experiments: ball speed detector example

experiments/ball_speed.py

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+import collections
+
+import numpy as np
+
+from flyvr.control.experiment import Experiment
+
+
+class _MyExperiment(Experiment):
+
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        self._speed_hist = collections.deque(maxlen=33)
+
+    def process_state(self, state):
+        self._speed_hist.append(state.speed)
+        if np.mean(state.speed) > 0.03:
+            print(self.is_started(), self.is_backend_ready(Experiment.BACKEND_VIDEO), self.is_stopped())
+            print("SPIN ", state.frame_cnt, "=", np.mean(state.speed))
+
+experiment = _MyExperiment()