Efficient Simulation of the Dynamic Effects in Surface-Oriented Robot Process Control
In thermal spraying, additional drives are usually used in industrial practice, such as a rotary plate on which rotationally symmetrical workpieces are located. This procedure has the advantage that the process parameter of the surface speed is not determined by the robot, but by the external drive. In this case, the robot only has the task of moving along the contour of the rotary table in order to achieve a uniform coverage of the spray jet on the workpiece. In addition to the relative speed of the tool to the surface, the parameters tool distance and angle of attack are the main control variables that can be influenced by the robot. However, the complex surfaces of the forming tools considered in this SFB do not allow such an approach. Therefore, in the purely robot-based implementation as investigated in the first project phase, compliance with these process parameters must be intensively monitored and enforced. This will be realised in cooperation with subprojects B1 and B4 of the SFB via an iterative optimisation process of the robot paths based on a process-specific robot simulation.
The aim of the sub-project is to further develop robot-assisted thermal spraying on the basis of efficient robot simulation. For this purpose, a generalised model is to be developed for application to different robots and also changing tools, which in particular also takes into account the dynamic effects and contributes to the optimisation of the overall process through a "fast simulation".
The intended simulation has the following development goals:
- Efficiency: The simulation should be capable of performing a high number of iterations for optimising path planning.
- Consideration of application-specific effects: The model to be developed should be easily extendable for application-specific loads. As an example application for thermal spraying, the additional load caused by the cable and hose package of the spraying tool should be included in the robot simulation.
- Manufacturer and model independence: The model and the determination of the necessary data should not be bound to a specific manufacturer or a specific robot model.
In order to develop an optimisation-suitable robot simulation for integration into the simulation of the overall process chain, an application-specific modelling of the dynamic effects is carried out. When choosing the modelling approach, the requirement to be able to integrate application-specific dynamic loads of the robot into the model is taken into account. Such additional loads result, for example, in thermal spraying mainly from the distinctive hose and cable packages that must be fed to the torch mounted on the robot flange and lead to high moments of inertia, especially in the case of rapid reorientations of the mould, as is necessary in the coating of complexly shaped surfaces. The thermal spraying process is to serve here as a test scenario for the concept of an application-specific disturbance detection to be implemented. The model is to be parameterised via empirically determined variables. The necessary data are to be obtained in a measurement and evaluation cell. For this purpose, a measurement procedure for the measurement of industrial robots is being developed that generates the necessary data for parameter estimation in a standardised way, independent of the concrete robot design. The measurement concept to be developed takes into account not only the actual robot but also the application-specific extensions that are mounted on the robot.
Subproject A4 is funded by the German Research Foundation (GRF) as part of Collaborative Research Centre 708.