TABLE OF COMPARISON

Comparison Data

Criterium	Hydraulics	Pneumatics
Energy carrier	Oil (Liquids in general)	Air
Energy transmission	Pipes,hoses, tubes,bores	Pipes,hoses, tubes,bores
Conversion from or into mechanical energy	Pumps,cylinder, hydraulics (HY) motors	Compressors, cylinder, pneumatics (HY) motors
Most important characteristic quantities	Pressure p (30…400 bar), flow Q	Pressure p (approx. 6 bar), flow Q
Power efficiency	Excellent Compact, reasonably priced components due to high operating pressures of up to approx. 400 bar. Most simple linear motor-cylinder	Good limitations though, due to max operating pressure of only 6 bar
Accuracy of motion (this can be improved through, in all system by positioning action	excellent because oil can hardly be compressed	Fair to good because air is compressible
efficiency	Fair to good, volumetric and frictional losses during primary and secondary energy conversion, as well as with the open and closed loop control of valves
Controllability	Excellent, by means of valves and variable displacement pumps servo valves for closed- loop techniques	Excellent by means of valves (for small to medium power)
Generation of linear movement	Extremely simple by means of cylinders	Extremely simple by means of cylinders
Signal linkage between hydraulic system and other system		pneumatics operation of directional- control valves
Criterium	Electrics/ electronics	Mechanics
Energy carrier	Electrons	Shafts, linkage, belts, chain, wheels etc.
Energy transmission	Electrically conductive material (cables etc.)
Conversion from or into mechanical energy	Generators,batteries, Electric (E) motors, magnets,solenoids, linear (induction) motor
Most important characteristic quantities	Voltage V, electric current i	Force,torque, velocity, rotational speed
Power efficiency	Fair to good Weight coefficient of E-motors is approx. 10 times that of HY motors. Electric switch, though,has considerable advantages compared to directional control valve	Good because energy conversion is not needed. Limitations become apparent when high demands are placed upon controllability
Accuracy of motion (this can be improved through , in all system by positioning action	Differs considerably on the one hand hysteresis and slippage, on the other hand synchronous motors and stepping motors	Excellent due to positive mechanical connection (index, toothed gearing, etc)
efficiency	Good. As long as electricity is available as primary energy	Good. Due to their being no energy conversion, mechanical frictional losses
Controllability	For small power: excellent,for larger powers fair to good By means of switches,relays ,semiconductors,variable speed motors and variable resistors etc.	Fair to good Through gearing and lever system etc.
Generation of linear movement	Slightly more complicated By means of linear motors	Simple by means of crank mechanism and spindle etc.
Signal linkage between hydraulic system and other system	Electromagnetic control of valves (solenoids,proportional valves),limits switches and pressure switches	Drive. Or drive take- off,on pumps, hydraulic motors, cylinders operation of valves through cams and contours