VEX Grippers Devices that can attach to objects

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 J. M. Gabrielse

Speed • Quickness covers mistakes – Quick to grab – Drop & re-grab • Fast – Servo gripper – Pneumatic gripper • Not fast – Roller gripper – Motor gripper J. M. Gabrielse

Servo Grip • Precise • Limited range of motion • Limited torque Robert’s ARL robot in 2006 J. M. Gabrielse

Motorized Grip • Can be geared for speed or torque • More complex FVC Team 31 in 2005 J. M. Gabrielse

Pneumatic Grip • Powerful • Reliable • Requires entire (unreliable) pneumatics system Some robot J. M. Gabrielse

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

Gripper Challenge J. M. Gabrielse

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. J. M. Gabrielse

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 J. M. Gabrielse

Thanks/Resources • Designing Competitive Manipulators: The Mechanics & Strategy by Greg Needel (www. robogreg. com) J. M. Gabrielse