1. VEX U Robotics Competition
MAE: Richard Stinson, Andrew Dearhart, Michael Darnell, Darryl Sampson, Allan Cahill, Timothy Clarke ECE: Daquan Styles, Alfredo Delos Santos, Matthew Staley
Advisors: Dr. Chung-Hao Chen & Dr. Gene Hou
Abstract
Purdue University Qualifier Robots
Software Summary
Realistic Constraints
Goal: The goal of this project is to design and build two robots intended to compete in the VEX Robotics “Nothing But Net” challenge.
Mission Statement: The VEX robotics organization works to educate and further the development of robotics at the college level. The objective of this project is to experimentally develop two robots for use in the 2015/2016 VEX U Nothing but Net tournament. These robots were created through holding design meetings, prototyping, coding, and testing. Through a semester of testing and coding, 3 final robots were built to compete and represent ODU in the Worlds competition.
The First Generation Robots
The first robots were built with the mindset of integrating all the systems that had been tested and proven as the most promising.
The large robot was made able to score high goal points from across the field with a powerful, four motor, double flywheel launcher that was able to fire balls at a speed of approximately 29.5 mph and a rate of about one ball every 2 seconds.
The small robot was built with the primary goal of being quick and agile and able to make high goal shots from around mid-field.
This was done by utilizing a single horizontally mounted flywheel that had a back plate to aim and compress the game pieces.
Technical:
All parts used for the construction of the robots had to be VEX official parts, or those of equivalent properties with the exception of sensors and 3D printed parts, though the 3D printed parts had to each be no larger than 3”x6”x6”. Some parts bought through VEX had inconsistencies upon arrival, with the biggest problem being the power/speed of motors. Motors that were going to be set up in sync with each other had to have their rpms tested and documented so as to mount motors that had either the same or similar rates.
Availability:
Each member on the team was an undergraduate degree seeking student, and most also had part times jobs. This limited the amount of times when the team could all meet together, but was a minor issues once plans had been drawn, as each member would work whenever they had the ability.
Communication/ Knowledge:
There was a rather large language gap between the mechanical and electrical engineers on the team whenever one would try to explain or trouble shoot for the other. It was not due to each side not speaking a common language, but rather to each side speaking their own jargon which was not easily recognized by the other. This issue was overcome through patience, consistency, and an initiative on both parts of the team to learn and understand the other. There were several occasions where the mechanicals would explain and teach certain principles and equations to the electrical and the electricals would explain some of the sensors and coding to the mechanicals.
The software functionality of our robots can be split into two separate function: driver controlled and autonomous control. From there the code was split into various subsections that make up the robots movement and object launching system. For driver position control, we used simple joystick mapping directly to the wheels. The joystick is analog based and therefore supports proportional output, giving us control over both the speed and direction of the system. The left stick is in control of the two axis movement throughout the field, while the right stick controls positive or negative rotation. To intake and launch game objects, we used the left side triggers to control the direction and operation of the intake, where the upper trigger feeds balls towards the launcher and the lower trigger pushes those outwards. Autonomous control utilizes an employed field centric perspective rather than a more common robot centric view. Rather than have the robot search for game objects relative to itself, the static field objectives were inserted onto a virtual game field that the robot moves around. We essentially send the signal to the robot telling it to move to a specific (x y) coordinate on our virtual field. The autonomous procedure tracks the position of the robot on the virtual field in terms of tiles. The game field is six tiles wide and six tiles long. Since balls aren’t positioned directly centered on tiles, half tiles are also supported. Motor encoders ended up being the ideal method for tracking movement, as accelerometers and gyroscopes were either too inaccurate or experienced significant drift over the course of the match. Using the physical characteristics of the wheel, we were able to determine the exact number of encoder ticks required to travel a single tile in any direction, as well as 90 degree rotation.
Project Objectives
The main goal for this project is to help build two functional robots for the 2016 VEX U “Nothing But Net” Competition. One small robot must be able to fit inside a 15” x 15” x 15” cube and a larger robot must be able to fit inside a 24” x 24” x 24”. These two robots must be able to operate autonomously for 45 seconds and via remote control for the driver period of the game totaling 75 seconds. The objective of the game is to outscore the opposing team by shooting green polyurethane foam balls into a high and low elevation triangular net. The nets are 3 feet 10 inches tall in the back of the net and 3 feet tall in the front of the net.
Competition Results
CSM Skills Challenge Robots
The competition was an overall success, despite many speedbumps along the road. The first part of the competition was to determine each University’s seeding for the elimination round. We encountered several game-changing events during this round. Our first unfortunate event was during our second round. Our strategy for the small robot was to stop the flywheel, intake 4 balls, start the flywheel, and then shoot the balls. Our driver managed to lock up the flywheel, effectively disabling the small robot for the majority of the round. After failing multiple times trying this we decided to change our strategy and make the small robot continuously spin its flywheel. From this point on the competition went fairly smoothly, except for one crucial referential call.
During round 7 we faced an opponent that we knew would utilize their lift during the last 30 seconds of the match. We decided to try and stop this lift, effectively stopping them from gaining 50 points. We succeeded in this but during our defense, the opponent pushed us into the restricted zone. The game coordinator saw this and said that it was alright because we were pushed. The referees did not see the push however and disqualified us for that match. Because of this, we were seeded 4th instead of 3rd. This had a ripple effect and eventually stopped us from obtaining the excellence award. Overall, we finished 3rd place in the competition, instead of 2nd.
The second part of this competition is the Program skills challenge. This is where we found redemption. We managed to earn a score that secured us 2nd place rank in the world for Programming skills. However, we were not satisfied. We returned home and worked on our robots for the next 2 weeks and attended CSM’s program skills challenge. During that time we managed to secure the first place in the world for program skills. This meant that we would be invited to the World Championship competition in Kentucky, 5 weeks from the CSM competition. This was a great success for us. Shown below is a picture of our competition trophy.
Mid-Season Robots
After attending the first competition at Purdue University, the build focus changed from standard competition to achieving the top world score in the autonomous skills challenge.
A small robot was built using a logarithmic spiral cam linear puncher with the ability to fire all 64 driver loaded game pieces into the high goals accurately, and be able to drive across the field for loading on both sides within 60 seconds
Large robot was built mostly the same as before, and made to score additional points with the small bot.
The primary challenge with the small robot was balancing the launching force with weight to keep the robot from skipping.
Engineering Standards
Throughout our senior design project we only had to adhere to two of IEEE’s engineering standards. These two standards are for working on any robotics or automation system.
IEEE Standard Ontologies for Robotics and Automation
Specifies the main, most general concepts, relations, and axioms of robotics and automation. This standard is intended as a reference for knowledge representation and reasoning in robots, as well as a formal reference vocabulary.
IEEE Standard for Robot Map Data Representation for Navigation
This standard is used to make sure a map data representation of environments of a mobile robot performing a navigation task is specified. With this standard, you must map out and document the navigational method that a robot moves in.
Design Ideas/Methodology
Methodology: Many ideas were discussed in the beginning, ranging from flywheel launchers to x-drive chassis that used Omni-directional wheels. To evaluate the early ideas, the team used rapid prototyping to learn and gauge the early ideas. After time had been spent evaluating the prototypes, the first robots were built with the systems that provided the best results. After attending competitions, the team then used what they learned from their performances, as well as what they had learned from watching other teams to develop and build new robots.
Design ideas: Design ideas that were discussed and experimented with include:
(MAE)
Dual vertical flywheel launcher
Single horizontal flywheel launcher,
Slip gear linear punchers
Logarithmic cam linear puncher
Scissor lift
X-Drive Chassis
(ECE)
Programmatic coordinate position system
PID control
An automated turret through the usage of a gyroscope
Accelerometer
Array of sensors (Line tracker, Ultrasonic Range Finders, Color sensors)
Analysis, Testing, Results, and Discussion
Conclusion
During the design and test phase of building our robots, the electrical design team decided to conduct tests using a gyroscope sensor in hopes of being able to make a turret like object shooter for our robots. After conducting multiple tests with the gyroscope, we initially had issues dealing with gyroscope drift that can be noted in our tables. Eventually we were able to overcome the issues of drift and minimized drift issues from a degree difference to only a 1-2 degree difference. Unfortunately, we decided to scrap the idea of using a gyroscope sensor completely due to its unpredictable nature when interacting with other electronics on the robot.
In conclusion, our project has been largely a success in terms of both a display of our technical abilities and our ability to cooperate with others. Over the course of the past two semesters, we have worked to design, implement, and test multiple robots and their associated control systems. These robots competed and had great success in multiple competitions, and we hope to continue our success at the World Championship competition in Kentucky.
World Championships Robots
Robots Built for Worlds
It was decided to bring a total of three robots to allow for maximum competitiveness.
Two robots were built for the standard head to head competition.
The competition robots were built to be more flexible while still maintaining a high capability and speed.
The small robot was built modular, quick, and efficient on space. It consisted of a single horizontal flywheel and a rubber band intake system.
The third robot was the cam launching robot, used in the earlier skills challenge.
The large robot was designed primarily by electrical engineers and optimized my mechanical engineers.
Robot is made to be easy to program, simple to design, and able to easily shoot across the game field with no problems.
This robot consisted of a low mounted fly wheel at 45 degrees relative towards the net, a spinning intake made of surgical tubing, and a lift mounted at 19 degrees from the ground for the small bot to drive up 15 inches for an extra 50 bonus points
Another test we ran to improve the completive efficiency of our robots was a battery vs. performance test used to determine the optimal voltage needed to power our batteries with enough to voltage to run all motors and electronics at max power throughout a match. Below is a table of the data. We concluded that we need to maintain our batteries between 7.5-8V in order to have the best performance when competing.