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1. Encoder-less Robot Control for Space Operations with Continuum Robots

   Frazaelle, C.G. ; Walker, I.D. ; AlAttar, A. ; Kormushev, P. ( March 2021 , IEEE Aerospace Conference)

   Continuum robots have strong potential for application in Space environments. However, their modeling is challenging in comparison with traditional rigid-link robots. The Kinematic-Model-Free (KMF) robot control method has been shown to be extremely effective in permitting a rigid-link robot to learn approximations of local kinematics and dynamics (“kinodynamics”) at various points in the robot’s task space. These approximations enable the robot to follow various trajectories and even adapt to changes in the robot’s kinematic structure. In this paper, we present the adaptation of the KMF method to a three-section, nine degrees-of-freedom continuum manipulator for both planar and spatial task spaces.more »Using only an external 3D camera, we show that the KMF method allows the continuum robot to converge to various desired set points in the robot’s task space, avoiding the complexities inherent in solving this problem using traditional inverse kinematics. The success of the method shows that a continuum robot can “learn” enough information from an external camera to reach and track desired points and trajectories, without needing knowledge of exact shape or position of the robot. We similarly apply the method in a simulated example of a continuum robot performing an inspection task on board the ISS.« less
2. Analytical and Experimental Decentralized Adaptive Control of a High-Degrees-of-Freedom Robot Manipulator

   https://doi.org/https://doi.org/10.1115/1.4049795  

   Bertino, Alexander ; Naseradinmousavi, Peiman ; Kelkar, Atul ( July 2021 , Journal of dynamic systems measurement and control)

   In this paper, we study the analytical and experimental control of a seven degrees-of-freedom (7DOF) robot manipulator. A model-free decentralized adaptive control strategy is presented for the tracking control of the manipulator. The problem formulation and experimental results demonstrate the computational efficiency and simplicity of the proposed method. The results presented here are one of the first known experiments on a redundant 7DOF robot. The efficacy of the adaptive decentralized controller is demonstrated experimentally by using the Baxter robot to track a desired trajectory. Simulation and experimental results clearly demonstrate the versatility, tracking performance, and computational efficiency of this method.
3. Validation of an Extensible Rod Model for Soft continuum Manipulators

   https://doi.org/10.1109/ROBOSOFT.2019.8722721  

   Gilbert, Hunter B. ; Godage, Isuru S. ( April 2019 , 2019 2nd IEEE International Conference on Soft Robotics (RoboSoft))

   Numerous soft and continuum robotic manipulators have demonstrated their potential for compliant operation in highly unstructured environments or near people. Despite their recent popularity, modeling of their smooth bending deformation remains a challenge. For soft continuum manipulators, the widespread, constant curvature approach to modeling is inadequate for modeling some deformations that occur in practice, such as combined bending and twisting deformations. In this paper, we extend the classical Cosserat rod approach to model a variable-length, pneumatic soft continuum arm. We model the deformation of a pneumatically driven soft continuum manipulator, and the model is then compared against experimental data collectedmore »from a three degree of freedom, pneumatically actuated, soft continuum manipulator. The model shows good agreement in capturing the overall behavior of the bending deformation, with mean Euclidean error at the tip of the robot of 2.48 cm for a 22 cm long robot. In addition, the model shows good numerical stability for simulating long duration computations.« less
4. Extensible High Force Manipulator For Complex Exploration

   https://doi.org/10.1109/RoboSoft48309.2020.9116024  

   Hughes, Josie ; Santina, Cosmio Della ; Rus, Daniela ( May 2020 , IEEE Conference on Soft Robotics (RoboSoft))

   The development of compliant robotic manipulators which can show length change, compliance and dexterity could assist many challenging applications. Potential applications range from dexterous manipulation, robotic surgery or exploration of challenging environments. Despite significant developments in both fabrication and control approaches for continuum body manipulators, there have been few demonstrations of continuum body systems which display all these properties. We present a method for fabricating a continuum manipulation which shows extension, high force movements and a range of dexterous position. This approach uses 3D printing to create a flexible rack and pinion system. These high torque mechanisms are mounted atmore »points along the 3D printed tracks to allow complex shape control of the continuum system. A controller has been also been developed based on a Piecewise Constant Curvature approximation to allow the position of the tip of the manipulator to be controlled, and motion paths to be followed. In this work, we show the force capabilities of this manipulator and demonstrate how multiple segments can be created for more complex movements.« less
5. Center-of-Gravity-Based Approach for Modeling Dynamics of Multisection Continuum Arms

   https://doi.org/10.1109/TRO.2019.2921153  

   Godage, Isuru S. ; Webster, Robert J. ; Walker, Ian D. ( June 2019 , IEEE Transactions on Robotics)

   Multisection continuum arms offer complementary characteristics to those of traditional rigid-bodied robots. Inspired by biological appendages, such as elephant trunks and octopus arms, these robots trade rigidity for compliance and accuracy for safety and, therefore, exhibit strong potential for applications in human-occupied spaces. Prior work has demonstrated their superiority in operation in congested spaces and manipulation of irregularly shaped objects. However, they are yet to be widely applied outside laboratory spaces. One key reason is that, due to compliance, they are difficult to control. Sophisticated and numerically efficient dynamic models are a necessity to implement dynamic control. In this paper,more »we propose a novel numerically stable center-of-gravity-based dynamic model for variable-length multisection continuum arms. The model can accommodate continuum robots having any number of sections with varying physical dimensions. The dynamic algorithm is of O(n2) complexity, runs at 9.5 kHz, simulates six to eight times faster than real time for a three-section continuum robot, and, therefore, is ideally suited for real-time control implementations. The model accuracy is validated numerically against an integral-dynamic model proposed by the authors and experimentally for a three-section pneumatically actuated variable-length multisection continuum arm. This is the first sub-real-time dynamic model based on a smooth continuous deformation model for variable-length multisection continuum arms.« less