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Search Results (4)

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Keywords = 4-RPU parallel mechanism

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33 pages, 7614 KB  
Article
Research on High Precision Stiffness Modeling Method of Redundant Over-Constrained Parallel Mechanism
by Sen Wang, Haoran Li, Xueyan Han, Jiahao Wei, Tao Zhang and Shihua Li
Sensors 2023, 23(13), 5916; https://doi.org/10.3390/s23135916 - 26 Jun 2023
Cited by 1 | Viewed by 1853
Abstract
Traditional stiffness modeling methods do not consider all factors comprehensively, and the modeling methods are not unified, lacking a global stiffness model. Based on screw theory, strain energy and the virtual work principle, a static stiffness modeling method for redundant over-constrained parallel mechanisms [...] Read more.
Traditional stiffness modeling methods do not consider all factors comprehensively, and the modeling methods are not unified, lacking a global stiffness model. Based on screw theory, strain energy and the virtual work principle, a static stiffness modeling method for redundant over-constrained parallel mechanisms (PMs) with clearance was proposed that considers the driving stiffness, branch deformation, redundant driving, joint clearance and joint contact deformation. First, the driving stiffness and branch deformation were considered. According to the strain energy and Castiliano’s second theorem, the global stiffness matrix of the ideal joint mechanism was obtained. The offset of the branch was analyzed according to the restraint force of each branch. The mathematical relationship between the joint clearance and joint contact deformation and the end deformation was established. Based on the probability statistical model, the uncertainty of the offset value of the clearance joint and the contact area of the joint caused by the coupling of the branch constraint force was solved. Finally, taking a 2UPR-RR-2RPU redundant PM as an example, a stiffness simulation of the mechanism was carried out using the finite element method. The research results show that the high-precision stiffness modeling method proposed in this paper is correct, and provides an effective method for evaluating the stiffness performance of the PM. Full article
(This article belongs to the Collection Robotics, Sensors and Industry 4.0)
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17 pages, 3723 KB  
Article
Dynamics Modeling and Adaptive Sliding Mode Control of a Hybrid Condenser Cleaning Robot
by Jiabao Li and Chengjun Wang
Actuators 2022, 11(5), 119; https://doi.org/10.3390/act11050119 - 24 Apr 2022
Cited by 5 | Viewed by 2814
Abstract
This study examines the pose control of the 4-RPU redundant parallel mechanism of a hybrid condenser cleaning robot in response to the poor control accuracy of current cleaning robots. The kinematics of the 4-RPU mechanism is analysed, and its dynamics model is constructed [...] Read more.
This study examines the pose control of the 4-RPU redundant parallel mechanism of a hybrid condenser cleaning robot in response to the poor control accuracy of current cleaning robots. The kinematics of the 4-RPU mechanism is analysed, and its dynamics model is constructed using the virtual work principle. The theoretical calculation and virtual prototype simulation of the constructed model are conducted in MATLAB and ADAMS, which yield basically consistent results, demonstrating the precision of the model. Based on this model, an adaptive sliding mode control method is proposed that can estimate and compensate for parameter uncertainties and load perturbations simultaneously. The system stability is analysed using Lyapunov functions. The results suggest that the adaptive sliding mode control method can significantly reduce the average tracking error of each degree of freedom of the moving platform and exhibits higher control stability and convergence accuracy than the conventional sliding mode control algorithm. This study provides a reference and research basis for attitude control of the cleaning robots affected by uncertainties such as water backlash during operation. Full article
(This article belongs to the Topic Motion Planning and Control for Robotics)
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14 pages, 3219 KB  
Article
Performance Index for Dimensional Synthesis of Robots for Specific Tasks
by Miguel Díaz-Rodríguez, Pedro Araujo-Gómez and Octavio Andrés González-Estrada
Robotics 2022, 11(2), 51; https://doi.org/10.3390/robotics11020051 - 16 Apr 2022
Cited by 2 | Viewed by 3477
Abstract
This study proposes a performance index for the dimensional optimization of parallel manipulators with specific tasks. In particular, the index evaluates the dexterity of the mechanism to be designed and compares it with that of the required specific task, e.g., rehabilitation tasks. The [...] Read more.
This study proposes a performance index for the dimensional optimization of parallel manipulators with specific tasks. In particular, the index evaluates the dexterity of the mechanism to be designed and compares it with that of the required specific task, e.g., rehabilitation tasks. The proposed index is implemented to design a 3UPS + RPU parallel manipulator for performing physical rehabilitation treatments on lower limbs. First, the condition numbers of both the mechanism and the lower limb are determined. Subsequently, the indexes are compared such that both systems exhibit similar dexterity. As a case study, the approach is implemented in the dimensional synthesis of the 3UPS + RPU parallel manipulator. The optimization approach enables obtaining a dexterity space of the mechanism that best matches that of the lower limb. The results are graphically presented, showing the matching areas of both workspaces, verifying the effectiveness of the proposed index. Full article
(This article belongs to the Special Issue Medical and Rehabilitation Robots)
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9 pages, 1095 KB  
Article
Reconfiguration Analysis of a 3-DOF Parallel Mechanism
by Maurizio Ruggiu and Xianwen Kong
Robotics 2019, 8(3), 66; https://doi.org/10.3390/robotics8030066 - 2 Aug 2019
Cited by 4 | Viewed by 7766
Abstract
This paper deals with the reconfiguration analysis of a 3-DOF (degrees-of-freedom) parallel manipulator (PM) which belongs to the cylindrical parallel mechanisms family. The PM is composed of a base and a moving platform shaped as equilateral triangles connected by three serial kinematic chains [...] Read more.
This paper deals with the reconfiguration analysis of a 3-DOF (degrees-of-freedom) parallel manipulator (PM) which belongs to the cylindrical parallel mechanisms family. The PM is composed of a base and a moving platform shaped as equilateral triangles connected by three serial kinematic chains (legs). Two legs are composed of two universal (U) joints connected by a prismatic (P) joint. The third leg is composed of a revolute (R) joint connected to the base, a prismatic joint and universal joint in sequence. A set of constraint equations of the 1-RPU−2-UPU PM is derived and solved in terms of the Euler parameter quaternion (a.k.a. Euler-Rodrigues quaternion) representing the orientation of the moving platform and of the Cartesian coordinates of the reference point on the moving platform. It is found that the PM may undergo either the 3-DOF PPR or the 3-DOF planar operation mode only when the base and the moving platform are identical. The transition configuration between the operation modes is also identified. Full article
(This article belongs to the Special Issue Kinematics and Robot Design II, KaRD2019)
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