Control system for a vehicle suspension

A method for operating a strut of a suspension system for supporting a suspended body relative to a support member which is subject to vibratory motion, the strut having a cylinder defining a cylinder chamber, a cylinder head defined by an aperture which extends through the cylinder head and through which a fluid displacement member moveably extends, the cylinder and the fluid displacement member being secured to different ones of the suspended body and the support member, a seal which sealingly engages between the fluid displacement member and the first cylinder head, and a compressible fluid disposed within the cylinder chamber and having a fluid pressure, wherein movement of the fluid displacement member in a first direction through the aperture and into the cylinder chamber increases the fluid pressure in the chamber, such that the fluid pressure exerts a resultant force which pushes against the fluid displacement member in a second direction, the method comprising the steps of:

• providing a damper element which is secured to the fluid displacement member and disposed interiorly within the cylinder chamber, such that the damper element is moveable with the fluid displacement member relative to the compressible fluid to restrict movement of the fluid displacement member relative to the compressible fluid;
• moveably securing the damper element to the fluid displacement member, such that the damper element is moveable between first and second positions to change the amount by which the damper element restricts movement of the fluid displacement member and the damper element relative to the compressible fluid;
• and
• biasing the damper element toward the first position, such that the damper element will remain proximate to the first position until predetermined pressure differentials are disposed across the damper element to urge the damper element to move in a direction from the first position toward the second position.

A strut suspension system for supporting a suspended body relative to a support member which is subject to vibratory motion, comprising in combination:

• a strut having a cylinder with an interior bore defining a cylinder chamber, a compressible fluid disposed within said cylinder chamber, a fluid displacement member which is moveably extensible into said cylinder chamber, a seal which sealingly engages between said cylinder and said fluid displacement member for retaining said compressible fluid within said chamber, and a dampening member secured to said fluid displacement member disposed within said cylinder chamber;
• said strut being supportively engaged between said suspended body and said support member, wherein one end of said strut is connected by said fluid displacement member to one of said suspended body and said support member, and another end of said strut is connected by said cylinder to the other of said suspended body and said support member;
• means for controlling pressures of said compressible fluid within said cylinder chamber of said strut in response to control signals, wherein said pressures within said cylinder chamber determine values for spring rate coefficients and dampening coefficients of said strut;
• at least a first sensor for detecting relative positions of said suspended body to said support member;
• a data processing unit being operatively connected to said first sensor and said means for controlling pressures, and for emitting said control signals and controlling said pressures of said compressible fluid within said strut to determine said spring rate coefficients and said dampening coefficients in response to sensed values from said first sensors;
• and
• said data processing system further being operable for frequency dependent filtering in determining values for said spring rate coefficients and said dampening coefficients, such that said spring rate coefficients are decreased in response to detecting changes in said relative positions of said suspended body occurring at frequencies beneath a low frequency threshold level, and said dampening coefficients are decreased in response to detecting changes in relative motion between said suspended body and said support member occurring at frequencies above a high frequency threshold level.

A strut suspension system for supporting a suspended body relative to a support member which is subject to vibratory motion, comprising in combination:

• a strut having a cylinder with an interior bore defining a cylinder chamber, a compressible fluid disposed within said cylinder chamber, a fluid displacement member which is moveably extensible into said cylinder chamber, a seal which sealingly engages between said cylinder and said fluid displacement member for retaining said compressible fluid within seal chamber, and a dampening member secured to said fluid displacement member and disposed within said cylinder chamber;
• said strut being supportively engaged between said suspended body and said support member, wherein one end of said strut is connected by said fluid displacement member to one of said suspended body and said support member, and another end of said strut is connected by said cylinder to the other of said suspended body and said support member;
• means for controlling pressures of said compressible fluid within said cylinder chamber of said strut in response to control signals, wherein said pressures within said cylinder chamber determine values for spring rate coefficients and dampening coefficients of said strut;
• at least a first sensor for determining positions of said suspended body;
• a data processing unit being operatively connected to said first sensor and said means for controlling pressures, and emitting said control signals and controlling said pressures of said compressible fluid within said strut to determine control values for said spring rate coefficients and said dampening coefficients in response to sensed values from said first sensor;
• said data processing with applying frequency dependent filtering for determining said spring rate coefficients and said dampening coefficients, such that said spring rate coefficients are decreased in response to detecting changes in said relative positions of said suspended body to said support member occurring at frequencies beneath a low frequency threshold level, and said dampening coefficients are decreased in response to detecting changes in relative motion between said suspended body and said support member occurring at frequencies above a high frequency threshold level;
• said spring rate coefficients and said dampening coefficients being decreased in proportion to the differences in values between respective ones of said detected frequencies and respective ones of said low and high frequency thresholds;
• wherein said suspension system is used for automotive applications and said support member is directly connected to a wheel, and said low and high frequency thresholds correspond to detected frequencies of movement of said wheel;
• and
• said low frequency threshold being disposed at a first selected offset beneath said detected frequencies of movement of said wheel, and said high frequency threshold being disposed at a second offset beneath said detected frequencies of movement of said wheel.

A method for operating a strut suspension system for supporting a suspended body relative to a support member which is subject to vibratory motion, the suspension system having a strut with a cylinder defining a cylinder chamber, a cylinder head defined on an end of said cylinder by an aperture which extends through said cylinder head and through which a fluid displacement member moveably extends, the cylinder chamber and the fluid displacement member being secured to different ones of said suspended body and said support member, a seal which sealingly engages between the fluid displacement member and said cylinder head, a compressible fluid disposed within the cylinder chamber and having a fluid pressure, and a dampening member secured to said fluid displacement member and disposed within said cylinder chamber, wherein movement of the fluid displacement member in a first direction through the aperture and into the cylinder chamber increases the fluid pressure in the chamber, such that the fluid pressure exerts a resultant force which pushes against the fluid displacement member in a second direction, the method comprising the steps of:

• providing a control system which selectively disposes the compressible fluid within the cylinder chamber, to control pressures of the compressible fluid within the cylinder chamber of the strut of the suspension system in response to control signals, wherein the pressures of the compressible fluid within the cylinder chamber determine values for spring rate coefficients and dampening coefficients of the strut;
• providing at least a first sensor for detecting relative positions of said suspended body relative to said support member;
• emitting the control signals and controlling the pressures of the compressible fluid within the strut to determine the spring rate coefficients and the dampening coefficients in response to sensed values from the first sensors;
• and
• filtering the control signals for determining the spring rate coefficients and the dampening coefficients according to detected wheel frequencies, such that the spring rate coefficients are decreased in response to detecting changes in the relative positions of the suspended body to said support member which occur at frequencies beneath a low frequency threshold level, and the dampening coefficients are decreased in response to detecting changes in relative motion between the suspended body and the support member which occur at frequencies above a high frequency threshold level.