Road Roughness Index Estimation for Adaptive EGR and VDE Control
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Solution Overview
Problem
Existing methods for estimating road roughness are inaccurate due to improper combination of sensor outputs and fail to provide information on generic road surface variation over distance, limiting the full fuel economy potential of exhaust gas recirculation (EGR) and variable displacement engine (VDE) operations, which can result in increased noise, vibration, and harshness (NVH).
Innovation Solution
A method for estimating a road roughness index (RRI) based on pitch energy, roll energy, and wheel speed deviation of a vehicle, using a weighted combination of sensor outputs from longitudinal and latitudinal accelerometers, yaw rate, and wheel speed sensors over a distance, allowing for adaptive adjustment of EGR flow and VDE mechanisms to improve fuel economy without increasing NVH.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If EGR flow rate is increased to improve fuel economy, then fuel consumption is reduced, but noise, vibration, and harshness (NVH) increases
Solution Approach 1:
The system dynamically changes EGR flow rate based on road roughness conditions. When road roughness exceeds a threshold, the system increases EGR flow rate to maximize fuel economy benefits while the road-induced NVH masks the engine NVH. When road roughness is low, the system reduces EGR flow rate to maintain acceptable NVH levels, thus adapting the parameter to external conditions to resolve the contradiction.
2Loss of energy
If VDE operation is implemented to improve fuel economy, then fuel consumption is reduced, but noise, vibration, and harshness (NVH) increases
Solution Approach 1:
The system dynamically adjusts VDE operation status based on road roughness conditions. When road roughness exceeds the threshold, the system enables VDE operation to achieve fuel economy benefits while the road-induced NVH masks the engine NVH. When road roughness is below the threshold, the system disables VDE operation to maintain acceptable NVH levels, thus adapting the operational parameter to external conditions to resolve the contradiction.
3Measurement precision
If road roughness estimation is improved by combining multiple sensor outputs, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The system uses existing vehicle sensors (accelerometers, wheel speed sensors, yaw rate sensors) that are already part of the vehicle's standard equipment for other functions. By repurposing these existing sensors for road roughness estimation, the system improves measurement precision without adding new hardware, thus avoiding increased device complexity while still achieving accurate road surface characterization.
Data Source
AI summary
Methods and systems are provided for estimation of a road roughness index (RRI) and adjusting vehicle operation based on the metric. In one example, a method may include estimating the RRI as a function of a pitch energy and a roll energy of the vehicle travelling on the road. In response to the RRI being higher than a threshold, engine operation such as EGR flow rate may be adjusted.