Week 17:

Objectives:

• What will it do?
• Who's done what beforehand?
• What materials and components will be required?
• What parts and systems will be made?
• What processes will be used?
• What tasks need to be completed?
• What questions need to be answered?
• What is the schedule?
• How will it be evaluated?

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What will it do?

The Sphere robot will be able to drive it through a web interface or a physical joystick. The communication between the robot and the pc/joystick will occur via bluetooth. The robot will have two geared motors to make the outer shell spin and two ( maybe one ) servo motor to move the counterweight which will make the ball tilt ( steer ).
The mainboard will be a Particle Photon with integrated Wifi module i’ll add to the board few mosfets to drive the geared DC motors. To measure the tilting angle i’ll use a 6 DOF IMU ( MPU6050 ) and a PID algorithm will try to stabilize it.

Who's done what beforehand?

As far as I could get from Google this kind of robot isn't very popular. I found a company who make a small toy sphere robot ( http://www.sphero.com/sprk-plus ) but they use wheels inside the shell to move the latter instead i want to have the shaft of the motors connected directly to the shell and use the low center of gravity to transfer the torque to the shell.
On youtube i found some videos of university students or DIY project which did something close to what i’m going to do.
https://www.youtube.com/watch?v=o43ZVkoWe44
https://www.youtube.com/watch?v=LmvUkbdXNbM

What materials and components will be required?

The total price should be around 75$ but i'll try to make as much as i can things instead of buy them.

What parts and systems will be made?

• Software: i’ll totally write the software which will control the kinematics of the robots.
• Hardware: i’ll build using the 3D printer the robot shell and all the motor-to-shell connectors, servo holders and so on.
• Interface: I hope to be able to develope a nice web interface to control wirelessly the robot .

What processes will be used?

• 3D Printing: To build all the mechanical parts.
• CNC Milling: For the electronics production.
• Resin: The outer shell will need to be reinforced with several coat of epoxy resin, after i'll paint it.
• Laser Cutting: To cut the inner robot plate and some other flat parts.

What tasks need to be completed?

I divided the workflow into seven steps:

• Design the parts and assembly them virtually. ( SolidWorks ).
• Build the outer shell and all the mechanical parts.
• Fix everything to the main plate and test if there’s anything that prevent the movement.
• Start testing the electronics.
• Write and tune a PID algorithm that stabilize the robot.
• Write and test an interface to control the robot.
• Final tuning.

What questions need to be answered?

• Will the weight of the inner part be enough to make the outer shell spin?
• Will the weight of the pendulum make the ball tilt?
• If so, will it be able to stabilize the robot?
• Will it roll?
• Will it blend? question sponsored by Blendtec

What is the schedule?

• 26/05 - Complete the 3D design
• 02/06 - Electronics and SOftware
• 09/06 - Testing and Video

How will it be evaluated?

I wish i had enough time to implement the communication between the joystick i made during networking week and my final project. But i think is a great success if, using the android app, the robot move and react fast enough to be human controllable.