Method for controlling motion using a two-stage adjustable damper

• US 5,732,370 A
• Filed: 04/26/1996
• Issued: 03/24/1998
• Est. Priority Date: 04/26/1996
• Status: Expired due to Fees

• Current Assignee: Camp Inc.
• Original Assignee: The Lubrizol Corporation (Berkshire Hathaway Incorporated)
• Inventors: Smith, Dale P., Petek, Nicholas K., Boyle, Frederick P.
• Primary Examiner(s): NGUYEN, TAN QUANG
• Application Number:
  US08/639,142
• Time in Patent Office: 697 Days
• Field of Search: 701/36, 701/37, 701/38, 701/40, 280/707, 280/840, 180/41, 267/136, 248/550, 248/562, 248/636, 248/638
• US Class Current: 701/37
• CPC Class Codes: B60G 17/018 characterised by the use of a specific signal treatment or control method
• CPC Class Codes: B60G 2500/10 Damping action or damper
• CPC Class Codes: B60N 2/501 actively controlled suspension, e.g. electronic control
• CPC Class Codes: B60N 2/502 attached to the base of the seat B60N2/504 takes precedence
• CPC Class Codes: B60N 2/505 Adjustable suspension including height adjustment
• CPC Class Codes: B60N 2/508 Scissors-like structure
• CPC Class Codes: B60N 2/522 characterised by dampening means
• CPC Class Codes: B60N 2/525 using gas
• CPC Class Codes: F16F 15/02 Suppression of vibrations of non-rotating, e.g. reciprocating systems; Suppression of vibrations of rotating systems by use of members not moving with the rotating systems F16F15/005 takes precedence ; layered products B32B; suppression of vibration in ships B63; relieving load on bearings, using magnetic means F16C39/06

Abstract

The relative motion and force between two interconnected elements can be controlled by a semi-active two-stage adjustable damper to maximize isolation between the elements, while minimizing the instances of the motion exceeding acceptable limits. An algorithm determines when to apply the high force state of the damper to provide excellent isolation from input vibration and shocks. The dampers and control algorithms are useful in primary vehicle suspension systems, cab mounts, seat mounts and engine mounts.

Claims

1. A method for controlling the relative motion between two elements movably interconnected through a linkage which includes a spring assembly which tends to maintain the elements at an equilibrium position, at least the first element thereof being subjected to externally generated motion inputs and tending to transmit a first force in response thereto to the second element thereof;

the extreme limits of acceptable displacement of said elements being between of x_+limit in a positively defined direction and x_-limit in a negatively fined direction;

said elements being provided with a means for applying a second force therebetween, opposed to the direction of the relative motion of the elements, which means can be switched between a state characterized by a high force and a state characterized by a low force, the difference between said high force and said low force being defined as the controlled force;

said method comprising;

(a) measuring the displacement x_rel of the second element relative to the first element, x_rel being defined as zero at the equilibrium position;

(b) determining the relative velocity v_rel of the two elements; and

(c) applying the high force between the first and second elements if ##EQU11## otherwise applying the low force;

where;

v_db is a velocity deadband with a preselected value greater than or equal to zero,

m is the effective mass of the second element,

d is the distance from the displacement x_rel to the acceptable extreme displacement limit x_+limit or x_-limit in the direction of the relative velocity v_rel,

F_sys is the sum of the forces acting between the first and second elements other than the controlled force of the second force means;

whereby the force transmitted from the first element to the second element and the relative displacement between said elements are controlled.

2. The method of claim 1 wherein F_sys is taken as F_sys =-kx'"'"'-Cv_rel, where, x'"'"' is the relative displacement of the elements in excess of a displacement deadband x_db with a preselected value of zero or greater, such that x'"'"'=0 if |x_rel |≦

x_db and x'"'"'=x_rel -x_db sgn(x_rel) if |x_rel |>

x_db, k is the spring rate of the spring assembly at displacement x_rel, and C is an adjustable constant.

3. The method of claim 1 wherein the means for applying the second force is a damper containing a field responsive fluid.

4. The method of claim 1 wherein the first element comprises a vehicle chassis and the second element comprises an engine, a tractor cab, or a seat, suspended thereon.

5. The method of claim 1 wherein the first element is a wheel assembly and the second element comprises a vehicle body, and wherein mass m is taken as that portion of the total mass of the vehicle body which is supported by said wheel assembly when said vehicle body is at rest.

6. The method of claim 1 wherein the high force is additionally applied if v_rel F_sys >

0.

7. The method of claim 6 wherein F_sys is taken as F_sys =-kx'"'"'-Cv_rel, where, x'"'"' is the relative displacement of the elements in excess of a displacement deadband x_db with a preselected value of zero or greater, such that x'"'"'=0 if |x_rel |≦

x_db and x'"'"'=x_rel -x_db sgn(x_rel) if |x_rel |>

x_db, k is the spring rate of the spring assembly at displacement x_rel, and C is an adjustable constant.

8. The method of claim 6 wherein the means for applying the second force is a damper containing a field responsive fluid.

9. The method of claim 6 wherein the first element comprises a vehicle chassis and the second element comprises an engine, a tractor cab, or a seat, suspended thereon.

10. The method of claim 6 wherein the first element is a wheel assembly and the second element comprises a vehicle body, and wherein mass m is taken as that portion of the total mass of the vehicle body which is supported by said wheel assembly when said vehicle body is at rest.

11. The method of claim 1, further comprising measuring the absolute acceleration of the second element and calculating the absolute velocity v_abs of the second element, and wherein the high force is additionally applied if ##EQU12## where ζ

is a number greater than 0 and less than or equal to 1, and k is the spring rate of the spring assembly at the relative displacement X_rel.

12. The method of claim 11 wherein F_sys is taken as F_sys =-kx'"'"'-Cv_rel, where, x'"'"' is the relative displacement of the elements in excess of a displacement deadband x_db with a preselected value of zero or greater, such that x'"'"'=0 if |x_rel |≦

x_db and x'"'"'=x_rel -x_db sgn(x_rel) if |x_rel |>

x_db, and C is an adjustable constant.

13. The method of claim 11 wherein the means for applying the second force is a damper containing a field responsive fluid.

14. The method of claim 11 wherein the first element comprises a vehicle chassis and the second element comprises an engine, a tractor cab, or a seat, suspended thereon.

15. The method of claim 11 wherein the first element is a wheel assembly and the second element comprises a vehicle body, and wherein mass m is taken as that portion of the total mass of the vehicle body which is supported by said wheel assembly when said vehicle body is at rest.

16. A method for controlling the relative motion between two elements movably interconnected through a linkage which includes a spring assembly which tends to maintain the elements at an equilibrium position, at least the first element thereof being subjected to externally generated motion inputs and tending to transmit a first force in response thereto to the second element thereof;

said elements being situated within extreme limits of acceptable displacement therebetween of x_+limit in a positively defined direction and x_-limit in a negatively defined direction;

said elements being provided with a means for applying a second force therebetween, opposed to the direction of the relative motion of the elements, which means can be switched between a state characterized by a high force and a state characterized by a low force, the difference between said high force and said low force being defined as the controlled force;

said method comprising;

(a) measuring (i) the displacement x_rel of the second element relative to the first element, x_rel being defined as zero at the equilibrium position; and

(ii) the absolute acceleration of the second element;

(b) determining (i) the relative velocity v_rel of the elements and (ii) the absolute velocity v_abs of the second element; and

(c) applying the high force between the first and second elements if ##EQU13## otherwise applying the low force;

where;

v_db is a velocity deadband with a preselected value greater than or equal to zero,

m is the effective mass of the second element,

k is the spring rate of the spring assembly at the relative displacement x_rel,

F_sys is the sum of the forces acting between the first and second elements other than the controlled force of the second force means,

ζ

is a number greater than 0 and less than or equal to 1;

whereby the force transmitted from the first element to the second element and the relative displacement between said elements are controlled.

17. The method of claim 16 where F_sys is approximated by F_sys =-kx'"'"'-Cv_rel, where, x'"'"' is the relative displacement of the elements in excess of a displacement deadband x_db with a preselected value of zero or greater, such that x'"'"'=0 if |x_rel ≦

x_db and x'"'"'=x_rel -x_db sgn(x_rel) if |x_rel |>

x_db, k is the spring rate of the spring assembly at displacement x_rel, and C is an adjustable constant.

18. The method of claim 16 wherein the means for applying the second force is a damper containing a field responsive fluid.

19. The method of claim 16 wherein the first element comprises a vehicle chassis and the second element comprises an engine, a tractor cab, or a seat, suspended thereon.

20. The method of claim 16 wherein the first element is a wheel assembly and the second element comprises a vehicle body, and wherein mass m is taken as that portion of the total mass of the vehicle body which is supported by said wheel assembly when said vehicle body is at rest.

21. A method for controlling the relative motion between two elements movably interconnected through a linkage which includes a spring assembly which tends to maintain the elements at an equilibrium position, at least the first element thereof being subjected to externally generated motion inputs and tending to transmit a first force in response thereto to the second element thereof;

said elements being situated within extreme limits of acceptable displacement therebetween of x_+limit in a positively defined direction and x_-limit in a negatively defined direction;

said elements being provided with a means for applying a second force therebetween, opposed to the direction of the relative motion of the elements, which means can be switched between a state characterized by a high force and a state characterized by a low force, the difference between said high force and said low force being defined as the controlled force;

said method comprising;

(a) measuring the displacement x_rel of the second element relative to the first element, x_rel being defined as zero at the equilibrium position;

(b) determining the relative velocity v_rel elements; and

(c) applying the high force between the first and second elements if

space="preserve" listing-type="equation">|v.sub.rel |>

v.sub.db and v.sub.rel F.sub.sys >

0,

otherwise applying the low force;

where;

v_db is a velocity deadband with a preselected value greater than or equal to zero,

F_sys is the sum of the forces acting between the first and second elements other than the controlled force of the second force means;

whereby the force transmitted from the first element to the second element and the relative displacement between said elements are controlled.

22. The method of claim 21 where F_sys is approximated by F_sys =-kx'"'"'-Cv_rel, where, x'"'"' is the relative displacement of the elements in excess of a displacement deadband x_db with a preselected value of zero or greater, such that x'"'"'=0 if |x_rel |≦

x_db and x'"'"'=x_rel -x_db sgn(x_rel) if |x_rel |>

x_db, k is the spring rate of the spring assembly at displacement x_rel, and C is an adjustable constant.

23. The method of claim 21 wherein the means for applying the second force is a damper containing a field responsive fluid.

24. The method of claim 21 wherein the first element comprises a vehicle chassis and the second element comprises an engine, a tractor cab, or a seat, suspended thereon.

25. The method of claim 21 wherein the first element is a wheel assembly and the second element comprises a vehicle body, and wherein mass m is taken as that portion of the total mass of the vehicle body which is supported by said wheel assembly when said vehicle body is at rest.

26. A device for controlling the relative motion between two elements movably interconnected through a linkage which includes a spring assembly which tends to maintain the elements at an equilibrium position, at least the first element thereof being subjected to externally generated motion inputs and tending to transmit a first force in response thereto to the second element thereof;

said elements having extreme limits of acceptable displacement therebetween of x_+limit in a positively defined direction and x_-limit in a negatively defined direction;

said device comprising;

(A) a damper for applying a second force between said two movably interconnected elements, which damper can be switched between an "on" state characterized by a high force and an "off" state characterized by a low force, the difference between said high force and said low force being defined as the controlled force; and

(B) a controller adapted to send a control signal to said damper in response to the condition of the two movably interconnected elements, said control signal corresponding to the high force state or the low force state of said damper;

wherein the controller is adapted to select the high force state if ##EQU14## otherwise to select the low force state;

where;

v_db is a velocity deadband with a preselected value greater than or equal to zero,

v_rel is the relative velocity of the two elements,

m is the effective mass of the second element,

d is the distance from the displacement x_rel to the acceptable extreme displacement limit x_+limit or x_-limit in the direction of the relative velocity v_rel, and

F_sys is the sum of the forces acting between the first and second elements other than the controlled force of the damper.

27. The device of claim 26 wherein the controller is additionally adapted to select the high force state if v_rel F_sys >

0.

28. The device of claim 26 wherein the controller is additionally adapted to select the high force if ##EQU15## where ζ

is a number greater than 0 and less than or equal to 1, and k is the spring rate of the spring assembly at the relative displacement x_rel.

29. A device for controlling the relative motion between two elements movably interconnected through a linkage which includes a spring assembly which tends to maintain the elements at an equilibrium position, at least the first element thereof being subjected to externally generated motion inputs and tending to transmit a first force in response thereto to the second element thereof;

said elements having extreme limits of acceptable displacement therebetween of x_+limit in a positively defined direction and x_-limit in a negatively defined direction;

said device comprising;

(A) a damper for applying a second force between said two movably interconnected elements, which damper can be switched between an "on" state characterized by a high force and an "off" state characterized by a low force, the difference between said high force and said low force being defined as the controlled force; and

(B) a controller adapted to send a control signal to said damper in response to the condition of the two movably interconnected elements, said control signal corresponding to the high force state or the low force state of said damper;

wherein the controller is adapted to select the high force state if ##EQU16## otherwise to select the low force state;

where;

v_db is a velocity deadband with a preselected value greater than or equal to zero,

v_rel is the relative velocity of the two elements,

m is the effective mass of the second element,

k is the spring rate of the spring assembly at the relative displacement x_rel,

F_sys is the sum of the forces acting between the first and second elements other than the controlled force of the damper, and

ζ

is a number greater than 0 and less than or equal to 1.

30. A device for controlling the relative motion between two elements movably interconnected through a linkage which includes a spring assembly which tends to maintain the elements at an equilibrium position, at least the first element thereof being subjected to externally generated motion inputs and tending to transmit a first force in response thereto to the second element thereof;

said elements having extreme limits of acceptable displacement therebetween of x_+limit in a positively defined direction and x_-limit in a negatively defined direction;

said device comprising;

(A) a damper for applying a second force between said two movably interconnected elements, which damper can be switched between an "on" state characterized by a high force and an "off" state characterized by a low force, the difference between said high force and said low force being defined as the controlled force; and

(B) a controller adapted to send a control signal to said damper in response to the condition of the two movably interconnected elements, said control signal corresponding to the high force state or the low force state of said damper;

wherein the controller is adapted to select the high force state if

space="preserve" listing-type="equation">|v.sub.rel |>

v.sub.db and v.sub.rel F.sub.sys >

0,

otherwise to select the low force state;

where;

v_db is a velocity deadband with a preselected value greater than or equal to zero,

v_rel is the relative velocity of the two elements, and

F_sys is the sum of the forces acting between the first and second elements other than the controlled force of damper.