Chevva Konda Reddy

Controlled Lagrangian systems with gyroscopic forcing and dissipation

This paper describes a procedure for incorporating artificial gyroscopic forces and physical dissipation in the method of controlled Lagrangians. Energy-conserving gyroscopic forces provide additional freedom to expand the basin of stability and tune closed-loop system performance. We also study the effect of physical dissipation on the closed-loop dynamics and discuss conditions for stability in the presence of natural damping. We apply the technique to the inverted pendulum on a cart,a case study from previous papers. We develop a controller that asymptotically stabilizes the inverted equilibrium at a specific cart position for the conservative dynamic model. The region of attraction contains all states for which the pendulum is elevated above the horizontal plane. We also develop conditions for asymptotic stability in the presence of linear damping.

Modeling and Simulation Methodology for Impact Microactuators

Micro or nano distance manipulations are of prime importance in the MEMS industry. Microdevices are ideal for micropositioning systems due to their small size. Microactuators used to produce small displacements would need large actuation forces and a long driving distance. This would require large voltages to produce the desired forces. Actuators based on impulsive forces provide a solution to this problem. Many impact microactuators have been designed and fabricated in the past decade. Impacts are a source of nonlinearity and a careful study of the dynamics is essential in order to ensure consistent performance of the device. Currently, the state of the art lacks a robust design tool for such devices. The primary goal of this paper is to present a comprehensive modeling and simulation methodology for impact microactuators. The present study will aid in a more robust and consistent impact microactuator design.

Ground Target Localization and Tracking in a Riverine Environment from a UAV with a Gimbaled Camera

This paper develops a framework for ground target localization and tracking in a riverine environment from a UAV with a two axis gimbaled camera. Accurately determining the position of targets is a critical technology for reconnaissance, cooperative multi-vehicle formation operation, and path-planning through hostile environments. We assume that the UAV is operating in a riverine environment, which implies that the altitude of the target is a known constant. This simplification removes the range ambiguity, and target positions can be uniquely determined from pixel coordinates in a single image. An extended Kalman filter (EKF) and an unscented Kalman filter (UKF) are developed to localize the inertial position of a target identified by pixel coordinates in an image. In Monte Carlo simulations, the performance of the filters is virtually identical, and localization accuracy is limited by uncertainty in the aircraft position and orientation. Flight test results verify the performance of the target localization filters. In addition, an estimation-based approach is used to develop a gimbal control law that drives the target to the center of the camera field of view. In combined simulations with the EKF, the control law maintains the target in the center of the camera field of view while tracking a moving target from a maneuvering aircraft.

Energy shaping for vehicles with point mass actuators

This paper describes the application of the method of controlled Lagrangians to vehicles with moving point mass actuators. This class of systems includes certain spacecraft, atmospheric re-entry vehicles, and underwater vehicles. Two examples are presented. The first example is a spinning disk, a simplified, planar version of a spacecraft spin stabilization problem. The second example is an underwater vehicle moving in the horizontal plane

Bifurcations and Chaotic Dynamics in an Electrostatically Actuated Impact Microactuator: A Numerical Exploration

We study the dynamics of an electrostatically driven impact actuator. As the name suggests, the impact actuator uses impacts between its moving elements to produce nano-displacements. While on one hand, impact actuators provide a way to produce small displacements with moderate actuation voltages, on the other hand impacts make the underlying dynamics nonsmooth. Impacts are a source of nonlinearity and a careful study of the dynamics is essential in order to ensure a consistent performance of the device. We model the impact microactuator reported by Mita and associates using a two-degree-of-freedom system. A simple impact law based on the coefficient of restitution is used. Our results show that the dynamics can be very complex as the system parameters are varied. Namely, as the amplitude and frequency of excitation are varied, the system exhibits period doubling and grazing bifurcations onto the route to chaos.Copyright