Direct Tail Actuation vs Internal Rotor Propulsion in Aquatic Robots

It is common for scientists to look to nature for inspiration in developing robots. Many times biological creatures outperform even the best man made robots. We will be focusing on aquatic locomotion of robots inspired by the locomotion of fish. There are two different means of propulsion of the robots tested in this paper. One model of the robot is propelled only through the oscillations of an internal momentum wheel, while the other is propelled by the direct actuation of a tail structure. Both of these models achieve net propulsion through vortex shedding past their trailing edge, and two of the robots locomotion is also aided by the change in shape from either a passive or active tail. Tests were conducted to highlight the locomotion performance differences of the two different means of locomotion.

Orientation Control Using Oscillating Momentum Wheels

This paper addresses the problem of controlling a rigid body’s orientation by actuating sinusoidal oscillations of internal momentum wheels. We consider the rotational dynamics of a rigid body having three momentum wheels (one for each body-fixed axis) that are attached to the body by springs. Each wheel is actuated by an internal sinusoidal torque of fixed frequency. The frequency of all sinusoidal torques is equal, but the amplitudes and phases can be varied independently. We analyze the inverse-dynamics problem of determining the amplitudes and phases for each sinusoidal torque such that a desired orientation is achieved. We then present two closed-loop orientation controllers based on this analysis. Numerical simulations demonstrate the effectiveness of the control techniques.

Non-anticommutative quantum gravity

A calculation of the one loop gravitational self-energy graph in non-anticommutative quantum gravity reveals that graviton loops are damped by internal momentum dependent factors in the modified propagator and the vertex functions. The non-anticommutative quantum gravity perturbation theory is finite for matter-free gravity and for matter interactions.

The Multitude and the Many-Headed Hydra: Autonomist Marxist Theory and Labor History

The autonomist Marxist critique of determinist Marxism offers even more valuable insights for labor historians than that mounted by earlier antideterminists, such as Sartre and Thompson, who emphasized proletarian agency to counter determinist orthodoxy in which the accumulative logic of capital unilaterally shapes the world. Autonomist Marxism is more far-reaching. It places labor at the very beginning of the labor-capital dialectic: Labor can exist independently of capital, but capital needs to command labor to ensure profit; therefore, capitalist development does not occur due to internal momentum but in reaction to labor's tendency to unloose itself from capital. Linebaugh and Rediker offer a similar hypothesis in exploring the myth of the many-headed hydra—and demonstrate the fruitfulness of such an approach. By contrast, the notion of the multitude in Hardt and Negri'sEmpirehas not been well received by labor historians due to its inexplicable abstraction when read in isolation from other autonomist texts. This article attempts to rescue the ideas of autonomist Marxist philosophers, especially Toni Negri, from the enormous condescension of labor history.