respect to the landmark state. If you knew the state of the robot and landmark, what function would you use to predict what the measurement would be? If you have a range sensor, it would be the distance ...

2

if __name__ == '__main__': doesn't matter at here (in the second code), also you could run your code without it like here: Second code: . . . # MAIN try: process() except rospy.ROSInterruptException: pass i.e. when you don't want your code to run when it imported in another python code, you should use if __name__ == '__main__': More ...

1

The movement you are seeing is what I would expect to see if your ground was rising becouse of current draw. Basically as you turn on more servos you will see there current draw will make the apparent voltage drop and the pulses for PWM grow more indistinct, digital servos will generally still work ok but analog servos like you have will stutter as you show. ...

1

This looks similar to this problem, where the user was missing qt5-base. (added this as an answer to make the community bot happy)

1

The choice of motors is a trade off between cost/power/ease of implementation/etc. that only you can make. But hobby servos like you linked to are a common choice for low-cost, low-power, hobby arms. Simple max-torque calculations for a robot arm are pretty straight forward. (This is a simple tutorial). But there are a few online calculators to help: [1],...

1

You must use one matrix, because you must manage the cross covariances. The best way to add a landmark is to expand the matrix, by copying it into a larger one (with two extra rows for x,y and two extra columns for the same). Then, you have to initialize all the off-diagonal terms using the jacobian matrix. Similarly, the state vector must be expanded to ...

1

I've addressed your first two questions below. Firstly, does the inverse sensor model have to compute range and bearing, as opposed to cartesian coordinates? Why is this approach used? Given your current state (which includes the pose of the robot and the position of the landmarks), the inverse sensor model predicts what the observation should be. In ...

1

I found out what was wrong. The pdf I linked (as well as many others) state that you need to multiply your inverse jacobian matrix by a step x/y/z distance, but that results in an infinite loop. Multiplying the inverse jacobian matrix by the overall change in distance from x/zcurrent to the goals made the python code work smoothly. I'll keep this question up ...

1

The (inverse) Jacobi Matrix is pose dependent. It is not constant, it is dependent on pose (joint angles or TCP coords, based on formulation) and so it characterizes a pose not a robot. By implementing it as a constant you basicly assume that the same joint velocity will always cause the same TCP velocity. In reality it is clear that joint positions play an ...

1

The program shown below illustrates two ways of determining result size, and a method that reads the right number of bytes to combine. The first method suggested in the program below is to define singleSet, a set containing the packet numbers of sensors that return single-byte results. [The function resultSize() as shown uses return ord(sizesList[sensor]) -...

1

Many of the sensors send data in 2 bytes and I need a way to make sure that it is combined automatically. Robb, I have been working on a project and have faced a similar problem. The best way that I have found to combine individual bytes has been to use bit shifting to concatenate the bytes into a single variable. I am using Arduino to interface with the ...

1

I think you have a number of errors: Your R matrix is the covariance of the measurement. You are using a diagonal matrix which is fine. The elements along the diagonal should be the variance of each input variable. It looks like you are passing a deviation instead. You would need to square those values to turn them into variances. Your Jacobians look ...

1

Have you figured out yet that these two devices use incompatible protocols?: Pololu Mini Maestro 18-Channel USB Servo Controller https://www.pololu.com/product/1354 Pololu 8-channel Micro Serial Servo Controller https://www.pololu.com/product/207 I'm guessing that you're using a Pololu Mini Maestro 18-Channel USB Servo Controller, connected to UART1 of a ...

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