Study on multi-section continuum robot wire-tension feedback control and load manipulability

Continuum manipulators are type of hyper-redundant robots that without traditional rigid-links, and their intrinsic properties assure continuum manipulators can work in highly unstructured environments. To extend the potential applications of continuum manipulators, this paper presents a novel biased channel retractable (BCR) continuum manipulator. BCR continuum manipulator possesses a hollow channel when reserving its main backbone, and this structure provides the manipulator 'swallow' functions without sacrificing the stiffness generated by the backbone. This paper also establishes its kinematics model based on constant curvature assumption, and experimental result validates its correctness.

Due to the space constraints and obstacles, the traditional industrial manipulator is too difficult to achieve some tasks, such as the gluing for the wing bulkhead of the aircraft and the maintenance for cooling pipes of the nuclear power plant, etc. Continuum manipulator, inspired by the trunk and the tentacle, proves to be very effective for above-mentioned tasks. A novel octopus-like biomimetic robots, is proposed in this paper, which is consisting of continuum joints and discrete joints, and provide a host of benefits, such as the large space of movement, the high flexibility and the heavy load. A novel analytical approach for solving kinematics of the octopus-like arm manipulator with mixed joints is presented in this paper. Based on the bionic mechanism of the continuum manipulator constructed from mixed joints, the robot configuration is established. In this paper, we present a detailed formulation and explanation of a novel kinematic model for the continuum robots with mixed joints. The modeling method based on the Denavit–Hartenberg parameters(also called DH parameters) is used to depict the motion of robot. The robot is comprised of the continuum joint and the rotated joint, so the kinematic model of continuum joint is crucial for constructing that of the whole robot. The continuum joint is equivalent to a section of elastic body, whose D-H parametors can be obtain from the constant-curvature method. Then the forward kinematics of the whole robot can be builded in a D-H frame. Research results will create a new modeling method for the octopus-like continuum manipulators with mixed joints, which can give a new approach for the design on the biomimetic manipulators operating in the unstructured envirement.

Compliant joints are widely used in the structural design of 3D-printed continuum robots as their monolithic structure can greatly simplify the assembly process. However, some highly flexible compliant joints, such as the leaf-spring joints, still suffer from unstable rotation centers when interfered by external forces, which greatly reduces the motion stability of the constructed continuum robots. To cope with this problem, we propose a topology-optimization-based method in this paper to achieve efficient structural design of the complaint joints in continuum robots. With our method, the rotation stability of compliant joints can be improved without causing stress concentration problems. Experiments were also carried out to evaluate the bending performance of the 3D-printed continuum robots equipped with optimized compliant joints. Results demonstrated that, compared to continuum robots with the conventional leaf-spring joints, the optimized robots showed much less twisting deformation caused by out-of-plane loads, which exhibited the high rotation stability of the optimized joints. In future work, the proposed method can be further developed to achieve optimization of other mechanical properties of the compliant joints in continuum robots.

It is important to enable a robot to manipulate a target object that has no 3-D model information and is situated in an environment with other unknown objects nearby. This poses an open problem of how to combine perception and manipulation to enable the robot to build an appearance-based model of the target object on the spot to facilitate further manipulation of the object while avoiding the other unknown obstacles in the way. In this paper, we introduce an approach to enable a continuum manipulator, which is apt to maneuver through a crowded environment, to gradually build a 3-D surface model of the target object by moving an RGB-D sensor around the object while also detecting and avoiding surrounding unknown obstacles. Our approach interleaves perception and manipulation such that perception guides the manipulator movement, which in turn allows more perception of the target object for object model building and further manipulator motion. Our approach is characterized by a progressive strategy to register RGB-D images of the target object to build and extend a partial model of the object and the corresponding motion planning strategy for the continuum robot to carry out model building and avoid obstacles at the same time. To demonstrate the effectiveness of our approach, experiments on progressive model building of real objects from real RGB-D images are conducted, where a simulated continuum robot plans and executes its motion to carry the RGB-D camera around a target object for taking those images in an augmented reality setting.

Human operation of continuum "continuous-backbone" manipulators remains difficult, because of both the complex kinematics of these manipulators and the need to coordinate their many degrees of freedom. We present a novel synergy-based approach for operator interfaces, by introducing a series of octopus-arm inspired grasp-synergies. These grasp-synergies automatically coordinate the degrees of freedom of the continuum manipulator, allowing an operator to perform kinematically complex grasping motions through simple and intuitive joystick inputs. This effectively reduces the complexity of operation and allows the operator to devote more of his attention to higher-level concerns (e.g. goal, environment). We demonstrate the grasp-synergies interface design in both simulation and hardware using the nine degree of freedom Octarm continuum manipulator.

Continuum manipulators, inspired by the natural capabilities of elephant trunks and octopus tentacles, may find niche applications in areas like human-robot interaction, multiarm manipulation, and unknown environment exploration. However, their true capabilities will remain largely inaccessible without proper analytical tools to evaluate their unique properties. Ellipsoids have long served as one of the foremost analytical tools available to the robotics researcher, and the purpose of this paper is to first formulate, and then to examine, three types of ellipsoids for continuum robots: manipulability, force, and compliance.

Tendon driven continuum robots have attracted a significant amount of attention in the last decade. As a result several discrete and continuous modeling approaches have been explored in order to understand their behavior. The following article proposes an analytical model describing the influence of frictional effects between the tendon and its conduit in tendon driven continuum robotic manipulators. Existing constant curvature models ignore internal device friction completely and treat it as a negligible effect. This results in an assumption that the tendon tension is always constant along the length of the continuum manipulator. While this assumption is reasonable for small articulation angles, internal device friction can significantly change internal tension distribution deteriorating performance of constant curvature models at high articulation angles. The proposed model departs from the constant tension assumption and predicts a tension distribution along the tendon. From the tension distribution a curvature distribution is determined. It is observed that the proposed nonlinear friction model performs better than the existing linear elastic constant curvature model. Following this, a consequence of internal device friction: hysteresis effects are predicted. An algorithm that estimates tendon tension distribution given applied tendon tension history is proposed.

Rigid manipulators are applicable for a very structured environment and standard applications. For real world applications, continuum manipulators are used which has required high degrees of freedom, and compliance. The current work focus on the trajectory optimization of continuum robot for a specified application to minimize energy usage. To achieve this task Lagrangian mechanics is used to develop the mathematical model of the continuum robot with the payload. In this case the trajectory optimization has been carried out by treating the problem as a nested optimization problem. The outer optimization task is to optimize the trajectory using minimization of input force as primary goal where initial and final configurations of the arm are already available. Here, Genetic Algorithm is used as the optimizer for the selected tasks. The purpose of inner optimization loop is to find the feasible inverse solution for the manipulator that is required to calculate input forces which is further required to optimize the trajectory of the arm. A constrained non-linear optimization algorithm is used for the task. The optimization results show 30-80 % decrease in the input force required for the specified trajectories of the arm. The current paper shows that various tasks can be optimized using the formulated strategy to save the energy required by the arm to execute specified task.

Continuum manipulators enable minimally-invasive surgery on the beating heart, but the challenges involved in manually controlling the manipulator’s tip position and contact force with the tissue result in failed procedures and complications. The objective of this work is to achieve autonomous robotic control of a continuum manipulator’s position and force in a beating heart model. We present a model-less hybrid control approach that regulates the tip position/force of manipulators with unknown kinematics/mechanics, under unknown constraints along the manipulator’s body. The algorithms estimate the Jacobian in the presence of heartbeat disturbances and sensor noise in real time, enabling closed-loop control. Using this model-less control approach, a robotic catheter autonomously traced clinically relevant paths on a simulated beating heart environment while regulating contact force. A gating procedure is used to tighten the treatment margins and improve precision. Experimental results demonstrate the capabilities of the robot ([Formula: see text][Formula: see text]mm–[Formula: see text][Formula: see text]mm tracking error) while user demonstrations show the difficulty of manually performing the same task ([Formula: see text][Formula: see text]mm–[Formula: see text][Formula: see text]mm tracking error). This new, robotically-enabled contiguous ablation method could reduce ablation path discontinuities, improve consistency of treatment, and therefore improve clinical outcomes.

Aerial manipulators can manipulate objects while flying, allowing them to perform tasks in dangerous or inaccessible areas. Advanced aerial manipulation systems are often based on rigid-link mechanisms, but the balance between dexterity and payload capacity limits their broader application. Combining unmanned aerial vehicles with continuum manipulators emerges as a solution to this trade-off, but these systems face challenges with large actuation systems and unstable control. To address these challenges, we propose Aerial Elephant Trunk, an aerial continuum manipulator inspired by the elephant trunk, featuring a small-scale quadrotor and a dexterous, compliant tendon-driven continuum arm for versatile operation in both indoor and outdoor settings. We develop state estimation for the quadrotor using an Extended Kalman Filter, shape estimation for the continuum arm based on piecewise constant curvature, and whole-body motion planning using minimum jerk principles. Through comprehensive fundamental verifications, we demonstrate that our system can adapt to various constrained environments, such as navigating through narrow holes, tubes, or crevices, and can handle a range of objects, including slender, deformable, irregular, or heavy items. Our system can potentially be deployed in challenging conditions, such as pipeline maintenance or electricity line inspection at high altitudes.

For decades, the field of biologically inspired robotics has leveraged insights from animal locomotion to improve the walking ability of legged robots. Recently, “biomimetic” robots have been developed to model how specific animals walk. By prioritizing biological accuracy to the target organism rather than the application of general principles from biology, these robots can be used to develop detailed biological hypotheses for animal experiments, ultimately improving our understanding of the biological control of legs while improving technical solutions. Much of this work involves biologically inspired walking controllers informed by the morphology and dynamics of the insect nervous system, which necessitate a robot with highly animal-like structure to prevent a brain-body mismatch. However, methods for codifying suitable fidelity in biomimetic robots currently vary, with limited generalizable methods for robot design. In this work, I outline a general framework for developing biomimetic robots that ensures kinematic and dynamic similarity between the robot and target animal. I then use this framework to develop and validate the robot Drosophibot II, a meso-scale robotic model of an adult fruit fly, Drosophila melanogaster. The resulting robot is novel for its close attention to the kinematics and dynamics of Drosophila, an increasingly important model of legged locomotion. Each leg’s proportions and degrees of freedom are modeled after Drosophila 3D pose estimation data. The predominant actuators for the robot are characterized to determine their inertial, elastic, and viscous properties and subsequently dynamically scale the robot's motions. I then use a developed program to automatically solve the inverse kinematics and inverse dynamics necessary for walking for the robot's structure and that of a to-scale model of the fly. By comparing the output of these models, I demonstrate that the robot and fly are kinematically and dynamically similar. The robot's electromechanical design is presented, then validated by having the robot’s walk forward, backward, and up an incline via open-loop straight line stepping with biologically inspired foot trajectories. Strain data from locations throughout the robot's legs is also recorded during these tests as an analog for mechanosensory feedback in a freely walking animal. Through these experiments, Drosophibot II demonstrates its utility for neuromechanical investigations by providing plausible neural data currently unobtainable in the animal.

The design and analysis of continuum robots have consistently been a prominent research focus in the field of mechanics. However, portable continuum robots with minimal spatial occupancy, which have great potential for applications such as search and rescue, are scarcely available. This paper presents a novel helical-coiled multi-segment flexible continuum robot featuring helical deployment and compact design, with an integrated framework for structural design, kinematic modeling, and experimental validation. The design of the helical-coiled multi-segment flexible continuum robot for unstructured environment detection, including a flexible body, an actuation module, a feed module, and a sensing module, is presented systematically. Kinematic models of both single- and multi-segment continuum robots were established based on the constant curvature model to analyze the parameter mapping relationship from the end-effector position and orientation to the driving inputs. Furthermore, the feedforward motion of the robot was examined, and an uncoiling strategy based on S-curve compensation was employed to complete the kinematic analysis. Finally, the accuracy of the kinematic model considering the active uncoiling feed motion was validated through experimental analysis, demonstrating the motion characteristics of the continuum robot. Altogether, this study provides a framework for the design and analysis of helical-coiled continuum robots.

This research presents the development of a Sit-to-Stand and Stand-to-Sit model for regenerative energy recovery with applications in orthoses, protheses and humanoid robot design. Sit-to-Stand and Stand-to-Sit are routine activities and are crucial pre-requisites to walking and running. Determining design parameters for devices which can aid people to perform these activities in an effective manner is a key goal here. MapleSim was used to simulate a 1/10-scale multi-domain model and a nonlinear torque controller was used to control the trajectory profiles of the Sit-to-Stand-to-Sit gait. The model allows accurate simulation of hardware components for use in a future robot. This study addresses the usage in regenerative braking towards sit-to-stand-to-sit and the relationship between Coriolis/centrifugal torque components to inertial and gravitational torque components. This study examines the level of regeneration at ankle, knee and hip. Furthermore, it examines the significance of Coriolis and centrifugal versus inertial and gravitational components of a nonlinear controller in order to determine if these components would be needed in a real robot controller. By applying joint trajectories from human trials it was found that the regenerative effect in the robot model was most significant in the hip and least significant in the ankle. Furthermore, we determined that the Coriolis and centrifugal terms were approximately 1% of the inertial and gravitational terms in the applied nonlinear controller, making them insignificant. We also determined upper bounds for gearing in the joints such that battery autonomy is maximized without encountering motor saturation and inaccurate trajectory following. From these findings, we recommend that robot designs neglect the Coriolis and centrifugal terms and that regenerative hardware be prioritized at the hip.

Teaching young graduate students in the field of mechanical design has always been a challenging task. In particular, imparting some aspects on the creative design of mechanisms and robotics by far introduces additional difficulties. Because almost all existing systematic design or synthesis methodologies for the creative design, have a close connection with complicate mathematic tools. The objective of this paper is therefore to present a teaching approach based on an overview of pedagogical challenges of the authors in the past 8 years in teaching “Creative Design of Mechanisms and Robotics” to graduate students enrolled in mechanical engineering. One of the major components of the course is screw theory and its application to creative design of mechanical devices. In view of the fact that a large number of abstract concepts concerned, which heavily hinders the understanding of kernel knowledge, a reconfigurable model, based on the modularity design paradigm and latest study on flexures-based compliant mechanisms, is developed recently and integrated into impartation of a series of associating abstract knowledge. This paper outlines latest one-year experience of how the students are guided to learn the model-theory-integrated approach to creative design in a comparatively simple way.

This paper shows the design of a low-cost upper limb rehabilitation robot that can be applies to various symptoms of shoulder disorders. The 3-dimensional shoulder tracking mechanism was implemented to allow the translational movement of the shoulder joint. A gravity compensation mechanism was designed to compensate the weight of device and arm so that the patient would not feel the inconvenience caused by the weight. We designed an alignment mechanism for converting direction of rotation so that the patient could implement shoulder rehabilitation in various directions. By changing the relative direction of the actuator with respect to the user, 5 typical shoulder rehabilitation movement could be implemented which are flexion/extension, abduction/adduction, oblique raise, horizontal abd/adduction and internal/external rotation. At the same time, the device can allow the translational movement of shoulder joint during the rehabilitation exercise for the natural upper limb motion. This paper shows that even a low-end robot using an actuator can effectively applicate with various shoulder diseases.