I am having trouble getting the engine speed to 0 rpm when simulating a series hybrid vehicle controller.

Hi, I am having trouble controlling the motor block speed to 0 when the motor start signal is 0. It works fine when I give the motor speed 800rpm when the start signal is 0

However when I give the speed 0 rpm when the signal is 0, the result is that the motor speed decreases.

I have attached the simulink model and the driving cycle I built with this question. It's built on matlab r2022a and based on the model in the following link: https://www.mathworks.com/help/sdl/ug/series-hybrid-transmission.html

If someone have any idea about a solution to my problem, I will be very grateful.

Thanks in advance to anybody that awnser to this post ! :)

Answer 1

[Sam Chak]

Hi @Thang

The Simulink file contains many components, including blocks from Stateflow and Simscape. Could you provide the same mathematical representation of the entire system that you intend to describe in a journal article, technical report, or your thesis? The requirement must be 100% the same!

We typically do not attempt to design everything or control multiple components within a single file. Instead, we divide a large system into manageable subsystems. Once all subsystems are controllable and their performances are satisfactory, we can integrate them into a single Simulink file.

My suggestion:

If the nominal model of the subsystem is available, either derived from first principles or estimated using system identification tools, then one should attempt to design a set of linear or nonlinear input signals that stabilize the subsystem and ensure that the subsystem's output behaves like the reference signal, .

Assume that the nominal model can be expressed in this simple form:

.

If the model is in transfer function, then convert it to state-space.

Design the input signal

,

such that all subsystem states in the state vector are measurable. <-- This is the initial assumption!

The model's dynamics is then forcefully transformed to

which can be rearranged to

.

If the error signal is properly defined, then

guarantees that subsystem's output tracks the reference signal.

[Thang]

I've divided the model into a subsystem as follow. My purpose is to control the speed of the engine based on the pulse, when the pulse is 1 then the speed is 4000, otherwise it will be 0, however it does not work effectively, I have attached the file below

[Sam Chak]

Do you have the mathematical model of the motor to which you would like to apply the controller? Generally, it is 90% easier to work on the mathematical model first before integrating the controller into the Simulink model.

For example, ...

%% if the motor's model is available
Gp  = tf(2, [1 2 3]);

%% then we can design a controller based on the model.
opt = pidtuneOptions('PhaseMargin', 65, 'DesignFocus', 'reference-tracking');
Gc  = pidtune(Gp, 'PIDF', opt)

Gc =
 
             1            s    
  Kp + Ki * --- + Kd * --------
             s          Tf*s+1 

  with Kp = 3.14, Ki = 3.36, Kd = 0.73, Tf = 0.00336
 
Continuous-time PIDF controller in parallel form.

%% closed-loop subsystem
Gcl = feedback(Gc*Gp, 1)

Gcl =
 
          441.2 s^2 + 1878 s + 1998
  ------------------------------------------
  s^4 + 299.7 s^3 + 1040 s^2 + 2772 s + 1998
 
Continuous-time transfer function.

%% step response
step(Gp,  10), hold on
step(Gcl, 10), grid on
legend('Open-loop', 'Closed-loop')

[Sam Chak]

Hi @Thang

The pulse wave with 50% duty cycle can be mathematically constructed in MATLAB.

Before you design the Simscape system based on a derived mathematical model, do you recall where you have stored the differential equation or transfer function of the motor? Perhaps in a personal notebook or in a piece of paper that you sandwiched in a textbook?

t   = (0:0.001:200)';
amp = 4000;     % amplitude
P   = 50;       % period
y   = amp*(1 + sign(sin(2*pi/P*t)))/2;
plot(t, y), grid on, ylim([-1e3, 5e3])
xlabel('t')
ylabel('R(t)')
title('Reference Pulse signal')

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