KUKA robot base coordinate measurement

The base coordinate measurement of the KUKA robot is implemented by determining a specific reference system in the robot’s workspace. This process includes teaching using the three-point method, that is, defining the origin of the base coordinate system and the directions of the X and Y axes by moving the tool center point (TCP) to three specific positions. In addition, there are other methods such as indirect method and digital input method to complete the setting of the base coordinates.

The base coordinate system measurement of KUKA robot is crucial. First, ensure the robot is in a stable position. Then, use appropriate measuring tools like a laser tracker. Mark reference points on the base. Measure the distances and angles between these points relative to a known global reference. Precise measurements help accurately define the robot’s base position, enabling better path planning and operation.

1. Base coordinates
   The base coordinate system is a freely definable, user-defined coordinate system that describes the position of the base coordinate system in the world coordinate system. The robot tool can move according to the coordinate direction of the base coordinate system. The base coordinate system can be measured individually and can often be adjusted along the edge of the workpiece, the workpiece support or the pallet. As long as the base coordinate system is known, the movement of the robot can always be predicted.
   Base coordinate system determination means creating a coordinate system at a certain position around the robot based on the world coordinate system, with the purpose of making the robot’s manual operation movement and programmed position refer to this coordinate system. Therefore, the edges of the workpiece support and drawer, the outer edge of the pallet or the machine can be used as reasonable reference points in the base coordinate system.
2. Base coordinate measurement method    The origin and coordinate direction of the base coordinate system can be determined by the 3-point method, the indirect method or direct digital input.
   (1) 3-point method
   Teach 3 points, namely the origin of the coordinate system, 1 point in the X-axis direction, and 1 point on the XY plane. When measuring the base coordinates using the 3-point method, the 3 points are not allowed to be on a straight line, and the angle between these points must be no less than 2.5°.
   (2) Indirect method    When it is impossible to approach the origin of the base, for example, because the point is inside the workpiece or outside the robot workspace, the indirect method must be used. At this time, 4 points whose coordinate values ​​(CAD data) are known relative to the base coordinate to be measured must be approached, and the robot control system will calculate the benchmark based on these points. Therefore, the indirect method teaches 4 points, namely the starting point parallel to the X-axis of the coordinate system, 1 point in the X-axis direction, 1 point on the O-XY plane, and the origin of the coordinate system.
   (3) Digital input
   Directly input the distance (X, Y, Z) and angle (A, B, C) to the world coordinate system. It should be noted that the three measuring points are not allowed to be located on a straight line when measuring with the three-point method. There must be a minimum angle between these points (the standard setting is 2.5°)
3. The significance of base coordinate measurement
   (1) Can move along the edge of the workpiece
   (2) Can be used as a reference coordinate system
   Changing the reference coordinate system does not require repeated programming for the trajectory of the same workpiece.
   (3) Correction/shift of the coordinate system    If the base coordinate system is offset, the trajectory that has been taught will move with it and will not change due to the offset.
   (4) Multiple base coordinate systems can be used simultaneously    KUKA robots can establish up to 32 different coordinate systems, and multiple base coordinate systems can be used in one program.
4. Three-point method base coordinate determination steps
   Prerequisites:

• Operation mode T1
• User authority: Expert mode (KUKA main menu – Configuration – User group – Expert – Login – Password kuka)
• Deselect program (R is gray) Operation steps:
  (1) Select the main menu in the teach pendant – Select Start – Measurement – Base coordinate system – 3 points.
  (2) Assign a number and a name to the base coordinate, and confirm with the [Continue] key.
  (3) Enter the number of the tool whose TCP is to be used to measure the base coordinate, and confirm with the [Continue] key.
  (4) Move the TCP to the origin of the new base coordinate system, click the [Measure] soft key and confirm the position.
  (5) Move the TCP to a point on the positive X axis of the new base, click [Measure] and confirm the position with the [Yes] key.
  (6) Move the TCP to a point with a positive Y value on the XY plane, click Measure and confirm the position with the [Yes] key.
  (7) Press the Save key.
  (8) Close the menu.
  The base coordinate system measurement of the KUKA robot involves not only precise operating steps, but also the specific scenarios and technical requirements in actual applications to ensure that the robot can complete the task accurately. These details and considerations are key factors in achieving an efficient automated production environment.