Abstract: A stair-climbing wheelchair having a sensor at the front end thereof for sensing the presence of a stair step or an inclined ramp. The sensor emits signals which reflect from a surface and to a receptor in the sensor, the receptor being coupled to a microprocessor which determines not only the linear distance traveled by the wheelchair in a forward direction, but also the height of a stair step. Thus, when the tracks are down, a microprocessor associated with the sensor will shut off the drive motors to the tracks if the slope of the stairway is too great when the tracks are down. In such a case, the wheelchair backs away from the stairway and does not go down it. If the slope is less than a predetermined value, such as 30.degree.-35.degree., the wheelchair can move down the stairway in the normal fashion.

Abstract: A stair-climbing wheelchair having wheels defining a first wheel base and a pair of endless, flexible tracks providing a second wheel base, there being a motor-driven structure for moving the tracks into and out of ground-engaging positions. A first pivotal arm is pivotally mounted on the wheelchair near the front end thereof. The first arm is coupled to a fluid piston and cylinder assembly which actuates and cushions the pivotal movement of the arm as the wheelchair moves from a horizontal position to an inclined position, such as moving from the top of a stairway to the slope of the stairway as the wheelchair moves down the stairway. Similarly, a second arm coupled with a fluid piston and cylinder assembly is coupled to the wheelchair to cushion the movement of the wheelchair and its occupant as they move from an inclined position to a generally horizontal position, such as at the top of a stairway.

Abstract: An improved drive circuit for steering a motorized wheelchair. A control mechanism produces right and left drive signals to respective right and left wheel drive motors. These right and left drive signals are amplified by right and left amplifiers to provide the necessary magnitude power signal to the motors. The input to the amplifiers are cross-coupled so that each amplifier will amplify its own input signal plus a portion of the cross-coupled input signal.