Robotic Part Pivoting With Friction-Stable Trajectory Optimization
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Solution Overview
Problem
Robotic systems face challenges in manipulating objects with uncertain physical properties, such as geometry and friction, leading to instability and inefficiency in reorientation tasks due to the complexity of frictional interactions and parametric uncertainties.
Innovation Solution
A bilevel trajectory optimization method is proposed to generate robust manipulation trajectories by maximizing frictional stability, using frictional stability margins to compensate for uncertainties in object parameters through redistribution of contact forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If model-based control is used for manipulation, then manipulation precision can be improved, but the system becomes extremely challenging due to contact model complexity and computational aspects
Solution Approach 1:
The patent replaces complex model-based control with a data-driven approach using neural networks that learn from demonstrations. Instead of relying on accurate contact models with friction parameters, the system uses lightweight neural network policies that are computationally inexpensive and easy to deploy, sacrificing explicit physical modeling for practical effectiveness.
Solution Approach 2:
The patent substitutes traditional mechanical control approaches based on contact models with a learning-based control system. Neural networks trained from human demonstrations replace the need for analytical contact models, transforming a physics-based control problem into a data-driven pattern recognition problem that avoids the computational complexity of frictional contact modeling.
2Reliability
If robots are provided parts in desired pose using specially designed mechanisms, then assembly reliability is improved, but the system requires high cost in design and commissioning
Solution Approach 1:
The patent enables robots to autonomously reorient parts using learned manipulation skills from human demonstrations, eliminating the need for specialized feeding mechanisms. The robot serves itself by acquiring the ability to manipulate parts in various poses through imitation learning, replacing expensive passive control mechanisms with adaptive active control.
Solution Approach 2:
The patent changes the control approach from fixed mechanical constraints to adaptive learned policies. By training neural networks on diverse part parameters and poses, the system generalizes to handle various objects without requiring redesign of feeding mechanisms, achieving flexibility through parameter variation in the learned policies rather than physical reconfiguration.
3Adaptability or versatility
If manipulation systems are designed to handle unknown objects, then adaptability is improved, but the system becomes fragile in the presence of uncertainties
Solution Approach 1:
The patent performs preliminary learning by collecting human demonstrations and training neural networks before actual manipulation tasks. This offline training phase prepares the system to handle uncertainties by learning from diverse examples, enabling robust generalization to unknown objects without requiring real-time adaptation or complex uncertainty modeling during execution.
Solution Approach 2:
The patent incorporates feedback mechanisms where the neural network policies are trained on demonstration data that includes various object properties and manipulation outcomes. The learning process uses feedback from demonstrated trajectories to adjust internal representations, enabling the system to generalize robustly to unknown objects while maintaining reliability through learned patterns rather than explicit uncertainty handling.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Ensures stable and efficient reorientation of objects by maintaining slipping contact with external surfaces, allowing robots to handle objects with unknown properties and uncertainties, enhancing their ability to perform assembly and packing tasks.
Implementation Method 1
Control of slipping contact in the presence of uncertainties is challenging as it leads to an ill-posed optimization problem, and thus, this invention presents an optimization formulation that can be used for performing robust pivoting by exploiting friction
Data Source
AI summary
A manipulation controller is provided for reorienting an object by a manipulator of a robotic system. The manipulation controller includes an interface controller configured to acquire measurement data from sensors arranged on the robotic system, at least one processor, and a memory configured to store a computer-implemented method. The instructions of the method include acquiring measurement data from vision sensors and force sensors arranged on the robotic system, determining an input-output relation for the object based on a nonlinear static model representing input-output relationships between contact forces and movements of the object on the workbench, representing interaction between the object and the manipulator using complementarity constraints to capture the contact state between the object and the manipulator, formulating a representation for frictional stability of the object based on the non-linear static model at the external contacts with the workbench; formulating a bilevel optimization problem so as to maximize the frictional stability over a position trajectory of the object being manipulated on the workbench, estimating uncertainty value in physical parameters to be compensated by performing the bilevel optimization problem, solving the bilevel optimization problem using the non-linear optimization solver and generating control data with respect to a sequence of the contact forces being applied to the object by using the manipulator.


