#Scilab filter design how to#

In the next section, we will connect some input to this plant and measure its output by an oscilloscope. For our transfer function (12), the data is typed in as shown in Figure 5.įigure 5 A dialog window for setting transfer function parameters For this block, numerator and denominator in terms of polynomial of s can be put into the input field directly. When a user clicks on this block, a parameter dialog window emerges.

The standard block for transfer function can be located in Continuous time systems palette, under the name CLR. Here we assume that the reader has some familiarity with basic functionality of Xcos to the level that she could create some simple diagram using blocks from standard palettes. Xcos is a simulation engine that comes with Scilab. Note that the row vector passed to poly(), representing the polynomial coefficients, starts with the lowest order of s. In this method, the numerator and denominator of P are created first, as a number 1 for the former and a polynomial of ‘s’ for the latter. Now P is ready to be used by other commands such as bode, freqresp etc.Īnother method that eventually yields the same P is shown below. But the first argument ‘c’ passed to syslin tells Scilab that this is a continuous-time system. The interactive response shown in Scilab console does not look any different than before. So one more step is needed to convert it to a continuous-time linear transfer function, by using the syslin() command However, this data format still lacks some inside information necessary for further processing such as frequency response plot. One method begins by creating the Laplace variable sĪnd then use it to form P as described by (12)

#Scilab filter design how to#

Now we demonstrate how to construct a transfer function such as (12) in Scilab. Hence the resulting transfer function becomes Let’s put some values to the parameters, say, J = 10, B = 0.1. So, the transfer function for a robot joint driven by DC motor we will be using in our study modules is in the form The reduced block diagram of (10) can be drawn as in Figure 4.įigure 4 reduced block diagram of robot joint dynamics With B = B m + k ek t/R represents effective damping, u = (K_t/R)V control input, and d = τ l(t)/r disturbance input. These two equations correspond to second order differential equation in time domainīy omitting parameter subscripts, (9) can be rewritten as So the transfer functions in (5) and (6) reduce to To simplify the equation further, we can assume that the electrical constant L/R is much smaller than the mechanical constant J m/B m. Similarly, the transfer function from τ l to θ m is found by setting V=0. The transfer function from V(s) to θ m can be derived by setting τ l = 0, which gives This can be drawn as a block diagram in Figure 3.įigure 3 block diagram of the robot joint dynamics in Figure 1 It is left to the reader to verify that, in Laplace domain, the joint dynamics in Figure 1 can be described by From now on we omit the a subscript in the armature inductance and resistance. To develop the electrical side of DC motor, consider the model shown in Figure 2.įigure 2 a model of permanent magnet DC motor We want to describe a model in transfer function form so that a block diagram can be drawn. By simple calculation, it is easy to show that the rotational motion in terms of θ m is described by Let J m = J a + J g be the sum of motor and gear inertia. įigure 1 robot joint connected to DC motor via a gear transmission

To be concrete, we consider in Figure 1 a simple diagram of robot joint driven by DC motor through a gear transmission with ratio r:1. Hence, in this module we show how to formulate a transfer function in Scilab and plot its frequency response. For analysis and design in frequency domain such as the so-called classical method, loopshaping, or Quantitative Feedback Theory (QFT), some form frequency response data is needed. Then a feedback diagram is constructed with this plant model and a controller described as transfer functions, either in continuous or discrete time domain. In general, the first step for control system analysis and design is to acquire a model that represents the actual plant to be controlled. Scilab commands for plotting frequency responses.How to create a transfer function in Scilab.This article is contained in Scilab Control Engineering Basics study module, which is used as course material for International Undergraduate Program in Electrical-Mechanical Manufacturing Engineering, Department of Mechanical Engineering, Kasetsart University.