Pulse Width Modulation Control System Research Articles

Compensation of Pulse Width Modulated Control System in the Parameter Plane

The parameter plane technique is exploited in designing discrete compensating network for ensuring a given degree of stability to PWM systems with higher type transfer functions. Since the system is equivalent to a multi-nonlinear discrete one, the most unstable open loop frequency response loci is first determined corresponding to unique sinusoidal input signal amplitude. The nonlinear gains of the nonlinearities at this amplitude are used in characteristic equation of the closed loop system and the parameter plane method is adopted to find the compensating network parameters.

Frequency Response Analysis of Pulse Width Modulated Control System with Higher Type Transfer Functions

This paper extends the frequency response approach to the analysis of PWM system with a linear transfer function having distinct and repeated poles at the origin. With the pulse width modulator having linear or nonlinear characteristics, the scheme is always equivalent to a multi nonlinear sampled data system with interaction from several channel inputs determining the state vectors. The nonlinearity in each channel can only be approximated by straight line segments for type zero to type three transfer function. For higher type transfer functions or system with repeated distinct poles such approximations are not easy and harmonic linearisation by digital computer must be resorted to. The open loop frequency response of type two and type three systems with several steady state sinusoidal input magnitudes have been obtained and the most unstable frequency response locus determined for each case. Based on this information, system compensation and possibility of harmonic oscillations can be studied. It is als...

First Order Combined Integral Pulse Frequency and Pulse Width Modulated Control Systems

New results obtained in this paper are: (i) the extension of necessary condition of stability to necessary and sufficient condition, (ii) the relation of the condition for stability to the decision function which determines the pulse rate, (iii) determination of the zone of stability, limit cycle and instability, (iv) the improvement of the existing stability boundary and (v) the relation of system response to the characteristic roots within a unity circle.

On a Piezoelectric Flapper Type Servovalve Operated by a Pulse-Width-Modulated-Signal

As a first step to developing a servovalve with minimum moving parts, a new servovalve is devised in which a piezoelectric flapper (a quartz strip) is used instead of a conventional flapper actuated through a torque motor. A servovalve of this type is desirable from the viewpoint of fast response, however it has not been in common use because of the strong hysteresis of piezoelectric material. In order to linearize the nonlinear characteristics of the flapper, a pulse width modulated wave is used as the input signal to the flapper. The frequency characteristics of the pulse width modulator is theoretically analyzed in detail to establish the theoretical basis of the pulse width modulation control system. As well-known, this basis has been ambiguous so far. The experimental frequency responses show that the bandwidth of the servovalve using this new technique is comparable to that of conventional valves having the same power output in spite of its simple construction in comparison with conventional ones.

A Popov-type stability criterion for control systems with natural pulse-width modulation†

A sufficient L 2(0, ∞) stability criterion for a class of pulse-width modulated control systems with ‘ natural sampling ’ of the ramp type is presented. The condition provides a straightforward geometric interpretation of the Popov plane.

Periodic Modes in Pulse Width Modulated Control Systems by a Modified Discrete Sequence Method

Periodic Modes in Pulse Width Modulated Control Systems by a Modified Discrete Sequence Method

Essential Linearization: A Synthesis Technique for P.W.M. Control System

Pulse-width modulated control systems are very attractive for the practicing control engineer due to their low cost, and ruggedness of design. Unfortunately these interesting features are impaired by the mathematical difficulties associated with the design of these systems, as they are known to be highly non-linear. In most cases the control engineer must resort to simulation or bench design in order to achieve desired objectives both in transient and steady-state specifications. This paper presents a method to overcome these problems and shows how the design of pulse-width modulated systems, or more generally, duration-modulated control input systems, may be achieved using standard linear synthesis techniques. The method is based on the fact that any duration modulated control input may be considered, on a sampling period; to be the sum of its mean value plus an alternative component. Then it is shown that the plant’state vector depends linearly upon the mean-value component and that the alternative terms are responsible for the non-linearity of duration-modulated control systems.Instead of controlling the true plant’s output, only the part of the output depending on the mean-value component is controlled ; this part is called the essential output. To get the essential output signal, the alternative term on each sampling period are obtained via a special design of the duration-modulator device. These alternative components are then fed into a reduced model (excluding the plant’s integrators) of the plant. By substracting the model’s output from that of the plant the essential output is obtained and can be used as a feedback signal in a linear control scheme.It is shown that if the reduced model is asymptotically stable, the true plant’s output mean value converges asymptotically towards that of the essential output ; thus the control of the essential output implies that of the plant, at least in terms of mean-value. The method is applied to the dead-beat control of a P.W.M. second order system, it is shown that the essential output feedback control system gives a quasi-optimal response.The basic schemes of duration-modulators of the lead and lag types are given. When the plant has two open loop integrators a combined lead-lag modulator (centered modulator) must be used.A circuit for linear thyristor control is given.The method has actually be applied to the linear bidirectionnal speed control of a small D.C. motor.

Open loop pulse-width modulated control system with signal plus noise as input

Open loop pulse-width modulated control system with signal plus noise as input

Statistical study of pulse-width modulated control systems

This paper describes a statistical study of pulse-width modulated control systems. The pulse-width modulator is first considered for positive signals only. The output of this is then compared with the output of the approximate model where the pulse-width modulator is replaced by sampler, a saturating nonlinear element, and a hold circuit based on equal area approximation. An example is worked to show that there is little error involved in the use of this approximation. Using this as the basis, the open loop case is worked out for Gaussian inputs. The results have been tabulated and graphed. In the solution of the closed loop system, the difficulty of the calculation of the cross-correlation function is overcome by making another approximation based on the separability property of the Gaussian process. This facilitates the solution of the whole problem and the relationship of output mean square value to input mean square value is graphed for a simple example.