This letter presents two long continuum robots, inserted through small holes, and working collaboratively in a crammed space to manipulate an extreme-temperature (>2000 °C) flame for coating repair on aeroengines without the need of their disassembly. One robot (Adder) carries a thermal spray nozzle while the other (Observer) carries cameras and a flame ignitor, supporting the locomotion and operation of the Adder, which was demonstrated on a real aeroengine offering advantages in both operational time and repair costs.

The maintenance of critical industrial components is often hindered by limited access, tortuous passages, and complex geometries. In highly constrained environments, inspection tasks are currently performed with borescopes, but even skilled operators struggle with hard-to-reach targets, and the limited mobility prevents in situ repair when defects are identified. Thanks to an active shape control, snakelike and continuum robots can outperform borescopes for short-range inspection as well as enable intervention. However, their actuation technology limits their scalability in length, as longer bodies pose control challenges due to their intrinsically low stiffness and space constraints. To overcome the limitations of both borescopes and continuum robots, here, we propose a modular design at their intersection, with both active tendon-driven and passively flexible segments. The main elements of the novel design, including the actuation and control interface, are described, and the system is demonstrated in scenarios for aerospace assets, nuclear installations, and robotassisted surgery.

Efficient path planning for hyper-redundant continuum and snake-like robots is a challenging task due to limited sensing capabilities, high computational loads, multiple possible solutions, and non-linear models. This letter presents a new approach to snake robot navigation and coiling, with an algorithm that enables online step-by-step position adjustment with a follow-the-leader strategy, significantly improving the performance of the robot when compared to previous methods. The proposed algorithm is demonstrated on a 16-degree-of-freedom snake-like robot for inspection and maintenance tasks in nuclear facilities.

Continuum robots (CRs) outperform the conventional rigid-link manipulators in aspects of hyper-redundant and compliant features. They provide universal and efficient solutions to access to constrained environments, e.g., aero engines and industrial vessels. In this article, a slender tendon-driven CR (length/diameter: 715/12.7 mm) is introduced for in situ maintenance of aero engine combustors. Two control challenges, the piecewise-constant-curvature (PCC) assumption mismatch and sections coupling issues, are discussed to explain the defect of model-based kinematic controllers on specific designs. Then, inspired by the tug of war, a novel local model-less controller utilizing a fuzzy logic algorithm is proposed for the feedback control of a single section. This implements the control policies directly from the task space to the actuation space, avoiding the model mismatch of the PCC assumption owing to the explicit call of arc parameters. Experiments on a single section of the tendon-driven CR, in comparison with PCC-based method, validate the stability and universality of the developed controller, which can reach $ \pm 1 - $ mm overall positioning accuracy and $ \pm 0.5$ - mm positional accuracy for 75% of the test points in both X and Y directions. Further, a set of trails on two distal sections of a long robot demonstrate that the controller can also effectively minimize the section coupling issue.

Continuum robots are able of in-situ inspection tasks in cluttered environments and narrow passages, where conventional robots and human operators cannot intervene. However, such intervention often requires the robot to interact with the environment, and the low stiffness and payload of continuum robots limits their intervention capabilities. In this letter, we propose a paradigm shift from individual to multiple continuum robots, which can reach the target environment from different paths and then physically connect, reconfiguring into a parallel architecture to enhance precision, stiffness, and payload. The main challenges in modelling and controlling cooperative continuum robots are outlined, and an experimental comparison between individual and cooperating continuum robots that connect through a novel shape-memory-alloy-based clutch highlights the advantages of the proposed technology.