Abstract: An automatically controlled manually steerable vehicle has power steering in both manual and automatic control modes. A torque sensing means for the coupling between the steering handle and the steerable wheel uses a flexible coupling and a photocell detecting system to control the power steering for the vehicle in the manual mode.

Abstract: A vehicle guidance mechanism for guiding a vehicle along a surface by means of an invisible guide line containing fluorescent material comprises an ultraviolet lamp that causes the guide line to fluoresce and emit visible light; photocell sensors mounted in the vehicle and adapted to sense the visible radiation and produce an error output signal proportional to the variation of vehicle position from a predetermined lateral position with respect to the guide line; and a control device in the vehicle adapted to steer the vehicle in response to the error signal so as to cause the vehicle to follow the guide line. An automatic contrast control circuit eliminates the effect of background illumination in the output signal and produces a constant closed loop gain with respect to the signal received from the guide line. Modulation circuitry and appropriate filters further reduce the effects of background illumination and improve the reliability and line detecting ability of the guide system.