Introductory Curriculum

Transcription

1 Introductory Curriculum v

2 Introductory Curriculum TABLE OF CONTENTS Activity #1 ED the Robot Activity #2 Belt Drives Activity #3 Gearing Down Activity #4 Gears, Belts, and Pawls 11 Activity #5 Robot Toy Activity #6 Extendo Robot Arm. 19 Activity #7 End Effector Activity #8 Wheeled Robotic Vehicle 28 Activity #9 Programming Motors 32 Activity #10 Programming Motors 36 Activity #11 Robot Linkages Activity #12 Houdini Robot Appendix

3 BACKGROUND: SCHEDULE 1. Review class objectives. 2. Presentation of background material. 3. Students pairs will check out kits. 4. Students will construct the "Belts, Gears, and Pawls," model. 5. Students will brainstorm how their models could be integrated into a robotic device. 6. Students will deconstruct their model and return parts to the kit. 7. Collect kits. 8. Ask students to identify machines that use belts, gears, and pulleys. Belt drives use pulleys and belts to transfer power. Gear trains use gear pairs to transfer power. Both belt-pulley and gear systems can be arranged to produce either additional torque or speed in an output. Speed refers to the rate at which the output is turning. Torque is the force of rotary motion. Some robotic devices need a lot of torque, while others require speed to accomplish a particular task. Both belt drive and gear train systems can be used to power robotic devices! Gear reduction occurs when the ratio between the input into a machine is different than the output. For example, if the input gear has fewer teeth than the output gear, the input must turn more in order to turn the output gear once. A 10-toothed spur gear must turn twice to turn a 20- toothed spur gear once. In this model, a one-toothed worm gear turns a 20 toothed spur gear. This means the worm must turn 20 times in order to turn the spur gear once, resulting in increased torque. This is an example of a power ratio, where the speed of the output gear's rotary motion is reduced and its torque is amplified. In this model, the large pulley drives a Clip 5 (acting as a small pulley). The Clip 5 will turn many times for every turn of the large pulley. This is an example of a speed ratio, where the torque of of an output is reduced, but the speed is amplified. This model uses several gear combinations combined with a belt drive and a pawl. A pawl is a hinged catch that fits into a notch of a ratchet to prevent it from moving in a particular direction (or to move a wheel forward). Robotic devices often combine different mechanisms and systems together in their design. This model can serve as a guide for integrating several basic assemblies together in one design. OPTIONAL CHALLENGE ACTIVITY: Should students finish early, challenge them to design and construct an original gear and pulley system for a robotic device. 11

4 Make sure you have: Build Building Plate 15x30x5 with 3 Grooves 1 - Locking Worm m= Clip Building Block Bearing Sleeve 5 - Building Block This project experiments with several combinations of gears and pulleys that can serve as a model for different robots. All robots need some sort of power system. Knowing how to integrate different systems together is invaluable information to robotic design. 2. Start by sliding a Building Block 15 into the seventh and fifteenth slots of a Base Plate 120x60. Add a Building Block 15 with Bore on top of each block, with the axle holes lined up. 2 - Cog Wheel T 10 Narrow 3 - Building Block Clip Axle Base Plate 120x Clip Axle Clip Axle Clip Axle Clip Axle Clip Adapter 9 - Building Block 15 with Bore 1 - Crank Shaft 3 - Hub Nut 1 - Hub Nut (Worm) 3. Insert a Clip Axle 90 through the two axle holes. As the axle is sliding through the holes, add a Hub Nut Worm and the Locking Worm between the posts and pressed against the nearest post. Add a Cog Wheel T 10 on the near extended axle end. 4. Build two posts consisting of a Building Block 30, Building Block 5, and a Building Block 15 with Bore. Slide the posts into the twelfth slot on each side of the Base Plate, being sure that the axle holes line up. 3 - Link Flat Hub Collet 1 - Belt 1 - Large Pulley Rack 60 m= Gear Wheel T20 Name: Date: 12

5 5. Insert a Clip Axle 75 through the two axle holes. As the axle is sliding through the holes, add a Flat Hub Collet, Gear Wheel T20, and a Hub Nut onto the axle. Fix the gear so that it meshes with the worm gear. Push the axle so it doesn t stick out on the far side. 6. Add a Flat Hub Collet, a Large Pulley 60 and a Hub Nut onto the extended end of the Clip Axle 75. Fix the pulley in place. 7. Create a post consisting of a Building Block 30, Building Block 5, and a Building Block 15 with Bore. Slide the post into the fourth slot of the base plate. 8. Insert a Clip Axle 60 into the Building Block 15 with Bore. Fix the axle in place with two Clip 5s. On the near extended end, fix a Hub Nut, Gear Wheel T20, and a Flat Hub Collet onto the axle. 9. Connect the two near posts with two Building Block 30s and a Building Block 15. Insert a Link 15 halfway through the first Building Block 30. Connect the large pulley with the Clip 5 on the Clip Axle 75 with a belt. 10. To construct the pawl, connect two Building Block 15 with Bores with a Clip Axle 45 and two Clip 5s. Slide a Link 15 into the slot of a Building Block 15 with Bore, and attach a Building Block 15. Add the Rack 60 onto the Building Block 15. Name: Date: 13

6 11. Slide the pawl assembly to the model, adjusting it so the rack meshes at a slight angle onto the gear. Add a Clip Adapter and a Link 15 to the extended end of the Clip Axle Create two posts with a Building Block 15 with Bore and a Building Block 15. Slide the posts into the first and seventh slots on the far side of the base plate, being sure the axle holes line up. Fix a Clip Axle 30 in the Building Block 15 in the seventh slot with a Cog Wheel T 10. Insert a Clip Axle 45 into the other block. Add a Crank Shaft and a Bearing Sleeve onto the extended axle end. Use a Building Plate 15x30x5 to connect the two posts with the Cog Wheels, and attach a Clip 5 in between the two posts. 13. Your finished model should look like this: Try this Trace how you think power will be transferred, from the Crank Shaft input to Clip Adapter/Link 15 output. Record the order of gear pairs and pulleys: 2. Test the model by turning the Crank Shaft in a counter clockwise fashion. Then, turn the Crank Shaft in a clockwise fashion. Does the output turn both ways? If not, explain why it does not: Yes No 3. How many times must you turn the input in order to turn the output once? 4. Identify one reason for including a pawl in a mechanical system: Name: Date: 14