Automobile speed control method and system

DETAILED DESCRIPTION One object of the present invention is to obtain a negative feedback signal to stabilize the speed control of the automobile without connecting the transducer to the throttle drive system.
Another object of the present invention is to facilitate the operation of the transducer for generating the negative feedback signal.
Yet another object of the present invention is to provide an automobile speed control system which can be easily installed in an automobile and which has stabilized preselected speed control characteristics.
According to the present invention, a first electric signal which indicates the actual road speed of the automobile is compared with a second electric signal which indicates a driving command speed.
A first error signal is generated which indicates the difference between the actual road speed and the driving command speed preselected by a driver.
Then the first error signal is compared with a third electric signal which indicates the intake air flow rate of the engine of the automobile so as to generate a throttle valve position control signal.
The intake air flow rate when the vehicle is traveling at a steady speed is approximately proportional to the throttle position and engine rotational speed.
Therefore the third electric signal may be considered to be the negative feedback signal needed for stabilizing the preselected speed control characteristic of the automobile.
The third electric signal, which indicates the intake air flow rate, is easily obtained from a signal generator means such as a potentiometer which is linked to a flow rate detector means, such as a fin or butterfly piece, which will be driven by the intake air flow.
The intake air flow passage is large enough to accommodate the fin or butterfly piece, and the outer space around the passage is sufficient to install the potentiometer.
Therefore installation on the signal generator means is easy, and the load of the throttle valve is reduced.
The output signal of the potentiometer, i