| 摘要 |
An automatic player piano includes keys driven for the angular motion through a hybrid feedback control loop; a controller, a key position sensor, a plunger velocity sensor and a solenoid-operated key actuator form parts of the hybrid feedback control loop for each key, and a current key position and a plunger velocity are reported to the controller; the controller determines a series of target position or a reference trajectory and a target velocity, and periodically compares a composite current position and a composite current velocity, which are determined on the basis of the current key position and current plunger velocity, with the target position and target velocity to see whether or not the key travels on the reference trajectory; if the answer is negative, the controller adjusts the driving signal to a proper duty ratio so as to force the key to travel on the reference trajectory.
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