F15: Minion

Minion

Abstract

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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

Sensor Controller:-

Bhupendra Naphade

Motor & I/0 Controller:-

Communication Bridge & Android Controller:-

Akshay Kanchar
Asmita Deshpande

Geographical Controller:-

Amit Pachore
Sindhuja Gopalakrishnan Elango

Master Controller:-

Gaurao Chaudhari
Akshay Dabholkar

Tester:-

Bhupendra Naphade

Treasurer:-

Keerthanaa Alagudurai

Hardware:-

Amit Pachore
Gaurao Chaudhari
Bhupendra Naphade

Release:-

Akshay Kanchar

Schedule

Common Schedule

Sl. No	Start Date	End Date	Task	Status
1	9/22/2015	9/28/2015	RC Car and important component buying	Completed
2	9/29/2015	10/6/2015	1) Algorithm and architecture 2) Setup of car and decision on CAN Id's	Completed
3	10/7/2015	10/13/2015	1) Coding and final set-up of car 2) Successful communication of CAN bus. 3) Car in running position.	Completed
4	10/14/2015	10/20/2015	Sensor Data gathering and movement according to sensors.	Completed
5	10/21/2015	10/27/2015	1) LCD Display working and finalizing the data to be displayed on LCD module. 2) GEO data gathering and controlling of car using Android module.	Completed
6	10/28/2015	11/3/2015	Integration of all the modules into one.	Completed
7	11/4/2015	11/10/2015	Inclusion of new features in the car.
8	11/11/2015	11/17/2015	Testing depending upon the newly added features.
9	11/18/2015	11/24/2015	Testing of Car and testing the self driving capability	Completed
10	11/25/2015	12/1/2015	Testing of Car

Sensor Controller Schedule

Sl. No	Start Date	End Date	Task	Status	Actual Completion Date
1	9/20/2015	10/5/2015	Study available sensors and place order	Completed	10/4/2015
2	10/6/2015	10/13/2015	Collaborate with the other sub teams to finish the CAN bus communication	Completed	10/13/2015
3	10/13/2015	10/20/2015	Develop simple test code for the sensors	Completed	10/18/2015
4	10/21/2015	10/30/2015	Interface all sensors and develop code for reading all sensors.	Completed	10/30/2015
5	10/30/2015	11/2/2015	Positioning of sensors and identifying dead band if any	Completed	11/2/2015
6	11/2/2015	11/5/2015	Work on light and battery sensor (optional)
7	11/06/2015	12/17/2015	Final testing and debugging

Motor & I/0 Controller Schedule

Sl. No	Start Date	End Date	Task	Status	Actual Completion Date
1	9/21/2015	9/25/2015	Order LCD Display	Completed	9/25/2015
2	9/28/2015	10/3/2015	Going through the motor concepts and PWM	Completed	10/2/2015
3	10/4/2015	10/9/2015	Intreface the DC and SERVO Motors with SJONE board	Completed	10/8/2015
4	10/10/2015	10/13/2015	Establishing basic CAN communication with other modules	Completed	10/13/2015
5	10/11/2015	10/16/2015	Getting the car to run with the PWM signals from Motor controller	Completed	10/15/2015
6	10/17/2015	10/23/2015	Research on Speed cotrol method and sensor for the same interface LCD display with LPC1758 via UART	Completed	10/21/2015
7	10/23/2015	11/4/2015	Establishing reliable CAN communication for IO & Motor with others	Completed	11/4/2015
8	11/5/2015	11/12/2015	Integrate Speed sensor and get feedback. Start working on start,stop buttons and headlight	Completed	11/11/2015
9	11/13/2015	11/20/2015	Testing substantial self driving capability of the car
10	11/21/2015	11/30/2015	Complete integration, Debugging and Fine tuning
11	12/1/2015	12/5/2015	Final Validation

Geographical Controller Schedule

Sl. No	Start Date	End Date	Task	Status	Actual Completion Date
1	09/27/2015	10/07/2015	Ordering Parts and understanding each module	Completed	10/11/2015
2	10/07/2015	10/13/2015	CAN Communication with other boards and understanding each module	Completed	10/13/2015
3	10/07/2015	10/30/2015	Algorithm for distance and heading calculation and coding	Completed	10/30/2015
4	10/14/2015	10/20/2015	Interfacing of compass(I2C) and GPS (UART) with SJONE board	Completed	10/20/2015
5	10/20/2015	10/30/2015	Coding, Compass Calibration,GPS Calibration	Completed
5	10/25/2015	11/15/2015	Individual unit testing	Completed
6	10/30/2015	11/30/2015	Interfacing with Android, Master and IO controllers
7	10/30/2015	11/30/2015	Integration Testing,On Car Calibration	First level of On Car Calibration Completed

Master Controller Schedule

Sl. No	Start Date	End Date	Task	Status	Actual Completion Date
1	09/30/2015	10/6/2015	a) Design of Algorithm and Architecture for Master Module. b) Setup of CAN communication between two controllers.	Completed	10/6/2015
2	10/7/2015	10/13/2015	a) Development of CAN message system for Android, Sensor and GPS, I/O reception. b) Decide about periodic function frequencies that’ll be handling different modules.	Completed	10/13/2015
3	10/14/2015	10/20/2015	a) Development of driving,stopping and obstruction avoidance algorithm for motor. b) Implementation of LED Display to display number of messages on CAN bus. c) Implementation of turning algorithm as per the data received from the Geo Controller.	Completed	10/20/2015
4	10/21/2015	10/27/2015	a) Designing of Kill switch with the help of Motor, I/O and Android. b) Design the system to restore the last known configuration. c) Implementation to reset modules if the CAN bus reaches BUS off state.	Completed	10/27/2015
5	10/28/2015	11/3/2015	a) Design of Head Light functionality with the help of Sensor module. b) Implementation of log files saving to SD card.	Completed
6	11/4/2015	11/10/2015	a) Integration of all the modules with Master module and check it after combining everything. b) Probable implementation of additional features.	On going
7	11/11/2015	11/17/2015	a) Refine the work done earlier.Change areas that need a change. b) Test the Master module while all the modules are integrated together and list down modifications and additions to be done.	Completed
8	11/18/2015	11/24/2015	Testing of system and specially making sure that last week’s shortcomings are taken care of.
9	11/25/2015	12/1/2015	a) Final testing of individual modules. b) Testing the self-driving capability of the car.
10	12/2/2015	12/8/2015	Final working on the shortcomings in the previous week.
11	12/9/2015	12/15/2015	Final Testing of Car.

Communication Bridge & Android Controller Schedule

Sl. No	Start Date	End Date	Task	Status	Actual Completion Date
1	9/29/2015	10/06/2015	Ordering bluetooth module and setting up android dev enviornment	Completed	10/06/2015
2	10/06/2015	10/13/2015	Implementing basic UI with Start and Stop buttons and testing bluetooth module	Completed	10/12/2015
3	10/13/2015	10/27/2015	Integrating android app with bluetooth module and SJ One board	Completed	11/01/2015
4	10/27/2015	11/03/2015	Establishing communication with other modules using CAN and testing Prototype	Completed	11/07/2015
5	11/03/2015	11/17/2015	Enhancing UI features with Google Maps and display of sensor data from different modules	Ongoing
6	11/17/2015	12/01/2015	Setting up Communication with GPS and Master and prototype testing
7	12/01/2015	12/08/2015	Final app testing

Parts List & Cost

Sr. No	Part Name	Source of Purchase	Part Number	Quantity	Cost($)
1	RC Car	Sheldons Hobbies	360541 Stampede RTR	1	239.99
2	Battery	Sheldons Hobbies	VEN1548 - 5000NiMh 7.2 V	1	44.99
3	Traxx AC Adaptor	Sheldons Hobbies	TRAXXAS 2976 AC Adaptor to 12V	1	24.99
4	Compass	Dx.com	HMC5883L Digital Compass Module - Blue	1	2.47
5	GPS Module	Sparkfun.com	SparkFun Venus GPS with SMA Connector GPS 11058	1	44.08
6	LCD module	mouser.com	NHD-0420D3Z-NSW-BBW-V3-ND	1	29.68
7	Bluetooth Module	Amazon.com	Sunkee HC-05	1	8.88
8	Ultrasonic sensors	Amazon.com	HC-SR04	5	8.59
9	PCB	Amazon.com	PCB	2	10.6
10	Female to Female connectors	aliexpress.com	Female to Female connectors	2	1.5
11	Compass	aliexpress.com	HMC5883L Digital Compass Module - Blue	1	6.73
12	GPS Antenna	Sparkfun.com	Antenna GPS Embedded SMA	1	19.49
13	female to female connectors+bergstrip+lm7805+SJ 32 pin socket	Excess solution	female to female connectors+bergstrip+lm7805+SJ 32 pin socket	1	4.7
14	Components	Excess solution	Connector+screws+Nuts+Standoffs	1	10
15	Component cable and led and other	Excess solution	Component cable and led and other	1	17.29
16	Ultrasonic sensors	Amazon.com	HC-SR04	5	8.69

DBC Implementation

   VERSION ""


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


BS_:
BU_: NOONE SENSOR MASTER MOTORIO ANDROID GEO

BO_ 220 MOTORIO_CMD: 4 MASTER
 SG_ MOTORIO_CMD_LeftRightdirection : 0|8@1+ (1,0) [0|2] "" MOTORIO
 SG_ MOTORIO_CMD_LevelOfDirection : 8|8@1+ (1,0) [0|5] "" MOTORIO
 SG_ MOTORIO_CMD_FrontBackDirection : 16|8@1+ (1,0) [0|2] "" MOTORIO
 SG_ MOTORIO_CMD_LevelOfSpeed : 24|8@1+ (1,0) [0|5] "" MOTORIO

BO_ 010 KILL_REQUEST: 0 ANDROID
 SG_ KILL_REQUEST : 0|0@1+ (1,0) [0|0] "" MASTER

BO_ 020 KILL_MESSAGE: 0 MASTER
 SG_ KILL_REQUEST : 0|0@1+ (1,0) [0|0] "" MOTORIO,SENSOR,GEO,ANDROID

BO_ 030 STOP_REQUEST: 0 ANDROID
 SG_ STOP_REQUEST : 0|0@1+ (1,0) [0|0] "" MASTER

BO_ 040 STOP_COMMAND: 0 MASTER
 SG_ ANDROID_HEARTBEAT_cmd : 0|0@1+ (1,0) [0|0] "" MOTOR

BO_ 210 SONARS: 4 SENSOR
 SG_ SENSOR_SONARS_FrontDistance : 0|8@1+ (1,0) [0|0] "" MASTER,MOTORIO
 SG_ SENSOR_SONARS_LeftDistance : 8|8@1+ (1,0) [0|0] "" MASTER,MOTORIO
 SG_ SENSOR_SONARS_RightDistance : 16|8@1+ (1,0) [0|0] "" MASTER,MOTORIO
 SG_ SENSOR_SONARS_RearDistance : 24|12@1+ (1,0) [0|0] "" MASTER,MOTORIO

BO_ 230 TOTAL_DISTANCE_TO_TRAVEL: 4 ANDROID
 SG_ TOTAL_DISTANCE_TO_TRAVEL: 0|16@1+ (1,0) [0|0] "" GEO

BO_ 240 SEND_CHECKPOINTS: 8 ANDROID
 SG_ SEND_CHECKPOINTS_Latitude: 0|32@1+ (1,0) [0|0] "" GEO
 SG_ SEND_CHECKPOINTS_Longitude: 32|64@1+ (1,0) [0|0] "" GEO

BO_ 250 DISTANCE: 4 GEO
 SG_ DISTANCE_FinalDistance : 0|16@1+ (1,0) [0|0] "" MASTER
 SG_ DISTANCE_CheckpointDistance : 16|16@1+ (1,0) [0|0] "" MASTER

BO_ 260 TURN_ANGLE_DIRECTION: 2 GEO
 SG_ TURN_ANGLE_DIRECTION_TurnAngle : 0|8@1+ (1,0) [0|0] "" MASTER
 SG_ TURN_ANGLE_DIRECTION_TurnDirection : 8|8@1+ (1,0) [0|0] "" MASTER

BO_ 270 RUN_PAUSE: 0 ANDROID
 SG_ RUN_PAUSE : 0|0@1+ (1,0) [0|0] "" MASTER

BO_ 280 HEARTBEAT_: 0 MOTORIO
 SG_ MOTORIO_HEARTBEAT_cmd : 0|0@1+ (1,0) [0|0] "" MASTER

BO_ 281 HEARTBEAT: 0 GEO
 SG_ GEO_HEARTBEAT_cmd : 0|0@1+ (1,0) [0|0] "" MASTER

BO_ 282 HEARTBEAT: 0 ANDROID
 SG_ ANDROID_HEARTBEAT_cmd : 0|0@1+ (1,0) [0|0] "" MASTER

BO_ 283 HEARTBEAT: 0 SENSOR
 SG_ SENSOR_HEARTBEAT_cmd : 0|0@1+ (1,0) [0|0] "" MASTER

BO_ 410 DESTINATION_REACHED: 0 MASTER
 SG_ SENSOR_HEARTBEAT_cmd : 0|0@1+ (1,0) [0|0] "" MASTER

BO_ 420 BATTERY_STATUS: 1 SENSOR
 SG_ BATTERY_STATUS_VALUE : 0|0@1+ (1,0) [0|0] "" MASTER,MOTORIO

BO_ 610 BOOT_REQUEST: 0 MASTER
 SG_ BATTERY_STATUS_VALUE : 0|0@1+ (1,0) [0|0] "" MOTORIO,SENSOR,ANDROID,GEO

BO_ 620 BOOT_REPLY_MOTORIO: 0 MOTORIO
 SG_ BOOT_REPLY_MOTORIO : 0|0@1+ (1,0) [0|0] "" MASTER

BO_ 621 BOOT_REPLY_SENSOR: 0 SENSOR
 SG_ BOOT_REPLY_SENSOR : 0|0@1+ (1,0) [0|0] "" MASTER

BO_ 622 BOOT_REPLY_GEO: 0 GEO
 SG_ BOOT_REPLY_GEO : 0|0@1+ (1,0) [0|0] "" MASTER

BO_ 623 BOOT_REPLY_ANDROID: 0 ANDROID
 SG_ BOOT_REPLY_ANDROID : 0|0@1+ (1,0) [0|0] "" MASTER

BO_ 630 BOOT_STATUS: 0 MASTER
 SG_ BOOT_STATUS : 0|0@1+ (1,0) [0|0] "" MOTORIO,ANDROID

BO_ 650 SOURCE_COORDINATE: 8 GEO
 SG_ SOURCE_COORDINATE_LATITUDE : 0|32@1+ (1,0) [0|0] "" ANDROID
 SG_ SOURCE_COORDINATE_LONGITUDE : 32|32@1+ (1,0) [0|0] "" ANDROID

CM_ BU_ NOONE "No node, used to indicate if it's a debug message going to no one.";
CM_ BU_ MASTER "The Master controller driving the car.";
CM_ BU_ SENSOR "The Sensor controller of the car.";
CM_ BU_ MOTORIO "The Motor-IO controller of the car.";
CM_ BU_ ANDROID "The Android controller of the car.";
CM_ BU_ GEO "The Geo controller of the car.";
CM_ BO_ 100 "Sync message used to synchronize the controllers";

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

BA_DEF_DEF_ "BusType" "CAN";
BA_DEF_DEF_ "FieldType" "";

BA_ "GenMsgCycleTime" BO_ 220 10;
BA_ "GenMsgCycleTime" BO_ 210 10;
BA_ "GenMsgCycleTime" BO_ 250 10;
BA_ "GenMsgCycleTime" BO_ 260 10;
BA_ "GenMsgCycleTime" BO_ 280 1;
BA_ "GenMsgCycleTime" BO_ 281 1;
BA_ "GenMsgCycleTime" BO_ 282 1;
BA_ "GenMsgCycleTime" BO_ 283 1;
BA_ "GenMsgCycleTime" BO_ 420 1;

VAL_ 100 MASTER_HEARTBEAT_cmd 0 "MASTER_HEARTBEAT_cmd_NOOP" 1 "MASTER_HEARTBEAT_cmd_SYNC" 2 "MASTER_HEARTBEAT_cmd_REBOOT";

Design & Implementation

CAN Communication Table

Sr. No	Message ID	Message function	Message Data	From	To
High
1	0x220	Motor Control (Direction Control- Straight, Left or Right Level of Direction-Level 0, Level1, Level 2 Motion Control- Stop, Forward or Reverse Speed Control - Stop, Level1, Level2 or Level3)	Byte[0] -> Direction Control Byte[1] -> Level of Direction Byte[2] -> Motion Control Byte[3] -> Speed Control	Master	Motor
2	0x010	Kill Message (User request to stop the car under emergency)	Control Frame. No data bytes.	Android	Master
3	0x020	Kill Message (Master request to stop all controllers and reboot under emergency)	Control Frame. No data bytes.	Master	All
4	0x030	Stop (User request to stop the car)	Control Frame. No data bytes.	Android	Master
5	0x040	Stop (Master stops the motor)	Control Frame. No data bytes.	Master	Motor
6	0x210	Sensor Data (Distance in cms)	Byte[0] -> Forward Distance Byte[1] -> Left Distance Byte[2] -> Right Distance Byte[3] -> Back Distance	Sensor	Master/Motor-IO
7	0x230	Total Distance to Travel	Byte[0-1]	Android	Geo
8	0x240	Send Checkpoints	Byte[0-3] -> Latitude Byte[4-7] -> Longitude	Android	Geo
9	0x250	Distance (Distance in foot)	Byte[0-1] -> Final Distance remaining Byte[2-3] -> Checkpoint distance	Geo	Master
10	0x260	Turn Angle and Direction	Byte[0] -> Turn Angle Byte[1] -> Direction (1-Left,2-Right)	Geo	Master
11	0x270	Run and Pause Command	Control Frame. No data bytes	Android	Master
12	0x280	Heartbeat Message	Control Frame. No data bytes	Motor	Master
13	0x281	Heartbeat Message	Control Frame. No data bytes	Geo	Master
14	0x282	Heartbeat Message	Control Frame. No data bytes	Android	Master
15	0x283	Heartbeat Message	Control Frame. No data bytes	Sensor	Master
Medium
16	0x410	Destination reached. (Stops the car when destination is reached)	Control Frame. No data bytes	Master	All
17	0x420	Battery Status	Byte[0-1]	Sensor	Master/IO
Low
18	0x610	Boot Request	Control Frame. No data bytes	Master	All
19	0x620	Boot Reply (Date and time will be sent to Master)	Byte[0-4]	Motor-IO	Master
20	0x621	Boot Reply (Date and time will be sent to Master)	Byte[0-4]	Sensor	Master
21	0x622	Boot Reply (Date and time will be sent to Master)	Byte[0-4]	Geo	Master
22	0x623	Boot Reply (Date and time will be sent to Master)	Byte[0-4]	Android	Master
23	0x630	Boot Status (Enable the map and run button in Android)	Control Frame. No data bytes	Master	Motor-IO/Android
24	0x640	System Start	Control Frame. No data bytes	Android	All
25	0x650	Source Co-ordinates	Byte[0-3] -> Source Latitude Byte[4-7] -> Source Longitude	Geo	Android

Car Framework and Components

The RC car, Traxxas Stampede, in its raw form consists of a Titan 12T 550 Brushed DC motor, a Servo motor, an XL-5 ESC (Electronic Speed Control) unit, battery and a pre-programmed wireless receiver and controller. The Battery used in the RC car is an 8.4 V, 3000 NiMH from Traxxas. The wireless receiver gets commands from the remote control and drives the motors accordingly, but the DC motor can be controlled only through ESC.

The ESC (Electronic Speed Control) unit is an electronic module, which receives PWM signals from the controller and varies speed and direction of the DC motor and also acts as dynamic brakes. ESCs are often used in RC models. The ESC has the capability to provide dynamic braking depending on the mode in which it is being operated.

Motor and I/O Controller

Hardware Design

Motor Module

The motor module comprises of a servo motor for the direction control and a DC motor for speed control. The servo motor helps the car in turning left and right where as the DC motor on the other hand helps the car move forward and backward. The DC motor used in the project is a brushed motor. Conventionally, brushless motors are faster and more efficient than brushed motors. But, the reason for selecting a brushed motor over a brushless motor is that we employ a dedicated battery for the motor such that we do not have any issues with power and efficiency. Moreover, we need not operate the car at high speeds.

The initial task in the motor module is to find the operating ranges of the motor so that we get to know the output signal range and frequency from the SJONE board which would be replacing the pre-programmed controller. The simplest way to find the operating ranges of the motor is to tap and analyze PWM signal that is being supplied to the motor over an oscilloscope. The results as shown in the below pictures indicate that the operating duty cycle of both the motors lie between 10% to 20% and the frequencies at which the motors operate is 100Hz.

The hardware interface of the Motors and SJONE board includes the following connections.

Sl. No	Connection on the car	Pin on SJSU One Board	Purpose
1	Input to DC Motor	P2.1	PWM input to drive DC motor
2	Input to Servo Motor	P2.0	PWM input to drive DC motor
3	Speed sensor	P2.4	PWM output from speed sensor

The Motor controller receives the commands from the Master controller which guides it to navigate the car based on the information from the Sensors and GPS. While it does so, it also needs to get feedback from the DC motor and control the motor independently in order to ensure that the car is moving with the speed requested by the Master. This requires increasing or decreasing the actual speed level that is being provided to the Motor in case of movement along uphill, downhill, glass and high friction tracks.

The feedback is achieved through a shaft encoder which works based on Hall-effect. The installation of the speed sensor was pretty easy as we went with the one from Traxass, the same manufacturer as our RC car. It involves removing the DC motor casing, placing the sensor over the spur gear and the magnet holder. The sensor would sense the rotation of the axle. It produces a pulse when the magnet comes into the line of the sensor, which is then detected by the Motor controller.

IO Module

The IO module Consists of a 4 line * 20 characters serial LCD. Data from GPS and sensor module is displayed continuously by refreshing it every second. SJ one board communicates with LCD through UART. GPS data :-

Latitude
Longitude
Final distance remaining

Sensor data:-

Left sensor reading
Right sensor reading
Front sensor reading
Rear sensor reading

Additionally, IO module controls lighting up headlights/taillights based on the direction of the car movement.

Hardware Interface

LCD unit requires 5V power supply for its working. The VCC and Ground pins are connected to common power supply lines that is used to power up all the boards. The Rx pin of LCD is connected to TXD2 (p2.8) pin on SJ one board. Two of the GPIO pins p2.6 and p2.7 controls the headlights LED’S and taillights LED’S respectively.

Sl. No	Pin on IO Module	Pin on SJSU One Board	Purpose
1	Vcc	Common power supply	5V for LCD
2	Ground	Common Ground	Ground for LCD
3	Rx	P2.8(TXD2)	Receive data from SJone board through UART
4	Headlight LED’s(2)	P2.6	Turn on headlights when car is moving in the forward direction
5	Taillight LED’s (2)	P2.7	Turn on tail-lights when car is moving in the reverse direction

Software Design

Motor/IO Module

The controller on boot up initializes the CAN communication, UART and also the PWM for initialization pulse required for the motor to run. The inter-controller communication is done over CAN bus. It is configured to receive and transmit messages at 100K baud-rate. The type of CAN ID is Standard. Later these are accomplished at run time using the periodic scheduler task.

LCD communicates with SJ one board through UART. The UART port is configured to operate at the default baud rate of 9600 bps. “FO” character is sent to initialize the UART port after a delay of 100 ms, upon powering up the board. The display unit responds after 100 ms. Now the LCD module is configured and can receive further messages to display on it. Data from modules such as GPS and sensor are received continuously through CAN. It is decoded, converted into proper format and displayed on the LCD periodically.

The Motor controller, after sending the initialization pulse to the DC motor, waits for a start command from the Master over CAN and then controls the motors in order to reach the destination with required levels of speed and direction. The control algorithm for the Motor operation is as shown below.

Software Implementation

“Can receive” function is called in periodic scheduler 100 Hz task. This function lets the Motor/IO module receive CAN messages from other modules connected to it. CAN set up filter function has been used to accept only essential messages required by this module. Based on the CAN message identifier, corresponding action is performed. These are the CAN messages required by the motor/IO module.

CAN MESSAGE ID:-

0x210 – Sensor data
0x220 – motor control message from master
0x240 , 0x250 – GPS data

Data from sensor and GPS modules are stored in global message buffers. Sensor data is 8 bit whereas GPS data ranges between 16-32 bits. These integer values are converted into character type and then sent to LCD through UART. LCD display function is called in 1Hz periodic scheduler task. Thus Sensor and GPS data get displayed on the LCD every sec.

The 3D design used as a support for mounting the LCD is shown below:

3D design for LCD mounting

Motor Control

On receiving the CAN message(0x220) from the Master, the data is extracted and and used for specific functions as shown below.

          *Byte0 --> Servo Direction
          *Byte1 --> Servo Level
          *Byte2 --> DC Direction
          *Byte3 --> DC Level

Based on this data, the first two bytes decide the direction(left/right) and the level(angle), respectively in which the car should turn using the Servo motor. Similaly, the next two bytes decide the direction(forward/backward) and the level(speed) in which the car has to move.

To implement all the motor related functions, we have employed a dedicated task. Initially, the pre-scaled PWM values are fed to the motors based on the direction and level from the Master. We have a bit robust algorithm to obtain these PWM values which has offsets and level multipliers. The advantage of this is we can change the code to function for multiple levels with minimum effort.

Motor Feedback

After feeding the motors with the required levels, we have to check if the car is actually moving at that speed. This is ensured through feedback and control based on that. The feedback is obtained through the speed sensor collaborated with the DC motor, which triggers a pulse on every rotation and this is recorded by a rising edge based interrupt. The interrupt callback function increments the number of pulses. A separate logic is used to calculate and then compare the actual and required(from Master) speed levels. The corrective measures are enforced to achieve the desired speed.

The transmit messages, except Heart beat message(sent every one second), are transmitted once every 100ms. The Motor/IO controller, on receiving a boot request from Master controller, transmits a boot reply message in order to let the Master know that it has booted successfully. The heart beat message is transmitted continuously to indicate that the controller is active and this will be acknowledged by the Master.

Master Controller

As the name suggests, it is main controller on the car which interacts with all other controllers over the CAN Bus to achieve real-time functionality. Basic function of the Master Controller is to receive data from Android, Geo and Sensor Modules and develop the algorithm to drive the car autonomously based on the received data through the Motor Controller.