Showing papers in "Journal of Robotic Systems in 2004"
TL;DR: In this article, a vector pursuit approach based on the theory of screws was used to track a nonholonomic ground vehicle along a given path using a set of screws, which was developed by Sir Robert Ball in 1900 to generate a desired vehicle turning radius based on vehicle position and orientation relative to the position of a point ahead on the planned path and the desired orientation along the path at that point.
Abstract: Autonomous ground vehicle navigation requires the integration of many technologies such as path planning, position and orientation sensing, vehicle control, and obstacle avoidance The work presented here focuses on the control of a nonholonomic ground vehicle as it tracks a given path A new path tracking technique called “vector pursuit” is presented This new technique is based on the theory of screws, which was developed by Sir Robert Ball in 1900 It generates a desired vehicle turning radius based on the vehicle's current position and orientation relative to the position of a point ahead on the planned path and the desired orientation along the path at that point The vector pursuit algorithm is compared to other geometrical approaches, and it is shown to be more robust, resulting in more accurate path tracking © 2004 Wiley Periodicals, Inc
121 citations
TL;DR: In this paper, the design and architecture of a low-cost and light-weight inertial and visual sensing system for a small-scale autonomous helicopter is described, where a custom 6-axis IMU and a stereo vision system provide vehicle attitude, height, and velocity information.
Abstract: This paper describes the design and architecture of a low-cost and light-weight inertial and visual sensing system for a small-scale autonomous helicopter. A custom 6-axis IMU and a stereo vision system provide vehicle attitude, height, and velocity information. We discuss issues such as robust visual processing, motion resolution, dynamic range, and sensitivity. © 2004 Wiley Periodicals, Inc.
91 citations
TL;DR: A new path planning algorithm is presented where these three methods are integrated for the first time in a single architecture and generally yields shorter paths than the Voronoi and potential field methods, and faster than the visibility graph.
Abstract: Numerous methods have been developed to solve the motion planning problem, among which the Voronoi diagram, visibility graph, and potential fields are well-known techniques. In this paper, a new path planning algorithm is presented where these three methods are integrated for the first time in a single architecture. After constructing the generalized Voronoi diagram of C-space, we introduce a novel procedure for its abstraction, producing a pruned generalized Voronoi diagram. A broad freeway net is then developed through a new a-MID (maximal inscribed discs) concept. A potential function is assigned to the net to form an obstacle-free network of valleys. Afterwards we take advantage of a bidirectional search, where the visibility graph and potential field modules execute alternately from both start and goal configurations. A steepest descent mildest ascent search technique is used for local planning and avoiding local minima. The algorithm provides a parametric tradeoff between safest and shortest paths and generally yields shorter paths than the Voronoi and potential field methods, and faster than the visibility graph. It also performs well in complicated environments. © 2004 Wiley Periodicals, Inc.
91 citations
TL;DR: In this article, a mathematical model for a model-scale unmanned helicopter robot, with emphasis on the dynamics of the flybar, is presented, and the interaction between the fly bar and the main rotor blade is explained in detail.
Abstract: This paper presents a mathematical model for a model-scale unmanned helicopter robot, with emphasis on the dynamics of the flybar. The interaction between the flybar and the main rotor blade is explained in detail; it is shown how the flapping of the flybar increases the stability of the helicopter robot as well as assists in its actuation. The model helicopter has a fast time-domain response due to its small size, and is inherently unstable. Therefore, most commercially available model helicopters use the flybar to augment stability and make it easier for a pilot to fly. Working from first principles and basic aerodynamics, the equations of motion for full six degree-of-freedom with flybar-degree of freedom are derived. System identification experiments and results are presented to verify the mathematical model structure and to identify model parameters such as inertias and aerodynamic constants. © 2004 Wiley Periodicals, Inc.
90 citations
TL;DR: In this paper, a method is presented for the synthesis of 3- R RR planar parallel mechanisms using a genetic algorithm while considering three different design criteria: the optimized workspace to approach a prescribed workspace, the maximization of the mechanism's dexterity, and the avoidance of singularities inside the mechanism workspace.
Abstract: In this paper, a method is presented for the synthesis of 3- R RR planar parallel mechanisms. The method uses a genetic algorithm while considering three different design criteria: the optimization of the mechanism workspace to approach a prescribed workspace, the maximization of the mechanism's dexterity, and the avoidance of singularities inside the mechanism workspace. It is shown that, for a given mechanism, some working modes do not have any corresponding singularity curves located inside the mechanism workspace. Furthermore, a case is presented where, for a given orientation range of the mechanism's end-effector, there are no parallel singularities located inside the workspace. Finally, two methods are described and compared to deal with the nonuniform units of the mechanism's Jacobian matrix during the dexterity computation. © 2004 Wiley Periodicals, Inc.
80 citations
TL;DR: In this paper, a complete dynamic model on task space for a 6 degrees of freedom (DOF) Gough-Stewart platform-type computer numerical control (CNC) machine is derived.
Abstract: In this paper, a complete dynamic model on task space for a 6 degrees of freedom (DOF) Gough-Stewart platform-type computer numerical control (CNC) machine is derived. The rotation terms of the legs are included for those inertia effects cannot be negligible in the machine tool applications. The formulation derived by means of the Euler-Lagrange method is convenient for designing the adaptive control law. Also, the average-type force model for end milling process is derived and included in the dynamic model and control. A composite adaptive control scheme is developed by use of filtering dynamics technique. An appropriate estimator gain is designed in the parameter adaptation law that is useful for estimating the selected important cutting parameters. Experimental results verify the proposed adaptive control scheme can achieve good tracking performance. © 2004 Wiley Periodicals, Inc.
72 citations
TL;DR: In this article, a new class of omnidirectional mobile robot is proposed, which is called an omnidirected mobile robot (OMR-SOW), and it has synchronously steerable omnidefirectional wheels, and one steering DOF can function as a continuously variable transmission.
Abstract: Omnidirectional mobile robots are capable of arbitrary motion in an arbitrary direction without changing the direction of wheels, because they can perform 3 degree-of-freedom (DOF) motion on a two-dimensional plane. In this research, a new class of omnidirectional mobile robot is proposed. Since it has synchronously steerable omnidirectional wheels, it is called an omnidirectional mobile robot with steerable omnidirectional wheels (OMR-SOW). It has 3 DOFs in motion and one DOF in steering. One steering DOF can function as a continuously variable transmission (CVT). CVT of the OMR-SOW increases the range of velocity ratio from the wheel velocities to robot velocity, which may improve performance of the mobile robot. The OMR-SOW with four omnidirectional wheels has been developed in this research. Kinematics and dynamics of this robot will be analyzed in detail. Various tests have been conducted to demonstrate the validity and feasibility of the proposed mechanism and control algorithm. © 2004 Wiley Periodicals, Inc.
64 citations
TL;DR: This article focuses on a sculpting metrology tool, assisting a human artist in generating a piece from a computer model, but applications exist in manufacturing, rapid prototyping, robotics, and automated construction.
Abstract: A novel cable-based metrology system is presented wherein six cables are connected in parallel from ground-mounted string pots to the moving object or tool of interest. Cartesian pose can be determined for feedback control and other purposes by reading the lengths of the six cables via the string pots and using closed-form forward pose kinematics. This article focuses on a sculpting metrology tool, assisting a human artist in generating a piece from a computer model, but applications exist in manufacturing, rapid prototyping, robotics, and automated construction. We present experimental data to demonstrate the operation of our system, we study the absolute accuracy and also measurement resolution, and we discuss various error sources. The proposed real-time cable-based metrology system is less complex and more economical than existing commercial Cartesian metrology technologies. © 2004 Wiley Periodicals, Inc.
55 citations
TL;DR: A practical validation strategy including detailed test cases was developed along with a set of quantitative criteria for judging the validation test results for practically verifying that the complex simulation facility preserves the dynamics of the truth model of the space robot for space-representative contact robotic tasks.
Abstract: This paper describes a methodology for validating a ground-based, hardware-in-the-loop, space-robot simulation facility. This facility, called “SPDM task verification facility,” is being developed by the Canadian Space Agency for the purpose of verifying the contact dynamics performance of the special purpose dexterous manipulator (SPDM) performing various maintenance tasks on the International Space Station because the real SPDM cannot be physically tested for 3D operations on the ground due to the gravity. The facility uses a high-fidelity SPDM mathematical model, known as the “truth model” of the space robot, to drive a hydraulic robot to mimic the space robot performing contact operations. In this research different techniques were studied for practically verifying that the complex simulation facility preserves the dynamics of the truth model of the space robot for space-representative contact robotic tasks. Based upon the study and many years of experience in developing and verifying space robotic systems, a practical validation strategy including detailed test cases was developed along with a set of quantitative criteria for judging the validation test results. © 2004 Wiley Periodicals, Inc.
53 citations
50 citations
TL;DR: In this paper the filter equations for an extended Kalman filter are derived together with considerations of the tuning and simulations with real sensor data show the successful implementation of this concept.
Abstract: This paper presents a method to fuse measurements from a rigid sensor rig with a stereo vision system and a set of 6 DOF inertial sensors for egomotion estimation and external structure estimation. No assumptions about the sampling rate of the two sensors are made. The basic idea is a common state vector and a common dynamic description which is stored together with the time instant of the estimation. Every time one of the sensor sends new data, the corresponding filter equation is updated and a new estimation is generated. In this paper the filter equations for an extended Kalman filter are derived together with considerations of the tuning. Simulations with real sensor data show the successful implementation of this concept. © 2004 Wiley Periodicals, Inc.
TL;DR: Inertial sensors attached to a camera can provide valuable data about camera pose and movement and provide an image independent location of the image focus of expansion and center of rotation useful during visual based navigation tasks.
Abstract: Inertial sensors attached to a camera can provide valuable data about camera pose and movement. In biological vision systems, inertial cues provided by the vestibular system are fused with vision at an early processing stage. In this article we set a framework for the combination of these two sensing modalities. Cameras can be seen as ray direction measuring devices, and in the case of stereo vision, depth along the ray can also be computed. The ego-motion can be sensed by the inertial sensors, but there are limitations determined by the sensor noise level. Keeping track of the vertical direction is required, so that gravity acceleration can be compensated for, and provides a valuable spatial reference. Results are shown of stereo depth map alignment using the vertical reference. The depth map points are mapped to a vertically aligned world frame of reference. In order to detect the ground plane, a histogram is performed for the different heights. Taking the ground plane as a reference plane for the acquired maps, the fusion of multiple maps reduces to a 2D translation and rotation problem. The dynamic inertial cues can be used as a first approximation for this transformation, allowing a fast depth map registration method. They also provide an image independent location of the image focus of expansion and center of rotation useful during visual based navigation tasks. © 2004 Wiley Periodicals, Inc.
TL;DR: This method models the teleoperation system in the state space, considering all the possible interactions that could appear in the operator-master-slave-environment set, and it uses the Taylor expansion to model the time delay.
Abstract: This paper describes a new control method of teleoperation systems with communication time delay. This method models the teleoperation system in the state space, considering all the possible interactions that could appear in the operator-master-slave-environment set, and it uses the Taylor expansion to model the time delay. The control system allows that the slave manipulator follows the master in spite of the time delay in the communication channel. The tracking is achieved by state convergence between the master and the slave. The method is also able to establish the desired dynamics of this convergence and the dynamics of the slave manipulator. Furthermore, a simple design procedure is provided to obtain the control system gains. These control gains are calculated solving a set of seven equations. The control method is robust to the uncertainty of the design parameters, so it is not necessary to obtain good estimations of these parameters. Simulations and experiments with a one DOF teleoperation system are presented to verify the control method. © 2004 Wiley Periodicals, Inc.
TL;DR: The WiRo-6.3 as discussed by the authors is a parallel robotic structure with six degrees of freedom, whose end effector is driven by nine wires operated by motors, and it has been numerically analyzed and solved in closed form.
Abstract: 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.
TL;DR: In this paper, the authors presented a method to generate three-dimensional robot working paths off-line based on CAD data in an automatic adhesive spray system for shoe outsoles and uppers.
Abstract: Most shoe manufacturing processes are not yet automated; it puts restrictions on increasing productivity. Among them, adhesive application processes particularly are holding the most workers and working hours. In addition, the working environment is very poor due to the toxicity of adhesive agents. In the case of automating an adhesive application process by using a robot, robot teaching by playback is difficult to produce high productivity because the kinds of shoes to be taught mount up to several thousands. To cope with it, it is necessary to generate robot working paths automatically according to the kind, the size, or the right and the left of shoes, and also to teach the generated paths to a robot automatically. This paper presents a method to generate three-dimensional robot working paths off-line based on CAD data in an automatic adhesive spray system for shoe outsoles and uppers. First, this paper describes how to extract the three-dimensional data of an outsole outline from a two-dimensional CAD drawing file. Second, it describes how to extract the three-dimensional data of an upper profiling line from the three-dimensional scanning data that is opened in a three-dimensional CAD program. Third, it describes how to generate robot working paths based on the extracted data and the nozzle setting parameters for adhesive spray. Also, a series of experiments for adhesive spray is performed to verify the effectiveness of the presented methods. This study will do much for increasing productivity in shoe manufacturing as a core work of a robotic adhesive spray system. © 2004 Wiley Periodicals, Inc.
TL;DR: A minimum jerk approach is exploited to define the trajectory in the Cartesian space and cubic splines are adopted in the joint space, guaranteeing a natural movement of the finger as well as reduced vibrations in the mechanical structure and increased control performances.
Abstract: In this paper we propose a method, based on both physiologic and engineering considerations, for the motion planning of a prosthetic finger. In particular, we exploit a minimum jerk approach to define the trajectory in the Cartesian space. Then, cubic splines are adopted in the joint space. The redundancy problem arising from the presence of three links is solved by assuming that there is a constant ratio between the second and the third joint motion. The value of the proportional constant is determined by minimizing the maximum jerk in the joint space. It is found that this constant value can be suboptimally but effectively set to one for all the movements. This approach guarantees a natural movement of the finger as well as reduced vibrations in the mechanical structure and increased control performances. © 2004 Wiley Periodicals, Inc.
TL;DR: A method for estimating mobile robot ego-motion is presented, which relies on tracking contours in real-time images acquired with a calibrated monocular video system, and inertial information is used to obtain better estimates.
Abstract: A method for estimating mobile robot ego-motion is presented, which relies on tracking contours in real-time images acquired with a calibrated monocular video system. After fitting an active contour to an object in the image, 3D motion is derived from the affine deformations suffered by the contour in an image sequence. More than one object can be tracked at the same time, yielding some different pose estimations. Then, improvements in pose determination are achieved by fusing all these different estimations. Inertial information is used to obtain better estimates, as it introduces in the tracking algorithm a measure of the real velocity. Inertial information is also used to eliminate some ambiguities arising from the use of a monocular image sequence. As the algorithms developed are intended to be used in real-time control systems, considerations on computation costs are taken into account. © 2004 Wiley Periodicals, Inc.
TL;DR: In this article, an adaptive controller is designed for rigid-link flexible-joint robot manipulators based on link and actuator position measurements only, which achieves asymptotic tracking of link positions while keeping all states and signals bounded.
Abstract: In this paper, an adaptive controller is designed for rigid-link flexible-joint robot manipulators based on link and actuator position measurements only. It is based on the adaptive integrator backstepping method and the link and actuator velocity filters are used to estimate the unknown velocity terms. Moreover, the proposed controller exploits the estimate of the joint stiffness matrix inverse to overcome the overparametrization problem, which has been a significant drawback in adaptive partial state feedback controllers. It achieves asymptotic tracking of link positions while keeping all states and signals bounded. The tracking capability of the presented method is shown through simulation results of one- and two-link flexible joint manipulators. © 2004 Wiley Periodicals, Inc.
TL;DR: A kinematic modeling method, which is directly applicable to any type of planar mobile robots, is proposed in this work and an algorithm estimating a sensed forward solution for the given information of the rotational velocities of the four wheels is discussed.
Abstract: A kinematic modeling method, which is directly applicable to any type of planar mobile robots, is proposed in this work. Since holonomic constraints have the same differential form as nonholonomic constraints, the instantaneous motion of the mobile robot at current configuration can be modeled as that of a parallel manipulator. A pseudo joint model denoting the interface between the wheel and the ground (i.e., the position of base of the mobile robot) enables the derivation of this equivalent kinematic model. The instantaneous kinematic structures of four different wheels are modeled as multiple pseudo joints. Then, the transfer method of augmented generalized coordinates, which has been popularly employed in modeling of parallel manipulators, is applied to obtain the instantaneous kinematic models of mobile robots. The kinematic models of six different types of planar mobile robots are derived to show the effectiveness of the proposed modeling method. Lastly, for the mobile robot equipped with four conventional wheels, an algorithm estimating a sensed forward solution for the given information of the rotational velocities of the four wheels is discussed. © 2004 Wiley Periodicals, Inc.
TL;DR: This research aims at the development of a fully mobile, completely self-contained tracking system, that is able to estimate sensor motion from known 3D scene structure, that requires a highly modular and scalable software architecture for algorithm design and testing.
Abstract: Fusion of vision-based and inertial pose estimation has many high-potential applications in navigation, robotics, and augmented reality. Our research aims at the development of a fully mobile, completely self-contained tracking system, that is able to estimate sensor motion from known 3D scene structure. This requires a highly modular and scalable software architecture for algorithm design and testing. As the main contribution of this paper, we discuss the design of our hybrid tracker and emphasize important features: scalability, code reusability, and testing facilities. In addition, we present a mobile augmented reality application, and several first experiments with a fully mobile vision-inertial sensor head. Our hybrid tracking system is not only capable of real-time performance, but can also be used for offline analysis of tracker performance, comparison with ground truth, and evaluation of several pose estimation and information fusion algorithms. © 2004 Wiley Periodicals, Inc.
TL;DR: A systematic analytical method, based on the theory of screws, is presented for identification of limb structures of general and over-constrained 3-degree-of-freedom (DOF) translational parallel manipulators.
Abstract: A systematic analytical method, based on the theory of screws, is presented for identification of limb structures of general and over-constrained 3-degree-of-freedom (DOF) translational parallel manipulators. Given a system of wrenches of constraint, the corresponding reciprocal basis screws are determined. Then, the joint screws of a limb are obtained by a linear combination of these basis screws. Feasible limbs that can be used for construction of translational platforms are enumerated according to the type of constraint and the number of joints making up the limbs. © 2004 Wiley Periodicals, Inc.
TL;DR: In this article, the stiffness and strength of the materials used in the wire-actuated robots were investigated using finite element analysis, and a design methodology was developed and presented, which is beneficial to those working on designing and prototyping a new robot or modifying an existing robot.
Abstract: Currently, wire-actuated robots are not used extensively in industry, but they are gaining more attention due to advantages they possess. Low weight, cost, and power consumption are features that make wire-controlled robots worth researching. This article investigates the designs of two different, 4 degrees of freedom parallel, wire-actuated robots so that a prototype of one of these can be built. A design methodology is developed and presented. The process will be beneficial to those working on designing and prototyping a new robot or modifying an existing robot. Stability of both designs is considered first to ensure that the robots are able to exert and withstand end effector forces in different positions throughout their respective workspaces. The stiffness and strength of the materials used in the designs is also investigated using finite element analysis. © 2004 Wiley Periodicals, Inc.
TL;DR: An airborne reconfigurable measurement system being developed at Swedish Defence Research Agency (FOI), Sensor Technology, Sweden is described, and an image processing oriented sensor management architecture for UAV (unmanned aerial vehicles) IRsEO-surveillance is presented.
Abstract: This paper describes an airborne reconfigurable measurement system being developed at Swedish Defence Research Agency (FOI), Sensor Technology, Sweden. An image processing oriented sensor management architecture for UAV (unmanned aerial vehicles) IRsEO-surveillance is presented. Some preliminary results of navigation aided image processing in UAV applications are demonstrated, such as SLAM (simultaneous localization and mapping), structure from motion and geolocation, target tracking, and detection of moving objects. The design goal of the measurement system is to emulate a UAV-mounted sensor gimbal using a stand-alone system. The minimal configuration of the system consists of a gyro-stabilized gimbal with IR and CCD sensors and an integrated high-performance navigation system. The navigation system combines dGPS real-time kinematics (RTK) data with data from an inertial measurement unit (IMU) mounted with reference to the optical sensors. The gimbal is to be used as an experimental georeferenced sensor platform, using a choice of carriers, to produce military relevant image sequences for studies of image processing and sensor control on moving surveillance and reconnaissance platforms. Furthermore, a high resolution synthetic environment, developed for sensor simulations in the visual and infrared wavelengths, is presented. © 2004 Wiley Periodicals, Inc.
TL;DR: The RPPM is designed to act as a testbed manipulator for theories on redundant actuation of parallel manipulators and can reconfigure into three different revolute-jointed mechanism types.
Abstract: This work presents the design of a reconfigurable planar parallel manipulator (RPPM). The RPPM is designed to act as a testbed manipulator for theories on redundant actuation of parallel manipulators and can reconfigure into three different revolute-jointed mechanism types: a 2-branch 2-DOF (degree-of-freedom) 5-bar mechanism; a 2-branch 3-DOF 6-bar mechanism; and a 3-branch 3-DOF 8-bar mechanism. The design of the RPPM allows for any shoulder or elbow joint to be actuated. In this work, the criteria and constraints of the design are presented. The final design of the RPPM is shown, followed by a discussion of the final design and how it relates to the initial design criteria and constraints. © 2004 Wiley Periodicals, Inc.
TL;DR: Way to improve the performance by incorporating inertial sensors for vision based mobile robot navigation for wheel chairs is investigated.
Abstract: This paper describes ongoing research on vision based mobile robot navigation for wheel chairs. After a guided tour through a natural environment while taking images at regular time intervals, natural landmarks are extracted to automatically build a topological map. Later on this map can be used for place recognition and navigation. We use visual servoing on the landmarks to steer the robot. In this paper, we investigate ways to improve the performance by incorporating inertial sensors. © 2004 Wiley Periodicals, Inc.
TL;DR: A method for estimating mobile robot egomotion is presented, which relies on tracking contours in real-time images acquired with a calibrated monocular video system, which introduces in the tracking algorithm a measure of the real velocity.
Abstract: A method for estimating mobile robot egomotion is presented, which relies on tracking contours in real-time images acquired with a calibrated monocular video system. After fitting an active contour to an object in the image, 3D motion is derived from the affine deformations suffered by the contour in an image sequence. More than one object can be tracked at the same time yielding some different pose estimations. Then, improvements in pose determination are achieved by fusing all these different estimations. Inertial information is used to obtain better estimates, as it introduces in the tracking algorithm a measure of the real velocity. Inertial information is also used to eliminate some ambiguities arising from the use of a monocular image sequence. As the algorithms developed are intended to be used in real-time control systems, considerations on computation costs are taken into account.
TL;DR: In this article, the possibility of fusion of navigation data obtained by two separate navigation systems (strap-down inertial one and dynamic vision based one) is considered, and the attention is primarily focused on principles of validation of separate estimates before their use in a combined algorithm.
Abstract: The possibility of fusion of navigation data obtained by two separate navigation systems (strap-down inertial one and dynamic vision based one) is considered in this paper. The attention is primarily focused on principles of validation of separate estimates before their use in a combined algorithm. The inertial navigation system (INS) based on sensors of medium level quality has been analyzed on one side, while a visual navigation method is based on the analysis of a sequence of images of ground landmarks produced by an on-board TV camera. The accuracy of INS estimations is being improved continuously by optimal estimation of a flying object's angular orientation while the visual navigation system offers discrete corrections during the intervals of presence of landmarks inside the camera's field of view. The concept is illustrated by dynamic simulation of a realistic flight scenario. © 2004 Wiley Periodicals, Inc.
TL;DR: This paper investigates ways to improve the performance by incorporating inertial sensors in vision based mobile robot navigation for wheel chairs.
Abstract: This paper describes ongoing research on vision based mobile robot navigation for wheel chairs. After a guided tour through a natural environment while taking images at regular time intervals, natural landmarks are extracted to automatically build a topological map. Later on this map can be used for place recognition and navigation. We use visual servoing on the landmarks to steer the robot. In this paper, we investigate ways to improve the performance by incorporating inertial sensors.