F17: Alpha

Project Title

Alpha - Self-navigating RC car using CAN communication based on FreeRTOS.

Git Link - ALPHA
Git Users:

Anirudh1313
chhavi17
DoyalPatel
jigar29
kthnptl
rajvisharia
ShubhamKulkarni93
SnehaSharma
SushmaSJSU
SuchetaCiyer

Abstract

This section should be a couple lines to describe what your project does.

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.

Team Members & Responsibilities

Master Controller
- Jigar Agarwal
- Sucheta Iyer

Motor Controller
- Raj Visharia
- Shubham Kulkarni

Geographical Controller
- Krishna Sai Anirudh Katamreddy
- Chhavi Mehta

Sensor Controller
- Sneha Sharma
- Sushma Macha

Communication Bridge Controller + LCD
- Kathan Patel

Android Application
- Doyal Patel
- Sneha Sharma

Testing
- Doyal Patel
- Jigar Agarwal
- Sucheta Iyer

Schedule

Week#	Start Date	End Date	Task	Status
1	09/15/2017	09/16/2017	Read previous projects, gather information and discuss among the group members. Distribute modules to each team member.	Completed
2	09/17/2017	10/03/2017	Set up individual Git accounts and perform individual git commits on a GIT file. Create a project report template on Wiki. Finalize the scope of each individual modules. Study the datasheet and prepare the high-level design. Order an RC Car (appropriate height and suspension), rechargeable batteries, sensors, GPS and compass module.	Completed
3	10/04/2017	10/10/2017	Sensor: Interface individual sensor and observe the sensor readings under different conditions. Determine pins and architecture of board for all four sensors. Motor: Test DC and servo motors using RC Transmitter and Receiver. Master: CAN bus test interface with the sensor. Communication Bridge Controller: Refer previous projects and get an overview of ‘Communication Bridge Controller’. Deciding the Bluetooth module and place orders based on the requirements. Geo: Testing GPS and compass modules by checking connections from the datasheet. Android: Android development environment setup and basic Android application development.	Completed
4	10/11/2017	10/17/2017	Sensor: Generate a DBC structure and acceptance filter for the sensor, and send the distance of an obstacle if any over the CAN bus. Interface multiple sensors and experiment with the angles of the sensors to have minimum interference. Motor: Get the motors running using SJOne board based on the observation of the PWM waveforms for DC and servo motors on the Oscilloscope. Master: Finalizing the PCB design and general hardware model layout. Brainstorming on CAN message details like ID, priority, etc. Communication Bridge Controller: Understanding the RFCOMM Protocol for Bluetooth communication and Bluetooth hardware. Configure Bluetooth module using Bluetooth terminal. Android: Work towards enabling Bluetooth in the Android environment and create a basic application for controlling a Bluetooth-enabled phone.	Completed
5	10/18/2017	10/24/2017	Complete all the Hardware setup for the project and prepare sensor stands of suitable height (positioned at suitable angle on the car). Sensor: Develop an algorithm to trigger all the sensors sequentially i.e., MIDDLE, LEFT, RIGHT, and BACK. Interface sensors with LEDs to indicate the direction to be taken. Motor: Get the motors to move Left, Right, Forward and Reverse through CAN communication from Master module (pressing the switches on Master module). Master: Establish CAN communication between all the modules. Communication Bridge Controller: Interfacing Bluetooth module with SJOne board and test the working of the module. Geo: Interface GPS module to SJOne board using UART and collect the data from GPS and calcualte bearing angle. Android: Establish basic communication between SJOne and mobile application.	Completed
6	10/25/2017	10/31/2017	Sensor: Calculate minimum and maximum range of obstacle detection and send the values to Master module. Interface the sensors to RC Car and take real-time readings on a moving car. Motor: Design a robust algorithm to avoid obstacles based on the communication with Master and Sensor modules. Master: Interfacing with the Motor Module and Sensor Module. Communication Bridge Controller & Android: Bi-directional communication between SJOne board and Android application. Geo: Take checkpoints at varios locations on the campus.	Completed
7	11/01/2017	11/07/2017	3D print the sensor stands and place them on the board at proper angle and orientation. Sensor: Test the obstacle detection algorithm with various obstacles like hard flat surfaces, curved surface etc. Stress test the sensors under different temperatures. Motor: Get wheel feedback using RPM sensor values for vehicular movement on the slope. Communication Bridge Controller: Interfacing Bluetooth module with the Master module over the CAN Bus. Geo: Integrate GPS module with the compass and calibrating them with SJOne board as per the values obtained. Send Latitude and Longitude of the current position of the car on CAN Bus. Android: Get important data required for the Android application over CAN Bus with the help of the Bluetooth module.	Completed
8	11/08/2017	11/14/2017	Motor: Modify the code to move slight left/right, half left/right, full left/right, straight or stop as per the GPS data sent by the Master module. Master: Develop an algorithm to calculate the servo motor angle as er the data from Geo controller in order to move the car closer to the destination. Geo: Send the heading and bearing angle difference based on the current position and next position to the Master module. Communication Bridge Controller: Interfacing Bluetooth module with GPS module over the CAN bus. Android: Add Google map to the application and get current location of the car. Implement an algorithm to find the shortest path by using different position marker on the Google map.	Completed
9	11/15/2017	11/21/2017	Car: Get Destination and Routing Path from the Android app. Develop an algorithm to move the car in the given routing path as well as avoiding the obstacles on its way. Android: Communication between Android application and Master node to pass GPS coordinates and routing details.	Completed
10	11/22/2017	11/29/2017	Add additional functionalities and indicators on the car. Integrating RC Car controllers as a single unit. Start with the testing, debugging and optimization process. Make the PCB design for the entire unit. Give extra Vcc and ground pins at the ends for added functionalities like headlights and indicators.	In Progress
11	11/30/2017	12/14/2017	Completion of the final Wiki page and the report. Further testing and optimization of the project on campus routes.	In Progress
			************Final Demonstration.*************	To Do

Parts List & Cost

Item#	Part Desciption	Vendor	Datasheet	Qty	Cost
1	RC Car			1
2	CAN Transceivers MCP2551-I/P	Microchip [1]	MCP2551-I/P Datasheet	8	Free Samples
3	Sonar Sensor	Amazon [2]	Maxbotix EZ1 MB 1010 Datasheet	4	$24.95
4	Headlights
5	NiMH Battery	From seniors		2
6	Charger for NiMH/NiCd Battery	From seniors		1
7	Character LCD Display

Sensor Module

The sensor module refers to the sensors and the embedded board that controls the sensors. In this project we have used four Maxbotix EZ0 ultrasonic sensors. Each of these is mounted in four positions. Three sensors face the front of the car and are positioned in the centre, the left edge and right edge of the car. One sensor is mounted on the back of the car.

The main goal of the sensor module is to detect the distance to an obstacle, from the car and provide this information to the driver module so that it can successfully avoid the obstacle.

Hardware Design

The sensors used are LV-MaxSonar-EZ1 Ultrasonic Range Finder MB1010.

The valid sensors output is a value between 6 and 254. This value is in inches and represents the distance to the obstacle, from the sensor. It is to be noted that if the obstacle is closer than 6 inches from the sensor it will not be detected.

The sensor provides output in three forms; As a pulse on the PW pin, where pulse width represents the distance to obstacle; As an analog voltage on the AN pin; As a digital output on the TX pin, in RS-232 format. We have used the PW pin in this project to receive the input from the sensor.

It is to be noted that if two sensors which are placed so that their beams/detection areas overlap, are ranging at the same time, they cause each other interference and hence incorrect values. Hence we trigger each sensor separately one by one so that at any time, only one sensor is ranging.

<insert image of sensor here. mark all the pins - vcc gnd tx rx pw> <insert image of two sensors placed close by so that their beams are overlapping>

Pin connections - middle sensor

Hardware Interface

Pin connections for each sensor is as follows:

PW (Pin 2) - GPIO Pin configured as interrupt to receive input from sensor

RX (Pin 4) - GPIO Pin configured as output to trigger the sensor

VCC (Pin 6) - +5V

GND (Pin 7) - GND

Pin connections for the middle sensor are displayed.

Software Design

Sensor CAN message

As described in the previous section, the sensors are triggered one by one to prevent corruption of data. In our implementation the sensors are triggered in the following order: middle, right, left and back. The back and left sensors are triggered together since they would not interfere with each other.

Every sensor needs a power up time of 250 ms and some time to calibrate and take the first reading. After this period the sensor can provide a reading every 49 ms. In our implementation, all 4 sensor values are taken every 120 ms and put on the CAN bus. The format of the CAN message is shown in the following snippet taken from the DBC file. It can be observed that the sensor message has a high priority since it is critical to the operation of the car.

Implementation

The following steps are followed to get a valid sensor reading.

1. Initialize the sensors - account for power up and calibration delay.

2. Enable falling edge interrupts and setup callback functions - this is to record the pulse width output of the sensor

3. Trigger each sensor and record the current time. This is the start time.

4. When falling edge interrupt occurs record the time. This is the end time.

5. Calculate pulse width using the start and end time. This pulse width would indicate the distance to the obstacle.

Sensor operation flowchart

Testing & Technical Challenges

There were a few difficulties during implementation and testing of the sensors. Lessons learned include the following:

1. Research different types of sensors, find out the strengths and weaknesses of each before making a decision.

2. Ultrasonic sensors need to be slightly tilted upwards when mounted on the car to prevent them from accidentally detecting ground as an obstacle. This becomes especially necessary when testing on a slope/ramp.

3. Ultrasonic sensors are very sensitive and care needs to be taken while soldering them. Accidental overheating can cause them to be destroyed.

4. The ultrasonic sensors provide more range when +5V is used as supply rather than +3.3V.

5. Testing both indoors and outdoors is necessary to check if the sensor readings are accurate in both conditions.