Designing and Building a Self-Driving Car – Part 4

Topics:  The many lessons of Pulse Width Modification or “Where have I seen this before?” Thoughts on Motor Speed and where to look for inspiration for a project.

This blog will be about the many lessons one learns throughout his or her life – and boy! have I’ve learned many!  In college I took electrical and electronics engineering courses, but one of the biggest lessons learned were not about resistors, capacitors, or Kirchhoff’s Voltage Law, or transistors; it was: ” You will forget what you learn quickly, if you don’t apply it in practice.”  This is the lesson that I intend to instill in my child throughout this project.

My “Parent’s Guide” tip is to create a project that will continuously reinforce the concepts that you will be using for the project.  The best way, in my opinion, to do this is to have a project that will last many months (or in years in my case).  Take a detour now and then to do a science fair or demonstration in from of the grandparents, science clubs and assortment of friends; in between boy scouts, or girl scouts, baseball, volleyball, tennis, swimming, or the myriad of activities children do throughout their lives, you need one project that is consistent and continuous and big for which they can take into college or whatever the next big step in their lives will be.

Learned about pulse modifications throughout my education.  First in an electronics lab course in 1993, and again in 1997 and 1999.  When I began working on the autonomous car project with my child, we began working on the PWM circuit for the electric motor that was to go into the car.  I forgot how it worked or what it would take to build this circuit.

The morale is working on a project such as this she help to continuously reinforce concepts of STEM throughout a child’s life and should not just be about getting it done!

We decided to create multiple prototypes (4), varying in difficulty, size, configuration and purpose.

Prototype 1:  Will be the an simplified Arduino and RaspberryPi prototype built for the sole purpose of controlling a DC Motor and a Servo with OpenCV and a RaspberryPi camera.  It’s a non-functional RC model.

IMG_2630[1]

Prototype 2:  Will be a workable RC Car that will do everything that Prototype 1 will do, but will have a Brushless motor with ESC and will move.

IMG_0849

Prototype 3:  Will be a 3D printed model designed in Bender and then 3D printed.  This prototype will better emulate an “actual car”.  It will have all the essentials such as a transmission, steering, suspension, differential, axle, etc.  It will not have all the other things a car has that have nothing to do with power, acceleration or steering.  I will be a working model with an actual brushless motor, computers and microcontrollers.  It will not have cameras, but will be operated by a dataset from actual road video.

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Figure 1:  Blender open source design software

Prototype 4:   An actual gasoline car rebuilt into an electrified self-driving car.  My hope is to rebuild an old Geo Metro.  But the chances are a little small at this point, because Geo Metros all over the country are being snapped up to convert to electric.  The advantages of rebuilding an electric car using a Geo Metro are:

  1. They’re cheap.  Many have bad engines which make them even cheaper.  You could find one from $300 to $1500.
  2. They’re lightweight.  Geo Metros are three cylinder and don’t have all the stuff that weights modern cars down.
  3. The shape is conducive to the space you would need for an electric car.  Since the car that I’m building will also contain computers and other mechanisms to make it self-driving, the hatchback is particularly attractive.

 

Chevrolet_Metro_hatchback_rear

 

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