MARCBot

Project: In Cahners Computer Place, there is 1/3 (cut lengthwise) of an automobile against the wall, around which is a Plexiglas barrier, behind which is a mural of a civic emergency.   Hidden in this car is a faux improvised explosive device (IED).  Within this small corral is a MARCbot.  The MARCbot is a small, wheeled robot with a camera at the end of an articulated boom designed and built specifically to inspect potential IEDs.  It is operated with a remote control unit called an Operator Control Unit (OCU).  This is where I came in.  Even though OCU was designed for combat situations, it was nowhere near robust enough to withstand the museum-going public.  (The preceding sentence is in no way a joke.)  I was asked to design and construct a kiosk that would house the OCU, make it more accessible for people with varying manual dexterity, and to add one final feature, to be explained below. For a sneak preview, see the video below.


Challenges: Two main challenges: 1) The OCU was equipped with very delicate, fine controls that were specifically designed to be operated by the finger tips.  This situation will simply not do in the museum environment and is not even vaguely ADA compliant.  Further, the OCU comes equipped with a small television monitor that would not last long if exposed.  2) The manager of CCP wanted the visitor to experience operating the robot without the benefit of line-of-sight operation (using only the small monitor mentioned above), just as technicians must often do in real situations.  The problem is that we wanted the visitor to have the option of line-of-sight or monitor operations.

Solutions: 1) To handle the accessibility issue, I decided to rest the actual OCU in a shallow recess in the kiosk.  Over this recess, I placed a piece of ½ inch Plexi into which I had cut holes for the placement of control extensions – meta-controls, if you will.  I constructed joy sticks that extend below the surface of the Plexi cover.  At the lower end of these joysticks is a small cup into which the actual OCU controls fit.  By adding these meta-controls, I was able to make a more robust handle that is controllable by people of various fine-motor skills.  Further, it allowed me to add mechanical stops to the controls so that they could not be over-extended by the visitors.  Below are pictures of the meta-controls.

2) To allow the visitor to choose between line-of-sight or “blind” operations, I decided to provide a “blast shield” that could be raised or lowered by the visitor.  Due to space limitations, the exhibit is arranged so that the visitor must look to the left to operate the MARCBot visually.  I arranged the kiosk so that when the “blast shield” was raised, it would block the view of the MARCBot, forcing the visitor to operate the vehicle by only the monitor in the cabinet.  The “blast shield” (I’ll stop using quotes now) is really a piece of ¼ inch Starbord sandwiched between two pieces of clear Plexi.  The mechanism for raising and lower the shield is simple: I attached a geared rack to either side of the panel and meshed a pinion to each rack.  A small DC gearmotor is attached to the pinions via a toothed rubber belt.  The controls are simple, as well.  Latching relays are activated by either the raise or lower button, and the shield will travel to the end of the rails where a magnetic sensor will open the latching relay, stopping the panel.  There is, however, one twist.  To prevent the visitor from simply raising and lowering the blast shield over and over, I installed a delay timer in the circuit.  When the shield reaches the end of its travel in either direction, a timer picks up and disables the circuit for ten seconds.  This action is indicated by the lights of the “Blast Shield Status Panel” pictured below.

One final note: I was particularly pleased with the way the kiosk, itself, turned out.  I was aiming for a mechanistic, perhaps military feel for the cabinet.  Click here to see a few pictures of the cabinet in progress and the end result.