Abstract
This study sets out to demonstrate the practical application of PRBS (Pseudo-Random Binary Sequence) as an accurate 'on-line' identification technique for electro-hydraulic velocity servos. This was achieved by a comparison with classical step response and frequency response methods which gave close agreement between the three methods (Section 3 and 4). Although slower than the step response technique, PRES has the advantage of providing a more rapid identification than other conventional techniques. In addition, PRBS gives 'on-line' identification of a fully loaded system during its normal operation which is not possible with conventional forms of identification such as are currently used by fluid power engineers. Furthermore, the use of the cross-correlation technique minimises the effect of system noise on the identification process. Up to the present time PRBS has only been found most satisfactory for linear system identification-although some experimental work has been carried out in the dead zone and saturation regions of the servo-valve. Finally, the PRBS technique is used in conjunction with a minicomputer (Section 5) and the results compared with results obtained using hardwired equipment. The use of this identification technique is then further extended to encompass an adaptive loop application (Section 6).