Method and system for controlling active suspensions of a vehicle during acceleration and deceleration

• US 5,515,277 A
• Filed: 12/14/1994
• Issued: 05/07/1996
• Est. Priority Date: 11/29/1990
• Status: Expired due to Fees

• Current Assignee: Fuji Heavy Industries Limited (Subaru Corp.)
• Original Assignee: Fuji Heavy Industries Limited (Subaru Corp.)
• Inventors: Mine, Atsushi
• Primary Examiner(s): PARK, COLLIN
• Application Number:
  US08/358,547
• Time in Patent Office: 510 Days
• Field of Search: 364/424.05, 280/707, 280/840, 280/6.1, 280/6.12
• US Class Current: 701/37
• CPC Class Codes: B60G 17/016 characterised by their responsiveness, when the vehicle is travelling, to specific motion, a specific condition, or driver input B60G17/017 takes precedence
• CPC Class Codes: B60G 17/0162 mainly during a motion involving steering operation, e.g. cornering, overtaking B60G17/0164 takes precedence
• CPC Class Codes: B60G 2400/10 Acceleration; Deceleration
• CPC Class Codes: B60G 2400/102 vertical
• CPC Class Codes: B60G 2400/104 lateral or transversal with regard to vehicle
• CPC Class Codes: B60G 2400/106 longitudinal with regard to vehicle, e.g. braking
• CPC Class Codes: B60G 2400/20 Speed
• CPC Class Codes: B60G 2400/204 Vehicle speed
• CPC Class Codes: B60G 2400/252 vertical
• CPC Class Codes: B60G 2400/41 Steering angle
• CPC Class Codes: B60G 2400/42 Steering torque
• CPC Class Codes: B60G 2400/61 Load distribution
• CPC Class Codes: B60G 2400/822 Road friction coefficient determination affecting wheel traction
• CPC Class Codes: B60G 2400/90 Other conditions or factors
• CPC Class Codes: B60G 2600/02 Retarders, delaying means, dead zones, threshold values, cut-off frequency, timer interruption
• CPC Class Codes: B60G 2600/14 Differentiating means, i.e. differential control
• CPC Class Codes: B60G 2600/604 low pass
• CPC Class Codes: B60G 2600/70 Computer memory; Data storage, e.g. maps for adaptive control
• CPC Class Codes: B60G 2800/012 Rolling condition
• CPC Class Codes: B60G 2800/18 Starting, accelerating
• CPC Class Codes: B60G 2800/22 : Braking, stopping
• CPC Class Codes: B60G 2800/24 : Steering, cornering

Abstract

An active suspension system of a vehicle has a feed back control system for controlling four suspensions for the four wheels to maintain a reference vehicle height responsive to detected vertical relative displacements between the wheels and the vehicle body at said suspensions, and a feed forward control system for controlling the suspension to reduce pitching of the vehicle responsive to detected longitudinal acceleration. There is further provided a circuit for changing the reference vehicle height which is responsive to the absolute value of the detected longitudinal acceleration or deceleration for reducing the reference vehicle height with increase of the absolute value so that the vehicle body is lowered while the pitching is maintained at a predetermined value so as to obtain better driver'"'"'s sensation during vehicle acceleration and deceleration and to improve the performance of acceleration and deceleration.

Claims

1. A system for controlling a plurality of active suspensions in a vehicle which is provided corresponding to each wheel of a vehicle, by charging and discharging a fluid to independently control height of said active suspensions to attain a reference vehicle height, the system comprising:

a longitudinal G-sensor mounted on said vehicle for detecting a longitudinal acceleration of said vehicle and for producing a longitudinal acceleration signal;

longitudinal hysteresis control means responsive to said longitudinal acceleration signal for attaining longitudinal control without fluctuation and for generating a longitudinal control signal;

a vertical height adjusting switch mounted on said vehicle for simultaneously changing a stroke by a same amount for each active suspension and for generating a signal of reference vehicle height for said each active suspension;

longitudinal variation calculating means responsive to said longitudinal control signal and said reference vehicle height signal for computing a quantity of said fluid in accordance with said longitudinal acceleration and for producing a first quantity signal;

a lateral G-sensor mounted on said vehicle for sensing a lateral acceleration of said vehicle and for generating a lateral acceleration signal;

lateral hysteresis control means responsive to said lateral acceleration signal for attaining lateral control without fluctuation and for generating a lateral control signal;

lateral variation calculating means responsive to said lateral control signal and said reference vehicle height signal for computing a quantity of said fluid in accordance with said lateral acceleration and for producing a second quantity signal;

control quantity calculating means responsive to said first and second quantity signals for calculating a control quantity and for generating a control quantity signal;

a vertical G-sensor provided for each active suspension to detect an acceleration in a vertical direction of said active suspension and to produce a vertical acceleration signal;

vertical acceleration control means responsive to said vertical acceleration signal for attaining vertical control without fluctuation and for generating a vertical control signal;

a suspension stroke sensor provided for each active suspension to detect a stroke of said active suspension and to generate a stroke signal, and stroke control means responsive to said stroke signal for generating a stroke control signal;

control means responsive to said vertical control signal and said stroke control signal to control said active suspension system;

means for supplying said control quantity signal to said active suspension system to reduce delay in vehicle attitude control by said active suspension system;

calculating means responsive to said longitudinal acceleration signal for computing a changing amount of vehicle height dependent on an actual amount of said longitudinal acceleration; and

correcting means responsive to said calculating means for simultaneously lowering said reference vehicle height in a linearly proportional function of said actual amount so as to lower said reference vehicle height by a same displacement amount for said each active suspension, wherein said control means controls said active suspension system based on said lowered reference vehicle height.

2. The system according to claim 1, further comprising:

rolling oscillation calculating means responsive to said vertical acceleration signal from each of said active suspensions for calculating a rolling oscillation component and for outputting a oscillation component signal;

gravitational acceleration calculating means responsive to said stroke signal for calculating a gravitational acceleration and for outputting a gravitational acceleration signal; and

said lateral hysteresis control means further responsive to said oscillation component signal and said gravitational acceleration signal for generating said lateral control signal.

3. The system according to claim 2, wherein

said reference vertical height is increases as a proportional function of an absolute value of said actual amount of the longitudinal acceleration.

4. The system according to claim 1, wherein

said reference vertical height increases as a proportional function of an absolute value of said actual amount of the longitudinal acceleration.

5. A method for controlling an active suspension system in a vehicle having a plurality of wheels, an active suspension for each of said plurality of wheels for charging and discharging a fluid of said active suspension to independently control height of said active suspension to attain a reference vehicle height, comprising:

detecting a longitudinal acceleration of said vehicle using a longitudinal G-sensor mounted on said vehicle and producing a longitudinal acceleration signal,

generating a longitudinal control signal responsive to said longitudinal acceleration signal for attaining longitudinal control without fluctuation,

simultaneously changing a stroke of said active suspension by a same amount for said each active suspension using a vertical height adjusting switch mounted on said vehicle and generating a reference vehicle height signal,

computing a quantity of said fluid in accordance with said longitudinal acceleration responsive to said longitudinal control signal and said reference vehicle height signal, and producing a first quantity signal,

generating a lateral acceleration signal using a lateral G-sensor mounted on said vehicle for sensing a lateral acceleration of said vehicle,

generating a lateral control signal responsive to said lateral acceleration signal for attaining lateral control without fluctuation,

computing a quantity of said fluid in accordance with said lateral acceleration responsive to said lateral control signal and said reference vehicle height signal, and producing a second quantity signal,

calculating a control quantity responsive to said first quantity signal and said second quantity signal, and generating a control quantity signal,

detecting an acceleration in a vertical direction of said active suspension using a vertical G-sensor provided for each active suspension of said active suspension system, and producing a vertical acceleration signal,

generating a vertical control signal responsive to said vertical acceleration signal for attaining vertical control without fluctuation,

detecting a stroke of said active suspension using a suspension stroke sensor provided for each active suspension,

generating a stroke signal based on said stroke,

generating a stroke control signal based on said stroke signal for attaining stroke control without fluctuation,

controlling the active suspension system responsive to said vertical control signal and said stroke control signal,

supplying said control quantity signal to said active suspension system to reduce a delay in a vehicle attitude control by the active suspension system,

detecting an actual amount of said longitudinal acceleration of said vehicle,

calculating a changing amount of vehicle height dependent on said actual amount of said longitudinal acceleration,

simultaneously lowering said reference vehicle height in a linearly proportional function of said actual amount responsive to the calculation of said changing amount so as to lower said reference vehicle height by a same displacement amount for said each active suspension, and producing a lowered reference vehicle height signal, and

using said lowered reference vehicle height signal for controlling active suspension system.

6. The method according to claim 5, further comprising the steps of:

detecting lateral acceleration of the vehicle by the lateral G-sensor during rolling of the vehicle;

removing from the detected lateral acceleration a sine component, at a vehicle rolling angle, of gravitational acceleration generated due to the rolling of the vehicle and a rolling oscillation component at an installation position of said lateral G-sensor to obtain a value of lateral acceleration; and

using the computed value as a lateral acceleration information for controlling the active suspensions.

7. The method according to claim 6, wherein:

said step of removing said sine component comprises;

obtaining a difference between strokes of left and right suspensions;

dividing the difference by a tread to obtain a quotient; and

multiplying the quotient by gravitational acceleration.

8. The method according to claim 6, wherein:

the rolling oscillation component is computed by;

obtaining a difference between vertical accelerations at left and right sides of the vehicle;

dividing the difference by a lateral-direction span of said left and right sides to obtain a quotient; and

multiplying the quotient by a vertical distance between a position where the lateral acceleration is detected and a position where a rolling center axis is.

9. The method according to claim 6, wherein:

said reference vertical height increases as a proportional function of an absolute value of said actual amount of the longitudinal acceleration.

10. The method according to claim 5, wherein:

said reference vertical height increases as a proportional function of an absolute value of said actual amount of the longitudinal acceleration.