Add markov example

KybernetikJo · KybernetikJo · commit 4c1f4ca33b0d · 2024-07-04T17:45:24.000+02:00
diff --git a/examples/markov.py b/examples/markov.py
@@ -0,0 +1,60 @@
+# markov.py
+# Johannes Kaisinger, 4 July 2024
+#
+# Demonstrate estimation of markov parameters.
+# SISO, SIMO, MISO, MIMO case
+
+import numpy as np
+import matplotlib.pyplot as plt
+import os
+
+import control as ct
+
+# set up a mass spring damper system (2dof, MIMO case)
+# m q_dd + c q_d + k q = u
+m1, k1, c1 = 1., 1., .1
+m2, k2, c2 = 2., .5, .1
+k3, c3 = .5, .1
+
+A = np.array([
+    [0., 0., 1., 0.],
+    [0., 0., 0., 1.],
+    [-(k1+k2)/m1, (k2)/m1, -(c1+c2)/m1, c2/m1],
+    [(k2)/m2, -(k2+k3)/m2, c2/m2, -(c2+c3)/m2]
+])
+B = np.array([[0.,0.],[0.,0.],[1/m1,0.],[0.,1/m2]])
+C = np.array([[1.0, 0.0, 0.0, 0.0],[0.0, 1.0, 0.0, 0.0]])
+D = np.zeros((2,2))
+
+
+xixo_list = ["SISO","SIMO","MISO","MIMO"]
+xixo = xixo_list[3] # choose a system for estimation
+match xixo:
+    case "SISO":
+        sys = ct.StateSpace(A, B[:,0], C[0,:], D[0,0])
+    case "SIMO":
+        sys = ct.StateSpace(A, B[:,:1], C, D[:,:1])
+    case "MISO":
+        sys = ct.StateSpace(A, B, C[:1,:], D[:1,:])
+    case "MIMO":
+        sys = ct.StateSpace(A, B, C, D)
+
+dt = 0.5
+sysd = sys.sample(dt, method='zoh')
+
+t = np.arange(0,5000,dt)
+u = np.random.randn(sysd.B.shape[-1], len(t)) # random forcing input
+
+response = ct.forced_response(sysd, U=u)
+response.plot()
+plt.show()
+
+markov_true = ct.impulse_response(sysd,T=dt*100)
+markov_est = ct.markov(response,m=100,dt=dt)
+
+markov_true.plot(title=xixo)
+markov_est.plot(color='orange',linestyle='dashed')
+plt.show()
+
+if 'PYCONTROL_TEST_EXAMPLES' not in os.environ:
+    plt.show()
