Ultrasonic distance scanning techniques for mobile robots

This paper discusses the application of ultrasound to mobile robot navigation. Two methods employing transducer arrays are described, namely the phased array (PA) method and the maximum-likelihood-estimation (MLE) method. These two methods are compared with the conventional time-of-flight (ToF) method. The paper shows that the PA method has advantages such as giving focused beams and allowing efficient beam steering. Limitations of the method are also discussed, including the need to assume a far-field, the undesired side grating lobes and the unavailability of suitably-sized transmitters. In order to understand the measurement uncertainty, a quantified estimation of the effective range and bearing measurement is calculated. The MLE method has the advantage of only involving one transmitter. The locations of the reflectors employed with this method can be represented in a probability map. Experimental results show that the reliability can be improved through the use of multiple receivers