Denavit-Hartenberg Research Articles

Precise Robot Calibration Method-Based 3-D Positioning and Posture Sensor

This article presents a distance accuracy technique for zero-offset industrial robot calibration based on 3-D positioning and posture (3DPP) sensor along with modified Denavit–Hartenberg (MDH) for robot kinematics identification. Industrial robots’ distance and positioning accuracy tend to diminish rapidly due to repetitive tasks and heavy loads. Many aspects can be involved in reducing the distance and positioning accuracy of the industrial robot; therefore, using the proper sensors and identification methods is essential to increase or restore the accuracy back to the original state. Normally, maintenance requires apparatus made specifically for robot kinematic calibration which are costly, time-consuming, and must be done by trained operators, while traditional calibration techniques suffer from cumulative error between the calibration device coordinates and robot coordinates. In this article, a 3DPP measurement device and MDH robot kinematic identification method is proposed for a six-degree-of-freedom (6DOF) industrial manipulator calibration, and a distance error calibration model is applied. The results indicate that the proposed 3DPP sensor and calibration model based on MDH improved the absolute position accuracy and distance accuracy greatly, the positioning maximum and average error were reduced by 94% and 96% respectively, and the distance maximum and average error were reduced by 95% and 96% respectively. The experimental results confirm the efficiency of the sensor and proposed method.

Kinegami: Algorithmic Design of Compliant Kinematic Chains From Tubular Origami

Origami processes can generate both rigid and compliant structures from the same homogeneous sheet material. In this article, we advance the origami robotics literature by showing that it is possible to construct an arbitrary rigid kinematic chain with prescribed joint compliance from a single tubular sheet. Our “Kinegami” algorithm converts a Denavit–Hartenberg specification into a single-sheet crease pattern for an equivalent serial robot mechanism by composing origami modules from a catalogue. The algorithm arises from the key observation that tubular origami linkage design reduces to a Dubins path planning problem. The automatically generated structural connections and movable joints that realize the specified design can also be endowed with independent user-specified compliance. We apply the Kinegami algorithm to a number of common robot mechanisms and hand-fold their algorithmically generated single-sheet crease patterns into functioning kinematic chains. We believe this is the first completely automated end-to-end system for converting an abstract manipulator specification into a physically realizable origami design that requires no additional human input.

Kinematic geometry of spatial RSSR mechanisms

Two different novel methods to derive the input–output (IO) equation of arbitrary RSSR linkages are described. Both methods share some common elements, i.e., they use the standard Denavit–Hartenberg notation to first describe the linkage as an open kinematic chain, and Study’s kinematic mapping to describe the displacement of the coordinate frame attached to the end-effector of the chain with respect to the relatively non-moving base frame. The kinematic closure equation is obtained in the seven-dimensional projective kinematic mapping image space by equating the eight Study soma coordinates to the identity array. Then two methods are successfully applied to eliminate the intermediate joint angle parameters leading to the degree four biquadratic implicit algebraic IO equation: (a) the linear implicitisation algorithm, which can be applied after rearranging the closure equation such that the linkage can be viewed as two serial RS chains, and (b) numerical elimination theory using pseudowitness sets. Both approaches lead to the same IO equation. The utility of this algebraic form of the IO equation is illustrated with three detailed application examples.

Kinematic Calibration of a Space Manipulator Based on Visual Measurement System with Extended Kalman Filter

The calibration of kinematic parameters has been widely used to improve the pose (position and orientation) accuracy of the robot arm. Intelligent measuring equipment with high accuracy is usually provided for the industrial manipulator. Unfortunately, large noise exists in the vision measurement system, which is provided for space manipulators. To overcome the adverse effect of measuring noise and improve the optimality of calibrating time, a calibration method based on extended Kalman filter (EKF) for space manipulators is proposed in this paper. Firstly, the identification model based on the Denavit–Hartenberg (D-H) modeling method is established. Then, the camera which is rigidly attached to the end-effector takes pictures of a calibration board that is settled around the manipulator. The actual pose of the end-effector is calculated based on the pictures of the calibration board. Subsequently, different data between the actual pose and theoretical pose as input, whilst error parameters are estimated by EKF and compensated in the kinematic algorithm. The simulation result shows that the pose accuracy has been improved by approximately 90 percent. Compared with the calibration method of the least squares estimate (LSE), EKF is beneficial to further optimize the calibrating time with a faster computation speed and ensure the stability of the calibration.

Variable-curvature elephant trunk robot in nuclear industry

In this paper, a variable curvature Elephant trunk robot (ETR) is designed based on the bionic principle to complete the visual inspection and assisted flaw detection tasks in the bottom of the divertor and the vertical port complex pipe area of the China Fusion Engineering Test Reactor (CFETR). It offers a miniaturized and lightweight structure with similar load capacity and position accuracy to a rigid robot. It can be installed as a sub-system of the CFETR remote handling maintenance system on various mobile maintenance platforms such as the CFETR multipurpose overload robot and can penetrate various confined spaces and multi-obstacle environments to complete operational tasks. The kinematic model of the ETR is established based on the Denavit Hartenberg (DH) method. A prototype is built according to the design method and trajectory tests are carried out to verify the rationality of the structural design. For ETR trajectory control requirements, three different trajectory tracking control methods are proposed in this paper. The effectiveness of the trajectory tracking methods is verified by simulation. The Elephant Trunk Robot design and control strategy provides a reference for narrow space maintenance task in the CFETR.

Modeling and Simulation of an Octorotor UAV with Manipulator Arm

In this paper, the conceptual design, modeling, and simulation are proposed for an octorotor UAV with a manipulator arm. The conceptual design of the octorotor UAV with a manipulator arm is developed, and for the study and analysis, the design is implemented and validated in Matlab (Simulink-SimMechanics) software. The kinematics and dynamics models of the octorotor UAV with a manipulator arm are obtained using the classical Denavit–Hartenberg convention and the recursive Newton–Euler method, respectively. In this sense, a cascade PID controller for the attitude and navigation of the UAV and a simple PID controller for the manipulator arm are proposed and simulated in a closed-loop system in order to highlight the performance of the proposed design. Finally, simulations show the feasibility and behavior of the mathematical model and the flight controller in a closed-loop system.

Kinematic calibration for collaborative robots on a mobile platform using motion capture system

For modern robotic applications that go beyond the typical industrial environment, absolute accuracy is one of the key properties that make this possible. There are several approaches in the literature to improve robot accuracy for a typical industrial robot mounted on a fixed frame. In contrast, there is no method to improve robot accuracy when the robot is mounted on a mobile base, which is typical for collaborative robots. Therefore, in this work, we proposed and analyzed two approaches to improve the absolute accuracy of the robot mounted on a mobile platform using an optical measurement system. The first approach is based on geometric operations used to calculate the rotation axes of each joint. This approach identifies all rotational axes, which allows the calculation of the Denavit–Hartenberg (DH) parameters and thus the complete kinematic model, including the position and orientation errors of the robot end-effector and the robot base. The second approach to parameter estimation is based on optimization using a set of joint positions and end-effector poses to find the optimal DH parameters. Since the robot is mounted on a mobile base that is not fixed, an optical measurement system was used to dynamically and simultaneously measure the position of the robot base and the end-effector. The performance of the two proposed methods was analyzed and validated on a 7-DoF Franka Emika Panda robot mounted on a mobile platform PAL Tiago-base. The results show a significant improvement in absolute accuracy for both proposed approaches. By using the proposed approach with the optical measurement system, we can easily automate the estimation of robot kinematic parameters with the aim of improving absolute accuracy, especially in applications that require high positioning accuracy. • A geometric and numerical approach for the calibration of collaborative robots. • Sensitivity analysis for MoCap noise position measurement on DH parameter estimation. • A novel approach to map the optical base frame and robot base frame. • Statistical analysis of different methods for estimating DH parameters.

Robot-mounted sensing and local calibration for high-accuracy manufacturing

Positional accuracy is critically important for application of industrial robots in fixtureless precision manufacturing; thus, this paper presents a method for simultaneously calibrating the kinematic parameters of robot and robot-mounted measurement devices. In the modeling step, the Modified Denavit–Hartenberg parameters are extended to include the world and tool frames within a minimal parameter set using a systematic approach. Closed-loop calibration is performed using the data collected in the local target workspace using the robot-mounted measurement device. The presented modeling and calibration methods are applied to a case study in which a machining task is performed using a DENSO VS-6556 W industrial robot equipped with a cutting tool, force sensor, and laser profile scanner. In the case study, local models are calibrated for the laser and tool frames using common 1-2-3 blocks as calibration artifacts . The robot/laser model is identified by scanning the artifacts with a robot-mounted laser scanner , and the robot/tool model is calibrated by touching the artifacts with a robot-mounted force sensor. In this application, the robot/laser model is used to scan and register a sheet metal workpiece, and the robot/tool model is used to plan a tool path to machine the periphery. Positional accuracy of the tool path was evaluated to be ± 0.15 mm within the target workspace, which shows significant improvement compared with the mean error of 0.8 mm achieved by global calibration of the robot/tool model. • Simultaneous calibration of robot and extrinsic parameters of robot-mounted sensors. • Closed-loop calibration without external measurement devices. • Local calibration to improve accuracy within target workspace. • Systematic approach to include world and tool/sensor frame in MDH parameter set. • Case study for high-accuracy robotic machining application.

A 2-DoF Kinematic Chain Analysis of a Magnetic Spring Excited by Vibration Generator Based on a Neural Network Design for Energy Harvesting Applications

In this paper, an original mathematical model and experimental results for the vibration generator and the magnetic spring prototype that converts mechanical energy to electrical energy are proposed. The magnetic spring model is developed by a robotic approach based on Denavit–Hartenberg’s notation and designed by the 2-degrees of freedom kinematic chain for determination of its motion and estimation of several resonance frequencies useful in many energy harvesting applications. The vibration generator that moves the magnetic spring is modeled by neural networks and the magnetic spring potential energy is calculated by the finite elements method (FEM). Furthermore, the magnetic spring and the vibration generator are designed by the Simulink block diagram. Testing results of the magnetic spring and vibration generator displacement conducted in laboratory have shown good agreement with simulation results.

Planar and spherical four-bar linkage [formula omitted] algebraic input–output equations

The algebraic polynomial input–output (IO) equations relating any two of the relative joint displacement parameters, called vi and vj, between any of the six distinct pairs of rigid links in arbitrary planar and spherical four-bar mechanisms are derived. First, the forward kinematics transformation matrices of the corresponding serial kinematic chains are computed in terms of their Denavit–Hartenberg parameters, but with all angles converted to tangent half-angle parameters. These matrices are mapped to their corresponding Study soma coordinates. The serial kinematic chain is closed by equating the soma coordinates to the identity array. Algebraic polynomial elimination methods are then used to obtain a single polynomial in terms of only the design and the selected IO joint displacement parameters. This yields six independent algebraic IO Equations for each of the planar and spherical 4R linkages; the same techniques are applied to derive six additional algebraic IO equations for each of the RRRP and PRRP planar linkages providing a catalogue of 24. The utility of these IO equation sets is demonstrated via discussion of the associated mobility and design parameter spaces.

Kinematic parameters calibration of industrial robot based on RWS-PSO algorithm

The positioning accuracy of an industrial robot has a significant impact on its application in precision manufacturing, and it is necessary to calibrate robot kinematic parameters. Previous studies have established numerous nonlinear equations to solve the kinematic parameters, which are complicated and time consuming. A standard particle swarm optimization (PSO) algorithm is limited by long running time and low solution efficiency. Therefore, in this study, a dynamic particle swarm optimization algorithm based on roulette wheel selection (RWS-PSO) is proposed to realize the kinematic parameters calibration. First, a kinematics model is constructed using the standard Denavit-Hartenberg (D-H) method, and the theoretical and actual values of the spatial position of the robot endpoint are obtained via forward kinematics and a Laser Tracker, respectively. Next, the kinematic parameters calibration problem is transformed into a solution of a high-dimensional nonlinear equation using the proposed RWS-PSO algorithm. In the proposed RWS-PSO algorithm, the inertia factor is considered as linearly decreasing and the number of particles is selected by the roulette wheel selection (RWS) to improve its computational efficiency. The proposed RWS-PSO and standard PSO algorithms are compared based on various indices by simulation. The results reveal that the time cost of the RWS-PSO algorithm is much lower than that of the standard PSO algorithm on the basis of high precision and a reduced running time of approximately 53%. Finally, the kinematic parameter errors obtained by the two algorithms are compensated. According to the experimental results, the positioning accuracy of the robot in three ( x-, y-, and z-) directions is improved by 78%, 46%, and 67%, respectively, compared to that of before compensation, which proves that the RWS-PSO algorithm is effective and practical for kinematic parameters calibration.

Novel kinematic model of articulated arm coordinate measuring machine with angular position measurement errors of rotary axes

The measurement accuracy of an articulated arm coordinate measuring machine (AACMM) is determined by its kinematic model to estimate the end effector position from angular positions of rotary axes. In conventional studies, the Denavit–Hartenberg (DH) model, containing position and orientation errors of the rotary axis average lines as error sources, has been widely employed. This study first proposes a novel kinematic model including angular position measurement errors of rotary axes. To identify the proposed model, a new Single Point Articulation Test (SPAT) setup is presented with the R-Test to measure the stylus sphere's three-dimensional displacement. The prediction accuracy of the proposed model is experimentally evaluated.

Exoskeleton Design Using Kinematics Analysis for Upper Limb Rehabilitation in Post-Stroke Patients

Robotic technology in the last decade has developed to support the rehabilitation of post-stroke patients. The exoskeleton design model approach is carried out to simulate kinematics according to the needs of upper limb rehabilitation. The simulated design is identical to the structure of the human arm, so it requires planning and method according to the needs of human arm anatomy movements. The exoskeleton model must meet comfort and adjustment for medical rehabilitation, so it is essential to consider the kinematic analysis in its design. In this paper, we will analyze the kinematics of the exoskeleton and simulate flexion/extension and supination/pronation movements, with the targeted area being the forearm with the 3 Degrees of Freedom (DoF) mechanism consisting of two DoF. Kinematic simulations are carried out with the RoboAnalyzer software using predefined Denavit-Hartenberg parameters. The simulation results show that the end effector's initial position on the X axis is to coordinate 0 on the base 45o joint shoulder, then the rotational movement on the elbow is 1150 . In the wrist position, the action is supination and pronation because the joint is parallel to the elbow. Hence, the coordinates of the x and y-axis rotation changes follow elbow coordinates.

A Novel Calibration Method for Robot Kinematic Parameters Based on Improved Manta Ray Foraging Optimization Algorithm

The positioning accuracy has a significant impact on the application of the robotic arm. In this study, a novel method based on improved manta ray foraging optimization (MRFO) algorithm is presented for kinematic parameters calibration, which can reduce the absolute positioning error of the manipulator. The error model of the robot is established according to the Denavit–Hartenberg (D–H) method. The redundancy of the model is analyzed, and the redundant parameters are eliminated. The kinematic parameter identification of the robot is transformed into a nonlinear optimization problem. The original MRFO algorithm is improved by using the natural selection strategy and adaptive parameter control strategy to improve searching performance and convergence speed. The calibration experiment of the self-designed 6-DOF robot arm is carried out. A measurement method for measuring the position of the robot end using a 3-D scanner is introduced. The improved MRFO (IMRFO) algorithm is used to identify the kinematic parameter errors of the robot. The experimental results show that by using the IMRFO algorithm to calibrate the parameter error, the position error of the robot end is reduced from 10.2357 to 0.5483 mm or by 94.6%. The results show that the IMRFO algorithm proposed in this article has high identification accuracy and fast convergence speed, which can effectively identify the kinematic parameter error of the robot.

Formulation Method of Robot Kinematics Considering Versatility and Mobility of Each Joint

This paper proposes a method of formulating the robot kinematics. The proposed method can be applied to mobile manipulators, parallel link robots, and legged robots by the same procedure. The proposed forward kinematics formulation is based on tree-structured rigid-body system and is compared with the Denavit–Hartenberg method and URDF. The proposed differential kinematics formulation is represented by a block lower triangular matrix, which is a generalized form of the basic Jacobian matrix. In addition, an application example of the proposed formulation to the numerical inverse kinematics method is also shown. The usage of the proposed method is demonstrated by simulation experiments using a dual-arm mobile manipulator and a parallel link robot.

Inverse Kinematics Analysis of Humanoid Robot Arm by Fusing Denavit–Hartenberg and Screw Theory to Imitate Human Motion With Kinect

Inverse Kinematics Analysis of Humanoid Robot Arm by Fusing Denavit–Hartenberg and Screw Theory to Imitate Human Motion With Kinect

Описание программного комплекса для моделирования робота-манипулятора

The article proposes the development of a software module for modeling the kinematics and dynamics of a manipulator with five degrees of freedom. To solve the forward kinematics problem of the manipulator, the Denavit–Hartenberg method was used. To solve the inverse kinematics and dynamics problem of the manipulator, analytical methods (the Levenberg-Marquardt method, the Newton–Euler method) and a soft computing method (adaptive neurofuzzy inference system) were used. The software module for modeling the kinematics and dynamics of the manipulator was developed using the software package of the SolidWorks computer-aided design system and the MatLab program. The developed software module is able to simulate the kinematics and dynamics of the manipulator based on the described methods, visualize the simulation results, generate a trajectory for the target position and orientation of the end-effector of the manipulator, simulate the movement of the manipulator along a given trajectory.

Design and 3D printing of the Robot, articulated with 6 degrees of freedom with educational applications

This work presents the complete manufacturing of an articulated robot of 6 degrees of freedom, with educational applications. With the purpose of increasing the motivation of the students in the significant learning of the subject of robotics. The methodology was developed from the design of each link of the robot in Solid Word, to later print it in 3D, followed by the mechanical and electrical/electronic implementation. In accordance with this, we worked with the mathematical modeling through the RoboAnalyzer software based on the Denavit Hartenberg parameters. To control the robot, so that the student has options to be able to control the robot, a control card was developed which is compatible with: Raspberry, Arduino and PIC microcontroller. In addition to the above possibilities of programming, another programming option is provided to only manipulate the robot with an application on a laptop, tablet or cell phone, these applications are free; it refers to Universal Gcode Sender and Bluetooth Electronics that simulate a teach pendant. With the development of this robotic equipment, it is intended to form integral students in their technological assets.

Modeling and experimental design of a generalized gripper

In this paper, a generalized gripper with multiple grasping modes is designed to grasp various sheet parts. The novelty of the gripper lies in two sets of fingers and two sets of compact force transmission mechanisms with large mechanical gain. In order to achieve the above functions of the gripper, link-type fingers and sucker-type fingers are integrated together so the gripper has multiple grasping modes. At the same time, the force transmission system was redesigned, and the kinematic model of the force transmission system is established by means of D-H (Denavit-Hartenberg) method. Secondly, workspace, mechanical gain and linkage length are taken as the objective functions to obtain these optimized structural parameters of the gripper. For the purpose of further validating optimization results, the comparison of results of the proposed optimization procedure with these in commercial software. And compared results indicate that the proposed optimization procedure can acquire a larger workspace and greater mechanical gain. Finally, according to the optimized parameters, a generalized gripper is manufactured. The design experiments prove that the gripper can realize multiple grasping modes.

Inclusion of Bidirectional Angular Positioning Deviations in the Kinematic Model of a Six-DOF Articulated Robot for Static Volumetric Error Compensation

To improve a robot’s absolute positioning accuracy, researchers have extensively studied the robot kinematic model containing position and orientation errors of rotary axis average lines, widely known as Denavit–Hartenberg (D-H) parameters. To further improve the absolute positioning accuracy of industrial robots, this article proposes a novel kinematic model and its identification scheme. The proposed kinematic model for a serial-linked industrial robot contains the bidirectional angular positioning deviations of each rotary axis, represented in a lookup table, in addition to its D-H parameters. The angular positioning deviations of the rotary axes are modeled as a function of angular command positions, along with the direction of rotation to model the influence of backlash. This article also proposes a novel approach to identify the proposed kinematic model with the bidirectional angular positioning deviations using a laser tracker with indexing each rotary axis at specified angular positions (“circle point method”). Moreover, the model-based compensation technique is being experimentally investigated to validate the prediction accuracy of the proposed model. The findings of the experiment show that the proposed model enhances the robot’s absolute positioning accuracy significantly over the entire workspace.