The Duplex Pendulum Seismograph

The Earss Digital Seismograph : System Description and Field Trials

An earthquake detection and recording system known as EARSS has been developed for permanent seismograph stations and temporary field installations. It records three components of ground motion with a dynamic range of 120 dB. A frequency-domain algorithm detects earthquakes and initiates the recording of data on magnetic tape. Alternatively, EARSS can record data continuously, for preselected p...

The Lunar Surface Gravimeter as a Lunar Seismograph

Controlling the Inverted Pendulum

The strategies involved in swinging up and balancing the inverted pendulum are discussed. The nonlinear swing-up controller drives the system input according to the energy of the pendulum. The balancing controller is a digital linear quadratic regulator that is based on a model of the plant that has been linearized about the pendulum’s upright equilibrium position. Relays with hysteresis are em...

The Magnetic Pendulum

Nonlinearity is a profound concept in the study of physical systems. The characteristics of seemingly very simple systems may turn out to be extremely intricate and practically unpredictable due to the nonlinearities associated with them. The study of chaos–that essentially has its basis in nonlinear dynamics–begins with the study of such simple systems. The magnetic pendulum can be one such sy...

The Inverted Pendulum

Over the course of a few decades, the pendulum problem has become a prime example in the instruction of many concepts in linear and nonlinear dynamics. Particularly, the inverted pendulum has been illuminating in the areas of dynamical stability and control. Our intent with this dynamics problem was to explore the stability of the inverted state while vertically driving the pivot point. Forcing...