S24: Team X

Project Title

Team X

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Abstract

Our main goal of this project was to utilize the knowledge acquired from the lectures in CMPE 243. The report summarizes the overall process taken to develop an autonomous driving RC car using FreeRTOS, various periodic tasks, and the CAN bus to combine and run the different code modules.

Introduction

The project was divided into 5 modules:

• Sensor Node
• Motor Node
• Driver Node
• Geo Node
• Mobile Application

Team Members & Responsibilities

<Team Picture>

Gitlab Project - Team X

Team Members	Task Responsibility
Priyanka Shah	Geo Controller, Mobile App
Faaris Khilji	Sensor and Bridge Controller
Ashley Ho	Driver and LCD Controller
All/TBD	Motor Controller

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Schedule

Week#	Start Date	End Date	Task	Status
1	02/19/2024	02/25/2024	Read previous projects, gather information, and discuss among the group members. Schedule weekly online meetings Order CAN transceivers Test GPS and UART communication.	Completed Completed Completed
2	02/26/2024	03/03/2024	Distribute modules to each team member. Create parts list and Bill of Materials Test CAN Bus communication between 2 boards	Completed Completed Completed
3	03/04/2024	03/11/2024	Order all sensors Research on RC car brands and features. Create project schedule and milestones.	Completed Completed Completed
4	03/18/2024	03/24/2024	Setup project repository Order RC car Test CAN bus with DBC file messages via BusMaster	Completed Completed Completed
5	03/25/2024	03/31/2024	Set up driver node to handle CAN messages received from sensor node Set up sensor node to send CAN messages Set up motor controller node to receive driver commands	Completed Completed Completed
6	04/01/2024	04/07/2024	Set up Geo Controller to receive destination coordinates Link Geo controller to GPS module Integrate sensor hardware into sensor node Test LCD module to display using I2C Begin wiki documentation	Completed Completed Completed Completed Completed
7	04/08/2024	04/14/2024	Enhance obstacle avoidance algorithm Integrate RPM and ultrasonic sensor Integrate LCD module with debug messages Setup preliminary mobile app structure Test obstacle avoidance Start working on power supply for SJ2 boards	Completed Completed Completed Completed Completed Completed
8	04/15/2024	04/21/2024	Fine tune obstacle avoidance algorithm Hack RC car's RPM and install RPM sensor Integrate compass module Begin RC car design and assembly	Completed Completed Completed Completed
9	04/22/2024	04/28/2024	Finish RC car prototype 1 Start outdoor testing at garage rooftop Complete basic mobile app with destination, start/stop button Interface motor and steering Set up LED fault indicators	Completed Completed Completed Completed Completed
10	04/29/2024	05/05/2024	Edit Wiki report, continue updating through next few weeks Fine tune mobile app to display map to choose destination Display debug information on LCD Continue RC outdoor tests	Completed Completed Completed Completed
11	05/06/2024	05/12/2024	Fine tune obstacle avoidance algorithm Fine tune motor controller and sensor controller Fine tune DBC file messages Continue updating wiki report and documentation	Completed Completed Completed Completed
12	05/06/2024	05/12/2024	Tidy RC car mounted hardware Continue outdoor testing Fine tune navigational system	In Progress Completed Completed
13	05/13/2024	05/19/2024	Finish writing project report Final RC car tests on North Garage Reimburse team members for RC car parts and sensors	In Progress In Progress In Progress
14	05/20/2024	05/26/2024	Final Project Demos	Incomplete

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Parts List & Cost

Item#	Part Desciption	Vendor	Qty	Cost
1	RC Car	Traxxas	1	$250.00
2	RC Car Battery	Traxxus	2	$110
3	CAN Transceivers MCP2551-I/P	Microchip	8	Free Samples
4	MB1010 LV-MaxSonar	<Insert Company>	4	$29.95
5	GPS	<Insert Company>	<Insert Amount>	<Insert Price>
6	Compass	<Insert Company>	<Insert Amount>	<Insert Price>
7	LCD	Amazon	1	$11.69

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CAN Communication

Each node is connected to a CAN transceiver that are connected to a bus with a 120 Ohm resistor on each end. We handled each message on the 10Hz, with the sensor and motor messages having the highest priority.

Specifically, we classified each node with these (see table below) message IDs.

	Node	Message ID Range
1	MOTOR	300 - 310
2	SENSOR	200
3	GEO	400 - 450
4	DEBUG	600 - 700

Hardware Design

DBC File

Gitlab DBC File

Shown below are the messages utilized in our DBC file:

BO_ 200 SENSOR_SONARS: 4 SENSOR
 SG_ SENSOR_SONARS_left : 0|10@1+ (1,0) [6|254] "inch" DRIVER
 SG_ SENSOR_SONARS_right : 10|10@1+ (1,0) [6|254] "inch" DRIVER
 SG_ SENSOR_SONARS_middle : 20|10@1+ (1,0) [6|254] "inch" DRIVER

BO_ 300 MOTOR_CMD: 1 DRIVER
 SG_ MOTOR_CMD_steer: 0|4@1- (1,0) [-2|2] "" MOTOR
 SG_ MOTOR_CMD_forward: 4|4@1- (1,0) [-5|5] "" MOTOR

BO_ 310 MOTOR_STOP: 1 SENSOR
 SG_ MOTOR_STOP_stop: 0|1@1+ (1,0) [0|0] "" MOTOR

BO_ 400 GPS_NAV: 2 GEO
 SG_ GPS_NAV_latitude : 0|8@1- (1,0) [-90|90] "" DRIVER
 SG_ GPS_NAV_longitude : 8|8@1- (1,0) [-180|180] "" DRIVER

BO_ 420 GPS_HEADING: 4 SENSOR
 SG_ GPS_HEADING_RAW_DEGREES: 0|16@1+ (1,0) [0|0] "Degrees" GEO 

BO_ 430 GEO_STATUS: 4 GEO
  SG_ GEO_STATUS_COMPASS_HEADING : 0|5@1+ (1,0) [0|18] "Degrees" DRIVER
  SG_ GEO_STATUS_COMPASS_BEARING : 5|5@1+ (1,0) [0|18] "Degrees" DRIVER
  SG_ GEO_STATUS_DISTANCE_TO_DESTINATION : 10|16@1+ (0.1,0) [0|0] "Meters" DRIVER

BO_ 450 GPS_DESTINATION_LOCATION: 8 DRIVER
 SG_ GPS_DEST_LATITUDE_SCALED_100000 : 0|32@1- (1,0) [0|0] "Degrees" GEO
 SG_ GPS_DEST_LONGITUDE_SCALED_100000 : 32|32@1- (1,0) [0|0] "Degrees" GEO

BO_ 600 DBG_MSG_MOTOR: 4 MOTOR
 SG_ SPEED_M_PER_S : 0|32@1+ (0.001,-100) [0|0] "" SENSOR

BO_ 700 DBG_MSG_GPS: 3 GEO 
 SG_ DBG_GPS_latitude : 0|8@1- (1,0) [-90|90] "" DBG
 SG_ DBG_GPS_longitude : 8|8@1- (1,0) [-180|180] "" DBG
 SG_ DBG_GPS_lock : 16|1@1+ (1,0) [0|0] "" DBG

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Sensor and Bridge Controller ECU

Gitlab Sensor and Bridge Controller Node Link

Software Design

void ultrasonic_sensor__run_once() {

 // left, middle, right respectively
 for (int i = 0; i < 8; i++) {
   uint16_t adc_raw[3];

   // start range and wait till all sensors are done
   ultrasonic_range_once();

   adc_raw[0] = adc__get_adc_value(ADC__CHANNEL_2);
   adc_raw[1] = adc__get_adc_value(ADC__CHANNEL_4);
   adc_raw[2] = adc__get_adc_value(ADC__CHANNEL_5);

   // printf("adc2: %d\n", adc_raw[0]);
   sensor_data.left = ((float)adc_raw[0] * SCALE_FACTOR);   // / 2.0;
   sensor_data.middle = ((float)adc_raw[1] * SCALE_FACTOR); // / 2.0;
   sensor_data.right = ((float)adc_raw[2] * SCALE_FACTOR);  // / 2.0;

   if (sensor_data.left < 36) {
     gpio__reset(board_io__get_led3());
   } else {
     gpio__set(board_io__get_led3());
   }

   if (sensor_data.middle < 36) {
     gpio__reset(board_io__get_led2());
   } else {
     gpio__set(board_io__get_led2());
   }

   if (sensor_data.right < 36) {
     gpio__reset(board_io__get_led1());
   } else {
     gpio__set(board_io__get_led1());
   }
 }

}

Technical Challenges

< List of problems and their detailed resolutions>

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Motor ECU

<Picture>

Gitlab Motor Node Link

Hardware Design

The motor is directly connected to the RC car's ESC device, which is what initially controlled the car's PWMs prior to hijacking. The SJ2 now becomes the PWM transmitter as opposed to the remote and sends the corresponding PWMs based on driver signals (see Software Design for more details)

Software Design

The motor software takes in driver-motor commands through the CAN bus and based on those commands, modifies the PWMs of the motor and the servo to move the wheels forward, backward, left, or right. We mapped the PWM values as seen in the table below:

	Motor PWM	Direction
1	16.2	Forward
2	14.5	Backward
3	15.02	Idle

	Servo PWM	Direction
1	11.0	Hard Left
2	13.0	Slight Left
3	15.48	Straight
4	17.0	Slight Right
5	19.0	Hard Right

void motor_pwm__set_pwm(void) {
  motor_pwm__set_motor_pwm();
  motor_pwm__set_servo_pwm();
}

static void motor_pwm__set_servo_pwm(void) {
  static float set_servo_duty_cycle = servo_pwm_idle_duty_cycle;

  if (motor_cmd_local.MOTOR_CMD_steer == 0) {
    // idle
    set_servo_duty_cycle = servo_pwm_idle_duty_cycle;
  } else if (motor_cmd_local.MOTOR_CMD_steer == 1) {
    // slightly right
    set_servo_duty_cycle = 17.00;
  } else if (motor_cmd_local.MOTOR_CMD_steer == 2) {
    // max right
    set_servo_duty_cycle = 19.00;
  } else if (motor_cmd_local.MOTOR_CMD_steer == -1) {
    // slightly left
    set_servo_duty_cycle = 13.00;
  } else if (motor_cmd_local.MOTOR_CMD_steer == -2) {
    // max left
    set_servo_duty_cycle = 11.00;
  }

  pwm1__set_duty_cycle(servo_pwm, set_servo_duty_cycle);
}

static void motor_pwm__set_motor_pwm(void) {
  static float set_motor_duty_cycle = motor_pwm_idle_duty_cycle;

  if (motor_stop_local.MOTOR_STOP_stop) {
    motor_speed_pid_set_target_pwm(motor_pwm_idle_duty_cycle);
  } else {
    if (!ignore_cmds) {
      if (motor_cmd_local.MOTOR_CMD_forward == -1) { // Reverse
        set_motor_duty_cycle = 14.50;
        if (reverse_flag == false) {
          motor_speed_pid_set_target_pwm(motor_pwm_idle_duty_cycle);
          ignore_cmds = true;
          start_time = sys_time__get_uptime_ms();
          reverse_flag = true;
          return;
        }
      } else if (motor_cmd_local.MOTOR_CMD_forward == 0) { // Stop
        set_motor_duty_cycle = motor_pwm_idle_duty_cycle;
      } else if (motor_cmd_local.MOTOR_CMD_forward == 3) { // Forward
        set_motor_duty_cycle = 16.2;                       // 15.7 originally?, 16.2

        if (reverse_flag == true) {
          motor_speed_pid_set_target_pwm(motor_pwm_idle_duty_cycle);
          ignore_cmds = true;
          start_time = sys_time__get_uptime_ms();
          reverse_flag = false;
          return;
        }
      }
      motor_speed_pid_set_target_pwm(set_motor_duty_cycle);
    } else if (sys_time__get_uptime_ms() - start_time >= DIRECTION_CHANGE_DELAY) {
      ignore_cmds = false;
    } else {
    }
  }
}

Technical Challenges

The main issue we had with the motor controller occurred during PWM hacking because we did not want the motor running the car too fast. As such, we had to guess and check a good PWM value to run the motor so that the car would move at the slowest speed possible without running into issues where it could not move. However, with continual tests, we managed to identify the ideal range we wanted to run the motor.

Additionally, we encountered minor issues where, when transitioning from reverse to forward and vice versa, the car would go into neutral and never exit from the neutral state. We found that this issue occurred due to the delay being too small, and so the motor would not have enough time to truly go into neutral and thus would remain in that state. To counter this, we increased the delay and also slightly increased the forward PWM in order to combat the potential that it was stopping due to having too low of a PWM value.

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Geographical Controller

<Picture>

Gitlab Geo Node Link

Software Design

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

Technical Challenges

Most of our problems occurred due to an inaccurate compass reading. Mainly, the compass heading angles would not return as very stable values, which resulted in unstable driving behavior for the car. We initially thought it would resolve itself with some software calibration; however, we found that even with software calibration for the LSM, it would still be inaccurate and would not even give the full 360 degree heading range. As such, we resolved to simply buying a more expensive and more accurate magnetometer, which solved our issues. The new module returned more stable values, despite it still fluctuating, the angle changing was not enough to affect the driving behavior since we built our module with the intent of not needing the exact degree of the angles. We also found some trouble mounting the compass due to not wanting to have to handle any further offsets after mounting. Because of this, when mounting the compass, we identified where the compass was detecting north and faced the front of the car in that direction. Following that step, we mounted the compass so that it, along with the front of the car, was facing north.

Additionally, we ran into some errors with the GPS module due to us receiving latitude and longitude values that were miles away from our current location. However, we identified an error on our end where we had misinterpreted the data returned from the GPS module and thus were calculating the wrong latitude and longitude values. Once we identified the error, we found the correct way to extract the correct latitude and longitude values for a more accurate location.

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Driver and LCD Module

<Picture>

Gitlab Driver & LCD Node Link

Hardware Design

The driver node, aside from its connection to the CAN bus, is also connected the the LCD module through I2C. the SJ2 board provides the LCD with 3.3V power and sends data through SDA and SCL.

Software Design

The driver logic came down to a basic logic (show in table below) where 0 implies there is no obstacle, and 1 implies an obstacle is present.

dbc_MOTOR_CMD_s driver__get_motor_commands(void) {
  driver__avoid_obstacle();
  return motor_commands;}

static void driver__avoid_obstacle(void) {
  obstacle_below_threshold_s below_thresholds = driver__closest_obstacle();

  if (!(below_thresholds.MIDDLE) && !(below_thresholds.LEFT) && !(below_thresholds.RIGHT)) {
    driver__go_to_destination();
  } else {
    driver__steering();
  }
  driver__led_indicators();}

dbc_MOTOR_CMD_s driver__get_motor_commands(void) {
  driver__avoid_obstacle();
  return motor_commands;
}

// slight turns for destination movement
static void driver__go_to_destination(void) {
  int angle_difference = local_geo_status.GEO_STATUS_COMPASS_HEADING - local_geo_status.GEO_STATUS_COMPASS_BEARING;
  if (local_geo_status.GEO_STATUS_DISTANCE_TO_DESTINATION > 0) {
    if (angle_difference > 0) {
      // go right
      motor_commands.MOTOR_CMD_steer = 1;
      motor_commands.MOTOR_CMD_forward = 3;
    } else if (angle_difference < 0) {
      // go left
      motor_commands.MOTOR_CMD_steer = -1;
      motor_commands.MOTOR_CMD_forward = 3;
    } else { // go straight
      motor_commands.MOTOR_CMD_steer = 0;
      motor_commands.MOTOR_CMD_forward = 3;
    }
  } else { // reached destination
    motor_commands.MOTOR_CMD_forward = 0;
    motor_commands.MOTOR_CMD_steer = 0;
  }}

Technical Challenges

Most of the issues surrounding the driver node occurred after field testing. We found there were some issues regarding how soon the driver made the decision compared to when it received the sensor data. As such, we made adjustments so that, despite the delay, there would be time for the driver to receive the sensor data, identify the correct action to take, and then move the wheels. Overall, our driver node worked as expected once we started field testing due to the multitude of unit tests that were done to ensure proper logic. We also identified some minor issues when testing the reverse; however, this was easily fixed by modifying the sensor priorities so that the middle sensor's values, when below the threshold, had the most precedence. In this way, the car would not fluctuate between going forward and reverse when there was clearly an object in front of it.

Additionally, we ran into issues integrating the LCD screen through I2C. The screen's slave address would not get detected, despite the device having the proper connections and power supply. However, it was found to have just been a hardware issue and worked with a different I2C LCD device.

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Mobile Application

<Picture>

Gitlab Mobile App Node Link

Software Design

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

Technical Challenges

< List of problems and their detailed resolutions>

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Conclusion

Overall, through the course of this project, we learned a lot of different types of skills. Starting with the obvious, we learned better coding habits such as code modularization and code decoupling. We also understood how to utilize the CAN bus and messages in addition to PWM hacking for the RC car. In the scope of the project, we learned communication and group coordination and distribution skills. Although we had a bit of a rough start, as the project continued, we better understood how to organize weekly goals and tasks that needed to be done and properly distributed these tasks to each member. In addition, we learned how to collaborate with each other to build the RC car.

Project Source Code

Team X Gitlab Link

Advice for Future Students

• Start early! Order things as soon as you have your team, and keep track of finances for reimbursements
• Unit-testing lets you know the obstacle avoidance works the way you generally want it to and saves a lot of time when field testing
• Try to keep the logic simple, over-complicating the code modules makes your debugging time a lot harder since you won't know where things went wrong

Acknowledgement

Thank you Preet for the class and for guiding us through the process of building the RC car.

References

1. LCD Datasheet
2. LCD Display Initialization and Configuration Example Tutorial