Vehicle speed control systems
First Claim
1. A vehicle speed control system arranged when rendered operative to control the engine of the vehicle so as to tend to hold the vehicle to run at a desired speed, and disabling means responsive to the speed of the vehicle and the desired speed to render the system inoperative when the actual vehicle speed exceeds the desired speed by more than a predetermined amount and when the actual vehicle speed falls below the desired speed by more than a predetermined amount.
1 Assignment
0 Petitions
Accused Products
Abstract
A vehicle speed system is described in which an electrical signal representing actual vehicle speed is compared with a stored signal representing desired vehicle speed. Any speed error is used in a servo loop to generate a control signal which tends to reduce the error to zero. In addition, signals representing the actual and desired vehicle speeds are compared in a comparator unit so as to produce a disabling signal when the actual vehicle speed either exceeds the desired speed by more than a predetermined amount, or falls below the desired speed by more than a predetermined amount, (e.g. because road conditions prevent the vehicle engine from driving the vehicle at or close to the desired speed). This enabling signal is used to switch the control system out of operation.
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Citations
16 Claims
- 1. A vehicle speed control system arranged when rendered operative to control the engine of the vehicle so as to tend to hold the vehicle to run at a desired speed, and disabling means responsive to the speed of the vehicle and the desired speed to render the system inoperative when the actual vehicle speed exceeds the desired speed by more than a predetermined amount and when the actual vehicle speed falls below the desired speed by more than a predetermined amount.
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6. A vehicle speed control system, comprising
storage means for storing a first electrical signal representing a desired speed for the vehicle, means for producing a second electrical signal dependent on the actual speed of the vehicle, means for comparing the first and second electrical signals to produce a control signal dependent on the magnitude and sign of the difference between the actual and desired vehicle speeds, speed correcting means operative in response to the control signal to change the speed of the engine of the vehicle by an amount and in a direction tending to reduce the said difference to zero, and disabling means connected to disable the speed correcting means when the said difference falls outside predetermined positive and negative limits, so as to enable the vehicle speed to be thereafter manually controlled by the driver.
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15. A system according to claim 14, in which the means for controlling the base of the transistor includes a diode whose resistance is dependent on the ambient temperature.
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16. A system according to claim 10, including an adjustable impedance in series with the first and second circuit elements and in which the means for comparing the first and second electrical signals to produce the said control signal is connected to compare a voltage representing the second electrical signal with a voltage differing from the voltage at the junction between the first and second circuit elements by an amount which is dependent on the adjustment of the variable impedance element and is such as substantially to eliminate offset between the desired vehicle speed and the speed to which the speed correcting means controls the vehicle speed.
Specification