Transport vehicle and control system

Abstract

Provided are a transport vehicle and a control system that enable the condition of a travelled road surface to be ascertained using a simple method. A dump truck comprises: a travel-use electric motor for driving rear wheels; a steering device for steering front wheels; an inverter for detecting an operation amount of the travel-use electric motor; a steering angle sensor for detecting the operation amount of the steering device; and a control device for calculating operation amounts of the travel-use electric motor and the steering device which serve to perform autonomous travel according to a target route and a target speed, and for performing travel control based on the calculated operation amounts. The control device has: a reference operation amount estimation unit that estimates a reference operation amount which is the operation amount of the steering device in a case where the travelled road surface is in a reference condition; an operation amount comparison unit that compares the reference operation amount estimated by the reference operation amount estimation unit with the calculated operation amount of the steering device; and a road surface condition determination unit that determines, on the basis of the comparison result from the operation amount comparison unit, whether the travelled road surface is more slippery than in the reference condition, and that outputs the determination result.

Description

Transport vehicles and control systems

[0001] The present invention relates to a transport vehicle and a control system.

[0002] Dump trucks, which are one type of transport vehicle, are used to transport ore and other materials in mines, for example. To explain in more detail, dump trucks load ore and other materials at a loading site, travel along a transport route, and discharge the ore and other materials at a dumping site. They then travel along the transport route back to the loading site. Dump trucks repeat this process many times.

[0003] Patent Document 1 discloses a control device that transmits instructions regarding autonomous driving of a dump truck. The control device transmits a target route and a target speed to the dump truck. A control device mounted on the dump truck calculates the operation amounts of the drive device and steering device for autonomous driving according to the target route and the target speed, and performs driving control based on the calculated operation amounts.

[0004] Japanese Patent Application Laid-Open No. 2020-157923

[0005] For example, the transport volume per unit time is used as an index representing the work efficiency of a transport vehicle. According to this index, increasing the speed of the transport vehicle improves the work efficiency of the transport vehicle. However, the speed of the transport vehicle is limited from the perspective of traveling safety. In particular, if the road surface becomes slippery due to weather conditions, the speed limit of the transport vehicle needs to be lowered. Therefore, in order to increase the work efficiency of the transport vehicle while ensuring the traveling safety of the transport vehicle, it is desirable to set the target speed of the transport vehicle after understanding the condition of the road surface.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a transport vehicle and a control system that can grasp the condition of the road surface on which the vehicle is traveling in a simple manner.

[0007] In order to achieve the above-mentioned object, a representative aspect of the present invention is a transport vehicle equipped with a drive unit for driving the rear wheels, a steering unit for steering the front wheels, a detector for detecting the operation amounts of the drive unit and the steering unit, and a control unit for calculating the operation amounts of the drive unit and the steering unit for autonomous driving according to a target route and a target speed, and for performing driving control based on the calculated operation amount, wherein the control unit has a reference operation amount estimation unit for estimating a reference operation amount which is the operation amount of at least one of the drive unit and the steering unit when the road surface being traveled is in a reference state, an operation amount comparison unit for comparing the reference operation amount estimated by the reference operation amount estimation unit with an operation amount of at least one of the drive unit and the steering unit which corresponds to the estimated reference operation amount and which has been calculated or detected by the detector, and a road surface condition determination unit for determining whether the road surface being traveled is more slippery than the reference state based on the comparison result of the operation amount comparison unit, and outputting the determination result.

[0008] According to the present invention, the condition of the road surface on which the vehicle is traveling can be grasped in a simple manner.

[0009] 1 is a diagram showing the configuration of a control system in a first embodiment of the present invention. FIG. 2 is a side view showing the structure of a dump truck in a first embodiment of the present invention. FIG. 3 is a block diagram showing equipment mounted on a dump truck in a first embodiment of the present invention. FIG. 4 is a diagram showing the relationship between the steering angle of the front wheels of a dump truck in a first embodiment of the present invention and the lateral force of the front wheels. FIG. 5 is a flowchart showing the road surface condition determination process of a control device for a dump truck in a first embodiment of the present invention. FIG. 6 is a flowchart showing the road surface condition determination process of a control device for a dump truck in a second embodiment of the present invention.

[0010] A first embodiment of the present invention will be described with reference to the drawings.

[0011] Fig. 1 is a schematic diagram showing the configuration of a control system in this embodiment. Fig. 2 is a side view showing the structure of a dump truck in this embodiment. Fig. 3 is a block diagram showing equipment mounted on the dump truck in this embodiment.

[0012] The control system of this embodiment includes a plurality of dump trucks 1 that transport ore or the like in a mine, for example, and a control device 3 that can communicate with the plurality of dump trucks 1 via a communication device 2.

[0013] The control device 3 is a computer, and has, as functional components, a road surface condition storage unit 4, a target route setting unit 5, and a target speed setting unit 6. The control device 3 transmits to each dump truck 1 the target route (e.g., map data) set by the target route setting unit 5 and the target speed set by the target speed setting unit 6 (more specifically, the target speed set for the entire target route, or a plurality of target speeds set for each of a plurality of sections into which the target route is divided).

[0014] The dump truck 1 includes a body frame 11, a loading platform 13 rotatably supported on the body frame 11 via support shafts 12, a hoist cylinder 14 for rotating the loading platform 13, a plurality of rear wheels 15 attached to the rear side of the body frame 11, and a plurality of front wheels 16 attached to the front side of the body frame 11. The loading platform 13 carries ore or the like. The loading platform 13 rotates about the support shafts 12 to discharge the ore or the like.

[0015] The dump truck 1 includes a traveling electric motor 17 that drives the rear wheels 15, an inverter 18 that detects and controls the operation amount (more specifically, braking / driving torque) of the traveling electric motor 17, and a speed sensor 19 that detects the speed of the dump truck 1. The inverter 18 detects and controls the braking / driving torque of the traveling electric motor 17 by detecting and controlling the power supplied to the traveling electric motor 17. The speed sensor 19 detects the speed of the dump truck 1 from the rotational speed of the rear wheels 15, for example.

[0016] The dump truck 1 includes a steering device 20 that steers the front wheels 16, a steering electric motor 21 that drives the steering device 20, and a steering angle sensor 22 that detects the amount of operation of the steering device 20 (more specifically, the steering angle of the front wheels 16). Although not shown in detail, the steering device 20 is made up of, for example, a steering hydraulic cylinder that varies the steering angle of the front wheels 16, a steering control valve that controls the flow of pressure oil from a hydraulic pump to the steering hydraulic cylinder, and a shaft that is rotated by the steering electric motor 21 and operates the steering control valve.

[0017] The dump truck 1 includes a position measurement device 23 that measures the position and orientation of the vehicle itself. The position measurement device 23 measures the position and orientation of the vehicle itself based on signals from a plurality of satellites, for example.

[0018] The dump truck 1 is equipped with a control device 25 that can communicate with the control device 3 via a communication device 24. Although not shown in detail, the control device 25 has a processor that executes processing according to a program, a memory that stores programs and data, etc. The control device 25 has a travel control unit 26 as a functional configuration.

[0019] The cruise control unit 26 of the control device 25 calculates operation amounts (more specifically, steering angle and braking / driving torque) of the steering device 20 and the traction electric motor 17 for autonomous driving in accordance with the target route and target speed received from the control device 3, and performs cruise control based on the calculated operation amounts. More specifically, the cruise control unit 26 of the control device 25 calculates the steering angle of the steering device 20 based on the target route and the position and orientation measured by the position measurement device 23, and controls the steering device 20 via the steering electric motor 21 based on the calculated steering angle and the steering angle detected by the steering angle sensor 22. The cruise control unit 26 of the control device 25 calculates the braking / driving torque (more specifically, positive driving torque or negative braking torque) of the traction electric motor 17 based on the target speed and the speed measured by the speed sensor 19, and controls the traction electric motor 17 via the inverter 18 based on the calculated braking / driving torque. In detail, the driving electric motor 17 is controlled to be driven in accordance with the calculated driving torque, or the driving electric motor 17 is controlled to be regeneratively driven in accordance with the calculated braking torque (in other words, the driving electric motor 17 is operated as a generator, and braking torque is generated by its rotational resistance).

[0020] A feature of this embodiment is that the control device 25 has a function of determining the state of the road surface on which the dump truck 1 is traveling, based on the steering angle calculated by the travel control unit 26 (or the steering angle detected by the steering angle sensor 22 (detector)). This function will be explained using Fig. 4(a) and Fig. 4(b). Fig. 4(a) is a diagram showing the steering angle and lateral force of the front wheels in this embodiment, and Fig. 4(b) is a diagram showing the relationship between the steering angle of the front wheels and the lateral force of the front wheels.

[0021] 4(a), the steering angle θ of the front wheels 16 is the angle (slip angle) between the traveling direction A of the dump truck 1 and the rotation direction B of the front wheels 16. A lateral force F of the front wheels 16 is generated in accordance with the steering angle θ of the front wheels 16, and a rotational moment is generated by the lateral force F of the front wheels 16 (more specifically, its component FL in the lateral direction of the vehicle body), causing the dump truck 1 to turn.

[0022] As shown in Figure 4(b), when the steering angle θ of the front wheels 16 is small, a lateral force F of the front wheels 16 is generated in approximately proportion to the steering angle θ, and when the steering angle θ of the front wheels 16 is large, the lateral force F of the front wheels 16 saturates. The lateral force F of the front wheels 16 changes depending on the condition of the road surface. When the road surface is in a reference state, the lateral force F of the front wheels 16 changes as shown by the solid line in Figure 4(b), and when the road surface is more slippery than the reference state, the lateral force F of the front wheels 16 changes as shown by the dashed line in Figure 4(b).

[0023] For example, assume that a lateral force F1 of the front wheels 16 is required to turn the dump truck 1, and consider the steering angle of the front wheels 16 to obtain this. When the road surface is in a reference state, the steering angle of the front wheels 16 is θ1, but when the road surface is more slippery than the reference state, the steering angle of the front wheels 16 is θ2 (where θ2 > θ1). Therefore, it is possible to determine the state of the road surface based on the steering angle θ of the front wheels 16.

[0024] Returning to FIG. 3 described above, the control device 25 further includes a reference operation amount estimating section 27, an operation amount comparing section 28, and a road surface condition determining section 29 as functional components.

[0025] The reference operation amount estimating unit 27 of the control device 25 estimates a reference steering angle of the steering device 20 as a reference operation amount, which is an operation amount when the traveling road surface is in a reference state. The reference operation amount estimating unit 27 calculates the reference steering angle every time the dump truck 1 moves, based on the traveling conditions (more specifically, the vehicle speed, the road surface gradient, the route curvature, etc.).

[0026] Alternatively, the reference operation amount estimation unit 27 may acquire and store in advance the relationship between the position of the dump truck 1 and the reference steering angle, and read out the reference steering angle corresponding to the position measured by the position measurement device 23. That is, for example, in response to a command from the control device 3, it may recognize that the traveling road surface is in a reference state, and in this case, the steering angle calculated by the traveling control unit 26 or the steering angle detected by the steering angle sensor 22 may be set as the reference steering angle, and stored in advance in association with the position measured by the position measurement device 23. Then, the pre-stored reference steering angle may be read out according to the position measured by the position measurement device 23.

[0027] An operation amount comparison unit 28 of the control device 25 compares the steering angle calculated by the cruise control unit 26 (or the steering angle detected by the steering angle sensor 22) with the reference steering angle estimated by the reference operation amount estimation unit 27. The steering angle calculated by the cruise control unit 26 may be a value averaged over time.

[0028] The road surface condition determination unit 29 of the control device 25 determines whether the road surface is more slippery than the reference state based on the comparison result of the operation amount comparison unit 28. That is, if the steering angle calculated by the cruise control unit 26 (or the steering angle detected by the steering angle sensor 22) is larger than the reference steering angle, the road surface is determined to be more slippery than the reference state, and if the steering angle calculated by the cruise control unit 26 (or the steering angle detected by the steering angle sensor 22) is smaller than the reference steering angle, the road surface is determined to be in the reference state. Note that the road surface may also be determined to be more slippery than the reference state if the steering angle calculated by the cruise control unit 26 (or the steering angle detected by the steering angle sensor 22) remains larger than the reference steering angle for a certain period of time.

[0029] Next, the road surface condition determination process of the control device 25 of the dump truck 1 in this embodiment will be described with reference to Fig. 5. Fig. 5 is a flowchart showing the road surface condition determination process of the control device of the dump truck in this embodiment.

[0030] In step S1 , the control device 25 of the dump truck 1 acquires the position of the vehicle measured by the position measuring device 23 .

[0031] Thereafter, the process proceeds to step S2, where the operation amount comparison unit 28 of the control device 25 of the dump truck 1 compares the steering angle calculated by the traveling control unit 26 (or the steering angle detected by the steering angle sensor 22) with the reference steering angle estimated by the reference operation amount estimation unit 27. The road surface condition determination unit 29 of the control device 25 of the dump truck 1 determines whether the traveling road surface is more slippery than the reference state based on the comparison result of the operation amount comparison unit 28.

[0032] Thereafter, the process proceeds to step S3, where the road surface condition determination unit 29 of the control device 25 of the dump truck 1 outputs the state of the traveling road surface determined in step S2 in association with the position acquired in step S1. That is, the control device 25 of the dump truck 1 transmits the determined state of the traveling road surface to the control device 3 in association with the position.

[0033] The road surface condition storage unit 4 of the control device 3 stores the state and position of the traveling road surface received from the dump truck 1. The target route setting unit 5 and target speed setting unit 6 of the control device 3 set a target route and target speed for each dump truck 1 based on the state and position of the traveling road surface stored in the road surface condition storage unit 4. In other words, the target speed is set lower for positions on the traveling road surface that are more slippery than the reference state, or the target route is set to avoid those positions.

[0034] As described above, in this embodiment, the state of the traveling road surface can be grasped using information obtained by the autonomous traveling control of the dump truck 1. Therefore, the state of the traveling road surface can be grasped in a simple manner without requiring a dedicated sensor for measuring the state of the traveling road surface.

[0035] A second embodiment of the present invention will be described. In this embodiment, the same parts as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted as appropriate.

[0036] In this embodiment, the control device 25 has a function of determining the state of the road surface on which the dump truck 1 travels, based on the braking / driving torque (more specifically, the positive driving torque or the negative braking torque) calculated by the travel control unit 26. To explain this function, for example, assume the acceleration required for the dump truck 1 and consider the driving torque required to obtain this acceleration. When the traveling road surface is in a reference state (in other words, the wheel slip ratio is low), the driving torque is D1. However, when the traveling road surface is more slippery than the reference state (in other words, the wheel slip ratio is high), the driving torque is D2 (where D2 > D1). Furthermore, for example, assume the deceleration required for the dump truck 1 and consider the braking torque required to obtain this deceleration. When the traveling road surface is in a reference state (in other words, the wheel slip ratio is low), the braking torque is B1. However, when the traveling road surface is more slippery than the reference state (in other words, the wheel slip ratio is high), the driving torque is B2 (where B2 < B1). Therefore, it is possible to determine the state of the traveling road surface based on the braking / driving torque.

[0037] The reference operation amount estimating unit 27 of the control device 25 stores the reference braking / driving torques (more specifically, the positive reference driving torque and the negative reference braking torque) of the traveling electric motor 17 as the reference operation amounts that are the operation amounts when the traveling road surface is in a reference state. The reference operation amount estimating unit 27 calculates the reference braking / driving torques based on the traveling conditions every time the dump truck 1 moves.

[0038] Alternatively, the reference operation amount estimating unit 27 may, for example, acquire and store in advance the relationship between the position of the dump truck 1 and the reference braking / driving torque, and read out the reference braking / driving torque corresponding to the position measured by the position measuring device 23. That is, in response to a command from the control device 3, it is recognized that the traveling road surface is in a reference state, and in this case the braking / driving torque calculated by the traveling control unit 26 is set as the reference braking / driving torque and stored in advance in association with the position measured by the position measuring device 23. Then, the pre-stored reference braking / driving torque may be read out according to the position measured by the position measuring device 23.

[0039] The operation amount comparison unit 28 of the control device 25 compares the braking / driving torque calculated by the travel control unit 26 with the reference braking / driving torque estimated by the reference operation amount estimation unit 27. The braking / driving torque calculated by the travel control unit 26 may be a time-series averaged value.

[0040] The road surface condition determination unit 29 of the control device 25 determines whether the road surface is more slippery than the reference state based on the comparison result of the operation amount comparison unit 28. That is, if the driving torque calculated by the driving control unit 26 is greater than the reference driving torque, the road surface is determined to be more slippery than the reference state. If the driving torque calculated by the driving control unit 26 is smaller than the reference driving torque, the road surface is determined to be in the reference state. Also, if the braking torque calculated by the driving control unit 26 is smaller than the reference braking torque, the road surface is determined to be in the reference state. Note that the road surface may be determined to be more slippery than the reference state if the driving torque calculated by the driving control unit 26 remains greater than the reference driving torque for a certain period of time. Alternatively, the road surface may be determined to be more slippery than the reference state if the braking torque calculated by the driving control unit 26 remains smaller than the reference braking torque for a certain period of time.

[0041] Next, the road surface condition determination process of the control device 25 of the dump truck 1 in this embodiment will be described with reference to Fig. 6. Fig. 6 is a flowchart showing the road surface condition determination process of the control device of the dump truck in this embodiment.

[0042] In step S1 , the control device 25 of the dump truck 1 acquires the position of the vehicle measured by the position measuring device 23 .

[0043] Thereafter, the process proceeds to step S4, where the operation amount comparison unit 28 of the control device 25 of the dump truck 1 compares the braking / driving torque calculated by the traveling control unit 26 with the reference braking / driving torque estimated by the reference operation amount estimation unit 27. The road surface condition determination unit 29 of the control device 25 of the dump truck 1 determines whether the traveling road surface is more slippery than the reference condition, based on the comparison result of the operation amount comparison unit 28.

[0044] Thereafter, the process proceeds to step S3, where the road surface condition determination unit 29 of the control device 25 of the dump truck 1 outputs the state of the traveling road surface determined in step S4 in association with the position acquired in step S1. That is, the control device 25 of the dump truck 1 transmits the determined state of the traveling road surface to the control device 3 in association with the position.

[0045] As described above, in this embodiment, the state of the traveling road surface can be grasped using information obtained by the autonomous traveling control of the dump truck 1. Therefore, the state of the traveling road surface can be grasped in a simple manner without requiring a dedicated sensor for measuring the state of the traveling road surface.

[0046] In the first embodiment, the control device 25 determines whether the road surface is more slippery than a reference state based on a comparison result between the steering angle of the steering device 20 and a reference steering angle, and in the second embodiment, the control device 25 determines whether the road surface is more slippery than a reference state based on a comparison result between the braking / driving torque of the traveling electric motor 17 (drive device) and a reference braking / driving torque, but the present invention is not limited to these. The control device 25 may determine whether the road surface is more slippery than a reference state based on a comparison result between the steering angle of the steering device 20 and a reference steering angle, and may also determine whether the road surface is more slippery than a reference state based on a comparison result between the braking / driving torque of the traveling electric motor 17 and the reference braking / driving torque. Then, based on the comparison result between the steering angle of the steering device 20 and the reference steering angle, it may be determined that the road surface is more slippery than the reference state, or based on the comparison result between the braking / driving torque of the traveling electric motor 17 and the reference braking / driving torque, it may be determined that the road surface is more slippery than the reference state.

[0047] Furthermore, in the first and second embodiments, the control device 25 has been described as determining whether the road surface is more slippery than the reference state based on the comparison result between the operation amount and the reference operation amount, but the slipperiness of the road surface may also be evaluated depending on the magnitude of the difference between the operation amount and the reference operation amount.

[0048] Furthermore, in the first and second embodiments, the dump truck 1 has been described as having a regenerative brake (i.e., the control device 25 regeneratively controls the traveling electric motor 17 in accordance with the calculated braking torque), but this is not limiting. The dump truck 1 may also have a hydraulic brake. In other words, the control device 25 may drive and control the hydraulic brake in accordance with the calculated braking torque.

[0049] Furthermore, in the first and second embodiments, the dump truck 1 has been described as having only the function of autonomously traveling according to the target route and target speed received from the control device 3, but this is not limiting. In addition to the above-mentioned functions, the dump truck 1 may have a function of traveling according to the operation of the occupant, and one of the functions may be selectable.

[0050] In the first and second embodiments, the transport vehicle to which the present invention is applied is described as a dump truck, but the present invention is not limited to this. The present invention may be applied to transport vehicles other than dump trucks.

[0051] REFERENCE SIGNS LIST 1 Dump truck 3 Control device 15 Rear wheels 16 Front wheels 17 Travel electric motor (drive device) 18 Inverter (detector) 20 Steering device 22 Steering angle sensor (detector) 25 Control device 27 Reference operation amount estimation unit 28 Operation amount comparison unit 29 Road surface condition determination unit

Claims

1. A transport vehicle equipped with a drive unit for driving the rear wheels, a steering unit for steering the front wheels, a detector for detecting the amounts of operation of the drive unit and the steering unit, and a control unit for calculating amounts of operation of the drive unit and the steering unit for autonomous driving according to a target route and a target speed, and for performing driving control based on the calculated amount of operation, wherein the control unit has: a reference operation amount estimating unit for estimating a reference operation amount which is the operation amount of at least one of the drive unit and the steering unit when the road surface being traveled is in a reference state; an operation amount comparing unit for comparing the reference operation amount estimated by the reference operation amount estimating unit with an operation amount of at least one of the drive unit and the steering unit which corresponds to the estimated reference operation amount and which has been calculated or detected by the detector; and a road surface condition determining unit for determining whether the road surface being traveled is more slippery than the reference state based on the comparison result of the operation amount comparing unit, and outputting the determination result.

2. A transport vehicle as described in claim 1, characterized in that the reference operation amount estimation unit estimates a reference steering angle of the steering device as the reference operation amount, and the operation amount comparison unit compares the steering angle of the steering device calculated or detected by the detector with the reference steering angle estimated by the reference operation amount estimation unit.

3. A transport vehicle as described in claim 1, characterized in that the reference operation amount estimation unit estimates a reference braking / driving torque of the drive unit as the reference operation amount, and the operation amount comparison unit compares the calculated braking / driving torque of the drive unit with the reference braking / driving torque estimated by the reference operation amount estimation unit.

4. A transport vehicle according to claim 1, wherein the reference operation amount estimating unit calculates the reference operation amount based on driving conditions.

5. A transport vehicle as described in claim 1, characterized in that the reference operation amount estimation unit stores the operation amount calculated or detected by a detector when the traveling road surface is in the reference state as a reference operation amount.

6. A control system comprising: a control device that transmits a target route and a target speed; and a transport vehicle equipped with a control device that receives the target route and the target speed, calculates operation amounts for the drive device and the steering device for autonomous driving in accordance with the target route and the target speed, and controls the drive device and the steering device based on the calculated operation amounts to perform driving control, wherein the control device of the transport vehicle has: a reference operation amount estimating unit that estimates a reference operation amount which is the operation amount of at least one of the drive device and the steering device when the road surface being traveled is in a reference state; an operation amount comparing unit that compares the reference operation amount estimated by the reference operation amount estimating unit with an operation amount of at least one of the drive device and the steering device which corresponds to the estimated reference operation amount and which has been calculated or detected by a detector of the transport vehicle; and a road surface condition determining unit that determines whether the road surface being traveled is more slippery than the reference state based on a comparison result of the operation amount comparing unit and outputs the determination result, and the control device sets the target route and the target speed based on a determination result of the road surface condition determining unit.

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