Apparatus and method for pitch state estimation for a vehicle

An improved apparatus for generating a pitch state signal used in control of a ground-traversing vehicle, the apparatus being of the type including

• at least three inertial sensors positioned in three or more non-collinear orientations on the vehicle, having outputs by which may be derived three or more digital inertial orientation signals;
• a three-axis state estimator module, having an input coupled to the three or more digital inertial orientation signals, for calculating a first pitch state signal;
• an additional orientation sensor, positioned on the vehicle, having an output by which may be derived an additional digital orientation signal;
• logic for performing a single-axis state estimation of a second pitch state signal based on the digital inertial orientation signals and the additional digital orientation signal;
• and
• a first slew logic estimator module, having an input coupled to the first and second pitch state signals, for providing a pitch state output signal, the first slew logic module mediating between an output from the three-state estimator module and a second slew logic estimator module wherein the improvement comprises:
• a first single-axis state estimator module, having an input coupled to the three or more digital inertial orientation signals for calculating a first intermediate pitch state signal;
• a second single-axis state estimator module having an input coupled to the additional digital orientation signal, for calculating a second intermediate pitch state signal;
• and
• the second slew logic estimator module, having an input coupled to the first and second intermediate pitch state signals, and an output coupled to an input of the first slew logic estimator module,
• so that, in the presence of a fault condition associated with either one or more of the three digital inertial orientation signals or the additional digital orientation signal, the second slew logic estimator module nevertheless provides a single-axis state estimation substantially devoid of discontinuity.

An computerized method for generating an orientation signal used in control of a ground traversing vehicle, the method being of the type including:

• from at least three inertial sensors positioned in three or more non-collinear orientations on the vehicle, deriving three or more digital inertial orientation signals;
• calculating a first orientation signal in a three-axis state estimator module based on the three or more digital inertial orientation signals;
• from an additional orientation sensor positioned on the vehicle, deriving an additional digital orientation signal;
• calculating a second orientation signal in a single-axis state estimation based on the digital inertial orientation signals and the additional digital orientation signal;
• and using the first and second orientation signals in a first slew logic estimator module providing an orientation output signal that mediates between an output from the three-axis state estimator module and the single-axis state estimation;
• wherein the improvement comprises:
• calculating a first intermediate orientation signal in a first single-axis estimator based on the digital inertial orientation signals;
• calculating a second intermediate orientation signal in a second single-axis state estimator based on the additional digital orientation signal;
• and
• using the first and second intermediate orientation signals in a second slew logic estimator module to provide the second orientation signal;
• so that, in the presence of a fault condition associated with either one or more of the three digital inertial orientation signals or the additional digital orientation signal, the second slew logic estimator module nevertheless provides a single-axis state estimation substantially devoid of discontinuity.