Industrial robot calibration is an important aspect of robotics research. It is a comprehensive process integrating modeling, measurement, identification of actual robot parameters, and error compensation. It holds significant theoretical and engineering importance in the context of robotics industrialization.
Causes of robot errors:
The kinematic model established using existing CAD data and theoretical structural parameters of the robot contains errors compared to actual conditions. Furthermore, uncertainties in system integration, equipment damage, component aging, and environmental temperature variations often lead to high repeatability but low precision during normal robot operation. Therefore, it is essential to evaluate and calibrate the robot's performance, measure and analyze errors, and continuously refine the established model.
Experience shows that uncalibrated robot bases typically have an error of 15-30mm; the TCP center point has an error of 5-10mm; and the entire robot system has an error of 5-10mm. Adding a calibration step significantly improves robot accuracy (achieving ±0.25-1mm) and enhances algorithm stability. Calibration enables robots to be used in more complex, variable, and precision-critical environments.
Why do industrial robots need frequent calibration?
Calibration necessity:
1. Without calibration, robots cannot use shared programs, resulting in low and unstable accuracy. Changes in the robot's geometric parameters due to maintenance or other factors necessitate reprogramming, forcing a halt to its operation. Robot calibration, requiring only a small fraction of the programming time, offers significant research and economic value.
2. Calibration can improve a robot's ability to handle environmental uncertainties. As the application fields of robots become more complex, the uncertainty of the working environment will have a significant impact on robot tasks. A fixed and unchanging environmental model is very likely to cause robot failure.
Why do industrial robots need frequent calibration?
3. The development of modern automatic control theory has led to widespread attention being paid to offline programming systems for robots equipped with sensor-assisted devices. To complete relatively complex offline programming tasks (such as precision industrial manufacturing), not only is high repeatability of the robot's movements required, but also high precision. The main reason for low robot precision is the discrepancy between the robot's design parameters and its actual parameters, often caused by manufacturing errors. Robot calibration is a measure to improve robot precision by adjusting the robot's control software, often improving precision by several orders of magnitude.
Why do industrial robots need frequent calibration?
4. During the robot development process, it is essential to obtain sufficient accurate data to analyze and evaluate the robot's static and dynamic states. This includes measuring the robot's joint positions, the coordinates of specific points on the end effector in a specified coordinate system; whether the robot's movement truly follows our designed trajectory; whether the robot overshoots during acceleration; whether the robot deviates from its intended angle when moving; the impact of vibration on the robot; analyzing data on the weight of objects the robot carries; and conducting repeatability tests on the robot's accuracy, etc. All of this data must be obtained through a complete calibration system.
Why do industrial robots need frequent calibration?
The aforementioned factors often lead to low accuracy in the robot itself and during normal operation. In particular, trajectory accuracy often fails to meet usage requirements, necessitating robot performance evaluation and calibration. Errors are measured and analyzed, and the robot's actual parameters are continuously corrected to meet the flexibility and adaptability required in production and application. Rapid calibration of the robot's TCP point, home point, link length, and the included angles of each axis, along with detection of joint gear backlash, reduction ratio, coupling ratio, etc., and subsequent compensation, typically takes about twenty minutes to calibrate a robot. This rapidly improves robot performance.
