Revision as of 22:31, 22 May 2014

Grading Criteria

Anti-Crash Car

Abstract

This project involves a GPS-controlled car that drives to a user determined destination. To prevent self-damage, when an obstacle is in its path, the car will move around the obstacle and determine a new path towards the destination. In addition, any time the car cannot move around the obstacle (all sides are blocked), the car will stop.

Objectives & Introduction

Show list of your objectives. This section includes the high level details of your project. You can write about the various sensors or peripherals you used to get your project completed.

The car is driven by the motors and steered by a single servo. It is guided by a compass which points to the direction of the destination set by the user. The compass determines this direction through calculations, comparing its current location (coordinates found by the GPS Receiver) with the destination's coordinates. To avoid collision with interfering obstacles, 3 sensors are used--one being sonar, two being infrared.

Team Members & Responsibilities

• Geff Lozano
  • Infrared Sensor Module
  • GPS Module
    • Parser
    • Information Processing
  • System State Machine

• Koko Maung
  • Car Kit Assembly
    • Servos
    • Motor
  • Infrared Sensor Module
  • Sonar Sensor Module
  • Compass Module
  • State Machine

• Matthew Pham
  • GPS Module
    • UART Interface
    • Parser
    • Information Processing
  • System State Machine

Schedule

Parts List & Cost

Design & Implementation

The design section can go over your hardware and software design. Organize this section using sub-sections that go over your design and implementation.

Hardware Design

Main Components:

• SJ-one Board
• Rock Crawler
• IR sensor
• Sonar sensor
• GPS module
• Compass module

Hardware Interface

In this section, you can describe how your hardware communicates, such as which BUSes used. You can discuss your driver implementation here, such that the Software Design section is isolated to talk about high level workings rather than inner working of your project.

Software Design

Sonar task

Left IR task

Right IR task

GPS task Updates a struct of type "coordinates." This struct contains two double types (one for longitude and one for latitude).

Case task

Compass task

Design Flow

Sonar tasks

Left IR tasks

Right IR tasks

GPS tasks

Case tasks

Compass tasks

Design Flow

Implementation

This section includes implementation, but again, not the details, just the high level. For example, you can list the steps it takes to communicate over a sensor, or the steps needed to write a page of memory onto SPI Flash. You can include sub-sections for each of your component implementation.

State machine

Our State machine is designed with

 STOP :       Forever stop loop
 START:       Car turned on / reset button is pressed
 CURRENT:  1. current location is collected from GPS
           2. set L,M,R = 0,0,0
           3. ( destination == current) ? if true : stop ; else : compass 
 COMPASS:  1. check head direction
           2. check where the coordinate of destination
           3. set L,M,R bits accordingly
           4. move to decision
 DECISION: 1. depending on the L,M,R bit it will make decision on which sensor to check
           2. ( Object )? if : next sensor; else move
 MOVE :    1. move accordingly
           2. move back to current

Servo and Wheel motor Communication (PWM)

Servo and Wheel motor communication is done by using PWM communication. Interface for PWM is already given by Professor Preet.

1. We must set the pin that we want to use with the waveform period

2. set percentage of waveform to be stay at high.

  eg.PWM pwm1(PWM::pwm1, 50); // pw1 = p0.0, period = 50
     pwm1.set(10);            // percent = 10   1/5 of the time signal gonna be high

Sonar and Compass Communication (I2C)

Sonar and Compass communication is done by using I2C communication. Interface for I2C is already given by Professor Preet. Since I2C module already take care of turning the LSB to high and low accordingly, we don't have to worry about it.

1. Get device address from datasheet.

2. If device requires commands to perform operation, write command to appropriate register.

3. Read information from appropriate register.

notice : If you try to read value before its ready, you will get zero.

  eg. i2c.writeReg(0xE0,0x00,0x50); //writing: device address = 0xE0, register address = 0x00, writing value = 0x50;
      char high_byte = i2c.readReg(0xE0, 0x02); // reading: device address = 0xE0, register address = 0x02
      char low_byte = i2c.readReg(0xE0, 0x03);  // register address = 0x02

Infrared Communication (ADC)

Infrared communication is done by using ADC communication. Interface for ADC is already given by Professor Preet.

1. set a pin for ADC

2. select mode

3. initialize the pin

4. read value at appropriate time.

  // initialization 
  eg. LPC_PINCON -> PINSEL1 |= ( 1 << 20 ); // P0.30
      LPC_PINCON -> PINMODE1 |= ( 2 << 20 ); // output mode
      adc0_init(); // initilize
  // reading
      IR_Left_distance = adc0_get_reading(4);

GPS Communication (UART)

The GPS Receiver communicates with the SJ One board through UART via NMEA sentences.

Examples:

• The user can configure the update (baud) rate of the GPS module with the following example commands:
  • 38400bps - $PMTK251,38400*27<CR><LF>
  • 57600bps - $PMTK251,57600*2C<CR><LF>
• The user can filter out unwanted NMEA sentences with the following example commands:
  • Only RMC at 1Hz - $PMTK314,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0*29<CR><LF>
  • Only GGA at 1Hz - $PMTK314,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0*29<CR><LF>

Pin Configuration

Testing & Technical Challenges

Describe the challenges of your project. What advise would you give yourself or someone else if your project can be started from scratch again? Make a smooth transition to testing section and described what it took to test your project.

Include sub-sections that list out a problem and solution, such as:

Test Stage 1: Individual Peripherals

In the first stage of testing, each individual peripheral was tested separately.

GPS Module

• Checked for UART communication
  • The console for the SJ One board should at least read characters (unreadable or unrecognized characters are a result of mismatched (GPS Receiver)<->(SJ One) baud rates)
• Checked for data consistency and reliability
  • The GPS Receiver must first be able to detect any nearby satellites
  • No LED blinking or inconsistent blinking rates are a result of satellites not being detected.
  • GPS Receiver was tested in open outdoors (The GPS Receiver was moved around EAST, WEST, NORTH, and SOUTH to check for change of data.)

Infrared and Sonar Sensors

• Checked for correct functionality
  • Checked whether sensor detected objects in front by analyzing converted values
  • Checked whether values sent to board are consistent with proximity of objects in front of sensors

Compass

• The compass should return a value between 0 and 359 degrees to the SJ One Board
  • NORTH: 0°
  • WEST: 90°
  • SOUTH: 180°
  • EAST: 270°

Test Stage 2: System State Cases with Peripherals

• Individual State Testing
  • Interact with sensors to control state machine paths
  • Analyze variables to verify correct conditions to state entry
  • Print out current state upon entering state

Test Stage 3: Field Testing

After each individual peripheral has been thoroughly tested, the car was brought out for field testing (literally!). To test the car, the destination of the car was set to be equal to the car's current location plus a certain amount of coordinates away. The car was then dropped off and set to drive. The following criteria were to be met:

• The car should drive in the direction pointed to its destination
• The car should stop when it has reached its destination
• The car should move around obstacles present in its path

SJ One Board - PWM API

Problems:

• Due to the SJ One Board's PWM API, PWMs connected to the SJ One Board must run at 50Hz. Although the servos and motors are capable of handling faster frequencies, they cannot handshake without matching.

Solution:

• We end up using 50Hz and we had to operate motor at slower speed.

Software Related Crashing

Problems:

• Combinations of function calls and interrupts would sometimes crash the system.

Solution:

• Convert functions for GPS, motor, state machine, sensors, etc., to tasks
  • As tasks, the functions were able to run in the background

Compass Issues

Problems:

• The first compass (UBLOXLEA-6) ordered was not compatible with the SJ One Board
  • It was designed for Plug-n-Play with specific Android related devices.
  • There was no specifications document for individual pins of the device.
• The second compass (HMC58830) ordered had incomplete datasheets.
  • A search online was made for further specifications, but no documentation was found.

Solution:

• A third compass was bought. However, it had trouble returning values pointing in the NORTH-EAST direction (270° to 359°).
  • All expected values located in that range returned inconsistently incorrect values instead.
  • During Field Testing, it was found that the compass DOES guide the car to its destination. However, when the car needs to go NORTH-EAST, the car has to recalibrate more often than when it is required to go in another direction.
• Due to having to reorder three different compasses, time had taken its toll. The compass still has trouble reading values in the NORTH-EAST range.

GPS Issues

Problems:

• The ordered GPS Receiver (LS20031) was not the one received (LS23060).
• There were no specific datasheets for the acquired model (LS23060).
  • The datasheet for LS20031 was used instead. NOTE: Use LS20031 specifications with caution.
• The baud rate specified in the datasheet (57600bps) did not match the baud rate of the acquired GPS Receiver (38400bps).
  • Communication between the GPS Receiver and the SJSU development board was not possible due to mismatched baud rates. The GPS Receiver baud rate cannot even be set to a desired baud rate through PTMK commands without being in sync with the command sender in the first place.

Solution:

The solution was to use an FDTI cable (UART to USB) with Realterminal (http://realterm.sourceforge.net/index.html#downloads_Download) for synchronization.

• Using Realterminal, users can determine the baud rate of the GPS Receiver through trial and error--changing the port baud rate until NMEA sentences are displayed.
  • e.g. $--GGA,hhmmss.ss,llll.ll,a,yyyyy.yy,a,x,xx,x.x,x.x,M,x.x,M,x.x,xxxx.
  • See GPS - NMEA sentence information for more examples.
• Only until the Port is initially synced with the GPS Receiver, users cannot set the GPS Receiver to a desired baud rate. When the port is in sync, the following actions can be taken:
  • With Realterminal open, click the Send Tab and check "+CR" and "+LF" flags.
  • Send the string "$PMTK314,-1*04" as ASCII to reset the GPS to its default configuration. The baud rate will then be reset to 38400bps.
  • Now the SJSU development board can communicate through PTMK commands at UART - 38400bps.

Conclusion

Much of the car's functionalities were implemented correctly.

From the project, the team gained firsthand experience after applying concepts and protocols such as state machines, ADC, UART, and I2C. Also, the team learned how to test individual modules and the system itself. Sensors were tested manually to make sure that they functional and were outputting correct values. System states had to be tested with great attention to detail to make sure the system transitioned to the correct state. The team learned the benefits of implementing functions as tasks to allow the system to execute multiple tasks concurrently.

Also, the team learned how to work together and work efficiently by dividing up tasks and working side by side to design, implement, and test the project.

Project Video

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Project Source Code

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References

Acknowledgements

We would like to thank Dr. Ozemek for giving us detailed knowledge of how circuits and components works.

We would like to thank Preetpal Kang for teaching us how to use microcontrollers and FreeRTOS.

We would like to thank James Loo for guiding me [Koko] throughout this whole project, making sure our project was being put together correctly.

References Used

For datasheet

http://www.robotshop.com/en/devantech-ultrasonic-range-finder-srf08.html

http://www.google.com/url?q=http%3A%2F%2Fwww.robotshop.com%2Fen%2Fsharp-gp2y0a21yk0f-ir-range-sensor.html%3F___SID%3DU&sa=D&sntz=1&usg=AFQjCNF_wpjNxO10zTRNNgvF22dwLX-BBg

http://www.robotshop.com/en/devantech-tilt-magnetic-compass.html

https://www.sparkfun.com/products/8975

Appendix

You can list the references you used.