Duty cycle controller for anti-lock brake pressure regulating valve, using wheel speed deviation from target value and time derivative thereof

Claim 2

A control apparatus for controlling an anti-lock brake system for a vehicle having a plurality of wheel speed sensors for detecting actual speeds of respective wheels of the vehicle, an electrically controlled brake pressure regulating device including at least one solenoid-operated valve for regulating a braking pressure applied to each of said plurality of wheels, and a controller for controlling said pressure regulating device so as to prevent locking of each said wheel, on the basis of a relationship between the actual speed of the wheel detected by the corresponding wheel speed sensor, and a running speed of the vehicle, said control apparatus comprising: a ground-speed sensor for detecting as said running speed a ground-speed of the vehicle relative to a road surface; and said controller controlling each of said at least one solenoid-operated valve at a controlled duty cycle, so as to prevent the locking of each said wheel, said controller comprising duty cycle determining means for determining the duty cycle of each said solenoid-operated valve, on the basis of at least a wheel speed error and a time derivative of said wheel speed error, said wheel speed error being a deviation of said actual speed of the wheel detected by said corresponding wheel speed sensor, from a target wheel speed obtained on the basis of the ground-speed of the vehicle detected by said ground-speed sensor.

Claim 3

A control apparatus according to claim 1, wherein said duty cycle determining means of said controller determines as said duty cycle a sum of a first product of said wheel speed error and a proportional control gain, and a second product of said time derivative of said wheel speed error and a derivative control gain.

Claim 4

A control apparatus according to claim 2, wherein said duty cycle determining means comprises gain determining means for determining said proportional control gain such that said proportional control gain is zero when said wheel speed error is not lower than a threshold, and such that said proportional control gain is equal to a value other than zero when said wheel speed error is higher than said threshold.

Claim 5

A control apparatus according to claim 1, wherein said controller comprises target speed determining means for determining said target wheel speed by subtracting from said ground-speed of the vehicle a product of said ground-speed and a target slip ratio of the wheels.

Claim 6

A control apparatus according to claim 1, wherein said controller comprises target speed determining means for determining said target wheel speed by subtracting from said ground-speed of the vehicle a product of said ground-speed and a target slip ratio of the wheels when said ground-speed is higher than a threshold, and by subtracting a predetermined constant value from said ground-speed when said ground-speed is not higher than said threshold.

Claim 7

A control apparatus according to claim 1, wherein said duty cycle determining means of said controller determines said duty cycle on the basis of said ground-speed of the vehicle, as well as on the basis of said wheel speed error and said time derivative of said wheel speed error.

Claim 8

A control apparatus according to claim 6, wherein said duty cycle determining means determines as said duty cycle a sum of a first product of said wheel speed error and a proportional control gain, and a second product of said time derivative of said wheel speed error and a derivative control gain, said duty cycle determining means changing at least one of said proportional and derivative control gains with said ground-speed of the vehicle.

Claim 9

A control apparatus according to claim 1, wherein said duty cycle determining means of said controller determines said duty cycle on the basis of at least a rate of increase in a slip amount of the wheel, during an initial period following commencement of an anti-lock brake pressure control operation of each said solenoid-operated valve at said controlled duty cycle.

Claim 10

A control apparatus according to claim 8, wherein said duty cycle determining means uses said time derivative of said wheel speed error as said rate of increase in said slip amount, and determines, as said duty cycle during said initial period, a product of said time derivative and an initial derivative control gain which increases with said ground-speed of the vehicle, said duty cycle control means determining, as said duty cycle during a subsequent period of said anti-lock brake pressure control operation which follows said initial period, a sum of a first product of said time derivative and a fixed subsequent derivative control gain, and a second product of said time derivative and a proportional control gain.

Claim 11

A control apparatus according to claim 1, wherein said ground-speed sensor is a Doppler-effect type sensor including: (a) a transmitter attached to a body of the vehicle and transmitting a wave toward a road surface in a predetermined direction of propagation; (b) a receiver attached to said body and receiving a portion of said wave which is irregularly reflected by said road surface, said receiver being spaced apart from said transmitter in one of opposite running directions of the vehicle in which said predetermined direction of propagation is inclined with respect to a downward direction perpendicular to the running directions; and (c) a signal processor which provides an output representative of said ground-speed of the vehicle, on the basis of frequencies of said wave transmitted by said transmitter and said portion received by said receiver.

Claim 12

A control apparatus for controlling an anti-lock brake system for a vehicle having a plurality of wheel speed sensors for detecting actual speeds of respective wheels of the vehicle, an electrically controlled brake pressure regulating device including at least one solenoid-operated valve for regulating a braking pressure applied to each of said plurality of wheels, and a controller for controlling said pressure regulating device so as to prevent locking of each said wheel, on the basis of a relationship between the actual speed of the wheel detected by the corresponding wheel speed sensor, and a running speed of the vehicle, said control apparatus comprising: a ground-speed sensor for detecting as said running speed a ground-speed of the vehicle relative to a road surface; and said controller controlling each of said at least one solenoid-operated valve at a controlled duty cycle, so as to prevent the locking of each said wheel, said controller comprising duty cycle determining means for determining the duty cycle of each said solenoid-operated valve, on the basis of at least a wheel speed error and an actual wheel acceleration value, said wheel speed error being a deviation of said actual speed of the wheel detected by said corresponding wheel speed sensor, from a target wheel speed obtained on the basis of the ground-speed of the vehicle detected by said ground-speed sensor, said actual wheel acceleration value being a time derivative of said actual speed of the wheel.

Claim 13

A control apparatus for controlling an anti-lock brake system for a vehicle having a plurality of wheel speed sensors for detecting actual speeds of respective wheels of the vehicle, an electrically controlled brake pressure regulating device including at least one solenoid-operated valve for regulating a braking pressure applied to each of said plurality of wheels, and a controller for controlling said pressure regulating device so as to prevent locking of each said wheel, on the basis of a relationship between the actual speed of the wheel detected by the corresponding wheel speed sensor, and a running speed of the vehicle, said control apparatus comprising: a ground-speed sensor for detecting as said running speed a ground-speed of the vehicle relative to a road surface; and said controller controlling each of said at least one solenoid-operated valve at a controlled duty cycle, so as to prevent the locking of each said wheel, said controller comprising duty cycle determining means for determining the duty cycle of each said solenoid-operated valve, on the basis of at least a wheel speed error and an actual wheel acceleration value, said wheel speed error being a deviation of said actual speed of the wheel detected by said corresponding wheel speed sensor, from a target wheel speed obtained on the basis of the ground-speed of the vehicle detected by said ground-speed sensor, said actual wheel acceleration value being a time derivative of said actual speed of the wheel.

Claim 14

A control apparatus according to claim 11, wherein said duty cycle determining means of said controller determines said duty cycle on the basis of said ground-speed of the vehicle, as well as on the basis of said wheel speed error and said actual wheel acceleration.

Claim 15

A control apparatus according to claim 11, wherein said duty cycle determining means of said controller determines said duty cycle on the basis of at least a rate of increase in a slip amount of the wheel, during an initial period following commencement of an anti-lock brake pressure control operation of each said solenoid-operated valve at said controlled duty cycle.

Claim 16

A control apparatus according to claim 11, wherein said ground-speed sensor is a Doppler-effect type sensor including: (a) a transmitter attached to a body of the vehicle and transmitting a wave toward a road surface in a predetermined direction of propagation; (b) a receiver attached to said body and receiving a portion of said wave which is irregularly reflected by said road surface, said receiver being spaced apart from said transmitter in one of opposite running directions of the vehicle in which said predetermined direction of propagation is inclined with respect to a downward direction perpendicular to the running directions; and (c) a signal processor which provides an output representative of said ground-speed of the vehicle, on the basis of frequencies of said wave transmitted by said transmitter and said portion received by said receiver.