Semi-active suspension control

• US 5,189,615 A
• Filed: 02/14/1991
• Issued: 02/23/1993
• Est. Priority Date: 06/29/1989
• Status: Expired due to Fees

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Panther, Michael, Gatter, Klaus, Rubel, Erich, Haegele, Karl-Heinz
• Primary Examiner(s): Black, Thomas G.
• Assistant Examiner(s): AUCHTERLONIE, THOMAS
• Application Number:
  US07/654,641
• Time in Patent Office: 740 Days
• Field of Search: 364/424.01, 364/424.05, 280/707, 188/267, 188/299
• 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 17/08 Characteristics of fluid dampers adjusting fluid dampers in general F16F9/44 - F16F9/53
• CPC Class Codes: B60G 2202/24 Fluid damper
• CPC Class Codes: B60G 2204/80 Interactive suspensions; arrangement affecting more than one suspension unit
• CPC Class Codes: B60G 2206/011 Modular constructions
• CPC Class Codes: B60G 2400/102 vertical
• CPC Class Codes: B60G 2400/252 vertical
• CPC Class Codes: B60G 2400/518 in damper
• CPC Class Codes: B60G 2400/8424 of ground or road
• CPC Class Codes: B60G 2500/104 continuous
• CPC Class Codes: B60G 2600/14 Differentiating means, i.e. differential control
• CPC Class Codes: B60G 2600/16 Integrating means, i.e. integral control
• CPC Class Codes: B60G 2600/184 Semi-Active control means
• CPC Class Codes: B60G 2600/602 high pass
• CPC Class Codes: B60G 2600/604 low pass

Abstract

The invention concerns a method and a device for the suspension control of vehicles, in particular motorcars and commercial vehicles, with the following steps:

Sensory ascertainment of the dynamic rolling condition and processing of the established rolling condition data, to generate a control signal for a semi-active damper, preferably one allocated to each wheel of the vehicle, the damping force of which is adjustable in certain situations which are dependent on the driving condition, to as small a value as possible. It is suggested that the semi-active damper, depending on the control signal and the actual value of the damper force is set in substitution for an active damper function which though desired with regard to the prevailing operating point, is not however achievable, this substitute setting being made with maximum hardness or maximum softness.

Claims

1. A process for the undercarriage control of vehicles, particularly of passenger cars and trucks, the vehicles having a plurality of semiactive shock absorbers arranged between the vehicle superstructure and the wheels, each semiactive shock absorber including a cylinder subdivided into two working spaces by a piston wherein a fluid may flow through a variable valve from one working space to the other, each valve being adjustable dependant on factors of absorber force and piston velocity when a factor pair falls within specific limits and each valve being adjustable according to maximally soft or maximally hard shock absorber settings when the factors fall outside said specific limits, said process comprising the steps of:

determining the piston velocity of the shock absorbers;

determining the dynamic state of vehicular travel and processing the determined state of travel for calculation of factors of shock absorber force and piston velocity for each shock absorber to provide a momentarily optimal shock absorber force; and

adjusting each valve according to the momentarily optimal shock absorber force and the corresponding factor pair of calculated shock absorber force and piston velocity, wherein;

(1) if the corresponding factor pair of calculated shock absorber force and piston velocity falls within said specific limits, the corresponding valve is adjusted dependent on the piston velocity, and

(2) if the corresponding factor pair of calculated shock absorber force and piston velocity falls outside said specific limits, the corresponding valve is adjusted to said maximally soft or maximally hard shock absorber setting depending on which of the two shock absorber settings most closely approximates the effect of the momentarily optimal shock absorber force applied to the determined dynamic state of vehicular travel.

2. The process of claim 1 wherein said step of determining the state of vehicular travel utilizes input variables including relative spring deflection path, wheel acceleration, damping force, body acceleration, road unevenness, and road unevenness speed.

3. The process of claim 1 wherein said step of calculating desired factors includes selecting damping forces so that during steering the vehicles into a bend, slight oversteering is produced, and during return to straight-ahead driving, a slight understeer is produced.

4. The process of claim 1 wherein said adjusting step includes activation of electrorheological fluid in the semi-active dampers.

5. The process of claim 1 wherein said adjusting step, if the factor pair of shock absorber force and piston velocity falls outside said specified limits, includes utilizing the piston velocity at the time of reaching the specified limit for deciding whether the maximally soft or maximally hard shock absorber setting approximates the optimal shock absorber force the closest.

6. The process of claim 5 wherein said step of deciding whether the maximally soft or maximally hard shock absorber setting approximates the optimal shock absorber the closest includes comparing the piston velocity at the time of reaching said specified limits with a threshold value, and said adjusting step includes effecting said maximally hard shock absorber setting if the amount of the piston velocity is smaller than said threshold value, while said adjusting step includes effecting said maximally soft shock absorber setting if the amount of the piston velocity is greater than said threshold value.

7. A device for suspension control on vehicles, particularly of passenger cars and trucks, the vehicles having a superstructure and wheels, said suspension control device comprising:

a plurality of semiactive shock absorbers, each said semiactive shock absorber including a cylinder adapted to contain a fluid and being subdivided into two working spaces by a piston, said piston including a variable valve for fluid communication from one working space to the other, each said variable valve being adjustable depending on a factor pair of absorber force and piston velocity when said factor pair falls within specific limits and each said variable valve being adjustable according to maximally soft or maximally hard shock absorber settings when the factor pair falls outside said specific limits; and

means for adjusting said variable valve, said adjusting means comprising means for determining the piston velocity of said shock absorbers, means for determining the dynamic state of vehicular travel, and means for calculating factors of shock absorber force and piston velocity for each said shock absorber to provide a momentarily optimal shock absorber force, said adjusting means controlling each said variable valve according to the momentarily optimal shock absorber force and said corresponding factor pair of calculated shock absorber force and piston velocity, said adjusting means operating such that;

(1) if said corresponding factor pair of calculated shock absorber force and piston velocity falls within said specific limits, said adjusting means adjusts said corresponding variable valve dependent on the piston velocity, and

(2) if said corresponding factor pair of calculated shock absorber force and piston velocity falls outside said specific limits, said adjusting means adjusts said corresponding variable valve to said maximally soft or maximally hard shock absorber settings most closely approximates the effect of the momentarily optimal shock absorber force applied to the determined state of vehicular travel.