Patent Application
20120059554
The present invention relates generally to earth-grading machines, and more particularly to an automatic blade control system for dozers.
Global navigation satellite system (GNSS) sensors can determine locations with high accuracy. Currently deployed global navigation satellite systems include the United States Global Positioning System (GPS) and the Russian GLONASS. Other global navigation satellite systems, such as the European GALILEO system, are under development. In a GNSS, a navigation receiver receives and processes radio signals transmitted by satellites located within a line-of-sight distance of the navigation receiver. The satellite signals include carrier signals modulated by pseudo-random binary codes. The navigation receiver measures the time delays of the received signals relative to a local reference clock or oscillator. Code measurements enable the navigation receiver to determine the pseudo-ranges between the navigation receiver and the satellites. The pseudo-ranges differ from the actual ranges (distances) between the navigation receiver and the satellites due to various error sources and due to variations in the time scales of the satellites and the navigation receiver. If signals are received from a sufficiently large number of satellites, then the measured pseudo-ranges can be processed to determine the code coordinates and time scales at the navigation receiver. This operational mode is referred to as a stand-alone mode, since the measurements are determined by a single navigation receiver. A stand-alone system typically provides meter-level accuracy.
To improve the accuracy, precision, stability, and reliability of measurements, differential navigation (DN) systems have been developed. In a DN system, the position of a user is determined relative to a base station (also referred to as a base) whose coordinates are precisely known (for example, by precision GNSS measurements collected over an extended period of time or by surveying measurements). The base contains a navigation receiver that receives satellite signals. The user, whose position is to be determined, can be stationary or mobile and is often referred to as a rover. The rover also contains a navigation receiver that receives satellite signals. Signal measurements processed at the base are transmitted to the rover via a communications link. The communications link, for example, can be provided over a cable or optical fiber. To accommodate a mobile rover, the communications link is often a wireless link.
The rover processes the measurements received from the base, along with measurements taken with its own navigation receiver, to improve the accuracy of determining its position. Accuracy is improved in the differential navigation mode because errors incurred by the navigation receiver at the rover and by the navigation receiver at the base are highly correlated. Since the coordinates of the base are accurately known, measurements from the base can be used to accurately compute the coordinates of the rover. A differential global positioning system (DGPS) computes locations based on pseudo-ranges only.
The location determination accuracy of a differential navigation system can be further improved by supplementing the code pseudo-range measurements with measurements of the phases of the satellite carrier signals. If the carrier phases of the signals transmitted by the same satellite are measured by both the navigation receiver at the base and the navigation receiver at the rover, processing the two sets of carrier phase measurements can yield a location determination accuracy to within several percent of the carrier's wavelength. A differential navigation system that computes locations based on real-time carrier signals, in addition to the code pseudo-ranges, is often referred to as a GNSS real-time kinematic (RTK) mode system (GNSS RTK system).
GNSS sensors, either alone or in combination with other sensors, have been used for control of earth-moving equipment. In particular, GNSS RTK systems can provide sufficiently high accuracy (on the order of one centimeter) for precision grading operations. For example, a combination of a GNSS RTK system and inertial sensors can be used to automatically control the blade of a dozer for precision grading operations. If there is a GNSS RTK system outage, however, precise control is lost. Method and apparatus for maintaining precise control during a GNSS RTK system outage would be advantageous.
For precision grading of terrain by a dozer, the dozer blade is automatically controlled based on measurements from a combination of a global navigation satellite system real-time kinematic mode (GNSS RTK) system and inertial sensors. At least one GNSS sensor and at least one inertial sensor are mounted on the dozer. The dozer blade elevation and the dozer blade slope angle are controlled during periods of normal GNSS RTK system operation. Accurate control of the dozer blade is typically lost during a GNSS RTK system outage. In an embodiment of the invention, accurate blade control is maintained during a period of GNSS RTK system outage by controlling the dozer blade slope angle and the dozer blade pitch angle. The dozer blade slope angle and the dozer blade pitch angle are controlled based on an extrapolated target value of the dozer blade slope angle and an extrapolated target value of the dozer blade pitch angle. The extrapolated target values of the angles are extrapolated from target values of the angles prior to the GNSS RTK system outage with the use of a distance travelled by the dozer. The dozer blade slope angle and the dozer blade pitch angle are measured by various combinations of inertial sensors and hydraulic cylinder stroke sensors.
In one embodiment, at least one GNSS sensor and at least one inertial sensor are mounted on the dozer blade. In a second embodiment, at least one GNSS sensor and at least one inertial sensor are mounted on the dozer body, and at least one stroke sensor is operatively coupled to at least one hydraulic cylinder controlling the dozer blade. In a third embodiment, at least one GNSS sensor and at least one inertial sensor are mounted on the dozer body, and at least one inertial sensor is mounted on the dozer blade.
These and other advantages of the invention will be apparent to those of ordinary skill in the art by reference to the following detailed description and the accompanying drawings.
The base 110 includes a navigation receiver 112 and an antenna 116 that receives satellite signals 101 from the constellation 102 of navigation satellites (shown are four representative navigation satellites, denoted navigation satellite 102A—navigation satellite 102D). Similarly, the rover 120 includes a navigation receiver 122 and an antenna 126 that receives satellite signals 103 from the constellation 102. The base 110 further includes a communications transceiver 114 and an antenna 118, and the rover further includes a communications transceiver 124 and an antenna 128. The base 110 and the rover 120 communicate (exchange data) via communication signals 105 that are transmitted and received by the transceiver 114 and the transceiver 124. In an embodiment, communication signals 105 are radiofrequency (RF) signals. Other communications signals, such as free-space optical signals, can be used. Note that
Note that the navigation receiver 122 and the communications transceiver 124 can be two separate units or a single integrated unit. Similarly, the navigation receiver 112 and the communications transceiver 114 can be two separate units or a single integrated unit.
The base 110 calculates its coordinates from the satellite signals 101; similarly, the rover 120 calculates its coordinates from the satellite signals 103. There are errors in calculating the coordinates of the base 110 and the coordinates of the rover 120. Since the coordinates of the base 110 are precisely known in advance, however, the errors in calculating the coordinates of the rover 120 from the satellite signals 103 can be calculated and compensated for. If the base 110 and the rover 120 are sufficiently close, many of the errors (such as satellite clock drift, troposphere delays, and ionosphere delays) in calculating the coordinates of the base 110 and the coordinates of the rover 120 are correlated. Therefore, correction parameters calculated by the base 110 can be used by the rover 120 to improve the accuracy of the coordinates calculated by the rover 120. The correction parameters are transmitted as data from the base 110 to the rover 120 via the communications signals 105.
To determine the coordinates of the rover 120 with high accuracy from a GNSS RTK system, therefore, the rover 120 needs to receive both the satellite signals 103 from the constellation 102 and the communications signals 105 from the base 110 and compute coordinates from the received satellite signals 103 and the received communications signals 105.
Herein, a GNSS RTK solution refers to a set of GNSS coordinates computed by a GNSS RTK algorithm executed by the GNSS receiver in the rover. A period of GNSS RTK outage refers to a time interval during which a GNSS RTK solution is not available.
A period of GNSS RTK system outage can occur for various reasons. Examples of conditions under which a GNSS RTK system outage occurs include the following: (a) the rover 120 moves into a position in which there is poor reception of the satellite signals 103 or the communication signals 105, (b) strong interference disrupts reception of the satellite signals 103 or the communications signals 105 by the rover 120, (c) the navigation receiver 122 in the rover 120 has not locked on to the satellite signals 103, (d) strong interference disrupts reception of the satellite signals 101 by the base 110, (e) the communications signals 105 are not generated and transmitted by the base 110, and (f) there is equipment failure at the base 110 or at the rover 120.
GNSS sensors have been extensively used in the area of construction machine control, particularly in grading applications. Although a control system using only a GNSS sensor for positioning can result in appropriate grading quality in some types of machines, such as graders and scrapers, it has certain limitations in other types of machines. A control system equipped only with GNSS sensors, for example, does not provide accurate control of dozers for grading at high speeds.
Improved machine control can be attained by a control system using a combination of GNSS sensors and other sensors, such as inertial sensors. U.S. Patent Application Publication No. US 2009/0069987, publication date Mar. 12, 2009, referred to herein as “Omelchenko”, which is incorporated by reference herein, describes a control system using a combination of GNSS sensors and inertial sensors to control the blade of a dozer.
In
In
In an embodiment, a set of sensors are used for blade control. A GNSS receiver receives signals from the GNSS antenna 220. Two GNSS antennas are used in some embodiments. Herein, GNSS antennas are also referred to as GNSS sensors. The inertial measurement unit IMU 226 includes three orthogonally-placed rate gyros and three orthogonally-placed accelerometers. The accelerometers measure the acceleration vector components of the acceleration along each of the axes (Xb, Yb, Zb) in the blade frame 250. The rate gyros measure the angular velocity vector components along each of the axes (Xb, Yb, Zb). Herein, rate gyros and accelerometers are also referred to as inertial sensors. In some embodiments, IMU 226 includes additional sensors, such as magnetic compasses.
In the embodiment shown in
The parameters to be controlled include the blade elevation and the blade slope angle. To control the blade elevation, the blade elevation and the blade vertical velocity are measured and estimated. To control the blade slope angle, the blade slope angle and the blade slope angular velocity are measured and estimated.
The blade elevation and the orientation of the blade relative to the dozer body are typically controlled by hydraulic cylinders. The blade elevation is typically controlled by two hydraulic cylinders (commonly referred to as the right hydraulic cylinder and the left hydraulic cylinder). The blade pitch angle is also controlled by the blade elevation hydraulic cylinders. The blade assembly is pivoted on the dozer frame; therefore, as the blade elevation is varied, the blade pitch angle is varied. The blade slope angle is typically controlled by one or two hydraulic cylinders; and the blade heading angle is typically controlled by one or two hydraulic cylinders.
The set of all hydraulic cylinders is referred to collectively as the hydraulic cylinders 208. In
To measure the blade elevation and the blade vertical velocity, both GNSS RTK data and data from the IMU 226 are used. A period of GNSS RTK system outage, therefore, can directly reduce the accuracy of the blade elevation control. To measure the blade slope angle and the blade slope angular velocity, data only from the IMU 226 is used. A period of GNSS RTK system outage, therefore, does not directly reduce the accuracy of measured values of the blade slope angle and the blade slope angular velocity. In an embodiment described below, however, GNSS RTK data is used to compute the projection of the dozer blade 206 onto a three-dimensional digital terrain model. A three-dimensional digital terrain model represents a set of points, each specified by three coordinates, that map the geometry of the terrain. The projection is then used to generate a blade slope angle reference value, also referred to as a target blade slope angle, which is provided as a reference input into a blade slope angle control system (further details are discussed below). A period of GNSS RTK system outage, therefore, can also reduce the accuracy of the blade slope angle control.
Herein, a target plane includes a set of target values for blade slope angle, blade pitch angle, blade heading angle, and blade elevation. This set of parameters uniquely defines a plane in three-dimensional space; this plane represents a current design plane. A current design plane is a small neighborhood around a point on a digital terrain model; the neighborhood can be considered as flat. Grading is performed along the target plane. The target plane is computed from the projection of the current dozer blade position onto a digital terrain model for a current GNSS epoch and is valid until the next GNSS measurements are available. When a GNSS RTK solution is available, the target plane is updated every GNSS epoch. If automatic steering is not used in the control system, the current heading angle of the dozer blade is used as a target heading angle. If automatic steering is used in the control system, the target heading angle can be computed from the digital terrain model.
Omelchenko describes a control system that controls the blade elevation and the blade slope angle. In embodiments described herein, a control system controls the blade elevation, the blade slope angle, and the blade pitch angle.
Various control algorithms can be used to control the blade pitch angle. In an embodiment, a proportional-and-derivative (PD) control algorithm is used.
The control signal uθ307 is inputted into a dozer hydraulic system 308 that controls the blade pitch angle θ311. In an embodiment, the dozer hydraulic system 308 controls blade elevation hydraulic cylinders. The blade assembly is pivoted on the dozer frame; therefore, as the blade elevation is varied, the blade pitch angle is varied.
Sensors (described below) measure the blade pitch angular velocity {dot over (θ)}309, which is inputted into the blade pitch angle estimation algorithm 312. At operation 310, the blade pitch angular velocity {dot over (θ)}309 is integrated over time to calculate the blade pitch angle θ311, which is also inputted into the blade pitch angle estimation algorithm 312. Measurements of the blade pitch angular velocity and the blade pitch angle can be provided by various sensors. In one embodiment, they are provided by the IMU 226 fixed to the dozer blade 206 (
The values of the blade pitch angular velocity {dot over (θ)}309 and the blade pitch angle θ311 include measurement errors. These values are processed by a blade pitch angle estimation algorithm 312 to reduce various errors. Omelchenko provides details of a blade elevation estimation algorithm and a blade slope angle estimation algorithm. A blade pitch angle estimation algorithm can be formulated similar to the blade slope angle estimation algorithm.
The outputs of the blade pitch angle estimation algorithm 312 are the blade pitch angular velocity estimate {dot over ({circumflex over (θ)}313 and the blade pitch angle estimate {circumflex over (θ)}315. At operation 314, the blade pitch angular velocity estimate {dot over ({circumflex over (θ)}313 is multiplied by the velocity control gain Kv,θ to yield the product Kv,θ{dot over ({circumflex over (θ)}317.
The control signal uθ307 is calculated as follows. The input θref 301 represents the reference (desired or target) value of the blade pitch angle. At operation 302, the blade pitch angle estimate {circumflex over (θ)}315, previously calculated by the blade pitch angle estimation algorithm 312, is subtracted from the reference blade pitch angle θref 301 to yield the blade pitch angle error eθ303. At operation 304, the blade pitch angle error eθ303 is multiplied by the proportional control gain Kp,θ to yield the product Kp,θeθ305. At operation 306, the product Kv,θ{dot over ({circumflex over (θ)} 317 is subtracted from the product Kp,θeθ305 to yield the control signal uθ307.
In the decision step 406, if there is no GNSS RTK system outage, then the blade control system maintains the normal operating state 402. If there is a GNSS RTK system outage, then the blade control system enters the GNSS RTK system outage mitigation state, in which (a) the blade slope angle controller is in the active state, (b) the blade elevation controller is in the inactive state, (c) the blade pitch angle controller is in the active state, and (d) the blade slope reference angle value and the blade pitch angle reference value are selected from the target plane.
Prior to a GNSS RTK system outage, the dozer blade is positioned by a control action at a correct target blade elevation value and a correct target blade pitch angle value. When a GNSS RTK system outage occurs, switching from blade elevation control to blade pitch angle control will exclude GNSS RTK data from the blade control process and will allow for smooth continuation of grading operation across the period of GNSS RTK system outage.
When GNSS RTK data is not available, the digital terrain model cannot be used. In an embodiment, an extrapolation mode is enabled to update the target plane based on a history of target plane values recorded over a specified period of time prior to the GNSS RTK system outage. The use of the target plane extrapolation requires the knowledge of the distance travelled by the dozer relative to a local navigation frame, such as the ENU navigation frame 240 (
During a period of GNSS RTK system outage, the distance travelled by the dozer cannot be computed from GNSS RTK measurements. An additional sensor, referred to as an odometer, is used to provide measurements of the distance travelled by the dozer relative to the ground and, therefore, relative to the ENU navigation frame 240. The additional sensor, which operates independently of GNSS RTK data, is included in the blade control system.
Returning to
In the decision step 420, if there is no longer a GNSS RTK system outage (that is, the GNSS RTK system operation has been re-instated), then the blade control system returns to its normal operating state 402. If the GNSS RTK system outage still continues, then the process passes to step 422, in which the GNSS RTK system outage mitigation state is maintained. The process then returns to step 410, in which updated odometer measurements are received.
The system configuration shown in
In the system configuration shown in
The hydraulic cylinder 208A is equipped with a stroke sensor 506A, which measures the stroke length of the hydraulic cylinder 208A. Other hydraulic cylinders can be similarly equipped with stroke sensors (the set of stroke sensors is referred to collectively as stroke sensors 506). The position and orientation of the dozer body 204 relative to a local navigation frame, such as the ENU navigation frame 240, can be computed using measurements from the GNSS antenna 502 and the IMU 504. The position and orientation of the dozer blade 206 relative to the dozer body 204, including roll, pitch, and heading angles, and elevation of the blade, as well as rates of change of these parameters, can be computed using measurements from the stroke sensors 506.
In the system configuration shown in
In
The location of the origin Ov 601 of the vehicle frame 602 relative to the origin On 241 of the navigation frame 240 is represented by the vector {right arrow over (P)}a,n 611, resolved in the navigation frame 240. The location of the right lower blade edge end point Pr 610 relative to the origin Ov 601 is represented by the vector {right arrow over (P)}r,v 613, resolved in the vehicle frame 602. The location of the left lower blade edge end point Pl 612 relative to the origin Ov 601 is represented by the vector {right arrow over (P)}l,v 615, resolved in the vehicle frame 602. (Note that left and right are specified from the perspective of the dozer operator.)
The values of the vectors {right arrow over (P)}r,v 613 and {right arrow over (P)}l,v 615 are determined from measurements obtained from the stroke sensors 506 with the use of additional measurements of dozer geometric parameters that can be taken during installation of the blade control system onto the dozer. Dozer geometric parameters include, for example, dimensions, locations, and orientations of various mechanical parts (such as the dozer frame, the dozer blade, hydraulic cylinders, GNSS sensors, IMUs, and stroke sensors). The values of the dozer geometric parameters can be stored in a data storage device that is a component of a control box such as the control box described in Omelchenko.
The location of the central point Pc 614 of the blade edge relative to the origin Ov 601 is represented by the vector {right arrow over (P)}c,v 617, resolved in the vehicle frame 602. The value of the vector {right arrow over (P)}c,v 617 is computed as follows:
The values of the components of the vector {right arrow over (P)}c,v 617 can be expressed in the navigation frame 240 by applying a coordinate transformation such as a sequence of Euler angle rotations, including rotations through vehicle roll angle, vehicle pitch angle, and vehicle heading angle. A sequence of Euler angles is a well-known method for coordinate transformation in the field of three-dimensional geometry and is a well-known method used in the field of three-dimensional construction machine control; therefore details are not described herein. Other methods of coordinate transformations, such as quaternions, can be used. The vector {right arrow over (P)}c,v expressed in the navigation frame 240 is denoted as {right arrow over (P)}(c,v)n.
The location of the central point Pc 614 of the blade edge relative to the origin On 241 is represented by the vector {right arrow over (P)}c,n 619, resolved in the navigation frame 240. The value of the vector {right arrow over (P)}c,n is computed as follows:
{right arrow over (P)}
c,n
={right arrow over (P)}
a,n
+{right arrow over (P)}
(c,v)n. (E2)
The value of the vector {right arrow over (P)}c,n can be used for blade elevation estimation and control. Examples of blade elevation estimation and control algorithms are described in Omelchenko.
The location of the right lower blade edge end point Pr 610 relative to the origin On 241 is represented by the vector {right arrow over (P)}r,n 621, resolved in the navigation frame 240. The values of the components of the vector {right arrow over (P)}r,v 613 can be expressed in the navigation frame 240 by applying a coordinate transformation such as a sequence of Euler angle rotations, including rotations through vehicle roll angle, vehicle pitch angle, and vehicle heading angle. The vector {right arrow over (P)}r,v expressed in the navigation frame 240 is denoted as {right arrow over (P)}(r,v)n. The value of the vector {right arrow over (P)}r,n is computed as follows:
{right arrow over (P)}
r,n
={right arrow over (P)}
a,n
+{right arrow over (P)}
r,v)n. (E3)
The location of the left lower blade edge end point Pl 612 relative to the origin On 241 is represented by the vector {right arrow over (P)}l,n 623, resolved in the navigation frame 240. The values of the components of the vector {right arrow over (P)}l,v 615 can be expressed in the navigation frame 240 by applying a coordinate transformation such as a sequence of Euler angle rotations, including rotations through vehicle roll angle, vehicle pitch angle, and vehicle heading angle. The vector {right arrow over (P)}l,v expressed in the navigation frame 240 is denoted as {right arrow over (P)}(l,v)n. The value of the vector {right arrow over (P)}l,n is computed as follows:
{right arrow over (P)}
l,n
={right arrow over (P)}
a,n
+{right arrow over (P)}
(l,v)n. (E4)
The values of the vectors {right arrow over (P)}r,n 621 and {right arrow over (P)}l,n 623 can be used to compute projections of the end points of the blade edge onto a digital terrain model.
An example of calculation of a slope angle of the dozer blade 204 relative to the navigation frame 240 in the System Configuration 2 is described below for a special case illustrated in
The slope angle φb,v 625 of the dozer blade 206 relative to the dozer body 204 is defined as the angle between the −Yb axis aligned with the negative direction of the Yb-axis 255 of the blade frame 250 (
The slope angle φv,n 627 of the dozer body 204 relative to the Xn−Yn plane 249 of the navigation frame 240 is defined as the angle between the Yv-axis 605 and the Yv,n-axis 695 representing the projection of the Yv-axis onto the Xn−Yn plane 249 of the navigation frame 240. The sign of the slope angle φv,n is determined in accordance with the direction of positive rotation about the Xv-axis 603 of the vehicle frame 602. The value of the slope angle φv,n 627 is determined from measurements obtained from the IMU 504 fixed to the dozer body 204.
The slope angle φb,n 629 of the dozer blade 206 relative to the Xn−Yn plane 249 of the navigation frame 240 is defined as the angle between the −Y-axis and the Yv,n-axis. The value of the slope angle φb,n 629 is computed as follows:
φb,n=φb,v+φv,n. (E5)
In a more general case, for any orientation of the dozer body 204 relative to the navigation frame 240 and for any orientation of the dozer blade 206 relative to the dozer body 204, the value of the slope angle φb,n can be computed in a similar manner through the sequence of the following steps. The value of the slope angle φb,v is determined from measurements obtained from the stroke sensors 506. The value of the slope angle φv,n is determined from measurements obtained from the IMU 504 fixed to the dozer body 204. The value of the slope angle φb,n is then computed from the values of the slope angle φb,v and the slope angle φv,n. The value of the slope angle φb,n can be used for blade slope estimation and control. Examples of blade slope estimation and control algorithms are described in Omelchenko.
An example of a calculation of a pitch angle of the dozer blade 206 relative to the navigation frame 240 in the System Configuration 2 is described below for a special case illustrated in
The pitch angle θb,v 631 of the dozer blade 206 relative to the dozer body 204 is defined as the angle between the Xb-axis 253 of the blade frame 250 and the Xv-axis 603 of the vehicle frame 602. The sign of the pitch angle θb,v 631 is determined in accordance with the direction of positive rotation about the Yb-axis 255 of the blade frame 250. The value of the pitch angle θb,v 631 is determined from measurements obtained from the stroke sensors 506 with the use of known values of dozer geometric parameters.
The pitch angle θv,n 633 of the dozer body 204 relative to the Xn−Yn plane 249 of the navigation frame 240 is defined as the angle between the Xv-axis 603 and the Xv,n-axis 693 representing the projection of the Xv-axis 603 onto the Xn−Yn plane 249 of the navigation frame 240. The sign of the pitch angle θv,n 633 is determined in accordance with the direction of positive rotation about the Yv-axis 605 of the vehicle frame 602. The value of the pitch angle θv,n 633 is determined from measurements obtained from the IMU 504 fixed to the dozer body 204.
The pitch angle θb,n 635 of the dozer blade 206 relative to the Xn−Yn plane 249 of the navigation frame 240 is defined as the angle between the Yb-axis 253 and the Xv,n-axis 693. The value of the pitch angle θb,n is computed as follows:
θb,n=θb,v−θv,n. (E6)
In a general case, for any orientation of the dozer body 204 relative to the navigation frame 240 and for any orientation of the dozer blade 206 relative to the dozer body 204, the value of the pitch angle θb,n can be computed in a similar manner through the sequence of the following steps. The value of the pitch angle θb,v is determined from measurements obtained from the stroke sensors 506. The value of the pitch angle θv,n is determined from measurements obtained from the IMU 504 fixed to the dozer body 204. The value of the pitch angle θb,n is then computed from the values of the pitch angle θb,v and the pitch angle θv,n.
The value of the pitch angle θb,n can be used for blade pitch angle estimation and control. The blade pitch angle estimation algorithm can be implemented similar to the blade slope angle estimation algorithm described in Omelchenko. The blade pitch angle control algorithm can be implemented as described herein.
In the System Configuration 3, the position and orientation of the dozer blade relative to the dozer body, including roll, pitch, and heading angles, and the elevation of the blade, as well as the rates of change of these parameters, can be computed using measurements from the IMU-1510 and the IMU2-512.
Algorithms for calculations of various vectors relating to the determination of the dozer blade position and orientation in the System Configuration 3 are described for a general case, for any orientation of the dozer body 204 relative to the navigation frame 240 and for any orientation of the dozer blade 206 relative to the dozer body 204.
The location of the origin Ov 601 of the vehicle frame 602 relative to the origin On 241 of the navigation frame 240 is represented by the vector {right arrow over (P)}a,n 611, resolved in the navigation frame 240. The location of the center PIMU 1 616 of the IMU-1510 relative to the origin Ov 601 is represented by the vector {right arrow over (P)}IMU 1,v 637, resolved in the vehicle frame 602. The value of the vector {right arrow over (P)}IMU 1,v 637 can be measured during installation of the GNSS antenna 502 and the IMU-1510 onto the dozer body 204. The value of this vector is constant during the system operation.
The location of the center PIMU 2 618 of the IMU-2512 relative to the center PIMU 1 616 of the IMU-1510 is represented by the vector {right arrow over (P)}IMU 12,v 639, resolved in the vehicle frame 602. The value of the vector {right arrow over (P)}IMU 12,v 639 is determined from measurements obtained from the IMU-1510 and the IMU-2512 with the use of additional measurements that can be taken during installation of the IMU-1510 and the IMU-2512 onto the dozer body 204. These additional measurements, for example, include a number of measured values of the vector {right arrow over (P)}IMU 12,v 639 taken for selected orientations of the dozer blade 206 relative to the dozer body 204. The values of these additional measurements can be stored in a data storage device that is a component of a control box such as the control box described in Omelchenko and can be used during the system operation.
The location of the central point Pc 614 of the blade edge relative to the center PIMU 2 618 of the IMU-2512 is represented by the vector {right arrow over (P)}IMU 12c,v 641, resolved in the vehicle frame 602. The value of the vector {right arrow over (P)}IMU 2c,v 641 can be measured during the installation of the IMU-2512 onto the dozer blade 206. The value of this vector is constant during the system operation.
The value of the vector {right arrow over (P)}c,v 617 is computed as follows:
{right arrow over (P)}
c,v
={right arrow over (P)}
IMU 1,v
+{right arrow over (P)}
IMU 12,v
+{right arrow over (P)}
IMU 2c,v. (E7)
The values of the components of the vector {right arrow over (P)}c,v 617 can be expressed in the navigation frame 240 by applying a coordinate transformation such as a sequence of rotations through a sequence of Euler angles, including vehicle roll angle, vehicle pitch angle, and vehicle heading angle. The vector {right arrow over (P)}c,v expressed in the navigation frame 240 is denoted as {right arrow over (P)}(c,v)n.
The location of the central point Pc 614 of the blade edge relative to the origin On 241 of the navigation frame 240 is described by the vector {right arrow over (P)}c,n 619, resolved in the navigation frame 240. The value of the vector {right arrow over (P)}c,n 619 is computed as follows:
{right arrow over (P)}
c,n
={right arrow over (P)}
a,n
+{right arrow over (P)}
(c,v)n. (E8)
The value of the vector {right arrow over (P)}c,n can be used for blade elevation estimation and control. Blade elevation estimation and control algorithms can be implemented as described in Omelchenko.
The values of the blade slope angle φb,n and the blade pitch angle θb,n relative to the navigation frame 240 can be determined from measurements obtained from the IMU-2512 fixed to the dozer blade 206. The value of the blade slope angle φb,n can be used for blade slope estimation and control. Blade slope estimation and control algorithms can be implemented as described in Omelchenko. The value of the blade pitch angle θb,n can be used for blade pitch angle estimation and control. The blade pitch angle estimation algorithm can be implemented similar to the blade slope angle estimation algorithm described in Omelchenko. The blade pitch angle control algorithm can be implemented as described herein.
The dozer blade heading angle is important for automatic grading. The dozer body heading angle is important for automatic steering of the dozer. In the System Configuration 2 and the System Configuration 3, the blade heading angle relative to the dozer body is known; therefore, the System Configuration 2 and the System Configuration 3 allow for automatic steering of a dozer while performing automatic grading. Automatic steering capability is not available in the System Configuration 1.
In the System Configuration 2 and the System Configuration 3, the dozer body heading angle can be computed using measurements from a magnetic compass mounted on the dozer body. The magnetic compass, for example, can be installed in the IMU mounted on the dozer body. In combination with the known blade heading angle relative to the dozer body, these measurements allow for the extension of automatic dozer steering operation during periods of GNSS RTK system outage via the extrapolation of the target plane, which includes target heading angle as one of its parameters, based on a recorded history of target plane values over a user-specified period of time prior to GNSS RTK system outage.
In the System Configuration 3, a magnetic compass can also be mounted on the dozer blade to determine the dozer blade heading angle. The magnetic compass, for example, can be installed in the IMU mounted on the dozer blade.
In the System Configuration 1 (
An embodiment of a computational system 800 for implementing an automatic blade control system is shown in
The computational system 800 includes a computer 802, which includes a central processing unit (CPU) 804, memory 806, and a data storage device 808. The data storage device 808 includes at least one persistent, non-transitory, tangible computer readable medium, such as non-volatile semiconductor memory, a magnetic hard drive, or a compact disc read only memory.
The computational system 800 can further include a user input/output interface 810, which interfaces computer 802 to user input/output devices 830. Examples of user input/output devices 830 include a keyboard, a mouse, a local access terminal, and a video display. Data, including computer executable code, can be transferred to and from the computer 802 via the user input/output interface 810.
The computational system 800 can further include a GNSS receiver interface 812, which interfaces the computer 802 with the GNSS receiver 122.
The computational system 800 can further include a communications transceiver (XCVR) interface 814, which interfaces the computer 802 with the communications transceiver 124.
The computational system 800 can further include inertial measurement units interface 816, which interfaces the computer 802 with various inertial measurement units, such as IMU 226, IMU 504, IMU-1510, and IMU-2512.
The computational system 800 can further include stroke sensors interface 818, which interfaces the computer 802 with the stroke sensors 506.
The computational system 800 can further include an auxiliary sensors interface 820, which interfaces the computer 802 with auxiliary sensors 840. Examples of auxiliary sensors 840 include odometers and magnetic compasses.
The computational system 800 can further include a dozer hydraulic system interface 822, which interfaces the computer 802 with the dozer hydraulic system 308.
The computational system 800 can further include a communications network interface (not shown), which interfaces the computer 802 with a communications network. Examples of a communications network include a local area network and a wide area network. A user can access the computer 802 via a remote access terminal (not shown) communicating with the communications network. Data, including computer executable code, can be transferred to and from the computer 802 via the communications network interface.
Each of the interfaces described above can operate over different communications media. Examples of communications media include wires, coax cable, optical fibers, free-space optics, and electromagnetic waves (typically in the radiofrequency range and commonly referred to as a wireless interface).
As is well known, a computer operates under control of computer software, which defines the overall operation of the computer and applications. The CPU 804 controls the overall operation of the computer and applications by executing computer program instructions that define the overall operation and applications. The computer program instructions can be stored in the data storage device 808 and loaded into the memory 806 when execution of the program instructions is desired. The automatic blade pitch angle control algorithm shown schematically in
The foregoing Detailed Description is to be understood as being in every respect illustrative and exemplary, but not restrictive, and the scope of the invention disclosed herein is not to be determined from the Detailed Description, but rather from the claims as interpreted according to the full breadth permitted by the patent laws. It is to be understood that the embodiments shown and described herein are only illustrative of the principles of the present invention and that various modifications may be implemented by those skilled in the art without departing from the scope and spirit of the invention. Those skilled in the art could implement various other feature combinations without departing from the scope and spirit of the invention.
This application claims the benefit of U.S. Provisional Application No. 61/379,465 filed Sep. 2, 2010, which is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61379465 | Sep 2010 | US |
