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发表于 2009-9-6 22:27:15
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来自: 中国四川成都
The comaprison is an electrohydraulic servo vs electhydraulic proportional valve?
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$ k! J- a) R6 R( W8 _9 V* VThe main difference is the overlap of the spool when in it's nuetral position. The servo valve has a slightly negative overlap, the proportional has a positive overlap which creates a dead-band. It is this dead-band that effects the response time of a proportional valve, even the ones that do have position feed-back.
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There is usually another difference in the amplifier card that drives the proportional valve. They will often have dead-band compensation circuitry to get a more linear response from the valve with regards to it's input signal. This can make the proportinal valve seem stepless with regards to it's deadband however there still is a response time issue as it takes a given amount of time for the spool to travel past the overlap.. e8 M9 h. G- _( ]+ x( x* u0 C
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To make matters more confusing, an electro hydraulic servo valve is a proportional valve and is sometimes referred to as a proportinal valve. I like to stick with the term proportional servo. |
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