Parking assistance device and method

Abstract

To precisely prohibit a vehicle from riding over a comparatively high step, according to a wheel contacting with the step when the wheel contacts with the step on a road surface during parking assistance.SOLUTION: A controller 10 of a parking assisting system 100 controls drive torque and brake torque applied to a vehicle so as to move and stop a vehicle for parking assistance of a vehicle 1, and determines whether a wheel contacting with a step is a driving wheel or a driven wheel, when the wheel contacts with the step on a road surface in the parking assist. Especially, the controller 10, when the wheel contacts with the step, applies drive torque to the vehicle so that the vehicle rides over the step, and on the other hand, limits the driving torque applied to the vehicle to be less than predetermined limited torque so as to prohibit the vehicle from riding over a step that is a limited height or more, changes the limited torque applied to the drive torque depending on whether the wheel contacting the step is the driving wheels or the driven wheel.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present invention relates to a parking assistance device and method for assisting in parking a vehicle. [Background technology]

[0002] Conventionally, there has been known a technology (i.e., automatic parking) that controls a vehicle to automatically move to a specified space and stop the vehicle in order to assist parking of the vehicle. For example, Patent Document 1 discloses a technology in which, when a vehicle comes into contact with a step on the road surface while moving toward a parking space, if the wheel that hits the step is a driven wheel (non-driven wheel), the vehicle is temporarily moved in the opposite direction to the direction in which it should move, so that the vehicle can get a running start and overcome the step. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-066329 A Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, when assisting a vehicle in parking, if there is a step on the road surface, it is desirable to perform parking assistance so as to ensure that the vehicle can quickly get over a relatively low step, while prohibiting the vehicle from getting over a relatively high step. The latter is done in order to prevent the vehicle from going over a wheel stopper or the like. One method for achieving this is to limit the drive torque applied when the vehicle tries to get over a step to less than a predetermined limit torque according to the height of the step that prohibits the vehicle from getting over (for example, 70 to 80 mm or more). In other words, the limit torque is set based on the height of the step that prohibits the vehicle from getting over, and the drive torque is controlled so that the drive torque applied when the vehicle tries to get over the step does not exceed this limit torque.

[0005] The limit torque applied to the drive torque when going over such a step is desirably set to an appropriate value from the viewpoint of ensuring both the quick going over of a relatively low step and the prohibition of going over a relatively high step. In other words, it is not desirable to set the limit torque to a value that is too large or too small. In particular, the inventors have considered that in order to set the limit torque to an appropriate value, the limit torque to be applied should be changed depending on the wheel (i.e., the driving wheel or the driven wheel) that contacts the step. This is because the drive torque required to go over the step, even if the step is of the same height, differs depending on whether the wheel that goes over the step is a driving wheel or a driven wheel. This difference is considered to be caused by, for example, the load on the driving wheel and the load on the driven wheel, i.e., the front wheel load and the rear wheel load (depending on the front-rear weight distribution of the vehicle), etc.

[0006] Incidentally, the above-mentioned Patent Document 1 only describes a technique for enabling a vehicle to overcome a step in a reliable manner, and does not state anything about prohibiting a vehicle from overcoming a step.

[0007] The present invention has been made to solve the above-mentioned problems, and has an object to provide a parking assistance device and method that, when a wheel comes into contact with a step on the road surface during parking assistance, can accurately prohibit a vehicle from climbing over a relatively high step depending on the wheel that comes into contact with the step. [Means for solving the problem]

[0008] In order to achieve the above-mentioned object, the present invention is a parking assistance device comprising: a control unit configured to control a driving torque and a braking torque applied to a vehicle to move and stop the vehicle in order to assist in parking the vehicle in a specified space; and a judgment unit configured to determine whether a wheel of the vehicle contacts a step on a road surface when parking assistance is being provided by the control unit, the wheel contacting the step being a driving wheel or a driven wheel; the control unit is configured to apply a driving torque to the vehicle when a wheel of the vehicle contacts a step on the road surface so that the vehicle overcomes the step, while limiting the driving torque applied to the vehicle to less than a predetermined limit torque so as to prohibit the vehicle from climbing over a step that is equal to or greater than a limit height, and is configured to change the limit torque applied to the driving torque applied to the vehicle depending on whether the judgment unit determines that the wheel contacting the step is a driving wheel or a driven wheel.

[0009] According to the present invention configured as described above, the control unit changes the limit torque applied to the drive torque applied to the vehicle to make the vehicle overcome the step, depending on whether the wheel in contact with the step is determined by the determination unit to be a drive wheel or a driven wheel. This makes it possible to accurately prohibit the vehicle from overcoming a step of the same limit height or more, regardless of whether the wheel in contact with the step is a drive wheel or a driven wheel. In other words, it is possible to accurately prevent the height of the step that is prohibited from being overtaken in the control from changing depending on whether the wheel in contact with the step is a drive wheel or a driven wheel. Therefore, according to the present invention, when a wheel comes into contact with a step on the road surface during parking assistance, it is possible to accurately prohibit the vehicle from overtaking a step (such as a wheel stopper) of the limit height or more, depending on the wheel in contact with the step.

[0010] In the present invention, the control unit is preferably configured to gradually increase the driving torque applied to the vehicle when the wheels of the vehicle come into contact with a step on the road surface so that the vehicle overcomes the step, and when this driving torque reaches a limit torque, to reduce the driving torque applied to the vehicle to prohibit the vehicle from climbing over the step. According to the present invention configured in this manner, it is possible to accurately balance between allowing a vehicle to quickly overcome a step that is less than the height limit and prohibiting a vehicle from overcoming a step that is equal to or greater than the height limit.

[0011] In the present invention, the control unit is preferably configured to change the amount or the speed at which the driving torque is reduced when the driving torque reaches the limit torque, depending on whether the judgment unit judges that the wheel contacting the step is a driving wheel or a driven wheel. Because the load on the drive wheels and the load on the driven wheels differ depending on the front-rear weight distribution of the vehicle, the ease of riding over the step (possibility of riding over the step) after the drive torque reaches the limit torque changes depending on whether the wheel that comes into contact with the step is a drive wheel or a driven wheel. Therefore, in the present invention, the amount or speed at which the drive torque is reduced after the drive torque reaches the limit torque is changed depending on whether the wheel that comes into contact with the step is a drive wheel or a driven wheel. This makes it possible to reliably prevent the vehicle from riding over a step that is equal to or higher than the limit height.

[0012] In the present invention, the limit torque is preferably set based on the radius of the wheels of the vehicle, the limit height of a step that the vehicle is prohibited from going over, and the front wheel load and rear wheel load of the vehicle. According to the present invention configured in this manner, it is possible to accurately set the limit torque for the driving wheels and the limit torque for the driven wheels that should be applied to prevent the vehicle from climbing over a step that is equal to or higher than the limit height.

[0013] In the present invention, the judgment unit is preferably configured to acquire the wheel speed of each of a plurality of wheels possessed by the vehicle, and to determine whether the wheel contacting the step is a driving wheel or a driven wheel based on the change in the wheel speed of each of the plurality of wheels acquired when the wheel of the vehicle contacts a step on the road surface. According to the present invention configured as above, it is possible to accurately determine which wheel is in contact with the step.

[0014] In another aspect, in order to achieve the above-mentioned object, the present invention is a parking assistance method comprising a control step of controlling a driving torque and a braking torque applied to a vehicle to move and stop the vehicle in order to assist in parking the vehicle in a specified space, and a judgment step of judging whether a wheel of the vehicle contacts a step on a road surface while parking assistance is being performed by the control step, the wheel contacting the step is a driving wheel or a driven wheel, the control step is characterized in that, when a wheel of the vehicle contacts a step on the road surface, a driving torque is applied to the vehicle so that the vehicle overcomes the step, while limiting the driving torque applied to the vehicle to less than a predetermined limit torque to prohibit the vehicle from climbing over a step that is equal to or greater than a limit height, and changing the limit torque applied to the driving torque applied to the vehicle depending on whether the wheel contacting the step is determined to be a driving wheel or a driven wheel by the judgment step. With the present invention configured in this manner, when a wheel comes into contact with a step on the road surface during parking assistance, the vehicle can be appropriately prohibited from climbing over a step (such as a wheel stopper) that is equal to or higher than the restricted height, depending on the wheel that comes into contact with the step. Effect of the Invention

[0015] According to the parking assistance device and method of the present invention, when a wheel comes into contact with a step on the road surface during parking assistance, the vehicle can be appropriately prohibited from climbing over a relatively high step depending on the wheel that comes into contact with the step. [Brief description of the drawings]

[0016] [Figure 1]1 is a block diagram showing a parking assistance system to which a parking assistance device according to an embodiment of the present invention is applied. [Diagram 2] FIG. 2 is an explanatory diagram of a basic operation of parking assistance according to an embodiment of the present invention. [Diagram 3] 5 is a time chart showing step-over control executed during parking assistance to allow a vehicle to overcome a step having a height less than a limit in an embodiment of the present invention. [Figure 4] 5 is a time chart showing step climbing control executed to prohibit the vehicle from climbing over a step having a height equal to or greater than a limit during parking assistance in an embodiment of the present invention. [Diagram 5] 7 is an explanatory diagram of a method for setting a limit torque that is applied when a wheel that comes into contact with a step is a drive wheel in the embodiment of the present invention. FIG. [Figure 6] 7 is an explanatory diagram of a method for setting a limit torque that is applied when a wheel that comes into contact with a step is a driven wheel in the embodiment of the present invention. FIG. [Figure 7] 13 is an explanatory diagram of a method for setting a limit torque that is applied when a wheel that comes into contact with a step is a driven wheel in a modified embodiment of the present invention. FIG. [Figure 8] 4 is a flowchart showing an overall process of step clearance control according to an embodiment of the present invention. [Figure 9] 10 is a flowchart showing a step handling process according to an embodiment of the present invention. [Figure 10] 13 is a flowchart showing an overall process of step clearance control according to a modified example of the embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a parking assistance device and method according to an embodiment of the present invention will be described with reference to the accompanying drawings.

[0018] [Basic configuration] First, the basic configuration of the parking assistance device according to this embodiment will be described with reference to Figures 1 and 2. Figure 1 is a block diagram showing a parking assistance system to which the parking assistance device according to this embodiment is applied, and Figure 2 is an explanatory diagram of the basic operation of the parking assistance according to this embodiment.

[0019] The parking assistance system 100 shown in FIG. 1 is mounted on a vehicle 1, and operates to perform parking assistance (automatic parking) for automatically moving and stopping the vehicle 1 to a predetermined space SP as shown in FIG. 2. Basically, the parking assistance system 100 performs such parking assistance in response to the operation of the communication terminal 5 by a user U outside the vehicle. In this case, the user U operates the communication terminal 5 to instruct the start of parking assistance (i.e., the start of movement of the vehicle 1), the stop of movement of the vehicle 1, the restart of movement of the vehicle 1, and the like. The communication terminal 5 is, for example, a key fob for locking and unlocking the doors of the vehicle 1, and the user U operates one or more switches (parking switches) related to parking assistance provided on the key fob. Note that the user U is not limited to performing operations for parking assistance using the communication terminal 5 from outside the vehicle in this way, and in another example, the user U may perform operations for parking assistance using a predetermined switch provided in the vehicle cabin (the communication terminal 5 may be used inside the vehicle).

[0020] 1, the parking assistance system 100 mainly includes a camera 21, a sonar 22, a wheel speed sensor 23, an acceleration sensor 24, a communication unit 25, a controller 10, an engine control system 31, a brake control system 32, and a steering control system 33. In the parking assistance system 100, the controller 10 outputs control signals to the engine control system 31, the brake control system 32, and the steering control system 33 based on signals input from the camera 21, the sonar 22, the wheel speed sensor 23, the acceleration sensor 24, and the communication unit 25, thereby automatically controlling the movement, steering, and stopping of the vehicle 1, thereby realizing assistance in parking the vehicle 1 in the space SP.

[0021] The camera 21 includes a plurality of cameras (front cameras and rear cameras) that capture images in front of and behind the vehicle 1. The camera 21 is also provided facing diagonally downward so as to capture images of ranges including the road surface in front of and behind the vehicle 1. The camera 21 outputs an image signal corresponding to the captured image to the controller 10.

[0022] The sonar 22 detects the presence or absence of an object present within a predetermined range around the vehicle 1 (for example, relatively close to the vehicle 1), and detects the distance from the vehicle 1 to the object. For example, the sonar 22 is an active ultrasonic sonar, and is disposed at each of the four corners of the vehicle 1. The sonar 22 outputs a detection signal related to an object present around the vehicle 1 to the controller 10. Note that instead of or in addition to the sonar 22, a laser (millimeter wave radar or laser radar) or the like may be used to detect the presence or absence of an object around the vehicle and the distance to the object.

[0023] The wheel speed sensor 23 detects the rotation speed (wheel speed) of each of the four wheels of the vehicle 1 and outputs the detection signal to the controller 10. For example, the wheel speed sensor 23 includes a rotary encoder and detects the wheel speed from the amount of rotational displacement of the wheel (axle) per unit time. The acceleration sensor 24 detects the acceleration of the vehicle 1 and outputs the detection signal to the controller 10.

[0024] The communication unit 25 is a device that communicates with the above-mentioned communication terminal 5. The communication unit 25 receives a signal corresponding to an operation on the communication terminal 5 by the user U, in particular a signal (instruction signal) indicating an instruction related to parking assistance by the user U, from the communication terminal 5. As described above, this instruction signal indicates the start of parking assistance (i.e., the start of movement of the vehicle 1), the stop of movement of the vehicle 1, the resumption of movement of the vehicle 1, etc. The communication unit 25 outputs the instruction signal received from the communication terminal 5 to the controller 10.

[0025] The engine control system 31 controls the engine (not shown) of the vehicle 1. The engine control system 31 is a component capable of adjusting the driving torque (engine torque) of the engine, and includes, for example, a spark plug, a fuel injection valve, a throttle valve, and a variable valve mechanism that changes the opening and closing timing of the intake and exhaust valves. When a control signal for accelerating or decelerating the vehicle 1 is input from the controller 10, the engine control system 31 operates to adjust the driving torque of the engine in response to the control signal.

[0026] The brake control system 32 controls a brake device (not shown) of the vehicle 1. The brake control system 32 is a component capable of adjusting the braking torque of the brake device, and includes, for example, a hydraulic pump and a valve unit. When a control signal for decelerating the vehicle 1 is input from the controller 10, the brake control system 32 operates to adjust the braking torque of the brake device in response to this control signal. Note that, in addition to the above-mentioned brake devices, the objects to be controlled by the brake control system 32 may include a so-called parking brake device.

[0027] The steering control system 33 controls a steering device (not shown) of the vehicle 1. The steering control system 33 is a component capable of adjusting the steering angle of the steering device, and includes, for example, an electric motor of an electric power steering system. When a control signal for changing the traveling direction of the vehicle 1 is input from the controller 10, the steering control system 33 operates to change the steering direction by the steering device in response to the control signal.

[0028] The controller 10 is composed of a computer equipped with one or more microprocessors 10a (typically a CPU), a memory 10b (ROM, RAM, etc.) that stores various programs, and input / output devices, etc. The controller 10 executes various calculations based on signals input from a camera 21, a sonar 22, a wheel speed sensor 23, an acceleration sensor 24, and a communication unit 25, and outputs control signals to an engine control system 31, a brake control system 32, and a steering control system 33 for appropriately operating the engine, the brake device, and the steering device, respectively.

[0029] In this embodiment, the controller 10 corresponds to an example of the "parking assistance device" of the present invention, and functions as a "controller" and a "determiner". That is, the controller 10 is configured to control the driving torque and braking torque applied to the vehicle 1 to move and stop the vehicle 1 in order to assist in parking the vehicle 1 in a predetermined space SP. Specifically, the controller 10 first identifies the predetermined space SP in which the vehicle 1 should be parked, based on signals from the camera 21, the sonar 22, and the like. This space SP not only means a relatively wide range in which the vehicle 1 can be parked, but also means here a position (stopping position) within such a range where the vehicle 1 is actually parked (the same applies hereinafter).

[0030] Then, the controller 10 controls the engine control system 31 to apply a driving torque to the vehicle 1 while controlling the steering control system 33 to appropriately adjust the traveling direction of the vehicle 1 in order to move the vehicle 1 to the specified space SP. In this case, the controller 10 controls the brake control system 32 to apply a braking torque to the vehicle 1 in addition to the driving torque. More specifically, the controller 10 controls the engine control system 31 to maintain the driving torque applied to the vehicle 1 constant, while controlling the brake control system 32 to appropriately adjust the braking torque so that the vehicle 1 moves at a predetermined target vehicle speed. In this way, a stable response can be ensured by controlling a braking torque with a small response delay so as to realize the target vehicle speed, and the control configuration can be simplified by limiting the control target to the braking torque. After this, when the movement of the vehicle 1 to the space SP is completed, the controller 10 controls the brake control system 32 to stop the vehicle 1.

[0031] In this embodiment, when the wheels of the vehicle 1 come into contact with a step on the road surface while the controller 10 is performing the parking assistance as described above, the controller 10 applies a driving torque to the vehicle 1 so that the vehicle 1 overcomes the step, while controlling the engine control system 31 to limit the driving torque applied to the vehicle 1 to less than a predetermined limit torque so as to prohibit the vehicle 1 from climbing over a step of a height equal to or greater than a limit (e.g., 70 to 80 mm or more). Specifically, the controller 10 gradually increases the driving torque applied to the vehicle 1 so that the vehicle 1 overcomes the step, and when the driving torque reaches the limit torque, the controller 10 quickly reduces the driving torque applied to the vehicle 1 so as to prohibit the vehicle 1 from climbing over the step.

[0032] On the other hand, when the wheels of the vehicle 1 come into contact with a step on the road surface, the controller 10 determines whether the wheels that come into contact with the step are driving wheels or driven wheels. For example, the controller 10 determines whether the wheels that come into contact with the step are driving wheels or driven wheels based on the change in the wheel speed of each of the four wheels (typically, the timing of the decrease in the wheel speed of each of the four wheels, etc.) acquired by the wheel speed sensor 23 when the wheels come into contact with the step. Then, the controller 10 changes the limit torque applied to the driving torque applied when the vehicle 1 goes over the step as described above, depending on whether the wheels that come into contact with the step are driving wheels or driven wheels. This is because the driving torque required to make the vehicle 1 go over the step differs depending on whether the wheels that go over the step are driving wheels or driven wheels, even if the steps are the same height. This is caused by, for example, the loads applied to the driving wheels and the driven wheels, that is, the front wheel load and the rear wheel load (corresponding to the front-rear weight distribution of the vehicle 1), etc.

[0033] [Step-over control] Next, we will explain the control that is performed in this embodiment when the wheels of the vehicle 1 come into contact with a step on the road surface during parking assistance, specifically, the control that allows the vehicle 1 to overcome steps that are less than the limit height while prohibiting the vehicle 1 from overcoming steps that are equal to or greater than the limit height (hereinafter referred to as "step overcoming control" as appropriate).

[0034] Fig. 3 is a time chart showing an example of step overcoming control executed in this embodiment to allow the vehicle 1 to overcome a step less than the height limit during parking assistance. From the top, Fig. 3 shows the time change in vehicle speed (the solid line represents the target vehicle speed, and the dashed line represents the actual vehicle speed), the time change in driving torque, and the time change in braking torque. Note that the driving torque and braking torque indicate the target driving torque and target braking torque to be applied to the vehicle 1, which are instructed by the controller 10.

[0035] First, at time t11, the user U operates the communication terminal 5 to instruct the start of parking assistance (i.e., the start of movement of the vehicle 1). At this time, the controller 10 increases the set target vehicle speed, and in response to the increase in the target vehicle speed, starts applying a constant driving torque and reduces the applied braking torque. However, in this example, even if the driving torque is applied and the braking torque is reduced, the wheels of the vehicle 1 are in contact with a step on the road surface, so that the actual vehicle speed remains 0, that is, the vehicle 1 remains stopped. In this case, at time t12, the controller 10 temporarily reduces the driving torque so that the vehicle 1 continues to be stopped until there is a further instruction from the user U. Thereafter, at time t13, the user U performs a predetermined operation on the communication terminal 5 to instruct the vehicle 1 to resume movement (i.e., to get over the step). For example, the user U performs another operation on the communication terminal 5 (pressing the button again) or an operation on the communication terminal 5 that continues for a predetermined time (long press operation).

[0036] From such time t13, the controller 10 gradually increases the driving torque applied to the vehicle 1 so that the vehicle 1 overcomes the step. In this case, the controller 10 maintains the braking torque at the torque reduced as described above and gradually increases the driving torque applied so that the vehicle 1 overcomes the step. As a result, the vehicle 1 moves little by little, and a certain degree of actual vehicle speed is generated. Then, around time t14, the vehicle 1 begins to overcome (start to climb) the step, and the actual vehicle speed increases. From time t15 after this time t14, the controller 10 quickly reduces the applied driving torque and temporarily increases the limit torque in order to suppress an increase in the actual vehicle speed after the vehicle 1 overcomes the step.

[0037] In the example shown in Fig. 3, the driving torque applied to the vehicle 1 to get over the step does not exceed the above-mentioned limit torque Thr (a limit value applied to the driving torque to prohibit the vehicle 1 from getting over a step that is equal to or greater than a limit height). In other words, the driving torque that is gradually increased so that the vehicle 1 gets over the step does not reach the limit torque Thr before the vehicle 1 gets over the step. Therefore, in the example shown in Fig. 3, the controller 10 does not limit the driving torque applied to the vehicle 1 to get over the step.

[0038] Next, Fig. 4 is a time chart showing an example of step overrunning control executed in this embodiment to prohibit the vehicle 1 from overrunning a step (e.g., a wheel stopper) that is equal to or higher than a limit height during parking assistance. Fig. 4 also shows, from top to bottom, the time change in vehicle speed (the solid line indicates the target vehicle speed, and the dashed line indicates the actual vehicle speed), the time change in driving torque, and the time change in braking torque. Note that the driving torque and braking torque indicate the target driving torque and target braking torque.

[0039] The situation up to time t23 is the same as in Fig. 3, and therefore a description thereof will be omitted here. In the example of Fig. 4, from time t23, the controller 10 gradually increases the driving torque applied to the vehicle 1 so that the vehicle 1 overcomes the step, and at time t24, this driving torque reaches the limit torque Thr. Therefore, at time t24, the controller 10 quickly reduces the driving torque applied to the vehicle 1. As a result, the vehicle 1 does not overcome the step, that is, the vehicle 1 is prohibited from overcoming the step. In this case, the vehicle 1 descends the step that it had been climbing partway up, and a negative actual vehicle speed (actual vehicle speed when traveling in the opposite direction to the direction in which it should travel) is generated.

[0040] Next, a specific example of a method for setting the limit torque Thr applied to the drive torque when going over a step will be described with reference to Fig. 5 and Fig. 6. The limit torque Thr is a limit value applied to the drive torque applied for going over a step in order to prohibit the vehicle 1 from going over a step having a height equal to or greater than a limit. As described above, in this embodiment, the limit torque Thr applied is changed depending on whether the wheel contacting the step is a drive wheel (e.g., a front wheel) or a driven wheel (e.g., a rear wheel).

[0041] First, Fig. 5 is an explanatory diagram of a method of setting the limit torque Thr applied in this embodiment when the wheel that comes into contact with the step is a driving wheel. Fig. 5 is a side view that shows a schematic representation of the driving wheel 2 and the driven wheel 3 of the vehicle 1, and the step St that comes into contact with the driving wheel 2. First, the driving force F of the driving wheel 2 is calculated from the driving torque T applied to the driving wheel 2 and the tire radius r. f "F f =T / r". Also, the rear wheel load m r and the acceleration of vehicle 1, a x From the above, the force Te acting on the shaft connecting the driving wheel 2 and the driven wheel 3 is f When the forces in the forward and backward directions are balanced, r a x =Te f =0".

[0042] Here, as shown in FIG. 5, if an angle θ is defined between the contact point between the driving wheel 2 and the tip of the step St and the center point of the driving wheel 2, this angle θ is calculated as follows, using the tire radius r and the height h of the step St: -1 {(rh) / r}". If we consider that the driving torque reaction force acts on the center point of the driving wheel 2, the balance of the moment around the center point of the driving wheel 2 is expressed as the above angle θ and the front wheel load m f Using the above, "{m f gcosθ+Te f cos(π / 2-θ)}r=F f It is expressed as "r".

[0043] By rearranging this formula, we get "Te f =0" so "Ff =m f gcosθ". Therefore, the driving torque T applied to the driving wheel 2 is "T = F f r”, T=m f grcosθ". This driving torque T is the driving torque when the driving wheel 2 starts to climb the step St, that is, the driving torque required for the driving wheel 2 to overcome the step St. Since "θ" in the formula is determined by the height h of the step St, the driving torque T also has a value according to the height h of the step St, that is, the driving torque T is the driving torque required for the driving wheel 2 to overcome the step St of height h. Therefore, by determining the height h (restricted height) at which the vehicle 1 should be prohibited from climbing over the step and then calculating the driving torque T for the step St of this height h, it is possible to set the limit torque Thr to be applied when the driving wheel 2 tries to climb over the step St from this driving torque T. Specifically, the calculated driving torque T or a value slightly smaller than the driving torque T may be set as the limit torque Thr.

[0044] Next, Fig. 6 is an explanatory diagram of a method for setting the limit torque Thr applied in this embodiment when the wheel that contacts the step is a driven wheel. Fig. 6 is also a side view that shows a schematic representation of the driving wheel 2 and the driven wheel 3 of the vehicle 1, and the step St that contacts the driving wheel 2. First, the driving force F of the driving wheel 2 is f As in Figure 5, f = T / r". In addition, the force Te acting on the shaft connecting the driving wheel 2 and the driven wheel 3 is f Due to the balance of the driving wheel 2 in the front-rear direction, "m f a x =F f -Te f =0", that is, "F f =Te f "

[0045] And the balance of the moment around the center point of the driven wheel 3 is "m r grcosθ=Te f rsinθ". Therefore, "Te f =m rgcosθ / sinθ". Therefore, the driving torque T applied to the driving wheel 2 is "T = F f r=Te f r=m r grcosθ / sinθ". This drive torque T is the drive torque when the driven wheel 3 starts climbing the step St, that is, the drive torque required for the driven wheel 3 to overcome the step St (the above-mentioned formula for the drive torque T required for the driving wheel 2 to overcome the step St is "T=m f grcosθ"). Since "θ" in the formula is determined by the height h of the step St, the drive torque T also takes a value according to the height h of the step St, that is, the drive torque T is the drive torque required for the driven wheels 3 to overcome the step St of height h. Therefore, by determining the height h (restricted height) at which the vehicle 1 should be prohibited from overcoming the step and then calculating the drive torque T for the step St of height h, the limit torque Thr to be applied when the driven wheels 3 attempt to overcome the step St can be set from this drive torque T. Specifically, the limit torque Thr can be set to the calculated drive torque T or a value slightly smaller than the drive torque T.

[0046] Here, the front wheel load m f 927kg, rear wheel load m r Let us take the case where the vehicle weight is 613 kg, the tire radius r is 0.3425 m, and the limit height h is 70 mm as an example. In this case, the angle θ is approximately 0.92. The driving torque T required for the driving wheel 2 to overcome the step St with the limit height h is calculated by the above "T = m f grcosθ" is about 1886 Nm. The driving torque T required for the driven wheel 3 to overcome the step St with the restricted height h is calculated by the above "T = m r From the formula "grcosθ / sinθ", the torque limit Thr is approximately 1566 Nm. Therefore, the torque limit Thr applied when the driving wheels 2 attempt to overcome the step St may be set to 1886 Nm or a value slightly smaller than this, and the torque limit Thr applied when the driven wheels 3 attempt to overcome the step St may be set to 1566 Nm or a value slightly smaller than this.

[0047] Next, referring to Fig. 7, a modified method of setting the limit torque Thr that is applied when the wheel that contacts the step is the driven wheel 3 will be described. This modified example is applied when, for example, the driving wheel 2 has already overcome the step St by driving by the user U (driver), specifically, the driving wheel 2 is on the step St extending in the front-rear direction, and thereafter, the driven wheel 3 attempts to overcome the step St during parking assistance. First, the driving force F of the driving wheel 2 is f As in Figs. 5 and 6, f = T / r". In addition, the force Te acting on the shaft connecting the driving wheel 2 and the driven wheel 3 is f Using the inclination α of this axis, the balance of the driving wheel 2 in the front-rear direction is given by "m f a x =F f -Te f cosα=0, that is, "Te f =F f / cosα". If the wheelbase is "L", the inclination of the axis α is "α = sin -1 (h / L)".

[0048] And the balance of the moment around the center point of the driven wheel 3 is "m r grcosθ=Te f rsin(θ+α)”. Therefore, “Te f =m r gcosθ / sin(θ+α)". Therefore, the driving torque T applied to the driving wheel 2 is "T = F f r=Te f rcosα=m rgrcosθcosα / sin(θ+α)". This drive torque T is the drive torque required for the driven wheels 3 to overcome the step St when the driving wheels 2 are on the step St. Since "θ" and "α" in the formula are determined by the height h of the step St, the drive torque T also has a value according to the height h of the step St, that is, the drive torque T is the drive torque required for the driven wheels 3 to overcome the step St of height h. Therefore, by determining the height h (restricted height) at which the vehicle 1 should be prohibited from overtaking the step, and then calculating the drive torque T for the step St of this height h, the limit torque Thr to be applied when the driven wheels 3 attempt to overcome the step St can be set from this drive torque T. Specifically, the limit torque Thr may be set to the calculated drive torque T or a value slightly smaller than the drive torque T.

[0049] Here, the front wheel load m f 927kg, rear wheel load m r As an example, let us take a case where the vehicle weight is 613 kg, the tire radius r is 0.3425 m, the wheelbase L is 2.75 m, and the limit height h is 70 mm. In this case, the angle θ is approximately 0.92, and the inclination α is approximately 0.0255. When the driving wheel 2 is already on the step St, the driving torque T required for the driven wheel 3 to overcome the step St with the limit height h is calculated by the above "T = m r From the formula "gr cos θ cos α / sin(θ+α)", the torque limit Thr applied when the driven wheels 3 attempt to overcome the step St should be set to 1536 Nm or a value slightly smaller than this.

[0050] The method for setting the limit torque Thr described in FIG. 5 to FIG. 7 is merely an example, and the limit torque Thr may be set using other methods. In another example, the limit torque Thr may be set taking into consideration the spring force and dent when the wheel contacts a step. In yet another example, the limit torque Thr may be set taking into consideration the gradient of the road surface (road surface gradient) on which the step exists. In this example, the limit torque Thr may be set to be larger on an upward gradient than on a flat road, and smaller on a downward gradient than on a flat road. In yet another example, the limit torque Thr may be set taking into consideration wheel air pressure information. This is because the stiffness and strain of the wheels change depending on the wheel air pressure, and these affect the vehicle 1's ability to overcome steps.

[0051] [Control Flow] Next, a process flow (control flow) relating to step overcoming control according to this embodiment will be described with reference to FIGS.

[0052] FIG. 8 is a flowchart showing the overall process of the step-over-running control according to this embodiment. In particular, this overall process of the step-over-running control is started when the user U operates the communication terminal 5 to move the vehicle 1 in a state where the wheels of the vehicle 1 have already contacted the step (more specifically, in a state where the vehicle 1 is in contact with the step and does not move). At the start of this process, the controller 10 performs control to appropriately adjust the braking torque so that the vehicle 1 moves at a predetermined target vehicle speed while maintaining the driving torque constant. On the other hand, FIG. 9 is a flowchart showing a specific process (hereinafter referred to as a "step-over-running response process") for dealing with a step on the road surface, which is performed in the overall process of the step-over-running control in FIG. 8. The controller 10 (more specifically, the microprocessor 10a) reads out and executes a program stored in the memory 10b, thereby realizing the processes shown in FIG. 8 and FIG. 9. In addition, these processes are repeatedly executed at a predetermined period.

[0053] 8 is started, the controller 10 acquires various information necessary for the step-over control in step S101. Specifically, the controller 10 acquires at least signals input from the camera 21, the sonar 22, the wheel speed sensor 23, the acceleration sensor 24, and the communication unit 25 (see FIG. 1).

[0054] Next, in step S102, the controller 10 determines the wheel that contacts the step (hereinafter referred to as the "step-contact wheel"), that is, determines (distinguishes) whether the step-contact wheel is the driving wheel 2 or the driven wheel 3. In one example, the controller 10 determines whether the step-contact wheel is the driving wheel 2 or the driven wheel 3 based on an image captured by the camera 21 that captures an area including the road surface in front of and behind the vehicle 1. In this example, when the front wheel is the driving wheel 2 and the rear wheel is the driven wheel 3 (this information is stored in the memory 10b or the like, and the controller 10 reads and uses the information thus stored. The same applies below), if the image captured by the camera 21 that captures the front of the vehicle 1 includes a step, the controller 10 determines that the step-contact wheel is the driving wheel 2, whereas if the image captured by the camera 21 that captures the rear of the vehicle 1 includes a step, the controller 10 determines that the step-contact wheel is the driven wheel 3. In another example, the controller 10 uses the sonar 22 instead of or in addition to the camera 21 to determine whether the step-contacting wheel is the driving wheel 2 or the driven wheel 3 in the same manner as in the case of using the camera 21. That is, in the case where the front wheels are the driving wheels 2 and the rear wheels are the driven wheels 3, the controller 10 determines that the step-contacting wheel is the driving wheel 2 when a step is detected by the sonar 22 covering the front of the vehicle 1, while determining that the step-contacting wheel is the driven wheel 3 when a step is detected by the sonar 22 covering the rear of the vehicle 1. In yet another example, the controller 10 determines whether the step-contacting wheel is the driving wheel 2 or the driven wheel 3 based on the traveling direction of the vehicle 1 (either forward or backward, and basically a step exists ahead in this direction) instructed by the user U using the communication terminal 5. In this example, when the front wheels are driving wheels 2 and the rear wheels are driven wheels 3, the controller 10 determines that the step-contacting wheel is the driving wheel 2 when the user U instructs the vehicle 1 to move forward, and determines that the step-contacting wheel is the driven wheel 3 when the user U instructs the vehicle 1 to move backward.

[0055] Next, in step S103, in order to deal with a step on the road surface, specifically before performing the next step response process (step S104), the controller 10 sets a vehicle speed that is a lowered target vehicle speed applied during normal driving in parking assistance as a target vehicle speed to be applied during the step response process. Then, in step S104, the controller 10 performs the step response process shown in FIG. 9 (details will be described later).

[0056] Next, in step S105, the controller 10 determines whether or not the vehicle 1 has gone over a step by the step handling process in step S104. Specifically, when the actual vehicle speed of the vehicle 1 corresponding to the wheel speed detected by the wheel speed sensor 23 becomes equal to or higher than a predetermined speed, the controller 10 determines that the vehicle 1 has gone over a step (step S105: Yes), and proceeds to step S106.

[0057] In step S106, since the vehicle 1 has overcome the step, the controller 10 starts normal driving control that is performed when no step exists in parking assistance. Specifically, the controller 10 controls the engine control system 31 to apply a driving torque that is applied during normal driving in parking assistance, while controlling the brake control system 32 to appropriately adjust the braking torque so that the vehicle 1 moves at a target speed that is applied during normal driving in parking assistance. In this case, the controller 10 performs such normal driving control until the vehicle 1 reaches a predetermined space SP. Then, the controller 10 proceeds to step S107.

[0058] On the other hand, if the controller 10 does not determine in step S105 that the vehicle 1 has gone over the step (step S105: No), specifically, if the actual vehicle speed of the vehicle 1 has not reached or exceeded the predetermined speed, the controller 10 proceeds to step S107 without performing the normal driving control in the above-mentioned step S106.

[0059] In step S107, the controller 10 stops the vehicle 1. Specifically, the controller 10 controls the engine control system 31 to end the application of the drive torque to the vehicle 1, and controls the brake control system 32 to apply a braking torque so that the vehicle 1 continues to stop. More specifically, when the vehicle 1 has overcome the step, the controller 10 sets the target vehicle speed to 0 in accordance with a command related to parking assistance, thereby controlling the vehicle 1 to stop in this manner, while when the vehicle 1 has not overcome the step, the controller 10 forcibly sets the target vehicle speed to 0 regardless of the command related to parking assistance, thereby controlling the vehicle 1 to stop in this manner. In the latter case, the vehicle 1 stops before the step that the vehicle 1 has not overcome. After the above step S107, the controller 10 ends the entire process of the step-over-step control.

[0060] Next, the step response process shown in Fig. 9 will be specifically described. This step response process is a subroutine performed in step S104 in Fig. 8. When the step response process is started, first, in step S201, the controller 10 confirms an instruction to run (move) the vehicle 1. Specifically, the controller 10 confirms the continuation of the driving instruction from the user U (i.e., confirms the user U's intention to overcome the step), and confirms that the vehicle 1 is not moving despite the driving instruction (i.e., confirms that a step certainly exists).

[0061] Next, in step S202, the controller 10 controls the engine control system 31 to apply a driving torque for pressing the wheels of the vehicle 1 against the step in order to confirm that the vehicle 1 is in contact with the step. Then, the process proceeds to step S203, where the controller 10 determines whether the vehicle 1 is not moving, that is, whether pressing the wheels against the step is complete. As a result, if the vehicle 1 is not moving (step S203: Yes), the controller 10 proceeds to step S204 since pressing the wheels against the step is complete. On the other hand, if the vehicle 1 is moving (step S203: No), pressing the wheels against the step is not complete, so the controller 10 returns to step S202. In this case, the controller 10 repeats steps S202 and S203 until the vehicle 1 stops moving.

[0062] In step S204, the controller 10 sets the limit torque Thr according to the step-contact wheel determined in step S102 of Fig. 8. That is, when the step-contact wheel is determined to be the drive wheel 2, the controller 10 sets the limit torque Thr for the drive wheel, whereas when the step-contact wheel is determined to be the driven wheel 3, the controller 10 sets the limit torque Thr for the driven wheel. The limit torques Thr for the drive wheels and the driven wheels are set and stored in advance, for example, by the method described in Fig. 5 and Fig. 6, and the controller 10 reads out and applies the limit torque Thr thus stored.

[0063] Next, in step S205, the controller 10 determines whether the driving torque currently being applied to the vehicle 1 via the engine control system 31 is less than the limit torque Thr set in step S204. As a result, if the driving torque currently being applied to the vehicle 1 is less than the limit torque Thr (step S205: Yes), the controller 10 proceeds to step S206. In step S206, the controller 10 controls the engine control system 31 to increase the driving torque applied to the vehicle 1 so as to allow the vehicle 1 to overcome the step. Specifically, the controller 10 gradually increases the driving torque at a predetermined rate of change set in advance.

[0064] Next, in step S207, the controller 10 determines whether the vehicle 1 has started to go over a step. Specifically, the controller 10 determines whether the vehicle 1 has started to go over a step based on the amount of change and the rate of change of the acceleration of the vehicle 1 detected by the acceleration sensor 24. As a result, when the vehicle 1 has started to go over a step (step S207: Yes), the controller 10 proceeds to step S208. In this case, since the vehicle 1 has started to go over a step, the controller 10 controls the engine control system 31 to maintain the current driving torque (step S208). Then, after step S208, the controller 10 ends the step response process. Note that in another example, the controller 10 may control the engine control system 31 to reduce the driving torque instead of maintaining it when the vehicle 1 starts to go over a step in this way.

[0065] On the other hand, if the vehicle 1 has not started to go over the step (step S207: No), the controller 10 returns to step S205 and performs the processes from step S205 onwards again. That is, as long as the driving torque applied to the vehicle 1 is less than the limit torque Thr (step S205: Yes) and the vehicle 1 has not started to go over the step (step S207: No), the controller 10 gradually increases the driving torque applied to the vehicle 1 (step S206). In this way, the vehicle 1 is allowed to go over a step that is less than the limit height.

[0066] On the other hand, if the driving torque currently applied to the vehicle 1 is not less than the limit torque Thr (step S205: No), that is, if the driving torque reaches the limit torque Thr, the controller 10 proceeds to step S209. In this case, the controller 10 controls the engine control system 31 to quickly reduce the driving torque applied to the vehicle 1 in order to prohibit the vehicle 1 from climbing over a step that is equal to or greater than the limit height (step S209). In addition, the controller 10 changes the amount or speed at which the driving torque is reduced depending on whether the step-contact wheel is the driving wheel 2 or the driven wheel 3. Specifically, the controller 10 changes the amount or speed at which the driving torque is reduced depending on whether the step-contact wheel is the driving wheel 2 or the driven wheel 3, depending on the magnitude relationship between the load on the driving wheel 2 and the load on the driven wheel 3 with respect to the vehicle weight, that is, the magnitude relationship between the front wheel load and the rear wheel load. More specifically, when the controller 10 determines that the load applied to the step-contacting wheel (one of the driving wheel 2 and the driven wheel 3) is greater than the load applied to the step-non-contacting wheel (the other of the driving wheel 2 and the driven wheel 3) based on the magnitude relationship between the front wheel load and the rear wheel load, the controller 10 reduces the amount or speed of reducing the drive torque. In this case, since the load applied to the step-contacting wheel is relatively large, it is unlikely that the step-contacting wheel will overcome the step after the drive torque reaches the limit torque Thr, so the controller 10 suppresses the amount or speed of reducing the drive torque. On the other hand, when the controller 10 determines that the load applied to the step-contacting wheel (one of the driving wheel 2 and the driven wheel 3) is less than the load applied to the step-non-contacting wheel (the other of the driving wheel 2 and the driven wheel 3) based on the magnitude relationship between the front wheel load and the rear wheel load, the controller 10 increases the amount or speed of reducing the drive torque. In this case, since the load on the step contact wheel is relatively small, there is a possibility that the step contact wheel will overcome the step after the driving torque reaches the limit torque Thr. Therefore, in order to reliably prevent the step from being overcome, the amount or speed at which the driving torque is reduced is increased.

[0067] For example, in a vehicle 1 in which the front wheel load is larger than the rear wheel load, when the step-contacting wheel is the front wheel (drive wheel 2), the controller 10 reduces the amount or speed of reducing the drive torque compared to when the step-contacting wheel is the rear wheel (driven wheel 3). This is because the load on the front wheel (drive wheel 2) is relatively large, so the possibility of the front wheel climbing over the step after the drive torque reaches the limit torque Thr is low. On the other hand, in a vehicle 1 in which the front wheel load is larger than the rear wheel load, when the step-contacting wheel is the rear wheel (driven wheel 3), the controller 10 increases the amount or speed of reducing the drive torque compared to when the step-contacting wheel is the front wheel (drive wheel 2). This is because the load on the rear wheel (driven wheel 3) is relatively small, so there is a possibility that the rear wheel (driven wheel 3) will climb over the step after the drive torque reaches the limit torque Thr, and therefore the controller 10 reliably prohibits the rear wheel from climbing over the step. It should be noted that the controller 10 performs a control opposite to the above-described control in the vehicle 1 in which the front wheel load is smaller than the rear wheel load. After step S209, the controller 10 ends the step response process.

[0068] Next, another overall process of the step-over-step control will be described with reference to FIG. 10. FIG. 10 is a flowchart showing the overall process of the step-over-step control according to a modified example of this embodiment. The overall process of the step-over-step control shown in FIG. 10 differs from the overall process shown in FIG. 8 in that it is executed when the wheels of the vehicle 1 are not in contact with a step, that is, during normal driving with parking assistance. In this case, there is a possibility that the vehicle 1 may come into contact with a step while moving with parking assistance. The overall process shown in FIG. 10 is realized by the controller 10 (more specifically, the microprocessor 10a) reading and executing a program stored in the memory 10b. This process is also executed repeatedly at a predetermined cycle.

[0069] 10 is started, the controller 10 acquires various information necessary for the step-over control in step S301. Specifically, the controller 10 acquires at least signals input from the camera 21, the sonar 22, the wheel speed sensor 23, the acceleration sensor 24, and the communication unit 25 (see FIG. 1).

[0070] Next, the controller 10 judges whether or not a step on the road surface has been detected, specifically, whether or not the wheels of the vehicle 1 have come into contact with the step. In one example, the controller 10 judges that a step exists on the road surface when the amount of change and / or the rate of change of the running resistance of the vehicle 1 is equal to or greater than a predetermined value. This running resistance can be obtained from the driving torque and braking torque applied to the vehicle 1 by an observer model that indicates the equation of motion of the vehicle 1. In another example, the controller 10 judges that a step exists on the road surface when the difference between the target acceleration of the vehicle 1 and the actual acceleration detected by the acceleration sensor 24 is equal to or greater than a predetermined value. If the controller 10 judges that a step exists in this way (step S302: Yes), it proceeds to step S303, whereas if it is not judged that a step exists (step S302: No), it ends the entire process of the step overcoming control. In the latter case, the controller 10 continues the normal driving control in the parking assistance.

[0071] Next, in step S303, the controller 10 judges the step-contacting wheel, that is, judges (discriminates) whether the step-contacting wheel is the driving wheel 2 or the driven wheel 3. In one example, the controller 10 judges whether the step-contacting wheel is the driving wheel 2 or the driven wheel 3 based on the manner of change in the wheel speed of each of the four wheels detected by the wheel speed sensor 23 when it is judged that a step exists (i.e., when a wheel comes into contact with a step), particularly based on the timing of the decrease in the wheel speed of each of the four wheels. In this example, when the front wheels are the driving wheels 2 and the rear wheels are the driven wheels 3, the controller 10 judges that the step-contacting wheel is the driving wheel 2 when the timing of the decrease in the wheel speed of the front wheels is earlier than the timing of the decrease in the wheel speed of the rear wheels, whereas it judges that the step-contacting wheel is the driven wheel 3 when the timing of the decrease in the wheel speed of the rear wheels is earlier than the timing of the decrease in the wheel speed of the front wheels. In another example, similar to step S102 in FIG. 8, the controller 10 may determine whether the step-contacting wheel is a driving wheel 2 or a driven wheel 3 based on the image captured by the camera 21, the detection results of the sonar 22, the traveling direction of the vehicle 1 (not limited to the traveling direction indicated by the user U using the communication terminal 5, but may be the current traveling direction of the vehicle 1), etc.

[0072] Next, in step S304, the controller 10 decelerates the vehicle 1. This prevents the vehicle 1 from going over a relatively high step due to inertial force. Therefore, the degree of deceleration of the vehicle 1 is determined according to the height of the relatively high step that the vehicle 1 is prevented from going over due to the inertial force of the vehicle 1. To explain the process of step S304 more specifically, first, the controller 10 reduces the set target vehicle speed, and controls the engine control system 31 to reduce the driving torque to idle torque so as to realize the target vehicle speed, while controlling the brake control system 32 to increase the braking torque. Then, when the actual vehicle speed is decelerated to a constant vehicle speed, the controller 10 returns to normal control. That is, the controller 10 performs control so as to appropriately adjust the braking torque according to the target vehicle speed while maintaining the driving torque constant.

[0073] Next, in step S305, the controller 10 determines whether or not the vehicle 1 has gone over a step. Specifically, when the actual vehicle speed of the vehicle 1 corresponding to the wheel speed detected by the wheel speed sensor 23 is equal to or higher than a predetermined speed, the controller 10 determines that the vehicle 1 has gone over a step (step S305: Yes), and proceeds to step S306.

[0074] In step S306, since the vehicle 1 has overcome the step, the controller 10 starts normal driving control that is performed when no step exists in parking assistance. Specifically, the controller 10 controls the engine control system 31 to apply a driving torque that is applied during normal driving in parking assistance, while controlling the brake control system 32 to appropriately adjust the braking torque so that the vehicle 1 moves at a target speed that is applied during normal driving in parking assistance. In this case, the controller 10 performs such normal driving control until the vehicle 1 reaches the predetermined space SP.

[0075] Next, in step S307, the controller 10 stops the vehicle 1. Specifically, the controller 10 controls the engine control system 31 to end the application of drive torque to the vehicle 1, and controls the brake control system 32 to apply braking torque so that the vehicle 1 continues to be stopped. More specifically, the controller 10 sets the target vehicle speed to 0 in accordance with a command related to parking assistance, and thus performs control to stop the vehicle 1. After step S307, the controller 10 ends the entire process of the step-crossing control.

[0076] On the other hand, when the controller 10 does not determine in step S305 that the vehicle 1 has gone over the step (step S305: No), the process proceeds to step S308. In step S308, the controller 10 stops the vehicle 1 when the vehicle 1 descends the step. This is to avoid an unstable state in which the vehicle 1 stops halfway over the step. Specifically, the controller 10 first determines that the vehicle 1 has descended the step when the actual acceleration detected by the acceleration sensor 24 switches from negative acceleration to positive acceleration. Then, the controller 10 controls the engine control system 31 to restore the drive torque, while controlling the brake control system 32 to increase the braking torque in order to hold the vehicle 1 in a stopped state after decelerating it.

[0077] Next, the controller 10 proceeds to step S309. The processes of the following steps S309, S310, S311, S306, and S307 are similar to the processes of steps S103, S104, S105, S106, and S107 in Fig. 8, respectively, and therefore will not be described.

[0078] [Action and Effects] Next, the operation and effects of the parking assistance device according to the embodiment of the present invention will be described.

[0079] In this embodiment, when the wheels of the vehicle 1 come into contact with a step on the road surface, the controller 10 applies a driving torque to the vehicle 1 so that the vehicle 1 overcomes the step, while limiting the driving torque applied to the vehicle 1 to less than a predetermined limit torque Thr in order to prohibit the vehicle 1 from overcoming a step of a height equal to or greater than the limit. The controller 10 changes the limit torque Thr applied to the driving torque applied to the vehicle 1 depending on whether the wheel in contact with the step is the driving wheel 2 or the driven wheel 3. This makes it possible to accurately prohibit the vehicle 1 from overcoming a step of the same height equal to or greater than the limit, regardless of whether the wheel in contact with the step is the driving wheel 2 or the driven wheel 3. In other words, it is possible to accurately prevent the height of the step that is prohibited from being overtaken in terms of control from changing depending on whether the wheel in contact with the step is the driving wheel 2 or the driven wheel 3.

[0080] Furthermore, in this embodiment, when the wheels of the vehicle 1 come into contact with a step on the road surface, the controller 10 gradually increases the drive torque applied to the vehicle 1 so that the vehicle 1 overcomes the step, and when this drive torque reaches the limit torque Thr, reduces the drive torque applied to the vehicle 1 so as to prohibit the vehicle 1 from overcoming the step. This makes it possible to accurately balance between the vehicle 1 quickly overcoming a step that is less than the limit height and prohibiting the vehicle 1 from overcoming a step that is equal to or greater than the limit height.

[0081] In addition, in this embodiment, the controller 10 changes the amount or speed of reducing the driving torque when the driving torque reaches the limit torque Thr, depending on whether the wheel in contact with the step is the driving wheel 2 or the driven wheel 3. Since the load on the driving wheel 2 and the load on the driven wheel 3 differ due to the front-rear weight distribution of the vehicle 1, the possibility of the wheel climbing over the step after the driving torque reaches the limit torque Thr changes depending on whether the wheel in contact with the step is the driving wheel 2 or the driven wheel 3. Therefore, the amount or speed of reducing the driving torque after the driving torque reaches the limit torque Thr is changed depending on whether the wheel in contact with the step is the driving wheel 2 or the driven wheel 3. This makes it possible to reliably prevent the vehicle 1 from climbing over a step that is equal to or greater than the limit height.

[0082] Furthermore, in this embodiment, the limit torque Thr is set based on the tire radius, the limit height of the step, and the front wheel load and rear wheel load of the vehicle 1. This makes it possible to accurately set the limit torque Thr for the driving wheels and the limit torque Thr for the driven wheels to be applied in order to prohibit the vehicle 1 from climbing over a step that is equal to or greater than the limit height.

[0083] In this embodiment, the controller 10 judges whether the wheel that comes into contact with the step is a driving wheel or a driven wheel based on the change in the wheel speed of each of the four wheels acquired when the wheel comes into contact with the step on the road surface. This makes it possible to accurately distinguish the wheel that comes into contact with the step.

[0084] [Variations] In the above embodiment, an example was shown in which the present invention is applied to a vehicle 1 using an engine as a drive source, but the present invention can also be applied to vehicles using an electric motor as a drive source (electric vehicles and hybrid vehicles). In addition, in the above embodiment, a braking torque is applied to the vehicle 1 by a brake device (brake control system 32), but in other examples, a braking torque may be applied to the vehicle by regeneration of an electric motor.

[0085] In the above embodiment, the limit torque Thr is changed according to the determination result of whether the step-contacting wheel is the driving wheel 2 or the driven wheel 3. In another example, in addition to the determination result of whether the step-contacting wheel is the driving wheel 2 or the driven wheel 3, it may be determined whether the step-contacting wheel is two wheels or one wheel (i.e., it is determined whether both wheels of the driving wheel 2 or the driven wheel 3 are in contact with the step or only one wheel is in contact with the step), and the limit torque Thr may be changed according to this determination result. In this example, when there is one step-contacting wheel, it is easier to overcome the step than when there are two step-contacting wheels, so the limit torque Thr may be made smaller. Whether there is two step-contacting wheels or one wheel can be determined based on the image captured by the camera 21 and the change in the wheel speed detected by the wheel speed sensor 23. [Explanation of symbols]

[0086] 1 vehicle 2 Drive wheels 3. Driven wheels 5. Communication terminals 10 Controller 21 Camera 22 Sonar 23 Wheel speed sensor 24 Acceleration Sensor 25 Communications Department 31 Engine Control System 32 Brake Control System 33 Steering control system 100 Parking Assist System

Claims

1. A parking assistance device, A control unit configured to control a driving torque and a braking torque applied to the vehicle to move and stop the vehicle in order to assist in parking the vehicle in a predetermined space; a determination unit configured to determine whether a wheel of the vehicle that comes into contact with a step on a road surface is a drive wheel or a driven wheel when the wheel comes into contact with the step while the parking assistance is being performed by the control unit; having The control unit is When a wheel of the vehicle comes into contact with a step on a road surface, the driving torque is applied to the vehicle so that the vehicle overcomes the step, while the driving torque applied to the vehicle is limited to less than a predetermined limit torque in order to prohibit the vehicle from climbing over a step having a height equal to or greater than a limit; and The limit torque applied to the drive torque applied to the vehicle is changed depending on whether the wheel that contacts the step is determined to be a drive wheel or a driven wheel by the determination unit. A parking assistance device comprising:

2. 2. The parking assistance device according to claim 1, wherein the control unit is configured to, when a wheel of the vehicle comes into contact with a step on a road surface, gradually increase the driving torque applied to the vehicle so that the vehicle overcomes the step, and, when the driving torque reaches the limit torque, reduce the driving torque applied to the vehicle to prohibit the vehicle from climbing over the step.

3. 3. The parking assistance device according to claim 2, wherein the control unit is configured to change an amount or a speed by which the drive torque is reduced when the drive torque reaches the limit torque, depending on whether the determination unit determines that the wheel in contact with the step is a drive wheel or a driven wheel.

4. 4. The parking assistance device according to claim 1, wherein the limit torque is set based on a radius of a wheel of the vehicle, the limit height of a step that the vehicle is prohibited from crossing, and a front wheel load and a rear wheel load of the vehicle.

5. 5. The parking assistance device according to claim 1, wherein the determination unit is configured to acquire a wheel speed of each of a plurality of wheels of the vehicle, and determine whether the wheel that contacts the step is a driving wheel or a driven wheel based on a change in the wheel speed of each of the plurality of wheels acquired when the wheel of the vehicle contacts the step on a road surface.

6. A parking assistance method, comprising: a control process for controlling a driving torque and a braking torque applied to the vehicle so as to move and stop the vehicle in order to assist in parking the vehicle in a predetermined space; a determination step of determining whether a wheel of the vehicle that comes into contact with a step on a road surface is a drive wheel or a driven wheel when the parking assistance is being performed by the control step; having The control step includes: When a wheel of the vehicle comes into contact with a step on a road surface, the driving torque is applied to the vehicle so that the vehicle overcomes the step, while limiting the driving torque applied to the vehicle to less than a predetermined limit torque in order to prohibit the vehicle from climbing over a step having a height equal to or greater than a limit; and changing the limit torque applied to the drive torque applied to the vehicle depending on whether the wheel that comes into contact with the step is determined to be a drive wheel or a driven wheel in the determination step; A parking assistance method comprising:

Images