Hyper-redundant Manipulator Research Articles

Solving kinematics and stiffness of a novel n(2-UPS/PS+RPS) spatial hyper-redundant manipulator

SUMMARYA novel n(2-UPS/PS+RPS) spatial hyper-redundant manipulator (SHRM) formed by an optional number of 2-UPS/PS+RPS(2-universal joint-prismatic joint-spherical joint/prismatic joint-spherical joint+revolute joint-prismatic joint-spherical joint) parallel manipulators(PMs) connected in series is proposed and analyzed in this paper. First, the forward kinematics of the 2-UPS/PS+RPS PM is derived in close form. By extending this result to the whole SHRM, the forward kinematics model of the n(2-UPS/PS+RPS) SHRM is established. Second, the compact and elegant expressions for solving the forward velocity of the n(2-UPS/PS+RPS) SHRM are derived. Third, the statics and stiffness of the n(2-UPS/PS+RPS) SHRM are analyzed systematically by considering both active forces and constrained forces existed in each 2-UPS/PS+RPS PM. Finally, an analytically solved example is given for a 4(2-UPS/PS+RPS) SHRM formed by four 2-UPS/PS+RPS PMs. The analytical results are verified by CAD software.

Simulation Analysis of Pneumatic Rubber Bellows for Segment of Hyper-Redundant Robotic Mechanism

The paper deals with a design and simulations of segment for hyper-redundant manipulator. In the paper 6-DOF manipulator segment, which consists of pneumatic and electromagnetic actuators, is designed. CAD model of the segment is introduced and basic parts are described. The basic motion is reached by pneumatic actuator which works through the rubber bellows and it utilizes their expansion properties. Main focus of the study besides segment design is analysis of rubber bellows. From this reason FEM analysis is done in software SolidWorks. In the conclusion the results are discussed.

Biologically Inspired Node Generation Algorithm for Path Planning of Hyper-redundant Manipulators Using Probabilistic Roadmap

This article describes a biologically inspired node generator for the path planning of serially connected hyper-redundant manipulators using probabilistic roadmap planners. The generator searches the configuration space surrounding existing nodes in the roadmap and uses a combination of random and deterministic search methods that emulate the behaviour of octopus limbs. The strategy consists of randomly mutating the states of the links near the end-effector, and mutating the states of the links near the base of the robot toward the states of the goal configuration. When combined with the small tree probabilistic roadmap planner, the method was successfully used to solve the narrow passage motion planning problem of a 17 degree-of-freedom manipulator.

Collision Free Control of Variable Length Hyper Redundant Robot Manipulator

Hyper-redundant robot (HRR) manipulators are useful at navigating convoluted paths, but conventionally complicated to control. The control of a hyper-redundant manipulator is complex due to its redundancy. In this paper, a simple but effective control algorithm for obstacle avoidance is proposed. The algorithm derives a collision free path around known obstacles so that the end-effector of a variable length hyper redundant robot (VHRR) is able to reach the target location following the path without hitting the obstacles. The algorithm can be grouped into two tasks to drive the end-effector along the collision free trajectories: first, solve the inverse kinematics without disregarding the existence of obstacles in the system; and second, fit the manipulator to the respective prescribe trajectories. This method has the capability to allow VHRR maneuver within its workspace without penetrating to the neighboring obstruction. Further, this method is very effective in the sense that it forms a nice coil profile avoiding zig-zag configuration, and thus eliminates sharp turn on the robot. The performance of a VHRR was tested through simulation to demonstrate the effectiveness of the proposed method. The approach succeeded in delivering the path that avoids obstacle.

Design and Control of a Hyper-Redundant Manipulator for Mobile Manipulating Unmanned Aerial Vehicles

Manipulating objects using arms mounted to unmanned aerial vehicles (UAVs) is attractive because UAVs may access many locations that are otherwise inaccessible to other mobile manipulation platforms such as ground vehicles. Despite recent work, several major challenges remain to be overcome before it will be practical to manipulate objects from UAVs. Among these challenges are: (a) The constantly moving UAV platform and compliance of manipulator arms make it difficult to position the UAV and end-effector relative to an object of interest precisely enough for manipulation, and (b) The motions of the manipulator impact the stability of the host UAV, further complicating positioning. Solving these challenges will bring UAVs one step closer to being able to perform meaningful tasks such as infrastructure repair, disaster response, casualty extraction, and cargo resupply. Toward solutions to these challenges, this paper describes a hyper-redundant manipulator, manipulator control approaches and system design considerations to position the manipulator relative to objects of interest in such a way that impacts on platform stability are minimized.

Discrete kinematic synthesis of discretely actuated hyper-redundant manipulators

SUMMARYDiscrete kinematic synthesis of discretely actuated hyper-redundant manipulators is a new practical problem in robotics. The problem concerns with determining the type of each manipulator module from among several specific types, so that the manipulator could reach several specified target frames with the lowest error. This paper suggests using a breadth-first search method and a workspace mean frame to solve this problem. To reduce errors, two heuristic ideas are proposed: two-by-two searching method and iteration. The effectiveness of the proposed method is verified through several numerical problems.

A new obstacle avoidance method for discretely actuated hyper-redundant manipulators

In this paper, a new method is proposed for solving the obstacle avoidance problem of discretely actuated hyper-redundant manipulators. In each step of the solution, the closest collision to the base is removed and then the configuration of the next part of the manipulator is modified without considering the obstacles. This process is performed repeatedly until no collision is found. The Suthakorn method is applied to solve the inverse kinematics problem. Two new ideas are proposed to reduce the errors of this method: the two-by-two searching method, and iterations. To verify the proposed method, some problems are solved numerically for 2D and 3D manipulators, each in two different obstacle fields, and the results are compared with those obtained by the genetic algorithm method.

The position control of a spatial binary hyper redundant manipulator through its inverse kinematics

This article is about the position control of a binary hyper redundant manipulator, which is driven by pneumatic on-off actuators. The end platform of the binary hyper redundant manipulator bears a small fine tuning manipulator, which is a continuously actuated six-joint manipulator attached as a versatile error-compensation tool. It is employed to compensate especially the discretization errors. The position control aims to make the end-effector of the fine tuning manipulator track a specified sequence of successive poses as required by the task to be performed. This aim is achieved by solving the inverse kinematics problem of the binary hyper redundant manipulator, i.e. by determining the binary positions of the on-off actuators, so that the end platform of the binary hyper redundant manipulator enters the inverted working volume of the fine tuning manipulator for each specified target pose of the end effector. As to solve the inverse kinematics problem of the binary hyper redundant manipulator, three methods are presented. They are the plain spline fitting method, the extended spline fitting method, and the workspace filling method. The plain spline fitting method is based on forcing the actual backbone curve of the binary hyper redundant manipulator to approximate a spatial reference spline which is specified as the desired backbone curve. In the extended spline fitting method, the result found in the plain spline fitting method is improved by using a genetic algorithm. In the workspace filling method, the workspace of the binary hyper redundant manipulator is filled randomly with a sufficiently large finite number of discrete configurational samples. If it is desired to have a concentration on a particular region of the workspace, then that region is filled by using a genetic algorithm. After the filling stage, the sample closest to the desired configuration is determined by a suitable searching algorithm. The three methods are demonstrated and comparatively discussed by means of several examples.

The conceptual design of a spatial binary hyper redundant manipulator and its forward kinematics

The hyper redundant manipulators (HRMs) have excessively many degrees of freedom. As a special but practicable subset of them, the binary hyper-redundant manipulators (BHRMs) use binary (on–off) actuators with only two stable states such as pneumatic cylinders and/or solenoids. This article describes the conceptual design of a spatial BHRM together with its forward kinematics. This BHRM consists of many modules with the same constructive characteristics. The modules increase in size from the tip to the base so that the actuator powers also increase in the same order. Each module consists of three submodules. The first and second submodules have the shapes of variable geometry trusses and they work in mutually orthogonal planes. The third submodule is a discrete twister. The manipulator is assumed to be driven by pneumatic on–off actuators. Because of the discrete nature of the on–off actuators, a small but continuously actuated six-joint manipulator is installed as the last module of the BHRM in order to compensate the discretization errors.

The kinematics of modular spatial hyper-redundant manipulators formed from RPS-type limbs

This study addresses the kinematics, including position, velocity and acceleration analyses, of a modular spatial hyper-redundant manipulator built with a variable number of serially connected identical mechanical modules with autonomous motions. First, the kinematics of the base module, a three-legged in-parallel manipulator, is formulated using the theory of screws. After that, the results thus obtained, are applied recursively for accomplishing the kinematic analyses of the hyper-redundant manipulator at hand. A numerical exampled is included.

A worm-inspired new spatial hyper-redundant manipulator

SUMMARYIn this work a novel spatial hyper-redundant manipulator inspired in the motions of the worms is introduced. The displacement analysis is presented in a semi-closed form solution, whereas the velocity and acceleration analyses are carried out by means of the theory of screws. Among typical applications of most hyper-redundant manipulators, interesting biomechanical applications such as the simulation of the motion of the spine are available for this newartificial worm.

Geometrical approach of planar hyper-redundant manipulators: Inverse kinematics, path planning and workspace

A new method for inverse kinematics for hyper-redundant manipulators is proposed in this paper to plan the path of the end-effector. The basic idea is that for a given smooth path consisting of points close enough to each other; computing the inverse kinematics for these points is carried out geometrically using the proposed method. In this method, the angles between the adjacent links are set to be the same, which makes lining up of two or more joint axes impossible; therefore, avoiding singularities. The manipulability index has been used to show how far the manipulator from the singularity configuration is. The determination of the workspace of the manipulator using the proposed method has been presented in this paper. The simulation results have been carried out on a planar and a three dimensional manipulators. The effectiveness of the proposed method is clearly demonstrated by comparing its result with results calculated by the well-known method of measuring manipulability which is used for singularity avoidance for the last two decades.

Redundancy Resolution Using Tractrix—Simulations and Experiments

Hyper-redundant robots are characterized by the presence of a large number of actuated joints, a lot more than the number required to perform a given task. These robots have been proposed and used for many applications involving avoiding obstacles or, in general, to provide enhanced dexterity in performing tasks. Making effective use of the extra degrees-of-freedom or resolution of redundancy has been an extensive topic of research and several methods have been proposed in literature. In this paper, we compare three known methods and show that an algorithm based on a classical curve, called the tractrix, leads to a more “natural” motion of the hyper-redundant robot with the displacements diminishing from the end-effector to the fixed base. In addition, since the actuators nearer the base “see” a greater inertia due to the links farther away, smaller motion of the actuators nearer the base results in better motion of the end-effector as compared with other two approaches. We present simulation and experimental results performed on a prototype eight-link planar hyper-redundant manipulator.

Motion Control of a Hyper Redundant Manipulator Built by Serially Connecting Many Parallel Mechanism Units with a Few DOF

This paper describes the kinematic analysis and motion control of a hyper redundant robot built by serially connecting many units with a few DOF. Each unit of the manipulator is a spatial parallel mechanism with 3 DOF and is composed of 2 stages connected with 3 linear actuators, 7 spherical joints, and a center rod. The forward kinematic analysis of the manipulator based on the forward kinematics of each unit by numerical calculation was carried out. The inverse kinematic analysis, the iterative calculation so as to converge output error while output displacement is distributed into each unit with weighting coefficient, was proposed and formulated. Motion control of the robot was theoretically and experimentally examined based on the inverse kinematics. It was confirmed that a prototype with 3 units could generate the desired trajectories.

A fractional approach for the motion planning of redundant and hyper-redundant manipulators

The trajectory planning of redundant robots through the pseudoinverse control leads to undesirable drift in the joint space. This paper presents a new technique to solve the inverse kinematics problem of redundant manipulators, which uses a fractional differential of order α to control the joint positions. Two performance measures are defined to examine the strength and weakness of the proposed method. The positional error index measures the precision of the manipulator's end-effector at the target position. The repeatability performance index is adopted to evaluate if the joint positions are repetitive when the manipulator execute repetitive trajectories in the operational workspace. Redundant and hyper-redundant planar manipulators reveal that it is possible to choose in a large range of possible values of α in order to get repetitive trajectories in the joint space.

2A1-A12 ゾウの鼻を模したパラレルメカニズム連結型超冗長マニピュレータの形状把握

In a nuclear reactor and a chemical plant, since it is very complicated environment with apparatus, it cannot fully function by the manipulator of 6 degree of freedom (DOF). But, trunk can wrap and catch in the thing of any form at the intricate place. The manipulator that has such a function having far more DOF is called a hyper-redundant manipulator. We made the hyper-redundant manipulator constituted of several 3-RRS parallel link mechanisms. This manipulator can be used in the intricate environments described above. It is necessary to understand the whole shape to control this manipulator. In order to grasp the whole shape of this manipulator, the degree of rotation angle of a servo motor and the angle between arm and rod are required. In this report, we did the design improvement to measure the above-mentioned two angles, led the forward kinematics, and grasped the shape of this manipulator.

A real-time algorithm for simulation of flexible objects and hyper-redundant manipulators

Flexible objects such as a rope or snake move in a way such that their axial length remains almost constant. To simulate the motion of such an object, one strategy is to discretize the object into large number of small rigid links connected by joints. However, the resulting discretised system is highly redundant and the joint rotations for a desired Cartesian motion of any point on the object cannot be solved uniquely. In this paper, we revisit an algorithm, based on the classical tractrix curve, to resolve the redundancy in such hyper-redundant systems. For a desired motion of the ‘head’ of a link, the ‘tail’ is moved along a tractrix, and recursively all links of the discretised objects are moved along different tractrix curves. The algorithm is illustrated by simulations of a moving snake, tying of knots with a rope and a solution of the inverse kinematics of a planar hyper-redundant manipulator. The simulations show that the tractrix based algorithm leads to a more ‘natural’ motion since the motion is distributed uniformly along the entire object with the displacements diminishing from the ‘head’ to the ‘tail’.

Kinematics of a hyper-redundant manipulator by means of screw theory

In this work the kinematics of a hyper-redundant manipulator built with an optional number of parallel manipulators with identical topologies assembled in series connection is carried out by using the theory of screws. First, closed-form solutions to solve the kinematics, up to the acceleration analysis, of the base module, an asymmetrical three-degree-of-freedom (dof) parallel manipulator with mixed motions, are derived using geometric procedures and the theory of screws; later, the symbolic results thus obtained are applied recursively to solve the kinema-tics of the proposed hyper-redundant manipulator. A 12-dof hyper-redundant manipulator is included as a case study.

Solving the kinematics and dynamics of a modular spatial hyper-redundant manipulator by means of screw theory

In this contribution, a systematic methodology for solving the kinematic and dynamic analyses of a modular spatial hyper-redundant manipulator built with an optional number of serially connected three-legged in-parallel manipulators are presented.

Anti-windup adaptive control of concatenated closed-link hyper-redundant manipulators

This paper addresses the problem of controlling serial link hyper-redundant manipulators (HRM). Due to the large number of degrees of freedom (DOF) in such devices, the associated dynamics are relatively complicated, non-linear, and subject to a high level of parameter uncertainty. This makes the control problem particularly difficult to solve. An adaptive control scheme based on the minimum control synthesis (MCS) algorithm has therefore been proposed that has been successfully used for controlling similarly complex machines and devices across a number of diverse fields. MCS has a number of attractive features: e.g. no a priori knowledge of the robot structure is required, there is no need for parameter identification, no precise adjustment of control parameters is necessary, and stability proofs have been well established. After a brief summary of the basic MCS algorithm, an improved algorithm is introduced, which provides a more robust environment in terms of adaptive gain windup protection. A proof of stability, based upon the passivity criterion, is also provided. Simulation results are included, which demonstrate the control effectiveness of the new adaptive algorithm when applied to a manipulator consisting of serially connected, closed-link units.