Difference between revisions of "F17: Optimus"

Parts List & Cost

The Project bill of materials is as listed in the table below.

CAN Communication

System Nodes : MASTER , MOTOR , BLE , SENSOR , GEO

DBC File

https://gitlab.com/optimus_prime/optimus/blob/master/_can_dbc/243.dbc

Hardware & Software Architecture

Master Controller Design & Implementation

Software Architecture Design

The Master Controller Integrates the functionality of all other controllers and it acts as the Central Control Unit of the R/C car. Two of the major functionalities handled by Mater Controller is Obstacle avoidance and Route Manuevering.

The overview of Master Controller Software Architecture is to shown in the below figure.

SW Architecture

As an analogy to Human driving, it receives the imputs from sensors to determine the surrounding of the R/C car and take decisions based on the environments and commands from the user. The input data it receives includes the following. The output of the Master controller is to direct the Motor with target Speed and Steering direction.

1. Lidar Object Detections - To determine if there is any obstacle in the path of navigation

2. GPS and Compass Reading - To understand the Heading and Bearing angle to decide the direction of movement

3. User command from Android - To stop or Navigate to the Destination

Software Implementation

To Add:

Obstacle Detection design

Obstacle Avoidance Algorithm

Overall Control Flow

Debug Leds map

GPIO interface to led, CAN txrx

Description of control flow(periodic tasks)

Handling of Can messages

Unit testing

Issues

Motor Controller

Sensor Controller

The Sensor is for detecting and avoiding obstacles. For this purpose we have used RPLIDAR by SLAMTEC.

Introduction

The RPLIDAR A2 is a 360 degree 2D laser scanner (LIDAR) solution developed by SLAMTEC. It can take up to 4000 samples of laser ranging per second with high rotation speed. And equipped with SLAMTEC patented OPTMAG technology, it breakouts the life limitation of traditional LIDAR system so as to work stably for a long time. The system can perform 2D 360-degree scan within a 6-meter range. The generated 2D point cloud data can be used in mapping, localization and object/environment modeling. The typical scanning frequency of the RPLIDAR A2 is 10hz (600rpm). Under this condition, the resolution will be 0.9°. And the actual scanning frequency can be freely adjusted within the 5-15hz range according to the requirements of users. The RPLIDAR A2 adopts the low cost laser triangulation measurement system developed by SLAMTEC, which makes the RPLIDAR A2 has excellent performance in all kinds of indoor environment and outdoor environment without direct sunlight exposure.

This LIDAR consists of a range scanner core and the mechanical powering part which makes the core rotate at a high speed. When it functions normally, the scanner will rotate and scan clockwise. And users can get the range scan data via the communication interface of the RPLIDAR (UART) and control the start, stop and rotating speed of the rotate motor via PWM.

Hardware Implementation

Software Implementation

Android Application

Bluetooth Controller

Hardware Implementation

Bluetooth Module: We are using HC-05 Bluetooth module to send and receive the data from our android application.

GPS and Compass Module

Pin Configuration:

pin configuration

The Bridge controller is connected to the bluetooth module through the uart serial interface (Uart3) with 9600 baud rate 8-bit data and 1 stop bit.

Software Implementation

Pseudo code of Bridge controller:

1. Turn on bridge controller.

2. Initialise Bluetooth controller with Uart3 settings.

3. Initialise CAN-BUS with 100 kbps speed.

4. Handle Incoming IO messages it receives from Geo and Sensor over CAN Bus.

5. Send the received CAN message to the Android over Bluetooth each second.

6. Send the heartbeat message every second to the Master controller.

7. Read Bluetooth message it received from the Android app.

8. Forward the Android message to GEO controller if it received checkpoints otherwise forward it to Master.

DBC messages:

Geographical Controller

Design & Implementation

GPS and Compass Module: We are using DJI’s NAZA GPS/COMPASS to get the GPS coordinates and Heading angle. The diagram of the module is as follows:

GPS and Compass Module

Message Structure: The 0x10 message contains GPS data. The message structure is as follows: 55 AA 10 3A DT DT DT DT LO LO LO LO LA LA LA LA The payload is XORed with a mask that changes over time. Values in the message are stored in little endian.

HEADER

BYTE 1-2: message header - always 55 AA BYTE 3: message id (0x10 for GPS message) BYTE 4: length of the payload (0x3A or 58 decimal for 0x10 message)

PAYLOAD

BYTE 5-8 (DT): date and time BYTE 9-12 (LO): longitude (x10^7, degree decimal) BYTE 13-16 (LA): latitude (x10^7, degree decimal)

CHECKSUM

BYTE 63-64 (CS): checksum

XOR mask

All bytes of the payload except 53rd (NS), 54th, 61st (SN LSB) and 62nd (SN MSB) are XORed with a mask. Mask is calculated based on the value of byte 53rd (NS) and 61st (SN LSB).

Pin Configuration:

The Pin Configuration is as follows:

Block Diagram

Software Design

Algorithm:

Distance calculation:

We are using the ‘haversine’ formula to calculate the great-circle distance between two points – that is, the shortest distance over the earth’s surface

Haversine formula:

a = sin²(Δφ/2) + cos φ1 ⋅ cos φ2 ⋅ sin²(Δλ/2) c = 2 ⋅ atan2( √a, √(1−a) ) d = R ⋅ c

where φ is latitude, λ is longitude, R is earth’s radius (mean radius = 6,371km)

Bearing Angle calculation:

Formula:

θ = atan2( sin Δλ ⋅ cos φ2 , cos φ1 ⋅ sin φ2 − sin φ1 ⋅ cos φ2 ⋅ cos Δλ )

where φ1,λ1 is the start point, φ2,λ2 the end point (Δλ is the difference in longitude)

Since atan2 returns values in the range –π to +π (that is, -180° to +180°), to normalize the result to a compass bearing (in the range 0° to 360°), negative values are transformed into the range 180° to 360°) by converting to degrees first and then using (θ+360) % 360, where % is (floating point) modulo.

DBC Messages:

Messages sent from GEO module:

BO_ 4 GEO_TURNING_ANGLE: 2 GEO

SG_ GEO_TURNING_ANGLE_degree : 0|9@1- (1,0) [-180|180] "" MASTER,BLE

BO_ 37 GEO_HEARTBEAT: 1 GEO

SG_ GEO_HEARTBEAT_signal : 0|8@1+ (1,0) [0|255] "" MASTER

BO_ 195 GEO_TELECOMPASS: 6 GEO

SG_ GEO_TELECOMPASS_compass : 0|12@1+ (0.1,0) [0|360.0] "" MASTER,BLE
SG_ GEO_TELECOMPASS_bearing_angle : 12|12@1+ (0.1,0) [0|360.0] "" MASTER,BLE
SG_ GEO_TELECOMPASS_distance : 24|12@1+ (0.1,0) [0|0] "" MASTER,BLE
SG_ GEO_TELECOMPASS_destination_reached : 36|1@1+ (1,0) [0|1] "" MASTER,BLE
SG_ GEO_TELECOMPASS_checkpoint_id : 37|8@1+ (1,0) [0|0] "" MASTER,BLE,SENSOR

BO_ 196 GEO_TELEMETRY_LOCK: 1 GEO

SG_ GEO_TELEMETRY_lock : 0|8@1+ (1,0) [0|0] "" MASTER,SENSOR,BLE

BO_ 214 GEO_TELEMETRY: 8 GEO

SG_ GEO_TELEMETRY_LONG : 0|32@1- (0.000001,0) [0|0] "" MASTER
SG_ GEO_TELEMETRY_LAT : 32|32@1- (0.000001,0) [0|0] "" MASTER

Messages received by GEO module:

BO_ 212 BLE_GPS_DATA: 8 BLE

SG_ BLE_GPS_long : 0|32@1- (0.000001,0) [0|0] "" GEO
SG_ BLE_GPS_lat : 32|32@1- (0.000001,0) [0|0] "" GEO

BO_ 213 BLE_GPS_DATA_CNT: 1 BLE

SG_ BLE_GPS_COUNT : 0|8@1+ (1,0) [0|0] "" GEO,SENSOR

Implementation

Periodic callback function description:

1 Hz Function:

a. Check CAN bus

b. Send Heartbeat to Master module

c. Send GPS lock to Master and Sensor modules

100 Hz Function:

a. Get GPS coordinates

b. Get Heading angle

c. Get Checkpoints count

d. Calculate Bearing angle

e. Calculate Turning angle

f. Calculate Distance remaining

g. Send Heading angle

h. Send Bearing angle

i. Send Turning angle

j. Send Distance remaining

k. Check Destination reached

Testing & Technical Challenges

Git Project Management

Common Technical Challenges

Project Videos

Conclusion

Project Source Code

References

Acknowledgement