Mechanical Analysis of high precision manipulator

Abstract

It is of great importance that high precision manipulators are well designed from a mechanical point of view. A thorough analysis of all mechanical aspects concerning an accurate manipulator will make a good basis for further design. This paper presents a new approach to mechanical analysis of high-precision manipulators. A typical six axis anthropomorphic manipulator configuration is chosen as a model for the analysis. The paper is divided into two main parts ; static deformation analysis and dynamic analysis. The static deformation analysis consists of three sub-parts ; link deformation, joint deformation and total mechanical deformation. A simple fixed beam deformation model is used to simulate every link. Both specific gravity and a load attached at the end of the beam is considered. By varying material, outer dimensions and wall thickness it is possible to determine optimal values. Looking at the whole structure with an attacking force at the end, it is possible to select appropriate motor/transmission combinations. Each combination represents compliance and combined with the arm compliance the total deformation can be found. The result shows that deformation due to compliance in the joints represents 97% of the total. Based on the result of the previous section, the dynamic model can be simplified significantly. The arm elements are supposed to be rigid and all the compliances are due to the joint deformation. This gives a coupled mass/spring system to be analysed. The resonance frequencies of the system are found through theoretical analysis and through simulation in a Finite Element based program for Dynamic analysis of Elastic Mechanisms (FEDEM) (Sintef Production Engineering 1993).