Analysis of a Six-Axis Industrial Robot's Dynamic Path Accuracy Based on an Optical Tracker
Although robot calibration has maturational fundamental theories, its practical application is still in the primary phase. In fact, most users are hard to manipulate an industrial robot with high absolute positioning accuracy. Thus, this study intends to measure the dynamic path accuracy of a six-axis industrial robot based on an optical tracker, instead of an expensive laser tracker. The motion tracking approach was based on three robot motions, i.e. linear motion, circular motion, and cornering motion, with a series of varied motion speeds from 100 to 800mm/s. Results show the dynamic path errors (the difference between the presupposed position and the measured position) for linear, circular, and corner motions were 0.662±0.169mm, 1.901±0.109mm, and 17.334±7.572mm, respectively. Obviously, the corner path error was far more than the other two motions. Furthermore, we found that the relationship between path error and the robot motion speed, was not completely linear. The performance assessment aims to provide feedback information for the accurate robot motion control in a specific target workspace. It is therefore of paramount importance for industrial robot users who are interested in precise applications to fully understand the test methods used for assessing robot path precision.
Development of high precision robotic arm-based bike frame measurement system
Currently, the quality check of bike frame still heavily relies on human operation. In practice, an entire checking process usually takes more than 30 min to complete. To overcome this dilemma, this paper aims to develop a fast high-precision measurement system using robotic arm based on 3D geometry mathematical model. Instead of four points needed to find coefficients of a space sphere, only three investigation points are required to achieve the sphere axis coordinates for measurement. The personal computer (PC) works as a control core, which to perform the mathematical model and control robotic arm movement. The robotic arm combined with contact sensor (probe) is used to move to the desired inspection points in shaft length, internal diameter, verticality, and parallelism following up the designated path planning route. The experimental results confirm that the proposed system can accurately reach the measurement outcomes. The entire checking cycle can be completed in 3 min at the range of 0.15 mm error, effectively reducing the process time with a high precision.
Modeling of chemical reactors—XXIX mixing-cell model for packed bed reactors. Steady state considerations. Problems of multiplicity
Abstract The axial heat and mass transfer in tubular catalytic reactors may be described by mixing-cell model and diffusion model as well. The diffusion description yields for a strong exothermic reaction and adiabatic conditions three steady state profiles, on the other hand the mixing-cell model gives rise to more than three steady states. A simple numerical and graphical analysis for mixing-cell model is presented.