Control of a suspension system of a vehicle provided with four semi-active suspensions

• US 8,473,157 B2
• Filed: 04/26/2012
• Issued: 06/25/2013
• Est. Priority Date: 04/29/2011
• Status: Active Grant

• Current Assignee: Politecnico di Milano, Fiat Group Automobiles S.P.A. (Stellantis NV)
• Original Assignee: Politecnico di Milano, Fiat Group Automobiles S.P.A. (Stellantis NV)
• Inventors: Campo, Sebastiano, Savaresi, Sergio M., Spelta, Cristiano, Delvecchio, Diego, Bonaccorso, Gabriele, Ghirardo, Fabio
• Primary Examiner(s): Black, Thomas
• Assistant Examiner(s): PAIGE, TYLER D
• Application Number:
  US13/456,924
• Publication Number:
  US 20120277953A1
• Time in Patent Office: 425 Days
• Field of Search: None
• US Class Current: 701/38
• CPC Class Codes: B60G 17/018 characterised by the use of a specific signal treatment or control method
• CPC Class Codes: B60G 2400/102 vertical
• CPC Class Codes: B60G 2500/10 Damping action or damper

Abstract

A method for controlling four semi-active suspensions of a vehicle comprising the steps of: determining, for each semi-active suspension, a first and a second signal representative of the acceleration and speed of the sprung mass; determining, for a pair of semi-active suspensions arranged on one side of the vehicle a third and a four signal representative of the acceleration and pitch speed; calculating for each semi-active suspension, a first damping coefficient as a function of the difference between the first and second signal squared; calculating for each semi-active suspension, a second damping coefficient as a function of the difference between the third and the four signal squared; for each semi-active suspension, comparing the first and the second damping coefficient for determining the higher coefficient; applying to each force generator device, an electronic control signal indicative of the respective high damping coefficient.

Claims

1. A method for controlling a suspension system (4) of a vehicle (1) comprising four semi-active suspensions (5) associated to four respective wheels (3) of the vehicle (1) itself;

each semi-active suspension (5) being interposed between a sprung mass (Msi) of the vehicle (1) and a unsprung mass (Nsi) associated to a wheel (3) of the vehicle (1) and being controlled by a respective force generator device (7);

said method being characterized in that it comprises the steps of;

determining, for each of the four semi-active suspensions (5), a first signal representative of the acceleration of the sprung mass (Msi) associated to the semi-active suspension (5) itself;

determining, for each of the four semi-active suspensions (5), a second signal representative of the vertical speed of the sprung mass (Msi) associated to the semi-active suspension (5) itself;

determining, for a pair of semi-active suspensions (5) arranged on a same side (Dx,Sx) of the vehicle (1) parallel to the longitudinal axis (L) of the vehicle (1) itself, a third signal representative of the pitch acceleration of the vehicle (1);

determining, for a pair of semi-active suspensions (5) arranged on a same side (Dx,Sx) of the vehicle (1) parallel to the longitudinal axis (L) of the vehicle (1) itself, a fourth signal representative of the pitch speed of the vehicle (1);

calculating for each of the four semi-active suspensions (5), a first damping coefficient (c^H_i) associated to the vertical dynamics of said semi-active suspension (5), as a function of the difference between said first signal squared and said second signal squared;

calculating for each of the four semi-active suspensions (5), a second damping coefficient (c^P_i) associated to the pitch of the vehicle (1), as a function of the difference between the third signal squared and the fourth signal squared;

for each semi-active suspension (5), comprising the first damping coefficient (c^H_i) with the second damping coefficient (c^P_i);

for each semi-active suspension (5), selecting the first (4) or the second damping coefficient (c^P_i) on the basis of the comparison;

applying to each of the four force generators (7), an electric control signal (Sci) indicative of the respective selected damping coefficient (c^H_i)(c^P_i).

2. A method according to claim 1, comprising the steps of:

measuring a first ({umlaut over (z)}₁), a second ({umlaut over (z)}₂) and a third vertical acceleration ({umlaut over (z)}₃) of a respective first (Ms₁), second (Ms₂) and third sprung mass (Ms₃);

estimating a fourth acceleration ({umlaut over (z)}₄) associated to a fourth sprung mass (Ms₄) on the basis of said first ({umlaut over (z)}₁) second ({umlaut over (z)}₂) and third measured acceleration ({umlaut over (z)}₃);

determining the first signal associated to the first (Ms₁), to the second (Ms₂) and to the third sprung mass (Ms₃) as a function of the first ({umlaut over (z)}₁), second ({umlaut over (z)}₂) and third measured acceleration) ({umlaut over (z)}₃);

determining the first signal associated to the fourth sprung mass (Ms₄) as a function of said fourth estimated acceleration ({umlaut over (z)}₄).

3. A method according to claim 1, wherein in said step of selecting, for each semi-active suspension (5), the first (c^H_i) or the second damping coefficient (c^P_i) on the basis of said comparison, comprises the step of selecting the damping coefficient (C^T_i) which, through the step of comparing, was found to be the highest damping coefficient (C^T_i=MAX(c^H_i,c^P_i)) between the first (c^H_i) and the second damping coefficient (c^P_i).

4. A method according to claim 1, wherein the step of calculating, for each of the four semi-active suspensions (5), a first damping coefficient (c^H_i) comprises the steps of:

determining a first value representative of the frequency of the energizing energy to which said semi-active suspension is subjected by means of a first function (Si(t)) associated to the difference between the first signal squared and the second signal squared;

determining the first damping coefficient (c^H_i) on the basis of said first value by means of a second function (fi(Si(t))) adapted to provide a third value which is indicative of the variation (c(t)^H_i) of said first damping coefficient (c^H_i) to be set on the force generator device (7) of said semi-active suspension (5), as said first value varies.

5. A method according to claim 4, wherein:

said first value is determined by means of the following first function;

Si(t)={umlaut over (z)}_i²(t)−

α

_i²ż

_i²(t)

said third value is determined by means of the following second function;

c(t)^H_i=fi(Si(t))

where;

ż

_i(t) is the speed expressed in m/s of the i-th sprung mass Msi determined in instant t;

{umlaut over (z)}_i(t) is the acceleration expressed in m/s² of the i-th sprung mass Msi determined in instant t;

α

_i is a first value indicative of the invariance frequency;

Si(t) corresponds to said first function which provides said first value indicative of the frequency of the energizing energy to which the i-th sprung mass is subjected in instant t; and

fi(S(t)) is the second function.

6. A method according to claim 2, wherein the step of calculating, for each of the four semi-active suspensions (5), a second damping coefficient (c^P_i), comprises the steps of:

determining a third signal associated to a pitch acceleration ({umlaut over (θ

)}(t))) on the basis of the difference between the vertical accelerations ({umlaut over (z)}₁(t), {umlaut over (z)}₃(t)) of said pair of semi-active suspensions (5);

determining the fourth signal associated to a pitch speed ({dot over (θ

)}(t)) by integrating the third signal over time;

determining a fourth value representative of the frequency of the energizing energy to which said semi-active suspension (5) is subjected during pitch, by means of a third function associated to the difference between the third signal squared and the fourth signal squared;

determining the second damping coefficient (c^P_i) on the basis of said fourth value by means of a fifth function (f_front(S_θ

(t)), (f_reart(S_θ

(t)) adapted to provide a sixth value which is indicative of the variation of said second damping coefficient (c^p_i) to be set on the force generator device (7) of the semi-active suspension (5), as said fourth value varies.

7. A method according to claim 6, wherein:

a third signal is determined by means of the following equation;

{umlaut over (θ

)}(t)={umlaut over (z)}₁(t)−

{umlaut over (z)}₃(t)

the fourth value is determined by means of said third function;

S_θ

(t)={umlaut over (θ

)}²(t)−

(α

_θ

{dot over (θ

)}(t))²

the second damping coefficient is determined by means of said fifth function;

C₁^p(t)=C₂^p(t)=f_front(S_θ

(t))

C₃^p(t)=C₄^p(t)=f_rear(S_θ

(t))

where;

{umlaut over (θ

)}(t) is the pitch acceleration of the vehicle in instant t expressed in m/s²;

{dot over (θ

)}(t) is the pitch speed of the vehicle in instant t expressed in m/s;

α

_θ

is the first value indicative of the invariance frequency or cross-over frequency expressed in radians/second for the pitch motion of the vehicle;

S_θ

(t) is the third function which provides the fourth value indicative of the frequency of the energizing energy to which the i-th sprung mass is subjected in instant t caused by the pitch dynamics of the vehicle;

f_front(S_θ

(t)) is the fifth function providing the sixth value which is indicative of the variance of the two second damping coefficients C₁^p(t) and C₂^p(t) to be set on the force generators 7 of the respective semi-active suspensions 5 arranged in the angles 2a and 2b present on the front side of the vehicle; and

f_rear(S_θ

(t)) is the fifth function providing the sixth value which is indicative of the variance of the two second damping coefficients C₁^p(t) and C₂^p(t) to be set on the force generators 7 of the respective semi-active suspensions 5 arranged in the angles 2c and 2d present on the rear side of the vehicle.

8. An electronic device for controlling a suspension system (4) of a vehicle comprising four semi-active suspensions 5 associated to four respective wheels 3 of the vehicle itself;

each semi-active suspension being interposed between a sprung mass of the vehicle and a unsprung mass associated to a wheel of the vehicle and being controlled by a respective force generator device;

said device being configured for;

determining, for each of the four semi-active suspensions (5), a first signal representative of the acceleration of the sprung mass (Msi) associated to the semi-active suspension (5) itself;

determining, for each of the four semi-active suspensions (5), a second signal representative of the vertical speed of the sprung mass (Msi) associated to the semi-active suspension (5) itself;

determining, for a pair of semi-active suspensions (5) arranged on a same side (Dx,Sx) of the vehicle (1) parallel to the longitudinal axis (L) of the vehicle (1) itself, a third signal representative of the pitch acceleration of the vehicle (1);

determining, for a pair of semi-active suspensions (5) arranged on a same side (Dx,Sx) of the vehicle (1) parallel to the longitudinal axis (L) of the vehicle (1) itself, a fourth signal representative of the pitch speed of the vehicle (1);

calculating for each of the four semi-active suspensions (5), a first damping coefficient (c^H_i) associated to the vertical dynamics of said semi-active suspension (5), as a function of the difference between said first signal squared and said second signal squared;

calculating for each of the four semi-active suspensions (5), a second damping coefficient (c^P_i) associated to the pitch of the vehicle (1), as a function of the difference between the third signal squared and the fourth signal squared;

for each semi-active suspension (5), comprising the first damping coefficient (c^H_i) with the second damping coefficient (c^P_i);

for each semi-active suspension (5), selecting the first (c^H_i) or the second damping coefficient (c^P_i) on the basis of the comparison;

applying to each of the four force generators (7), an electric control signal (Sci) indicative of the respective selected damping coefficient (c^H_i)(c^P_i).

9. A device according to claim 8 comprising:

acceleration measuring means adapted to measure a first ({umlaut over (z)}₁), and a second ({umlaut over (z)}₂) and a third vertical acceleration ({umlaut over (z)}₃) of a respective first (Ms₁), second (Ms₂) and third sprung mass (Ms₃);

electronic control means configured for;

estimating a fourth acceleration ({umlaut over (z)}₄) associated to a fourth sprung mass (Ms₄) on the basis of said first ({umlaut over (z)}₁), second ({umlaut over (z)}₂) and third measured acceleration ({umlaut over (z)}₃);

determining the first signal associated to the first (Ms₁), to the second (Ms₂) and to the third sprung mass (Ms₃) as a function of the first ({umlaut over (z)}₁), second ({umlaut over (z)}₂) and third measured acceleration) ({umlaut over (z)}₃);

determining the first signal associated to the fourth sprung mass (Ms₄) as a function of said fourth estimated acceleration ({umlaut over (z)}₄).

10. A device according to claim 9, wherein in said step of selecting, for each semi-active suspension (5), the first (c^H_i) or the second damping coefficient (c^P_i) on the basis of said comparison, comprising the step of selecting the damping coefficient (C^T_i) which, through the step of comparing, was found to be the highest damping coefficient (C^T_i=MAX(c^H_i,c^P_i)) between the first (c^H_i) and the second damping coefficient (c^P_i).

11. A device according to claim 8, wherein said electronic control means (11) are further configured for:

determining a first value representing the frequency of the energizing energy to which said semi-active suspension is subjected by means of a first function (Si(t)) associated to the difference between the first signal squared and the second signal squared;

determining the first damping coefficient (c^H_i) on the basis of said first value by means of a second function (fi(Si(t))) adapted to provide a third value which is indicative of the variation (c(t)^H_i) of said first damping coefficient (c^H_i) to be set on the force generator device (7) of said semi-active suspension (5), as said first value varies.

12. A device according to claim 11, wherein said electronic control means (11) are further configured for:

determining said first value by means of the following first function;

Si(t)={umlaut over (z)}_i²(t)−

α

_i²ż

_i²(t)

determining said third value by means of the following first function;

c(t)^h_i=fi(Si(t))

where;

ż

_i(t) is the speed expressed in m/s of the i-th sprung mass Msi determined in instant t;

{umlaut over (z)}_i(t) is the acceleration expressed in m/s² of the i-th sprung mass Msi determined in instant t;

α

_i is a first value indicative of the invariance frequency;

Si(t) corresponds to said first function which provide said first value indicative of the frequency of the energizing energy to which the i-th sprung mass is subjected in instant t; and

fi(S(t)) is the second function.

13. A device according to claim 9, wherein said electronic control means (11) are further configured for:

determining a third signal associated to a pitch acceleration ({umlaut over (θ

)}(t)) on the basis of the difference between the vertical accelerations ({umlaut over (z)}₁(t), {umlaut over (z)}₃(t)) of said pair of semi-active suspensions (5);

determining the fourth signal associated to a pitch speed ({dot over (θ

)}(t)) by integrating the third signal over time;

determining a fourth value representative of the frequency of the energizing energy to which said semi-active suspension (5) is subjected during pitch, by means of a third function associated to the difference between the third signal squared and the fourth signal squared;

determining the second damping coefficient (c^P_i) on the basis of said fourth value by means of a fifth function (f_front(S_θ

(t)), (f_reart(S_θ

(t)) adapted to provide a sixth value which is indicative of the variation of said second damping coefficient (c^p_i) to be set on the force generator device (7) of the semi-active suspension (5), as said fourth value varies.

14. A device according to claim 13, wherein said electronic control means (11) are further configured for:

determining the third signal by means of the following equation;

{umlaut over (θ

)}(t)={umlaut over (z)}₁(t)−

{umlaut over (z)}₃(t)

determining the fourth value by means of said third function;

S_θ

(t)={umlaut over (θ

)}²(t)−

(α

_θ

{dot over (θ

)}(t))²

determining the second damping coefficient by means of one of said fifth functions;

C₁^p(t)=C₂^p(t)=f_front(S_θ

(t))

C₃^p(t)=C₄^p(t)=f_rear(S_θ

(t))

where;

{umlaut over (θ

)}(t) is the pitch acceleration of the vehicle in instant t expressed in m/s²;

{dot over (θ

)}(t) is the pitch speed of the vehicle in instant t expressed in m/s;

α

_θ

is the first value indicative of the invariance frequency or cross-over frequency expressed in radians/second for the pitch motion of the vehicle;

S_θ

(t) is the third function which provides the fourth value indicative of the frequency of the energizing energy to which the i-th sprung mass is subjected in instant t caused by the pitch dynamics of the vehicle;

f_front(S_θ

(t)) is the fifth function providing the sixth value which is indicative of the variance of the two second damping coefficients C₁^p(t) e C₂^p(t) to be set on the force generators 7 of the respective semi-active suspensions 5 arranged in the angles 2a and 2b present on the front side of the vehicle;

f_rear(S_θ

(t)) is the fifth function providing the sixth value which is indicative of the variance of the two second damping coefficients C₃^p(t) e C₄^p(t) to be set on the force generators 7 of the respective semi-active suspensions 5 arranged in the angles 2c and 2d present on the rear side of the vehicle.

15. A program product stored in a non-transitory computer readable medium, the program product causing a vehicular electronic control unit to control a suspension system (4) of a vehicle (1), the suspension system (4) comprising four semi-active suspensions (5) associated to four respective wheels (3) of the vehicle (1) itself;

each semi-active suspension (5) being interposed between a sprung mass (Msi) of the vehicle (1) and a unsprung mass (Nsi) associated to a wheel (3) of the vehicle (1) and being controlled by a respective force generator device (7);

the program product making the vehicular electronic control unit execute the steps of;

determining, for each of the four semi-active suspensions (5), a first signal representative of the acceleration of the sprung mass (Msi) associated to the semi-active suspension (5) itself;

determining, for each of the four semi-active suspensions (5), a second signal representative of the vertical speed of the sprung mass (Msi) associated to the semi-active suspension (5) itself;

determining, for a pair of semi-active suspensions (5) arranged on a same side (Dx,Sx) of the vehicle (1) parallel to the longitudinal axis (L) of the vehicle (1) itself, a third signal representative of the pitch acceleration of the vehicle (1);

determining, for a pair of semi-active suspensions (5) arranged on a same side (Dx,Sx) of the vehicle (1) parallel to the longitudinal axis (L) of the vehicle (1) itself, a fourth signal representative of the pitch speed of the vehicle (1);

calculating for each of the four semi-active suspensions (5), a first damping coefficient (c^H_i) associated to the vertical dynamics of said semi-active suspension (5), as a function of the difference between said first signal squared and said second signal squared;

calculating for each of the four semi-active suspensions (5), a second damping coefficient (c^P_i) associated to the pitch of the vehicle (1), as a function of the difference between the third signal squared and the fourth signal squared;

for each semi-active suspension (5), comprising the first damping coefficient (c^H_i) with the second damping coefficient (c^P_i);

for each semi-active suspension (5), selecting the first (c^H_i) or the second damping coefficient (c_Pⁱ) on the basis of the comparison;

applying to each of the four force generators (7), an electric control signal (Sci) indicative of the respective selected damping coefficient (c^H_i)(c^P_i).