Circular motion

About: Circular motion is a research topic. Over the lifetime, 2465 publications have been published within this topic receiving 28961 citations.

Strapdown Inertial Navigation Integration Algorithm Design Part 1: Attitude Algorithms

Abstract: This series of two papers provides a rigorous comprehensive approach to the design of the principal software algorithmsutilized in modern-day strapdown inertial navigation systems: integration ofangular rateinto attitude, acceleration transformation/integration into velocity, and integration of velocity into position. The algorithms are structured utilizing the two-speed updating approach originally developed for attitude updating in which an analytically exact equation is used at moderate speed to update the integration parameter (attitude, velocity, or position) with input provided from a high-speed algorithm measuring dynamic angular rate/acceleration effects within the parameter update time interval [coning for attitude updating, sculling for velocity updating, and scrolling (writer’ s terminology ) for high-resolution position updating]. The algorithm design approach accounts for angular rate/specie c force acceleration measurements from the strapdown system inertial sensors as well as rotation of the navigation frame used for attitude referencing and velocity integration. This paper, Part 1, dee nes the overall design requirement for the strapdown inertial navigation integration function and develops direction cosine and quaternion forms for the attitude updating algorithms. Part 2 [Savage, P. G., “ Strapdown Inertial Navigation Integration Algorithm Design Part 2: Velocity and Position Algorithms,”Journal of Guidance, Control, and Dynamics (to be published )] deals with design of the velocity and position integration algorithms. Although Parts 1 and 2 often cover fundamental inertial navigation concepts, the material presented is intended for use by the practitioner who is already familiar with basic inertial navigation concepts.

Stabilization of Planar Collective Motion: All-to-All Communication

Abstract: This paper proposes a design methodology to stabilize isolated relative equilibria in a model of all-to-all coupled identical particles moving in the plane at unit speed. Isolated relative equilibria correspond to either parallel motion of all particles with fixed relative spacing or to circular motion of all particles with fixed relative phases. The stabilizing feedbacks derive from Lyapunov functions that prove exponential stability and suggest almost global convergence properties. The results of the paper provide a low-order parametric family of stabilizable collectives that offer a set of primitives for the design of higher-level tasks at the group level

Stabilization of Planar Collective Motion With Limited Communication

Abstract: This paper proposes a design methodology to stabilize relative equilibria in a model of identical, steered particles moving in the plane at unit speed. Relative equilibria either correspond to parallel motion of all particles with fixed relative spacing or to circular motion of all particles around the same circle. Particles exchange relative information according to a communication graph that can be undirected or directed and time-invariant or time-varying. The emphasis of this paper is to show how previous results assuming all-to-all communication can be extended to a general communication framework.

Effect of vision and stance width on human body motion when standing: implications for afferent control of lateral sway.

Abstract: 1. Measurements of human upright body movements in three dimensions have been made on thirty-five male subjects attempting to stand still with various stance widths and with eyes closed or open. Body motion was inferred from movements of eight markers fixed to specific sites on the body from the shoulders to the ankles. Motion of these markers was recorded together with motion of the point of application of the resultant of the ground reaction forces (centre of pressure). 2. The speed of the body (average from eight sites) was increased by closing the eyes or narrowing the stance width and there was an interaction between these two factors such that vision reduced body speed more effectively when the feet were closer together. Similar relationships were found for components of velocity both in the frontal and sagittal planes although stance width exerted a much greater influence on the lateral velocity component. 3. Fluctuations in position of the body were also increased by eye closure or narrowing of stance width. Again, the effect of stance width was more potent for lateral than for anteroposterior movements. In contrast to the velocity measurements, there was no interaction between vision and stance width. 4. There was a progressive increase in the amplitude of position and velocity fluctuations from markers placed higher on the body. The fluctuations in the position of the centre of pressure were similar in magnitude to those of the markers placed near the hip. The fluctuations in velocity of centre of pressure, however, were greater than of any site on the body. 5. Analysis of the amplitude of angular motion between adjacent straight line segments joining the markers suggests that the inverted pendulum model of body sway is incomplete. Motion about the ankle joint was dominant only for lateral movement in the frontal plane with narrow stance widths (< 8 cm). For all other conditions most angular motion occurred between the trunk and leg. 6. The large reduction in lateral body motion with increasing stance width was mainly due to a disproportionate reduction in the angular motion about the ankles and feet. A mathematical model of the skeletal structure has been constructed which offers some explanation for this specific reduction in joint motion.(ABSTRACT TRUNCATED AT 400 WORDS)