Controlling Baxter robot using HTC Vive

asked 2018-07-16 13:17:36 -0500

flightlesskite gravatar image

Hi

I'm very new to ROS & robotics in general so any help/advice/videos are welcome! I am currently trying to accurately map controller movements (from a HTC Vive device) to a Baxter robot. I only have access to a Linux Ubuntu 16.04 machine so any projects requiring Windows I have probably already tried but failed. However, I suspect what I am trying to achieve is not so far off.

Now I have adapted some code I found online & found a way to extract pose data from the controllers, this is my publisher. I will post the code at the end just in case. But basically running rostopic echo /topicname allows me to see the x, y, z points and qx, qy, qz, qw co-ordinates. It seems to be right but how can I double check that these co-ordinates are accurate?

My second question involves the actual mapping to Baxter. I'm struggling to find resources to learn about how mapping actually works. I've gone through the ROS tutorials & read a lot about the IK services that Baxter offers. I assume that is what I need. I know I will need to create a subscriber (possibly 2) for each controller. But I'm still very misty on the process of actually using the Pose data (x ,y, z & quaternions) & how this is used to map the position for the Baxter robot. Can anyone point me in the right direction of what steps I should be taking? or any resources online is appreciated too. Thank you!

Code for controllers: (I've also got a main.py script which imports from this & creates a HTCViveTracking using a vr system object accessed through openvr)

#!/usr/bin/env python

import math

# OpenVR package
import openvr

# ROS packages
import rospy
import tf

# ROS messages
from sensor_msgs.msg import Joy
from geometry_msgs.msg import Point, Pose, Quaternion

# Constants
topic_name = "openvr"

# --- adapted from triad_openvr --- #
#Convert the standard 3x4 position/rotation matrix to a x,y,z location and the appropriate Quaternion
def convert_to_quaternion(pose_mat):
    # Per issue #2, adding a abs() so that sqrt only results in real numbers
    r_w = math.sqrt(abs(1+pose_mat[0][0]+pose_mat[1][1]+pose_mat[2][2]))/2
    r_x = (pose_mat[2][1]-pose_mat[1][2])/(4*r_w)
    r_y = (pose_mat[0][2]-pose_mat[2][0])/(4*r_w)
    r_z = (pose_mat[1][0]-pose_mat[0][1])/(4*r_w)

    x = pose_mat[0][3]
    y = pose_mat[1][3]
    z = pose_mat[2][3]
    return [x,y,z,r_w,r_x,r_y,r_z]

def openvr_state_to_ros_joy(pControllerState, timestamp, device_name):
    """ 
    Converts an OpenVR pControllerState (https://github.com/ValveSoftware/openvr/wiki/IVRSystem::GetControllerState)
    for the HTC Vive Controller (https://docs.unity3d.com/560/Documentation/Manual/OpenVRControllers.html)
    to a 
    ROS Joy MSG (http://docs.ros.org/api/sensor_msgs/html/msg/Joy.html)
    """

    # See http://docs.ros.org/api/sensor_msgs/html/msg/Joy.htm
    joy_msg = Joy()

    # Standard ROS header msg http://docs.ros.org/api/std_msgs/html/msg/Header.html
    joy_msg.header.frame_id = device_name
    joy_msg.header.stamp = timestamp

    # the x axis ...
(more)
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Comments

This is asking a lot of different things. As to the visualizing of the poses, rviz is the best thing to use for that. And if you are doing VR work, you may want to check out a ROS VR project like vrviz which can visualize the robot in VR as well as control it.

john.j.oneill gravatar imagejohn.j.oneill ( 2018-09-19 04:53:42 -0500 )edit