A constant speed running control device is disclosed for use on an automobile or motorcycle which permits automatic constant speed operation at a desired speed by a setting operation, and more particularly, to an improvement in a cancellation system for the automatic constant speed operation. The cancellation system being responsive to a throttle opening change in a closing direction of the engine throttle within a fixed period of time which is greater than a predetermined value or is responsive to irregular combustion in the engine during low operating speeds.

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.

A system and method for automatically controlling a vehicle speed to a desired cruise speed are disclosed in which in addition to a control unit and a throttle actuator through which an opening angle of an engine throttle valve is adjusted so that the vehicle speed detected by a vehicle speed sensor coincides with a target cruise speed set by a vehicle driver through a set switch, a vehicle speed determining circuit is provided for determining whether the vehicle speed detected by the vehicle speed sensor exceeds a lowest speed limit above which the cruse control by the control unit and throttle actuator becomes effective. When the vehicle speed is below the lowest speed limit, the power supply to the throttle actuator is interrupted so that the cruise control by means of the throttle actuator is cancelled.

An electronic control system for a motor vehicle friction clutch and which has an electrical reference signal generator, an engine speed sensor and signal means, and a throttle position sensor which produces a signal indicative of throttle opening. The throttle signal is combined with the engine speed signal to form a modified engine speed signal and a comparator receives the modified engine speed signal and reference signal to produce an error signal derived from the two. A clutch position control is operated by the error signal to vary the state of engagement of the clutch to equalize the modified engine speed and reference signals.

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. Another comparator detects when the vehicle speed on the uphill section has fallen to the original desired speed and closes the memory switch so that the reference reverts to Vr. Another unit closes the memory switch to ensure that the reference is brought back from Vr' to Vr if the vehicle speed increases (such as if the downhill section is followed by a level section of an uphill section).