System for detecting road roughness for suspension control and automotive suspension control system utilizing thus detected road roughness as control parameter

• US 5,487,006 A
• Filed: 11/16/1993
• Issued: 01/23/1996
• Est. Priority Date: 11/14/1988
• Status: Expired due to Fees

• Current Assignee: Atsugi Unisia Corporation
• Original Assignee: Atsugi Unisia Corporation
• Inventors: Taniguchi, Minoru, Kanai, Fukashi, Kakizaki, Shinobu
• Primary Examiner(s): Cosimano, Edward R.
• Assistant Examiner(s): PIPALA, EDWARD J
• Application Number:
  US08/152,880
• Time in Patent Office: 798 Days
• Field of Search: 364/424.05, 364/424.01, 364/426.01, 364/434, 280/707, 280/714
• US Class Current: 701/38
• CPC Class Codes: B60G 17/0165 to an external condition, e.g. rough road surface, side wind
• 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 2400/204 Vehicle speed
• 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 2400/922 Travelling distance
• CPC Class Codes: B60G 2500/102 stepwise
• CPC Class Codes: B60G 2500/30 Height or ground clearance
• CPC Class Codes: B60G 2600/02 Retarders, delaying means, dead zones, threshold values, cut-off frequency, timer interruption
• CPC Class Codes: B60G 2800/162 Reducing road induced vibrations

Abstract

An automotive suspension control system employs a lateral acceleration sensor monitoring a lateral acceleration exerted on a vehicular body. The output level of the lateral acceleration sensor is processed to detect frequency of a occurrence of lateral acceleration magnitude greater than a predetermined threshold level within a predetermined period of time or a predetermined distance to travel. Judgement is made that the vehicle is on a rough road when the detected frequency becomes higher than or equal to a predetermined rough road criterion. The suspension control system, according to the present invention, is responsive to the judgement of rough road condition, to order softer suspension characteristics for satisfactorily suppressing vehicular body attitude change by absorbing vibration energy.

Claims

1. A system for detecting rough road conditions comprising;

sensor means, constructed and oriented to be exclusively responsive to lateral acceleration, for monitoring lateral acceleration exerted on a vehicular body and for producing a lateral acceleration indicative signal;

means for detecting each occurrence of a lateral acceleration indicative signal having a magnitude greater than a predetermined value and for producing a detection signal in response to each occurrence, said predetermined value being set larger than or equal to a maximum value (B) of a band having a predetermined width and a center which corresponds to a zero level of said lateral acceleration indicative signal;

means for counting each occurrence of said detection signal over a predetermined time period to provide a counter signal indicative of the counted value, said counting means varying said predetermined time period depending upon vehicle speed; and

means for comparing the counter signal value with a predetermined threshold value for producing a rough road indicative signal when the counter signal value is greater than or equal to the threshold value, said predetermined threshold value being defined by a first predetermined number of times per said predetermined time period which exceeds a second predetermined number of times per said predetermined time period by a predetermined amount, said second predetermined number of times per said predetermined time period being generally indicative of a rolling motion of the vehicle, and said predetermined amount being selected to separate said first

2. A system as set forth in claim 1, wherein said sensor means is designed to produce a first polarity of lateral acceleration indicative sensor signal in response to the lateral acceleration in a first direction and a second polarity of lateral acceleration indicative sensor signal in response to the lateral acceleration in a second direction, in which said second polarity is opposite to said first polarity and said second direction is opposite to said first direction, and said detecting means produces said detection signal when the lateral acceleration indicative signal value is out of a predetermined range of values defined by a first polarity of criterion value and a second polarity of criterion value.

3. A system for detecting road conditions comprising:

a lateral G sensor for monitoring lateral acceleration exerted on a vehicular body and for producing a lateral acceleration signal indicative thereof;

means for detecting each occurrence of the lateral acceleration indicative signal having a magnitude greater than a predetermined value and for producing a detection signal each time the magnitude of the lateral acceleration signal is greater than the predetermined value, said predetermined value being set larger than or equal to a maximum value (B) of a bandwidth which has a center that generally corresponds to a zero level of the longitudinal acceleration signal;

means for counting each occurrence of said detection signal over a predetermined period and for providing a counter signal indicative of the counted value over said predetermined period; and

means for comparing the counter signal value with a predetermined threshold value for producing a rough road indicative signal when the counter signal value is greater than or equal to the threshold value, said predetermined threshold value being a first number of times per said predetermined time period which exceeds a second number of times per said predetermined time period by a predetermined amount, said second number of times per said predetermined time period being generally indicative of a rolling motion of the vehicle, and said predetermined amount being selected to separate said first predetermined number from said second number sufficiently to ensure that rolling motion of the vehicle body and rough road conditions can be distinguished from one another.

4. A system as set forth in claim 3, wherein said sensor means is designed to produce a first polarity of longitudinal acceleration indicative sensor signal in response to the longitudinal acceleration in a first direction and a second polarity of longitudinal acceleration indicative sensor signal in response to the longitudinal acceleration in a second direction, in which said second polarity is opposite to said first polarity and said second direction is opposite to said first direction, and said detecting means produces said detection signal when the longitudinal acceleration indicative signal value is out of a predetermined range of values defined by a first polarity of criterion value and a second polarity of criterion value.

5. A suspension control system for an automotive vehicle comprising:

a variable characteristic suspension system disposed between a vehicular body and a suspension member which rotatably supports a road wheel, said variable characteristic suspension system being variable to enable a plurality of characteristics ranging between a hard suspension characteristic and a soft suspension characteristic, to be selectively produced;

a sensor means for exclusively monitoring an acceleration which acts on a vehicular body in a plane which is essentially horizontal with respect to the vehicle body and for producing an acceleration signal specifically indicative of horizontal acceleration;

means for detecting each occurrence of said acceleration signal having a magnitude greater than a predetermined value to produce a detection signal, said predetermined value being set approximately equal to a value corresponding to a maximum value of a predetermined bandwidth (B);

first screening means for counting said detection signals over a predetermined time period to provide a counter signal indicative of the counted value, said counting means varying a length of said predetermined period in accordance with vehicle speed;

second screening means for comparing the counter signal value with a predetermined threshold value for producing a rough road indicative signal when the counter signal value is greater than or equal to the threshold value, said predetermined threshold value being a first predetermined number of times per said predetermined time period which exceeds a second predetermined number of times per said predetermined period by a predetermined amount, said second predetermined number of times being approximately equal to a number of times per said predetermined period which is generated when the acceleration indicative signal of the acceleration sensor which exceeds the maximum magnitude of said predetermined bandwidth (B) is generated in response to at least one of rolling motion, lifting motion, or pitching motion of the vehicle, and wherein said predetermined amount is selected to separate said first predetermined number from said second number sufficiently to ensure that the rough road conditions can be distinguished from the at least one of rolling, lifting and pitching motions; and

means for deriving a suspension control signal for adjusting suspension characteristics of said variable characteristic suspension system, said suspension control signal deriving means being responsive to said rough road indicative signal to produce said suspension control signal which selects a predetermined soft suspension characteristic from among said plurality of suspension characteristics irrespective of the suspension control characteristics which would, in the absence of said rough road indicative signal, be selected on the basis of said acceleration signal which has not been respectively screened for magnitude and frequency by said first and second screening means.

6. A suspension control system as set forth in claim 5, wherein said sensor means monitors a lateral acceleration exerted on the vehicular body.

7. A suspension control system as set forth in claim 5, wherein said variable characteristics suspension system has variable suspension characteristics between a hard suspension characteristic, a soft suspension characteristic and a medium suspension characteristic which is set between said hard suspension characteristic and said soft suspension characteristic, and wherein said suspension control system selects said medium suspension characteristic in response to said rough road indicative signal.

8. A suspension control system as set forth in a claim 7, wherein said variable characteristic suspension system employs a three-way variable damping force shock absorber.

9. A suspension control system as set forth in claim 7, which further comprises a vehicle speed sensor for monitoring vehicle speed to produce a vehicle speed indicative signal, and said suspension control signal deriving means is responsive to said vehicle speed indicative signal having a value smaller than or equal to a vehicle speed reference value representative of a substantially low vehicle speed criterion, to select soft suspension characteristics and selects said medium suspension characteristic otherwise.

10. A suspension control system as set forth in claim 7, wherein said sensor means is designed to produce a first polarity of acceleration indicative sensor signal in response to the acceleration in a first direction and a second polarity of acceleration indicative sensor signal in response to the acceleration in a second direction, in which said second polarity is opposite to said first polarity and said second direction is opposite to said first direction, and said detecting means produces said detection signal when the acceleration indicative signal value is out of a predetermined range of values defined by a first polarity criterion value and a second polarity of criterion value.

11. A suspension control system for an automotive vehicle comprising:

a variable characteristic suspension system disposed between a vehicular body and a suspension member which rotatably supports a road wheel, said variable characteristic suspension system being conditionable to produce a suspension characteristic which is selected from among a plurality of suspension characteristics that include a hard suspension characteristic and a soft suspension characteristic;

a first sensor means for exclusively monitoring an acceleration which acts in a plane that is horizontal with respect to the vehicle body, and for producing a rough road indicative signal in response to a frequency, at which the monitored acceleration exceeds a predetermined magnitude, being in excess of a predetermined limit;

a second sensor means for monitoring a vehicle speed to produce a vehicle speed indicative signal;

means responsive to said vehicle speed indicative signal for detecting a vehicle speed which is lower than or equal to a predetermined low vehicle speed, and for producing a low vehicle speed indicative signal; and

means responsive to said rough road indicative signal and said low vehicle speed indicative signal for producing a suspension control signal which (a) sets the suspension characteristic to a setting selected from among said plurality of suspension characteristics when at least one of said low vehicle speed indicative signal and said rough road indicative signal is absent, and which (b) sets said suspension characteristic to a predetermined suspension characteristic which is selected from among said plurality of characteristics and which is suitably soft for damping vertical vibration produced when the vehicle traverses a rough road, when said low vehicle speed indicative signal and said rough road indicative signal are concurrently present.

12. A suspension control system as set forth in claim 11, wherein said first sensor means includes:

means for producing a monitored acceleration signal indicative of the monitored acceleration;

means for counting a number of times said monitored acceleration signal has a magnitude greater than the predetermined limit over a predetermined period, and for producing a counter signal indicative of the counted value; and

means for comparing the counter signal value with a predetermined threshold value for producing said rough road indicative signal when the counter signal value is greater than or equal to the threshold value.

13. A suspension control system as set forth in claim 12, wherein said first sensor means monitors a lateral acceleration exerted on the vehicular body.

14. A suspension control system as set forth in claim 13, wherein said variable characteristic suspension system has variable suspension characteristics including a hard suspension characteristic, a soft characteristic and a medium suspension characteristic which is set between said hard and soft suspension chacteristics, and said suspension control system selecting said medium suspension characteristic in response to said rough road indicative signal.

15. A suspension control system as set forth in claim 14, wherein said variable characteristic suspension system employs a three-way variable damping force shock absorber.

16. A suspension control system as set forth in claim 15, wherein said suspension control signal deriving means is responsive to said vehicle speed indicative signal to select said soft suspension characteristic when said vehicle speed indicative signal has a value smaller than or equal to a vehicle speed reference value representative of a substantially low vehicle speed and selects said medium suspension characteristic when said vehicle speed indicative signal has a value greater than said vehicle speed reference value.

17. A suspension control system as set forth in claim 16, wherein said counting means varies the length of said predetermined period in accordance with vehicle speed so that the predetermined period is reduced as the vehicle speed increases.

18. A suspension control system as set forth in claim 17, wherein said first sensor means is designed to produce a first polarity of acceleration indicative sensor signal in response to the acceleration in a first direction and a second polarity of acceleration indicative sensor signal in response to the acceleration in a second direction, in which said second polarity is opposite to said first polarity and said second direction is opposite to said first direction, and said detecting means produces said detection signal when the acceleration indicative signal value is out of a predetermined range of values defined by a first polarity criterion value and a second polarity criterion value.

19. In a control system for an automotive suspension system including:

damping means disposed between a road wheel and a vehicular body for generating a damping force which resists relative motion between said road wheel and said vehicular body, said damping means including means for producing a plurality of predetermined damping characteristics which can be selected by a control command to vary a damping mode of said damping means between at least a rough road mode and a normal mode, and

a control unit electrically connected to said damping means for supplying said control command for varying the damping characteristics produced by said damping means in accordance with a vehicle traveling condition, said control unit being sensitive to a road roughness condition for setting said damping characteristic of said damping means to produce said rough road mode,

a system for detecting roughness of the road comprising;

a lateral acceleration sensor for monitoring lateral acceleration exerted on the vehicular body and for producing a lateral acceleration indicative signal exclusively representative of the magnitude of the detected lateral acceleration;

a vehicle speed sensor for monitoring vehicle speed for producing a vehicle speed indicative signal representative of the detected vehicle speed;

a detecting means for receiving said lateral acceleration indicative signal and comparing the magnitude of said lateral acceleration indicative signal with a predetermined threshold value and for outputting a pulse form detection signal each time said lateral acceleration indicative signal has a magnitude greater than or equal to said threshold value;

a counting means responsive to said pulse form detection signal for detecting occurrence of said detecting signal over a predetermined time period so that a rough road condition is detected when the detected occurrence is greater than a given threshold value, said given threshold value being at least larger than (a) one and (b) a first predetermined number of times per predetermined time period which exceeds a second number of times by a predetermined amount, said second number of times per said predetermined time period being generally indicative of a number of times said pulse form detection signal is generated per said predetermined time period in response to rolling of the vehicle, and for outputting a rough road condition detection signal to said control unit, said predetermined amount being selected to separate said first predetermined number from said second number sufficiently to ensure that the rough road condition can be distinguished from the rolling motion; and

speed discrimination means responsive to said vehicle speed indicative signal for comparing a vehicle speed indicative signal value with a predetermined vehicle speed and for discriminating between a low traveling speed condition and a high traveling speed condition, said counting means being responsive to said speed discrimination means to vary said predetermined time period in accordance with the discriminated speed, condition.

20. In a control system for an automotive suspension system including damping means disposed between a road wheel and a vehicular body for generating a damping force which resists relative motion between said road wheel and said vehicular body, said damping means including means for producing a plurality of predetermined damping characteristics which can be selected by a control command to produce at least a rough road mode and a normal mode, and

a control unit electrically connected to said damping means for supplying said control command for varying the damping characteristic depending upon a vehicle traveling condition, said control unit being sensitive to an indication of a road roughness condition for setting said damping characteristic of said damping means to produce said rough road mode,

a system for detecting roughness of the road comprising:

a lateral acceleration sensor which is constructed and arranged to exclusively monitor lateral acceleration exerted on the vehicular body and for producing a lateral acceleration indicative signal representative of a magnitude of the detected lateral acceleration;

a vehicle speed sensor for monitoring vehicle traveling speed and for producing a vehicle speed indicative signal representative of the detected vehicle speed;

detecting means for receiving said lateral acceleration indicative signal, comparing the magnitude of said lateral acceleration indicative signal with a predetermined threshold value and for outputting a pulse form detection signal at each occurrence of said lateral acceleration indicative signal having a magnitude greater than or equal to said threshold value;

counting means for receiving said detection signal, detecting a frequency of occurrence of said detection signal over a predetermined period so that a rough road condition is detected when the detected frequency is higher than a given frequency threshold, said given frequency threshold being a predetermined amount higher than that at which said lateral acceleration indicative signal is produced in response to a rolling motion of the vehicle, and for outputting a rough road condition detection signal to said control unit; and

means responsive to said vehicle speed indicative signal for comparing the vehicle speed indicative signal value with a predetermined vehicle speed and for discriminating between a low traveling speed condition and a high traveling speed condition, said counting means being responsive to said discriminating means in a manner effective to vary said given frequency threshold in accordance with the discriminated speed condition, said damping means being responsive to said rough road condition detection signal in a manner which induces said rough road mode.

21. A control system for an automotive suspension system comprising:

damping means disposed between a road wheel and a vehicular body, and responsive to a control command, for generating a variable damping force which resists relative motion between said road wheel and said vehicular body and produces at least a rough road mode and a normal mode;

a control unit electrically connected to said damping means for supplying said control command to said damping means and varying said damping characteristic depending upon a vehicle traveling condition, said control unit being sensitive to an indication of rough road condition for setting said damping characteristic of said damping means to produce said rough road mode;

a system for detecting roughness of the road comprising;

a lateral acceleration sensor for exclusively monitoring lateral acceleration exerted on the vehicular body and for producing a lateral acceleration indicative signal representative of the magnitude of the detected lateral acceleration;

a vehicle speed sensor for monitoring vehicle travelling speed to produce a vehicle speed indicative signal representative of the detected vehicle speed;

detecting means for receiving said lateral acceleration indicative signal and comparing the magnitude of said lateral acceleration indicative signal with a predetermined threshold value for outputting a pulse form detection signal at each occurrence of said lateral acceleration indicative signal having a magnitude greater than or equal to said threshold value;

counting means for receiving said detection signal for detecting a frequency of occurrence of said detection signal over a predetermined period, for detecting a rough road condition when the detected frequency is higher than a given frequency threshold, and for outputting a rough road condition detection signal to said control unit and induces said control unit to issue a control command which causes said damping means to produce said rough road mode, said given frequency threshold being set as a first predetermined frequency which exceeds a second predetermined frequency by a predetermined amount, said second predetermined frequency being a frequency indicative of vehicle roll, and said predetermined amount being selected to separate said first frequency from said second frequency sufficiently to ensure that the rough road conditions can be distinguished from the rolling motion; and

means responsive to said vehicle speed indicative signal for comparing the vehicle speed indicative signal value with a predetermined vehicle speed criterion, for discriminating between a low traveling speed condition and a high traveling speed condition and for modifying said given frequency threshold in accordance with he vehicle speed condition which is discriminated.

22. A system comprising:

sensor means for exclusively monitoring a horizontally acting lateral acceleration exerted on a vehicular component for producing a lateral acceleration indicative signal;

vehicle speed detecting means;

means for detecting each occurrence of said lateral acceleration indicative signal having a magnitude greater than a predetermined value and for producing a detection signal for each occurrence;

means for counting said detection signal over one of a predetermined time period and a predetermined running distance, to provide a counter signal indicative of the counted value,

means for comparing the counter signal value with a predetermined threshold value for producing a rough road indicative signal when the counter signal value is greater than or equal to the threshold value, said predetermined threshold value being such as a first predetermined number of times per said predetermined time period which exceeds a second predetermined number of times per said predetermined time period or per said predetermined running distance, said second predetermined number of times per said predetermined time period or per said predetermined running distance being equal to a number of times per said predetermined time period or per said predetermined running distance generated in response to vehicle roll; and

suspension control means for controlling a damping force of each suspension unit located between the vehicle body and each wheel according to the rough road indicative signal and according to the vehicle speed.

23. A system for detecting rough road conditions as set forth in claim 22, wherein one of said predetermined period and predetermined running distance is varied in accordance with increase in vehicle speed.

24. A system comprising:

suspension means selectively conditionable to produce one of a hard and a soft damping characteristic

a single sensor for sensing horizontal acceleration and for outputting a signal indicative of the sensed horizontal acceleration to said suspension means;

screening means for screening said signal for a frequency with which said signal has a magnitude greater than a predetermined value; and

means responsive to a detection of the frequency which exceeds the predetermined value for issuing a rough road indicative signal to said suspension means and for inducing said suspension means to produce said soft damping characteristic irrespective of what conditioning would otherwise be induced by said signal.