Abstract: A vertical axis wind turbine that can be actively controlled is provided. This invention includes mechanisms and methods for enabling high-efficiency wind energy extraction by a vertical axis wind turbine using active pitch and camber control of individual blades. Blade control is further integrated with generator control and power electronics. Integrated control algorithms are systematically constructed, and transmitted to the wind turbine through a wireless communications interface. The interface also allows the user to continuously monitor the state of the wind turbine system. This invention includes sensors and procedures for periodic self-calibration of wind turbine parameters for preserving the long-term efficiency of wind energy extraction. Furthermore, a capability to intelligently interact with other wind turbine systems in a wind-farm setting is incorporated.

Abstract: A Multimode Optical Sensor (MMOS) is a laser radar (ladar) that employs both coherent, or heterodyne, and noncoherent detection at long range, i.e. ranges for which the target is no more than a pixel in dimension. Coherent detection provides much higher velocity resolution while the noncoherent detection can provide better detectability.

Abstract: A vertical axis wind turbine that can be actively controlled has the potential to extract wind energy efficiently, and consequently be economically viable for distributed harvesting of wind energy. This invention includes mechanisms and methods for enabling high-efficiency wind energy extraction by a vertical axis wind turbine using active pitch and camber control of individual blades. Blade control is further integrated with generator control and power electronics. Integrated control algorithms are systematically constructed, and transmitted to the wind turbine through a wireless communications interface. The interface also allows the user to continuously monitor the state of the wind turbine system. This invention includes sensors and procedures for periodic self-calibration of wind turbine parameters for preserving the long-term efficiency of wind energy extraction. Furthermore, a capability to intelligently interact with other wind turbine systems in a wind-farm setting is incorporated.

Abstract: The invention is an efficient matrix converter for wind energy conversion systems (WECS) using permanent magnet DC generators, incorporating control algorithms integrated with rotor aerodynamics, generator dynamics and the wind environment. Using a complete model of the system enables the design of an integrated control scheme for the WECS that improves the overall system efficiency. Estimates of wind velocity and rotor speed measurements are fed forward to the matrix converter subsystem for efficient switching.

Abstract: A method and system for generating funds to allow tourists to fly in space. A customer buys a lottery ticket (14), which gives the customer the chance to fly in space should the ticket be selected. The revenue generated by the lottery pays for the training of the customer and the launch and flight costs for the customer. Customers may optionally enroll in a training class (26) that qualifies (22) the tourist for flight. Customers who do so are given a greater chance of winning future lotteries. In each lottery a number of customers greater than the number of available flight slots are selected. All receive flight training (38). Customers who receive training may enter future lotteries (42) and would have a greater chance of winning, just as those who pay for training have a greater chance of winning. Customers who cannot meet the physical standards are disqualified. The lottery is conducted both on the Internet and also using existing lottery ticket systems.

Abstract: A method and system for advertising and selling products while a customer awaits his turn for service in a wait queue. The invention permits the customer to chose to listen to advertisements while in this wait queue. If he chooses these advertisements, the customer then enters the advertisement queue, where the first gets a summary list of ads. The customer then listens to the advertisements(s) he selects. If the customer decides to buy a product, the customer can choose to register with the on-hold add systems permitting future “one-button” purchases. If not, the customer would then enter credit card and shipping information. While in the advertisement queue, the customer continues to advance in the wait queue. The customer is guaranteed to advance at the same rate as if the customer were in the on-hold queue. The customer can choose to leave the ad queue at any time.

Abstract: A spacecraft is controlled by a composite attitude signal including two components with different passbands. In one embodiment, a spacecraft attitude control system includes an attitude sensor and a controller which provides a time derivative function. High frequency noise components of the sensed attitude signal are enhanced by the derivative, and tend to cause attitude jitter or excess power consumption. The jitter is reduced by low pass filtration of the sensor signal, but this undesirably reduces the high frequency response of the attitude sensor. The high frequency response is restored by high pass filter coupled to a reaction or momentum wheel tachometer, which produces a signal representative of the high frequency components of the body rate. A summing circuit couples together the filtered attitude sensor signals with the high frequency components of the wheel speed signal to produce a relatively noise free broadband body rate signal.

Abstract: A 3-axis stabilized spacecraft includes roll and yaw magnetic torquers, and a momentum wheel oriented with its spin axis orthogonal to, and pivotable about, the roll axis. Roll control may be applied by pivoting the wheel. Secular increases in pivot angle may result in loss of control authority when the mechanical limits of the pivot are reached. The pivot angle is sensed, and an unloading control loop is closed, by which magnetic torquers are energized to torque the spacecraft, to return the pivot angle toward zero. The unloading control loop includes a bandpass filter, which eliminates constant components of pivot angle offset. This prevents the unload control loop from attempting to maintain the pivot at a position in which the wheel axis is offset from the desired normal to the orbit plane. Consequently, the magnetic torquers do not expend system energy attempting to maintain an undesirable attitude.

Abstract: A pitch momentum stabilized spacecraft includes an earth sensor for generating roll signals. The roll signals are applied to torquers for proportional (P) or proportional-integral PI control of roll and yaw. According to the invention, the sensed roll signals are bandpass filtered at the orbit rate, phase adjusted and applied to the roll and yaw torquers for closing a high gain degenerative feedback loop at the orbit rate, which reduces orbit-rate components of roll and yaw. A second bandpass filter at the second harmonic of the orbit rate is also connected to the earth sensor, for producing second harmonic signals, which are phase controlled and summed with the fundamental orbit rate signals, for degeneration of attitude perturbations occurring at twice the orbit frequency.

Abstract: A spacecraft includes an attitude control system using one or more reaction wheels, the speed of which from time to time lie near and pass through zero angular velocity. When operated for extended periods of time at low speeds, the lubrication films are not distributed uniformly on the wheel bearings, leading to reduced lifetime. Reliability is maintained by a threshold comparator coupled to compare wheel speed with a lower limit value, for operating a torquer associated with the spacecraft body when the wheel speed drops below the lower limit, in a manner which tends to raise the wheel speed. In a particular embodiment of the invention, the lower limit is integrated with a wheel overspeed unloading.

Abstract: A spacecraft attitude control system uses one or more momentum or reaction wheels. Wheel bearing viscous (velocity-dependent) friction reduces the actual torque imparted to the spacecraft in response to a torque command signal. Friction compensation is provided by applying the torque command signal to a model of an ideal, friction-free wheel, and calculating the speed which the ideal wheel achieves in response to the torque command. An error signal is generated from the difference between the ideal wheel speed and the actual wheel speed. The error signal is summed with the torque command signal to produce the wheel drive signal. This results in a closed-loop feedback system in which the actual wheel speed tends toward the ideal wheel speed, thereby causing a torque on the spacecraft which is substantially equal to that commanded.

Abstract: A spacecraft attitude and/or velocity control system includes a controller which responds to at least attitude errors to produce command signals representing a force vector F and a torque vector T, each having three orthogonal components, which represent the forces and torques which are to be generated by the thrusters. The thrusters may include magnetic torquer or reaction wheels. Six difference equations are generated, three having the form ##EQU1## where a.sub.j is the maximum torque which the j.sup.th thruster can produce, b.sub.j is the maximum force which the j.sup.th thruster can produce, and .alpha..sub.j is a variable representing the throttling factor of the j.sup.th thruster, which may range from zero to unity. The six equations are summed to produce a single scalar equation relating variables .alpha..sub.j to a performance index Z: ##EQU2## Those values of .alpha. which maximize the value of Z are determined by a method for solving linear equations, such as a linear programming method.

Abstract: A three-axis attitude control system for a spacecraft in an equatorial orbit includes at least a horizon sensor for producing pitch-representative signals. A star sensor has a boresight parallel to the spacecraft pitch axis, and produces signals representative of the two-axis location of a selected pole star relative to the boresight. The star sensor signals are processed in conjunction with the pitch-representative signals and with orbit-location information, to produce roll and yaw information. The pitch, roll and yaw information controls spacecraft torquing. In a particular embodiment of the invention, the horizon sensor arrangement also produces roll signals, which are processed with the roll signals from the star sensor.

Abstract: The magnitude and direction of the residual magnetic field or dipole of an orbiting spacecraft is estimated from the attitude-perturbing effects of its interaction with the magnetic field of the heavenly body about which it orbits. The measurements are performed over a significant portion of an orbit. The estimate uses h, the total spacecraft momentum in the body frame, and its body angular rate .omega.. The Earth's magnetic flux density B is determined either by magnetometer measurements, or by recourse to stored historical and ephemeris information.