Dimensional Optimization of Multi-legged Climbing Robot for Asteriod Exploration Based on Performance Atlas

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Optimal design of an asymmetrical parallel mechanism

Aiming at the aircraft composite skin grinding, a Three-DOF Asymmetrical Mechanism (TAM) is proposed to replace manual grinding. Considering asymmetrical characteristics of the TAM, the linear superposition principle is adopted to derive the total stiffness matrix of the mechanism. The driving force curves of numerical calculation and simulation are almost coincident; thus the correctness of the dynamic model is verified. The global kinematics condition number index is established with the velocity ellipsoid method. Similarly, the global stiffness performance evaluation index is constructed according to the stiffness ellipsoid method. Moreover, a new global acceleration dexterity index is proposed to overcome the limitations of the dynamics ellipsoid method. Based on the above models and performance indices, a new optimization method is proposed which combines both single and multi-objective optimization. Among the method, the multi-objective optimization is carried out with normalized weighted sum algorithm and genetic algorithm. This optimization method can not only improve the convergence speed, but also balance the weight of different performance indices. After optimization, the kinematics, stiffness and dynamics performance are significantly improved by contrast with the initial performance atlas. Therefore, the results indicate the effectiveness of the multi-objective optimization method.

Dimensional Optimization of Multi-legged Climbing Robot for Asteriod Exploration Based on Performance Atlas

Multi-legged climbing robots have appealing applications to extreme terrain on asteroids with the microgravity. The robot usually consists of multiple legs and grippers with hierarchical arrays of microspines. The dimensional optimization of the robot with the complicated structure is still a challenge. This paper proposes a multi-parameter grouping optimization method for the multi- legged climbing robot based on performance atlas. First, the structure of the multi-legged climbing robot is described and the kinematic model is established. Second, four performance evaluation indices of the robot, namely the global conditioning index (GCI), the global stiffness index (GSI), the global transmission index(GTI), and the global adhesion efficiency index (GAEI), are derived from the kinematic equations. Third, 11 dimensional parameters of the robot are catergorized into three groups and the detailed optimization process is poposed. Non-dimensional design spaces of three groups of parameters are established and performance atlases regarding the aforementioned evaluation indices are drawn. Finally, the optimal diemensions of the robot are obtained. Besides, the proposed multi-parameter optimization method can be further applied to other legged robots, and the global adhesion efficiency index can be used to guide the design of other grippers.

Static Decoupling Performance Analysis and Design of Bionic Elbow Joint

The static decoupling performance is closely related to the efficiency of the bionic elbow joint mechanism. The bionic elbow joint has good static decoupling and has high efficiency and carrying capacity. First, the movement structure and characteristics of the elbow joint are analyzed, a kind of bionic elbow joint is proposed, the position inverse solution is deduced, and force Jacobin matrix of the bionic elbow joint is obtained. Second, the static coupling performance evaluation index and the global static coupling performance index are established, the performance atlas are drawn. Thirdly, by use of the Monte Carlo method the structural parameters of the bionic elbow joint are optimized and selected based on the spatial model theory, and a novel the bionic elbow joint is designed based on parameters optimization, and the static decoupling is verified by the simulation experiment of the bionic elbow joint. The analysis results shows the static decoupling performance of the bionic elbow joint is symmetrical, and with the working space of the attitude output angle increases, the static decoupling decreases gradually. Structural parameters and have great influence on the global static decoupling performance. The structural parameters of is 90mm, is 70mm,and is 30mm, the bionic elbow joint has good static decoupling. This paper lays a foundation for further analysis and research of the bionic elbow joint.

Analysis of Kinematics and Design of Structure Parameters for a Bionic Parallel Leg

This paper proposed a novel bionic walking leg which has three branches of 6-DOF, using 3-UPS parallel mechanism as the prototype, it has good advantage of compact structure and strong bearing capacity. Kinematics research of mechanism is very important, the dynamic analysis and the design are based on kinematics analysis. And the kinematics performance of the bionic walking leg is analyzed and the structure parameters are optimized. First, the kinematics transmission equation of the bionic walking leg is established, and using the norm theory the kinematics performance evaluation indexes are defined, and kinematics characteristics are analyzed. Then, application space model theory the structure parameters of the bionic walking leg are designed, and using of the Monte Carlo parameters selecting method based on the global kinematics performance atlas, the optimal structural parameters are given. Analysis results show that kinematics transmission performance indexes display the symmetric distribution of the bionic walking leg, the static platform radius is 120mm, moving platform radius is 50mm, and the height of the static platform and moving platform initial posture is 700mm. Finally, using the optimal structural size parameters, the virtual prototype of the bionic walking leg is designed. So,it has very important significances of theory and engineering to study and open out parallel mechanisms as the leg mechanisms of bionic walking legs.

Kinematics Analysis and Design of a Novel Robot Shoulder Joint

Kinematics research of mechanism is very important, the dynamic analysis and the design are based on kinematical analysis. In this paper, a novel robot shoulder joint based on 3-RRR orthogonal spherical parallel mechanism is proposed, and the kinematics transmission equation of shoulder joint is derived by using the kinematics inverse solution, and Jacobin matrix is established. Then Jacobin matrix is introduced into the global performance index, and the velocity of global performance evaluation index is defined. Furthermore, the shoulder joint dimensions are changed, and the global performance index is analyzed, then a performance atlas is given at the work spaces of shoulder joint with different dimension. It is found that the Jacobin matrix has more important influence on the kinematics performance of the shoulder joint. Having a good kinematics performance, structure dimensions ranges of shoulder joint are gained, thus the evaluation of kinematics of shoulder joint is more comprehensive. Finally, a novel robot shoulder joint is designed with the kinematics performance evaluation index.

Analysis of Static and Optimization of Structural Parameters for a Novel Leg Mechanism

In order to increase wosrkspace and carrying capacity of leg mechanism and improve popularity and adaptability of leg mechanism, a novel mechanism is proposed which has three branches of 6-DOF, which used 3-UPS parallel mechanism as the prototype of the mechanism. The static performance of the leg mechanism is analyzed and the structure parameters are designed. First, the static transmission equation of the leg mechanism is established by using the principle of virtual works which simplifies the calculation process of the leg mechanism. Further, the static performance evaluation index and the global torque performance evaluation index are defined, and the performance atlas of the static performance evaluation index is plotted at the work spaces of the leg mechanism. Moreover, by using of the space model theory, the structural dimensions parameters are optimized of the leg mechanism. Finally, using a set of optimal structural dimensions parameters and the virtual prototype of leg mechanism is designed. The research provides a theoretical basis for further investigation on leg mechanism.

Local Stiffness and Dexterity Analysis of a 3-SPS-S Orientation Fine-Tuning Manipulator for Segment Assembly Robots in Shield Tunneling Machines

This study focus on the stiffness analysis of a three-DOF orientation fine-tuning manipulator for segment assembly robots in shield tunneling machines. In underground space development, shield tunneling machines are widely used in subway tunnels, channel tunnels and other kinds of tunnels. As one of the key sub-devices in a shield tunneling machine, a segment assembly robot is used to automatically form the segment lining. In order to evaluate the operational capacity, an analysis of the inverse kinematics is conducted. The local performance atlas, including stiffness and dexterity, are investigated. The results show that the proposed orientation fine-tuning manipulator has good performances and it can meet the needs.