Origin

The origin point in different robot arms tends to vary between manufacturers. To have truly plug and play arms, we need common ground on this. Thats is why the first thing the user should do is to calibrate the origin and apply the necessary corrections through parameters.

Although the robots are totally different (surely your robot is not identical to those described in the images), take the general structure of the arms into account. The following figure shows where the origin should be placed on different arm configurations:

Mandatory topics

x = the front (in case of not being well defined the front of the robot will be taken as the front the user sees more appropriate)

As the image shows, these configurations can be generalized in three different groups:

  • Articulated, Scara, Cylindrical, Spherical: they all start from a base from which the whole robot has been built.
  • Cartesian: a robot that moves by rails, usually based on linear servo motors. Once the front is defined, the origin will be placed in the left rear part. The z-axis will be positive in the direction of the workspace. In case the workspace is in both directions (up and down) the positive will be down. The bridge canes are categorized like cartesian robots.
  • Parallel: the origin is placed in the center of the base, and the z-axis will look towards the end effector.

In case of placing the robot in another direction (for example, hanging it from the ceiling instead of fixing it on the ground) the axes will rotate with the robot.

The manufacturer explains where the origin of the robot is (and how it differs from the definition above), so you have to change the origin though parameters.

change origin

Mandatory Parameter Value Unit Description
x_angle_y_direction - rad Turn the X axis in the direction where the Y axis is
x_angle_z_direction π/2 rad Turn the X axis in the direction where the Z axis is
y_angle_x_direction - rad Turn the Y axis in the direction where the X axis is
y_angle_z_direction π/2 rad Turn the Y axis in the direction where the Z axis is
z_direction false true/false T: the z-axis direction is fine | F: reverse direction
x_position -0.22 m X axis position according to the marked origin
y_position -0.34 m Y axis position according to the marked origin
z_position 0.0 m Z axis position according to the marked origin

Take into account that the first value affects the following ones