The Mobile Pneumatic Multi Arm Series

So, quite a long time ago, I decided to make a mobile arm.  Too simple?  I also wanted to use pneumatics.  Still simple?  I wanted to get more than three functions out of three motors.  So, MPMA was born.

All in all, it wasn't a bad start to the series.  The drive base was pretty quick, using a white clutch gear to drive forward and turn in reverse off of one motor.  The pneumatic switching mechanism, using a differential and inspired by this project, also worked quite well.  Even the compressor, operating off one RIS motor, worked pretty well.  However, I knew it was possible to drag even more functions out of three motors (MPMA derived 5) and I also toyed with the idea of using more than one motor to move the robot.  And thus was formed MPMA V2...

 MPMA V2 was built around the idea that an output from each of two aforementioned differential "multiplexor" units could drive a tread.  This would give the robot the ability to move forward with the power of two motors.  However, since the treads never rotated backward, MPMA V2 could not be maneuvered in even somewhat tight spaces.  The pumping unit was very slow (though this might have been due to a broken motor) and I never implemented the third pneumatic switch.  The machine's chassis was also weak, adding to the myriad of issues.  Leaning from this, I moved on...

 MPMA V3 was the best robot in the series so far.  It employed a much faster pumping mechanism and a two-jointed arm with a working claw.  The structure was not very strong, but it held together.  MPMA V3 also enjoyed better ground clearance than MPMA V1, and the NXT Intelligent Brick could be easily accessed and removed for battery change.  However, the second joint in the arm did nothing more than move the arm into a more nonfunctional range and was thus rarely used.  Also, the drive base could only go forward and turn in reverse, leading to the next member of the series...

MPMA V4 is probably the best robot in the MPMA series thus far.  Instead of clutch gears and differentials, MPMA uses a mechanical multiplexor custom-built by myself but inspired by this project.  Gaining six outputs from only three motors, MPMA has a fully functional drive base, a single-joint robot arm with working claw on a rotating turntable, and an on-board compressor.  Unlike its predecessors, only two of these functions can operate at the same time (drive base, switches, or rotation/compressor are the combinations) but they are fully functional.  I think that this is a good trade-off.  However, the mechanical multiplexor is prone to slipping the outputs are placed under too much load.  Also, the compressor is slow.

MPMA V4 will hopefully be entered into an unofficial NXT Robotic Arm building challenge.