Transcript VEX Grippers

VEX Grippers
(Devices that can attach to
objects)
J.M. Gabrielse
Outline
• Gripper Theory
– Control
– Speed
• Common Types of Grippers
–
–
–
–
Servo Grip
Motorized Grip
Pneumatic Grip
Roller Grip
• Challenge
• Hints
Vex Labs Gridiron Robot
– Use Lock Bars to attach devices to axles
– Use an Ultrasonic Ranger to find objects
J.M. Gabrielse
Control
• Holy grail of gripping:
– Get object fast
– Hang on
– Let go quickly
• This must be done under excellent control
– Limit switches
– Auto-functions
– Ease of operation
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Speed
• Quickness covers mistakes
– Quick to grab
– Drop & re-grab
• Fast
– Servo gripper
– Pneumatic gripper
• Not fast
– Roller gripper
– Motor gripper
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Servo Grip
• Precise
• Limited
range of
motion
• Limited
torque
Robert’s ARL robot in 2006
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Motorized Grip
• Can be
geared for
speed or
torque
• More
complex
FVC Team 31 in 2005
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Pneumatic Grip
• Powerful
• Reliable
• Requires
entire
(unreliable)
pneumatics
system
Some robot
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Roller Grip
• Slow
• Allows for
misalignment
when grabbing
• Won’t let go
• Extends object
as releasing
• Simple
mechanism
FVC Team 34 in 2005
J.M. Gabrielse
Vex Challenge #3:
Gripper
Due Date: Friday
Vex Inventor’s Guide: Vex Inventors Guide (3.3): Motors and Servomotors
EasyC for Vex Help: Search for “servo”
C Level Challenge (70 points):
 Build a robot that uses a servo to grab an empty soda can
o Drive up to the soda can and grab it
o Drag the soda can to a designated point
o Release the soda can and drive away.
 Make a design drawing of your gripper
Gripper
Challenge
B Level Hardware Challenge (85 points):
 Build a robot that uses a motorized grip to grab, drag, and release a full soda can
 Make a design drawing of your gripper
B Level Software Challenge (85 points):
 Build a robot that can complete the C Level Challenge autonomously
o You will be given the distance between the starting position and the soda can
o You will be given the distance you need to drag the soda can
o The robot must return to operator control after releasing the soda can and driving
away
A Level Hardware Challenge (100 points):
 Build a robot that uses a roller grip to grab a soda can.
 Make a design drawing of your gripper
A Level Software Challenge (100 points):
 Build a robot that can autonomously detect and collect a soda can
 The robot will be placed in the center of a 6’ x 6’ taped square
with a soda can
 The robot must find the soda can and bring it back to the center of
the square
Use lock-bars to attach metal pieces to axles
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Lock-Bars
• Axles fit through the square holes.
• Bolts fit through the round holes.
Lock-bars allow for any component to be attached to an
axle and rotated by a motor or servo.
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Ultrasonic Range Finder
• Detect the distance to the nearest object or wall
– Bounces sound waves off of objects and measures the time it takes
sound waves to return
– The time can be used to calculate distances from 3 cm to 3 m
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Thanks/Resources
• Designing Competitive Manipulators: The
Mechanics & Strategy
by Greg Needel (www.robogreg.com)
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