Driving force control device

Abstract

To provide a drive power control device that enables a vehicle to surely reach a destination even when an abnormality occurs in a part of driving sources.SOLUTION: A drive power control device includes: an abnormality detection unit configured to detect abnormalities in a plurality of driving sources; an external environment estimation unit configured to estimate a state of a road on which a vehicle travels after a certain time; and a drive power control unit configured to, when abnormalities in the driving sources are detected by the abnormality detection unit, for each of a plurality of road sections constituting a route to a destination, estimate drive power required to travel on the road sections for each of the plurality of driving sources except for one driving source based on estimation by the external environment estimation unit, estimate total drive power required to travel on the road sections based on an estimation result and specify a high-load driving source expected to be applied with high load during traveling on the road sections, and control the plurality of driving sources so that the drive power of the high-load driving source during traveling on the road sections is smaller than the estimated drive power on the high-load driving source when the total drive power is smaller than a first threshold value.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a driving force control device. [Background technology]

[0002] Conventionally, a driving force control device is known that, even if an abnormality such as a failure occurs in one of a plurality of electric motors, continues traveling by controlling the driving force of the other electric motors that are functioning normally (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-119647 Summary of the Invention [Problem to be solved by the invention]

[0004] The driving force control device described in Patent Document 1 may not provide the expected driving force if an overload is placed on the other electric motors that compensate for the driving force of the failed electric motor, and the vehicle may not be able to reach its destination.

[0005] The present invention aims to provide a driving force control device that can more reliably allow a vehicle to reach its destination even if an abnormality occurs in one of the driving sources without placing an overload on the other driving sources. [Means for solving the problem]

[0006] A driving force control device according to one aspect of the present invention is a driving force control device for a vehicle having multiple driving sources that generate driving force independently of each other, and comprises: an abnormality detection unit that detects abnormalities in the multiple driving sources; a route notification unit that notifies the vehicle of a route from the vehicle's current location to a destination; an external environment estimation unit that estimates the state of the road along which the vehicle will travel in a certain period of time; and, when an abnormality in at least one driving source is detected by the abnormality detection unit, for each of multiple road sections that make up the route to the destination, estimates the driving force required to travel on that road section for each of the multiple driving sources excluding the driving source in which the abnormality was detected based on the estimation by the external environment estimation unit, estimates the total driving force required to travel on that road section based on the result of the estimation, and identifies a high-load driving source from the multiple driving sources excluding the driving source in which the abnormality was detected that is expected to be under high load when traveling on that road section, and, if the total driving force is smaller than a first threshold, controls the multiple driving sources so that the driving force of the high-load driving source when traveling on that road section is smaller than the driving force estimated for the high-load driving source. [Effects of the Invention]

[0007] According to the present invention, a driving force control device can be provided that can more reliably allow a vehicle to reach its destination even if an abnormality occurs in one of the driving sources without placing an overload on the other driving sources. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of a vehicle equipped with a driving force control device according to a first embodiment. [Figure 2] FIG. 2 is a flowchart showing the overall processing of the driving force control device. [Figure 3] FIG. 3 is a schematic diagram showing an example of the driving force estimation process in step S202. [Figure 4] FIG. 4 is a schematic diagram showing an example of the control plan update process in steps S208 and S209. [Figure 5]FIG. 5 is a schematic diagram showing a modified example of the control plan update process in steps S208 and S209. [Figure 6] FIG. 6 is a schematic diagram showing an example of the planned driving route update process in step S206. DETAILED DESCRIPTION OF THE INVENTION

[0009] (First embodiment) A driving force control device according to an embodiment of the present invention will be described with reference to FIGS.

[0010] FIG. 1 is a schematic diagram showing the configuration of a vehicle 10 equipped with a driving force control device 20 according to a first embodiment. The vehicle 10 has a body equipped with the driving force control device 20, an accelerator pedal 40, a brake pedal 50, a steering wheel 60A, a steering mechanism 60B, and electric motors 70 (left front 70FL, right front 70Fr, left rear 70RL, and right rear 70Rr). These components are interconnected via a controller area network 90 (hereinafter referred to as CAN 90). In addition to the components described above, the vehicle 10 also has tires 80 (left front 80FL, right front 80Fr, left rear 80RL, and right rear 80Rr). The driving force control device 20 includes an abnormality detection unit 100 (left front 100FL, right front 100Fr, left rear 100RL, and right rear 100Rr), an external environment estimation unit 110, a route notification unit 120, and a driving force control unit 130. Other components and power wiring to each device are the same as those in a normal vehicle, but are not necessary for the explanation of the first embodiment, so illustrations and explanations thereof will be omitted.

[0011] An electric motor 70FL is connected to the front left tire 80FL of the vehicle, an electric motor 70Fr is connected to the front right tire 80Fr, an electric motor 70RL is connected to the rear left tire 80RL, and an electric motor 70Rr is connected to the rear right tire 80Rr. These four tires 80FL, 80Fr, 80RL, and 80Rr are collectively referred to as tires 80. Similarly, these four electric motors 70FL, 70Fr, 70RL, and 70Rr are collectively referred to as electric motors 70. Driving and braking torques are independently generated in the four tires 80 by the electric motors 70 provided for each tire 80. In other words, the four electric motors 70 are four driving sources that independently generate driving force. The driving force control device 20 drives the vehicle 10 by referring to input to the accelerator pedal 40 and causing the electric motors 70 of each wheel to generate driving force. The driving force control device 20 can adjust the driving force generated by the electric motor 70 depending on the driving conditions of the vehicle 10 and the like.

[0012] The driving force control device 20 changes the traveling direction of the vehicle 10 by turning the front wheels using the steering mechanism 60B in accordance with the input to the steering wheel 60A. The vehicle 10 shown in this embodiment is configured as a so-called by-wire system in which the steering wheel 60A and the steering mechanism 60B are connected by electric wires. The driving force control device 20 brakes the vehicle 10 by causing the electric motor 70 to generate a braking force in accordance with the input to the brake pedal 50. If the braking force provided by the electric motor 70 alone is insufficient, a friction brake is used or used in combination with the electric motor 70; however, this is not necessary for the description of the first embodiment and will not be illustrated or described here.

[0013] An abnormality detection unit 100FL is connected to the front left electric motor 70FL of the vehicle, an abnormality detection unit 100Fr is connected to the front right electric motor 70Fr, an abnormality detection unit 100RL is connected to the rear left electric motor 70RL, and an abnormality detection unit 100Rr is connected to the rear right electric motor 70Rr. These four abnormality detection units 100FL, 100Fr, 100RL, and 100Rr are collectively referred to as abnormality detection unit 100. The abnormality detection units 100 detect abnormalities in the electric motors 70 connected to them. The abnormalities detected by the abnormality detection unit 100 include, for example, a failure or malfunction of the electric motor 70, and include not only abnormalities that completely disable the electric motor 70 from being driven, but also abnormalities that disable the electric motor 70 from exerting its intended driving force. Well-known techniques can be used to detect abnormalities in the electric motor 70 using the abnormality detection unit 100. For example, when the resistance value of the armature coil of the electric motor 70 becomes higher than a predetermined threshold value, the abnormality detection unit 100 determines that a coil break, which is one type of abnormality of the electric motor 70, has occurred.

[0014] The external environment estimation unit 110 estimates the state of the road on which the vehicle 10 will travel in a certain time. The road state includes, for example, the congestion level of the road, the presence or absence of obstacles, the road shape, and the road surface condition. The congestion level of the road and the presence or absence of obstacles may be measured by various sensors such as sonar, radar, and LiDAR, or may be detected by a known image processing method on images captured by an on-board camera mounted on the vehicle 10. The road shape may be estimated by using data on gradients and turns in map data used in a car navigation system or the like, or by measuring with various sensors such as LiDAR, or by applying a known image processing method to images captured by an on-board camera mounted on the vehicle 10. The road surface condition may be estimated by applying a known image processing method to images captured by an on-board camera mounted on the vehicle 10, for example.

[0015] The route notification unit 120 notifies the driver of the route from the current location to the destination of the vehicle 10. The route notification unit 120 can search for the route from the current location of the vehicle 10 to the destination by using, for example, road data stored in a storage medium (not shown).

[0016] The driving force control unit 130 determines the driving force to be generated by each of the four electric motors 70, and controls the electric motors 70 to cause each of the electric motors 70 to generate the determined driving force. When the abnormality detection unit 100 detects an abnormality in at least one of the electric motors 70, the driving force control unit 130 performs control that is different from that when no abnormality is detected. The details of the control performed by the driving force control unit 130 will be described later.

[0017] Vehicle 10 according to the first embodiment may be a vehicle that is driven by a driver operating accelerator pedal 40, brake pedal 50, and steering wheel 60A, or may be a so-called autonomous vehicle that is driven by driving force control unit 130 along a route set in advance without following instructions from the driver. In the following description, vehicle 10 will be described as being driven by a driver.

[0018] Next, the flow of the driving force control process in the driving force control device 20 will be described using a flowchart.

[0019] 2 is a flowchart showing the overall processing of the driving force control device 20. In step S201, each abnormality detection unit 100 determines whether it has detected an abnormality, such as a failure or malfunction, in each electric motor 70. If each abnormality detection unit 100 has not detected an abnormality, the process proceeds to step S210, where the driving force control unit 130 does not change the driving force control plan and allows the vehicle 10 to continue traveling. If any abnormality detection unit 100 detects an abnormality, such as a failure or malfunction, the process proceeds from step S201 to step S202.

[0020] In process S202, the driving force control unit 130 estimates the driving force required by each electric motor 70 when traveling along each road section that constitutes the planned traveling route of the vehicle 10. Here, the planned traveling route is the route to the destination that was set by the route notification unit 120 before the occurrence of a breakdown or malfunction. In other words, in process S202, the driving force control unit 130 estimates the driving force required by each electric motor 70 to travel along each of the multiple road sections that constitute the route to the destination. The method of estimating driving force will be described later.

[0021] In the following process S203, the driving force control unit 130 estimates the total driving force required for traveling along each road section using the required driving force for each electric motor 70 estimated in process S202. The method for estimating the total driving force will be described later. In the next process S204, the driving force control unit 130 uses the required driving force for each electric motor 70 estimated in process S202 to identify electric motors 70 that are expected to be subjected to a high load in the subsequent traveling. Here, a high load means that the load amount (driving force required for traveling) exceeds a predetermined threshold. In the following description, the predetermined threshold used in process S203 for identifying electric motors 70 that are expected to be subjected to a high load is referred to as a high load threshold. Furthermore, the electric motor 70 identified in process S204 is referred to as a high-load electric motor 70. The high-load electric motor 70 is a different electric motor 70 from the electric motor 70 in which a malfunction, such as an abnormality or a failure, has been detected. The high-load electric motor 70 is expected to be subjected to a high load because an abnormality, such as a failure, has occurred in a specific electric motor 70.

[0022] In the next step S205, the driving force control unit 130 determines whether the total driving force estimated in step S203 will be equal to or greater than a predetermined threshold in any road section included in the planned travel route. In the following description, the predetermined threshold used in step S205 is referred to as the route update determination threshold. If it is determined that the total driving force will be equal to or greater than the route update determination threshold in any road section, the process proceeds to step S206. If it is determined that the total driving force is less than the route update determination threshold in all road sections, the process proceeds to step S208.

[0023] In step S206, the route notification unit 120 updates the planned driving route to a route in which the load of each electric motor does not exceed the high-load threshold in any road section. In the following step S207, the driving force control unit 130 plans control of the driving force of each electric motor in each road section that makes up the planned driving route. Then, the process proceeds to step S210.

[0024] In process S208, the driving force control unit 130 plans the control of the driving force of the high-load electric motor 70 in each road section that constitutes the planned travel route. Specifically, the driving force control unit 130 plans the control of the driving force so that the driving force of the high-load electric motor 70 when traveling on that road section is smaller than the required driving force of the high-load electric motor 70 estimated in process S202. In process S209, the driving force control unit 130 plans the control of the driving forces of the electric motors 70 other than the high-load electric motor 70 in each road section that constitutes the planned travel route. Instead of reducing the driving force of the high-load electric motor 70, the driving force control unit 130 plans the control of the driving force so that the driving force of any electric motor 70 for which no other abnormality has been detected is increased. This compensates for the decrease in driving force of the high-load electric motor 70 when traveling on that road section. The process then proceeds to process S210. The planning of the driving force control in processes S208 and S209 will be described later.

[0025] In step S210, the driving force control unit 130 controls the electric motor 70 in accordance with the planned driving force to make the vehicle 10 run.

[0026] FIG. 3 is a schematic diagram showing an example of the driving force estimation process (step S202) and the total driving force estimation process (step S203) performed by the driving force control unit 130. In the example shown in FIG. 3, the driving force (load) and total driving force required for each electric motor 70 are estimated based on the location of an electric motor 70 in which an abnormality, such as a breakdown or malfunction, has been detected and the curve radius and gradient of the road section along which the vehicle is traveling. The driving force control unit 130 according to this embodiment first estimates the driving forces of each of the four electric motors 70 using the method described below, and then calculates the sum of these driving forces as the total driving force. That is, for each of the multiple road sections along the route to the destination, the driving force control unit 130 estimates the driving force of each electric motor 70 required for traveling along that road section based on the estimation by the external environment estimation unit 110 from each electric motor 70, excluding the electric motor 70 in which an abnormality has been detected. Then, the driving force control unit 130 estimates the total driving force required for traveling along that road section.

[0027] Figure 3 shows an example of traveling on a road section with a right curve and an uphill gradient when a malfunction occurs in the left front electric motor 70FL. The numbers in Figure 3 represent the ratio of the driving force expected to be required by each electric motor 70 under each condition, assuming that the driving force of each electric motor 70 when traveling on a straight road with no gradient and all electric motors 70 are normal is 1.

[0028] First, let us consider the drive force of each electric motor 70 when traveling on a straight, flat road in the event of a failure in the front left electric motor 70FL. In the event of a failure in the front left electric motor 70FL, in order to maintain the straightness of the vehicle 10 and travel as normal without steering, the drive force of the electric motor 70RL mounted on the same side as the failed electric motor 70FL, i.e., the left rear electric motor 70RL, can be changed to 2 (FIG. 3(a)).

[0029] Next, let us consider the driving force of each electric motor 70 when traveling on a right-curve, flat road with all electric motors 70 functioning normally. In this case, it is necessary to rotate the electric motors 70FL and 70RL on the left side of the vehicle, which are on the outside of the curve, more than the electric motors 70Fr and 70Rr on the right side of the vehicle, which are on the inside of the curve. Therefore, when traveling on a right curve, the ratio of the driving force of the electric motors 70FL and 70RL on the left side of the vehicle is set to be greater than that of the electric motors 70Fr and 70Rr on the right side of the vehicle (Figure 3(b)). The opposite is true for a left curve.

[0030] Note that the value of the ratio of the required driving force in the right curve shown in Figure 3(b) is an example. Because the required driving force in a road section is affected by the curve radius of the road section, the ratio of the required driving force of each electric motor 70 according to the curve radius in each road section is desirably determined based on the road shape estimated by the external environment estimation unit 110. For example, the smaller the curve radius of the estimated road shape (in other words, the larger the curvature, or the smaller the turning radius of the vehicle 10), the larger the ratio of the driving force of the electric motor 70 on the outside of the curve and the smaller the ratio of the driving force of the electric motor 70 on the inside of the curve.

[0031] Next, let's consider the driving force of each electric motor 70 when traveling on a straight road with an upward gradient, assuming that all electric motors 70 are functioning normally. In this case, it is expected that the electric motors 70RL and 70Rr on the rear wheels, which are at the bottom of the gradient, will be subjected to a greater load than the electric motors 70FL and 70Fr on the front wheels, which are at the top of the gradient. Therefore, when traveling on an upward gradient road, the ratio of driving force of the electric motors 70RL and 70Rr on the rear side of the vehicle is set to be greater than that of the electric motors 70RL and 70Rr on the front side of the vehicle (FIG. 3(c)). The opposite is true when traveling on a downward gradient.

[0032] The values ​​of the ratios of the required driving force according to the gradient shown in Figure 3(c) are just an example. Because the required driving force in a road section is affected by the magnitude of the gradient of the road section, it is desirable to determine the ratio of the required driving force of each electric motor 70 according to the gradient of each road section based on the road shape estimated by the external environment estimation unit 110. For example, the greater the estimated gradient, the greater the ratio of the driving force.

[0033] 3, the driving force control unit 130 estimates the required driving force for each electric motor 70 in that road section as a value obtained by multiplying, for each electric motor 70, the ratio of the driving force expected to be required for each electric motor 70, which is determined based on the location of the failed electric motor 70, the curve radius of the road section (or the curvature of the road section, the turning radius of the vehicle 10, etc.), and the gradient of the road section. Specifically, as shown in FIG. 3(d), the driving force control unit 130 estimates the required driving force L of the left front electric motor 70F to be 0, the required driving force of the right front electric motor 70Fr to be 0.9, the required driving force of the left rear electric motor 70RL to be 2.64, and the required driving force of the right rear electric motor 70Rr to be 1.08.

[0034] The driving force control unit 130 adds up the required driving forces for each electric motor 70 estimated as described above to estimate the total driving force for that road section. For example, in the example shown in Figure 3(d), the total driving force for the road section being estimated is 0.9 + 2.64 + 1.08 = 4.62.

[0035] The process of identifying a high-load electric motor (process S204) by the driving force control unit 130 will now be described. The driving force control unit 130 compares the required driving force for each electric motor 70 (FIG. 3(d)) estimated as described above with the high-load threshold, and identifies an electric motor 70 whose required driving force is equal to or greater than the high-load threshold as an electric motor 70 expected to be subjected to a high load (i.e., a high-load electric motor). For example, if the high-load threshold is 2.5, then in the example shown in FIG. 3(d), the required driving force of the left rear electric motor 70RL is 2.64, which is greater than 2.5. In this case, the driving force control unit 130 identifies the left rear electric motor 70RL as a high-load electric motor.

[0036] FIG. 4 is a schematic diagram showing an example of the process of updating the driving force control plan for the electric motor 70 by the driving force control unit 130 (steps S208 and S209). FIG. 4(a) shows the driving force ratios of the electric motors 70 in the control plan before updating. The numerical values ​​shown in FIG. 4(a) are not applicable in practice because they were planned when no abnormality was detected in the electric motor 70FL. The driving control unit 130 sets the driving force of the high-load electric motor 70RL to a value less than the high-load threshold value. In the example of FIG. 4(b), a driving force ratio of 2.4, which is smaller than the high-load threshold value of 2.5, is set for the high-load electric motor 70RL.

[0037] When planning the driving forces of the electric motors 70Fr and 70Rr other than the high-load electric motor 70RL and the electric motor 70FL for which an abnormality has been detected, the driving force control unit 130 first adopts the required driving force estimated in step S202 of FIG. 2 as a candidate value. Next, the driving force control unit 130 increases the driving force of (at least one of) the other electric motors 70Fr and 70Rr by the amount corresponding to the reduction in the planned driving force of the high-load electric motor 70RL from the required driving force estimated in step S202, as described above, so that the required driving force for the entire vehicle 10 is achieved. In the example of FIG. 4(b), the driving force of the electric motor 70Fr is set to 1.04, which is higher than the estimated driving force of 0.9 shown in FIG. 3(d). Similarly, the driving force of the electric motor 70Rr is set to 1.18, which is higher than the estimated driving force of 1.08 shown in FIG. 3(d).

[0038] The planned driving route update process (process S206) by the route notification unit 120 will be described. The route from the current location to the destination can be determined by, for example, assigning a weight to each road section and adopting a route that minimizes the sum of the weights of the road sections that make up the route. The route notification unit 120 searches for a new planned driving route by using a route search algorithm such as the Dijkstra algorithm, including the required driving force estimated in the aforementioned process S202 as a weight, in addition to the length of the road section, speed limit, magnitude of turns and gradients, etc., which are commonly used as weights for road sections, so that the destination can be reached even if an abnormality occurs in one of the electric motors 70. Here, the required driving force included in the weight may be, for example, the required driving force of the high-load electric motor 70 in each road section, or the total driving force in each road section. Using the total driving force as a weight can improve the energy efficiency of the entire vehicle 10 and prevent battery exhaustion, etc. Alternatively, the planned driving route may be searched for so that the required driving force of all electric motors 70 is below a certain level (below a predetermined threshold) in all road sections that make up the planned driving route. It is desirable to notify the driver that the planned driving route has been updated, for example, by a message display or voice message.

[0039] When the estimated total driving force is smaller than the route change determination threshold, it means that the vehicle can travel along that road section without generating much driving force. For example, in a road section with a small gradient and a large curve radius (small curvature, large turning radius of the vehicle 10), the total driving force is relatively small, so it is highly likely that the total driving force will be less than the route update determination threshold. Conversely, in a road section with a large gradient or a small curve radius (large curvature, small turning radius of the vehicle 10), the total driving force is relatively large, so it is highly likely that the total driving force will be equal to or greater than the route update determination threshold.

[0040] When the estimated total driving force is smaller than the route change determination threshold, the total driving force can be achieved by suppressing the driving force of the high-load electric motor 70 and increasing the driving force of the other normal electric motors 70 accordingly. In contrast, when the estimated total driving force is equal to or greater than the route change determination threshold, suppressing the driving force of the high-load electric motor 70 makes it difficult to achieve the total driving force using only the other normal electric motors 70. In other words, suppressing the driving force of the high-load electric motor 70 requires increasing the driving force of the other electric motors 70 by that amount to achieve the required total driving force. However, if the increase is too great, the driving force of the other electric motors 70 may exceed the high-load threshold. Therefore, in this embodiment, when the total driving force is equal to or greater than the route change determination threshold, the route itself is changed, thereby controlling the driving forces of all electric motors 70 to be below the high-load threshold.

[0041] In addition, in a road section with a small gradient and a large curve radius (small curvature, large turning radius of the vehicle 10), if there is sufficient driving force from the other electric motors 70 that are normal, control may be performed to further reduce the driving force of the high-load electric motor 70.

[0042] FIG. 5 is a schematic diagram illustrating an example of further reducing the driving force of the high-load electric motor 70. As with FIG. 3, the numbers in FIG. 5 represent the ratio of the driving force expected to be required by each electric motor 70. FIG. 5(a) illustrates the maximum driving force in the control plan before the update, and FIG. 5(b) illustrates the maximum driving force in the control plan after the update. It can be seen that the maximum driving force required by the left rear high-load electric motor 70RL before the update was 2.05, whereas after the update, the maximum driving force required by the left rear high-load electric motor 70RL has decreased to 1.9. Conversely, it can be seen that the maximum driving force required by the right front electric motor 70Fr and the right rear electric motor 70Rr has increased from 0.95 to 1.05 and from 1.05 to 1.15, respectively. Therefore, under the updated control plan, the driving force (load) of the high-load electric motor 70RL is lower, and heat generation is also reduced. The corresponding decrease in driving force is compensated for by an increase in the driving force of the other electric motors 70Fr and 70Rr.

[0043] The high-load electric motor 70 requires a higher driving force than the other electric motors 70 and is expected to operate for a longer period of time, so the risk of failure is higher than when all electric motors 70 are operating normally. Therefore, as described above, in road sections where the driving force required for traveling is originally low, the risk of failure can be further reduced by planning control to reduce the driving force while maintaining the traveling stability of the vehicle 10. Note that when the control plan is changed as illustrated in FIG. 5, the turning of the vehicle 10 caused by the change can be offset by operating the steering wheel 60A (operating the steering mechanism 60B). This reduces the driving force of the high-load electric motor 70 while maintaining the straightness of the vehicle 10, preventing excessive overheating. When the control plan is updated in steps S208 and S209, the driving force control unit 130 may control the steering wheel 60A in this manner.

[0044] FIG. 6 is a schematic diagram illustrating an example of the planned travel route update process in step S206. As with FIG. 3, the numbers in FIG. 6 represent the ratio of the driving force expected to be required by each electric motor 70. FIG. 6(a) illustrates the maximum value of the required driving force for the planned travel route before updating, and FIG. 6(b) illustrates the maximum value of the required driving force for the planned travel route after updating. Before updating, the maximum value of the required driving force for the high-load electric motor 70RL was 2.75, exceeding the high-load threshold value of 2.5. In contrast, after updating, the maximum value of the required driving force for the high-load electric motor 70RL has decreased to 2.45, below the high-load threshold value. Furthermore, the maximum values ​​of the required driving force for the other electric motors 70 are also below the high-load threshold value. Therefore, on the new planned travel route, all electric motors 70 can travel without excessive load, and no electric motors 70 reach high temperatures that would interfere with travel.

[0045] According to the above-described embodiment, the following advantageous effects are achieved.

[0046] (1) When the abnormality detection unit 100 detects an abnormality in at least one electric motor 70, the driving force control unit 130 estimates the driving force required for traveling along each of the road sections constituting the route to the destination based on the estimation by the external environment estimation unit 110. The driving force control unit 130 then estimates the total driving force based on the estimated driving force and identifies a high-load electric motor expected to be subjected to a high load when traveling along the road section from among the electric motors 70, excluding the electric motor 70 for which the abnormality was detected. If the total driving force is less than the route update determination threshold (first threshold), the driving force control unit 130 controls the electric motors 70 so that the driving force of the high-load electric motor when traveling along the road section is less than the estimated driving force. Therefore, even if an abnormality such as a breakdown or failure occurs in one of the electric motors 70, the temperature of the electric motor 70 expected to be subjected to a high load is not excessively increased. In other words, according to this embodiment, even if an abnormality occurs in one of the driving sources, the vehicle can continue traveling without overloading the other driving sources, allowing the vehicle to more reliably reach the destination.

[0047] (2) When an abnormality is detected in at least one electric motor 70, the driving force control unit 130 controls the multiple electric motors 70 so that the driving force of the high-load electric motor 70 during travel on each road section is smaller than the estimated driving force, and so that the driving force of at least one of the electric motors 70 other than the electric motor 70 for which the abnormality has been detected and the high-load electric motor 70 is larger than the estimated driving force. In this way, even if an abnormality such as a breakdown or failure occurs in one of the electric motors 70, it is possible to achieve the total driving force required for travel while reducing the temperature of the electric motor 70 that is expected to be under a high load, and to more reliably continue travel to the destination.

[0048] (3) When an abnormality is detected in at least one electric motor 70, the driving force control unit 130 estimates the total driving force according to the position of that electric motor 70 in the vehicle 10. This makes it possible to accurately estimate the total driving force and the driving force required for each electric motor 70.

[0049] (4) The driving force control unit 130 estimates the total driving force based on the shape of the road section. This makes it possible to more accurately estimate the total driving force and the driving force required for each electric motor 70.

[0050] (5) When an abnormality is detected in at least one electric motor 70, and the driving force control unit 130 estimates that the estimated total driving force in any of the multiple road sections is greater than the route update determination threshold, the route notification unit 120 notifies the vehicle of a new route from the current location to the destination in which the driving forces required by each of the multiple electric motors 70 are estimated to be equal to or less than the high-load threshold. This makes it possible to avoid traveling on road sections requiring a large total driving force, and to more reliably continue traveling to the destination.

[0051] (Second embodiment) A driving force control device 20 according to a second embodiment of the present invention will be described. Components that are the same as or equivalent to those described in the first embodiment will be given the same reference symbols, and differences will be mainly described.

[0052] The driving force control unit 130 according to this embodiment controls the driving force taking into account traffic congestion in road sections. This is because the actual driving force required for each electric motor 70 in each road section estimated in step S202 of FIG. 2 may differ from the driving force required for each electric motor 70 in each road section due to factors such as traffic congestion in each road section. For example, if traffic congestion occurs during travel according to the driving force required for each electric motor 70 in each road section estimated in step S202, the driving force required for travel will be smaller than when the road is not congested. Therefore, the driving force control unit 130 according to this embodiment reduces the driving force of the high-load electric motor 70 identified in step S203 as being expected to have a high load when traveling on a road section estimated by the external environment estimation unit 110 to be congested, compared to the driving force control unit 130 according to the first embodiment. The driving force control unit 130 also controls steering by the steering wheel 60A (or steering by the steering mechanism 60B) to prevent the vehicle 10 from becoming unstable due to the reduction in driving force of the high-load electric motor 70. Specifically, when the vehicle 10 is likely to turn in the direction where the high-load electric motor 70 is located due to a reduction in the driving force of the high-load electric motor 70, the steering of the vehicle 10 is controlled in the opposite turning direction so as to prevent the vehicle 10 from turning.

[0053] According to the second embodiment described above, in addition to the effects achieved by the first embodiment, the following effects are further achieved.

[0054] (1) When the external environment estimation unit 110 estimates that a traffic jam is occurring on a road, the driving force control unit 130 controls the multiple electric motors 70 and also controls the steering of the vehicle 10 so as to prevent the vehicle 10 from turning due to the control. In this way, the load and heat generated by the high-load electric motor 70 can be effectively reduced when a traffic jam occurs.

[0055] (Third embodiment) A driving force control device 20 according to a third embodiment of the present invention will be described. Components that are the same as or equivalent to those described in the second embodiment will be given the same reference symbols, and differences will be mainly described.

[0056] Like the driving force control unit 130 according to the second embodiment, the driving force control unit 130 according to the present embodiment controls the driving force taking into account congestion in road sections. When the driver is driving the vehicle 10, the vehicle may deviate from the planned driving route found in step S206 of FIG. 2. In this case, the route notification unit 120 according to the present embodiment searches for a planned driving route to the destination in step S205, using the point where the deviation from the planned driving route is detected as a new starting point. The driving force control unit 130 then re-plans the driving force of each electric motor 70 for each road section on the planned driving route in step S207.

[0057] Furthermore, while the driver is driving the vehicle 10, the driver may attempt to generate a driving force greater than the driving force required for each electric motor 70 for each road section, as planned in step S207. For example, if the road section being traveled is not congested, the driver may attempt to accelerate the vehicle 10 by depressing the accelerator pedal 40 more deeply than the driving force control unit 130 expects. If such acceleration is attempted when an abnormality, such as a failure or malfunction, occurs in one of the electric motors 70, a load greater than the driving force control unit 130 expects will be applied to the high-load electric motor identified in step S203 as being expected to be subjected to a high load. As a result, the high-load electric motor generates a large amount of heat, making it impossible to generate the expected driving force, which may result in the vehicle not being able to reach its destination.

[0058] Therefore, when the driver operates the accelerator pedal 40 in a manner that causes any part of the electric motor 70 to generate a driving force equal to or greater than the high load threshold while the abnormality detection unit 100 detects an abnormality in the electric motor 70, the driving force control unit 130 according to this embodiment notifies the driver that an abnormality such as a failure or malfunction of the electric motor 70 has been detected and that the driving force control unit 130 is performing control that is different from normal. The notification may be performed, for example, by displaying a message such as "Acceleration is being limited due to a motor abnormality" on a display device (not shown) or by playing an audio message from a speaker device (not shown). The driving force control unit 130 notifies the driver and controls the electric motor 70 so that the driving force equal to or greater than the high load threshold is not generated in the electric motor 70 due to the operation of the accelerator pedal 40.

[0059] According to the above-described third embodiment, in addition to the effects achieved by the first embodiment, the following effects are further achieved.

[0060] (1) If the vehicle 10 deviates from the route to the destination while an abnormality is detected in at least one of the electric motors 70, the route notification unit 120 notifies the vehicle 10 of a new route to the destination. This allows the vehicle 10 to reliably reach the destination even when the vehicle deviates from the route.

[0061] (2) When an abnormality is detected in at least one electric motor 70 and the driver of the vehicle 10 performs an operation to cause one of the multiple electric motors 70 to generate a driving force equal to or greater than the high load threshold (second threshold), the driving force control unit 130 functions as an abnormality notification unit that notifies the driver that the driving force control unit 130 is performing control that is different from normal due to the detected abnormality. The driving force control unit 130 controls the multiple electric motors 70 so that such an operation does not cause the multiple electric motors 70 to generate a driving force equal to or greater than the high load threshold (second threshold). In this way, excessive load and heat generation do not occur even when the driver accelerates, and the vehicle can reliably reach its destination.

[0062] (Fourth embodiment) A driving force control device 20 according to a fourth embodiment of the present invention will be described. Components that are the same as or equivalent to those described in the first embodiment will be given the same reference symbols, and differences will be mainly described.

[0063] The driving force control unit 130 according to this embodiment performs control different from that of the above-described embodiments when a road section in which the curvature and gradient are smaller than predetermined thresholds continues for a certain distance or longer while the vehicle 10 is traveling while an abnormality such as a failure or malfunction is detected in one of the electric motors 70. Specifically, in such a case, the driving force control unit 130 first prompts the driver to steer the vehicle 10 to cool the high-load electric motors 70. For example, a message such as "Please turn the steering wheel to the right" may be displayed on a display device (not shown) or a sound may be played from a speaker device (not shown). When the driver steers the vehicle 10 in accordance with this notification, the driving force control unit 130 controls the vehicle 10 to reduce the driving force of each electric motor 70 in accordance with the steering operation to promote cooling of the high-load electric motors 70. The driving force control unit 130 similarly prompts the driver to return the steering to its original position a certain time or more before the vehicle 10 finishes traveling on the road section. When the driver returns the steering to its original position in accordance with the notification, the driving force control unit 130 returns the driving force control of each electric motor 70 to its original position to avoid a sharp turn.

[0064] Instead of prompting the driver to steer, the system may ask the driver whether to automatically control the steering and the driving force of the electric motor 70. If the driver allows the execution of such control, the driving force control unit 130 reduces the driving force of the high-load electric motor 70 while maintaining the straight-line running ability of the vehicle 10, and automatically controls the driving force and steering of the other electric motors 70. The driving force control unit 130 may notify the driver that the automatic control will end a certain amount of time before the end of the road section, and may return the vehicle to normal operation by the driver.

[0065] According to the above-described fourth embodiment, in addition to the effects achieved by the first embodiment, the following effects are further achieved.

[0066] (1) When an abnormality is detected in at least one electric motor 70, the driving force control unit 130 controls the steering of the vehicle 10 together with the plurality of electric motors 70. This makes it possible to more effectively reduce the load and heat generated by the high-load electric motor 70, thereby improving the reliability of the vehicle.

[0067] (2) If an abnormality is detected in at least one electric motor 70 and the total driving force is less than the route update determination threshold, the driving force control unit 130 controls the multiple electric motors 70 so that the driving force of the high-load electric motor 70 when traveling on the road section is less than the driving force estimated for the high-load electric motor 70, thereby causing the vehicle 10 to reach the destination without relying on operation by the driver of the vehicle 10. In this way, the vehicle can be reliably caused to reach the destination without bothering the driver.

[0068] (3) When the external environment estimation unit 110 estimates that a road with a curvature and gradient below a certain level continues for a certain distance or more while an abnormality is detected in at least one electric motor 70, the driving force control unit 130 notifies the driver of the vehicle 10 to steer the vehicle 10 so as to reduce the maximum driving force among the driving forces to be generated by the electric motors 70 while traveling on the road, and also functions as a steering notification unit that notifies the driver to return the steering to the state before traveling on the road a certain time before traveling on the road ends. This makes it possible to more effectively reduce the load and heat generated by the high-load electric motor 70 while avoiding sharp turns, thereby improving vehicle reliability.

[0069] (4) When the external environment estimation unit 110 estimates that a road with a certain degree of turning and gradient or less continues for a certain distance or more in a state where an abnormality has been detected in at least one electric motor 70, the driving force control unit 130 controls the steering of the plurality of electric motors 70 and the vehicle 10 without the operation of the driver of the vehicle 10 while traveling on that road, and notifies the driver of the vehicle 10 of this fact. In this way, the vehicle can be reliably driven to its destination without bothering the driver.

[0070] The following modified examples are also within the scope of the present invention, and it is possible to combine the configuration shown in the modified example with the configuration described in the above embodiment, to combine the configurations described in the different embodiments above, or to combine the configurations described in the different modified examples below.

[0071] <Variation 1> The driving force control device 20 may further include a function as a driving extraction unit that extracts the driving tendency of the driver. In the above embodiment, the electric motor 70 expected to be under high load was identified using the ratio of driving force expected to be required for each electric motor 70 based on the position of the electric motor 70 where the abnormality was detected, the curvature of the road section, and the gradient. However, for example, a driving tendency extraction unit may be further provided that extracts driving operation tendencies such as sudden acceleration, sudden deceleration, and sharp turns from the driver's past driving history, and the ratio of driving force expected to be required for each electric motor 70 may be set in accordance with the shape of each road section based on the driving operation tendencies extracted by the driving tendency extraction unit. This allows for more flexible control tailored to the driver's characteristics.

[0072] <Variation 2> If the re-search process for the planned driving route in step S206 does not find a route on the road section of the planned driving route where the estimated driving force required does not exceed a predetermined threshold, the driver may be notified that it will be difficult to reach the destination with the electric motor 70 broken or missing, and may be prompted to change the destination to a location where the electric motor 70 can be repaired, such as the nearest dealership, on which the estimated driving force required for each of the multiple electric motors 70 on the road section is estimated to be equal to or less than a predetermined threshold (e.g., a high-load threshold). Furthermore, if it is difficult to reach a dealership on the road section of the route where the estimated driving force required for each of the multiple electric motors 70 on the road section is estimated to be equal to or less than a predetermined threshold, the driver may be notified that it will be difficult to reach not only the destination but also a location where repairs can be made, such as the dealership, and may be prompted to change the destination to a reachable location where the electric motor can be stopped safely. Examples of a location where the electric motor can be stopped safely include a shoulder strip with sufficient width, an emergency parking lane, a waiting area, etc. The place where the vehicle can be stopped safely may be identified by the external environment estimation unit 110 using camera information or the like, or by the route notification unit 120 using map information or the like. In this way, even in a situation where a route cannot be found, the vehicle and the driver can be reliably placed in a safe situation.

[0073] The components of the driving force control device 20, as well as their functions and execution processes, may be partially or entirely implemented by hardware (for example, by designing logic for executing each function using an integrated circuit). The components of the driving force control device 20 may also be implemented as a program (software) that is read and executed by an arithmetic processing device (for example, a CPU) to implement the functions of the components of the driving force control device 20. Information related to the program can be stored in, for example, a semiconductor memory (flash memory, SSD, etc.), a magnetic storage device (hard disk drive, etc.), or a recording medium (magnetic disk, optical disk, etc.).

[0074] Although the embodiments of the present invention have been described above, the above embodiments merely illustrate some of the application examples of the present invention, and it is not intended that the technical scope of the present invention be limited to the specific configurations of the above embodiments. [Explanation of symbols]

[0075] 10...vehicle, 20...driving force control device (abnormality detection unit, external environment estimation unit, route notification unit, driving force control unit, abnormality notification unit, driving tendency extraction unit), 40...accelerator pedal, 50...brake pedal, 60...steering wheel, 60B...steering mechanism, 70, 70FL, 70Fr, 70RL, 70Rr...electric motor, 80, 80FL, 80Fr, 80RL, 80Rr...tires, 90...controller area network, 100, 100FL, 100Fr, 100RL, 100Rr...abnormality detection unit, 110...external environment estimation unit, 120...route notification unit, 130...driving force control unit

Claims

1. A driving force control device for a vehicle having a plurality of driving sources that generate driving forces independently of each other, an abnormality detection unit that detects an abnormality in the plurality of drive sources; a route notification unit that notifies the user of a route from the current location of the vehicle to a destination; an external environment estimation unit that estimates the state of a road on which the vehicle will travel after a certain time; a driving force control unit that, when an abnormality is detected in at least one of the driving sources by the abnormality detection unit, estimates, for each of a plurality of road sections constituting the route to the destination, a driving force required for traveling in that road section for each of the plurality of driving sources excluding the driving source in which the abnormality was detected, based on the estimation by the external environment estimation unit, estimates a total driving force required for traveling in that road section based on the estimation result, and identifies a high-load driving source that is expected to be under a high load when traveling in that road section from the plurality of driving sources excluding the driving source in which the abnormality was detected, and, when the total driving force is smaller than a first threshold value, controls the plurality of driving sources so that the driving force of the high-load driving source when traveling in that road section is smaller than the driving force estimated for the high-load driving source; A driving force control device comprising:

2. 2. The driving force control device according to claim 1, When the total driving force is smaller than the first threshold value, the driving force control unit controls the multiple driving sources so that the driving force of the high-load driving source when traveling on the road section is smaller than the driving force estimated for the high-load driving source, and so that the driving force of another driving source that is neither the driving source in which the abnormality has been detected nor the high-load driving source is larger than the driving force estimated for that driving source.

3. 3. The driving force control device according to claim 2, The driving force control unit is a driving force control device that controls steering of the vehicle together with the plurality of driving sources when an abnormality is detected in one of the driving sources.

4. 4. The driving force control device according to claim 3, The driving force control device is configured to estimate the total driving force in accordance with a position of the one driving source in the vehicle when an abnormality is detected in the one driving source.

5. 5. The driving force control device according to claim 4, The driving force control unit is a driving force control device that estimates the total driving force based on the shape of the road section.

6. 6. The driving force control device according to claim 5, The route notification unit is a driving force control device that, when an abnormality is detected in one of the driving sources and the driving force control unit estimates that the total driving force estimated in any of the multiple road sections is greater than the first threshold, notifies the driver of a new route from the current location to the destination in which the driving forces required for each of the multiple driving sources are estimated to be less than a predetermined threshold.

7. 7. The driving force control device according to claim 6, The driving force control device, wherein the route notification unit notifies the driver of a location where the one driving source can be repaired as a new destination when the new route does not exist.

8. 7. The driving force control device according to claim 6, If the new route does not exist, the route notification unit notifies the driver of a location where the vehicle can be safely stopped and which can be reached via a route where the driving forces required by each of the multiple driving sources are estimated to be below a predetermined threshold as a new destination.

9. The driving force control device according to any one of claims 1 to 8, The driving force control unit controls the plurality of driving sources when the external environment estimation unit estimates that a traffic jam is occurring on the road, and also controls the steering of the vehicle so as to prevent the vehicle from turning due to the control.

10. The driving force control device according to any one of claims 1 to 8, The route notification unit is a driving force control device that, when the vehicle deviates from the route to the destination while an abnormality is detected in one of the driving sources, notifies the driver of either a new route to the destination, a new route having a destination of a location where the one driving source can be repaired, or a new route having a destination of a location where the vehicle can be stopped safely.

11. The driving force control device according to any one of claims 1 to 8, and an abnormality notification unit that, when an abnormality in one of the driving sources is detected and a driver of the vehicle performs an operation to cause one of the plurality of driving sources to generate a driving force equal to or greater than a second threshold, notifies the driver that the abnormality has been detected and the driving force control unit is performing control that is different from normal, The driving force control unit is a driving force control device that controls the plurality of driving sources so that the operation does not generate a driving force equal to or greater than the second threshold value in the plurality of driving sources.

12. The driving force control device according to any one of claims 1 to 8, When an abnormality in one of the driving sources is detected and the total driving force is smaller than the first threshold value, the driving force control unit controls the multiple driving sources so that the driving force of the high-load driving source when traveling on the road section is smaller than the driving force estimated for the high-load driving source, thereby allowing the vehicle to reach the destination without operation by the driver of the vehicle.

13. The driving force control device according to any one of claims 1 to 8, a steering notification unit that, when the external environment estimation unit estimates that a road with a curvature and gradient below a certain level continues for a certain distance or more in a state in which an abnormality is detected in one of the drive sources, notifies the driver of the vehicle to perform steering that can reduce the maximum drive force among the drive forces to be generated by the multiple drive sources while traveling on that road, and notifies the driver to return the steering to the state it was before traveling on that road a certain time before traveling on that road ends.

14. The driving force control device according to any one of claims 1 to 8, When the external environment estimation unit estimates that a road with a curvature and gradient below a certain level will continue for a certain distance or more in a state in which an abnormality is detected in one of the driving sources, the driving force control unit controls the multiple driving sources and the steering of the vehicle while traveling on that road without the operation of the driver of the vehicle, and notifies the driver of the vehicle of this.

15. The driving force control device according to any one of claims 1 to 8, The vehicle further includes a driving tendency extraction unit that extracts driving tendencies of the driver from a past driving operation history of the driver of the vehicle, The driving force control unit is a driving force control device that estimates the total driving force based on the driving tendency of the driver extracted by the driving tendency extraction unit.

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