ros-simple-examples

Some ROS code examples for the Fetch and HSR. Some of the code will be robot-agnostic. I'll test in simulation and hopefully it's just a toggle to figure out which robot to use, plus a list of the appropriate robot's ROS topic names.

Versions:

• Fetch: Ubuntu 14.04, Ros Indigo
• HSR: Ubuntu 14.04, Ros Kinetic (though really we should use 16.04)
• Python 2.7.6, :(

I'm sure there's a better way to manage versions, but I simply use one machine with 14.04 and switch between Fetch and HSR code by switching their ordering in my .bashrc file manually. Bleh.

Examples:

• arm: Adjust Fetch's arm.
• base: Adjust Fetch and HSR base.
• camera: Processes the Fetch and HSR camera images.
• gripper: Adjust Fetch's gripper.
• head: Adjust Fetch's head.
• torso: Adjust Fetch's torso.

There are also topics for the robots listed in topics. However, these might be dependent on what kind of launch file we used for the simulator?

TODOs and Questions

• Get joint state reader set up in an easy fashion, i.e., physical robot goes to a point, and then we extract the Cartesian position and such.

  • Looks like the solution is here.

• Figure out why we group ros topics into those with cancel, feedback, goal, result, and status topics. I think these form an "action interface," but I'd like to know deeply.

  • Update: somewhat answered in the HSR docs.

• Figure out movement of the Fetch's arm in detail, and understand MoveIt.

  • Or, could we use the inverse kinematics method from the arm/arm.py code? Because then that gives us joint angles, and we can call that on the robot. Should this be an alternative to MoveIt?

• (Lower priority?) Use HSR code examples in the case of when Fetch's motion requires MoveIt, for compatibility with our existing HSR code base.

Robots

Here is some additional information about the robots we have.

Fetch

See the docs for details on the joint angles. For the Fetch, with the Gazebos simulator running in the background, I get this from echo-ing the /joint_states ros topic:

daniel@daniel-ubuntu-mac:~/ros-simple-examples/states$ rostopic echo -n 1 /joint_states 
header: 
  seq: 2502
  stamp: 
    secs: 25
    nsecs:  74000000
  frame_id: ''
name: ['l_wheel_joint', 'r_wheel_joint', 'torso_lift_joint', 'bellows_joint', 'head_pan_joint', 'head_tilt_joint', 'shoulder_pan_joint', 'shoulder_lift_joint', 'upperarm_roll_joint', 'elbow_flex_joint', 'forearm_roll_joint', 'wrist_flex_joint', 'wrist_roll_joint', 'l_gripper_finger_joint', 'r_gripper_finger_joint']
position: [0.0904709937685535, -0.13369708805940572, -2.1922572375654923e-08, 0.00663651940159223, 0.001038524967845511, 0.0023006007164765307, 1.320004990825269, 1.3999840248157627, -0.19984345342595944, 1.71997015957281, 3.2424016920273857e-06, 1.6600004833253479, -1.3478056999360888e-06, 0.04986168604674154, 0.04989492635705342]
velocity: [1.0627606486403384e-05, 0.0013527573505002295, 5.7977575865534834e-05, -4.450639518941297e-05, -0.0013211152971605432, 0.001643271318197307, -0.0003535670947248451, -0.00019485233294148, 0.00013064563488349577, -0.0001666420730967442, -0.0003557676420180161, 0.00014203296699294974, 0.00021448259548277236, -0.008826693605311384, -0.0088349170683755]
effort: [0.0, 0.0, 0.0, -1.6580199308398567, -0.0015118692770609578, -0.07394783544888785, -0.03427439973805562, 11.822129377258655, -0.7697657524232971, 18.351679878283072, 0.2756228700101902, -0.3805430747091004, -0.02469191997828887, 10.033240310311884, 9.966759689688116]
---

In easier-to-read form, the joint names are:

// Wheel, torso
'l_wheel_joint', 
'r_wheel_joint', 
'torso_lift_joint', 
'bellows_joint',  // actually I can't find this in docs!!

// For the head
'head_pan_joint', 
'head_tilt_joint', 

// These are the 7DOF arm joints.
'shoulder_pan_joint',
'shoulder_lift_joint', 
'upperarm_roll_joint', 
'elbow_flex_joint', 
'forearm_roll_joint', 
'wrist_flex_joint', 
'wrist_roll_joint',

// Finally, the gripper
'l_gripper_finger_joint', 
'r_gripper_finger_joint',

HSR

For the HSR, the joint states are:

daniel@daniel-ubuntu-mac:~/ros-simple-examples/states$ rostopic echo -n 1 /hsrb/joint_states 
header: 
  seq: 147
  stamp: 
    secs: 175
    nsecs: 636000000
  frame_id: ''
name: ['arm_flex_joint', 'arm_lift_joint', 'arm_roll_joint', 'base_l_drive_wheel_joint', 'base_r_drive_wheel_joint', 'base_roll_joint', 'hand_l_spring_proximal_joint', 'hand_motor_joint', 'hand_r_spring_proximal_joint', 'head_pan_joint', 'head_tilt_joint', 'wrist_flex_joint', 'wrist_roll_joint']
position: [-9.120342727531039e-05, 0.01637693306919232, -1.5700004646044103, -5.950544798150048e-05, -1.861907801536944e-05, 9.602650967721615e-07, 0.00015512160125652485, -3.5844492282777196e-05, 0.00016245653104984825, 2.974513302334003e-07, 0.0009638909841056531, -1.5731330858686743, -5.8117104977384315e-05]
velocity: [9.180129606437106e-05, 0.007555368244559862, 0.00031475762415357614, -0.0013761978010660126, 0.0014498472922710932, 0.0006561699685778806, 0.00456957118478556, 5.528347479977406e-05, 6.169668895067484e-05, 4.669170088413178e-05, -9.264681426704654e-05, -0.00013081460253357293, -9.149466419448049e-05]
effort: [0.18621821422218382, 55.08541747733215, 0.0010732245617894253, -0.039412425624447765, 0.04216265206354866, 0.17697903979233284, 0.0, 0.0, 0.0, -0.005823677186356235, -1.156852470296954, 2.8196592257856423, 0.05220894967870038]
---

There are some similar joint names, so that's good. Here's a sketch of a possible grouping.

// Arm and wrist
'arm_flex_joint', 
'arm_lift_joint', 
'arm_roll_joint',
'wrist_flex_joint', 
'wrist_roll_joint'

// The base
'base_l_drive_wheel_joint', 
'base_r_drive_wheel_joint', 
'base_roll_joint',

// The hand (i.e., gripper)
'hand_motor_joint',
'hand_l_spring_proximal_joint',
'hand_r_spring_proximal_joint',

// The head
'head_pan_joint',
'head_tilt_joint',

If we consider the two hand proximal joints as part of the "arm" then I assume we can call this 7DOF? Not entirely sure.

See the HSR core repository and files such as the sensors.py for information on how to deal with sensors. That one has joint states.