Apparatus and method for controlling damping force characteristic of vehicular shock absorber

A method for controlling damping force characteristics of front left, front right, rear left, and rear right road wheel positioned shock absorbers of a vehicle, comprising the steps of:

• a) determining a first vehicular vertical behavior at a first position near a front right road wheel of the vehicle and outputting a first vehicular behavior signal which is indicative thereof and which is used to control damping force characteristics of the front and rear road wheel positioned shock absorbers;
• b) determining a second vehicular behavior at a second position near a front left road wheel of the vehicle and outputting a second vehicular behavior signal which is indicative thereof and which is used to control damping force characteristics of the front and rear road wheel positioned shock absorbers;
• c) forming first and second processed signals having frequency-dependent characteristics by filtering the first and second vehicular behavior signals, respectively;
• d) computing front and rear road wheel side rolling rates based on said first and second vehicular vertical behavior signals:
• e) forming a respective control signal for the front left road wheel positioned shock absorber based on the first processed signal and the front road wheel side rolling rate, forming a respective control signal for the front right road wheel positioned shock absorber based on the second processed signal and the front road wheel side rolling rate, forming a respective control signal for the rear left road wheel positioned shock absorber based on the first processed signal and the rear road wheel side rolling rate, and forming a respective control signal for the rear right road wheel positioned shock absorber based on the second processed signal and the rear road wheel side rolling rate, and outputting a respective drive signal to a corresponding one of stepping motors associated with each of the road wheel positioned shock absorbers according to a value of a respective one of the control signals;
• f) controlling damping force characteristics of the front left and front right road wheel positioned shock absorbers on the basis of the respective control signals formed in the step e);
• and
• g) at the same time as the step f), controlling damping force characteristics of the rear left and rear right road wheel positioned shock absorbers on the basis of the respective control signals formed in the step e),
• wherein the respective control signals for the rear left and rear right road wheel positioned shock absorbers have, at any given vehicle speed, phases generally matching phases of the actual vehicular vertical behavior velocity at the rear left and rear right road wheels.

An apparatus for an automotive vehicle having a vehicular body, comprising:

• a) front left, front right, rear left, and rear right road wheel positioned shock absorbers, each shock absorber being positioned on the vehicular body adjacent to a corresponding one of the front left, front right, rear left, and rear right road wheels, and being constructed and arranged so that a damping force characteristic of said each shock absorber can be changed during an extension or compression phase of a piston installed therein;
• b) a damping force characteristic changing actuator, responsive to an input drive signal, for changing the damping force characteristic of a corresponding one of the respective shock absorbers;
• c) first and second vehicular vertical sprung mass acceleration sensors, both arranged at a front portion of the vehicular body, for detecting a first and a second vehicular vertical sprung mass acceleration, respectively, at the front portion of the vehicle body and for outputting a first and a second vehicular vertical sprung mass acceleration signal, respectively;
• d) a processed signal forming unit for filtering said first and second vehicular vertical sprung mass acceleration signals to respectively form first and second processed signals having a corresponding frequency dependent characteristic;
• e) a wheel rolling rate computing unit for computing front and rear road wheel side rolling rates based on said first and second vehicular vertical behavior signals;
• and
• f) a damping force characteristic controller for forming a respective control signal for each one of the respective shock absorbers on the basis of the first and second processed signals and the front and rear wheel side rolling rates, and for outputting the respective input drive signals according to values of the respective control signals to said damping force characteristic changing actuator so as to control the damping force characteristic of said each one of said shock absorbers,
• wherein the respective control signal for the front left road wheel positioned shock absorber is based on the first processed signal and the front road wheel side rolling rate, the respective control signal for the front right road wheel positioned shock absorber is based on the second processed signal and the front road wheel side rolling rate, the respective control signal for the rear left road wheel positioned shock absorber is based on the first processed signal and the rear road wheel side rolling rate, and the respective control signal for the rear right road wheel positioned shock absorber is based on the second processed signal and the rear road wheel side rolling rate,
• wherein the respective control signals supplied to control the rear left and rear right road wheel positioned shock absorbers are phase-adjusted so that, at any given vehicle speed, phases of the respective control signals for the rear left and rear right road wheel positioned shock absorbers generally match phases of vehicular sprung mass velocity signals which would be generated at the rear left and rear right road wheels if vehicular vertical sprung mass acceleration sensors were located adjacent to the rear left and rear right road wheels.

A method for controlling a damping force characteristic of each of front left, front right, rear left, and rear right road wheel positioned shock absorbers, each shock absorber being positioned on the vehicular body adjacent to a corresponding one of the front left, front right, rear left, and rear right road wheels, and being constructed and arranged so that the damping force characteristic can be changed during an extension or compression phase of a piston installed therein, said method comprising the steps of:

• a) determining a vehicular vertical behavior at a first position and at a second position of the vehicular body, the first position and the second position being located forward with respect to the rear left and rear right road wheel positioned shock absorbers;
• b) outputting first and second vehicular vertical behavior signals according to the determined vehicular vertical behavior at the first position and at the second position, respectively;
• c) forming first and second processed signals having a corresponding frequency dependent characteristic by filtering said first and second vehicular vertical behavior signals, respectively;
• d) computing front and rear road wheel side rolling rates based on said first and second vehicular vertical behavior signals;
• e) forming a first control signal on the basis of the first processed signal and the front road wheel side rolling rate, the first control signal being supplied to the front left road wheel positioned shock absorber and phase-adjusted as a phase-adjusted first control signal to have, at any given vehicle speed, phases which generally match phases of actual vehicular vertical behavior velocity signals which would be generated at the rear left road wheel, the phase-adjusted first control signal being supplied to the rear left road wheel positioned shock absorber;
• f) forming a second control signal on the basis of the second processed signal and the front road wheel side rolling rate, the second control signal being supplied to the front right road wheel positioned shock absorber and phase-adjusted as a phase-adjusted second control signal to have, at any given vehicle speed, phases which generally match phases of actual vehicular vertical behavior velocity signals which would be generated at the rear right road wheel, the phase-adjusted second control signal being supplied to the rear right road wheel positioned shock absorber;
• g) outputting an input drive signal for each one of the respective shock absorbers according to a value of the respective first and second control signal;
• and
• h) changing the damping characteristic of said each one of the respective shock absorbers on the basis of the respective input drive signal.