Design Of Parallel Manipulator Research Articles

Design and analysis of a novel 3-DOF planar parallel manipulator with two kinematic chains

In this work, to enlarge the workspace, a novel 3-DOF planar parallel manipulator (PPM) with two identical RRR kinematic chains is proposed, and this manipulator has a significant advantage in orienting the moving platform (MP) across a wide range of angles. Resorting to the closed-loop vector approach, the inverse position equation and Jacobian matrix of the novel manipulator are established. Payload performance, dexterity performance, and singularity of the proposed manipulator are analyzed based on the Jacobian matrix. To investigate the distribution characteristics of the constant orientation workspace, orientation workspace, and reachable workspace of the proposed manipulator, a numerical discretization method is employed. Under the same working mode and structural parameters, constant orientation workspace and reachable workspace comparisons between the proposed manipulator and another two traditional PPMs are conducted. Focused on three kinds of performance indices, link lengths optimization of the proposed manipulator is carried out. A 4-DOF pick-and-place equipment is fabricated, and the rotational and translational capabilities are verified based on two examples.

Design, Analysis and Implementation of a 3-DOF Spherical Parallel Manipulator

Design, Analysis and Implementation of a 3-DOF Spherical Parallel Manipulator

A design of 2-DoFs spherical parallel manipulator with adjustable workspace

Spherical parallel manipulators (SPMs) have promising industrial applications due to their strong mechanical performance. However, they face challenges such as singularity avoidance, tight tolerance manufacturing requirements, and the need for versatile and dexterous end-effector functionalities. Additionally, SPMs lack customizability due to singularity and collision issues. This work introduces a novel design principle that addresses these challenges by benchmarking two analytical methods: structural synthesis using screw theory and dimensional synthesis using dimensionless parameters. A proof of concept of a 2-DoF SPM that can operate within a cylindrical constraint and realize a full workspace without collision is presented. This design allows for adjustable reachable workspace at the end-effector, despite significant geometric constraints. These findings on mechanical design solutions provide customizability for SPMs, and a 3D model with an aspect ratio of 1/12 is presented and discussed for potential practical applications. Overall, it is identified that both a simulation using Recurdyn and inverse kinematic model show the desired movements at the moving platform with the maximum error of 0.0013°.

A Forward Solution Algorithm of 6RUS Parallel Mechanism Based on Dual Quaternion Method

The 6RUS parallel manipulator is a highly versatile and widely used robotic mechanism with six degrees of freedom. Its intricate kinematic structure and its capability to perform complex motion tasks have garnered significant research interest in recent years. The kinematic analysis of the 6RUS mechanism plays a crucial role in understanding its operational characteristics and optimizing its performance for various applications. In this paper, we present a state-of-the-art kinematic algorithm for the 6RUS parallel manipulator. Our algorithm is aimed at addressing the challenges associated with accurately determining the pose and motion of the end-effector relative to the base, considering the complexity of the mechanism’s architecture. By leveraging advanced mathematical modeling techniques and utilizing efficient computational algorithms, our proposed algorithm offers improved accuracy, efficiency, and robustness in determining the kinematic parameters of the 6RUS mechanism. The key contributions of this work include the development of a comprehensive forward and inverse kinematic model for the 6RUS parallel manipulator, incorporating the effects of joint constraints, singularities, and workspace limitations. We also present a detailed analysis of the algorithm’s performance in comparison to existing approaches, demonstrating its superiority in terms of computational efficiency and accuracy. The proposed kinematic algorithm holds significant potential for enhancing the design, control, and trajectory planning of 6RUS parallel manipulators. It provides a solid foundation for advanced applications such as robotic surgery, industrial automation, and virtual reality systems. The results presented in this paper contribute to the growing body of knowledge in parallel manipulator research and pave the way for future developments in the field.

Multi-objective optimization design of parallel manipulators using a neural network and principal component analysis

Abstract. In this work, a multi-objective optimization design method is proposed based on principal component analysis (PCA) and a neural network to obtain a mechanism's optimal comprehensive performance. First, multi-objective optimization mathematical modeling, including design parameters, objective functions, and constraint functions, is established. Second, the sample data are obtained through the design of the experiment (DOE) and are then standardized to eliminate the adverse effects of a non-uniform dimension of objective functions. Third, the first k principal components are established for p performance indices (k<p) using the variance-based PCA method, and then the factor analysis method is employed to define its physical meaning. Fourth, the overall comprehensive performance evaluation index is established by objectively determining weight factors. Finally, the computational cost of the modeling is improved by combining the neural network and a particle swarm optimization (PSO) algorithm. Dimensional synthesis of a Sprint (3RPS) parallel manipulator (PM) is taken as a case study to implement the proposed method, and the optimization results are verified by a comprehensive performance comparison of robots before and after optimization.

Design and Simulation Analysis of Parallel Manipulator

With the rapid development of domestic manufacturing, industrial robots have become widely used and become a research hotspot. In this paper, the classical three-degree-of-freedom parallel manipulator is taken as the analysis object, the plane three-degree-of-freedom parallel positioning platform is designed, its kinematics model is established, and the dynamic simulation analysis is carried out in ADAMS software, and the drive motor is selected according to the simulation results.

Design, static analysis, and dynamic system modeling of 3-PPRS parallel manipulator with load-balancing UPS leg

AbstractAs a heavy load is applied to the parallel manipulators, it causes inaccuracies while positioning the end-effector or unbalanced dynamic forces in the legs. Various load-balancing techniques overcome this. However, the disadvantage of most load-balancing mechanisms is that they add inertia to the assembly and decrease the speed of motion. This article studies a new load-balancing method (a passive damper mechanism). The passive balancing mechanism is proposed to negate the inertia effects while countering the static inaccuracies in the parallel mechanism. This is verified by the structural analysis of the mechanism. The impact of the damper element on the dynamics of the mechanism is unknown. Hence, a complete mathematical model for the balancing mechanism has been developed to study its impact on the dynamics of the entire structure. Laplace transformations characterize the system response. The inclusion of a passive damper in a 3-prismatic-prismatic-revolute-spherical system was examined and found to be stable and critically damped. Such a passive damper was envisaged to facilitate additional force transmission for the actuators, and the DC gain from the system response validates the torque support for the actuators.

Design and experiment of a new translational parallel manipulator with large payload and high repeatability

Parallel manipulators are known to have higher structural rigidity and end-effector speed than serial manipulators. However, the size, payload, rigidity, and repeatability of parallel manipulators highly depend on the types of active and passive joints used. Compared with other joint types, revolute joints are structurally simpler and have an unlimited rotation range. They can be easily preloaded to increase the stiffness and eliminate clearance. Hence, revolute joints are preferable for parallel manipulators that need to have a smaller size, larger payload, and higher reparability. This paper presents a new translational parallel manipulator (TPM) that uses only revolute joints as the active and passive joints. The kinematics, workspace analysis, and singularity analysis are provided to facilitate the design of the new TPM. Finite element analyses are given to evaluate the compliance contribution of the revolute joints and links of the new TPM. Compliance, payload, and repeatability experiments are provided to verify the merits of the proposed design. We expect that the proposed TPM can provide an alternative for selecting parallel manipulators to meet different industrial applications.

Design and prototyping of an accelerometer based parallel manipulator for endoscope position control

The advancement of embedded controllers in minimally invasive robotic surgery (MIRS) provides an innovative and safe alternative to traditional open surgery. This paper illustrates the Accelerometer-based Embedded prototype of 4 link novel parallel manipulator design and endoscope end position control scheme. The parallel manipulator proposed is of 4 leg quadra model with 4 servo actuators to drive the end effector to which endoscope camera integrated with micro electro-mechanical system (MEMS) accelerometer. The parallel manipulator is modeled in Coppeliasim computer-aided design (CAD) and embedded control logic is implemented in the ATmega328P microcontroller. The achieved end effector movement is +/-10cm from the ground clearance validated it in CAD tool. The potentiometer-based position control of the endoscope and its image magnification is recorded. The internet of things (IoT) infrastructure extension to the demonstrated protype is proposed. This cost-effective model is compared with the existed models available in the market.

Synthesis of kinematotropic parallel manipulators by inclusion of additional motion generators

Linkages able to change their finite degree of freedom due to geometric constraints are commonly known as kinematotropic linkages. Although a considerable number of examples of such linkages can be found in the literature, the amount of reported kinematotropic parallel manipulators remains small. Even more rare are publications presenting systematic methods for the design of such parallel manipulators. Hence, in this paper, a design method for kinematotropic parallel manipulators is introduced. It takes existing parallel manipulators with a constant degree of freedom and shows how to design an additional limb that renders the manipulator kinematotropic. The method is applied in two examples, a manipulator that can switch between 1-, 2- and 3-DOF motion modes, and a different manipulator with two 1- and one 2-DOF motion modes.

A novel 6 DOFs generalized parallel manipulator design and analysis based on humanoid leg

In this paper, a 6 degrees of freedom (DOFs) generalized parallel manipulator is presented which can be used as a humanoid leg. Based on the Number Synthesis and Graph Synthesis method, all the possible contracted graphs of the 6-DOFs leg are provided. Then, a novel method named as Node Response Method (NRM) is presented to identify the isomorphism of contracted graphs. In order to obtain the optimal manipulator, the Lie group is used to analyze all limbs. Furthermore, a terrain adaptive index named as Global Maximum Stride Distance Ratio (GMSDR) is established, which is used to assess the performance of a biped robot in different terrains. The DOF of proposed manipulator is verified by translating into a two-layer and two-loop (TL-TL) topological structure. Afterwards, the kinematics and the Jacobian matrix of the manipulator are calculated. Moreover, the performance indexes of the manipulator are analyzed. In order to obtain an optimal kinematics performance, the structural parameters are optimized using genetic algorithm. Finally, two basic gaits are proposed for a biped robot which consists of two manipulators and a simulation is carried out.

Feasibility Design and Control of a Lower Leg Gait Emulator Utilizing a Mobile 3-Revolute, Prismatic, Revolute Parallel Manipulator

Abstract Design and control of lower extremity robotic prostheses are iterative tasks that would greatly benefit from testing platforms that would autonomously replicate realistic gait conditions. This paper presents the design of a novel mobile 3-degree-of-freedom (DOF) parallel manipulator integrated with a mobile base to emulate human gait for lower limb prosthesis evaluation in the sagittal plane. The integrated mobile base provides a wider workspace range of motion along the gait direction and reduces the requirement of the parallel manipulator’s actuators and links. The parallel manipulator design is optimal to generate the defined gait trajectories with both motion and force requirements using commercially available linear actuators. An integrated active force control with proportional integral derivative (PID) control provided more desirable control compared to traditional PID control in terms of error reduction. The novelty of the work includes the methodology of human data-oriented optimal mechanism design and the concept of a mobile parallel robot to extend the translational workspace of the parallel manipulator with substantially reduced actuator requirements, allowing the evaluation of prostheses in instrumented walkways or integrated with instrumented treadmills.

2PPaRR-2PPaRU: Design, analysis, and optimization of a new 3T1R parallel manipulator with rotational pitch motion

A new 3T1R parallel manipulator (PM) 2PPaRR-2PPaRU with rotational pitch motion is proposed in this paper. In such a mechanism, there are four limbs connected to the moving platform (MP) through several revolute joints and universal joints, and all actuated joints are prismatic joints with an axis along a vertical direction. Mobility and motion characteristics are verified by constraint screw theory. The inverse kinematic solutions and the singularity configurations are derived through kinematic analysis. Next, the workspace analysis and the connection between [Formula: see text] and the volume of the reachable workspace are performed. The local motion/force transmission index is selected to evaluate the local transmission performance of 2PPaRR-2PPaRU PM. Finally, the global motion/force transmission index and the volume of reachable workspace are considered simultaneously to optimize the structural parameters. The 2PPaRR-2PPaRU PM with improved local transmission performance and reachable workspace has been achieved after optimization.

A Compact Mirror-Symmetrical XY Compliant Parallel Manipulator for Minimizing Parasitic Rotations

Abstract The design of XY compliant parallel manipulators (CPMs) remains challenging considering the tradeoff between mirror-symmetry for better constrained undesired rotations and a small footprint, although a significant number of XY CPMs have been reported in extensive applications. This paper presents a new XY CPM using mirror-symmetry without increasing its footprint, mainly aiming to reduce the undesired parasitic rotations of input and output motion stages. The concept of mirror-symmetry is deployed to tackle the parasitic rotations, with the help of using a multilayer compact XY CPM design method. A nonlinear and analytical model of the proposed XY CPM is derived using free body diagrams and the beam constraint model (BCM) to accurately analyze its performance characteristics over a large range of motion. The designed XY CPM is then verified by the nonlinear finite element analysis (FEA) method. Finally, the proposed multilayer design is fabricated using two pieces of aluminum plate and it is mounted in a measurement system to experimentally validate several performance characteristics. The analytical, FEA, and/or experimental results show that the proposed design can sufficiently constrain undesired motions including parasitic rotation of input and output stages, cross-axis coupling error, and actuator isolation index. Compared with exiting designs, the proposed design also shows its merits in large motion range and out-of-plane stiffness.

Design of Asymmetric Parallel Manipulator for Axial-Bending Dynamic Stiffness Analysis

This paper presents an asymmetric 5-bar parallel manipulator capable of characterizing the dynamic stiffness properties of materials used in robotic joints in 2 degrees of freedom, axial and bending, simultaneously. The end effector is actuated by two stepper motors with linear rails. Two force sensors were added to estimate axial force and moment. Experiments were performed in axial compression, bending, and a mixed axial-bending motion. A spring-mass-spring system was constructed to evaluate the fabricated apparatus for frequency analysis up to 20Hz. The frequency analysis result was accurate when compared to the theoretical response of the system. Axial stiffness estimation had an error of 1.5%, bending stiffness had an error of 3.4%, and mixed-mode had a total error of 1.8%. Future experiments will showcase the versatility of the apparatus and test nonlinear samples.

Sensitivity Analysis and Multi-objective Optimization Design of Parallel Manipulators

Sensitivity Analysis and Multi-objective Optimization Design of Parallel Manipulators

Design of Four-DoF Compliant Parallel Manipulators Considering Maximum Kinematic Decoupling for Fast Steering Mirrors

Laser beams can fluctuate in four directions, which requires active compensation by a fast steering mirror (FSM) motion system. This paper deals with the design of four-degrees-of-freedom (DoF) compliant parallel manipulators, for responding to the requirements of the FSM. In order to simplify high-precision control in parallel manipulators, maximum kinematic decoupling is always desired. A constraint map method is used to propose the four required DoF with the consideration of maximum kinematic decoupling. A specific compliant mechanism is presented based on the constraint map, and its kinematics is estimated analytically. Finite element analysis demonstrates the desired qualitative motion and provides some initial quantitative analysis. A normalization-based compliance matrix is finally derived to verify and demonstrate the mobility of the system clearly. In a case study, the results of normalization-based compliance matrix modelling show that the diagonal entries corresponding to the four DoF directions are about 10 times larger than those corresponding to the two-constraint directions, validating the desired mobility.

An integrated structure and control design of a coaxis planar parallel manipulator for pick-and-place applications based on elastic potential energy

During high-speed pick-and-place operations, elastic deformations are quite apparent if the mass of the manipulator is low. These irregular deformations are accompanied by vibrations, then errors. Since elastic potential energy reflects elastic deformation, the vibration of the whole manipulator can be controlled well when the elastic potential energy is decreased. In this article, to design manipulators with flexible links for pick-and-place operations, an integrated structure and control design framework is proposed. The dynamic model of a coaxis planar parallel manipulator is obtained by the finite element method, an effective method. A proportional–derivative controller is utilized for this industrial application. Simultaneously, the optimal structural and control parameters are derived by minimizing the elastic potential energy via integrated design, in which actuated systems and accuracies are regarded as constraints. Finally, simulations show that the performance of the parallel manipulator is improved by this design methodology.

Mechatronics Design and Kinematic Analysis of SMA Spring Actuated Parallel Manipulator

Flexible parallel manipulators can be used as an orienting device because of their precise positioning ability and better stiffness. The flexibility to the manipulator induces challenges in the selection of actuator, sensors and control. The paper presents a novel mechatronics design of a flexible symmetric parallel manipulator with minimum number of actuators used as an orienting device. Shape memory alloy springs (SMA) are used as an actuator because of ease of integration and higher deflection. In order to avoid any contact type sensor which could affect the compliance of the manipulator, the position of SMA spring is calculated indirectly from the kinematic model with the end effector orientation data measured from IMU sensor. The complete experimental set up design including electrical and control circuitry is explained in detail in the work. Preliminary open loop test is conducted on the prototype to understand the SMA response to various current input and to verify the effectiveness of the kinematic model in the actuator length measurement. Closed loop control based on ON/OFF control is implemented in the controller and is tested for step input.

Design and Optimization of a 6-DOF Singularity-Free Parallel Manipulator

A novel six degrees-of-freedom (DOF) singularity-free parallel manipulator (PM) is presented. The PM consists of five peripheral limbs and a centre limb, which makes the mechanism have high stiffness and large tilting capability . Due to the special architecture, the doubly actuated centre limb of the manipulator could have infinite inverse solutions. In every configuration of the end-effector, the manipulator can adapt its centre limb to the position and orientation with best dexterities. Targeting for further analysis of the manipulator, its detailed kinematic analysis is developed, including the solutions of the inverse position problems, the singularity, the dexterity and the workspace. The analysis results show that the proposed manipulator has good performance and thus may be suitable candidate for complicated surface machining.