Denavit-Hartenberg Method Research Articles

Robot error compensation strategy based on error sensitivity

Abstract Due to the errors in manufacturing and assembly, there are differences between the actual model and the theoretical model of the robot, which affects the positioning accuracy of the robot end-effector. In order to improve the accuracy of robot end-effector position, a robot error compensation strategy based on error sensitivity is proposed.Firstly, the robot kinematic model is established by Denavit-Hartenberg (D-H) method, and the sensitivity of end-effector position error is analyzed. According to the influence degree of different kinematic parameters on the robot end-effector position accuracy in the whole workspace, different weights are given to different kinematic parameters. {\color{red}Secondly, the kinematic error model is established, and the redundancy of the error parameter matrix is analyzed to obtain an independent error model. Thirdly, based on the error sensitivity analysis, a Weighted Levenberg-Marquard (WLM) algorithm with adaptive penalty factor is proposed, and the kinematic parameters are iteratively identified.} Finally, an error compensation experiment is carried out by using a universal serial six-degree-of-freedom robot. The experimental results show that the maximum error, mean absolute error and root mean square error of the position error on the test set are reduced by 90.75%, 89.86% and 95.64% respectively. The research in this paper provides a theoretical basis for robot end error compensation.

Gait planning based on bionic quadruped robot

Based on the ankylosaurus, a four-legged robot structure with 14 degrees of freedom was designed in this study. The kinematic model was established using the Denavit-Hartenberg (D-H) method. The inverse kinematics of the robot was analyzed, and the angle equations of each leg joint were obtained. In order to reduce the kinetic energy generated when leaving the ground and landing, the compound cycloid was modified. The modified foot curve effectively reduces energy and meets the kinematic requirements. On the basis of the foot trajectory, the diagonal leg phase difference was set to 0.5, and the diagonal gait was adopted as the gait of the bionic quadrupled robot. Simulink software was used to construct the simulation environment, and the maximum error of the simulation results and the theoretical step height was 2.05%, and the step length maximum error was 2.39%. During walking, the thigh joint angle was −92.82° to −80.21°, and the hip joint angle was 22.23° to 43.83°. Compared with the simulation trajectory and the theoretical curve, because the experiment did not consider the balance of the fuselage, there was a certain error when the leg was raised to the highest point. Overall, the gait planning strategy designed in this study basically achieves the expected effect, lays a certain foundation for the practical application of the bionic quadruped dinosaur robot, and also provides a reference for the subsequent research.

Trajectory Tracking Algorithm Study of Coal Mine Water Detector Drilling Bar Installation

Mechanical water detection is recognized as the most reliable and safe production technology for coal mines, mainly for the detection of water hazards in pre-mining operations. Intelligent water detectors are currently the main research direction in mechanical water detection, and the automatic installation of drilling bars is the key to achieving intelligent water detection. Improving the connection accuracy in the process of installing drilling bars is an important research topic for the improvement of control links. To improve the connection accuracy of the drilling bars at the time of supplying material, we used the modified Denavit–Hartenberg method to analyze the motion gestures of the supplied material device and the Lagrange equation to establish a dynamic analysis model. We aimed at better control precision by improving the sliding mode control algorithm and at increasing the convergence rate of tracking errors with a sliding controller based on an exponential approximation law and using saturated functions instead of the symbol functions in the reaching law to weaken the vibration in the control process. We then used particle swarm optimization (PSO) to find the optimum combination parameters of the sliding mode controllers and test the performance of the sliding mode controllers before and after PSO with MATLAB/Simulink. The results showed that the optimized controller has a strong resistance to parameter fluctuations, and the system responds quickly, achieves a good performance, and improves the convergence rate of tracking errors.

Multibody dynamics modeling and simulation of a three-wheeled mobile robot using a robotic approach

PurposeThis paper focuses on the application of a robotic technique for modeling a three-wheeled mobile robot (WMR), considering it as a multibody polyarticulated system. Then the dynamic behavior of the developed model is verified using a physical model obtained by Simscape Multibody.Design/methodology/approachFirstly, a geometric model is developed using the modified Denavit–Hartenberg method. Then the dynamic model is derived using the algorithm of Newton–Euler. The developed model is performed for a three-wheeled differentially driven robot, which incorporates the slippage of wheels by including the Kiencke tire model to take into account the interaction of wheels with the ground. For the physical model, the mobile robot is designed using Solidworks. Then it is exported to Matlab using Simscape Multibody. The control of the WMR for both models is realized using Matlab/Simulink and aims to ensure efficient tracking of the desired trajectory.FindingsSimulation results show a good similarity between the two models and verify both longitudinal and lateral behaviors of the WMR. This demonstrates the effectiveness of the developed model using the robotic approach and proves that it is sufficiently precise for the design of control schemes.Originality/valueThe motivation to adopt this robotic approach compared to conventional methods is the fact that it makes it possible to obtain models with a reduced number of operations. Furthermore, it allows the facility of implementation by numerical or symbolical programming. This work serves as a reference link for extending this methodology to other types of mobile robots.

Design and analysis of redundant electro-hydraulic-driven manipulator for tokamak vacuum vessel

Remote handling (RH), as one of the key technologies for fusion reactors in the future, has been the focus of research by researchers. This paper presents the design and analysis of a redundant manipulator with 10° of freedom (DOF) intended for use in vacuum vessel of the Tokamak. With a span of 3.15 m and a payload of 10 kg, the manipulator is powered by a combination of hydraulics and motors. The manipulator is mainly composed of the macro-operating arm, the micro-operating arm, and an end-effector, each serving its specific functions. This paper introduces and discusses the roles and capabilities of these components in the manipulation process. The finite element analysis (FEA) of the manipulator's structure reveals that the maximum stress of the structure is significantly lower than the permissible stress of the material Aluminium alloy 2A14. By utilizing the modified Denavit-Hartenberg (DH) method, the kinematic model was created, the forward kinematic matrix was established, and the workspace was analysed accordingly. The inverse kinematics solution was elaborated by the combination of geometric and numerical solutions. Given velocity and acceleration of the joints and the mass of the links, the force and torque of each joint were computed by the inward iterations method based on the Newton-Euler equation, and the rationality of the results was verified by ADAMS simulation. The results indicate that the manipulator, with sufficient strength and appropriate kinematic and dynamic properties, can fulfill the design objective and functional requirements.

An Origami Continuum Manipulator with Modularized Design and Hybrid Actuation: Accurate Kinematic Modeling and Experiments

Herein, this study contributes significantly to the advancement of continuum manipulators in two main aspects. First, a modularization concept and a hybrid actuation scheme to create a novel origami continuum manipulator with exceptional deformability are introduced. Second, an accurate model and framework for the forward and inverse kinematic analysis of origami manipulators are proposed. Specifically, each origami manipulator module can achieve axial extension and bending deformation by coordinated actuation of shape memory alloy (SMA) and pneumatic muscles, and the manipulator's end is equipped with a deformable gripper based on waterbomb origami and actuated by SMA. Through careful consideration of the self‐weight and torque balance, an accurate kinematic model based on the Denavit–Hartenberg method is established, which enables one to effectively predict the reachable extreme positions and spatial poses of the manipulator and solve the inverse kinematics using a genetic algorithm. Comprehensive experiments are conducted to validate the design's rationality and model's accuracy . In these tests, the rich spatial configurations are not only demonstrated that can be achieved by integrating hybrid actuators with origami modules but also the accuracy and reliability of the kinematic model are confirmed, opening up possibilities for the advancement and application of origami‐inspired robotics in various fields.

The structure design and kinematics analysis of the manipulator for the upper port remote maintenance in DEMO

As part of the upper port remote maintenance in DEMO, the design of seven degrees of freedom (DOFs) redundant manipulator with a ceiling-mounted configuration was presented in this work. The proposed manipulator is capable of flexibly maneuvering around the big manipulator, extracting the stop elements, and placing them into a basket. It can also fold itself to create more space for the operation of the big manipulator. The kinematic model of the redundant manipulator was established based on the application of the Modified Denavit-Hartenberg (MDH) method, and an unconstrained optimization equation was formulated using quaternions. To solve this equation, an improved artificial bee colony (IABC) algorithm was developed by enhancing the local search capability of the employed bees and improving the search efficiency of the observation bees. The feasibility of the structural design and the IABC algorithm was verified by carrying out trajectory planning simulations of the manipulator. The design of the 7 DOFs manipulator and the corresponding offline inverse kinematics algorithm provide valuable references for the maintenance work in the upper port remote maintenance of the DEMO.

Adaptive motion planning for CFETR multipurpose overload robot based on iterative tractrix

In this paper, an adaptive motion planning method is proposed for the control requirements of the China Fusion Engineering Test Reactor multipurpose overload robot (CMOR). Firstly, a kinematic model of CMOR is established by Denavit-Hartenberg method, and the working process of entering and leaving the vacuum chamber to complete the maintenance operation is analyzed. An iterative tractrix-based motion planning method is proposed by expanding the basic principle of tractrix. Assuming that the CMOR any link has two mutually perpendicular degrees of freedom to achieve spatial motion capability, a more natural and smooth movement of the CMOR is achieved by recursive operations on the tractrix traction. To accelerate the calculation process and avoid each joint rotation angle of CMOR exceeding the set value, a bidirectional iterative tractrix method and a joint limit rotation angle optimization method based on the bidirectional iterative tractrix method are proposed to improve the convergence speed and motion safety. Finally, a CMOR visualization simulation system is built, and the results show that the CMOR adaptive motion planning method can effectively track the target trajectory and avoid joint rotation angle overrun.

Uncertainty Inverse Analysis of Positioning Accuracy for Error Sources Identification of Industrial Robots

Uncertainties widely exist in modeling parameters of industrial robots due to wear during service. These uncertainties are too small to be directly measured and may severely affect the positioning accuracy of end-effector through multi-stage propagation. An uncertainty inverse analysis method of positioning accuracy is proposed to identify uncertainty of typical structural parameters with the selected optimal position information. The Denavit–Hartenberg method is employed to establish the kinematic model. For the probability uncertainty of modeling parameters, the inverse analysis model, which reflects propagation mapping between uncertain variables and end-effector position response is obtained by first-order second-moment method. The partial-derivative information is used to improve calculation efficiency through removing low-contributing parameters. To further reduce measurement noise interference, orthogonal matching pursuit strategy is presented to search optimal sensor placement with the objectives of maximum coefficient modulus and minimum correlation, then pseudoinverse matrix method is employed to obtain the exact solution of identification equation. Finally, numerical simulation results for 6 degrees-of-freedom robots indicate that the proposed method with improved solution efficiency can accurately identify uncertainties of joint angles within the error 5% under large measurement errors.

Development of a Compliant Lower-Limb Rehabilitation Robot Using Underactuated Mechanism

Most existing lower-limb rehabilitation robots (LLRR) for stroke and postoperative rehabilitation are bulky and prone to misalignments between robot and human joints. These drawbacks hamper LLRR application, leading to poor arthro-kinematic compatibility. To address these challenges, this paper proposes a novel robot with portability and compliance features. The developed robot consists of an underactuated mechanism and a crus linkage, respectively corresponding to the hip and knee joints. The underactuated mechanism is a new type of remote center of motion (RCM) mechanism with two sets of contractible slider cranks that can reduce the misalignments between robot and human joints. The underactuated mechanism is then optimized using the particle swarm optimization method, and the developed robot’s kinematic analysis is presented. The proposed robot can be simplified as a two-link mechanism with the ability to easily plan its trajectory using the modified Denavit–Hartenberg method. Finally, passive exercise trials demonstrate that the mismatch angles between the human and robot knee joints are less than 2.1% of the range of motion, confirming the feasibility and effectiveness of the proposed robot.

Identification of Exoskeleton Dynamics Parameters and Control Based on Series Elastic Actuator

The lower limb exoskeleton is used for rehabilitation, assistance and maturing. Taking an exoskeleton based on a serial elastic actuator as an object, a method of dynamic parameter identification is proposed. Firstly, the modular SEA structure is introduced, and the exoskeleton is modeled by using the Modified Denavit-Hartenberg (MDH) method. Then, the exoskeleton dynamic model is derived and linearized. Secondly, the excitation trajectory required for exoskeleton parameter identification is designed, which is optimized by using the genetic algorithm. Then, the exoskeleton is tested by using the excitation trajectory to decouple the dynamic parameters. Finally, the exoskeleton impedance control algorithm based on dynamic compensation is designed and compared with the algorithm without dynamic compensation. The results show that the parameters obtained from the identification algorithm and the control algorithm are effective.

A kinematic modeling scheme of three-axis "Satcom-on-the-Move" antenna based on modified Denavit-Hartenberg method

The current three-axes Satcom-on-the-Move(SOTM) antenna modeling method has some shortcomings, such as low model accuracy, poor portability and so on. In order to solve the above-mentioned shortcomings, a new modified Denavit-Hartenberg(NMDH) kinematics modeling scheme for the three-axes SOTM antenna was proposed. To overcome the modeling difficulties caused by the inherent mechanical structure of the antenna, and meet the requirements of the modified Denavit-Hartenberg(MDH) method, the virtual coordinate system and auxiliary coordinate systems are designed and added respectively on the basis of the MDH method, the forward kinematics model and inverse kinematics solution of the three-axes SOTM antenna are obtained. The correctness of the NMDH modeling scheme is verified by digital simulation. Finally, the system tests are carried out. The test results show that the NMDH modeling scheme proposed in this paper achieves good effect of antenna tracking satellite, and has stronger portability than the system identification modeling method commonly used in engineering.

Kinetostatics of a serial robot in screw form

Kinetostatics of a robot is an essential component of robotic analysis that includes actuation distribution and torque control. The extant methods mainly include the static transfer formulae and force Jacobian matrix algorithms based on the Denavit-Hartenberg (D-H) method. They can calculate the joint driving torque, but there are some limitations. This paper proposes a kinetostatics approach for analyzing the driving torque of serial manipulators. The instantaneous work done by the external load is expressed with reciprocal screw. It is the key idea of the approach to derive the kinetostatics equation in screw form and determine the required torque at each joint. This methodology is straightforward for programming. Through kinetostatic analysis of some typical serial manipulators, this paper shows the process of establishing the kinetostatics of every joint to calculate the torque in Plücker coordinates. The general spatial manipulator was analyzed and the solution demonstrates the universality of the method presented in this paper. In addition, the kinetostatic analysis method applies to all kinds of serial manipulators.

Design And Implementation Of Pose Recording System With Denavit Hartenberg Method In A 6-Dof Robot Rotaric

Robot developments have been integrated into several industrial and home appliances. To keep up with the development, UNIKA Atma Jaya created a group called PATRIOT as a head start, and started the development on ROTARIC robot. One of the early robot research discussed in this paper is to design and implement ROTARIC 6-DOF robot pose recording system which is drawn using forward kinematics with Denavit Hartenberg method. The system has a GUI with several function inside such as robot pose recording, 2-D display of the robot recorded pose using Forward Kinematics analysis, and playback recorded pose. The system uses several hardware that have been connected serially such as 6 Dynamixel MX-28 servo, OpenCM 9.04 +485 EXP microcontroller, and a Computer. The Software used in the system is C# .NET with WinForms App as the GUI and Arduino IDE. From the test done in this research, the recording and 2-D drawing system achieved error <±1cm or 6.67% relative error caused by the resolution value while reading the servo position sensor and the value rounding inside the program. Meanwhile, the playback recording function that uses queue system achieved error of <±1cm and error of ±5cm or 33.3% relative error when the recorded pose is played using real time delay used in recording. The error is caused by the robot failure to keep up with the speed of the recorded pose and the limited torque in servo number 2 in the robot.

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.

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.

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.

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.

Kinematic analysis of intelligent petrochemical fluid handling arm

In view of the low degree of automation of fluid transfer device in China's petrochemical industry, 
 this paper designs and develops an intelligent fluid transfer operator arm instead of manual 
 operation and draws its three-dimensional model based on the common structure type of 
 land-based fluid loading and unloading arm in the current market. The kinematic model of the 
 arm was developed based on the Denavit-Hartenberg method, and the forward and inverse 
 kinematics were analyzed; then the Jacobi matrix of the arm was obtained based on the 
 chi-square transformation matrix and vector product method. Finally, the positive kinematic 
 simulation was carried out by using the Robotics Toolbox toolkit in Matlab software, and the 
 conclusion that the linkage coordinate system established by the D-H method is consistent with 
 the actual structure of the manipulator arm in this paper.

Vector model for solving the inverse kinematics problem in the system of external adaptive control of robotic manipulators

A new approach that allows to solve the problems of forward and inverse kinematics for robotic manipulators is proposed by the authors. The approach is to represent the kinematic model of a robotic arm with six rotational joints in the form of a vector model. The first 4 vectors make their movements and turn in the same plane, because of the geometric features of the robot. Thus, on the basis of a vector equation, a system of nonlinear algebraic equations was formed, which were solved by the numerical Newton method, at each iteration of which a system of linear algebraic equations was solved by the Seidel method. The algorithm was tested on a trajectory set in the form of an Archimedean spiral approximated by straight line segments. Trajectory was checked by a real robot KUKA KR6 R900 and it was shown that deviation between calculated and real position of flange point was less than 0.005 mm. It is shown that in comparison with the common Denavit–Hartenberg method the method proposed by the authors has an order of magnitude fewer mathematical operations (790 versus 52).