查看更多>>摘要：This paper presents an approach for designing a novel coaxial indexing mechanism composed of conjugate cams and parallelogram linkage. Compared with the conventional indexing cam mechanisms, the mechanism has a more compact mechanical structure thanks to the coaxial input/output shaft arrangement, and produces higher number of stops at the same speed of input shaft. Firstly, on the basis of systematically describing the working principle of the mechanism, the conjugate cam profiles, curvature radius of cam profiles and meshing equation between the cam and roller are established. Then, the main factors affecting the geometric characteristic and the force transmission performance of the mechanism are analyzed. The dimensional synthesis of this mechanism is further researched. Finally, prototypes are developed and experiment is performed to verify the feasibility of the mechanism. The research provides a train of new thoughts for the mechanical design of indexing mechanisms.
查看更多>>摘要：Among the robots, compared with wheeled robots and crawler robots, legged robots with characteristics of discontinuous support are more suitable for walking in the unknown and complex environment. Hydraulic drive has many advantages, such as fast response and high power to weight ratio, etc. [1-4] Combining the advantages of legged robots and hydraulic drive, the hydraulic driven legged robot can show great potential for application in the field of rescue and heavy cargo transportation, and has been a research hotspot in various countries. In the motion control of legged robot, it is necessary to detect the real-time contact force generated between the foot end and the ground [5]. There are two methods usually used to obtain the foot end contact force through sensor measuring. One method is to directly measure through the multi-dimensional force sensor attached to the foot end of the robot [6-8]. The other method is to indirectly obtain the foot end contact force through the one-dimensional force sensor of hydraulic drive unit (HDU) combined with statics [9-11]. Generally, multi-dimensional force sensors are expensive, have a short service life and are easily damaged in the actual application [12]. Therefore, the latter method is widely adopted to obtain the foot end contact force of the robot.
查看更多>>摘要：Geometric accuracy is the direct embodiment of the assembly deviation of a precision motion system. This paper proposes a novel methodology for predicting the geometric accuracy induced by assembly deviation of a precision motion system and tracing the sensitivity of the assembly deviation with respect to geometric accuracy terms. The small displacement torsor is first characterized as the periodic function of the assembly deviation and dimension parameters of the components of ball-screw feeding system, the vector constraint relationship of the parallel assembly of the feeding system is established, and a spatial propagate model of the assembly deviation for the feeding system is then constructed. A random balance design and Fourier amplitude sensitivity test method are introduced to trace the effect of each assembly feature on the geometric accuracy. The experiments were performed on a single-axis feeding system to verify the effectiveness of the proposed method. This method has the advantage that the mapping relationship between the assembly deviation and geometric accuracy with respect to the instructed position is quantified, and the assembly and adjustment is pertinent to the traceability analysis. The model has the potential to accurately allocate and maintain the machining centre.
NSTL
Elsevier