Difference between revisions of "F15: ThunderBird"

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	== Objectives & Introduction ==		== Objectives & Introduction ==
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		+	=== Objective ===
	=== Team Members & Responsibilities ===		=== Team Members & Responsibilities ===

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Revision as of 04:46, 14 December 2015

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

Objective

Team Members & Responsibilities

• Master Controller and Android application
  • Sravani Aitha
    
  • Vishnu Vardhana Reddy Mandalapu
  • James Sushanth Anandraj
  • Athavan Kanagasabapathy
• Motors and I/O
  • Dheeraj Dake
    
  • Akhil Bhargav Josyabhatla
• 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	Completed	10/13/15
4	10/14/2015	10/20/2015	Test motors using PWM	Completed	10/16/15
5	10/21/2015	10/28/2015	Interface sensor modules	Completed	10/26/15
6	10/29/2015	11/05/2015	Interface GPS and compass
7	11/12/2015	11/19/2015	Interface LCD	Completed	11/28/15
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	Completed	10/27/15
4	10/27/2015	11/3/2015	Implement code to accept messages from other modules over CAN bus and display it on the LCD	Completed	11/28/15
5	11/3/2015	11/10/2015	Update motor speeds on the LCD in real time	Completed	11/28/15
6	11/10/2015	11/17/2015	Interface I/O and motor modules with master controller and establish communication	Completed	11/28/15
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.	Completed	10/18/2015
3	10/19/2015	11/01/2015	Transfer the sensor data to master controller via can bus.	Completed	10/31/2015
4	11/2/2015	11/9/2015	Implement and integrate the code for all the sensors.	Completed	11/15/2015
5	11/2/2015	11/15/2015	Test and Debug the integrated module.	Completed	10/15/2015
6	11/16/2015	11/29/2015	Collaborate with the other module teams to make sure that the sensors are in working condition.	Completed	11/30/2015
7	11/30/2015	12/06/2015	Test for stability of sensors and report.	Ongoing
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

CAN 11-bit ID Format

MSG	DST	SRC
5 bits (11-6)	3 bits (5-3)	3 bits (2-0)

Controller ID Table

Controller ID	Controller Type
0x000	All Controller
0x001	Master Controller
0x010	Motor Controller
0x011	GPS
0x100	Sensor
0x101	I/O Controller
0x110	Android Controller

Controller Communication Table

Message ID	Destination ID	Source ID	CAN ID	Message function	Message Data	From	Receieved By
0x00000	0x000	0x000	0x000	Kill	NoData	Master	All
0x00001	0x001	0x110	0x04E	Android stop	NoData	Android Bridge	Master
0x00010	0x001	0x110	0x08E	Android start	NoData	Android Bridge	Master
0x00011	0x001	0x100	0x0CC	Sensor data	Byte[0]: Left sensor Byte[1]: Front sensor Byte[2]: Right sensor Byte[3]: Rear sensor Byte[4]: Speed	Sensors	Master
0x00100	0x011	0x001	0x119	Current position request	NoData	Master	GPS
0x00101	0x001	0x011	0x14B	Geo direction	Byte[0]: Current Angle Byte[1]: Desired Angle	GPS	Master
0x00110	0x001	0x011	0x18B	Geo data	Byte[0]: Latitude1 Byte[1]: Latitude2 Byte[2]: Longitude1 Byte[3]: Longitude2 Byte[4]: Distance to next checkpoint Byte[5]: Checkpoint reached?	GPS	Master
0x00111	0x010	0x001	0x1D1	Motor Command	Byte[0] Forward : 0 Byte[0] Left : 1 Byte[0] Right : 2 Byte[0] Reverse : 3 Byte[0] Stop : 4	Master	I/O & Motor
0x01000	0x101	0x001	0x229	Display Start	NoData	Master	I/O & Motor
0x01001	0x101	0x001	0x269	Display data	Byte[0]: Speed Byte[1]: Distance to next checkpoint	Master	I/O & Motor

Hardware Design

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Hardware Interface

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Software Design

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Implementation

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Sensor Controller

We have used four Maxbotix LV-EZ Ultrasonic Range Finder sensors (MB1010), three for front (left, right, mid) and one for the rear. These ultrasonic sensors are used to detect the obstacle which our car can encounter on its route. These sensors are connected to the SJOne board and the CAN bus and can work on 3.3V-5.0V.

The pin configuration for the sensor is as follows:
1) Pin 2-PW: This pin outputs a pulse width representation of range. The distance can be calculated using the scale factor of 147uS per inch.
2) Pin 4-RX: This pin is internally pulled high. The LV-MaxSonar-EZ will continually measure range and output if RX data is left unconnected or held high. If held low the sensor will stop ranging. Bring high for 20uS or more to command a range reading.
3) Pin 6-+5V: Vcc – Operates on 2.5V - 5.5V. Recommended current capability of 3mA for 5V, and 2mA for 3V.
4) Pin 7-GND: Return for the DC power supply. GND (& Vcc) must be ripple and noise free for best operation.

Sensor Hardware Design

250mS after power-up, the LV-MaxSonar-EZ is ready to accept the RX command. If the RX pin is left open or held high, the sensor will first run a calibration cycle (49mS), and then it will take a range reading (49mS). After the power up delay, the first reading will take an additional ~100mS. Subsequent readings will take 49mS. The LV-MaxSonar-EZ checks the RX pin at the end of every cycle. Range data can be acquired once every 49mS.

Each 49mS period starts by the RX being high or open, after which the LV-MaxSonar-EZ sends the transmit burst, after which the pulse width pin (PW) is set high. When a target is detected the PW pin is pulled low. The PW pin is high for up to 37.5mS if no target is detected. The remainder of the 49mS time (less 4.7mS) is spent adjusting the analog voltage to the correct level. When a long distance is measured immediately after a short distance reading, the analog voltage may not reach the exact level within one read cycle. During the last 4.7mS, the serial data is sent.

Sensor Software Design and Algorithm

The following steps are for initializing, getting readings and calculating distance in inches for one sensor-

1) Configure the PW pin of sensor as input.

2) Configure RX pin of the sensor as output and set it high.

3) Enable the Rising and the Falling edge interrupt on the PW pin of the sensor

4) Note down the sys_get_uptime_us() at the rising interrupt. Let this time be T1.

5) Note down the sys_get_uptime_us() again when the falling edge is encountered. Let this time be T2.

6) To calculate the distance in inches, do - (T2-T1)/147.

7) Send this value to the Master controller via the CAN bus.

Sensor: Technical Challenges

1) Fluctuating sensor values: We observed random shoots in the sensor values. Sometimes, the value was even zero.

2) The beams from two adjacent sensors collided with one another.

3) The sensor when mounted on the car detected ground as obstacle

4) The sensors did not work on independent 5V supply.

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.

Motors

Pulse Width Modulation - Controlling DC motor

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

I/O

Liquid Crystal Display

A 20x4 LCD(CM 204-1) is used for displaying the speed, sensor values and the start and end coordinates. A LCD driver by SJValley Engineering is used for accessing the LCD through UART. The driver and LCD are soldered on to the prototype board. A USB jack is soldered on-board to power the LCD using the 5V supply from the external battery. The connections between the driver and SJOne board is shown in figure 5. As soon as the LCD is powered on, it displays to enter 0xF0 which is the command for detecting the baud rate. After 0xF0 is sent, the data can be transmitted using UART. A baud rate of 38400 is used for displaying information on the LCD. If you are getting some junk values, make sure that the baud rate is set correct and check the soldering.

The LCD with displaying the values is shown in figure 6. The following helps you to organize information on your LCD.

• Commands for displaying information on LCD
  • urt.put displays a character on the LCD
  • urt.putlin displays a character on the LCD and moves the cursor to the next line
  • $CLR_SCR is used to clear the screen

Common Problems and troubleshooting

1. LCD is displaying only 2 lines, line 1 and line 3 when i power it on.

A. Check the connections. Make sure that the LCD is properly soldered to the driver.

2. I am getting garbage values printed on the screen when i try to transfer information over UART

A. LCD is not initialized properly. Make sure you get the detecting baudrate information displayed on screen when the LCD is powered on.

3. Is it okay to program the LCD while being connected to the SJOne board?

A. I didn't find any issues while programming the SJOne board with the LCD connected to it. However, some teams had issues with it.

4. How do i update a single field on the LCD keeping the rest static?

A. I cleared the entire screen every 100 ms and it looked like only the values are being updated!

GPS Controller

Geographical controller module plays an important role in heading and positioning of autonomous car.It consists of 20GHZ GPS module and 9-DOF RAZOR IMU interfaced to SJ-one board.

The GPS module provides Latitude and Longitude co-ordinates for current position of car.The 9DOF Razor IMU incorporates three sensors - an ITG-3200 (MEMS triple-axis gyro), ADXL345 (triple-axis accelerometer), and HMC5883L (triple-axis magnetometer) - to give you nine degrees of inertial measurement.

SPARKFUN VENUS GPS with SMA CONNECTOR

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

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References

Acknowledgement

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References Used

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Appendix

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