The RobotEditor is a modelling tool that allows to easily create models of scientific robots. It has been moved from Github to GitLab recently.
- Geometric modeling: The modelling of new robots requires a tool that excels in modeling of the geometrical components (i.e. meshes).
- Semantic modeling: Even more important is the ability to allow the description of semantic properties of the robot manipulator, such as the definition of kinematic chains or rigid body dynamics parameter.
Blender: The plguin has been developed under version 2.69 and it is hence required to at least use this version (Download it here: http://www.blender.org/download/).
After cloning/downloading the plugin from the Github repository, copy the (unzipped) folder containing all the RobotEditor files to /.../Blender/2.69/scripts/addons. Then open Blender and navigate to the Addons tab
located in File -> User Preferences. Find RobotEditor in the list and activate the plugin by checking the checkbox in the top right corner.
Now the User Interface of the plugin can be found at the bottom of the toolbar on the left side of the 3D View (expand the toolbar by clicking the (+) in the top left corner).
Tip: If you don't want to activate the plugin on every start-up of Blender, click the Save User Settings button in the bottom left corner of the User Preferences window after activating it for the first time.
The RobotEditor differentiates between the semantic properties of a robot (that is its kinematics and optionally visual markers and physical properties) and the actual visualization of the robot (which is defined through meshes for the individual links).
The first step is to create the kinematics representation of a robot. The plugin aggregates the kinematics within a so called Armature object. The Select Armature menu allows to create a new Armature by choosing the New list entry. This list will also contain all previously defined kinematic chains.
A newly created Armature will appear at the current position of the 3D pointer in the 3D View. Additionally, a Bone object is created. Bone objects represent the reference frames through which a kinematic chain is defined and the actual joint configuration of the joint within this reference frame. All Bone functionality can be found in the Bones tab of the RobotEditor.
By convention, the tail of a bone is located in the actual point origin of the reference frame while the head points at the direction of the local y-axis (and thus, is perpendicular to the x-z plane).
Transformations of Bones from parent reference frames can be defined in two ways:
- Euler mode: the transformation is defined through three translations along the local axes and three rotations (around the local x-axis, around the resulting new local y'-axis and finally around the resulting new local z''-axis)
- DH mode: the transformation is defined through two rotations and two rotations according to the Denavit-Hartenberg convention
Joints always represent one Degree of Freedom and can either be revolute(rotational) or prismatic(translational). By selecting the active axis, the joint type and value, offset, minimum and maximum, the configuration of a joint can be set.
New children Bones can be created by clicking on the Create new child bone button.
The hierarchy of the kinematic chain can be seen in the Outliner which can be found in the top right corner of the Blender User Interface.
Tip: If parts of the User Interface of the RobotEditor seem to have disappeared from the toolbar, make sure to re-select an Armature by right-clicking on it in the 3D View or left-clicking in the Outliner or by selecting it from the Armature drop-down menu in the toolbar. Also, always return back to either Object Mode or Pose Mode if you should accidentally or intentionally end up in Edit Mode before further interacting with the RobotEditor interface.
Tip: To better visualize the location and orientation of the reference frame defined by a Bone object, change the Interaction mode from Object Mode to Pose Mode and change the Transformation orientation from Global to Local.
Tip: Bones can be either selected through the Active Bone drop-down menu in the RobotEditor toolbar or by left-clicking on them in the Outliner.
Tip: To create spherical joints, create three Bones within the same position but with different active axes to account for the three Degrees of Freedom of a spherical joint.
After the kinematic representation of the robot has been defined, meshes of the individual links have to be assigned to the respective Bones. By doing so, the mesh's position and orientation is made dependent of the Bone it is assigned to and thus, moves along accordingly when the joint configuration of the Bone is changed.
This can be done in the Meshes tab of the RobotEditor. To assign a mesh to a Bone, select the respective mesh from the Select mesh drop-down menu. Afterwards, select the Bone the mesh belongs to and click on Assign selected mesh to active bone. The mesh is now assigned to the bone.
Tip: Multiple meshes can be assigned to the same Bone.
Tip: To link the visualization of a spherical joint to its kinematics, assign the respective mesh to the thrid Bone of the sub-chain that defines the kinematics of a spherical joint.