Difference between revisions of "S23: Meh-sla Automotive"

Revision as of 06:38, 25 May 2023

Project Title

¯\_(ツ)_/¯ Meh-Sla Automotive ¯\_(ツ)_/¯

Abstract

The ultimate goal of the project is to design an autonomous car which navigate from its current location to a destination. Along it's way it needs to avoid the obstacles and follow the waypoints. To achieve this we are using four SJ2 boards which communicates with each other via CAN bus along with required sensors and a mobile app which communicates with one of the SJ2 boards via Bluetooth. Through our experience, we knew that we wouldn't be the Worst-Sla. We say that we are Meh-Sla even though we know we are the Best-Sla.

Introduction

The project was divided into 5 modules:

1) Sensor and bridge controller:

• Interfaced with 4 ultrasonic sensors for obstacle detection.
• Interfaced with a Bluetooth module for the controller to mobile app communication.

2) Motor controller:

• Interfaced with vehicle motor to control its speed and steering.
• Interfaced with RPM sensors to get feedback about the vehicle's speed.

3) Geographical controller:

• Interfaced with a magnetometer to get the current heading of the vehicle.
• Interfaced with a GPS module to get the current location information.

4) Driver and LCD controller:

• Process information from the sensor and geological board, and send speed and steering to the motor board based on obstacle avoidance and path determination algorithm.
• Interfaced with an LCD module to display the vehicle status.

5) Mobile App:

• Communicates over Bluetooth.
• Sends destination location or start/stop signal to the car.
• Receives sensor and other navigation status and displays it.

Team Members & Responsibilities

Gitlab Project Link

Tony Zunino

• Team Lead
• Motor Board

Sindhuja Ravi

• Geo Board
• Android App

Stephen Oneto

• Driver and LCD Board

Karthigai Amutha Ezhilarasu

• Sensor Board
• Geo Board

Phil Bloxom

• Hardware Design
• Software Testing

Schedule

Parts List & Cost

System Hardware Design

Block Diagram

Layout Diagram

Layout Description

The four SJTwo boards were placed facing upwards and poking out from underneath the PCB. Placing the boards in the orientation allowed for use of the on board LEDs and to have access to the Reset buttons on each board. We chose to sacrifice compactness of the design for the ability to use the LEDs early on in development. This setup also allowed for the PCB to be divided into four quadrants for the rest of the design.

The entire system was powered by a portable 20,000mAh power bank that connected to the PCB via a micro USB connector. From the connector, a 5V and GND bus were ran down the center of the PCB using bus wire to power the four SJTwo boards and other peripherals. Powering all boards from the same 5V line ensured that all voltages were relative to each other and, with the bus stretching down the length of the PCB, cleaned up the need for excessive wires because it gave multiple points for 5V and GND.

The four CAN transceivers were placed upright, to save PCB space, in a 2x2 formation between two of the SJTwo boards so that a CANH and CANL bus could be created nearby and be easily accessible for the PCAN dongle to easily reach. The CAN transceivers were powered via a 3.3V bus that was created by connecting all the 3.3V SJTwo outputs together ensuring that all voltages were relative to each other.

The four ultrasonic sensors were placed on daughter boards so that they could better be adjusted in the correct direction without affecting the rest of the system. Three were placed in the front of the car for the right, front and left sensors and one was placed in the rear as the rear sensor. The LCD screen was placed behind the front sensors to prevent any interference to the sensors and to prevent the LCD screens from moving in the case that it might become dislodged for any reason.

The compass was placed on a pole that limited the amount of interference it would receive from the other components in the system. A PVC pipe was used for the lightweight aspect and so that the wires could be run down through the PVC pipe giving a cleaner look.

The GPS and Bluetooth modules were placed next to the SJTwo board that was controlling them. The battery for the motor, the esc and the rpm sensor were all mounted on the chassis of the vehicle.

Each board had a red LED to signal CAN MIA. The two front yellow LEDs signaled obstacle avoidance. If an object on the right or left was detected then the corresponding side would light up and if an obstacle was detected in the front then both would light up. If neither was lit up then the car was running via path determination instead of obstacle avoidance. The green led under the PCB would light up when power was supplied and the blue LED on the back would blink while the GPS was trying to pair and stay lit up after the GPS locked on to a signal.

CAN Communication

<Talk about your message IDs or communication strategy, such as periodic transmission, MIA management etc.>

Hardware Design

<Show your CAN bus hardware design>

DBC File

Gitlab link to DBC file

VERSION ""

NS_ :
	BA_
	BA_DEF_
	BA_DEF_DEF_
	BA_DEF_DEF_REL_
	BA_DEF_REL_
	BA_DEF_SGTYPE_
	BA_REL_
	BA_SGTYPE_
	BO_TX_BU_
	BU_BO_REL_
	BU_EV_REL_
	BU_SG_REL_
	CAT_
	CAT_DEF_
	CM_
	ENVVAR_DATA_
	EV_DATA_
	FILTER
	NS_DESC_
	SGTYPE_
	SGTYPE_VAL_
	SG_MUL_VAL_
	SIGTYPE_VALTYPE_
	SIG_GROUP_
	SIG_TYPE_REF_
	SIG_VALTYPE_
	VAL_
	VAL_TABLE_

BS_:

BU_: DBG DRIVER MOTOR SENSOR GEO

BO_ 100 DRIVER_HEARTBEAT: 1 DRIVER
 SG_ DRIVER_HEARTBEAT_cmd : 0|8@1+ (1,0) [0|0] "" SENSOR,MOTOR

BO_ 101 MOTOR_SPEED: 1 DRIVER
 SG_ DC_MOTOR_DRIVE_SPEED_sig : 0|8@1+ (0.1,-10) [-10|10] "kph" SENSOR,MOTOR

BO_ 102 MOTOR_ANGLE: 1 DRIVER
 SG_ SERVO_STEER_ANGLE_sig : 0|8@1+ (1,-45) [-45|45] "degrees" SENSOR,MOTOR


BO_ 200 SENSOR_SONARS: 4 SENSOR
 SG_ SENSOR_SONARS_left : 0|8@1+ (1,0) [0|158] "inch" DRIVER
 SG_ SENSOR_SONARS_right : 8|8@1+ (1,0) [0|158] "inch" DRIVER
 SG_ SENSOR_SONARS_front : 16|8@1+ (1,0) [0|158] "inch" DRIVER
 SG_ SENSOR_SONARS_rear : 24|8@1+ (1,0) [0|158] "inch" DRIVER

BO_ 202 GPS_DESTINATION_LOCATION: 8 SENSOR
 SG_ GPS_DEST_LAT_SCALED_1000000 : 0|32@1- (1,0) [0|0] "Degrees" GEO
 SG_ GPS_DEST_LONG_SCALED_1000000 : 32|32@1- (1,0) [0|0] "Degrees" GEO

BO_ 203 GEO_STATUS: 8 GEO
 SG_ GEO_STATUS_COMPASS_HEADING : 0|12@1+ (1,0) [0|359] "Degrees" DRIVER,SENSOR
 SG_ GEO_STATUS_COMPASS_BEARING: 12|12@1+ (1,0) [0|359] "Degrees" DRIVER,SENSOR
 SG_ GEO_STATUS_DISTANCE_TO_DESTINATION : 24|16@1+ (0.01,0) [0|0] "Meters" DRIVER,SENSOR

BO_ 204 GPS_CURRENT_INFO: 8 GEO
 SG_ GPS_CURRENT_LAT_SCALED_1000000 : 0|32@1- (1,0) [0|0] "degrees" DRIVER,SENSOR
 SG_ GPS_CURRENT_LONG_SCALED_1000000 : 32|32@1- (1,0) [0|0] "degrees" DRIVER,SENSOR
 
BO_ 205 GPS_CURRENT_DESTINATIONS_DATA: 8 GEO
 SG_ CURRENT_DEST_LAT_SCALED_1000000 : 0|32@1- (1,0) [0|0] "Degrees" DRIVER
 SG_ CURRENT_DEST_LONG_SCALED_1000000 : 32|32@1- (1,0) [0|0] "Degrees" DRIVER

BO_ 206 BRIDGE_APP_COMMANDS: 1 SENSOR
 SG_ APP_COMMAND : 0|2@1+ (1,0) [0|0] "" MOTOR

BO_ 300 MOTOR_STATUS: 3 MOTOR
 SG_ MOTOR_STATUS_wheel_error : 0|1@1+ (1,0) [0|0] "" DRIVER,IO
 SG_ MOTOR_STATUS_speed_kph : 8|16@1+ (0.001,0) [0|0] "kph" DRIVER,IO
 
BO_ 401 MOTOR_DEBUG: 1 MOTOR
 SG_ IO_DEBUG_test_unsigned : 0|8@1+ (1,0) [0|256] "sec" DBG

BO_ 402 COMPASS_RAW_DEBUG: 6 GEO
 SG_ COMPASS_RAW_X : 0|15@1- (1,0) [0|0] "" DBG
 SG_ COMPASS_RAW_Y : 16|15@1- (1,0) [0|0] "" DBG
 SG_ COMPASS_RAW_Z : 32|15@1- (1,0) [0|0] "" DBG

BO_ 403 SENSOR_BEFORE_AVERAGE_DEBUG: 4 SENSOR
 SG_ SENSOR_BEFORE_AVG_left : 0|8@1+ (1,0) [0|0] "inch" DBG
 SG_ SENSOR_BEFORE_AVG_right : 8|8@1+ (1,0) [0|0] "inch" DBG
 SG_ SENSOR_BEFORE_AVG_front : 16|8@1+ (1,0) [0|0] "inch" DBG
 SG_ SENSOR_BEFORE_AVG_rear : 24|8@1+ (1,0) [0|0] "inch" DBG

CM_ BU_ DBG "The debugging node for testing dbc with the car";
CM_ BU_ DRIVER "The driver controller driving the car";
CM_ BU_ MOTOR "The motor controller of the car";
CM_ BU_ SENSOR "The sensor controller of the car";
CM_ BU_ GEO "The geological Controller of the car";
CM_ BO_ 100 "Sync message used to synchronize the controllers";
CM_ SG_ 100 DRIVER_HEARTBEAT_cmd "Heartbeat command from the driver";
CM_ SG_ 101 DC_MOTOR_DRIVE_SPEED_sig "The speed in kph to set the motor speed. TODO: choose kph/mph";
CM_ SG_ 102 SERVO_STEER_ANGLE_sig "The direction in degrees to set the RC car servo direction.";

BA_DEF_ "BusType" STRING ;
BA_DEF_ BO_ "GenMsgCycleTime" INT 0 0;
BA_DEF_ SG_ "FieldType" STRING ;

BA_DEF_DEF_ "BusType" "CAN";
BA_DEF_DEF_ "FieldType" "";
BA_DEF_DEF_ "GenMsgCycleTime" 0;

BA_ "GenMsgCycleTime" BO_ 100 1000;
BA_ "GenMsgCycleTime" BO_ 200 50;
BA_ "FieldType" SG_ 100 DRIVER_HEARTBEAT_cmd "DRIVER_HEARTBEAT_cmd";

VAL_ 100 DRIVER_HEARTBEAT_cmd 2 "DRIVER_HEARTBEAT_cmd_REBOOT" 1 "DRIVER_HEARTBEAT_cmd_SYNC" 0 "DRIVER_HEARTBEAT_cmd_NOOP" ;

Sensor and Bridge Controller

• Bridge Controller Gitlab link

Hardware Design

Bridge controller connections

Ultrasonic Sensors

We used HC-SR04 ultrasonic sensors for obstacle detection. It could provide a range from 2 cm to 400 cm non-contact measurement. The ranging accuracy is approximately 3mm and the effectual angle is less than 15°. It needs to be powered by a 5V power supply. We are using 4 HC-SR04 sensors in the RC car(front, rear, left, and right).

HC-SR04 specifications

• Operating voltage: +5V
• Theoretical Measuring Distance: 2cm to 450cm
• Practical Measuring Distance: 2cm to 80cm
• Accuracy: 3mm
• Measuring angle covered: <15°
• Operating Current: <15mA
• Operating Frequency: 40Hz

The pinout and the timing diagram of the HC-SR04 sensor are shown in the following figures. The module includes an ultrasonic transmitter, a receiver, and a control circuit. The basic principle of work: When the trigger pin is set HIGH for at least 10us, the module automatically sends a 40 kHz ultrasonic wave from the Ultrasonic transmitter. This wave travels in the air and when it gets obstructed by any material it gets reflected back toward the sensor. This reflected wave is observed by the Ultrasonic receiver module. Once the wave is returned the Echo pin goes high for a particular amount of time which will be equal to the time taken for the wave to return back to the sensor. The amount of time during which the Echo pin stays high is measured by the SJ2 board as it gives the information about the time taken for the wave to return back to the Sensor. Using this information the distance is measured as explained in the above heading. From that duration, the distance at which the object is present can be measured using the formula, Distance = Speed × Time.

HC-SR04 Pinout

HC-SR04 Timing Diagram

HC-SR04 Working Principle

Bluetooth Module

For the communication between the mobile and the RC Car, we are using Adafruit Bluefruit LE UART Friend - BLE module. This module communicates with the SJ2 board through UART at a baud rate of 9600. It also has the capability of working in two modes (data mode and command mode). We can toggle between the two modes using the MOD pin through a GPIO signal or manually using the onboard switch. It supports AT command set, which can be used to control the device's behavior. In data mode, the data written to the UART in the form of a string will be sent through Bluetooth.

Magnetometer Orientation

Adafruit Bluefruit specifications

• ARM Cortex M0 core running at 16MHz
• 256KB flash memory
• 32KB SRAM
• Transport: UART @ 9600 baud with HW flow control (CTS+RTS required)
• 5V-safe inputs
• On-board 3.3V voltage regulation
• Bootloader with support for safe OTA firmware updates
• Easy AT command set to get up and running quickly

Software Design

Ultrasonic Sensors

We read about the signal interference of adjacent sensors from many of the past projects. So we decided to avoid that interference by triggering two non-adjacent sensors at a time. The FRONT_REAR sensor pair is triggered first. Once both of the sensors compute the distance from the obstacle, then the next pair, RIGHT_LEFT is triggered. For the ultrasonic sensors, we used a separate task instead of the periodic callbacks since this task sleeps on a semaphore which might affect the other functions in the periodic callback function.

SONAR task

void sonar_task(void *p) {
 sonar__init();
 front_rear_echo_received = xSemaphoreCreateBinary();
 left_right_echo_received = xSemaphoreCreateBinary();
 lpc_peripheral__enable_interrupt(LPC_PERIPHERAL__GPIO, sonar__interrupt_dispatcher, "sonar_timing_handler");
 NVIC_EnableIRQ(GPIO_IRQn);
 while (1) {
   sonar__send_trigger_for_10us(FRONT_REAR);
   if (xSemaphoreTake(front_rear_echo_received, 100)) {
     sonar_pair_info[0].distance_from_obstacle_sonar1 = sonar__compute_obstacle_distance_single_sensor(FRONT_SONAR);
     sonar_pair_info[0].distance_from_obstacle_sonar2 = sonar__compute_obstacle_distance_single_sensor(REAR_SONAR);
   }
   vTaskDelay(10);
   sonar__send_trigger_for_10us(LEFT_RIGHT);
   if (xSemaphoreTake(left_right_echo_received, 100)) {
     sonar_pair_info[1].distance_from_obstacle_sonar1 = sonar__compute_obstacle_distance_single_sensor(LEFT_SONAR);
     sonar_pair_info[1].distance_from_obstacle_sonar2 = sonar__compute_obstacle_distance_single_sensor(RIGHT_SONAR);
   }
   sonar__averaging_sensor_values();
 }
}

Bluetooth Module

Bluetooth module is used to send the debug information such as sensor values, current heading, bearing, distance to the destination, and current GPS location to the mobile app. Also, it receives the destination coordinates and start/stop signal from the mobile app. To differentiate between the coordinates and the start/stop signal we used the first char as '@' or '#'. If the starting char is '@', the message contains the destination coordinate. Similarly, "#0' represents the stop signal, and '#1' represents the start signal.

Bluetooth initialization

void bt_module__init(void) {
 line_buffer__init(&line_buffer, line, sizeof(line));
 gpio__construct_with_function(GPIO__PORT_4, 28, GPIO__FUNCTION_2);
 gpio__construct_with_function(GPIO__PORT_4, 29, GPIO__FUNCTION_2);
 uart__init(bt_module_uart_port, clock__get_peripheral_clock_hz(), 9600);
 QueueHandle_t rxq = xQueueCreate(500, sizeof(char));
 QueueHandle_t txq = xQueueCreate(500, sizeof(char));
 uart__enable_queues(bt_module_uart_port, txq, rxq);
 bt_pin__mod = gpio__construct_as_output(GPIO__PORT_0, 15);
 bt_pin__cts = gpio__construct_as_output(GPIO__PORT_0, 18);
 bt_pin__rts = gpio__construct_as_input(GPIO__PORT_2, 9);
 gpio__reset(bt_pin__cts);
 bt_set_mode(bt_data_mode);
}

Bluetooth data handler

static void bt_data_handler__parse_data(char *data) {
 switch (data[0]) {
 case '@':
   bt_data_handler__parse_coordinates(data + 1);
   break;
 case '#':
   bt_data_handler__parse_start_or_stop(data + 1);
   break;
 default:
   break;
 }
}

Technical Challenges

Sensor module

• Issue: Sometimes the front sensor was detecting some obstacles even though there was nothing in front.
• Solution: We included a delay of 10ms in between triggering the first and second pair of sensors.

• Issue: We see some noise in the sensor measurement which makes the car's steering very wobbly.
• Solution: We included a sensor value averaging logic which will return the average of the last 5 readings instead of a single value

Bluetooth module

• Issue: We faced a weird problem in the geo node when computing the distance between the origin and destination. It gave us bizarre values. First, we thought the problem was with the Geo node distance computation formula. But when we trace back the issue, it was with the line buffer initialization in the sensor board. We mistakenly initialized the line buffer with a size of 20 instead of 200. This truncates the coordinates of the destination received (sometimes sets longitude = 0) from the mobile which in turn, affects the distance computation at the Geo node.
• Solution: We initialized the line buffer with a bigger size.

Motor Controller

Traxxas Antenna PWM Connections

Traxxas TQ Top Qualifier Module

• Motor Controller Gitlab link

Hardware Design

PCB Design

Phil to talk about PCB design and choices for layout

Battery Management

Phil to talk about the peripheral battery and main motor battery separation

Software Design

<List the code modules that are being called periodically.>

RPM Module

Tony will write about how the RPM module was implemented using triggers.

void sonar_task(void *p) {
  Test
}

Motor Module

Tony will write about the motor and how forward/reverse works

static float test_task(float lol) {
  Just wanted to see if this is cool;
}

Steering Module

Tony will write about the motor and how forward/reverse works

static float test_task(float lol) {
  Preet is cool;
  if(Phil_is_reading) Phil is cooler;
  else Tony is the coolest
}

Technical Challenges

< List of problems and their detailed resolutions>

Geological Controller

• Geological Controller Gitlab link

Hardware Design

Compass

The compass we used is from Adafruit, LSM303AGR breakout. It has both a magnetometer and an accelerometer. But, We didn't use the accelerometer which is also needed to properly calibrate the compass because the compass couldn't be aligned exactly parallel to the ground when mounting on a car(instead we used a simple trick - see technical challenges for a detailed description). The compass communicates with the SJ2 board via I2C. It operates on 3.3V. It is a triple-axis accelerometer/magnetometer compass module. The magnetometer is mounted on the car with the Z axis pointing away from the ground and X and Y axis pointing as shown in the image below (we can also switch the x and y, but the formula remains the same). The x and y values shown in the formula correspond to the raw x and y values of the magnetometer. The compass should be placed as much as away from all the electronics in the car. We used a PVC pipe to place the compass in an elevated position. Even after the elevated positioning, we faced interference that makes it necessary to calibrate the compass. For the compass calibration, we used a third-party calibration tool. Magneto.

LSM303AGR

Magnetometer Orientation

We wrote a simple Python script to visualize how the calibration affects the compass output. The outputs of the Python script show how the compass raw data gets affected after mounting on the car and after calibration.

Magneto Calibration tool

Compass raw data before mounting on the car

Compass raw data after mounting on the car - before calibration

Compass raw data after mounting on the car - after calibration

GPS

The GPS module we used is MTK3339-based breakout from Adafruit. It is interfaced with the SJ2 board through UART. It will output NMEA strings at a default baud rate of 9600. We parsed the latitude and longitude from the GPGGA data and used them to compute the bearing and distance to the destination.

GPS module

Software Design

Waypoint Algorithm

Waypoints we chose

Technical Challenges

< List of problems and their detailed resolutions>

Driver/LCD Controller

• Driver and LCD Controller Gitlab link

<Picture of LCD> <Picture of Block Diagram>

Hardware Design

Software Design

<List the code modules that are being called periodically.>

Technical Challenges

< List of problems and their detailed resolutions>

Mobile Application

<Picture and link to Gitlab>

Hardware Design

Software Design

<List the code modules that are being called periodically.>

Technical Challenges

< List of problems and their detailed resolutions>

Conclusion

<Organized summary of the project>

<What did you learn?>

Project Video

Project Source Code

Advise for Future Students

<Bullet points and discussion>

Acknowledgement

=== References ===