MBSDLecture 202-Motor Model, Display Subsystem

Lecture 2:Motor Model andLecture 2: Motor Model and Display SubsystemMotor Motor Battery Motor V I ωτ=−f h b Thfrom the battery. ÎThe motor current should be negative to discharge the battery.Motor Motor Battery Motor V I ωτ=−into the battery.The motor current into the battery. ÎThe motor current should be positive to charge the battery.MotorMotor Battery Motor V I ωτ=−complicated as our understanding of the complicated as our understanding of the system increases.M d l O t t(Si D i li)•Model Outputs (SimDriveline):–Motor Torque7 Place a new subsystem part (Simulink/Commonly Used Blocks)in your circuit and change the nameto “Electric_Motor.”Double-click on the subsystem block to open it:•Motor_CurrentM t C t•Motor_Diagnostics9 We also have one SimDriveline connection port(SimDriveline/Utilities).Place this part in your model and rename it as“Motor_Port.”10 We now have all of the input and output ports forWe now have all of the input and output ports forour motor model. All that is left is for us to buildthe actual model.•The inertia part is located in theSimDriveline/Solver & Inertias library.12 The inertia part specifies the inertia for all rotating parts of the motor. We will define this inertia in the init file. Double-click on the inertia part and change the value to “Motor_Inertia.”13We should find the inertia from the motor specifications ormeasure the inertia. Once a value is obtained, we will specify it in the init file:Next, we can calculate the motor current asBatteryMotorMotorMotor V I ωτ−=Use a Motion Sensor (SimDriveline/Sensors &Actuators ) to measure the motor shaft speed in r/s.14_q_–Motor torque Nm–Motor_Current_Adouble-click on the bus creator part and change the number from 2 to 3.Bus creator after makingchange.18 Complete the model as shown below.input and outputs as shown:input and outputs as shown:Top Level Block Diagram20•Connect the blocks as shown:22 The motor port is not in a convenient location to connect it to the reardiff. We can fix this problem by:•Double-clicking on the Electric_Motor subsystem to open it.•Double-clicking on the “Motor_Port” part to open its dialog box.You will see the dialog box shown next:23Double-click here.Change this to right.After making this change, we can easily connect the motor and rear diff.busses using the bus creator part busses using the bus creator part (Simulink/Commonly Used Blocks).28 Top Level Block Diagramphysical system.It is for simulation purposes physical system. It is for simulation purposes only and generates a torque request that would normally come from the vehicle’s accelerator and brake pedals.•The desired speed will be stored in a variable.•Rename the subsystem Driver. Rename the subsystem“Driver”±1.•Use the Saturation part located in the Simulink/Commonly Used Blocks library.and1and -1.•Rename the output terminal to “Driver Torque Request.”36•The saturation limits are specified asshown:as shown: as shown:create several plots to display varioussignals in different configurations.•We will also use this subsystem to logdata.We will show two methods of creating adisplay The first method will use a Scope display. The first method will use a Scopeblock. The seconds will be shown laterand use the Signal and Scope Manager.(Simulink/Commonly Used Blocks) and the Scope(Simulink/Commonly Used Blocks) to create a display of the important signals.43 Creating the Display•Double-click on the Bus Selector part •Click on the +Click on the+signs in the“Signals in theBus” windowto view theil blavailablesignals.•Select the signals in the order you want Select the signals in the order you want them to appear on the bus extractor.Selector part.•Next, double-click on the Scope part:Double-click here.47 Click on this button.•Click on the Parameters buttonChange this to 5.48Click on the Data historyTab.Click here to uncheck thisbox. Deselecting this boxbox.Deselecting this boxwill display all data in oursimulation.49 Box unchecked.Click the OK Button.Close the scopewindow and returnwindow and returnto the model.Resize the scopepart and connectthe signals.5052Set to 60.Select ode23tbSet to Auto.54Set to error.Diagnostics selected.Set to error.•These selections will highlight an algebraic if one is detected.Running the Simulation•Click the OK button.•Select Simulation and then Start from the Simulink menus or click the play button 55Simulink menus or click the play button.•It appears that we have an error.two of our subsystems The Algebraic loop two of our subsystems. The Algebraic loop is highlighted in red:57 Algebraic Loop•If you look inside the Electric_Motor subsystem, you will see the offending components in that subsystem:In order for Simulink to calculate the motor current, it needs to know the battery voltage.58 Algebraic Loop•If you look inside the Battery subsystem, you will see the offending components in that subsystem:In order to calculate the battery voltage, Simulink needs to know the motor current!information it needs to perform this information it needs to perform this calculation.part (to either the Battery model or the motor61•The memory block is a one time step delay. In the division calculation, Simulink will use the battery voltage from the previous time step. Thus the batterywill use the battery voltage from the previous time step.Thus the battery voltage is know, and Simulink can calculate the motor current.•Rerun the simulation and see if this fixes the problem.•You may want to ask yourself the question, what is the output value of the memory block at time zero (when the simulation starts)? (Obviously this implies that the block knows the input at time less than zero, which has all kinds of philosophical implications about the space-time continuum….)62•The problem is fixed, but we get anothererror.•Click on the link to jump to the error.63 According to the errormessage, this signal mustmessage,this signal mustbe Infinite, or Nan.65•For the first time step, what is the input to the Divide block?For the first time step what is the input to the Divide block?•The Memory block outputs the value from the previous time step.•For the first time step, what is the previous value.•If the block outputs a 0, we get a divide by zero, and the Divide block either outputs Inf or Nan.•We need to move the Memory block somewhere else to eliminate the algebraic loop.66Memory block removed.67 Memory block added to thebattery model.Rerun the Simulation68rpm signal.rpm signal.Demo___________ Debugging the ModelDebugging the Model72 Vehicle speedOK.Motor rpm spike.Motor rpm spike74•If there is no skidding, the tire speeds should be the same as the vehiclespeed.•Run the simulation75Zoom in here.76Tire speed same as vehicle speed.Tire speeddifferent than vehicle speed.Open the driver block and add a scope to •Open the driver block and add a scope tothe driver torque request signal.Rerun the simulation and view the scope.78 Max torque (1).Tire skiddinghappens here.Vehicle cruising gat 60 mph here.Rate Limiter80•The rate limiter places a limit on how fasta signal can increase or decrease.•The default rising and falling rates are1/second.•We will use the default values.•Since the driver torque request signal isbetween -1 and +1•Our motor will go from no torque (0)•Our motor will go from no torque(0)to full torque (1) in one second.•Our motor will go from full forwardtorque (1) to full reverse torque (-1) intwo seconds.Run a simulation with the rate limiter.81Things areworse!82 Motor rpm goingnegative.What do younotice aboutthis?•Let s plot the motor torque using a scope.Let’s plot the motor torque using a scopeRate limiterremoved.84 Scope added.85Tire skiddinghappens here.h hZoom in on thissection.86Traces in natureare very rarelystraight. Usuallythings are curved.Zoom in someZoom in somemore.87Simulation point.Simulation point.pLooks like at i ht listraight lineconnecting twosimulation points.Model Debugging•Another hint comes from the MATLAB command window.88What is this?p glike we had a step of 0.35 seconds that was too large.•Let’s try a smaller step size.•Select Simulation and then Configuration Parameters from the Simulink menus.•Change the Max Step size from Auto to 0.01 (seconds)90This was set to Auto.Change it to 0.01.•This parameter specifies that the maximum time between simulation points will be 0.01 seconds. (It between simulation points will be001seconds(Itcan be smaller if necessary.)•Rerun the simulation with this change.91 and negative battery voltages.•How does our model breakdown if the motor current is too large?Demo___________。