Designing a Voice Activated Compartmentalized Safe with

Speech Processing using Matlab

Preliminary Design Review

Amy AndersonErnest BryantMike JoynerCollins Pratt

October 19, 2007

Georgia Institute of TechnologyECE 4007 Senior Design

Project Overview

• Design a voice activated, motor driven, compartmentalized safe using computer, Matlab software and microcontroller

• Intend for residential and commercial use; specifically homeowners and small business owners

• Estimate costs for retail unit at $1200

Design Objectives

• Build a wooden cylindrical compartmentalized safe prototype

• Allow access to each compartment through specific, user programmed voice password

• Develop Matlab program capable of identifying and verifying two specific speakers

• Develop GUI to allow user to easily configure and operate safe

• Interface computer and microcontroller through Matlab and serial cable

• Use microcontroller to control stepper motor that rotates safe top

Block Diagram of Safe Prototype

Safe Prototype Design• Dimensions: 18” diameter

x 6” height• Base constructed of ¾”

plywood• Compartment interior walls

constructed of ¼” plywood• Side walls constructed of

1/16” door skin plywood• Top constructed of ¼”

plexi-glass for demonstration purposes

• Slot routed out for motor• Center PVC designed to

house motor shaft• Motor and microcontroller

contained inside blanked off, spare compartment

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1.8o, 24V Unipolar Stepper Motor

• Rotates top of safe clockwise and counterclockwise to allow access to all compartments

• Receives a predetermined sequence of applied currents to the stator windings from the microcontroller

For Clockwise Rotation: Winding 1a 1100110011001100110011001Winding 1b 0011001100110011001100110 Winding 2a 0110011001100110011001100 Winding 2b 1001100110011001100110011

0: de-energized, 1: energizedFor Counterclockwise Rotation: reverse sequence

1.8o, 24V Unipolar Stepper Motor

The animation illustrates the rotor turning proportionally to the sequence of applied currents to the stator windings

Animation borrowed from http://www.cs.uiowa.edu/~jones/step/typesf/2anim.html

PIC18F452 Microcontroller• Protected from back feed

of high motor voltage by Darlington transistor (UL2003) array

• Controls motor rotation by energizing wires through Port B of the PIC

• Determines how much to rotate motor based on data received from Matlab program through 9 pin serial cable

Serial Port Communications

• Serial Port connects computer with the PIC

• Matlab sends specified speaker number through port to PIC

• Serial port transmits 8 bits one bit at a time – need program to recognize when full 8 bits received

RS232 9-pin serial port

Serial Port Program

• Written in assembly language • Written to recognize when 8 bits are sent

– Checks to see when full word (8 bits) is received by checking a bit within the register that turns on high when the full word is received by the microcontroller

- When full word is received, the PIC turns the motor according to specified word received

Matlab Overview

1. Receives speech data (1 password per compartment) through microphone for initial configuration

2. Extracts features of received speech to create model for later comparison

3. Receives input speech to be verified4. Compares input speech to stored model for each compartment5. Verifies speech and password and sends 8 bit word to

microcontroller through serial port to access the specified user’s compartment

Matlab Speech Algorithms

Used two main algorithms for speech processing:

• For feature extraction: Mel Frequency Cepstral Coefficients

• For speaker modeling and classification: Vector Quantization Code Book

Mel Frequency Cepstral Coefficients

• Representation of a person’s speech signal in frequency domain

• Envelope of the FFT of the speech signal

• Used in speaker recognition because variations in a person’s speech are minimized in the frequency domain compared to the time domain

Extracts cepstral coefficients

Vector Quantization Code Book

• Speaker Modeling– Models of passwords are configured for

specified compartment– Creates a vector of centroids for each modeled

word• Classification

– Compares features from input signal with the features from the modeled words by calculating the differences

– Chooses the modeled word that produces the smallest difference

– Rejects the speaker if the minimum difference is not above a specified number (threshold)

Matlab GUI Operation

• Add words to database from microphone or audio files

• Verify speaker and words from microphone or audio files

• Clear database for reconfiguration

Design Changes

• Determined that Simulink is no longer needed; were using Simulink to link Matlab and PIC but determined that Matlab will link directly with the microcontroller

• Built a Plexi-glass top because wood one warped in humidity and for demonstration purposes

Design Advantages

• Wood construction allows for easy alteration

• Modular construction allows for easy removal of key parts if necessary

• Design allows for future modifications and upgrades (pinpad, LCD screen, etc)

Disadvantages

• Will not be a stand alone prototype; must rely on computer for most items

• Computer is slower than we would like for some calculations

• More users, longer calculation time

Current Project Status

• Speaker identification complete• Speaker verification 95% complete• Prototype compartment built• Matlab linking correctly with

microcontroller• Microcontroller turning motor

Future Work

• Determine how to gear motor correctly• Implement proper protection circuit for

microcontroller• Determine threshold for speaker

verification with high quality microphone• Test algorithm to increase accuracy• Test links between all equipment• Test motor control and turning• Test entire unit

QUESTIONS?