advertisement

To days Outline Callbacks MATLAB And Simulink S-functions Project suggestions MATLAB and Simulink Lecture 7 1 Callbacks A callback is a MATLAB command that executes when a certain event occurs. Opening a model Double-click, moving etc of Simulink blocks Callback are installed using the MATLAB command Set_param(object, parameter, value) object: A MATLAB string containing the name of the model or a path to the block parameter: A MATLAB string containing the name given to the event of interest. value: A MATLAB string containing the callback. MATLAB and Simulink Lecture 7 2 Callbacks MATLAB and Simulink Lecture 7 3 Callbacks Example Create a simple model in Simulink that contains a gain a sine wave a scope. When a user tries to run the model he should be prompted for a gain value MATLAB and Simulink Lecture 7 4 MATLAB and Simulink When running a simulink model we have access to variables in the MATLAB workspace What if we want to set variables from a function All parameter values in the different simulink blocks can be set with the command: set_param Set_param(’Object’, ’parameter’, value’) All parameter values in the different simulink blocks can be viewed with the command: get_param get_param(’Object’, ’parameter’,) MATLAB and Simulink Lecture 7 5 MATLAB and Simulink Example: Set the gain value in the model: Mymod.mdl MATLAB and Simulink Lecture 7 6 MATLAB and Simulink How can we set parameters in a closed model? What if the model has several levels of subsystems? MATLAB and Simulink Lecture 7 7 MATLAB and Simulink Example: Create a Graphical user interface and a simulink model of the double tank system. A user should be able to set process parameters: Bottom area Area of the bottom hole Pump constant. The user should also be able to set gain values in the controller. MATLAB and Simulink Lecture 7 8 MATLAB and Simulink MATLAB and Simulink Lecture 7 9 S-functions Allows us to define custom Simulink blocks S-function represents a general Simulink block with: input vector u output vector y state vector x Continuous states xc Discrete states xd MATLAB and Simulink Lecture 7 10 S-functions We must define: S-function must compute the output Initial values of each state Define the size of the state vector Define the size of the output vector Define the size of the input vector Set sample time if there is a discrete model. y=g(x,u,t,p) Update the discrete states xd(k+1)=fd(x,u,t,p) Compute the derivatives xc’=fc(x,u,t,p) MATLAB and Simulink Lecture 7 11 S-functions / m-file sfunc_name(t,x,u,flag,p1..pn) function [sys,X0,str,ts]=sfunc_name(t,x,u,flag,p1..pn) switch flag, case 0, [sys,x0,str,ts]=mdlInitializeSizes; case 1, sys=mdlDerivatives(t,x,u); case 2, sys=mdlUpdate(t,x,u); case 3, sys=mdlOutputs(t,x,u); case 4, sys=mdlGetTimeOfNextVarHit(t,x,u); case 9, sys=mdlTerminate(t,x,u); otherwise error(['Unhandled flag = ',num2str(flag)]); end MATLAB and Simulink Lecture 7 12 S-functions mdlInitializeSizes Return the sizes, initial conditions, and sample times for the Sfunction. function [sys,x0,str,ts]=mdlInitializeSizes sizes = simsizes; sizes.NumContStates = 0; sizes.NumDiscStates = 0; sizes.NumOutputs = 0; sizes.NumInputs = 0; sizes.DirFeedthrough = 1; sizes.NumSampleTimes = 1; % at least one sample time is needed sys = simsizes(sizes); x0 = []; % initialize the initial conditions str = []; % str is always an empty matrix ts = [0 0]; % initialize the array of sample times return MATLAB and Simulink Lecture 7 13 S-functions mdlDerivatives Return the derivatives for the continuous states. function sys=mdlDerivatives(t,x,u) sys = []; return MATLAB and Simulink Lecture 7 14 S-functions mdlUpdate Handle discrete state updates, sample time hits, and major time step function sys=mdlUpdate(t,x,u) sys = []; return MATLAB and Simulink Lecture 7 15 S-functions mdlOutputs Calculate the output function sys=mdlOutputs(t,x,u) sys = []; return MATLAB and Simulink Lecture 7 16 S-functions mdlGetTimeOfNextVarHit Return the time of the next hit for this block. Note that the result is absolute time. Note that this function is only used when you specify variable discrete-time sample time [-2 0] in the sample time array in mdlInitializeSizes. Example, set the next hit to be one second later. function sys=mdlGetTimeOfNextVarHit(t,x,u) sampleTime = 1; sys = t + sampleTime; return MATLAB and Simulink Lecture 7 17 S-functions mdlTerminate Perform any end of simulation tasks. function sys=mdlTerminate(t,x,u) sys = []; return MATLAB and Simulink Lecture 7 18 S-functions Example: Create a continuous s-function that describes the double tank system. Initial condition Upper 0.1m Lower 0.2m Output should be the difference between the two tanks. MATLAB and Simulink Lecture 7 19 S-functions We must define: Initial values of each state Define the size of the state vector Define the size of the output vector Define the size of the input vector Compute the derivatives xc’=fc(x,u,t,p) S-function must compute the output y=g(x,u,t,p) MATLAB and Simulink Lecture 7 20 Exercises on this days topics Work on the second laboration. It’s time to start thinking about a project. MATLAB and Simulink Lecture 7 21 Project suggestions Design of a Water Clock Double Pendulum DC and AC motors Two Salty Tanks Animate a bouncing ball Search the internet and library for interesting projects. MATLAB and Simulink Lecture 7 22 Design of a Water Clock A 12-hour water clock is to be designed with the dimensions shown in the sketch. The shape of the clock is obtained by revolving the curve y = f(x) around the y axis. Define the shape function, f(x), and the radius of the circular hole at the bottom that gives a constant water level decrease of 4 in/hr. MATLAB and Simulink Lecture 7 23 Double Pendulum The position of the two masses x1 l1 sin(1) y1 l1 cos(1) x2 l1 sin(1) l2 sin( 2 ) y2 l1 cos(1) l2 cos( 2 ) The differential equation describing the movement 0 (m1 m2 )l11 m2l22 cos(1 2 ) m2l222 sin(1 2 ) g (m1 m2 ) sin(1) 0 m2l22 m2l11 cos(1 2 ) m2l112 sin(1 2 ) gm2 sin(2 ) MATLAB and Simulink Lecture 7 24 Two Salty Tanks Consider the cascade of two tanks as shown in the figure. Assume that the volumetric flow rate throughout the system is constant with q = 5 gal/s. With a constant flow rate the volumes of both Tank 1 and Tank 2 are also constant with V1 = 100 gal and V2 = 200 gal. If the inlet to Tank 1 is pure water and the initial masses of the salt dissolved in the tanks are m1 = m2 = 50 lbm, determine the amount of salt in each tank versus time. Also determine the time and magnitude of the mass in Tank 2 when m2 is at its highest value. MATLAB and Simulink Lecture 7 25 DC and AC motors DC Motor AC Motor Change frequancy, magnetic field, view voltage, current and emc. MATLAB and Simulink Lecture 7 26 Animate a bouncing ball Throw or drop an elastic ball with some initial velocity and angel Simulate how the ball will bounce A user should be able to set different parameters as Elastic constant Initial angle Initial velocity MATLAB and Simulink Lecture 7 27