Patent Application
20180164126
The present invention relates to work vehicles, and, more particularly, to work vehicles equipped with an auto-guidance system.
Work vehicles can generally be thought of as vehicles which are primarily equipped to do functional work. Such work vehicles can typically be found in the agricultural, construction, industrial and forestry technology sectors. For example, an agricultural harvester is used to harvest grain, a backhoe or excavator (also known as a track hoe) are used to dig and move dirt, a front end loader is used to pick up and move various types of material, depending on the type of attachment at the front end, a swather is used to cut and windrow crop, a crane is used to pick up and move heavy loads, and a feller/buncher is used to cut down, cut to length, stack and move trees. There are also many other types of work vehicles in these technology sectors.
In recent years, work vehicles have more commonly been equipped with an auto-guidance (AG) system, which automatically drives the vehicle on a predefined path through a geographic area such as a field. The AG system can be autonomous or semi-autonomous. In the case of a semi-autonomous AG system, an operator rides in the operator cab and can take over manual operation of the vehicle, if needed or desired. In the case of an autonomous AG system, no operator is present in the vehicle.
Such vehicles are typically equipped with a geo-reference unit (GRU), such as a global positioning system (GPS). The work vehicle can also include other types of electronic equipment which can be relevant to and work in conjunction with the AG system, such as an Inertial Measurement Unit (IMU), etc. An IMU can measure the roll angle, pitch angle, yaw angle, acceleration, etc. of the vehicle. The various electronic systems associated with the AG system are typically connected and in communication with a Vehicle Control Unit (VCU) via a CAN bus, wireless link, or the like.
While traversing the geographic area using an AG system, the roll angle of the vehicle to a horizontal or vertical reference can be relevant. For example, the GPS unit may not be positioned at the center of the vehicle longitudinal axis (i.e., the GPS may be offset relative to the centerline of the vehicle), and it may be desirable to position the vehicle such that a towed implement is positioned accurately relative to a previous swath of the implement. The roll angle of the vehicle can further affect the actual position of the GPS unit, relative to a theoretical centerline of the vehicle. Thus, it may be desirable to know the offset of the GPS unit relative to the vehicle centerline, the roll angle of the vehicle, etc. to accurately position the vehicle and attached implement during operation of the vehicle using AG.
What is needed in the art is a work vehicle that may be operated with AG, which takes into account the roll angle of the vehicle for accurately carrying out AG operations.
The present invention provides a method of calibrating a roll angle on a work vehicle in which the vehicle is engaged in a first of a sequence of calibration maneuvers in a first direction, reversed in an opposite second direction, and then engaged in a second of a sequence of calibration maneuvers in the second direction.
The invention in one form is directed to a method of calibrating a roll angle associated with a work vehicle having a GRU and an IMU. The method includes the steps of: positioning the vehicle on a substantially level surface in a first direction; taking a first calibration reading, by using the IMU to measure a roll of the vehicle while the vehicle is in a first of a sequence of calibration maneuvers in the first direction; positioning the vehicle on the substantially level surface in a second direction, generally opposite the first direction; taking a second calibration reading, by using the IMU to measure a roll of the vehicle while the vehicle is in a second of the sequence of calibration maneuvers in the second direction; and reconciling the first calibration reading and the second calibration reading to determine a calibrated roll angle of the vehicle.
An advantage of the present invention is that an off track correction factor for the roll angle can be determined, based on the error of the roll angle in opposite directions of the vehicle.
The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:
Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate embodiments of the invention, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.
Referring now to the drawings, and more particularly to
Tractor 10 generally includes a chassis 14 which carries most structural components of the tractor, such as the rear axle 16, operator cab 18, engine compartment (visible in
A GRU 22 is usually positioned at the top of the operator cab on a tractor equipped with AG. In the USA, the GRU is typically configured as a GPS unit, while in other parts of the world the exact configuration of the GRU can vary. The GPS unit may include the IMU 24, or the IMU can be separate from the GPS unit. The IMU is configured to measure predetermined dynamic criteria associated with tractor 10 while it is in operation, such as the roll angle, pitch angle, yaw angle, acceleration, etc. of the vehicle as it moves across the ground surface 12.
The GRU can communicate with a Vehicle Control Unit (VCU) 26, which in the illustrated embodiment is located in the console region within the operator cab 18. The GRU, including the GPS and IMU, can be coupled with the VCU 26 via a CAN buss, wireless connection, etc (not shown). In the illustrated embodiment, the VCU 26 is configured as a digital controller, but could also be configured as an analog or hardwired processor or an Application Specific Integrated Circuit (ASIC).
The GRU 22, including the GPS unit and the IMU 24, can be positioned at a known location on top of the operator cab 18. The tractor 10 includes a theoretical longitudinal axis 28 and a lateral axis 30 which extends through the rear axle 16. The GRU 22 can be positioned at a known location relative to the longitudinal axis 28 and lateral axis 30. For example, the GRU 22 can be positioned in line with the longitudinal axis 28 (side-to-side), and forward of the lateral axis 30 (front to back), as shown in
As will be appreciated, the actual position of the GRU 22 relative to the longitudinal axis 28 and lateral axis 30 must be taken into account when determining the actual position of the tractor 10 or an attached towed implement (not shown). For example, if the GRU 22 is positioned offset relative to the longitudinal axis 28, and it is desired to position a number of rows units on a towed implement at precise locations relative to a previous swath of the implement, then the lateral offset of the GRU 22 must be taken into account in the AG algorithm.
Moreover, the roll angle of the tractor 10 (or other work vehicle, as the case may be) must be taken into account when determining the actual position of the tractor 10 or an attached towed implement. Due to the offset of the GRU 22 relative to the longitudinal axis 28 and lateral axis 30, and the magnitude of the roll angle, the actual position of the GRU 22 will vary.
Referring to
The method of calibrating a roll angle associated with the vehicle 10 includes positioning the vehicle on a substantially level surface in a first direction A. The vehicle 10 is positioned such that that the rear axle (and lateral axis 30) is at a known location, represented by the point 32. After the vehicle 10 is positioned at the known point 32, a first calibration reading is taken using the IMU 24 to measure a roll angle α of the vehicle 10 while the vehicle 10 is in a first of a sequence of calibration maneuvers in the first direction A. Thus, the first of the sequence of calibration maneuvers includes driving the vehicle in a first direction, stopping the vehicle at a known reference location, and measuring the roll angle when the vehicle is heading in the first direction.
Then the vehicle 10 is turned around and headed in a direction B, which is generally opposite to direction A. The vehicle 10 is again positioned in the opposite direction B at the known location such that the rear axle (and lateral axis 30) aligns with the point 32. A second calibration reading is taken using the IMU 24 to measure a roll angle α of the vehicle 10 while the vehicle is parked at the point 32. Thus, the second of the sequence of calibration maneuvers includes driving the vehicle in a second direction B opposite to the direction A, stopping the vehicle at a known reference location, and measuring the roll angle when the vehicle is heading in the second direction.
The first calibration reading and the second calibration reading are then reconciled to determine a calibrated roll angle of the vehicle. To that end, the sequence of calibration maneuvers can be represented with mathematical expressions:
Roll angle α direction A*GPS antenna Height=Off track error direction A; a.
Roll angle α direction B*GPS antenna Height=Off track error direction B; and b.
(Off track error direction A+off track error direction B)/2=Off track error correction factor. c.
The off track error correction factor is then used to determine a calibrated roll angle α. If the GRU is offset from the longitudinal axis 28 and/or lateral axis 30, then the calibrated roll angle α is dependent upon the lateral offset distance and/or longitudinal offset distance, respectively.
Referring now to
The first calibration readings and the second calibration readings are then reconciled to determine a calibrated roll angle of the vehicle. To that end, the sequence of calibration maneuvers can be represented with mathematical expressions:
Avg. roll angle α direction A*GPS antenna Height=Off track error direction A; a.
Avg. roll angle α direction B*GPS antenna Height=Off track error direction B; b.
(Off track error direction A+off track error direction B)/2=Off track error correction factor. c.
The off track error correction factor is then used to determine a calibrated roll angle α.
Referring now to
The first calibration readings and the second calibration readings are then reconciled to determine a calibrated roll angle of the vehicle. To that end, the sequence of calibration maneuvers can be represented with mathematical expressions:
Avg. roll angle α direction A*GPS antenna Height=Off track error direction A; a.
Avg. roll angle α direction B*GPS antenna Height=Off track error direction B; b.
(Off track error direction A+off track error direction B)/2=Off track error correction factor. c.
The off track error correction factor is then used to determine a calibrated roll angle α.
In the calibration sequences described above, the sequences have the common factor of taking calibration readings while the vehicle 10 is in opposite directions. Examples of a point, line and circle are described. It is also possible that other calibration sequences can be used with the assistance of the AG system, such as an oval shaped travel path, etc.
While this invention has been described with respect to at least one embodiment, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.
