Drive-slip control system

In a drive-slip control system for a wheeled vehicle including a driven wheel sensor means for measuring the speed of a driven wheel and for producing a drive wheel speed signal, a non-driven wheel sensor means for measuring the speed of a non-driven wheel and for producing an unfiltered speed signal for the non-driven wheel, and a reducing means, responsive to the driven wheel speed signal and to a filtered reference speed signal, for reducing the speed of the driven wheel if the speed of the driven wheel exceeds, by a predetermined first amount, a reference speed obtained by filtering of the unfiltered speed signal of the non-driven wheel;

• the improvement comprising:
• a filter means for filtering the unfiltered speed signal from the non-driven wheel sensor means to produce the filtered reference speed signal fed to said reducing means and for increasing the filtered reference speed signal when said filter means receives a filter activation signal;
• and
• a comparator means for comparing the unfiltered speed signal from the non-driven wheel sensor means with the filtered reference speed signal to determine whether the unfiltered speed signal for the non-driven wheel is smaller by at least a predetermined second amount than the filtered reference speed signal and, if this condition occurs, for producing said filter activation signal for said filter means to cause the filtered reference speed signal to be increased.