Electronic speed control system for vehicles

A speed control system for an automotive vehicle driven by an internal combustion engine under control of a throttle valve, the control system comprising:

• first means for producing a timing signal with a period of time responsive to the actual speed of the vehicle;
• second means for producing a series of clock signals at a frequency inversely proportional to the actual speed of the vehicle;
• third means for producing a command signal indicative of a predetermined period of time defined by a desired speed of the vehicle;
• fourth means responsive to the timing signal for calculating a first time difference between the predetermined period of time and an instant period of time of the timing signal and for producing a first difference signal indicative of an absolute value of the calculated first time difference and a first sign signal indicative of one of positive and negative signs of the calculated first time difference;
• fifth means responsive to the timing signal for calculating a second time difference between respective instant periods of time of the preceding and following timing signals and for producing a second difference signal indicative of an absolute value of the calculated second time difference and a second sign signal indicative of one of positive and negative signs of the calculated second time difference;
• sixth means responsive to the timing signal for calculating the first number of the clock signals corresponding with a sum of the absolute values respectively defined by the first and second difference signals when respective signs of the first and second sign signals are identical to each other and for calculating the second number of the clock signals corresponding with a difference between the absolute values respectively defined by the first and second difference signals when respective signs of the first and second sign signals are opposite to each other, said sixth means selectively producing first and second correction signals respectively indicative of the calculated first number of the clock signals and the calculated second number of the clock signals and ceasing to produce the first and second correction signals when the respective calculated values are zero;
• seventh means responsive to the timing signal and one of the first and second correction signals for selectively producing first and second control signals respectively in relation to the positive and negative signs of the second sign signal;
• and
• actuator means for decreasing and increasing the opening angle of said throttle valve respectively in response to the first and second control signals.