|
In general there are three ways to make machines like Robots do anything: electrically,
hydraulically or pneumatically. Each has their good points and bad. Even today there are still things that can be done better
pneumatically. Pneumatics do not need limit switches and they can exert a constant force without the need for complex feed
back systems. And compaired to hydraulics pneumatics have a great advantage: They leak only air and not oil.
Along with the obvious air pump a pneumatic system should have a means to store the compressed air,
a control system to say when the air pump is running and a means to regulate the pressure supplied to the loads. Having
an appropriately sized storage tank is most important: it allows the air pump to run less often. Below are the general components
I used:
 The Slime tire inflator seems well suited for this application. It can generate
high pressures (much higher then I will ever need) and pumps enough air to fill the storage tank in a short time. It works
well because the electric motor in it drives the actual single cylinder air pump through reduction gears, the motor runs fast,
the pump runs slower, everything is happy.
Most important is the pressure switch. It has an adjustable set point and a resonably wide deadband.
At the moment its set to turn the pump on at about 25 psi and turn it off when the pressure reaches 30 psi. Most critical
is that the pressure switch be reliable so the pressure tank does not burst due to the pump running too long.
The part over on the lower right is a manifold with solenoid valves. There are lots of different solenoid
valves available, these are simple normally closed 3 way valves. With no power applied their outlet is connected to atmosphere.
Apply power and pressure from the regulator is available. This is fine for single acting loads like spring loaded air cylinders.
Below is the assembly rearranged a bit and mounted to the tank:
 All this is mounted to supports epoxied to the bottom of the torso. The supports
also allow the pneumatic package to be removed when necessary. Having the pneumatic system located in the back helps to counter
balance the weight of the claws.
|
