Cezary Zieliński, Krzysztof Mianowski, Kazimierz Nazarczuk and Wojciech Szynkiewicz
The paper describes a prototype robot which due to its serial‐parallel structure exhibits, high stiffness and has a large work envelope. These features make this robot suitable…
Abstract
The paper describes a prototype robot which due to its serial‐parallel structure exhibits, high stiffness and has a large work envelope. These features make this robot suitable for relatively high precision machining operations on large workpieces. The conroller for this robot was based on MRROC++, which is a robot programming framework. Thus the controller could be tailored to the tasks at hand, including the capability of in‐program switching of kinematic model parameters. To obtain those parameters for different locations in the work‐space a calibration procedure using linear measurement guides has been devised.
Details
Keywords
Cezary Zieliński, Włodzimierz Kasprzak, Tomasz Kornuta, Wojciech Szynkiewicz, Piotr Trojanek, Michał Walęcki, Tomasz Winiarski and Teresa Zielińska
Machining fixtures must fit exactly the work piece to support it appropriately. Even slight change in the design of the work piece renders the costly fixture useless. Substitution…
Abstract
Purpose
Machining fixtures must fit exactly the work piece to support it appropriately. Even slight change in the design of the work piece renders the costly fixture useless. Substitution of traditional fixtures by a programmable multi‐robot system supporting the work pieces requires a specific control system and a specific programming method enabling its quick reconfiguration. The purpose of this paper is to develop a novel approach to task planning (programming) of the reconfigurable fixture system.
Design/methodology/approach
The multi‐robot control system has been designed following a formal approach based on the definition of the system structure in terms of agents and transition function definition of their behaviour. Thus, a modular system resulted, enabling software parameterisation. This facilitated the introduction of changes brought about by testing different variants of the mechanical structure of the system. A novel approach to task planning (programming) of the reconfigurable fixture system has been developed. Its solution is based on constraint satisfaction problem approach. The planner takes into account physical, geometrical, and time‐related constraints.
Findings
Reconfigurable fixture programming is performed by supplying CAD definition of the work piece. Out of this data the positions of the robots and the locations of the supporting heads are automatically generated. This proved to be an effective programming method. The control system on the basis of the thus obtained plan effectively controls the behaviours of the supporting robots in both drilling and milling operations.
Originality/value
The shop‐floor experiments with the system showed that the work piece is held stiffly enough for both milling and drilling operations performed by the CNC machine. If the number of diverse work piece shapes is large, the reconfigurable fixture is a cost‐effective alternative to the necessary multitude of traditional fixtures. Moreover, the proposed design approach enables the control system to handle a variable number of controlled robots and accommodates possible changes to the hardware of the work piece supporting robots.