FRC Team 2283
Panteras ROBOT TECHNICAL SPECS
FIRST ROBOTICS COMPETITION 2010 ATLANTA WORLD CHAMPIONSHIP
panteras.up.edu.mx
Panteras FRC Team 2283
Team Strenghts
Panteras FRC Team 2283 | 1
Team 2238´s Robot is an ideal team player for defensive play and long-distance offensive action. Positioned in the back or middle fields it is an ideal complement for teams with fast forward-action robots, thanks to these unique capabilities:
1.- Enemy ball starving and defensive play: With its ability of strafing and rotating independently, our robot can quickly reach the balls and automatically position itself to safely kick them forward toward the Goal, without the need for much maneuvering. This keeps the enemy’s forward area empty of balls and makes it difficult for them to score goals
2.- Quick action Kick. With its optical ball sensor, the complexity of judging the ideal robot position to prepare a shot is eliminated. The operator only has to reach the ball and the optical sensor will make sure the kicker fires when the robot is ideally positioned.
3.- Persistent goal tracking With its combination of camera tracking and gyroscope stabilization, the software in the robot keeps it persistently aligned to the Goal, minimizing the need for operator aiming. The operator can concentrate on “reaching� the balls, knowing that when the robot gets there, it will already be properly oriented towards the goal.
4.- Powerful, variable force striker. The kicker is automatically controlled by the calculated distance to the goal, with a PID (Advanced control) system that continuously and automatically adjusts the force of the kick to prevent balls from being sent out of bounds , while still having the force to kick balls from the rear of the play area to the goals.
5.- Advanced autonomous logic. The robot can kick up to three balls from the back area into the goal, with significant probability of scoring, by using predefined paths, keeping the robot aligned to the goal with the camera and gyroscope, and automating the kick thru optical ball sensing. After the end of the autonomous period, the enemy team will find less balls in their forward area, and there is a good chance of scoring some points in the opening moves.
6.- Team mindset. Our robot controllers and coaches understand and internalize the need for team playing. We try hard to understand our teammates and our adversaries’ strengths and weaknesses and adjust our play strategy to maximize the team score
TECHNICAL FEATURES
We are very proud of the advanced technical design incorporated into our robot. Considering that our team has much less time to prepare the robot than other teams, due to the shipping, Customs, and freight forwarding issues involved in sending equipment to Mexico, our robot had to be built using simple components and off-theshelf parts. Unfortunately, our school does not possess any significant manufacturing capabilities, so we had to compensate this limitation by the use of ingenuity, hard manual labor and smart integration and software design. We are forced to work harder and smarter.
1.- Holonomic Drive. By Using 4 Mecanum Wheels, the robot has extraordinary agility, being capable of driving, strafing and rotation, independently of each other. This allows the robot to position itself for forward kicking while it reaches the balls.
While Mecanum wheels do not provide for the fastest forward motion possible, the agility they bring into play can be used by a good driver to take defensive action and escape pinning.
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2.- Smart and efficient goal . The software uses a very effective combination of camera tracking and gyroscopic sensing to maintain the robot aligned towards the goal while minimizing the computer power needed.
The camera operates at a low update rate, a few cycles per second, to find the goals in relationship to the “front� of the robot. The software then uses a high update rate from the gyroscope, and a PID (Proportional Integral Derivative) Control system to orient and keep track of the needed position.
The Camara also provide Azimuth (Height angle) measurement to the goal, which can be used to compute an estimated distance, and this is used to adjust the needed kicking force.
3.-
High-Power,PID-Controlled
variable
force
kicker.
We designed and built a high power, high reload rate Kicker, based on the principle of stored energy. Our storage components are two high-K bedsprings which are stretched by a CIM motor through a spool-and-cable mechanism.
The variable force is achieved by using variable stretching of the springs. The actual kicker position is measured thru the use of a Magnetic rotation sensor, attached to the axis of the Kicker, and this provides information for a PID controller that automatically determines the force applied to the spool motor.
4.- High-speed -self cocking trigger. By programming in LabView a State Machine based on two switches, a spool actuator and hysteresis built in by the use of a spring, we created a reliable, fastacting trigger mechanism for releasing the Kicker Spool.
Curiously, this component took the longest to design and implement , since response times under 100 milliseconds were needed , and the force needed to trigger the spool release was found to be quite significative.
Many designs were analyzed, some were built and finally we settled into the current design, which has proved very reliable and fast-acting
5.- OPTICAL BALL SENSING
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Very early into the design phase, we realized that one of the difficulties in controlling the robot would be the need to properly position the robot before the Kicker is activated. Too Soon and the ball is not yet into position. Too late and the ball will bounce off the robot before the Kicker activates. This would cause the driver to do trial and error, and “guess� the relative positions of the robot and the balls. Also, programming the autonomous would have been much more difficult.
By using an infrared LED and a phototransistor in the front of the robot, the software can detect the presence of the ball and activate the kicker at the right time, whether in the autonomous or teleoperated modes.
6.- Smart Autnonomus Programming By using state-machine diagrams, different scenarios for the autonomous actions can be programmed into the robot.
By having access to the Goal-aligning routines, distance estimation, variable kickforce and optical ball-sensing, it is not difficult to build auntonomous routines that move the robot in a specified path, keeping track of the goal and kicking balls as the robot finds them. Ideally the robot should be put in midfield or backfield to maximize the advantage of these capabilities.
MECHANICAL DESIGN CONSIDERATIONS: MECANUM WHEELS
MECHANICAL DESIGN CONSIDERATIONS: KICKER Computations for Force necessary to kick the ball 50ft Rotation center for the desired ball contact (Using SolidWorks)
The rotation center is geometrically determined with the following considerations:
The initial position for the ball is 3in inside the robot frame The final position of the ball is 3in outside of the robot frame The angle of the force transmitted from the kicker to the ball at the end of the movement is 30°
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The rotation center is shown in the figure below with the distances in [mm] and with a corner of the robot frame as the reference.
Coefficient of restitution = 0.45 Impact Force: 10.12N
Finite Element Analysis for the kicker
Kinetic Energy: K.E.=45.57 J
Impact force with the mechanical break of the kicker: Mass (kicker): m= 2kg Speed (after impacting the ball): Kinetic Energy: K.E.=78.5 J Coefficient of restitution: 0.03 Impact Force: 2613.33N CAD of the kicker in ANSYS
Impact force with the ball:
Mass (ball): m= .5kg Speed:
Although the kicker is made mostly from aluminum, the shaft that allows for the rotation of the mechanism is made from steel and it is welded to a couple of steel plates screwed to the rest of the kicker. The Yield Stress for the steel used is: ﾏペ=64976psi But the welding effects on the yield stress have not been considered.
The maximum value of the equivalent stress is 76194psi, but it only occurs in a very small volume (0.002 in2) and can be neglected if
we are not considering failure due to fatigue.
Simulation using WorkingModel WorkingModel is a software for the simulation of multi-body systems. It supports the use of springs, rigid bodies and friction losses. We were able to simulate a simplified model of our kicker that is shown in the following figure:
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The figure below shows the simulation with the value for the spring constant “K� that was previously calculated. With the consideration of the friction losses, the spring strength calculated is not enough to kick the ball as far as desired.
Electronics Circuit Design
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