Dynamic Trajectory Planning Between Continuous Waypoints for the Redundant Cable-Driven Parallel Robot

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.

Cable-driven parallel robots are parallel robots where light-weight cables replace rigid bodies to move an end-effector. Their peculiar design allows obtaining large workspaces, high-dynamic handlings, ease of reconfigurability and, in general, low-cost architecture. Knowing the full state variables of a cable robot may be essential to implement advanced control and monitoring strategies and imposes the development of state observers. In this work a general approach to develop nonlinear state observers based on an extended Kalman filter (EKF) is proposed and validated both numerically and experimentally by referring to a cable-suspended parallel robot. The state observer is based on a system model obtained by converting a set of differential algebraic equations into ordinary differential equations through different formulations: the penalty formulation, the Udwadia–Kalaba formulation, and the Udwadia–Kalaba–Phohomsiri formulation, which have been chosen since they can handle the presence of redundant constraints as often happens in cable-driven parallel robots. In the numerical investigation, the EKF is validated simulating encoders heavily affected by quantization errors to demonstrate the filtering capabilities of EKF. In the experimental investigation, a very challenging validation is proposed: only two sensors measuring the rotations of two motors are used to estimate the actual position and velocity of the end-effector. This result cannot be achieved by sole forward kinematics and clearly proves the effectiveness of the proposed observer.

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.

The research explores the design and fabrication of a cable-driven parallel robot (CDPR) as an innovative and alternative method for in-situ robotic construction. CDPRs consist of a mobile platform attached to a fixed frame by several cables that are controlled through actuating winches. Their increased mobility reveals an immense potential for in-situ design-fabrication solutions emphasizing the importance of local materials and local economies. The paper presents a facet of this research focusing on the development of a novel design tool for the control and simulation of cable-suspended parallel robots in order to facilitate architectural design-fabrication explorations while addressing the complexities associated with parallel robots.

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 much attention due to a lot of advantages over conventional parallel robots. One of the main issues is the stability of the robot, which employs cables with strong flexibility and unidirectional restraint to operate the end-effector leads. As a result, this presented article aims to propose a systematic approach to the stability measures for the CDPRs by means of combining the cable tensions and poses of the end-effector. First, two position-influencing factors having important effects on the stability of the CDPRs are presented based on their kinematic model. Then, two cable tension-influencing factors also having essential effects on the stability of the robot are developed based on the determinations of cable tensions. Meanwhile, a function representing the effects of the end-effector's attitudes on the stability of the robots is constructed. Furthermore, the stability measures for the CDPRs are addressed, where a systematic stability measure approach is presented and three stability measure applications, average stability, minimum stability, and weighted average stability, are presented. Subsequently, a specified stability workspace is designed with the proposed force-pose stability measure approach. Finally, the approach to the force-pose stability measures and specified stability workspace generation algorithm are explained through simulation results of a spatial cable-driven parallel robot with 6-DOF with eight cables.

In this paper, the kinetostatic performance and collision-free workspace of a developed 3-DOF parallel robot is investigated. Kinetostatic indices that examine the performance of robot are essential in robot design and control. The popular indices, manipulability, dexterity and kinematic sensitivity are all investigated in order to evaluate the performance of the developed 3-DOF Delta parallel robot. In addition, as parallel robots generally have a limited workspace, obtaining the workspace by considering the mechanical interference is of paramount importance. The mechanical interference, including collision of links, collision of links with obstacles, collision of the end-effector with obstacles, are also examined by using a new geometrical approach. The proposed method is based on the segment-to-segment intersection test and can be expanded to a wide range of robotic mechanical systems, including, among others, cable-driven parallel robots. Moreover, in this paper, a new CFW index is defined which can be used to investigate the workspace with respect to mechanical interference. Furthermore, the aforesaid index provides some insight into obtaining a well-conditioned workspace.

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.

Cable-driven parallel robots (CDPRs) are a new type of parallel robots that use cables to control a mobile platform. They possess several advantages, including large workspace, low inertia, and high payload capacity. However, there are several problems in the high-precision trajectory tracking control of CDPRs. On the one hand, all the cables must remain in tension during the entire motion process. On the other hand, the controller design is subjected to model uncertainties and external disturbances. Accordingly, this article proposes a robust synchronization control (RSC) scheme in the cable length space to achieve high-precision trajectory tracking. The synchronization control ensures motion coordination among all the cables and prevents cable relaxation, whereas the robust control eliminates modeling errors and restrains external disturbances. The uniformly ultimate boundedness of the tracking and synchronization errors in the closed-loop system equation was proved using the Lyapunov theory. Simulations and experiments of the trajectory tracking control were both implemented on a three-degree-of-freedom CDPR. Compared with the adaptive robust control scheme and the augmented proportional derivative scheme on the premise of the approximate energy consumption, the proposed RSC scheme could reduce not only the tracking errors of the cables but also the synchronization errors between adjacent cables. Moreover, the RSC scheme could significantly improve the trajectory tracking accuracy of the mobile platform. The robustness of this scheme was verified using load experiments and torque-disturbance experiments.

Cable-Driven Parallel Robots (CDPRs) are a special kind of parallel manipulator that uses cables to control the position and orientation of the mobile platform or end effector. The use of cables instead of rigid links offers some advantages over their conventional rigid counterparts. As cables can only pull but not push, the number of cables (n) required to command the end-effector is always n+1. This configuration is known as fully-constrained, and it is the most extended configuration for CDPRs. Although CDPRs have many advantages, such as their ability to cover large working areas, one of their main problems is that their working area (workspace) is limited in comparison to its frame area (planar case) or frame volume (spatial case), due to the minimum and maximum allowed tensions. Depending on these tension values, the workspace can notoriously decrease. In order to tackle this problem, lots of works focus on solving kinematics or dynamics problems for cable sagging, i.e., they take into account sagging when modelling the robot kinematic and include these poses inside the usable robot workspace. Taking into account phenomena such as this increases the mathematical complexity of the problem, and much more complex techniques are required. On the other hand, the lack of workspace problem can be tackled by adding active or passive elements to the robot design. In this sense, this paper proposes two mechanical modifications: to add passive carriages to the robot frame and to use a single cable loop to command the end-effector position and orientation. This work presents the kinematic, static, and dynamic models of the novel design and shows the gain of workspace for a planar case while taking into account different parameters of the robot.

(also presented ar ICRA'19)

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.

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.