US-12626482-B2 - Speed and slip determinations for a vehicle using optical flow technology

US12626482B2US 12626482 B2US12626482 B2US 12626482B2US-12626482-B2

Abstract

A vehicle speed and/or slip of a vehicle is determined. At least first and second images of a traveling surface captured by an image sensor using an optical lens are received by a processor. The images are used to determine the distance travelled by one or more pixels in first and second directions. These distances, along with the sampling rate of the image sensor, determine pixel speed in the first and second directions. The pixel speeds in the first direction, the second direction, or both, may be used to calculate the vehicle speed, a side slip angle, or a longitudinal slip. A tire speed may also be similarly determined using a second image sensor, a second optical lens, and a second processor capturing images of the tire surface. These vehicle parameters may be used for testing or operating the vehicle, including modifying vehicle behavior during operation.

Inventors

Thomas Johnson
Hugh W. Larsen

Assignees

MICHIGAN SCIENTIFIC CORPORATION

Dates

Publication Date: 20260512
Application Date: 20210708

Claims (17)

1 . A method, comprising: receiving a sequence of images of a traveling surface captured by an image sensor using an optical lens, wherein the image sensor is arranged on a vehicle with a wheel in contact with the traveling surface, the image sensor has a sampling rate, and the optical lens is arranged between the image sensor and the traveling surface; determining a first distance traveled by one or more pixels in a longitudinal direction along the traveling surface by comparing at least two images of the sequence; determining a second distance traveled by one or more pixels in a lateral direction along the traveling surface by comparing at least two images of the sequence; determining a first pixel speed in the longitudinal direction using the first distance and the sampling rate; determining a second pixel speed in the lateral direction using the second distance and the sampling rate; determining at least one of: a vehicle speed using at least one of the first pixel speed or the second pixel speed; a side slip using the first pixel speed and the second pixel speed; or a longitudinal slip using the first pixel speed and a tire speed; and outputting the at least one of the vehicle speed, the side slip, or the longitudinal slip for modifying a vehicle operation.
2 . The method of claim 1 , comprising: determining the tire speed as a tire longitudinal speed using a second apparatus comprising: a second image sensor arranged on the vehicle, the second image sensor having a second sampling rate; and a second optical lens arranged between the second image sensor and a wheel surface, wherein determining the tire speed comprises: receiving a sequence of images of the wheel surface captured by the second image sensor using the second optical lens; determining a first longitudinal distance traveled by one or more pixels in the longitudinal direction by comparing at least two images of the sequence of images of the wheel surface; determining a third pixel speed in the longitudinal direction using the first longitudinal distance and the second sampling rate; and determining the tire longitudinal speed using the third pixel speed.
3 . The method of claim 1 , wherein outputting the at least one of the vehicle speed, the side slip, or the longitudinal slip comprises: outputting the vehicle speed in the longitudinal direction, the vehicle speed in the lateral direction, and the side slip to a traction control system, an anti-lock braking system, or both.
4 . The method of claim 1 , wherein outputting the at least one of the vehicle speed, the side slip, or the longitudinal slip comprises: transmitting, by a wireless communication transmitter, the at least one of the vehicle speed, the side slip, or the longitudinal slip.
5 . The method of claim 1 , comprising: measuring, by a height sensor, a measured distance between the optical lens and the traveling surface; and adjusting, using the measured distance, a speed calibration value for determining the vehicle speed using at least one of the first pixel speed or the second pixel speed.
6 . An apparatus, comprising: an image sensor arranged on a vehicle with at least one wheel in contact with a traveling surface, the image sensor having a sampling rate; an optical lens arranged between the image sensor and the traveling surface; and a processor coupled to the image sensor, the processor configured to: receive a sequence of images of the traveling surface captured by the image sensor using the optical lens; determine a first distance traveled by one or more pixels in a longitudinal direction along the traveling surface by comparing at least two images of the sequence; determine a second distance traveled by one or more pixels in a lateral direction along the traveling surface by comparing at least two images of the sequence; determine a first pixel speed in the longitudinal direction using the first distance and the sampling rate; determine a second pixel speed in the lateral direction using the second distance and the sampling rate; determine at least one of: a vehicle speed using at least one of the first pixel speed or the second pixel speed; a side slip using the first pixel speed and the second pixel speed; or a longitudinal slip using the first pixel speed and a tire speed; and output the at least one of the vehicle speed, the side slip, or the longitudinal slip for modifying a vehicle operation.
7 . The apparatus of claim 6 , comprising: an illumination system directed at the traveling surface and mounted adjacent to the optical lens.
8 . The apparatus of claim 7 , wherein the illumination system comprises a light emitting diode illumination system.
9 . The apparatus of claim 7 , wherein the illumination system comprises infra-red light elements, white light elements, or some combination of infra-red light elements and white light elements.
10 . The apparatus of claim 6 , wherein the optical lens and the image sensor are mounted within one of a bumper, a body panel, a frame, or a chassis of the vehicle.
11 . The apparatus of claim 6 , wherein the optical lens and the image sensor are mounted on a bearing positioned at a spindle center of the at least one wheel.
12 . The apparatus of claim 6 , wherein the optical lens is mounted at an initial working distance from the traveling surface.
13 . The apparatus of claim 12 , comprising: an autofocus assembly coupled to the optical lens to adjust to the initial working distance during relative movement between the traveling surface and the vehicle.
14 . The apparatus of claim 6 , wherein: to determine the vehicle speed using at least one of the first pixel speed or the second pixel speed comprises to determine the vehicle speed using the first pixel speed and a speed calibration value that converts the first pixel speed to the vehicle speed; the speed calibration value is determined using an initial working distance between the optical lens and a surface; the apparatus comprises a height sensor arranged to determine a measured distance between the optical lens and the traveling surface; and the processor is configured to adjust, using the measured distance, the speed calibration value when the measured distance varies from the initial working distance.
15 . The apparatus of claim 6 , wherein the image sensor includes an adjustable sampling rate.
16 . An apparatus, comprising: an image sensor arranged on a vehicle with at least one wheel in contact with a traveling surface, the image sensor having a sampling rate; an optical lens arranged between the image sensor and a wheel surface; and a processor coupled to the image sensor, the processor configured to: receive a sequence of images of the wheel surface captured by the image sensor using the optical lens; determine a first distance traveled by one or more pixels in a longitudinal direction by comparing at least two images of the sequence; determine a second distance traveled by one or more pixels in a lateral direction by comparing at least two images of the sequence; determine a first pixel speed in the longitudinal direction using the first distance and the sampling rate; determine a second pixel speed in the lateral direction using the second distance and the sampling rate; determine a tire longitudinal speed using the first pixel speed; determine a tire lateral speed using the second pixel speed; and output at least one of the tire longitudinal speed or the tire lateral speed for modifying a vehicle operation.
17 . The apparatus of claim 16 , wherein the processor is configured to: determine a longitudinal slip using the tire longitudinal speed and a vehicle speed in the longitudinal direction.

Description

CROSS-REFERENCE(S) TO RELATED APPLICATION(S) This application claims priority to U.S. Provisional Application No. 63/049,483, filed Jul. 8, 2020, and to U.S. Provisional Application No. 63/088,033, filed Oct. 6, 2020, each of which is incorporated herein in its entirety by reference. TECHNICAL FIELD This disclosure relates generally to determining speed and slip values for vehicle usage and vehicle performance improvement using optical flow technology. BACKGROUND Vehicle testing and evaluation commonly requires real-time performance monitoring of operating vehicles. This often includes determination of the actual or true speed of the vehicle and/or a tire of the vehicle. Speed has traditionally been determined by monitoring the rotation of the vehicle wheels during operation. True speed often differs from the speed determined in such a manner. SUMMARY An aspect of the teachings herein is a method that includes receiving a sequence of images of a traveling surface captured by an image sensor using an optical lens, wherein the image sensor is arranged on a vehicle with a wheel in contact with the traveling surface, the image sensor has a sampling rate, and the optical lens is arranged between the image sensor and the traveling surface. The method also includes determining a first distance traveled by one or more pixels in a longitudinal direction along the traveling surface by comparing at least two images of the sequence, determining a second distance traveled by one or more pixels in a lateral direction along the traveling surface by comparing at least two images of the sequence, determining a first pixel speed in the longitudinal direction using the first distance and the sampling rate, and determining a second pixel speed in the lateral direction using the second distance and the sampling rate. Further, the method incudes determining at least one of a vehicle speed using at least one of the first pixel speed or the second pixel speed, a side slip using the first pixel speed and the second pixel speed, or a longitudinal slip using the first pixel speed and a tire speed, and outputting the at least one of the vehicle speed, the side slip, or the longitudinal slip for modifying a vehicle operation. An aspect of the teachings herein is an apparatus that includes an image sensor arranged on a vehicle with at least one wheel in contact with a traveling surface, the image sensor having a sampling rate, an optical lens arranged between the image sensor and the traveling surface, and a processor coupled to the image sensor. The processor is configured to receive a sequence of images of the traveling surface captured by the image sensor using the optical lens, determine a first distance traveled by one or more pixels in a longitudinal direction along the traveling surface by comparing at least two images of the sequence, determine a second distance traveled by one or more pixels in a lateral direction along the traveling surface by comparing at least two images of the sequence, determine a first pixel speed in the longitudinal direction using the first distance and the sampling rate, determine a second pixel speed in the lateral direction using the second distance and the sampling rate, determine at least one of a vehicle speed using at least one of the first pixel speed or the second pixel speed, a side slip using the first pixel speed and the second pixel speed, or a longitudinal slip using the first pixel speed and a tire speed, and output the at least one of the vehicle speed, the side slip, or the longitudinal slip for modifying a vehicle operation. Another aspect of the teachings herein is an apparatus that includes an image sensor arranged on a vehicle with at least one wheel in contact with a traveling surface, the image sensor having a sampling rate, an optical lens arranged between the image sensor and a wheel surface, and a processor coupled to the image sensor. The processor is configured to receive a sequence of images of the wheel surface captured by the image sensor using the optical lens, determine a first distance traveled by one or more pixels in a longitudinal direction by comparing at least two images of the sequence, determine a second distance traveled by one or more pixels in a lateral direction by comparing at least two images of the sequence, determine a first pixel speed in the longitudinal direction using the first distance and the sampling rate, determine a second pixel speed in the lateral direction using the second distance and the sampling rate, determine a tire longitudinal speed using the first pixel speed, determine a tire lateral speed using the second pixel speed, and output at least one of the tire longitudinal speed or the tire lateral speed for modifying a vehicle operation. Details of these and other aspects of the teachings herein are described in further detail below with reference to the drawings. BRIEF DESCRIPTION OF THE DRAWINGS The disclosure is best understood from the