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Energy efficient cruise control (EE Cruise)

IP.com Disclosure Number: IPCOM000201326D
Publication Date: 2010-Nov-10
Document File: 6 page(s) / 45K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is an algorithm to produce a more energy efficient method of maintaining a constant speed in vehicles. The goal is to maintain a specified speed (range) while maintaining a specified energy efficiency goal. The algorithm is a priority system based on desired speed, minimum allowable speed, and the ratio for the desirable level of energy efficiency.

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Energy efficient cruise control (EE Cruise)

Existing vehicle cruise control systems make decisions based only on Desired Speed and Current Speed. By not taking energy expenditure into account, current cruise control systems waste fuel in a number of situations. A cruise control system which makes decisions based on Desired Speed, Current Speed, Current Energy Expenditure, and Current Acceleration can save energy in a number of ways.

As drawbacks to current cruise control systems, there are two main factors that reduce energy efficiency: over-acceleration and maintaining constant speed at all costs. Following is a description of each along with a proposed solution.

• Over-acceleration. Current systems continue opening the throttle until reaching the desired speed. This effect happens whenever cruise controls accelerate, but it is most noticeable when there is a large difference between the current speed and the desired speed (e.g., re-engaging cruise control after braking) When engaged, conventional cruise controls open the throttle to accelerate, as expected. However, the cruise control continues to open the throttle wider for as long as the vehicle has not reached the desired speed. The driver can feel this as the gas pedal is pushed lower and lower. Sometimes the ever-increasing request for acceleration even causes the car to down-shift, compounding the negative impact to fuel economy.

This point is subtle, but important: During the time-frame in which the vehicle accelerates, it also increases its rate of acceleration. Therefore, not only does the speed of the car increase, but also the rate at which it is speeding up. The latter is not necessarily desirable and may contribute to energy waste.

A more efficient approach is for the vehicle to reach a realistic rate of acceleration and then maintain that constant rate until it reaches the desired speed. As long as the vehicle is accelerating it will eventually reach the desired speed.

Example: A vehicle with conventional cruise control is at a constant speed. The driver engages the cruise control. The desired speed is 20 mph greater than the current speed. The car begins to accelerate. Within a few seconds the car is accelerating at a rate of 5 mph every 60 seconds (i.e., at that acceleration the speedometer reading increases 5 mph every minute). However, because the car has not yet reached the desired speed, the conventional cruise control opens the throttle further. Five seconds after engaging the cruise control, the car is now accelerating at a rate of 5 mph every 40 seconds; a few seconds later, more throttle: 5 mph every 30 seconds; later, 5 mph every 20 seconds. Conventional cruise control continually requests greater acceleration until reaching the desired speed.

Solution: As a solution presented in this disclosure, a more efficient cruise control

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system considers taking 60 seconds to accelerate 10 mph is an acceptable delay. This energy efficient cruise c...