F15: ThunderBird

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ThunderBird : Self Driving Car

Abstract

ThunderBird is a 1/10 2 WD electric short self-driving truck. The truck is equipped with sensors to detect obstacles, GPS for getting directions, Compass for the truck's orientation, Bluetooth for communicating with the android device and LCD for displaying the sensor values on screen. The modules are interfaced using 5 SJ One boards which features a Cortex-M3 LPC1758. CAN bus is used for communicating between the modules. Android device is used to enter the destination coordinates through bluetooth. When the sensors detect obstacles, it signals the motors to drive the car accordingly.

Objectives & Introduction

Team Members & Responsibilities

  • Master Controller and Android application
    • Sravani Aitha
    • Vishnu Vardhana Reddy Mandalapu
    • James Sushanth Anandraj
    • Athavan Kanagasabapathy
  • Motors and I/O
  • Sensors
    • Nitesh Jain
    • Rajashree Kambli
  • GPS
    • Rishit Borad
    • Ravi Vanjara

Schedule

Team Schedule

Sl.No Start Date End Date Task Status Actual Completion Date
1 09/22/2015 09/29/2015 Order RC Car Completed 09/26/2015
2 09/30/2014 10/6/2015 Ordered components Completed 10/04/2015
3 10/07/2015 10/13/2015 Study about the modules and the RC car
4 10/14/2015 10/20/2015 Test motors using PWM
5 10/21/2015 10/28/2015 Interface sensor modules
6 10/29/2015 11/05/2015 Interface GPS and compass
7 11/12/2015 11/19/2015 Interface LCD
8 11/20/2015 11/27/2015 Interface modules over CAN bus
9 11/28/2015 12/05/2015 Integrating modules
10 12/6/2015 12/13/2015 Testing
11 12/14/2015 12/19/2015 More Testing

Motor and I/O Schedule

Sl. No Start Date End Date Task Status Actual Completion Date
1 10/6/2015 10/13/2015 Determining the ESC initialization sequence Completed 10/11/15
2 10/13/2015 10/20/2015 Testing the Servo and DC motor using SJ One board PWM's Completed 10/16/2015
3 10/20/2015 10/27/2015 Design motor control using messages from the CAN bus
4 10/27/2015 11/3/2015 Implement code to accept messages from other modules over CAN bus and display it on the LCD
5 11/3/2015 11/10/2015 Update motor speeds on the LCD in real time
6 11/10/2015 11/17/2015 Interface I/O and motor modules with master controller and establish communication
7 11/17/2015 11/24/2015 Fine turning motors for precise control
8 11/24/2015 12/01/2015 Fine tuning (buffer)
9 12/01/2015 12/08/2015 Testing and debugging

Geographical Position Controller Schedule

Sl. No Start Date End Date Task Status Actual Completion Date
1 10/6/2015 10/13/2015 Research & order GPS module Completed 10/8/2015
2 10/13/2015 10/20/2015 Interface GPS using I2C with SJOne board Ongoing
3 10/20/2015 10/27/2015 Interface Compass with SJOne board
4 10/27/2015 11/3/2015 Calibrate Compass and GPS
5 11/3/2015 11/10/2015 Parse raw data and create meaningful data
6 11/10/2015 11/17/2015 Implement CAN communication with SJOne board
7 11/17/2015 11/24/2015 Test and debug GPS & Compass locally
8 11/24/2015 12/01/2015 Integrate GPS/Compass module with Master board
9 12/01/2015 12/08/2015 Implement routing algorithm for Car
10 12/08/2015 12/15/2015 Test and Debug GPS/Compass integration with master

Sensor Controller Schedule

Sl. No Start Date End Date Task Status Actual Completion Date
1 10/5/2015 10/11/2015 Finalize and order the sensors Completed 10/11/2015
2 10/12/2015 10/18/2015 Wire the sensors and write a sample test code to check the sensors. Ongoing
3 10/19/2015 11/01/2015 Transfer the sensor data to master controller via can bus.
4 11/2/2015 11/9/2015 Implement and integrate the code for all the sensors.
5 11/2/2015 11/15/2015 Test and Debug the integrated module.
6 11/16/2015 11/29/2015 Collaborate with the other module teams to make sure that the sensors are in working condition.
7 11/30/2015 12/06/2015 Test for stability of sensors and report.
8 12/07/2015 12/13/2015 Prepare for Demo.

Master controller and android controller Schedule

Sl. No Start Date End Date Task Status Actual Completion Date
1 10/6/2015 10/13/2015 Car purchase ,dismantle and setup for project Completed 10/8/2015
2 10/13/2015 10/20/2015 Can setup components purchase, Can bus design and soldering Ongoing
3 10/20/2015 10/27/2015 Basic Can communication testing by sending and receiving data and can msg specification for all controllers and messages.
4 10/27/2015 11/3/2015 Development and implementation of Algorithm for driving car and obstacle avoidance.
5 11/3/2015 11/10/2015 Interface bt dongle with sjone board and android device and test with commands
6 11/10/2015 11/17/2015 Develop Android GUI and application to interact with car using bluetooth. Implement all necessary commands on sjone board for communication with android device. Interface with Motor and IO Controller.
7 11/17/2015 11/24/2015 Test and debug Master algorithm and Android interface locally and with Motor controller interfaced by providing predetermined directional commands.
8 11/24/2015 12/01/2015 Integrate Master Board with all boards and implement heartbeat protocol.
9 12/01/2015 12/08/2015 Test run 1 with all boards integrated and with all planned features developed.
10 12/08/2015 12/15/2015 Test run 2 after solving issues found in test run 1.

Parts List & Cost

S.R. Description Manufacturer Part Number Qty Total Cost
1 SJOne Board - - 5 $400.00
2 RC Car Furry Arrma - 2 Wheel Drive - 1/10 - 1 $185.00
3 Ultrasonic Sensor LV-MaxSonar - EZ1 MB1010 5 $140.00
4 1.8 Color TFT LCD display with MicroSD Card Breakout Adafruit ST7735R 1 $19.95
5 SparkFun Venus GPS with SMA Connector Sparkfun GPS-11058 1 $49.95
6 Triple-axis Magnetometer (Compass) Board Adafruit HMC5883L 1 $9.95
7 CAN Transceiver (Free Samples) Microchip MCP2551 6 $0.00
Total (Including Shipping and Taxes ----

Design & Implementation

Controller Communication Table

CAN ID Source Destination Message Description
0x000 Master Controller Motor Controller Stop message
0x001 Master Controller Motor Controller Speed,Direction,start receiving
0x002 Motor Controller Master Controller Current speed
0x003 Master Controller Sensor Controller Start sensing
0x004 Master Controller GPS Controller Destination location, start sensing
0x005 Master Controller Bridge Controller Start Bridge
0x006 GPS Controller Master Controller Distance to location, Angular deviation to destination
0x007 Sensor Controller Master Controller Obstacle information
0x008 Bridge Controller Master Controller New destination set,start,stop
0x009 Master Controller IO Controller Data to be displayed on lcd screen from master,start
0x00A IO Controller Master Controller LCD ready status
0x00B Master Controller Broadcast - Any broadcast data
0x00C Motor Controller Broadcast - Any Broadcast data
0x00D Sensor Controller Broadcast - Any Broadcast data
0x00E GPS Controller Broadcast - Any Broadcast data
0x00F IO Controller Broadcast - Any Broadcast data
0x010 Master Controller Broadcast (Reset all) - Reset all controllers
0x011 Master Controller Motor Controller(Reset mesg) Reset motor controller
0x012 Master Controller GPS Controller(Reset mesg) Reset gps controller
0x013 Master Controller Sensor Controller(Reset mesg) Reset sensor controller
0x014 Master Controller Bridge Controller(Reset mesg) Reset Bridge controller

Hardware Design

Discuss your hardware design here. Show detailed schematics, and the interface here.

Hardware Interface

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Software Design

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Implementation

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Sensor Controller

Motor and I/O Controllers

ThunderBird is a 2 WD truck. It is equipped with a ARRMA BLX brushless DC motor connected to an BLX80 ESC(Electronic Speed Control). The ESC drives the DC motor according to the PWM(Pulse Width Modulation) signal. The truck's front wheels are connected to a waterproof ADS-7M Metal Geared Steering Servo. The servo and the DC motor are controlled using the PWM pins of the SJOne board.

Pulse Width Modulation - Controlling DC motor

Fig 1. Initializing pwm signal
Fig 2. Forward pwm signal
Fig 3. Reverse pwm signal
Fig 4. Servo pwm signal

Pulse width modulation is a technique which is used to encode the analog signal into a pulsating signal. The signal is represented as a series of pulses. This signal can be easily generated using the pwm pins of the SJOne board. The ESC is initialized upon passing a PWM signal which is sent by the RF module on the truck. The type of signal is observed by hooking the PWM pin to the digital oscilloscope. The initialization signal is shown in figure 1. A resolution of 1ms is set on the oscilloscope. The PWM signal has a width of 1.5 ms. This signal initializes the ESC. Once the ESC's are initialized, the motors require a signal to accelerate and decelerate. The type of signals for moving the motor forward and backward are realized by hooking the output pin of the RF module to the digital oscilloscope. The forward and backward pwm signals at full throttle are shown in figures 2 and 3 respectively. The respective pwm signal pulses for moving the motors forward and backward are shown below.

  • Acceleration PWM signal
    • Forward full throttle - 2 ms
    • Forward medium throttle - 1.8 ms
    • Neutral - 1.5 ms
  • Reverse PWM signal
    • Reverse full throttle - 1 ms
    • Reverse medium throttle - 1.2 ms
    • Neutral - 1.5 ms


PWM Calculations

The PWM value to be set is determined from these calculations:

  • PWM is a percentage of the signal frequency
  • The signal is of 50 Hz i.e. 20 ms duration
  • A 10% of the signal value gives a duration of 2 ms - 10/100 * 20 = 2 ms

The respective percentages for all the signal were calculated and the PWM signals were generated using the PWM.set function. The generated pulses from the SJOne PWM pin is passed to the ESC for initialization and controlling the DC motor. The ESC has 3 connections - Vcc, GND and PWM. SJOne board's GND and PWM are connected to the ESC. The Vcc is supplied from the battery pack.

A sample code demonstrating the PWM signals is written and the motors were controlled using the on-board SJOne switches.

DC motor demo


Controlling Servo motor

The servo motor channel in the RF module is hooked to the digital oscilloscope to determine the initial sequence. It is observed that when the RF transmitter is switched on, the RC remote sends a pwm signal which resets the servo to its starting position. This PWM signal re-centers the truck's wheels. The signal is realized by hooking the data pin from the first channel of the RF module to the digital oscilloscope. The PWM signal is shown in figure 4. The signal is having a pulse of 1.6 ms. The steering on the RC is moved left and right to determine the PWM signals. The signal values were noted from the oscilloscope. The values are tabulated below.

  • Steering PWM signal
    • Steer full right - 2 ms
    • Steer full left - 1 ms
    • Steer center - 1.6 ms

A PWM signal having a pulse width between 1.6 ms to 2 ms is used to control the steering towards right precisely. Similarly, a PWM signal having a pulse width between 1 ms to 1.6 ms is used to control the steering towards left precisely. The servo has 3 connections - Vcc, GND and PWM. The servo motor is not connected to a ESC. It doesn't get any voltage if it is not connected to the RF module. The servo motor operates at 6V. For testing, the Vcc of the servo motor is connected to the RF module. The GND from the RF module is made common with the GND from SJOne board. The PWN signal is given as an input from the SJOne board. The PWM signal values were calculated using the procedure shown above. The respective PWM signals were then sent to the servo motor using the PWM pin on the SJOne board for steering the truck.

The on-board switches on the SJOne board are used to steer the truck left and right. A sample code demonstrating this functionality is written and tested.

Servo motor demo

GPS Controller

Master Controller

Bluetooth Control and Android application

Testing & Technical Challenges

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My Issue #1

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Conclusion

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Project Video

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Project Source Code

References

Acknowledgement

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References Used

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Appendix

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