Topological Design Methods for Mecanum Wheel Configurations of an Omnidirectional Mobile Robot

A simple and efficient bottom-roller axle intersections approach for judging the omnidirectional mobility of the Mecanum wheel configuration is proposed and proved theoretically. Based on this approach, a sub-configuration judgment method is derived. Using these methods, on the basis of analyzing the possible configurations of three and four Mecanum wheels and existing Mecanum wheel configurations of robots in practical applications, the law determining wheel configuration is elucidated. Then, the topological design methods of the Mecanum wheel configurations are summarized and refined, including the basic configuration array method, multiple wheels replacement method, and combination method. The first two methods can be used to create suitable multiple-Mecanum-wheel configurations for a single mobile robot based on the basic Mecanum wheel configuration. Multiple single robots can be arranged by combination methods including end-to-end connection, side-by-side connection, symmetrical rectangular connection, and distributed combination, and then, the abundant combination configurations of robots can be obtained. Examples of Mecanum wheel configurations design based on a symmetrical four-Mecanum-wheel configuration and three centripetal configurations using these topological design methods are presented. This work can provide methods and a reference for Mecanum wheel configurations design.

Numerical investigation on the flow field of a modified vortex spinning system for producing core-spun yarns

A modified vortex spinning technology, which produces core-spun yarns by means of a tangentially injected swirling airflow, is of great prospect in view of its production rate and yarn structure. In this paper, a numerical study based on computational fluid dynamics is presented to investigate the characteristics of the flow field of this system. In the simulation, the effect of the rotating front rollers on the flow field is taken into consideration. Flow characteristics inside the spinning nozzle, flow field of the front rollers, and streamline patterns have been revealed. The results show that a high-speed swirling flow is generated in the near-wall region in the nozzle chamber due to the ejection of air-jets from the tangential injectors. An asymmetric sub-pressure zone is formed in the core region of the nozzle chamber where the interactions of the high-speed swirling flow and three streams of secondary flows generate three vortices. Airflows in the vicinity of the front rollers generally converge toward the nozzle entrance from all directions except those in the boundary layer of the front roller surfaces, which is helpful for the delivery of fibers into the nozzle. A vortex is formed above the top roller and another beneath the bottom roller. The results of the streamline patterns show that the flow characteristics of the modified vortex spinning can facilitate the formation process of the core-spun yarn, which presents a qualitative explanation to the dynamic behavior of the fibers that was experimentally obtained.

Simulating three-dimensional dynamics of flexible fibers in a ring spinning triangle: chitosan and cotton fibers

A three-dimensional particle-level simulation method is developed to simulate fiber dynamics in the ring spinning triangle. The fiber is modeled as a chain of beads connected through massless rods, and its flexibility is defined by the stretching, bending and twisting displacements. As the application of the proposed approach, the effects of the chitosan (CS)/cotton (CT) fiber initial position and length on fiber motion and yarn properties are discussed. The deflections of CS fibers along the roller axis are larger compared with those of CT fibers, which will lead to CS migrating outwards in CS/CT blended yarn. The short CS fibers (22 mm) will move toward the top roller surface and shift quickly out of the roller nip, and thus yarn strength is lower. The tailing end of the longest CS fiber (46 mm) will drift off the roller nip, which makes little or no contribution to the yarn strength. For 38 mm length CS fiber, it moves toward the bottom roller surface and is bound into the roller nip, and thus can produce the highest tenacity CS/CT blended yarns. The simulation results agree with the spinning experimental data reported by other researchers.

An Investigation of Forces during Roller Forming Process

The tubular sections or shells for forming channels, drums, tanks or pressure vessel are manufactured by bending plates generally through three-roller bending machine and then welding the ends of bent plate to form a cylinder or cone. Force exerted on rollers during bending is one of the important criteria which must not exceed the capacity of bending machine. Secondly, Total bender capacity must be utilised during bending of desired curvature, which reduces number of passes and hence time required to attain desired curvature. Thus, it necessary to estimate the forces during bending, based on the roller position, so that it does not exceeds the bender capacity and simultaneously reduces number of passes. In this regards, some analytical models are available to predict the forces during three roller bending process with assumption of constant bend radius during bending. In fact, the radius continuously changes during bending operation which affects the magnitude and the direction of the forces exerted on the roller. An attempt is made to simulate the roller bending using FEA. Variation of curvature of plate and effect of various parameters such as plate thickness, bottom roller inclination and top roller inclination on bending forces during cylindrical and conical bending operation are studied using FEA analysis.

Comparison of Analytical Models of Force Prediction during Dynamic Bending Stage for 3-Roller Conical Bending Process

Conical bending process using three rollers with different configurations is a widely used process for manufacturing conical sections and shells in the industries. The process involves static as well dynamic stages. For optimum design of the machine, accurate analytical model of the force prediction is required for static as well dynamic bending stages. In this paper the analytical models considering three different stress conditions have been compared with the experimental results. The observations of the comparison have been reported. It is concluded that for higher bottom roller inclination, the shear stress has to be considered for evaluation of bending force whereas for lower bottom roller inclination it can be neglected.

The Machining Process and Stress-Strain Analysis of the Imprinter Bottom Roller Based on FEM

The imprinter bottom roller is under very high linear pressure during the work, which often causes wear and damage between bottom roller and anvil roller. Traditionally, the extra strength design method is frequently used in the design of imprinter bottom roller, which leads to the waste of materials and increase of weights. So, reasonable processing craft and appropriate theoretical analysis method should be adopted to improve the manufacturing of bottom roller and make the material strength into full use, in the condition of meeting the structure safety standard. This paper gives a brief analysis of the process craft of bottom roller and uses finite element technique to give the bottom roller numerical simulation and FEA of its deflection and strength. The results show that: in the process of work, the distribution of stress changes largely and unevenly. The stress and deformation in middle part prove the largest with decreasing to both sides successively. The imprinter bottom roller produces a maximum displacement of 0.0516 mm, which meets the work requirements.

The Research of Re-Winder Bottom Roller Feed-Forward Control Tactic

As the last working procedure in the paper production process, re-winder control technology is crucial to the quality of finished paper scroll. To obtain the paper scroll with inner tight and outer loose, the control of bottom rollers must satisfy the double closed-loop feedback control with torque difference. While the feedback control exists time-delay and may cause the slowness of system response. Here on the basis of re-winder production process and control requirements, a novel feed-forward control tactics is proposed to combine with feedback control. According to the compensation of feed-forward control, rapid system response is obtained and system performance is improved. And corresponding simulation shows the validity and feasibility of the feed-forward control tactics.