AC : AUDITORY, VISUAL AND TACTILE STIMULI SYSTEM? A SENIOR DESIGN PROJECT

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1 AC : AUDITORY, VISUAL AND TACTILE STIMULI SYSTEM? A SENIOR DESIGN PROJECT Chandra Sekhar, Purdue University-Calumet CHANDRA R. SEKHAR is a member of the faculty of the Electrical and Computer Engineering Technology at Purdue University Calumet. Professor Sekhar earned a Bachelor s Degree in Chemistry from the University of Madras (India), a Diploma in Instrumentation from Madras Institute of Technology and Master s Degree in Electrical Engineering from University of Pennsylvania. Professor Sekhar s primary teaching and research focus is in the areas of Biomedical and Process Control Instrumentation and Clinical Engineering. Omer Farook, Purdue University-Calumet OMER FAROOK is a member of the faculty of the Electrical and Computer Engineering Technology Department at Purdue University Calumet. Professor Farook received the Diploma of Licentiate in Mechanical Engineering and BSME in 1970and 1972 respectively. He further received BSEE and MSEE in 1978 and 1983 respectively from Illinois Institute of Technology. Professor Farook s current interests are in the areas of Embedded System Design, Hardware Software Interfacing, Digital Communication, Networking, C++ and Java Languages Scott Reimer, Purdue University Calumet SCOTT REIMER graduated with a B.S. degree in EET in fall 2005, and is currently working as a management trainee at US steel. Ilija KaramacoskiI, Purdue University Calumet ILIJA KARAMACOSKI graduated with a B.S. degree in EET in fall 2005 and is currently working as an engineer for CS industry. American Society for Engineering Education, 2007

2 TACTILE AND AUDITORY STIMULI SYSTEM A SENIOR DESIGN PROJECT Abstract This paper describes the design and development of an instrumentation system to study the human response time while driving an automobile to visual, auditory and tactile stimuli. The human response time to the applied stimuli along with results from other ongoing research projects will be used in the development of safety features in the automobile. The project was successfully completed by two students as a senior design project. The project provided a unique opportunity for the students, to learn project development from a concept, time management and achieving the final results within cost constraints. Introduction The Tactile and Auditory Stimuli, an intra-departmental project came out of a casual conversation between the author and a research professor from the department of Behavioral Science. The project idea was conceived by the professor of the Behavioral Science department who wanted to study the effect of auditory, visual and tactile response of elderly people driving an automobile. Most vehicle crashes occur due to human errors. According to US Department of Transportation 1 there were 6,328,000 auto crashes in 2003, of those fatalities and 2,888,601 sustaining injuries. In many accidents the drivers were distracted by various audio and visual distractions and took crash remedial action rather slowly. The goal of this project is to measure the response times to different stimuli and provide a tactile signal to warn the driver that an impact may occur. The tactile signal warning will be especially useful for drivers who may have hearing problems. System Description The system consists of a driving simulator comprised of a steering wheel with gas and brake pedal assembly with transducers to convert mechanical movements to electrical signals. Precision potentiometers are connected to the pedals and the steering wheel. The change of potentiometer position due to the movements of the pedals and the steering wheel provided a current variation signal for analysis. The current signal is sent to the game port of a computer where it is converted from analog to digital signal for reading into a file. A Program written in C ++ (Appendix-A) analyzes the data on pedal and wheel positions. The Program also calculates the response time with respect to the stimuli and

3 the reaction of the driver in taking a corrective action. The Program has the provision to choose which sequence of stimuli should be activated. For visual stimuli, a set of six LEDs are used. A set of four buzzers are utilized for audio stimuli. The tactile assembly is for providing tactile stimuli. Figure-1 shows an overview of the project. Fig-1 System overview. Design approach 1. Mechanical system overview The original idea was to design a full scale interactive driving simulator. One way was to make the simulator built into a car that would give the test subjects a feeling of real life experience. However this idea was scuttled due to lack of funds. The project was implemented using a vehicle driver module. The vehicle module consists of a driver seat with a steering wheel, brake and acceleration pedals. The potentiometers were mounted to the brake, acceleration pedals and to the steering wheel to sense the mechanical movements of the pedals and the wheel. (Fig-2).

4 Fig-2 Line drawing of potentiometer layout 2. Stimuli: There are three different types of stimuli used in the project. The stimuli were applied to the left and right side of the driver. For the auditory stimuli buzzers with variable frequency responses are used. The buzzers are mounted to the headrest bars of the seat. LEDs are used for the visual stimuli and are placed on a structure mounted in front of the driver s seat. The LEDs are mounted in a 45 degree field of view and at a height equal to a persons view sitting in the seat. The commercial tactile transducers that we could find were expensive. We investigated and came up with the idea of using the vibrating mechanism that is used in a cell phone. The cell phone has a small offset motor and a tactile transducer to generate the vibrations. A breadboard (Fig-3) is used to mount the transducer and motor from the cell phone. This assembly is attached to the back of the seat. A screen is mounted eight feet from the driver s seat to project videos.

5 Fig-3 Breadboard mounting of the tactile transducer taken out from the cell phone 3. Simulation: To achieve the goals of the project, a simulator program has to be implemented. When doing research we found that commercial software are very expensive (over $10,000) and did not allow us to make changes easily that we might need. We settled on using Borland Builder to create an Object Oriented Program that would use the PC to get the positions of the steering wheel and pedals through the standard game port. An I/O board is used to activate the stimuli and gather current variable data from the potentiometers. The control program written in C ++ (Appendix-A) would trigger a stimulus based on set parameters. The stimulus could be set manually or it could be set on a time based driving instructor videos 2. These videos have simulations where a car may pull in front of the screen, stop in front of you or a passing car door would open in your direction. When the stimulus is engaged, the program would record the position of the wheel and pedals to a file and calculate the reaction time. 4. Interface I/O board. We used PMD-1024LS USB-based Digital I/O Module made by Measurement Computing. This module has three digital ports PortA, PortB and PortC with eight bits per port. Each bit on each port can be configured as input or output. For our project, we only used one port for output. The connections for the module are shown in Table-1.

6 Port Pin Number Connection PortB0 32 Audio Left PortB1 33 Audio Right PortB2 34 Visual Left PortB3 35 Visual Right PortB4 36 Tactile Left PortB5 37 Tactile Right GND 40 Ground Table- 1 Port configuration 5. Transistor Relay circuit The I/O module produces 5 volts/18ma output. This is enough to power the LEDS but it is not enough to power the tactor and buzzers. For this we designed a circuit that would supply more power to these components when activated. A power supply that converted 120AC to 6V/800mA VDC is used. Each tactor and buzzer had their own circuit. The circuit is shown in figure 4. Figure- 4 Driver circuit for the tactile transducers and buzzers

7 6. Software The software part of this project (Appendix-A) ended up being the largest and most challenging of the project. We used Borland Builder C++ 6.0, along with windows API commands; this allowed us to create user friendly object oriented programs. The main objective of the program is to monitor the steering wheel and pedal assembly. The current passing through the potentiometers changes with the change of steering wheel/brake pedal position. This current signal is sent to the game port of the computer where it is converted from analog to digital signal. The program reads the value on an X and Y scale that has a range of For this project the X scale corresponds to the steering wheel position. The zero value gives the center position of the steering wheel. The weight of the value determines which direction the steering wheel is turning. The Y scale corresponds with the gas and brake pedals. When the pedal is moved, the program will see the movement as either a positive or negative value. Positive scale corresponds with gas and negative scale with brake pedals. The three stimuli are independently controlled from a control box. This would allow more than one stimuli to be presented if needed. When using the program, a left side and right side impact could be predefined or entered manually. When the all the information for the test is entered, the program will start on the engagement of the start button. If the information needed is not complete, the program will let the user know by bringing up an error box explaining what information is missing. When the program runs, a timer will start and when the time reaches one second before the preset time, the values of the steering wheel and pedal positions are written to a file and will continue to write the value for two seconds after the stimuli is engaged. To be able to capture the moving variable, the data is captured in an edit box for each value. This is done for the first loop of the timer, this way it would only be done when the timer first started. When the program is running, these edit boxes are not visible. A text file is created in the C drive of the computer. The data in the file can easily be copied into an Excel file and graphs can be generated for the wheel and pedal positions with respect to time. This data stored in the file, could be analyzed at a later time. Conclusion The objective of this project is to create a driving simulator that would record the movement of the steering wheel and pedals in order to calculate the reaction time of a person s response to different stimuli that is engaged. The stimuli used are auditory (buzzers), visual (LEDs), and tactile (tactor). A program is written to capture the position of the steering wheel and pedals over duration of three seconds; one second before and two seconds after the stimuli is engaged. The program uses the values it stored to calculate the reaction time of the test subject in milliseconds. This data is stored in a file and could be used for further analysis. We used small buzzers and LEDs that could be replaced with speakers and lights that would enhance the sense of the stimuli. One big improvement for this project would be

8 the use of an interactive simulator that would allow more functionality to this project and provide more precise measurements. Pedagogy This project is a two semester capstone senior design two person project in the baccalaureate program. The students were able to integrate different segments of competencies from the discipline into a viable commercial grade end project. The team concept is emphasized and provides an environment for cooperative and discovery learning. References 1. The Bureau of Transportation Statistics html 2. Archive's Moving Images Collection: 3. Morrison, Michael, Sams Teach Yourself Game Programming in 24 Hours, October 2002

9 Appendix-A C ++ Borland Builder Code for TACTILE AND AUDITORY STIMULI SYSTEM

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22 Appendix Table 1. Calculations. Gas Pedal Resistance I calc = V / R I meas Depressed 5.41 K Ohms.9242 mamps.9124 mamps Resting 15.7 K Ohms.3184 mamps.3173 mamps Brake Pedal Resistance I calc = V / R I meas Depressed 29.6 K Ohms.1692 mamps.1569 mamps Resting K Ohms.2670 mamps.2537 mamps Steering Wheel Resistance I calc = V / R I meas Center K Ohms.2317 mamps.2231 mamps Left 4.1 K Ohms.0012 mamps.0127 mamps Right 39.0 K Ohms.1282 mamps.1270 mamps