An Acoustic Navigation System for Mobile RobotsProject DescriptionMajor GoalsImplementation RobotController BoardBudgetMicrophone ArrayElectret Condenser MicrophoneMicroprocessor InterfaceBlock Diagram of the InterfaceDesign TestingProtel SchematicProtel PCBMicrophone Array PCBPCB ManufacturingPCBProblemsSoftwareSoftware calibrationSoftware RunMore informationAn Acoustic Navigation System for Mobile RobotsThomas GarnerChris GonzalesTrent FoleyJosh EarleyComputer EngineeringSenior Design ProjectSpring 2003page 201/14/19Acoustic Navigation System for Mobile Robots Project DescriptionThe goal of this project is to develop a microphone array module that will allow a mobile robot to detect acoustic beacons in its surroundings. The array will consist of miniature microphones in a ring configuration to provide 360 degree sound localization. This will allow the robot to display a number of phonotaxis behaviors, e.g. homing in or fleeing from acoustic sources.page 301/14/19Acoustic Navigation System for Mobile Robots Major Goals•Develop an printed circuit board (PCB) interface for the microphone array•Develop acoustic fixtures to improve the directionality of the individual microphones•Develop algorithms to estimate the angular position of acoustic beaconspage 401/14/19Acoustic Navigation System for Mobile Robots Implementation Robot•Controller board•Sensors•Pre-programmed PIC•Chassis•Wheels•Motors•Software•Assembly required !!Mark III Robotpage 501/14/19Acoustic Navigation System for Mobile Robots Controller Board•OOPic microprocessor•40-pin I/O interface•Programmed using C, Java, or Basic•Programmable via serial and parallel ports•Brains of the robotMicrocontrollerpage 601/14/19Acoustic Navigation System for Mobile Robots Budget•Proposed - $481.12•Actual - $496.26page 701/14/19Acoustic Navigation System for Mobile Robots Microphone Array•Implementing 8 microphones, spaced at 45° angles•Electret condenser microphones ― best compromise between response, cost, and ease of design•Acoustic fixture is made of plexi-glass and is covered with sound dampening material ― rejects sound from sides of each microphonepage 801/14/19Acoustic Navigation System for Mobile Robots Electret Condenser MicrophonePanasonic WM-65A103 Wiring Schematicpage 901/14/19Acoustic Navigation System for Mobile Robots Microprocessor Interface•513 bits would be required to send full data from 8 microphones containing frequency information to the microprocessor simultaneously ― not feasible•Multiplexers simplify hardware solution and reduce the interface to 17 bits while allowing microprocessor control over the sampling process•Microprocessor decides which microphone to be currently sampled•Microprocessor also decides what frequency band to listen for on that particular microphonepage 1001/14/19Acoustic Navigation System for Mobile Robots Block Diagram of the Interface•Fabrication of two separate printed circuit boards: one for the microphone array itself and one for the interface•Allows for more modularity and ease of maintenance and fabricationpage 1101/14/19Acoustic Navigation System for Mobile Robots Design TestingBefore fabrication of a PCB, the design is fully tested on a breadboardpage 1201/14/19Acoustic Navigation System for Mobile Robots Protel Schematic•The pin out for each component is designated•A footprin t must be designated for each component so that Protel can update the schematic to the PCBDeveloping a Schematic for a PCBpage 1301/14/19Acoustic Navigation System for Mobile Robots Protel PCBA Powerful Tool•Protel automatically manages the traces between connections•Protel shows where a component should or should not be placed due to traceability•After placing components where desired, using the Protel autorouter, all traces are drawn automatically according to design rules setpage 1401/14/19Acoustic Navigation System for Mobile Robots Microphone Array PCB•Purpose mainly for acting as a mounting device for the microphones and the acoustic fixture•Contains a ground mesh on each side to reduce noisepage 1501/14/19Acoustic Navigation System for Mobile Robots PCB Manufacturinghttp://www.apcircuits.comManufactures boards fairly cheaply at around $75 per boardAllow Protel designs and perform professional services such as drill-thru and silk screeningpage 1601/14/19Acoustic Navigation System for Mobile Robots PCBpage 1701/14/19Acoustic Navigation System for Mobile Robots Problems•Microphones do not work well in a room environment.•Software was much more of a challenge.•Debugging was difficult, software did not allow us to monitor outputs.page 1801/14/19Acoustic Navigation System for Mobile Robots Software•Parallel port programming - does not share any of the I/O lines we used in our interface design•Initialization - establishes the I/O lines to be used for controlling the microphone and filter multiplexers, the analog-to-digital converter enable, the servos, and the signal inputpage 1901/14/19Acoustic Navigation System for Mobile Robots Software calibration•Accurately compare microphone signals•Obtain an average of the ambient noise signal on each microphone and then the average maximum audio signal on each microphone•These values are stored in a global array so that they can be accessed for computation in later routinespage 2001/14/19Acoustic Navigation System for Mobile Robots Software Run•Performs sampling on each microphone Scaled value = (signal – minimum signal) * 127 (maximum signal – minimum signal)•The calculated scaled values for each microphone are then compared for the maximum value and then to a threshold value•Robot directed in the direction of the microphone receiving the greatest sound source or not to move at allpage 2101/14/19Acoustic Navigation System for Mobile Robots More
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