Engineering at its Peak

High Performance Actuators

“Fast” and “large” are very relative terms. In the context discussed here, “fast” implies fractions of a second, while “large” implies very large forces to open/close. For instance, opening or closing valves, particularly large valves, in fractions of a second is extremely challenging.  There are currently three possible techniques available: hydraulic, pneumatic, or electromagnetic.

Actuator/valve design is inherently complex combining aspects of fluid, thermo, and mechanical dynamics with both compressible and incompressible fluids. To grossly simplify however;

   *Electromagnetic actuators are limited in force production to around 200 psi due to magnetic field separation.  
   *Hydraulic systems can produce large loads but are inherently slow.
   *Pneumatic systems are fast but produce low loads generally around 100 psi.

The figure at right from the reference above graphically shows the abilities and limitations of these technologies.

Combustion Driven Pneumatic Actuators (CDPA's) push the “state of the art” boundaries. Basically the driving pneumatics are a combustible gaseous fluid. The combustion process very rapidly heats and expands the gases to high pressures. These high pressure gases then act on the load with the speed of pneumatics and the force of hydraulics.

Th ese CDPA devices use common and readily available gases such as propane and natural gas mixed with air. For even faster performance the air can be replaced by a helium-oxygen mixture or even hydrogen-air. Such valves can be self-contained one use devices or fully automated to reset and refill after use.

Applications include extremely fast electrical breakers for high current situations where zero arcing is desired, large valves used to shutoff systems in emergencies, military protection devices such as active doors/armor, and collision avoidance system such as steering, braking, and track switching where ms time decisions and corrections are needed at high loads, to name a few.

Blue Summit has years of experience using combustible gas mixtures for a variety of applications. The figure at right shows a pressure time curve produced in a Blue Summit Technologies test facility.

The figure at below shows methane and hydrogen combustion results for a 45mm bore gun system developed and operated by current Blue Summit personnel. In this device, both high pressures and fast rise times were achieved.  For these cases the oxygen is mixed with helium which allows it to be purchased from any gas vendor since the mixture is no more hazardous than bottled air with the helium replacing the nitrogen like that used for very deep diving. 

The CDPA in an inherently simple device as shown in below. Note that in addition to controlling the rise time and pressures achieved by adjusting the mixture constituents and pressure Blue Summit Technologies can also change the ignition technique and location if needed with optimized laser based ignition.

Do you have an application need that is "beyond the current state of the art" for other technologies, then contact us and we will go there!