Data-Driven Kinematic Control Scheme for Cable-Driven Parallel Robots Allowing Collisions

In order to improve the performance of cable-driven parallel robots (CDPRs), the configuration of the redundantly actuated CDPRs is optimized, and a feasible continuous tension distribution method for tracking the trajectory of the robot is proposed. A convex analysis method is used to determine the wrench-feasible workspace of CDPRs and the grouped coordinate descent method is used to determine the size of the redundantly actuated six-degree-of-freedom CDPRs. By changing the cable layout and using the geometric analysis method for the redundantly actuated CDPRs, the maximum rotation angle of the mobile platform in 3-D space is determined. The optimal size and layout of the CDPR are determined by comparison and analysis. The high dynamic CDPRs require real-time control to adjust the cable tension. In order to solve this issue, a real-time cable tension distribution algorithm for a non-iteration two-degree-of-freedom actuation redundancy CDPR is proposed. The proposed tension distribution algorithm is applied to the optimized six-degree-of-freedom eight-cable CDPR, and compared with other existing cable tension distribution algorithms. The simulation results demonstrated that the feasibility and the advantages of the proposed cable tension distribution algorithm.

This paper presents a novel cable-driven parallel robot with the aim of rehabilitating/exercising young and disabled children in drawing and writing tasks. The pyramidal topology was identified as providing the required three active translational Degrees of Freedom with a redundant set of five cables in a compact portable shape. In addition, this robot was designed with new features, as it is inexpensive, easy to control, easy to move to any place at home or school as it is fitting a home desk or classroom table. In this paper, we present the main steps for designing the proposed cable-driven pyramidal parallel robot. Specific attention is addressed to the design of the structure and the end effector as well as to establishing proper simulation models. Several simulations are proposed by implementing both kinematic and dynamic models to demonstrate the feasibility of multiple writing/drawing tasks. A specific user interface is proposed allowing both continuous and intermittent trajectories. A sliding mode control is implemented to achieve suitable tracking accuracy on a desired path. Finally, an experimental validation is successfully carried out by considering multiple trajectories for demonstrating the engineering feasibility and effectiveness of the proposed design and simulation models.

Cable-driven parallel robots (CDPR) with spatial configuration are widely used while ones with plannar configuration are rarely applied. Therefore, this paper studies the modeling and control characteristics of a three degree-of-freedom cable-driven planar parallel robot with great application prospects. Aiming at the shortcomings of the existing control methods towards CDPR, a new method based on fuzzy adaptive PD computing torque control is proposed which contains a reasonable optimal distribution of cable forces. To validate the method, the tracking control simulation research and analysis are carried out for the trajectory of high-order interpolation planning, the results of which show that the control method has favorable dynamic tracking accuracy and mechanical properties. Moreover, compared with the fixed-gain computed torque control, the proposed control method can overcome the influence of model inaccuracy more effectively.

This paper presents a compact-sized haptic device based on a cable-driven parallel robot (CDPR) mechanism for teleoperation. CDPRs characteristically have large workspaces and lightweight actuators. An intuitive and user-friendly remote control has not yet been achieved, owing to the unfamiliar multiple-cable configuration of CDPRs. To address this, we constructed a portable compact-sized CDPR with the same configuration as that of a larger fully constrained slave CDPR. The haptic device is controlled by an admittance control for stiffness adjustment and implemented in an embedded microprocessor-based controller for easy installation on an operator’s desk. To validate the performance of the device, we constructed an experimental teleoperation setup by using the prototyped portable CDPR as a master and larger-size CDPR as a slave robot. Experimental results showed that a human operator can successfully control the master device from a remote site and synchronized motion between the master and slave device was performed. Moreover, the user-friendly teleoperation could intuitively address situations at a remote site and provide an operator with realistic force during the motion of the slave CDPR.

Cable-driven parallel robots (CDPRs) have attracted extensive attentions in the past few years due to their advantages in both the large workspace and the large payload capacity. Furthermore, CDPRs have potential in reconfiguration. In this research, a re-configurable CDPR is presented, and its modular design is detailed. Then, kinematics of the proposed CDPR is analyzed including the inverse and direct kinematics. Based on the kinematic model, simulation validations are made by using two kinds of trajectories, i.e. a line and a circle. Finally, prototypes are built and preliminary experiments are made, including the alphabetic writing and the Chinese character writing tests. Results show that the performance of the robot is good, which further validates the kinematic modeling and modular design of the proposed reconfigurable CDPR.

In the past decades, cable-driven parallel robots (CDPRs) have been proven the extraordinary performance for various applications. However, the multiple cables lead the robot easy to interfere with environments. Especially the large workspace of CDPR may introduce unknown moving obstacles. In this study, a sampling-based path planning method is presented for a CDPR to find the collision-free path in the presence of the moving obstacle. The suggested method is based on rapidly exploring random tree (RRT) algorithm which gives CDPRs advantages to handle complex constraints such as cable collision and dynamic feasible workspace (DFW). Moreover, we conduct the forward simulation to check the feasibility in a closed-loop system. The moving parts of both CDPRs and the moving obstacle are assumed as convex bodies, so that Gilbert-Johnson-Keerthi (GJK) algorithm is adopted to detect collision in real-time. Finally, the related simulation is carried out to illustrate the algorithm. The experiment is also presented using the drone as a moving obstacle and YOLO vision algorithm to detect the drone. The experiment results demonstrate the reliability of the suggested method.

Considering a simplified model of cables is an essential assumption in the design of state-estimator and vibration control of cable-driven parallel robots (CDPRs). Such an assumption however, impacts the effectiveness of controllers and state-estimators in such systems. This article presents a reaction-based stabilizer for nonmodel-based vibration control of CDPRs to address such model dependence. It is proved analytically that by using only three actuators and not involving the cable-connected winches, the proposed stabilizer regulates all undesired vibrations of the platform. It is also shown that the proposed stabilizer needs only the directly measurable position and velocity of its actuators to form its closed-loop control feedback signals. Effectiveness of the proposed system is more significant in CDPRs with considerable nonlinear effects of cables, where such effects are computationally costly to model, such that the performance of real-time controllers and state-estimators are spoiled. To provide a case study, a multibody nonlinear dynamic model of a suspended CDPR equipped-with the proposed stabilizer with zero cable damping effects is developed in SimMechanics/MATLAB, where a fine-tuned proportional-derivative controller is applied on each actuator to suppress all vibrations of the system. In addition, a suspended CDPR with extremely stretchable nonlinear-stiffness elastomer cables is fabricated and tested, where performance of the proposed stabilizer to suppress the high-amplitude nonlinear oscillations of the whole system is demonstrated.

Cable-driven parallel robot is a special kind of robot, which is actuated by cables. It is already applied in the low speed wind tunnel to get aerodynamic measurement of aircraft model, and the aircraft pose could be adjusted by changing the cable length. Whether it can be used in hypersonic wind tunnel still needs further discussion. This paper presents the dynamics and aerodynamics analysis of a large-scale model supported by 6-DOF cable-driven parallel robot to investigate the feasibility of this special kind of suspension system in hypersonic wind tunnel. The description of this setup with a X-51A-like model is given, and then based on the system dynamic equations, aerodynamic force and stiffness matrix are derived. In the simulation, properties of dynamics and aerodynamics are mainly concerned. A typical shock tunnel with flow duration of about 100 milliseconds is taken as an example, and results show that the system is stable enough to meet the fundamental static wind tunnel test. From the cable tension variation under impact load and the sensitivity analysis, it is likely accessible to derive the aerodynamic forces. Compared with the sting suspension method, cable-driven parallel robot has the priority of higher inherent frequency and more flexible degrees. The interference to the flow field induced by cables is also preliminarily proved to be small by the CFD simulation, which can be acceptable and corrected. Researches conducted show the feasibility of cable-driven parallel robot’s application in hypersonic wind tunnel.

This paper describes a mobile cable driven parallel robot that can be temporarily mounted on existing structures like lamp posts or trees. Existing works have introduced various concepts for mobile cable driven parallel robots and analyzed some of their characteristics like workspace. The proposed robots require either heavy equipment like truck-mounted telescoping poles, or deformative installation techniques like using concrete anchors in existing structures. Those works ignored the design of the hardware to which the winches would be attached. The present article is the first describing the design of a winch system and its attachment method for an ultra-portable cable driven parallel robot, one that can be quickly mounted and unmounted from existing structures. A novel application for robotics is selected as a case study and relevant performance goals drive the design of a mountable cable driven parallel robot winch. The design is fabricated and shown in the field. The prototype mounts to trees in such a way that the growth of the tree is not inhibited. This is achieved by using nylon ratchet straps to affix the robot winches. This design represents an extremely low-cost and portable approach to cable driven parallel robots because no structure needs to be constructed.

Cable-driven parallel robots (CDPR) represent an emerging field of research that has vast applications across different fields of science and engineering, such as medical, aerospace, construction, etc. Dynamic modeling plays an important role in understanding the behavior of these complex systems as well as in enhancing their performances. The state of the art in cable-driven parallel robots (CDPRs) is thoroughly summarized in this review, which covers both basic ideas and cutting-edge advancements in a variety of design modeling control and application domains. The study starts with a thorough examination of the geometric layout and essential elements of CDPR systems describing how the special arrangement of flexible cables allows for better workspace scalability and dynamic performance. It also looks at the complex kinematic and dynamic models that portray the nonlinear behaviors that are essential for attaining accurate motion control like cable sagging elasticity and friction. The optimization of workspace and tension distribution is prioritized in order to preserve system stability and energy efficiency. Furthermore, the review looks at a number of control and planning strategies such as motion planning methods and advanced algorithms like reinforcement learning which guarantee reliable trajectory tracking and operational safety. The wide-ranging effects of CDPR technology are demonstrated through a variety of case studies in the fields of construction entertainment, medical care, agriculture, disaster response, material handling, and space research. Lastly, new developments that promise to improve the capabilities and uptake of CDPRs in next-generation robotic systems are explored, including the incorporation of artificial intelligence machine learning and innovative materials.

The article presents a cable-driven parallel robot for the in situ construction with designed granular materials at full architectural scale. Granular materials are defined as high numbers of particles larger than a micrometer, between which only short-range repulsive forces are acting. Therefore, they can have the properties of both a solid and a liquid. These materials are, thus, highly pertinent as construction materials, since they are fully recyclable and reconfigurable. Going even beyond these basic properties, a designed granular material allows to tune its overall characteristics through the design of the individual particle. Granular materials can only be deployed in situ and at full scale. Suitable robotic construction systems need to be developed. Cable-driven parallel robots are defined as robotic systems, in which an “end effector” is operated by a set of cables, which are driven by computer numerically controlled motors. The cables are running through elevated pulleys. A cable-driven parallel robot, thus, allows for a “working space”, which covers an entire building site. It is comparatively lightweight and, thus, transportable between different construction sites, it is rapidly deployable, since the entire set-up takes one day only, and it is adaptable, since the pulleys can be installed in various geometric configurations. The results of this investigation show that cable-driven parallel robots are suitable as construction systems for the full-scale in situ construction of spatial enclosures with designed granular materials. This opens up a new field of research into the potentials of these full-scale, lightweight, rapidly deployable and adaptable robotic construction systems.

Cable-driven parallel robots are a special type of robot in which an end-effector is attached to a fixed frame by means of several cables. The position and orientation of the end-effector can be controlled by controlling the length of the cables. These robots present a wide range of advantages, and the control algorithms required have greater complexity than those in traditional serial robots. Measuring the cable tension is an important task in this type of robot as many control algorithms rely on this information. There are several well-known approaches to measure cable tension in cable robots, where a trade-off between complexity and accuracy is observed. This work presents a new device based on strain gauges to measure cable tension specially designed to be applied in cable-driven parallel robots. This device can be easily mounted on the cable near the fixed frame, allowing the cable length and orientation to change freely, while the measure is taken before the cable passes through the guiding pulleys for improved accuracy. The results obtained from the device show a strong repeatability and linearity of the measures

The cable sagging problem of cable-driven parallel robots (CDPRs) is very complicated, because several models for calculating cable sag based on the well-known catenary equation have been studied, but time and computational efficiency are a problem to be solved. There is still no simple mathematical model to calculate cable sag by considering all relevant conditions due to the complexity and nonlinearity of the cable sagging model, which involves many dominant variables and their influence on the position accuracy of CDPRs. In this study, we proposed an ANFIS (adaptive neuro-fuzzy inference system) architecture to estimate cable sag for large-sized CDPRs. The ANFIS model can be used to solve nonlinear functions and detect nonlinear factors online in the control system; this characteristic is consistent with the nonlinear model of cable sag. The trained data for ANFIS models were taken from calculation results by Trust-Region-Dogleg algorithm based on two cable tension calculation algorithms as Dual Simplex Algorithm and Force Distribution in Closed Form. Cable sagging data obtained from ANFIS and Trust-Region-Dogleg algorithm are compared and evaluated by statistical factors of evaluations consisting of root-mean-square error, correlation coefficients, and scatter index. The analytical results show that the ANFIS gave computed results with small errors and can be applied to predict cable sagging for any CDPR configuration, with the advantage of fast calculation time and high precision. The results of these models are also applied on a CDPR that contains two redundant actuators.

Utilizing the encoders mounted on redundant actuators, the auto-calibration method of the kinematic uncertainties of cable-driven parallel robots (CDPRs) with redundant actuation is firstly discussed in this paper. According to the kinematic model, the relation between the structural parameters and the measurement errors is analyzed and the auto-calibration workflow is designed. In addition, due to the mechanical design of CDPRs and the characteristics of cables, the transmission ratio between the cable length and the actuator angle may change during the motion process and cannot be calibrated offline. To obtain the actual value of the ratio, the online-adjustment scheme using an extra camera is then presented. To validate the proposed auto-calibration method and online-adjustment scheme, the corresponding experiments are carried out on our 8-6 (6 DOFs with 8 cables) CDPR. The results of the experiments indicate that the auto-calibration method is very useful to enhance the structural accuracy. Meanwhile, the mechanical structure of our self-built CDPR is also reliable. Moreover, the online-adjustment scheme is also effective to improve the motion accuracy indirectly.

A cable-driven parallel robot (CDPR) consists of elastic cables instead of rigid links. The lightweight of cables enables the CDPR applications for high payload, high speed and large workspace. However, the elongation of polymer cables can cause positioning error of the end-effector (EE) especially for heavy material handling application. In this paper, we propose an open loop load compensation algorithm to increase the relative accuracy of a CDPR. Since the force distribution of cables and cable lengths are different in different EE position, the elongation of cables will be different. Therefore, the algorithm are implemented with three different height (600, 800 and 1000mm) in straight line path. The payload of the robot system is 190kg. The experiment result shows that the root mean square error (RMSE) of EE position are 30.02mm for without load compensation and 0.65mm for with load compensation.