A new 6‐DOF parallel robotic structure actuated by wires: The WiRo‐6.3

This paper describes a novel parallel robotic structure with six degrees of freedom, whose end effector is driven by nine wires operated by motors: the WiRo‐6.3. The ideas that led to the conception of the robot are thoroughly discussed and analyzed. The workspace of WiRo‐6.3 has been numerically analyzed, and it is significantly larger than the one of other analogous seven‐wire structures. The forward and inverse kinematics are both solved in closed form. © 2004 Wiley Periodicals, Inc.     

Control of minimally constrained cobots

Cobots are devices which use computer‐oriented passive constraints to guide an end‐effector driven by a human. This synergistic union of human skill and robotic precision is desired in fields such as surgical robotics (our application area of interest) where the surgeon would prefer not to hand over control of a procedure to an autonomous robot. Typical cobot designs intrinsically allow at most one degree of freedom of motion, but there are some tasks (such as using a bone saw to cut a plane in knee replacement surgery) where allowing two or more degrees of freedom is desireable. While it is possible to use selective constraint alignment to increase the apparent degrees of freedom of a cobot, this requires more actuators than are strictly necessary for the task, as well as a force sensor to detect the user's intent. We, therefore, introduce here the concept of minimally constrained cobots for multiple degree of freedom (DOF) tasks such as planar cutting, and outline a general framework for controlling such devices. We illustrate our control algorithms by using a planar cart example and discuss how they might be applied to potential designs for three‐dimensional parallel cobots intended for surgical applications. © 2002 Wiley Periodicals, Inc.     

Development of a sweet pepper harvesting robot

This paper presents the development, testing and validation of SWEEPER, a robot for harvesting sweet pepper fruit in greenhouses. The robotic system includes a six degrees of freedom industrial arm equipped with a specially designed end effector, RGB‐D camera, high‐end computer with graphics processing unit, programmable logic controllers, other electronic equipment, and a small container to store harvested fruit. All is mounted on a cart that autonomously drives on pipe rails and concrete floor in the end‐user environment. The overall operation of the harvesting robot is described along with details of the algorithms for fruit detection and localization, grasp pose estimation, and motion control. The main contributions of this paper are the integrated system design and its validation and extensive field testing in a commercial greenhouse for different varieties and growing conditions. A total of 262 fruits were involved in a 4‐week long testing period. The average cycle time to harvest a fruit was 24 s. Logistics took approximately 50% of this time (7.8 s for discharge of fruit and 4.7 s for platform movements). Laboratory experiments have proven that the cycle time can be reduced to 15 s by running the robot manipulator at a higher speed. The harvest success rates were 61% for the best fit crop conditions and 18% in current crop conditions. This reveals the importance of finding the best fit crop conditions and crop varieties for successful robotic harvesting. The SWEEPER robot is the first sweet pepper harvesting robot to demonstrate this kind of performance in a commercial greenhouse.     

Robotic welding system with parallel degrees of freedom

This paper considers some problems concerning robotic welding of large structures. If spot welding is applied, then the task consists of fast motions between welding points, and at each point the end effector stops and maintains position for a short time. Similar examples can be found in arc welding applications. Since large structures and, accordingly, large robots are considered, a significant problem appears when extremely nonuniform motion is required. One way to solve this problem is to introduce parallel degrees of freedom. Two methods for this distribution of motion to parallel degrees of freedom are discussed. The theory resulted in the design of a large portal robot with high dynamic capabilities.     

Robot manipulator control for hazardous waste-handling applications

The U.S. Department of Energy has identified robotics as a major technology to be utilized in its program of environmental restoration and waste management, and in particular has targeted robotic handling of hazardous waste to be an essential element in this program. Successful performance of waste-handling operations will require a robot to perform complex tasks involving both accurate positioning of its end effector and compliant contact between the end effector and the environment, and will demand that these tasks be completed in uncertain surroundings. This article focuses on the development of a robot control system capable of meeting the requirements of hazardous-waste-handling applications and presents as a solution an adaptive scheme for controlling the mechanical impedance of kinematically redundant manipulators. The proposed controller is capable of accurate end effector impedance control and effective redundancy utilization, does not require knowledge of the complex robot dynamic model or parameter values for the robot or the environment, and is implemented without calculation of the robot inverse kinematic transformation. Computer simulation results are given for a 4 degree of freedom redundant robot under adaptive impedance control. These results indicate that the proposed controller is capable of successfully performing tasks of importance in robotic waste-handling applications.     

Inverse Kinematics of Binary Manipulators Using a Continuum Model

Binary actuators have only two discrete states, both of which are stable without feedback. As a result, manipulators with binary actuators have a finite number of states. The major benefits of binary actuation are that extensive feedback control is not required, reliability and task repeatability are very high, and two-state actuators are generally very inexpensive, resulting in low cost robotic mechanisms. These manipulators have great potential for use in both the manufacturing and service sectors, where the cost of high performance robotic manipulators is often difficult to justify. The most difficult challenge with a binary manipulator is to achieve relatively continuous end-effector trajectories given the discrete nature of binary actuation. Since the number of configurations attainable by binary manipulators grows exponentially in the number of actuated degrees of freedom, calculation of inverse kinematics by direct enumeration of joint states and calculation of forward kinematics is not feasible in the highly actuated case. This paper presents an efficient method for performing binary manipulator inverse kinematics and trajectory planning based on having the binary manipulator shape adhere closely to a time-varying curve. In this way the configuration of the arm does not exhibit drastic changes as the end effector follows a discrete trajectory.     

On manipulator control by exact linearization

Comments on the application to rigid link manipulators of geometric control theory, resolved acceleration control, operational space control, and nonlinear decoupling theory are given, and the essential unity of these techniques for externally linearizing and decoupling end effector dynamics is discussed. Exploiting the fact that the mass matrix of a rigid link manipulator is positive definite, and the fact that there is an independent input for each degree of freedom, it is shown that a necessary and sufficient condition for a locally externally linearizing and output decoupling feedback law to exist is that the end effector Jacobian matrix be nonsingular     

Robot perception of impedance

This paper proposes an algorithm for robot perception of impedance, which can be used as a fundamental technique for real‐time and qualitative perception of physical constraints imposed on the robot's end‐effector. This algorithm (1) estimates the impedance that represents the motion‐force relation of the end‐effector; (2) calculates the uncertainties of the estimates; and (3) detects discontinuous changes in the impedance. The estimated impedance can be used to recognize local dynamic properties of the environment and temporary constraint conditions imposed on the end‐effector. The detected discontinuities can be used to segment the manipulated tasks and to recognize the geometric structure of the environment. This method can be implemented in both autonomous and remote‐controlled robots because it is designed separately from control methodologies. Results of preliminary experiments are presented. © 2005 Wiley Periodicals, Inc.     

The actuation efficiency,a measure of acceleration capability for nonredundant robotic manipulators

This article presents a performance measure, the actuation efficiency, which describes the imbalance between the end‐effector accelerations achievable in different directions of nonredundant robotic manipulators. A key feature of the proposed measure is that in its development the differences in units between translational and rotational accelerations are treated in a physically meaningful manner. The measure also indicates oversized actuators, since this contributes to the imbalance in achievable accelerations. The development of this measure is based on the formulation of the dynamic capability equations. The shape of the dynamic capability hypersurface, which is defined by the dynamic capability equations, is a weak indicator of the level of imbalance in achievable end‐effector accelerations. © 2005 Wiley Periodicals, Inc.     

The dexterity and singularities of an underactuated robot

Underactuated robots are robotic systems with more joints than actuators. A robot may be underactuated by design as in the case of a hyper‐redundant robot with passive joints or may become underactuated as a result of an actuator failure. In this article, we examine the dexterity of underactuated robots whose passive joints operate in either a locked or free‐swinging mode. The ability to an analyze the dexterity of an underactuated robot has important applications especially for the control of passive joints with brakes and for the fault tolerance analysis of an otherwise fully actuated kinematically redundant robot. The approach applied here is to use kinematics and dynamics‐based formulations of manipulator dexterity. We then characterize passive‐joint singularities, i.e., configurations where full end‐effector control is lost because one or more joints are passive instead of active. Lastly, we introduce a new characterization of joint‐limit singularities, which are configurations where full end‐effector control cannot be achieved because one or more joints are at their joint limits. © 2001 John Wiley & Sons, Inc.     

A neuro-simulated annealing approach to the inverse kinematics solution of redundant robotic manipulators

The neural-network-based inverse kinematics solution is one of the recent topics in the robotics because of the fact that many traditional inverse kinematics problem solutions such as geometric, iterative and algebraic are inadequate for redundant robots. However, since the neural networks work with an acceptable error, the error at the end of inverse kinematics learning should be minimized. In this study, simulated annealing (SA) algorithm was used together with the neural-network-based inverse kinematics problem solution robots to minimize the error at the end effector. The solution method is applied to Stanford and Puma 560 six-joint robot models to show the efficiency. The proposed algorithm combines the characteristics of neural network and an optimization technique to obtain the best solution for the critical robotic applications. Three Elman neural networks were trained using separate training sets and different parameters, since one of them can give better results than the others can. The best result is selected within three neural network results by computing the end effector error via direct kinematics equation of the robotic manipulator. The decimal part of the neural network result was improved up to 10 digits using simulated annealing algorithm. The obtained best solution is given to the simulated annealing algorithm to find the best-fitting 10 digits for the decimal part of the solution. The end effector error was reduced significantly.     

Integrated Data Management for a Fleet of Search‐and‐rescue Robots

Search‐and‐rescue operations have recently been confronted with the introduction of robotic tools that assist the human search‐and‐rescue workers in their dangerous but life‐saving job of searching for human survivors after major catastrophes. However, the world of search and rescue is highly reliant on strict procedures for the transfer of messages, alarms, data, and command and control over the deployed assets. The introduction of robotic tools into this world causes an important structural change in this procedural toolchain. Moreover, the introduction of search‐and‐rescue robots acting as data gatherers could potentially lead to an information overload toward the human search‐and‐rescue workers, if the data acquired by these robotic tools are not managed in an intelligent way. With that in mind, we present in this paper an integrated data combination and data management architecture that is able to accommodate real‐time data gathered by a fleet of robotic vehicles on a crisis site, and we present and publish these data in a way that is easy to understand by end‐users. In the scope of this paper, a fleet of unmanned ground and aerial search‐and‐rescue vehicles is considered, developed within the scope of the European ICARUS project. As a first step toward the integrated data‐management methodology, the different robotic systems require an interoperable framework in order to pass data from one to another and toward the unified command and control station. As a second step, a data fusion methodology will be presented, combining the data acquired by the different heterogenic robotic systems. The computation needed for this process is done in a novel mobile data center and then (as a third step) published in a software as a service (SaaS) model. The SaaS model helps in providing access to robotic data over ubiquitous Ethernet connections. As a final step, we show how the presented data‐management architecture allows for reusing recorded exercises with real robots and rescue teams for training purposes and teaching search‐and‐rescue personnel how to handle the different robotic tools. The system was validated in two experiments. First, in the controlled environment of a military testing base, a fleet of unmanned ground and aerial vehicles was deployed in an earthquake‐response scenario. The data gathered by the different interoperable robotic systems were combined by a novel mobile data center and presented to the end‐user public. Second, an unmanned aerial system was deployed on an actual mission with an international relief team to help with the relief operations after major flooding in Bosnia in the spring of 2014. Due to the nature of the event (floods), no ground vehicles were deployed here, but all data acquired by the aerial system (mainly three‐dimensional maps) were stored in the ICARUS data center, where they were securely published for authorized personnel all over the world. This mission (which is, to our knowledge, the first recorded deployment of an unmanned aerial system by an official governmental international search‐and‐rescue team in another country) proved also the concept of the procedural integration of the ICARUS data management system into the existing procedural toolchain of the search and rescue workers, and this in an international context (deployment from Belgium to Bosnia). The feedback received from the search‐and‐rescue personnel on both validation exercises was highly positive, proving that the ICARUS data management system can efficiently increase the situational awareness of the search‐and‐rescue personnel.     

Disturbance rejection for space‐based manipulators

Most industrial manipulators operate from a fixed base. Hence, there are no disturbances from the environment to alter the position of the end‐effector. On the other hand, manipulators that are mounted on mobile platforms are subject to disturbances emerging from unwanted motion at the base. Similarly, manipulators that perform delicate operations in space while on board in‐orbit spacecraft experience disturbances. This article describes the design and implementation of a disturbance rejection controller for a 6 degree‐of‐freedom (DOF) programable universal manipulator for assembly (PUMA) manipulator mounted on a 3‐DOF platform. A control algorithm is designed to track the desired position and attitude of the end‐effector in inertial space, subject to unknown disturbances in the platform axes. Experimental results are presented for step, sinusoidal, and random disturbances in the platform rotational axis and in the neighborhood of kinematic singularities. ©1999 John Wiley & Sons, Inc.     

End‐Point Regulation and Vibration Suppression of a Flexible Robotic Manipulator

In this paper, end‐point regulation and vibration suppression are investigated for a flexible robotic manipulator subject to the external disturbances. The dynamics of the flexible robotic manipulator is represented by one partial differential equation (PDE) and five ordinary differential equations (ODEs). Based on the Lyapunov's direct method, boundary control is developed to drive the manipulator to the desired set‐point and simultaneously suppress the vibrations of the flexible manipulator. Considering the unknown spatiotemporally varying disturbance, uniform boundedness of the closed‐loop system is achieved. The control performance of the closed‐loop system is guaranteed by suitably choosing the design parameters. Simulations are provided to illustrate the effectiveness of the proposed control.     

Dynamic Analysis of Tendon Driven Robotic Mechanisms

In this paper, a systematic methodology for the dynamic analysis of tendon‐driven robotic mechanisms is presented. The approach utilizes the recursive Newton‐Euler equations to compute the kinematic and dynamic equations of all links that locate on the transmission line of a tendon‐driven robotic mechanism. The inertias of the intermediate links in the mechanism are taken into account. It is shown that the dynamic equations can be established in a recursive manner from the end‐effector links toward the proximal links and can be solved at the proximal end without the need of solving the simultaneous system equations. The joint reaction forces and the tension in each segment of tendon can be also obtained. The methodology can be applied to both endless and open‐ended tendon drives. © 2003 Wiley Periodicals, Inc.     

Payload‐centric autonomy for in‐space robotic assembly of modular space structures

The paper addresses the problem of constructing large space structures (～100 m) by using autonomous robots to assemble modular components in space. We are motivated by the problem of creating space structures at a scale greater than what is feasible with a single self‐deploying design. We had two goals in this work. The first was to investigate and demonstrate the feasibility of long‐order multitask autonomy. The second was to study the balance between required tolerances in hardware design and robotic autonomy. This paper reports on a payload‐centric autonomy paradigm and presents results from laboratory demonstrations of automated assembly of structures using a multilimbed robotic platform. We present results with deployable 20 lb payloads (1 m trusses) that are robotically assembled to form a 3‐m diameter kinematically closed loop structure to subcentimeter accuracy. The robot uses its limbs to deploy the stowed modular structural components, manipulate them in free space, and assemble them via dual‐arm force control. We report on results and lessons learned from multiple successful end‐to‐end in‐lab demonstrations of autonomous truss assembly with JPL's RoboSimian robot originally developed for the Defense Advanced Research Projects Agency (DARPA). Videos of these demonstrations can be seen at https://goo.gl/muNLJp (JPL, 2017 ). Each end‐to‐end run took precisely 26 min to execute with very little variance across runs. We present changes/improvements to the RoboSimian system post‐DARPA Robotics Challenge (DRC) (Karumanchi et al., 2016 ). The new architecture has been improved with a focus on scalable autonomy as opposed to semiautonomy as required at the DRC.     

A guidance‐based motion‐planning methodology for the docking of autonomous vehicles

In this paper, a generic line‐of‐sight‐sensing (LOS)‐based guidance methodology is proposed for the docking of autonomous vehicles/robotic end‐effectors: A multi‐LOS task‐space sensing system is used in conjunction with a guidance algorithm in a closed‐loop feedback environment. The novelty of the overall system is its applicability to cases that do not allow for the direct proximity measurement of the vehicle's pose (position and orientation). In such instances, a guidance‐based technique must be employed to move the vehicle to its desired pose using corrective actions at the final stages of its motion. Namely, after the vehicle/end‐effector has failed to move to its desired docking pose within acceptable tolerances, LOS sensors initiate short‐range corrective motion commands. The objective of the proposed guidance method is, thus, to successfully minimize the systematic errors of the vehicle, accumulated after a long‐range motion, while allowing it to converge within the random noise limits. An additional advantage of the proposed system is its applicability to varying vehicle mobility requirements for high‐precision docking. The proposed system was successfully tested via simulation on a 6 degree‐of‐freedom (DOF) vehicle. Numerous simulation tests of the behavior of the vehicle under the command of the guidance algorithm were conducted, one of which is presented herein. © 2005 Wiley Periodicals, Inc.     

SMA驱动的微型平面关节机器人的研究

近年来，利用形状记忆合金（ＳＭＡ）的形状记忆效应原理制作的驱动器已在机器人领域中得到应用，ＳＭＡ驱动器以其重量轻、结构紧凑、易控制等优点，大大推动了微型机器人的发展．本课题使用所研制的推挽式直线位移型和旋转关节型ＳＭＡ驱动器代替传统的伺服驱动系统，研制了一台三自由度（两个旋转自由度和一个直线自由度）且带末端夹持器的微型平面关节机器人．本文将介绍该机器人的结构设计，控制系统及其软件设计．     

Tracking and force control for a class of robotic manipulators

The increasing utilization of robotic manipulators in industrial tasks, such as assembly, forming or shaping of surfaces, and handling hazardous materials, depends greatly on available hybrid force and position control schemes. Since the robot and its environment are often subject to parameter uncertainties that cannot be neglected, it is necessary to design controllers that are robust with respect to these uncertainties. In addition, the dynamics of the robot are nonlinear, requiring consideration of nonlinear control concepts. Another aspect to be taken into account is the relative stiffness of the robot, the force sensor, and the manipulated surface. That is, the behavior of the system normal to the surface is relatively stiff, while that tangential to the surface is relatively free. Separation of the controller for these two directions is therefore indicated. We propose a controller design that accounts for this point of view and demonstrate its efficacy with respect to robustness and accuracy of position and force tracking by means of numerical simulations. The design is based on the control concept of Corless and Leitmann [l]. The example considered is a Manutecr3 robot with three degrees of freedom. In addition, we account for the dynamics of the actuator, which also possesses three degrees of freedom. The considered parameter uncertainties are friction moments in the links and friction between the end effector and the manipulated object, as well as nonlinear dynamics, which are difficult to characterize.Recommended by J. Skowronski     

CAT4 (Cable Actuated Truss—4 Degrees of Freedom): A Novel 4 DOF Cable Actuated Parallel Manipulator

The CAT4 (Cable Actuated Truss—4 degrees of freedom) robot is a novel, passively jointed, parallel robot utilizing six control cables for actuation. The architecture has been under development at the Queen's University Robotics Laboratory. The robot utilizes a passive jointed linkage with 18 revolute joints to constrain the end effector motion and provide the desired structural stability, restricting the end effector to 3 translational degrees of freedom (DOF) and 1 DOF for end effector pitch. This central mechanism together with winched cable actuation gives a number of important benefits for applications where the advantages of a parallel robot are required in conjunction with light weight. Six electric motor driven winches control the length of the cable actuators that extend from the top frame to points on the end effector raft and jointed linkage to create a stiff, but lightweight, actuated robot. Simulation work on the robot is presented giving the kinematics, including a computational estimate of the workspace for a specific configuration. Results of computational simulation of the motion of the manipulator and a discussion of the advantages and potential difficulties are also presented. © 2002 Wiley Periodicals, Inc.