Position Of Manipulator Research Articles

Properties of boron layers deposited during boronisations in W7-X

Boronisation was first used for wall conditioning in W7-X during the OP 1.2b operational period, which was characterized by the use of the fine-grain graphite Test Divertor Unit (TDU) and inertial cooling only. After this period, deposited layers were observed on all inner surfaces. Deposited layers were analyzed on 21 inner wall tiles using ion beam analysis methods, the deposited layers consisted mostly of boron with additional carbon and oxygen. During the operational period OP2.1 with an actively water cooled divertor made of carbon fiber reinforced carbon, different materials were exposed during two individual boronisations using the multi-purpose manipulator. Deposited boronisation layers on the samples were analyzed using nuclear reaction analysis. The deposited layer thicknesses showed some variation depending on substrate material and surface roughness, but a systematic dependence on material and/or roughness was not observed. Under the typical boronisation conditions at W7-X, one A × h (Ampere times hour) of boronisation results in a boronisation layer with a thickness of about 30 ± 15 × 1015B-atoms/cm2 (about 3 ± 1.5 nm) at the position of the multi-purpose manipulator. The oxygen gettering capacity of the layers is up to 0.5 – 0.9O/B.

Innovative Designs for Cotton Bionic Topping Manipulator

Topping reduces the growing point at the top of cotton plants. This process enables the plant to allocate more energy and nutrients to fruit growth, thereby enhancing both the quantity and quality of the fruit. Current cotton-topping machinery often leads to over-topping, which can affect crop yield and quality. Manual topping is effective in controlling over-topping due to its adherence to agronomic requirements, but it is labor-intensive. This study integrated principles from biology (bionics) to design a manipulator that mimics the action of hand pinching during manual topping. Screening grids of different sizes were designed based on a statistical analysis of the biological parameters of cotton tops to optimize the topping process. A disc cam mechanism was developed to enable the automatic opening and closing of the manipulator. From the results, it was evident that the spring tension must exceed 81.5 N to properly cut the cotton stem near the top. The spacing of the screening grid (40 mm) and the position of the topping manipulator (less than 50 mm) were optimized based on experimental results. Performance testing showed promising results with a 100% topping rate. This study not only identified the challenges with current cotton-topping methods but also proposed a bionics-inspired solution; a bionic manipulator equipped with a screening grid was proposed to achieve high accuracy in cotton topping, which significantly reduced over-topping rates to 6.67%. These findings are crucial for advancing agricultural technology and improving efficiency in cotton cultivation.

Control system of the electric drive of a robot with a dc motor

Problem. Robotics and flexible production systems are the most important technical basis for the intensification of production. The use of robotic systems is expanding every year. This paper considers a two-circuit servo control system using the example of a DC motor current and speed control system and examines the functional diagram of the third circuit, a digital angle control system. Using the Matlab + SIMULINK software package, the servo drive and the digital system for controlling the angular position of the robot manipulator were modelled. Goal. As a result of the analysis, the purpose of the study was highlighted: the development of a digital system for adjusting the angular position of the manipulator, improve the quality of its positioning. Tasks: to study work management systems; to study the drives of robots; to get a mathematical model of an electric motor; to develop a machine diagram of a digital electric drive; to synthesize a three-loop robot positioning control system. Methodology. The research problems should be solved by methods of analysis and synthesis of automatic control systems. Results. In the work, a three-circuit control system of the electric drive of a robot with a direct current motor was developed. Thus, as a result of modeling the operation of a digital electric drive with three control circuits for current, speed and positioning, an aperiodic transient process was provided with quality indicators. Originality. Thus, the results of simulation of the two-loop servo control system showed that the dynamic characteristics of the electric motor in terms of current and speed of rotation, which meet the requirements of the task, are provided by the PI controller in the current control circuit and the PID controller in the speed control circuit. Thus, as a result of modeling the operation of a digital electric drive with three control circuits for current, speed and positioning, an aperiodic transient process was provided with quality indicators. Practical value. The following results were obtained during the research: the best control law for the current circuit is the proportional-integral (PI) law; the best control law for the speed contour is the proportional-integral-differential (PID) law; the best control law for a digital positioning control loop is the proportional (P) law.

An interactive gesture control system for collaborative manipulator based on Leap Motion Controller

Gesture control is often used for the control of robotic manipulators. However conventional methods always focus on position control of robotic manipulators and use a fixed position to place gesture detection devices, which limits the flexibility to control and interact. This paper presents an interactive gesture control system based on Leap Motion Controller that can overcome these shortcomings. A coordinate transformation is performed between the position of the left palm detected by Leap Motion Controller and the tool center point (TCP) of the collaborative manipulator to obtain gesture data first. This gesture data is used to control the posture of a six-joint collaborative manipulator-Lite6. The position of gripper is controlled by grip level of the right palm. A controller is designed to manipulate a lift table on which Leap Motion Controller is placed to achieve adaptive ascending and descending movements to meet the needs of operators of different heights and arm spans. A modified Kalman filter is used to filter noise and smooth the signal captured by Leap Motion Controller. The experiments demonstrate that the system can operate stably and accurately control the position, posture, and gripper position of a collaborative manipulator in real time using human palms’ gestures.

Synchronous planning of initial and target positions of redundant space manipulator based on deterministic configuration tree

Planning the operating position of redundant space manipulators (RSMs) can effectively improve the performance of manipulators while improving the quality of on-orbit servicing (OOS) is of great significance. For RSM, OOS with synchronous planning of initial and target positions (ITPs) has many combinations of positions or configurations, making it difficult to apply existing methods directly. To address this problem, this study proposes a method for synchronous planning ITPs of RSMs based on a deterministic configuration tree (DCT). First, the planning area is divided into grids, with the global performance analyzed utilizing self-motion manifolds. Then, a DCT is constructed based on the analysis results of global performance. Finally, a position planning strategy of pre-planning, rewiring, and regrowth is proposed to achieve synchronized planning of the ITP of the RSM on the DCT. This method is conducted alternately in operational space and joint space. The gridding and regrowth process in operational space avoids the considerable calculation required by gridding in high-dimensional joint space and improves the efficiency of position planning. In joint space pre-planning and rewiring, the ITP is optimized with the constraint of motion planning results while position planning is realized. The simulation experiment results of the 3-degree-of-freedom (DOF) planar RSM, 4-DOF RSM, and 7-DOF RSM indicate that the proposed method reduces time consumption by 34.81%, 18.15%, and 16.26% compared to conventional methods. Furthermore, energy consumption is reduced by 30.68%, 16.93%, and 15.64%, respectively. A typical ITPs synchronous planning task is also simulated, and the results also show that this planning method can effectively optimize the ITPs and reduce energy consumption.

Observer-Based Neural Control of N-Link Flexible-Joint Robots.

This article concentrates on the adaptive neural control approach of n -link flexible-joint electrically driven robots. The presented control method only needs to know the position and armature current information of the flexible-joint manipulator. An adaptive observer is designed to estimate the velocities of links and motors, and radial basis function neural networks are applied to approximate the unknown nonlinearities. Based on the backstepping technique and the Lyapunov stability theory, the observer-based neural control issue is addressed by relying on uplink-event-triggered states only. It is demonstrated that all signals are semi-globally ultimately uniformly bounded and the tracking errors can converge to a small neighborhood of zero. Finally, simulation results are shown to validate the designed event-triggered control strategy.

Dynamic robust path-following control of UVMS subject to manipulator disturbance

This study addresses path-following control issue of underwater vehicle-manipulator systems (UVMS) in the presence of manipulator disturbances. It considers disturbance forces arising from manipulator position changes, including restorative forces and coupling forces, to achieve precise UVMS path-following control. By analysing the variations in the center of mass and buoyant center of manipulator links during motion, the corresponding restorative torque is deduced, and disturbance forces are calculated. Additionally, joint coupling forces generated during manipulator startup, braking, and rotation are taken into account. These aspects collectively yield the expression for disturbance forces. Subsequently, adaptive sliding mode control are employed to achieve accurate control of the UVMS system. This study effectively addresses the issue of UVMS body control under manipulator disturbances. By analysing the motion of manipulator links, the disturbance forces exerted by the manipulator on the UVMS are identified, offering insights for similar control challenges arising from manipulator disturbances. Simulation results are conducted to show the effectiveness of the proposed control method.

Application of the crow search algorithm to achieve an optimal solution for a double link manipulator

Robotic manipulators are mechanical devices that are electronically controlled and have several linkages that allow them to do specific jobs under specified situations. Here, a double-link manipulator is explored and modified using uncertainty factors that impact the robot manipulator's performance in monitoring the angular position. Unlike, the standard Lagrangian technique is employed to derive the motion equations and calculate the performance of the Two Link Robot Manipulator. Because the motion equation involves a nonlinear system of ordinary differential equations, getting to the target place is challenging. Meta-heuristic search algorithms were standard methodologie to solve any optimization problem, mainly real-time problems. Meta-heuristic algorithms depend upon the natural behaviour of the animals or birds. This paper uses a Crow search algorithm to minimize the trajectory and position of the double link manipulator. It also demonstrates how the Crow search algorithm can easily be used to solve optimal control problems (OCP) with constraints in MATLAB simulation. The Crow search algorithm depends on the crow's behaviour of keeping their excess food in a safe place and getting it as needed. The Crow search algorithm (CSA) was compared with particle swarm optimization (PSO), differential evolution (DE), and Grey Wolf Optimization (GWO). The double link manipulator's fundamental Model's performance is computed to find a solution. The Crow search method has produced notable results in terms of performance, i.e. 25 % to 98 % better, compared to other algorithms such as DE, PSO, and GWO.

Optimized leader‐follower consensus control using combination of reinforcement learning and sliding mode mechanism for multiple robot manipulator system

AbstractThis article is to develop an optimized leader‐follower consensus control for multiple robot manipulator system by combining sliding mode control (SMC) and reinforcement learning (RL). The SMC mechanism aims to steer both position and velocity states of multiple manipulator reaching the predefined trajectory. And the RL is designed and performed under identifier‐critic‐actor architecture for the achievement of optimized control performance. Compared to traditional optimal control, this proposed method has two main advantages: (i) the RL updating laws for training both the actor and critic networks are simpler; (ii) the optimized control can not require the complete dynamic knowledge because the adaptive identifier is designed into the RL learning. Consequently, this optimized control method can smoothly steer the multiple robot manipulator system to achieve the leader‐follower consensus. Finally, feasibility of this control method is verified through both theory and simulation.

Comparative Analysis of Nonlinear Dynamics of an Angular Velocity System of 2-DOF Aerial Manipulator with Different Physical Parameters

The two-degree-of-freedom (2-DOF) aerial manipulator is composed of a quadrotor aircraft and a 2-DOF manipulator, which significantly expands the scope of grabbing and transporting objects. After the manipulator is installed on the quadrotor, the manipulator and the load will cause serious interference to the quadrotor, resulting in difficulty of system control and even instability. This paper presents a mathematical model of the angular velocity system of the 2-DOF aerial manipulator. The model considers the influence of the manipulator and the load on the quadrotor. Based on this model, the nonlinear dynamics of the angular velocity system of the 2-DOF aerial manipulator are analyzed by solving the equilibrium points, calculating the Lyapunov exponents, analyzing the dynamic bifurcation diagram, and drawing the dynamic region distribution map. It is found that angular velocity can produce the dynamic behaviors of sink, period-doubling, and chaos under certain circumstances. By analyzing the nonlinear dynamic behaviors of the angular velocity system under different manipulator postures, different manipulator configurations, different load masses, and different load resistances, the stability of the angular velocity system is analyzed to guide the use of the aerial manipulator more safely and efficiently.

Monitoring and Path Avoiding Method of Singular Position of the Redundant Manipulator

Monitoring and Path Avoiding Method of Singular Position of the Redundant Manipulator

Dynamics Analysis and Control of a Two-Link Manipulator

This article develops a practicable, efficient, and robust PID controller for the traditional double pendulum system. Utilizing the Lagrangian method, the equations of motion for the two-link robot manipulator are initially derived. The system of ordinary differential equations for this nonlinearity describes these equations. As closed-form solutions for the equations of motion are absent, we approximate the solution of the initial-value problem. Securing precise user-defined positions while controlling the motion of the two-link robot manipulator proves to be a formidable challenge due to its non-linear behavior. The primary objective is to achieve the intended position of the robot manipulator by implementing the computed torque control method. Once the equation of motion has been derived, MATLAB is utilized to represent the control simulation. Several computational simulations are employed to validate the controller performance. Specifically, we implement a PID controller to simulate the balancing of the two links on a mobile robot at any given angle, including inverted.

Application of the Kuka Kube Test-Bed for the Hardware-in-the-Loop Validation of the Space Manipulator Control System

Abstract The on-ground validation of control systems designed for manipulators working in orbit is very difficult due to the necessity of simulating the microgravity environment on Earth. In this paper, we present the possibilities of utilising the KUKA KUBE test-bed with industrial robots to experimentally verify space systems using hardware-in-the-loop tests. The fixed-base KUKA industrial robot is operated in gravitational environment, while the space system model plant is solved in real time parallel to on-ground experiment. The test-bed measurements are the input of the model plant, and the output of the model is treated as an input for the industrial robot actuation. In the performed experiment, the control system based on the Dynamic Jacobian is validated. The desired point that is reached by the manipulator's end-effector is constant in the simulated environment and moving with respect to the test-bed frame. The position of the space manipulator's end-effector is calculated by evaluating dynamics of the satellite in real-time model. The results show that the control system applied to the KUKA robot works correctly. The measurements from the torque sensors mounted in KUKA robot's joints are in accordance with the simulation results. This fact enhances the possibilities of gravity compensation, thus simulating microgravity environment on the test-bed.

Robust Position Control of a Continuum Manipulator Based on Selective Approach and Koopman Operator

Continuum manipulators have infinite degrees of freedom and high flexibility, making it challenging for accurate modeling and control. Some common modeling methods include mechanical modeling strategy, neural network strategy, constant curvature assumption, etc. However, the inverse kinematics of the mechanical modeling strategy is difficult to obtain while a strategy using neural networks may not converge in some applications. For algorithm implementation, the constant curvature assumption is used as the basis to design the controller. When the driving wire is tight, the linear controller under constant curvature assumption works well in manipulator position control. However, this assumption of linearity between the deformation angle and the driving input value breaks upon repeated use of the driving wires which get inevitably lengthened. This degrades the accuracy of the controller. In this work, the Koopman theory is proposed to identify the nonlinear model of the continuum manipulator. Under the linearized model, the control input is obtained through model predictive control (MPC). As the lifted function can affect the effectiveness of the Koopman operator-based MPC (K-MPC), a novel design method of the lifted function through the Legendre polynomial is proposed. To attain higher control efficiency and computational accuracy, a selective control scheme according to the state of the driving wires is proposed. When the driving wire is tight, the linear controller is employed; otherwise, the K-MPC is adopted. Finally, a set of static and dynamic experiments has been conducted using an experimental prototype. The results demonstrate high effectiveness and good performance of the selective control scheme.

Safety evaluation of tubing and sucker rod vertically handling equipment under stochastic wind load

Workover operations are crucial for maintain the normal production of oil, gas and water wells and require significant manpower and material resources. In recent years, automation equipment has become more widely used in the operations of oilfield workover operations. The present paper established the finite element model of the newly developed tubing and sucker rod vertically handling equipment, and the deformation, equivalent stress and wind-resistant ability of the structure model under dead weight load and wind load are investigated. The wind load is equivalent to the wind pressure acting on the structural unit, and the transient wind field is composed through linear superposition of harmonic function with random amplitude and frequency. Results show that the maximum equivalent stress is much lower than the yield stress of the structural material under typical working conditions, the maximum displacement of the manipulator position meets the design requirements of positioning accuracy.

Positioning system design of closed-loop magnetically driven laser steering manipulator for endoscopic microsurgery

This study presents a closed-loop magnetically driven laser steering manipulator positioning system for endoscopic microsurgery. A multimagnetic field strength sensor circuit is embedded in a 16−mm diameter analog laser steering manipulator. The magnetic field distribution of a cylindrical permanent magnet in three-dimensional space is first modeled using an integral model to overcome the large error induced by the magnetic dipole model when the sensor and permanent magnet are close. The integral in the model is then decomposed using the Gauss–Legendre quadrature to improve the computational efficiency of the formulation. Moreover, five commonly used global search optimization methods are compared. Then, the algorithm with the fastest computational rate among these five algorithms, the tree-seed algorithm, is fused with the Levenberg–Marquardt algorithm, which performs well in local search, to obtain a hybrid optimization algorithm. Finally, it is demonstrated through static and dynamic experiments that the system based on the hybrid algorithm can obtain satisfactory computational errors while maintaining a high computational rate.

Adaptive Proportional Integral Derivative Nonsingular Dual Terminal Sliding Mode Control for Robotic Manipulators

This article aims to develop a new Adaptive Proportional Integral Derivative (PID) Nonsingular Dual Terminal Sliding Mode Control, designed for tracking the position of robot manipulators under disturbances and uncertainties. Compared with existing PID Nonsingular Fast Terminal Sliding Mode (PIDNFTSM) controllers, this work effectively avoids singularity problems in control while significantly enhancing the convergence speed of errors. An adaptive reaching law is proposed to estimate the bound information of the first derivative of lumped disturbance by regulating itself based on sliding variables. The overall system stability is proven by using the Lyapunov approach. Subsequent simulation results verify the effectiveness of the proposed controller regarding tracking error reduction, energy efficiency enhancements, and singularity avoidance.

A novel spring gravity-balance method for spatial articulated manipulators without auxiliary links

Previous studies developed spring-gravity balancing methods for articulated manipulators using auxiliary links. However, these links caused extra inertia and motion interference. To address these issues, a spring balancing method based on the quadratic form was proposed. In this form, matrix components represent the energy change due to the manipulator's posture, i.e., stiffnesses. Gravity balancing can be simplified as the summation of matrices that remain unchanged. However, the matrix component contains the polar angles, which can only describe the links’ direction on a plane, thus making this form applicable only to planar manipulators. To extend its applicability to spatial manipulators, we have reformulated it using local coordinates to describe the manipulator's posture in space. The improved quadratic form can be applied to both planar and spatial manipulators, unifying energy representations of articulated manipulators. By arranging the springs to maintain a constant summation of matrices, energy balance is achieved. The criteria of spring attachment and the rules of using springs are proposed. Simulation of a spatial four-link manipulator show perfect balance can be achieved without auxiliary links using our approach.

Sliding Mode Control with Feedforward Compensation for a Soft Manipulator That Considers Environment Contact Constraints

Soft manipulators have desirable environmental compatibility because of their pliability. However, this pliability also brings challenges to modeling and control when considering contact or collision with the environment. In previous work, we established several mathematical models for describing fluidic soft manipulators under environmental effects and verified their accuracy. However, the controller design for a soft manipulator is still a significant challenge, especially under the conditions of environmental contact. In this paper, we build upon our previously established work by conducting feedforward compensation for a soft manipulator under contact constraints and designing a sliding mode controller based on an operational space dynamics model. Then, we combine the feedforward compensation model with the sliding mode controller to realize accurate position control of the soft manipulator. Finally, simulation and experimental results show that this controller can accurately and effectively control the position of the soft manipulator.

Vision-Based Hierarchical Impedance Control of an Aerial Manipulator

This paper presents an image-based impedance control scheme for an under-actuated aerial manipulator. Unlike the existing Cartesian cascade control (admittance control) scheme, we design an image-space visual servoing controller at the dynamic level to achieve compliant interaction with unknown environments. Furthermore, compared with the state of the art in aerial interaction control, feedback of both the external wrench and the Cartesian position of the aerial manipulator are not required. To cope with the under-actuation property of the system, an attitude tracking control task is designed in such a way that it is dynamically decoupled with the visual impedance control task. Convergence of the task-space tracking error is proven based on the Lyapunov theory. The finite-gain <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\mathcal{L}}_2$</tex-math></inline-formula> stability of the system regarding external force/disturbance is also proven. Indoor experiments are conducted to demonstrate the proposed method.