Accuracy Synthesis of Redundant Parallel Kinematic Mechanism with Weighted Least Square Method

2012 ◽  
Vol 499 ◽  
pp. 3-8
Author(s):  
Xin You Li ◽  
Wu Yi Chen
Keyword(s):  
Machine Tool ◽  
Conventional Method ◽  
Least Square Method ◽  
Least Square ◽  
Tolerance Allocation ◽  
Manufacturing Processes ◽  
Manufacturing Cost ◽  
Parallel Kinematic Mechanism ◽  
Parallel Kinematic ◽  
Kinematic Mechanism

In order to reduce manufacturing cost, a methodology of accuracy synthesis for machine tool was recommended by combining both machining cost and Least Square method. Weighted coefficients representing the machining difficulty of manufacturing processes were introduced. 3PRS/UPS redundant parallel kinematic mechanism (3PRS/UPS PKM) was taken as an example, and its component tolerances were derived by the proposed method. Comparing with conventional method, the component tolerances were allocated reasonably. A further tolerance allocation for spherical and rotational joints was studied in detail. And hence, the producibility of component was improved and the manufacturing cost was reduced. The results showed that the proposed method was capable of producing tolerance allocations economically and accurately.

Elastic Deformation Error Model for Calibration and Compensation of Parallel Kinematic Mechanism Machine Tool

2012 ◽  
Vol 6 (2) ◽  
pp. 188-195
Author(s):  
Tetsuya Matsushita ◽  
◽  
Hiroshi Ueno ◽  
Atsushi Matsubara ◽  
Keyword(s):  
Machine Tool ◽  
Elastic Deformation ◽  
Calibration Method ◽  
Compensation System ◽  
Error Model ◽  
Parallel Kinematic Mechanism ◽  
Internal Forces ◽  
Parallel Kinematic ◽  
Deformation Error ◽  
Kinematic Mechanism

In the motion error of parallel kinematic mechanism machine tools, the elastic deformation caused by external forces, such as gravity, as well as the kinematic parameter error, is a significant factor. Internal forces generated by the rotational resistance of passive joints also deform mechanical components. In this paper, an elastic deformation error model that can deal with external and internal forces is presented. A compensation system and a calibration method of kinematic parameters employing this model are also presented. It is experimentally verified that this calibration method and compensation system improve the motion accuracy of a parallel kinematic mechanism machine tool.

scholarly journals Calibration of In-Plane Center Alignment Errors in the Installation of a Circular Slide with Machine-Vision Sensor and a Reflective Marker

Sensors ◽  
2020 ◽  
Vol 20 (20) ◽  
pp. 5916
Author(s):  
Hyungjin Jeong ◽  
Jiwon Yu ◽  
Donghun Lee
Keyword(s):  
Machine Vision ◽  
Machine Tool ◽  
Alignment Error ◽  
Stop And Go ◽  
Parallel Kinematic Mechanism ◽  
Center Position ◽  
Parallel Kinematic ◽  
The Difference ◽  
Alignment Errors ◽  
Kinematic Mechanism

This paper describes a method for calibrating in-plane center alignment error (IPCA) that occurs when installing the circular motion slide (CMS). In this study, by combini ng the moving carriage of the CMS and the planar PKM (parallel kinematic mechanism) with the machine tool, the small workspace of the PKM is expanded, and the workpiece is placed on the table with the CMS installed is processed through the machine tool. However, to rigidly mount the CMS on the table, the preload between the guide and the support bearings must be adjusted with the eccentric bearing, and in this process, the IPCA occurs. After installing a reflective marker on the PKM, the PKM is slowly rotated along with the ring guide in the way of stop-and-go without the PKM’s own motion. Then, using a machine vision camera installed at the top of the CMS, the IPCA, which is the difference between the actual center position and the nominal center position of the CMS with respect to the camera, can be successfully calibrated through the circular fitting process. Consequently, it was confirmed that the IPCA of 0.37 mm can be successfully identified with the proposed method.

Influence of Servo Characteristics on Motion Accuracy of Parallel Kinematic Mechanism

2012 ◽  
Vol 523-524 ◽  
pp. 762-767 ◽  
Author(s):  
Ryuta Sato ◽  
Michitaka Maegawa ◽  
Gen Tashiro ◽  
Keiichi Shirase
Keyword(s):  
Machine Tool ◽  
Machine Tools ◽  
Servo Motor ◽  
Motion Error ◽  
Center Point ◽  
Parallel Kinematic Mechanism ◽  
Parallel Kinematic ◽  
Motion Characteristics ◽  
Dimensional Errors ◽  
Kinematic Mechanism

Parallel kinematic mechanism (PKM) is applied to machine tools and robots since its flexibility and speed. In machine tools, additionally, motion accuracy is strongly desired. Although various research works aimed to calibrate static geometrical deviations of the PKM machines in order to improve motion accuracy, influence of dynamic motion error of servo system has not been investigated well up to now. In this study, the influence of servo characteristics on motion accuracy of a PKM machine tool driven by six servo motors is discussed, because it is expected that the contouring motion accuracy of a PKM machine tool is strongly depends on the servo characteristics. A servo motor which installed to the machine is modeled to simulate the motion characteristics of each servo motor. The motor models are coupled with a model of link mechanism, and the motion accuracy of a tool center point is simulated. Also, both of positional and angular errors are simulated successfully. As the results of the simulations, it is clarified that the motion accuracy is strongly depends on the servo characteristics and location of the tool center point. In addition, the motion errors are observed as six dimensional errors. It is also discussed that the influence of friction torques on the motion accuracy.

Kinematic Analysis of a Novel 3-DOF Parallel Mechanism with Actuation Redundancy

2013 ◽  
Vol 816-817 ◽  
pp. 821-824
Author(s):  
Xue Mei Niu ◽  
Guo Qin Gao ◽  
Zhi Da Bao
Keyword(s):  
Kinematic Analysis ◽  
Parallel Mechanism ◽  
Rbf Neural Network ◽  
Analysis Method ◽  
Parallel Kinematic Mechanism ◽  
Redundantly Actuated ◽  
Parallel Kinematic ◽  
Forward Kinematic ◽  
Kinematic Mechanism ◽  
Kinematic Solution

Kinematic analysis plays an important role in the research of parallel kinematic mechanism. This paper addresses a novel forward kinematic solution based on RBF neural network for a novel 2PRRR-PPRR redundantly actuated parallel mechanism. Simulation results illustrate the validity and feasibility of the kinematic analysis method.

Soft pneumatic actuator-driven origami-inspired modular robotic “pneumagami”

2020 ◽  
pp. 027836492090990 ◽  
Author(s):  
Matthew A Robertson ◽  
Ozdemir Can Kara ◽  
Jamie Paik
Keyword(s):  
High Strength ◽  
Small Scale ◽  
Task Space ◽  
Pneumatic Actuators ◽  
Construction Methods ◽  
Parallel Kinematic Mechanism ◽  
Parallel Kinematic ◽  
Structural Mechanisms ◽  
High Degree ◽  
Kinematic Mechanism

This article presents a new modular robotic platform for enabling reconfigurable, actively controlled, high-degree-of-freedom (high-DoF) systems with compact form factor. The robotic modules exploit the advantages of origami-inspired construction methods and materials, and soft pneumatic actuators (SPAs) to achieve an actuator embedded, parallel kinematic mechanism with three independently controlled “waterbomb” base legs. The multi-material, layer-fabricated body of the modules features selectively compliant flexure hinge elements between rigid panels that define the module as a kinematic 6R spherical joint. The precision layer-fabrication technique is also used to form embedded distribution channels within the module base to connect actuators to onboard control hardware. A decentralized control architecture is applied by integrating each module with small-scale solenoid valves, communication electronics, and sensors. This design approach enables a single pneumatic supply line to be shared between modules, while still allowing independent control of each leg joint, driven by soft, inflatable pouch actuators. A passive pneumatic relay is also designed and incorporated in each module to leverage the coupled, inverted inflation, and exhaust states between antagonistic actuator pairs allowing both to be controlled by a single solenoid valve. A prototype module is presented as the first demonstration of integrated modular origami and SPA design, or pneumagami, which allows predefined kinematic structural mechanisms to locally prescribe specific motions by active effect, not just through passive compliance, to dictate task space and motion. The design strategy facilitates the composition of lightweight, high-strength robotic structures with many DoFs that will benefit various fields such as wearable robotics.

Complete kinematic calibration of a 6-RRRPRR parallel kinematic machine based on the optimal measurement configurations

2019 ◽  
Vol 234 (1) ◽  
pp. 121-136 ◽  
Author(s):  
Chunyang Han ◽  
Yang Yu ◽  
Zhenbang Xu ◽  
Xiaoming Wang ◽  
Peng Yu ◽  
...  
Keyword(s):  
Kinematic Model ◽  
Inverse Kinematic ◽  
Error Model ◽  
Kinematic Calibration ◽  
Universal Joint ◽  
Parallel Kinematic Mechanism ◽  
Simulation And Experiment ◽  
Parallel Kinematic ◽  
Kinematic Mechanism ◽  
Selection Of

This paper presents a kinematic calibration of a 6-RRRPRR parallel kinematic mechanism with offset RR-joints that would be applied in space positioning field. In order to ensure highly accurate and highly effective calibration process, the complete error model, which contains offset universal joint errors, is established by differentiating inverse kinematic model. A calibration simulation comparison with non-complete error model shows that offset universal joint errors are crucial to improve the calibration accuracy. Using the error model, an optimal calibration configuration selection algorithm is developed to determine the least number of measurement configurations as well as the optimal selection of these configurations from the feasible configuration set. To verify the effectiveness of kinematic calibration, a simulation and experiment were performed. The results show that the developed approach can effectively improve accuracy of a parallel kinematic mechanism with relatively low number of calibration configurations.

Design of an Ankle Rehab Robot With a Compliant Parallel Kinematic Mechanism

2020 ◽  
Author(s):  
Nishant Jalgaonkar ◽  
Adam Kim ◽  
Shorya Awtar
Keyword(s):  
Degrees Of Freedom ◽  
Functional Requirements ◽  
Key Factors ◽  
Center Of Rotation ◽  
Ankle Motion ◽  
Natural Motion ◽  
Parallel Kinematic Mechanism ◽  
Parallel Kinematic ◽  
Kinematic Mechanism ◽  
Clinical Adoption

Abstract In this paper, we present the design of a novel ankle rehabilitation robot (ARR), called the Flex-ARR, that employs a compliant parallel kinematic mechanism (PKM) with decoupled degrees of freedom. The Flex-ARR is designed to collocate the biological center of rotation of the ankle with that of the robot’s center of rotation to allow natural ankle motion. While multiple ARR designs have been developed in research labs and some are commercially available, their clinical adoption has been limited because they do not emulate the natural motion of the ankle. The Flex-ARR leverages a unique PKM design that uses compliance to absorb minor misalignments between the center of rotation of the ankle and the robot, thereby allowing natural ankle motion. Also, because of its unique design, the PKM inherently accommodates variations in user foot sizes with minimal adjustments. The Flex-ARR is designed to provide multiple training modes that allow for both rehabilitation and assessment modalities. This paper provides a review of the literature to identify the key factors that have limited the clinical adoption of existing ARRs. Based on this, functional requirements and design specifications for an optimal ARR are defined. This is then used to develop a design strategy, followed by conceptual and detailed design.

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