Ultrasonic distance measurement for linear and angular position control

A robot-arm positioning control is described. It makes use of a microprocessor-based ultrasonic system and of a novel time-of-flight measurement technique. The experimental system consists of a three aligned ultrasonic transducers mounted on a rod. Two transducers work as receivers, while the third works both as a transmitter and a receiver. The system achieves a positioning accuracy of ±0.1° in the field of ±10° of misalignment for a distance ranging from a few centimeters up to 200 mm. For a higher distance range up to 300 mm, the position accuracy is ±0.4°. The system also performs distance measurement, using the same group of transducers. The system can be used in robotic applications in industrial environments, such as for orientation control or object grasping