Motor control circuit for a simulated weight stack

• US 5,117,170 A
• Filed: 04/20/1990
• Issued: 05/26/1992
• Est. Priority Date: 12/23/1985
• Status: Expired due to Term

• Current Assignee: Brunswick Corporation
• Original Assignee: Life Fitness (Brunswick Corporation)
• Inventors: Keane, Martin A., Englehardt, William H.
• Primary Examiner(s): IP, SHIK LUEN PAUL
• Application Number:
  US07/511,830
• Time in Patent Office: 767 Days
• Field of Search: 318/434, 318/287, 318/588, 318/621, 318/678, 318/632, 388/823, 272/DIG. 6, 272/116-146, 272/129
• US Class Current: 318/646
• CPC Class Codes: A63B 21/0058 using motors
• CPC Class Codes: A63B 2220/13 Relative positions
• CPC Class Codes: G05D 15/01 characterised by the use of electric means
• CPC Class Codes: Y10S 482/90 Ergometer with feedback to load or with feedback comparison

Abstract

A control for a DC motor coupled to a user interface to provide a counterforce which simulates a weight stack in an exercise machine. The control includes a position transducer coupled to the motor to provide a signal proportional to the displacement of the user interface. In one embodiment a circuit is provided to generate a control signal which follows the displacement signal when it is less than a maximum torque signal, the control voltage following maximum torque signal when it is less than the displacement signal. In a second embodiment a microprocessor control unit is responsive to the displacement signal to provide a control signal for the motor which starts increasing from a first value when the user interface is displaced an initial amount and which continues gradually increasing to a maximum value as the user interface is moved through a given displacement from the initial displacement. The control signal is used to soft start the motor such that the counterforce provided by the motor simulates a weight stack supported by a spring over small displacements of the user interface.

Claims

1. An exercise machine having a user interface engaged by the user for simulating a weight stack comprising:

a DC motor coupled to the user interface to exert a counterforce that simulates the weight of a weight stack;

means for sensing the displacement of the user interface to provide a displacement signal proportional thereto; and

means responsive to said displacement signal for controlling said motor to provide a force which starts increasing from a first value at a rest position and gradually increases to said counterforce in response to movement of the interface through an initial displacement from said rest position.

2. An exercise machine as recited in claim 1 wherein said first value represents a force necessary to maintain the user interface in said rest position.

3. An exercise machine as recited in claim 1 wherein said initial displacement is less than or equal to one half inch from said rest position.

4. An exercise machine as recited in claim 2 wherein said initial displacement is less than or equal to one half inch from said rest position.

5. An exercise machine having a user interface engaged by the user for simulating a weight stack comprising:

a DC motor coupled to the user interface to exert a counterforce that simulates the weight of a weight stack;

means for sensing the displacement of the user interface to provide a displacement signal proportional thereto; and

means responsive to said displacement signal for soft starting said DC motor to cause the motor to provide a force which simulates a weight stack initially supported by a short spring.

6. The exercise machine of claim 5 wherein said soft start means includes means for providing to said motor a control signal which increases to a maximum value in proportion with said displacement signal when the user interface is initially displaced to control the DC motor to provide said force which increases gradually to said counterforce over a short displacement of the user interface from a rest position.

7. The exercise machine of claim 6 wherein said user interface is displaceable along a line and said short displacement is on the order of one half of an inch.

8. The exercise machine of claim 6 wherein said user interface is displaceable along an arc and said short displacement is not greater than 20°

.

9. An exercise machine having a user interface engaged by the user comprising:

selection means for permitting the user to select a counterforce;

a DC motor coupled to the user interface to exert said counterforce against the user;

means for sensing the displacement of the user interface to provide a displacement signal proportional thereto;

means responsive to said displacement signal and said selection means for providing a control signal which increases to a maximum value in proportion with said displacement signal, said control signal being coupled to said DC motor to control the motor to exert a force which increases gradually to said counterforce at said maximum value over a short displacement of said user interface from a rest position.

10. The exercise machine of claim 9 wherein said control signal providing means includes:

a first voltage follower to the input of which is applied said displacement signal to provide a voltage which is proportional to the displacement of the user interface from said rest position;

a second voltage follower to the input of which is applied a signal representing said counterforce to be exerted by said motor; and

means coupled to the outputs of said first and second voltage followers for selecting the minimum voltage output from the followers as said control signal.

11. An exercise machine having a user interface engaged by the user comprising:

a DC motor coupled to the user interface to exert a preselected maximum counterforce against the user, said motor having an armature the rotation of which represents the displacement of said user interface;

means for sensing the rotation of said armature to provide a displacement signal proportional thereto; and

means responsive to said displacement signal and coupled to said DC motor for providing an armature current which increases to a maximum value in proportion with said displacement signal to control said motor to provide a counterforce which is proportional to said armature current and equals said maximum counterforce at said maximum value when the user interface has been displaced a short distance from a rest position.

12. The exercise machine of claim 11 wherein said armature current providing means provides said armature current which increases to said maximum value over said short displacements of said user interface from said rest position on the order of one half of an inch for an interface displaceable along a line.

13. The exercise machine of claim 11 wherein said armature current providing means provides said armature current which increases to said maximum value over said short displacements of said interface on the order of 20°

or less of the rotation of said armature.

14. The exercise machine of claim 11 wherein said armature current providing means additionally provides a minimum value of said armature current to control said DC motor to provide a minimum counterforce when the user interface is in said rest position.

15. The exercise machine of claim 14 wherein said armature current providing means additionally provides said minimum value of said armature current for a first portion of said short distance from said rest position and then increase said armature current to said maximum value in proportion with said displacement value over the remaining portion of said short distance.

16. The exercise machine of claim 15 wherein said short distance is equivalent to approximately 18°

of rotation of said armature.

17. The exercise machine of claim 16 wherein said first portion of said short distance is equivalent to approximately 4°

of rotation of said armature.

18. An exercise machine for simulating a weight stack comprising:

a user interface displaceable from a rest position;

input means for permitting a user to select a weight to be simulated;

displacement means for generating a displacement signal representing the displacement of said user interface;

a DC motor operatively coupled to said user interface; and

control means operatively connected to said input means, said displacement means and said D.C. motor for applying a first current to said D.C. motor to generate a maximum force on said user interface to simulate said selected weight and wherein said control means additionally includes soft start means for increasing said armature current from a minimum value to said first value over an initial displacement of said user interface from said rest position.

19. The machine of claim 18 wherein said initial displacement is approximately one-half inch.

20. The machine of claim 18 wherein said minimum current value is approximately zero.

21. The machine of claim 18 wherein said soft start means simulates a short spring over said initial displacement.

22. The machine of claim 18 wherein said current increases linearly from said minimum value to said first value over said initial displacement.

23. The machine of claim 18 wherein said soft start means additionally maintains said current at said minimum value for an offset portion of said initial displacement and then increases said current to said first value over the remaining portion of said initial displacement.

24. The machine of claim 23 wherein said minimum current applied to said DC motor is sufficient to generate sufficient force on said user interface to retain said user interface in said rest positions.

25. The machine of claim 23 wherein the slope of said increase of said current over said remaining portion of said initial displacement is equal to:

##EQU3## where F_MAX is said maximum force, F_MIN is the minimum force generated on said user interface by said minimum value of the current and RL is said remaining portion of said initial displacement.

26. The machine of claim 25 wherein said control means includes means for computing said offset portion of the initial displacement in response to a value of F_MAX input by the user into said input means.

27. The machine of claim 23 wherein said initial displacement is approximately one-half inch.

28. The machine of claim 27 wherein said offset portion is between 20% and 30% of said initial displacement.

29. An exercise machine for simulating a weight stack comprising:

a user interface displaceable from a rest position;

input means for permitting a user to select a weight to be simulated;

displacement means for generating a displacement signal representing the displacement of said user interface;

a DC motor operatively coupled to said user interface; and

control means operatively connected to said input means, said displacement means and said DC motor for applying a first current to said DC motor to generate a maximum force on said user interface to simulate said selected weight and wherein said control means additionally includes soft start means for increasing said armature current from a minimum value to said first value over an initial displacement of said user interface from said rest position, said soft start means additionally able to maintain said current at said minimum value for an offset portion of said initial displacement and then increase said current to said first value over the remaining portion of said initial displacement.

30. The machine of claim 29 wherein said minimum current applied to said DC motor is sufficient to generate sufficient force on said user interface to retain said user interface in said rest positions.

31. The machine of claim 29 wherein the slope of said increase of said current over said remaining portion of said initial displacement is equal to:

##EQU4## where F_MAX is said maximum force, F_MIN is the minimum force generated on said user interface by said minimum value of the current and RL is said remaining portion of said initial displacement.

32. The machine of claim 31 wherein said control means includes means for computing said offset portion of the initial displacement in response to a value of F_MAX input by the user into said input means.

33. The machine of claim 29 wherein said initial displacement is approximately one-half inch.

34. The machine of claim 33 wherein said offset portion is between 20% and 30% of said initial displacement.