Tightening the Screws on Robotic Reliability

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Author: Denis Avetisyan

A new control framework combines telerobotics, active compliance, and supervisory control to significantly improve the dependability of automated bolting operations.

The system anticipates inevitable failure in bolting operations, not through prevention, but through a control architecture designed to manage the cascading effects of compromised fasteners—a recognition that dependability lies not in flawless execution, but in graceful degradation.
The system anticipates inevitable failure in bolting operations, not through prevention, but through a control architecture designed to manage the cascading effects of compromised fasteners—a recognition that dependability lies not in flawless execution, but in graceful degradation.

This review details a robotic system designed for fault-tolerant and reliable bolting, integrating haptic feedback and advanced control architectures.

Despite the increasing prevalence of robotic assembly, ensuring dependable operation—particularly in critical tasks like bolting—remains a significant challenge. This paper, ‘Improving dependability in robotized bolting operations’, introduces a novel control framework and robotic system designed to address this gap, integrating active compliance, telerobotics, and a supervisory control architecture for robust performance even under fault conditions. Experimental validation demonstrates enhanced operator situational awareness and improved fault detection capabilities in a representative pipe flange joining operation. Could this approach pave the way for truly autonomous and resilient robotic assembly systems in complex industrial environments?

The Inevitable Imperfection of Automated Fastening

Traditional bolting, crucial for applications like pipe flange connections, remains a manual process prone to inconsistency. Skilled labor is essential, yet human error impacts operational efficiency and system reliability, particularly in safety-critical industries like oil and gas. Manual methods suffer from issues like cross-threading and incomplete tightening, compromising joint integrity and increasing the risk of failure. Quality control, reliant on visual inspection and torque verification, is inherently variable. Automating this process demands systems capable of accommodating real-world imperfections, not simply replacing human effort.

The experimental setup utilizes a UR5e robotic arm fitted with a custom mechanical end-effector and associated piping for validation purposes at a remote location.
The experimental setup utilizes a UR5e robotic arm fitted with a custom mechanical end-effector and associated piping for validation purposes at a remote location.

Every tightened bolt is a promise made to the past, a guarantee against entropy that no system can truly keep.

Precision and Oversight: A Hybrid Robotic Approach

This system utilizes a UR5e Robotic Arm to automate bolting, enhancing speed and consistency while addressing the limitations of manual processes. It’s not a fully autonomous solution, but integrates within a Supervisory Control architecture, allowing human intervention when necessary. This hybrid approach leverages robotic precision alongside human adaptability, maximizing efficiency and safety.

A generic telerobotic supervisory control operation involves a high-level supervisory controller directing a low-level robot controller to execute tasks.
A generic telerobotic supervisory control operation involves a high-level supervisory controller directing a low-level robot controller to execute tasks.

Real-Time Control is critical, enabling the robot to respond to changing conditions during bolting. This responsiveness is achieved through continuous monitoring of force sensors and visual feedback, allowing immediate adjustments to maintain optimal performance and prevent damage.

Compliance and Sensing: Adapting to the Unforeseen

The robotic system utilizes six degrees of freedom for access to bolts, essential for navigating complex geometries and ensuring proper tool orientation. A vision system estimates bolt pose, providing the robot with necessary location information. This visual guidance is paired with a Force/Torque Sensor, providing crucial feedback for precise control. An Admittance Controller enables Active Compliance, allowing the robot to adapt to slight misalignments and maintain stable contact during bolting.

The tightening torque profile demonstrates the application of torque during a fastening process.
The tightening torque profile demonstrates the application of torque during a fastening process.

This combination of force sensing and compliant control ensures consistent and safe interaction with bolted components, preventing damage and enhancing the robustness of the assembly process, even with component variations.

Anticipating Failure: The Necessity of Human Oversight

The system incorporates robust Fault Detection capabilities, identifying mechanical failures like bolt driver malfunction or thread damage, and robotic jamming. Continuous monitoring enables preemptive identification of potential problems. Upon detection of a fault, the Supervisory Control system alerts the human operator, triggering a transition to Manual Control when automated protocols are insufficient.

Teleoperation is enabled through a high-fidelity Haptic Device, allowing the operator to remotely guide the robot through complex maneuvers. Validation through 20 trials demonstrates a 95% success rate in manual contingency handling, confirming the efficacy of this collaborative approach. Every line of code written anticipates the inevitable moment it will need to yield to a human touch.

The pursuit of dependable robotic bolting, as detailed in this work, echoes a fundamental truth about complex systems. One strives for precision, for fault tolerance, for active compliance – yet, these very efforts introduce new avenues for unforeseen failure. Andrey Kolmogorov observed, “The most important thing in science is not knowing many scientific facts, but knowing how to apply a scientific method.” This framework, integrating telerobotics and supervisory control, isn’t about building a perfectly reliable system, but cultivating one capable of graceful degradation. Scalability, in this context, isn’t a feature; it’s simply the word used to justify the inevitable complexity that arises when attempting to control the unpredictable nature of physical systems. The perfect architecture is a myth, a comforting illusion in the face of entropy.

What Lies Ahead?

This work, focused on dependable bolting, sketches a boundary – not a solution. It demonstrates a potential architecture, yet architectures are merely prophecies cast in steel and code. The system’s successes reveal less about achieving perfect reliability, and more about the inevitable distribution of failure. Resilience does not reside in eliminating error, but in cultivating forgiveness between components, allowing the system to absorb disturbances without catastrophic cascade.

The pursuit of dependability often fixates on anticipating every contingency, a fool’s errand in complex systems. A more fruitful path lies in understanding the garden of failures that will emerge. What methods allow the system to gracefully accommodate unanticipated errors, to re-route force, to signal limitations before they become critical? The focus should shift from preventing failure, to understanding its forms and building pathways for recovery.

Future work must confront the inherent limitations of telerobotic control. Human intention, however skilled, introduces its own variability. The challenge isn’t to automate precision, but to create systems that augment human capability while acknowledging its fallibility. The goal is not a perfect robot, but a partnership – a system that learns from, and compensates for, the imperfections of both machine and operator.

Original article: https://arxiv.org/pdf/2511.10448.pdf

Contact the author: https://www.linkedin.com/in/avetisyan/

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2025-11-14 15:20