Technical Specs
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Transcript of Technical Specs
panteras.up.edu.mx
FIRST ROBOTICS COMPETITION 2010
ATLANTA WORLD CHAMPIONSHIP
FRC Team 2283
Panteras ROBOT TECHNICAL SPECS
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Panteras FRC Team 2283
Team Strenghts
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
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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-the-
shelf 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.
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, fast-
acting trigger mechanism for releasing the Kicker Spool.
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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
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:
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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°
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 Finite Element Analysis for the kicker
Impact Force: 10.12N
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:
σy=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
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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:
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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