Anti-skid control system employing integral-plus-proportional control of pulsed modulation

In an anti-skid type control system for wheeled vehicles having both braked wheels and a prime mover for applying an accelerating torque to said wheels, apparatus for maintaining wheel slip (s) in a region of values associated with a maximum coefficient of road friction .mu., comprising

• first means for determining the variation of the coefficient of friction from a maximum value and including pulse modulation means for periodically increasing and decreasing alternately an alternative one of a braking action and accelerating torque;
• and
• second means responsive to said first means for changing said alternative one of an applied braking action and an applied accelerating torque in such sense as to increase said coefficient of friction and including integral-plus-proportional control means for both applying the pulse modulation of said pulse modulation means and biasing the average system acceleration condition about which such modulation is applied, said modulation being varied in a sense to maximize said coefficient of friction;
• said first means for determining further comprising
• third means for determining the time-averaged wheel acceleration averaged over an interval between two successive points of inflection of such acceleration as a function of time and representing an interval of a time rate of change of acceleration having a preselected sense;
• fourth means for determining the time-averaged wheel acceleration over a control cycle or interval between three successive points of inflection of such acceleration and representing two successive intervals of a time rate of change of acceleration having mutually opposed senses;
• and
• comparator means responsive to said third and fourth means for providing an output indicative of the difference between a respective output of said third and fourth means.

In an anti-skid type control system for wheeled vehicles having both braked wheels and a prime mover for applying an accelerating torque to said wheels, apparatus for maintaining wheel slip (s) in a region of values associated with a maximum coefficient of road friction .mu., comprising

• first means for determining the variation of the coefficient of friction from a maximum value;
• and
• second means responsive to said first means for changing an alternative one of an applied braking action and an applied accelerating torque in such sense as to increase said coefficient of friction;
• said first means for determining further comprising
• pulse modulation means for periodically increasing and decreasing said alternative one of said braking action and accelerating torque over a control cycle;
• third means for determining the time-averaged wheel acceleration averaged over an interval between two successive points of inflection of such acceleration as a function of time and representing a pulse width modulation interval of said pulse width modulation means;
• fourth means for determining the time-averaged wheel acceleration over said control cycle or interval between three successive points of inflection of such acceleration and representing the periodicity of said pulse width modulation means;
• and
• comparator means responsive to said third and fourth means for providing an output indicative of the difference between a respective output of said third and fourth means, a modulation control input of said pulse modulation means being responsively coupled to said output of said comparator.

In an anti-skid type control system for wheeled vehicles having both braked wheels and a prime mover for applying an accelerating torque to said wheels, apparatus for maintaining wheel slip (s) in a region of values associated with a maximum coefficient of road friction .mu., comprising

• first means for determining the variation of the coefficient of friction from a maximum value;
• and
• second means responsive to said first means for changing an alternative one of an applied braking action and an applied accelerating torque in such sense as to increase said coefficient of friction;
• said first means for determining further comprising
• pulse modulation means for periodically increasing and decreasing said alternative one of said braking action and accelerating torque over a preselected control cycle corresponding to the periodicity of said pulse modulation means;
• gated fourth means gated by said pulse modulation means for determining the time-averaged wheel acceleration averaged over an interval between two successive points of inflection of such acceleration as a function of time and representing an alternative one of said pulse modulation periods of increasing and decreasing;
• and
• gated fifth means gated by said pulse modulation means for determining the time-averaged wheel acceleration averaged alternatively over the remaining one of said periods of increasing and decreasing and said control cycle representing the periodicity of said pulse width modulation means;
• comparator means responsive to said third and fourth means for providing an output indicative of the difference between a respective output of said third and fourth means, a modulation control input of said pulse modulation means being responsively coupled to said output of said comparator.

In an anti-skid type braking control system for avoiding wheel lock-up in braked wheeled vehicles, apparatus for maintaining wheel slip (s) in a region of values associated with a maximum coefficient of road friction .mu., comprising

• first means for determining the sense of the slope d.mu./ds of the coefficient of friction as a function of slip;
• and
• second means responsive to said first means for changing an applied braking action in the same sense as the sense of said rate of change function d.mu./ds;
• said first means for determining further comprising
• third means for determining the time-averaged wheel acceleration averaged over an interval between successive points of inflection of such acceleration and representing an interval of a time rate of change of acceleration having a preselected sense;
• fourth means for determining the time-averaged wheel acceleration over a control cycle or interval between three successive points of inflection of such acceleration and representing two successive intervals of a time rate of change of acceleration having mutually opposed senses;
• and
• comparator means responsive to said third and fourth means for providing an output indicative of the difference between the respective outputs of said third and fourth means.