System, work vehicle, and method

Abstract

This system controls a work vehicle provided with a fuel cell. A device for controlling the system determines whether or not the work vehicle is traveling downhill. The control device controls the amount of power generated by the fuel cell on the basis of the determination result.

Description

Systems, work vehicles and methods

[0001] This application claims priority to Japanese Patent Application No. 2024-028539, filed February 28, 2024, the contents of which are incorporated herein by reference.

[0002] Work vehicles equipped with fuel cells that use hydrogen gas as fuel are being considered. Fuel cell-powered work vehicles typically have a battery to limit the amount of fuel cell they carry and to absorb regenerative power when going downhill. Therefore, the work vehicle's control device must perform energy management to appropriately distribute the energy between the fuel cell and the battery.

[0003] Patent Document 1 discloses a technique for controlling the output of a fuel cell based on the topography of a travel route.

[0004] Japanese Patent Application Laid-Open No. 2023-073113

[0005] The power required for a work vehicle to travel varies depending on the road. If the road is uphill, more power is required for powering, and if the road is downhill, regenerative power is generated. Since fluctuations in output can accelerate deterioration of fuel cells, it is preferable to suppress changes in output. On the other hand, when a constant amount of power is output from a fuel cell, there is a possibility that the power may be excessive or insufficient depending on the operating state of the work vehicle and the state of the power storage device. The purpose of the present disclosure is to provide a system, work vehicle, and method that can appropriately determine the power that should be output by a fuel cell mounted on a work vehicle.

[0006] According to one aspect of the present invention, a system for controlling a work vehicle equipped with a fuel cell includes a control device that determines whether the work vehicle is traveling downhill and controls the amount of power generated by the fuel cell based on the result of the determination.

[0007] According to the above aspect, the system can appropriately determine the power that should be output by the fuel cell mounted on the work vehicle.

[0008] FIG. 1 is a perspective view schematically showing a haulage vehicle according to a first embodiment; FIG. 2 is a schematic block diagram showing the configuration of a haulage vehicle according to the first embodiment; FIG. 3 is a schematic block diagram showing the configuration of a control system provided in the haulage vehicle according to the first embodiment; FIG. 4 is a block diagram showing a calculation algorithm by a control amount determination unit according to the first embodiment; FIG. 5 is a flowchart showing a control method for the haulage vehicle according to the first embodiment; and FIG. 6 is a schematic block diagram showing the configuration of a computer according to at least one embodiment.

[0009] <First embodiment> <Configuration of transporter vehicle 10> Hereinafter, an embodiment will be described in detail with reference to the drawings. Fig. 1 is a perspective view that schematically shows a transporter vehicle 10 according to a first embodiment. The transporter vehicle 10 includes a dump body 11, a vehicle body 12, and a traveling device 13. The transporter vehicle 10 is, for example, a dump truck, which is an example of a work vehicle.

[0010] The dump body 11 is a member on which a load is loaded. The dump body 11 is an example of a work machine. At least a portion of the dump body 11 is disposed above the vehicle body 12. The dump body 11 performs a dumping operation and a lowering operation. By the dumping operation and the lowering operation, the dump body 11 is adjusted to a dump position and a loaded position. The dump position refers to a position in which the dump body 11 is raised. The loaded position refers to a position in which the dump body 11 is lowered.

[0011] The dumping operation refers to an operation of moving the dump body 11 away from the vehicle body 12 and tilting it in the dumping direction. The dumping direction is toward the rear of the vehicle body 12. In the embodiment, the dumping operation includes lifting the front end of the dump body 11 and tilting the dump body 11 rearward. Due to the dumping operation, the loading surface of the dump body 11 tilts downward toward the rear.

[0012] The lowering operation refers to an operation of bringing the dump body 11 closer to the vehicle body 12. In the embodiment, the lowering operation includes lowering the front end of the dump body 11.

[0013] When performing an earth removal operation, the dump body 11 performs a dumping operation to change from a loaded posture to a dump posture. If a load is loaded on the dump body 11, the load is discharged rearward from the rear end of the dump body 11 by the dumping operation. When a loading operation is performed, the dump body 11 is adjusted to the loaded posture.

[0014] The vehicle body 12 includes a vehicle body frame. The vehicle body 12 supports the dump truck body 11. The vehicle body 12 is supported by a traveling device 13.

[0015] The traveling device 13 supports the vehicle body 12. The traveling device 13 causes the transporter vehicle 10 to travel. The traveling device 13 causes the transporter vehicle 10 to move forward or backward. At least a portion of the traveling device 13 is disposed below the vehicle body 12. The traveling device 13 has a pair of front wheels and a pair of rear wheels. The front wheels are steered wheels, and the rear wheels are driven wheels. Note that the combination of steered wheels and driven wheels is not limited to this, and the traveling device 13 may be four-wheel drive or four-wheel steering.

[0016] Fig. 2 is a schematic block diagram showing the configuration of the transporter vehicle 10 according to the first embodiment. As shown in Fig. 2, the transporter vehicle 10 includes a power system 14, a drive system 15, and a control system 16. The power system 14 is configured to generate power for driving the dump body 11 and the traveling device 13, which are working machines. The drive system 15 is configured to drive the dump body 11 and the traveling device 13, which are working machines, with the power generated by the power system 14. The control system 16 is configured to control the power system 14 and the drive system 15.

[0017] The power system 14 generates electric power as a power source and includes a hydrogen tank 141, a hydrogen supply device 142, a fuel cell 143, a first power converter 144, a battery 145, a second power converter 146, and a retarder 147.

[0018] The hydrogen supply device 142 supplies the hydrogen filled in the hydrogen tank 141 to the fuel cell 143. The fuel cell 143 generates electricity by causing an electrochemical reaction between the hydrogen supplied from the hydrogen supply device 142 and oxygen contained in the outside air.

[0019] The first power converter 144 controls the output of the power generated by the fuel cell 143. The first power converter 144 is, for example, a DC-DC converter. The first power converter 144 converts the power generated by the fuel cell 143 into power of a predetermined voltage and outputs it in accordance with commands from the control system 16. The power output by the first power converter 144 is output to the drive system 15 via the bus B.

[0020] The battery 145 stores the power generated in the fuel cell 143. The battery 145 is an example of a power storage device. In other embodiments, the transport vehicle 10 may include another power storage device, such as a capacitor, instead of the battery 145. The battery 145 is provided with a monitoring device (not shown) that monitors the state of the battery 145. The monitoring device determines the maximum chargeable power and the maximum dischargeable power to prevent breakdown of the battery 145. The monitoring device determines the maximum chargeable power and the maximum dischargeable power using various measurement data indicating the state of the battery 145, such as the temperature, charging rate, and voltage of the battery 145. For example, the maximum chargeable power and the maximum dischargeable power become smaller as the temperature of the battery 145 increases.

[0021] The second power converter 146 controls the input and output of power to and from the battery 145. It converts the input power and outputs it. The second power converter 146 is, for example, a DC-DC converter. The second power converter 146 converts the power input from the battery 145 into power of a predetermined voltage and outputs it in accordance with a command from the control system 16. The power output by the second power converter 146 is output to the drive system 15 via the bus B.

[0022] The retarder 147 converts regenerated electric power generated by the electric traction motor 156 (described later) into thermal energy, for example, when the regenerated electric power cannot be charged into the battery 145. The retarder 147 is an example of a consumption device for consuming surplus electric power.

[0023] The drive system 15 includes an inverter 151, an electric pump motor 152, a hydraulic pump 153, a hoist cylinder 154, an inverter 155, and an electric travel motor 156. The inverter 151 converts DC current from the bus B into three-phase AC current and supplies it to the electric pump motor 152. The electric pump motor 152 drives the hydraulic pump 153. Hydraulic oil discharged from the hydraulic pump 153 is supplied to the hoist cylinder 154 via a control valve (not shown). The supply of hydraulic oil to the hoist cylinder 154 activates the hoist cylinder 154. The hoist cylinder 154 performs a dumping or lowering operation on the dump body 11. The inverter 155 converts DC current from the bus B into three-phase AC current and supplies it to the electric travel motor 156. The rotational force generated by the electric travel motor 156 is transmitted to the drive wheels of the travel device 13.

[0024] 3 is a schematic block diagram showing the configuration of the control system 16 provided in the transporter vehicle 10 according to the first embodiment. The control system 16 includes a measuring device 161, an operating device 162, and a control device 163.

[0025] The measurement device 161 acquires measurement data related to the operating state of the haulage vehicle 10. The measurement device 161 acquires various measurement data indicating the state of the battery 145. The measurement device 161 includes an IMU (Inertial Measurement Unit) for measuring the attitude of the haulage vehicle 10, a temperature sensor for measuring the temperature of the battery 145, a fuel gauge for measuring the charging rate of the battery 145, a current sensor for measuring the current passing through the inverter 155, and a voltage sensor for measuring the voltage of the bus bar B. The IMU is an example of an inclination sensor (attitude sensor) for measuring the inclination angle of the haulage vehicle 10 with respect to the ground surface, i.e., the attitude of the haulage vehicle 10. The measurement device 161 outputs the acquired measurement data to the control device 163.

[0026] The operation device 162 is provided in the driver's cab and receives operations by the operator. The operation device 162 includes an accelerator pedal, a brake pedal, a steering wheel, a dump lever, etc. The operation device 162 outputs an operation signal to the control device 163.

[0027] The control device 163 drives the transport vehicle 10 in accordance with an operation signal from the operation device 162. The control device 163 includes a data acquisition unit 201, a reference generated power setting unit 202, a vehicle body control unit 203, a required power calculation unit 204, a regenerative power calculation unit 205, a battery capacity determination unit 206, a control mode determination unit 207, a control amount determination unit 208, a fuel cell control unit 209, and a battery control unit 210.

[0028] The data acquisition unit 201 acquires measurement data from the measurement device 161. The data acquisition unit 201 acquires an operation signal from the operation device 162.

[0029] The reference generated power setting unit 202 sets the reference generated power of the fuel cell 143 based on the charging rate of the battery 145 acquired by the data acquisition unit 201. Specifically, the reference generated power setting unit 202 sets the reference generated power to a lower value the higher the charging rate of the battery 145, and sets the reference generated power to a higher value the lower the charging rate of the battery 145. The reference generated power, for example, monotonically decreases (does not monotonically increase) with respect to the charging rate of the battery 145.

[0030] The vehicle body control unit 203 generates a control signal for controlling the transporter vehicle 10 based on an operation signal from the operation device 162. For example, the vehicle body control unit 203 generates a control signal for controlling the steering, accelerator, brake, and operation of the dump body of the traveling device 13.

[0031] The required power calculation unit 204 calculates the required power required in the power system 14 based on the control signal generated by the vehicle body control unit 203. The required power calculation unit 204 is an example of a required power determination unit.

[0032] The regenerative power calculation unit 205 calculates the regenerative power generated by the haulage vehicle 10 based on the measurement data of the voltage of the bus B and the current passing through the inverter 155 acquired by the data acquisition unit 201 .

[0033] The battery capability determination unit 206 determines the maximum chargeable power and the maximum dischargeable power by using various measurement data indicating the state of the battery 145 acquired by the data acquisition unit 201. Note that the battery capability determination unit 206 may determine the maximum chargeable power and the maximum dischargeable power by inquiring about the maximum chargeable power and the maximum dischargeable power from a monitoring device for the battery 145.

[0034] The control mode determination unit 207 determines whether the haulage vehicle 10 is traveling downhill based on the attitude measurement data of the haulage vehicle 10 acquired by the data acquisition unit 201, and determines the control mode of the fuel cell 143 based on the determination result. The control modes of the fuel cell 143 include a first mode in which the fuel cell 143 outputs the reference generated power set by the reference generated power setting unit 202 or power greater than the reference generated power, and a second mode in which the fuel cell 143 outputs the reference generated power set by the reference generated power setting unit 202 or power less than the reference generated power. The first mode is, for example, a control mode for traveling uphill or on flat ground. The second mode is, for example, a control mode for traveling downhill. If the control mode determination unit 207 determines that the haulage vehicle 10 is not traveling downhill, it determines the control mode of the fuel cell 143 to be the first mode. If the control mode determination unit 207 determines that the haulage vehicle 10 is traveling downhill, it determines the control mode of the fuel cell 143 to be the second mode. When the haulage vehicle 10 travels downhill, regeneration lapse can be prevented by controlling the fuel cell 143 in the second mode. The relationship between the first mode and the second mode may be as follows: The first mode may be a control mode that outputs power equal to or greater than the reference generated power, and the second mode may be a control mode that outputs power less than the reference generated power. The first mode may be a control mode that outputs power greater than the reference generated power, and the second mode may be a control mode that outputs power equal to or less than the reference generated power. In other words, the control device 200 according to the embodiment may be capable of outputting the reference generated power in either the first mode or the second mode, but may not output the reference generated power in the other control mode.

[0035] The control amount determination unit 208 determines the target power generation of the fuel cell 143 and the target charge power or target discharge power of the battery 145 based on the required power, the regenerative power, the reference power generation power, the maximum chargeable power and maximum dischargeable power of the battery 145, and the control mode. The method of determining the control amount by the control amount determination unit 208 will be described later.

[0036] The fuel cell control unit 209 controls the amount of power generated by the fuel cell 143 in accordance with the target power generation determined by the control variable determination unit 208. The fuel cell control unit 209 controls the amount of hydrogen supplied by the hydrogen supply device 142 and the first power converter 144 connected to the fuel cell 143 so that the fuel cell 143 generates power in accordance with the target power generation determined by the control variable determination unit 208.

[0037] The battery control unit 210 controls the second power converter 146 connected to the battery 145 so as to discharge the battery 145 in accordance with the target discharge power determined by the control amount determination unit 208, or to charge the battery 145 in accordance with the target charge power determined by the control amount determination unit 208. The battery control unit 210 is an example of a power storage device control unit.

[0038] Here, the calculation of the control amount determiner 208 according to the first embodiment will be described. Fig. 4 is a block diagram showing a calculation algorithm by the control amount determiner 208 according to the first embodiment. The control amount determiner 208 includes a first subtraction block 221, a second subtraction block 222, a MAX block 223, a first MIN block 224, a third subtraction block 225, a second MIN block 226, an addition block 227, a third MIN block 228, and a fourth subtraction block 229.

[0039] The first subtraction block 221 subtracts the maximum dischargeable power from the required power. The second subtraction block 222 subtracts the regenerative power from the maximum chargeable power. The regenerative power and the required power shown in FIG. 4 are represented by the difference between the required power calculated by the required power calculation unit 204 and the regenerative power calculated by the regenerative power calculation unit 205. Specifically, the required power is the value obtained by subtracting the regenerative power from the required power, and the regenerative power is the value obtained by subtracting the required power from the regenerative power. In other words, the required power is equal to the value obtained by multiplying the regenerative power by -1.

[0040] The MAX block 223 selects the larger of the reference generated power and the calculation result of the first subtraction block 221 .

[0041] When the control mode is the second mode, the first MIN block 224 selects the smaller of the calculation result of the MAX block 223 and the calculation result of the second subtraction block 222. In other words, when the haulage vehicle 10 is traveling downhill, the first MIN block 224 outputs the reference generated power if the subtracted regenerative power can be absorbed within the charge capacity of the battery 145. Furthermore, when the haulage vehicle 10 is traveling downhill, the first MIN block 224 outputs the difference between the maximum chargeable power of the battery 145 and the subtracted regenerative power if the subtracted regenerative power cannot be absorbed within the charge capacity of the battery 145. However, when the calculation result is a negative number, the first MIN block 224 outputs zero as the calculation result.

[0042] On the other hand, when the control mode is the first mode, the first MIN block 224 outputs the calculation result of the MAX block 223 regardless of the calculation result of the second subtraction block 222. In other words, the first MIN block 224 outputs the reference generated power even if regenerative power is temporarily generated by braking when the haulage vehicle 10 is traveling uphill or on flat ground. The calculation result of the first MIN block 224 indicates the target generated power of the fuel cell 143.

[0043] The third subtraction block 225 subtracts the calculation result of the first MIN block 224 from the net required power. The second MIN block 226 determines the smaller of the calculation result of the third subtraction block 225 or the maximum dischargeable power as the target discharge power of the battery 145.

[0044] The addition block 227 adds the subtracted regenerative power to the calculation result of the first MIN block 224. The third MIN block 228 determines the smaller of the maximum chargeable power and the calculation result of the addition block 227 as the target charge power for the battery 145.

[0045] The fourth subtraction block 229 subtracts the calculation result of the third MIN block 228 from the calculation result of the addition block 227 and determines the result as the surplus power to be consumed by the retarder 147 .

[0046] At least one of the target discharge power and the target charge power determined by the control amount determination unit 208 is zero.

[0047] 5 is a flowchart showing a method for controlling the transport vehicle 10 according to the first embodiment. When the transport vehicle 10 according to the first embodiment starts traveling, the data acquisition unit 201 of the control device 163 acquires measurement data relating to the temperature of the battery 145, the charging rate of the battery 145, the passing current of the inverter 155, the voltage of the bus bar B, and the attitude of the transport vehicle 10 from the measurement device 161, and acquires an operation signal from the operation device 162 (step S1).

[0048] Next, the reference generated power setting unit 202 sets the reference generated power of the fuel cell 143 based on the measurement data of the charging rate of the battery 145 acquired in step S1 (step S2). The vehicle body control unit 203 generates a control signal for controlling the transporter vehicle 10 based on the operation signal acquired in step S1 (step S3).

[0049] The required power calculation unit 204 calculates the required power based on the control signal generated in step S3 (step S4). The regenerative power calculation unit 205 calculates the regenerative power based on the measurement data of the voltage of the bus B and the current passing through the inverter 155 acquired in step S1 (step S5).

[0050] The battery capacity determination unit 206 determines the maximum chargeable power and maximum dischargeable power of the battery 145 using various measurement data indicating the state of the battery 145 acquired in step S1 (step S6).

[0051] The control mode determination unit 207 determines whether the haulage vehicle 10 is traveling downhill based on the measurement data related to the attitude of the haulage vehicle 10 acquired in step S1, and determines the control mode of the fuel cell 143 based on the determination result (step S7). Specifically, the control mode determination unit 207 determines the control mode in the following procedure. The control mode determination unit 207 applies a low-pass filter to the measurement data of the pitch angle of the haulage vehicle 10. The control mode determination unit 207 determines the control mode to be the second mode if the moving average value of the pitch angle indicates a forward tilt attitude. For example, if the sign of the measurement data value of the pitch angle is negative when the vehicle is tilted forward and positive when the vehicle is tilted backward, the control mode determination unit 207 determines that the vehicle is traveling downhill if the moving average value of the pitch angle is smaller than a predetermined negative threshold. On the other hand, the control mode determination unit 207 determines the control mode to be the first mode if the moving average value of the pitch angle does not indicate a forward tilt attitude.

[0052] The control quantity determination unit 208 determines the target generated power of the fuel cell 143, the target charging power or target discharging power of the battery 145, and the surplus power to be consumed by the retarder 147 based on the reference generated power set in step S2, the required power calculated in step S4, the regenerated power calculated in step S5, the maximum chargeable power and maximum dischargeable power determined in step S6, and the control mode determined in step S7 (step S8).

[0053] The fuel cell control unit 209 controls the amount of power generated by the fuel cell 143 in accordance with the target power generation determined in step S8 (step S9). If the target power generation determined in step S8 is zero, the fuel cell control unit 209 may stop power generation by the fuel cell 143. The battery control unit 210 also controls the second power converter 146 in accordance with the target discharge power or target charge power determined in step S8 (step S10).

[0054] <<Actions and Effects>> As described above, the control device 163 according to the first embodiment functions as follows. The regenerative power calculation unit 205 calculates the regenerative power generated by the haulage vehicle 10. The control mode determination unit 207 determines whether the haulage vehicle 10 is traveling downhill. The control mode determination unit 207 determines the control mode of the fuel cell 143 based on the determination whether the haulage vehicle 10 is traveling downhill. If the control mode determination unit 207 determines that the haulage vehicle 10 is not traveling downhill, it determines the control mode of the fuel cell 143 to be the first mode. If the control mode determination unit 207 determines that the haulage vehicle 10 is traveling downhill, it determines the control mode of the fuel cell 143 to be the second mode. The fuel cell control unit 209 controls the amount of power generated by the fuel cell 143 in either the first mode, which outputs the reference generated power set by the reference generated power setting unit 202 or power greater than the reference generated power, or the second mode, which outputs the reference generated power set by the reference generated power setting unit 202 or power less than the reference generated power. As a result, when regenerative power is continuously generated by traveling downhill, the control device 163 can suppress the output of the fuel cell 143 so that the power generated by the fuel cell 143 does not become excessive. On the other hand, when regenerative power is temporarily generated due to braking, deceleration, etc. while not traveling downhill, the control device 163 does not suppress the output of the fuel cell 143. As a result, the control device 163 can suppress fluctuations in the output of the fuel cell 143 and prevent deterioration of the fuel cell 143.

[0055] In the first embodiment, when the control mode is the first mode, the first MIN block 224 outputs the value output by the MAX block 223. The MAX block 223 outputs the greater of the reference generated power set by the reference generated power setting unit 202, or the difference between the net required power and the maximum dischargeable power. In other words, in the first mode, when the sum of the reference generated power and the maximum dischargeable power is greater than the required power for operating the work vehicle, the fuel cell control unit 209 controls the amount of power generated by the fuel cell 143 to output the reference generated power. Furthermore, in the first mode, when the sum of the reference generated power and the maximum dischargeable power is less than the required power, the fuel cell control unit 209 controls the amount of power generated by the fuel cell 143 to output power greater than the reference generated power.

[0056] In the first embodiment, when the control mode is the second mode, the first MIN block 224 outputs the smaller of the value output by the MAX block 223 and the value output by the second subtraction block 222. Because the net required power is small when the haulage vehicle 10 is traveling downhill, the first MIN block 224 outputs the reference generated power set by the reference generated power setting unit 202. The second subtraction block 222 outputs the power that is the difference between the maximum chargeable power and the net regenerative power. In other words, in the second mode, when the sum of the reference generated power and the regenerative power is smaller than the maximum chargeable power of the battery 145, the fuel cell control unit 209 controls the amount of power generated by the fuel cell 143 to output the reference generated power. Furthermore, in the second mode, when the sum of the reference generated power and the regenerative power is greater than the maximum chargeable power of the battery 145, the fuel cell control unit 209 controls the amount of power generated by the fuel cell 143 to output power that is smaller than the reference generated power.

[0057] The control device 163 according to the first embodiment functions as follows: The required power calculation unit 204 determines the amount of power required to operate the haulage vehicle 10. When the sum of the reference generated power set by the reference generated power setting unit 202 and the maximum dischargeable power of the battery 145 is smaller than the required power, the fuel cell control unit 209 controls the amount of power generated by the fuel cell 143 to output power greater than the reference generated power. Specifically, when the sum of the reference generated power set by the reference generated power setting unit 202 and the maximum dischargeable power of the battery 145 is smaller than the required power, the fuel cell control unit 209 controls the amount of power generated by the fuel cell 143 to output power equal to the difference between the required power and the maximum dischargeable power of the battery 145. This allows the control device 163 to determine the power to be output by the fuel cell 143 so as not to cause a power shortage depending on the operating state of the haulage vehicle 10 or the state of the battery 145. In other embodiments, the fuel cell control unit 209 may control the amount of power generated by the fuel cell 143 to output power greater than the difference between the required power and the maximum dischargeable power of the battery 145. Furthermore, according to the control of the first embodiment, the output of the fuel cell 143 is changed less frequently than in the prime mover system, so that deterioration of the fuel cell 143 can be suppressed.

[0058] The control device 163 according to the first embodiment functions as follows. The regenerative power calculation unit 205 calculates the magnitude of regenerative power generated by the transport vehicle 10. When the sum of the reference power generation power of the fuel cell 143 set by the reference power generation power setting unit 202 and the regenerative power is greater than the maximum chargeable power of the battery 145, the fuel cell control unit 209 controls the amount of power generated by the fuel cell 143 to output power less than the reference power generation power or to stop power generation. Specifically, when the sum of the reference power generation power set by the reference power generation power setting unit 202 and the regenerative power is greater than the maximum chargeable power of the battery 145, the fuel cell control unit 209 controls the amount of power generated by the fuel cell 143 to output power equal to the difference between the maximum chargeable power and the regenerative power. This allows the control device 163 to determine the power to be output by the fuel cell 143 so as to prevent regeneration failure due to the power generated by the fuel cell 143. In other embodiments, the fuel cell control unit 209 may control the amount of power generated by the fuel cell 143 to output power less than the difference between the maximum dischargeable power of the battery 145 and the regenerative power. Furthermore, frequent switching between power generation and stopping by the fuel cell 143 and power generation in an extremely low output range can affect the deterioration of the fuel cell 143. Therefore, in another embodiment, when the difference between the maximum dischargeable power of the battery 145 and the regenerative power is zero or extremely low, the amount of power generated by the fuel cell 143 can be controlled so as to output a predetermined lower limit power that is less affected by the deterioration of the fuel cell 143. In this case, the magnitude of the power output by the fuel cell 143 can be greater than the difference between the maximum dischargeable power of the battery 145 and the regenerative power.

[0059] Second Embodiment The control device 163 according to the first embodiment determines whether the haulage vehicle 10 is traveling downhill based on measurement data of the inclination angle of the haulage vehicle 10. In contrast, the control device 163 according to the second embodiment determines whether the haulage vehicle 10 is traveling downhill based on measurement data of the position of the haulage vehicle 10 measured by GNSS (Global Navigation Satellite System).

[0060] The measurement device 161 according to the second embodiment includes at least a GNSS sensor, which measures the position of the transport vehicle 10 and the direction in which the transport vehicle 10 is facing. The position of the transport vehicle 10 is expressed in a world coordinate system. The direction in which the transport vehicle 10 is facing is determined, for example, by the deviation between positions measured by two antennas installed in different positions on the transport vehicle 10. The control device 163 also stores topographical data of the work site. The topographical data expresses a planar position in a world coordinate system and has height values.

[0061] The control mode determination unit 207 according to the second embodiment determines whether the haulage vehicle 10 is traveling downhill based on the measurement data from the GNSS sensor and the terrain data. Specifically, the control mode determination unit 207 identifies the position of the haulage vehicle 10 from the measurement data from the GNSS sensor. Next, the control mode determination unit 207 identifies the magnitude and direction of the gradient at the location where the haulage vehicle 10 is located from the terrain data. The gradient direction is a direction from a lower side to a higher side. If the magnitude of the gradient is equal to or less than a predetermined threshold, the control mode determination unit 207 determines that the haulage vehicle 10 is traveling on flat ground and determines the control mode to be the first mode. If the magnitude of the gradient exceeds the predetermined threshold, and the difference between the orientation of the haulage vehicle 10 and the direction of the gradient is within ±90 degrees, the control mode determination unit 207 determines that the haulage vehicle 10 is traveling uphill and determines the control mode to be the first mode. When the magnitude of the gradient exceeds a threshold value and the difference between the direction in which the transport vehicle 10 is facing and the direction of the gradient exceeds ±90 degrees, the control mode determination unit 207 determines that the transport vehicle 10 is traveling downhill and determines the control mode to be the second mode.

[0062] Third Embodiment A control device 163 according to a third embodiment determines whether the haulage vehicle 10 is traveling downhill based on the operation signal of the operation device 162 and measurement data of the speed and acceleration of the haulage vehicle 10.

[0063] The control mode determination unit 207 according to the third embodiment calculates the acceleration when traveling on flat ground from the accelerator pedal operation amount and measurement data of the speed of the haulage vehicle 10. If the value obtained by subtracting the measured acceleration of the haulage vehicle 10 from the acceleration when traveling on flat ground is greater than a predetermined negative threshold, the control mode determination unit 207 determines that the haulage vehicle 10 is traveling downhill and determines the control mode to be the second mode. On the other hand, if the value obtained by subtracting the measured acceleration of the haulage vehicle 10 from the acceleration when traveling on flat ground is equal to or less than a predetermined negative threshold, the control mode determination unit 207 determines that the haulage vehicle 10 is traveling on flat ground or uphill and determines the control mode to be the first mode.

[0064] <Computer Configuration> Fig. 6 is a schematic block diagram showing the configuration of a computer according to at least one embodiment. The computer 90 includes a processor 91, a main memory 92, a storage 93, and an interface 94. The control device 163 described above is implemented in the computer 90. The operations of each of the processing units described above are stored in the storage 93 in the form of a program. The processor 91 reads the program from the storage 93, loads it into the main memory 92, and executes the above-described processing in accordance with the program. The processor 91 also allocates storage areas in the main memory 92 corresponding to each of the storage units described above in accordance with the program. Examples of the processor 91 include a CPU (Central Processing Unit), a GPU (Graphic Processing Unit), and a microprocessor.

[0065] The program may be for implementing some of the functions to be performed by the computer 90. For example, the program may be implemented in combination with other programs already stored in storage or in combination with other programs implemented in other devices. In another embodiment, the computer 90 may include a custom large-scale integrated circuit (LSI) such as a programmable logic device (PLD) in addition to or instead of the above configuration. Examples of PLDs include programmable array logic (PAL), generic array logic (GAL), complex programmable logic device (CPLD), and field programmable gate array (FPGA). In this case, some or all of the functions implemented by the processor 91 may be implemented by the integrated circuit. Such an integrated circuit is also an example of a processor. In another embodiment, the computer 90 may be virtualized on one or more computers.

[0066] Examples of storage 93 include a magnetic disk, a magneto-optical disk, an optical disk, and a semiconductor memory. Storage 93 may be an internal medium directly connected to the bus of computer 90, or an external medium connected to computer 90 via interface 94 or a communication line. Furthermore, when this program is distributed to computer 90 via a communication line, computer 90 that receives the program may load the program into main memory 92 and execute the above-described processing. In at least one embodiment, storage 93 is a non-transitory tangible storage medium.

[0067] The program may also be a program for realizing part of the above-described functions. Furthermore, the program may be a so-called differential file (differential program) that realizes the above-described functions in combination with another program already stored in storage 93.

[0068] Other Embodiments Although one embodiment has been described in detail above with reference to the drawings, the specific configuration is not limited to the above, and various design modifications are possible. That is, in other embodiments, the order of the above-described processes may be changed as appropriate. Furthermore, some processes may be executed in parallel. The control device 163 according to the above-described embodiment may be configured by a single computer 90. Alternatively, the configuration of the control device 163 may be divided into multiple computers 90, and the multiple computers 90 may function as the control device 163 by cooperating with each other. In this case, some of the computers 90 constituting the control device 163 may be mounted inside the haulage vehicle 10, and other computers 90 may be provided outside the haulage vehicle 10. For example, when the haulage vehicle 10 according to other embodiments is remotely operated, components other than the fuel cell control unit 209 and the battery control unit 210 may be provided in the remote computer 90. Furthermore, when the haulage vehicle 10 is controlled by an external control device, the control device may determine whether the haulage vehicle 10 is traveling downhill.

[0069] Furthermore, although the reference generated power setting unit 202 of the control device 163 according to the embodiment described above sets the reference generated power based on the charging rate of the battery 145, this is not limitative. For example, in other embodiments, the reference generated power may be set independently of the charging rate of the battery 145.

[0070] Furthermore, the control mode determination unit 207 of the control device 163 according to the above-described embodiment may determine the control mode based on the duration of time that the generation of regenerative power continues. For example, in another embodiment, the control mode determination unit 207 may calculate a moving average value of the regenerative power calculated by the regenerative power calculation unit 205. The control mode determination unit 207 may determine the control mode to be the second mode when the moving average value of the regenerative power exceeds a predetermined threshold value continuously over a predetermined period of time. The control mode determination unit 207 may maintain the control mode in the first mode when the moving average value of the regenerative power does not exceed the threshold value and when a predetermined period of time has not elapsed since the moving average value of the regenerative power exceeded the threshold value.

[0071] Furthermore, although the transport vehicle 10 according to the embodiment described above is equipped with the retarder 147 that consumes surplus power, this is not limiting. For example, the transport vehicle 10 according to another embodiment may not be equipped with the retarder 147, and may consume surplus power by the electric pump motor 152 or an auxiliary device mounted on the transport vehicle 10.

[0072] In the above-described embodiment, the transport vehicle 10 such as a dump truck has been described as a work vehicle equipped with the fuel cell 143 and the battery 145, but the present invention is not limited to this. For example, the work vehicle according to other embodiments may be another work vehicle such as a hydraulic excavator, a bulldozer, a wheel loader, a crane, a forklift, or a motor grader.

[0073] According to the above aspect, the system can appropriately determine the power that should be output by the fuel cell mounted on the work vehicle.

[0074] DESCRIPTION OF SYMBOLS 10...Transport vehicle 11...Dump body 12...Vehicle body 13...Travel device 14...Power system 141...Hydrogen tank 142...Hydrogen supply device 143...Fuel cell 144...First power converter 145...Battery 146...Second power converter 147...Retarder 15...Drive system 151...Inverter 152...Electric pump motor 153...Hydraulic pump 154...Hoist cylinder 155...Inverter 156...Electric travel motor 16...Control system 161...Measuring device 162...Operation device 163...Control device 201...Data acquisition unit 202...Reference generated power setting unit 203...Vehicle body control unit 204...Required power calculation unit 205...Regenerative power calculation unit 206...Battery capacity determination unit 207...Control mode determination unit 208...Control amount determination unit 209...Fuel cell control unit 210...Battery control unit 221...First subtraction block 222...Second subtraction block 223...MAX block 224...First MIN block 225...Third subtraction block 226...Second MIN block 227...Addition block 228...Third MIN block 229...Fourth subtraction block 90...Computer 91...Processor 92...Main memory 93...Storage 94...Interface B...Bus

Claims

1. A system for controlling a work vehicle equipped with a fuel cell, comprising a control device, the control device determining whether the work vehicle is traveling downhill, and controlling the amount of power generated by the fuel cell based on the result of the determination.

2. The system described in claim 1, wherein the control device controls the amount of power generated by the fuel cell in a first mode when it is determined that the work vehicle is not traveling downhill, and controls the amount of power generated by the fuel cell in a second mode when it is determined that the work vehicle is traveling downhill.

3. The system according to claim 1, wherein the control device determines whether the work vehicle is traveling downhill based on the slope angle at which the work vehicle is located.

4. The system described in claim 2, wherein the work vehicle is equipped with a power storage device, the control device sets a reference generated power based on the charging rate of the power storage device, the first mode is a mode in which the fuel cell outputs the reference generated power or power greater than the reference generated power, and the second mode is a mode in which the fuel cell outputs the reference generated power or power less than the reference generated power.

5. The system described in claim 4, wherein the control device can cause the fuel cell to output the reference generated power only when the control device is in either the first mode or the second mode.

6. The system described in claim 4, wherein, when the mode is the first mode, the control device controls the amount of power generated by the fuel cell to output the reference generated power when the sum of the reference generated power and the maximum dischargeable power of the power storage device is greater than the required power for operating the work vehicle, and controls the amount of power generated by the fuel cell to output power greater than the reference generated power when the sum of the reference generated power and the maximum dischargeable power is less than the required power.

7. The system described in claim 4, wherein, when the mode is the second mode, the control device controls the amount of power generated by the fuel cell to output the reference generated power when the sum of the reference generated power and the regenerated power is smaller than the maximum chargeable power of the storage device, and controls the amount of power generated by the fuel cell to output power smaller than the reference generated power when the sum of the reference generated power and the regenerated power is greater than the maximum chargeable power.

8. A work vehicle comprising: a work implement; a traveling device; a fuel cell that generates power to drive the work implement and the traveling device; and a control device, wherein the control device determines whether the work vehicle is traveling downhill, and controls the amount of power generated by the fuel cell based on the result of the determination.

9. A method for controlling a work vehicle equipped with a fuel cell, comprising the steps of: determining whether the work vehicle is traveling downhill; and controlling the amount of power generated by the fuel cell based on the result of the determination.

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