Lawn mower

Abstract

Even when the running surface is sloped, the drive wheels are controlled according to the slope. [Solution] The lawnmower 1 includes a plurality of motors 32, each provided for a plurality of tires 31; a tilt acquisition unit 11 that acquires the tilt of the running surface R; a direction acquisition unit 12 that acquires the direction of travel of the lawnmower 1; and a drive control unit 13 that controls the rotational speed of the plurality of motors 32. Based on the tilt of the running surface R and the direction of travel, the drive control unit 13 determines which of the plurality of motors 32 will be controlled at a rotational speed different from that of the other motors 32, and controls the motor 32 to be controlled at a rotational speed different from that of the other motors 32.

Description

Technical Field

[0001] The present invention relates to a self-propelled lawn mower.

Background Art

[0002] For example, Patent Document 1 describes a self-propelled lawn mower that can travel and mow grass by remote operation by an operator. This lawn mower includes a mowing unit having a mowing blade and a traveling unit having four drive wheels for driving the lawn mower.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Here, when mowing grass on an inclined surface such as a bank with such a self-propelled lawn mower, for example, even if trying to move horizontally on the inclined surface, the lawn mower may be attracted in the downward direction of the inclined surface and may not be able to travel straight horizontally.

[0005] Therefore, an object of the present invention is to provide a lawn mower capable of controlling drive wheels according to an inclination even when the traveling surface is inclined.

Means for Solving the Problems

[0006] The present invention relates to a self-propelled lawnmower (1) which has a plurality of drive wheels (31) on the right side and the left side of the vehicle body, and comprises a plurality of drive sources (32) provided for each of the plurality of drive wheels (31), a tilt acquisition unit (11) that acquires the tilt of the running surface (R), a direction of travel acquisition unit (12) that acquires the direction of travel of the lawnmower (1), and a drive control unit (13) that controls the rotational speed of each of the plurality of drive sources (32), wherein the drive control unit (13) determines which of the plurality of drive sources (32) is to be controlled at a rotational speed different from the other drive sources (32) based on the acquired tilt of the running surface (R) and the direction of travel, and controls the drive source (32) to be controlled at a rotational speed different from the other drive sources (32).

[0007] In this lawnmower (1), the inclination acquisition unit (11) acquires the inclination of the running surface (R). Then, the drive control unit (13) determines which drive source (32) to control at a different rotational speed than the other drive sources (32) based on the inclination of the running surface (R) and the direction of travel. As a result, in this lawnmower (1), the drive wheels (31) can be controlled according to the inclination even when the running surface (R) is inclined.

[0008] The above-mentioned lawnmower may also be [2] "the lawnmower (1) described in [1] above, wherein the drive control unit (13) slows down the rotational speed of the drive source (32) to be controlled by the rotational speed control unit to slow down the rotational speed of the other drive sources (32)."

[0009] For example, if the rotational speed of one of the multiple drive sources (32) whose rotational speed is to be controlled is made slower than that of the other drive sources (32), the vehicle body will be dragged by the slower-rotating drive wheels (31), and the direction of travel of the lawnmower (1) will change. In this way, the direction of travel of the lawnmower (1) can be controlled by making the rotational speed of the drive source (32) whose rotational speed is to be controlled slower than that of the other drive sources (32).

[0010] The above-mentioned lawnmower may also be the lawnmower (1) described in [2] above, wherein the drive control unit (13) slows down the rotational speed of the drive source (32) that is subject to rotational speed control when the slope of the running surface (R) is steep compared to when the slope is gentle.

[0011] For example, if the rotational speed of the drive source (32) that is subject to rotational speed control is made slower than that of the other drive sources (32), the vehicle body will be dragged by the slower-rotating drive wheels (31), causing a large change in the direction of travel of the brush cutter (1). In this way, the direction of travel of the brush cutter (1) can be controlled according to the slope (angle) of the running surface (R) by controlling the rotational speed of the drive source (32) that is subject to rotational speed control according to the degree of slope (angle) of the running surface (R).

[0012] The above-mentioned lawnmower may also be the lawnmower (1) described in [3] above, in which the drive control unit (13) acquires the rotational speed of the drive source (32) that is subject to rotational speed control, corresponding to the acquired inclination of the travel surface (R), based on a rotational speed control map in which the rate of decrease of the rotational speed of the drive source (32) is associated with each inclination angle of the travel surface (R).

[0013] In this case, the brush cutter (1) can easily obtain the rotational speed of the drive source (32) whose rotational speed is to be controlled by using a rotational speed control map.

[0014] The above-mentioned lawnmower may also be the lawnmower (1) described in any one of [1] to [4] above, wherein the drive control unit (13) determines the drive source (32) to be controlled for rotational speed when the direction of travel intersects the vertical direction of the inclination of the running surface (R).

[0015] The lawnmower (1) can control the drive source (32) subject to rotational speed control at a different rotational speed than the other drive sources (32) when the direction of travel intersects the vertical direction of the slope of the running surface (R), that is, when the direction of travel is likely to change because the lawnmower (1) is pulled to the lower side in the direction of the slope due to the slope of the running surface (R). As a result, the lawnmower (1) can control the rotational speed of the drive source (32) subject to rotational speed control according to the direction of travel of the lawnmower (1) with respect to the slope of the running surface (R).

[0016] The above-mentioned lawnmower may also be the lawnmower (1) described in any one of [1] to [5] above, wherein the drive control unit (13) determines the drive source (32) on the rear side in the direction of travel and on the uphill side in the vertical direction of the inclination of the running surface (R) as the drive source (32) to be controlled by rotational speed control.

[0017] In this case, even if the grass cutter (1) is pulled downwards by the slope of the running surface (R), the grass cutter (1) can change its direction of travel in a way that counteracts the change in direction of travel caused by being pulled downwards. As a result, the grass cutter (1) can travel in the desired direction of travel even when the running surface (R) is sloped. [Effects of the Invention]

[0018] According to the present invention, it is possible to provide a lawnmower that can control the drive wheels according to the incline, even when the running surface is sloped. [Brief explanation of the drawing]

[0019] [Figure 1] Figure 1(a) is a front view showing a schematic configuration of a lawnmower according to the embodiment. Figure 1(b) is a top view showing a schematic configuration of a lawnmower according to the embodiment. [Figure 2] Figure 2 is a block diagram showing the functional configuration of a lawnmower. [Figure 3]FIG. 3(a) is a side view of the lawn mower for explaining the pitch angle of the lawn mower measured by the tilt sensor. FIG. 3(b) is a front view of the lawn mower for explaining the roll angle of the lawn mower measured by the tilt sensor. [Figure 4] FIG. 4 is a top view showing a lawn mower traveling on an inclined traveling surface. [Figure 5] FIG. 5 is a diagram showing an example of the rotational speed control map stored in the storage unit. [Figure 6] FIG. 6 is a flowchart showing the flow of the rotational speed control process of the motor.

BEST MODE FOR CARRYING OUT THE INVENTION

[0020] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each figure, the same or corresponding elements are denoted by the same reference numerals, and redundant descriptions are omitted.

[0021] As shown in FIGS. 1(a) and 1(b), the lawn mower 1 includes a plurality of tires (drive wheels) 31 and a cutting blade 21. The lawn mower 1 includes a plurality of tires 31 on each of the right side and the left side of the vehicle body. The lawn mower 1 is a self-propelled device that can travel by rotating the tires 31. The cutting blade 21 is provided on the lower surface of the lawn mower 1. The cutting blade 21 cuts grass and the like growing on the ground by being rotated. The traveling and mowing of the lawn mower 1 are controlled, for example, by remote operation by an operator.

[0022] More specifically, as shown in FIG. 2, the lawn mower 1 includes an ECU (Electronic Control Unit) 10, a mowing unit 20, a traveling unit 30, and a tilt sensor 40. The ECU 10 includes, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). In the ECU 10, various functions are realized, for example, by the CPU executing a program stored in the ROM or the RAM.

[0023] The grass cutting unit 20 is a mechanism for cutting grass. The grass cutting unit 20 includes a cutting blade 21 and an engine 22. The cutting blade 21 is driven by the engine 22. The rotational speed (revolutions per unit time) of the engine 22 is controlled by the ECU 10.

[0024] The travel unit 30 is a mechanism for moving the lawnmower 1. The travel unit 30 is equipped with multiple tires 31 and multiple motors (drive sources) 32. The travel unit 30 is equipped with multiple tires 31 on both the right and left sides of the vehicle body. In this embodiment, the travel unit 30 is equipped with two tires 31 on the right side of the vehicle body and two tires 31 on the left side of the vehicle body (see Figure 1(b)). In other words, the lawnmower 1 is equipped with four tires 31. Hereinafter, the installation position of each of the four tires 31 may be specified and the tire 31 will be referred to as the right front tire 31A, the right rear tire 31 is referred to as the right rear tire 31B, the left front tire 31 is referred to as the left front tire 31C, and the left rear tire 31 is referred to as the left rear tire 31D.

[0025] Furthermore, multiple motors 32 are provided for each of the multiple tires 31. In this embodiment, four motors 32 are provided. Hereinafter, each of the four motors 32 may be specified and referred to as such. In this case, of the four motors 32, the motor 32 provided for the right front tire 31A will be called the right front motor 32A, the motor 32 provided for the right rear tire 31B will be called the right rear motor 32B, the motor 32 provided for the left front tire 31C will be called the left front motor 32C, and the motor 32 provided for the left rear tire 31D will be called the left rear motor 32D.

[0026] Each of the four motors 32 has its rotational speed controlled by the ECU 10. In this way, the travel unit 30 can independently control the rotational speed of each of the four tires 31. The motors 32 may be, for example, in-wheel motors provided within the wheels on which the tires 31 are mounted. The travel unit 30 also includes a battery or the like to supply power to each motor 32. The travel unit 30 may also include a steering unit to control the steering of the lawnmower 1.

[0027] The tilt sensor 40 is a sensor that measures the inclination of the lawnmower 1 with respect to a horizontal plane. In other words, the tilt sensor 40 can measure the inclination of the lawnmower 1 as the inclination of the running surface on which the lawnmower 1 travels. As shown in Figure 3(a), the tilt sensor 40 can measure the pitch angle, which is the inclination of the lawnmower 1 in the front-to-back direction with respect to a horizontal plane. Also, as shown in Figure 3(b), it can measure the roll angle, which is the inclination of the lawnmower 1 in the left-to-right direction with respect to a horizontal plane. The measurement results of the tilt sensor 40 are input to the ECU 10.

[0028] In addition, the lawnmower 1 is equipped with a wireless communication unit that receives remote control signals from an operator who remotely controls the lawnmower 1. These remote control signals include instructions for mowing by the mowing unit 20 and instructions for driving (direction of travel, etc.) by the driving unit 30.

[0029] Functionally, the ECU10 comprises a tilt acquisition unit 11, a direction of travel acquisition unit 12, a drive control unit 13, and a map storage unit 14. The tilt acquisition unit 11 acquires the tilt of the travel surface R on which the lawnmower 1 travels. Based on the measurement results of the tilt sensor 40, the tilt acquisition unit 11 can acquire the tilt (direction and angle of tilt) of the travel surface R.

[0030] The direction of travel acquisition unit 12 acquires the direction of travel of the lawnmower 1. This direction of travel is the target direction of travel for the lawnmower 1. This direction of travel includes the forward or reverse direction of the lawnmower 1. This direction of travel may be acquired based on remote control signals from an operator remotely controlling the lawnmower 1.

[0031] The drive control unit 13 controls the rotational speed of each of the multiple motors 32 based on remote control signals from an operator remotely controlling the grass trimmer 1, thereby driving the grass trimmer 1. The following description will focus on the control of each motor 32 performed by the drive control unit 13 when the running surface R on which the grass trimmer 1 travels is inclined.

[0032] Here, for example, let's assume that the running surface R on which the lawnmower 1 travels is inclined, as shown in Figure 4. The upper side of the running surface R in the direction of inclination is the uphill side (mountain side) of the slope, and the lower side of the running surface R in the direction of inclination is the downhill side (valley side) of the slope. In other words, the running surface R is inclined downwards from the upper side to the lower side in the direction of inclination. Also, the direction of inclination of the running surface R has the same meaning as the vertical direction of the inclination of the running surface R.

[0033] When traveling on an inclined travel surface R, the grass cutter 1 is gradually pulled downwards in the direction of the incline as it travels, and the actual travel path tends to deviate downwards in the direction of the incline relative to the target direction of travel. In this embodiment, the drive control unit 13 can perform control to suppress the deviation of the actual travel path relative to the target direction of travel when the grass cutter 1 travels on an inclined travel surface R.

[0034] Specifically, the drive control unit 13 determines which of the multiple motors 32 will be controlled at a different rotational speed from the other motors 32, based on the inclination of the travel surface R acquired by the inclination acquisition unit 11 and the direction of travel of the brush cutter 1 acquired by the direction of travel acquisition unit 12. When the brush cutter 1 is in motion, the drive control unit 13 controls the determined motor 32 to be controlled at a different rotational speed from the other motors 32.

[0035] As shown in Figure 4, the drive control unit 13 determines which motor 32 is subject to rotational speed control when the direction of travel of the grass trimmer 1, as acquired by the direction of travel acquisition unit 12, intersects with the vertical direction of the inclination of the travel surface R (the inclination direction of the travel surface R). In other words, the drive control unit 13 does not determine which motor 32 is subject to rotational speed control when the direction of travel of the grass trimmer 1 is aligned with the inclination direction of the travel surface R (when the grass trimmer 1 is moving straight up or down the travel surface R along the inclination direction). The drive control unit 13 determines which motor 32 is subject to rotational speed control when the grass trimmer 1 is traveling horizontally on the inclined travel surface R, or when it is traveling diagonally up or down the inclined travel surface R relative to the horizontal direction.

[0036] In this embodiment, the drive control unit 13 determines that the motor 32 located on the rear side in the direction of travel and on the upward side in the vertical direction (inclination direction) of the inclination of the travel surface R is the motor 32 to be controlled by rotational speed control. For example, in the example shown in Figure 4, the lawnmower 1 moves forward diagonally upward on the inclined travel surface R. In this case, the drive control unit 13 determines that the right rear tire 31B of the four tires 31 is the motor 32 to be controlled by rotational speed control.

[0037] The drive control unit 13 slows the rotational speed of the motor 32 to be controlled compared to the rotational speeds of the other motors 32. Furthermore, when the inclination (slope in the direction of inclination) of the running surface R is steep, the drive control unit 13 slows the rotational speed of the motor 32 to be controlled compared to when the inclination is gentle. The drive control unit 13 acquires the rotational speed of the motor 32 to be controlled, which corresponds to the inclination of the running surface R acquired by the inclination acquisition unit 11, based on the rotational speed control map stored in the map storage unit 14.

[0038] Thus, when the drive control unit 13 operates the lawnmower 1 based on the operator's remote control, it slows down the rotational speed of the motor 32 whose rotational speed is controlled compared to the other motors 32. For example, in the example shown in Figure 4, the drive control unit 13 slows down the rotational speed of the right rear tire 31B compared to the other tires 31. By slowing down the rotational speed of the right rear tire 31B compared to the other tires 31, the vehicle body is dragged by the slower-rotating right rear tire 31B, causing the direction of travel of the lawnmower 1 to face upwards in the direction of the incline. In other words, by slowing down the rotational speed of the right rear tire 31B compared to the others, the lawnmower 1 can counteract the gradual pull of the lawnmower 1 downwards in the direction of the incline caused by the incline of the running surface R. As a result, the lawnmower 1 can travel toward the target direction of travel while suppressing the shift in the direction of travel toward downwards in the direction of the incline caused by the incline of the running surface R.

[0039] The drive control unit 13 performs a process to determine which motor 32 is subject to rotational speed control when the inclination angle of the travel surface R is greater than or equal to a predetermined angle threshold. For example, if the rotational speed control map shown in Figure 5 is set, the drive control unit 13 may determine which motor 32 is subject to rotational speed control when the inclination angle of the travel surface R acquired by the inclination acquisition unit 11 is 30° or greater. If the inclination angle of the travel surface R is less than the predetermined angle threshold, the drive control unit 13 performs normal control. In other words, the drive control unit 13 controls the rotational speed of each of the multiple motors 32 based on instructions from the operator and drives the lawnmower 1 in the instructed direction of travel.

[0040] The map storage unit 14 stores the rotational speed control map used by the drive control unit 13. This rotational speed control map associates the rate of decrease in rotational speed of the motor 32 subject to rotational speed control with each inclination angle (slope) of the running surface R. The rate of decrease in rotational speed of the motor 32 subject to rotational speed control is the rate of decrease in rotational speed of the motor 32 subject to rotational speed control relative to the rotational speed of other motors 32 not subject to rotational speed control. For example, the map storage unit 14 stores the rotational speed control map shown in Figure 5 as an example. In the rotational speed control map shown in Figure 5, it is shown that the rate of decrease in rotational speed is 0% when the inclination angle is less than 30°, 10% when the inclination angle is 30° or more and less than 50°, and 30% when the inclination angle is 50° or more. However, the rotational speed control map shown in Figure 5 is just an example, and the inclination angle classifications and the values ​​of the decrease rates are not limited to the example shown in Figure 5.

[0041] In this rotational speed control map, the rate of decrease in rotational speed increases as the inclination angle of the running surface R increases. As a result, the drive control unit 13 can use this rotational speed control map to slow down the rotational speed of the motor 32 being controlled when the inclination of the running surface R is steeper compared to when the inclination is gentler.

[0042] Next, the flow of the motor 32 rotation speed control process performed by the ECU 10 will be explained using the flowchart in Figure 6. The ECU 10 starts the process shown in Figure 6 when, for example, the power to the lawnmower 1 is turned ON and the lawnmower 1 begins to move. Furthermore, when the process shown in Figure 6 reaches its end, it restarts from the beginning after a predetermined time. Here, we will explain using the case where the drive control unit 13 performs control using the rotation speed control map shown in Figure 5 as an example.

[0043] As shown in Figure 6, the drive control unit 13 acquires the inclination of the travel surface R on which the grass trimmer 1 travels from the inclination acquisition unit 11 (S101). The drive control unit 13 determines whether the inclination angle of the travel surface R is greater than or equal to a predetermined angle threshold (S102). Here, the drive control unit 13 determines whether the inclination angle of the travel surface R is 30° or greater. If the inclination angle of the travel surface R is not greater than or equal to the predetermined angle threshold (S102: NO), the drive control unit 13 controls the rotational speed of each of the multiple motors 32 based on instructions from the operator and performs normal control to drive the grass trimmer 1 in the instructed direction of travel (S108).

[0044] If the inclination angle of the travel surface R is greater than or equal to a predetermined angle threshold (S102: YES), the drive control unit 13 and the travel direction acquisition unit 12 acquire the travel direction of the brush cutter 1 (S103). The drive control unit 13 determines whether the acquired travel direction intersects the vertical direction of the inclination of the travel surface R (the inclination direction of the travel surface R) (S104). If the travel direction does not intersect the vertical direction of the inclination, that is, if the travel direction is parallel to the vertical direction of the inclination (S104: NO), the drive control unit 13 performs the process described in S108 above.

[0045] If the direction of travel intersects the up-down direction of the incline (S104: YES), the drive control unit 13 determines which of the four motors 32 will be subject to rotational speed control (S105) based on the incline of the travel surface R and the direction of travel of the brush cutter 1. In this case, the drive control unit 13 determines the motor 32 on the rear side of the direction of travel and on the up-side in the up-down direction (incline direction) of the incline of the travel surface R to be the motor 32 subject to rotational speed control.

[0046] The drive control unit 13 acquires the rotational speed of the motor 32 to be controlled, corresponding to the inclination of the running surface R acquired by the inclination acquisition unit 11, based on the rotational speed control map stored in the map storage unit 14 (S106). Here, the rate of decrease in rotational speed is acquired as the rotational speed of the motor 32 to be controlled. Then, the drive control unit 13 controls the four motors 32 based on the operator's instructions. At that time, the drive control unit 13 makes the rotational speed of the motor 32 to be controlled slower than the rotational speed of the other motors 32 based on the acquired rate of decrease in rotational speed (S107).

[0047] As described above, in this lawnmower 1, the inclination acquisition unit 11 acquires the inclination of the travel surface R on which the lawnmower 1 travels. Then, the drive control unit 13 determines which motor 32 will be controlled at a different rotational speed than the other motors 32 based on the inclination of the travel surface R and the direction of travel. As a result, in this lawnmower 1, even when the travel surface R is inclined, the tires 31 (motors 32) can be controlled according to the inclination.

[0048] For example, if the rotational speed of the motor 32 targeted for rotational speed control is set slower than that of the other motors 32, the vehicle body will be dragged by the slower-rotating tires 31, changing the direction of travel of the lawnmower 1. In this way, the direction of travel of the lawnmower 1 can be controlled by setting the rotational speed of the motor 32 targeted for rotational speed control slower than that of the other motors 32.

[0049] The drive control unit 13 slows down the rotational speed of the motor 32 subject to rotational speed control when the slope of the travel surface R is steep, compared to when the slope is gentle. For example, the slower the rotational speed of the motor 32 subject to rotational speed control is set compared to the other motors 32, the more the vehicle body is dragged by the slower-rotating tires 31, causing a significant change in the direction of travel of the lawnmower 1. In this way, the lawnmower 1 can control the direction of travel of the lawnmower 1 according to the slope of the travel surface R by controlling the rotational speed of the motor 32 subject to rotational speed control according to the degree of slope (angle of inclination) of the travel surface R.

[0050] The drive control unit 13 acquires the rotational speed of the motor 32 to be controlled, corresponding to the inclination of the travel surface R, based on the rotational speed control map stored in the map storage unit 14. In this case, the brush cutter 1 can easily acquire the rotational speed of the motor 32 to be controlled by using the rotational speed control map.

[0051] The drive control unit 13 determines which motor 32 is subject to rotational speed control when the direction of travel of the grass trimmer 1 intersects the vertical direction of the slope of the travel surface R. In this case, when the direction of travel of the grass trimmer 1 intersects the vertical direction of the slope of the travel surface R, that is, when the grass trimmer 1 is easily pulled to the lower side in the direction of the slope due to the slope of the travel surface R and its direction of travel is likely to change, the motor 32 subject to rotational speed control can be controlled at a different rotational speed than the other motors 32. As a result, the grass trimmer 1 can control the rotational speed of the motor 32 subject to rotational speed control according to the direction of travel of the grass trimmer 1 with respect to the slope of the travel surface R.

[0052] The drive control unit 13 determines that the motor 32 located on the rear side in the direction of travel and on the upward side in the vertical direction of the inclination of the travel surface R is the motor 32 to be controlled by rotational speed control. In this case, even if the grass cutter 1 is pulled downwards by the inclination of the travel surface R, the grass cutter 1 can change its direction of travel in a way that counteracts the change in direction of travel caused by being pulled downwards. As a result, the grass cutter 1 can travel in the desired direction of travel even when the travel surface R is inclined.

[0053] The drive control unit 13 selects the motor 32 at the rear in the direction of travel as the motor 32 whose rotational speed is to be controlled. As a result, even if the rotational speed of the motor 32 whose rotational speed is to be controlled is reduced, the rotational speed of the front tire 31 in the direction of travel does not decrease. When the rotational speed of the front tire 31 in the direction of travel is fast, the force that causes the grass cutter 1 to move forward in the direction of travel becomes stronger, which suppresses the grass cutter 1 from being pulled downward in the direction of the slope of the running surface R. As a result, the grass cutter 1 can travel in the desired direction of travel while suppressing being pulled downward in the direction of the slope of the running surface R.

[0054] Although embodiments of the present invention have been described above, the present invention is not limited to the above embodiments. For example, the lawnmower 1 is not limited to being driven by remote control by an operator, but may be an automatically operated lawnmower that drives automatically and cuts grass according to external conditions. [Explanation of symbols]

[0055] 1...grass trimmer, 11...slope acquisition unit, 12...direction acquisition unit, 13...drive control unit, 31...tire (drive wheel), 32...motor (drive source), R...running surface.

Claims

1. A self-propelled lawnmower (1) equipped with multiple drive wheels (31) on both the right and left sides of the vehicle body, Multiple drive sources (32) are provided for each of the multiple drive wheels (31), An inclination acquisition unit (11) that acquires the inclination of the running surface (R), A direction acquisition unit (12) acquires the direction of travel of the lawnmower (1), A drive control unit (13) controls the rotational speed of each of the multiple drive sources (32), Equipped with, The drive control unit (13) is Based on the acquired inclination of the running surface (R) and the direction of travel, the drive source (32) to be controlled at a rotational speed different from the other drive sources (32) is determined from among the plurality of drive sources (32). A brush cutter (1) that controls the drive source (32) whose rotational speed is to be controlled at a different rotational speed from the other drive sources (32).

2. The lawnmower (1) according to claim 1, wherein the drive control unit (13) slows down the rotational speed of the drive source (32) to be controlled to slow down the rotational speed of the other drive sources (32).

3. The lawnmower (1) according to claim 2, wherein the drive control unit (13) slows down the rotational speed of the drive source (32) that is subject to rotational speed control when the inclination of the running surface (R) is steep, compared to when the inclination is gentle.

4. The lawnmower (1) according to claim 3, wherein the drive control unit (13) acquires the rotational speed of the drive source (32) to be controlled for rotational speed, corresponding to the acquired inclination of the travel surface (R), based on a rotational speed control map in which the rate of decrease of the rotational speed of the drive source (32) is associated with each inclination angle of the travel surface (R).

5. The lawnmower (1) according to claim 1, wherein the drive control unit (13) determines the drive source (32) to be controlled for rotational speed when the direction of travel intersects the vertical direction of the inclination of the travel surface (R).

6. The lawnmower (1) according to any one of claims 1 to 5, wherein the drive control unit (13) determines the drive source (32) located on the rear side in the direction of travel and on the upward side in the vertical direction of the inclination of the travel surface (R) as the drive source (32) to be controlled by rotational speed control.

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