Motor startup and braking simulation in Simulink - Mini Project: Build & Apply

Motor startup and braking simulation

📖 Scenario: You are working as an engineer to simulate how a motor starts up and then brakes. This helps understand how the motor behaves in real life when it is turned on and then stopped.

🎯 Goal: Create a simple model that simulates a motor starting up with a constant voltage and then braking by applying a braking torque. You will set up the motor parameters, configure the startup and braking phases, run the simulation, and observe the motor speed over time.

📋 What You'll Learn

Create a DC motor model

Set motor parameters: resistance, inductance, torque constant, inertia

Add a voltage input to start the motor

Add a braking torque input to stop the motor

Simulate motor speed over time

Plot motor speed to see startup and braking behavior

💡 Why This Matters

🌍 Real World

Simulating motor startup and braking helps engineers design motor controllers and predict motor behavior in machines like electric vehicles or industrial equipment.

💼 Career

Understanding motor dynamics and simulation is important for roles in electrical engineering, control systems, and automation industries.

1

Set up motor parameters

Create variables in the MATLAB workspace for the motor parameters: R (resistance) = 2 ohms, L (inductance) = 0.5 H, Kt (torque constant) = 0.1 Nm/A, and J (inertia) = 0.01 kg.m^2.

Simulink

% Define motor parameters
% Your code here

Hint

Use simple assignment statements to create each variable with the exact values.

2

Configure startup and braking inputs

Create two time vectors: t_startup from 0 to 2 seconds and t_brake from 2 to 4 seconds. Create a voltage input vector V that is 24 volts during startup and 0 volts during braking. Create a braking torque vector Tb that is 0 during startup and 0.5 Nm during braking.

Simulink

R = 2;  % Resistance in ohms
L = 0.5;  % Inductance in henrys
Kt = 0.1; % Torque constant in Nm/A
J = 0.01; % Inertia in kg.m^2
% Create time vectors and input signals
% Your code here

Hint

Use ones and zeros functions to create constant vectors for voltage and braking torque.

3

Simulate motor speed using differential equation

Write code that calculates motor speed omega over time using the equations: J * d(omega)/dt = Kt * I - Tb and L * dI/dt = V - R * I - Kt * omega. Use Euler's method with time step 0.01 seconds to simulate from 0 to 4 seconds. Store the speed values in omega.

Simulink

R = 2;  % Resistance in ohms
L = 0.5;  % Inductance in henrys
Kt = 0.1; % Torque constant in Nm/A
J = 0.01; % Inertia in kg.m^2
t_startup = 0:0.01:2;  % Time from 0 to 2 seconds
 t_brake = 2.01:0.01:4; % Time from 2.01 to 4 seconds
V = [24*ones(size(t_startup)) zeros(size(t_brake))];  % Voltage input
Tb = [zeros(size(t_startup)) 0.5*ones(size(t_brake))];  % Braking torque
% Simulate motor speed omega over time
% Your code here

Hint

Use a for loop from 2 to N to update current and speed using Euler's method.

4

Plot motor speed over time

Plot the motor speed omega against time vector t which combines t_startup and t_brake. Label the x-axis as 'Time (s)' and y-axis as 'Motor Speed (rad/s)'.

Simulink

R = 2;  % Resistance in ohms
L = 0.5;  % Inductance in henrys
Kt = 0.1; % Torque constant in Nm/A
J = 0.01; % Inertia in kg.m^2
t_startup = 0:0.01:2;  % Time from 0 to 2 seconds
 t_brake = 2.01:0.01:4; % Time from 2.01 to 4 seconds
V = [24*ones(size(t_startup)) zeros(size(t_brake))];  % Voltage input
Tb = [zeros(size(t_startup)) 0.5*ones(size(t_brake))];  % Braking torque

dt = 0.01;
N = length(V);
omega = zeros(1, N);
I = 0;
for k = 2:N
    dI = (V(k-1) - R*I - Kt*omega(k-1))/L;
    I = I + dI*dt;
    domega = (Kt*I - Tb(k-1))/J;
    omega(k) = omega(k-1) + domega*dt;
end

% Plot motor speed
% Your code here

Hint

Use plot(t, omega) and label axes with xlabel and ylabel. Add a title and grid for clarity.