The Mather Jackknife Control Unit

Jackknifing occurs with and without braking. It occurs whenever the slip angles of the rear tractor wheels exceed the value at which the maximum side force is developed. Jackknifing will occur even with partial skid of rear tractor wheels because the semi-trailer pushes on the hitch introducing a yaw moment, which in turn, increases the tractor's yaw rate.

Since no satisfactory solution is available to the jackknifing problem through controlled braking, the Mather Control Unit is developed to employ the velocity² or V² damping characteristic so desirable to driver control, which provides low damping at low yaw rates, but increases rapidly to provide adequate counter torque at about 5°/second and thus effectively control jackknifing with or without braking.