Victor S. Trent

A genetic algorithm predictor for vehicular rollover

A model-based genetic algorithm predictor is developed to estimate the potential for vehicular rollover. The model is based on a 1997 Jeep Cherokee Sports Utility Vehicle (SUV) and is discretized at 100 Hz. Preliminary simulation results indicate rollover prediction of 400 ms in advance of the actual event. Such advance prediction would then allow the use of active anti-roll algorithms and systems such as differential braking or active suspension control.

A Predictive Rollover Sensor

A simple system composed of a single axis accelerometer or inclinometer, an inexpensive solid-state rate gyro and a micro-controller is explored as a predictive rollover sensor. Inclinometers or accelerometers alone cannot predict rollover due to the effects of lateral forces during turns. These forces cause such systems to over estimate the roll angle of the vehicle by a wide margin, resulting in false alarms and rendering them useless. Inexpensive solid-state rate gyros are likewise not up to the task because of large variations in the bias both under temperature and parametric variations. Using both of these sensors along with proprietary algorithms similar to those developed for the Archangel Air Data Attitude Heading Reference System (ADAHRS) for aviation, a successful predictive system can be constructed. Using Fuzzy Logic Adaptive Signal Processing (FLASP) algorithms, the drift is removed from the gyro in real time without extensive calibrations or modeling and the effects of lateral forces are removed from the accelerometer/inclinometer. This results in a system possessing redundant and, therefore, highly reliable information concerning both the roll rate and angle of the vehicle. The efficacy of this method is clearly demonstrated by the flight proven Archangel ADAHRS used in aircraft. In the system, the combination of the roll rate and angle are used to predict an impending rollover up to 500 ms in advance. This information used in conjunction with an active yaw control system could be used to prevent the rollover. Failing prevention, the information could be used to deploy airbags to minimize passenger danger.

Software algorithms in air data attitude heading reference systems

An introduction to air data attitude heading reference systems (ADAHRS) is presented along with the developments and discussion of software algorithms used in such systems. Both Kalman filtering and fuzzy logic adaptive signal processing are presented and discussed. Quaternions are used in this paper as the basis for the discussion of both algorithms. Flight results from Archangel Systems AHR150 ADAHRS are also presented and discussed.

Full state feedback control of a magnetic bearing system using optimal estimation

A continuous-continuous extended Kalman filter (CCEKF) is developed for optimal state estimation for use with full state feedback control of a magnetic bearing system. The model describing the magnetic bearing system is a set of four nonlinear differential equation which include integral augmentation of the plant. All simulations are performed with process noise, measurement noise, and an initial perturbation from the nominal operating position acting on the system. Additionally, the effects of a static load disturbance force and a sinusoidal disturbance force on system performance are investigated. The results indicate the CCEKF used in conjunction with full state feedback provides regulation of the system about the nominal operating position for static load and sinusoidal disturbance forces in the presence of process and measurement noise.<<ETX>>

Radiation effects on multiple DOF MEMS inertial sensors

Much work has been conducted and published in the area of radiation hardening of electronics. These efforts have yielded an array of techniques and design protocols for mitigating radiation effects in hardware. However, in the field of MEMS sensor systems, radiation can impact not only the support structure but the MEMS structure itself. In this work, a new multiple degree-of-freedom MEMS inertial sensor called MARS (MEMS Annular Rotating Sensor) has been subjected to Co60 gamma-ray irradiation and results analyzed for total dose effects. Pre- and post-radiation tests reveal that the sensors accelerometer noise performance is enhanced by the exposure. Quantitatively, noise levels improved after radiation by roughly 40% in the X and Y axes and 75% in the Z axes. Additionally, any effects of radiation on sensor offset were not discernable.

A Study of Integrally Augmented State Feedback Control for an Active Magnetic Bearing Supported Rotor System

State feedback controller designs allow for pole-placement in an effective manner, but reduction of static offset is difficult. On the other hand, classical control methodology allows for the increase of system type and the elimination of static offset. An integrally augmented state feedback controller provides the benefits of standard feedback designs while allowing for the elimination of static offsets (through the increase of system type). Static offset is a particular problem with magnetic bearing supported rotor systems, in that gravitational effects, current biasing, and operational loading tend to exacerbate this problem. In order to assess the effectiveness of this technique, an integrally augmented state feedback controller is developed, implemented, and tested for a magnetic bearing supported rotor system. Results for several selected configurations are presented and compared. Some conclusions and recommendations concerning the effectiveness of integrally augmented state feedback controller designs are presented.Copyright

Precision pointing error analysis in a satellite optical communication optical system

The authors present details of the design considerations for two candidate precision pointing and tracking control subsystems proposed for use in an optical intersatellite communication system. In addition, disturbance effects are identified, and appropriate models for the disturbances are developed. Simulations of the control system are performed. Preliminary simulation results indicate superior disturbance rejection of a complementary filter-based precision pointing and tracking subsystem when compared with a rate-integrating-gyro- (G-) based system. However, both systems fail to meet the 0.5- mu murad (r.m.s.) pointing constraint imposed by optical intersatellite communication links.<<ETX>>

Issues in wearable biomechanical inertial sensor systems

Wearable inertial sensors present designers with additional challenges not seen in conventional systems where power at fixed voltage is abundant. This work discusses the critical concerns in designing a wearable inertial sensor including component selection, power distribution and the use of sleep/shutdown modes.