S15: Real Time Brake Assist (RTBA) - Revision history

Proj user10: /* Objectives & Introduction */

2015-05-25T05:03:45Z

‎Objectives & Introduction

Proj user10: /* Abstract */

2015-05-25T05:02:18Z

‎Abstract

Proj user10: /* Objectives & Introduction */

2015-05-25T04:49:28Z

‎Objectives & Introduction

Proj user10: /* Abstract */

2015-05-25T04:46:22Z

‎Abstract

Proj user10: /* Acknowledgement */

2015-05-25T04:35:27Z

‎Acknowledgement

Proj user10: /* Testing & Technical Challenges */

2015-05-25T04:30:57Z

‎Testing & Technical Challenges

Proj user10: /* Interface to Lidar Laser Distance Sensor */

2015-05-25T04:11:08Z

‎Interface to Lidar Laser Distance Sensor

Proj user10: /* Acknowledgement */

2015-05-25T03:56:56Z

‎Acknowledgement

Proj user10: /* Validation of CAN Interface */

2015-05-25T03:55:32Z

‎Validation of CAN Interface

Proj user10: /* 29 ID per J1939 Standard */

2015-05-25T03:50:36Z

‎29 ID per J1939 Standard

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 **Changed boring normal font to big digital font for better looking indicators.
 **7-Segment display on the SJ-One board shows the car's speed(mph) in real time.
 === Team Members & Responsibilities ===

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 == Abstract ==
-Real time brake assist is an automotive application that helps the driver avoid a front end collision by calculating the safe braking distance with respect to the car in the front. The system makes use of a LiDAR sensor for judging the car’s proximity to the car ahead of it and uses the diagnostic port (OBDII) to pull up the car’s current speed from the ECU. Based on the collected data, it calculates the safe braking distance and provides visual indicators to alert the driver. This system works between the speed range of 20 mph to 60 mph. Below 20 mph it acts as a proximity detector. It detects an obstacle up to 130 ft in the front. When the obstacle is out of range the proximity is zero. Also when there is an error reading over the LiDAR sensor, the proximity becomes maximum i.e. 255.
+Real time brake assist is an automotive application that helps the driver avoid a front end collision by calculating the safe braking distance with respect to the car in the front. The system makes use of a LiDAR sensor for judging the car’s proximity to the car ahead of it and uses the diagnostic port (OBDII) to pull up the car’s current speed from the ECU. Based on the collected data, it calculates the safe braking distance and provides visual indicators to alert the driver. This system works between the speed range of 20 mph to 60 mph. Below 20 mph it acts as a proximity detector. It detects an obstacle up to 130 ft in the front.
 == Objectives & Introduction ==

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 **PWM as well as I2C codes are both provided for Lidar.
 **Changed boring normal font to big digital font for better looking indicators.
 === Team Members & Responsibilities ===

@@ Line 3: / Line 3: @@
 == Abstract ==
-Real time brake assist is an automotive application that helps the driver avoid a front end collision by calculating the safe braking distance with respect to the car in the front. The system makes use of a LiDAR sensor for judging the car’s proximity to the car ahead of it and uses the diagnostic port (OBDII) to pull up the car’s current speed from the ECU. Based on the collected data, it calculates the safe braking distance and provides visual indicators to alert the driver.
+Real time brake assist is an automotive application that helps the driver avoid a front end collision by calculating the safe braking distance with respect to the car in the front. The system makes use of a LiDAR sensor for judging the car’s proximity to the car ahead of it and uses the diagnostic port (OBDII) to pull up the car’s current speed from the ECU. Based on the collected data, it calculates the safe braking distance and provides visual indicators to alert the driver. This system works between the speed range of 20 mph to 60 mph. Below 20 mph it acts as a proximity detector. It detects an obstacle up to 130 ft in the front. When the obstacle is out of range the proximity is zero. Also when there is an error reading over the LiDAR sensor, the proximity becomes maximum i.e. 255.
 == Objectives & Introduction ==

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 === Acknowledgement ===
-We would like to acknowledge Preet Kang for providing us the base knowledge and the tools like the Hyperload and APIs that allowed us to complete the project in a short time.
+We would like to thank Preet Kang for his constant support and encouragement and for providing us the required knowledge and tools like  Hyperload and APIs that allowed us to complete the project in a short time.
 === References Used ===

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 There were several technical challenges in this project. One of the objectives was to use one SJ-One boards to be more like a real system where there is one processor. This offered the challenge of how to communicate to the laser sensor since it had to be mounted at the front of the car. We opted for using a differential buffer to drive 14ft of cable. A low cost wireless controller with an I2C interface to the laser sensor would be the right way to go to market this product, but this would take some time to develop.
-The biggest challenge in the Real Time Break assist project was establishing communication with the car through the CAN interface. First we had to determine if the communication to the test car was at 250 or 500Kbps and then use an external crystal which is required when using the SJ-One board's CAN controller at higher than 100Kbps. Proper communication with the car requires determining the right source and destination address to request information like vehicle speed from the car.  Having access to the SAE J1939 standard in very important but may be costly. Another option is to learn the communication with the car by examining what a car OBDII reader is doing. This is the path that we chose.
+The biggest challenge in the Real Time Brake Assist project was establishing communication with the car through the CAN interface. First we had to determine if the communication to the test car was at 250 or 500Kbps and then use an external crystal which is required when using the SJ-One board's CAN controller at higher than 100Kbps. Proper communication with the car requires determining the right source and destination address to request information like vehicle speed from the car.  Having access to the SAE J1939 standard in very important but may be costly. Another option is to learn the communication with the car by examining what a car OBDII reader is doing. This is the option we chose.
 == Issues Found ==

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 The Lidar laser distance sensor requires 5V and I2C interface operating at a maximum rate of 100Kbps for communication. To provide a reliable and low cost communication to the sensor, a PCA9615 differential driver was chosen. The PCA9615 provides the noise immunity and capability to drive long cables necessary for this application. For cable connectivity, a standard CAT5 RJ45 cable was used because of its low cost and twisted pair connectivity for differential signals.
 The diagram below shows the connectivity of the differential pairs. In order to provide the maximum differential swing, VDDB1 and VDDB2 should be connected to 5V and use 120ohms for R1 and 60 ohms for R2. VDDA1 and VDDA2 should be pulled up to 3.3V as required by the I2C interface. The PCA9615 provides separate voltage pins for the I2C interface which should be 3.3V and for the differential signaling it should be 5V.
-The Lidar laser sensor used in this project is capable of measuring distances of 100ft which makes it suitable for this project.
+The Lidar laser sensor used in this project is capable of measuring distances of 130ft which makes it suitable for this project.

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 == Validation of CAN Interface ==
-The CAN interface was first validated by using a CAN analyzer from Microchip to ensure data requests for information on the coolant temperature as well are responses to the PID for coolant temperature (0x05). The picture below shows two nodes responding to the request.
+The CAN interface was first validated by using a CAN analyzer from Microchip. Both data requests for information on the coolant temperature as well as responses to the PID for coolant temperature (0x05) were verified. The analyzer proved to be a useful tool also to ensure an error free bus. The picture below shows two nodes responding to the request for coolant temperature.
 [[File:S15 244 Grp9 coolant data.jpg]]

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 == 29 ID per J1939 Standard ==
-For vehicles, a higher layer protocol resides above the CAN frames and it is specified in the SAE J1939 standards. To send and receive messages, the extended 29 bit identifier must be used. The format of the 29 bit identifier is shown in the picture below.
+For vehicles, a higher layer protocol resides above the CAN frames and it is specified in the SAE J1939 standards. To send and receive messages, the extended 29 bit identifier must be used. The format of the 29 bit identifier used in vehicles is shown in the picture below.
 [[File:S15 244 Grp9 29bitframe.jpg]]