Showing papers on "Parallel manipulator published in 2014"
TL;DR: In this paper, a novel adaptive wearable ankle robot for the treatments of ankle sprain through physical rehabilitation is presented, which employs lightweight but powerful pneumatic muscle actuators which mimics skeletal muscles in actuation.
Abstract: This paper presents the development of a novel adaptive wearable ankle robot for the treatments of ankle sprain through physical rehabilitation. The ankle robot has a bioinspired design, devised after a careful study of the improvement opportunities in the existing ankle robots. Robot design is adaptable to subjects of varying physiological abilities and age groups. Ankle robot employs lightweight but powerful pneumatic muscle actuators (PMA) which mimics skeletal muscles in actuation. To address nonlinear characteristics of PMA, a fuzzy-based disturbance observer (FBDO) has been developed. Another instance of an adaptive fuzzy logic controller based on Mamdani inference has been developed and appended with the FBDO to compensate for the transient nature of the PMA. With the proposed control scheme, it is possible to simultaneously control four parallel actuators of the ankle robot and achieve three rotational degrees of freedom. To evaluate the robot design, the disturbance observer, and the adaptive fuzzy logic controller, experiments were performed. The ankle robot was used by a neurologically intact subject. The robot-human interaction was kept as active-passive while the robot was operated on predefined trajectories commonly adopted by the therapists. Trajectory tracking results are reported in the presence of an unpredicted human user intervention, use of compliant and nonlinear actuators, and parallel kinematic structure of the ankle robot.
176 citations
TL;DR: In this paper, a robust PID controller is proposed for the cable-driven parallel manipulators to ensure that all cables remain in tension and internal force concept is used in the proposed PID control algorithm.
174 citations
TL;DR: In this paper, control of fully-constrained parallel cable robots with elastic cables is studied in detail and the effectiveness of the proposed control law is verified through simulations.
Abstract: In this paper, control of fully–constrained parallel cable robots with elastic cables is studied in detail. In the modeling process, longitudinal vibration of cables is considered as their dominant dynamics, and the governing equations of motion are rewritten to the standard form of singular perturbation. The proposed composite controller consists of two main components. A rigid controller is designed based on the slow or rigid model of the system and a corrective term is added to guarantee asymptotic stability of the fast dynamics. Then, by using Tikhonov theorem, slow and fast variables are separated and incorporated into the stability analysis of the overall closed–loop system, and a set of sufficient conditions for the stability of the total system is derived. Finally, the effectiveness of the proposed control law is verified through simulations.
151 citations
TL;DR: This article focuses on the design, modeling, and control of an aerial manipulator prototype, i.e., an innovative configuration consisting of a miniature quadrotor helicopter endowed with a robotic manipulator.
Abstract: This article focuses on the design, modeling, and control of an aerial manipulator prototype, i.e., an innovative configuration consisting of a miniature quadrotor helicopter endowed with a robotic manipulator. The overall system is designed to accomplish operations that require physical interaction with the surrounding environment while remaining airborne. To investigate the dynamical model of the aerial manipulator, a simple planar benchmark is used to analyze the interactions between the quadrotor, the robotic manipulator, and the environment. A control strategy for the planar system is designed to guarantee robustness in the presence or absence of contacts. Experiments on a real setup validate the control in the two different scenarios in which the aerial manipulator is either freely flying or physically interacting with the environment.
138 citations
29 Sep 2014
TL;DR: A new kinematical coupling for control is proposed by introducing an additional manipulation DoF realized by helicopter rotation around its yaw axis and dynamical coupling which is implemented by modification of the helicopter controller feeding the interaction force/torque, measured between manipulator base and fuselage, directly to the actuators of the rotor blades.
Abstract: This paper is devoted to a system for aerial
manipulation, composed of a helicopter and an industrial manipulator. The usage of an industrial manipulator is motivated by practical applications which were identified in different cooperation projects with the industry. We address the coupling between manipulator and helicopter and show that even in case when we have an ideal controller for manipulator and a highperformance controller for helicopter, an unbounded energy flow can be generated by internal forces between helicopter and manipulator if both controllers are used independently. To solve this problem we propose a new kinematical coupling for control by introducing an additional manipulation DoF realized by helicopter rotation around its yaw axis. The new experimental setup and required modifications in the manipulator controller for this purpose are described. Further, we propose dynamical coupling which is implemented by modification of the helicopter controller feeding the interaction force/torque, measured between
manipulator base and fuselage, directly to the actuators
of the rotor blades. At the end, we present experimental results for aerial manipulation and their analysis
130 citations
TL;DR: The main contribution of this paper is to determine the control action with the aid of the fractional-order PI λDμ controller different from previously defined controller structures.
Abstract: In this paper, a 3-degrees-of-freedom parallel manipulator developed by Tsai and Stamper known as the Maryland manipulator is considered. In order to provide dynamic analysis, three different sequential trajectories are taken into account. Two different control approaches such as the classical proportional-integral-derivative (PID) and fractional-order PID control are used to improve the tracking performance of the examined manipulator. Parameters of the controllers are determined by using pattern search algorithm and mathematical methods for the classical PID and fractional-order PID controllers, respectively. Design procedures for both controllers are given in detail. Finally, the corresponding results are compared. Performance analysis for both of the proposed controllers is confirmed by simulation results. It is observed that not only transient but also steady-state error values have been reduced with the aid of the PIλDμ controller for tracking control purpose. According to the obtained results, the fractional-order PIλDμ controller is more powerful than the optimally tuned PID for the Maryland manipulator tracking control. The main contribution of this paper is to determine the control action with the aid of the fractional-order PI λDμ controller different from previously defined controller structures. The determination of correct and accurate control action has great importance when high speed, high acceleration, and high accuracy needed for the trajectory tracking control of parallel mechanisms present unique challenges.
127 citations
TL;DR: In this paper, the development of the cable-driven parallel manipulator is first introduced in general and the latest advance in theory and applications is presented in detail, especially some notable implementations.
Abstract: In the last two decades, cable-driven parallel robots have attracted a lot of attention in robot community as a hot topic of robot research. In this paper, the development of the cable-driven paral...
98 citations
TL;DR: The minimal interaction forces needed to generate compliant motion are quantified and the ability of the controller to minimize interaction forces during insertion through tortuous passages is demonstrated.
Abstract: During exploration through tortuous unstructured passages by continuum robots, methods are required to minimize the force interaction between the environment and the robot along its length. This paper presents and evaluates an algorithm for compliant motion control of continuum robots subjected to multiple unknown contacts with the environment. A mapping of external wrenches to a generalized force in the configuration space of a multisegment continuum robot is presented and related to measured joint-level actuation forces. These measurements are applied as inputs to a low-level compliant motion controller. Friction and modeling uncertainties, presenting an unknown nonlinear deviation from the nominal system model, are corrected via a feed-forward estimate provided by a support vector machine. The controller is evaluated on O9 and O5 mm multisegment continuum robots. We quantify the minimal interaction forces needed to generate compliant motion and demonstrate the ability of the controller to minimize interaction forces during insertion through tortuous passages.
98 citations
TL;DR: In this paper, a reconfigurable modular parallel robot is presented, where the spherical joint which connects each leg to the end-effector is realized as a combination of revolute pairs; a locking system allows one to alternatively fix one of the revolute joints, giving the machine different 3-CPU kinematic configurations which correspond to different types of mobility.
90 citations
TL;DR: This paper investigates the type synthesis of the RPR-equivalent PM, which can undergo a 3-degree-of-freedom (DOF) motion that is the product of a rotation followed by a translation and another rotation.
Abstract: The moving platform of an RPR-equivalent parallel mechanism (PM) can undergo a 3-degree-of-freedom (DOF) motion that is the product of a rotation followed by a translation and another rotation. A 5-DOF hybrid parallel manipulator can be developed by adding an x-y gantry or an RR serial mechanism to an RPR-equivalent PM, which is suitable for manipulations requiring high rigidity and accuracy with good dexterity along surfaces of the 3-D space. This paper investigates the type synthesis of the RPR-equivalent PM. First, the RPR motion is briefly discussed. Then, the kinematic bonds of limb chains and their mechanical generators are presented. Structural conditions for constructing an RPR-equivalent PM are presented. Furthermore, the RPR-equivalent PMs are classified into several categories, depending on the DOF of its limb chains. Numerous new architectures of the RPR-equivalent PMs are synthesized.
89 citations
01 May 2014
TL;DR: This paper describes the construction of a prototype manipulator structure with six compliant legs connected in a parallel pattern similar to that of a Stewart-Gough platform, and forms the static forward and inverse kinematics problems for such manipulators as the solution to multiple Cosserat-rod models with coupled boundary conditions.
Abstract: In this paper, we investigate continuum manipulators that are analogous to conventional rigid-link parallel robot designs. These “parallel continuum manipulators” have the potential to inherit some of the compactness and compliance of continuum robots while retaining some of the precision, stability, and strength of rigid-link parallel robots, yet they represent a relatively unexplored area of the broad manipulator design space. We describe the construction of a prototype manipulator structure with six compliant legs connected in a parallel pattern similar to that of a Stewart-Gough platform. We formulate the static forward and inverse kinematics problems for such manipulators as the solution to multiple Cosserat-rod models with coupled boundary conditions, and we test the accuracy of this approach in a set of experiments, including the prediction of leg buckling. An inverse kinematics simulation of slices through the 6 degree-of-freedom (DOF) workspace illustrates the kinematic mapping, range of motion, and force required for actuation, which sheds light on the potential advantages and tradeoffs that parallel continuum manipulators may bring. Potential applications include miniature wrists and arms for endoscopic medical procedures, and lightweight compliant arms for safe interaction with humans.
TL;DR: In this article, a geometric and kinematic analysis of the 3-RPS parallel manipulator is performed using algebraic equations, and conditions for singular poses are derived from the constraint equations by discussing the Jacobian of the set of constraint equations.
TL;DR: Two trajectory-planning approaches for the point-to-point motion of planar two-degree-of-freedom (dof) cable-suspended parallel mechanisms using trigonometric functions to ensure continuity of the accelerations are presented.
Abstract: This paper presents two trajectory-planning approaches for the point-to-point motion of planar two-degree-of-freedom (dof) cable-suspended parallel mechanisms. The proposed techniques can be used to plan trajectories that extend beyond the static workspace of the mechanism. Trajectories are specified as a list of target points that must be reached in sequence, with a zero velocity at each of the target points. In the first technnique, polynomial trajectories are designed to connect the target points, while the second approach uses trigonometric functions. Both techniques ensure continuity of the accelerations. Based on the dynamic model of the robot, algebraic inequalities are obtained that represent the constraints on cable tensions. These inequalities are used to determine the feasibility of the planned trajectories. Polynomial trajectories must be discretized in order to verify feasibility, while trajectories that are based on trigonometric functions can be verified globally, based on a set of simple algebraic equations. Example trajectories are given in order to illustrate the approach. An experimental validation is also presented using a two-dof prototype, and two video extensions are provided to demonstrate the results.
01 Jan 2014
TL;DR: An improved method to compute force distributions for cable-driven parallel robots by modifying the closed-from solution such that the region where a solution is found is extended almost to the theoretical maximum, i.e. the wrench-feasible workspace.
Abstract: In this paper we present an improved method to compute force distributions for cable-driven parallel robots. We modify the closed-from solution such that the region where a solution is found is extended almost to the theoretical maximum, i.e. the wrench-feasible workspace. At the same time continuity along trajectories as well as real-time efficiency are maintained. The algorithm’s complexity and thus the computational burden scales linearly in the number of redundant cables. Therefore, the algorithm can also be used for highly redundant cable robots. The proposed algorithm is compared to known methods and computational results are presented based on the IPAnema prototype.
TL;DR: In this article, a case study on a reconfigurable hybrid parallel robot dubbed ReSl-Bot is presented, which addresses the realm of 6-DOF parallel mechanisms for sustainable manufacturing.
Abstract: This paper presents a case study on a reconfigurable hybrid parallel robot dubbed ReSl-Bot. It addresses the realm of reconfigurable 6-DOF parallel mechanisms, for sustainable manufacturing. It also features a self-reconfigurable architecture. A systematic analysis involving kinematics, constant orientation workspace, singularity and stiffness is developed in detail. Interesting features are discussed, revealing some unique characteristics of the studied architecture. A multi-objective optimization procedure is also carried out with weighted stiffness, dexterity and workspace volume as the performance indices.
TL;DR: The proposed approach is illustrated with the design optimization of an unlimited-roll spherical parallel manipulator with a main objective to minimize the mechanism mass in order to enhance both kinematic and dynamic performances.
TL;DR: In this paper, the effects of joint clearance on the dynamic performance of a planar 2-DOF pick-and-place parallel manipulator are investigated by using a continuous analysis approach that is combined with a contact force model considering hysteretic damping.
Abstract: In this study, the effects of joint clearance on the dynamic performance of a planar 2-DOF pick-and-place parallel manipulator are investigated. The parallel manipulator is modeled by multi-body system dynamics. The contact effect in revolute joints with clearance is established by using a continuous analysis approach that is combined with a contact force model considering hysteretic damping. The evaluation of the contact force is based on Hertzian contact theory that accounts for the geometrical and material properties of the contacting bodies. Furthermore, the incorporation of the friction effect in clearance joints is performed using a modified Coulomb friction model. By numerical simulation, variations of the clearance joint's eccentric trajectory, the joint reaction force, the input torque, the acceleration, and trajectory of the end-effector are used to illustrate the dynamic behavior of the mechanism when multiple clearance revolute joints are considered. The results indicate that the clearance joints present two obvious separation leaps in a complete pick-and-place working cycle of the parallel manipulator, following a collision. The impact induces system vibration and thus reduces the dynamic stability of the system. The joint clearances affect the amplitudes of the joint reaction force, the input torque, and the end-effector's acceleration, additionally the joint clearances degrade the kinematic and dynamic accuracy of the manipulator's end-effector. Finally, this study proposes related approaches to decrease the effect of joint clearances on the system's dynamic properties for such parallel manipulator and prevent ''separation-leap-impact'' events in clearance joints.
TL;DR: This paper investigates the dynamic modeling and passivity-based control of a planar cable-actuated system using a lumped-mass method that explicitly considers the change in cable stiffness and winch inertia that occurs when the cables are wound around their respective winches.
Abstract: This paper investigates the dynamic modeling and passivity-based control of a planar cable-actuated system. This system is modeled using a lumped-mass method that explicitly considers the change in cable stiffness and winch inertia that occurs when the cables are wound around their respective winches. In order to simplify the modeling process, each cable is modeled individually and then constrained to the other cables. Exploiting the fact that the payload is much more massive than the cables allows the definition of a modified output called the μ -tip rate. Coupling the μ-tip rate with a modified input realizes the definition of a passive input-output map. The two degrees of freedom of the system are controlled by four winches. This overactuation is simplified by employing a set of load-sharing parameters that effectively reduce four inputs to two. The performance and robustness of the controllers are evaluated in the simulation.
TL;DR: In this article, a new cascade load force control design for a parallel robot platform is proposed, where a parameter search based on particle swarm optimization (PSO) is suggested to effectively search the parameters of the cascade controller.
Abstract: A new cascade load force control design for a parallel robot platform is proposed. A parameter search for a proposed cascade controller is difficult because there is no methodology to set the parameters and the search space is broad. A parameter search based on particle swarm optimization (PSO) is suggested to effectively search the parameters of the cascade controller. We used a unified mathematical model of a hydraulic actuator of parallel robot platform. These equations are readily applicable to various types of proportional valves, and they unify the cases of critical center, overlapped, and underlapped valves. These unified model equations are useful for nonlinear controller design. Simulation results show the advantages of the proposed optimal tuned cascade controller to solve the formulated tracking problem in relation to the classical proportional–integral (PI) controller.
TL;DR: In this article, the authors proposed a novel one-translational-three-rotational (1T3R) parallel manipulator with an articulated travelling plate, which can provide high stiffness and good accuracy performances in the assemblage.
Abstract: Driven by the requirements of the large-scale component assemblage for the docking platform, this paper proposes a novel one-translational-three-rotational (1T3R) parallel manipulator with an articulated travelling plate, which can provide high stiffness and good accuracy performances in the assemblage. The underlying architecture of this manipulator is briefly addressed with emphasis on the practical realization of the articulated travelling plate. On the basis of the kinematic analysis of the 1T3R parallel manipulator, its optimal design considering the force and motion transmissibility is carried out, in which the generalized virtual power transmissibility of this manipulator is defined. This paper aims at laying a solid theoretical and technical foundation for the prototype design and manufacture of the 1T3R parallel manipulator.
30 Jun 2014
TL;DR: A systematic procedure to solve a complex nonlinear optimization problem to find optimal reconfiguration for the robot is presented and critical issues regarding various constraints and performance criteria are addressed.
Abstract: In this paper, a new type of large-dimension reconfigurable suspended cable-driven parallel robots (CDPR) is introduced as a means to substitute for conventional methods of handing large and heavy parts across wide workspaces. The reconfigurability of the proposed CDPR offers better performances in term of workspace, flexibility and power consumption. A systematic procedure to solve a complex nonlinear optimization problem to find optimal reconfiguration for the robot is presented. Critical issues regarding various constraints and performance criteria are addressed. The robot can operate in offline reconfiguration or online reconfiguration modes which offer wide range of solutions to the end-users.
TL;DR: In this paper, a novel conveyor that uses redundantly actuated parallel manipulators was proposed to obtain the maximum dynamic load-carrying capacity of the conveyor by optimizing the internal forces of the redundant manipulators.
Abstract: Conveyors are important equipment in the painting shop. Conveyors with cantilever beams have low load-carrying capacity and can carry small cars. To solve this problem, this paper presents a novel conveyor that uses redundantly actuated parallel manipulators. A method is proposed to obtain the maximum dynamic load-carrying capacity of the conveyor by optimizing the internal forces of the redundantly actuated parallel manipulators. To improve the dynamic load-carrying capacity, approaches using counterweights are utilized and compared. Furthermore, the maximum dynamic load-carrying capacity of the redundant parallel manipulator is compared with that of its nonredundant counterpart.
TL;DR: In this paper, an adaptive control scheme for a 3DOF parallel manipulator is proposed to cope with some of the structural uncertainties in model-based control, e.g. friction parameters and unknown payload.
Abstract: Model-based control improves robot performance provided that the dynamics parameters are estimated accurately. However, some of the model parameters change with time, e.g. friction parameters and unknown payload. Particularly, off-line identification approaches omit the payload estimation (due to practical reasons). Adaptive control copes with some of these structural uncertainties. Thus, this work implements an adaptive control scheme for a 3-DOF parallel manipulator. The controller relies on a novel relevant-parameter dynamic model that permits to study the cases in where the uncertainties affect: (1) rigid body parameters, (2) friction parameters, (3) actuator dynamics, and (4) a combination of the former cases. The simulations and experiments verify the performance of the proposed controller. The control scheme is implemented on the modular programming environment Open Robot Control Software (OROCOS). Finally, an experimental setup evaluates the controller performance when the robot handles a payload.
TL;DR: In this article, a new method is proposed to analyze the dynamic reliability and parameter sensitivity of space manipulator with harmonic drive, which is suitable for reliability apportionment when the design information has not been clearly identified, particularly in early design phrase.
TL;DR: This paper creatively proposes a flow path to synthesize a novel class of n-degree-of-freedom (n-DoF) for five-axis numerical control machine for its executive mechanism.
Abstract: Driven by requirements of five-axis numerical control (NC) machine for its executive mechanism, this paper creatively proposes a flow path to synthesize a novel class of n-degree-of-freedom (n-DoF, ...
TL;DR: In this article, a 3-degrees-of-freedom (DoF) parallel robot with wire-actuated prismatic legs is presented for the insertion of perimodiolar electrode arrays into the inner ear.
Abstract: Cochlear implant surgery is a procedure that requires delicate insertion of an electrode array into the inner ear. This paper reports the clinical motivation, design considerations, analysis, and design optimization of a new robot for electrode arrays insertion. This paper describes a new approach for coordinated insertion of perimodiolar electrode arrays in order to minimize shape discrepancy between the shape of the electrode array and the shape of the inner ear anatomy. A new design of a 3-degrees-of-freedom (DoF) parallel robot with wire-actuated prismatic legs is presented. The dimensional synthesis of the robot design was based on satisfying the accuracy, speed, system size, and workspace requirements. The robot prototype is validated experimentally to execute electrode insertions in plastic models of temporal bones.
TL;DR: Results show that the DSC framework can further improve the control performances of the current control algorithms designed in the physical space of spatial multi-DOF parallel robots, by solving the problem of dynamic coupling effects.
Abstract: This paper proposes a decoupled-space control (DSC) framework for spatial multi-degrees-of-freedom (DOF) parallel robots, to further improve the control performances of the currently studied control algorithms, via realizing the decoupling of the control space, using singular value decomposition (SVD) algorithms. Making use of the positive definite property of the mass/inertia matrix of spatial multi-DOF parallel robots, the decoupled matrix, an orthogonal matrix, can be derived by applying SVD algorithms. Through space transformation with the decoupled matrix, a spatial multi-DOF parallel robot model can be expressed in an uncoupled space. The independent control design can be implemented for each control channel in the uncoupled space, and the strongly dynamic coupling effects in the current control strategies can be removed. To confirm the proposed DSC framework, a simple controller, as an example, is developed in the decoupled space with the desired and real actuator position as its input and the valve command as its output. Under the proposed DSC strategy, the control performances of spatial multi-DOF parallel robots are evaluated in simulation and experiment. Results show that the DSC framework can further improve the control performances of the current control algorithms designed in the physical space of spatial multi-DOF parallel robots, by solving the problem of dynamic coupling effects.
06 Nov 2014
TL;DR: Key sensing and manipulator capabilities of the r-one robot are detailed, including a flexible IR communication/localization/obstacle detection system, high-precision quadrature encoders, gyroscope, accelerometer, integrated bump sensor, and light sensors.
Abstract: Multi-robot manipulation allows for scalable environmental interaction, which is critical for multi-robot systems to have an impact on our world. A successful manipulation model requires cost-effective robots, robust hardware, and proper system feedback and control. This paper details key sensing and manipulator capabilities of the r-one robot. The r-one robot is an advanced, open source, low-cost platform for multi-robot manipulation and sensing that meets all of these requirements. The parts cost is around $250 per robot. The r-one has a rich sensor suite, including a flexible IR communication/localization/obstacle detection system, high-precision quadrature encoders, gyroscope, accelerometer, integrated bump sensor, and light sensors. Two years of working with these robots inspired the development of an external manipulator that gives the robots the ability to interact with their environment. This paper presents an overview of the r-one, the r-one manipulator, and basic manipulation experiments to illustrate the efficacy our design. The advanced design, low cost, and small size can support university research with large populations of robots and multi-robot curriculum in computer science, electrical engineering, and mechanical engineering. We conclude with remarks on the future implementation of the manipulators and expected work to follow.
01 Oct 2014-Precision Engineering-journal of The International Societies for Precision Engineering and Nanotechnology
TL;DR: In this article, a flexure-based parallel manipulator (FPM) is presented that delivers nanometric co-planar alignment and direct-force imprinting capabilities to automate an ultra-violet nano-imprint lithography (UV-NIL) process.
Abstract: This paper presents a flexure-based parallel manipulator (FPM) that delivers nanometric co-planar alignment and direct-force imprinting capabilities to automate an ultra-violet nanoimprint lithography (UV-NIL) process. The FPM is articulated from a novel 3-legged prismatic-prismatic-spherical (3PPS) parallel-kinematic configuration to deliver a theta(x)-theta(y)-Z motion. The developed FPM achieves a positioning and orientation resolution of +/-10 nm and 0.05" respectively, and a continuous output force of 150 N/Amp throughout a large workspace of 5 degrees x5 degrees x 5 degrees mm. Part I mainly focuses on a new theoretical model that is used to analyze the stiffness characteristics of the compliant joint modules that formed the FPM, and experimental evaluations of each compliant joint module. Part II presents the stiffness modeling of the FPM, the performance evaluations of the developed prototype, and the preliminary results of the UV-NIL process. (C) 2014 Elsevier Inc. All rights reserved.
08 Jul 2014
TL;DR: This work considers a CDPR platform within a 6D workspace, and as sources of interference the collisions with the robot's environment and self interference are considered.
Abstract: The main advantage of CDPRs is large workspaces. However, multiple legs and large workspace are both factors for interference. We consider a CDPR platform within a 6D workspace, and as sources of interference the collisions with the robot's environment and self interference. We present two algorithms and their interval analysis-based applications to handle the different types of interference. Finally, the efficiencies of the algorithms are presented.