The recent advent of angular optical trapping techniques has allowed for rotational control and direct torque measurement on biological substrates. Here we present a method that increases the versatility and flexibility of these techniques. We demonstrate that a single beam with a rapidly rotating linear polarization can be utilized to apply a constant controllable torque to a trapped particle ...

The control is designed from the condition of decreasing Lyapunov function on the trajectories of the closed loop system. This control may be chosen a priori bounded. As example we consider the rotational system with nonlinear dissipative force and disturbances which periodically depends on the angle. We consider also the problem of evaluating unknown external periodic torque of this rotational...

In this paper the problem of variable admittance control in human-robot cooperation tasks is investigated, considering rotational motion of the robot’s end-effector. A Fuzzy Model Reference Learning algorithm is used to determine online the appropriate virtual damping of the admittance controller with partial state representation of the system. The learning algorithm is trained according to the...

Methods for exerting and measuring forces on single molecules have revolutionized the study of the physics of biology. However, it is often the case that biological processes involve rotation or torque generation, and these parameters have been more difficult to access experimentally. Recent advances in the single-molecule field have led to the development of techniques that add the capability ...

A method of systematically controlling the rotational state of a sample levitated in a high vacuum using the photon pressure is described. A zirconium sphere was levitated in the high-temperature electrostatic levitator and it was rotated by irradiating it with a narrow beam of a high-power laser on a spot off the center of mass. While the laser beam heated the sample, it also rotated the sampl...

In living cells, a fluctuating torque is exerted on the nuclear surface but the origin of the torque is unclear. In this study, we found that the nuclear rotation angle is directionally persistent on a time scale of tens of minutes, but rotationally diffusive on longer time scales. Rotation required the activity of the microtubule motor dynein. We formulated a model based on microtubules underg...

nAture methods | ADVANCE ONLINE PUBLICATION | single-molecule measurements of dnA twist and extension have been used to reveal physical properties of the double helix and to characterize structural dynamics and mechanochemistry in nucleoprotein complexes. however, the spatiotemporal resolution of twist measurements has been limited by the use of angular probes with high rotational drag, which p...

We consider the rotational motion of an elongated nanoscale object in a fluid under an external torque. The experimentally observed dynamics could be understood from analytical solutions of the Stokes equation, with explicit formulae derived for the dynamical states as a function of the object dimensions and the parameters defining the external torque. Under certain conditions, multiple analyti...

In this research, the effects of parameters include tool rotational and traverse speeds were investigated on heat generation and material flow during friction stir welding of Ti-6Al-4V alloy with computational fluid dynamics (CFD) method. Simulation results showed that with increasing of tool rotational and decreasing tool traverse speed, the more frictional heat generates which causes formatio...