Motor vehicle cruise control system having mode dependent gain
First Claim
1. In a motor vehicle speed control system for positioning an engine throttle in relation to a position command generated to maintain an actual speed at a desired speed, control apparatus comprising:
- means for generating an error signal according to a difference between the actual and desired speeds;
means effective during a first control mode for generating said position command as a first function of said error signal;
means effective during a second control mode for generating said position command as a second function of said error signal, a change in said position command during said second control mode for a given change in said error signal being low relative to a corresponding change in said position command during said first control mode; and
transition control means effective in response to a change between said first and second control modes for offsetting the error signal such that said position command is substantially equal immediately before and after said change in control modes, thereby to effect a smooth transition between said first and second control modes.
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Accused Products
Abstract
A motor vehicle cruise control in which the control gain is relatively high in the normal mode of operation and relatively low in the resume and acceleration modes of operation. In the normal mode of operation, a position command for an engine throttle actuator is retrieved from a high gain look-up table as a function of the vehicle speed error. In the resume and acceleration modes of operation, the position command is retrieved from a low gain look-up table as a function of the vehicle speed error. Changes in the position command at transitions between the low gain and high gain tables are eliminated through a suitable offset of the speed error used in the position command look-up, thereby assuring a smooth transition between the normal mode and the resume or acceleration modes.
39 Citations
4 Claims
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1. In a motor vehicle speed control system for positioning an engine throttle in relation to a position command generated to maintain an actual speed at a desired speed, control apparatus comprising:
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means for generating an error signal according to a difference between the actual and desired speeds; means effective during a first control mode for generating said position command as a first function of said error signal; means effective during a second control mode for generating said position command as a second function of said error signal, a change in said position command during said second control mode for a given change in said error signal being low relative to a corresponding change in said position command during said first control mode; and transition control means effective in response to a change between said first and second control modes for offsetting the error signal such that said position command is substantially equal immediately before and after said change in control modes, thereby to effect a smooth transition between said first and second control modes.
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2. A motor vehicle speed control system for positioning an engine throttle in relation to a position command generated in relation to a speed error representing a difference between actual and desired vehicle speeds, comprising:
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means effective during a normal mode of operation for retrieving said position command from a high gain look-up table of position command vs. speed error for achieving accurate steady state vehicle speed control; means effective during a resume/acceleration mode of operation for retrieving said position command from a low gain look-up table of position command vs. speed error in which a change in said position command for a given change in said speed error is low relative to a corresponding change in said position command during said normal mode of operation, thereby to smoothly accelerate the vehicle to a higher speed; and transition control means effective in response to a change in mode of operation for offsetting the speed error such that position commands retrieved from said high gain and low gain look-up tables are substantially equal immediately before and after said change in mode of operation, thereby to effect a smooth transition between said normal and resume/acceleration modes of operation. - View Dependent Claims (3, 4)
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Specification