In this article, explicit expressions for the frequency equation, mode shapes, and orthogonality of the mode shapes of a Single Flexible-link Flexible-joint manipulator (SFF) are presented. These explicit expressions are derived in terms of non-dimensional parameters which make them suitable for a sensitivity study; sensitivity study addresses the degree of dependence of the system’s characteristics to each of the parameters. The SFF carries a payload which has both mass and mass moment of inertia. Hence, the closed-form expressions incorporate the effect of payload mass and its mass moment of inertia, that is, the payload mass and its size. To check the accuracy of the derived analytical expressions, the results from these analytical expressions were compared with those obtained from the finite element method. These comparisons showed excellent agreement. By using the closed-form frequency equation presented in this article, a study on the changes in the natural frequencies due to the changes in the joint stiffness is performed. An upper limit for the joint stiffness of a SFF is established such that for the joint stiffness above this limit, the natural frequencies of a SFF are very close to those of its flexible-link rigid-joint counterpart. Therefore, the value of this limit can be used to distinguish a SFF from its flexible-link rigid-joint manipulator counterpart. The findings presented in this article enhance the accuracy and time-efficiency of the dynamic modeling of flexible-link flexible-joint manipulators. These findings also improve the performance of model-based controllers, as the more accurate the dynamic model, the better the performance of the model-based controllers.

No abstract

An efficient synthesis of 2,4-diarylpyrroles is described.Heating a mixture of a 4-nitro-1,3-diarylbutan-1-one and ammonium acetate in the presence of morpholine and sulfur afforded the corresponding 2,4-diarylpyrroles in excellent yields.

No abstract

A fully integrated navigation strategy of a wheeled mobile robot in farm settings and off-road terrains is described here. The proposed strategy is composed of four main actions which are: sensor data analysis, obstacle detection, obstacle avoidance, and goal seeking. Using these actions, the navigation approach is capable of autonomous row-detection, row-following and path planning motion in outdoor settings such as farms. In order to drive the robot in off-road terrain, it must detect holes or ground depressions (negative obstacles), that are inherent parts of these environments, in real-time at a safe distance from the robot. Key originalities of the proposed approach are its capability to accurately detect both positive (over ground) and negative obstacles, and accurately identify the end of the rows of trees/bushes in farm/orchard and enter the next row. Experimental evaluations were carried out using a differential wheeled mobile robot in different farm settings. The mobile robot, used for experiments, utilizes a tilting unit which carries a laser range finder to detect objects in the environment, and a RTK-DGPS unit for localization. The experiments demonstrate that the proposed technique is capable of successfully detecting and following rows (path following) as well as robust navigation of the robot for point-to-point motion.