Cable-driven Parallel Mechanism Research Articles

A hybrid vibration suppression strategy for redundant cable-driven parallel mechanisms

Suppressing the vibration of cable-driven parallel mechanisms (CDPMs) is of great significance for improving their performance such as positioning accuracy. In this paper, a hybrid vibration suppression strategy based on stiffness enhancement and input shaping is proposed to reduce the vibration of a CDPM in the process of moving. Firstly, the stiffness model and vibration model of the CDPM are established. Then, based on the stiffness model and the vector set [Formula: see text] that meets the requirements of the cable tensions, a stiffness enhancement algorithm is proposed to improve the stiffness of the mechanism by adjusting cable tensions. In order to reduce the vibration of the mechanism to the maximum extent, a hybrid vibration suppression strategy is proposed by combining the stiffness enhancement algorithm with the multi-modal input shaping technique. Finally, the effect of stiffness enhancement algorithm and hybrid vibration suppression strategy on reducing mechanism vibration is verified by experiments. The hybrid vibration suppression strategy proposed in this paper does not require additional components and therefore does not increase the cost of vibration suppression, and it has good performance.

Data-Driven Kinematic Modeling and Control of a Cable-Driven Parallel Mechanism Allowing Cables to Wrap on Rigid Bodies

Data-Driven Kinematic Modeling and Control of a Cable-Driven Parallel Mechanism Allowing Cables to Wrap on Rigid Bodies

Variables increment configuration synthesis method for suspended cable-driven parallel mechanisms

Variables increment configuration synthesis method for suspended cable-driven parallel mechanisms

The CathCam: A Novel Angioscopic Solution for Endovascular Interventions.

Peripheral arterial diseases are commonly managed with endovascular procedures, which often face limitations in device control and visualization under X-ray fluoroscopy guidance. In response, we developed the CathCam, an angioscope integrated into an expandable cable-driven parallel mechanism to enhance real-time visualization, precise device positioning and catheter support for successful plaque crossing. The primary objective of this study was to assess and compare the performance of the novel CathCam with respect to conventional catheters and the CathPilot (i.e., CathCam without the angioscope), for applications in crossing chronic total occlusions (CTO). We first assessed the system in 3D-printed phantom models, followed by an ex vivo evaluation with CTO samples from a patient's superficial femoral artery. We measured and compared success rates, crossing times, and fluoroscopy times in both experiments. The CathCam demonstrated a 100% success rate in phantom experiments and a 75% success rate in ex vivo experiments with CTO samples, compared to conventional catheters, with 35% and 25% success rates, respectively. The average crossing times for the CathCam and the conventional catheter were 31s and 502s for the phantom experiments and 210s and 511s for the actual CTO lesions. The Cathcam also showed to be a reliable endovascular imaging approach in an in vivo experiment. Compared to conventional catheters, the CathCam significantly increased the success rate and reduced crossing and fluoroscopy times in both phantom and ex vivo setups. CathCam can potentially improve clinical outcomes for minimally invasive endovascular interventions by offering high-resolution real-time imaging alongside accurate device control.

Kinematic Analysis of a Spatial Cable-Driven Mechanism and Its Equivalent Hybrid Mechanism for Elliptical Trajectory

In this paper, a spatial cable-driven parallel mechanism in a V-shaped cable arrangement is proposed. It is further simplified as a planar hybrid cable-driven parallel mechanism to analyze its kinematics, which consists of two identical active cable chains and a passive cross-slide mechanism. In order to investigate the degrees of freedom (DoFs) of the hybrid mechanism using screw theory, cable chains are represented as rotational–prismatic–rotational (RPR) chains. The motion pairs of all the chains are denoted according to screw theory. Firstly, the number and the types of DoFs of each chain are determined. Then, the number and the types of DoFs for the hybrid mechanism are calculated. Furthermore, the theoretical result is verified using the modified Grübler–Kutzbach (G-K) formula. It shows that the unique DoF of the equivalent mechanism is a rotation with a continuously changing axis, which is consistent with the V-type cable-driven mechanism with elliptical trajectories. Finally, the kinematics analysis of the cross-slider mechanism driven by two cables is carried out. The length, velocity and acceleration of the cables are obtained from numerical calculation in MATLAB, and the results are demonstrated using ADAMS simulation.

Tension Characteristics of Cable-Driven System Based on ALE Formulation

This paper mainly studies the tension characteristics of cables in Cable-Driven Parallel Mechanisms (CDPMs). The exact catenary model and cable model based on the Arbitrary Lagrangian Eulerian description (ALE) are used. First, the ALE cable model and the exact catenary model are used to analyze and compare the tension at each point of a single cable, which proves the calculation accuracy of the ALE cable model. Then, the cable model described by ALE is used to model the Cable-Driven Parallel Mechanisms, the end effector is enabled to do a specific helical motion, the tension characteristics of the cable are extracted and analyzed, and the mesh independence of the ALE elements and calculation convergence are verified.

Robust Adaptive Backstepping Motion Control of Underwater Cable-Driven Parallel Mechanism Using Improved Linear Model Predictive Control

This paper proposes a novel motion-tracking control methodology for an underwater cable-driven parallel mechanism (CDPM) that achieves calculation of dynamic tension constraint values, tension planning, parameter linearization, and motion tracking. The control objective is divided into three sub-objectives: motion tracking, horizontal displacement suppression, and cable-tension restriction. A linear model predictive control (LMPC) method is designed to plan cable tensions for motion-tracking and displacement suppression. The robust adaptive backstepping controller converts cable tension into winch speed based on the joint-space method and command filtering. Moreover, the X−swapping method is used to linearize and identify the time−varying nonlinear parameters. An essential prerequisite for restricting cable tension is to obtain cable-tension constraint values. A novel dynamic minimum tension control (DMTC) method, based on the equivalent control concept, is proposed for this aim. The DMTC can adaptively obtain the lower cable-tension threshold through the platform posture and motion status, anchor distribution position, and cable integrity status. Compared to traditional fixed tension constraint values, DMTC can more effectively cope with sudden changes in cable tension than fixed tension constraints. Finally, several simulations are carried out to verify the effectiveness and robustness of the proposed approach.

Comprehensive Compensation Method for Motion Trajectory Error of End-Effector of Cable-Driven Parallel Mechanism

The accuracy of the end-effector motion trajectory is a critical performance indicator for cable-driven parallel mechanisms. This study aims to address the problem of trajectory error during the end-effector motion in a cable-driven parallel mechanism. It proposes a comprehensive compensation method based on the simultaneous application of the improved sparrow search algorithm and the cable length space error compensation algorithm, leveraging kinematic analysis. To compensate for the motion trajectory error of the end-effector caused by the geometric parameter error, the study establishes the kinematic model of the cable-driven parallel mechanism using the vector method. It creates the end-effector position error model and motion trajectory error model using the differential kinematic theory, analyzes the impact of the geometric parameter error on the motion trajectory error, constructs the kinematic parameter identification matrix, and uses an improved sparrow search algorithm to compensate for the position error of the motion trajectory interpolation point. For the motion trajectory error of the end-effector caused by non-geometric parameter error, the study analyzes the intrinsic correlation between the adjacent position error of the end-effector and the variation of the cable length using the error similarity theory. It then compensates for the position error of the interpolation point of the trajectory using a cable length space interpolation compensation method to enhance the motion trajectory accuracy of the end-effector. The study experimentally verifies the proposed comprehensive compensation method for end-effector motion trajectory error on a 4-cable-driven 2-DOF parallel mechanism, which reduces the motion trajectory error of the end-effector by 75%.

Modeling and control strategy of a haptic interactive robot based on a cable-driven parallel mechanism

Abstract. This study proposes a haptic interactive robot (HIR) configuration and a control strategy based on a cable-driven parallel mechanism. The ball screw drives the cable to improve the motion control accuracy. The robot system control strategy improves the accuracy and stability of haptic interaction. Through configuration optimization design and analysis, eight cables are used to ensure that the robot end effector exerts force and enables motion. Moreover, a forward and inverse kinematics model of the robot is developed. According to the configuration of the HIR, an improved cable tension distribution algorithm can facilely determine the cable tension. Hence, each cable is consistently in a tight state, and the change in tension is not sudden. Drive unit and robot system control strategies are proposed to render the haptic interaction accurate and stable. A simulation experiment of a complex space motion track is implemented through the robot end effector, thus verifying the accuracy of the established forward and inverse kinematics model. The accuracy of the tension distribution algorithm, control strategy, and robot stability are verified through simulation experiments, considering different forces and motion tracks of robot end effectors.

Dual-space configuration synthesis method for rigid-flexible coupled cable-driven parallel mechanisms

As wave motion compensation devices, rigid-flexible coupled cable-driven parallel mechanisms composed of cables and rigid rods can ensure the safety of cargo transportation. Therefore, a dual-space configuration synthesis method for rigid-flexible coupled cable-driven parallel mechanisms is proposed to synthesise configurations with high load-carrying and anti-sway functions. Anti-sway substructures are proposed to reveal the essence of rigid-flexible coupled structures with anti-sway functions. An equivalent rigid-body method and branch distribution constraints are presented to construct the anti-sway substructures and offer iterative conditions for the dual-space configuration synthesis method. Then, thirty-two types of configurations for rigid-flexible coupled cable-driven parallel mechanisms are synthesised through the dual-space configuration synthesis method. Finally, compensation performance evaluation and experimental results for wave motion compensation devices verify the feasibility of the dual-space configuration synthesis method.

Research on stiffness control of a redundant cable-driven parallel mechanism

Research on stiffness control of a redundant cable-driven parallel mechanism

Reconfigurable fully constrained cable-driven parallel mechanism for avoiding collision between cables with human

AbstractProductivity can be increased by manipulators tracking the desired trajectory with some constraints. Humans as moving obstacles in a shared workspace are one of the most challenging problems for cable-driven parallel mechanisms (CDPMs) that are considered in this research. One of the essential primary issues in CDPM is collision avoidance among cables and humans in the shared workspace. This paper presents a model and simulation of a reconfigurable, fully constrained CDPM enabling detection and avoidance of cable–human collision. In this method, unlike conventional CDPMs where the attachment points are fixed, the attachment points on the rails can be moved (up and down on their rails), and then the geometric configuration is adapted. Karush–Kuhn–Tucker method is proposed, which focuses on estimating the shortest distance among moving obstacles (human limbs) and all cables. When cable and limbs are close to colliding, the new idea of reconfiguration is presented by moving the cable’s attachment point on the rail to increase the distance between the cables and human limbs while they are both moving. Also, the trajectory of the end effector remains unchanged. Some simulation results of reconfiguration theory as a new approach are shown for the eight-cable-driven parallel manipulator, including the workspace boundary variation. The proposed method could find a collision-free predefined path, according to the simulation results.

Trajectory Planning of the Exit Point for a Cable-Driven Parallel Mechanism by Considering the Homogeneity of Tension Variation

Considering the uniformity of cable tension variation, in this paper, the trajectory planning problem of the exit point for a continuously reconfigurable four-cable-driven two-degrees-of-freedom (DOF) parallel mechanism was studied. Furthermore, an improved quadratic programming model-based trajectory planning method is proposed, which greatly reduces the change in cable tension and can be used to solve the problem of excessive cable tension change when the existing mechanism moves on the moving platform. First, the structural characteristics of the parallel mechanism with a fixed exit point were analyzed, and the static model was established. Considering the cable length and tension constraints, the feasible workspace of the mechanism force was solved. Then, based on the dynamic modeling, an improved quadratic programming model was used to solve the cable tension values under the typical trajectory in the force-feasible workspace. Finally, considering the influence of structural parameters on the change in cable tension, the improved quadratic programming model was transformed, and an exit point trajectory planning model was proposed. The uniform change in cable tension was realized by continuously changing the exit point position. The results show that the cable tension can change uniformly in a very small range by planning the trajectory of the exit point, and the stability of the moving platform movement is guaranteed to the greatest extent.

Robust Adaptive Control Based on Variable Boundary for a Twin-Motor Cable-Driven System

Cable-driven parallel mechanism has been widely studied due to its advantages of fast response and large workspace. The structural uncertainties in the system often introduce internal disturbance and unavoidably influence its motion precision. Generally, to reduce the influence, robust control is adopted and the boundary of the disturbance is regarded as a fixed value given by rough estimation. This method often causes large vibration of the motion component, which certainly compromises the dynamic performance of the system. Therefore, to solve this problem, a variable boundary analytical scheme based on the decoupling of control law and internal disturbance is proposed in this article. Specifically, sufficient condition for the solvability of disturbance boundary is proved by the boundedness of the structural matrix error. Then, the disturbance boundary is modeled analytically, so that its particular value can be determined with respect to the system status. Following that, a robust adaptive control algorithm based on the variable boundary of disturbance is developed. It is verified that the tracking error is globally uniformly bounded. The experimental results show that the proposed control method can effectively reduce the tracking errors and attenuate the tension chattering compared with the conventional robust adaptive control scheme with a roughly estimated boundary.

Parameter Estimation and Tracking of an Expandable Cable-Driven Parallel Mechanism for Minimally Invasive Interventions

Conventional catheter-based procedures suffer from inaccurate device steering, and navigation limitations as the long and flexible devices are manipulated remotely from outside the patient body. A recently developed approach aims to overcome these limitations by using an expandable cable-driven parallel mechanism for local device manipulation and tracking relative to the anatomy. However, as the frame of this system is flexible and may be constrained by unknown anatomical constraints inside the patient body, accurate system identification is a key and critical step which would ultimately determine the accuracy in device steering and tracking. In this paper, we present an optimization approach to identify the parameters of an expandable cable-driven parallel mechanism deployed in an unknown environment, merely based on measurements of the cable length variations that would be available outside the patient body. We have verified and validated the proposed approach in terms of accuracy in the prediction of the frame shape and cable anchor locations, as well as its tracking accuracy. Both simulations and experimental studies have been performed, and we have demonstrated that the proposed method allows for rapid frame shape and anchor position estimation with unknown anatomical constraints and permits localized device tracking and steering with submillimeter accuracy.

Offline Reference Trajectory Shaping for a Cable-Driven Earthquake Simulator Based on a Viscoelastic Cable Model

In an earthquake simulator, which is a device for reproducing seismic waves, it is necessary to accurately reproduce the acceleration. In this letter, the authors propose an offline reference trajectory shaping method for precise acceleration control based on the dynamic model of an earthquake simulator, composed of a planar three-degrees-of-freedom cable-driven parallel mechanism, considering the effect of the viscoelasticity of a synthetic fiber cable. First, Flory’s model representing cable viscoelasticity was introduced into the dynamic model of the system constructed in the authors’ previous study, and a precise dynamic system model including the cable was derived. Next, the viscoelastic behavior of the cable including instantaneous elasticity and tension relaxation was measured experimentally, and the cable model parameters were identified. Based on these, a control method to accurately generate the desired platform acceleration by offline reference trajectory shaping was developed. The effectiveness of the method was confirmed through simulations and experiments.

Workspace analysis and optimal design of dual cable-suspended robots for construction

Given their advantages of large workspaces and high payload-to-weight ratios, cable-driven parallel mechanisms have great potential for use in on-site autonomous construction. This paper proposes a configuration containing two cable-suspended robots driven by eight cable pairs (four cable pairs each), which form parallelograms, to perform construction efficiently in terms of time and space. A core issue of this system is the collision problems that occur in dynamic construction processes. The use of the distance between two spatial line segments is proposed to calculate collision detection, and the wrench-feasible workspace is examined to analyze the collision-free buildable workplace. The operation mode of dual cable-suspended robots for construction is discussed herein. Further, the design variables of the dual cable-suspended robot are optimized using multi-objective particle swarm algorithm to ensure a sufficiently large collision-free buildable workspace with suitable scale and payload of the frame of the cable robots for construction.

Analysis of Cable-Force Transmission Characteristics and Disturbing Force/Moment of High-Acceleration Cable-Driven Parallel Mechanism

During the landing process of a probe, the backshell separation stage is full of uncertainty and risk. To mitigate this, it is necessary to simulate spacecraft separation prior to launch to verify safety and performance. A high-acceleration cable-driven parallel mechanism is normally used to simulate the force state required for the backshell to separate. Unfortunately, little attention has been paid to research the cable force on the end-effector, especially under high acceleration. In this article, a dynamic model of the cable-force transmission is proposed. The influences of disturbing force/moment on the position and orientation of the end-effector and axial force are analyzed. Indices for evaluating the performance of the cable-force transmissions are proposed. The factors affecting the performance are also explored. Finally, the experimental results are used to verify the correctness of the proposed dynamic model. The deviation caused by the disturbing force/moment is basically consistent with the desired deviation. The increase in the disturbing force/moment correspondingly reduces the resultant force of the end-effector. A series of experiments provide guidance and a theoretical basis for a ground simulation experiment of spacecraft separation.

Haptic User Interface of a Cable-Driven Input Device to Control the End Effector of a Surgical Telemanipulation System

Abstract In robotic telemanipulation for minimally-invasive surgery, lack of haptic sensation and non-congruent movement of input device and manipulator are major drawbacks. Input devices based on cable-driven parallel mechanisms have the potential to be a stiff alternative to input devices based on rigid parallel or serial kinematics by offering low inertia and a scalable workspace. In this paper, the haptic user interface of a cable-driven input device and its technical specifications are presented and assessed. The haptic user interface allows to intuitively control the gripping movement of the manipulator’s end effector by providing a two-finger precision grasp. By design, the interface allows to command input angles between 0° and 45°. Furthermore, interaction forces from the manipulator’s end effector can be displayed to the user’s twofinger grasp in a range from 0 N to 6 N with a frequency bandwidth of 17 Hz.

A New Approach of Soft Joint Based on a Cable-Driven Parallel Mechanism for Robotic Applications

A soft joint has been designed and modeled to perform as a robotic joint with 2 Degrees of Freedom (DOF) (inclination and orientation). The joint actuation is based on a Cable-Driven Parallel Mechanism (CDPM). To study its performance in more detail, a test platform has been developed using components that can be manufactured in a 3D printer using a flexible polymer. The mathematical model of the kinematics of the soft joint is developed, which includes a blocking mechanism and the morphology workspace. The model is validated using Finite Element Analysis (FEA) (CAD software). Experimental tests are performed to validate the inverse kinematic model and to show the potential use of the prototype in robotic platforms such as manipulators and humanoid robots.