Actuators: Choosing the right technology

Machine designers should take a cross-technology view of power technology, choosing the most appropriate for their application.

04/26/2007


Hoffman Estates , IL —Machine designers should take a cross-technology view of power technology, choosing the most appropriate for their application. Potential choices for driving translational degrees of freedom include electric, hydraulic, and pneumatic actuators. This strategy helps build efficiency, performance, and sustainable competitive advantage into their designs. Start with a broad generalization about the primary application then consider using hydraulic, electric, or pneumatic motion (see table below), knowing that many exceptions exist and that many applications embrace more than one technology.

 

Motion technology considerations include:

 

Flexibility: Servo systems are ideal for allowing setup parameters to be easily changed so the system can be reconfigured with changes only to the control program. Pre-packaged and customized application programs make tooling changeovers fast and easy.

 

Reliability and maintainability: Great progress has been made in materials, component packaging, and installation methods. Advanced diagnostics and predictive maintenance have also advanced considerably for all three technologies.

 

Many applications are not limited to one technology and can take advantage of the unique characteristics of each. Closed-loop control—once seen as the special advantage of electric control—is now possible with hydraulics and pneumatics, significantly raising their capabilities. And the new technologies of mechatronics–electropneumatics and electrohydraulics–are the result.

 

Machine designers should take a cross-technology view of their machine, using the best, most appropriate technology for their equipment, and thus building in efficiency, performance, and sustainable competitive advantage. In addition, newer software tools aim to integrate three, once-separate realms of programming into one platform, helping to speed up and simplify engineering tasks from project planning and programming to visualization and diagnostics.

 

Additional guidelines appear in the May 2007 “Back to Basics,” called “Motion: Electric, hydraulic, pnuematic.” See other automation tutorials at controleng.com/tutorials .

- Rodney Rusk, Dan Warmus, Brian Rogers, and Thomas Dwyer are pneumatic, hydraulic and electric technology specialists from Bosch Rexroth Corp .

Edited by C.G. Masi and Mark T. Hoske, Control Engineering Machine Control eNewsletter

 

TABLE: Motion technology comparison for electric, hydraulic, pneumatic technologies

 


Hydraulic

Electric

Pneumatic

Working speed (velocity)

5 m/s

10 m/s

4 m/s

Power density

High

Low

Low

Achievable force

High

High

Limited, ~ 20 kN

Achievable stroke

High, to 10m+

High

High, to 10M+

Change of forces

Simple and accurate

Simple to complex

Simple and accurate

Efficiency

Best

Good

Good

Connections

Simple

Simple

Very simple

Overload safety

Complete

Complete

Complete

Explosion proof

Available

Available

Yes

 

Source: Control Engineering and Bosch Rexroth

 


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