Design Of Parallel Mechanism Research Articles

Design and parameter optimization of solid-surface antenna parallel mechanism constructed by multi-loop spatial coupling units

The optimization of design and structural parameters of solid-surface antennas is crucial for the development of aerospace satellites. In this paper, the study explores an innovative parallel solid-surface antenna mechanism, inspired by the daisy bloom pattern, which realizes the characteristics of Fewer input-More output (Fi-Mo). A single-DOF deployable/foldable spatial multi-loop coupled mechanism model of the bionic daisy solid-surface antenna is established based on the single-axis tilting hinge, RSSR mechanism, and Bennett mechanism. The motion characteristics of the antenna mechanism are analyzed using the topology, position and orientation characteristic (POC) and inverse screw theory. The error transfer law of multi-loop mechanism is derived by the low-layer-loop sequence. The optimal configuration parameter set of the antenna deployment mechanism is determined using the NSGA-II genetic algorithm. Finally, the optimized antenna mechanism is subjected to physical simulation analysis to verify its stability and the accuracy of its deployment path.

Optimization Design of Redundant Parallel Posture Adjustment Mechanism for Solar Wing Docking Based on Response Surface Methodology

The parallel mechanism exhibits high stiffness and excellent dynamic response, making it ideal for high-precision applications. In our early work, a novel 6-DOF redundant parallel posture mechanism with four limbs for solar wing docking has been proposed; each limb consists of three links and four joints. This paper primarily focuses on optimization design of the mechanism. The calculation of workspace volume reveals that factors influencing the range of posture adjustment include dynamic platform parameters, static platform parameters, the drive trajectory of each kinematic pair, and the angles between each kinematic pair. A sensitivity analysis was conducted to examine the impact of each parameter on the range of posture adjustment. To reduce computational complexity and improve analysis efficiency, a combined approach of single-factor analysis and response surface methodology (RSM) is used in the paper. Single-factor analysis is utilized to evaluate the effect of each parameter on the posture adjustment range. Based on these results, RSM is used to establish a regression model for parameters; thereby, the optimal parameter combination for the mechanism is determined. The regression coefficient R2 = 0.9374 attests to the validity of the proposed model. Finally, a comparison of the posture adjustment range before and after optimization is presented, providing a foundation for the practical application of the redundant parallel mechanism. This paper introduces a novel structural design concept aimed at resolving the conflict between heavy loads and compact sizes in redundant parallel mechanisms while providing valuable insights for miniaturized design.

Design and Analysis of a New Non-Parasitic Parallel Mechanism for 2T1R Motion

Abstract Two-limb parallel mechanisms (PMs) can have several advantages, such as avoidance of mechanical collision, fairly simple architecture, easy assembly, and large workspace. The paper presents a novel two-limb three-degree-of-freedom (DOF) PM with two translations and one-rotation (2T1R) that are actuated by two sliders. The manipulator runs with decoupled position and orientation with forward position solution without parasitic motions. The main topological characteristics of the PM such as position and orientation characteristic (POC), DOF, and coupling degree are analyzed. Second, using the kinematic modeling method based on topological characteristics, the unified symbolic forward and inverse position solutions of the two configurations of the PM (I and II) are derived together with the workspace, rotational capacity, and singularity. Finally, a comparative analysis regarding the kinematics of two configurations (I and II) is carried out to find an optimal design configuration I of a PM for 2T1R motion.

Design and Analysis of a Metamorphic Wrist Rehabilitation Parallel Mechanism

Design and Analysis of a Metamorphic Wrist Rehabilitation Parallel Mechanism

Performance evaluation and dimensional optimization design of planar 6R redundant actuation parallel mechanism

AbstractAiming at the problems of small good workspace, many singular configurations, and limited carrying capacity of non-redundant parallel mechanisms, a full-redundant drive parallel mechanism is designed and developed, and its performance evaluation, good workspace identification, and scale optimization design are studied. First, the kinematics analysis of the planar 6R parallel mechanism is completed. Then, the motion/force transmission performance evaluation index of the mechanism is established, and the singularity analysis of the mechanism is completed. Based on this, the fully redundant driving mode of the mechanism is determined, and the good transmission workspace of the mechanism in this mode is identified. Then, the mapping relationship between the performance and scale of the mechanism is established by using the space model theory, and the scale optimization of the mechanism is completed. Finally, the robot prototype is made according to the optimal scale, and the performance verification is carried out based on the research of dynamics and control strategy. The results show that the fully redundant actuation parallel mechanism obtained by design optimization has high precision and large bearing capacity. The position repeatability and position accuracy are 0.053 mm and 0.635 mm, respectively, and the load weight ratio can reach 15.83%. The research results of this paper complement and improve the performance evaluation and scale optimization system of redundantly actuated parallel mechanisms.

Design and implementation of a 2-DOF 5R parallel mechanism with a coaxial-driven layout

In order to expand and improve the reachable workspace of planar parallel manipulators, a 2-DOF 5R parallel mechanism with a coaxial-driven layout is proposed. The configuration analysis and structural design are carried out, and the kinematic model is presented to conduct simulation analysis. The results indicate that the layout with the axes of the two driving devices overlapping has a larger workspace and a more compact structure. Meanwhile, a closed-loop PID control system is established to evaluate the accuracy of the proposed mechanism and analyse the kinematic error under different gain parameters. Simulation results indicate that the kinematic performance of the mechanism has improved. The control system is constructed based on using a motion control card as the primary control component and two servo motors as the drive device. Additionally, gain values are adjusted by the driver to reduce the deviation of the servo motors. Finally, the design of the prototype is deployed, and the experiment proved that the 2-DOF 5R planar parallel mechanism (PPM) with a coaxial-driven layout has the advantages of a large workspace, fast dynamic response, high stiffness, and easy control. The design of the 2-DOF 5R PPM solves the problem of single operation and high repeatability, which is increasingly utilized in the fields of electronics, food, daily chemicals, and pharmaceuticals.

Drive Layout Configuration Strategy and Scale Optimization Design of Multi-Drive Mode Parallel Mechanism

Abstract Aiming at the inherent defects of single-drive mode parallel mechanisms, such as small good workspace and many singular configurations, a new multi-drive mode parallel mechanism is proposed from the perspective of driving innovation. Taking the planar 6R parallel mechanism as an example, the driving layout configuration strategy and scale optimization design are studied. First, the potential driving layout of the mechanism is analyzed, and the inverse kinematics model of the mechanism is established. Then, based on the motion/force transmission index, the singular space and good transmission workspace of the mechanism are identified, and the mechanism-driven layout configuration strategy is formulated to complete the performance comparison analysis. Finally, based on the performance map method, the scale optimization design of the mechanism is carried out, the prototype is developed and manufactured, and the experimental verification is carried out. The research results show that the multi-drive mode parallel mechanism can improve its kinematic performance without changing the topological structure and scale parameters of the mechanism.

Design and Motion Principle Analysis of new parallel mechanisms with fewer active inputs than the degrees of freedom

AbstractIn this paper, two new parallel mechanisms (PMs) with fewer active inputs than the degrees of freedom (DOFs)are proposed: (i) an nSPS (n = 7, 8, 9) six‐DOF PM with n‐6 active inputs and six lockable joints. and (ii) a 3RPS‐SPS 3‐DOF PM with one active input and three lockable joints. Compared with the traditional PMs, the difference is that the proposed PMs can achieve the same mobility by using a minimal number of active joints. Moreover, the load‐carrying capacity is also improved compared with the original standard mechanisms, since the new PMs become statically redundant when all the branches are locked. For this purpose, a sequential motion control principle is introduced that requires both inverse and forward kinematics of PMs. Kinematic modeling, dimensional optimization, and structural design are carried out for the 7SPS and 3RPS‐SPS mechanisms, and the two prototypes are constructed for experimental validation. Both simulation and experiment results have shown that the proposed hybrid PM can achieve the original mobility while significantly reducing the number of actuators.

Disain CAD Mekanisme Paralel Tiga Derajat Translasi Murni Dengan Rantai Kinematik Kombinasi Sambungan Revolut dan Prismatik


 
 
 
 In this study it was discussed kinematic design of a 3-RRRPP translational parallel mechanism. The design was carried out by using simulation performed using CAD software. Motion platform was analyzed based on screw and reciprocal screw theory. The evaluation mechanism performance was determined by introducing the stages of research in the form to determine mechanism parts such as base, links, and platform. The work was continued with the assembly process of each part. Furthermore, kinematic response represented by displacement of platform positions was figured out by a CAD simulation. Based on the results of the simulation, it was successfully designed the mechanism performing the translational motion of the Platform.
 
 
 
 
 

Configuration Design and Kinematic Performance Analysis of a Novel 4-DOF Parallel Ankle Rehabilitation Mechanism with Two Virtual Motion Centers

Aiming at the problem that the existing ankle rehabilitation robot is difficult to fully fit the complex motion of human ankle joint and has poor human-machine motion compatibility, an equivalent series mechanism model that is highly matched with the actual bone structure of the human ankle joint is proposed and mapped into a parallel rehabilitation mechanism. The parallel rehabilitation mechanism has two virtual motion centers (VMCs), which can simulate the complex motion of the ankle joint, adapt to the individual differences of various patients, and can meet the rehabilitation needs of both left and right feet of patients. Firstly, based on the motion properties and physiological structure of the human ankle joint, the mapping relationship between the rehabilitation mechanism and ankle joint is determined, and the series equivalent model of the ankle joint is established. According to the kinematic and constraint properties of the ankle equivalent model, the configuration design of the parallel ankle rehabilitation robot is carried out. Secondly, according to the intersecting motion planes theory, the full-cycle mobility of the mechanism is proved, and the continuous axis of the mechanism is judged based on the constraint power and its derivative. Then, the kinematics of the parallel ankle rehabilitation robot is analyzed. Finally, based on the OpenSim biomechanical software, a human-machine coupling rehabilitation simulation model is established to evaluate the rehabilitation effect, which lays the foundation for the formulation of a rehabilitation strategy for the later prototype.

Design and Analysis of a Novel Redundant Parallel Mechanism for Long Bone Fracture Reduction

Abstract In recent years, parallel robots have become a hot research topic in trauma fracture treatment because of their high precision, high load capacity, and compact structure. However, compared with serial robots, parallel robots have disadvantages like smaller workspaces and more complex dexterity. In this paper, a novel redundant parallel mechanism (RPM) for long bone fracture reduction is proposed based on Stewart parallel mechanism (SPM). 6 kinematically redundant DOFs (Degrees of freedom) are added to the RPM. First, the kinematics of the RPM is established, and its workspace is calculated. The analysis results indicate that the position workspace of the RPM is about 19 times larger than that of the SPM. The RPM has a similar range of torsion angles as the SPM, but a more extensive range of tilt angles than the SPM. Second, the singularities of the two parallel mechanisms are compared based on the dimensionally homogeneous Jacobian matrix. The results show that the dexterity of the RPM is much better than the SPM. Third, a multi-parameter multi-objective optimization method is proposed to optimize the geometry parameters of the RPM. The statics of the RPM is analyzed by finite element analysis. To further expand the performance of the RPM, the unfixed RPM (URPM) is proposed. The analysis results show that the URPM is superior to the RPM in terms of workspace and dexterity. Finally, experiments are conducted to verify the effectiveness of the proposed methods in this paper.

Design and kinematical performance analysis of a novel reconfigurable parallel mechanism with three remote center-of-motion modes

In view of the demands for variability and safety in surgical procedures, this paper presents a novel reconfigurable parallel mechanism (RPM) capable of performing three remote center-of-motion (RCM) modes: 1R1T, 2R1T, and 3R1T. One of the RCM modes can transform into two distinct configurations from the switch configuration, in which one configuration offers a rotational degree-of-freedom (DOF) and a translational DOF in the YOZ plane, and the other configuration provides identical DOFs in the XOZ plane. A novel device is introduced for switching between the active and passive modes of the revolute joint, which serves as the basis for the RPM reconfiguration process. Utilizing screw theory, the mobility and actuation scheme of the RPM in each configuration are analyzed. Inverse kinematic analysis and Jacobian matrices are then carried out. Subsequently, kinematical performances, such as singularity, workspace, and dexterity, are studied. All results indicate that the proposed RPM has the ability to switch motion modes without requiring reassembly and can effectively meet the diverse demands of surgical procedures based on specific minimally invasive surgery (MIS) requirements.

Design of a Redundant 6-DOF Parallel Platform for Mirror Precision Pose Adjustment

The pose control of 6-DOF parallel mechanism depends on the measurement accuracy of the position of the active driving strut, which affects the pose control accuracy of 6-DOF parallel mechanism. In order to overcome the influence of heavy load large impact force on the measurement accuracy of the active drive strut, a redundant 6-DOF parallel mechanism that separates the measurement struts from the active drive struts was proposed. The fixed platform and the moving platform are connected by six identical active drive struts and six redundant measurement struts. The active driving strut is an active motion unit used to achieve various pose movements of the parallel mechanism, and the follower redundant measurement strut is a precision measurement unit, and does not constrain any DOF of the platform. Only the follower accurately measures the distance between the upper and lower hinge points of the redundant hinges. The accurate position and pose of the 6-DOF parallel mechanism are obtained by using the forward kinematics solution. The controller is used to implement the pose closed-loop control algorithm to achieve precise pose control. The design of this redundant 6-DOF parallel mechanism improves the movement accuracy of the parallel mechanism under heavy load. It can be applied to the precision adjustment of the primary mirror or secondary mirror under heavy load in large aperture optics, and has strong engineering application value.

A Novel Integrated Design Method of Parallel Mechanisms Based on Performance Requirements

Abstract Due to the lack of connection between configuration synthesis and performance indices, many configurations obtained cannot meet the performance requirements, increasing the difficulty of configuration selection and prolonging the design cycle of the parallel mechanism (PM). In order to solve this problem, this paper proposes an inverse Jacobian matrix construction method based on performance indices. The method is realized by constructing singular values and singular vectors directly related to the performance indices. Furthermore, based on the screw expression form of the inverse Jacobian matrix, a new integrated design method that can directly meet the performance requirements is proposed. Finally, a novel ankle rehabilitation mechanism is presented using this method, and the correctness and effectiveness of the integrated design method are verified by theoretical analysis. Meanwhile, the analysis results show that the proposed method can effectively shorten PM’s design time and simplify PM’s design process, which has a good application value.

Design and multi-objective optimization of a novel 5-DOF parallel mechanism with two double-driven chains

AbstractThis paper focuses on the design, analysis, and multi-objective optimization of a novel 5-degrees of freedom (DOF) double-driven parallel mechanism. A novel 5-DOF parallel mechanism with two double-driven branch chains is proposed, which can serve as a machine tool. By installing two actuators on one branch chain, the proposed parallel mechanism can achieve 5-DOF of the moving platform with only three branch chains. Afterwards, analytical solution for inverse kinematics is derived. The 5 $\times$ 5 homogeneous Jacobian matrix is obtained by transforming actuator velocities into linear velocities at three points on the moving platform. Meanwhile, the workspace, dexterity, and volume are analyzed based on the kinematic model. Ultimately, a stage-by-stage Pareto optimization method is proposed to solve the multi-objective optimization problem of this parallel mechanism. The optimization results show that the workspace, compactness, and dexterity of this mechanism can be improved efficiently.

Modeling and control system design of 6-DOF bionic parallel mechanism with compliant modules

Quadrupeds are capable of dynamic movements such as fast running and long-distance jumping due to their flexible and elastic torso structures. In this paper, a compliant parallel mechanism is proposed as a bionic torso to simulate the diversified behaviors and agile locomotion of the tetrapod torso. The spring module is incorporated into the limb of the parallel mechanism to absorb external shocks, cushion, and dampen vibrations, thus improving the compliance performance of the bionic torso. For the compliant parallel mechanism, its kinematics and kinetics are analyzed, and the overall electromechanical system and control framework are devised. The multidimensional damping dynamic characteristics of the proposed mechanism are qualitatively analyzed by simplifying the limb into a spring–mass damping system. The parallel mechanism with compliant spring modules absorbs external forces to different degrees with different stiffness coefficients to avoid damage to the structure by external impacts. The parallel mechanism with different initial positions exhibits the inherent variable stiffness characteristics of the mechanism. The parallel mechanism simulates the diverse behavior of the animal torso, with independent and synthesized locomotor behavior of the six underlying motion patterns. Simulations and experiments demonstrated that the compliant parallel mechanism is effective in vibration damping and cushioning, with a rapid response and small steady-state error. The motion of the compliant parallel mechanism in one direction and the motion of the integrated multi-degree of freedom (DOF) are confirmed and exhibited in the behavioral experiment.

Serial–Parallel Mechanism and Controller Design of a Robotic Brace for Dynamic Trunk Support

This article presents a robotic trunk support system that provides dynamic support and direct force/moment measurement, to assist trunk movement and train related core muscle groups. The proposed system has four degrees of freedom, three in the coronal plane and one in flexion/extension motion, which has a larger range than the existing robotic braces. The system was designed based on the serial–parallel mechanism. The serial module is responsible for the flexion/extension motion, and the parallel module is responsible for three degrees of freedom in the coronal plane. The kinematic modeling and singularity analysis of the parallel mechanism were discussed in detail. Then, the position control and force control of the serial control actuator were implemented, and the experiments were carried out to evaluate the performance of the controller. The effects on human body in force control were discussed and explained. A reduction in anterior muscles activation and an increase of dorsal muscles activation were exhibited when flexion torque was applied, while the trunk core muscle groups have opposite activation when extension torque was applied. The results indicate that the proposed robotic brace has potentials in the application to trunk core muscle groups training and corresponding rehabilitation.

Configuration design and dimensional synthesis of an asymmetry 2R1T parallel mechanism

AbstractThis paper focuses on configuration design, dimensional synthesis, and engineering application of a novel asymmetric 2R1T parallel mechanism (PM) with zero-coupling degree. The analytical forward and inverse displacement solutions are deduced by the means of vector method. The mathematical models between Euler angles and the orientational parameters (i.e., azimuth and tilt angles) of the offset output axis are established. Using screw theory as mathematical tool, this paper worked out evaluation indices of motion/force transmissibility and presented the definitions and calculation methods of good transmission orientation workspace and good transmission orientation capacity (GTOC). Furthermore, a comparative example with respect to kinematic performance of asymmetric UPS-RPU-PU PM and planar symmetric 2UPS-PU PM is carried out, and the result demonstrates that UPS-RPU-PU significantly outperforms 2UPS-PU in terms of GTOC. The constrained optimization model is constructed to formulate optimal problem of dimensional parameters on the maximizing GTOC, which is then solved by differential evolution algorithm. Finally, an engineering case demonstrates that the optimized mechanism has a good application prospect in hydraulic support test bed.

Multi-Objective Optimization Design of 6-UPS Parallel Mechanism Based on Taguchi Method and Entropy-Weighted Gray Relational Analysis

Nowadays, parallel mechanisms are widely used in many fields because of their excellent structural performance. In order to improve the comprehensive performance of 6-UPS parallel mechanism, this article proposes a multi-objective optimization design method for parallel mechanism based on the Taguchi method and entropy-weighted gray relational analysis (EGRA) method. By establishing a parametric model of the 6-UPS parallel mechanism, taking the peak force on the drive pair of the drive branch chain of the mechanism, the minimum value of the projection angle of the body-fixed coordinate system (BCS) relative to the inertial coordinate system (ICS), and the minimum value of the average projected angle of the BCS relative to the ICS as the objective functions, the relationship between the design variables and the objective function is investigated under the condition that the constraints are satisfied. Using the optimization method proposed in this article, the multi-objective optimization problem is transformed into a single-objective optimization problem based on gray relational grade (GRG). Compared with the non-optimized 6-UPS parallel mechanism, the simulation results show that the peak force on the drive pair of the drive branch chain is reduced by 17.73%, and the minimum value of the projected angle and the minimum value of the average projected angle of the BCS relative to the ICS are increased by 27.36% and 36.17%, respectively, which effectively improves the load-bearing capacity and motion range of the 6-UPS parallel mechanism and verifies the reliability of the optimized design method.

Design and analysis of a class of two-limb non-parasitic 2T1R parallel mechanism with decoupled motion and symbolic forward position solution - influence of optimal arrangement of limbs onto the kinematics, dynamics and stiffness

The two-limb11Throughout this paper, the two-limb parallel mechanism means that the base and moving platforms of a parallel mechanism are directly connected with two independent limbs, despite the existence of closed sub-loop in one limb (i.e., in this work, it is named as hybrid-single-ordered-chain, and HSOC for short). parallel mechanisms (PMs) can have the advantages, in terms of avoidance of mechanical collision, simple architecture, rapid configuration transformation and large workspace volume. This paper consists of two major contents. The first aspect pertains to the design of a class of two-limb PMs with two translations and one rotation (2T1R), where a family of PMs featuring two translations actuated by sliding units are proposed, with decoupled position and orientation as well as symbolic forward position solution, without parasitic motions. The second aspect is to analyze the influence of the arrangement of limbs onto the kinematic, dynamic and stiffness performance of the PMs. Using the kinematic modeling method based on topological characteristics, the unified symbolic forward and inverse position solutions of the PMs are derived, together with the workspace, rotational capacity and singularity. Finally, a comparative study regarding the kinematics, dynamics and stiffness of the two PMs is carried out to find the optimal PM configuration. This paper presents a systematic analysis for the synthesis, optimal design and performance evaluation of two-limb parallel mechanisms.