Autonomous Formation Keeping of Geostationary Satellites with Regional Navigation Satellites and Dynamics
Journal of Guidance Control and Dynamics, Mar 1, 2017
In this paper, the reduced dynamic autonomous formation control of geostationary-Earth-orbit sate... more In this paper, the reduced dynamic autonomous formation control of geostationary-Earth-orbit satellites using Indian Regional Navigation Satellite System observables is presented. Generally, the na...
Attitude Estimation and Control of Spacecraft Using Global Positioning System
This paper is concerned with attitude estimation and pointing accuracy of a remote sensing satell... more This paper is concerned with attitude estimation and pointing accuracy of a remote sensing satellite with off-nadir spinning scatterometer using GPS (Global Positioning System) carrier phase signals. The spinning scatterometer disturbs the three-axis desired pointing of the satellite. A three-axis controller is designed to control the earth-pointing attitude of the satellite, and its pointing accuracy is determined. The GPS satellite visibility plots identify the GPS satellites visible to the remote sensing satellite. Using single-differenced carrier phase observables of GPS an Extended Kalman Filter (EKF) is developed to estimate the attitude of the satellite over time. Simulation results are shown demonstrating the above mentioned steps.
Reentry vehicles are required to meet stringent boundary conditions and path constraints, while m... more Reentry vehicles are required to meet stringent boundary conditions and path constraints, while minimizing certain cost functional. Parameter optimal control is easier and faster to solve than indirect methods for complex problems, such as the problem of re-entry trajectory optimization subject to multiple path constraints. In this paper, a direct transcription method is applied for finding optimal trajectory of 2 problems. Firstly, Newtonian method is used for finding aerodynamic coefficients of blunt nose conical re-entry capsule in hypersonic regime. Using these coefficients, trajectory satisfying path constraints corresponding to heat influx, G-load and control angles is generated while minimizing the vehicle manoeuvres. In the second problem Apollo capsule's multiphase optimization problem is solved based on the aerodynamic coefficients obtained from wind tunnel test data.
Air-to-Air Tracking of a Maneuvering Target with Gimbaled Radar
Journal of Guidance Control and Dynamics, Feb 1, 2016
This paper is concerned with the steering of an antenna beam for an air-to-air tracking system wh... more This paper is concerned with the steering of an antenna beam for an air-to-air tracking system where an airborne radar antenna senses an airborne maneuvering target. A mechanical gimbal-mounted airborne radar is used to steer the antenna beam. The difficulty with a gimbaled radar is that the radar measurement becomes inaccurate if the target is outside the antenna beam width, which is usually less than 2 deg. An extended Kalman filter is developed to estimate the relative position, relative velocity, and absolute acceleration of the target in Cartesian coordinates, which are further used to drive the antenna beam. Realistic noise models of sensors are incorporated in the measurements. A high-fidelity model is developed to accommodate the sensors operating at different frequencies. The mathematical formulation of initializing the state vector and process noise matrix using measurements, the measurement sensitivity matrix, and the process noise covariance matrix are presented. The flight dynamics of two fig...
Precision Munition Guidance and Moving-Target Estimation
Journal of Guidance Control and Dynamics, Sep 1, 2016
The efficacy of a munition depends on target detection, estimation of its motion, guidance, track... more The efficacy of a munition depends on target detection, estimation of its motion, guidance, tracking and control; in fact even more so if the target is moving. This paper is concerned with flight dynamics of a munition in atmosphere under four different guidance schemes to intercept an evasive ground target. The miss distances and commanded acceleration required by these guidance laws are compared. Two-dimensional planar flight of the munition and its pitch motion model is developed and simulated. The forward and/or backward motion of a target tank on the ground is modeled as a second-order Gauss–Markov process. To estimate the target location on the ground and the line-of-sight rate to intercept it, an Extended Kalman filter is composed whose state vector consists of cascaded state vectors of missile dynamics and target dynamics. The line-of-sight angle measurement from the infrared seeker and range measurement from the millimeter wave radar are used in the Kalman Filter for relative navigation of the mu...
Synthesis of a modern/classical controller for large space structures
The paper is concerned with wide-sense stationary random vibrations of a representative large spa... more The paper is concerned with wide-sense stationary random vibrations of a representative large space structure subject to nonwhite excitations, and with synthesis of its controller amid modeling uncertainties due to truncated modes. Dynamics is analyzed by residue calculus in frequency domain. Steady state variance of a modal coordinate is shown to depend on, among other things, power spectral density of excitation at the modal frequency. Modal cost analysis is performed for an order reduction with a performance objective of attitude, attitude rate and energy control. Optimal and suboptimal output feedback controllers are compared. By treating deleted modes as an additive and a multiplicative perturbation in an idealized transfer function, the low frequency modes omitted according to modal cost analysis are found to cause instability. Finally, the size of the idealized model is shown to be governed by light damping and stringency in performance and stability specifications.
Relative navigation of GEO satellites in formation using double-difference carrier phase measurements with integer ambiguity resolution
A carrier phase differential global positioning system relative navigation estimator is developed... more A carrier phase differential global positioning system relative navigation estimator is developed for relative navigation of two GEO satellites in orbit. This technique is applied to the high altitude satellites such as geostationary and geosynchronous satellites. This is helpful in determining the satellite formations in the higher altitudes. The algorithm incorporates carrier phase ambiguity resolution technique to determine the relative position between two satellites. The carrier phase and code ranging measurements from GPS to GEO satellite are modeled and simulated using MATLAB software. A satellite visibility algorithm is applied in order to determine the visible GPS satellite.
Dynamics of Tisserand's frame for an elastic spacecraft with stored angular momentum
Tisserand's frame represents a frame in which the deformations in elastic members and the mot... more Tisserand's frame represents a frame in which the deformations in elastic members and the motions in a central rigid body add zero translational and angular momenta to the overall momentum of the vehicle. The considered relations have been known for some time in the case of nongyroscopic spacecraft. The present investigation is concerned with an extension of the relations to gyroscopic systems, taking into account an entirely elastic spacecraft with significant stored angular momentum. A two-dimensional free, rectangular, elastic structure with axisymmetric rotors is considered. Equations of motion are obtained with the aid of the Newton-Eulerian technique and Hamilton's principle. An analysis is conducted of the dynamics of an elastic gyroscopic free vehicle, and the dynamics of the Tisserand's frame in response to external stimuli is examined.
This paper considers the vehicle navigation problem for an autonomous underwater vehicle (AUV) wi... more This paper considers the vehicle navigation problem for an autonomous underwater vehicle (AUV) with six degrees of freedom. We approach this problem using an error state formulation of the Kalman filter. Integration of the vehicle's high-rate inertial measurement unit's (IMU's) accelerometers and gyros allow time propagation while other sensors provide measurement corrections. The low-rate aiding sensors include a Doppler velocity log (DVL), an acoustic long baseline (LBL) system that provides round-trip travel times from known locations, a pressure sensor for aiding depth, and an attitude sensor. Measurements correct the filter independently as they arrive, and as such, the filter is not dependent on the arrival of any particular measurement. Different navigation systems are constructed each consisting of a particular set of sensors. The navigation solution from all these systems is fused using decentralized Kalman filtering approach. Autonomous operation requires that there is to be no sharing of measurement information among local filters. Simulation results are provided.
This paper addresses the problem of the compensation of the motion errors in an airborne syntheti... more This paper addresses the problem of the compensation of the motion errors in an airborne synthetic aperture radar (SAR). The motion errors are caused by the sensor's unintended translational and rotational motion. The motion errors cause amplitude and phase modulation of the echo, thus making the image defocused and geometrically distorted. A method of estimating the motion error based on the movement of the line-of-sight unit vector is proposed. The range-Doppler algorithm is used for processing the SAR raw data. A motion compensation algorithm is also proposed and is applied after the range compression to compensate for the effective range error in single-step. Effectiveness of the proposed algorithm is evaluated using the experimental data acquired by Disaster Management SAR system developed in Space Applications Centre, ISRO,
Precision targeting in guided munition using infrared sensor and millimeter wave radar
Journal of Applied Remote Sensing, 2016
Abstract. Conventional munitions are not guided with sensors and therefore miss the target, parti... more Abstract. Conventional munitions are not guided with sensors and therefore miss the target, particularly if the target is mobile. The miss distance of these munitions can be decreased by incorporating sensors to detect the target and guide the munition during flight. This paper is concerned with a precision guided munition equipped with an infrared (IR) sensor and a millimeter wave radar (MmW). Three-dimensional flight of the munition and its pitch and yaw motion models are developed and simulated. The forward and lateral motion of a target tank on the ground is modeled as two independent second-order Gauss–Markov processes. To estimate the target location on the ground and the line-of-sight (LOS) rate to intercept it, an extended Kalman filter is composed whose state vector consists of cascaded state vectors of missile dynamics and target dynamics. The LOS angle measurement from the IR seeker is by centroiding the target image in 40 Hz. The centroid estimation of the images in the focal plane is at a frequency of 10 Hz. Every 10 Hz, centroids of four consecutive images are averaged, yielding a time-averaged centroid, implying some measurement delay. The miss distance achieved by including image processing delays is 1.45 m.
Autonomous Formation Keeping of Geostationary Satellites with Regional Navigation Satellites and Dynamics
Journal of Guidance Control and Dynamics, Mar 1, 2017
In this paper, the reduced dynamic autonomous formation control of geostationary-Earth-orbit sate... more In this paper, the reduced dynamic autonomous formation control of geostationary-Earth-orbit satellites using Indian Regional Navigation Satellite System observables is presented. Generally, the na...
Attitude Estimation and Control of Spacecraft Using Global Positioning System
This paper is concerned with attitude estimation and pointing accuracy of a remote sensing satell... more This paper is concerned with attitude estimation and pointing accuracy of a remote sensing satellite with off-nadir spinning scatterometer using GPS (Global Positioning System) carrier phase signals. The spinning scatterometer disturbs the three-axis desired pointing of the satellite. A three-axis controller is designed to control the earth-pointing attitude of the satellite, and its pointing accuracy is determined. The GPS satellite visibility plots identify the GPS satellites visible to the remote sensing satellite. Using single-differenced carrier phase observables of GPS an Extended Kalman Filter (EKF) is developed to estimate the attitude of the satellite over time. Simulation results are shown demonstrating the above mentioned steps.
Reentry vehicles are required to meet stringent boundary conditions and path constraints, while m... more Reentry vehicles are required to meet stringent boundary conditions and path constraints, while minimizing certain cost functional. Parameter optimal control is easier and faster to solve than indirect methods for complex problems, such as the problem of re-entry trajectory optimization subject to multiple path constraints. In this paper, a direct transcription method is applied for finding optimal trajectory of 2 problems. Firstly, Newtonian method is used for finding aerodynamic coefficients of blunt nose conical re-entry capsule in hypersonic regime. Using these coefficients, trajectory satisfying path constraints corresponding to heat influx, G-load and control angles is generated while minimizing the vehicle manoeuvres. In the second problem Apollo capsule's multiphase optimization problem is solved based on the aerodynamic coefficients obtained from wind tunnel test data.
Air-to-Air Tracking of a Maneuvering Target with Gimbaled Radar
Journal of Guidance Control and Dynamics, Feb 1, 2016
This paper is concerned with the steering of an antenna beam for an air-to-air tracking system wh... more This paper is concerned with the steering of an antenna beam for an air-to-air tracking system where an airborne radar antenna senses an airborne maneuvering target. A mechanical gimbal-mounted airborne radar is used to steer the antenna beam. The difficulty with a gimbaled radar is that the radar measurement becomes inaccurate if the target is outside the antenna beam width, which is usually less than 2 deg. An extended Kalman filter is developed to estimate the relative position, relative velocity, and absolute acceleration of the target in Cartesian coordinates, which are further used to drive the antenna beam. Realistic noise models of sensors are incorporated in the measurements. A high-fidelity model is developed to accommodate the sensors operating at different frequencies. The mathematical formulation of initializing the state vector and process noise matrix using measurements, the measurement sensitivity matrix, and the process noise covariance matrix are presented. The flight dynamics of two fig...
Precision Munition Guidance and Moving-Target Estimation
Journal of Guidance Control and Dynamics, Sep 1, 2016
The efficacy of a munition depends on target detection, estimation of its motion, guidance, track... more The efficacy of a munition depends on target detection, estimation of its motion, guidance, tracking and control; in fact even more so if the target is moving. This paper is concerned with flight dynamics of a munition in atmosphere under four different guidance schemes to intercept an evasive ground target. The miss distances and commanded acceleration required by these guidance laws are compared. Two-dimensional planar flight of the munition and its pitch motion model is developed and simulated. The forward and/or backward motion of a target tank on the ground is modeled as a second-order Gauss–Markov process. To estimate the target location on the ground and the line-of-sight rate to intercept it, an Extended Kalman filter is composed whose state vector consists of cascaded state vectors of missile dynamics and target dynamics. The line-of-sight angle measurement from the infrared seeker and range measurement from the millimeter wave radar are used in the Kalman Filter for relative navigation of the mu...
Synthesis of a modern/classical controller for large space structures
The paper is concerned with wide-sense stationary random vibrations of a representative large spa... more The paper is concerned with wide-sense stationary random vibrations of a representative large space structure subject to nonwhite excitations, and with synthesis of its controller amid modeling uncertainties due to truncated modes. Dynamics is analyzed by residue calculus in frequency domain. Steady state variance of a modal coordinate is shown to depend on, among other things, power spectral density of excitation at the modal frequency. Modal cost analysis is performed for an order reduction with a performance objective of attitude, attitude rate and energy control. Optimal and suboptimal output feedback controllers are compared. By treating deleted modes as an additive and a multiplicative perturbation in an idealized transfer function, the low frequency modes omitted according to modal cost analysis are found to cause instability. Finally, the size of the idealized model is shown to be governed by light damping and stringency in performance and stability specifications.
Relative navigation of GEO satellites in formation using double-difference carrier phase measurements with integer ambiguity resolution
A carrier phase differential global positioning system relative navigation estimator is developed... more A carrier phase differential global positioning system relative navigation estimator is developed for relative navigation of two GEO satellites in orbit. This technique is applied to the high altitude satellites such as geostationary and geosynchronous satellites. This is helpful in determining the satellite formations in the higher altitudes. The algorithm incorporates carrier phase ambiguity resolution technique to determine the relative position between two satellites. The carrier phase and code ranging measurements from GPS to GEO satellite are modeled and simulated using MATLAB software. A satellite visibility algorithm is applied in order to determine the visible GPS satellite.
Dynamics of Tisserand's frame for an elastic spacecraft with stored angular momentum
Tisserand's frame represents a frame in which the deformations in elastic members and the mot... more Tisserand's frame represents a frame in which the deformations in elastic members and the motions in a central rigid body add zero translational and angular momenta to the overall momentum of the vehicle. The considered relations have been known for some time in the case of nongyroscopic spacecraft. The present investigation is concerned with an extension of the relations to gyroscopic systems, taking into account an entirely elastic spacecraft with significant stored angular momentum. A two-dimensional free, rectangular, elastic structure with axisymmetric rotors is considered. Equations of motion are obtained with the aid of the Newton-Eulerian technique and Hamilton's principle. An analysis is conducted of the dynamics of an elastic gyroscopic free vehicle, and the dynamics of the Tisserand's frame in response to external stimuli is examined.
This paper considers the vehicle navigation problem for an autonomous underwater vehicle (AUV) wi... more This paper considers the vehicle navigation problem for an autonomous underwater vehicle (AUV) with six degrees of freedom. We approach this problem using an error state formulation of the Kalman filter. Integration of the vehicle's high-rate inertial measurement unit's (IMU's) accelerometers and gyros allow time propagation while other sensors provide measurement corrections. The low-rate aiding sensors include a Doppler velocity log (DVL), an acoustic long baseline (LBL) system that provides round-trip travel times from known locations, a pressure sensor for aiding depth, and an attitude sensor. Measurements correct the filter independently as they arrive, and as such, the filter is not dependent on the arrival of any particular measurement. Different navigation systems are constructed each consisting of a particular set of sensors. The navigation solution from all these systems is fused using decentralized Kalman filtering approach. Autonomous operation requires that there is to be no sharing of measurement information among local filters. Simulation results are provided.
This paper addresses the problem of the compensation of the motion errors in an airborne syntheti... more This paper addresses the problem of the compensation of the motion errors in an airborne synthetic aperture radar (SAR). The motion errors are caused by the sensor's unintended translational and rotational motion. The motion errors cause amplitude and phase modulation of the echo, thus making the image defocused and geometrically distorted. A method of estimating the motion error based on the movement of the line-of-sight unit vector is proposed. The range-Doppler algorithm is used for processing the SAR raw data. A motion compensation algorithm is also proposed and is applied after the range compression to compensate for the effective range error in single-step. Effectiveness of the proposed algorithm is evaluated using the experimental data acquired by Disaster Management SAR system developed in Space Applications Centre, ISRO,
Precision targeting in guided munition using infrared sensor and millimeter wave radar
Journal of Applied Remote Sensing, 2016
Abstract. Conventional munitions are not guided with sensors and therefore miss the target, parti... more Abstract. Conventional munitions are not guided with sensors and therefore miss the target, particularly if the target is mobile. The miss distance of these munitions can be decreased by incorporating sensors to detect the target and guide the munition during flight. This paper is concerned with a precision guided munition equipped with an infrared (IR) sensor and a millimeter wave radar (MmW). Three-dimensional flight of the munition and its pitch and yaw motion models are developed and simulated. The forward and lateral motion of a target tank on the ground is modeled as two independent second-order Gauss–Markov processes. To estimate the target location on the ground and the line-of-sight (LOS) rate to intercept it, an extended Kalman filter is composed whose state vector consists of cascaded state vectors of missile dynamics and target dynamics. The LOS angle measurement from the IR seeker is by centroiding the target image in 40 Hz. The centroid estimation of the images in the focal plane is at a frequency of 10 Hz. Every 10 Hz, centroids of four consecutive images are averaged, yielding a time-averaged centroid, implying some measurement delay. The miss distance achieved by including image processing delays is 1.45 m.
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