Pedal actuator with nonlinear sensor
View Patent ↗A piano is equipped with an actuator that moves the piano pedal mechanism in a manner 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. An actuator assembly used to drive a mechanical portion of a musical instrument, comprising:
an actuator operable to drive the mechanical portion of the musical instrument;
a nonlinear sensor operable to sense a displacement of an element movable by of the actuator;
control logic operable to calculate a drive to be applied to the actuator, the drive being calculated based on a commanded position and an output of the nonlinear sensor; and
wherein the control logic determines a velocity, wherein the velocity is used to stabilize the drive.
2. The actuator assembly of claim 1 , wherein the output of the nonlinear sensor is proportional to the inverse square of the distance from the nonlinear sensor to the moveable element.
3. The actuator assembly of claim 1 , wherein the nonlinear sensor is an optical sensor.
4. The actuator assembly of claim 1 , wherein the nonlinear sensor is a Hall-effect sensor.
5. The actuator assembly of claim 1 , wherein the control logic contains a sensor output linearization block operable to find a linearized value based on the output of the nonlinear sensor.
6. The actuator assembly of claim 5 , wherein the sensor output linearization block calculates the linearized value according to the equation:
v (linear)=√( k/v (out))− v (0)
where v(linear) is the linearized value, v(out) is the output of the nonlinear sensor, and k and v(0) are constants.
7. The actuator assembly of claim 5 , wherein the sensor output linearization block finds the linearized value using a lookup table.
8. The actuator assembly of claim 1 , wherein the control logic contains a modification block operable to find a modified value based on the commanded position, the modified value being comparable to the output of the nonlinear sensor.
9. The actuator assembly of claim 8 , wherein the modified value is a Hall-modified value.
10. The actuator assembly of claim 8 , wherein the modification block calculates the modified value according to the equation:
v (modified)= k /( v (command)+ v (0)) 2
where v(modified) is the modified value, v(command) is the commanded position, and k and v(0) are constants.
11. The actuator assembly of claim 8 , wherein the modification block finds the modified value using a lookup table.
12. The actuator assembly of claim 1 , wherein the drive is calculated based on the commanded position and a linearized value, the linearized value being based on the output of the nonlinear sensor.
13. The actuator assembly of claim 1 , wherein the drive is calculated based on a modified value and the output of the nonlinear sensor, the modified value being based on the commanded value.
14. The actuator assembly of claim 1 , wherein the commanded position is the desired position of the moveable element.
15. The actuator assembly of claim 1 , wherein the musical instrument is a piano, and the mechanical portion of the musical instrument is a pedal mechanism in the piano.
16. An actuator assembly used to drive a mechanical portion of a musical instrument, comprising:
an actuator operable to drive the mechanical portion of the musical instrument;
a nonlinear sensor operable to sense a displacement of a moveable element of the actuator assembly; and
control logic operable to calculate a drive to be applied to the actuator, the drive being calculated based on a commanded position and an output of the nonlinear sensor,
wherein the control logic contains a controller that determines a velocity, wherein the velocity is used to stabilize the drive.
17. The actuator assembly of claim 16 , wherein the moveable element is a moveable element of the actuator.
18. The actuator assembly of claim 16 , wherein the moveable element is the mechanical portion of the musical instrument.
19. The actuator assembly of claim 16 , further comprising a sense coil, wherein the velocity is based on the output of the sense coil.
20. A control circuit used to calculate a drive to be provided to an actuator, comprising:
control logic operable to calculate a drive to be applied to the actuator, the drive being calculated based on a commanded position and an input received from a nonlinear sensor, the nonlinear sensor operable to sense a displacement of a moveable element of the actuator; and
wherein the control logic determines a velocity, wherein the velocity is used to stabilize the drive.
21. The control circuit of claim 20 , wherein the control logic contains a sensor output linearization block operable to find a linearized value based on the input.
22. The control circuit of claim 21 , wherein the sensor output linearization block calculates the linearized value according to the equation:
v (linear)=√( k/v (out))− v (0)
where v(linear) is the linearized value, v(out) is the input, and k and v(0) are constants.
23. The control circuit of claim 21 , wherein the sensor output linearization block finds the linearized value using a lookup table.
24. The control circuit of claim 20 , wherein the control logic contains a modification block operable to find a modified value based on the commanded position, the modified value being comparable to the input.
25. The control circuit of claim 24 , wherein the modified value is a Hall-modified value.
26. The control circuit of claim 24 , wherein the modification block calculates the modified value according to the equation:
v (modified)= k /( v (command)+ v (0)) 2
where v(modified) is the modified value, v(command) is the commanded position, and k and v(0) are constants.
27. The control circuit of claim 24 , wherein the modification block finds the modified value using a lookup table.
28. The control circuit of claim 20 , wherein the nonlinear sensor is an optical sensor.
29. The control circuit of claim 20 , wherein the nonlinear sensor is a Hall-effect sensor.
30. A control circuit used to calculate a drive to be provided to an actuator, comprising:
control logic operable to calculate a drive to be applied to the actuator, the drive being calculated based on a commanded position and an input received from a nonlinear sensor,
wherein the control logic contains a controller that determines a velocity, wherein the velocity is used to stabilize the drive.
31. The control circuit of claim 30 , wherein the Proportional-Integral-Derivative controller calculates the drive based on the commanded position and a linearized value, the linearized value being based on the input.
32. The control circuit of claim 30 , wherein the Proportional-Integral-Derivative controller calculates the drive based on a modified value and the input, the modified value being based on the commanded value.
33. The control circuit of claim 30 , wherein the velocity is based on a measurement from a sense coil.
34. The control circuit of claim 30 , wherein the nonlinear sensor is operable to sense a displacement of an element moveable by the actuator.
35. A method for calculating a drive to be applied to an actuator, the method comprising:
receiving a nonlinear sensor output from a nonlinear sensor, the nonlinear sensor operable to sense a displacement of an element moveable by of the actuator;
receiving a commanded position;
calculating a drive to be applied to the actuator based on the nonlinear sensor output and the commanded position; and
determining a velocity, wherein the velocity is used to stabilize the drive.
36. The method of claim 35 , wherein the nonlinear sensor output is proportional to the inverse square of the distance from the nonlinear sensor to the moveable element.
37. The method of claim 35 , wherein the nonlinear sensor is an optical sensor.
38. The method of claim 35 , wherein the nonlinear sensor is a Hall-effect sensor.
39. The method of claim 35 , further comprising finding a linearized value based on the nonlinear sensor output.
40. The method of claim 39 , wherein finding a linearized value comprises calculating the linearized value according to the equation:
v (linear)=√( k/v (out))− v (0)
where v(linear) is the linearized value, v(out) is the nonlinear sensor output, and k and v(0) are constants.
41. The method of claim 39 , wherein finding the linearized value comprises:
finding the linearized value using a lookup table.
42. The method of claim 35 , further comprising finding a modified value based on the commanded position, the modified value being comparable to the nonlinear sensor output.
43. The method of claim 42 , wherein the modified value is a Hall-modified value.
44. The method of claim 42 , wherein finding the modified value comprises calculating the modified value according to the equation:
v (modified)= k /( v (command)+ v (0)) 2
where v(modified) is the modified value, v(command) is the commanded position, and k and v(0) are constants.
45. The method of claim 42 , wherein finding the modified value comprises:
finding the modified value using a lookup table.
46. The method of claim 35 , wherein the drive is calculated based on the commanded position and a linearized value, the linearized value being based on the nonlinear sensor output.
47. The method of claim 35 , wherein the drive is calculated based on a modified value and the nonlinear sensor output, the modified value being based on the commanded value.
48. The method of claim 35 , wherein the commanded position is the desired position of the moveable element.
49. The method of claim 35 , further comprising applying the drive to the actuator.
50. The method of claim 35 , wherein the actuator effects movement of a pedal mechanism in a piano.
51. A method for calculating a drive to be applied to an actuator, the method comprising:
receiving a nonlinear sensor output from a nonlinear sensor, the nonlinear sensor operable to sense a displacement of a moveable element of an actuator assembly;
receiving a commanded position; and
calculating a drive to be applied to the actuator based on the nonlinear sensor output and the commanded position; and
determining a velocity, wherein the velocity is used to stabilize the drive.
52. The method of claim 51 , wherein the moveable element is a pedal mechanism in a piano.
53. The method of claim 51 , wherein the moveable element is the actuator.
54. The method of claim 51 , wherein the velocity is based on the output of a sense coil.
55. A computer-readable medium encoded with instructions executable to perform a method comprising:
receiving a nonlinear sensor output from a nonlinear sensor, the nonlinear sensor operable to sense displacement of an element moveable by of the actuator;
receiving a commanded position;
calculating a drive to be applied to the actuator based on the nonlinear sensor output and the commanded position; and
determining a velocity, wherein the velocity is used to stabilize the drive.
56. The computer-readable medium of claim 55 , wherein the nonlinear sensor output is proportional to the inverse square of the distance from the nonlinear sensor to the moveable element.
57. The computer-readable medium of claim 55 , wherein the nonlinear sensor is an optical sensor.
58. The computer-readable medium of claim 55 , wherein the nonlinear sensor is a Hall-effect sensor.
59. The computer-readable medium of claim 55 , wherein the method further comprises finding a linearized value based on the nonlinear sensor output.
60. The computer-readable medium of claim 59 , wherein finding a linearized value comprises calculating the linearized value according to the equation:
v (linear)=√( k/v (out))− v (0)
where v(linear) is the linearized value, v(out) is the nonlinear sensor output, and k and v(0) are constants.
61. The computer-readable medium of claim 59 , wherein finding the linearized value comprises:
finding the linearized value using a lookup table.
62. The computer-readable medium of claim 55 , wherein the method further comprises finding a modified value based on the commanded position, the modified value being comparable to the nonlinear sensor output.
63. The computer-readable medium of claim 62 , wherein the modified value is a Hall-modified value.
64. The computer-readable medium of claim 62 , wherein finding the modified value comprises calculating the modified value according to the equation:
v (modified)= k /( v (command)+ v (0)) 2
where v(modified) is the modified value, v(command) is the commanded position, and k and v(0) are constants.
65. The computer-readable medium of claim 62 , wherein finding the modified value comprises:
finding the modified value using a lookup table.
66. The computer-readable medium of claim 55 , wherein the drive is calculated based on the commanded position and a linearized value, the linearized value being based on the nonlinear sensor output.
67. The computer-readable medium of claim 55 , wherein the drive is calculated based on a modified value and the nonlinear sensor output, the modified value being based on the commanded value.
68. The actuator assembly of claim 55 , wherein the commanded position is the desired position of the moveable element.
69. The computer-readable medium of claim 55 , wherein the actuator effects movement of a pedal mechanism in a piano.
70. A computer-readable medium encoded with instructions executable to perform a method comprising:
receiving a nonlinear sensor output from a nonlinear sensor, the nonlinear sensor operable to sense displacement of a moveable element of an actuator assembly;
receiving a commanded position; and
calculating a drive to be applied to an actuator based on the nonlinear sensor output and the commanded position; and
determining a velocity, wherein the velocity is used to stabilize the drive.
71. The computer-readable medium of claim 70 , wherein the moveable element is a pedal mechanism in a piano.
72. The computer-readable medium of claim 70 , wherein the moveable element is a moveable element of the actuator.
73. The computer-readable medium of claim 70 , wherein the velocity is based on the output of a sense coil.