Automatic navigation makes ocean-going and flying safer and less expensive: Safer because machines are tireless and always vigilant; inexpensive because it does not use human navigators who are, unavoidably, highly trained and thus expensive people. What is more, unmanned deep space travel would be impossible without automatic navigation. Navigation can be automated with the radio systems Loran, Omega, and the Global Positioning System (GPS) of earth satellites, but its most versatile form is completely self-contained and is called inertial navigation. It uses gyroscopes and accelerometers (inertial sensors) to measure the state of motion of the vehicle by noting changes in that state caused by accelerations. By knowing the vehicle's starting position and noting the changes in its direction and speed, one can keep track of the vehicle's present position. Mankind first used this technology in World War n, in guided weapons where cost was unimportant; only 20-30 years later did it become cheap enough to be used commercially. The electronics revolution, in which vacuum tubes were replaced by integrated circuits, has dramatically altered the field of inertial navigation. Early inertial systems used complex mechanical gimbal structures and mechanical gyroscopes with spinning wheels. The gimbals allowed the gyroscopes to stabilize a mass (called a "platform") so that it remained in a fixed attitude relative to a chosen coordinate frame, even as the vehicle turned around any or all of its three major axes.
Sprache
Verlagsort
Verlagsgruppe
Dateigröße
ISBN-13
978-1-4684-0444-9 (9781468404449)
DOI
10.1007/978-1-4684-0444-9
Schweitzer Klassifikation
1. An Outline of Inertial Navigation.- Navigation's Beginnings.- Inertial Navigation.- Maps and Reference Frames.- The Inertial Navigation Process.- Inertial Platforms.- Strapdown Systems.- System Alignment.- Advantages and Disadvantages of Platform Systems.- Advantages and Disadvantages of Strapdown Systems.- Star Trackers.- The Global Positioning System.- Applications of Inertial Navigation.- Conclusions.- References.- 2. Gyro and Accelerometer Errors and Their Consequences.- Effect of System Heading Error.- Scale Factor.- Non-linearity and Composite Error.- Bias.- Random Drift.- Random Walk.- Dead Band, Threshold, and Resolution.- Hysteresis.- Day-to-Day Uncertainty.- Gyro Acceleration Sensitivities.- Rotation Induced Errors.- Angular Accelerometers.- Angular Accelerometer Threshold Error.- The Statistics of Instrument Performance.- Typical Instrument Specifications.- References.- 3. The Principles of Accelerometers.- The Parts of an Accelerometer.- The Spring-Mass System.- Open-Loop Pendulous Sensors.- Closed-Loop Accelerometers.- Open-Loop Versus Closed-Loop Sensors.- Sensor Rebalance Servos.- The Voltage Reference Problem.- Novel Accelerometer Principles.- References.- 4. The Pendulous Accelerometer.- A Generic Pendulous Accelerometer.- The IEEE Model Equations.- The Sundstrand "Q-Flex" Accelerometer.- Other Electromagnetic Pendulous Accelerometers.- The Silicon Accelerometer.- References.- 5. Vibrating Beam Accelerometers.- The Vibration Equation.- The Resolution of a Vibrating Element Accelerometer.- The Quartz Resonator.- VBAs in General.- The Sundstrand Design.- The Kearfott Design.- Comparison of Free and Constrained Accelerometers.- Conclusion.- References.- 6. The Principles of Mechanical Gyroscopes.- Angular Momentum.- The Law of Gyroscopics.- TheSpinning Top - Nutation.- Coriolis Acceleration.- Gyroscopes with One and Two Degrees of Freedom.- Conclusion.- References.- 7. Single Degree of Freedom Gyroscopes.- The Rate Gyro.- The Rate-Integrating Gyro.- A Digression into Accelerometers.- Conclusion.- References.- 8. Two Degree of Freedom Gyroscopes.- The Two Degree of Freedom (Free) Gyro.- The External Gimbal Type.- Two-Axis Floated Gyros.- Spherical Free Rotor Gyros.- The Electrically Suspended Gyro.- The Gas Bearing Free Rotor Gyro.- References.- 9. The Dynamically Tuned Gyroscope.- The DTG Tuning Effect.- The Tuning Equations.- Damping and Time Constant.- Biases Due to Damping and Mistuning.- Quadrature Mass Unbalance.- Synchronous Vibration Rectification Errors.- Wide Band Vibration Rectification Errors.- The Pickoff and Torquer for a DTG.- The DTG Model Equation.- Conclusion.- References.- 10. Vibrating Gyroscopes.- The Vibrating String Gyro.- The Tuning Fork Gyro.- Vibrating Shell Gyros.- The Hemispherical Resonator Gyro.- The Vibrating Cylinder (START) Gyro.- The Advantages of Vibrating Shell Gyros.- The Multisensor Principle and Its Error Sources.- Conclusion.- References.- 11. The Principles of Optical Rotation Sensing.- The Inertial Property of Light.- The Sagnac Effect.- The Shot Noise Fundamental Limit.- The Optical Resonator.- Optical Fibers.- The Coherence of an Oscillator.- Types of Optical Gyro.- Conclusion.- References.- 12. The Interferometric Fiber-Optic Gyro.- The History of the Fiber-Optic Gyro.- The Basic Open-Loop IFOG.- Biasing the IFOG.- The Light Source.- Reciprocity and the "Minimum Configuration".- Closing the Loop-Phase-Nulling.- Fiber-to-Chip Attachment - The JPL IFOG.- The Effect of Polarization on Gyro Drift.- The Kerr Electro-Optic Effect.- The Fundamental Limit of IFOGPerformance.- Conclusions.- References.- 13. The Ring Laser Gyro.- The Laser.- The Ring Laser.- Lock-in.- The Multi-oscillator.- Shared-Mirror RLG Assemblies.- The Quantum Fundamental Limit.- Quantization Noise.- Conclusion.- References.- 14. Passive Resonant Gyros.- The Discrete Component Passive Ring Resonator.- The Resonant Fiber-Optic Gyro.- The Micro-Optic Gyro.- IFOG, RFOG, and MOG Size Limits.- Fundamental Limits for RFOG, IFOG, and RLG.- Conclusions.- References.- 15. Testing Inertial Sensors.- Inertial Sensor Test Labs.- Accelerometer Testing.- Gyroscope Testing.- Conclusion.- References.- 16. Design Choices for Inertial Instruments.- A Platform or a Strapdown System?.- Aiding the IMU.- Choice of Sensor Type.- Reliability.- Sensor Design Check Lists.- Conclusions.- References.
