Time Optimal Operation of Flexural Ultrasonic Transducers For Enhanced Ranging

Flexural Ultrasonic Transducers (FUTs) exhibit sustained residual vibrations after their excitation has ceased. This results in a long decaying tail in the FUT's terminal voltage affecting the Time of Flight estimation and ranging capability for reflectors situated near the FUT. Time optimal control principles are applied to design the excitations to accelerate damping, improve ToF estimation, and improve ranging near the FUT without compromise in the strength of the transmitted pressure wave. Numerical solutions for the control problem are obtained using Nonlinear Programming. An algorithm is described to operate Pulse Width Modulation peripherals found on commercial off-the-shelf microcontroller units to realize the excitation signals at the output of H-Bridge modules. Experimental results show an improvement of 15% in the minimum range with the designed time optimal excitations.