JP2012210916A - Device and method for controlling braking and driving force of vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable giving more appropriate braking force, even in the scene where the stop position is coming at once after getting over the difference.SOLUTION: When the braking force and the driving force of a vehicle 1 are controlled, and guiding or parking the vehicle 1 to the target position, the additional driving force to be added is presumed according to the fluctuation of the vehicle speed by running resistance, and the braking force instruction is output in the decrease of the presumed addition driving force. The braking command output means includes a braking force adding means that adds the additional braking force command value to the braking force command value based on the distance that the distance detection means detected when presuming that the command value for the additional driving force is a state in the decrease.

Description

  The present invention relates to a technology for controlling braking / driving force of a vehicle that controls braking force and driving force of the vehicle to guide or park the vehicle at an acquired target position.

  The parking assistance apparatus described in Patent Literature 1 detects the presence of a step based on measured vehicle movement data. And the parking assistance apparatus of patent document 1 is controlled to the driving force which added the additional driving force to the basic driving force, when it determines with a level | step difference existing. Patent Document 1 discloses that the vehicle can be advanced to the target position even when there is a step by determining the additional driving force based on the pattern learned from the history of overcoming the previous step. Yes.

JP 2008-174102 A

When an additional driving force for overcoming the step is added, the vehicle climbs up the step with a so-called momentum. At this time, if the target position exists immediately after the step, depending on the braking timing, the braking may not be in time, or the target position may be passed, or the braking force may be excessively emphasized on the target position.
The present invention has been made paying attention to the above points, and an object of the present invention is to allow more appropriate braking force to be applied even in a scene where the stop position comes immediately after overcoming a step.

  In order to solve the above-described problem, an aspect of the present invention is directed to a target position generated by running resistance such as climbing a step when the braking force and driving force of a vehicle are controlled to guide or park the vehicle at the target position. The additional driving force added according to the fluctuation of the relative speed of the vehicle with respect to is estimated, and when it is estimated that the estimated additional driving force is decreasing, the braking force command value added with the additional braking command value is It outputs to a braking device and performs braking.

According to the present invention, if there is a running resistance large enough to occur when the vehicle travels over a level difference that may cause the vehicle to stop or decelerate when traveling at an extremely low speed, it corresponds to the running resistance. By adding the additional driving force, the vehicle can travel to the target position.
Further, when it is estimated that the additional driving force is decreasing, a braking command corresponding to at least the additional braking command value is output, so that even in a scene where the stop position comes immediately after overcoming the step, it is more appropriate. A braking force can be applied. As a result, the vehicle can be guided more stably to the target position.

It is a block diagram of the whole vehicle which concerns on embodiment based on this invention. It is a figure explaining the structure of a parking assistance controller. It is a figure which shows the flowchart of the process which concerns on 1st Embodiment based on this invention. It is a figure explaining the structure of the braking / driving force calculating part which concerns on 1st Embodiment based on this invention. It is a time chart which shows the operation example in 1st Embodiment based on this invention. It is the figure illustrated about the effective and typical parking pattern for applying this invention. It is a figure explaining the structure of the braking / driving force calculating part which concerns on 2nd Embodiment based on this invention. It is a time chart which shows the operation example in 2nd Embodiment based on this invention. It is a figure explaining the structure of the braking / driving force calculating part which concerns on 3rd Embodiment based on this invention. It is a figure explaining the lifting of a wheel. It is a figure explaining the structure of a control torque control part. It is a figure showing typically operation of a 3rd embodiment. It is the figure which represented typically the operation | movement (when a stop distance is shorter than FIG. 12) of 3rd Embodiment. It is a figure which shows the response at the time of applying 3rd Embodiment.

“First Embodiment”
Next, embodiments of the present invention will be described with reference to the drawings.
The present embodiment is an example in which the braking / driving force control device of the present invention is applied to a parking assistance device.
FIG. 1 is a diagram illustrating an overall configuration of a vehicle on which the parking assist device according to the present embodiment is mounted.
(Constitution)
The vehicle 1 includes a braking device that generates a braking force and a driving device that generates a driving force (driving torque). As shown in FIG. 1, the braking device includes brake devices 14 a to 14 d provided on the wheels, a fluid pressure circuit 15 including pipes connected to the brake devices 14 a to 14 d, and a brake actuator 12. The brake actuator 12 controls the braking force generated by the brake devices 14a to 14d via the fluid pressure circuit 15 to a value corresponding to the braking force command value. The brake device is not limited to a device that applies a braking force with fluid pressure, and may be an electric brake device or the like.

As shown in FIG. 1, the drive device includes an engine 16 as a drive source and an engine controller 13 that controls torque (drive force) generated by the engine 16. The drive source of the drive device is not limited to the engine 16, and may be an electric motor or a hybrid configuration in which the engine and the motor are combined.
The brake actuator 12 and the engine controller 13 are configured to receive respective command values of a braking command and a driving command from the parking assist controller 10 which is a host controller.

  Moreover, the wheel speed detection sensor 17 which detects a wheel speed is installed in the wheel. In the present embodiment, as the wheel speed detection sensor 17, pulse generators 17a and 17b such as a rotary encoder are illustrated. The wheel speed detection sensor 17 outputs a detection signal to the parking assist controller 10. The detection signal of the wheel speed detection sensor 17 is used to calculate the moving distance y (t) of the vehicle 1 and the relative speed of the vehicle with respect to the target position (vehicle speed when the target position is a fixed position).

A support switch 11 is provided near the driver's seat in the passenger compartment. For example, the support switch 11 is set to the steering wheel. Then, the operation information of the support switch 11 is transmitted to the parking support controller 10.
The parking assist controller 10 is a controller that includes a microcomputer and its peripheral circuits. As shown in FIG. 2, the parking support controller 10 functionally includes a control start determination unit 10A, a movement distance detection unit 10B, a target position acquisition unit 10C, a control end determination unit 10D, and a braking / driving command value calculation unit 10E. Is provided.

When the control start determination unit 10A determines that the operation switch has been turned on based on the signal from the support switch 11, if the control is not underway, the control start determination unit 10A initializes the control flag, moves the distance y (t), the distance threshold, and the like Is set, and the in-control flag indicating the start of control is set to ON.
Based on a signal (pulse count) from the wheel speed detection sensor 17, the movement distance detection unit 10B calculates the movement distance y (t) of the vehicle 1 after the in-control flag is turned on. The moving distance y (t) can be calculated from the signal from the wheel speed detection sensor 17 and the radius of the wheel. For example, the moving distance y (t) can be obtained by multiplying the number of pulses at a preset time interval by the radius of the wheel.

The target position acquisition unit 10C acquires information on a target position where the vehicle 1 is guided and stopped. The information on the target position of the present embodiment is a target distance y ^* that moves forward or backward from the vehicle position when the support switch 11 is turned on. Whether the traveling direction of the vehicle is the forward direction or the backward direction may be determined, for example, based on the shift position of the transmission when the support switch 11 is turned on. The target position acquisition unit 10C of the present embodiment acquires a preset setting value (for example, 50 cm) from the storage unit as the target distance y ^* .

  Here, the driver may set a target position (distance or position to move). For example, the driver inputs the moving distance y (t) or sets the target position by instructing the target position on the map displayed on the display unit of the navigation device. In this case, the target position acquisition unit 10C acquires information on the target position by specifying the set target position with coordinates. In addition, an external recognition sensor such as an ultrasonic sensor is provided in the vehicle 1 to measure the distance between the vehicle 1 and an obstacle located in the traveling direction such as the front or rear of the vehicle 1 detected by the external recognition sensor. You may employ | adopt the structure which acquires the measured distance (a positional information with respect to a vehicle is included) as the information of the target position of the vehicle 1. FIG.

The braking / driving command value calculation unit 10E is based on the target position information (target distance y ^* ) detected by the target position acquisition unit 10C and the movement distance y (t) detected by the movement distance detection unit 10B. A power command is calculated, and the calculated driving force command and braking force command are output to the engine controller 13 and the brake actuator 12, respectively. The configuration of the braking / driving command value calculation unit 10E will be described later.

Next, the process of the parking assistance controller 10 will be described with reference to FIG.
First, in step S31, the parking support controller 10 reads the operation state of the support switch 11 by the control start determination unit 10A. If it is determined that the support switch 11 has been operated and turned on, the process proceeds to step S32. On the other hand, when the support switch 11 remains OFF, the process of step S31 is repeated at a preset sampling cycle.

  In step S32, the control start determination unit 10A determines whether the braking / driving control is already being executed. When the braking / driving control is not being executed, the process proceeds to step S33. On the other hand, when the braking / driving control is already being executed, that is, when the support switch 11 is pressed but the vehicle has not reached the target position and the braking / driving control is continuing, the switch of the support switch 11 is switched. It is assumed that the operation is ignored and the process proceeds to step S34 to continue the braking / driving control being executed.

In step S33, the control start determination unit 10A sets a control flag indicating that control is in progress and resets the movement distance y (t) in order to start control. Further, the target position acquisition unit 10C acquires target position information. Thereafter, the process proceeds to step S34.
In step S34, the braking / driving command value calculation unit 10E generates a driving force command and a braking force command based on the target position acquired by the target position acquisition unit 10C and the movement distance y (t) detected by the movement distance detection unit 10B. A value is calculated, and command values of the calculated driving force command and braking force command are output to the engine controller 13 and the brake actuator 12, respectively. Thus, braking / driving control is performed.

  In step S35, the control end determination unit 10D determines whether or not the position of the vehicle 1 has reached the target position. If the target position has not been reached, the process proceeds to step S34 and the braking / driving control is continued. On the other hand, when the position of the vehicle 1 has reached the target position, the process proceeds to step S36. In step S36, the flag indicating that control is in progress is cleared, and a series of drive control operations are terminated.

Next, the braking / driving command value calculation unit 10E will be described with reference to FIG.
The braking / driving command value calculation unit 10E includes a difference distance detection unit 40, a throttle command calculation unit 41, a brake command calculation unit 42, a peak hold unit 43, a non-linear braking command calculation unit 44, and a braking command addition unit 47.
The difference distance detection unit 40 inputs the target distance y ^* as target position information from the target position acquisition unit 10C and also inputs the movement distance y (t) from the movement distance detection unit 10B. Then, the difference distance detector 40 calculates the remaining distance from the vehicle position to the target position (hereinafter also referred to as difference distance Δy), which is the difference between the target distance y ^* and the movement distance y (t).

The difference distance Δy obtained by the difference distance detector 40 is output to the throttle command calculator 41, the brake command calculator 42, and the nonlinear brake command calculator 44.
The throttle command calculation unit 41 obtains a throttle opening command value θ (t) as a drive command value according to a difference distance Δy that is a difference between the target distance y ^* and the actual travel distance y (t).
In the present embodiment, a throttle opening command value θ (t) as a drive command value is obtained by the following equation (1).
The throttle command calculation unit 41 outputs the obtained throttle opening command value θ (t) to the peak hold unit 43 and the engine controller 13.

Here, α and β are control gains, which are preset constants.
The first term in the equation (1) becomes smaller as the remaining distance becomes smaller and becomes “0” at the target position. That is, the first term in the equation (1) calculates a command value for the basic driving force for guiding the vehicle to the target position.

  The second term in the equation (1) is obtained by time-integrating the reciprocal of the time differential of the difference distance Δy (that is, the moving speed of the vehicle per unit time when the target position is stopped). Yes. As a result, if there is a running resistance that slows down the vehicle speed, such as when the vehicle 1 is caught by a step and the vehicle speed decreases, the second term becomes large. As a result, the throttle opening command value θ (t) increases, so that the driving force increases. Thus, for example, when the vehicle 1 is caught by a step and the vehicle speed decreases, the second term increases, and a driving force sufficient to climb the step is ensured. The value of the second term becomes the command value for the additional driving force. That is, the second term in the formula 1) calculates a command value for the additional driving force.

Note that when the apparatus is mounted, if the speed falls below a certain speed, the value used for the calculation is limited to a prescribed value to prevent the zero division calculation. Here, for the sake of simplicity, description will be made assuming that the above equation (1) is used.
The brake command calculating unit 42 calculates a braking command value for guiding the vehicle to the target position according to a difference distance Δy that is a difference between the target distance y * and the actual moving distance y (t). In the present embodiment, the braking force command value B (t) is calculated based on the following equation (2).

  The first term in the equation (2) is a substantially zero value at the start of movement of the vehicle 1, and becomes a value that increases exponentially as the target position is approached. As a result, the braking command value increases as the vehicle approaches the target position, so that the vehicle stops at the target position as much as possible. In addition, the second term in the equation (2) is a value based on a movement amount within a preset control time δt seconds, and increases as the relative speed with respect to the target position (the vehicle speed when the target position is a fixed position) increases. Become. As a result, when the vehicle speed tends to be excessively higher than the vehicle speed assumed in advance, the braking command value is increased in a feedback manner so that the vehicle speed does not become excessively high. As a result, the vehicle can be stopped at the target position.

The peak hold unit 43 inputs the throttle opening command value θ (t) as the drive command value calculated by the throttle command calculation unit 41 at every preset control time, and the throttle opening command value θ ( The maximum value θ _peak of t) is stored. That is, when the maximum value θ _peak is compared with the throttle opening command value θ (t) input in the current control cycle, and the throttle opening command value θ (t) input this time is larger than the maximum value θ _peak. Sets the throttle opening command value θ (t) input this time to the maximum value θ _peak . This maximum value θ _peak is used for calculating the braking timing by additional braking.

Here, when the maximum value θ _peak is larger than a preset value (such as the maximum value when driving on a flat road at extremely low speed), the vehicle may stop or stop during extremely low speed driving. It can be estimated that the relative speed with respect to the target position of the vehicle has fluctuated due to the large running resistance to the extent of the step.
The nonlinear braking command calculation unit 44 includes a distance threshold setting unit 44A, a braking addition determination unit 44B, and an additional braking command output unit 44C.

The distance threshold value setting unit 44A refers to a preset map 45 or function to obtain a distance threshold value y _ref for braking timing determination according to the maximum value θ _peak . When the maximum value θ _peak is large, the distance threshold y _ref is set to be a larger value than when the maximum value θ _peak is small. It is preferable to set so that the distance threshold y _ref increases as the maximum value θ _peak increases.

The braking addition determination unit 44B determines whether or not the distance threshold y _ref is equal to or less than the difference distance Δy. When this condition is satisfied, it is determined that the additional braking force is output.
If the additional braking command output unit 44C determines that additional braking is output by the braking addition determination unit 44B, the additional braking command output unit 44C outputs a preset nonlinear braking force command value B _FF (t) to the braking command addition unit 47.
That is, the processes of the braking addition determination unit 44B and the additional braking command output unit 44C can be described as follows.

The braking command adding unit 47 is based on the following equation from the command value B (t) output by the brake command calculating unit 42 and the nonlinear braking force command value B _FF (t) output by the nonlinear braking command value calculating unit. The braking force command value B ′ (t) is calculated, and the calculated braking force command value B ′ (t) is output to the brake actuator 12 as a braking command value.
B ′ (t) = B (t) + B _FF (t)
Here, depending on the function of the brake actuator 12, the command value may be sent as the hydraulic pressure command value of the hydraulic oil (fluid), but only the conversion of the hydraulic pressure value and the braking force command value is changed. The braking force command value of this embodiment may be replaced with a command hydraulic pressure value. The same applies to the throttle opening command, and may be replaced with a drive torque command (drive command) depending on the function of the engine controller 13.

(Operation other)
When control is started and the road surface to the target position is flat and there is no step on the road surface, or there is a step and the step is very small, the corresponding basic braking / driving control is As described above, this is realized by the command values of θ (t) and B (t) that are constituted by PD control (or PI control).
Furthermore, in the present embodiment, in addition to the simple PD control (or PI control) as described above, there is a step that is large enough to stop or decelerate the vehicle at an extremely low speed. In order to cope with a situation where there is a running resistance having a magnitude that affects the vehicle speed for the purpose, a non-linear braking command calculation unit 44 is provided.

Here, the explanation is made mainly assuming a step as the target running resistance, but the operation is the same even if there is a large dent, etc., and the operation when exiting the dent is the same as when overcoming the step It becomes.
That is, when the running resistance increases to overcome the step and the vehicle speed for guiding to the target position decreases, the command value for the additional driving force based on the second term of the above equation (1) increases, so the maximum value θ _peak increases. As a result, the distance threshold y _ref that determines the control timing of the nonlinear braking force increases, and the nonlinear braking force is applied at an earlier braking timing than when there is no step.

  As a result, when the throttle is greatly opened to overcome a large level difference, that is, when the driving force for guiding to the target position is increased by the additional driving force, the command value calculated by the brake command calculating unit 42 Regardless of the state, the braking force is raised by the amount of the additional braking force in a feedforward manner, so that the braking command is output by the output from the nonlinear braking command calculation unit 44 even while the additional driving force is decreasing. become. In the actual vehicle 1, there is a certain time delay in the braking force rising of the brake, but in order to generate a braking force of a preset value in a feed forward manner, the vehicle must be stopped at the target position after overcoming the step. Can do.

However, when it is estimated that there is no problem with the basic braking force for guiding to the target position even if the step position is far from the target position and the additional driving force is added to get over the step. By suppressing the output from the non-linear braking command calculation unit 44, it is possible to avoid applying braking more than necessary.
Further, in the present embodiment, the presence of a step is not determined, and it is not necessary to determine using a past history of learning the step. For this reason, the processing load of braking / driving control for guidance to the target position is small accordingly.
Furthermore, since the feedforward braking force can be expected by adding the additional braking force, it is possible to set α and β, which are gains at the time of throttle command calculation, to relatively high values. As a result, the effect of increasing the driving force response when riding on the step is also obtained.

FIG. 5 shows an example of a time chart of the operation based on this embodiment.
The horizontal axis in FIG. 5 indicates time. The state of the vehicle 1 starts from a state where the wheel hits the step and stops at time 0 as shown in the lower left of FIG. 5, and at time t7, the vehicle has just crossed the step as shown in the lower right of FIG. It is an example in the case of stopping as a target position.

  The driver's switch operation is input between time t1 and time t2. In response to the switch operation, control is started, and the throttle opening is commanded from time t3. Then, since the wheel is pressed against the step from time t4, the wheel rotates by the elastic amount of the wheel, and a wheel speed pulse starts to be generated. At this stage, the wheels have not yet started climbing the steps. In order to increase the level difference, the throttle opening is gradually increased by increasing the second term of the above equation (2) (˜t5). That is, the additional driving force is increased. Along with this, the wheels start to climb up the step, and the throttle opening becomes a constant value.

Furthermore, at time t6 when the value of the difference distance Δy (= y ^* −y (t)) becomes equal to y _ref , the braking command value corresponding to the nonlinear braking force command value B _FF (t) rises. Here, since the gain of the braking command is intentionally high, the braking command rises almost stepwise. The actual braking force is generated slightly behind the command value. Finally, when the movement distance y (t) reaches the target distance y ^* and reaches the target position at time t7, the throttle opening degree returns to zero and the vehicle 1 is stopped.

In this way, by using this embodiment, it is possible to explicitly raise the braking force before the throttle opening decreases, and it is necessary to stop immediately after overcoming the step as shown in FIG. Even in situations where it is necessary, it can be stopped reliably.
Here, FIG. 6 is an explanatory view of a typical scene which is a problem when the vehicle 1 is parked.
FIG. 6A shows a scene where the vehicle 1 is moved backward and the vehicle 1 is going to park over the step 2. A tree 3 exists behind the parking position. From the state of FIG. 6 (a) to the state of FIG. 6 (b) finally, the parking is completed. In this state, it is considered that the tree 3 and the vehicle 1 are close to each other.

  When the parking assist device by the braking / driving control of the present embodiment is not applied (the assist switch 11 is turned OFF), when the driver performs a parking operation in such a scene, the accelerator in the state of FIG. Stepping on the pedal gradually and when the vehicle 1 begins to move, the vehicle steps over the step 2 with a force, so the driver changes his foot from the accelerator pedal to the brake pedal and performs a braking operation so as not to collide with the tree 3 Need to hurry up. Although this series of operations is a heavy burden for a general driver, when the parking assist device of this embodiment is applied (the assist switch 11 is turned on), it is surely stopped in the state of FIG. I can do it.

  In this way, regardless of the presence or absence of a step, it is possible to reduce the operation load on the driver when moving a short distance. In other words, if the vehicle 1 is equipped with a system that travels a preset distance, the driver can determine only the distance traveled (target distance) even when there is a step that causes a predetermined amount of running resistance. It is only necessary to perform a heavy-duty operation such as quickly changing the pedal.

In the above description, the case where the target position is at a fixed position is described. For this reason, the relative speed of the vehicle with respect to the target position is the vehicle speed. When the target position moves, such as a moving obstacle, the processing is the same as when the target position is at a fixed position by calculating the difference distance Δy each time the target position is detected.
Here, the peak hold unit 43 is configured to _receive the output of the throttle command calculation unit 41 and store the maximum value as θ _peak . Instead, the peak hold unit 43 may be configured to input the value of the second term of (1) and store the maximum value as θ _peak .

  In the above description, the target position acquisition unit 10C constitutes a target position acquisition unit. The moving distance detector 10B constitutes a distance detector. The first term of the above equation (1) constitutes a basic driving force calculation means. The second term of the above equation (1) constitutes an additional driving force calculating means. The throttle command calculation unit 41 constitutes drive command output means. The brake command calculation unit 42, the non-linear braking command calculation unit 44, and the braking command addition unit 47 constitute a braking command output unit. The peak hold unit 43, the non-linear braking command calculating unit 44, and the braking command adding unit 47 constitute a braking force adding unit. The distance threshold setting unit 44A constitutes a distance threshold setting means.

(Effect of this embodiment)
This embodiment has the following effects.
(1) The braking / driving force control device for the vehicle 1 is a braking / driving force control device for a vehicle that controls the braking force and driving force of the vehicle to guide or park the vehicle. The target position acquisition unit 10C acquires the target position. The movement distance detection unit 10B detects the distance from the vehicle position to the target position. The braking / driving command value calculation unit 10E calculates a command value for the basic driving force for guiding the vehicle toward the target position acquired by the target position acquisition unit 10C based on the distance detected by the movement distance detection unit 10B. The braking / driving command value calculation unit 10E calculates a command value for an additional driving force corresponding to a change in the relative speed of the vehicle with respect to the target position caused by the running resistance. The braking / driving command value calculation unit 10E outputs the driving force command value obtained based on the command value for the basic driving force and the command value for the additional driving force to the driving device that generates the driving force. The braking / driving command value calculation unit 10E calculates a braking force command value based on the distance detected by the movement distance detection unit 10B, and outputs the calculated braking force command value to the braking device. When the braking / driving command value calculation unit 10E estimates that the command value for the additional driving force is decreasing, it adds the additional braking force command value to the braking force command value to be output.

By outputting a braking command while the additional driving force generated when climbing over a step is decreasing, for example, even when the stop position comes immediately after overcoming a step, a more appropriate braking force Granting is possible.
Further, the device of the present embodiment does not need to memorize the step pattern, and therefore it is possible to realize reliable braking by braking / driving force control with a low calculation load.

(2) The braking / driving command value calculation unit 10E includes a distance threshold setting unit 44A that obtains a distance threshold based on the driving force command value including the command value for the additional driving force, and is detected by the moving distance detection unit 10B. When the distance to be operated is equal to or less than the distance threshold, a braking force command to which an additional braking force command value is added is output.
As a result, when the vehicle speed fluctuates due to a running resistance such as a step, a more appropriate braking force can be applied by outputting a braking command in a feed-forward manner than when traveling on a flat road.
Further, when the step is far from the target position, the additional braking force command value is not added, and unnecessary braking can be prevented.
(3) When the driving force command value including the command value for the additional driving force is large, the distance threshold setting unit 44A sets the distance threshold larger than when the driving command value is small.
As a result, it becomes possible to add the additional braking force command value earlier as the running resistance increases.

“Second Embodiment”
Next, a second embodiment will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected and demonstrated about the structure similar to the said 1st Embodiment.
The basic configuration of this embodiment is the same as that of the first embodiment. However, the braking / driving command value calculation unit 10E of the present embodiment is different in that it includes a brake command characteristic calculation unit as shown in FIG. Other configurations are the same as those in the first embodiment.
The brake command characteristic calculation unit inputs the braking force command value B ′ (t) obtained by the braking addition unit and outputs the braking force command value B ″ (t) to the brake actuator 12.

The brake command dynamic characteristic calculation unit 46 is configured to multiply the braking force command value B ′ (t) calculated up to the previous stage by a plurality of low-pass filters. Further, the final value of the braking force command value B ″ (t) is obtained by switching the values that have passed through the plurality of filters according to the value of the maximum value θ _peak when the throttle command is calculated.
That is, the brake command dynamic characteristic calculation unit 46 performs processing such as the following equation (4).

Here, θ ₁ , θ ₂ , and θ ₃ are preset specified values. Moreover, it has the following relationship.
K ₁ <K ₂ <K ₃
T ₁ > T ₂ > T ₃
And
That is, the values of the plurality of filters are set so that the gain of the filter increases and the time constant decreases as the value of the maximum value θ _peak increases.
With this configuration, when the throttle is greatly opened to increase the level difference (that is, when the additional driving force is large), the gain of the final braking force command value B ″ (t), that is, absolute The braking force value is large and the braking force rises quickly (the slope of the braking force time-series curve becomes steep), so it can be stopped reliably in situations where it must stop immediately after stepping over a step. ,

  On the contrary, in a scene where the step does not need to be raised, the throttle cannot be opened so much, so that the gain of the final braking force command value B ″ (t) is small (the absolute braking force is small), and Since the start-up (braking force time-series curve) is delayed, the fluctuation in deceleration at the time of stopping is reduced, and the riding comfort can be kept in a good state.

In this embodiment, in the above equation (4), both the gain K and the time constant T are changed and the three filters are switched. However, it is only necessary to change either the gain or the time constant. The effect may be obtained, or the filter can function even with two switches. Therefore, what is necessary is just to determine the structure mounted according to the characteristic of the brake and throttle of the vehicle 1 actually applied, and this invention is not limited to the form of the said Example.
In addition, here, an example in which a linear first-order lag filter is used to change the way the braking force rises and the magnitude of the absolute braking force is shown. For example, a linear first-order advance element is added here, You may perform control which advances braking timing itself, so that an additional drive force is large.

(Operation other)
FIG. 8 schematically shows an example of a time chart of an operation in the case of using an operation in this embodiment that switches two filters that differ only in time constant.
CASE 1 represents a case where the driver performs a switch operation in a state where there is no level difference on the road surface and moves the target distance y ^* . CASE 2 represents a case where the target distance y ^* is moved in a situation where there is a step on the traveling road surface and the vehicle 1 is stopped immediately after overcoming the step.

First, in CASE 1, the driver performs a SW operation to generate a throttle command. However, since there is no step, the maximum value θ _peak of the throttle command is small. Therefore, a large time constant T ₁ is selected from the filter of the above equation (4), and as a result, the braking command rises gently, and unnecessary deceleration does not occur.
On the other hand, since the maximum value θ _peak of the throttle command is larger than CASE 1 for CASE 2, a filter having a short time constant is selected, and as a result, the braking command rises quickly. Therefore, it is possible to reliably stop at the target distance y ^* even immediately after getting over the step.

In the above description, as a system for reducing the operation load on the driver, the driving support system that always moves by the target distance y ^* regardless of the presence or absence of a step when the driver performs a button operation is taken as an example. Have been used. In addition to this, as in the first embodiment, for example, a system in which the driver can input an arbitrary movement distance may be used, or an obstacle is detected by using an external recognition sensor such as a radar. A parking assistance system that can stop the vehicle 1 immediately before the obstacle may be used.
Here, the brake command dynamic characteristic calculation unit 46 constitutes characteristic setting means. Others are the same as the first embodiment.

(Effect of this embodiment)
The present embodiment has the following effects in addition to the effects of the first embodiment.
(1) The braking / driving command value calculation unit 10E includes a brake command dynamic characteristic calculation unit 46 that sets an increasing slope of the braking command to be output according to the driving force command value including the command value for the additional driving force. Prepare.
The dynamic characteristics of the braking force can be adjusted according to the magnitude of the additional driving force and the difference between the target position and the current position. For this reason, it is possible to generate a braking force command at an appropriate timing so that the vehicle can be stopped at a position where it should be properly stopped in a scene where the stop position comes immediately after overcoming the step.

  Here, using a control system that has advanced braking timing (increasing slope) without any ingenuity is good for scenes that cross a step, but in a scene that does not cross a step (when stopping at a target position on flat ground) There is a risk of getting up too early and inferior riding comfort. On the other hand, by adjusting the transient characteristics, it is possible to achieve both stopping at a reliable target position and riding comfort.

(2) When the driving force command value including the command value for the additional driving force is large, the brake command dynamic characteristic calculation unit 46 increases the braking command inclination as compared with the case where the driving force command value is small. Set larger.
When a large driving force is applied to overcome a large step, the braking force is raised quickly and sharply to achieve a reliable stop, and when the step is small or there is no step, the braking force is increased. The effect of preventing the deterioration of riding comfort by getting up slowly is obtained.

(3) When the driving force command value including the command value for the additional driving force is large, the brake command dynamic characteristic calculation unit 46 determines the command value of the braking force command as compared with the case where the driving force command value is small. Set a larger value.
Since the braking command is set to be larger as the additional driving force is larger, when a large driving force is added to overcome a large step, the braking force is increased greatly to realize a reliable stop. At the same time, when the level difference is small or there is no level difference, an effect of preventing the deterioration of riding comfort by reducing the braking force can be obtained.

(4) When the driving force command value including the command value for the additional driving force is large, the characteristic setting unit uses a filter having a larger gain or a smaller time constant than when the driving force command value is small. The braking command for outputting the braking force command is adjusted.
By adopting a configuration implemented with a filter, it is possible to realize a process with a small calculation load when mounted on an in-vehicle device such as a microcomputer.

“Third Embodiment”
Next, a third embodiment will be described with reference to the drawings.
FIG. 9 is a diagram illustrating a configuration of the braking / driving command value calculation unit 10E according to the present embodiment.
As shown in FIG. 9, the braking / driving command value calculation unit 10E of the present embodiment is an example in which the calculation method of the braking force command value output to the brake actuator 12 is different from that of the first embodiment. That is, in this embodiment, as shown in FIG. 9, instead of the peak hold unit 43, the non-linear braking command calculation unit 44, the brake command calculation unit 42, and the braking command addition unit 47 (see FIG. 4) in the first embodiment. The following processing unit is provided. The processing units are a wheel lift determination unit 51, a step shape estimation unit 61, a step passage determination unit 71, a stop position deriving unit 81, a target braking behavior deriving unit 91, and a braking torque control unit 101.

In this embodiment, when controlling the stopping operation of the vehicle, the braking torque after exceeding a road surface obstacle such as a step existing between the vehicle position and the target position is controlled.
The wheel lift determination unit 51 determines a state in which the wheel is lifted from the ground based on a step existing while moving to the target position. Here, when the wheel comes into contact with the step and gets over the step, the driving torque increases.

  The lifting of the wheel means the moment when the wheel makes a transition from the state of FIG. 10 (a) in contact with the step to the state of FIG. 10 (b). When the state shown in FIG. 10A is changed to the state shown in FIG. 10B, the wheel speed pulse waveform when the wheel rotates suddenly changes. Therefore, the wheel lift determination unit 51 can determine the state in which the wheel is lifted from the ground based on the change in the wheel speed pulse waveform.

The step shape estimating unit 61 estimates the shape of the step from the driving torque Trq at the moment when the wheel is lifted up when the wheel lift is determined based on the determination of the wheel lift determining unit 51.
Here, the driving torque Trq and the step height have the following relationship.
Trq = mg√ (2Rh−h ² ) (5)
here,
m: vehicle front axle load g: gravitational acceleration R: wheel radius

The drive torque may be obtained by multiplying the throttle opening command value θ (t) calculated by the throttle command calculation unit 41 by a preset gain or obtained from the engine controller 13.
The step shape estimation unit 61 of the present embodiment estimates the step height h as the step shape by the driving torque Trq that lifts the wheel to the state of FIG. Here, in the present embodiment, in consideration of the premise that the wheel speed pulse and the driving torque can be directly measured or estimated, as described above, the step height h is estimated as the step shape. To do. Of course, the step shape estimation unit 61 may be configured to measure the step shape using an apparatus capable of directly measuring the shape of the step.
The step passage determination unit 71 determines that the wheel has passed the step.
Here, the angle θ _p0 formed by the line segment connecting the step corner, the wheel center, and the wheel ground contact center CP in a state where the wheel is in contact with the step (FIG. 10A) has a geometrical relationship as follows.

Then, the step passage determination unit 71 changes the wheel angle at the moment when the wheel lift determination is made from the state where the wheel is in contact with the step, and determines that the wheel has passed the step when the wheel angle changes by θ _p0. To do.
The stop position deriving unit 81 obtains a stop distance x _BG from the vehicle position when it is determined that the wheel has passed the step based on the determination of the step passing determination unit 71 to the target position. The stop distance x _BG to the target position can be obtained from the difference between the wheel speed pulse count (wheel movement amount) and the target position. The stop position deriving unit 81 may use the input information as the stop distance _xBG . The stop position deriving unit 81 may acquire the stop distance x _BG to the target position based on the detection value of a sensor that acquires information around the vehicle such as an ultrasonic sensor.

The target braking behavior deriving unit 91 obtains the target deceleration acceleration α _ref based on the vehicle speed V _B at the moment when it is determined that the vehicle has passed the step and the stop distance x _BG obtained by the stop position deriving unit 81. The vehicle speed can be calculated, for example, by differentiating a wheel speed pulse count (wheel movement amount).
The target deceleration acceleration α _ref is calculated by the following equation based on the instantaneous vehicle speed V _B and the stop distance x _BG , for example. In this example, acceleration is obtained as the target braking behavior.

The braking torque control unit 101 controls the braking torque so as to realize a target deceleration.
As shown in FIG. 11, the braking torque control unit 101 of this embodiment includes a braking torque deriving unit 102 and a braking torque correcting unit 103. The braking torque correction unit 103 includes a correction gain map 104.
The braking torque deriving unit 102 calculates a braking torque command for realizing the target deceleration acceleration α _ref (target braking behavior) obtained by the target braking behavior deriving unit 91 by feedforward control. Specifically, the braking torque deriving unit 102 derives a braking torque command that takes into account the dynamic characteristics of the braking system by using an inverse model of the braking system model that can be expressed by a transfer function of the braking behavior with respect to the braking torque command.

On the other hand, depending on brake pad wear and road surface characteristics, the actual response may not be the same as the brake system model. In view of this, the braking torque correction unit 103 obtains a braking torque correction value corresponding to the difference between the target braking behavior and the actual braking behavior. Then, the braking torque command obtained by the braking torque deriving unit 102 is corrected by the obtained braking torque correction value.
The braking torque correction unit 103 shown in FIG. 11 includes the target deceleration acceleration α _ref (target vehicle behavior) obtained by the target braking behavior deriving unit 91 and the actual deceleration acceleration (the vehicle that is actually generated). The braking torque correction value is obtained by multiplying the difference from the behavior) by the correction gain.

As shown in the correction gain map 104 in FIG. 11, the correction gain is changed by a stop distance _xBG that is a distance to the target position. That is, the correction gain k1 is adjusted to be larger when the stop distance x _BG is short than when the stop distance x _BG is long. In the correction gain map 104 shown in FIG. 11, the correction gain k1 is adjusted to a higher value as the stop distance _xBG is shorter. By adjusting the correction gain in this manner, the closer to the target position, the more accurately it can be stopped.

(Operation other)
FIG. 12 is a diagram schematically showing the operation according to the present embodiment.
Assume that the stop operation to the target position is started at time T ₀ in FIG. At the time T ₁ are moving a substantially flat road surface. Subsequently, when the wheel is in contact with the step at time T _2, the drive torque increases to beyond the step. Here, in the present embodiment, the example of the drive torque shown in FIG. 12 is shown, but the present invention can be applied regardless of the waveform of the drive torque if the actual response of the drive torque is taken into account.

Then, when the driving torque is increased from time T ₂ and time T ₃ is reached, the wheel angle that has shown a constant value until then changes. The driving torque when the wheel angle changes becomes Trq, and Trq and the step height h have the relationship of the above formula (5). For this reason, the height h is obtained, and further, the angle θ _p0 formed by the line segment connecting the step angle portion, the wheel center, and the wheel ground contact center is geometrically obtained as shown in Equation (6).

Further, the transition from time T ₃ to time T ₄ is a transition state from the state where the wheel is lifted to the level difference. When the wheel rotation angle changes by θ _p0 from the state at time T ₃ , it is determined that the vehicle has passed the step, and the time at that time becomes time T ₄ .
At time T ₄ , based on the stop distance x _BG from the position determined to have passed the step to the target position and the vehicle speed V _B at the instant determined to have passed the step, the above formula (7) is used to calculate the target deceleration acceleration. Calculate α _ref . As a result, the braking torque rises, the braking operation is performed until time T5, and the vehicle stops at the target position.

Here, the description has been made on the premise that the target braking torque can be realized. However, there may be a case where the desired response is necessarily obtained depending on the operation delay of the braking device, the signal processing dead time, or the like. In that case, the braking torque control unit 101 corrects the braking torque.
Next, FIG. 13 shows a schematic diagram of a response when the target position with respect to the step position is closer (when the stop distance _xBG is relatively short) than in the case of FIG. 12 described above.
The difference between the case of the operation example shown in FIG. 13 and the case of the operation example of FIG. 12 described above is that the time for starting up the braking torque is different.

That is, if the target position is close to the stepped passage determination before the wheel comes just above the step of the projection (position at time T ₄ in FIG. 13). That is, the step passage determination is relatively advanced as compared with the case of FIG. Then, the target deceleration acceleration α _ref is obtained from V _B and the stop distance x _BG to the target position when the step passage determination is made. As a result, the dead time of the brake system is corrected and it becomes easier to stop at a closer position.

FIG. 14 is a diagram illustrating a torque response and a longitudinal acceleration response with respect to the longitudinal movement amount when the present embodiment is applied.
As can be seen from FIG. 14, when the step and the wheel come into contact with each other, the wheel rotates, and when it is determined that the step has passed, the braking torque rises, the target position is highly accurate, the change in the braking G is small, and the vehicle stops. It becomes possible. In FIG. 14, the braking acceleration (deceleration) is described as a negative value.

(Modification)
The braking / driving command value calculation unit 10E of the present embodiment may be configured to include the brake command calculation unit 42 described in the first embodiment. In this case, for example, the output value of the braking torque control unit 101 and the output value of the brake command calculation unit 42 and the larger value (select high) are set as the input value of the brake actuator 12.
This makes it possible to stop at the target position more reliably even when there is no step or the like that causes speed fluctuations between the vehicle position at the control start position and the target position.
Here, the wheel lift determination unit 51 and the step shape estimation unit 61 constitute a step estimation unit. The step passage determination unit 71 constitutes a step passage determination unit. The braking torque correction unit 103 constitutes correction means. The braking torque command value of the present embodiment corresponds to the second braking force command value.

(Effect of this embodiment)
This embodiment has the following effects.
(1) The braking / driving command value calculation unit 10E estimates a step existing between the vehicle position and the target position. The step passage determination unit 71 determines the passage of the wheel with respect to the estimated step. When the braking / driving command value calculation unit 10E determines that the vehicle has passed the step, the braking / driving command value calculation unit 10E adds a braking force command value necessary to stop at the target position according to the vehicle behavior when the step is passed and the stop distance to the target position. The braking force command value including the braking force command value is calculated, and the calculated braking force command value is output to the brake actuator 12.
According to this configuration, braking is performed so that the vehicle stops at the target position based on the estimated position of the step and the vehicle behavior when the step passes. For this reason, the vehicle can be reliably stopped at the target position.

(2) The braking torque correction unit 103 corrects the braking force command value according to the difference between the target vehicle behavior for stopping at the target position and the actual vehicle behavior.
According to this configuration, since the behavior of the actual vehicle can be brought close to the target vehicle behavior, it is possible to improve the accuracy of the target position and the position where the vehicle is actually stopped.

(3) When the stop distance is short, the braking torque correction unit 103 increases the braking force by an amount corresponding to the difference between the target vehicle behavior and the actual vehicle behavior, compared to when the stop distance is long. Correct in the direction.
According to this configuration, when the level difference is relatively close to the target position, correction is made in a direction that relatively increases the braking force. As a result, even when the target position is close, the accuracy of the target position and the position where the vehicle is actually stopped can be further improved.

(4) When the stop distance is short, the step passage determination unit 71 accelerates the step passage determination compared to when the stop distance is long.
According to this configuration, when the step is relatively close to the target position, the passage of the step is determined relatively early. As a result, the braking acceleration after exceeding the step can be kept low, and the vehicle can be smoothly stopped at the target position.

DESCRIPTION OF SYMBOLS 1 Vehicle 2 Level | step difference 10 Parking assistance controller 10A Control start determination part 10B Movement distance detection part 10C Target position acquisition part 10D Control end determination part 10E Braking / driving command value calculating part 10E
DESCRIPTION OF SYMBOLS 11 Support switch 12 Brake actuator 13 Engine controller 15 Fluid pressure circuit 16 Engine 17 Wheel speed detection sensor 40 Difference distance detection part 41 Throttle command calculation part 42 Brake command calculation part 43 Peak hold part 44 Nonlinear braking command calculation part 44A Distance threshold value setting part 44B braking addition determination unit 44C additional braking command output unit 46 brake command dynamic characteristic calculation unit 47 braking command addition unit 51 wheel lift determination unit 61 step shape estimation unit 71 step passage determination unit 81 stop position derivation unit 91 target braking behavior derivation unit 101 Brake torque control unit 102 Brake torque derivation unit 103 Brake torque correction unit 104 Correction gain map

Claims (13)

A braking / driving force control device for a vehicle that controls braking force and driving force of the vehicle to guide or park the vehicle,
Target position acquisition means for acquiring the target position;
Distance detecting means for detecting the distance from the vehicle position to the target position;
Basic driving force calculating means for calculating a command value for basic driving force for guiding the vehicle toward the target position acquired by the target position acquiring means based on the distance detected by the distance detecting means;
An additional driving force calculating means for calculating a command value for the additional driving force according to a change in the relative speed of the vehicle with respect to the target position caused by the running resistance;
Drive command output means for outputting the drive force command value obtained based on the command value for the basic drive force and the command value for the additional drive force to the drive device for generating the drive force;
A braking command output means for calculating a braking force command value based on the distance detected by the distance detection means, and outputting the calculated braking force command value to the braking device;
When the braking command output means estimates that the command value for the additional driving force is decreasing, the braking force adding means adds the additional braking force command value to the braking force command value based on the distance detected by the distance detecting means. A braking / driving force control device for a vehicle, comprising: The braking force adding means is
Distance threshold setting means for obtaining a distance threshold based on the driving force command value including the command value for the additional driving force,
2. The braking / driving force control device for a vehicle according to claim 1, wherein when the distance detected by the distance detecting means is equal to or less than the distance threshold, a braking force command to which the additional braking force command value is added is output.   The distance threshold value setting means sets the distance threshold value larger when the driving force command value including the command value for the additional driving force is larger than when the driving command value is small. Item 3. The braking / driving force control device for a vehicle according to Item 2.   The braking command output means comprises characteristic setting means for setting an increasing slope of a braking command to be output in accordance with the driving force command value including a command value for the additional driving force. The braking / driving force control device for a vehicle according to any one of claims 3 to 4.   The characteristic setting means is characterized in that when the driving force command value including the command value for the additional driving force is large, the increase slope of the braking command is set larger than when the driving force command value is small. The braking / driving force control device for a vehicle according to claim 4.   The characteristic setting means sets the command value of the braking force command to be larger when the driving force command value including the command value for the additional driving force is larger than when the driving force command value is small. The braking / driving force control device for a vehicle according to claim 4 or 5.   When the driving force command value including the command value for the additional driving force is large, the characteristic setting means uses a filter having a larger gain or a smaller time constant than when the driving force command value is small. The braking / driving force control device for a vehicle according to claim 4, wherein a braking command for outputting the braking force command is adjusted. A step estimating means for estimating a step existing between the vehicle position and the target position;
Step passage determining means for determining the passage of the wheel with respect to the step estimated by the step estimating means,
When the braking force command output means estimates that the wheel has passed the level difference based on the determination result of the level difference determination means, the command value of the additional driving force unit is decreasing, and determines that the level difference has passed. The second braking force command value required to stop at the target position according to the vehicle behavior when passing the step and the stopping distance to the target position is set as a braking force command value including the additional braking force command value. 2. The vehicle braking / driving force control device according to claim 1, wherein the vehicle braking / driving force control value is calculated and the calculated second braking force command value is output to the braking device.   The correction means for correcting the second braking force command value according to a difference between a target vehicle behavior for stopping at a target position and an actual vehicle behavior is provided. Vehicle braking / driving force control device.   The correction means corrects the braking force in a direction in which the braking force is increased by an amount corresponding to the difference between the target behavior and the actually occurring behavior when the stopping distance is short and when the stopping distance is long. The braking / driving force control device for a vehicle according to claim 9.   11. The step according to claim 8, wherein when the stop distance is short, the step passage determination means accelerates the step passage determination compared to when the stop distance is long. Vehicle braking / driving force control device. A braking / driving force control method for a vehicle that controls braking force and driving force of the vehicle to guide or park the vehicle at the acquired target position,
Estimating an additional driving force applied to the vehicle according to a change in the relative speed of the vehicle with respect to a target position caused by the running resistance, and determining a distance threshold according to the estimated additional driving force;
A braking / driving force control for a vehicle, characterized in that when a distance from the vehicle position to the target position is determined to be equal to or less than the distance threshold, a command for a preset additional braking force is added to a braking command output to the braking device. Method. A braking / driving force control method for a vehicle that controls braking force and driving force of the vehicle to guide or park the vehicle at the acquired target position,
Estimate the step existing between the vehicle position and the target position, determine the passage of the wheel to the estimated step, calculate the vehicle behavior when passing the step or passing the step, and the wheel passed the step Is determined, the braking force command value necessary to stop at the target position corresponding to the stop distance to the target position is calculated from the calculated vehicle behavior during or after passing the step, and the calculated braking force A braking / driving force control method for a vehicle, wherein a command value is output to a braking device.

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