bluuebunny/crossref_metadata_2025 huggingface dataset:
Null space damping method for local joint torque optimization of redundant manipulators
Authors: Kang Hee‐Jun , Freeman Robert A.
Published: July 2007

In this article, a null space damping method is proposed that solves the stability problem commonly encountered in existing local joint torque optimization techniques applied to redundant manipulators. The damped joint motion is stable and globally outperforms undamped techniques in the sense of torque minimization capability. In addition, simulation results show that the resulting damped joint motion becomes conservative after an initial transient stage for cyclic end‐effector trajectories, while undamped pseudoinverse solutions are reported to never lead to conservative motion. Three undamped and damped joint torque optimization algorithms are considered and discussed with comparison to the previous literature. The effectiveness of the proposed null space damping method is demonstrated by the results of two computer simulations. In addition, the minimization of electrical power consumption is addressed with respect to the results of this article.
Real‐time trajectory generation in multi‐RCCL
Authors: Lloyd John , Hayward Vincent
Published: July 2007

This article describes the design of the trajectory generator for a robot programming system called Multi‐RCCL, which is a package of “C” routines for doing real‐time manipulator control in a UNIX environment. RCCL has been used successfully in developing robot control applications in numerous research and industry facilities over the last several years. One of its strongest features is the ability to integrate real‐time sensor control into the manipulator task specification. RCCL primitives supply the trajectory generator with target points for motions in joint or Cartesian coordinates. Other primitives allow the code developer to specify on‐line functions that can modify the target points, or possibly cancel motion requests, in response to various sensor or control inputs. The design requirements of the trajectory generator are that it be able to integrate these on‐line modifications into the overall robot motion and provide a smooth path between adjacent motions even when sensor inputs make the future trajectory uncertain. © 1993 John Wiley & Sons, Inc.
Analysis and design of a robotic distance sensor
Authors: Partaatmadja O. , Benhabib B. , Goldenberg A. A.
Published: July 2007

Analysis and design of a robotic electrooptical distance sensor, based on the phase‐shift measurement of a modulated light intensity, is addressed in this article. The transducer of this sensor employs two light sources (light‐emitting diodes), whose intensities are modulated by different‐phase sine‐wave signals, and one photodiode receiver. The distance of an object's surface with respect to the sensor is measured by investigating the received phase shift. The experimental set‐up of the sensor, used in this research, was designed and manufactured such that various mechanical and electronic design parameters could be investigated independently. Experiments undertaken show that these parameters indeed affect the performance of the sensor. The exemplary optimization analysis carried out considered only two performance aspects of the sensor, namely, sensitivity and operational range, and yielded corresponding optimal design parameters. The optimal distance sensor analyzed illustrated that it has sufficient resolution to be useful for most existing industrial robots.
Synthesis and analysis of a new class of six‐degree‐of‐freedom parallel minimanipulators
Authors: Tsai Lung‐Wen , Tahmasebi Farhad
Published: July 2007

A new class of 6‐degree‐of‐freedom (dof) parallel minimanipulators is introduced. The minimanipulators are designed to provide high resolution and high stiffness for fine position and force control in a hybrid serial‐parallel manipulator system. Two‐dof planar linkages and inextensible limbs are used to improve positional resolution and stiffness of the minimanipulators. The 2‐dof linkages serve as drivers for the minimanipulators. The minimanipulators require only three inextensible limbs and, unlike most of the six‐limbed parallel manipulators, their direct kinematics can be reduced to solving a polynomial in a single variable. In addition, by using three limbs instead of six other benefits such as lower possibility of mechanical interference between limbs can be realized. All of the minimanipulator actuators are base‐mounted. As a result, higher payload capacity, smaller actuator sizes, and lower power dissipation can be obtained. In addition to the design discussion, kinematic analysis of the minimanipulators is also presented. © 1993 John Wiley & Sons, Inc.
Adaptive control of a stewart platform‐based manipulator
Authors: Nguyen Charles C. , Antrazi Sami S. , Zhou Zhen‐Lei , Campbell Charles E.
Published: July 2007

This article presents the implementation of a joint‐space adaptive control scheme used to control noncompliant motion of a Stewart platform‐based manipulator (SPBM) that is used in a facility called the Hardware Real‐Time Emulator (HRTE) developed at Goddard Space Flight Center to emulate space operations. The SPBM is comprised of two platforms and six linear actuators driven by dc motors, and possesses six degrees of freedom. The article briefly reviews the development of the adaptive control scheme, which is composed of proportional‐derivative (PD) controllers whose gains are adjusted by an adaptation law driven by the errors between the desired and actual trajectories of the SPBM actuator lengths. The derivation of the adaptation law is based on the concept of model reference adaptive control (MRAC) and Lyapunov direct method under the assumption that SPBM motion is slow as compared to the controller adaptation rate. An experimental study is conducted to evaluate the performance of the adaptive control scheme implemented to control the SPBM to track a vertical and circular paths under step changes in payload. Experimental results show that the adaptive control scheme provides superior tracking capability as compared to fixed‐gain controllers.
Kinematics and control of a fully parallel force‐reflecting hand controller for manipulator teleoperation
Authors: Bryfogle Mark D. , Nguyen Charles C. , Antrazi Sami S. , Chiou Peter C.
Published: July 2007

Force feedback can enhance the efficiency of a teleoperation system by providing the operator with a sense offeelof the forces and torques arising from the interaction of the slave manipulator with the remote environment. This article addresses the kinematic analysis and control of a Parallel FOrce‐Reflecting Hand Controller (PFORHC) whose design and implementation are based on a fully parallel mechanism. Kinematic analysis on the PFORHC is performed and results in a closed‐form solution for the inverse kinematics. The forward kinematics is solved by Newton‐Raphson's method. A fixed‐gain PD control scheme is developed for force feedback control. Experiments are conducted to study the performance of the force‐reflecting capability of the PFORHC. Experimental results show that the force control scheme utilizing a handgrip force sensor provides smaller steady‐state errors as compared to the case utilizing no handgrip force sensor.
Kinematic decoupling in mechanisms and application to a passive hand controller design
Authors: Hayward Vincent , Nemri Chafye , Chen Xianze , Duplat Bertrand
Published: July 2007

Observations regarding the kinematics of mechanisms are applied to the synthesis of a passive hand controller. It is argued that stiffness (and damping) properties are central to the effectiveness of such devices and in particular that the simplicity of these properties is crucial. What simple means is analyzed and it is shown that only certain types of manipulators can appropriately be used. In effect, decoupling is shown to be architecture and configuration dependent. The properties of parallel mechanisms are reviewed and found appropriate for restricted‐workspace hand controllers. A particular kinematic design is then derived and a practical implementation described.
Null torque‐based dynamic control for kinematically redundant manipulators
Authors: Chung W. J. , Chung W. K. , Youm Y.
Published: July 2007

For the dynamic control of kinematically redundant manipulators, conventional approaches to local torque minimization have induced physically unachievable joint torques that may exceed the torque limits in the tracing motion of a long end‐effector trajectory. This article presents a new control method for redundant manipulators, named the “Null Torque‐Based Dynamic Control” (NTDC), which can guarantee stability for joint torques. The proposed method resolves the redundancyat the torque level.The command torque induced by the proposed method is composed of two terms: (1) theminimum‐norm torque, which locally minimizes torque loadings at the joints; and (2) thenull torque, which is intermittently added to the minimum‐norm torque according to a kinematic criterion to globally reduce excessively large torque requirements. In particular, the concept of null torque is based on the property offull row‐rank minorsfor a Jacobian matrix—theaspectthat is a function of a manipulator's configuration. The simulation results illustrate that the proposed method is effective for torque optimization when compared with conventional methods.
Design of global tracking controllers for flexible‐joint robots
Authors: Nicosia S. , Tomei P.
Published: July 2007

An approach to design control laws for trajectory tracking of robots having flexible joints is presented. An application to the adaptive control is also given with reference to a single‐link robot with one revolute elastic joint whose parameters are unknown.
Tracking control for end‐effector position and orientation of structurally flexible manipulators
Authors: Carusone Joseph , D'Eleuterio Gabriele M. T.
Published: July 2007

A simple and effective feedback control strategy is presented for end‐effector position and orientation tracking of structurally flexible manipulators free of external forces as in space applications. The fully feedback‐driven approach employs an augmented dynamical description in which derivatives of the control inputs are included in the state. This ensures smooth control inputs to the manipulator joints. The feedback law uses gain scheduling of a series of steady‐state regulators derived by considering the manipulator at intermediate (nominally rigid and stationary) configurations along the desired trajectory. The performance of the control method is demonstrated in simulations of a planar three‐link manipulator system. Examples show that the controller can be applied successfully in discrete‐time, and that spillover does not appear to be a problem.
The applications of harmonic functions to robotics
Authors: Connolly Christopher I. , Grupen Roderic A.
Published: July 2007

Harmonic functions are solutions to Laplace's equation. Such functions can be used to advantage for potential‐field path planning because they do not exhibit spurious local minima. Harmonic functions are shown here to have a number of properties that are essential to robotics applications. Paths derived from harmonic functions are generally smooth. Harmonic functions also offer a complete path‐planning algorithm. We show how a harmonic function can be used as the basis for a reactive admittance control. Such schemes allow incremental updating of the environment model. Methods for computing harmonic functions respond well to sensed changes in the environment, and can be used for control while the environment model is being updated.
Estimate of the two smallest singular values of the Jacobian Matrix: Application to damped least‐squares inverse kinematics
Authors: Chiaverini Stefano
Published: July 2007

The smallest singular value of the Jacobian matrix is known to be the sole reliable measure of closeness to singular configurations; its computation via a full singular value decomposition, however, is demanding in view of real‐time applications. In this article, a standard singular value estimation procedure is extended to improve the handling of singular values crossing along a given trajectory. The proposed algorithm maintains the computational efficiency of the original technique and shows higher estimation accuracy with respect to the original procedure. Case studies are developed to verify the effectiveness of the estimation procedure applied to an industrial manipulator. © 1993 John Wiley & Sons, Inc.
Experimental determination of dynamic parameters of robotic arms
Authors: Lu Ziren , Shimoga Karunakar B. , Goldenberg Andrew A.
Published: July 2007

This article presents a practical method for determining the dynamic parameters of robotic arms. The two unique features of the method are that it determines the friction parameters along with the inertia and mass parameters and that it does not require the measurement of joint accelerations. The method is demonstrated experimentally by determining the dynamic parameters of a closed‐chain direct‐drive arm. The precision of the determined parameter was verified in the context of computed torquebased controllers. Statistical analysis also shows that the estimated values are reliable. © 1993 John Wiley & Sons, Inc.
Stable interaction control and coulomb friction compensation using natural admittance control
Authors: Newman Wyatt S. , Zhang Yuandao
Published: July 2007

A new control system design formulation is presented for achieving high‐performance, guaranteed‐stable impedance control. While the bandwidth of the resulting controller is no higher than alternative techniques, the new formulation significantly improves performance when Coulomb friction is present in the system. The technique requires a careful choice of the target impedance. The resulting feedback compensators are causal and have stable poles, although they are often non‐minimum phase. General rules for controller synthesis are derived. Experimental performance results are presented for a two‐mass system with internal compliance and Coulomb friction. Results demonstrate that the technique is successful in rejecting internal friction force disturbances while maintaining a passive driving‐point impedance. © 1994 John Wiley & Sons, Inc.
Minimum effort factor approach for sensor‐based control of a four‐joint 6‐dof redundant manipulator
Authors: Malladi Srinivasa R. , Valavanis Kimon P. , Mulder Michael C.
Published: July 2007

A sensor‐driven control model and a minimum effort control algorithm in terms of time and energy expended during the execution of a movement strategy are described and validated for a multijointed cooperating robotic manipulator. Considering smooth, human‐like (anthropomorphic) movements, using joint motion profiles achievable in real time as well as sensory information from all joints, and evaluating the total work expended by each manipulator joint during the execution of a movement strategy, a minimum effort motion trajectory is synthesized to precisely and efficiently position the robotic arm end‐effector. This sensor‐based approach significantly reduces the computational requirements for such cooperative motion. The minimum effort control algorithm generates several human‐like arm movement strategies and selects the best strategy on the basis of expendable effort. The algorithm has an inherent basis to deal with obstacles in an efficient way. Detailed examples are described from the simulation studies. © 1994 John Wiley & Sons, Inc.
Vision‐based path following by using a neural network Guidance System
Authors: Luebbers P. G. , Pandya A. S.
Published: July 2007

This article describes a neural network controller for guidance of a robot arm, used to model some aspects of autonomous vehicle technology. The controller uses video images with adaptive view‐angles for the sensory input, and the system was configured to simulate an autonomous vehicle guidance system on a flat terrain using a high‐contrast guiding path. To demonstrate the feasibility of using neural networks in this type of application, an Intelledex 405 robot fitted with a video camera and associated vision system was used. Phase I of the project consisted of a single‐speed implementation and limited network training. Phase II featured a multi‐speed implementation using adaptively varied view‐angles based on robot arm velocity. It was shown that the neural network controller was able to control the robot arm along a path composed of path segments unlike those with which it was trained. In addition it was shown that a multi‐speed implementation with adaptive view angles improved system performance. © 1994 John Wiley & Sons, Inc.
Design of a robust adaptive control law for robotic manipulators
Authors: Lee Ho‐Hoon , Culick Fred E. C.
Published: July 2007

In this article, a robust adaptive control scheme for robotic manipulators is designed based on the concept of performance index and Lyapunov's second method. Compensators are selected for a given feedback system by using a quadratic performance index. Then the stability of the system is proven based on Lyapunov's method, where a Lyapunov function and its time‐derivative are derived from the selected compensators. In the process of stabilization, stability bounds are obtained for disturbances, control gains, adaptation gains, and desired trajectories, in the presence of feedback delay due to digital computation and first‐order hold in the control loop. © 1994 John Wiley & Sons, Inc.
Torque optimization schemes for kinematically redundant manipulators
Authors: Chen Tsing‐Hua , Cheng Fan‐Tien , Sun York‐Yih , Hung Min‐Hsiung
Published: July 2007

One of the important applications for the resolution of redundant manipulators is torque optimization, due to the fact that the actuators used for driving a manipulator have finite power ratings. Nevertheless, not many algorithms have been proposed to accomplish this objective. A survey of the existing local torque optimization control schemes is given in this article. It will be shown that all of them either encounter instability problems for long trajectories or fail in certain cases. For remedying these problems, the authors present the Minimum Velocity Norm (MVN) method, which is the most common approach for kinematic redundancy resolution and has never been adopted for torque optimization by other researchers. Simulation results show that the simple MVN method is moderate for short movements and is stable for long movements. Also, the MVN method can be applied to cases that may not be accomplished by some other approaches. Therefore, the MVN method is better than the other existing approaches for torque optimization. © 1994 John Wiley & Sons, Inc.
Relation between global velocity and local torque optimization of redundant manipulators
Authors: Hu B. , Teo C. L. , Lee H. P.
Published: July 2007

In this article, the relation between the global optimization of joint velocity and local optimization of joint torque is investigated. The local minimization of the weighted joint torques can be matched to the global optimization of the corresponding weighted joint velocities when the weighted matrices satisfy certain sufficient conditions. A straightforward matching is obtained using the local optimization of the inertia inverse weighted dynamic torque and the global minimization of the kinetic energy. Another easy solution can be found, as will be shown later, if the inertia matrix is a constant and gravity is neglected. Based on that, it can be seen why a Cartesian robot, which has a constant inertia matrix, is always stable. © 1994 John Wiley & Sons, Inc.
Inverse cartesian trajectory control and stabilization of a three‐axis flexible manipulator
Authors: Yim Woosoon
Published: July 2007

This article treats the question of end point trajectory control of a flexible manipulator based on the nonlinear inversion technique. The manipulator has two rigid links and the third link is elastic. A parameterization of the Cartesian coordinates of a point close to the end effector position is suggested. Using these coordinates as output variables, an inverse feedback control law is derived for tracking reference Cartesian trajectories. The stability of the zero dynamics associated with the end point motion control is examined. It is shown that inverse control of the end point causes divergent oscillatory flexible modes. In addition, for regulating the end point to a fixed position, a linear stabilizer is designed to damp the elastic vibration. Simulation results are presented to show that in the closed‐loop system, reference end point trajectories can be accurately followed in spite of the parameter uncertainty in the arm dynamic model. © 1994 John Wiley & Sons, Inc.
Operating robot manipulators through kinematic singularities using a continuously sliding mode control
Authors: Chang Tai‐Heng , Hurmuzlu Yildirim
Published: July 2007

Planning the motion of end‐effectors of robot manipulators can be carried out more directly in the Cartesian space compared to the joint space. Yet, Cartesian paths may include singular configurations where conventional control schemes suffer from excessive joint velocities and loss of tracking accuracy. The difficulties arise because the Jacobian matrix that is used to establish a linear relation between the velocities in the task and joint spaces loses rank at singularities. The problem can be resolved by using a local second‐order approximation of robot kinematics for the joint velocities, which is called Resolved Motion Quadratic Rate Control. In this article, we present a control strategy based on this approach and a recently developed variable structure control scheme. The controller receives Cartesian inputs whenever the manipulator is outside the singular domain. Otherwise, it uses resolved motion quadratic rate control to compute the required joint inputs. Numerical simulation is performed to show that the proposed control scheme provides accurate tracking of the desired motion without inducing excessive control activity when operating robot manipulators through singular configurations. © 1994 John Wiley & Sons, Inc.
A correlation between the state‐space and the task‐oriented path in the presence of obstacles for mechanical manipulators
Authors: Marchis V. , Petrone F. , Sinatra R.
Published: July 2007

This article proposes workspace analysis for redundant robot manipulators in the presence of obstacles. The analysis, based on a 3R planar robot and disk‐shaped obstacles, is considered in detail and a computer program is developed for the calculation of the collision‐free region of redundant robots. The research focuses on the state space of the robot with its end‐effector forced to follow a linear path, with particular consideration of the effects of the link geometries and the location of the obstacles. © 1994 John Wiley & Sons, Inc.
Joint stick‐slip friction compensation of robot manipulators by using smooth robust controllers
Authors: Cai L. , Songag G.
Published: July 2007

In this article, two new smooth robust nonlinear compensators have been developed, respectively, for positional regulation and trajectory tracking of rigid robot manipulators with internal joint stick‐slip friction. The proposed controllers can improve not only the positioning accuracy but also the smoothness of motion. No exact knowledge of the friction models is required for the design of the controllers. Furthermore, the tracking controller is also robust with respect to the uncertain link parameters. Using Lyapunov's direct method, we can show that the time‐invariant positional regulation controller guarantees the global boundedness stability of the closed‐loop system, while the time‐varying positional tracking controller guarantees the global asymptotic stability of the closed‐loop system. The numerical simulations of the controllers on a two‐link robot are presented as illustrations. © 1994 John Wiley & Sons, Inc.
Vsc motion and force control of robot manipulators in the presence of environmental constraint uncertainties
Authors: Yao Bin , Chan S. P. , Wang Danwei
Published: July 2007

Due to task kinematic modelling inaccuracy, constraint functions imposed on robot manipulators may not be known exactly. In this article, a variable structure control (VSC) method is developed for robust motion and constrained force control of robot manipulators in the presence of parametric uncertainties, external disturbances, and constraint function uncertainties. The method is based on a particular structure of the constrained robot, in which motion control and force control are treated together. The proposed VSC controller provides the sliding mode and reaching transient response with prescribed qualities. A sufficient condition to guarantee the robot does not lose contact with the constraint surface is given. Detailed simulation results illustrate the proposed method. © 1994 John Wiley & Sons, Inc.
Robustness analysis of a pd controller with approximate gravity compensation for robot manipulator control
Authors: Hsia T. C.
Published: July 2007

Asymptotically stable robot manipulator control in both joint space and Cartesian space can be achieved by using a PD controller with gravity torque compensation. However, the stability of this class of control law has not been analyzed with the use of estimated gravity torques. The objective of this article is to present such a stability proof assuming uncertainty in the gravity estimate. The proof is carried out for the Cartesian space controller. The result is supported by computer simulation. © 1994 John Wiley & Sons, Inc.
Mobile robot path planning based on hierarchical hexagonal decomposition and artificial potential fields
Authors: Hou Edwin S. H. , Zheng Dan
Published: July 2007

In this article, a new algorithm based on an artificial potential field and hierarchical cell decomposition technique is developed to solve the find‐path problem for a mobile robot. The complete map of the workspace including obstacle locations is assumed to be known a priori. The basic cell structure used for decomposition is a hexagon. The artificial potential field is based on an attractive force from the goal position and repelling forces from the obstacles. Computer simulations of the algorithm for various obstacle scenarios are also presented. © 1994 John Wiley & Sons, Inc.
Optimal motion coordination of two robots—a polynomial parameterization approach to trajectory resolution
Authors: Tabarah E. , Benhabib B. , Fenton R. G.
Published: July 2007

A novel approach is presented for the optimal coordination of two robots performing continuous‐path manufacturing tasks. Two types of operations are considered: contact operations, such as deburring, which require the tool to maintain contact with the workpiece during the operation execution, or non‐contact operations, such as arc‐welding, where the tool moves relative to the workpiece without contact. In both cases, the required tool‐path is specified with respect to the workpiece. A task is performed by mounting the tool on a robot, while a second robot grips the workpiece; the two robots are then coordinated to move simultaneously relative to one another so that the tool follows its prescribed trajectory at a constant speed relative to the workpiece, and provides sufficient contact force in the case of contact operations. The original tool‐trajectory is thus resolved into a pair of conjugate trajectories, specified in task space relative to an inertial frame, describing the motion of the two robots. In cases where the two robots form a kinematically redundant system, the trajectory resolution process can yield an infinity of conjugate‐trajectory pairs corresponding to a given original tool‐trajectory, of which one pair may be chosen based on a specific choice of cost function. This article presents a technique whereby the robot's conjugate trajectories are parameterized using polynomial functions. A method is then developed for optimizing the robot's motion by selecting the optimal pair of conjugate trajectories. The proposed optimal trajectory‐resolution technique is further enhanced by coupling it to a procedure for selecting the optimal relative placement of the two robots, resulting in the best achievable solution. This method of coordinating two robots yields lower cycle‐time values than the corresponding single‐robot operation, as well as reduces the need for complex jigs and fixtures. Numerical simulations are presented to illustrate the proposed technique. © 1994 John Wiley & Sons, Inc.
Workspace analysis of stewart platforms via vertex space
Authors: Ji Zhiming
Published: July 2007

This article introduces the concept of “vertex space” for the study of the workspace of Stewart platforms. It shows that the vertex space has potential to link the dimensional parameters to the characteristics of the workspace of a platform. A method for constructing vertex spaces is developed. An example is provided to illustrate the influence of dimensional parameters on the vertex space. © 1994 John Wiley & Sons, Inc.
Robot guidance using ultrasonic arrays
Authors: Webb P. , Gibson I. , Wykes C.
Published: July 2007

The flexibility of robots can be considerably increased by having sensors that can detect the location and orientation of the components that are being manipulated by the robots. Vision systems have been widely applied to this problem, but there has been very little reported work on the use of ultrasonic sensors. This article reports the use of novel ultrasonic sensors that have been manufactured in‐house to measure the range and bearing of a target and guide the robot in a pick and place operation. The configuration of the transducer is described as well as the signal processing method employed. Experimental results are given and future developments and applications of the system are described. © 1994 John Wiley & Sons, Inc.
Inverse dynamics of a parallel manipulator
Authors: Pang Hyunsok , Shahinpoor Mohsen
Published: July 2007

Presented is an analysis of the kinematics and the inverse dynamics of a proposed three degree of freedom (dof) parallel manipulator resembling the Stewart platform in a general form. In the kinematic analysis, the inverse kinematics, velocity, and acceleration analyses are performed, respectively, using vector analysis and general homogeneous transformations. An algorithm to solve the inverse dynamics of the proposed parallel manipulator is then presented using a Lagrangian technique. In this case, it is found that one should introduce and subsequently eliminate Lagrange multipliers to arrive at the governing equations. Numerical examples are finally carried out to examine the validity of the approach and the accuracy of the numerical technique employed. The trajectory of motion of the manipulator is also performed using a cubic spline. © 1994 John Wiley & Sons, Inc.
Collision avoidance by fuzzy logic control for automated guided vehicle navigation
Authors: Lee Pai‐Shih , Wang Ling‐Ling
Published: July 2007

A fuzzy approach to collision avoidance for automated guided vehicle (AGV) navigation is proposed. Static obstacles with no a priori position information as well as moving obstacles with unknown trajectories are considered in this study. Intuitive and subjective human ideas of collision avoidance are modeled into fuzzy rules. Fuzzy logic is applied in the inference procedure for AGV navigation, such that the AGV is guided from the starting point toward the target without colliding with obstacles. Furthermore, the proposed method can also be used for the navigation of multiple AGVs, where each AGV must avoid other AGVs as well as obstacles in the environment. Simulation results are presented to show the feasibility of the proposed fuzzy approach. © 1994 John Wiley & Sons, Inc.
Control of a two‐degree‐of‐freedom lightweight flexible arm with friction in the joints
Authors: Feliu Vincente , Rattan Kuldip S. , Brown H. Benjamin
Published: July 2007

This article describes the design and control of a two‐joint, two‐link flexible arm. This flexible arm was built with very light links, has most of its mass concentrated at the tip and uses a special mechanical configuration to approximately decouple radial tip motions from angular tip motions. The lightweight design and decoupling maximize the efficiency of power transmitted to the load. An important problem when controlling lightweight flexible arms is the large Coulomb friction of the motors. A two‐nested‐loop multivariable controller is used to control the lightweight flexible arm with friction in the joints. The inner loop controls the position of the motors while the outer loop controls the tip position. The resolved acceleration method is generalized to control this flexible arm. The compliance matrix is used to model the oscillations of the structure and is included in the decoupling/linearizing term of this controller. Experimental results are presented. © 1995 John Wiley & Sons, Inc.
Control of a single‐link flexibe manipulator fabricated form composite laminates
Authors: Choi Seung‐Bok , Thompson Brian S. , Gandhi Mukesh V.
Published: July 2007

An experimental investigation on the control performances of a single‐link flexible manipulator fabricated from composite laminates is presented. The dynamic modeling of the flexible manipulator is accomplished by employing Hamilton's principle, prior to developing a finite element formulation. An output feedback controller associated with two collocated angular position and velocity sensors is designed and experimentally implemented. Comparative works are undertaken to demonstrate some of the advantages to be accrued from this proposed methodology. It is shown that the manipulator fabricated from composite laminates has superior performance characteristics, such as smaller tip deflections and a smaller input torque relative to the manipulator fabricated from aluminum. © 1995 John Wiley & Sons, Inc.
Two‐arm kinematic posture optimization for fixtureless assembly
Authors: Ro Paul I. , Lee Byung R. , Seelhammer Mark A.
Published: July 2007

This article focuses on finding optimal kinematic postures for two robot arms performing various assembly tasks without the aid of jigs and fixtures. The goal of the work is to identify the manipulator postures that would result in some optimum kinematic conditions for initiating a typical male‐female assembly. Specifically, the article addresses issues related to the following question: In the absence of preset jigs and fixtures, where are the optimum location in the 3‐dimensional work space and the optimum orientations of the assembly parts (therefore, the postures of the manipulators holding the parts) to perform a fixtureless assembly? First, using velocity and force ellipsoids a performance criterion is developed for the optimal kinematic posture based on constraints that are imposed by the kinematic coupling of the two robot arms as well as the environment. Next, an algorithm based on a null‐space search technique is formulated to “search” for the posture of the two‐arm system that maximizes the performance criterion within the set of postures that satisfy given constraints. Finally, the algorithm is demonstrated numerically for two planar robots performing typical fixtureless assembly operations. ©1995 John Wiley & Sons, Inc.
Control and simulation for a closed‐chain dual redundant ' manipulator system
Authors: Cheng Fan‐Tien , Lee Jou‐Jye , Tsing‐hua  , Kung Chen Fan‐Chu
Published: July 2007

The two‐level hierarchical control scheme is adopted to solve a dual‐chain robotic system formed by two redundant manipulators grasping a common object with hard point contacts. The upper‐level coordinator gathers all the necessary information to resolve the force distribution problem so as to generate all the desired contact forces With all the desired contact forces being specified, the dynamics of each chain are decoupled. Therefore, the lower‐level local control problem can be treated as a general open‐chain redundant manipulator problem. Furthermore, the Compact‐Dual LP method is applied to resolve the upper‐level coordination problem; while the Compact QP method associated with the computed torque control method is adopted to solve the redundant manipulator problem. To obtain proper simulation results, the simulated actual contact forces are formulated and the corresponding simulation problem of the closed‐chain robotic system is also completely solved in the article. Simulation results show that the two‐level hierarchical control scheme is an effective and efficient algorithm for resolving the large‐scale control problem of multiple‐chain robotic systems. © 1995 John Wiley & Sons, Inc.
A fast approach for the robust trajectory planning of redunant robot manipulators
Authors: Mayorga R. V. , Janabi‐sharifi F. , Wong A. K. C.
Published: July 2007

In this article, a fast approach for robust trajectory planning, in the task space, of redundant robot manipulators is presented. The approach is based on combining an original method for obstacle avoidance by the manipulator configuration with the traditional potential field approach for the motion planning of the end‐effector. This novel method is based on formulating an inverse kinematics problem under an inexact context. This procedure permits dealing with the avoidance of obstacles with an appropriate and easy to compute null space vector; whereas the avoidance of singularities is attained by the proper pseudoinverse perturbation. Furthermore, it is also shown that this formulation allows one to deal effectively with the local minimum problem frequently associated with the potential field approaches. The computation of the inverse kinematics problem is accomplished by numerically solving a linear system, which includes the vector for obstacle avoidance and a scheme for the proper pseudoinverse perturbation to deal with the singularities and/or the potential function local minima. These properties make the proposed approach suitable for redundant robots operating in real time in a sensor‐based environment. The developed algorithm is tested on the simulation of a planar redundant manipulator. From the results obtained it is observed that the proposed approach compares favorably with the other approaches that have recently been proposed. © 1995 John Wiley & Sons, Inc.
Deadlock avoidance schemes in a distributed robotic system: Petri net modeling and analysis
Authors: Zhou Mengchu
Published: July 2007

This article presents a Petri net‐based approach to modeling and evaluating four different deadlock avoidance schemes for a distributed robotic system, i.e., a five‐robot‐five‐assembly‐line system. Among these four schemes are the conventional, full synchronization, global semaphore, and partial synchronization schemes. To explore such issues as the system performance and control structure complexity, this article conducts detailed Petri net modeling for this system and evaluates performance of the deadlock avoidance schemes using stochastic Petri nets. The interesting results presented include that: (1) any possible system deadlock can seriously degrade the system performance even if effective deadlock resolution techniques are available; (2) conservative use of resources is likely to be the best policy; and (3) higher resource utilization may not necessarily imply higher system production rate in a resource‐sharing environment. The related results need to be further explored for the larger resource‐sharing discrete event systems. ©1995 John Wiley & Sons, Inc.
Path tracking with the links of a planar hyper‐ redundant robotic manipulator
Authors: Schilling R. J. , Read R. , Lovass‐nagy V. , Walker G.
Published: July 2007

A technique for path tracking with the links of a planar hyper‐redundant robotic manipulator is presented. It is a joint‐space trajectory planning method that can be used for obstacle avoidance by ensuring that the links of the manipulator closely follow a collision‐free path planned for the tool. A closed‐form formulation of resolved‐motion rate control equations is developed that decomposes the manipulator into proximal and distal parts. The joint velocities are constrained to ensure that the far distal links remain tangent to the tool path, while the near distal links and the proximal links assume a compressed configuration near the base. Path tracking is illustrated with several examples that examine the effects of controller gain, link length, and number of links. ©1995 John Wiley & Sons, Inc.
Contril of rigid‐link, flexible‐joint robots:a survey of backstepping approaches
Authors: Bridges M. M. , Dawson D. M. , Abdallah C. T.
Published: July 2007

The purpose of this article is to show how the design procedure commonly referred to as integrator backstepping can be used to design globally stable trajectory tracking controllers for Rigid‐Link Flexible‐Joint (RLFJ) robot manipulators. Three different types of controllers are developed: (1) an exact model knowledge‐based controller, (2) an adaptive controller that compensates for parametric uncertainty, and (3) a robust controller that compensates for parametric uncertainty and unknown bounded disturbances. All three controllers are based on previously published work but are presented here in a unifying framework. ©1995 John Wiley & Sons, Inc.
Toeard a formulation of the human grasping quality sense
Authors: Hershkovitz M. , Tasch U. , Teboulle M.
Published: July 2007

This article examines the grasping quality problem and suggests a formulation that can capture the major mechanisms that generate the human grasping quality sense. Here, the quality of a grasp is examined from the gripper, object, and grasping‐configuration perspectives. These perspectives are incorporated into the formulation by selecting an appropriate objective function that is minimized subject to constraints that represent the geometry, friction, and force‐balance conditions of a grasp. The quality of a grasp is depicted as a polar plot that demonstrates the dependency of grasping quality on the external‐loading direction. The suggested grasping quality measures possess characteristics that are in agreement with basic human intuition. In particular this article proves that the three proposed quality measures are improved when the number of contact points is increased. In summary, the suggested grasping quality formulation captures some of the physical mechanisms that characterize a human grasp, and therefore it may lead to a powerful mathematical model of the human grasping quality sense. ©1995 John Wiley & Sons, Inc.
Geometry‐based efficient rata coordination for manipulators with kinematic redundancy
Authors: Hareendra Varma K. R. , Huang Ming Z.
Published: July 2007

The redundancy resolution problem for kinematically redundant serial chain manipulators is addressed. In this article we present a generalization of the geometry‐based rate allocation algorithm, developed initially for only a minimum norm solution, to obtain the optimal joint rate solution for any specified objective function, with or without weightage. This generalization is made possible through a physial interpretation of the common pseudoinverse‐based gradient solution scheme, and by developing a modified formulation for the objective function as a minimum criterion not with respect to the origin of the joint rate space, but with respect to another point in the joint rate space represented by the gradient of the specified objective. Application examples of the algorithm including procedures of solution are demonstrated using 7R manipulators with two generic types of geometry. Moreover, a closed form optimal solution for the class of 7R anthropomorphic arms is also given. ©1995 John Wiley & Sons, Inc.
Joint space trajectory planning for flexible manipulators
Authors: Yao Chih‐Min , Cheng Wen‐Hon
Published: July 2007

A trajectory planning approach for controlling flexible manipulators is proposed. It is demonstrated that choosing actual joint angles as the generalized rigid coordinates is the key to applying the proposed approach. From the observation of the special structure of the input matrix, the concepts of motion‐induced vibration and inverse dynamics under a specified motion history of the joints are formed naturally. Based on the above concepts, trajectory planning in joint space is proposed by using the optimization technique to determine the motion of joints along a specified path in joint space or work space and for general point‐to‐point motion. The motion for each joint is assumed to be in a class consisting of a fifth‐order polynomial and a finite terms of Fourier series. This parameterization of motion allows the optimal trajectory planning to be formulated as a standard nonlinear programming problem, which avoids the necessity of solving a two‐point‐boundary‐value problem and using dynamic programming. Setting the accelerations to zero at the initial and the final times is used to obtain smoother motion to reduce the spillover energy into unmodeled high‐frequency dynamics. A penalty term on vibration energy contained in the performance index is used to minimize the vibration of the system modeled by lower frequency only. The final simulation results show the effectiveness of the proposed approach and the advantage for proper trajectory planning. © 2995 John Wiley & Sons, Inc.
Impact reduction for redundant manipulators using augmented impedance control
Authors: Lin Z. C. , Patel R. V. , Balafoutis C. A.
Published: July 2007

In this article, the problem of controlling redundant manipulators to reduce collision impact effects is considered, and an augmented kinematics and impedance control scheme is proposed for its solution. The proposed scheme achieves satisfactory performance by minimizing the magnitudes of impulsive forces as well as reducing rebound effects of the end‐effector. In the proposed control scheme, kinematic redundancy is resolved using an augmented kinematics approach where the augmentation of the Jacobian matrix is based on an impact model derived using the Cartesian‐space dynamic model of the manipulator. The proposed impact controller uses a simplified impedance control scheme aimed at reducing impulsive forces as well as rebound effects. The performance of the proposed controller is illustrated by computer simulations. © 2995 John Wiley & Sons, Inc.
A risc approach to sensing and manipulation
Authors: Canny John F. , Goldberg Kenneth V.
Published: July 2007

This article describes sensing and manipulation strategies that use simple, modular robot hardware. To bridge the gap between automation and robotic technologies, we suggest that traditional automation hardware, such as parallel‐jaw grippers and optical beam sensors, can be combined with geometric planning and sensing algorithms. The resulting systems should be cost‐effective, reliable, and easy to set up and reconfigure. They should also be flexible enough to support small batch sizes and rapid changes in part design needed in forthcoming flexible/agile manufacturing systems. The RISC acronym, borrowed from computer architecture, suggests the parallels between the two technologies. RISC robots perform complex operations by composing simple elements. The elements may be individual light beam sensors, grouped together to form an array for recognition. Or a complex manipulation task may be performed via a sequence of grasp steps by different grippers specialized for acquisition and placement. This article emphasizes three areas: (i) RISC sensing, primarily optical beam sensing, (ii) RISC manipulation using simple parallel‐jaw grippers or minimal configurations of fingers, and (iii) Computer‐aided design of RISC workcells. © 1995 John Wiley & Sons, Inc.