You can also download the file for this system by right-clicking here and selecting Save link as. Name the subsystem "DC Motor" and then save the model. In order to save all of these components as a single subsystem block, first select all of the blocks, then select Create Subsystem from Selection after right-clicking on the selected portion. The final design should look like the example shown in the figure below.
Tap a line off the rotational Integrator's output and connect it to the "Ke" block.Edit it's value to "K" to represent the motor back emf constant and Label it "Ke".Insert a Gain block attached to the other negative input of the current Add block with a line.To build the simulation model, open Simulink and open a new model window.
First, we will model the integrals of the rotational accelerationĪnd of the rate of change of the armature current. This system will be modeled by summing the torques acting on the rotor inertia and integrating the acceleration to give velocity.Īlso, Kirchoff's laws will be applied to the armature circuit. In SI units, the motor torque and back emf constants are equal, that is, therefore, we will use to represent both the motor torque constant and the back emf constant. The back emf,, is proportional to the angular velocity of the shaft by a constant factor. This is referred to as an armature-controlled motor. Only the armature current by a constant factor as shown in the equation below.
In this example we will assume that the magnetic field is constant and, therefore, that the motor torque is proportional to In general, the torque generated by a DC motor is proportional to the armature current and the strength of the magnetic field. The physical parameters for our example are: (J) moment of inertia of the rotor 0.01 kg.m^2 (b) motor viscous friction constant 0.1 N.m.s (Ke) electromotive force constant 0.01 V/rad/sec (Kt) motor torque constant 0.01 N.m/Amp (R) electric resistance 1 Ohm (L) electric inductance 0.5 H We further assume a viscous friction model, that is, the friction torque is The rotor and shaft are assumed to be rigid. The electric circuit of the armature and the free-body diagram of the rotorįor this example, we will assume that the input of the system is the voltage source ( ) applied to the motor's armature, while the output is the rotational speed of the shaft. It directly provides rotary motion and, coupled with wheels or drumsĪnd cables, can provide translational motion. A common actuator in control systems is the DC motor.
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