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RotoSonar: Intelligent Local Mapping and Position Localization Sensor System

RotoSonar is a versatile and effective ultrasonic range finding device that makes an ideal navigational sensor for research and industrial applications in autonomous navigation and guidance. As supplied, the kit of three printed circuit boards consists of a rotating head, interface card, cabling, technical manual and software disc. RotoSonar is an intelligent and low memory using ultrasonic mapping sensor that can be used on moving platforms such as automated guided vehicle systems (AGVS) and mobile robots to give rapid surface data and related information supporting autonomous navigation, guidance and path following such as those in parametric mapping.

The stepper motor controlled rotating head carries four Polaroid sonar transducers. These transducers transmit coded ultrasonic bursts of ultrasound at around 50khz which are reflected by the objects around the head, returning echoes and enabling fast and accurate acquisition of angular range information. Electronic signal processing provides high resolution suitable for scene analysis and feature extraction. All control and signal lines are transmitted through a 360 degree slip ring so that continuous rotating scans of the environment is assured. The versatile head has the capability of changing its configuration: supporting 1, 2, 3 or 4 sonar transducers as required by the experimenter and spaced equally for symmetrical map scanning. Transducers are individually wired and can be accessed in any pattern. With all four heads in operation the unit can regenerate a full 360 degree map of its surroundings within a nominal 0.2 seconds. This smart sensor configoration represents an alternative over traditional multi-element ring type sonar navigational devices, affording the experimenter not only high mapping speeds at low cost, but providing much higher resolutions. The stepper motor is direct drive to the rotating head mechanism and stepping 7.5 degrees each pulse. Total number of readings per 360 degree scan is therefore 48. Since standard stepper specifications are used, the researcher may change the motor to any other step angle desired. For example 3 degree angle steppers have been used to give 120 readings per revolution.

The interface electronics includes stepper motor control, stepper home positioning, individual sonar drivers, reduced and user settable dead time control circuitry, vectored interrupts, time out detection, of board TOF counting, and connection to a standard PC I/O slot. The innovative hardware enables the head, its stepper motor, direction sensing, and all four sonars to be operated entirely "on the interrupt" on an IBM compatible PC. This means that no real-time programming time need be lost in operating the device. All an application need do is peruse a buffer that is constantly being refreshed.

The C++ source code to drive this hardware is supplied in disk and hardcopy form. Non-interrupt driven modifications such as polling can be made to the hardware and software as desired.

The screen picture shown in the next column is from the artificial intelligence scene analysis and parametric mapping of a low cost smart mobile robot designed for task applications in unknown environments. The system accumulates a world map and then keeps it refreshed as the environment changes using a RotoSonar with 4 heads and 3 degree steps. This is a 2 dimensional example, with sensor fusion solutions to extend to 3 degrees.

Compatible with Denning Branch International robots and adaptable to others, the software package is designed to deliver the most from the RotoSonar and to give an immediate start on any navigational research. RotoSonar is currently in use in industrial, commercial and research applications such as robot floor scrubbing, autonomous AGVs, and research robotics. Denning Branch International Robotics has considerable experience developing and implementing complete autonomous navigation systems including software, hardware and mechanical navigation, guidance, mapping and route packages for this and other sensors. We can be engaged as outsource contractor or consultant for customer applications. RotoSonar is an integral part of the Moulinex D'Entrecasteaux and General Electric's Florbot smart robotic floor cleaners, and the Fander and MaxiFander series research robots.

Tax Free Price:			$18,750 USD
Freight and insurance are extra. Limited parts and labor warranty applies.

Sonar transducer frequency:	49.4 KHz
Sonar type:			4 x Polaroid 300V electrostatic
Range:				6 inches to 35 feet
Accuracy:			+/- 2% at one foot or greater 
Acquisition speed:		nominally 360 degree map within 0.2 seconds depending on environment size
Stepper motor:			optional 6 or 12 V, 7.5 degree increments
Dimensions:			12cm x 12cm x 13 cm
Weight:				700gm
Power consumption:		700-900mA at 6 volts dc
				(2 Amps per sonar instantaneous)

Suggested Applications:
·	Local and reference mapping
·	Object avoidance
·	Object tracking
·	Object following
·	Robot guidance
·	Non-tactile touch sensing, surface proximity detection
·	Security and intrusion sensing

©Copyright 1984-2003 all rights reserved, specifications are subject to change without notice. Patents and trademarks apply.

Polaroid is a registered trademark of the Polaroid Corporation.
RotoSonar is a reserved name of Branch and Associates Pty Ltd.

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