Papers by Keyword: Parallel Mechanism

Abstract: In order to help patients with wrist injuries to carry out recovery training, a simple and portable parallel 3-RSR wrist rehabilitation mechanism was introduced in order to achieve the expected therapeutic effect. Firstly, the parallel 3-RSR wrist rehabilitation mechanism is described. Taking the parallel mechanism as the research object, the degree of freedom is calculated and the pose is solved by analytical method, which verifies the rationality of the mechanism motion. Then, based on the boundary search method, the reachable workspace of the parallel wrist rehabilitation mechanism is analyzed, and the relevant workspace map is drawn. Finally, considering the reasonable optimization of the structural size of the workspace, the results show that the optimized reachable attitude workspace is significantly larger than the initial workspace. This study provides a theoretical reference for the ontology design of rehabilitation institutions.

Abstract: This paper presents the development of a three degrees-of-freedom (DOF) compliant parallel mechanism (CPM) with spatial motions, i.e., two rotations about the X and Y axes and one translation along the Z axis (θX-θY-Z). Such CPM is synthesized by the improved beam-based structural optimization method. The obtained results suggest that the proposed CPM is able to produce totally decoupled motions illustrated by a diagonal stiffness/compliance matrix, a large workspace of ±22,5 degrees × ±22,5 degrees × ±9,6 mm, fast dynamic response with the first natural frequency of ~100 Hz and high stiffness ratios between actuating and non-actuating directions (with stiffness ratios of 6210 and 2706 for translations and rotations respectively). Finite element analysis (FEA) is employed to evaluate the actual performance of the synthesized CPM with Ti6Al4V material in order to verify the correctness of the synthesis method. The effectiveness of the improved beam-based structural method is demonstrated by the good agreement between the simulation and predicted data with the highest deviations are 8.8% and 6.7% for the stiffness and dynamic properties respectively. In addition, some comparisons are carried out to investigate the advantages as well as disadvantages of the proposed CPM and existing designs. The comparison results show that the 3-DOF CPM presented in this paper has many merits compared to its counterparts. It can be used in various applications, e.g., the micro/nano positioners and alignment systems in precision engineering field due to its good mechanical properties (high stiffness ratios and fast dynamic behavior), large work range and fully-decoupled motion characteristic.

Abstract: The objective of kinematic synthesis is to determine the mechanism dimensions such as link lengths, positions or joint coordinates, in order to approximate its output parameters such as link positions, trajectory points, and displacement angles. Kinematic synthesis is classified into three categories: function generation, path generation, and motion generation. This paper is dedicated only to path generation. As the number of trajectory points increases, analytical methods are limited to obtain precisely mechanism solutions. In that case, numerical methods are more efficient to solve such problems. Our study proposes an improved heuristic algorithm applied to four-bar mechanism path-generation. The objective of this work is to find optimum dimensions of the mechanism and minimize the error between the generated trajectory and the desired one, taking into consideration constraints such as: Grashof condition, transmission angle, and design variables constraints. Finally, our results are compared with those found by other evolutionary algorithms in the literature.

Abstract: In order to improve ability of walking and crossing the barriers , increase the carrying capacity, and enhance its popularity and adaptability, a novel lower limb bionic leg is presented based on 3-UPS parallel mechanism, which has the characteristics of movement flexible and strong adaptability. It is very important analysis to statics of lower limb bionic leg. Firstly, statics equation of the lower limb bionic leg of driving force and output force is established based on virtual work principle. Secondly, static performance evaluation index is defined and the evaluation index distribution map is drawn. The relationship between the structure parameters and the static performance evaluation indexes is analyzed, obtained the influence of structure parameters on the static performance evaluation index, and a set of reasonable structural parameters is selected. The circum-radius of moving platform is 50mm, the circum-radius of the static platform is 150mm, the moving platform angle and static platform angle are equal to 60°, the lower limb bionic leg has the best load carrying capacity. Thirdly, the lower limb bionic leg is designed based on statics analysis and structure parameters optimization. Analysis results show that the lower limb bionic leg has good static transmission performance at the initial position, and the static transmission performance decreases with increasing turning workspace. The static transmission performance decreases with z axle displacement increasing. The analysis results laid a foundation for further analysis and research of the lower limb bionic leg.

Abstract: Mechanism kinematic influence coefficient deeply reflects the essence of the kinematics and dynamics mechanism, analysis of the problems of many institutions can use the influence coefficient of clear and clearly expressed. In this paper, with less degree of freedom parallel mechanism as the research object, through the virtual mechanism method to derive one or two order influence coefficient matrix, based on the analysis of the mechanism and influence of speed and acceleration coefficient matrix. Finally, the precision of the method for solving the kinematics is proved by examples of numerical analysis.

Abstract: Shift manipulator requires the transmission shift lever end Chinese characters ‘Wang’ motion, this paper proposes a kind of 2-Dof asymmetric spherical parallel mechanism to realize the movement. The structure characteristic and the trajectory of the manipulator are described. The position inverse solution of the 2-Dof spherical parallel mechanism is obtained by inverse kinematics analysis. Inverse kinematics simulation of the parallel mechanism is proposed finally.

Abstract: It’s one of the research difficulties of parallel mechanism because of the multi-DOF and complex solution of workspace. Workspace of the 6-UPS parallel mechanism was studied based on the envelope method. It searched the boundary of workspace by three-dimensional research method directly on the premise of satisfying the constraint conditions, which is based on the inverse kinematic. According to the multi-DOF, the orientation space was fixed to simplify the workspace parameters, and searched for the envelope surface of the position space. The relationship that the increasing orientation space leads to the reduction of the position space is reached by researching the position space under different orientation space.

Abstract: This paper is contrary to the seat multi-dimensional problem basing on task space. Using double triangle steward parallel mechanism as the main structure of the seat suspension, according to the sensitive frequency range and the natural frequency of vehicle body, we optimize the design of the suspension system. Research shows that the optimized design of the double triangle Stewart parallel suspension seat suspension system to ensure vertical, pitch, roll three of the more important natural frequency both directions away from the vehicle's natural frequency, but also avoid the human body sensitive frequency range.

Abstract: The paper study position positive solution method based on 6-TPS parallel mechanism, and establish general kinematics model of 6-TPS parallel mechanism, gives the numerical method of positive solution based on a kind of position, deduced the forward position solution iteration format, and use MATLAB for the 6-TPS parallel mechanism kinematics to simulation, results show that solving program has stability, fast, effective.

Abstract: Position equation of 3-RRC parallel mechanism is established and its position direct and inverse solution is solved. The mechanism rate equation is established and its kinematics analysis is done. The result shows that it is easier to solve the kinematics inverse solution of the parallel mechanism.