Autonomous traveling work machine

To make it possible to correct a current position detected by an autonomous traveling work machine to the correct position with a simple configuration. A robot lawn mower includes a first position detecting unit for detecting a current position by using odometry and a second position detecting unit for detecting a current position by using an image capture. When position detection accuracy of both of the first and second position detecting units decreases to less than or equal to a predetermined value, the robot lawn mower is controlled to travel to either of zones Z1 and Z2 in which the position detection accuracy of the second position detecting unit is relatively high, and when the robot lawn mower moves to either of the zones Z1 and Z2, a current position used for autonomous traveling is corrected to the current position detected by the second position detecting unit.

TECHNICAL FIELD

The present invention relates to an autonomous traveling work machine that autonomously travels in a working area.

BACKGROUND ART

There has been an autonomous traveling work machine that detects a relative position from a station (hereinafter referred to as a relative position) by means of odometry and autonomously travels in a working area based on the relative position. Odometry is a technique of detecting a relative position from a reference position based on the amount of rotation of wheels, wheel diameter, tread and the like. Accordingly, a longer movement distance results in an increased error, decreasing the position detection accuracy. Thus, an unmanned carrier vehicle that is further provided with an ID tag detector (corresponding to a sensor) to correct the amount of deviation of the current position such as based on absolute position information from an ID tag (see Patent Literature 1, for example).

CITATION LIST

Patent Literature

Patent Literature 1

SUMMARY OF INVENTION

Technical Problem

To ensure return to the station, a possible method is to track wire buried in the ground. However, this requires burying the wire, and a wireless autonomous traveling work machine cannot be operated like that. Also, in the case of an autonomous traveling work machine using wire, it is likely that wheel tracks are produced along the wire, increasing the positional deviation such as due to spinning of wheels.

Also, the method of using an ID tag requires that the ID tag be buried in the floor or stuck on the wall. If there are surrounding objects and noise blocking the communication in the movement area, the impossibility of receiving information of the ID tag may increase the positional deviation. If the positional deviation is significant, it is impossible to return to the station and correct (e.g., reset) the odometry to the correct position.

Thus, it is an objective of the present invention to make it possible to correct a current position detected by an autonomous traveling work machine to the correct position with a simple configuration.

Solution to Problem

To achieve the above objective, an aspect of the present invention provides an autonomous traveling work machine that detects a current position by a first detecting means for detecting the current position and a second detecting means for detecting the current position by a different method from the first detecting means, and autonomously travels in a working area based on the detected current position, the autonomous traveling work machine being characterized by including: a zone identifying unit for identifying a zone in which position detection accuracy of the second detecting means is relatively high, a travel controlling unit for controlling the autonomous traveling work machine to travel to the zone identified by the zone identifying unit when position detection accuracy of both of the first and second detecting means decreases to less than or equal to a predetermined value; and a position correcting unit for correcting a current position used for autonomous traveling to the current position detected by the second detecting means when the autonomous traveling work machine moves to the zone.

In the above configuration, the autonomous traveling work machine is characterized in that the autonomous traveling work machine includes a holding unit for holding position detection accuracy data in which a position and position detection accuracy of the second detecting means at the position are associated, and the zone identifying unit identifies the zone based on the position detection accuracy data.

Also, in the above configuration, the autonomous traveling work machine is characterized in that the travel controlling unit controls the autonomous traveling work machine to travel to the zone identified by the zone identifying unit when position detection accuracy of both of the first and second detecting means continues being less than or equal to a predetermined value.

Also, in the above configuration, the autonomous traveling work machine is characterized in that the zone identifying unit identifies a plurality of the zones, and the travel controlling unit identifies a distance from the current position of the autonomous traveling work machine to each zone, and controls the autonomous traveling work machine to travel to a nearest zone of the plurality of the zones.

Also, in the above configuration, the autonomous traveling work machine is characterized in that the zone identifying unit identifies a plurality of the zones, and the travel controlling unit identifies an area of each zone, and controls the autonomous traveling work machine to travel to a zone with a largest area of the plurality of the zones.

Also, in the above configuration, the autonomous traveling work machine is characterized in that the first detecting means is a relative position detecting means for detecting a relative position with respect to a reference position. Also, in the above configuration, the autonomous traveling work machine is characterized in that the relative position detecting means is odometry or a non-contact sensor.

Also, in the above configuration, the autonomous traveling work machine is characterized in that the travel controlling unit controls the autonomous traveling work machine to travel to a nearer one of the zone and a station used as the reference position for the first detecting means. Also, in the above configuration, the autonomous traveling work machine is characterized in that the travel controlling unit controls the autonomous traveling work machine to travel toward a center of the zone. Also, in the above configuration, the autonomous traveling work machine is characterized in that the second detecting means is an image capturing means or a GPS sensor.

Advantageous Effect of Invention

According to the aspect of the present invention, when position detection accuracy of both of first and second detecting means decreases to less than or equal to a predetermined value, the autonomous traveling work machine is controlled to travel to a zone in which position detection accuracy of the second detecting means is relatively high, and when the autonomous traveling work machine moves to the zone, a current position used for autonomous traveling is corrected to a current position detected by the second detecting means, so that the current position detected by the autonomous traveling work machine can be corrected to the correct position with a simple configuration.

DESCRIPTION OF EMBODIMENTS

The following describes embodiments of the present invention with reference to the drawings.

First Embodiment

FIG.1is a side view of a robot lawn mower according to a first embodiment of the present invention.

A robot lawn mower10is an autonomous traveling work machine that autonomously travels in a working area, which is a lawn mowing area, in a wireless manner, and is hereinafter referred to as a lawn mower10.

The lawn mower10includes a housing11, left and right front wheels12provided at a front part of the housing11, left and right rear wheels13provided at a rear part of the housing11, and a work unit14provided at a lower central part of the housing11. The work unit14is a cutting blade disc provided with a cutting blade, and can cut lawns when the cutting blade disc is rotationally driven.

The lawn mower10includes, inside the housing11, left and right travel motors15for separately driving the left and right rear wheels13, a work unit driving motor16for driving the work unit14, a battery17for supplying operational electrical power to each unit of the lawn mower10, a wheel speed sensor18for detecting rotational speed of the left and right rear wheels13, which are drive wheels, and an electrical unit30.

FIG.2is a block diagram of the lawn mower10.

As shown inFIG.1andFIG.2, the electrical unit30includes an electronic component such as an ECU (Electronic Control Unit)31. In this embodiment, the electrical unit30includes, in addition to the ECU31, drivers32and33for generating drive signals for the motors15and16, a first sensor unit34for detecting movement of the lawn mower10other than the wheels, and a communication unit35for inputting and outputting various information.

The driver32separately controls the rotation of the left and right travel motors15according to signals received from the ECU31. The driver33controls the rotation of the work unit driving motor16according to signals received from the ECU31.

The first sensor unit34includes an angular velocity sensor34A for detecting the angular velocity of the lawn mower10and an acceleration sensor34B for detecting the acceleration of the lawn mower10. The ECU31identifies the traveling direction of the lawn mower10from a detection result of the angular velocity sensor34A, and identifies the moving speed of the lawn mower10from a detection result of the acceleration sensor34B. The sensors34A and34B are sensors used such as when the ECU31(a first position detecting unit62, which will be described later) detects the current position by means of odometry.

Further, the lawn mower10includes an image capturing means36A for capturing images outside (in this configuration, forward of) the lawn mower10as a second sensor unit36used for detecting the current position of the lawn mower10. The image capturing means36A can employ various known cameras capable of capturing static images or moving images. Also, the number of cameras may be one or more, or there may be a stereo camera consisting of two cameras.

The communication unit35sends and receives information to/from an external device via wireless communication under control of the ECU31. The communication unit35is, for example, a communication module for performing short-range wireless communication such as Bluetooth (registered trademark), IrDA, or Wi-Fi (registered trademark).

The ECU31is composed of a microcomputer including a processing unit40such as a CPU (Central Processing Unit) and a storage unit50(a holding unit) such as a RAM (Random Access Memory) or a ROM (Read Only Memory). The storage unit50holds data such as map data51about the working area and control programs.

The processing unit40functions as an information input unit61, a first position detecting unit62, a second position detecting unit63, a travel controlling unit64, a zone identifying unit65, and a position correcting unit66by executing control programs stored in the storage unit50. Note that any of the information input unit61, the first position detecting unit62, the second position detecting unit63, the travel controlling unit64, the zone identifying unit65, and the position correcting unit66may be composed of hardware such as an analog circuit.

Before describing each unit of the processing unit40, the map data51will be described.

FIG.3is a diagram illustrating an example of a working area. InFIG.3, a region enclosed by a solid line70is a working area (hereinafter indicated with a reference numeral71).

There may be trees, buildings and the like inside and outside the working area71.FIG.3illustrates a case in which there are trees (hereinafter referred to as a first object72) on the left of the working area71and a building (hereinafter referred to as a second object73) on the upper right of the working area71. Also, in the working area71shown inFIG.3, the position of a station75for housing the lawn mower10is indicated as well as the lawn mower10traveling in the working area71.

The map data51is information used by the lawn mower10to travel in the working area71, and in this embodiment includes positional information D1indicating the working area71, object information D2indicating objects (the first object72and the second object73) present inside and outside the working area71, and position detection accuracy data D3indicating position detection accuracy of the second position detecting unit63using the image capturing means36A. The position detection accuracy data D3is data in which each position in the working area71and the position detection accuracy of the second position detecting unit63at the position are associated. By referencing the position detection accuracy data D3, zones Z1and Z2, which are regions where the position detection accuracy of the second position detecting unit63is high, can be easily identified.

Note that the zone Z1is a region that is particularly close to the first object72, and is a region where the current position of the lawn mower10can be accurately detected by the image capturing means36A because the positional relationship between the lawn mower10and the first object72is apparent when photographed. Also, the zone Z2is a region that is particularly close to the second object73, and is a region where the current position of the lawn mower10can be accurately detected by the image capturing means36A because the positional relationship between the lawn mower10and the second object73is apparent when photographed.

The position detection accuracy data D3described above may be created by a user or the like, or may be automatically created based on a result of automatically collecting the position detection accuracy of the second position detecting unit63by the ECU31during a test run of the lawn mower10.

The information input unit61shown inFIG.2inputs user instructions via an operational panel (not shown) provided on the lawn mower10, inputs various information from an external device via the communication unit35, and inputs information from other portions of the lawn mower10. The information input unit61is used to acquire the map data51or update the map data51stored in the storage unit.

The first position detecting unit62functions as a relative position detecting means (corresponding to a first detecting means) for detecting a relative position corresponding to a reference position as the current position of the lawn mower10by means of odometry, which is a technique of estimating the current position such as from the amount of rotation of wheels. More specifically, the first position detecting unit62arithmetically acquires the distance by which the lawn mower10has moved based on a detection result of the wheel speed sensor18. The first position detecting unit62can also detect the turning angle of the lawn mower10based on the rotational difference between the left and right rear wheels13.

Further, the first position detecting unit62accurately identifies the traveling direction of the lawn mower10from a detection result of the angular velocity sensor34A, and accurately identifies the moving speed of the lawn mower10from a detection result of the acceleration sensor34B. Then, based on the identified information, the first position detecting unit62detects, as the current position, a relative movement distance from a predetermined reference position.

Note that the specific calculation method and the like for the odometry can employ various known operations.

The reference position for the odometry is set at the position of the station75(FIG.3), for example. The station75is in this embodiment configured as a charging station having a charging function for charging the battery17of the lawn mower10, but may not have the charging function.

The second position detecting unit63functions as a second detecting means for detecting the current position by a different method from the first position detecting unit62, and detects the current position of the lawn mower10by using an image captured by the image capturing means36A. More specifically, the second position detecting unit63performs image analysis on an image captured by the image capturing means36A to extract an object in the captured image, and determines whether the extracted object matches with either of the first object72and the second object73in the object information D2in the map data51. If so, the second position detecting unit63identifies the position where the extracted object is captured in the image, and extracts positional information indicating the position from the positional information D1in the map data51.

Note that the operation of detecting the current position by using the captured image can employ various known operations.

The positional information indicating the current position detected by the first position detecting unit62and the second position detecting unit63is in a corresponding relationship with the positional information D1in the map data51.

The travel controlling unit64controls the left and right travel motors15such that the lawn mower10travels in the working area71defined in the positional information D1in the map data51by using the current position detected by the first position detecting unit62. Meanwhile, the travel controlling unit64also drives the work unit driving motor16to perform the lawn cutting work.

Also, the travel controlling unit64controls the lawn mower10to travel toward the station75by using positional information of the station75included in the map data51when the remaining capacity of the battery17becomes less than or equal to a predetermined value. When the lawn mower10moves to the station75, the charging of the battery17is started.

When the lawn mower10moves to the station75, the position correcting unit66performs an operation of correcting the current position detected by the first position detecting unit62(corresponding to a current position used for travel control) to the positional information of the station75included in the map data51(this operation is also referred to as a reset operation). The position correcting unit66also performs an operation of correcting the current position detected by the first position detecting unit62to the current position detected by the second position detecting unit63(this operation is included in the reset operation) during a position correcting operation, which will be described later.

In general, the position detection accuracy based on odometry decreases as the movement distance increases. Accordingly, if the travel control is performed based only on the current position detected by the first position detecting unit62, the positional deviation becomes larger as the movement distance increases.

If the positional deviation is significant, it may be impossible to return to the station75. On the other hand, the position detection accuracy of the second position detecting unit63is not necessarily high at a position where the position detection accuracy of the first position detecting unit62decreases. Thus, in this embodiment, the following position correcting operation is performed.

FIG.4is a flow chart illustrating a position correcting operation. Note that the position correcting operation is an operation that is repeatedly performed while the lawn mower10travels in the working area71during work.

The ECU31determines whether the position detection accuracy of the first position detecting unit62(=position detection accuracy based on the first sensor unit34) and the position detection accuracy of the second position detecting unit63(=position detection accuracy based on the second sensor unit36) have decreased to less than or equal to a predetermined value by the travel controlling unit64(step S).

Since the position detection accuracy of the first position detecting unit62decreases in accordance with the travel distance, it is determined that the position detection accuracy has decreased to less than or equal to the predetermined value when the travel distance from the previous reset operation exceeds a predetermined threshold, for example. However, there is no limitation thereto, and the slip ratio of the lawn mower10may be constantly measured so that it is determined that the position detection accuracy has decreased to less than or equal to the predetermined value such as when the slip ratio becomes greater than or equal to a threshold (when a large slip occurs) or when the number of large slips exceeds a threshold.

Also, the position detection accuracy of the second position detecting unit63is based on image recognition accuracy or the like, and can be detected such as by using known calculation methods for calculating image recognition accuracy. In this embodiment, it is determined that the position detection accuracy has decreased to less than or equal to the predetermined value when a detected value of the position detection accuracy becomes lower than a predetermined threshold.

Note that the position detection accuracy of the first position detecting unit62and the second position detecting unit63can be calculated by using various known detection methods.

If the determination in step S is YES, the flow proceeds to the operation of step S2. If the determination in step S1is NO, the flow ends. Note that, if the position detection accuracy of the first position detecting unit62using the odometry is less than or equal to the predetermined value while the position detection accuracy of the second position detecting unit63exceeds the predetermined value, the traveling position used for autonomous traveling may be corrected to the current position detected by the second position detecting unit63.

In step S2, the ECU31determines whether the position detection accuracy of the first position detecting unit62and the second position detecting unit63continues decreasing for a time longer than or equal to a predetermined time by the travel controlling unit64.

The predetermined time here is set to a time longer than a period of time for which the position detection accuracy of the second position detecting unit63momentarily decreases due to a special event such as entry of direct sunlight into the image capturing means36A, for example.

If the determination in step S2is YES, the flow proceeds to the operation of step S3. If the determination in step S2is NO, the flow proceeds to the operation of step S5.

In step S3, the ECU31performs an operation of identifying a zone in which the position detection accuracy of the second position detecting unit63is high by the zone identifying unit65.

In the example shown inFIG.3, zones Z1and Z2are identified by referencing the position detection accuracy data D3. If a plurality of zones Z1and Z2are identified, the ECU31arithmetically identifies the distance from the current position of the lawn mower10to each of the zones Z1and Z2by the travel controlling unit64to identify the nearest zone of the zones Z1and Z2.

Upon identifying the zone in step S3, the ECU31controls the lawn mower10to travel toward the zone identified by the travel controlling unit64(step S4), and then proceeds to the operation of step S5. Note that, in addition to controlling the lawn mower10to move to the identified zone, the travel control in step S4involves controlling the direction of the lawn mower10to change such that the objects used for identifying the current position (the first object72and the second object73) are included in an image captured by the image capturing means36A when the objects are not included in it.

In step S5, the ECU31performs an operation of detecting the current position by the second position detecting unit63and correcting the current position detected by the first position detecting unit62to the current position detected by the second position detecting unit63(the reset operation). The actions of the position correcting operation have been described above.

As described above, in this embodiment, the zone identifying unit65identifies a zone in which the position detection accuracy of the image capturing means36A, which functions as a position sensor, is relatively high, and the travel controlling unit64controls the lawn mower10to travel to the zone identified by the zone identifying unit65when the position detection accuracy of both of the first position detecting unit62(first detecting means) and the second position detecting unit63(second detecting means) decreases to less than or equal to a predetermined value. Further, the position correcting unit66corrects the current position used for autonomous traveling to the current position detected by the second position detecting unit63when the lawn mower10moves to the zone.

According to these configurations, the current position based on odometry can be corrected to the correct position without returning to the station75. Therefore, there is no need to employ the configuration of providing wire or an ID tag in the ground or on the wall so as to ensure return to the station75, and the current position detected by the lawn mower10can be corrected with a simple configuration, preventing the impossibility to return to the station75.

Also, the storage unit50holds the position detection accuracy data D3in which each position in the working area71and the position detection accuracy of the second position detecting unit63at the position are associated. Then, the zone identifying unit65identifies the above-mentioned zone based on the position detection accuracy data D3. This makes it possible to easily identify the zone.

Also, the travel controlling unit64controls the lawn mower10to travel to the zone identified by the zone identifying unit65when the position detection accuracy of both of the first and second position detecting units62and63continues being less than or equal to a predetermined value. This can prevent the movement to the zone every time the position detection accuracy temporarily decreases, improving convenience.

Further, when the zone identifying unit65identifies a plurality of zones, the travel controlling unit64identifies the distance from the current position of the lawn mower10to each zone, and controls the lawn mower10to travel to the nearest zone. This can minimize the error occurring before reaching the zone, enabling a heightened probability of entering the zone.

Second Embodiment

FIG.5is a block diagram of a lawn mower10according to a second embodiment.

The second embodiment is different from the first embodiment in that a GPS (Global Positioning System) sensor36B is used for the second sensor unit36. Note that components similar to those in the first embodiment are shown with the same reference numerals, and overlapping descriptions will be omitted.

FIG.6is a diagram illustrating an example of the working area71.

The GPS sensor36B receives electromagnetic waves from GPS satellites. Accordingly, in the shadow of the first object72and the second object73present inside and outside the working area71, the position detection accuracy decreases due to the impossibility to receive the electromagnetic waves or a decreased number of captured GPS satellites. For that reason, in the case of the second position detecting unit63using the GPS sensor36B, the position detection accuracy is higher at a more distant position from the first object72and the second object73.

FIG.6illustrates an example where the zone identifying unit65identifies a zone Z3distant from the first object72and the second object73in the working area71as a region in which the position detection accuracy of the second position detecting unit63is high.

In the second embodiment, the travel controlling unit64controls the lawn mower10to travel to the zone Z3when the position detection accuracy of both of the first and second position detecting units62and63continuously decreases to less than or equal to a predetermined value. In this manner, various effects can be obtained such as that the current position based on odometry can be corrected to the correct position with a simple configuration, as with the first embodiment.

Note that, in each of the above-described embodiments, when the zone identifying unit65identifies a plurality of zones, the lawn mower10may be controlled to travel to the zone with the largest area. In this case, even if a positional deviation occurs due to the error occurring before reaching the zone, the probability of entering the zone can be heightened.

Also, if the station75is at a position nearer than the zone, the travel controlling unit64may move the lawn mower10to the station75. In this case, the current position can be reset at the station75.

Further, the travel controlling unit64may control the lawn mower10to travel toward the center of the zone. In this case, even if a positional deviation occurs due to the error occurring before reaching the zone, the probability of entering the zone can be heightened.

Also, although each of the above-described embodiments has illustrated an example where the present invention is applied to the wireless lawn mower10without using area wire provided along the periphery of the working area71or the like, there is no limitation to this configuration, and the present invention may also be applied to a lawn mower10having a function to identify the working area71by using area wire, a marker or the like.

Also, the first sensor unit34used for detecting the current position based on odometry and the second sensor unit36used for detecting the current position without using odometry are not limited to the above-described sensors.

For example, the first position detecting unit62may use a non-contact sensor such as an optical flow sensor (also referred to as a relative speed detection sensor) or a gyro sensor to detect a relative position with respect to the position of the station or the like. Also in the case of using an optical flow sensor or the like, an increased movement distance causes an increased error as with the case of using odometry.

Also, although an example where the first position detecting unit62is a relative position detecting means for detecting a relative position with respect to a reference position has been illustrated, there is no limitation thereto, and other known configurations for detecting the current position may be applied.

Also, although each of the above-described embodiments has illustrated an example where the present invention is applied to the lawn mower10, there is no limitation thereto, and the present invention is widely applicable to autonomous traveling work machines other than the lawn mower10. Also, each of the above-described embodiments is merely a form of embodying the present invention, and any variations and applications are possible without departing from the spirit of the present invention.

For example, the second sensor unit36may include both of the image capturing means36A described in the first embodiment and the GPS sensor36B described in the second embodiment, the zones Z1and Z2in which the position detection accuracy of the image capturing means36A is high and the zone Z3in which the position detection accuracy of the GPS sensor36B is high may be identified in step S3, and the lawn mower10may be controlled to travel to the nearest zone of the zones Z1to Z3in step S4. In this configuration, the number of zones with high position detection accuracy can be increased, facilitating the shortening of the movement distance in step S4.

Also, even when the nearest zone of the zones Z1to Z3is identified, if the station75is at a position nearer than the identified zone, the lawn mower10may be moved to the station75in step S4.

REFERENCE SIGNS LIST