NXTLiftBoy Mark II is a fully functional fork lift truck from a single LEGO Mindstorms NXT set
About this creation
This is my second attempt at a forklift from a single NXT set. See "NXTLiftBoy" for the first attempt.
Look at the YouTube clip i made from it, or rebuild it yourself from a single LEGO Mindstorms NXT retail set AND a differential, by following the slideshow.
I think this one has better looks and a better design.
Getting pictures when taking it apart is planned for, like an upload to photobucket so you can build it yourself afterwards.
NXTLiftBoy Mark II is a fully functional fork lift truck from a single NXT set and a single differential, designed to find its way in e.g. a warehouse full of boxes from IKEA!
It is the successor to NXTLiftBoy, my first fork lift truck as published on nxtasy.org, youtube and MOCpages.com, with instructions on photobucket. That earlier truck had a caster wheel that i wanted to avoid this time, and i wanted the center of gravity down for better stability. I had to resort to allow myself a single part that is not in the NXT set, which is a differential.
I started with the steering back wheel construction that has a very tight fit. Then i connected the second motor, but i failed trying to gear it onto the differential, so i took the third motor and mounted it standing up, which worked out better, because the motor axis was now parallel to the differential. Later i fortified the lose end of the motor gear axis, to prevent gears slipping when fully accelerating in a turn.
The NXT brick was mounted just on top, but it had to be moved to the front as far as it could to prevent the inner front wheel from slipping when taking curves. The brick has the USB socket backwards to allow for easy "fuelling" of software!
Under the brick a cable duct is formed by two beams. The motor cables run from the back through the duct to the front and bend in rather tight turns, due to very compact building. One has to build it with the cables inserted in the motors, wiring them afterwards is totally impossible.
Then i made a mounting point for the mast, and fortified the construction to deliver the forces when lifting onto the front wheels.
The mast is the most obvious part i guess. I optimised the fork design to fit IKEA boxes. These boxes are the same as those colorful used for my NXT Container Crane. Routing the rope was not so easy, it takes a turn in the end, because the winch has a vertical axis.
From the remaining parts the cabin was made. It features a roll-over cage, backside motor lid with air inlets, chair with captain left armrest with controls, rightside controls, steer with turning knob, dashboard, gas- brake- and clutch pedals, left outside mirror (tilts and swivels), 4 outside spots for lighting the work place, backlights.
Finally the US transducer was put in. I first had it 'looking' sideways. I intended to program it to count the rows of IKEA boxes it is passing, take a left turn at row X, then count the columns it is passing take a left turn at column Y, in order to fetch one or more stacked IKEA boxes at height Z! That would allow for a fully automated warehouse.
I was skeptical when it comes to the required precision... and indeed i did not manage to program it properly, as without additional sensors (compass!) tiny errors accumulate.
To have the forklift doing something very useful (ahem) and funny, i came up with the idea to have it solve the Towers of Hanoi:
Towers of Hanoi is a well-known puzzle with three vertical pins. It starts with a pile of discs with top-to-down increasing diameters slided onto the first pin. The task is to get the pile to the third pin, but only a single disc may be moved at the time, and a bigger disc may never be put on a smaller disc. This is typically solved using a programming technique called recursion. For 3 discs already 15 moves are required, i think.
Rather than pins and discs, i wanted to start with a pile of IKEA boxes numbered top-down 1, 2, 3. A higher-numbered box may never be put on a lower numbered box. The forklift is programmed to move the stack of boxes, one box at the time according to the rules, from the starting position on its left side to the end position on its right side, while only using a third centered position for intermediate storage.
I failed to obtain sufficient reproducibility in moving, trying both NXT-G (the LEGO language) as well as Java iCommand. Even preventing slipping by gradually adapting speed would not help. Maybe LeJOS can do the trick?
So i challenge you to show me it can be done (without additional sensors).
I guess programming is not my strongest quality :)
I tried both NXT-G and Java via iCommand from LeJos, but i found both not satisfying, so i have nothing to share :(
i remember i wrote a routine for setting the wheels straight by turning to the extremes measuring angles and setting to the average.
i hope you have better luck in controlling this thing. Perhaps doing it only interactively is your best choice. Have fun!