Hyper-redundant Manipulator Research Articles

Solving the inverse kinematics problem of discretely actuated hyper-redundant manipulators using a narrowing-down search algorithm

Solving the inverse kinematics problem of discretely actuated hyper-redundant manipulators using a narrowing-down search algorithm

A local collision-free motion planning strategy for hyper-redundant manipulators based on dynamic safety envelopes

A local collision-free motion planning strategy for hyper-redundant manipulators based on dynamic safety envelopes

Real-Time Shape Estimation of Hyper-Redundant Flexible Manipulator Using Coiled Fiber Sensors.

The shape of flexible endoscopic surgical robot should be obtained to increase control accuracy and prevent unwanted tissue damage. To estimate the shape of flexible manipulator, space efficiency, cost-effectiveness, system complexity, and ease of calibration should be considered to integrate sensors into the manipulator. In this article, we propose a real-time method to estimate the shape of a hyper-redundant manipulator having embedded coiled fiber sensors. The main advantage of this method is guaranteeing shape recognition even when the manipulator is subjected to an external load. The fiber sensors are highly flexible, compact, and inexpensive, as well as they can functionally measure both compressive and tensile strain of hyper-redundant manipulator. The sensor design was optimized to achieve durability and sensitivity. The numbers of sensor and the placements were determined by the analysis of the kinematics and moment distribution of the manipulator. The accuracy of shape estimation was validated experimentally under both free-loading and loading conditions. The proposed method achieved real-time estimating capability with a mean maximum error of each joint position smaller than 3.54% in free-loading condition and 5.47% in loading condition.

Improving the stability of a planar tape-spring hyper-redundant manipulator

The planar tape-spring hyper-redundant manipulator presented in this paper is mainly constructed from tape springs, fixed-drive components, and mobile-drive components. It not only has high robustness and excellent transformability, but also high packaging efficiency. However, when the manipulator extends to a long range in motion experiments, some segments of the tape springs buckle. To address this drawback, a kinematic model of the planar tape-spring hyper-redundant manipulator is established, and, a configuration planning method based on a virtual spring model is proposed to solve the inverse kinematics problem. To enhance stability, the column stability is then incorporated into the configuration planning model. This approach relies on only configuration planning to prevent buckling. An alternative approach of adding auxiliary rods into the manipulator is also proposed. With this method, extra intermediate supports have been added to the manipulator. The effective column length of some segments is shortened, which effectively increases the critical buckling load of those segments of the tape spring. Finally, a prototype was subjected to motion and stability experiments to validate the presented approaches and analysis.

A Local Obstacle Avoidance and Global Planning Method for the Follow-the-Leader Motion of Coiled Hyper-Redundant Manipulators

A Local Obstacle Avoidance and Global Planning Method for the Follow-the-Leader Motion of Coiled Hyper-Redundant Manipulators

An obstacle avoidance path planning algorithm to simulate hyper redundant manipulators for tokamaks maintenance

The present work proposes an obstacle avoidance path planning algorithm for virtual simulations of hyper-redundant manipulators, with the possibility to customize the optimization criteria to select the best trajectory given in output. For test purposes, the effectiveness of the proposed Inverse Kinematic algorithm has been tested by simulating the Remote Maintenance (RM) tasks conducted by the HyRMan: the Hyper Redundant Manipulator developed for the Divertor Tokamak Test (DTT) project. The algorithm has been employed to simulate some critical handling tasks of the First Wall (FW) modules, with a specific optimization criterion as an example of its potentialities.

A Variable-Stiffness Planning Method Considering Both the Overall Configuration and Cable Tension for Hyper-Redundant Manipulators

A Variable-Stiffness Planning Method Considering Both the Overall Configuration and Cable Tension for Hyper-Redundant Manipulators

Solving the inverse kinematics problem of discretely actuated hyper-redundant manipulators using the multi-module searching method

AbstractHyper-redundant manipulators are produced by cascading several mechanisms on top of each other as modules. The discrete actuation makes their control easier because discrete actuators usually do not need any feedback to control. So far, several methods have been proposed to solve the inverse kinematic problem of discretely actuated, hyper-redundant manipulators. The two-by-two searching method is better than the other methods in terms of CPU time and error. In this article, the mentioned method is generalized by choosing an arbitrary number of modules as pending modules in each step of the solution instead of the necessary two. For validation, the proposed method is compared with nine meta-heuristic searching algorithms: simulated annealing, genetic algorithm, particle swarm optimization, ant colony optimization, gray wolf optimizer, stochastic fractal search, whale optimization algorithm, Giza pyramid construction, and flying fox optimization. Furthermore, the effect of the number of pending modules on CPU time and error is investigated. All the numerical problems have been solved for two case studies, one is planar and the other is spatial.

Modelling and control of manipulators for inspection and maintenance in challenging environments: A literature review

Nowadays, the use of robotic systems for inspection and maintenance is gaining importance due to the number of scenarios in which robots can operate. Indeed, robotic systems provide many advantages in harsh and hostile environments, improving workers’ safety and overall efficiency. Given their ability to perform different tasks, robotic manipulators constitute a significant proportion of the possible robotic systems employed in these environments. The category of manipulators is a heterogeneous group that comprises many different types of robots: non-redundant, redundant, and hyper-redundant manipulators, the latter being subdivided into discrete-joint manipulators and continuum manipulators. Among these types of robots, hyper-redundant manipulators play a crucial role in operating in challenging environments due to their ability to perform auxiliary tasks, such as obstacle avoidance and joint limits satisfaction. Furthermore, manipulators can be made of rigid or soft mechanisms and can be mobile, operating in aerial, ground, and underwater environments. The objective of this review article is to provide a reference point for researchers interested in modelling and controlling manipulators for inspection and maintenance in challenging environments.

Tension Maintenance Mechanism for Control Consistency of Twisted String Actuation-Based Hyper-Redundant Manipulator

Tension Maintenance Mechanism for Control Consistency of Twisted String Actuation-Based Hyper-Redundant Manipulator

Semiparametric dynamic model identification for hyper-redundant manipulator based on iterative optimization and neural network compensation

Semiparametric dynamic model identification for hyper-redundant manipulator based on iterative optimization and neural network compensation

Kinematic and Dynamic Models of Hyper-Redundant Manipulator Based on Link Eigenvectors

Kinematic and Dynamic Models of Hyper-Redundant Manipulator Based on Link Eigenvectors

Investigating the Stiffness Characteristics of a Tendon-Driven Continuum Manipulator Using Sensitivity Analysis: A Case Study in Transoral Laser Microsurgery

Continuum manipulators, with their characteristics of flexibility and dexterity, have gained significant interest in various applications across industries such as inspection, manufacturing, space exploration, and medical surgery. However, because of their inherent compliance, handling payloads may prove challenging due to shape distortion and deflection. This demonstrates the need to optimize the manipulator’s stiffness. The primary objective of this work was to show the merits of sensitivity analysis in the design of flexible surgical manipulators. Such analysis can guide important design decisions and enable the more efficient use of available resources, contributing to designing more effective prototypes. A new sensitivity analysis framework based on a multi-model and a multi-method approach was proposed to achieve this. This framework was then demonstrated by studying a tendon-driven rolling contact joint hyper-redundant manipulator for transoral laser microsurgery. In this analysis, the effects of independent design parameters on the stiffness of the manipulator were examined. Then, scaled-up 3D-printed prototypes were used to validate the accuracy of the stiffness model experimentally, which enabled us to assess the outcome of the sensitivity analysis framework. The results demonstrated that only two out of five design parameters for the considered manipulator significantly impacted the device’s performance. This information could enable the designer to efficiently allocate resources toward correctly setting these two most important parameters to achieve the desired system. Overall, the proposed analysis framework is a general tool that can be applied to any design architecture, helping to develop optimal manipulators for various applications.

Simulation of simple movements of Arm-Z oblique swivel joint chain manipulator

Arm-Z is a concept of a hyper-redundant manipulator based on linearly joined sequence of congruent modules by oblique swivel joint mechanism. Each module has one degree of freedom only, namely a twist relative to the previous module in the sequence. Although the concept of this type of manipulator is relatively old and simple, its control is very difficult an nonintuitive, which results in a limited use in industrial practice. This paper presents a simple simulation of Arm-Z in Mathematica programming environment which demonstrates a few simple but potentially useful movements.

Inverse Kinematics Solution Method of an Adaptive Piecewise Geometry for Cable-Driven Hyper-Redundant Manipulator

Abstract Cable-driven hyper-redundant manipulator (CDHM) with flexible and compliant configuration has high maneuverability in a tight space owing to its multiple degrees of freedom (DOFs). However, an increase in the DOFs of the manipulator makes it very challenging to solve its inverse kinematics. The present work proposes a novel adaptive piecewise geometry method to solve the inverse kinematics of the CDHM. The corresponding computation efficiency will be much lower for traditional methods, i.e., the generalized inverse of the Jacobian matrix and artificial neural network method. When the end-effector of the manipulator is required to move with a larger range, Joint angle physical limit needs to be considered and the proposed method can select the optimal arc configuration to solve the inverse kinematics aiming at reducing joint overrun. An adaptive adjustment coefficient is further introduced to optimize the double-arc configuration so that joint motion is more reasonable as well as avoiding singular configuration. The geometry and joint parameters solved with the proposed novel method are then compared to those of the existing method with the same desired target position to verify the effectiveness of the proposed novel method. Finally, a 12-DOFs hyper-redundant manipulator physical prototype is built, and corresponding experimental results show that with the novel solution method, the manipulator end can precisely reach the expected target position with significantly less computational complexity, which is beneficial to improve real-time control efficiency of the CDHM in practical applications.

Robust Shape-Distortion Prediction for a Wire-Driven Hyper-Redundant Manipulator With Engaging Rolling Joints

In Minimally Invasive Surgery (MIS), wire-driven hyper-redundant manipulators are widely used because of their flexibility, dexterity, and miniaturization. However, due to their limited structural stiffness, wire-elongation and unwanted distortion in the shape may occur during payload handling. For example, the surgical payload at the end-effector can distort an endoscope and cause positional deviation of the end-effector. In this paper, an endoscopic manipulator with robust Engaging Rolling Joints (ERJs) is proposed, where each ERJ is deployed with a pair of Auxiliary Super-elastic Ribbons (ASRs). Based on the design, we also developed a prediction model for shape-distortion, which is able to numerically predict the shape of the manipulator under payload applied to the end-effector. Experiments were conducted to verify that the ERJ and the ASR can better reject unwanted disturbances in shape prediction. The test results showed that the predicted distorted shape is in good agreement with the actual shape; the average prediction errors for the distal angle and position deflections were measured at 8.63% and 7.71%, respectively. We believe that the presented technique will help to improve the performance of the rolling joint manipulator by compensating the predicted shape-distortion.

Systems engineering approach for the iterative concept design and virtual simulation of the DTT hyper redundant manipulator

This paper proposes a System Engineering-based iterative design approach for the DTT HyRMan, an hyper redundant manipulator conceived to perform Remote Maintenance (RM) of the FW modules and inspection tasks in the DTT vacuum vessel. According to the “RFLP” paradigm of the “V-model” (Requirements, Functionalities, Logical and Physical architecture, with the respective test phases), after having defined the manipulator’s Requirements and Functionalities, the Logical and Physical architectures have been established. In particular, the current design of hyper redundant manipulator is characterized by twelve joints (two prismatic and ten revolute), with a Planar and a Dexterous Arm. Once defined the ideal operative procedures, the Verification phase of Systems Engineering approach has been carried out. The HyRMan behaviour has been simulated and tested in virtual environment under the in-vessel geometric constraints, to evaluate the overall encumbrance and the remote operations feasibility. The kinematic analyses were performed simulating links and joints as rigid bodies, using the software Delmia in the same Dassault Systèmes V5 platform used for 3D CAD modelling (CATIA V5). Flexibility analyses performed in SimSOFT have confirmed that the HyRMan can be modelled using the rigid body assumption with sufficient confidence, as flexible effects along the length of the links are negligible with the current design of the manipulator. The workflow of actions implemented within the virtual platform and the obtained results are discussed in the paper, further to the evaluation of alternative design solutions in case of reachability or collision avoidance criticalities for the HyRMan.

An iterative path-following method for hyper-redundant snake-like manipulator with joint limits

PurposeThis paper aims to present an iterative path-following method with joint limits to solve the problem of large computation cost, movement exceeding joint limits and poor path-following accuracy for the path planning of hyper-redundant snake-like manipulator.Design/methodology/approachWhen a desired path is given, new configuration of the snake-like manipulator is obtained through a geometrical approach, then the joints are repositioned through iterations until all the rotation angles satisfy the imposed joint limits. Finally, a new arrangement is obtained through the analytic solution of the inverse kinematics of hyper-redundant manipulator. Finally, simulations and experiments are carried out to analyze the performance of the proposed path-following method.FindingsSimulation results show that the average computation time is 0.1 ms per step for a hyper-redundant manipulator with 12 degrees of freedom, and the deviation in tip position can be kept below 0.02 mm. Experiments show that all the rotation angles are within joint limits.Research limitations/implicationsCurrently , the manipulator is working in open-loop, the elasticity of the driving cable will cause positioning error. In future, close-loop control based on real-time attitude detection will be used in in combination with the path-following method to achieve high-precision trajectory tracking.Originality/valueThrough a series of iterative processes, the proposed method can make the manipulator approach the desired path as much as possible within the joint constraints with high precision and less computation time.

Hyper-Redundant Manipulators for Operations in Confined Space: Typical Applications, Key Technologies, and Grand Challenges

In this article, we review the state of the art in hyper-redundant manipulators for applications in confined space such as <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> -orbit services. With their multiple degrees of freedom and slender links, hyper-redundant manipulators can offer superior dexterity and excellent operability. They can traverse freely, manipulate objects flexibly, and conform to curvilinear paths accurately in confined spaces. The by-design separation of the mechanical and electrical parts in these manipulators also offers inherent structural compliance and miniaturization. Due to the elastic characteristics of driving cables, hyper-redundant manipulators have both stiffness and flexibility. In this article, the overviews of the current state of the art in this field are provided from the perspectives of both typical applications and key technologies. We detailed the relevant studies on the configuration, obstacle avoidance, path planning, and control technologies for hyper-redundant manipulators and highlight the use of these studies in the development of practical applications. Furthermore, we propose several aspects that need to be further studied, namely efficient inverse kinematics solution, strong coupled dynamics modeling, variable stiffness control, and multiobjective trajectory optimization. Breakthroughs in these areas will provide valuable solutions for complex path planning and control of hyper-redundant manipulators. <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup>

Structural Optimisation and Design of a Cable-Driven Hyper-Redundant Manipulator for Confined Semi-Structured Environments.

Structural optimisation of robotic manipulators is critical for any manipulator used in confined semi-structured environments, such as in agriculture. Many robotic manipulators utilised in semi-structured environments retain the same characteristics and dimensions as those used in fully-structured industrial environments, which have been proven to experience low dexterity and singularity issues in challenging environments due to their structural limitations. When implemented in environments other than fully-structured industrial environments, conventional manipulators are liable to singularity, joint limits and workspace obstacles. This makes them inapplicable in confined semi-structured environments, as they lack the flexibility to operate dexterously in such challenging environments. In this paper, structural optimisation of a hyper-redundant cable-driven manipulator is proposed to improve its performance in semi-structured and challenging confined spaces, such as in agricultural settings. The optimisation of the manipulator design is performed in terms of its manipulability and kinematics. The lengths of the links and the joint angles are optimised to minimise any error between the actual and desired position/orientation of the end-effector in a confined semi-structured task space, as well as to provide optimal flexibility for the manipulators to generate different joint configurations for obstacle avoidance in confined environments. The results of the optimisation suggest that the use of a redundant manipulator with rigid short links can result in performance with higher dexterity in confined, semi-structured environments, such as agricultural greenhouses.