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Fire-Fighting Robot
By Merima Jahic and Christopher Elpers

I. Abstract

In this paper we will try to describe the process of designing a fire-fighting robot, by the standards of the IEEE SouthEastCon 2003 Student Hardware competition requirements. The robot has to be autonomous. It will ultimately wait for the 1500 Hz signal to start the movement, navigate through the house-like maze, detect the LED “candle”, cover it with a plastic cup and go back to the starting position. The design will include the circuits for the audible sensors, wall detector, encoder and light sensors and detectors. Phillips microcontroller incorporated in the Lego board version 6 designed by the University of Evansville faculty is used to provide the main control for the robot and separate hardware previously mentioned.

II. Acknowledgment

We would like to thank Dr. Dick Blandford, Dr. Anthony Richardson, and Mr. David Mitchell for their support and help with the design. Also, our thanks go to The University of Evansville College of Engineering and Computer Science for providing funding for this project.

1. Introduction

In this paper we will describe the process of designing a fire-fighting robot, by the standards of the IEEE SOUTHEASTCON 2003 Student Hardware competition requirements. The robot must be autonomous. It will wait for an audible signal with a frequency of 1500 Hz to begin movement, navigate through a house-like maze, detect an LED “candle”, cover it with a plastic cup and return back to the starting position. The design will include the circuits for the audible sensor, distance sensor, and light sensors. An 89C51RD2 Phillips microcontroller incorporated in the Lego board version 6 designed by the University of Evansville faculty was used to provide the main control for the robot and separate hardware previously mentioned.

2. Project Requirements

The requirements for this project are based on the IEEE SOUTHEASTCON 2003 hardware competition.2 The restrictions are set as follows:
· The Robot must be autonomous.
· It will start its movement after it detects the audio signal of 1500 Hz

3. Software and Hardware design

The design procedure can be broken down into several steps:
· Audible sensor design to detect the start signal
· Light sensor design to detect the LED “candle” in the room
· Distance sensor to determine the distance from the front of the robot to the “candle”
· Encoder design to determine the distance the robot traveled
· Software with functions to control hardware developed
· The chassis design of the robot
The performance of each piece of hardware can be tested separately which speeds up the process of the design, hence the software has been broken down into separate functions to allow the designers to control the separate pieces of hardware.

3.1 Audible sensor

The audible sensor has been designed using an analog filter and an amplifier. In order to trigger the robot’s movement at the desired frequency, other possible noises at different frequencies had to be filtered out. To filter a wide range of frequencies that are not desirable, a simple amplifier with the gain of 100 has been used. This op-amp acts like a low-pass filter with a cut-off frequency of 300

Hz because of the real time performance of the LM741 operational amplifier 3 (used in the implementation of the circuit), since f-3db=1.5MHz/Av, where Av is the gain of the amplifier. In this case the gain will be one hundred. Output from this op-amp is taken through a simple RC high-pass filter, with the desired frequency just greater than 1500 Hz. Using the rule of thumb which says that a
capacitor must be 10 times greater than the capacitor which gives the exact desired frequency if used in the high pass filter: C>10/( 2x3,14xRxf ) we chose values for R and C that satisfy the given equation. A gain of a 100 is used to amplify the small signal coming from the receiving microphone (as mentioned before). To achieve this gain a non-inverting amplifier is used as suggested previously, which also plays the role of the low pass filter. The values of the resistors for the amplifier are determined using the following equation: Av = (R1 + R2) / R2. Figure 3.1.1 illustrates the design and figure 3.1.2 illustrates the simulated performance of the filter.

Figure 3.1.1 Filter circuit

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