Design

Design Goals

The main design goal is to make the LEGO pneumatic controller as simple as possible with a focus on minimalism.  Sunset Spark wanted to use as few pieces as possible because that will make it easier to build around the motorized pumps.  Of course, innate to the project is that it had to be LEGO-based.  The team didn't want to use too many custom or difficult to find pieces so that this would be as accessible as possible.  Less weird LEGO parts makes it easier for schools to pull together the BOM without hunting down pieces.

They also kept the design simple to allow for easy adaption into other LEGO projects.  The pump + motor mechanism can easily removed from the programmable brick and repositioned elsewhere in a project.  This modularity allows for easier integration into rigid robots that may already have been designed.

Beyond simplicity, the team knew they needed to generate a lot of air flow.  One pump will generate the air pressure, but not in a very timely manner.  To achieve this, they designed it with two pumps, one per motor.  This double the amount of air flow and can cut the pressurizing time in half.

Mechanics

The controller pumps air using a cranking motion by directly connection the plunger of the pump to the rotor of the motor.  Both pumps are connected by two tubes with a tee piece.  The output of that tee piece is split with another tee piece, with one leading to the pressure sensor, and the other end leading to a pneumatic actuator.

Strengths

As with the stated goals, the EV3 pressure controller is very modular.  The two motor + pump components can be moved around to attach to more complicated builds.  Most importantly, the core goal of the prototype works -- it can generate air and pressurize to a specific value.    The two goals create a very simple yet useful air pneumatic controller.

Weaknesses

Slow and steady might win the race, but I do not think kids are going to wait 3+ minutes for a pneumatic actuator to fully pressurize.  The air pressure does not come soon enough to truly keep people interested in the robotics and engineering concepts.  This weakness is addressed in the next section.

The forces generated by the motor between the pump and the L beam are a bit too strong.  It has a tendency to pull itself apart.  The forces on the L beam in particular push and pull the beam off the project.  This can be managed by adding a second beam on top of the L-beams on the motor.  This second beam could help prevent the L beam from disconnecting and disabling the pumping mechanism.

Actuators need to be able to connect with the LEGO pneumatic tubing for a proper, sealed connection.  The tubing is quite large (3.5mm) and might not be suitable for all actuators.  While using the PneuNet with the LEGO tubing, we noticed that the tubing may be a bit too thick for many of the thinner actuators.   Below is a PneuNet with LEGO tubing.