Search results

The purpose of this paper is to present novel robust fault tolerant control design architecture to detect and isolate spacecraft attitude control actuators and reconfigure to redundant backups to improve the practicality of actuator fault detection.

The Robust Fault Tolerant Control is designed for spacecraft Autonomous Rendezvous and Docking (AR&D) using Lyapunov direct approach applied to non‐linear model. An extended Kalman observer is used to accurately estimate the state of the attitude control actuators. Actuators on all three axes (roll/pitch/yaw) sequentially fail one after another and the robust fault tolerant controller acts to reconfigure to redundant backups to stabilize the spacecrafts and complete the required maneuver.

In the simulations, the roll, pitch and yaw dynamics of the spacecraft are considered and the attitude control actuators failures are detected and isolated. Furthermore, by switching to redundant backups, the guarantee of overall stability performance is demonstrated.

A real time actuator failure detection and reconfiguration process using robust fault tolerant control is applied for spacecraft AR&D maneuvers. Finding an appropriate Lyapunov function for the non‐linear dynamics is not easy and always challenging. Failure of actuators on all three axes at the same time is not considered. It is a very useful approach to solve self‐assembly problems in space, spacecraft proximity maneuvers as well as co‐operative control of planetary vehicles in presence of actuator failures.

An approach has been proposed to detect, isolate and reconfigure spacecraft actuator failures occurred in the spacecraft attitude control system. A Robust Fault Tolerant Control scheme has been developed for the nonlinear AR&D maneuver for two spacecrafts. Failures that affect the control performance characteristics are considered and overall performance is guaranteed even in presence of control actuator failures. The architecture is demonstrated through model‐based simulation.

Recent advances in nano and picosatellite missions and future such missions require three axis attitude control system hardware for attitude control purposes. A simple, cost effective, yet an efficient devise that is used for active attitude control is magnetic torquer coil. The purpose of this paper is to describe the design and fabrication of a template to manufacture magnetic torquer coils of varying sizes and shapes.

Details about the development of the template design, analysis, and fabrication are discussed. The development status of the system is outlined and the working prototype of the device is described and some preliminary test results are given.

A fully functional prototype of the template has been developed and testing has been conducted that demonstrated the effectiveness of the device. Magnetic torquer coils of varying sizes were fabricated and tested. A finite element analysis was performed by modeling the characteristics of the fabricated coils to determine thermally induced stresses and deformations during its space operations.

The paper illustrates and demonstrates an effective application of torquer coil template in the satellite fabrication industry. The benefits from the approach are generally applicable to any future university and industry missions using picosatellite technology.

The designed template satisfied all the constraints and requirements. Furthermore, its advantages include scalability, modularity, and its capability to fabricate magnetic torquer coils of varying sizes and shapes.

Alternative energy sources and power generation techniques for long‐term space missions are gaining importance in recent years for future bases and colonies on the Moon or Mars. Current technologies used for manned or unmanned missions to the Moon or Mars use either solar panels (bulky, expensive/kilogram to space, and inefficient) or nuclear energy (extremely dangerous and unpopular). Enzyme based bio fuel cells can be used as alternative energy sources, but its survival depends on maintaining appropriate temperature and pressure in space. The purpose of this paper is to detail the concept design and development of a payload tank to house bio fuel cells for operations in space environment.

Details about the development of the design methodology for such housing are discussed. A full‐scale payload tank is designed to house a small biological fuel cell using space grade materials. Requirements analysis, design, validation, and manufacturing process are covered.

The outcome is a dimensionally optimized housing structure for housing biological fuel cells and maintaining the temperature and pressure for survival of the fuel cell.

The designed payload housing satisfies all the constraints and requirements. Furthermore, its advantages include scalability and modularity by virtue of using optimized design approach. The final product provides a planned procedure for designing larger housing for other missions.

The purpose of the paper is to present an approach to detect and isolate the sensor failures, using a bank of extended Kalman filters (EKF) using an innovative initialization of covariance matrix using system dynamics.

The EKF is developed for nonlinear flight dynamic estimation of a spacecraft and the effects of the sensor failures using a bank of Kalman filters is investigated. The approach is to develop a fast convergence Kalman filter algorithm based on covariance matrix computation for rapid sensor fault detection. The proposed nonlinear filter has been tested and compared with the classical Kalman filter schemes via simulations performed on the model of a space vehicle; this simulation activity has shown the benefits of the novel approach.

In the simulations, the rotational dynamics of a spacecraft dynamic model are considered, and the sensor failures are detected and isolated.

A novel fast convergence Kalman filter for detection and isolation of faulty sensors applied to the three‐axis spacecraft attitude control problem is examined and an effective approach to isolate the faulty sensor measurements is proposed. Advantages of using innovative initialization of covariance matrix are presented in the paper. The proposed scheme enhances the improvement in estimation accuracy. The proposed method takes advantage of both the fast convergence capability and the robustness of numerical stability. Quaternion‐based initialization of the covariance matrix is not considered in this paper.

A new fast converging Kalman filter for sensor fault detection and isolation by innovative initialization of covariance matrix applied to a nonlinear spacecraft dynamic model is examined and an effective approach to isolate the measurements from failed sensors is proposed. An EKF is developed for the nonlinear dynamic estimation of an orbiting spacecraft. The proposed methodology detects and decides if and where a sensor fault has occurred, isolates the faulty sensor, and outputs the corresponding healthy sensor measurement.

Recent advances in nano and picosatellite missions and future such missions require faster and accurate pointing accuracies using reaction wheels for attitude control purposes. The ability to put one or three reaction wheels on the spacecraft in the 1‐20 kg range enables new classes of missions. The purpose of this paper is to present the detailed design, analysis, and construction of a miniature reaction wheel prototype. The designed pico‐reaction wheel promises to fulfill the need for low cost, low mass, low power, high reliability, and high‐accuracy attitude control systems for applications such as communications, remote sensing, and space science.

Details about the design, analysis and development of pico‐reaction wheel are discussed. The development status of the system is outlined and the working prototype of the device is described and some preliminary test results are given. Requirements specifications, design and analysis and finite element analysis are covered.

A fully functional prototype has been developed and testing has been conducted that demonstrated the effectiveness of the device. The pico‐reaction wheel offers a new attitude control system implementation strategy for pico and nanosatellite missions that can help to significantly reduce the spacecraft costs. The key to our success has been to design the reaction wheel from ground‐up for simplicity.

The designed pico‐reaction wheel satisfied all the constraints and requirements. Furthermore, its advantages include scalability and modularity by virtue of using commercial‐off‐the‐shelf components. A pico‐reaction wheel has been successfully designed and is now available to pico and nanosatellite builders at a cost that is consistent with low‐cost research missions.

The purpose of this paper is to describe the design and construction of a custom‐built low‐cost thermal vacuum chamber (TVC) for spacecraft environmental testing and verification. The paper provides detailed analysis and an insight into the design and development of the chamber. The chamber was specifically constructed for carrying out the thermal and vacuum environmental tests in a 16″ dia × 16″ long horizontal thermal vacuum chamber. The chamber is constructed using a combination of mechanical (roughing) pump and turbo‐molecular pump, used to pump the chamber down to 10⁻⁵ Torr and a combination of radiation heaters and nitrogen gas is used to vary the temperature within the chamber from +80 to −50°C.

The TVC equipment is built as part of the picosatellite and nanosatellite program at Space Systems Research Laboratory of Saint Louis University. The equipment is built at a low cost and is suited for testing an entire picosatellite and several components and subsystems of nanosatellite simulating thermal and vacuum conditions similar to space environment. The different main parts of the equipment are described in a way which explains the choice of construction and partly makes it possible to replicate similar equipment.

The TVC equipment is successfully used to simulate the thermal and vacuum conditions of space similar to the conditions experienced by a picosatellite or nanosatellite in low earth orbit.

The design and construction of TVC in this paper have broader implications and can be a platform for future research on low‐cost TVC. This equipment can be utilized in the research areas of electronics and communications, biology and medicine to name a few. Thermal and vacuum experiments on several astro‐biological experiments can be performed.

The paper is intended to be a source of inspiration for industrial or academic space research laboratories which would like to design and construct a similar test‐equipment, instead of investing expensive commercially available alternatives.

The paper discusses in detail, the simplified cost‐effective approach of constructing TVC and also outlines the various issues to be considered. The TVC equipment is custom‐built and is described in an easily understandable way, which makes this a helpful paper for those who wish to produce similar equipment. This will be the only known manuscript in the literature to detail the design and construction of low‐cost, economical TVC.