Method and system for automatic calibration of pedal actuator in a reproducing piano
View Patent ↗A piano is equipped with an actuator that moves the piano pedal mechanism in a mariner that reproduces the pedaling effects of an original performance with high accuracy. The actuator comprises a solenoid, a permanent magnet, a velocity sense coil, and a Hall-effect sensor. The Hall-effect sensor provides an indication of the displacement of the solenoid plunger in accordance with an inverse-square law. Closed-loop feedback control is provided to effect a very true reproduction of pedaling effects. Automatic calibration allows for simple installation.
1. A method for calibrating an actuator assembly, comprising:
applying a minimum drive to the actuator;
while the minimum drive is applied to the actuator, finding a resting sensor output, the resting sensor output being an output of a sensor, the sensor operable to sense a displacement of an element moveable by the actuator;
applying a maximum drive to the actuator;
while the maximum drive is applied to the actuator, finding an actuated sensor output, the actuated sensor output being an output of the sensor;
calculating a constant based on the resting sensor output and the maximum sensor output; and
storing calibration information based on the constant.
2. The method of claim 1 , wherein the actuator drives a pedal mechanism in a piano.
3. The method of claim 2 , wherein the minimum drive is the smallest drive that may be applied to the actuator during a musical performance, and the maximum drive is the largest drive that may be applied to the actuator during a musical performance.
4. The method of claim 2 , wherein the element is the pedal mechanism.
5. The method of claim 4 , wherein output of the sensor is proportional to the inverse square of the distance from the sensor to the pedal mechanism.
6. The method of claim 4 , wherein the output of the sensor is directly proportional to the distance from the sensor to the pedal mechanism.
7. The method of claim 1 , wherein the element is the actuator.
8. The method of claim 7 , wherein the output of the sensor is proportional to the inverse square of the distance from the sensor to the actuator.
9. The method of claim 7 , wherein the output of the sensor is directly proportional to the distance from the sensor to the actuator.
10. The method of claim 1 , wherein the sensor is a nonlinear sensor.
11. The method of claim 10 , wherein the nonlinear sensor is an optical sensor.
12. The method of claim 10 , wherein the nonlinear sensor is a Hall-effect sensor.
13. The method of claim 1 , wherein the sensor is a linear sensor.
14. The method of claim 13 , wherein the linear sensor is a linear potentiometer.
15. The method of claim 1 , wherein the minimum drive is zero.
16. The method of claim 1 , wherein the actuator is in a resting position when the minimum drive is applied to the actuator.
17. The method of claim 1 , wherein actuator is in a fully actuated position when the maximum drive is applied to the actuator.
18. The method of claim 1 , wherein the maximum drive and the maximum drive are specified by protocol.
19. The method of claim 1 , wherein the constant is calculated according to the equation:
s (0)=(( m*s (actuate))− s (rest))/(1 −m ),
where s(0) is the constant, s(actuate) is a first known position, s(rest) is a second known position, m=√(v(actuate)/v(rest)), v(actuate) is the actuated sensor output, and v(rest) is the resting sensor output.
20. The method of claim 19 , wherein s(actuate) is the position of the actuator when the maximum drive is applied to the actuator.
21. The method of claim 19 , wherein s(rest) is the position of the actuator when the minimum drive is applied to the actuator.
22. The method of claim 19 , further comprising
calculating a second constant according to the equation:
k=v (rest)*( s (rest)+ s (0)) 2
where k is the second constant; and
storing second calibration information based on the second constant.
23. The method of claim 22 , wherein the second calibration information comprises the second constant.
24. The method of claim 22 , wherein the second calibration information comprises a lookup table.
25. The method of claim 1 , further comprising:
calculating a second constant based on the resting sensor output and the maximum sensor output; and
storing second calibration information based on the second constant.
26. The method of claim 25 , wherein the second calibration information comprises the second constant.
27. The method of claim 25 , wherein the second calibration information comprises a lookup table.
28. The method of claim 1 , wherein the calibration information comprises the constant.
29. The method of claim 1 , wherein the calibration information comprises a lookup table.
30. The method of claim 1 , wherein the constant is calculated according to the equation:
a =( v (actuate)− v (rest))/( s (actuate)− s (rest))
where a is the constant, v(actuate) is the actuated sensor output, v(rest) is the resting sensor output, s(actuate) is a first known position, an s(rest) is a second known position.
31. The method of claim 30 , wherein s(actuate) is the position of the actuator when the maximum drive is applied to the actuator.
32. The method of claim 30 , wherein s(rest) is the position of the actuator when the minimum drive is applied to the actuator.
33. The method of claim 1 , wherein the constant is calculated according to the equation:
b=v (actuate)−( s (actuate)*( v (actuate)− v (rest)))/( s (actuate)− s (rest))
where b is the constant, v(actuate) is the actuated sensor output, v(rest) is the resting sensor output, s(actuate) is a first known position, an s(rest) is a second known position.
34. The method of claim 33 , wherein s(actuate) is the position of the actuator when the maximum drive is applied to the actuator.
35. The method of claim 34 , wherein s(rest) is the position of the actuator when the minimum drive is applied to the actuator.
36. The method of claim 1 , further comprising:
calculating a second constant based on the resting sensor output and the maximum sensor output; and
storing second calibration information based on the second constant.
37. The method of claim 36 , wherein the second calibration information comprises the second constant.
38. The method of claim 36 , wherein the second calibration information comprises a lookup table.
39. The method of claim 1 , wherein the method is performed without intervention of a human operator.
40. A computer-readable medium encoded with instructions executable to perform a method comprising:
applying a minimum drive to the actuator;
while the minimum drive is applied to the actuator, finding a resting sensor output, the resting sensor output being an output of a sensor, the sensor operable to sense a displacement of an element moveable by the actuator;
applying a maximum drive to the actuator;
while the maximum drive is applied to the actuator, finding an actuated sensor output, the actuated sensor output being an output of the sensor;
calculating a constant based on the resting sensor output and the maximum sensor output; and
storing calibration information based on the constant.
41. The computer-readable medium of claim 40 , wherein the actuator drives a pedal mechanism in a piano.
42. The computer-readable medium of claim 41 , wherein the element is the pedal mechanism.
43. The computer-readable medium of claim 42 , wherein output of the sensor is proportional to the inverse square of the distance from the sensor to the pedal mechanism.
44. The computer-readable medium of claim 42 , wherein the output of the sensor is directly proportional to the distance from the sensor to the pedal mechanism.
45. The computer-readable medium of claim 41 , wherein the minimum drive is the smallest drive that may be applied to the actuator during a musical performance, and the maximum drive is the largest drive that may be applied to the actuator during a musical performance.
46. The computer-readable medium of claim 40 , wherein the element is the actuator.
47. The computer-readable medium of claim 46 , wherein the output of the sensor is proportional to the inverse square of the distance from the sensor to the actuator.
48. The computer-readable medium of claim 46 , wherein the output of the sensor is directly proportional to the distance from the sensor to the actuator.
49. The computer-readable medium of claim 40 , wherein the sensor is a nonlinear sensor.
50. The computer-readable medium of claim 49 , wherein the nonlinear sensor is an optical sensor.
51. The computer-readable medium of claim 49 , wherein the nonlinear sensor is a Hall-effect sensor.
52. The computer-readable medium of claim 40 , wherein the sensor is a linear sensor.
53. The computer-readable medium of claim 52 , wherein the linear sensor is a linear potentiometer.
54. The computer-readable medium of claim 40 , wherein the minimum drive is zero.
55. The computer-readable medium of claim 54 , wherein the method further comprises
calculating a second constant according to the equation:
k=v (rest)*( s (rest)+ s (0)) 2
where k is the second constant; and
storing second calibration information based on the second constant.
56. The computer-readable medium of claim 55 , wherein the second calibration information comprises the second constant.
57. The computer-readable medium of claim 55 , wherein the second calibration information comprises a lookup table.
58. The computer-readable medium of claim 40 , wherein the actuator is in a resting position when the minimum drive is applied to the actuator.
59. The computer-readable medium of claim 40 , wherein actuator is in a fully actuated position when the maximum drive is applied to the actuator.
60. The computer-readable medium of claim 40 , wherein the maximum drive and the maximum drive are specified by protocol.
61. The computer-readable medium of claim 40 , wherein the constant is calculated according to the equation:
s (0)=(( m*s (actuate))− s (rest))/(1 −m ),
where s(0) is the constant, s(actuate) is a first known position, s(rest) is a second known position, m=√(v(actuate)/v(rest)), v(actuate) is the actuated sensor output, and v(rest) is the resting sensor output.
62. The computer-readable medium of claim 61 , wherein s(actuate) is the position of the actuator when the maximum drive is applied to the actuator.
63. The computer-readable medium of claim 61 , wherein s(rest) is the position of the actuator when the minimum drive is applied to the actuator.
64. The computer-readable medium of claim 40 , wherein the method further comprises:
calculating a second constant based on the resting sensor output and the maximum sensor output; and
storing second calibration information based on the second constant.
65. The computer-readable medium of claim 64 , wherein the second calibration information comprises the second constant.
66. The computer-readable medium of claim 64 , wherein the second calibration information comprises a lookup table.
67. The computer-readable medium of claim 40 wherein the calibration information comprises the constant.
68. The computer-readable medium of claim 40 , wherein the calibration information comprises a lookup table.
69. The computer-readable medium of claim 40 wherein the constant is calculated according to the equation:
a =( v (actuate)− v (rest))/( s (actuate)− s (rest))
where a is the constant, v(actuate) is the actuated sensor output, v(rest) is the resting sensor output, s(actuate) is a first known position, an s(rest) is a second known position.
70. The computer-readable medium of claim 69 , wherein s(actuate) is the position of the actuator when the maximum drive is applied to the actuator.
71. The computer-readable medium of claim 69 , wherein s(rest) is the position of the actuator when the minimum drive is applied to the actuator.
72. The computer-readable medium of claim 40 wherein the constant is calculated according to the equation:
b=v (actuate)−( s (actuate)*( v (actuate)− v (rest)))/( s (actuate)− s (rest))
where b is the constant, v(actuate) is the actuated sensor output, v(rest) is the resting sensor output, s(actuate) is a first known position, an s(rest) is a second known position.
73. The computer-readable medium of claim 72 , wherein s(actuate) is the position of the actuator when the maximum drive is applied to the actuator.
74. The computer-readable medium of claim 73 , wherein s(rest) is the position of the actuator when the minimum drive is applied to the actuator.
75. The computer-readable medium of claim 40 , wherein the method further comprises:
calculating a second constant based on the resting sensor output and the maximum sensor output; and
storing second calibration information based on the second constant.
76. The computer-readable medium of claim 75 , wherein the second calibration information comprises the second constant.
77. The computer-readable medium of claim 75 , wherein the second calibration information comprises a lookup table.
78. The computer-readable medium of claim 40 , wherein the method is performed without intervention of a human operator.