Merge pull request #388 from Peter230655/pendulum-fixed-duration

docstrings as per #348, backend= nzmpy, reduced frames

examples-gallery/beginner/plot_pendulum_swing_up_fixed_duration.py

@@ -2,10 +2,27 @@
 Fixed Duration Pendulum Swing Up
 ================================
 
+Objective
+---------
+
+- Show the use of opty with likely the simplest example possible.
+
+
+Introduction
+------------
+
 Given a compound pendulum that is driven by a torque about its joint axis,
 swing the pendulum from hanging down to standing up in a fixed amount of time
 using minimal input torque with a bounded torque magnitude.
 
+
+Notes
+-----
+
+This example uses a fixed duration. There is an example which is mechanically
+identical to this one, but it uses a variable time interval, to get the
+pendulum up as fast as possible, given the torque limitations.
+
 """
 
 import numpy as np
@@ -75,7 +92,9 @@
                known_parameter_map=par_map,
                instance_constraints=instance_constraints,
                bounds=bounds,
-               time_symbol=t)
+               time_symbol=t,
+               backend='numpy',
+)
 
 # %%
 # Use a random positive initial guess.
@@ -129,8 +148,8 @@ def animate(i):
     return line, time_text
 
 
-ani = animation.FuncAnimation(fig, animate, range(num_nodes),
-                              interval=int(interval_value*1000), blit=True,
+ani = animation.FuncAnimation(fig, animate, range(0, num_nodes, 4),
+                              interval=int(interval_value*1000*4), blit=True,
                               init_func=init)
 
 plt.show()