Structure for and method of surface condition sensing and indicating and motor speed control

Abstract

Abstract The condition of a surface is sensed by cyclically moving two members having engaged surfaces relative to each other, driving the surfaces for only a portion of each cycle to set up a threshold kinetic energy level in accordance with the friction between the engaged surfaces, sensing the kinetic energy developed in one of the members due to moving the members relative to each other, comparing the developed kinetic energy with the threshold kinetic energy and controlling the cyclic movement of the members in accordance with the relationship between the kinetic energy threshold and the developed kinetic energy. The cyclic movement of the members is then used to provide a visual indication of the condition of one of the surfaces. The structure for surface condition sensing and indicating includes a pair of cyclically relatively movable members in surface-to-surface frictional engagement, means for driving the members relatively for a portion of a cycle of relative movement thereof, means preventing driving of the members for the rest of the cycle of relative movement thereof to establish a threshold of kinetic energy in one of the members necessary to maintain relative movement between the members during the portion of the cycle in which they are not driven relatively, means to sense the relation between the kinetic energy of the one of said members relative to the threshold kinetic energy established, means for varying the time between cycles of driving the members relatively in accordance with the relation between the established threshold of kinetic energy and the sensed kinetic energy of the one member and means for providing a visual indication of the relation between the kinetic energies. The means for controlling the cycle time includes means for immediately starting a new cycle of operation if the sensed kinetic energy is greater than the threshold kinetic energy established and for providing a predetermined dwell time between cycles of relative movement of the members if the sensed kinetic energy level is below the established kinetic energy level. Structure is also disclosed for varying the dwell time in accordance with the exact proportion between the established kinetic energy level and the sensed kinetic energy level in conjunction with particular structure for developing an electric signal proportional to speed of an electric motor. The particular structure for developing a signal proportional to motor speed includes one or more additional commutator brushes provided in conjuction with the motor through which a signal is developed from the motor proportional to motor speed. The particular structure for developing a signal proportional to motor speed is also disclosed in conjunction with a method of and means for motor speed control. The method of motor speed control includes driving an electric motor with an electric signal, taking an electric signal from the motor itself proportional to motor speed and controlling the signal electric siganl with the signal proportional to motor speed. The structure disclosed for controlling the speed of a motor includes a source of reference electric signal high gain structure for feeding electric energy to the motor, the particular structure including a third commutator brush on the motor for developing an electrical signal proportional to the speed of the motor, means for comparing the developed electric signal with the reference electric signal to provide an error signal controlling the high gain device to determine the amount of energy fed to the motor. The motor speed control structure disclosed includes pulse producing structure for energizing the motor with pulses of electric energy and has fail safe features for use with vehicles.

Inventors

• 👤 Robert W Kearns

Bibliographic Details