Antiskid control with surface friction compensation

Claim 2

An antiskid control system for the hydraulic braking system of a wheeled vehicle having means for lowering the fluid pressure of the braking system at a variable rate, comprising: means for detecting the speed of a vehicle wheel; means for detecting the acceleretion of said wheel; means responsive to the wheel speed and the wheel acceleration for detecting when the road surface has a high or a low value of friction; means responsive to the detection of said high friction value for detecting when the wheel speed and the wheel acceleration justify a down-pressure mode and operating said pressure lowering means at a lower rate and a higher rate in sequence and further detecting when said wheel speed and wheel acceleration justify an up-pressure mode and disabling said pressure lowering means; and means responsive to the detection of said low friction value for detecting when the wheel speed and the wheel acceleration justify said down-pressure mode and operating said pressure lowering means at said higher rate and further detecting when the wheel speed and the wheel acceleration justify said up-pressure mode and disabling said pressure lowering means.

Claim 3

An antiskid control system for the hydraulic braking system of a wheeled vehicle having means for lowering the fluid pressure of the braking system at a variable rate, comprising: means for detecting the speed of a vehicle wheel; and data processing means programmed to perform the steps of: a) deriving an acceleration of the wheel from the wheel speed; b) detecting when the wheel speed and the wheel acceleration satisfy predetermined conditions representing levels of surface friction of the road and giving a first indication that the detected surface friction level is high or a second indication that the detected surface friction level is low; c) if said first indication is given, detecting whether the wheel speed and the wheel acceleration justify a down-pressure mode or an up-pressure mode; d) if said down-pressure mode is justified, operating said pressure decreasing means at a lower rate and at a higher rate in sequence, and if said up-pressure mode is justified, disabling said pressure decreasing means; e) if said second indication is given, detecting whether the wheel speed and the wheel accleration justify said down-pressure or said up-pressure mode; and f) if said down-presssure mode is justified in the step (e), operating said pressure decreasing means at said higher rate, and if said up-pressure mode is justified in the step (e), disabling said pressure decreasing means.

Claim 4

An antiskid control system for the hydraulic braking system of a wheeled vehicle having means for lowering the fluid pressure of the braking system at a variable rate, comprising: means for detecting the speed of a vehicle wheel; and data processing means programmed to perform the steps of: a) deriving an acceleration of the wheel from the wheel speed; b) detecting when the wheel speed and the wheel acceleration satisfy predetermined conditions representing levels of surface friction of the road and giving a first indication that the detected surface friction level is high or a second indication that the detected surface friction level is low; c) if said first indication is given, detecting whether the wheel speed and the wheel acceleration justify a down-pressure mode or an up-pressure mode; d) if said down-pressure mode is justified, operating said pressure decreasing means at a lower rate and at a higher rate in sequence, and if said up-pressure mode is justified, disabling said pressure decreasing means; e) if said second indication is given, detecting whether the wheel speed and the wheel accleration justify said down-pressure or said up-pressure mode; and f) if said down-presssure mode is justified in the step (e), operating said pressure decreasing means at said higher rate, and if said up-pressure mode is justified in the step (e), disabling said pressure decreasing means.

Claim 5

An antiskid control system as claimed in claim 2, wherein the step (d) comprises the steps of: A) if said down-pressure mode is justified, operating the pressure decreasing means at a higher rate for a first period; B) disabling the pressure decreasing means for a second period in succession to the step (A); C) repeating the steps (A) and (B) until said up-pressure mode is justified; and D) disabling said pressure decreasing means in succession to the step (C).

Claim 6

An antiskid control system for the hydraulic braking system of a wheeled vehicle having means for decreasing the fluid pressure of the braking system at a variable rate comprising: means for detecting the speed of a vehicle wheel; and data processing means programmed to perform the steps of: a) deriving an acceleration of the wheel from the detected speed; b) detecting when said wheel acceleration becomes higher than a higher acceleration threshold for giving a first indication that the surface friction of the road is high and detecting when said wheel speed becomes lower than a lower speed threshold for giving a second indication that said surface friction is low; c) if said first indication is given, detecting a gradual down-pressure mode when the wheel speed is higher than a higher speed threshold and the wheel acceleration is simultaneously lower than a lower acceleration threshold; d) operating said pressure decreasing means at a lower rate during the detected gradual down-pressure mode; e) if said first indication is given, detecting a rapid down-pressure mode when the wheel speed is lower than said higher speed threshold and the wheel acceleration is simultaneously lower than a medium acceleration threshold; f) if said second indication is given, detecting said rapid down-pressure mode when the wheel speed is higher than said higher speed threshold and the wheel acceleration is simultaneously lower than said lower acceleration threshold or when the wheel speed is lower than said higher speed threshold and the wheel acceleration is simultaneously lower than said medium acceleration threshold; g) operating said pressure decreasing means at a higher rate during the rapid down-pressure mode detected by either the step (e) or step (f); h) detecting an up-pressure mode when the wheel speed is higher than said higher speed threshold and the wheel acceleration is simultaneously higher than a lower acceleration threshold or when the wheel acceleration is higher than said medium acceleration threshold; and i) disabling said pressure decreasing means during the detected up-pressure mode.

Claim 7

An antiskid control system for the hydraulic braking system of a wheeled vehicle having means for decreasing the fluid pressure of the braking system at a variable rate comprising: means for detecting the speed of a vehicle wheel; and data processing means programmed to perform the steps of: a) deriving an acceleration of the wheel from the detected speed; b) detecting when said wheel acceleration becomes higher than a higher acceleration threshold for giving a first indication that the surface friction of the road is high and detecting when said wheel speed becomes lower than a lower speed threshold for giving a second indication that said surface friction is low; c) if said first indication is given, detecting a gradual down-pressure mode when the wheel speed is higher than a higher speed threshold and the wheel acceleration is simultaneously lower than a lower acceleration threshold; d) operating said pressure decreasing means at a lower rate during the detected gradual down-pressure mode; e) if said first indication is given, detecting a rapid down-pressure mode when the wheel speed is lower than said higher speed threshold and the wheel acceleration is simultaneously lower than a medium acceleration threshold; f) if said second indication is given, detecting said rapid down-pressure mode when the wheel speed is higher than said higher speed threshold and the wheel acceleration is simultaneously lower than said lower acceleration threshold or when the wheel speed is lower than said higher speed threshold and the wheel acceleration is simultaneously lower than said medium acceleration threshold; g) operating said pressure decreasing means at a higher rate during the rapid down-pressure mode detected by either the step (e) or step (f); h) detecting an up-pressure mode when the wheel speed is higher than said higher speed threshold and the wheel acceleration is simultaneously higher than a lower acceleration threshold or when the wheel acceleration is higher than said medium acceleration threshold; and i) disabling said pressure decreasing means during the detected up-pressure mode.

Claim 8

An antiskid control system as claimed in claim 4, wherein the step (d) comprises the steps of: A) operating said pressure decreasing means at a higher rate in response to the detection of said gradual down-pressure mode; B) measuring the elapse of time from the initiation of the step (A); C) disabling said pressure decreasing means when the measured time reaches a first preset value; D) measuring the elapse of time from the initiation of the step (D); and E) repeating the steps (A) to (D) until the time measured by the step (D) reaches a second preset value.