Transmitter and Receiver Enhancements for Ultrasonic Distance Sensing Systems

Flexural ultrasonic transducers experience sustained residual vibrations after their excitation has ended. This behavior limits both the minimum range and the range resolution of single-transducer distance sensors operating in pulse-echo mode. Two methods are presented to address residual vibration issues without reducing the intensity of the transmitted pressure waves. The first method is a transmitter enhancement; a number of out-of-phase damping cycles is appended to the desired number of excitation cycles, thereby hastening the decay of the pulse-imposed transducer voltage. The second method is a receiver enhancement; the echo-induced transducer voltage is isolated from the pulse-imposed transducer voltage by subtracting a stored masking signal from the acquired receiver signal. The proposed methods rely on a simple learning procedure that does not require a mathematical model of the system. Because this procedure is executed on an embedded microcontroller, the proposed methods are insensitive to variations in components or parameters. Experiments demonstrate improvements in both minimum range and range resolution.