Stabilizing wheeled passenger carrier capable of traversing stairs

An actively stabilizing wheeled passenger carrier capable of traverse stairs comprising:

• a wheel assembly having at least two axially-spaced wheels, each said wheel having an axis of rotation;
• a rigid frame including a double-inverted pendulum having at least two pivots, wherein the first of said pivots attaches said frame to said wheel assembly;
• a chair, wherein the second of said pivots attaches said frame to said chair, allowing said chair rotational movement about the second pivot independent of the wheels;
• a first motor assembly to apple torque between the wheels and said frame;
• a second motor assembly to apply torgue between the frame and the chair;
• and
• control means to sense and control three degrees of freedom:
• the first being an angle between the chair and a vertical position, the second being an angle between the frame and the vertical position, and the third being an angle between the wheels and an initial position, such control being accomplished through application of torques from the first and second motor assemblies;
• wherein the control means controls the three degrees of freedom to actively stabilize the wheeled passenger carrier to keep a passenger essentially upright during movement, including traversing stairs and the like,
• wherein the control means includes an electronic controller that continually senses three measured outputs:
• the first being an absolute angular acceleration of the frame, the second beings a relative angular velocity between the frame and the chair, and the third being a relative angular velocity between the frame and the wheels and,
• wherein three velocity states are continually calculated from the continually sensed three measured outputs, wherein the first velocity state is an absolute angular velocity of the frame, the second velocity state is an absolute angular velocity of the wheels, and the third being an absolute angular velocity of the chair, and
• wherein estimates of the three degrees of freedom are continually made by an estimator based on the continually calculated velocity states, and are continually fed back to the controller to continually control the application of torque from the first and second motor assemblies to between the wheels and the frame and between the frame and the chair, respectively.