Automatic headlight leveling system for motor vehicles

• US 6,480,806 B1
• Filed: 09/29/2000
• Issued: 11/12/2002
• Est. Priority Date: 10/01/1999
• Status: Expired due to Term

• Current Assignee: Bayerische Motoren Werke AG
• Original Assignee: Bayerische Motoren Werke AG
• Inventors: Lehnert, Peter, Bilz, Frank
• Primary Examiner(s): Hilten, John S.
• Assistant Examiner(s): Cherry, Stephen J.
• Application Number:
  US09/676,214
• Time in Patent Office: 774 Days
• Field of Search: 362/460, 362/464, 362/465, 702/154
• US Class Current: 702/154
• CPC Class Codes: B60Q 1/115 by electric means details of the electric drive components, e.g. motors, shafts, ball joints B60Q1/076
• CPC Class Codes: B60Q 2300/112 Vehicle speed
• CPC Class Codes: B60Q 2300/114 Vehicle acceleration or deceleration
• CPC Class Codes: B60Q 2300/132 Pitch
• CPC Class Codes: B60Q 2300/312 Adverse weather
• CPC Class Codes: B60Q 2300/32 Road surface or travel path
• CPC Class Codes: B60Q 2300/41 preceding vehicle

Abstract

A system for automatic headlight leveling control in a motor vehicle has two level sensors which are offset in the longitudinal direction for measuring the vehicle body pitch angle in the form of a level difference. An electronic control unit determines a desired value for the headlight adjustment as a function of the first derivative of the directly measured or further processed level difference. In one embodiment of the invention, electronic control unit determines a static level difference and a dynamic level difference, and the desired value is determined as a function of the first derivative or the second derivative of the dynamic level difference.

Claims

1. An automatic leveling system for vehicle headlights comprising:

at least two level sensors which are offset in a longitudinal direction of the vehicle body for measuring vehicle body pitch angle in the form of a level difference; and

an electronic control unit for determining a target value for headlight adjustment as a function of the measured level difference;

wherein the control unit determines the target value as a function of the first derivative of at least one of the measured level difference and a further processed level difference.

2. The automatic headlight leveling system according to claim 1, further comprising a filter which averages said level difference over a determinable time period, said time period being a function of the first derivative of measured level difference.

3. The automatic headlight leveling system according to claim 1, wherein:

said electronic control unit determines a static level difference value by averaging at least the measured level difference over a first defined time period, and a dynamic level difference value by averaging at least the measured level difference over a second defined time period, the first time period being substantially longer than the second time period; and

the target value is determined as a function of the first derivative of the dynamic level difference value as a further processed level difference.

4. The automatic headlight leveling system according to claim 3, wherein the target value is determined as a function of the second derivative of the dynamic level difference value.

5. The automatic headlight leveling system according to claim 2, wherein the target value is determined as a function of additional vehicle information transmitted to the control unit, said additional vehicle information comprising at least one of vehicle speed, a brake light signal and accelerator pedal position.

6. A method of controlling an inclination angle of vehicle headlights, comprising:

measuring time varying vehicle pitch;

calculating a first derivative, with respect to time, of measured vehicle pitch;

averaging said vehicle pitch over a first time period, wherein said first time period is determined as a function of said calculated first derivative; and

generating a headlight adjustment control signal as a function of averaged vehicle pitch determined in said averaging step.

7. The method according to claim 6 wherein said step of averaging comprises filtering said vehicle pitch in a lowpass filter having a time constant which is adjustable based on said first derivative.

8. A method of controlling an inclination angle of vehicle headlights, comprising:

measuring time varying vehicle pitch;

determining a static vehicle pitch by averaging said time varying vehicle pitch over a first time period;

determining a dynamic vehicle pitch by averaging said time variable vehicle pitch over a second time period which is significantly shorter than said first time period;

calculating first and second derivatives, with respect to time, of measured time variable vehicle pitch; and

generating headlight adjustment control signals as a function of said static and dynamic averages and at least said first derivative.

9. The method according to claim 8, wherein said headlight control signal is generated as a function of said first and second derivatives.