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TAMU CSCE 483 - acoustic-report2

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ACOUSTIC NAVIGATION FOR MOBILE ROBOTS Bi-Weekly Report Josh Earley Trent Foley Thomas Garner Chris Gonzales CPSC 483 26 MAR 20032 Table of Contents Introduction ............................................................pg.3 Current Design........................................................pg.3 Microphone Directionality ......................................pg.4 Microphone Fixture.................................................pg.4 Filter Solution .........................................................pg.4 PCB Generation......................................................pg.5 Robot Progress........................................................pg.5 Order Status............................................................pg.6 Scheduling..............................................................pg.63 Introduction Our design project is going according to plan. We have already received all of the major parts and are working diligently on the final aspects of our design. We have passed some of our troubles and are working to complete the design. Below is on outline of our status concerning different aspects of the design, as well as an update on our scheduling, cost, and new issues with our design. Current Design Figure 1 illustrates our current design. We have decided to fabricate two separate printed circuit boards: one for the microphone array itself and one for the microcontroller. This will allow us more modularity and ease of maintenance and fabrication. The microphone array board will consist of the 8 microphones patterned in such a way that each microphone has 45o of coverage. Further, the board will have a resistor pack that will develop the output signal for each microphone. We will route the signals to the microcontroller board via a 10-pin connector. The microcontroller prepares the microphone signal to be presented to the microprocessor of the Mark III. This board will accept the eight microphones data into an 8:1 multiplexor that is controlled by the Mark III’s processor. Once a microphone is selected, it will be sent to the filter (LMF100). The filter has two inputs, one for the microphone data and one from the crystal and 4-bit counter (74LS191) circuit, which will provide 8 center frequencies through a processor controlled 8:1 multiplexor. The filter also provides us with gain, and we will use this to amplify the signal for rectification. After the filter, the signal will be rectified and sent to the A/D converter (ADC0801). This will convert the rectified signal into an 8-bit digital signal that is sent to the processor. In all, we will use 14 of the 16 interface bits on the Mark III. Six bits will be used for the multiplexers, and eight bits will be used for the microphone signal. However, we4 also have the capability to send the microphone signal to the processor in analog format, as the processor has analog capabilities. Microphone Directionality Our microphones, although described as unidirectional on the Panasonic datasheet, do not appear to be very directional. We have tested the microphone’s signal strength at varying levels and distances and although there is slight directionality, it is hardly practical. We will ultimately need to implement a sound-dampening fixture, which is described in the following section. This will give us the directionality that we need to really apply this design to real-world environments. We will get the sound dampening material this week, and begin testing soon. We plan on having a directionality polar graph after testing. Microphone Fixture Our microphone fixture has been designed and manufactured (Figure 2). We created it using plexi-glass, super glue, and a rubberized aluminum cylindrical shaft to support the dividing walls. This fixture will be mounted on our microphone array board, surrounding the mics. It will be covered in the sound dampening material and will provide 3 – 6 dB of attenuation. Although it is yet to be tested, we feel this will provide ample sound absorption and give us the directionality in the microphones we are seeking. Filter Solution The schematic for the LMF100 Switched Capacitor filter has now been finalized (Figure 3 & 4). Prior to this, the filter was not producing a signal consistent with any expected output. This was due to one pin, SIa, being incorrectly grounded, instead of being set to Vcc/2. The preliminary filter data, obtained with a single LMF100 on a bare, new motherboard, with two function generators generating both the square clock pulse and the sinusoidal input signal, gave some5 inconclusive and varying results but proved that a +5 V single supply operation could be achieved. When another LMF100 filter was placed on the breadboard with the rest of the components, and the clock input was from the multiplexed, clock-divided signal, our results proved to be much better. With the clock frequency to the filter at 125 kHz, and a signal generator set to a sinusoid at 1.25 kHz, the filter worked beautifully, achieving a bandpass at exactly 1.25 kHz, and providing the proper gain at that bandpass. PCB Generation After attempting to complete our first printed control board in EAGLE 4.0 software, we decided to change to the PROTEL software, mainly because we have a fully licensed version in the labs. Second, the EE department will etch our boards, and they only use PROTEL. However, we are not using the EE unless we are in a time restraint, as the EE department does not perform the drill-thru technique that would require the use of vias. This would make our assembly much more time consuming and subject to failure. We have found a site, http://www.olimex.com/pcb/index.html that will manufacture our boards fairly cheaply at around $75. They allow PROTEL designs and perform all the professional services such as drill-thru, silk screening, etc. Once our design is completed, we will send off for both boards to be etched. Robot Progress We have assembled the Mark III Robot and it is functioning properly. We carefully soldered the circuit board together and did not have many problems with it. After it was constructed, we need to make sure that it would be able to receive data from the computer via its serial port. At first, we could not get the Mark III to connect. We found a Yahoo Group forum on the Internet, which posts questions and answers about common problems with the robot. We found that we were using the connection


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