Difference between revisions of "S20: Tesla Model RC"

Revision as of 23:08, 21 May 2020

Model RC

Tesla Model RC

Abstract

Tesla Model RC is an electric, battery-powered, self-navigating RC car. The aim is to navigate to the destination set on the Android application by utilizing GPS navigation. The car combines the data received from multiple sensors to perceive its surroundings to avoid obstacles in its path.

Introduction

The project was divided into 5 modules:

• Bridge and Sensor Controller
• Motor Controller
• Geographical Controller
• Driver and LCD controller
• Android Application

Team Members & Responsibilities

<Team Picture>

Danny Nuch

• Git Project Link: Tesla Model RC

• Motor Controller
  • Salvatore Nicosia
  • Nickolas Schiffer

• Bridge Sensor Controller
  • Danny Nuch

• Geographical Controller
  • Salvatore Nicosia
  • Nickolas Schiffer

• Driver & LCD Controller
  • Ayesha Siddiqua

• Android Application
  • Andrew Kwon

• System Integration and Testing
  • Salvatore Nicosia

• RC Car Design: 3D Printing
  • Salvatore Nicosia

• Review Team
  • Nickolas Schiffer
  • Salvatore Nicosia
  • Danny Nuch

Schedule

Parts List & Cost

Printed Circuit Board

<Picture and information, including links to your PCB>

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> High Level Hardware Diagram

Figure #. CAN Bus Diagram

DBC File

https://gitlab.com/tesla-model-rc/sjtwo-c/-/blob/dev/dbc/tesla_model_rc.dbc

Bridge Sensor ECU

https://gitlab.com/tesla-model-rc/sjtwo-c/-/tree/dev/projects/sensor

Hardware Design

Figure #. Bridge Sensor Node

Software Design

Sensor Node

Sensor Node and CAN Periodics module
Wifi module
Battery Tracking module
Ultrasonics and GPIO Interrupts module
Average Buffer module
Ultrasonic smoothing by averaging
low pass filter for zeros (Ultrasonics received too quickly)

ESP8266

Bridging between ESP8266 and mobile application is done through the creation of an access point on the ESP8266. Furthermore, the ESP8266 opens a server socket through CoAP allowing other CoAP clients to transmit or receive data from a created resource (/topics). The mobile application serves as the CoAP client and currently performs:

(GET) /heartbeat will receive string: "tmrc:heartbeat"
(GET) /getRadars will receive string: "aa,bb,cc,dd" where a is front radar, b is left radar, c is right radar, and d is back radar
(PUT) /setStatus will send string - either "$stop\n" or "$start\n"
(PUT) /setCoordinates will send coordinates as string - i.e. "#Sxxx.xxxxxx,Syyy.yyyyyy\n" where S is the sign and x is latitude and y is longitude

/getRadars resource will update through UART from a microcontroller. The string must follow the format: "^%02,%02,%02,%02" where '^' is the identifier for setting this resource. This length is also fixed where each radar data must have a width of no more than 2.
/setStatus resource has an identifier of '$', while /setCoordinates resource has an identifier of '#'. Both resources require appending a new line character at the end of string. This is essential for parsing strings on microcontroller side as the ESP8266 echoes received data over UART.

Project Setup
This project is built with ESP8266 RTOS SDK for programming the ESP8266. FreeRTOS, UART, Wifi with CoAP libraries are fully utilized in this project.
See the Getting Started Guide for full steps to configure and use ESP-IDF to build projects.

softAP - Wifi Access Point
ESP8266 opens an access point for other wireless devices to connect too. This access point follows adaptation of this example:
https://github.com/espressif/ESP8266_RTOS_SDK/tree/master/examples/wifi/getting_started/softAP.

UART Configuration
UART is simply transmitted over UART0 TX/RX pins. This example is integrated.

CoAP Server
CoAP server would startup a daemon task, create resources and receive data from CoAP clients and transmit data to CoAP clients. This server follows adaptation of a couple examples:

https://github.com/espressif/ESP8266_RTOS_SDK/tree/master/examples/protocols/coap_server
https://github.com/obgm/libcoap-minimal/blob/master/server.cc
https://github.com/obgm/libcoap/blob/develop/examples/coap-server.c

The Constrained Application Protocol (CoAP) is a specialized web transfer protocol for use with constrained nodes and constrained networks in the Internet of Things.
The protocol is designed for machine-to-machine (M2M) applications such as smart energy and building automation.
Please refer to RFC7252 for more details.

Technical Challenges

ultrasonic sensors smoothing/filtering

Motor ECU

https://gitlab.com/tesla-model-rc/sjtwo-c/-/tree/dev/projects/motor_node

Hardware Design

Figure #. Motor Node

Software Design

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

Technical Challenges

< List of problems and their detailed resolutions>

Geographical ECU

https://gitlab.com/tesla-model-rc/sjtwo-c/-/tree/dev/projects/geo_node

Hardware Design

Figure #. Geo Node

Software Design

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

Technical Challenges

GPS (Ublox Neo-M8N)

• Problem:The enabled 2-stop bits in uart.c were causing communication problems between the SJTwo MCU and the Ublox M8N GPS module.
  • Solution:To solve the 2 stop bits configuration was disabled in uart.c in the uart__init() function as shown in figure # and issue was solved.

Figure #. 2-stop-bit configuration

• Problem:GPS module did not retain configurations and were lost after being powered off for many hours going back back to default settings. This problem was crucial since it was causing the SJ2 to parse the latitude and longitude incorrectly from other messages other than NMEA GNGGA.
  • Solution: To solve this configuration problem u-center which is an interface for the GPS Ublox module was used to read which strings the program sends over UART to configure the GPS module. This solution was implemented in the gps.c module creating a function called gps__private_configure_for_nmea_gngga() in which holds a char array with the hex representation of the configurations needed to disable all of the NMEA messages except GNGGA. This function then sends this configuration values back to the GPS module over UART and the GPS module responds back with an ACK message (8μ.......) from every configuration message meaning that the configurations were successfully applied as shown in figure #. The function gps__private_configure_for_nmea_gngga() could not be called in the periodic_callbacks__initialize() function has it required more time to properly configure the GPS. As a solution, a bool flag indicating that the configuration was done was used along with calling gps__private_configure_for_nmea_gngga() in the gps_run_once_10Hz() to allow it properly configure the GPS module.

Figure #. GPS Module NMEA Configuration

Compass (HMC5883L 3-Axis Magnetometer)

• Problem:SJTwo MCU could not detect the slave address of the HMC5883L magnetometer on the I2C Bus 2.
  • Solution:Upon reading the HMC5883L datasheet it was mentioned that it works at 400KHz. However, this was not the case as changing the speed in peripherals__init.c module from 400KHz to 100KHz solved the issue and the SJTwo board successfully detected the HMC5883L 3-Axis Magnetometer. In Figure # is shown the function a long with change it was made. In addition, changing the speed did not affect the other modules using I2C Bus 2.

Figure #. peripherals__init.c

• Problem:Compass heading degree true north was off by about 90 degree when compared to the compass of smart phone. This problem was due the fact the compass had to be completely flat to show proper values. In addition, the default calibration seemed also to be a problem in providing an accurate heading degree a long with hard iron and soft iron interferences.
  • Solution:To solve these problems a function to calibrate the compass was implemented in which calculates offset and scale correcting for hard iron and soft iron interferences respectively. The process to calibrate consisted in turning the compass at different angles to collect as many sample points as possible and store offsets values of x and y axes in const variables which were then used in the equations to compute the heading degree. Although this corrected some of the imprecision problems, not having the compass completely flat still provided results that were not precise. To solve this issue the compass was compensated for tilt by using the built-in accelerometer of the SJTwo board which provides roll and pitch and the tilt compensation algorithm described at this link. The challenge in making this work properly was that the axes of the magnetometer and the axes of the accelerometer need to be perfectly aligned. However, after finalizing the place of the compass on the RC car it was fairly easy to align the axes. The tilt compensation system for the compass is show in figure #.

Figure #. Tilt Compensated Compass System

• Problem:Compass heading degree was decreasing when turning clock-wise rather then increasing.
  • Solution:To solve this problem, the Azimuth rather then being calculated as atan2(Y / X) was calculated as atan2(X / Y). This fixed the Azimuth orientation however, North degree was shown as 180 degrees which was incorrect. Finally to compensate for this, π was subtracted from the Azimuth = atan2(X / Y) - π to show the correct decimal degree for true North which is 0 degrees.

Driver Controller & LCD

https://gitlab.com/tesla-model-rc/sjtwo-c/-/tree/dev/projects/driver_controller_node

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