DC motor modeling in Simulink - Step-by-Step Execution

Concept Flow - DC motor modeling in Simulink

Start: Define motor parameters

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Build electrical circuit model

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Build mechanical system model

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Connect electrical and mechanical parts

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Add input voltage and load torque

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Run simulation

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Observe motor speed and current outputs

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End

The flow shows building the DC motor model step-by-step in Simulink, from parameters to simulation and output observation.

Execution Sample

Simulink

1. Define motor constants (R, L, Kt, Ke, J, B)
2. Create electrical subsystem (Voltage, Resistor, Inductor)
3. Create mechanical subsystem (Inertia, Friction, Torque)
4. Connect subsystems with feedback
5. Run simulation to get speed and current

This code outlines the main steps to model a DC motor in Simulink and simulate its behavior.

Execution Table

Step	Action	Parameter/Variable	Value/State	Output/Result
1	Define resistance R	R	2 Ohms	R set
2	Define inductance L	L	0.5 H	L set
3	Define torque constant Kt	Kt	0.1 Nm/A	Kt set
4	Define back EMF constant Ke	Ke	0.1 V/(rad/s)	Ke set
5	Define inertia J	J	0.01 kg.m^2	J set
6	Define friction B	B	0.001 Nms	B set
7	Build electrical circuit	Voltage input	24 V step	Electrical subsystem ready
8	Build mechanical system	Load torque	0.05 Nm	Mechanical subsystem ready
9	Connect electrical and mechanical	Feedback loop	Connected	Complete motor model
10	Run simulation	Time	0 to 5 seconds	Simulation running
11	Observe speed output	Speed	Ramps to ~200 rad/s	Speed output plotted
12	Observe current output	Current	Peaks then stabilizes	Current output plotted
13	Simulation ends	Time	5 seconds	Simulation complete

💡 Simulation ends after 5 seconds, motor speed and current outputs are stable.

Variable Tracker

Variable	Start	After Step 6	After Step 9	After Step 12	Final
R (Resistance)	undefined	2 Ohms	2 Ohms	2 Ohms	2 Ohms
L (Inductance)	undefined	0.5 H	0.5 H	0.5 H	0.5 H
Kt (Torque Const.)	undefined	0.1 Nm/A	0.1 Nm/A	0.1 Nm/A	0.1 Nm/A
Ke (Back EMF Const.)	undefined	0.1 V/(rad/s)	0.1 V/(rad/s)	0.1 V/(rad/s)	0.1 V/(rad/s)
J (Inertia)	undefined	0.01 kg.m^2	0.01 kg.m^2	0.01 kg.m^2	0.01 kg.m^2
B (Friction)	undefined	0.001 Nms	0.001 Nms	0.001 Nms	0.001 Nms
Speed (rad/s)	0	0	starts rising	approx 200	approx 200
Current (A)	0	0	peaks ~12	stabilizes ~2.5	stabilizes ~2.5

Key Moments - 3 Insights

Why does the motor speed start at zero and then increase during simulation?

At step 11 in the execution table, the speed output ramps up because the motor starts from rest and accelerates due to the applied voltage and torque.

Why does the current peak early and then stabilize?

As shown in step 12, current peaks initially to overcome inertia and friction, then stabilizes as the motor reaches steady speed.

How are electrical and mechanical parts connected in the model?

Step 9 shows the feedback loop connection where electrical torque affects mechanical speed and back EMF affects electrical voltage.

Visual Quiz - 3 Questions

Look at the execution table, what is the value of resistance R after step 6?

A 0.1 Nm/A

B 0.5 H

C 2 Ohms

D Undefined

💡 Hint

Check the 'Parameter/Variable' and 'Value/State' columns at step 1 and step 6.

At which step does the simulation start running?

A Step 9

B Step 10

C Step 7

D Step 12

💡 Hint

Look for the row where 'Action' is 'Run simulation' in the execution table.

If the load torque is increased, how would the speed output change in the simulation?

A Speed would decrease or stabilize at a lower value

B Speed would increase faster

C Speed would remain the same

D Speed would become zero immediately

💡 Hint

Consider the mechanical load effect on speed from the 'Mechanical subsystem' step in the execution table.

Concept Snapshot

DC Motor Modeling in Simulink:
- Define motor parameters (R, L, Kt, Ke, J, B)
- Build electrical and mechanical subsystems
- Connect subsystems with feedback
- Apply input voltage and load torque
- Run simulation to observe speed and current outputs

Full Transcript

This visual execution trace shows how to model a DC motor in Simulink step-by-step. First, motor parameters like resistance, inductance, torque constant, back EMF constant, inertia, and friction are defined. Then, the electrical circuit and mechanical system are built separately. These subsystems are connected with feedback loops to represent the motor's behavior. Input voltage and load torque are applied. The simulation runs from 0 to 5 seconds, during which motor speed starts at zero and ramps up to about 200 radians per second, while current peaks initially and then stabilizes. Key moments include understanding why speed ramps up, why current peaks, and how electrical and mechanical parts interact. The quiz questions check understanding of parameter values, simulation steps, and effects of load torque on speed.