Parallel Manipulator Research Articles

Repetitive Impedance Learning-Based Physically Human-Robot Interactive Control.

Model-based impedance learning control can provide variable impedance regulation for robots through online impedance learning without interaction force sensing. However, the existing related results only guarantee the closed-loop control systems to be uniformly ultimately bounded (UUB) and require the human impedance profiles being periodic, iteration-dependent, or slowly varying. In this article, a repetitive impedance learning control approach is proposed for physical human-robot interaction (PHRI) in repetitive tasks. The proposed control is composed of a proportional-differential (PD) control term, an adaptive control term, and a repetitive impedance learning term. Differential adaptation with projection modification is designed for estimating robotic parameters uncertainties in the time domain, while fully saturated repetitive learning is proposed for estimating time-varying human impedance uncertainties in the iterative domain. Uniform convergence of tracking errors is guaranteed by the PD control and the use of projection and full saturation in the uncertainties estimation and is theoretically proved based on a Lyapunov-like analysis. In impedance profiles, the stiffness and damping are composed of an iteration-independent term and an iteration- dependent disturbance, which are estimated by repetitive learning and compressed by the PD control, respectively. Therefore, the developed approach can be applied to the PHRI where iteration-dependent disturbances exist in the stiffness and damping. The control effectiveness and advantages are validated by simulations on a parallel robot in a repetitive following task.

Finite-Time Variable-Gain ADRC for Master–Slave Teleoperated Parallel Manipulators

Finite-Time Variable-Gain ADRC for Master–Slave Teleoperated Parallel Manipulators

A Fast solution method for end-effector force extremum in redundant cable-driven parallel robots

A Fast solution method for end-effector force extremum in redundant cable-driven parallel robots

The novel synthesis of reconfigurable generalized parallel manipulators with kinematic redundancy

This paper presents an innovative method to construct reconfigurable Generalized Parallel Manipulators (GPMs) through the integration of kinematotropic single-loop linkages and configurable platforms. The approach puts forward, for the first time, the development of reconfigurable manipulators by introducing kinematic redundancy. Firstly, this study analyzes the geometric configurations of the twofold-symmetric 8-bar single-loop linkage across various working phases. Secondly, by combining the kinematotropic linkage with moving platforms in GPMs, reconfigurable manipulators with kinematic redundancy are achieved. To validate the kinematic constraints and reconfigurable characteristics of the derived mechanisms, the algebraic structure properties of Lie groups are investigated. Then, a novel class of reconfigurable GPMs with kinematic redundancy is synthesized. The ability to shape the configurations of the platforms enables the resulting manipulators to exhibit reconfigurability. Consequently, these manipulators can execute multiple motion models corresponding to different working phases of the 8-bar linkages. Finally, this research highlights the potential applications of deployable stage by using the kinematic redundancy. The idea presented in this paper explores new possibilities for the development of reconfigurable manipulators with adaptive capabilities, and extend the potential applications of GPMs.

Kinematic Parameter Identification for a Parallel Robot with an Improved Particle Swarm Optimization Algorithm

Kinematic Parameter Identification for a Parallel Robot with an Improved Particle Swarm Optimization Algorithm

Dynamic Modeling and Optimization of Tension Distribution for a Cable-Driven Parallel Robot

Dynamic Modeling and Optimization of Tension Distribution for a Cable-Driven Parallel Robot

Architecture Singularity Distance Computations for Linear Pentapods

Abstract The kinematic/robotic community is not only interested in measuring the closeness of a given robot configuration to its next singular one but also interested in a geometric meaningful index evaluating how far the robot design is away from being architecturally singular. Such an architecture singularity distance, which can be used by engineers as a criterion within the design process, is presented for a certain class of parallel manipulators called linear pentapods. Geometrically the architecture singular designs are well-understood and can be sub-classified into several cases, which allows for solving the optimization problem of computing the closest architecture singular design to a given linear pentapod with algorithms from numerical algebraic geometry.

Visual Servoing and Kalman Filter Applied to Parallel Manipulator 3-RRR

This study introduces a novel methodology integrating computer vision, visual servo control, and the Kalman Filter to precisely estimate object locations for a 3-RRR planar type parallel manipulator. Through kinematic analysis and the development of a vision system using color indicators, the research enhances the ability of the manipulator to track object trajectories, especially in cases of occlusion. Employing Eye-to-Hand visual servo control, the research further refines the visual orientation of the sensor for optimal end effector and object identification. The incorporation of the Kalman Filter as a robust estimator for occluded objects underscores the predictive accuracy of the system. Results demonstrate the effectiveness of the methodology in trajectory generation and object tracking, with potential implications for improving robotic manipulators in dynamic environments. This comprehensive approach not only advances the fields of kinematic control and visual servoing but also opens new avenues for future research in complex spatial manipulations.

Structural design and control strategy of a cable-driven robot under high-altitude facade conditions with large span and multiple constraints

Purpose This paper explores the challenges of using cable-driven parallel robots on high-altitude, large-span facades, where redundancy in multicable systems and the elastic deformation of the cables are significant issues. This study aims to improve the accuracy and stability of the work platform through enhanced control strategies. These strategies address the redundancy in multicable systems and reduce the risks associated with cable deformation and mechanical failures during large-span movements. Design/methodology/approach The paper proposes a dynamic model for a four-rope parallel robot designed explicitly for large-span applications. The study introduces a position–force control strategy incorporating kinematic inverse solutions and a rope dynamics model to account for rope elasticity and its effects. This approach increases the number of system equations to match the unknowns, effectively solving the redundancy problem inherent in multicable systems. In addition, the tension changes of ropes and the stability of the working platform are examined under different motion distances (X = 50 m and X = 100 m) and varying Young’s modulus values (K = 5000 MPa and K = 8000 MPa). Findings This study’s large-span rope force–position control strategy successfully resolves the typical nonlinear characteristics and external disturbances in multicable parallel systems. By continuously monitoring and adjusting cable tension and end positions, this strategy ensures precise control over each cable’s tension, optimizes the distribution of cable tensions and maintains the system’s stability and response speed. The analysis in this paper indicates that this control strategy significantly improves the motion accuracy of robots operating on large-span high-altitude facades. Practical implications Industry adoption: The design and control strategies developed for the four-cable-driven parallel robot can be adopted by companies specializing in facade maintenance, construction or inspection. This could lead to safer, more efficient and cost-effective operations, especially in challenging environments like high-rise buildings. Innovation in robotic solutions: The research can inspire innovation within the field of robotics, particularly in developing robots for specific applications such as large surface maintenance. It showcases how adaptive control and stability can be achieved in complex operational scenarios. Safety improvements: By demonstrating a more stable and precise control mechanism for navigating large facades, the study could contribute to significant safety improvements, reducing the risk of accidents associated with manual facade maintenance and inspection tasks. Originality/value This paper combines the force/position hybrid control method with actual robotic applications, offering a novel solution to the complex issue of controlling cable-driven parallel robots in challenging environments. Thus, it contributes to the field. The proposed method significantly enhances the precision and stability of such systems and provides robust technical support for high-precision tasks in complex mechanical settings.

A 3D pickup estimation method for industrial parallel robots based on point cloud simplification and registration

A 3D pickup estimation method for industrial parallel robots based on point cloud simplification and registration

A nonlinear optimal control approach for 3-DOF four-cable driven parallel robots

In this article, a nonlinear optimal control approach is proposed for the dynamic model of 3-DOF four-cable driven parallel robots (CDPR). To solve the associated nonlinear optimal control problem, the dynamic model of the 3-DOF cable-driven parallel robot undergoes approximate linearization around a temporary operating point that is recomputed at each time-step of the control method. The linearization relies on Taylor series expansion and on the associated Jacobian matrices. For the linearized state-space model of the 3-DOF cable-driven parallel robot a stabilizing optimal (H-infinity) feedback controller is designed. To compute the controller’s feedback gains an algebraic Riccati equation is repetitively solved at each iteration of the control algorithm. The stability properties of the control method are proven through Lyapunov analysis. The proposed nonlinear optimal control approach achieves fast and accurate tracking of reference setpoints under moderate variations of the control inputs and a minimum dispersion of energy.

Inverse Kinematics Analysis of a 2-DOF Stabilized Platform using Simulink and Simscape

Abstract This paper presents a parallel manipulator with two universal-prismatic-universal (UPU)-type active limbs and one revolute-spherical (RS)-type passive limb which is used as a stabilizing platform based on the shipboard helicopter’s landing process and its kinematics are studied systematically. First, a 3D model of this stabilized platform is constructed, and its degrees of freedom are analyzed. Second, analytic formulas for solving the inverse kinematics and calculating the required lengths of each limb are derived and modeled using Simulink®. Third, a Simscape™ model is constructed for the proposed design, and finally, the comparison of the results between the two models is done.

Event-Triggered Finite-Time Variable Gain ADRC for Master–Slave Teleoperated Parallel Manipulators

Event-Triggered Finite-Time Variable Gain ADRC for Master–Slave Teleoperated Parallel Manipulators

High-Precision Adaptive Control of Cable-Driven Parallel Robots With Convergence Guarantee

High-Precision Adaptive Control of Cable-Driven Parallel Robots With Convergence Guarantee

Construction and kinematic performance analysis of a suspension support for wind tunnel tests of spinning projectiles based on wire-driven parallel robot with kinematic redundancy

This paper presents a novel suspension support tailored for wind tunnel tests of spinning projectiles based on Wire-Driven Parallel Robot (WDPR), uniquely characterized by an SPM (Spinning Projectile Model)-centered mobile platform. First, an SPM-centered mobile platform, featuring two redundant and another unconstrained Degree of Freedom (DOF), and its suspension support mechanism are designed together, collectively constructing a WDPR endowed with kinematic redundancy. Afterward, the kinematics of the mechanism, boundary equations for the redundant DOFs, and relevant kinematic performance indices are then proposed and formulated. The results from both prototype experiments and numerical assessments are presented. The capability of the support mechanism to replicate the complex coupled motions of the SPM is verified by the experimental results, while the proposed kinematics and boundary equations are also validated. Furthermore, it is revealed by numerical assessments that the redundant DOFs of the mobile platform exert a minimal impact on the kinematic performance of the suspension support. Finally, the optimal global attitude performance is obtained when these DOFs are set to zero if they are restricted to constants. However, local attitude performance can be further improved by the variable values.

Optimization Design Method for Vibration Reduction of Frame Structure of Cable-Driven Parallel Robot

This paper proposes a comprehensive optimization algorithm for the crossbeam cross-section size to solve the vibration problem of the flexible cable-driven parallel robot frame. The goal is to achieve an innovative design of the cross-sectional structure. By using a differential evolution algorithm, a comprehensive scale analysis of the cross-section size of the beam is carried out. This optimization method effectively improves the cross-section moment of inertia and the bending stiffness of the beam. Additionally, based on the variable density penalty method, the topological optimization design of the cross-section is carried out under the condition of minimum flexibility, the optimization objective function is established, and the objective function is solved by the moving asymptote method. The optimization results show that the beam stiffness is maximized while meeting the minimum flexibility required by the project. Through comparative analysis with various aluminum profile structures and their constructed frames, it is verified that the cross-sectional shape obtained through the optimized design method can significantly improve the anti-vibration stability of the frame.

On the design of a macro‐micro parallel manipulator for cochlear microrobot operations

AbstractBackgroundThe method of stem cell transfer to narrow cochlear canals in vivo to generate hair cells is still an unclear operation. Thus, the development of any possible method that will ensure the usage of medical microrobots in small cochlear workspaces is a challenging procedure.MethodsThe current study tries to introduce a macro‐micro manipulator system composed of a 6‐DoF industrial serial manipulator as a macro manipulator and a proposed 5‐DoF parallel manipulator with dual end effectors as a micro manipulator carrying permanent magnets for tetherless microrobot actuation inside the cochlea.ResultsThroughout the study, structural synthesis and kinematic analysis of the proposed micro manipulator were introduced. A prototype of the manipulator was manufactured and its hardware verification procedures were carried out using motion capture cameras and surgical navigation registration methodologies.ConclusionsFollowing motion training, the assembled macro‐micro manipulator was successfully utilised to actuate a microrobot placed inside a manufactured cochlea mockup model.

Precision Sensitivity Optimization for Parallel Robotic System Based on Multi-Source Preventive Maintenance

This paper presents a multi-source preventive maintenance (MPM) based precision sensitivity optimization method for parallel robotic systems. Taking a parallel mechanism as an example, the input error can be divided into finite mutually independent uncertain error sources, and the probabilistic error model is established by the Monte Carlo stochastic method. Considering that several times of maintenance can lead to an increase of the accuracy degradation factor, a generalized hierarchy maintenance yield model is established, where the cost of preventive maintenance and failure replacement maintenance are distinguished between the independent error source and the overall error source. The nonlinear relationship between the maintenance yield per unit cost and influencing factors, including the error threshold and the maintenance times is obtained, which allows to develop an optimal maintenance strategy. Preventive maintenance is introduced to avoid unintended failure of the mechanism while extending the lifetime. The high-precision parallel mechanism has demonstrated promising applications in medical, industrial and other fields, and its economic benefits can be effectively improved by incorporating the MPM method. The experiment of manufacturing human lung models using a parallel 3D printing device demonstrates that the MPM method can improve the long-term precision and reliability of the parallel device, and the optimized human lung contour tracking precision can be improved by up to 55.56%.

Three-Degree-of-Freedom Cable-Driven Parallel Manipulator with Self-Sensing Nitinol Actuators

Three-Degree-of-Freedom Cable-Driven Parallel Manipulator with Self-Sensing Nitinol Actuators

Design and Control of a Pneumatic Muscle Servo Drive Applied to a 6-DoF Parallel Manipulator

Design and Control of a Pneumatic Muscle Servo Drive Applied to a 6-DoF Parallel Manipulator