Building a biped: Another year, another robot

With the experience of the first robot I knew that the
most important thing was to make the robot light and strong
enough to allow it to stand on one leg.

The first robot (model 1) had six degrees of freedom in each
leg. I decided that I could do with four.

The new model used power functions motors combined with
RCX rotation sensors. The robot was controlled with three
NXT bricks which was not enough to control all functions
but it did allow me to experiment with the legs.

The primary goal, building a robot which could stand on
one leg was achieved.

Unfortunately by solving one problem I ran into another
problem. When you control a motor you have to know the
exact angle of the axis. To do this you have to put
the robot in a starting position of which all angles
are known. From there you can move the axis relative to
the start position.



Next time: Fixing the reset and control issues...

Here´s something fantastic...
Stuff like this used to be science fiction:

HiTechnic Sensor Multiplexer Review Part 1

I just got the Sensor Multiplexer from HiTechnic the other day. I haven’t even plugged in a cord yet, but I wanted to share a few initial thoughts.

The first thing I noticed is that it is slightly bigger than I imagined. No big deal, I just imagined it to be a little smaller. It’s about 2 ¼ inches square and about 1 inch high or 7 studs square by 3 studs high. It is built to standard Lego dimensions so it will easily fit into your mounting.

HiTechnic carefully avoided infringing upon the Lego stud design my making all the protrusions and the distance between them one stud wide so a standard beam fits between them. You cannot snap the SMUX into your project so it must be captured between regular elements.

The second thing I noticed is that it has an external power source of a 9 volt battery box. There is a rather small red and black wire about six inches long connecting the battery box to the SMUX. I didn’t realize it required an external source because I was using the Touch SMUX as a reference which does not have the battery box requirement and I guess I didn’t look closely at the picture on the HiTechnic web site.

There is an indicator light on the battery box which has some functions related to the state of the SMUX and I will get into that more when I start to program it. There is a small on/off switch to turn the SMUX on during operation. You must use a small screwdriver to install the battery.

The battery box isn’t built to Lego dimensions, which makes mounting a little more cumbersome, but not overly difficult. The best way to mount is right now is probably using a couple of rubber bands and strapping it to other Lego elements. Personally, I wish that the battery box was incorporated into the SMUX. That way all the mounting could be done at the same time and I wouldn’t have to worry about breaking the small wires connecting the two during construction.

The distance between the ports on the SMUX are just wide enough for a beam to fit between them, but it is tight.