F17: Alpha
Contents
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
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Objectives & Introduction
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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 |
|
Completed |
2 | 09/17/2017 | 10/03/2017 |
|
Completed |
3 | 10/04/2017 | 10/10/2017 |
|
Completed |
4 | 10/11/2017 | 10/17/2017 |
|
Completed |
5 | 10/18/2017 | 10/24/2017 |
|
Completed |
6 | 10/25/2017 | 10/31/2017 |
|
Completed |
7 | 11/01/2017 | 11/07/2017 |
|
Almost Done |
8 | 11/08/2017 | 11/14/2017 |
|
To Do |
9 | 11/15/2017 | 11/21/2017 |
|
To Do |
10 | 11/22/2017 | 11/29/2017 |
|
To Do |
11 | 11/30/2017 | 12/14/2017 |
|
To Do |
**************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 | ||||
6 | Charger for NiMH/NiCd Battery | ||||
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>
Hardware Interface
Pin connections for each sensor was 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 each of the sensors is detailed below.
<insert image of connections from each sensor pins to the board or a table with that info>
Software Design
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.
<snippet of CAN sensor message from DBC>
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.
File:/Users/sneha/Desktop/243 imp 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.
Geographical Controller
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Hardware Design
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Hardware Interface
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Software Design
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Implementation
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Testing & Technical Challenges
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<Bug/issue name>
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Conclusion
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Project Video
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Project Source Code
References
Acknowledgement
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References Used
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Appendix
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