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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