Abstraction and Interfaces

12 acomplexblockdiagramtheronerobot 13

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Unformatted text preview: these links? information sensor: thermometer information computer: comparison energy actuator: furnace temperature physical effect: hot air We don’t care about the details. • Electrical signals? Hydraulic actuators? Smoke signals? • The interface to each component defines it’s input and output: temperature sensor: thermometer information 11 Block Diagramapalooza! 12 A Complex Block Diagram: The r‐one robot: 13 A Complex Block Diagram: The r‐one robot: [robot demo] 14 Measuring distance on the r‐one robot: Measure distance in three easy steps: 1. Each robot has two sensors that tell the computer how many turns the motor makes (Problem Set 3) 2. The motor is connected to the wheels, so the computer can also figure out how many turns the wheel makes (Problem Set 6) 3. With information about wheel rotations, the computer can compute the distance the robot has traveled (Problem Set 8) 15 Measuring distance on the r‐one robot: This sensor is called an encoder. Its block diagram is: motor rotations sensor: encoder information This is a simple block and a simple interface. How much complexity does this conceal? 16 rone v11 17 Motor Circuit Board Start with commercial motors • Pololu micro‐gearmotors with extended shafts Very inexpensive quadrature encoders • Composed of a plastic wheel and a photointerupter • 0.0625 mm/tick resolution • Cost around $5 each 18 18 Encoder 19 19 Encoder Wheel 20 Full Schematics: 21 Motors and Encoders Schematic Page 22 Encoder Circuit 23 Encoder Chip 24 Encoder Chip, complete 25 Encoder block diagram motor rotations sensor: encoder information 26...
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