Cruise Control Torque Modulation for Fuel Economy
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Solution Overview
Problem
Current cruise control systems are inefficient in maintaining speed on varying road grades, leading to lower fuel economy and unnatural vehicle behavior, such as aggressive tip-ins and downshifts while climbing hills or riding the brakes while descending.
Innovation Solution
A method that allows intelligent torque modulation within a set speed bandwidth, adjusting torque output based on speed errors and error rates, using a tiered structure that leverages efficiency modes like Active Fuel Management (AFM), current gear, and stoichiometric fueling to optimize fuel economy and handle road elevation changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If cruise control rigidly controls driver's set speed, then speed maintenance is improved, but fuel economy deteriorates and vehicle behavior becomes unnatural
Solution Approach 1:
The cruise control system dynamically adjusts torque commands based on predicted time to reach speed boundaries, transitioning from rigid constant-speed control to adaptive control that allows temporary speed variations to improve fuel economy. The controller modulates torque output according to the predicted time threshold, creating a dynamic control strategy that balances speed maintenance with fuel efficiency.
2Use of energy by moving object
If cruise control allows speed deviation, then fuel economy is improved, but speed control precision deteriorates
Solution Approach 1:
The system continuously monitors current vehicle speed and acceleration, calculates predicted time to reach speed boundaries, and adjusts torque commands based on this feedback. The closed-loop control uses speed error and error rate to modulate torque, maintaining speed within acceptable boundaries while optimizing fuel economy through intelligent torque management.
3Speed
If torque is aggressively adjusted to maintain speed, then speed control is improved, but fuel economy deteriorates
Solution Approach 1:
The controller performs preliminary calculation of the predicted time to reach speed boundaries before adjusting torque. By anticipating future speed boundary violations and preparing torque adjustment commands in advance, the system avoids aggressive last-minute corrections, enabling smoother and more fuel-efficient speed control.
4Speed
If torque output is constantly adjusted, then speed control is improved, but vehicle behavior becomes unnatural
Solution Approach 1:
The system applies partial torque adjustments only when necessary to prevent speed boundary violations, rather than continuously adjusting torque. By using a threshold-based approach where torque modulation is applied selectively based on predicted time to boundary, the system achieves adequate speed control while maintaining more natural vehicle behavior with fewer aggressive interventions.
Data Source
AI summary
A cruise control method to control a vehicle includes: receiving, by a controller of the vehicle, a set speed, a maximum allowed speed, and a minimum allowed speed, wherein each of the maximum allowed speed and the minimum allowed speed is a speed boundary; a propulsion system to produce a commanded axle torque to maintain the set speed; monitoring a current vehicle speed of the vehicle; determining a current vehicle acceleration of the vehicle; determining a time that the vehicle will take to reach the speed boundary; determining whether the time that the vehicle will take to reach the speed boundary is less than a predetermined time threshold; and in response to determining that the time that the vehicle will take to reach the speed boundary is less than the predetermined time threshold, commanding the propulsion system of the vehicle to adjust the commanded axle torque.