Some DDC system design procedures
J. B. Knowles · Institution of Engineering and Technology eBooks · 1982
As a result of the enormous impact of microprocessors, electronic engineers, with sometimes only a cursory back ground in control theory, are being involved in direct digital-control (D.D.C.) system design. There appears to be a real need for an easily understood and simply imple mented comprehensive design technique for single-input d.d.c. systems. The proposed design technique provides, first of all, a simple calculation that ensures that the data sampling rate is consistent with the control system's accuracy specification or the fatigue life of its actuators. Pulsed transfer-function design for a plant controller is based on two simple rules and a few standard frequency response curves, which are easily computed once and for all time. Structural resonances are eliminated by digital notch filters, the pole-zero locations of which are directly re lated to the frequency and bandwidth of an oscillatory mode; this is exactly as with analogue networks. In addition a computationally simple formula gives an upper bound on the amplitude of the control error (deviation) component due to multiplicative rounding effects in the digital computer; this thereby enables the selection of a suitable machine wordlength or machine. A distinct advantage of the proposed design technique is that its implementation does not necess arily involve a complex computer-aided-design facility.