Machine sensor calibration system
A sensor calibration system for a mobile machine is disclosed. The sensor calibration system may have a first machine mounted sensor configured to sense a characteristic of an offboard object and to generate a corresponding signal, and a second machine mounted sensor configured to sense the characteristic of the offboard object and to generate a corresponding signal. The sensor calibration system may also have a controller in communication with the first and second machine mounted sensors. The controller may be configured to compare the characteristic of the offboard object as sensed by the first machine mounted sensor to the characteristic of the offboard object as sensed by the second machine mounted sensor, and to correct subsequent signals received from the first machine mounted sensor based on the comparison.
Latest Patents:
- METHODS AND COMPOSITIONS FOR RNA-GUIDED TREATMENT OF HIV INFECTION
- IRRIGATION TUBING WITH REGULATED FLUID EMISSION
- RESISTIVE MEMORY ELEMENTS ACCESSED BY BIPOLAR JUNCTION TRANSISTORS
- SIDELINK COMMUNICATION METHOD AND APPARATUS, AND DEVICE AND STORAGE MEDIUM
- SEMICONDUCTOR STRUCTURE HAVING MEMORY DEVICE AND METHOD OF FORMING THE SAME
The present disclosure relates generally to a calibration system and, more particularly, to a sensor calibration system for a mobile machine.
BACKGROUNDMachines such as, for example, off-highway haul trucks, motor graders, snow plows, and other types of heavy equipment are used to perform a variety of tasks. Some of these tasks involve carrying or pushing large, awkward, loose, and/or heavy loads up steep inclines or along rough or poorly marked haul roads. And, because of the size and momentum of the machines and/or because of poor visibility, these tasks can be difficult for a human operator to complete effectively.
To help guide the machines safely and efficiently along the haul roads, some machines are equipped with sensors, for example, RADAR sensors, SONAR sensors, LIDAR sensors, IR and non-IR cameras, and other similar sensors. These sensors are often connected to a visual display and/or a guidance system of the machine such that control over machine maneuvering may be enhanced or even automated. In order for these display and guidance systems to operate properly, the information provided by the sensors must be accurate. And, even though most machine sensor systems are calibrated when first commissioned, vibrations, collisions, and damage to the machine during operation can reduce the quality of information provided by the sensors. As such, periodic recalibration can be beneficial.
An exemplary method used to calibrate multiple machine-mounted sensors is described in U.S. Pat. No. 6,393,370 (the '370 patent) issued to Soika on May 21, 2002. Specifically, the '370 patent describes an autonomous mobile system having a plurality of sensors configured to survey objects within an immediate environment of the system. In order to improve accuracy of the autonomous mobile system, the system selectively implements a self test during which it turns around on its own axis within a static, but not necessarily known environment, and evaluates each sensor. During the self test, each sensor surveys individual cells of the environment to produce a cellularly-structured environmental map. Each sensor then classifies each cell of the map as either being occupied by an object or free of the object. The autonomous mobile system then evaluates an extent to which the classifications of individual sensors confirm one another. And, sensors whose measured results deviate from a great number of other sensors are classified as faulty. Faulty sensors can then either be indicated as being faulty, shut off, or calibrated based on the occupancy state classification.
Although the autonomous mobile system of the '370 patent may be helpful in detecting and calibrating faulty sensors, the benefit thereof may be limited. That is, the system may be beneficial only when calibrating sensors that detect occupancy states (i.e., sensors that detect a presence of an object) and, therefore, may have limited applicability to sensors that detect characteristics of an object. Further, the system of the '370 patent requires the mobile machine to interrupt its current task and turn about its axis in order to complete the self test. This interruption may reduce a productivity and efficiency of the machine. In addition, the system of the '370 patent may be limited to use with a single machine.
The disclosed sensor calibration system is directed to overcoming one or more of the problems set forth above and/or other problems of the prior art.
SUMMARYIn one aspect, the present disclosure is directed to a sensor calibration system. The sensor calibration system may include a first machine mounted sensor configured to sense a characteristic of an offboard object and to generate a corresponding signal, and a second machine mounted sensor configured to sense the characteristic of the offboard object and to generate a corresponding signal. The sensor calibration system may also include a controller in communication with the first and second machine mounted sensors. The controller may be configured to compare the characteristic of the offboard object as sensed by the first machine mounted sensor to the characteristic of the offboard object as sensed by the second machine mounted sensor, and to correct subsequent signals received from the first machine mounted sensor based on the comparison.
In another aspect, the present disclosure is directed to another sensor calibration system. This sensor calibration system may include a first sensor mounted on a first mobile machine and configured to sense a characteristic of an object at a worksite, and a first positioning device configured to indicate a position of the first mobile machine at the worksite. The sensor calibration system may also include a second sensor mounted on a second mobile machine and configured to sense the characteristic of the object, and a second positioning device configured to indicate a position of the second mobile machine at the worksite. The sensor calibration system may further include a controller in communication with the first sensor, the second sensor, the first positioning device, and the second positioning device. The controller may be configured to compare the characteristic of the object as sensed by the first sensor when the first positioning device indicates the first mobile machine is at a first worksite location to the characteristic of the object as sensed by the second sensor when the second positioning device indicates the second mobile machine is at the first worksite location. The controller may further be configured to correct subsequent signals received from the first sensor based on the comparison.
In yet another aspect, the present disclosure is directed to a method of calibrating object sensing. The method may include sensing from a first mobile machine a characteristic of an object, sensing from a second mobile machine the characteristic of the object, and comparing the characteristic of the object as sensed from the first mobile machine to the characteristic of the object as sensed from the second mobile machine. The method may further include correcting subsequent characteristics sensed from the first mobile machine based on the comparison.
In one embodiment, machine 10 may be equipped with short range sensors 18S, medium range sensors 18M, and long range sensors 18L located at different positions around body 14 of machine 10. Each sensor 18 may embody a device that detects and ranges objects located offboard machine 10 (i.e., offboard objects), for example a LIDAR (light detection and ranging) device, a RADAR (radio detection and ranging) device, a SONAR (sound navigation and ranging) device, a camera device, or another device known in the art. In one example, sensor 18 may include an emitter that emits a detection beam, and an associated receiver that receives a reflection of that detection beam. Based on characteristics of the reflected beam, a distance and a direction from an actual sensing location of sensor 18 on machine 10 to a portion of the sensed object may be determined. Sensor 18 may then generate a position signal corresponding to the distance and direction, and communicate the position signal to a controller 20 of sensor calibration system 12 for subsequent conditioning, display, and/or control of machine 10.
In order for the information provided by sensors 18 to be most accurate and useful, the actual sensing location of sensor 18 should be precisely known, and a deviation from a desired sensing location accounted for. In one example, as shown in
Controller 20 may include means for monitoring, recording, conditioning, storing, indexing, processing, and/or communicating information received from sensors 18. These means may include, for example, a memory, one or more data storage devices, a central processing unit, or any other components that may be used to run the disclosed application. Furthermore, although aspects of the present disclosure may be described generally as being stored within memory, one skilled in the art will appreciate that these aspects can be stored on or read from different types of computer program products or computer-readable media such as computer chips and secondary storage devices, including hard disks, floppy disks, optical media, CD-ROM, or other forms of RAM or ROM.
Sensor calibration system 12 may include a positioning device 22 and a calibration object 24 used by controller 20 during calibration of sensors 18. Positioning device 22 may be configured to determine a geographical location of machine 10. In particular, positioning device 22 may embody an electronic receiver configured to communicate with one or more satellites or a local radio or laser transmitting system to determine a relative location of itself and thus a reference location on machine 10. In these embodiments, positioning device 22 may receive and analyze high-frequency, low power radio or laser signals from multiple locations to triangulate a relative 3-D position of the reference location. Alternatively, positioning device 22 may embody an Inertial Reference Unit (IRU) or another known positioning device operable to receive or determine localization information associated with machine 10. A location signal indicative of the reference location position on machine 10 may be communicated from positioning device 22 to controller 20.
Calibration object 24 may include one or more features 26 positioned at known relative locations. In one example, calibration object 24 may include features 26 positioned at different heights, at different distances from machine 10 and from each other, and at different angles relative to the reference location on machine 10. In addition, features 26 may each include characteristics detectable by sensors 18, for example a width, a height, a shape, a size, an orientation, a surface finish, a material composition, a reflectivity, etc. In one embodiment, features 26 may include characteristics recognizable by different types of sensors 18 (e.g., RADAR, LIDAR, SONAR, camera, etc.) such that multiple types of sensors 18 may be simultaneously calibrated with calibration object 24. In one example, features 26 of calibration object 24 may be fixed at a particular location and substantially unmovable.
Controller 20 may be configured to calibrate sensors 18 based on position signals received from sensors 18 during detection of calibration object 24 and based on signals received from positioning device 22. That is, controller 20 may, based on a position of the machine reference location relative to calibration object 24, as provided by positioning device 22, and based on actual sensing locations of sensors 18, reference a feature map stored in memory. The feature map may be a map of characteristics associated with each feature 26 of calibration object 24, as previously detected from the desired sensing location of each sensor 18. In one example, controller 20 may include a plurality of maps stored in memory, each map corresponding to a different position of the machine reference location relative to calibration object 24, different actual sensing locations of sensors 18, different types of sensors 18 being used/calibrated, etc. Controller 20 may compare signals received from each sensor 18 at their actual sensing locations to values found within the maps corresponding to the desired sensing locations and reference location of machine 10 relative to calibration object 24. If the signals indicate that the sensed characteristics of features 26 substantially match (i.e., match within an acceptable threshold margin) the known and mapped characteristics, it can be concluded that the actual sensing location of sensors 18 substantially match the desired sensing locations and the information provided by sensors 18 may be sufficiently accurate. However, if the signals indicate that the sensed characteristics of features 26 differ significantly from the mapped characteristics, it can be concluded that the actual sensing location of sensors 18 are substantially different from the desired sensing locations and calibration of one or more of sensors 18 may be required to improve the information accuracy of sensors 18.
Controller 20 may calibrate sensor 18 by determining transformations (adjustments to the signals received from sensors 18) required to correct characteristics of features 26 detected from the sensors' actual sensing location (i.e., by determining transformations required to make the sensed characteristic information substantially match the mapped characteristic information). Specifically, as shown in
Controller 20 may have stored in memory algorithms associated with each required transformation. That is, controller 20 may have stored in memory an x-transformation algorithm, a y-transformation algorithm, a z-transformation algorithm, a roll-transformation algorithm, a pitch-transformation algorithm, and a yaw-transformation algorithm. During a calibration event when machine 10 is positioned proximate calibration object 24, controller 20 may selectively determine which of sensors 18 requires calibration by comparing sensed characteristics of features 26 to mapped characteristics. And, when the sensed characteristics significantly differ from the mapped characteristics, controller 20 may select corresponding transformation algorithms from those stored in memory and apply the algorithm to future signals received from the sensors 18 requiring calibration, based on position information of the machine reference location provided by positioning device 22.
In one example, shown in
In the embodiment shown in
As shown in
In one embodiment machine 10 may be moving during calibration of sensors 18. That is, regardless of a scan direction or an overlapping scan range, information provided by one or more sensors 18 at different times during movement of machine 10 may be compared with respect to a heading or trajectory of machine 10 to determine a need for and to complete calibration. For example, as shown in the images of
In another embodiment, information provided by sensors 18 of one machine 10 may be used to help calibrate sensors 18 of another machine 10. That is, some machines 10 may include a limited number of sensors 18, for example only a single sensor 18. As such, sensor calibration without the use of calibration object 24 and pre-mapped feature characteristic information may be difficult. However, it may be possible to compare feature characteristic information associated with an obstacle and provided by a sensor 18 of a first machine 10 to feature characteristic information associated with the same obstacle provided by a sensor 18 of a second machine 10, when position information of each machine 10 is taken into account. For example, the first machine 10 may stop proximate to or pass by a stationary obstacle at worksite 28, for instance a fuel tank or an earthen berm, and record feature characteristic and position information from sensor 18 and positioning device 22 associated with the first machine 10. Similarly, the second machine 10 may stop proximate to or pass by the same stationary obstacle and record the same feature characteristic and position information. Then, based on the position information, the feature characteristic information from each machine 10 may be compared to determine differences in the feature characteristic information. And, as described above, when the differences become significant, corresponding transformation algorithms may be selected and used by controller 20 for calibration. It is contemplated that controller 20 may have stored in memory and periodically update characteristic feature information for multiple stationary obstacles located at worksite 28, as recorded by many different sensors 18 mounted on many different machines 10 over a long period of time, so as to improve machine-to-machine calibration accuracy. It is contemplated that a single sensor 18 may similarly rely upon feature characteristic information previously generated by itself and recorded by controller 20 for later calibration, if desired.
INDUSTRIAL APPLICABILITYThe disclosed sensor calibration system may be applicable to any mobile machine that utilizes object detecting and ranging sensors. The disclosed sensor calibration system may help determine a need for sensor calibration, and provide in situ sensor calibration. In addition, the disclosed sensor calibration system may provide calibration without physical service of the sensor being required, and may do so with or without machine proximity to a specific calibration object. The disclosed sensor system may be used in conjunction with a machine having a single sensor or multiple sensors, and may be used without requiring the machine to be precisely positioned at a known calibration location.
It will be apparent to those skilled in the art that various modifications and variations can be made to the sensor calibration system of the present disclosure. Other embodiments of the sensor calibration system will be apparent to those skilled in the art from consideration of the specification and practice of the system disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope of the disclosure being indicated by the following claims and their equivalents.
Claims
1. A sensor calibration system, comprising:
- a first machine mounted sensor configured to sense a characteristic of an offboard object and to generate a corresponding signal;
- a second machine mounted sensor configured to sense the characteristic of the offboard object and to generate a corresponding signal; and
- a controller in communication with the first and second machine mounted sensors, the controller being configured to: compare the characteristic of the offboard object as sensed by the first machine mounted sensor to the characteristic of the offboard object as sensed by the second machine mounted sensor; and correct subsequent signals received from the first machine mounted sensor based on the comparison.
2. The sensor calibration system of claim 1, wherein the first and second machine mounted sensors are mounted on a common mobile machine.
3. The sensor calibration system of claim 2, further including a third machine mounted sensor configured to sense the characteristic of the offboard object and generate a corresponding signal, wherein the controller is in further communication with the third machine mounted sensor and configured to:
- compare the characteristic of the offboard object as sensed by the first machine mounted sensor to the characteristic of the offboard object as sensed by the second and third machine mounted sensors; and
- correct subsequent signals received from the first machine mounted sensor only when the characteristic of the offboard object as sensed by the first machine mounted sensor differs substantially from the characteristic of the offboard object as sensed by the second and third machine mounted sensors.
4. The sensor calibration system of claim 3, wherein the first, second, and third machine mounted sensors have substantially identical scan directions with overlapping scan ranges.
5. The sensor calibration system of claim 4, wherein one of the first, second, and third machine mounted sensors is a short range forward-looking sensor, another of the first, second, and third machine mounted sensors is a medium range forward-looking sensor, and the remaining of the first, second, and third machine mounted sensors is a long range forward-looking sensor.
6. The sensor calibration system of claim 1, wherein the offboard object is a stationary object.
7. The sensor calibration system of claim 6, wherein a mobile machine upon which the first and second machine mounted sensors are mounted remains substantially stationary during the characteristic sensing of the first and second sensors.
8. The sensor calibration system of claim 6, wherein a mobile machine upon which the first and second machine mounted sensors are mounted is moving during the characteristic sensing of the first and second sensors.
9. The sensor calibration system of claim 8, further including a machine mounted positioning device configured to determine a machine heading during the characteristic sensing of the first and second machine mounted sensors, wherein the characteristic of the offboard object is a position of the offboard object with respect to the machine heading.
10. The sensor calibration system of claim 1, wherein:
- the first machine mounted sensor is mounted on the first mobile machine; and
- the second machine mounted sensor is mounted on a second mobile machine.
11. The sensor calibration system of claim 10, wherein the first machine mounted sensor is the only sensor mounted on the first mobile machine that is configured to sense the characteristic of the offboard object within an environment of the first mobile machine.
12. The sensor calibration system of claim 1, wherein the controller is further configured to generate a map having stored therein the characteristic of the offboard object as sensed by the first and second machine mounted sensors.
13. A sensor calibration system, comprising:
- a first sensor mounted on a first mobile machine and configured to sense a characteristic of an object at a worksite;
- a first positioning device configured to indicate a position of the first mobile machine at the worksite;
- a second sensor mounted on a second mobile machine and configured to sense the characteristic of the object;
- a second positioning device configured to indicate a position of the second mobile machine at the worksite; and
- a controller in communication with the first sensor, the second sensor, the first positioning device, and the second positioning device, the controller being configured to: compare the characteristic of the object as sensed by the first sensor when the first positioning device indicates the first mobile machine is at a first worksite location to the characteristic of the object as sensed by the second sensor when the second positioning device indicates the second mobile machine is at the first worksite location; and correct subsequent signals received from the first sensor based on the comparison.
14. The sensor calibration system of claim 13, wherein the object remains substantially stationary during the characteristic sensing of the first and second sensors.
15. The sensor calibration system of claim 14, wherein the first and second mobile machines remain stationary during the characteristic sensing of the first and second sensors.
16. The sensor calibration system of claim 14, wherein the first and second mobile machines are moving during the characteristic sensing of the first and second sensors.
17. The sensor calibration system of claim 16, wherein the first and second positioning devices are configured to determine a heading of the first and second mobile machines during the characteristic sensing of the first and second sensors, and the characteristic of the object is a position of the object with respect to the heading.
18. A method of calibrating object sensing, the method comprising:
- sensing from a first mobile machine a characteristic of an object;
- sensing from a second mobile machine the characteristic of the object;
- comparing the characteristic of the object as sensed from the first mobile machine to the characteristic of the object as sensed from the second mobile machine; and
- correcting subsequent characteristics sensed from the first mobile machine based on the comparison.
19. The method of claim 18, wherein the object, the first mobile machine, and the second mobile machine remain substantially stationary during the characteristic sensing.
20. The method of claim 18, wherein the first and second mobile machines are moving during the characteristic sensing, and the method further includes determining a heading of the first and second mobile machines during the characteristic sensing, the characteristic of the object being a position of the object relative to the headings of the first and second mobile machines.
Type: Application
Filed: Sep 19, 2008
Publication Date: Mar 25, 2010
Applicant:
Inventors: Ramadev Burigsay Hukkeri (Peoria, IL), Thandava Krishna Edara (Peoria, IL)
Application Number: 12/232,564
International Classification: G01C 25/00 (20060101);