Serial-link Robot Research Articles

Simplified model to study the kinematics of manipulators with parallelogram linkages

PurposeParallelogram linkages are used to increase the stiffness of manipulators and allow precise control of end-effectors. They help maintain the orientation of connected links when the manipulator changes its position. They are implemented in many palletizing robots connected with binary, ternary and quaternary links through both active and passive joints. This limits the motion of some joints and hence results in relative and negative joint angles when assigning coordinate axes. This study aims to provide a simplified accurate model for manipulators built with parllelogram linkages to ease the kinematics calculations.Design/methodology/approachThis study introduces a simplified model, replacing each parallelogram linkage with a single (binary) link with an active and a passive joint at the ends. This replacement facilitates countering motion while preserving subsequent link orientations. Validation of kinematics is performed on palletizing manipulators from five different OEMs. The validation of Dobot Magician and ABB IRB1410 was carried out in real time and in their control software. Other robots from ABB, Yaskawa, Kuka and Fanuc were validated using control environments and simulators.FindingsThe proposed model enables the straightforward derivation of forward kinematics and transforms hybrid robots into equivalent serial-link robots. The model demonstrates high accuracy streamlining the derivation of kinematics.Originality/valueThe proposed model facilitates the use of classical methods like the Denavit–Hartenberg procedure with ease. It not only simplifies kinematics derivation but it also helps in robot control and motion planning within the workspace. The approach can also be implemented to simplify the parallelogram linkages of robots with higher degrees of freedom such as the IRB1410.

Nonclassical Parametric Variational Technique to Manipulability Control of a Serial-Link Robot That Is Used in Treatment of Femoral Shaft Fractures

Robot-assisted intramedullary nailing is a minimally invasive surgical procedure commonly used to treat femur fractures. Despite its benefits, there are several disadvantages associated with this technique, such as frequent malalignment, physical fatigue, and excessive radiation exposure for medical personnel. Therefore, it is crucial to ensure that robotic surgery for fracture reduction is precise and safe. Precise calculation and regulation of the robot’s reduction force are of utmost importance. In this study, we propose a manipulator that utilises robot assistance and indirect contact with the femur to effectively reduce fractures in the shaft. The dynamics of the reduction robot are analysed using the implicit function theorem, which allows us to address the reduced problem. A parametric approach is presented to tackle the initial algebraic constraints, enabling the approximation of the state-space solution while simultaneously controlling the class of constraints in a multiway manner. This approach simplifies the problem from an infinite-dimensional one to a finite-dimensional one, leading to an approximate solution obtained by solving a set of control linear algebraic equations. The proposed robotic-assisted system enhances fracture repositioning while reducing radiation exposure for both the patient and the medical staff. Through numerical results and their practical application, we have developed an efficient method that yields positive outcomes.

DESIGN, KINEMATICS AND MANIPULABILITY ANALYSES OF A SERIAL-LINK ROBOT FOR MINIMALLY INVASIVE TREATMENT IN FEMORAL SHAFT FRACTURES

The application of robot in orthopedic clinical surgery is more and more accepted. A femoral fracture reduction robot is described in the paper. The mechanism of the manipulator comprises a six-DOF serial-link robot, referred to as a 3P3R robot, with three prismatic joints and three rotational joints (including one for the knee). The manipulability of the system was analyzed, and its operability over the entire whole work space was verified. In addition, the existence of an inverse kinematic solution of the system was established, and the same was analytically implemented with physical meaningfulness. The kinematic analysis and investigation of the workspace confirmed the feasibility of the mechanism for the given design parameters. The joint displacements and rotation angles required to achieve the desired posture of the end-effector of the mechanism were also determined. The results of simulation substantiated the effectiveness of the developed robotic system, and its prospect for practical application through further research.

Controls and process planning strategies for 5-axis laser directed energy deposition of Ti-6Al-4V using an 8-axis industrial robot and rotary motion

Interest in multi-axis additive manufacturing has grown significantly in recent years due to associated benefits that range from improved quality to support for greater geometric complexity. A method of 5-axis Laser Hot-Wire Directed Energy Deposition is developed and demonstrated in this study using an 8-axis industrial robot, comprised of a 6-axis serial link robot and a 2 degree‐of‐freedom positioner. Coordinated 5-axis motion is used to print Ti-6Al-4V objects predominantly through build plate rotation. Methods of slicing and toolpath generation are presented, including the use of an alternating toolpath direction philosophy and the manipulation of the CAD model surface normal vectors for determining the required build plate tilt angles for maintaining consistent deposition orientations relative to gravity. Another objective of the study was to determine the limits of conventional slicing and layer height control techniques for printing geometries with significant unsupported overhangs. A comparison is made between the behavior of normal and conformal bead alignment in this regard, and the performance of the layer height controller is reported as it relates to process stability and the limits of printing overhang geometries. Unsupported overhangs were successfully printed at 35° without build plate tilt and 45° with build plate tilt. Toolpath velocity and net-shape printing performance are reported as well, with 3D scans of the printed surfaces used for net-shape characterization. In all, the printing of three geometries is presented, including the overhang geometry, a 5-axis toolpath geometry, and a large-scale, multi-bead demonstrator part, which exceeded 500 mm in height and weighed 44 kg (97 lbs).

Fish-Like Robot with a Deformable Body Fabricated Using a Silicone Mold

This paper describes a fish-like robot with a deformable outer shell fabricated using a silicone mold. Based on the difference in the contact condition between the serial-link robot and the shell, the fabrication methods are classified into embedded type and skin type. This study analyzes the mechanical properties of embedded and skin-type underwater robots from the viewpoint of material mechanics. A low-torque motor can sufficiently drive the skin-type underwater robot if the friction coefficient and pressure between the skin and the link are appropriately selected. Furthermore, the outer skin of the fish-like robot can be easily fabricated by defoaming in the chamber of a vacuum-packaging machine. Finally, the performance of the skin-type robot in air and underwater was assessed through several experiments.

Design Stable Controller for PUMA 560 Robot with PID and Sliding Mode Controller Based on PSO Algorithm

The most significant challenge facing the researcher in the field of robotics is to control the robot manipulator with appropriate overall performance. This paper focuses mainly on the novel Intelligent Particle Swarm Optimization (PSO) algorithm that was used for optimizing and tuning the gain of conventional Proportional Integral Derivative (PID), and improve the parameters of dynamic design in Sliding Mode Control (SMC), which is considered a strong nonlinear controller for controlling highly nonlinear systems, particularly for multi-degree serial link robot manipulator. Additional modified Integral Sliding Mode Controller (ISMC) was implemented to the design of dynamic system with high control theory of sliding mode controller. Intelligent Particle Swarm Optimization (PSO) algorithm was introduced for developing the nonlinear controller. The algorithm demonstrates superior performance in determining the appropriate gains and parameters value in harmony with robot scheme dynamic layout in order to achieve suitable and stable nonlinear controller, besides reduce the chattering phenomenon. PUMA robot manipulator that was used as study case in this work, shows perfect result in step response, with acceptable steady state, and overshoot, besides, eliminating the disadvantage of chattering in conventional SMC. Matlab / Simulink presents to increase the speed of matrix calculation in forward, inverse kinematics and dynamic model of manipulator. Comparison was made between the proposed method with existing methods. Result shows that integral sliding mode with PSO (ISMC/PSO) gave best result for stable step response, minimum mean square error with best objective function, and stable torque.

A novel method to identify DH parameters of the rigid serial-link robot based on a geometry model

Purpose Every geometric model corresponding to a unique feature whose errors of parameters uncorrelated, so the linearization technique can be successfully applied. The solution of a linear least square problem can be applied straightforwardly. This method has advantages especially in calibrate the redundant robot because it’s relatively small. The parameters of kinematics are unique and determined by this algorithm. Design/methodology/approach In this paper, a geometric identification method has been studied to estimate the parameters in the Denavit–Hartenberg (DH) model of the robot. Through studying the robot’s geometric features, specific trajectories are designed for calibrating the DH parameters. On the basis of these geometric features, several fitting methods have been deduced so that the important geometric parameters of robots, such as the actual rotation centers and rotate axes, can be found. Findings By measuring the corresponding motion trajectory at the end-effector, the trajectory feature can be identified by using curve fitting methods, and the trajectory feature will reflect back to the actual value of the DH parameters. Originality/value This method is especially suitable for rigid serial-link robots especially for redundant robots because of its specific calibration trajectory and geometric features. Besides, this method uses geometric features to calibrate the robot which is relatively small especially for the redundant robot comparing to the numerical algorithm.

Kinematic Modeling and Visual Servo Control of a Soft-Bodied Magnetic Anchored and Guided Endoscope

In minimally invasive surgery (MIS), a number of instruments are inserted into the surgical cavity via the trocar(s), which makes the surgical site crowded and instruments tend to fence with each other. In addition, the motion of the endoscope is restricted by the trocar, which limits the field of view of the endoscope. To alleviate these problems, magnetic anchored and guided systems (MAGSs) have been proposed. Conventional MAGSs are built from rigid materials with small actuators and sensors. As a result, these MAGSs tend to be heavy, complex, difficult to make, and costly. In this article, we first present a soft-bodied MAGS endoscope weighing 13 g, which is made up of printable silicon rubber with embedded magnets and a camera module. The usage of soft 3-D printable material significantly reduces the complexity of the MAGS endoscope. The soft-bodied MAGS endoscope can be anchored and steered by an external magnet controlled by a serial-link robot arm. The kinematic modeling of the soft-bodied MAGS endoscope is developed. Visual servo based automatic instruments tracking of the soft-bodied MAGS endoscope is achieved for the first time. Experimental results validate that the soft-bodied MAGS endoscope can guide surgical instruments, showing its high potentials in MIS.

Multi-Agent System Inspired Distributed Control of a Serial-Link Robot

Multi-Agent System Inspired Distributed Control of a Serial-Link Robot

Development of a Self-tuning PID Controller on Hydraulically Actuated Stewart Platform Stabilizer with Base Excitation

Stewart platform is a six degrees of freedom (DOF) parallel robot manipulator with rather high powerto- weight ratio and more accurate positioning that of conventional serial-link robots. Nevertheless, modelling and control of parallel Stewart platform is so abstruse and significant for vibration isolation, especially in the case with base excitation in stabilizers. In this paper a clear nonlinear dynamic model of hydraulically actuated Stewart platform with 6-DOF is presented via Kane’s method. The dynamics of Stewart platform embedded with hydraulic actuator equations is utilized to design a modern control scheme with the aim of vibration isolation. In order to attenuate upper platform vibration under uncertain base excitation profile, a novel neural network based selftuning PID (NN-PID) control scheme is implemented. Following numerical simulation results, the proposed control method satisfies vibration isolation of the upper platform under uncertain base excitation and shows well robustness against external disturbances. It is concluded that the controller is of fine adjustability and can isolate a wide range of external disturbances.

Artificial Intelligent Fuzzy Logic Controller Applied on 6DOF Robot Arm Using LabVIEW and FPGA

In this work an efficient Artificial Intelligent Robotic Fuzzy Logic Controller (AIRFC) system have been constructed to control the robot arm. A serial link Robot manipulator with 6 Degree of Freedom (DOF) from DFROBOT of code ROB0036 is used as a case study. A fuzzy logic type1 controller is implemented on LabVIEW to control each joint of the robot arm for nonlinearity measurements and a fuzzy logic type2 controller is applied which is more suitable for uncertainty. The hardware design is implemented and finally downloaded using the Field Programmable Gate Array (FPGA) kit named PCI-7833R from National Instrument. By using the LabVIEW FPGA MODEL the target board can be detected for software implementation of the controllers’ systems. The work shows that in case of type2 fuzzy logic the rise time is less than that of type1 fuzzy logic for the shoulder, wrist roll and the gripper angles and it is higher for base, elbow and wrist pitch angles. The settling time is the same in elbow and wrist pitch angles and for the type2 fuzzy controller it is less for other angles.

Artificial Intelligent Fuzzy Logic Controller Applied on 6DOF Robot Arm Using LabVIEW and FPGA

In this work an efficient Artificial Intelligent Robotic Fuzzy Logic Controller (AIRFC) system have been constructed to control the robot arm. A serial link Robot manipulator with 6 Degree of Freedom (DOF) from DFROBOT of code ROB0036 is used as a case study. A fuzzy logic type1 controller is implemented on LabVIEW to control each joint of the robot arm for nonlinearity measurements and a fuzzy logic type2 controller is applied which is more suitable for uncertainty. The hardware design is implemented and finally downloaded using the Field Programmable Gate Array (FPGA) kit named PCI-7833R from National Instrument. By using the LabVIEW FPGA MODEL the target board can be detected for software implementation of the controllers’ systems. The work shows that in case of type2 fuzzy logic the rise time is less than that of type1 fuzzy logic for the shoulder, wrist roll and the gripper angles and it is higher for base, elbow and wrist pitch angles. The settling time is the same in elbow and wrist pitch angles and for the type2 fuzzy controller it is less for other angles.

A Closed Loop Inverse Kinematics Solver Intended for Offline Calculation Optimized with GA

This paper presents a simple approach to building a robotic control system. Instead of a conventional control system which solves the inverse kinematics in real-time as the robot moves, an alternative approach where the inverse kinematics is calculated ahead of time is presented. This approach reduces the complexity and code necessary for the control system. Robot control systems are usually implemented in low level programming language. This new approach enables the use of high level programming for the complex inverse kinematics problem. For our approach, we implement a program to solve the inverse kinematics, called the Inverse Kinematics Solver (IKS), in Java, with a simple graphical user interface (GUI) to load a file with desired end effector poses and edit the configuration of the robot using the Denavit-Hartenberg (DH) convention. The program uses the closed-loop inverse kinematics (CLIK) algorithm to solve the inverse kinematics problem. As an example, the IKS was set up to solve the kinematics for a custom built serial link robot. The kinematics for the custom robot is presented, and an example of input and output files is also presented. Additionally, the gain of the loop in the IKS is optimized using a GA, resulting in almost a 50% decrease in computational time.

Modeling of a Serial Link Robot Fabricated by Robot Packaging Method

Modeling of a Serial Link Robot Fabricated by Robot Packaging Method

An Analytic Approach to Converting POE Parameters Into D–H Parameters for Serial-Link Robots

The Denavit–Hartenberg (D–H) model and the product of exponentials (POE) model have been two popular methods for modeling the kinematics of a serial-link robot. While these two models are equivalent in essence, no study has revealed how to convert from the POE model to the D–H model. The conversion enables direct utilization of established algorithms formulated with D–H parameters or compensation of the D–H model after calibration with the POE parameters. It also provides a simpler method to determine the D–H parameters of a robot. For these reasons, this letter proposes an analytic approach to automatically convert a group of POE parameters into the associated D–H parameters. Three lemmas are proved for the derivation of the final algorithm. An implementation of the algorithm in MATLAB is provided as well.

Using General-Purpose Serial-Link Manipulators for Laparoscopic Surgery with Moving Remote Center of Motion

Minimally invasive surgical systems are being widely used to aid operating rooms across the globe. Although arguably successful in laparoscopic surgery, the da Vinci robotic system has limitations mostly regarding cost and lack of patient physiological motion compensation. To obtain a more cost-effective alternative, earlier works used general-purpose fully actuated serial-link robots to control instruments in laparoscopic research using constrained Jacobian techniques. In contrast with those works, we present a new technique to solve the laparoscopic constraints for the serial-link manipulator by using a constrained trajectory. This novel technique allows complex 3D remote center-of-motion trajectories to be taken into account. Moreover, it does not have problems related to drifting, and is less prone to singularity related issues as it can be used with redundant manipulators. The proof-of-concept experiments are done by performing artificial trajectories with static and moving trocar points using a physical robot manipulator. Furthermore, the system is tested using user input of 13 medically untrained personnel in an endoscope navigation task. The experiments show that the system can be operated reliably under arbitrary and unpredictable user inputs.

巻きつけ把持を行う劣駆動多関節シリアルリンク型ロボットハンドの開発

巻きつけ把持を行う劣駆動多関節シリアルリンク型ロボットハンドの開発

Five-degree-of-freedom manipulation of an untethered magnetic device in fluid using a single permanent magnet with application in stomach capsule endoscopy

This paper demonstrates magnetic three-degree-of-freedom (3-DOF) closed-loop position and 2-DOF open-loop orientation control of a mockup magnetic capsule endoscope in fluid with a single permanent magnet positioned by a commercial 6-DOF robotic manipulator, using feedback of only the 3-DOF capsule position measured by a localization system, with application in capsule endoscopy of a fluid-distended stomach. We analyze the kinematics of magnetic manipulation using a single permanent magnet as the end-effector of a serial-link robot manipulator, and we formulate a control method that enables the capsule’s position and direction to be controlled when the robot manipulator is not in a kinematic singularity, and that sacrifices control over the capsule’s direction to maintain control over the capsule’s position when the manipulator enters a singularity. We demonstrate the method’s robustness to a reduced control rate of 25 Hz, reduced localization rates down to 30 Hz, deviation in the applied magnetic field from that expected, and the presence of manipulator singularities. Five-DOF manipulation of an untethered magnetic device has been previously demonstrated by electromagnetic systems only.

冗長シリアルリンクロボットの多点接触における衝突回避制御

This paper proposes a control method for multi-point contact of a redundant serial-link robot with collision avoidance between an object and the robot. A redundant robot can move with dexterity using redundancy, which is extra degree of freedom. We derive a kinematic model of the robot system and propose a controller using kinematic redundancy. The controller consists of the two parts. One is tracking desired positions and the other is avoiding collision. We analyze a feature of redundancy of the system and design the part for collision avoidance considering the feature. In our proposed method, the controlled points simultaneously track the desired trajectory by proposed method and the collision avoidance of each part is accomplished without trade-off between the parts using the feature of redundancy of the system. Simulation results show the effectiveness of the proposed method.

A Novel Crowding Genetic Algorithm and Its Applications to Manufacturing Robots

A niche genetic algorithm (GA) based on a novel twin-space crowding (TC) approach is proposed for solving multimodal manufacturing optimization problems. The proposed TC method is designed in a parameter-free paradigm. That is, when cooperatively exploring solutions with GAs, it does not require prior knowledge related to the solution space to design additional problem-dependent parameters in the evolutionary process. This feature makes the proposed TC method suitable for assisting GAs in solving real-world engineering optimization problems involving intractable solution landscapes. A set of numerical benchmark functions is used to compare effectiveness and efficiency in the proposed TCGA, in different niche GAs, and in several evolutionary computation methods. The TCGA is then used to solve multimodal joint-space inverse problems in serial-link robots to compare its convergence performance with that of conventional methods that apply the sharing function. Finally, the TCGA is used to solve iterative collision-free design problems for linkage-bar robotic hands to demonstrate its effectiveness for generating diverse solutions during the design process.