We collaborated with Team 6 and formed Team 5.5. We designed a two-car project which includes a lead car and a follower car. You can find information about follower car in our team's page. More information about the lead car please refer to Team 6's page.
Our car is named BumbleBee. and the Team 6 car is named AutoPrime.
Team 5 Members
Zeyu Huang-Aerospace Engineering
Jason Almeda-Computer Engineering
Team 6 Members
Liam Fowler, Mechanical Engineering
Johannes Diehm, UCSD Extension
Camera and Lidar Mount: The camera and lidar mount is consist of three components, base, link, and brace. The linkage design allows the camera to freely adjust its amgle and height in order to find the best view for training, calibration, and driving.
Electronics Mounting Plate: The electronics are mount on this electronics plate which has trough to accomodate M4 screws. The distance between the center of two troughs is 12mm, and the trough allows us to easily adjust the positions of electronics.
Jetson Case: The jetson case is consist of a top case and a bottom case
Autonomous Laps Demonstration
Our goal was to develop a system of nodes in ROS to enable vehicle to vehicle communication between 2 cars. We took inspiration for our project from the "Black Ice" phenomenon, whereby cars in icy conditions slide out and crash due to difficult-to-see ice on the road. By allowing cars to communicate with one another, a car involved in a crash could tell other cars that there is an issue on the road ahead, allowing the cars to slow down or stop to avoid the road hazard.
Our project consists of two cars: the lead car and the follower car. If the lead car should crash, it shall publish a message to the follower car, which causes it to stop, thus preventing that the follower car from crashing into the same obstacle. For sensing the crash, we use the accelerometer sensor on an Openlog Artemis IMU in the lead car, which we initialized by adding the device when creating the Docker Container with the robot image. If a specific deceleration threshold is met (i.e. 10 milli g), the car publishes a message to a connected following car. If the follower car receives this specific message, it should cause an immediate stop.
In order to prevent hackers from slowing down or stopping the follower car without a road hazard being present, we also include a unique security string published by the lead car and subscribed to by the follower car. If the security string being sent to the follower car before a stop command does not match the expected security string stored on the follower car, then the follower car will not accept a message to stop, and will continue to move around the track.
In our case, we set the lead car to be the "Master" roscore, to which we connected the follower car (so that both cars use the same roscore). Both cars run many of the same nodes, clients, and servers as described in Dominic Nightingale's Simple ROS framework. However, in order to ensure the topics being published and subscribed do not cross cars (i.e. camera on one car is used by the lane guidance on the other car), we gave the each topic with the potential to cross over a new unique identifier.
Our car Bunblebee is the follower car implemented with listener node, by writing a listener node script and building a lisner node launch file. We also modified the ros racer launch file correspondingly to launch the listner node.
The listener node will first need to receive security message 'I am Autonomous Prime, Autobots, roll out!' from the lead car Autonomous Prime in order to process any further commands. After confirming the message is sent from Autonomous Prime, the listener node will pass the stop message to lane guidance node when the it receives the 'stop' command. The lane guidance node will then overwrite the throttle and the steering of the Bumblebee to zero and stops the driving.
All the innate node names and topic names are changed differently from Autonomous Prime in order to prevent overwriting information, including /camera_rgb, /centroid, /steering, /throttle.
Project Gantt Chart
On the lead car Autonomous Prime, we set up the talker node python file and its corresponding ROS launch file from scratch. We were able to read data from the IMU and filter the data we wanted to read from a certain axis. We achieved this by directly reading from serial ports with pySerial package, parsing the string we read from the serial, and converting them to numbers.
On the follower car Bumblebee, we have programmed a “listener_node“ and its corresponding launch file for reading the values and calling a newly developed function in the lane_guidance_node for stopping the car.
We have also been able to connect our follower car to the network and read the published values from the lead car. We are confident that this method is fully functioning. We have also implemented a security mechanism for the communication. In the listener node, we have specified that the "Stop" method is only getting called if a specific String is attached to the published message. We are able to publish and receive this message. Unfortunately, we have not been able to test our system and get rid of the last bugs.
We are confident that our mechanism of stopping the follower car after a crash of the lead car is in principle functioning, but in the end, even though we have worked all night, we haven't had enough time to finish our project. In the end, we have had an issue with messed up file names that stopped the follower car from working. We found out too late that the nodes are not allowed to have the same names on the lead and the follower car. If we had just a little more time, we could have better checked all of our nodes and topics and renamed them. Because of that, we weren't able to test the system, but think that it was essentially working based on a brief test in which it appeared that the ESC switched from forward throttle (i.e. no_error_throttle) to zero throttle. At that point however, we had run out of battery and it was too late to fully verify whether that was truly because our system worked in its entirety.
Instructor - Prof. Jack Silberman
TA - Dominic Nightingale
TA - Haoru Xue
Resources Used for Final Project
Jetson Nano Case (case used slightly modified from this one)
And countless Google queries for debugging...