Venkatasubramanian Kalpathy Venkiteswaran

Development of a 3-Spring Pseudo Rigid Body Model of Compliant Joints for Robotic Applications

Compliant mechanisms achieve motion utilizing deformation of elastic members. However, analysis of compliant mechanisms for large deflections remains a significant challenge. In this paper, we will develop a 3-spring pseudo-rigid-body model for 2D beams that are often used in compliant joints in robots. First, we utilize the Timoshenko beam theory to calculate the tip deflection for a large range of loading conditions. An optimization process is then carried out to calculate the values of the parameters of the PRB model. The errors in the model will be analyzed and compared to the beam model. An example based on a robotic grasper finger is provided to demonstrate how the model can be used in analysis of such a system. This model will provide a much simpler approach for the analysis of compliant robotic mechanisms.Copyright

Effect of Beam Geometry on the Accuracy of Pseudo-Rigid-Body Models

Pseudo-rigid-body models serve as a convenient numeric tool for the analysis of compliant elements. However, most PRB models are derived on the basis of Euler beam equations, without accounting for the effect of deformation on beam geometry. In this paper, we look at the effects of deformation on length and cross section of the beam, and try to understand these phenomena with respect to some dimensionless parameters. These effects are more pronounced for short beams of soft materials. A few PRB models listed in literature are compared against FEA results, and optimization methods are used to determine more accurate PRB models for varying beam geometry. A study of these results will guide the discussion on how the accuracy of the PRB models changes with the beam parameters. An example of a compliant mechanism which experiences significant axial loads will be used to prove the validity of these results.Copyright