The calibration based on laser of high absolute accuracy for industrial robots

This method, called 'Absolute precision ABB', a standard robot becomes one of precision using a system controlled by software to correct errors arising in the normal use of the equipment, due to overloading, kinematics and dynamics.

"An industrial robot really well is one that maintains the accuracy over throughout their life cycle, including the installation in factory, the power of the engine, the regroupment of media and everything that can experience a robot," explains Peter Fixell, product manager responsible for calibration and quality control of ABB in Västerås. "The difference in accuracy in a virtual 'ideal robot' and a real robot is usually about 8.15 mm." The difference is born of the mechanical tolerances and the cargo. "Accurately' absolute', reducing this margin to an average of 0.5 mm," concludes Peter Fixell.

ABB has two cells of work for calibration of robots, each of 10 x 10 meters. The Laser Tracker of Leica is installed between the two. The operator controls the phase of measurements from a PC located in such a way that allows you to have a complete perspective of both cells. While he is a robot in a cell, your colleagues can use the time riding or giving out a robot in the other. Once measured and calibrated robots, they are packed and are ready to deliver to the client.

The robot receives instructions to move up to 100 points traced by coordinates, within the work area. The Laser Tracker of Leica is responsible for determining the real positions. Then compares the theoretical positions and real and ABB creates a compensatory parameters which correct the positioning of the robot and, consequently, their movements. These parameters takes into account both the mechanical imperfections of the pattern of movements such as curves or negative distortions caused by the charges.

For companies that use the robot, 'Absolute precision' means that they can install it and putting it online directly, with the highest possible degree of accuracy. Used the same configuration of useful throughout all processes, from calibration and verification up to installation, operation and maintenance. ABB CalibWare, Calibration Pendulum Software and algorithms of the system operating (see below), are the same in ABB and the customer's premises, which basically reduces the risk of incompatibility to zero.

"For those companies that use a single robot, this means that your robot will maintain a level of precision high and consistent year after year," continued Peter Fixell. "The company can download with ease new simulated programmes with which the robot can work without the need for corrections."

Customers that invest in robots without 'Absolute precision' should not think that they are in a dead end, "continues. "We have teams allow us to effectively measure the robots in the own premises of the customer."

"Need a metering equipment that facilitates data (x, y, z), so that you can import to our calibration CalibWare useful." For measurements in the premises of the client, we use a Laser Station of Leica (ad 5005). "It is much lighter to carry that Laser Tracker (LTD 500), which is the model that we use in our production plant."

With a Laser Station in one hand and the tripod on the other, for an ABB engineer is easy to move through any of our customers production environment. When operating on batteries, the system is very flexible; just a few minutes are needed to bring it into operation. Measuring a position takes between 3 and 5 seconds, with an accuracy of 0.2 - 0.3 mm.

CalibWare ensures consistency between ABB and customer production environments and generates a check-list of simple calibration instructions and a menu of precision which relates the measurements of maintenance of the client with the fixed level of precision.

Summary of the "Absolute accuracy" method

Absolute accuracy (Absolute Accuracy) is a procedure intended to ensure that a robot will retain their precision throughout its life cycle. The method resolves the difference between the accuracy of a virtual robot in a CAD system and the work done by a real robot in the production plant. With Leica measuring equipment, establishes parameters of set-off to fix the positioning and movements of the robot. These parameters take into account both the mechanical imperfections in the pattern of movements and the negative curvature caused by the charges.

For the company that uses the robot, 'Absolute precision' means that you can install and set up a robot directly, with the highest possible degree of accuracy. It is also very simple to update their existing robots 'in situ' to introduce the 'Absolute precision' method. The same configuration of tools is used in all processes, from the calibration and verification on the ground of ABB in Västerås to the installation, operation and maintenance. Both ABB and the factory of the customer used the same ABB software: CalibWare, Calibration Pendulum and the algorritmos of the operating system, reducing to zero the risk of incompatibility.