Rebuild #1

August 21, 2013 
Hi, I’m back after a business trip. No pictures today.

I rebuilt the main structure using 3/8″ & 1/4″ 36 inch threaded rods. There are two 3/8 rods by each motor and two 1/4 in the front and back as well as one in the center. The 3/8 will support the shoulder/arms when I get around to adding them. I used three pizza pans on the body spaced out for holding equipment. I have two more as spares if I need to add more.

The body covering is a piece of 36×48″ sheet metal from Home Depot. This is used for duct work. It will be wrapped around and secured with sheet metal screws.

I worked on the head, but the body filler is not holding. On the weekend I will fiberglass the whole head. I stuck on 2 googly eyes from Michaels (40mm) just for fun.

 

Motor and Wheels – Attempt #1

August 10, 2013

Hi, I’m back again with details of the motor mounting and wheel attachment. 

Be sure to use Loctite™ or your favorite thread locker as the vibration and jerks can be severe and will loosen anything that is not secured well! The voice of experience speaks!

This is the basic Motor Stripped out of the case, The chuck removed and clutch locked.
The motor has 1 3/8-24 thread. This is uncommon as most bolts are 3/8-16. So I made an adaptor that also functions as the axel. I used a 3/8-24 nut, a 3/8-1/2 sleeve 1 1/4″ long, and a 3/8-16 nut. Assemble these. Use Loctite™ to lock the 3/8-24 nut in place. Drill the motor shaft for a locking screw (#8 or #10 is good). Insert the 3″ 3/8-16 threaded rod and drill for a similar lock bolts. Add the 3/8-24 jam nut (Don’t forget the Loctite™!)
This is how the wheels are mounted.
Nut, fender washer, rubber washer, sleeve, place wheel over sleeve, rubber washer, fender washer, (Loctite™) nut.
The rubber washers are an attempt to isolate vibrations. Only time will tell.
Note the toy car tire on motor. This will go under the hose clamps
Wheel and motor on axel.
Motor and wheels mounted on Base using hose clamps. Later I will use 3D printed Motor Mounts.
I used some old toy car tires that happened to fit as isolation/motor mounts under the rear clamps. This should keep it from slipping out or twisting.
Oblique view of base
Bottom showing casters


In the Beginning

August 9, 2013

Hi all,

This is the start of my Blog about building my Telepresence Robot. It will enable me to be somewhere else while my body is at home. It will also allow Linda to visit me in Oregon while she is at home in Colorado.

In addition the Bot will be able to run autonomously. This is a long term goal.

This is all experimental and I will post the dead ends as well at the successes.

The Bot will be controlled by a number of microprocessor boards, each devoted to a specific task. One thing I have learned in my 48 years of working as a Programmer/Software Engineer is to break the task down in to simple parts, test each part and then test the whole thing together. It makes life much easier.

Most boards will be Arduino of some sort. The Brain will be an Arm TI Tiva Launchpad.

1)      Base Motor Controller – Arduino Pro – Controls to Harbor Freight 18V Cordless Drill motors (running at 12V). Each motor has been removed from the case, the chuck was removed, clutch locked, and the control (trigger) circuit removed. At full speed these motors are rated to turn 900 RPM with the built-in gearbox. However, by use of a PWM board they will turn much slower. I have 8 inch diameter wheels, so one turn equals about 25 inches and 900 rpm is 180+ feet per minute of forward motion.
I will use PWM to reduce the speed to about 1 rpm. Each wheel will use an encoder disk on the back with a quadrature sensor. This will allow me to determine the speed each wheel is rotating.

2)      Sensor platform – Arduino Mega – Sensors for distance, Acceleration and position will connect here. The board will convert the raw sensor values into something of useful

a.       Ultrasonic Distance Sensor – To See if anything is in front of me. For collision avoidance

b.      Sharp IR Range Finder – for more accurate distance measurements and mapping the room.

c.       Accelerometer – Can be used as a “BUMP” sensor that will tell the Bot when it hit something. Also measures tilt.

d.      Gyroscope IC – Determines turning motion and tilt rate.

e.       GPS Interface – Tells where the Bot is. (GPS to be added later)

f.        Light Sensor – To tell if it is dark so the lights can be turned on.

3)      Arms – Fully articulated Shoulder, Elbow and Wrist with a gripper claw for the hand. About 7 motors or Servos will be used for each arm. This is the most complicated and will be last.

a.       Shoulder – two motors and a Pan/Tilt bracket

b.      Elbow – One motor and a simple hinge.

Wrist/Hand – This is the most complicated joint. I will probably use the Robotic Claw and the Robotic Claw Pan/Tilt Bracket from SparkFun Electronics. This will take 3 Servos (one of which is included).

4)      Face – A Visual Land 7-inch Android Table – This will use the built-in camera to allow the operator to see what the Bot is looking at. It will also display the face of the operator. This will connect via Skype or something similar via Wi-Fi. This function is independent of the rest of the Bot.

5)      Brain (Not Zombie food) – A ARM Development board – Either Texas Instruments TIVA Launchpad or a STM Discovery Board. Will connect to the operator for remote operation using a 2.4 GHz RF link (similar to Nordic).

Here are pictures of the prototype. This is put together to check fit and practicality and to figure out how to mount and control the motors and wheels. It is built on a 14 inch pizza pan using a plastic garbage can for the head. I found out I need to add braces or get a stronger base. I probably will add braces as the pan is a good base.