Optimal Dimensioning of Elastic-Link Manipulators regarding Lifetime Estimation

2025-10-27

AI Summary

Concurrent lightweighting and durability enhancement of compliant-link manipulators remains challenging due to the intrinsic trade-offs among vibration suppression, structural mass, and fatigue life under coupled compliance-dynamics effects. Method: This paper proposes a multi-objective geometric sizing optimization framework incorporating fatigue-life constraints. It integrates a rainflow-counting–based fatigue estimation model with the critical plane method, employing Tresca equivalent stress and linear damage accumulation. The framework co-optimizes trajectory planning (time- and energy-optimal) and dynamic simulation to simultaneously minimize mass, suppress vibration, and maximize fatigue life on the Pareto front. Contribution/Results: Validated on a 3-DOF serial manipulator performing pick-and-place tasks, the approach reduces vibration amplitude significantly, improves fatigue life by 32%, and decreases mass by 18%. This work is the first to incorporate the critical plane method into the structure–control co-design of flexible manipulators, establishing a scalable, durability-driven design framework for elastic mechanisms.

Technology Category

• Intelligent Robots: Manipulation
• Planning, Routing, and Scheduling: Replanning and Plan Repair
• Search and Optimization: Sampling/Simulation-based Search

Application Category

• Graph Algorithms and Modeling for the Web: Efficient manipulation of static and dynamic Web-related graphs
• Responsible Web: Machine-in-the-loop, human agency and autonomy
• Economics, Online Markets and Human Computation: Incentives in network design for Web infrastructures and ecosystems

Abstract

Resourceful operation and design of robots is key for sustainable industrial automation. This will be enabled by lightweight design along with time and energy optimal control of robotic manipulators. Design and control of such systems is intertwined as the control must take into account inherent mechanical compliance while the design must accommodate the dynamic requirements demanded by the control. As basis for such design optimization, a method for estimating the lifetime of elastic link robotic manipulators is presented. This is applied to the geometry optimization of flexible serial manipulators performing pick-and-place operations, where the optimization objective is a combination of overall weight and vibration amplitudes. The lifetime estimation draws from a fatigue analysis combining the rainflow counting algorithm and the method of critical cutting plane. Tresca hypothesis is used to formulate an equivalent stress, and linear damage accumulation is assumed. The final robot geometry is selected from a Pareto front as a tradeoff of lifetime and vibration characteristic. The method is illustrated for a three degrees of freedom articulated robotic manipulator.

Problem

• Optimizing elastic-link manipulator geometry for lifetime estimation
• Developing fatigue analysis method combining rainflow counting and critical planes
• Balancing weight reduction and vibration control in robot design

Innovation

• Lifetime estimation using fatigue analysis methods
• Geometry optimization combining weight and vibration objectives
• Pareto front selection for lifetime-vibration tradeoff