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Robot capabilities

AERobot (Affordable Education Robot)
Michael Rubenstein and Radhika Nagpal
Harvard University


Hardware Features: 

AERobot is a highly modified version of the Kilobot robot, re-designed specifically as a low-cost ($10.70 including assembly) education robot. Modifications include the removal of swarm capabilities of Kilobot, the addition of more sensors, and simplifying its charging and programing. AERobot has a built-in USB plug that allows it to directly plug into any computer with a USB port. Using this USB connection, it can recharge its lithium-ion battery and be reprogrammed all without any additional hardware. AERobot has holonomic 2D motion; using two low-cost vibration motors, it can move forward, backwards, and turn in place on a flat, smooth surface such as a table or whiteboard. It also has three pairs of outward-pointing infrared transmitters and phototransistors, allowing it to detect distance to obstacles using reflected infrared light, and passively detect light sources using just the phototransistors. Additionally, AERobot has one downward-pointing infrared transmitter and three infrared receivers to detect the reflectivity of the surface below, useful for line following. There is also a RGB LED which aids in learning simple programs and debugging.

  
(Left) Top view of AERobot; this is the robot’s orientation while in use. (Center) Bottom view of AERobot. (Right) An AERobot plugged into a USB port for recharging and/or reprogramming.


The bottom side of AERobot PCB showing the following components: A) Outward facing phototransistors (can sense both ambient light as well as IR light).  B) Outward facing IR transmitters. C) Downward facing phototransistors. D) Downward facing IR transmitter.  E) Vibration motors. F) Power switch. G) Rechargeable lithium-ion battery. H) USB connector. I) RGB LED.

Low-cost:

There are four main designs features that help keep the AERobot low-cost.

1) The robot electronics are designed to use only SMD components which can all be placed using a pick-and-place machine, drastically reducing assembly costs. Additionally, all components are mounted on a single side of the PCB, cutting assembly cost in half when compared to a PCB with components on both sides. All remaining assembly steps are very simple and can be done by the student in a few minutes. The PCB also doubles as the main robot chassis, further reducing robot cost and complexity.
2) The use of vibration motors greatly reduces the overall robot cost as vibration motors are cheaper than standard motors, and don’t use the extra hardware found in most robots such as gearboxes and wheels.
3) Using a USB interface built directly into the PCB removes the additional costs, incurred by most robots, of an external programmer and charger, which can easily double the cost of a complete robot system for robots at this price range.
4) AERobot uses purely optical sensors (the infrared transmitters and photodiodes) which have no moving parts, are generally lower cost than most other sensors, and are robust to dusty environments.

Assembly:


The robot kit will contain the following parts: 1 fully-populated PCB, 1 plastic base, 1 rechargeable battery, 2 plastic “legs”, and 5 plastic screws. Assembly requires no tools, but a small Phillips screwdriver will make assembly quicker. Assembly time is approximately 2 minutes. To assemble the robot, follow these four steps: 1) insert rechargeable battery into battery holder, positive side facing away from the PCB. 2) Insert 3 plastic screws into the holes on the plastic base. 3) Screw the 2 plastic legs into the two outside screws on the plastic base. 4) Use the two remaining screws to firmly attach the plastic legs to the PCB.

Contents of AERobot kit: 1 fully populated PCB, 1 plastic base, 1 rechargeable battery, 2 plastic “legs”, and 5 plastic screws


AERobot assembly

video of assembly and assembly steps.

AERobot PCB and bill of materials (BOM):

The AERobot is an open-source robot and details are made freely available under the creative commons "Attribution-NonCommercial-ShareAlike" open-source license.  Files for PCB creation including the bill of materials can be found here.  All part prices are assuming high volume purchase of 1000 robots using common part distributers.  The total robot cost, including all assembly, is $10.70.  We expect the robot cost would be greatly reduced if parts are acquired directly from manufactures.

AERobot behavior demonstration:

While cost constraints tend to force low capabilities, AERobot has enough hardware features to help a student with no programming or robotics experience go from a “hello world” program that just blinks an LED, to understanding classical behaviors used for learning about mobile robots, such as moving to a light source (phototaxis), edge-following/maze solving, and line following.  The following videos show AERobot demonstrating 3 behaviors: phototaxis, edge-following, line following.

Line following demo

Edge following

light seeking