Automotive suspension control system with road-condition-dependent damping characteristics

• US 5,034,890 A
• Filed: 01/18/1989
• Issued: 07/23/1991
• Est. Priority Date: 01/20/1984
• Status: Expired due to Term

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Fujishiro, Takeshi, Takahashi, Tohru, Ito, Ken, Takahashi, Sadahiro, Sugasawa, Fukashi
• Primary Examiner(s): Chin, Gary
• Application Number:
  US07/299,452
• Time in Patent Office: 916 Days
• Field of Search: 364/424.05, 364/550, 364/551.01, 73/105, 280/707
• US Class Current: 701/37
• CPC Class Codes: B60G 17/0165 to an external condition, e.g. rough road surface, side wind
• CPC Class Codes: B60G 17/019 characterised by the type of sensor or the arrangement thereof B60G17/01941 takes precedence
• CPC Class Codes: B60G 17/01941 characterised by the use of piezoelectric elements, e.g. sensors or actuators
• CPC Class Codes: B60G 2202/154 with an accumulator
• CPC Class Codes: B60G 2202/42 Electric actuator
• CPC Class Codes: B60G 2400/102 vertical
• CPC Class Codes: B60G 2400/106 longitudinal with regard to vehicle, e.g. braking
• CPC Class Codes: B60G 2400/204 Vehicle speed
• CPC Class Codes: B60G 2400/252 vertical
• CPC Class Codes: B60G 2400/50 Pressure
• CPC Class Codes: B60G 2400/60 Load
• CPC Class Codes: B60G 2400/82 Ground surface
• CPC Class Codes: B60G 2400/821 Uneven, rough road sensing affecting vehicle body vibration
• CPC Class Codes: B60G 2400/91 Frequency
• CPC Class Codes: B60G 2401/10 Piezoelectric elements
• CPC Class Codes: B60G 2401/12 Strain gauge
• CPC Class Codes: B60G 2401/176 Radio or audio sensitive means, e.g. Ultrasonic
• CPC Class Codes: B60G 2401/22 Radioactivity sensitive materials
• CPC Class Codes: B60G 2500/102 stepwise
• CPC Class Codes: B60G 2500/22 Spring constant
• CPC Class Codes: B60G 2600/02 : Retarders, delaying means, dead zones, threshold values, cut-off frequency, timer interruption
• CPC Class Codes: B60G 2600/182 : Active control means
• 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
• CPC Class Codes: B60G 2800/916 : Body Vibration Control
• CPC Class Codes: F16F 9/467 : using rotary valves
• CPC Class Codes: G01S 15/88 : Sonar systems specially adapted for specific applications seismic or acoustic prospecting or detecting G01V1/00

Abstract

A suspension control system for automotive vehicles automatically adjusts the damping strength of variable shock absorbers or other dampers in accordance with road surface conditions as recognized by frequency analysis of a vehicle height or vibration sensor signal. The sensor signal reflects vertical displacement of the vehicle body from the road surface and includes high-frequency components due solely to displacement of the wheels or unsprung mass relative to the road surface and low-frequency components due to displacement of the vehicle body or sprung mass. The sensor signal is filtered into these separate frequency bands, the amplitude of each of which is compared to a corresponding reference level. The results of comparison give an indication of the degree and scale of irregularities in the road surface; specifically, a high-amplitude low-frequency component indicates larger-scale bumps and dips capable of bouncing the vehicle whereas a strong high-frequency component reflects a rough-textured road surface, such as gravel. The comparison information is sent to a suspension system controller which causes actuation of the shock absorbers to a stiffer mode of operation when the low-frequency sensor signal components are relatively strong.

Claims

1. A road surface sensing system for an automobile having a sprung mass including a vehicle body and an unsprung mass including a wheel axle and a suspension control system with damping characteristics that adapts automatically to changes in road surface conditions, comprising:

a sensor producing a signal representative of a magnitude of relative displacement between the vehicle body and the wheel axle, said signal having a first frequency component and a second frequency component; and

road surface condition detecting means for extracting said first and second frequency components independently of each other and discriminating road surface condition at least between a smooth road and a rough road on the basis of a combination of magnitudes of said first and second frequency components.

2. A road surface sensing system as set forth in claim 1, wherein said road surface condition detecting means further discriminates an undulating road on the basis of a further combination of said magnitudes.

3. A road surface sensing system as set forth in claim 1, wherein said road surface condition detecting means further discriminates an uneven surfaced road on the basis of a further combination of said magnitudes.

4. A road surface sensing system for an automobile having a sprung mass and an unsprung mass and a suspension control system with damping characteristics that adapts automatically to changes in road surface conditions, comprising:

a sensor producing a signal representative of magnitude of relative displacement between the sprung mass and the unsprung mass, said signal having a first frequency component and a second frequency component;

a reference signal generator means for deriving a reference signal level on the basis of said second frequency component of said sensor signal; and

means for comparing amplitude of the first frequency component of said sensor signal with said reference signal level, said means for comparing producing first and second signals of predetermined levels indicative of a rough road surface and a smooth road surface, respectively, on the basis of the comparison.

5. A road surface sensing system as set forth in claim 4, wherein said first frequency component is within a frequency range of vibration characteristic of said sprung mass and said second frequency component is within a frequency range of vibration characteristics of said unsprung mass.