Patent Description:
In recent years, at a construction work site, it is popular to measure the position of a predetermined point (monitor point) set to a work machine, using a three-dimensional position measurement system such as a GNSS (Global Navigation Satellite System) and to perform work management. A typical example of the monitor point is a point set to a work device provided on a work machine, for example, a bucket distal end of a hydraulic excavator. If the position of the bucket distal end can be measured, by comparing measurement data by the measurement with terrain data or target shape data set in advance, a work progress situation during construction can be grasped, and accordingly, this enables management and control during construction. Further, by creating finished form data (for example, excavation terrain data) from a history of measurement data till the end of construction, construction management can be performed also after the construction.

Incidentally, for example, in a hydraulic excavator, a work device that can be positioned higher than a GNSS antenna such as a boom, an arm, and a bucket or an obstacle around the work device becomes an obstacle to a signal (GNSS signal, satellite signal) transmitted from a GNSS satellite. Therefore, there is the possibility that the GNSS antenna may receive a GNSS signal as a diffracted wave or a reflected wave called multipath. If a diffracted wave or a reflected wave is used in position measurement of a monitor point, the possibility that a position measurement result may include an error is high. As a solution method for eliminating the influence of the multipath, for example, a solution method disclosed in Patent Document <NUM> is available.

Patent Document <NUM> discloses a positioning apparatus that includes a reception device receiving signals from a plurality of transmitters (a plurality of satellites) and that decides transmitter positions of the individual transmitters (the plurality of satellites). Then, the positioning apparatus calculates transmitters (a plurality of satellites) from which signals can be received directly on the basis of the positions of the transmitters, a position of the positioning apparatus decided in a preceding operation cycle, and multipath information, and decides the present position of the positioning apparatus, ignoring the transmitters from which signals cannot be received directly. Patent document <NUM> discloses a work machine with the features of the preamble of claim <NUM>, comprising an operability range display device, a calculation unit which is configured to set a boundary between an operability range and an underbody area along a vertical direction in a global coordinate system when a vehicle body is horizontally oriented.

In the technology of Patent Document <NUM> described above, it is possible to reduce the influence of diffraction and reflection by an obstacle. However, in a work machine that repeats a series of operations such as excavation, swing, and dumping of loaded soil like a hydraulic excavator, the relative positions of the work machine and an obstacle around the work machine can change readily according to a change in posture of the work device or an upper swing structure. Therefore, there is the possibility that the combination of satellite signals to be used for position measurement may constantly switch. The position measurement by the GNSS has a subject that, if satellites to be used for position measurement switch, the position measurement error increases.

The present invention has been made to solve the subject described above, and it is an object of the present invention to provide a work machine that can prevent accuracy degradation in GNSS position measurement even if the posture of a work device or an upper swing structure changes during work of the work machine.

In order to achieve the object described above, according to the present invention, there is provided a work machine that includes a lower track structure, an upper swing structure swingably provided on the lower track structure and configuring a machine body together with the lower track structure, a work device rotatably provided on the upper swing structure, an inclination measurement device provided on the machine body, an angle measurement device provided on the work device, a three-dimensional position measurement device that calculates a three-dimensional position and a direction of itself on the basis of satellite signals of satellites, and a controller that calculates, on the basis of information from the inclination measurement device, the angle measurement device, and the three-dimensional position measurement device, a three-dimensional position and a posture of the machine body, and a three-dimensional position of a predetermined position of the work device, in which the three-dimensional position measurement device receives satellite signals of satellites, selects, from among the satellites whose satellite signals are received, the satellites to be used for calculation of a three-dimensional position and a direction of the three-dimensional position measurement device, and calculates a three-dimensional position and a direction of the three-dimensional position measurement device on the basis of the satellite signals of the selected satellites, and the work machine further includes a storage instruction device for instructing to store a combination of the satellites selected by the three-dimensional position measurement device. The controller stores, when the instruction is inputted through the storage instruction device, the combination of the satellites selected by the three-dimensional position measurement device as satellite selection information, and transmits, when a predetermined changing condition is satisfied, the satellite selection information to the three-dimensional measurement device, and the three-dimensional position measurement device preferentially selects, when the three-dimensional position measurement device receives the satellite selection information from the controller, the satellites included in the satellite selection information from among the satellites from which the satellite signals are received.

According to the present invention, even if the posture of the work device or the upper swing structure changes during work, switching of the satellite signals to be used in calculation of GNSS position measurement, deterioration of the position measurement accuracy by the GNSS can be suppressed, and as a result, the work accuracy can be improved.

In the following, an embodiment of the present invention is described with reference to the drawings. The present embodiment is an embodiment when the present invention is applied to a crawler type hydraulic excavator as a construction machine and a monitor point (control point) is set to a bucket distal end of the hydraulic excavator. It is to be noted that, in the figures, equivalent members are denoted by the same reference numerals and overlapping description is suitably omitted.

<FIG> is a view depicting an appearance of the hydraulic excavator of the present embodiment.

Referring to <FIG>, the hydraulic excavator <NUM> includes a lower track structure <NUM> that travels by crawlers driven by traveling hydraulic motors (not depicted), an upper swing structure <NUM> attached for swinging motion on the lower track structure <NUM> and configuring a machine body together with the lower track structure <NUM>, a cab <NUM> provided on the upper swing structure <NUM>, and a front work implement (work device) <NUM> attached to the upper swing structure <NUM>. The upper swing structure <NUM> is driven to swing leftward and rightward by a swing hydraulic motor (not depicted). The front work implement <NUM> is an articulated type work apparatus including a boom <NUM> rotatably provided in upward and downward directions on the upper swing structure <NUM>, an arm <NUM> rotatably provided in the upward and downward directions at a distal end of the boom <NUM>, and a bucket (attachment) <NUM> rotatably provided in the upward and downward directions at a distal end of the arm <NUM>. The boom <NUM>, the arm <NUM>, and the bucket <NUM> are driven by elongating or contracting a boom cylinder <NUM>, an arm cylinder <NUM>, and a bucket cylinder <NUM>, respectively. Each of the boom <NUM>, the arm <NUM>, and the bucket <NUM> is sometimes referred to as a front member.

Also, a machine body IMU <NUM> for detecting an inclination angle (pitch angle) of the upper swing structure <NUM> with respect to a predetermined plane (for example, a horizontal plane) is attached to the upper swing structure <NUM>. A boom IMU <NUM> for detecting an angle of the boom <NUM> (boom angle) with respect a predetermine plane (for example, the horizontal plane) is attached to the boom <NUM>. An arm IMU <NUM> for detecting an angle of the arm <NUM> (arm angle) with respect to a predetermined plane (for example, the horizontal plane) is attached to the arm <NUM>. A bucket IMU <NUM> for detecting an angle of the bucket <NUM> (bucket angle) with respect to a predetermined plane (for example, the horizontal plane) is attached to the bucket <NUM>. It is to be noted that, in the present specification, the boom IMU <NUM>, the arm IMU <NUM>, and the bucket IMU <NUM> are sometimes referred to collectively as front IMUs (refer to <FIG>).

Further, on the upper swing structure <NUM>, two GNSS antennae <NUM> and <NUM> for receiving satellite signals (navigation signals) transmitted from a plurality of GNSS satellites and an RTK correction data receiving antenna <NUM> for receiving RTK correction data (hereinafter described) from a reference station are provided. The two GNSS antennae <NUM> and <NUM> are installed on the left and right of a rear portion of the swing structure displaced from the center of swing of the upper swing structure <NUM>.

<FIG> is a block diagram of a position measurement system incorporated in the hydraulic excavator <NUM>. The position measurement system <NUM> depicted in <FIG> includes a wireless device <NUM>, a GNSS receiver <NUM>, a controller <NUM>, a display device <NUM> and a setting switch <NUM>.

The wireless device <NUM> receives RTK correction data (hereinafter described) from a reference station through the RTK correction data receiving antenna <NUM> and outputs the RTK correction data to the GNSS receiver <NUM>.

The GNSS receiver <NUM> calculates the position of the GNSS antenna <NUM> that is one of the two GNSS antennae <NUM> and <NUM> and a vector from the GNSS antenna <NUM> that is one of the two GNSS antennae <NUM> and <NUM> to the other GNSS antenna <NUM> on the real time basis on the basis of RTK correction data inputted from the wireless device <NUM> and signals from GNSS satellites received by the GNSS antennae <NUM> and <NUM>. Accordingly, the position and the azimuth angle of the upper swing structure <NUM> in a geographic coordinate system (global coordinate system) can be calculated.

The controller <NUM> receives the position and vector data calculated by the GNSS receiver <NUM> and angle data from the IMUs <NUM> to <NUM> as inputs thereto and calculates a position and an azimuth angle of the upper swing structure <NUM> and a position of the distal end (monitor point) of the bucket <NUM>. The controller <NUM> includes, as hardware, an arithmetic processing unit (for example, a CPU), a storage device (for example, a semiconductor memory such as a ROM and a RAM), and an interface (inputting/outputting device). In the controller <NUM>, a program (software) stored in advance in the storage device is executed by the arithmetic processing unit, and arithmetic processing is performed by the arithmetic processing unit on the basis of data prescribed in the program and data inputted from the interface. Then, a signal (calculation result) is outputted from the interface to the outside. It is to be noted that, though not depicted, the GNSS receiver <NUM> can also include hardware similar to that of the controller <NUM>.

The display device (monitor) <NUM> displays a calculation result of the controller <NUM> and various kinds of data acquired by utilizing the calculation result.

The setting switch (masking range reset switch) <NUM> is connected to the controller <NUM>. The setting switch <NUM> is a switch for cancelling (deleting) all mask ranges (hereinafter described) set at that time. The setting switch <NUM> is depressed at a timing desired by an operator, and as a result, the controller <NUM> deletes all mask ranges. Details of setting of a mask range and a scene in which the setting switch <NUM> is utilized are hereinafter described.

In addition, an external recording medium (external storage device) <NUM> such as a semiconductor memory can be connected to the controller <NUM>. The external recording medium <NUM> has stored therein terrain data including present terrain data and target terrain data (also referred to as design data). The operator connects the external recording medium <NUM> to the controller <NUM> at a predetermined timing such as at the time of system startup and downloads, when necessary, data into a storage device in the controller <NUM>. Then, at the time of end of a work or the like, for example, present terrain data after the work created from locus data on the bucket distal end position while the system is operating is recorded into the external recording medium <NUM> and is used in work management.

<FIG> is a block diagram of an office side measurement system (reference station system) <NUM> having a role as a GNSS reference station.

Referring to <FIG>, the office side measurement system <NUM> includes a GNSS antenna <NUM>, a GNSS receiver <NUM>, a wireless device <NUM>, and a wireless antenna <NUM>.

The GNSS antenna <NUM> is an antenna for receiving satellite signals (navigation signals) transmitted from a plurality of GNSS satellites.

The GNSS receiver <NUM> functions as a GNSS reference station (in the following description, the GNSS receiver <NUM> is sometimes represented as a GNSS reference station <NUM>), and generates, on the basis of data on a three-dimensional position measured in advance (for example, the position of the GNSS antenna <NUM>) and satellite signals received by the GNSS antenna <NUM>, correction data for allowing the GNSS receiver <NUM> of the hydraulic excavator <NUM> to perform RTK (real time kinematic) measurement, and outputs the correction data to the wireless device <NUM>.

The wireless device <NUM> transmits the correction data inputted from the GNSS receiver <NUM> to the wireless device <NUM> of the hydraulic excavator <NUM> through the wireless antenna <NUM>.

Now, an overview of operation of the position measurement system <NUM> according to the present embodiment is described.

In the present embodiment, in order to perform position measurement with high accuracy, RTK measurement is performed by the GNSS receiver <NUM> depicted in <FIG>. To this end, the GNSS reference station <NUM> that creates correction data depicted in <FIG> is first required. The GNSS reference station <NUM> creates correction data for RTK measurement on the basis of the position data on the GNSS antenna <NUM> three-dimensionally measured in advance as described hereinabove and satellite signals from a plurality of GNSS satellites received by the GNSS antenna <NUM>, and transmits the created correction data by the wireless device <NUM> in a fixed cycle through the antenna <NUM>.

On the other hand, the GNSS receiver <NUM> on the hydraulic excavator <NUM> side depicted in <FIG> performs RTK measurement on the three-dimensional position of the GNSS antenna <NUM> and the vector from the GNSS antenna <NUM> to the GNSS antenna <NUM> on the basis of the correction data received from the wireless device <NUM> through the antenna <NUM> and satellite signals from a plurality of GNSS satellites received by the GNSS antennae <NUM> and <NUM>. Due to this RTK measurement, the three-dimensional position of the GNSS antenna <NUM> in the geographic coordinate system and the vector from the GNSS antenna <NUM> to the GNSS antenna <NUM> are measured with high accuracy. Then, the measured three-dimensional position data and vector data are inputted to the controller <NUM>.

Meanwhile, the inclination angle of the hydraulic excavator <NUM> (upper swing structure <NUM>) (namely, a pitch angle and a roll angle) and the angles of the boom <NUM>, the arm <NUM>, and the bucket <NUM> are measured by the IMUs <NUM> to <NUM> and are similarly inputted to the controller <NUM>.

The controller <NUM> performs general vector calculation and coordinate transformation on the basis of the various kinds of inputted data to calculate a position and a posture (including an azimuth angle) of the upper swing structure <NUM> and the position of the distal end (monitor point) of the bucket <NUM> in a predetermined coordinate system (for example, a site coordinate system set to the ground of the work site). In addition, it is also possible for the controller <NUM> to display an image of the bucket and a target terrain on the screen of the display device <NUM> on the basis of the calculated position and posture of the upper swing structure <NUM> and the calculated position of the distal end of the bucket <NUM>, and the target terrain data inputted from the external recording medium <NUM> to notify the operator of the work situation.

Now, deterioration of reproducibility of position measurement by the GNSS receiver <NUM>, which is the subject of the present invention, is described with reference to <FIG>.

<FIG> schematically depicts a posture of the hydraulic excavator <NUM> upon excavation operation. Referring to <FIG>, the hydraulic excavator <NUM> performs a generally-called slope face forming work. The image depicted in <FIG> is generally equivalent to information displayed on the display device <NUM>, and the operator will perform an excavation operation of the hydraulic excavator <NUM> on the basis of this information such that a present terrain <NUM> approaches a target terrain <NUM>.

<FIG> schematically depicts a posture of the hydraulic excavator <NUM> upon swing operation. As depicted in <FIG>, usually the swing operation is performed in a state in which the boom <NUM> is raised after excavation operation ends, the arm <NUM> and the bucket <NUM> are moved inward, and a clearance between the bucket <NUM> and the ground is secured. Then, the arm <NUM> and the bucket <NUM> are dumped at a soil-dumping position to release the excavated soil down to a predetermined position. Thereafter, swing operation for returning to the excavation position is performed, and the excavation operation is repeated.

<FIG> schematically depicts an excavation position and a soil-dumping position of the hydraulic excavator <NUM> and arrangement of GNSS satellites <NUM> to <NUM> existing within a sky view of the GNSS antennae <NUM> and <NUM> at that time. Referring to <FIG>, a state in which the front work implement <NUM> is directed to the upper side is defined as an excavation position <NUM>, and a state in which the front work implement <NUM> is directed to the left side is defined as a soil-dumping position <NUM>. Also, it is assumed that movement from the excavation position <NUM> to the soil-dumping position <NUM> is performed by left swing and movement from the soil-dumping position <NUM> to the excavation position <NUM> is performed by right swing.

In position measurement by the GNSS, the GNSS receiver <NUM> performs various condition decisions regarding the quality of satellite signals from GNSS satellites received by the GNSS antennae <NUM> and <NUM>, arrangement of the GNSS satellites from which satellite signals are received, and so forth to select GNSS satellites (satellite signals) to be used in position calculation.

Here, the arrangement of GNSS satellites is evaluated with a numerical value called DOP (Dilution of Precision), and, for example, in such a case that GNSS satellites are distributed so as to be clustered to one direction of the sky view, the DOP is bad (the numerical value is high). As a result, the position accuracy in calculation is deteriorated. In contrast, where GNSS satellites are distributed without being clustered to the one direction in the sky view, the DOP is good (the numerical value is low), and the position accuracy in calculation is improved. This arises from that position measurement by the GNSS is a measurement system that applies triangulation.

Therefore, where the GNSS satellites <NUM> to <NUM> which can be caught are arranged in such arrangement as indicated in <FIG>, as GNSS satellites to be used for position calculation at the excavation position <NUM>, for example, the satellites <NUM>, <NUM>, <NUM>, and <NUM> indicated with hatched lines in <FIG> are selected.

However, when the excavation operation of the hydraulic excavator <NUM> ends and the hydraulic excavator <NUM> takes such a swing posture as depicted in <FIG> and swings leftward from the excavation position <NUM> to the soil-dumping position <NUM>, then since the front work implement <NUM> passes between the GNSS antennae <NUM> and <NUM> and the GNSS satellites <NUM>, <NUM>, and <NUM>, the satellite signals of the GNSS satellites <NUM>, <NUM>, and <NUM> are blocked by the front work implement <NUM>.

As a result, at the time of position calculation of the soil-dumping position <NUM>, for example, the GNSS satellites <NUM> to <NUM> indicated with hatched lines in <FIG> are selected, and the GNSS satellites sometimes change from those of the combination selected at the excavation position <NUM> in <FIG>.

Further, the hydraulic excavator <NUM> returns to the excavation position <NUM> by right swing and repeats the excavation operation. However, while the hydraulic excavator <NUM> swings rightward from the soil-dumping position <NUM> to the excavation position <NUM>, since the satellite signals of the GNSS satellites <NUM> to <NUM> are not blocked by the front work implement <NUM>, the combination of GNSS satellites to be used for position calculation is kept to be the GNSS satellites <NUM> to <NUM> also at the excavation position <NUM> as depicted in <FIG>. Consequently, the change from the combination of the GNSS satellites <NUM>, <NUM>, <NUM>, and <NUM> having been selected at the time of the excavation operation in the preceding operation cycle sometimes remains.

In position measurement by the GNSS, not only DOP but also error factors that are subtly different among GNSS satellites, such as a clock error among GNSS satellites or an error of orbit information are involved, and even if the hydraulic excavator <NUM> is positioned at the same position, if the combination of GNSS satellites to be used for position calculation differs, a displacement appears in position calculation results, resulting in the possibility that the reproducibility of position calculation may be deteriorated.

If the reproducibility of position calculation by the GNSS receiver <NUM> is deteriorated in this manner, then there is the possibility that the positional relation between the bucket <NUM> and the target terrain <NUM> displayed on the display device <NUM> may become different before and after excavation operation, and as a result, such a problem that the finished form becomes discontinuous may possibly occur.

Selection logic of satellites to be used which is to be executed by the controller <NUM> in a method for solving the problem just described is described with reference to a flow chart of <FIG> is a flow chart depicting an example of the satellite selection logic to be executed by the controller <NUM>. It is to be noted that the flow chart of <FIG> is calculated repeatedly in a fixed cycle (for example, <NUM>).

At step S10, the controller <NUM> decides whether a Fix solution is obtained by RTK based on information from the GNSS receiver <NUM>. Whether or not this state is achieved can be decided by referring to, for example, a GGA sentence of an NMEA message from the GNSS receiver <NUM>.

When it is decided at step S10 that a Fix solution is not obtained, the controller <NUM> decides that correct position measurement has not been performed, and the processing advances to step S20 at which the controller <NUM> displays on the display device <NUM> that correct measurement is not performed and returns to an initial state (waits till a next control cycle). On the other hand, when it is decided at step S10 that a Fix solution is obtained, the processing advances to step S30.

At step S30, the controller <NUM> performs, on the basis of a three-dimensional position of the GNSS antenna <NUM> inputted from the GNSS receiver <NUM>, vector information from the GNSS antenna <NUM> to the GNSS antenna <NUM>, and angle information inputted from the IMUs <NUM> to <NUM>, general vector calculation and coordinate transformation to calculate the position and the posture of the upper swing structure <NUM> and the position of the distal end of the bucket <NUM> in the site coordinate system. Then, the controller <NUM> displays posture information of the bucket <NUM>, a present terrain generated on the basis of terrain data acquired from the external recording medium <NUM> and information of a target shape on the display device <NUM>.

Then, the processing advances to step S40 at which the controller <NUM> decides by a decision method depicted in <FIG> whether or not the hydraulic excavator <NUM> is performing a work that requires accuracy. Here, the logic (decision logic) of the controller <NUM> for deciding whether or not the hydraulic excavator <NUM> is performing an excavation work that requires accuracy at step S40 is described with reference to <FIG> is a flow chart depicting one of particular examples of the process performed at step S40.

First at step S401, the controller <NUM> decides whether or not the distance between the front work implement <NUM> and a target surface (target surface distance) is equal to or smaller than a predetermined value d1. As the target surface distance, for example, the distance between the bucket distal end (claw tip) position and the target surface can be used. In this case, a perpendicular line is drawn from the position of the bucket distal end (monitor point) calculated at step S30, a point at which the perpendicular line crosses with the target terrain surface defined by the target terrain data is calculated, and the distance between the point and the bucket distal end can be determined as the target surface distance. When the target surface distance is greater than the predetermined value d1, the controller <NUM> decides that, because the bucket distal end is at a position spaced away from the target surface, an excavation work that requires accuracy is not being performed. On the other hand, when it is the decision that the target surface distance is equal to or smaller than the predetermined value d1, the processing advances to step S402.

At step S402, the controller <NUM> decides whether or not an excavation operation is inputted to an operation device (not depicted) for operating the front work implement <NUM> (the boom <NUM>, the arm <NUM>, and the bucket <NUM>) installed in the cab <NUM>. Whether or not an excavation operation is inputted is decided here depending upon whether or not the arm <NUM> (arm cylinder <NUM>) is being driven. Whether or not the arm <NUM> (arm cylinder <NUM>) is being driven can be decided, for example, by detecting the operation pilot pressure of the arm <NUM> outputted from the operation device by a pressure sensor and checking whether or not the detected pressure exceeds a predetermined value.

When an affirmative result is obtained both at steps S401 and S402 in this manner, the controller <NUM> deems that the hydraulic excavator <NUM> is performing an excavation work that requires accuracy. In this manner, even if the distance between the bucket distal end and the target surface is equal to or smaller than the predetermined value d1 at step S401, when it is decided at step S402 that an excavation operation is not being performed, for example, in such a state in which the arm <NUM> stops with the distal end of the bucket <NUM> contacting with the terrain excavated according to the target surface, a decision that an excavation work is not being performed is made. Therefore, a mask range hereinafter described can be prevented from being widened more than necessary. Further, when it is decided at step S401 that the target surface distance exceeds the predetermined value d1, for example, also when a rough finish work is being performed, the mask range hereinafter described can be prevented from being widened more than necessary. It is to be noted that, although it has been assumed that the decision of an excavation operation is decided only from the operation pilot pressure of the arm, decision of an excavation operation may be made additionally on the basis of the operation pilot pressure of the boom <NUM> or the bucket <NUM>. Further, the decision may be made taking not only an instantaneous value but also continuity of the operation pilot pressure in the past (namely, a time series of the detected operation pilot pressure), and the like into consideration. Further, not the operation pilot pressure, but, for example, an excavation reactive force or the like acting upon the arm cylinder <NUM> may be detected by a pressure sensor installed in the arm cylinder <NUM> to decide an excavation operation. Further, although it is decided here on the basis of both of the magnitude of the target surface distance (step S401) and the presence/absence of an excavation operation (step S402) whether or not the hydraulic excavator <NUM> is performing a work that requires accuracy, the decision may be made on one of these two processes (steps S401 and S402). In other words, the decision may be made based on at least one of the two processes.

Referring back to <FIG>, when it is decided at step S40 that the hydraulic excavator <NUM> is not performing a work that requires accuracy, the processing advances to step S45. At step S45, the controller <NUM> starts measurement of a time period (duration) T during which the state in which it is decided that the hydraulic excavator <NUM> is not performing a work that requires accuracy continues, and then, the processing advances to step S70. It is to be noted that, when measurement of the time period T is already started at the time of reaching step S45, the measurement is assumed to be continued.

On the other hand, when it is decided at step S40 that the hydraulic excavator <NUM> is performing a work that requires accuracy, the processing advances to step S50.

At step S50, the controller <NUM> sets a range within which, when each of the two GNSS antennae <NUM> and <NUM> receives satellite signals from a plurality of GNSS satellites, the front work implement <NUM> possibly becomes an obstacle to the satellite signals, as a mask range in a coordinate system (for example, a site coordinate system) set to the ground. As hereinafter described, a satellite signal from a GNSS satellite positioned within the mask range can be excluded from the satellite signals to be utilized for position measurement by the GNSS receiver <NUM>. In other words, a range of satellite arrangement that is not to be used for position measurement is calculated at step S50.

The controller <NUM> of the present embodiment sets a mask range at step S50 on the basis of the installation positions of the two GNSS antennae <NUM> and <NUM> on the upper swing structure <NUM> (hydraulic excavator <NUM>) (for example, coordinate positions in the machine body coordinate system set to the upper swing structure <NUM>) stored in the storage device of the controller <NUM> in advance, a movable range of the front work implement <NUM> (boom <NUM>, arm <NUM>, and bucket <NUM>), an inclination angle of the upper swing structure <NUM> detected by the machine body IMU <NUM>, and an azimuth angle of the upper swing structure <NUM> calculated from the vector information from the GNSS antenna <NUM> to the GNSS antenna <NUM>. The mask range is set for each of the two GNSS antennae <NUM> and <NUM>. The mask range can be defined by a combination of an azimuth angle range (angle range in the leftward and rightward direction) and an elevation angle range (angle range in the upward and downward direction) with reference to each of the GNSS antennae <NUM> and <NUM>.

Further, when it is possible at step S50 to acquire shape data on obstacles (for example, a present terrain, buildings, and structures) that exist around the hydraulic excavator <NUM> and can become obstacles to satellite signals (shape data includes also positions), the controller <NUM> can set also a range within which satellite signals can be blocked by the obstacles as a mask range in addition to the setting of the mask range arising from the front work implement <NUM> described above. For example, a mask range may be set in the following manner. Present terrain data from the external recording medium <NUM> is stored in advance as shape data on obstacles in the storage device in the controller <NUM>. Then at step S50, the controller <NUM> calculates, on the basis of the position, azimuth angle and inclination angle of the upper swing structure <NUM> in the geographic coordinate system (global coordinate system), installation positions of the two GNSS antennae <NUM> and <NUM> on the upper swing structure <NUM> (hydraulic excavator <NUM>) and the present terrain data, a cross sectional shape of the present terrain in a predetermined azimuth angle direction with reference to the azimuth angle of the upper swing structure <NUM>. Then, the controller <NUM> further takes into consideration a range within which the present terrain that has the cross sectional shape when each of the two GNSS antennae <NUM> and <NUM> receives satellite signals from a plurality of GNSS satellites may become an obstacle to the satellite signals, to thereby set the mask range.

Here, an example of the calculation process of a mask range at step S50 is described with reference to <FIG>. Although calculation of a mask range for the GNSS antenna <NUM> is described for the convenience of description, a mask range for the GNSS antenna <NUM> can also be calculated by a similar method.

For the elevation angle mask angle that defines an elevation angle range of a mask range, a direction from the horizontal plane to the sky is defined as a positive direction, and the zenith direction is defined as an elevation angle of <NUM> degrees. Therefore, as the elevation angle mask angle, the lower end is <NUM> degrees, and the upper end is <NUM> degrees in the maximum. Further, the azimuth angle mask angle that defines an azimuth angle range of a mask range is defined as a range from <NUM> degrees to <NUM> degrees with the north direction defined as <NUM> degrees and the clockwise direction defined as a positive direction.

In the storage device of the controller <NUM>, an screened portion of the front work implement <NUM> as viewed from the GNSS antenna <NUM> is stored as a front screening elevation angle αft for each azimuth angle with reference to the machine body (machine body reference azimuth angle). <FIG> is a view depicting an example of a relation between the machine body reference azimuth angle and the front screening elevation angle αft, and a front screening elevation angle αft is set for each machine body reference azimuth angle. For each machine body reference azimuth angle, a range equal to or smaller than the front screening elevation angle αft becomes a range (mask range) within which a satellite signal is blocked. The machine body reference azimuth angle and the front screening elevation angle αft here are defined in the machine body coordinate system set to the upper swing structure <NUM>. If, as depicted in <FIG>, using the GNSS antenna <NUM> as a reference, the forward direction of the hydraulic excavator <NUM> is defined as machine body reference azimuth angle of <NUM> degrees and the clockwise direction is a positive direction, the front screening elevation angle αft is defined at intervals of <NUM> degrees while the machine body reference azimuth angle reaches <NUM> degrees from <NUM> degrees. In the example of <FIG>, since the front work implement <NUM> does not become an obstacle to satellite signals except a range of the machine body reference azimuth angle from <NUM> degrees to <NUM> degrees, the front screening elevation angle is <NUM> degrees. The range of the machine body reference azimuth angle from <NUM> degrees to <NUM> degrees is indicated as a mask range (azimuth angle range) <NUM> in <FIG>. It is to be noted that the front screening elevation angle αft may be defined from a maximum movable range of each of the front members <NUM>, <NUM>, and <NUM> or may be defined by a predicted movable range that is predicted to be used during a work.

Here, for explanation, calculation of an elevation angle mask angle of an influence by the machine body when the machine body reference azimuth angle is <NUM> degrees is described with reference to <FIG>.

<FIG> is a view of a present terrain cross section when the machine body reference azimuth angle is <NUM> degrees as viewed from a side. As depicted in the figure, the elevation angle mask angle αs by the machine body (front work implement <NUM>) in the site coordinate system can be calculated according to the following expression (<NUM>) from the front screening elevation angle αft in the machine body coordinate system and the inclination angle αbd of the machine body calculated by the machine body IMU <NUM>.

Then, the elevation angle mask angle αg according to the present terrain in the site coordinate system is calculated. The present terrain depicted in <FIG> depicts a cross section of the present terrain in a direction of the machine body reference azimuth angle of <NUM> degrees. All straight lines that are tangential to the cross section of the present terrain are drawn from the position of the GNSS antenna <NUM> measured by the GNSS receiver <NUM>, and a maximum value among angles defined by all straight lines and the horizontal plane is determined as the elevation angle mask angle αg according to the present terrain.

It is to be noted that, since the present terrain data is represented in the site coordinate system in which the north azimuth is defined as <NUM> degrees (reference) as depicted in <FIG>, the cross section of the present terrain depicted in <FIG> can be acquired by taking a cross section of the present terrain data in an angle direction obtained by addition of a machine body reference azimuth angle αb to an azimuth angle αt of the upper swing structure <NUM> calculated by the GNSS receiver <NUM> (namely, αt + αb).

A greater one of the elevation angle mask angle αs by the machine body and the elevation angle mask angle αg by the present terrain calculated in such a manner as described above is determined as an elevation angle mask angle at the azimuth angle. In the example in <FIG>, αs > αg is satisfied, and therefore, the elevation angle mask angle αs by the machine body becomes the elevation angle mask angle, and the mask range <NUM> in the elevation angle range where the machine body reference azimuth angle is <NUM> degrees is as depicted in <FIG>. Similar calculation is performed for all azimuths to calculate elevation angle mask angles at all azimuths. Then, a mask range is set to the site coordinate system on the basis of the resulting elevation angle mask angles. It is to be noted that it is sufficient if the mask range is set to the coordinate system set to the ground, and for example, the mask range may be set to the geographic coordinate system.

Referring back to <FIG>, at step S60, the controller <NUM> adds (sums) the mask range calculated at step S50 (mask range set newly) to a mask range set before the present calculation cycle (mask range set in the past (however, except the mask ranges reset at steps S90 and S110 described hereinabove)). By this step S60, for example, when the inclination angle of the upper swing structure <NUM> changes after the process one cycle before or when the azimuth angle changes as a result of swing motion of the upper swing structure <NUM>, a new mask range is set according to such changes. Then, since the new mask range is added to the mask ranges in the past, the mask range is expanded according to a change in the inclination angle and the azimuth angle of the upper swing structure <NUM>.

At step S70, the controller <NUM> transmits the mask range stored in the storage device to the GNSS receiver <NUM>. When the step S70 is reached after carrying out the step <NUM>, the mask range at step S60 is transmitted to the GNSS receiver <NUM>, and when the step <NUM> is reached after carrying out the step S45, the last mask range set at step S60 is transmitted (however, where the step S60 is not carried out at all after the mask range is reset at step S90 or S110, the mask range is not transmitted).

At step S80, the controller <NUM> decides whether or not information that position measurement cannot be performed in a state in which the mask range is set is received from the GNSS receiver <NUM>. For this decision, a process described below is performed by the GNSS receiver <NUM>. In particular, the GNSS receiver <NUM> receives the mask range transmitted from the controller <NUM> at step S70, excludes satellites that are positioned within the mask range from among a plurality of GNSS satellites from which a satellite signal can be received, and decides whether or not position measurement calculation can be performed on the basis of satellite signals transmitted from the remaining satellites. When the GNSS receiver <NUM> decides that the position measurement calculation can be performed, the GNSS receiver <NUM> transmits information indicating that position measurement is possible in the state in which the mask range is set to the controller <NUM>. Further, the GNSS receiver <NUM> calculates the position of the GNSS antenna <NUM> and the vector from the GNSS antenna <NUM> to the GNSS antenna <NUM> and outputs a result of the calculation to the controller <NUM>. On the other hand, when position measurement calculation cannot be performed because the number of satellites to be used is insufficient (for example, less than five) as a result of setting of the mask range or because the arrangement of satellites to be used is biased (for example, the DOP is equal to or higher than a predetermined value), causing a risk of accuracy reduction, in order to allow position measurement calculation to be performed in a state in which the mask range is cancelled at step S90 hereinafter described, the GNSS receiver <NUM> transmits information indicating that position measurement cannot be performed in the state in which the mask range is set to the controller <NUM>.

It is to be noted that, although a case in which an azimuth angle range and an elevation angle range to be masked are calculated by the controller <NUM> and the ranges (mask range) are transmitted to the GNSS receiver <NUM> has been described here, the controller <NUM> may acquire satellite numbers of satellites from which satellite signals can be received and information of the azimuth angle and the angle of elevation of the satellites from the GNSS receiver <NUM>, calculate satellite numbers of satellites existing within the mask range calculated by the controller <NUM>, and transmit the satellite numbers that are not used for position measurement calculation to the GNSS receiver <NUM>, so that the decision described hereinabove may be carried out.

When the information that position measurement cannot be performed in a state in which the mask range is set is received from the GNSS receiver <NUM> at step S80, the controller <NUM> advances the processing to step S90 at which to display that there is the possibility that the position measurement accuracy may be deteriorated on the screen of the display device <NUM> and reset the information of the mask range stored in the controller <NUM>. Accordingly, all mask ranges are erased. It is to be noted that the time period T measured at step S45 is also reset simultaneously with the resetting of the mask range. On the other hand, when the information that position measurement is possible even in the state in which the mask range is set is received from the GNSS receiver <NUM> at step S80 (namely, when information that position measurement is impossible in the state in which the mask range is set is not received), the processing advances to step S100.

At step S100, the controller <NUM> decides whether or not it is necessary to reset (erase) the mask range. In this decision, the controller <NUM> decides that it is necessary to reset the mask range in any of a case in which the time period T measured at step S45 continues for a predetermined time period t1 or more (for example, for <NUM> minutes or more), another case in which the hydraulic excavator <NUM> moves by a predetermined distance or more (for example, <NUM> or more) by a traveling operation for the lower track structure <NUM> by the operation device in the cab <NUM>, a further case in which a demand of the operator that the mask range is to be reset is inputted through the setting switch (mask range reset switch) <NUM>, and a still further case of a first calculation cycle immediately after system startup. The movement of the hydraulic excavator <NUM> by the traveling operation can be detected, for example, from pilot pressure detection for traveling and position movement of the hydraulic excavator <NUM> that is performed on the basis of position measurement calculation of the GNSS receiver <NUM>.

When it is decided at step S100 that it is necessary to reset the mask range, the controller <NUM> advances the processing to step S110 at which resetting of the mask range is performed and the time period T measured at step S45 is also reset to zero at the same time.

By carrying out the processing described above, when a work that requires accuracy is being performed by the hydraulic excavator <NUM>, satellite signals that may possibly be influenced by an obstacle including the front work implement <NUM> are not used for position measurement calculation. Therefore, deterioration in the accuracy in position measurement calculation due to switching of the combination of satellites to be used for position measurement calculation on the way of excavation can be prevented, and deterioration in the accuracy in position measurement calculation due to use of a satellite signal influenced by diffraction of radio waves can be prevented.

In the hydraulic excavator <NUM> configured in such a manner as described above, a mask range according to the azimuth angle and the inclination angle of the upper swing structure <NUM> during a work is set to the site coordinate system, and position measurement calculation is performed by the GNSS receiver <NUM> without utilizing satellite signals of GNSS satellites positioned within the mask range. Consequently, it is prevented that the position measurement accuracy of the GNSS is deteriorated during a work by switching of satellites associated with operation of the front work implement <NUM> (principally, from boom raising operation) or diffraction of satellite signals. As a result, since the position calculation result of the monitor point is prevented from fluctuating, the control accuracy of the hydraulic excavator <NUM> can be improved.

Especially, the hydraulic excavator <NUM> described above has such a specification that a mask range is set while a work that requires accuracy is being performed, and in a state in which a work that does not require accuracy continues for the predetermined time period t1 or more, in another state in which the measurement position accuracy is deteriorated by setting of a mask range, or in a like state, the setting of the mask range is cancelled. In particular, the hydraulic excavator <NUM> is configured such that, while a mask range is set only in a scene in which the accuracy is required to secure position measurement accuracy, in another scene in which accuracy is not required or in a further scene in which accuracy cannot be secured, immediacy not of accuracy but of position measurement is prioritized such that position measurement suitable for a scene can be performed.

Further, in the hydraulic excavator <NUM> described above, when the azimuth angle or the inclination angle of the upper swing structure <NUM> changes, a mask range is set newly according to the change and the new mask range is added to a mask range set in the past thereby to expand the mask range. In particular, for example, when the upper swing structure <NUM> swings from an excavation position to a soil-dumping position, a mask range is set according to a change in azimuth angle of the upper swing structure <NUM> during the swing movement and is summed to the mask range in the past. Consequently, it can be avoided that different satellites are selected at the excavation position and the soil-dumping position, and therefore, the measurement accuracy can be prevented from being deteriorated by switching of satellites.

Further, if shape data on an obstacle is stored in advance in the controller <NUM>, then a mask range can be set taking into consideration an influence by not only the front work implement <NUM> but also the obstacle (for example, a present terrain) on position measurement. Consequently, position measurement calculation can be performed without utilizing signals of satellites blocked by the obstacle, and therefore, the position measurement accuracy can be improved further.

Although the embodiment of the present invention has been described in detail above, the present invention is not restricted to the embodiment described above but includes various modifications. For example, the embodiment described above has been described in detail in order to explain the present invention in an easy-to-understand manner and is not necessarily limited to what includes all configurations described above.

For example, although, in the flow chart of <FIG> described above, presence or absence of setting of a mask range is switched depending upon whether or not a work that requires accuracy is being performed, a mask range may be set in all cases.

Further, the individual configurations relating to the controller (control device) <NUM> described above and the functions, execution processes, and so forth of the individual configurations may be partly or entirely implemented by hardware (for example, by designing the logic for executing the functions with an integrated circuit). Further, a configuration relating to the controller <NUM> described above may be a program (software) by which the functions relating to the configuration of the controlling device are implemented by an arithmetic processing unit (for example, a CPU) by reading out and executing the program. Information relating to the program can be stored, for example, into a semiconductor memory (flash memory, SSD, or the like), a magnetic storage device (hard disk drive or the like), a recording medium (magnetic disk, optical disc, or the like), or the like.

Claim 1:
A work machine that includes a track structure (<NUM>), an upper swing structure (<NUM>) swingably attached on the track structure (<NUM>), a work device (<NUM>) attached to the upper swing structure (<NUM>), two GNSS antennae (<NUM>, <NUM>) installed on the upper swing structure (<NUM>), a receiver (<NUM>) configured to calculate a position and an azimuth angle of the upper swing structure (<NUM>) on a basis of satellite signals transmitted from a plurality of satellites and received by the two GNSS antennae(<NUM>, <NUM>), and a controller (<NUM>) configured to calculate a position of a monitor point on a basis of the position and the azimuth angle of the upper swing structure (<NUM>) calculated by the receiver (<NUM>), characterised in that
the controller (<NUM>) is configured to set, on a basis of installation positions of the two GNSS antennae(<NUM>, <NUM>) on the work machine (<NUM>), a movable range of the work device (<NUM>), an inclination angle of the upper swing structure (<NUM>), and an azimuth angle of the upper swing structure, a range within which, when the two GNSS antennae (<NUM>, <NUM>) individually receive satellite signals from the plurality of satellites, the work device (<NUM>) possibly becomes an obstacle to the satellite signals as a mask range in a coordinate system set to a ground, and
in that the receiver (<NUM>) is configured to calculate a position and an azimuth angle of the upper swing structure (<NUM>) on a basis of the satellite signals transmitted from remaining ones of the plurality of satellites, the remaining ones other than the satellites positioned within the mask range set by the controller (<NUM>).