Slide 1

FTC Mechanical design considerations 2012 edition by: Andrew Rudolph Slide 2 What were going to talk about the rulesmanipulatorsideas Slide 3 2012-2013 rules Youve already read them right? Slide 4 rules Only can use preformed robotics components from: Lego Tetrix Matrix Slide 5 matrix Observed at World Cmp Designed to bring costs down of FTC overseas Designed off standard lego grid Different motors Different motor controllers Different Gears and wheels Possibly thinner metal Belt system CV Axles Check some of the offerings at: http://matrixrobotics.com Slide 6 matrix http://www.chiefdelphi.com/forum s/showthread.php?t=106017 Slide 7 rules Only COTS (Custom Off The Shelf) items allowed: Linear Slide Non-motorized Turntables and Lazy Susan Lead screws and threaded rod plus compatible nuts Servo Blocks #25 Chain and connector or half links Slide 8 rules Unlimited in quantity or size of the following: Raw material available to all teams from standard distributors Standard bearings or bushings Fasteners Rope, Cord, Cable, monofilament, Rubber bands Latex tubing Zip ties Nonslip pad without adhesive backing Electrical solder, tape and any type of glue/cement Any COTS lubricant as long as it doesnt get on stuff Slide 9 materials Extrusions Readily available from many retailers Cut and drill with simple tools Strong and lightweight Most commonly 6061 Aluminum 7075 Aluminum for higher strength www.onlinemetals.com www.8020.net Slide 10 materials Sheet metal Readily available from many retailers Cut and drill with simple tools Or Water Jet, Laser Cut, CNC Break for complex parts Slide 11 materials Plastics Lexan (NOT ACRYLIC) easy to find and work with Bend with heat Lots of shapes and different mechanical characteristics available Polycarbonate (lexan) Coroplast Sintra Teflon Nylon Delrin HDPE Slide 12 materials Plastics You can now Rapid Prototype Parts! You can now 3D print Parts! ABS Polycarbonate PLA Slide 13 materials Rope, cord, etc Steel wire rope Solid steel wire Paracord Braided fishing line 150 lb test = 0.56mm diameter Slide 14 Shoulder Bolts materials drive components Bushing 6338K3116338K311 @ McMaster for $0.75 ea! Drill rod (tool steel rod) 88725K3388725K33 @ McMaster for $2.68 for 3 Lead screw or Acme screw Linear Bearing Lubricants Slide 15 Lifts! You mastered these last yearright? Slide 16 lifts We saw them last year Slide 17 lifts What did we miss last year? Precision liftingVariable position liftingLifts go upLifts go down Slide 18 lifts Scissor lift Short height, Wide base Lift over base Requires lots of power Lots of moving parts Difficult to synchronize two sides Difficult to lift from ground Difficult too have finite control Poor lateral loading Slide 19 lifts FRC 343 circa 2000 Lead screw or Acme screw Slide 20 lifts Single joint arm Simple to build Can move fast Can reach fore and aft Light weight Object orientation changes Strong Lateral load Lift outside base Object orientation changes Difficult to multi position Do not lift high Slide 21 lifts multi joint arm Lots of freedom keep lift inside or outside of base complex to build heavy Lots of motors Difficult to control Slide 22 lifts Four bar linkage Simple to build Light weight Object orientation stays the same Lift outside base Lots of torque required at shoulder Slide 23 lifts six bar linkage twice the weight of four bar Object stays the same Higher lift than four bar Lift outside base Lots of torque required at shoulder More joints to create friction and wobbles Slide 24 lifts Telescoping Straight lift multiple positions small footprint COMPLEX difficult to maintain high CG Slide 25 lifts hybrid Combine multiple mechanisms Slide 26 Ideas General design practices Slide 27 ideas Are you going to acquire it? manipulate it? store it? lift it? position it? release it? What tasks within my strategy do I need to perform? Let strategy drive your robot design, not the opposite Slide 28 ideas What does the game piece look like from the robots POV? What are all the ways the game piece could lay? What is the most usable or stable position? How does the object react? Think like a robot about the game piece Slide 29 ideas Maximize your Acquisition Zone other design considerations Slide 30 ideas other design considerations Alignment Devices Slide 31 ideas other design considerations Make it easy to drive Slide 32 ideas other design considerations Will stray objects interfere? Slide 33 ideas other design considerations Keep your Center of Gravity (CG) low Slide 34 ideas other design considerations Design is an iterative process Slide 35 Just the parts you want to work. ideas Really, simple IS better. Some design mantras You dont have to prototype everything Assume nothing. Sometimes wild ideas lead to champions. Slide 36 Slide 37 Celebrity Endorsed.