Improving dependability in robotized bolting operations

TL;DR

This paper tackles the dependability gap in autonomous robotized bolting by proposing a modular control framework that integrates active compliance, driving-torque control, manual teleoperation, multimodal HRI, and a high-level supervisor within a supervisory control (SVC) paradigm. The system uses a 6-DoF follower robot, with an admittance-based interaction controller and a bolt driver controller to ensure safe, compliant tightening, and it supports seamless transitions between automatic and manual control via an SV and HRI. Experimental validation on pipe flange bolting under fault conditions demonstrates improved fault detection, increased operator situational awareness, and accurate, compliant tightening, while revealing the limitation of a single camera for full situational awareness. The work provides TRL-5 proof-of-concept evidence and suggests directions for enhanced perception and broader scenario validation.

Abstract

Bolting operations are critical in industrial assembly and in the maintenance of scientific facilities, requiring high precision and robustness to faults. Although robotic solutions have the potential to improve operational safety and effectiveness, current systems still lack reliable autonomy and fault management capabilities. To address this gap, we propose a control framework for dependable robotized bolting tasks and instantiate it on a specific robotic system. The system features a control architecture ensuring accurate driving torque control and active compliance throughout the entire operation, enabling safe interaction even under fault conditions. By designing a multimodal human-robot interface (HRI) providing real-time visualization of relevant system information and supporting seamless transitions between automatic and manual control, we improve operator situation awareness and fault detection capabilities. A high-level supervisor (SV) coordinates the execution and manages transitions between control modes, ensuring consistency with the supervisory control (SVC) paradigm, while preserving the human operator's authority. The system is validated in a representative bolting operation involving pipe flange joining, under several fault conditions. The results demonstrate improved fault detection capabilities, enhanced operator situational awareness, and accurate and compliant execution of the bolting operation. However, they also reveal the limitations of relying on a single camera to achieve full situational awareness.

Figures (9)

• Figure 1: Example of coupling and tightening steps in a bolting operation.
• Figure 2: Control system for dependable bolting operations.
• Figure 3: Screenshot of the system's GUI during operation.
• Figure 4: Diagram of a generic telerobotic supervisory control operation.
• Figure 5: Remote site of the experimental setup, showing the UR5e robotic arm equipped with the mechanical end-effector and the pipes used for experimental validation.