Whiz on Wheels?

Yep..that's the name of the first robot that I built in my life! It is a mobile pick-and-place robot that had...wheels, and I wanted the robot to have some intelligence, though I kind of achieved this only in my future versions. Hence, the name...Whiz on Wheels.

The idea...

Like many amateur robotics enthusiasts, my rudimentary conception of a robot was something that 'had' to move around and pick up objects...a definition that sounds puerile to an embarassing extent, right now. My spontaneous instincts, dictated by this conception, coaxed me to opt for a four wheeler with a rear drive and front-end steering (basically a car), the simplest I could imagine.

Inspired by the modest environment, in which many robots are born, I started building this robot in the garage of my house. Every imaginable piece of scrap went towards making its structure. Luckily, I had access to machine tools from my friend's factory.

The design...

Whiz on Wheels has an evolution saga in which three versions were developed.

Evolution Phase 1

The robot has a rectangular base made of PVC (I used scrap from my friend's factory) with front and rear axles fitted to the base. Both the axles are mounted on bearings. The front axle has a movable pivot with end stops to restrict the steering angle.

A premature decision that I made was in choosing the drive motors. Completely flattered by the sheer size and power of a DC motor (17W, 24V) used for windshield wiping in buses, I mounted them without giving an iota of thought about my requirements. This eventually increased the size and weight of the robot drastically, something which I had to settle for considering the inexpensive but notorious source of the motors - I simply appropriated them from an old dumped robot built by some seniors, lying in the college junk...no questions asked!

I used three such motors - one for the linear drive, one for turning and the third to drive a cam. The cam has a follower that slides along a pair of guide-ways, with an end effector (not decided at that stage) attached to the follower.

This first version was built right in time for a demonstration in an annual symposium conducted by the Department of Mechanical Engineering of my college, IGNITION held in August 1999. This version was just a 'static' model, as the electronics and PC interfacing circuits were not ready at that time. However, the model received great appreciation for its design, aesthetic appeal and more importantly for the value addition to junk material.

Evolution Phase 2

After testing the patience of an electronics professor in my college with my oblivion in the subject, I got to know about PC interfacing through the parallel port and the motor drive circuits.

The robot did not have any distance feedback sensors. Hard pressed for time before a display in the Open Hardware competition at IIT, Bombay (Techfest 2001), I decided to use a computer mouse for feedback of distance traveled. I managed to drill holes in the mouse cover, without damaging it, and had it fitted beneath the robot base with the mouse ball just in contact with the floor. (This would have made any mouse manufacturer quit his business) The input from the mouse was obtained through the serial port. The inputs were by no means accurate, but I had to settle for it. I coded a control program in c++ with a GUI, capable of plotting the path traced by the robot in a sample workspace.

The robot was capable of executing a pre-determined set of motions automatically and could go to any destination given its rectangular co-ordinates in the workspace. The keyboard could also be used to manually control it.

I was given an 'honorable mention' in the winner's list for the innovation in using the computer mouse. As a bonus, I was invited to participate in a similar festival Techkriti 2001 conducted by IIT Kanpur.

Evolution Phase 3

In the third version, I added the end-effector - a gripper with two parallel plates. One plate was fixed, and the other plate movable. The movable plate was driven back and forth along a threaded shaft by a small DC motor.

The basic idea behind this design was the beautiful 'propelling' property of a helix. Because the movable plate is prevented from rotating along with the motor shaft, the rotation of the helical thread propels the plate forward or backward according to the direction of rotation of the motor.

The competition at IITK was Endeavor, a functional model contest. I was given a commendation certificate for my resourcefulness and creativity.