Method of estimating solenoid heat accumulation and compensating for solenoid force loss

#Not Applicable

#Not Applicable

#1. Field of the Invention

#The invention will be more fully understood by reference to the following drawings which are for illustrative purposes only:

#FIG. 1 is a graph of audio volume for a conventional player piano key which is subjected to repeated activations over a period of time.

#FIG. 2 is block diagram of a player piano solenoid drive in which temperature compensation according to an embodiment of the present invention may be practiced.

#Referring more specifically to the drawings, for illustrative purposes the present invention is embodied in the apparatus generally shown in FIG. 2 through FIG. 4. It will be appreciated that the apparatus may vary as to configuration and as to details of the parts, and that the method may vary as to the specific steps and sequence, without departing from the basic concepts as disclosed herein.

#FIG. 2 illustrates, by way of example, an embodiment of a player piano solenoid system which drives the solenoids in response to the combination of composition data and the execution of temperature compensation routines within a control device such as a microprocessor. The player piano system within the figure is shown by way of example, and not of limitation, to illustrate a control system within which the present invention may be practiced. A disk 10 containing musical composition data is shown configured for insertion in a reader 12 that communicates with a piano controller 14, which is preferably implemented as a microprocessor. It will be appreciated that a microprocessor is configured with a central processing unit (CPU) 16, a program store 18 which typically comprises read-only memory (ROM), universal asynchronous receiver-transmitter (UART) 20, random access memory (RAM) 22, and an output section 24. The method of the present invention is preferably embodied within routines 26 that are executed by piano controller 14, such as contained within the program store 18 for a microprocessor. Controller 14 is connected to a solenoid driver unit 28, also referred to herein as “driver”, by a driver communication line 30. Driver 28 is capable of controlling the FET driver transistors 32, through signal line 34, for activating a plurality of solenoids 36. In the depicted embodiment, each solenoid is associated with a particular key on the piano and subject to activation by the player-piano controller and driver circuits. It should, however, be appreciated that the present invention is applicable to a wide variety of devices and systems which require energizing one or more coils whose output is responsive to self-generated heat.

#Within the present invention, heat is tracked for each solenoid as a relative heat value contained in an array of heat values. Generally each solenoid gains heat when its coil is activated and continues to do so until coil current is discontinued or until maximum gain is reached. This is represented by the following array formula: