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This paper demonstrates the design of compliant grip-and-move manipulators by structural optimization using genetic algorithms. The manipulator is composed of two compliant mechanisms (each with two degrees of freedom) that work like two fingers so that the manipulator can grip an object and convey it from one point to another anywhere within a two-dimensional workspace. The synthesis of such compliant mechanisms is accomplished by formulating the problem as a structural topology and shape optimization problem with multiple objectives and constraints to achieve the desired behavior of the manipulator. A multiobjective genetic algorithm is then applied coupled with an enhanced morphological representation for defining and encoding the structural geometry variables. The solution framework is integrated with a nonlinear finite element code for large-displacement analyses of the compliant structures to compute the paths generated by these mechanisms, with the resulting optimal designs used to realize various manipulator configurations. [DOI: 10.1115/1.4001213]

The spherical 5R parallel manipulator is a typical parallel manipulator. It can be used as a pointing device or as a minimally invasive surgical robot. This study addresses the motion/force transmission analysis and optimization of the manipulator by taking into account the motion/force transmissibility. The kinematics of the manipulator is analyzed. Several transmission indices are defined by using screw theory for the performance evaluation and dimensional synthesis. The process of determining the optimal angular parameters based on performance charts is presented. The manipulator that has a large workspace and good motion/force transmissibility is identified. [DOI: 10.1115/1.4001129]

This paper presents a methodology for design of mobile vehicles, mounted with underactuated manipulators operating in a horizontal plane, such that the combined system is differentially flat. A challenging question of how to perform point-to-point motions in the state space of such a highly nonlinear system, in spite of the absence of some actuators in the arm, is answered in this paper. We show that, by appropriate inertia distribution of the links and addition of torsion springs at the joints, a range of underactuated designs is possible, where the underactuated mobile manipulator system is differentially flat. The differential flatness property allows one to efficiently solve the problem of trajectory planning and feedback controller design for point-to-point motions in the state space. The proposed method is illustrated by the example of a mobile vehicle with an underactuated three-link manipulator. [DOI: 10.1115/1.4000815]

Flexibility at the joint of a manipulator is an intrinsic property. Even 'rigid-joint' robots, in fact, possess a certain amount of flexibility. Previous experiments confirmed that joint flexibility should be explicitly included in the model when designing a high-performance controller for a manipulator because the flexibility, if not dealt with, can excite system natural frequencies and cause severe damage. However, control design for a flexible-joint robot manipulator is still an open problem. Besides being described by a complicated system model for which the passivity property does not hold, the manipulator is also underactuated, that is, the control input does not drive the link directly, but through the flexible dynamics. Our work offers another possible solution to this open problem. We use three-layer neural networks to represent the system model. Their weights are adapted in real time and from scratch, which means we do not need the mathematical model of the robot in our control algorithm. All uncertainties are handled by variable-structure control. Backstepping structure allows input efforts to be applied to each subsystem where they are needed. Control laws to adjust all adjustable parameters are devised using Lyapunov's second method to ensure that error trajectories are globally uniformly ultimately bounded. We present two state-feedback schemes: first, when neural networks are used to represent the unknown plant, and second, when neural networks are used to represent the unknown parts of the control laws. In the former case, we also design an observer to enable us to design a control law using only output signals--the link positions. We use simulations to compare our algorithms with some other well-known techniques. We use experiments to demonstrate the practicality of our algorithms. [DOI: 10.1115/1.3117185] Keywords: flexible-joint robot, backstepping, intelligent control, nonlinear systems, output feedback, variable-structure control neural networks

In this paper, a concept of totally decoupling is proposed for the design of a flexure parallel micromanipulator with both input and output decoupling. Based on flexure hinges, the design procedure for an XY totally decoupled parallel stage (TDPS) is presented, which is featured with decoupled actuation and decoupled output motion as well By employing (double) compound parallelogram flexures and a compact displacement amplifier, a class of novel XY TDPS with simple and symmetric structures are enumerated, and one example is chosen for further analysis. The kinematic and dynamic modeling of the manipulator are conducted by resorting to compliance and stiffness analysis based on the matrix method, which are validated by finite-element analysis (FEA). In view of predefined performance constraints, the dimension optimization is carried out by means of particle swarm optimization, and a prototype of the optimized stage is fabricated for performance tests. Both FEA and experimental studies well validate the decoupling property of the XY stage that is expected to be adopted into micro-/nanoscale manipulations. Index Terms--Dynamics, kinematics, mechanism design, micro-/nanorobots, parallel robots.

Safety is a critical factor when designing a robotic rehabilitation environment. Whole-limb or life-size haptic interaction would allow virtual robotic rehabilitation of daily living activities such as sweeping or shelving. However, it has been too dangerous to implement such an environment with conventional active robots that use motor, hydraulic, or pneumatic actuation. To address this issue, a life-size 6-degree-of-freedom (DOF) brake-actuated manipulator (BAM) was designed and constructed. This paper details the BAM's system models including mechanisms, kinematics, and dynamics, as well as detailed input and friction models. In addition, a new system-identification technique that utilizes human input to excite the robot's dynamics with unscented Kalman filtering was employed to identify system parameters. Noise sources are discussed, and the model is validated through force estimation with inverse dynamics. Model parameters and performance are compared with other commercially available haptic devices. The BAM shows a significantly larger workspace, maximum force, and stiffness over other devices exhibiting its promise toward rehabilitative applications. Index Terms--Brake-actuated manipulator (BAM), passive haptic, robotic rehabilitation, system identification, unscented Kalman filter.

The present paper describes the analytical solution of position kinematics for a three degree-of-freedom parallel manipulator. It also provides a numeric example of workspace calculation and a procedure for its optimization. The manipulator consists of a base and a moving platform connected to the base by three identical legs; each leg is provided with a PPS chain, where P designates an actuated prismatic pair, P stands for a passive prismatic pair, and S a spherical pair. The direct analysis yields a nonlinear system with eight solutions at the most. The inverse analysis is solved in three relevant cases: (i) the orientation of the moving platform is given, (ii) the position of a reference point of the moving platform is given, and (iii) two rotations (pointing) and one translation (focusing) are given. In the present paper it is proved that case (i) yields an inverse singularity condition of the mechanism; case (ii) provides a nonlinear system with four distinct solutions at the most; case (iii) allows the finding of some geometrical configurations of the actuated pairs for minimizing parasitic movements in the case of a pointing/focusing operation of the manipulator. [DOI: 10.1115/1.3116257]

In a master--slave system, improving the positioning performance and the stability is needed in the case of remote control. However, if there exists time delay, the system destabilizes the performance. Furthermore, it is important to maintain the stability of not only the system but also the controlled object. This paper describes a strategy to improve these problems. This strategy enables operators to get a degree of time delay and instability by keeping the motion performance and the stability. The unstable response with a time delay is restrained by adjusting PD controller gains based on the velocity error of master--slave. Furthermore, switching bilateral control and autonomous control of slave without falling into unstable state is constructed when that cannot be restrained because of long time delay or unexpected disturbances of slave motion. The validity of the proposed strategy is confirmed by experiments stabilizing an unstable component, i.e., an inverted pendulum of slave system. Index Terms--Bilateral control, inverted pendulum, manipulator, stabilizing control, time delay.

The multiobjective optimization of a four-degree-of-freedom symmetric parallel manipulator for Schonflies-motion generation is the subject of this paper. First, the inverse positioning problem is discussed, along with its velocity analysis. The workspace is then analyzed, thereby deriving a closed-form expression of the workspace volume, which depends on the orientation of the moving platform. Next, the isotropic design of the manipulator is obtained. Then, the dexterity analysis of the manipulator is conducted, which is one objective of the optimum design of the manipulator, a second objective being a normalized workspace volume. Finally, the results of the optimization process are reported in terms of a set of Pareto-optimum pairs of the design parameters. [DOI: 10.1115/1.3066659] Keywords: parallel manipulator, Schonflies-motion, optimization, multiobjective

This paper presents a sliding mode controller for a 2DOF planar pneumatic manipulator actuated by pleated pneumatic artificial muscle actuators. It is argued that it is necessary to account for the pressure dynamics of muscles and valves. A relatively detailed system model that includes pressure dynamics is established. Since the model includes actuator dynamics, feedback linearization was necessary to design a sliding mode controller. The feedback linearization and subsequent controller design are presented in detail, and the controller's performance is evaluated, both in simulation and experimentally. Chattering was found to be quite severe, so the introduction of significant boundary layers was required. [DOI: 10.1115/1.3023132] Keywords: pneumatic artificial muscles, flexible joints, sliding mode control, robotics

In this paper, a new four degrees of freedom 3T1R parallel manipulator with high-load carrying capacity is presented. This manipulator generates Schonflies motions, in which the moving platform carries out three independent translations and one rotation about one axis of fixed orientation. The particularity of the proposed architecture is the decoupling of the displacements of the platform in the horizontal plane from the platform's translation along the vertical axis. Such a decoupling allows the cancellation of the gravity loads on the actuators, which displace the platform in the horizontal plane. A prototype of the proposed manipulator with four degrees of freedom and an experimental validation of the suggested concept are also presented. Two cases have been examined on the built prototype: a manipulator with payload and one without. It was shown that the input torques of actuators displacing the platform in the horizontal plane for these two cases are the same; i.e., the payload does not bring any load to the actuators. [DOI: 10.1115/1.2991137] Keywords: parallel manipulators, kinematic decoupling, optimum design, Schonflies motions

In this paper, the authors examine the problem of designing nominal manipulator Jacobians that are optimally fault tolerant to one or more joint failures. Optimality is defined here in terms of the worst-case relative manipulability index. While this approach is applicable to both serial and parallel mechanisms, it is especially applicable to parallel mechanisms with a limited workspace. It is shown that a previously derived inequality for the worst-case relative manipulability index is generally not achieved for fully spatial manipulators and that the concept of optimal fault tolerance to multiple failures is more subtle than previously indicated. Lastly, the authors identify the class of 8-DOF Gough-Stewart platforms that are optimally fault tolerant for up to two joint failures. Examples of optimally fault-tolerant 7- and 8-DOF mechanisms are presented. Index Terms--Fault tolerance, kinematic redundancy, manipulability, parallel manipulators.

This paper proposes an analytical methodology of inverse kinematic computation for 7 DOF redundant manipulators with joint limits. Specifically, the paper focuses on how to obtain all feasible inverse kinematic solutions in the global configuration space where joint movable ranges are limited. First, a closed-form inverse kinematic solution is derived based on a parameterization method. Second, how the joint limits affect the feasibility of the inverse solution is investigated to develop an analytical method for computing feasible solutions under the joint limits. Third, how to apply the method to the redundancy resolution problem is discussed and analytical methods to avoid joint limits are developed in the position domain. Lastly, the validity of the methods is verified by kinematic simulations. Index Terms--Arm angle, inverse kinematics, joint limit, redundancy resolution, redundant manipulator.

This paper introduces a novel and general real-time adaptive motion planning (RAMP) approach suitable for planning trajectories of high-DOF or redundant robots, such as mobile manipulators, in dynamic environments with moving obstacles of unknown trajectories. The RAMP approach enables simultaneous path and trajectory planning and simultaneous planning and execution of motion in real time. It facilitates real-time optimization of trajectories under various optimization criteria, such as minimizing energy and time and maximizing manipulability. It also accommodates partially specified task goals of robots easily. The approach exploits redundancy in redundant robots (such as locomotion versus manipulation in a mobile manipulator) through loose coupling of robot configuration variables to best achieve obstacle avoidance and optimization objectives. The RAMP approach has been implemented and tested in simulation over a diverse set of task environments, including environments with multiple mobile manipulators. The results (and also the accompanying video) show that the RAMP planner, with its high efficiency and flexibility, not only handles a single mobile manipulator well in dynamic environments with various obstacles of unknown motions in addition to static obstacles, but can also readily and effectively plan motions for each mobile manipulator in an environment shared by multiple mobile manipulators and other moving obstacles. Index Terms--Adaptive, dynamic obstacles of unknown motion, loose coupling, mobile manipulators, partially specified goal, real time, redundant robots, trajectory optimization.

We propose a general and practical planning framework for generating 3-D collision-free motions that take complex robot dynamics into account. The framework consists of two stages that are applied iteratively. In the first stage, a collision-free path is obtained through efficient geometric and kinematic sampling-based motion planning. In the second stage, the path is transformed into dynamically executable robot trajectories by dedicated dynamic motion generators. In the proposed iterative method, those dynamic trajectories are sent back again to the first stage to check for collisions. Depending on the application, temporal or spatial reshaping methods are used to treat detected collisions. Temporal reshaping adjusts the velocity, whereas spatial reshaping deforms the path itself. We demonstrate the effectiveness of the proposed method through examples of a space manipulator with highly nonlinear dynamics and a humanoid robot executing dynamic manipulation and locomotion at the same time. Index Terms--Collision avoidance, dynamics, humanoid, motion planning, space manipulator.

In this paper, a singularity-robust inverse kinematics is newly suggested by using a Lagrange multiplier for redundant manipulator systems. Two tasks are considered with priority orders under the assumption that a primary task has no singularity. First, an inverse kinematics problem is formulated to be an optimization one subject to an equality constraint, in other words, to be a minimization problem of secondary task error subject to an equality constraint for primary task execution. Second, in the procedure of minimization for a given objective function, a new inverse kinematics algorithm is derived. Third, since nonzero Lagrange multiplier values appear in the neighborhood of a singular configuration of a robotic manipulator, we choose them as a natural choice of the dampening factor to alleviate the ill-conditioning of matrix inversion, ultimately for singularity-robust inverse kinematics. Finally, the effectiveness of the suggested singularity-robust inverse kinematics is shown through a numerical simulation about deburring and conveyance tasks of a dual arm manipulator system. [DOI: 10.1115/1.2957632]

Soft robotic manipulators, unlike their rigid-linked counterparts, deform continuously along their lengths similar to elephant trunks and octopus arms. Their excellent dexterity enables them to navigate through unstructured and cluttered environments and to handle fragile objects using whole arm manipulation. This paper develops optimal designs for OctArm manipulators, i.e., multisection, trunklike soft arms. OctArm manipulator design involves the specification of air muscle actuators and the number, length, and configuration of sections that maximize dexterity and load capacity for a given maximum actuation pressure. A general method of optimal design for OctArm manipulators using nonlinear models of the actuators and arm mechanics is developed. The manipulator model is based on Cosserat rod theory, accounts for large curvatures, extensions, and shear strains, and is coupled to the nonlinear Mooney-Rivlin actuator model. Given a dexterity constraint for each section, a genetic algorithm-based optimizer maximizes the arm load capacity by varying the actuator and section dimensions. The method generates design rules that simplify the optimization process. These rules are then applied to the design of pneumatically and hydraulically actuated OctArm manipulators using lOO psi and 1000 psi maximum pressures, respectively. [DOI: 10.1115/1.2943300]

This paper presents methodologies for the analysis and design of redundant manipulators, especially macro-/ministructures, for improved dynamic performance. Herein, the dynamic performance of a redundant manipulator is characterized by the end-effector inertial and acceleration properties. The belted inertia ellipsoid is used to characterize inertial properties, and the recently developed dynamic capability equations are used to analyze acceleration capability. The approach followed here is to design the ministructure to achieve the task performance and then to design the macrostructure to support and complement the ministructure, referred to here as modular design. The methodology is illustrated in the design of a six-degree-of-freedom planar manipulator. [DOI: 10.1115/1.2936892] Keywords: redundancy resolution, redundant manipulator, dynamic performance, acceleration, actuator, design

This paper proposes a systematic methodology for dimension synthesis, kinematics, and statics of a novel 2SPS + SPR + SP parallel manipulator with 3DOF. First, a workspace is varied and analyzed by varying the orientation of a revolute joint, and an optimum orientation of revolute joint is determined. Second, the inverse displacement is analyzed, and the formulas are derived for solving general inverse/forward velocities and accelerations. Third, the geometric constraints of constrained forces are determined and the formulas are derived for solving the active/constrained forces. [DOI: 10.1115/1.2936897] Keywords: parallel manipulator, workspace, kinematics, statics

This paper proposes a novel dynamic structure neural-fuzzy network (DSNFN) via a robust adaptive sliding-mode approach to address trajectory-tracking control of an n-link robot manipulator. In the DSNFN, a five-layer neural-fuzzy network (NFN) is used to model complex processes and compensate for structured and unstructured uncertainties. However, it is difficult to find a suitable-sized NFN to achieve the required approximation error. To deal with the mentioned problem, the number of rule nodes in the DSNFN can be either increased or decreased over time based on the tracking errors, and the adaptation laws in the sense of a projection algorithm are derived for tuning all parameters of the parameterized NFN. Using DSNFN, good tracking performance could be achieved in the system. Furthermore, the trained network avoids the problems of overfitting and underfitting. The global stability and the robustness of the overall control scheme are guaranteed, and the tracking errors converge to the required precision by the Lyapunov synthesis approach. Experiments performed on a two-link robot manipulator demonstrate the effectiveness of our scheme. Index Terms--Adaptive tuning algorithm, dynamic structure neural-fuzzy network (DSNFN), robot manipulator, stability and robustness.

This paper deals with the dynamic parameter identification of a 3DOF parallel manipulator with actuation redundancy. A method for finding the parameter linear form of the dynamic equation is presented. Based on the virtual work principle, the dynamic equation for the application of dynamic parameter identification is obtained by extracting the dynamic parameters from inertial forces and moments of moving parts. Two-step identification approach is used to identify the dynamic parameters of the redundantly actuated parallel manipulator. The approach consists of two steps and utilizes simple point-to-point motions that lead to a separation of friction and rigid-body dynamics. The identified results are validated by experiments. Moreover, the experimental application of the identified model to a machine tool, which is created by combining the parallel manipulator with a 2DOF worktable, demonstrates the efficiency of dynamic parameter identification. [DOI: 10.1115/1.2952823] Keywords: dynamic parameter identification, parallel manipulator, actuation redundancy, dynamic equation

The development of reliable and repeatable strategies to manipulate and assemble microobjects lies in the efficiency, reliability, and precision of the handling processes. In this paper, we propose a thermal-based microgripper working in an aqueous medium. Manipulating and assembling in liquid surroundings can indeed be more efficient than in dry conditions. A comparative analysis of the impact of dry and liquid media on surface forces, contact forces, and hydrodynamic forces is shown. In addition, ice grippers represent flexible manipulation solutions. Nevertheless, when micromanipulation tasks are performed in air, capillary forces can drastically perturb the release. Our submerged freeze microgripper exploits the liquid surroundings to generate an ice droplet to catch microobjects, and to avoid capillary forces during the release. The thermal principle, the first microgripper prototype, an ice generation simulation, and the first tests are presented. The main objective is to validate the manipulation principle. Further research will be focused on control and optimization of the ice generation and the miniaturization of the system. Index Terms--Ice gripper, micromanipulation, Peltier effect.

Unlike traditional rigid linked robots, soft robotic manipulators can bend into a wide variety of complex shapes due to control inputs and gravitational loading. This paper presents a new approach for modeling soft robotic manipulators that incorporates the effect of material nonlinearities and distributed weight and payload. The model is geometrically exact for the large curvature, shear, torsion, and extension that often occur in these manipulators. The model is based on the geometrically exact Cosserat rod theory and a fiber reinforced model of the air muscle actuators. The model is validated experimentally on the OctArm V manipulator, showing less than 5% average error for a wide range of actuation pressures and base orientations as compared to almost 50% average error for the constant-curvature model previously used by researchers. Workspace plots generated from the model show the significant effects of self-weight on OctArm V. Index Terms--Air muscle actuators, Cosserat rods, soft robots.

This paper proposes a new solution to the problem of torque minimization of spatial parallel manipulators. The suggested approach involves connecting a secondary mechanical system to the initial structure, which generates a vertical force applied to the manipulator platform. Two versions of the added force are considered: constant and variable. The conditions for optimization are formulated by the minimization of the root-mean-square values of the input torques. The positioning errors of the unbalanced and balanced parallel manipulators are provided. It is shown that the elastic deformations of the manipulator structure, which are due to the payload, change the altitude and the inclination of the platform. A significant reduction of these errors is achieved by using the balancing mechanism. The efficiency of the suggested solution is illustrated by numerical simulations and experimental verifications. The prototype of the suggested balancing mechanism for the Delta robot is also presented. [DOI: 10.1115/1.2901057] Keywords: balancing, torque compensation, parallel mechanisms, Delta robot

We report a new two-axis active optical fiber manipulator for on-chip optical manipulation and detection in microfluidic environment. The system comprising of air chambers, fiber channels, controllable moving walls, and membrane structures were fabricated by using microelectromechanical systems technology. By adjusting air pressures to control the deflection of the pneumatic chambers placed orthogonal to and underneath the fiber channels, accurate alignment of a pair of approximately coaxial optical fibers, which was indicated by maximizing fiber-to-fiber optical-coupling measured in real time, has been achieved. A maximum displacement of a buried fiber as large as 13 [micro]m at an applied pressure of 40 lb/[in.sup.2] for one air chamber has been demonstrated. It was sufficient to accurately align two approximately coaxial optical fibers to maximize the optical coupling efficiency. The maximum coupling efficiency for two single-mode optical fibers facing each other at a distance of 200 [micro]m was measured to be 4.1%. The following features have been successfully demonstrated with this system: 1) stable optical trapping and stretching of a single red blood cell; 2) stable optical trapping of multiple microparticles; 3) optically driven controlled motion of single and multiple microparticles; and 4) integration of a counterpropagating dual-beam trap with single-beam optical tweezers. In addition to optical trapping and manipulation, the proposed device is promising for applications requiring coaxial input/output fibers for in-line optical analysis. Furthermore, it can be easily integrated with other microfluidic devices such as microcapillary electrophoresis channels or microflow cytometers for DNA, protein, and cell analysis. [2007-0182] Index Terms--Microcoupler, microelectromechanical systems (MEMS), microfluidics chip, moving wall, optical detection, optical trappers.

Parallel manipulators feature relatively high payload and accuracy capabilities compared to their serial counterparts. However, they suffer from small workspace and low maneuverability. Kinematic redundancy for parallel manipulators can improve both of these characteristics. This paper presents a family of new kinematically redundant planar parallel manipulators with six actuated-joint degrees of freedom based on a 3-PRRR architecture obtained by adding an active prismatic joint at the base of each limb of the 3-RRR manipulator First, the inverse displacement of the manipulators is explained, then their reachable and dexterous workspaces are obtained. Comparing the proposed redundant manipulators to the original 3-RRR nonredundant manipulator, both reachable and dexterous workspaces are substantially larger. Next, the Jacobian matrices of the manipulators are derived, and different types of singularities are analyzed and demonstrated. It is shown that the vast majority of singularities can be avoided by using kinematic redundancy.

A six-DOF wrist-partitioned parallel manipulator is a parallel manipulator in which three of the six actuated joints are used to control the position of a point on the moving platform while the other three are further used to control the orientation of the moving platform. Such parallel manipulators are, in fact, the parallel counterparts of the wrist-partitioned serial manipulators, which are widely used in industry. Unlike parallel manipulators of a general structure, a six-DOF wrist-partitioned parallel manipulator usually has simple kinematic characteristics such as its forward displacement analysis and singularity analysis are easy to solve. This paper deals with the type synthesis of six-DOF wrist-partitioned parallel manipulators. An approach is first proposed for the type synthesis of this class of parallel manipulators. Using the proposed approach, six-DOF wrist-partitioned parallel manipulators can be constructed from the types of three-DOF nonoverconstrained spherical parallel manipulators. A large number of six-DOF wrist-partitioned parallel manipulators are then obtained, and several types of practical relevance are also identified. Keywords: parallel mechanism, wrist-partioned manipulator, type synthesis

In this article, the closed-form dynamic equations of planar flexible link manipulators (FLMs), with revolute joints and constant cross sections, are derived combining Lagrange's equations and the assumed mode shape method. To overcome the lengthy and complicated derivative calculation of the Lagrangian function of a FLM, these computations are done only once for a single flexible link manipulator with a moving base (SFLMB). Employing the Lagrange multipliers and the dynamic equations of the SFLMB, the equations of motion of the FLM are derived in terms of the dependent generalized coordinates. To obtain the closed-form dynamic equations of the FLM in terms of the independent generalized coordinates, the natural orthogonal complement of the Jacobian constraint matrix, which is associated with the velocity constraints in the linear homogeneous form, is used. To verify the proposed closed-form dynamic model, the simulation results obtained from the model were compared with the results of the full nonlinear finite element analysis. These comparisons showed sound agreement. One of the main advantages of this approach is that the derived dynamic model can be used for the model based end-effector control and the vibration suppression of planar FLMs. Keywords: flexible link manipulators, dynamics, Lagrange multipliers

Wire-based tracking devices are an affordable alternative to costly tracking devices. They consist of a fixed base and a platform, attached to the moving object, connected by six wires whose tension is maintained along the tracked trajectory. One important shortcoming of these devices is that they are forced to operate in reduced workspaces so as to avoid singular configurations. Singularities can be eliminated by adding more wires, but this causes more wire interferences, and a higher force exerted on the moving object by the measuring device itself. This paper shows how, by introducing a rotating base, the number of wires can be reduced to three, and singularities can be avoided by using an active sensing strategy. This also permits reducing wire interference problems and the pulling force exerted by the device. Index Terms--Active sensing, Kalman filtering, mutual information, parallel manipulators, tracking devices.

This note addresses the problem of position control of robotic manipulators both nonredundant and redundant in the task space. A computationally simple class of task space regulators consisting of a transpose adaptive Jacobian controller plus an adaptive term estimating generalized gravity forces is proposed. The Lyapunov stability theory is used to derive the control scheme. The conditions on controller gains ensuring asymptotic stability are obtained herein in a form of simple inequalities including some information extracted from both robot kinematic and dynamic equations. The performance of the proposed control strategy is illustrated through computer simulations for a direct-drive arm of a SCARA type redundant manipulator with the three revolute kinematic pairs operating in a two-dimensional task space. Index Terms--Adaptive control, Lyapunow stability, robotic manipulators.

In this paper a new topology of four degrees-of-freedom 3T1R fully-parallel manipulator is presented, which is defined only using lower kinematic pairs. The paper starts with a complete type synthesis of different topologies of fully-parallel manipulators that can perform the so-called Schonflies motion, based on the Theory of Groups of Displacements. After imposing some practical requirements, the different possibilities of manipulators are reduced to only one topology of fully-parallel and fully-symmetrical parallel manipulator. Then, the kinematic analysis of the manipulator is shown, including the closed-form resolution of both forward and inverse position problems, the velocity and the singularity analysis. Finally, a prototype of the manipulator is presented, which is intended to be used in pick and place applications. [DOI: 10.1115/1.2839005]

In this paper, the model reference zero vibration (MRZV) control design is introduced to improve transient performance of robotic manipulators. MRZV consists of a zero vibration (ZV) shaper as the feedforward control while utilizing model reference control to improve robustness and performance under plant model parameter variations. Performance analysis of the MRZV control is given in terms of residual vibration and it is shown that MRZV can tolerate significantly larger plant model variations while maintaining the performance characteristics compared to standard shaper designs such as ZV and ZV and Derivative. A synthesis procedure is provided for the MRZV method to guarantee a prespecified level of residual vibration. Experimental verifications based on a standard cycle time test are carried out on an Adept Technology Cartesian robot. Results confirm the effectiveness of the proposed method. Index Terms--Input shaping, model reference control, robotic workcell, vibration control.

This paper investigates two situations in which the forward kinematics of planar 3-R_PR parallel manipulators degenerates. These situations have not been addressed before. The first degeneracy arises when the three input joint variables P1, P2, and P3 satisfy a certain relationship. This degeneracy yields a double root of the characteristic polynomial in t =tan([phi]/2), which could be erroneously interpreted as two coalesce assembly modes. However, unlike what arises in nondegenerate cases, this double root yields two sets of solutions for the position coordinates (x, y) of the platform. In the second situation, we show that the forward kinematics degenerates over the whole joint space if the base and platform triangles are congruent and the platform triangle is rotated by 180 deg about one of its sides. For these 'degenerate' manipulators, which are defined here for the first time, the forward kinematics is reduced to the solution of a third-degree polynomial and a quadratic in sequence. Such manipulators constitute, in turn, a new family of analytic planar manipulators that would be more suitable for industrial applications. [DOI: 10.1115/1.2779893]

Based on the Lie-group-algebraic properties of the displacement set, the three-degree-of-freedom (3DOF) pseudoplanar motion often termed Y motion for brevity is first introduced. Then, all possible general architectures of the mechanical generators of a given Y subgroup are obtained by implementing serial arrays of 1DOF Reuleaux pairs or hinged parallelograms. In total five distinct mechanical generators of Y motion are revealed and seven ones having at least one parallelogram are also derived from them. In order to avoid the singularity that may occur in the limbs, all singular postures of Y-motion generators are also located by detecting the possible linear dependency of the joint twists and the group dependency of displacement sets. The parallel layout of three 4DOF limbs including Y-motion generators with orthogonal planes make up a Cartesian translational parallel manipulator, which produces a motion set of spatial translations. The 3DOF translation of the moving platform is directly controlled by the three 1DOF translations in three orthogonal prismatic fixed joints. [DOI: 10.1115/1.2779892] Keywords: pseudoplanar motion, Y motion, Lie group, singularity, twist, parallel manipulator, Cartesian manipulator

A parallelogram-based 4 degrees-of-freedom parallel manipulator is presented in this paper. The manipulator can generate the so-called Schonflies motion that allows the end effector to translate in all directions and rotate around an axis parallel to a fixed direction. The theory of group of displacements is applied in the synthesis of this manipulator, which employs parallelograms in every limb. The planar parallelogram kinematic chain provides a high rotational capability and an improved stiffness to the manipulator This paper shows the kinematic analysis of the manipulator, including the closed-form resolution of the forward and inverse position problems, the velocity, and the singularity analysis. Finally, a prototype of the manipulator, adding some considerations about its singularity-free design, and some technical applications in which the manipulator can be used are presented. [DOI: 10.1115/1.2779898]

In this paper, the application of a piezoelectric stack actuator for vibration control in a large-scale robotic manipulator, called a macromanipulator, is studied. In this regard, mechanical design and mathematical modeling of the actuator are discussed. The structural flexibility of the macromanipulator includes deflection and torsional vibration modes. The vibration modes are detected using appropriate sensor attachments. Furthermore, a nominal transfer function matrix between the input signals to the actuators and the output voltages of the sensors is obtained. A closed-loop controller based on the obtained model is designed. Because of the presence of deflection and torsional vibration modes and model uncertainties resulting from manipulator motion, an [H.sub.[infinity]] robust controller is utilized. Experimental results are presented to validate the robustness and performance of the designed controller. Index Terms--Flexible structures, large-scale robots, piezoelectric stack actuator, robust control, vibration control.

This paper addresses the problem of capturing an arbitrary convex object P in the plane with three congruent disc-shaped robots. Given two stationary robots in contact with P, we characterize the set of positions of a third robot, the so-called capture region, that prevent P from escaping to infinity via continuous rigid motion. We show that the computation of the capture region reduces to a visibility problem. We present two algorithms for solving this problem, and for computing the capture region when P is a polygon and the robots are points (zero-radius discs). The first algorithm is exact and has polynomial time complexity. The second one uses simple hidden surface removal techniques from computer graphics to output an arbitrarily accurate approximation of the capture region; it has been implemented, and examples are presented. Index Terms--Caging, capture region, capturing, motion-planning, multiple manipulators, robots.

Research on robotic manipulation has mainly focused on manipulating rigid objects so far. However, many important application domains require manipulating deformable objects, especially deformable linear objects (DLOs), such as ropes, cables, and sutures. Such objects are far more challenging to handle, as they can exhibit a much greater diversity of behaviors, and their manipulation almost inevitably requires two robotic arms, or more, performing well-coordinated motions. This paper describes a new motion planner for manipulating DLOs and tying knots (both self-knots and knots around simple static objects) using two cooperating robotic arms. This planner blends new ideas with preexisting concepts and techniques from knot theory, robot motion planning, and computational modeling. Unlike in traditional motion planning problems, the goal to be achieved by the planner is a topological state of the world, rather than a geometric one. To search for a manipulation path, the planner constructs a topologically biased probabilistic roadmap in the configuration space of the DLO. During roadmap construction, it uses inverse kinematics to determine the successive robot configurations implied by the DLO configurations and tests their feasibility. Also, inspired by the real life, the planner uses static "needles" (by analogy to the needles used in knitting) for maintaining the stability of the DLO during manipulation and to make the resulting manipulation plan robust to imperfections in the physical model of the DLO. The implemented planner has been tested both in graphic simulation and on a dual-PUMA-560 hardware platform to achieve various knots, like bowline, neck-tie, bow (shoe-lace), and stun-sail. Index Terms--Deformable objects, knot tying, manipulation planning, probabilistic roadmaps.