Type Of Parallel Robot Research Articles

Error analysis of a coaxis five-bar parallel mechanism

Abstract With societal advancement, robots are increasingly being deployed in production processes. Currently, high-precision robots predominantly found in the market are delta parallel robots. Common parallel robots, including delta robots, generally suffer from the drawback of having a smaller workspace compared to serial robots. Contrasted with other types of parallel robots, coaxis parallel robots feature a larger workspace, thereby offering greater potential for application. This paper focuses on a coaxis five-bar parallel mechanism as the subject of investigation. Firstly, by employing the perturbation method to model the errors in the parallel mechanism, a mapping relationship between error sources and the errors of the mechanism’s end-effector was derived. Then a sensitivity analysis of each error source was performed statistically, yielding sensitivity metrics. Last, under conditions where the magnitudes of errors are identical, the end-effector error of a coaxis parallel mechanism is notably larger compared to that of a common parallel mechanism. This makes it more essential to conduct precision design on coaxis parallel robots in the future study.

Simulation of suspended cable-driven parallel robot on SimulationX

Currently, research is being carried out on a new type of parallel robots, such as cable-driven parallel robot. The cable-driven parallel robot are parallel robots with flexible (cables), with a large workspace, with high speeds and accelerations of the end effector. In the cable-driven parallel robot, cables can only work in tension, and cable-driven parallel robot lose their performance when they are compressed. This feature severely limits the development and application of cable-driven parallel robots and requires further development of cable-driven parallel robot modeling on various software systems. Currently, Adams multibody dynamics software is widely used to create and test virtual prototypes of mechanical systems. But for cable-driven parallel robot modeling, the Adams program is quite complex and expensive to use. In this article, the simulation of the cable-driven parallel robot is carried out on the SimulationX software. Unlike other software packages, SimulationX is more accessible and cheaper and is well suited for cable-driven parallel robot simulation. Cable-driven parallel robot modeling on SimulationX allows you to identify the main design flaws even before its prototype is made. A model on the SimulationX software of a suspended cable-driven parallel robot with a point mass end effector, taking into account the elastic-dissipative properties of cables, was developed. The prototype of suspended cable-driven parallel robot with a point mass end effector was manufactured. Experimental researches of the prototype of the suspended cable-driven parallel robot with a point mass end effector confirmed the correctness of the application of the model on SimulationX for practical calculations.

Planar Cable-Driven Manipulators for Inspection of Large Surfaces

Cable-Driven Parallel Manipulators (CDPM) are a type of parallel robots in which the rigid links connecting the base with the terminal link, also called end-effector, are replaced by cables. This kind of system has been introduced during the last two decades, since then many issues have been addressed, but there are still open problems. Thanks to the nature of the cables, lightweight if compared to the overall structure, and the very large workplace, their possible applications are increasing. Recently, Robotics and Automation have been applied to the inspection of structures and infrastructure; therefore, they are starting to be used to substitute personnel in dangerous or unsafe operations. Related to the inspection, autonomous or tele-operated systems can be used for securing the access to the buildings or infrastructure. In this paper, we propose the application of CDPMs for the inspection of large surfaces, constituted by buildings facades, top roofs, and parts of infrastructures. The development of suitable model of the system, also called Digital Twin, allows the managing of the operation in safe conditions. As new application, we propose the use of a planar CDPM for being applied to the inspection and monitoring. The 3D model acts as a Digital Twin of the real prototype that has been developed and used for experimental testing. Since the purpose is to drive the end-effector to point of interest carrying suitable sensors, tests for trajectory planning and experimental tests are proposed. The inspection of structures and infrastructures has become a very important issue for the security of critical infrastructures, not only at European level but worldwide.

Adaptive Fuzzy Control of a Cable-Driven Parallel Robot

Cable robots are a type of parallel robot in which cables have replaced the usual rigid arms. In cable robots, due to the tensile strength of the cable, the workspace analysis is much more complex than in conventional robots. In this paper, we design an adaptive fuzzy controller for a cable-driven parallel robot (CDPR). In the proposed controller, the results show that the accuracy of the system performance in tracking the reference value as well as the controller performance speed is better than that of the robust method. In one of the simulation modes, the performance speed of the control system for convergence is reduced and its error is very small, which indicates the proper performance of the proposed adaptive fuzzy method. It should be noted that all simulations are performed in a MATLAB software environment.

Automation and performance analysis of tea filter bags packing process using delta configured robot

A delta robot is a type of parallel robot that consists of three arms connected to universal joints at the base. Industries take advantage of these robots in packaging and pick and place operations due to its high accuracy and fastness. This three degrees of freedom robot is used in the process that automates the tea filter bags packing process through pick and place operation. Electrostatic gripper has been used as the end effectors. The tea filter bags are allowed to go through the conveyor and this delta configured robot is used for pick and place operation. This robot reduces the time complexity of the laborers and it also helps in increasing productivity by reducing the cost. Thus the tedious process becomes simpler through the delta configuration. Comparative analysis of the performance of robot with manual process is also shown in the results.

Adaptive Synchronization Control of Cable-Driven Parallel Robots With Uncertain Kinematics and Dynamics

Cable-driven parallel robots (CDPRs) are a new type of parallel robots with a mobile platform driven by several cables. The flexibility of the structure not only helps them perform better than traditional parallel robots, but also brings about the issues of model uncertainty and multicable coordination. To handle these problems, a novel adaptive synchronization control (ASC) scheme is proposed to suppress the uncertainties of kinematics and dynamics simultaneously, regulate the coordination motion of multiple cables, and finish high-precision tracking tasks. In the proposed scheme, apart from tracking error, a new synchronization error is introduced to describe the coordination motion relationship between adjacent cables. According to these defined errors, the kinematic and dynamic adaptation laws are designed through the linear expressions of kinematic and dynamic models, respectively. Finally, the ASC scheme is presented as well as a tension distribution algorithm. The tracking experiments are implemented on a redundantly actuated 3-degree-of-freedom CDPR with four cables. The proposed ASC scheme can effectively complete the correction of the model parameters by using the feedback of errors and enhance the tracking accuracy of each cable and the synchronization accuracy between all the cables significantly, thereby ultimately improving the control performance of the mobile platform.

A brief overview of parallel robots and parallel kinematic machines

In this paper, a brief overview is presented, resulting from a recent literature review of some representative books or papers regarding various research on different types of parallel robots, parallel kinematic machines, or hybrid parallel mechanisms. Starting from a short introduction regarding the motivation and necessity of the emergence of such parallel mechanisms, some basic terms are presented, in the context of founding the existence of several terminologies for certain specific expressions of this subject, as well as different definitions for them. Then, after a short presentation of the advantages and disadvantages of the parallel robots, compared to serial ones, and of the parallel kinematic mechanisms compared to the conventional machine tools, some publications related to kinematics, dynamics, modeling and simulation of these types of mechanisms are highlighted. This research is realized in order to identify a solution that will be the basis for the development of a prototype, both virtual and experimental, for such mechatronic system.

High-Precision Trajectory Tracking Control of Cable-Driven Parallel Robots Using Robust Synchronization

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.

LW-RCP와 Odroid 기반의 Machine Vision을 이용한 Ball and Plate 시스템 구현에 관한 연구

In this paper, we propose the architecture of a ball-and-plate system as an educational platform that can help students comprehensively study control engineering, robotics, machine vision, and embedded systems. In addition, we describe how to implement the sub-systems and present an example of an education plan using the proposed system. In the proposed system, we use an LW-RCP(Light Weight-Rapid Control Prototyping) system, which is lab-built, to help students implement the control algorithm. An RCP system makes it easy for students who are not familiar with u-Controller or the C language to implement controllers. We also use Odroid, a low-cost SBC (single-board computer), and a single camera to calculate the position of ball using a machine vision algorithm. In this structure, the measurement subsystem is more durable compared with contact-based sensing systems and student can test their own machine vision algorithms for better measurements. We adopt the Stewart platform, a type of parallel robot, to generate roll-and-pitch actuation for the ball-and-plate system. By adopting the Stewart platform, we can handle more complicated control problems for movement that requires more than two degrees of freedom. Additionally, we implement an LQ controller, which is a typical model-based controller, and apply it to the ball-plate system. Finally, through experiments, we illustrate the usefulness of the proposed system.

Technology-Oriented Synchronous Optimal Design of a 4-Degrees-of-Freedom High-Speed Parallel Robot

Abstract Parameters optimization is complicated by various parameters and nonlinear design problems. In this paper, the interaction mechanism of motion/force transmissibility and various parameters on normalized motor torque and speed of a four degrees-of-freedom (4-DOF) high-speed parallel robot is analyzed. Based on this interaction mechanism, evaluation indices of acceleration capacity, speed ability, and adept cycle time are proposed. Through combining these indices with task requirements and technical criteria of driving systems, the technology-oriented constraints are set up and a parameter optimization method is proposed. With this method, the dimensional parameters, driving system specifications, and work pose of the robot have been synchronously optimized to ensure low driving torque and high pick-and-place frequency. This synchronous optimal design method is general and can be further applied to parameter optimization for different types of parallel robots.

Inverse Dynamics of a 3-P[2(US)] Translational Parallel Robot

SummaryIn this paper, a type of parallel robot with three translational degrees of freedom is studied. Inverse and forward kinematic equations are extracted for position and velocity analyses. The dynamic model is derived by Lagrange’s approach and the principle of virtual work and related computational algorithms implementing inverse and forward dynamics are presented. Furthermore, some numerical simulations are performed using the kinematic and dynamic models in which the results show good agreement with expected qualitative behavior of the mechanism. Comparisons with the results of work-energy and impulse-momentum methods quantitatively verify the validity of the derived equations of motion. Also, a relative computational effectiveness is observed in implementation of virtual work model via the simulations.

Robust Sliding Mode Control for Novel Type of Parallel Robot

In this paper we present a new control architecture based on the robust sliding mode control applied to control a nonlinear system (parallel cable robot). This approach is widely used to address the uncertainties and disturbances of nonlinear systems and to improve the performance of the robot in terms of tracking a desired path. A dynamic model is presented followed by the description of the control approach used. To do this, numerical simulations were carried out by developing a specific code including a graphical user interface for a user-friendly real time. The simulation results for a dynamic model with sliding mode control are discussed for different trajectories applied to this robot, to confirm the validity of accurate tracking of a desired path before future work description.

Dynamics and Control of a 6-dof Cable-driven Parallel Robot with Visco-elastic Cables in Presence of Measurement Noise

Cable robots are a type of parallel robots where the rigid links are replaced by flexible cables. This flexibility produces internal dynamic which challenges the rigid model based controller. In this paper, the dynamic equations of cable robots with viscoelastic cables are obtained. The Feedback Linearization (FL) method is used to provide a linearized dynamic error for the closed loop model of the system with rigid cables. Using the Lyapunov criterion, the stability analysis of the flexible system with the rigid FL control input is performed. It is shown that considering a minimum damping coefficient and employing the rigid FL controller, the system stability can be guaranteed. In order to achieve a trade-off between the control input and the tracking error, the FL gains are obtained using LQR method. In practice, measurement noise usually exists. On the other hand, the end-effector vibration caused by the cables elasticity can be considered as a process noise. Therefore, the LQG approach is used to estimate the states in presence of the process and measurement noise. Using simulation, it is shown that in presence of measurement noise, the LQG method effectively controls the system while the LQR and also the SMC approach, employed in Korayem et al. (Robotica 33(3), 578–598, 2015), lead to the system instability. Another simulation demonstrates that the system with damping less than the specified minimum value can be stable with the LQG approach, in contrary to the LQR controller. Moreover, in order to investigate the vibrational effect of the cable stiffness and damping coefficient, a frequency analysis is performed. Finally, experimental result obtained by implementation on a manufactured cable robot is presented and verified the approach.

Comparison performance between PID and PD controllers for three and four cable-based robots

Cable-based Robots are new type of parallel robots that use cables instead of metallic cylinders. They have good properties that can be used for various applications. The main objective of this work is: the first is to use the direct and inverse geometric model to study and simulate the end effector position of the robot with three and four cables. A graphical user interface has been implemented in order to visualizing the position of the robot. Secondly, we present the determination of static and dynamic tensions and lengths of cables required to flow different trajectories. At the end, we study the response of our systems in closed loop with a Proportional-Integrated-Derivative (PID) and Proportional-Integrated (PD) controllers then this last are compared the results for the same examples using MATLAB/Simulink.; we found that the PID method gives the better performance, such as rapidly speed response, settling time, compared to PD controller.