Articulated Arm Tool Alignment to Prevent Surface Slipping
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Solution Overview
Problem
Existing methods for positioning tools at the end of articulated arms in the aeronautic industry face challenges in preventing tool slipping during operations like drilling and riveting, leading to inaccuracies and increased complexity due to the need for multiple compensation mechanisms and high costs.
Innovation Solution
A method involving iterative steps to align and apply force to the tool, monitoring reaction forces, and adjusting tool orientation to maintain alignment with the surface normal, using a combination of ball joints and incremental force increments to prevent slipping, thereby ensuring accurate positioning and reduced bulk and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a force is applied according to a direction substantially normal to the surface, then the tool can be positioned against the surface, but deformations of the surface and articulations occur which cause the tool to slip
Solution Approach 1:
The patent applies preliminary action by pre-positioning the tool according to a predetermined orientation that accounts for expected deformations. Before the full force is applied, the tool is positioned with a predetermined angular offset that compensates for the deformation that will occur when the normal force is applied, preventing slipping and maintaining positioning accuracy.
Solution Approach 2:
The patent changes the parameter of tool orientation from the traditional normal-to-surface alignment to a predetermined orientation that is offset by a specific angle. This parameter change allows the tool to maintain accurate positioning despite the deformations caused by applying force normal to the surface, as the predetermined orientation compensates for the expected deformation.
2Manufacturing precision
If multiple compensation mechanisms are used to prevent tool slipping, then positioning accuracy is maintained, but device complexity and cost increase
Solution Approach 1:
The patent extracts and eliminates the need for complex compensation mechanisms by using a predetermined tool orientation approach. Instead of adding multiple sensors, actuators, and control systems to compensate for deformations, the solution removes these unnecessary components by pre-calculating and applying the correct tool orientation that inherently compensates for deformations.
Solution Approach 2:
The system uses self-service by relying on the predetermined orientation of the tool that automatically compensates for deformations without requiring external compensation mechanisms. The tool's pre-set orientation serves its own positioning needs, eliminating the requirement for additional complex compensation systems.
Data Source
AI summary
A method for pushing, with a force a tool at the end of an articulated arm against a surface with a normal, including the steps of: positioning the tool against the surface; applying an increasing force to the tool until reaching a value, corresponding to a fraction of the force, the value of the applied force being monitored; measuring the orientation of the tool with respect to the normal, after having reached the force value; and redirecting the tool so as to recover its initial orientation with respect to the normal. Iteration is carried out to proceed, by repetition of steps to, while progressively increasing the force at each iteration, and until reaching the force value, the increase increment between two successive steps being smaller than a determined value.