Work robot

Abstract

To provide a technique capable of smoothly progressing work to be done by a work robot.SOLUTION: A work robot includes: a work mechanism that performs work; a movement mechanism that moves the work robot; a work motor that drives the work mechanism; a movement motor that drives the movement mechanism; a battery that can be recharged and supplies electric power to the work motor and the movement motor; a voltage detection unit that detects a voltage value of the battery; and a control unit. The control unit can execute two-stage acquisition processing of acquiring as a first-stage voltage value a detection value of the voltage detection unit obtained when an object motor which is at least one of the work motor and the movement motor is in motion, thereafter halts the object motor, and acquires as a second-stage voltage value a detection value of the voltage detection unit obtained when the object motor is at a halt, and return determination processing of determining whether or not the work robot is returned to a charge station based on the first-stage voltage value and the second-stage voltage value.SELECTED DRAWING: Figure 8

Description

[Technical field] 【0001】 The technology disclosed in this specification relates to a working robot. [Background technology] 【0002】 Patent Document 1 discloses a work robot that performs work while moving autonomously. The work robot includes a work mechanism that performs work, a movement mechanism that moves the work robot, a work motor that drives the work mechanism, a movement motor that drives the movement mechanism, a rechargeable battery that supplies power to the work motor and the movement motor, a voltage detection unit that detects the voltage value of the battery, and a control unit. When the detection value of the voltage detection unit falls below a predetermined value, the control unit returns the work robot to a charging station. By returning to the charging station, the work robot is able to charge the battery. [Prior art documents] [Patent documents] 【0003】 [Patent Document 1] JP 2016-10382 A Summary of the Invention [Problem to be solved by the invention] 【0004】 If the timing of returning the work robot to the charging station is too late, the battery will run out while the work robot is returning. If the battery runs out while the work robot is returning, the work robot will stop before reaching the charging station. In this situation, the battery cannot be recharged without the user's help, and the work robot cannot perform work. As a result, the work by the work robot may not proceed smoothly. On the other hand, if the timing of returning the work robot to the charging station is too early, the work robot will return to the charging station even though the battery has enough remaining power for the work robot to continue working. As a result, the work by the work robot will be frequently interrupted, and the work by the work robot may not proceed smoothly. This specification provides a technology that allows the work by the work robot to proceed smoothly. [Means for solving the problem] 【0005】 The working robot disclosed in this specification performs work while moving autonomously. The working robot includes a working mechanism that performs work, a movement mechanism that moves the working robot, a working motor that drives the working mechanism, a movement motor that drives the movement mechanism, a rechargeable battery that supplies power to the working motor and the movement motor, a voltage detection unit that detects a voltage value of the battery, and a control unit. The control unit is configured to execute a two-stage acquisition process for a target motor, which is at least one of the working motor and the movement motor, of acquiring a detection value of the voltage detection unit when the target motor is operating as a first-stage voltage value, and then stopping the target motor and acquiring a detection value of the voltage detection unit when the target motor is stopped as a second-stage voltage value, and a return determination process of determining whether or not to return the working robot to a charging station based on the first-stage voltage value and the second-stage voltage value. 【0006】 When the motor is operating, the battery voltage value is lower than when the motor is stopped due to the internal resistance of the motor. Therefore, in order to appropriately determine the timing to return the work robot, it is preferable to obtain the detection value of the voltage detection unit for each operating status of the motor. According to the above configuration, the control unit of the work robot can obtain the detection value of the voltage detection unit for each operating status of the motor, so that the timing to return the work robot can be appropriately determined. In other words, the timing to return the work robot can be prevented from being too late or too early. Therefore, it is possible to prevent the battery from running out while the work robot is returning, and to prevent the work robot from being frequently interrupted. This allows the work by the work robot to proceed smoothly. [Brief description of the drawings] 【0007】 [Figure 1] 1 is a diagram showing an example of use of the robot lawnmower 2 according to the first embodiment. FIG. [Diagram 2] FIG. 2 is a left side view of the robotic lawnmower 2 according to the first embodiment. [Diagram 3] FIG. 2 is a rear view of the robotic lawnmower 2 according to the first embodiment. [Figure 4] 1 is a schematic configuration diagram of a robotic lawnmower 2 according to a first embodiment. [Diagram 5] 5 is a flowchart of a battery voltage management process executed by a control unit 8 of the robotic lawnmower 2 according to the first embodiment. [Figure 6] 5 is a flowchart of a battery voltage management process executed by a control unit 8 of the robotic lawnmower 2 according to the first embodiment. [Figure 7] FIG. 11 is a diagram showing a schematic change over time in the voltage value of the battery 18 in the robotic lawnmower 2 according to the first embodiment, assuming that a return determination to the charging station 110 is made without correcting the return threshold value Vre. [Figure 8]1 is a diagram showing a schematic diagram of a change in the voltage value of the battery 18 over time when the robotic lawnmower 2 according to the first embodiment returns to the charging station 110 in accordance with the battery voltage management process. FIG. [Figure 9] 5 is a flowchart of a motor burnout avoidance process executed by a control unit 8 of the robotic lawnmower 2 according to the first embodiment. [Figure 10] FIG. 11 is a schematic configuration diagram of a robotic lawnmower 202 according to a second embodiment. [Figure 11] FIG. 11 is a diagram showing a schematic diagram of changes in the voltage value of the battery 18 over time when the robotic lawnmower 2 according to the modified example returns to the charging station 110 in accordance with the battery voltage management process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 【0008】 Representative and non-limiting examples of the present invention are described in detail below with reference to the drawings. This detailed description is intended simply to provide those skilled in the art with details for implementing the preferred examples of the present invention, and is not intended to limit the scope of the present invention. Additionally, the additional features and inventions disclosed can be used separately or together with other features and inventions to provide further improved work robots. 【0009】 In addition, the combinations of features and steps disclosed in the following detailed description are not essential for implementing the present invention in the broadest sense, but are specifically described only to illustrate representative embodiments of the present invention. Furthermore, the various features of the following representative embodiments and the various features described in the claims do not have to be combined in the exact manner of the embodiments described herein or in the order listed in order to provide additional and useful embodiments of the present invention. 【0010】 All features described in the specification and / or claims are intended to be disclosed individually and independently of one another as limitations to the specific features described in the original disclosure and claims, apart from the configuration of features described in the examples and / or claims. Furthermore, all numerical ranges and group or aggregate descriptions are intended to disclose intermediate configurations thereof as limitations to the specific features described in the original disclosure and claims. 【0011】 In one or more embodiments, the control unit may be configured to acquire the detection value of the voltage detection unit as a first determination voltage value, execute the two-stage acquisition process when the first determination voltage value is equal to or less than a predetermined value, and not execute the two-stage acquisition process when the first determination voltage value exceeds the predetermined value. 【0012】 When the battery voltage value is relatively high, it is clear that there is no need to return the work robot even without executing the two-stage acquisition process. If the two-stage acquisition process is executed even when the battery voltage value is relatively high, the target motor (i.e., at least one of the work motor and the movement motor) will be unnecessarily temporarily stopped, which may prevent the work by the work robot from proceeding smoothly. According to the above configuration, the control unit is configured not to execute the two-stage acquisition process when the battery voltage value is relatively high. This makes it possible to prevent the target motor from being unnecessarily interrupted, allowing the work by the work robot to proceed smoothly. 【0013】 In one or more embodiments, the control unit may store a predetermined return threshold value. The control unit may be further configured to execute a threshold value correction process for correcting the return threshold value based on the first-stage voltage value and the second-stage voltage value. The return determination process may include a process for acquiring a detection value of the voltage detection unit as a second determination voltage value, and determining whether or not to return the work robot to the charging station depending on whether or not the second determination voltage value is equal to or less than the corrected return threshold value. 【0014】 According to the above configuration, the control unit determines whether or not to return the work robot to the charging station based on not only the first-stage voltage value and the second-stage voltage value but also the predetermined return threshold value, thereby making it possible to more appropriately determine the timing for returning the work robot to the charging station. 【0015】 In one or more embodiments, the control unit may be configured to acquire the detection value of the voltage detection unit as a third determination voltage value, execute the two-stage acquisition process when the third determination voltage value is equal to or less than the feedback threshold value, and not execute the two-stage acquisition process when the third determination voltage value exceeds the feedback threshold value. 【0016】 When the battery voltage value is relatively high, it is clear that there is no need to return the work robot even without executing the two-stage acquisition process. If the two-stage acquisition process is executed even when the battery voltage value is relatively high, the target motor (i.e., at least one of the work motor and the movement motor) will be unnecessarily temporarily stopped, which may prevent the work by the work robot from proceeding smoothly. According to the above configuration, the control unit is configured not to execute the two-stage acquisition process when the battery voltage value is relatively high. This makes it possible to prevent the target motor from being unnecessarily interrupted, allowing the work by the work robot to proceed smoothly. 【0017】 In one or more embodiments, in the threshold correction process, the control unit may correct the feedback threshold based on a recovery voltage value obtained by subtracting the first step voltage value from the second step voltage value. 【0018】 According to the above configuration, the feedback threshold value can be corrected by a simple means. 【0019】 In one or more embodiments, in the threshold correction process, the control unit may correct the feedback threshold by subtracting the recovery voltage value from the feedback threshold. 【0020】 The target motor may be configured to operate while the work robot is performing work and to stop while the work robot is returning to the charging station. In this case, when the work robot finishes work and starts to return, it is expected that the battery voltage value will recover by the recovery voltage value. For this reason, when determining whether to return the work robot, it is preferable to take into consideration that the battery voltage value will subsequently recover by the recovery voltage value. With the above configuration, when determining whether to return the work robot, it is possible to take into consideration that the battery voltage value will subsequently recover by the recovery voltage value. Therefore, it is possible to appropriately identify the timing to return the work robot to the charging station. 【0021】 In one or more embodiments, in the threshold correction process, when the recovery voltage value is equal to or greater than a predetermined upper limit value, the control unit may subtract the upper limit value from the feedback threshold value instead of subtracting the recovery voltage value from the feedback threshold value. 【0022】 When the recovery voltage value calculated in the threshold correction process is large, the amount of recovery of the battery voltage value at the timing when the work robot finishes the work and starts to return may be lower than the calculated recovery voltage value. Therefore, if the recovery voltage value is subtracted from the return threshold to perform correction even when the recovery voltage value calculated in the threshold correction process is large, the battery voltage value at the timing when the work robot starts to return will be smaller than expected. As a result, there is a risk that the battery will run out of power while the work robot is returning. According to the above configuration, when the recovery voltage value calculated in the threshold correction process exceeds the upper limit value, the corrected return threshold value is not the value obtained by subtracting the recovery voltage value from the return threshold, but the value obtained by subtracting the upper limit value from the return threshold. This makes it possible to prevent the battery voltage value at the timing when the work robot starts to return from being smaller than expected. This makes it possible to prevent the battery from running out of power while the work robot is returning. 【0023】 In one or more embodiments, in the threshold correction process, when the recovery voltage value is equal to or lower than a predetermined lower limit value, the control unit may set the feedback threshold value before correction to the feedback threshold value after correction. 【0024】 When the two-stage acquisition process and the threshold correction process are performed in a state where the battery voltage value has dropped to near the return threshold, the calculated recovery voltage value may be small. In this case, even if the target motor (i.e., at least one of the work motor and the movement motor) that was stopped in the two-stage acquisition process is operated again to resume the work of the work robot, the timing for the work robot to start returning arrives soon thereafter. Therefore, the operation of the work robot from when the work is resumed until the return starts is not enough to change the progress of the work and is considered to be an unnecessary operation. If the time for which the work robot performs an unnecessary operation is long, the work efficiency of the work robot decreases. According to the above configuration, when the recovery voltage value calculated in the threshold correction process is small, the corrected return threshold becomes the same value as the return threshold before correction. In other words, the corrected return threshold becomes a value larger than the value obtained by subtracting the recovery voltage value from the return threshold. As a result, the timing for the work robot to start returning is advanced, and the time for which the work robot performs an unnecessary operation can be shortened. This improves the work efficiency of the work robot. 【0025】 In one or more embodiments, one of the work motor and the movement motor may be the target motor. The other of the work motor and the movement motor may be a non-target motor that is not the target motor. The control unit may execute the two-stage acquisition process in a state where the non-target motor is stopped. 【0026】 The two-stage acquisition process is a process for observing a change in the voltage value of the battery caused by a change in the operating status of the target motor. However, the voltage value of the battery may also change depending on the operating status of the non-target motor. Therefore, if the operating status of the non-target motor changes while the two-stage acquisition process is being executed, there is a possibility that the change in the voltage value of the battery caused by the change in the operating status of the target motor cannot be correctly observed. According to the above configuration, since the operating status of the non-target motor does not change while the two-stage acquisition process is being executed, the change in the voltage value of the battery caused by the change in the operating status of the target motor can be correctly observed. 【0027】 In one or more embodiments, the control unit may execute the feedback determination process in a situation where the non-target motor is stopped. 【0028】 If the operating status of the non-target motor is not consistent between the two-stage acquisition process and the return determination process, it may not be possible to appropriately identify the timing to return the work robot to the charging station. With the above configuration, the operating status of the non-target motor is consistent between the two-stage acquisition process and the return determination process, so it is possible to appropriately identify the timing to return the work robot to the charging station. 【0029】 In one or more embodiments, the control unit may stop the non-target motor when the non-target motor continues to operate for a predetermined period of time. 【0030】 It is preferable that the two-stage acquisition process (or the return determination process) is repeatedly executed at appropriate time intervals until the timing for returning the work robot is identified. However, in a configuration in which the two-stage acquisition process (or the return determination process) is executed in a situation in which the non-target motor is stopped, the two-stage acquisition process (or the return determination process) cannot be executed while the non-target motor is operating. According to the above configuration, when the non-target motor continues to operate for a predetermined time, the non-target motor is forcibly stopped. This allows the two-stage acquisition process (or the return determination process) to be repeatedly executed at appropriate time intervals. 【0031】 In one or more embodiments, the work motor may be the target motor, and the locomotion motor may be the non-target motor. 【0032】 The work motor is expected to operate while the work robot is working and to stop while the work robot is returning to the charging station. Therefore, in determining the timing to return the work robot, it is highly necessary to acquire the battery voltage value for each operating condition of the work motor. On the other hand, the travel motor is expected to basically operate both while the work robot is working and while the work robot is returning to the charging station. Therefore, in determining the timing to return the work robot, it is less necessary to acquire the battery voltage value for each operating condition of the travel motor. Nevertheless, if a configuration is adopted in which the battery voltage value is acquired for each operating condition of the travel motor, the processing load of the control unit will increase unnecessarily. According to the above configuration, while the battery voltage value is acquired for each operating condition of the work motor, the battery voltage value is not acquired for each operating condition of the travel motor. Therefore, it is possible to appropriately identify the timing to return the work robot to the charging station while reducing the processing load of the control unit. 【0033】 In one or more embodiments, the working mechanism may include a cutting blade for cutting grass. The working robot may function as an autonomously mobile robotic lawnmower. 【0034】 According to the above configuration, the robotic lawnmower can be returned to the charging station at an appropriate time. 【0035】 Example 1 As shown in FIG. 1, the working robot of this embodiment is, for example, a robotic lawnmower 2 used within a site 100 where a lawn is laid. The site 100 is provided with, for example, a house 102, a pond 104, a road 106, and a fence 108. Also installed within the site 100 are a charging station 110 connected to an external power source (for example, a commercial power source) and a wire 112 that defines a working area WA of the robotic lawnmower 2. The working area WA here is the area surrounded by the wire 112. The working area WA of the robotic lawnmower 2 is divided into a main area MA that includes the charging station 110, and a sub-area SA that does not include the charging station 110. The robotic lawnmower 2 can detect the position of the wire 112 and move autonomously without straying from the working area WA (main area MA in the example of FIG. 1) in which the robotic lawnmower 2 is located. This allows the robotic lawnmower 2 to perform lawn mowing work while moving over the lawn, avoiding the house 102, the pond 104, the road 106, and the fence 108. 【0036】 2, 3, and 4, the robotic lawnmower 2 includes a robot body 4, a power supply unit 6, a control unit 8, an operation unit 10, a moving unit 12, a working unit 14, and a detection unit 16. The power supply unit 6, the control unit 8, the operation unit 10, the moving unit 12, the working unit 14, and the detection unit 16 are each supported by the robot body 4. 【0037】 The power supply unit 6 shown in FIG. 4 is capable of supplying power to each component of the robotic lawnmower 2 via a power supply circuit 26 of the control unit 8. The power supply unit 6 includes a rechargeable battery 18, such as a lithium-ion battery, and a charging interface 20 that electrically connects to the battery 18. The nominal capacity of the battery 18 is, for example, 5.0 Ah. The nominal voltage of the battery 18 is, for example, 18 V. The robotic lawnmower 2 can be docked to a charging station 110 (see FIG. 1) via the charging interface 20. When the robotic lawnmower 2 is docked to the charging station 110, the battery 18 can be charged by power supplied from the charging station 110. The charging method for the battery 18 may be wired charging. Specifically, the battery 18 may be charged in a state in which a terminal provided on the charging station 110 and a terminal provided on the charging interface 20 are connected to each other. Alternatively, the charging method for the battery 18 may be wireless charging. Specifically, the battery 18 may be charged by causing a power transmitting coil provided in the charging station 110 to generate an induced electromotive force in a power receiving coil provided in the charging interface 20. 【0038】 The control unit 8 includes a processor 22, a memory 24, and a power supply circuit 26. The memory 24 includes a ROM, a RAM, etc. The memory 24 stores a program for autonomously controlling the robotic lawnmower 2. The processor 22 is configured to autonomously control the robotic lawnmower 2 in accordance with the program stored in the memory 24. The memory 24 also stores settings related to the robotic lawnmower 2 (e.g., the mowing height of the lawn). The settings related to the robotic lawnmower 2 include settings related to the operation mode of the robotic lawnmower 2. The operation mode of the robotic lawnmower 2 is set to one of a number of modes including a main area compatible mode corresponding to the main area MA (see FIG. 1) and a sub-area compatible mode corresponding to the sub-area SA (see FIG. 1). 【0039】 The operation unit 10 is provided, for example, on the outer surface of the robot body 4 (see FIG. 2), and includes switches and the like that can be operated by the user. The user can perform various operations related to the robotic lawnmower 2 via the operation unit 10. The various operations referred to here include, for example, operations to switch the main power supply of the robotic lawnmower 2 on / off, operations to input instructions for the robotic lawnmower 2, and operations to change settings related to the robotic lawnmower 2. 【0040】 The moving unit 12 includes a pair of left and right casters 28L, 28R, a pair of left and right drive wheels 30L, 30R, and a pair of left and right moving motors 32L, 32R. The moving motors 32L, 32R are, for example, brushless DC motors. The drive wheels 30L, 30R are connected to the output shafts of the moving motors 32L, 32R, respectively. As shown in FIG. 2 and FIG. 3, the robot lawnmower 2 is placed on the ground G with the casters 28L, 28R and the drive wheels 30L, 30R in contact with the ground G. The moving unit 12 can move the robot body 4 forward, backward, and turn by operating the moving motors 32L, 32R (see FIG. 4) to rotate the drive wheels 30L, 30R. 【0041】 As shown in FIG. 2, the working unit 14 includes a cutting blade 34 and a work motor 36. The cutting blade 34 is a rotary blade formed in a substantially circular disk shape. The work motor 36 is, for example, a brushless DC motor. The work motor 36 is supported by the robot body 4 with its output shaft tilted from front to rear as it moves from top to bottom. The cutting blade 34 is connected to the output shaft of the work motor 36. The working unit 14 can cut the grass by operating the work motor 36 to rotate the cutting blade 34. 【0042】 As shown in FIG. 4, the detection unit 16 includes a wire detection sensor 38, a motor current detection circuit 40, and a battery voltage detection circuit . 【0043】 The wire detection sensor 38 is a sensor for detecting the wire 112 (see FIG. 1). The wire detection sensor 38 is, for example, a magnetic sensor. In this embodiment, a predetermined electric signal is applied to the wire 112 from the charging station 110 (see FIG. 1). As a result, a magnetic signal corresponding to the predetermined electric signal is generated around the wire 112. The wire detection sensor 38 is configured to detect this magnetic signal and output it to the processor 22. Based on the signal pattern and signal strength of the magnetic signal detected by the wire detection sensor 38, the processor 22 can determine whether the robotic lawnmower 2 is approaching the wire 112, whether the robotic lawnmower 2 is located above the wire 112, etc. 【0044】 The motor current detection circuit 40 is configured to detect the value of the current supplied to each of the movement motors 32L, 32R and the work motor 36, and output the detected value to the processor 22. 【0045】 The battery voltage detection circuit 42 is configured to detect the voltage value of the battery 18 and output it to the processor 22. This allows the processor 22 to grasp the voltage value of the battery 18. 【0046】 The following describes the operations or processes executed by the control unit 8 (specifically, the processor 22). 【0047】 (Lawn mowing) Mowing operation is the main operation of the robotic lawnmower 2 (see FIG. 1). Mowing operation is started, for example, when the power of the robotic lawnmower 2 is turned on and an instruction to start mowing operation is given via the operation unit 10 (see FIG. 4). When mowing operation is started, the control unit 8 checks that no abnormality has occurred in the robotic lawnmower 2, and then starts mowing work with the robotic lawnmower 2. That is, the control unit 8 drives the driving wheels 30L, 30R (see FIG. 2) with the moving motors 32L, 32R (see FIG. 4) while driving the cutting blade 34 (see FIG. 2) with the working motor 36 (see FIG. 2), thereby mowing the grass. During the mowing operation, the control unit 8 may interrupt or end the mowing work with the robotic lawnmower 2 depending on the situation and perform another operation. The control unit 8 ends the mowing operation when a predetermined operation end condition is met. The operation end condition here includes, for example, the time that has elapsed since the start of the lawnmowing operation reaching a time that is preset by the user. 【0048】 (Battery voltage management process; Fig. 5, Fig. 6) The battery voltage management process is executed repeatedly while the above-mentioned lawnmower operation is being performed when the operating mode of the robotic lawnmower 2 (see FIG. 1) is set to the main area compatible mode. The battery voltage management process is executed to return the robotic lawnmower 2 to the charging station 110 (see FIG. 1) and charge the battery 18 (see FIG. 4) when the voltage value of the battery 18 is low. The memory 24 (see FIG. 4) prestores the voltage value (return threshold Vre) of the battery 18 that must be ensured in order for the robotic lawnmower 2 to return to the charging station 110. In this embodiment, the return threshold Vre is set to 17.5V. The battery voltage management process mainly includes a process of correcting the return threshold Vre, and a process of returning the robotic lawnmower 2 to the charging station 110 based on the corrected return threshold Vre'. 【0049】 As shown in Fig. 5, in S2, the control unit 8 determines whether or not the correction flag is on. The correction flag is a status register included in the memory 24. The correction flag is off when the corrected feedback threshold value Vre' has not been acquired. When the correction flag is off (NO), the process proceeds to S4. 【0050】 In S4, the control unit 8 determines whether the movement motors 32L, 32R (see FIG. 4) are stopped. While the robotic lawnmower 2 is performing lawn mowing work, the movement motors 32L, 32R are basically operating, but the movement motors 32L, 32R may stop, for example, when the robotic lawnmower 2 changes direction. If the movement motors 32L, 32R are not stopped (NO), the process proceeds to S6. 【0051】 In S6, the control unit 8 determines whether the operation duration of the movement motors 32L, 32R is equal to or longer than a first upper limit time (e.g., 2 minutes). The operation duration of the movement motors 32L, 32R here means the time that has elapsed since the movement motors 32L, 32R started to operate most recently. If the operation duration of the movement motors 32L, 32R is less than the first upper limit time (NO), the process returns to S2. If the operation duration of the movement motors 32L, 32R is equal to or longer than the first upper limit time (YES), the process proceeds to S8. 【0052】 In S8, the control unit 8 stops the movement motors 32L and 32R. 【0053】 If it is determined in S4 that the moving motors 32L, 32R are stopped (YES), or after S8, the process proceeds to S10. In S10, the control unit 8 acquires the detection value of the battery voltage detection circuit 42 (see FIG. 4) as a determination voltage value, and determines whether the acquired determination voltage value is equal to or lower than the feedback threshold value Vre. Note that while the robotic lawnmower 2 is performing a lawnmowing operation, the working motor 36 (see FIG. 4) basically does not stop. For this reason, in S10, the voltage value of the battery 18 in a situation where the working motor 36 is operating and the moving motors 32L, 32R are stopped is acquired as the determination voltage value. If the determination voltage value exceeds the feedback threshold value Vre (NO), the process returns to S2. Note that if the determination result in S10 is NO after the moving motors 32L, 32R are stopped in S8, the control unit 8 operates the moving motors 32L, 32R again. If the determination voltage value is equal to or lower than the feedback threshold value Vre (YES), the process proceeds to S12. 【0054】 In S12, the control unit 8 acquires the detection value of the battery voltage detection circuit 42 as the first-stage voltage value V1. In S12, the voltage value of the battery 18 in a situation where the work motor 36 is operating and the travel motors 32L, 32R are stopped is acquired as the first-stage voltage value V1. After S12, the process proceeds to S14. 【0055】 In S14, the control unit 8 stops the work motor 36 in addition to the movement motors 32L, 32R. That is, the control unit 8 suspends the lawnmowing operation by the robotic lawnmower 2. The control unit 8 then waits for a predetermined time (e.g., 2 seconds) with the work motor 36 and the movement motors 32L, 32R stopped. This allows the voltage value of the battery 18 to recover by an amount equivalent to the voltage drop caused by the internal resistance of the work motor 36, compared to the voltage value immediately before the lawnmowing operation was suspended. After S14, the process proceeds to S16. 【0056】 In S16, the control unit 8 acquires the detection value of the battery voltage detection circuit 42 as the second-stage voltage value V2 while the lawnmower 2 is suspended from mowing. In S16, the voltage value of the battery 18 with the work motor 36 and the travel motors 32L, 32R stopped is acquired as the second-stage voltage value V2. After acquiring the second-stage voltage value V2, the control unit 8 operates the travel motors 32L, 32R and the work motor 36 again to resume the lawnmower 2 from mowing. After S16, the process proceeds to S18. 【0057】 In S18, the control unit 8 calculates the recovery voltage value Vdiff by subtracting the first-stage voltage value V1 from the second-stage voltage value V2. Therefore, the recovery voltage value Vdiff=V2-V1. After S18, the process proceeds to S20. 【0058】 In S20, the control unit 8 determines whether the recovery voltage value Vdiff calculated in S18 is equal to or lower than a predetermined lower limit value (for example, 0.1 V). If the recovery voltage value Vdiff is equal to or lower than the lower limit value (YES), the process proceeds to S22. 【0059】 In S22, the control unit 8 corrects the recovery voltage value Vdiff to 0V. 【0060】 If it is determined in S20 that the recovery voltage value Vdiff is not equal to or less than the lower limit (if NO), the process proceeds to S24. In S24, the control unit 8 determines whether the recovery voltage value Vdiff calculated in S18 is equal to or greater than a predetermined upper limit (e.g., 0.5 V). If the recovery voltage value Vdiff is equal to or less than the upper limit (if YES), the process proceeds to S26. 【0061】 In S26, the control unit 8 corrects the recovery voltage value Vdiff to make it the same value as the upper limit value (for example, 0.5 V) used in the determination in S24. 【0062】 If it is determined in S24 that the recovery voltage value Vdiff is not equal to or less than the upper limit value (NO), the process proceeds to S28 after S22 or after S26. In S28, the control unit 8 corrects the feedback threshold Vre by subtracting the recovery voltage value Vdiff from the feedback threshold Vre. Therefore, the corrected feedback threshold Vre'=Vre-Vdiff. The control unit 8 also stores the corrected feedback threshold Vre' in the memory 24 and switches the correction flag on. After S28, the process returns to S2. 【0063】 If it is determined in S2 that the correction flag is on (YES), the process proceeds to S30 shown in Fig. 6. In S30, the control unit 8 determines whether the movement motors 32L, 32R are stopped. If the movement motors 32L, 32R are not stopped (NO), the process proceeds to S32. 【0064】 In S32, the control unit 8 determines whether the operation duration of the movement motors 32L, 32R is equal to or longer than a second upper limit time (e.g., 1 minute). If the operation duration of the movement motors 32L, 32R is less than the second upper limit time (NO), the process returns to S2 (see FIG. 5). If the operation duration of the movement motors 32L, 32R is equal to or longer than the second upper limit time (YES), the process proceeds to S34. 【0065】 In S34, the control unit 8 stops the movement motors 32L and 32R. 【0066】 If it is determined in S30 that the travel motors 32L, 32R are operating (YES), or after S34, the process proceeds to S36. In S36, the control unit 8 acquires the detection value of the battery voltage detection circuit 42 as a voltage value for determination, and determines whether the acquired voltage value for determination is equal to or less than the corrected feedback threshold Vre'. In S36, the voltage value of the battery 18 in a situation in which the work motor 36 is operating and the travel motors 32L, 32R are stopped is acquired as the voltage value for determination. If the voltage value for determination is greater than the corrected feedback threshold Vre' (NO), the process returns to S2 (see FIG. 5). If the result of S36 is NO after the travel motors 32L, 32R are stopped in S34, the control unit 8 operates the travel motors 32L, 32R again. If the voltage value for determination is equal to or less than the corrected feedback threshold Vre' (YES), the process proceeds to S38. 【0067】 In S38, the control unit 8 ends the lawnmowing operation by the robotic lawnmower 2, and causes the robotic lawnmower 2 to return to the charging station 110. Specifically, with the working motor 36 stopped, the control unit 8 operates the transport motors 32L, 32R so that the robotic lawnmower 2 follows the wire 112 to the charging station 110. After S38, the process proceeds to S40. 【0068】 In S40, the control unit 8 docks the robotic lawnmower 2 to the charging station 110 and starts charging the battery 18. In response to the robotic lawnmower 2 docking to the charging station 110, the control unit 8 also erases the corrected return threshold Vre' from the memory 24 and switches the correction flag to OFF. Note that the corrected return threshold Vre' stored in the memory 24 is erased from the memory 24 even if the robotic lawnmower 2 docks to the charging station 110 regardless of S40 of the battery voltage management process. Similarly, note that the correction flag is switched to OFF even if the robotic lawnmower 2 docks to the charging station 110 regardless of S40 of the battery voltage management process. After S40, the process proceeds to S42. 【0069】 In S42, the control unit 8 determines whether or not a predetermined normal return condition is satisfied. The normal return condition includes, for example, that the voltage value of the battery 18 detected by the battery voltage detection circuit 42 is equal to or higher than a predetermined value (for example, 20 V). If the normal return condition is not satisfied (NO), the process repeats S42. If the normal return condition is satisfied (YES), the process proceeds to S44. 【0070】 In S44, the control unit 8 stops charging the battery 18, undocks the robotic lawnmower 2 from the charging station 110, and restarts the travel motors 32L, 32R and the work motor 36. In other words, the control unit 8 resumes mowing work by the robotic lawnmower 2. After S44, the battery voltage management process shown in Figures 5 and 6 ends. 【0071】 (Battery voltage management processing advantages) The robotic lawnmower 2 operates the work motor 36 (see FIG. 4) while performing lawn mowing work, but stops the work motor 36 while returning to the charging station 110 (see FIG. 1). Therefore, when the robotic lawnmower 2 finishes lawn mowing work and starts to return, the voltage value of the battery 18 (see FIG. 4) recovers by the amount of voltage drop caused by the internal resistance of the work motor 36. If, as shown in FIG. 7, the robotic lawnmower 2 starts to return at the timing when the voltage value of the battery 18 while performing lawn mowing work reaches the return threshold value Vre, the voltage value of the battery 18 recovers immediately thereafter and greatly exceeds the return threshold value Vre. Therefore, even if the remaining charge of the battery 18 is enough for the robotic lawnmower 2 to continue lawn mowing work, the robotic lawnmower 2 returns to the charging station 110. This causes the robotic lawnmower 2 to return to the charging station 110 frequently, and the proportion of time the robotic lawnmower 2 is not mowing (for example, time returned to the charging station 110 or time charging the battery 18) becomes larger compared to the time the robotic lawnmower 2 is mowing. As a result, the work efficiency of the robotic lawnmower 2 may decrease. 【0072】 As shown in FIG. 8, the battery voltage management process specifies the voltage drop caused by the internal resistance of the work motor 36 as the recovery voltage value Vdiff. The recovery voltage value Vdiff is subtracted from the predetermined return threshold value Vre to obtain the return threshold value Vre'. The robotic lawnmower 2 starts returning at the timing when the voltage value of the battery 18 while the robotic lawnmower 2 is performing lawnmowing work becomes the return threshold value Vre'. This causes the voltage value of the battery 18 immediately after the robotic lawnmower 2 starts returning to a value close to the return threshold value Vre. Therefore, the robotic lawnmower 2 can be returned to the charging station 110 at the timing when the remaining charge of the battery 18 has decreased to the limit at which the robotic lawnmower 2 can continue lawnmowing work. This makes it possible to reduce the frequency at which the robotic lawnmower 2 returns to the charging station 110 as much as possible, thereby making it possible to reduce the ratio of the time during which the robotic lawnmower 2 is not performing lawnmowing work to the time during which the robotic lawnmower 2 is performing lawnmower work. As a result, the work efficiency of the robotic lawnmower 2 can be improved. 【0073】 (Motor burnout prevention process; Fig. 9) The motor burnout avoidance process is repeatedly executed while the above-described lawnmower operation is being performed, regardless of the operating mode of the robotic lawnmower 2 (see FIG. 1). Note that the motor burnout avoidance process is also executed at the stage of verifying that no abnormalities have occurred in the robotic lawnmower 2 before the robotic lawnmower 2 begins mowing work. 【0074】 In S52, the control unit 8 judges whether the work motor 36 (see FIG. 2) is overheated. Overheating here means that the temperature of the work motor 36 becomes excessively high (for example, a temperature of 150° C. or higher), that the temperature of the work motor 36 becomes high enough to cause burning (melting the coating of the windings and causing a short circuit), or that the temperature of the work motor 36 becomes high enough to affect the life of the work motor 36. For example, when the detection value (i.e., the current supplied to the work motor 36) of the motor current detection circuit 40 (see FIG. 4) continues to be equal to or higher than a first current value (for example, 5 A) for a first duration (for example, 55 minutes) or longer, the control unit 8 estimates that the temperature of the work motor 36 has become excessively high and judges that the work motor 36 has overheated. The control unit 8 also determines that the work motor 36 has overheated if the state in which the detection value of the motor current detection circuit 40 is equal to or greater than a second current value (e.g., 6 A) higher than the first current value continues for a second duration time (e.g., 22 minutes) or more that is shorter than the first duration time. The control unit 8 also determines that the work motor 36 has overheated if the state in which the detection value of the motor current detection circuit 40 is equal to or greater than a third current value (e.g., 7 A) higher than the second current value continues for a third duration time (e.g., 10 minutes) or more that is shorter than the second duration time. If the work motor 36 has overheated (YES), the process proceeds to S54. 【0075】 In S54, the control unit 8 determines whether or not the robotic lawnmower 2 is within the main area MA (see FIG. 1). If the operating mode of the robotic lawnmower 2 is set to the main area compatible mode, the control unit 8 determines that the robotic lawnmower 2 is within the main area MA (YES). If the operating mode of the robotic lawnmower 2 is set to a mode other than the main area compatible mode, the control unit 8 determines that the robotic lawnmower 2 is not within the main area MA (NO). If the robotic lawnmower 2 is within the main area MA (YES), processing proceeds to S56. 【0076】 In S56, the control unit 8 causes the robotic lawnmower 2 to return to the charging station 110 (see FIG. 1). Specifically, with the working motor 36 stopped, the control unit 8 operates the transport motors 32L, 32R (see FIG. 4) so ​​that the robotic lawnmower 2 follows the wire 112 to the charging station 110. The control unit 8 also operates a light source device and buzzer (not shown) provided on the robot body 4 to notify the user of the occurrence of an abnormality by sound or light. After S56, the process proceeds to S58. 【0077】 In S58, the control unit 8 docks the robotic lawnmower 2 to the charging station 110 and begins charging the battery 18 (see FIG. 4). Note that the control unit 8 continues to notify the user that an abnormality has occurred even after it begins charging the battery 18. After S58, the process proceeds to S60. 【0078】 In S60, the control unit 8 judges whether a predetermined first abnormality return condition is satisfied. The first abnormality return condition in this embodiment includes a condition that the temperature of the work motor 36 is expected to become normal (for example, a temperature of 40° C. or less). For example, the first abnormality return condition includes the voltage value of the battery 18 detected by the battery voltage detection circuit 42 (see FIG. 4) becoming a predetermined value (for example, 20 V) or higher. This is because if the charging of the battery 18 is continued for a certain period of time, it can be estimated that the temperature of the work motor 36 has dropped to a normal temperature during that period. Alternatively, the first abnormality return condition includes the time elapsed since it was determined in the most recent execution of S52 that the work motor 36 has overheated reaching a predetermined time (for example, 20 minutes). If the first abnormality return condition is not satisfied (in the case of NO), the process repeats S60. If the first abnormality return condition is satisfied (in the case of YES), the process proceeds to S62. 【0079】 In S62, the control unit 8 stops charging the battery 18, undocks the robotic lawnmower 2 from the charging station 110, and restarts the travel motors 32L, 32R and the work motor 36. In other words, the control unit 8 resumes mowing work with the robotic lawnmower 2. The control unit 8 also stops the light source device and buzzer (not shown) that are in operation, and ends the abnormality notification. After S56, the process proceeds to S58. 【0080】 If it is determined in S54 that the robotic lawnmower 2 is not within the main area MA (NO), processing proceeds to S64. In S64, the control unit 8 stops the working motor 36 and the moving motors 32L, 32R, and causes the robotic lawnmower 2 to wait in place. The control unit 8 also operates a light source device and buzzer (not shown) provided on the robot body 4 to notify the user by sound or light that an abnormality has occurred. After S64, processing proceeds to S66. 【0081】 In S66, the control unit 8 judges whether a predetermined second abnormality return condition is satisfied. The second abnormality return condition in this embodiment includes a condition that the temperature of the work motor 36 (see FIG. 2) is expected to become normal (for example, a temperature of 40° C. or less). For example, the second abnormality return condition includes a condition that the elapsed time since it was determined in the most recent execution of S52 that the work motor 36 has overheated reaches a predetermined time (for example, 20 minutes). If the second abnormality return condition is not satisfied (NO), the process repeats S66. Therefore, while the second abnormality return condition is not satisfied, the robotic lawnmower 2 continues to wait at the same place. If the second abnormality return condition is satisfied (YES), the process proceeds to S68. 【0082】 In S68, the control unit 8 ends the standby state, and resumes operation of the movement motors 32L, 32R and the work motor 36. That is, the control unit 8 resumes lawn mowing work with the robotic lawnmower 2. The control unit 8 also stops the light source device and buzzer (not shown) that are in operation, and ends the abnormality notification. 【0083】 If it is determined in S52 that the work motor 36 is not overheated (NO), the motor burnout avoidance process shown in FIG. 9 ends after S62 or after S68. 【0084】 Example 2 10, the working robot of this embodiment is a robotic lawnmower 202 that has substantially the same components as the robotic lawnmower 2 of embodiment 1. Components that are common between the robotic lawnmower 2 and the robotic lawnmower 202 are given the same reference numerals, and descriptions thereof will be omitted. 【0085】 The robotic lawnmower 202 has a detection unit 204 instead of the detection unit 16 (see FIG. 4) of the first embodiment. The detection unit 204 differs from the detection unit 16 in that it has a motor temperature sensor 206. The motor temperature sensor 206 is configured to detect the temperature of the work motor 36 and output it to the processor 22 of the control unit 8. The temperature of the work motor 36 here includes, for example, the temperature of the stator of the work motor 36, the temperature of a hall sensor provided on the work motor 36, and the temperature of a motor driver board that controls the rotation of the work motor 36. 【0086】 In this embodiment, the control unit 8 also determines that the work motor 36 has overheated when the temperature of the work motor 36 detected by the motor temperature sensor 206 is excessively high (e.g., 150°C or higher) in S52 of the motor burnout avoidance process shown in Fig. 9. The first abnormality recovery condition used in S60 of the motor burnout avoidance process further includes that the temperature of the work motor 36 detected by the motor temperature sensor 206 is a normal temperature (e.g., 40°C or lower). The second abnormality recovery condition used in S66 of the motor burnout avoidance process further includes that the temperature of the work motor 36 detected by the motor temperature sensor 206 is a normal temperature (e.g., 40°C or lower). 【0087】 (Modification) The working robot may be a robot other than the robotic lawnmower 2, 202. For example, the working robot may be a robot vacuum cleaner equipped with a brush and / or a suction mechanism for collecting debris such as dust. In this case, the work motor 36 may be used as a motor for driving the brush and / or the suction mechanism. The working robot may also be a rebar binding robot equipped with a rebar binding mechanism for binding the intersections of multiple rebars. In this case, the work motor 36 may be used as a motor for driving the rebar binding mechanism. 【0088】 At least one of the working motor 36 and the moving motors 32L, 32R may be a motor other than a brushless DC motor (for example, a DC motor with brushes). 【0089】 The moving unit 12 may be provided with a pair of left and right crawlers instead of the casters 28L, 28R and the drive wheels 30L, 30R. The moving motors 32L, 32R may be used as motors for driving the pair of left and right crawlers. 【0090】 The battery 18 may be a rechargeable battery 18 other than a lithium-ion battery (e.g., a nickel-metal hydride battery, a nickel-cadmium battery). The nominal capacity and nominal voltage of the battery 18 may be changed as appropriate. The nominal capacity of the battery 18 may be, for example, 3.0 Ah. The nominal voltage of the battery 18 may be, for example, 36 V. 【0091】 The setting of the feedback threshold Vre may be changed as appropriate. The setting of the feedback threshold Vre may be changeable by the user via the operation unit 10, or may not be changeable by the user via the operation unit 10. 【0092】 5 and 6, the control unit 8 may skip S10 and execute S12 after S8. That is, the control unit 8 may be configured to execute the processes from S12 onward after S8, regardless of the remaining charge of the battery 18. 【0093】 The control unit 8 may use a threshold value Vth (for example, Vth=17.6V) different from the feedback threshold value Vre in the judgment process of S10 of the battery voltage management process. That is, in S10, the control unit 8 may obtain the detection value of the battery voltage detection circuit 42 as the judgment voltage value and judge whether the obtained judgment voltage value is equal to or lower than the threshold value Vth. In this example, as shown in FIG. 11, the voltage drop caused by the internal resistance of the work motor 36 is specified as the recovery voltage value Vdiff. As a result, the feedback threshold value Vre' is obtained in a manner similar to the embodiment, so that the voltage value of the battery 18 immediately after the robotic lawnmower 2, 202 starts to return is restored to a value close to the feedback threshold value Vre. Therefore, the robotic lawnmower 2, 202 can be returned to the charging station 110 with an appropriate remaining charge of the battery 18. 【0094】 In the battery voltage management process shown in FIG. 5 and FIG. 6, after determining NO in S20, the control unit 8 may skip S24 and execute S28. As a result, the recovery voltage value Vdiff may be allowed to exceed the upper limit value. Alternatively, the control unit 8 may skip S20 and execute S24 after S18. As a result, the recovery voltage value Vdiff may be allowed to become a value equal to or less than the lower limit value (a value greater than 0). Alternatively, after S18, the control unit 8 may skip S20, S22, S24, and S26 and execute S28. As a result, both the recovery voltage value Vdiff exceeding the upper limit value and the recovery voltage value Vdiff becoming a value equal to or less than the lower limit value (a value greater than 0) may be allowed. 【0095】 In S28 of the battery voltage management process, the control unit 8 may correct the feedback threshold Vre by multiplying the recovery voltage value Vdiff by a predetermined coefficient k (for example, k=0.8) and subtracting the result from the feedback threshold Vre. Therefore, Vre′=Vre−k×Vdiff may be satisfied. 【0096】 In the battery voltage management process, the control unit 8 may determine whether or not to return the robot lawnmower 2 to the charging station 110 without calculating the recovery voltage value Vdiff and correcting the return threshold value Vre. For example, the control unit 8 may obtain the first-stage voltage value V1 in S12, obtain the second-stage voltage value V2 in S16, and then determine whether or not the detection value (determination voltage value) of the battery voltage detection circuit 42 is equal to or less than 2×V1−V2. If the determination voltage value is equal to or less than 2×V1−V2 (if YES), the control unit 8 may execute the process from S38 onwards. If the determination voltage value is greater than 2×V1−V2 (if NO), the control unit 8 may restart the battery voltage management process from the start. In this example, the correction flag may always be off. 【0097】 After determining NO in S2 in the battery voltage management process, the control unit 8 may skip S4, S6, and S8 and execute S10. As a result, the processes after S10 may be executed in a situation where the movement motors 32L, 32R are not stopped (i.e., in a situation where the movement motors 32L, 32R are operating). However, it is preferable that the operating status (operation / stop) of the movement motors 32L, 32R is not switched in the process of executing S10, S12, S14, and S16. 【0098】 After determining YES in S2 in the battery voltage management process, the control unit 8 may skip S30, S32, and S34 and execute S36. As a result, the processes after S36 may be executed in a situation where the movement motors 32L, 32R are not stopped (i.e., in a situation where the movement motors 32L, 32R are operating). 【0099】 In the first and second embodiments, the control unit 8 is configured to stop the working motor 36 in operation in S12, S14, and S16 of the battery voltage management process, and observe the change in the voltage value of the battery 18. That is, the working motor 36 is the target motor as defined in this specification, and the moving motors 32L and 32R are the non-target motors as defined in this specification. In another embodiment, the control unit 8 may be configured to stop the working motor 36 and the moving motors 32L and 32R in operation in S12, S14, and S16, and observe the change in the voltage value of the battery 18. That is, both the working motor 36 and the moving motors 32L and 32R may be the target motors. In yet another embodiment, the control unit 8 may be configured to stop the moving motors 32L and 32R in operation in S12, S14, and S16, and observe the change in the voltage value of the battery 18. In other words, the movement motors 32L, 32R may be target motors, and the work motor 36 may be a non-target motor. 【0100】 After starting charging the battery 18 in S58 in the motor burnout prevention process shown in Fig. 9, the control unit 8 may end the motor burnout prevention process and end the ongoing lawnmowing operation instead of executing the processes from S60 onwards. Thereafter, the control unit 8 may end charging the battery 18 when the battery 18 is fully charged, for example, and have the robotic lawnmower 2, 202 wait at the charging station 110. In other words, the control unit 8 may be configured not to automatically resume lawnmowing operation after an abnormality occurs in the robotic lawnmower 2, 202 (overheating of the work motor 36). 【0101】 The detection unit 16, 204 may be capable of detecting various abnormalities related to the working unit 14, not limited to overheating of the work motor 36. An abnormality related to the working unit 14 here includes, for example, an excessive load being placed on the work motor 36, or the cutting blade 34 being worn to the point where replacement is required. When an abnormality related to the working unit 14 is detected by the detection unit 16, 204, the control unit 8 may execute the processing from S54 onwards of the motor burnout avoidance processing. In this way, when an abnormality related to the working unit 14 occurs, the control unit 8 can notify the user of the abnormality, return the robotic lawnmower 2, 202 to the charging station 110, or have the robotic lawnmower 2, 202 wait at that location. 【0102】 The first abnormality recovery condition (or the second abnormality recovery condition) may include a situation in which the detection value of the motor current detection circuit 40 (i.e., the current supplied to the work motor 36) remains below a predetermined current value for a predetermined period of time or more. 【0103】 The operation mode of the robotic lawnmower 2, 202 may be changed automatically, regardless of user operation. For example, the control unit 8 may use a GPS to identify the work area WA in which the robotic lawnmower 2, 202 is mowing, and change the operation mode of the robotic lawnmower 2, 202 to a mode corresponding to the identified work area WA. Alternatively, the control unit 8 may store map information of the work area WA in advance, and identify the work area WA in which the robotic lawnmower 2, 202 is mowing based on the map information. 【0104】 The detection units 16, 204 may be capable of detecting various abnormalities other than those described above. For example, the detection units 16, 204 may be capable of detecting that the robot body 4 has rolled over or that the robot body 4 has been lifted by someone. When such an abnormality is detected by the detection units 16, 204, the control unit 8 may notify the user that an abnormality has occurred by using a buzzer (not shown) provided in the robot body 4. 【0105】 (Features of the embodiment) In one or more embodiments, the robotic lawnmower 2, 202 (an example of a working robot) performs work while moving autonomously. The robotic lawnmower 2, 202 includes a cutting blade 34 (an example of a working mechanism) that performs work, drive wheels 30L, 30R (an example of a moving mechanism) that move the robotic lawnmower 2, 202, a working motor 36 that drives the cutting blade 34, moving motors 32L, 32R that drive the drive wheels 30L, 30R, a rechargeable battery 18 that supplies power to the working motor 36 and the moving motors 32L, 32R, a battery voltage detection circuit 42 (an example of a voltage detection unit) that detects the voltage value of the battery 18, and a control unit 8. The control unit 8 is configured to be able to execute a two-stage acquisition process (see S12, S14, S16 in FIG. 5) in which, for the work motor 36 (an example of a target motor), the detection value of the battery voltage detection circuit 42 when the work motor 36 is operating is acquired as a first-stage voltage value V1, and then the work motor 36 is stopped and the detection value of the battery voltage detection circuit 42 when the work motor 36 is stopped is acquired as a second-stage voltage value V2, and a return determination process (see S36 in FIG. 6) in which, based on the first-stage voltage value V1 and the second-stage voltage value V2, the return determination process determines whether or not to return the robotic lawnmower 2, 202 to the charging station 110. 【0106】 When the working motor 36 is operating, the voltage value of the battery 18 is lower than when the working motor 36 is stopped due to the internal resistance of the working motor 36. For this reason, in order to appropriately determine the timing to return the robotic lawnmower 2, 202, it is preferable to obtain the detection value of the battery voltage detection circuit 42 for each operating state of the working motor 36. With the above configuration, the control unit 8 of the robotic lawnmower 2, 202 can obtain the detection value of the battery voltage detection circuit 42 for each operating state of the working motor 36, so that the timing to return the robotic lawnmower 2, 202 can be appropriately determined. In other words, the timing to return the robotic lawnmower 2, 202 can be prevented from being too late or too early. For this reason, it is possible to prevent the battery 18 from running out of power while the robotic lawnmower 2, 202 is returning, and to prevent the work by the robotic lawnmower 2, 202 from being frequently interrupted. This allows the work by the robotic lawnmower 2, 202 to proceed smoothly. 【0107】 In one or more embodiments, the control unit 8 is configured to acquire the detection value of the battery voltage detection circuit 42 as a (first) judgment voltage value, and execute a two-stage acquisition process when the (first) judgment voltage value is equal to or less than the feedback threshold Vre (or threshold Vth) (an example of a predetermined value), and not execute the two-stage acquisition process when the (first) judgment voltage value exceeds the feedback threshold Vre (or threshold Vth). 【0108】 When the detection value of the battery voltage detection circuit 42 is relatively high, it is clear that there is no need to return the robotic lawnmower 2, 202 without even performing the two-stage acquisition process. If the two-stage acquisition process is performed even when the voltage of the battery 18 is relatively high, the work motor 36 will be unnecessarily temporarily stopped, which may prevent the work of the robotic lawnmower 2, 202 from proceeding smoothly. With the above configuration, the control unit 8 is configured not to perform the two-stage acquisition process when the voltage of the battery 18 is relatively high. This prevents the work motor 36 from being unnecessarily interrupted, allowing the work of the robotic lawnmower 2, 202 to proceed smoothly. 【0109】 In one or more embodiments, the controller 8 stores a predetermined feedback threshold Vre. The controller 8 is further configured to execute a threshold correction process (see S18 to S28 in FIG. 5) that corrects the feedback threshold Vre based on the first-stage voltage value V1 and the second-stage voltage value V2. The feedback determination process includes a process (see S36 in FIG. 6) that acquires the detection value of the battery voltage detection circuit 42 as a (second) determination voltage value, and determines whether or not to return the robotic lawnmower 2, 202 to the charging station 110 depending on whether or not the (second) determination voltage value is equal to or less than the corrected feedback threshold Vre'. 【0110】 With the above configuration, the control unit 8 determines whether or not to return the robotic lawnmower 2, 202 to the charging station 110 based not only on the first-stage voltage value V1 and the second-stage voltage value V2, but also on the predetermined returning threshold value Vre. This makes it possible to more appropriately determine the timing for returning the robotic lawnmower 2, 202 to the charging station 110. 【0111】 In one or more embodiments, the control unit 8 is configured to acquire the detection value of the battery voltage detection circuit 42 as a (third) determination voltage value, execute a two-stage acquisition process when the (third) determination voltage value is equal to or less than the feedback threshold Vre, and not execute the two-stage acquisition process when the (third) determination voltage value exceeds the feedback threshold Vre. 【0112】 When the detection value of the battery voltage detection circuit 42 is relatively high, it is clear that there is no need to return the robotic lawnmower 2, 202 without even performing the two-stage acquisition process. If the two-stage acquisition process is performed even when the voltage of the battery 18 is relatively high, the work motor 36 will be unnecessarily temporarily stopped, which may prevent the work of the robotic lawnmower 2, 202 from proceeding smoothly. With the above configuration, the control unit 8 is configured not to perform the two-stage acquisition process when the voltage of the battery 18 is relatively high. This prevents the work motor 36 from being unnecessarily interrupted, allowing the work of the robotic lawnmower 2, 202 to proceed smoothly. 【0113】 In one or more embodiments, in the threshold correction process, the control unit 8 corrects the feedback threshold Vre based on the recovery voltage value Vdiff obtained by subtracting the first-stage voltage value V1 from the second-stage voltage value V2. 【0114】 According to the above configuration, the feedback threshold Vre can be corrected by a simple means. 【0115】 In one or more embodiments, in the threshold correction process, the controller 8 corrects the feedback threshold Vre by subtracting the recovery voltage value Vdiff from the feedback threshold Vre. 【0116】 The working motor 36 may be configured to operate while the robotic lawnmower 2, 202 is working and to stop while the robotic lawnmower 2, 202 is returning to the charging station 110. In this case, when the robotic lawnmower 2, 202 finishes working and starts returning, the voltage value of the battery 18 is expected to recover by the recovery voltage value Vdiff. For this reason, when determining whether to return the robotic lawnmower 2, 202, it is preferable to take into consideration that the voltage value of the battery 18 will subsequently recover by the recovery voltage value Vdiff. With the above configuration, when determining whether to return the robotic lawnmower 2, 202, it is possible to take into consideration that the voltage value of the battery 18 will subsequently recover by the recovery voltage value Vdiff. Therefore, the timing to return the robotic lawnmower 2, 202 to the charging station 110 can be appropriately identified. 【0117】 In one or more embodiments, in the threshold correction process, when the recovery voltage value Vdiff is greater than or equal to a predetermined upper limit value (e.g., 0.5 V), the control unit 8 subtracts the upper limit value from the feedback threshold value Vre instead of subtracting the recovery voltage value Vdiff from the feedback threshold value Vre. 【0118】 When the recovery voltage value Vdiff calculated in the threshold correction process is large, the recovery amount of the voltage value of the battery 18 at the timing when the robotic lawnmower 2, 202 finishes work and starts returning may be lower than the calculated recovery voltage value Vdiff. Therefore, if the recovery voltage value Vdiff is subtracted from the return threshold Vre for correction even when the recovery voltage value Vdiff calculated in the threshold correction process is large, the voltage value of the battery 18 at the timing when the robotic lawnmower 2, 202 starts returning will be smaller than expected. As a result, the battery 18 may run out of power while the robotic lawnmower 2, 202 is returning. According to the above configuration, when the recovery voltage value Vdiff calculated in the threshold correction process exceeds the upper limit, the corrected return threshold Vre' is not the value obtained by subtracting the recovery voltage value Vdiff from the return threshold Vre, but the value obtained by subtracting the upper limit from the return threshold Vre. This makes it possible to prevent the voltage value of the battery 18 at the timing when the robotic lawnmower 2, 202 starts returning from being smaller than expected. This makes it possible to prevent the battery 18 from running out of power while the robotic lawnmower 2, 202 is returning home. 【0119】 In one or more embodiments, in the threshold correction process, when the recovery voltage value Vdiff is equal to or lower than a predetermined lower limit value (eg, 0.1 V), the control unit 8 sets the pre-correction feedback threshold value Vre to the corrected feedback threshold value Vre'. 【0120】 When the two-stage acquisition process and the threshold correction process are performed with the voltage value of the battery 18 having dropped to the vicinity of the feedback threshold Vre, the calculated recovery voltage value Vdiff may be small. In this case, even if the work motor 36 that was stopped in the two-stage acquisition process is operated again to resume the work of the robotic lawnmower 2, 202, the timing for the robotic lawnmower 2, 202 to start returning arrives soon thereafter. Therefore, the operation of the robotic lawnmower 2, 202 from the time the work is resumed until the return starts is not enough to change the progress of the work and is considered to be an unnecessary operation. If the robotic lawnmower 2, 202 performs unnecessary operations for a long time, the work efficiency of the robotic lawnmower 2, 202 will decrease. According to the above configuration, when the recovery voltage value Vdiff calculated in the threshold correction process is small, the corrected feedback threshold Vre' becomes the same value as the feedback threshold Vre before correction. In other words, the corrected feedback threshold Vre' becomes a value greater than the value obtained by subtracting the recovery voltage value Vdiff from the feedback threshold Vre. As a result, the timing at which the robotic lawnmower 2, 202 starts to return is accelerated, thereby shortening the time during which unnecessary operations are performed by the robotic lawnmower 2, 202. This improves the work efficiency of the robotic lawnmower 2, 202. 【0121】 In one or more embodiments, the controller 8 executes the two-stage acquisition process in a state where the movement motors 32L and 32R (examples of non-target motors) are stopped. 【0122】 The two-stage acquisition process is a process for observing changes in the voltage value of the battery 18 caused by changes in the operating conditions of the work motor 36. However, the voltage value of the battery 18 may also change depending on the operating conditions of the travel motors 32L, 32R. Therefore, if the operating conditions of the travel motors 32L, 32R change while the two-stage acquisition process is being executed, there is a possibility that the change in the voltage value of the battery 18 caused by the change in the operating conditions of the work motor 36 cannot be correctly observed. With the above configuration, the operating conditions of the travel motors 32L, 32R do not change while the two-stage acquisition process is being executed, so that the change in the voltage value of the battery 18 caused by the change in the operating conditions of the work motor 36 can be correctly observed. 【0123】 In one or more embodiments, the control unit 8 executes the feedback determination process in a situation where the movement motors 32L, 32R are stopped. 【0124】 If the operating conditions of the travel motors 32L, 32R are not consistent between the two-stage acquisition process and the return determination process, it may not be possible to properly identify the timing to return the robotic lawnmower 2, 202 to the charging station 110. With the above configuration, the operating conditions of the travel motors 32L, 32R are consistent between the two-stage acquisition process and the return determination process, so that it is possible to properly identify the timing to return the robotic lawnmower 2, 202 to the charging station 110. 【0125】 In one or more embodiments, the control unit 8 stops the movement motors 32L, 32R when the movement motors 32L, 32R continue to operate for a predetermined period of time (eg, two seconds). 【0126】 It is preferable that the two-stage acquisition process (or the return determination process) is repeatedly executed at appropriate time intervals until the timing for returning the robotic lawnmower 2, 202 is identified. However, in a configuration in which the two-stage acquisition process (or the return determination process) is executed in a state in which the moving motors 32L, 32R are stopped, the two-stage acquisition process (or the return determination process) cannot be executed while the moving motors 32L, 32R are operating. According to the above configuration, when the moving motors 32L, 32R are kept operating for a predetermined time, the moving motors 32L, 32R are forcibly stopped. This allows the two-stage acquisition process (or the return determination process) to be repeatedly executed at appropriate time intervals. 【0127】 In one or more embodiments, the work motor 36 is the target motor. The locomotion motors 32L, 32R are non-target motors. 【0128】 It is expected that the working motor 36 operates while the robotic lawnmower 2, 202 is working, and stops while the robotic lawnmower 2, 202 is returning to the charging station 110. Therefore, in determining the timing to return the robotic lawnmower 2, 202, it is highly necessary to obtain the voltage value of the battery 18 for each operating condition of the working motor 36. On the other hand, it is expected that the moving motors 32L, 32R are basically operating while the robotic lawnmower 2, 202 is working and while the robotic lawnmower 2, 202 is returning to the charging station 110. Therefore, in determining the timing to return the robotic lawnmower 2, 202, it is less necessary to obtain the voltage value of the battery 18 for each operating condition of the moving motors 32L, 32R. Nevertheless, if a configuration is adopted in which the voltage value of the battery 18 is obtained for each operating condition of the moving motors 32L, 32R, the processing load of the control unit 8 increases unnecessarily. With the above configuration, while the voltage value of the battery 18 is obtained for each operating state of the work motor 36, the voltage value of the battery 18 is not obtained for each operating state of the travel motors 32L, 32R. This reduces the processing load on the control unit 8 and makes it possible to appropriately identify the timing for returning the robotic lawnmower 2, 202 to the charging station 110. 【0129】 In one or more embodiments, the working mechanism includes a cutting blade 34 for cutting the grass. The working robot functions as an autonomously mobile robotic lawnmower 2, 202. 【0130】 According to the above configuration, the robotic lawnmower 2, 202 can be returned to the charging station 110 at an appropriate time. [Explanation of symbols] 【0131】 2: robot lawnmower, 4: robot body, 6: power supply unit, 8: control unit, 10: operation unit, 12: moving unit, 14: working unit, 16: detection unit, 18: battery, 20: charging interface, 22: processor, 24: memory, 26: power supply circuit, 28L: caster, 28R: caster, 30L: driving wheel, 30R: driving wheel, 32L: moving motor, 32R: moving motor, 34: cutting blade, 36: working motor, 38: wire detection sensor, 40: motor current detection circuit, 42: battery voltage detection circuit, 100: site, 102: house, 104: pond, 106: road, 108: fence, 110: charging station, 112: wire, 202: robot lawnmower, 204: detection unit, 206: motor temperature sensor

Claims

[Claim 1] A work robot that performs tasks while moving autonomously, The work mechanism that performs the work, A moving mechanism for moving the aforementioned work robot, A work motor that drives the aforementioned work mechanism, A motor for moving the aforementioned moving mechanism, A rechargeable battery that supplies power to the work motor and the moving motor, A voltage detection unit for detecting the voltage value of the aforementioned battery, It includes a control unit, The control unit, For a target motor which is at least one of the aforementioned work motor and the aforementioned moving motor, a two-stage acquisition process is performed in which the value detected by the voltage detection unit while the target motor is operating is acquired as the first-stage voltage value, the target motor is then stopped, and the value detected by the voltage detection unit while the target motor is stopped is acquired as the second-stage voltage value. A work robot configured to perform a return determination process that determines whether or not to return the work robot to a charging station based on the first stage voltage value and the second stage voltage value. [Claim 2] The control unit is configured to acquire the value detected by the voltage detection unit as a first determination voltage value, to execute the two-stage acquisition process when the first determination voltage value is less than or equal to a predetermined value, and not to execute the two-stage acquisition process when the first determination voltage value exceeds the predetermined value, as described in claim 1. [Claim 3] The control unit stores a predetermined feedback threshold, The control unit is configured to further perform a threshold correction process that corrects the feedback threshold based on the first stage voltage value and the second stage voltage value. The work robot according to claim 1, wherein the return determination process includes acquiring the value detected by the voltage detection unit as a second determination voltage value, and determining whether or not to return the work robot to the charging station depending on whether or not the second determination voltage value is less than or equal to the corrected return threshold. [Claim 4] The control unit is configured to acquire the value detected by the voltage detection unit as a third determination voltage value, execute the two-stage acquisition process when the third determination voltage value is less than or equal to the feedback threshold, and not execute the two-stage acquisition process when the third determination voltage value exceeds the feedback threshold, as described in claim 3. [Claim 5] In the threshold correction process, the control unit corrects the feedback threshold based on a recovery voltage value obtained by subtracting the first stage voltage value from the second stage voltage value, according to claim 3, the work robot. [Claim 6] In the threshold correction process, the control unit corrects the return threshold by subtracting the recovery voltage value from the return threshold, the work robot according to claim 5. [Claim 7] In the threshold correction process, if the recovery voltage value is greater than or equal to a predetermined upper limit, the control unit subtracts the upper limit from the return threshold instead of subtracting the recovery voltage value from the return threshold, the work robot according to claim 6. [Claim 8] The work robot according to claim 5, wherein in the threshold correction process, the control unit sets the feedback threshold before correction to the feedback threshold after correction if the recovery voltage value is less than or equal to a predetermined lower limit. [Claim 9] One of the aforementioned working motor and the aforementioned moving motor is the target motor, The other of the aforementioned work motor and the aforementioned moving motor is an outside motor that is not the target motor, The control unit performs the two-stage acquisition process while the motor not being targeted is stopped, according to claim 1. [Claim 10] The control unit executes the return determination process when the motor not being targeted is stopped, according to claim 9. [Claim 11] The control unit stops the non-target motor if the non-target motor continues to operate for a predetermined period of time, according to claim 9. [Claim 12] The work robot according to claim 9, wherein the work motor is the target motor and the movement motor is the non-target motor. [Claim 13] The aforementioned working mechanism is equipped with a cutting blade for cutting grass, A work robot according to any one of claims 1 to 12, which functions as an autonomously mobile robotic lawnmower.

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