API review (2011-10-17)

Proposer: John Hsu

Present at review:

• Attendees: Bhaskara, Gil, Ioan, John, Nate, Sachin, Tully

Proposed Robot Dynamics State Description Format

• <model_state>

  • Purpose: This is the root tag that for this document. All information is included in this tag.

  • Elements: <link_state> <joint_state>

  • Attributes:

  • <link_state>

    • Purpose: use this to specify the state of a link in the robot

    • Elements: <id> <time> <frame_id> <pose> <twist> <wrench>

    • Attributes: name is the name of the link

    • <id> unsigned long int

      • Purpose: an unique identifier for this state
      • Elements:
      • Attributes:

    • <time> double

      • Purpose: time stamp in seconds

    • <reference_frame> string

      • Purpose: A string indicating name of another link as the reference frame of states. Keywords inertial or world can be used to reference absolute inertial frame.

      • Elements:
      • Attributes:

    • <pose> 6-tuple

      • Purpose: A 6-tuplet (x,y,z,roll,pitch,yaw) used to specify the pose of a link, relative to the <reference_frame>

      • Elements:
      • Attributes:

    • <twist> 6-tuple

      • Purpose: A 6-tuplet (x,y,z,roll,pitch,yaw) used to specify the twist of a link, relative to the <reference_frame>

      • Elements:
      • Attributes:

    • <wrench> 6-tuple

      • Purpose: A 6-tuplet (x,y,z,roll,pitch,yaw) used to specify the wrench exerted on a link, relative to the <reference_frame>

      • Elements:
      • Attributes:

  • <joint_state>

    • Purpose: use this to specify the state of a joint in the robot

    • Elements: <position> <velocity> <time>

    • Attributes: name is the name of the link

    • <id> unsigned long int

      • Purpose: an unique identifier for this state
      • Elements:
      • Attributes:

    • <time> double

      • Purpose: time stamp in seconds

    • <position> double

      • Purpose: position of the joint
      • Elements:
      • Attributes:

    • <velocity> double

      • Purpose: velocity of the joint
      • Elements:
      • Attributes:

Examples

<model_state name="pr2">
  <link_state name="r_shoulder_pan_link">
    <id>0</id>
    <time>0</time>
    <reference_frame>base_link</reference_frame>
    <pose>0 0 1 0 0 0</pose>
    <twist>0 0 1 0 0 0</twist>
    <wrench>0 0 0 0 0 0</wrench>
  </link_state>
  <link_state name="r_shoulder_lift_link">
    <id>1</id>
    <time>0</id>
    <reference_frame>r_shoulder_pan_link</reference_frame>
    <pose>0 0 0 0 0 0</pose>
    <twist>0 0 0 0 0 0</twist>
    <wrench>0 0 0 0 0 0</wrench>
  </link_state>
</model_state>

<model_state name="pr2">
  <joint_state name="r_shoulder_lift_joint">
    <id>1</id>
    <time>0</id>
    <position>0</position>
    <velocity>0</velocity>
  </joint_state>
</model_state>

<model_state name="my_box">
  <reference_frame>r_shoulder_pan_link</reference_frame>
  <pose>0 0 0 0 0 0</pose>
  <link_state name="my_box0_link">
    <pose>0 0 0 0 0 0</pose>
  </link_state>
  <link_state name="my_box1_link">
    <pose>0 0 0.5 0 0 0</pose>
  </link_state>
</model_state>

Question / concerns / comments

• Attendees: Bhaskara, Gil, Ioan, John, Nate, Sachin, Tully
• Scope: Is this the corresponding state information description format (for URDF)? or is this more generic.
  • YAML? other *ML? (we should not restrict ourselves to either)
    • specification only, this should be format independent

• Is top level tag name: <model_state> appropriate? alternatives are <robot> or <state> or ... (model_state)

  • <model_state> is fine. add <frame> parallel to <model_state>

• Is <id> necessary?

  • (no, move to the meta-data of the model_state)

• <time>

  • (no, move out to meta-data of model_states)
• How to represent diff states?
  • (should be outside in meta-data).

• Determine optional vs. required for each element & attribute. Determine default values for each element & attribute.

  • will do online

• Is <joint_state> necessary?

  • yes
  • up to user to keep thing consistent
  • position/velocity should be vectors
  • add torque (measured torque)

• Default reference frame of each link state is its parent. Is <reference_frame> necessary?

  • yes, move under <model_state>

• gil: is a collection of model_states sufficient to describe a scene?
  • yes, it should be.
• think about adding twist reference point and wrench reference point?
  • leave out until needed.
• consider other simulation? vehicles, air traffic
  • out of scope for now. current state information focused on mobile manipulator robots that can be represented in URDF.
• john: write out conclusions, next round will be emailed.

Comments

• Ioan: I think <id> should be at the model level

Proposal: Rev 2

Option 1

• <world_state>

  • Purpose: This is the root tag that for this document. All information is included in this tag.

  • Elements: <frame> <model_state>

  • Attributes: name

  • name string

    • Purpose: A unique name of the world state

  • <model_state>

    • Purpose: This is the root tag that for this document. All information is included in this tag.

    • Elements: <frame> <link_state> <joint_state>

    • Attributes: name

    • name

      • Purpose: Name of the model

    • <frame>

      • Purpose: Contains a reference to the parent frame

      • Elements: <parent> <pose> <twist>

      • Attributes:

      • <parent> string

        • Purpose: A string indicating frame name or name of another model_state to be the reference frame of these states. Keywords world can be used to reference absolute inertial frame. If left empty, default is world

        • Elements:
        • Attributes:

      • <pose> 6-tuple

        • Purpose: A 6-tuplet (x,y,z,roll,pitch,yaw) used to specify the pose of a link, relative to the parent frame of the <model_state>.

        • Elements:
        • Attributes:

      • <twist> 6-tuple

        • Purpose: A 6-tuplet (x,y,z,roll,pitch,yaw) used to specify the twist of a link, relative to the <origin> of

        • Elements:
        • Attributes:

    • <link_state>

      • Purpose: use this to specify the state of a link in the robot

      • Elements: <pose> <twist> <wrench>

      • Attributes: name

      • name

        • Purpose: Name of the link

      • <pose> 6-tuple

        • Purpose: A 6-tuplet (x,y,z,roll,pitch,yaw) used to specify the pose of a link, relative to the frame of the <model_state>.

        • Elements:
        • Attributes:

      • <twist> 6-tuple

        • Purpose: A 6-tuplet (x,y,z,roll,pitch,yaw) used to specify the twist of a link, relative to the <origin> of the link

        • Elements:
        • Attributes:

      • <wrench> 6-tuple

        • Purpose: A 6-tuplet (x,y,z,roll,pitch,yaw) used to specify the wrench exerted on a link, relative to the <origin> of the link

        • Elements:
        • Attributes:

    • <joint_state>

      • Purpose: use this to specify the state of a joint in the robot

      • Elements: <positions> <velocities> <torques>

        • Attributes: name

        • name

          • Purpose: Name of the joint

      • <positions> double[]

        • Purpose: array of positions of the DOF's of the joint
        • Elements:
        • Attributes:

      • <velocities> double[]

        • Purpose: array of velocities of the DOF's of the joint
        • Elements:
        • Attributes:

      • <torques> double[]

        • Purpose: array of torques measured for each DOF of the joint
        • Elements:
        • Attributes:

  • <frame>

    • Purpose: Frame of reference relative to global frame or anth

    • Elements: <pose> <twist> <parent>

    • Attributes: name

    • name string

      • Purpose: Name of this frame

    • <parent>

      • Purpose: Name of the parent frame or model_state
      • Elements:
      • Attributes:

    • <pose> 6-tuple

      • Purpose: A 6-tuplet (x,y,z,roll,pitch,yaw) used to specify the pose of a link, relative to the frame of the <model_state>.

      • Elements:
      • Attributes:

    • <twist> 6-tuple

      • Purpose: A 6-tuplet (x,y,z,roll,pitch,yaw) used to specify the twist of a link, relative to the <origin> of the link

      • Elements:
      • Attributes:

Option 2

• <world_state>

  • Purpose: This is the root tag that for this document. All information is included in this tag.

  • Elements: <frame> <model_state>

  • Attributes:

  • <model_state>

    • Purpose: This is the root tag that for this document. All information is included in this tag.

    • Elements: <parent> <pose> <twist> <link_state> <joint_state>

    • Attributes: name

    • name

      • Purpose: Name of the model

    • <parent> name

      • Purpose: A string indicating frame name or name of another model_state to be the reference frame of these states. Keywords world can be used to reference absolute inertial frame. If left empty, default is world.

      • Elements:
      • Attributes:

    • <pose> 6-tuple

      • Purpose: A 6-tuplet (x,y,z,roll,pitch,yaw) used to specify the pose of a link, relative to the <parent> frame.

      • Elements:
      • Attributes:

    • <twist> 6-tuple

      • Purpose: A 6-tuplet (x,y,z,roll,pitch,yaw) used to specify the twist of a link, relative to the <parent> frame.

      • Elements:
      • Attributes:

    • <link_state>

      • Purpose: use this to specify the state of a link in the robot

      • Elements: <pose> <twist> <wrench>

      • Attributes: name

      • name

        • Purpose: Name of the link

      • <pose> 6-tuple

        • Purpose: A 6-tuplet (x,y,z,roll,pitch,yaw) used to specify the pose of a link, relative to the frame of the <model_state>.

        • Elements:
        • Attributes:

      • <twist> 6-tuple

        • Purpose: A 6-tuplet (x,y,z,roll,pitch,yaw) used to specify the twist of a link, relative to the <origin> of the link

        • Elements:
        • Attributes:

      • <wrench> 6-tuple

        • Purpose: A 6-tuplet (x,y,z,roll,pitch,yaw) used to specify the wrench exerted on a link, relative to the <origin> of the link

        • Elements:
        • Attributes:

    • <joint_state>

      • Purpose: use this to specify the state of a joint in the robot

      • Elements: <positions> <velocities> <torques>

        • Attributes: name

        • name

          • Purpose: Name of the joint

      • <positions> double[]

        • Purpose: array of positions of the DOF's of the joint
        • Elements:
        • Attributes:

      • <velocities> double[]

        • Purpose: array of velocities of the DOF's of the joint
        • Elements:
        • Attributes:

      • <torques> double[]

        • Purpose: array of torques measured for each DOF of the joint
        • Elements:
        • Attributes:

  • <frame>

    • Purpose: Frame of reference relative to global frame or anth

    • Elements: <pose> <twist> <parent>

    • Attributes: name

    • name string

      • Purpose: Name of this frame

    • <parent> name

      • Purpose: A string indicating frame name or name of another model_state to be the reference frame of these states. Keywords world can be used to reference absolute inertial frame. If left empty, default is world.

      • Elements:
      • Attributes:

    • <pose> 6-tuple

      • Purpose: A 6-tuplet (x,y,z,roll,pitch,yaw) used to specify the pose of a link, relative to the parent frame or the parent <model_state>.

      • Elements:
      • Attributes:

    • <twist> 6-tuple

      • Purpose: A 6-tuplet (x,y,z,roll,pitch,yaw) used to specify the twist of a link, relative to the <origin> of the link

      • Elements:
      • Attributes:

Example

Option 1:

<world name="world_1">
  <model_state name="pr2">
    <frame>
      <parent>odom</parent>
      <pose>0 0 0 0 0 0</pose>
      <twist>0 0 0 0 0 0</twist>
    </frame>
    <link_state name="r_shoulder_pan_link>
      <pose>1 0 1 0 0 0</pose>
      <twist>0 0 0 0 0 0</twist>
      <wrench>0 0 0 0 0 0</twist>
    </link_state>
  </model_state>
  <frame name="odom">
    <parent>world</parent>
    <pose>0 0 0 0 0 0</pose>
    <twist>0 0 0 0 0 0</twist>
  </frame>
</world>

Option 2:

<world name="world_1">
  <model_state name="pr2">
    <parent>odom</parent>
    <pose>0 0 0 0 0 0</pose>
    <twist>0 0 0 0 0 0</twist>
    <link_state name="r_shoulder_pan_link>
      <pose>1 0 1 0 0 0</pose>
      <twist>0 0 0 0 0 0</twist>
      <wrench>0 0 0 0 0 0</twist>
    </link_state>
  </model_state>
  <frame name="odom">
    <parent>world</parent>
    <pose>0 0 0 0 0 0</pose>
    <twist>0 0 0 0 0 0</twist>
  </frame>
</world>

Conclusion

Package status change mark change manifest)

• Action items that need to be taken.

• Major issues that need to be resolved