August 9, 2013
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.