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 |
Jumat, 21 Mei 2010
TABLE OF COMPARISON
Comparison Data
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