Nut Tightening Robot With Frustoconical Self-Alignment
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Solution Overview
Problem
Current robots are unable to reliably and efficiently tighten a series of bolt nuts on vehicle chassis, particularly those requiring high torque, due to reaction torque issues and alignment precision challenges, limiting them to tightening only a few bolts at a time without failure.
Innovation Solution
A robot equipped with a sleeve-shaped centering member that automatically realigns the nut tightening tool using a frustoconical surface to overcome alignment discrepancies, allowing for the successful tightening of multiple bolts by applying a 'wedge effect' to reposition the tool coaxially with the bolt axis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If a robot is used to tighten bolt nuts, then automation and productivity are improved, but the robot terminal axis cannot withstand the reaction torque over a long period, reducing reliability
Solution Approach 1:
A reaction torque absorption device is introduced as an intermediary component between the robot terminal and the tightening tool. This device absorbs the reaction torque generated during tightening operations, protecting the robot terminal axis from excessive stress while maintaining automation capability.
Solution Approach 2:
The reaction torque absorption function is extracted from the robot terminal axis and transferred to a dedicated absorption device. This separation allows the robot to focus on positioning and control while the specialized device handles the mechanical stress of reaction torque.
2Device complexity
If the robot trajectory precision is used as is, then device complexity is reduced, but the nut tightening tool axis is not perfectly aligned with the bolt axis due to hole axis dispersion, causing tightening failure
Solution Approach 1:
The alignment mechanism uses parameter changes through the frustoconical surface geometry. As the tool approaches the bolt, the conical surface guides radial adjustments, automatically adapting the tool position to match the actual bolt location within the dispersion tolerance.
Solution Approach 2:
The frustoconical alignment surface enables self-alignment of the tool with the bolt axis. The geometry itself provides the correction mechanism, eliminating the need for external sensors or complex control algorithms to achieve precise alignment.
3Manufacturing precision
If a vision system is added to locate and realign bolts, then alignment precision is improved, but device complexity and implementation difficulty increase significantly
Solution Approach 1:
The patent replaces the proposed vision system (optical/electronic system) with a mechanical alignment solution using the frustoconical surface. This mechanical approach achieves the same alignment function with simpler hardware and no complex software processing.
Solution Approach 2:
The frustoconical alignment surface acts as a mechanical intermediary that physically guides the tool to the correct position. This passive mechanical mediator eliminates the need for active vision systems and complex real-time computation.
4Productivity
If multiple bolts are tightened in succession, then productivity is improved, but the repetitive tightening causes accumulated errors and failures after only three bolts
Solution Approach 1:
The frustoconical alignment surface provides continuous feedback during the approach motion. Each tightening operation reinforces the alignment between tool and bolt axes, creating a self-correcting system that maintains precision across multiple successive operations rather than accumulating errors.
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
Enables the reliable and efficient tightening of up to 15 bolts in succession without failure, ensuring durability and reliability, even with high torque requirements like 175 N·m, by maintaining alignment and minimizing reaction torque on the robot.
Implementation Method 1
A sleeve-shaped centering member comprising a frustoconical surface is arranged around the nut tightening tool. The frustoconical surface is configured to contact the nut and reposition the nut tightening tool automatically in the axis of the nut by applying a 'wedge effect'.
Data Source
AI summary
The invention relates to a robot for tightening bolt nuts on a vehicle chassis, the robot comprising a polyarticulated arm at the end of which is a nut tightening tool. A sleeve-shaped centering member is fixed around the nut tightening tool and comprises a frustoconical surface which makes it possible, on contact with a nut, to reposition the nut tightening tool automatically in the axis of the nut.