Universal motion of mirror-symmetric microparticles in confined Stokes flow

Comprehensive understanding of particle motion in microfluidic devices is essential to unlock additional technologies for shape-based separation and sorting of microparticles like microplastics, cells, and crystal polymorphs. Such particles interact hydrodynamically with confining surfaces, thus altering their trajectories. These hydrodynamic interactions are shape dependent and can be tuned to guide a particle along a specific path. We produce strongly confined particles with various shapes in a shallow microfluidic channel via stop flow lithography. Regardless of their exact shape, particles with a single mirror plane have identical modes of motion: in-plane rotation and cross-stream translation along a bell-shaped path. Each mode has a characteristic time, determined by particle geometry. Furthermore, each particle trajectory can be scaled by its respective characteristic times onto two master curves. We propose minimalistic relations linking these timescales to particle shape. Together these master curves yield a trajectory universal to particles with a single mirror plane.

The Motion Beyond Sense

This paper first explores the relationship between cognition and motion. Our typical cognitive mode, based on sensory forms, is integrated and, therefore, non-motion in nature. This highlights stability and relativity for practical cognitive needs, but at the same time prevents us from developing cognition of the complete form of motion. The result is a fundamental cognitive barrier for us to understand motion. By discovering the underlying cognitive principles, however, we can revise the cognitive process and redevelop the cognitive mode to meet the purpose of direct cognition of motion. Based on this newly developed cognitive mode, we will learn motion features directly and understand motion laws and principles, to explain natural phenomena and establish wide-range connections between them. These include the underlying principles of motion, gravity, the creation of matter and material forms, universal motion, and spacetime.

Application of transverse functions to control differentially driven wheeled robots using velocity fields

This paper deals with control of a nonholonomic unicycle-like robot in a cluttered environment with static obstacles. The proposed solution is based on a combination of a universal motion controller taking advantage of transverse functions with a navigation velocity field determining a path in a free task space. The motion controller is used to imitate an omnidirectional planar kinematics such that nonholonomic constraints become hidden for a navigation layer. Then it is possible to generate vector fields which govern motion of the omnidirectional frame. The controller using the transverse function is discussed in depth. In particular, a possible parametrization of this function is considered and analysis of an augmented dynamics is provided for different motion patterns. Next, construction of obstacles and potential design for star-like shapes are presented. The navigation algorithm is verified experimentally and the results are discussed.

Calculation Method for Rocking Die Motion Track in Cold Orbital Forging

In cold orbital forging, the rocking die performs complex motions on the components and the intervention between them cannot emerge, otherwise the components cannot be shaped successfully. Calculating the rocking die motion track is essential to determining whether there is intervention between the rocking die and components. Thus, this study aims to comprehensively investigate the rocking die motion track in cold orbital forging. For this purpose, an analytical model for calculating the rocking die motion track is first established. Then a universal motion track equation that can denote any geometry and kinematics relationships between the rocking die and components is obtained using this analytical model. To verify the validity of this motion track equation, an experimental study is conducted. The result shows that the calculated rocking die motion track is consistent with the experimental one. According to this valid motion track equation, the characteristics of the rocking die motion track are revealed. Finally, to apply the calculated rocking die motion track for analyzing the intervention between the rocking die and components, two case studies are examined.

Research of an Open CNC System for MRF Machine Tool Based on UMAC

In order to use magnetorheological finishing (MRF) to accomplish ultra-precision machining of complex curve surfaces, an open computer numerical control (CNC) system based on universal motion and automation controller (UMAC) has been developed. The paper introduces the hardware structure of the system, elucidates the control algorithm and parameters tuning of PID + velocity/acceleration feed-forward + notch filter, and explains the design of a friendly human-machine interface (HMI) to satisfy the need of actual manufacturing and complicated numerical control. With the open CNC system, a 4mm-diameter circle is polished on the MRF experimental prototype with the contour error of 1.67% and the surface roughness Ra of 1.4nm. Experimental results prove that the open CNC system for the MRF machine tool meets the requirements of ultra-precision machining.