Friction coefficient estimation from camera and wheel speed data
First Claim
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1. A method for a moving vehicle, comprising:
- analyzing image data of a forward-looking camera in the vehicle to produce a camera friction coefficient regarding a road surface represented in the image data,analyzing a tire slip and a tire vibration of a tire of the vehicle based on a wheel speed signal to produce a wheel friction coefficient regarding adhesion between the tire and the road surface;
respectively assigning associated reliability information to the camera friction coefficient and the wheel friction coefficient; and
producing an estimated proactive friction coefficient as a merger of the camera friction coefficient and the wheel friction coefficient, wherein the camera friction coefficient is released directly as the estimated proactive friction coefficient when the associated reliability information assigned to the camera friction coefficient is high, a plausibility of the camera friction coefficient is checked and a value of the camera friction coefficient is confirmed based on the wheel friction coefficient to produce the estimated proactive friction coefficient when the associated reliability information assigned to the camera friction coefficient is low, and when the camera friction coefficient becomes unavailable then the wheel friction coefficient is released as the estimated proactive friction coefficient.
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Abstract
A method and an apparatus for estimating a friction coefficient in a moving vehicle analyze image data from a forward-looking vehicle camera to produce a camera friction coefficient μk, and analyze tire slip and tire vibration based on a wheel speed signal to produce a wheel friction coefficient μw. The camera and wheel friction coefficients are both considered to produce a proactive estimated friction coefficient that is primarily based on the camera friction coefficient μk, whereas the wheel friction coefficient μw is taken into account to check plausibility of the camera friction coefficient μk.
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Citations
16 Claims
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1. A method for a moving vehicle, comprising:
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analyzing image data of a forward-looking camera in the vehicle to produce a camera friction coefficient regarding a road surface represented in the image data, analyzing a tire slip and a tire vibration of a tire of the vehicle based on a wheel speed signal to produce a wheel friction coefficient regarding adhesion between the tire and the road surface; respectively assigning associated reliability information to the camera friction coefficient and the wheel friction coefficient; and producing an estimated proactive friction coefficient as a merger of the camera friction coefficient and the wheel friction coefficient, wherein the camera friction coefficient is released directly as the estimated proactive friction coefficient when the associated reliability information assigned to the camera friction coefficient is high, a plausibility of the camera friction coefficient is checked and a value of the camera friction coefficient is confirmed based on the wheel friction coefficient to produce the estimated proactive friction coefficient when the associated reliability information assigned to the camera friction coefficient is low, and when the camera friction coefficient becomes unavailable then the wheel friction coefficient is released as the estimated proactive friction coefficient. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. An apparatus for a moving vehicle,
including a forward-looking camera, at least one wheel speed sensor, and evaluation means, wherein: -
the evaluation means are configured to analyze image data of the camera in the vehicle to produce a camera friction coefficient regarding a road surface represented in the image data, the wheel speed sensor is configured and arranged to transmit a wheel speed signal to the evaluation means, the evaluation means are further configured to analyze a tire slip and a tire vibration of a tire of the vehicle based on the wheel speed signal to produce a wheel friction coefficient regarding adhesion between the tire and the road surface, the evaluation means are further configured to respectively assign associated reliability information to the camera friction coefficient and the wheel friction coefficient, and the evaluation means are further configured to produce an estimated proactive friction coefficient by a merger of the camera friction coefficient and the wheel friction coefficient, wherein the camera friction coefficient is released directly as the estimated proactive friction coefficient when the associated reliability information assigned to the camera friction coefficient is high, a plausibility of the camera friction coefficient is checked and a value of the camera friction coefficient is confirmed based on the wheel friction coefficient to produce the estimated proactive friction coefficient when the associated reliability information assigned to the camera friction coefficient is low, and when the camera friction coefficient becomes unavailable then the wheel friction coefficient is released as the estimated proactive friction coefficient.
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9. A method of estimating an actual friction coefficient of a road surface on which a vehicle is driving, comprising steps:
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a) obtaining image data of an image of said road surface, from a forward-looking camera of said vehicle; b) by analyzing said image data, producing therefrom a camera friction coefficient as a first estimate of said actual friction coefficient of said road surface; c) obtaining a wheel speed signal from a wheel speed sensor of said vehicle; d) by analyzing said wheel speed signal, determining therefrom a tire slip and a tire oscillation regarding motion of a tire of said vehicle relative to said road surface; e) based on said tire slip and said tire oscillation, determining a wheel friction coefficient as a second estimate of said actual friction coefficient of said road surface; f) respectively assigning associated reliability information to the camera friction coefficient and the wheel friction coefficient; and g) determining a proactive estimation of said actual friction coefficient of said road surface from said camera friction coefficient and said wheel friction coefficient, wherein said camera friction coefficient is released directly as said proactive estimation of said actual friction coefficient when said associated reliability information assigned to said camera friction coefficient is above a threshold, a plausibility of said camera friction coefficient is checked and a value of said camera friction coefficient is confirmed based on said wheel friction coefficient to produce said proactive estimation of said actual friction coefficient when said associated reliability information assigned to said camera friction coefficient is below said threshold, and when said camera friction coefficient becomes unavailable then said wheel friction coefficient is released as said proactive estimation of said actual friction coefficient. - View Dependent Claims (10, 11)
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12. A method of estimating an actual friction coefficient of a road surface on which a vehicle is driving, comprising steps:
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a) obtaining image data of an image of said road surface, from a forward-looking camera of said vehicle; b) by analyzing said image data, producing therefrom a camera friction coefficient as a first estimate of said actual friction coefficient of said road surface; c) obtaining a wheel speed signal from a wheel speed sensor of said vehicle; d) by analyzing said wheel speed signal, determining therefrom a tire slip and a tire oscillation regarding motion of a tire of said vehicle relative to said road surface; e) based on said tire slip and said tire oscillation, determining a wheel friction coefficient as a second estimate of said actual friction coefficient of said road surface; f) providing a first reliability information indicative of a reliability of said camera friction coefficient; g) when said first reliability information meets or exceeds a reliability threshold, then outputting said camera friction coefficient as an estimation of said actual friction coefficient; h) when said first reliability information falls below said reliability threshold, then performing a plausibility check of said camera friction coefficient by comparing said camera friction coefficient with said wheel friction coefficient; i) when said camera friction coefficient passes said plausibility check, then outputting said camera friction coefficient as an estimation of said actual friction coefficient; and j) when said camera friction coefficient fails said plausibility check, then producing and outputting an estimation of said actual friction coefficient dependent on said wheel friction coefficient. - View Dependent Claims (13, 14, 15, 16)
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Specification