Design and Comparative Analysis of Force-Balanced Two-Degree-of-Freedom Planar Robot Manipulator Concepts

A design methodology for the high-level analysis of inherently force-balanced manipulators is presented. It is applied for the analysis and comparison of three closed-chain, two-degree-of-freedom, planar robotic manipulator concepts. These designs are based on four-bar and five-bar linkages, and modeled at an abstracted component level in terms of an extendable link profile, counter masses, and additional attachments with mass/inertia. The methodology optimizes the balanced design counter masses within attachment position constraints. Different geometric parameter combinations for each concept in terms of workspace and total mass with balancing modifications are assessed. The balanced and unbalanced designs for the optimal parameters for each concept are then simulated using multibody dynamics software for different trajectories, with measurement of the reactions’ forces/moments and joint torques. Through this analysis, the various factors and tradeoffs that influence the design and balance optimization aspects for these force-balanced robot manipulator concepts are demonstrated.