Abstract: A vehicle speed control system is disclosed which is primarily intended for heavy vehicles and which is arranged to `anticipate` an uphill section of road immediately following a downhill section, so as to prevent loss of momentum gained on the downhill section. A comparator compares an actual speed signal Vs with a driver-settable desired speed signal Vr and produces an error signal. A level changing circuit produces an output equal to Vr in normal circumstances, but which follows Vs when the vehicle accelerates downhill. This output is fed through a memory via a switch which is open when an acceleration-deceleration unit detects that the vehicle has reached the foot of the hill. This memory therefore stores a signal Vr' representing the speed at that time, and the comparator therefore increases the engine power when the vehicle speed has fallen below this augmented reference speed, instead of waiting for the speed to fall to the original reference.

Abstract: Linkage is disclosed for adjusting the position of a diesel engine injection pump control rack in dependence on the position of the driver's accelerator pedal and also on a system for automatically maintaining the vehicle speed at a desired value. The injection pump rack is positioned by means of a pneumatic piston-cylinder assembly and connecting linkage. The pressure in the piston-cylinder assembly is adjusted by means of a driver-controlled valve in a supply line from a pressure source, and this valve is adjusted by the driver's accelerator pedal. A normally open valve is also connected in the pressure circuit and a normally closed exhaust valve is provided. When the automatic speed control system is in operation, the driver fully opens the driver-controlled valve (by fully depressing his foot pedal) and the automatic system adjusts the other valves to hold the speed at the desired value.

Abstract: An automatic speed control system is disclosed in which an error signal Ve, representing the speed error of the vehicle, is added to a ramp voltage, ramping between fixed values, to produce a control signal Vc. Two comparators compare Vc with upper and lower limits, respectively, so as to produce a pulse train on one of two lines depending on the sign of the error and having a mark-space ratio depending on the magnitude of the error. A circuit responds to the first pulse to occur in the pulse train from one of the two comparators when the vehicle is accelerating towards and overshooting a new desired speed and, via a switching circuit, lowers the upper limit applied to that comparator so as to lengthen the first pulses and help to reduce overshoot of the desired speed. When the vehicle ceases accelerating, the upper limit is switched back to the desired value, and is also switched back to its original setting when the speed falls by a preset amount.