Analysis of the mass distribution of a functionally extended delta robot

This paper is concerned with the functional extension of a delta robot. This research is a contribution to the project Ra 1736/10-1 which was funded by the German Research Foundation. The topic of the project addresses a task-oriented decision analysis for designing such extension mechanisms, since handling and assembly processes have significant effects on the required functionality of the production device. For this purpose, the mobile platform of a common delta robot is endowed with three additional, rotational DOF to enhance its motion capability. Each DOF requires an additional motor so that different drive concepts are conceivable. Since the motors and their positions within the structure are key components for a lightweight design, different motor arrangements are considered to influence moving masses. For this purpose, five elementary types of motor arrangement are analyzed. To this end, the paper investigates and evaluates the stress impact of the additional mechanisms on the delta robot, which is a crucial criterion out of many other necessary criteria for the decision problem. To exploit the advantages of delta robots, such as high acceleration and high payload, the analysis allows finding an appropriate design with respect to a given trajectory. The investigation is based on a dynamic model of the structure which is developed and validated with a second modeling approach. First, results are obtained with a pick-and-place operation as a sample application. Finally, possibilities for future developments are identified to enhance the benefit of the analysis.