Abstract:
A six-degree-of-freedom hand controller in which motions along six axes are resisted by motors (53-54, 63-64, 83-84) and in which the motors are arranged so as not to be required to carry the mass of another motor and to provide the proper "feel" for the motion of the hand grip (10) is provided.
Abstract:
A method for use in vehicle attitude determination includes generating GPS attitude solutions for a vehicle using three or more antennas receiving GPS signals from two or more space vehicles. An inertial navigation system is initialized by setting the attitude of the inertial navigation system to a GPS attitude solution generated for the vehicle and/or the attitude of the inertial navigation system is updated using the GPS attitude solutions generated for the vehicle or GPS estimated attitude error generated for the vehicle. A system for use in vehicle navigation is also provided. The system generally includes three or more GPS antenna/receiver sets associated with a vehicle, an inertial measurement unit that provides inertial measurements for the vehicle, a processing unit of the system having the capability for generating GPS attitude computations for the vehicle using the three or more GPS antenna/receiver sets and signals from two or more space vehicles; the GPS attitude computations include at least one of absolute attitudes and estimated attitude errors. The processing unit of the system also includes a filter for generating estimates of attitude for the vehicle using the inertial measurements from the inertial measurement unit and the attitude computations.
Abstract:
A multipath detection method for use in a GPS position determination system includes providing a code pseudorange measurement representative of a range of an antenna to a space vehicle and a carrier phase pseudorange measurement representative of the range of the antenna to the space vehicle. A code-carrier measurement difference is then generated between the code pseudorange measurement and the carrier phase pseudorange measurement. This code-carrier measurement difference is examined to determine if a multipath component is present. If the difference indicates that multipath is likely to be present, use of such measurements in computing position solutions, such as attitude solutions, is avoided. A multipath detection system for carrying out the method is also described.
Abstract:
A GPS receiver fault detection method for use in a GPS attitude determination system having Q Receivers, wherein Q > 3, includes providing R attitude solutions using subsets of P Receivers and signals from two or more space vehicles, wherein R 3
Abstract:
A GPS receiver fault detection method for use in a GPS attitude determination system having Q Receivers, wherein Q > 3, includes providing R attitude solutions using subsets of P Receivers and signals from two or more space vehicles, wherein R 3 ≤ P ≤ Q-1. Post-update measurement residual sets equal to the number R of attitude solutions are determined. Each of the post-update measurement residual sets corresponds to one of the attitude solutions. 'S' Receiver faults are detected by comparing the R post-update measurement residual sets, wherein 1 ≤ S ≤ Q-3. A faulty Receiver detection system for carrying out the method is also described.
Abstract:
A multipath detection method for use in a GPS position determination system includes providing a code pseudorange measurement representative of a range of an antenna to a space vehicle and a carrier phase pseudorange measurement representative of the range of the antenna to the space vehicle. A code-carrier measurement difference is then generated between the code pseudorange measurement and the carrier phase pseudorange measurement. This code-carrier measurement difference is examined to determine if a multipath component is present. If the difference indicates that multipath is likely to be present, use of such measurements in computing position solutions, such as attitude solutions, is avoided. A multipath detection system for carrying out the method is also described.
Abstract:
Multiple pulses of narrow band signals of varying frequency are detected by multiple spaced apart receivers such that average time difference of arrivals of the signals from an item to be located are determined. The average time differences are used to calculate a position of the item to be located with a desired accuracy, such as within one meter in one embodiment. One of multiple receivers or rangers initiates a location process by transmitting a sync pulse. The sync pulse is received by a scout and other rangers. The scout is a small robot which acts as a transponder, sending out its own narrow band return pulse in response to the sync pulse. Each ranger then determines a difference in time between the sync pulse it receives and the return pulse generated by the scout. The location process is then repeated again at different selected narrow band frequencies, and an average of the difference in time at each ranger is determined. Each ranger is networked together via a standard wireless network, and also obtains position information via standard GPS methods. An iterative calculation of the location of the scout is used to improve an estimated position solution. Time difference of arrival between two rangers is expressed as an equation with three unknown variables, x, y and z, which define a position of the scout in three dimensional space. The locus of a point that satisfies this equation is hyperbolic. The iterative calculation uses at least squares approach to improve the estimated position to within a required tolerance.
Abstract:
A method for use in vehicle attitude determination includes generating GPS attitude solutions for a vehicle using three or more antennas receiving GPS signals from two or more space vehicles. An inertial navigation system is initialized by setting the attitude of the inertial navigation system to a GPS attitude solution generated for the vehicle and/or the attitude of the inertial navigation system is updated using the GPS attitude solutions generated for the vehicle or GPS estimated attitude error generated for the vehicle. A system for use in vehicle navigation is also provided. The system generally includes three or more GPS antenna/receiver sets associated with a vehicle, an inertial measurement unit that provides inertial measurements for the vehicle, a processing unit of the system having the capability for generating GPS attitude computations for the vehicle using the three or more GPS antenna/receiver sets and signals from two or more space vehicles; the GPS attitude computations include at least one of absolute attitudes and estimated attitude errors. The processing unit of the system also includes a filter for generating estimates of attitude for the vehicle using the inertial measurements from the inertial measurement unit and the attitude computations.