DC Motor: Why are Step Responses Different for Transfer Function & State Space?

7 次查看（过去 30 天）
Connor Grant
Connor Grant 2019-4-11
回答： Arkadiy Turevskiy 2019-6-20
Hello All,
I am new to MATLAB and control systems in general, so this is hopefully a nice and easy novice question.
I am trying to plot the step response of a DC motor using both the transfer function and state space model. But I am getting different answers for each of them. I was expecting them to be the same as your plotting the same response from the same system... can anyone explain why they're different? Or is there something wrong in my code?
DC Motor Being Modeled and Graphs of Step Responses are here:
https://imgur.com/a/e4HWMjn
MATLAB Code Here:
% Parameters
J=0.0113;
b=0.028;
L= 0.1;
R=0.45;
K=0.067;
% Transfer Function - Open Loop Response
s = tf('s');
P_motor = K/(s*((J*s+b)*(L*s+R)+K^2))
t = 0:0.001:0.2;
step(P_motor,t)
% State Space - Open Loop Response
A = [-b/J K/J
-K/L -R/L];
B = [0
1/L];
C = [1 0];
D = 0;
motor_ss = ss(A,B,C,D)
t = 0:0.001:0.2;
step(motor_ss,t)

请先登录，再回答此问题。

回答（1 个）

Arkadiy Turevskiy
Arkadiy Turevskiy 2019-6-20
It looks like the transfer function is from voltage to angle, while state-space is from voltage to angular rate (speed).
If you remove the integrator from the transfer function, then the two are exactly the same.
P_motor = K/((J*s+b)*(L*s+R)+K^2)

社区

更多回答在  Power Electronics Control

类别

在 Help Center 和 File Exchange 中查找有关 Motor Drives 的更多信息

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by