Methods and systems for estimating vehicle speed

• US 9,086,481 B1
• Filed: 01/18/2013
• Issued: 07/21/2015
• Est. Priority Date: 01/18/2013
• Status: Active Grant

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: Google Inc. (Alphabet Inc.)
• Inventors: Dowdall, Jonathan Baldwin, Zhu, Jiajun
• Primary Examiner(s): Ratcliffe, Luke
• Application Number:
  US13/745,383
• Time in Patent Office: 914 Days
• Field of Search: 356 301- 315, 356 401- 41, 356 501- 515, 356 6- 22, 356/28, 356/28.5
• US Class Current: 1/1
• CPC Class Codes: G01C 3/08 Use of electric radiation detectors
• CPC Class Codes: G01S 13/58 Velocity or trajectory determination systems; Sense-of-movement determination systems
• CPC Class Codes: G01S 13/86 Combinations of radar systems with non-radar systems, e.g. sonar, direction finder
• CPC Class Codes: G01S 13/865 Combination of radar systems with lidar systems
• CPC Class Codes: G01S 13/867 Combination of radar systems with cameras
• CPC Class Codes: G01S 17/10 using transmission of interrupted, pulse-modulated waves determination of distance by phase measurements G01S17/32
• CPC Class Codes: G01S 17/42 Simultaneous measurement of distance and other co-ordinates indirect measurement G01S17/46
• CPC Class Codes: G01S 17/58 Velocity or trajectory determination systems; Sense-of-movement determination systems
• CPC Class Codes: G01S 17/89 for mapping or imaging
• CPC Class Codes: G01S 17/931 of land vehicles
• CPC Class Codes: G01S 2013/9316 combined with communication equipment with other vehicles or with base stations
• CPC Class Codes: G01S 2013/9318 Controlling the steering
• CPC Class Codes: G01S 2013/93185 Controlling the brakes
• CPC Class Codes: G01S 2013/9319 Controlling the accelerator
• CPC Class Codes: G01S 2013/9322 using additional data, e.g. driver condition, road state or weather data
• CPC Class Codes: G01S 2013/93273 on the top of the vehicles
• CPC Class Codes: G01S 7/4817 relating to scanning

Abstract

Methods and systems for estimating vehicle speed are disclosed. A light detecting and ranging (LIDAR) device obtains a set of spatial points indicative of locations of reflective surfaces in an environment of the LIDAR device. A plurality of target points that correspond to a target surface of a target vehicle is identified in the set of spatial points. The plurality of target points includes a first point indicative of a first location on the target surface obtained by the LIDAR device at a first time and a second point indicative of a second location on the target surface obtained by the LIDAR device at a second time. A speed of the target vehicle is estimated based on the first location, the first time, the second location, and the second time.

Claims

1. A method comprising:

receiving a set of spatial points obtained using a light detection and ranging (LIDAR) device associated with a vehicle, wherein the spatial points are indicative of locations of reflective surfaces in an environment of the vehicle;

identifying in the set of spatial points a plurality of target points that correspond to a target surface of a target vehicle, wherein the target surface is a front surface or a rear surface of the target vehicle;

identifying, in the plurality of target points, a first point indicative of a first location on the target surface, wherein the first point was obtained by the LIDAR device at a first time;

identifying, in the plurality of target points, a second point indicative of a second location on the target surface, wherein the second point was obtained by the LIDAR device at a second time;

determining an offset between the first location and the second location, wherein determining the offset between the first location and the second location comprises;

defining a coordinate frame that includes a longitudinal axis, wherein the longitudinal axis is defined based on a direction of motion of the LIDAR device;

determining a projected first point by projecting the first point onto the longitudinal axis;

determining a projected second point by projecting the second point onto the longitudinal axis; and

determining the offset as a distance between the projected first point and the projected second point on the longitudinal axis;

determining a time difference between the first time and the second time; and

determining, by a computing device, an estimate of a speed of the target vehicle based on the offset divided by the time difference and the direction of motion of the LIDAR device.

2. The method of claim 1, wherein the defining a coordinate frame comprises defining a fixed coordinate frame in the environment based on data from an inertial measurement unit (IMU) associated with the vehicle.

3. The method of claim 1, wherein the defining a coordinate frame comprises defining a fixed coordinate frame in the environment based at least in part on data from a global positioning system (GPS) associated with the vehicle.

4. The method of claim 1, wherein the vehicle is configured to operate in an autonomous mode.

5. The method of claim 1, wherein the vehicle travels in a reference direction located in a two-dimensional plane, and wherein the target vehicle travels in a target direction located in the two-dimensional plane.

6. The method of claim 5, wherein the target direction is parallel to the reference direction.

7. The method of claim 6, wherein the target direction is opposite the reference direction.

8. The method of claim 1, wherein the vehicle travels in a traffic lane, and wherein the target vehicle travels in the traffic lane.

9. The method of claim 1, wherein the vehicle travels in a first traffic lane, and wherein the target vehicle travels in a second traffic lane, wherein the first traffic lane is adjacent to the second traffic lane.

10. A system comprising:

a light detection and ranging (LIDAR) device;

a processing unit;

non-transitory data storage; and

program instructions stored in the non-transitory data storage and executable by the processing unit to carry out functions comprising;

receiving a set of spatial points obtained using the LIDAR device, wherein the spatial points are indicative of locations of reflective surfaces in an environment of the LIDAR device;

identifying in the set of spatial points a plurality of target points that correspond to a target surface of a target vehicle, wherein the target surface is a front surface or a rear surface of the target vehicle;

identifying, in the plurality of target points, a first point indicative of a first location on the target surface, wherein the first point was obtained by the LIDAR device at a first time;

identifying, in the plurality of target points, a second point indicative of a second location on the target surface, wherein the second point was obtained by the LIDAR device at a second time;

determining an offset between the first location and the second location, wherein determining the offset between the first location and the second location comprises;

defining a coordinate frame that includes a longitudinal axis, wherein the longitudinal axis is defined based on a direction of motion of the LIDAR device;

determining a projected first point by projecting the first point onto the longitudinal axis;

determining a projected second point by projecting the second point onto the longitudinal axis; and

determining the offset as a distance between the projected first point and the projected second point on the longitudinal axis;

determining a time difference between the first time and the second time; and

determining an estimate of a speed of the target vehicle based on the offset divided by the time difference and the direction of motion of the LIDAR device.

11. The system of claim 10, wherein the defining a coordinate frame comprises defining a fixed coordinate frame in the environment based on data from an inertial measurement unit (IMU) associated with the LIDAR device.

12. The system of claim 10, wherein the defining a coordinate frame comprises defining a fixed coordinate frame in the environment based at least in part on data from a global positioning system (GPS) associated with the LIDAR device.

13. The system of claim 10, wherein the LIDAR device is associated with a vehicle.

14. The system of claim 13, wherein the vehicle is configured to operate in an autonomous mode.

15. A non-transitory computer-readable medium having program instructions stored therein executable by a computing device to cause the computing device to perform functions comprising:

receiving, via a processor of the computing device, a set of spatial points obtained using a light detection and ranging (LIDAR) device, wherein the spatial points are indicative of locations of reflective surfaces in an environment of the LIDAR device;

identifying in the set of spatial points a plurality of target points that correspond to a target surface of a target vehicle, wherein the target surface is a front surface or a rear surface of the target vehicle;

identifying, in the plurality of target points, a first point indicative of a first location on the target surface, wherein the first point was obtained by the LIDAR device at a first time;

identifying, in the plurality of target points, a second point indicative of a second location on the target surface, wherein the second point was obtained by the LIDAR device at a second time;

determining an offset between the first location and the second location, wherein determining the offset between the first location and the second location comprises;

defining a coordinate frame that includes a longitudinal axis, wherein the longitudinal axis is defined based on a direction of motion of the LIDAR device;

determining a projected first point by projecting the first point onto the longitudinal axis;

determining a projected second point by projecting the second point onto the longitudinal axis; and

determining the offset as a distance between the projected first point and the projected second point on the longitudinal axis;

determining a time difference between the first time and the second time; and

determining an estimate of a speed of the target vehicle based on the offset divided by the time difference and the direction of motion of the LIDAR device.

16. The non-transitory computer-readable medium of claim 15, wherein the defining a coordinate frame comprises defining a fixed coordinate frame in the environment based on data from an inertial measurement unit (IMU) associated with the LIDAR device.

17. The non-transitory computer-readable medium of claim 15, wherein the defining a coordinate frame comprises defining a fixed coordinate frame in the environment based at least in part on data from a global positioning system (GPS) associated with the LIDAR device.