The description herein makes reference to the accompanying drawings wherein like reference numerals refer to like parts throughout the several views, and wherein:
In these previous vehicle travels controllers, as long as the vehicle is not traveling correctly on the designated road speed reduction control is not performed with respect to approaching curves ahead. This is an undesirable result, In order to prevent this problem, it has been proposed that the course of the vehicle be predicted, and speed reduction control is performed when there is a curve on the predicted course. However, because the predicted course may not be the road taken by the vehicle, speed reduction control may be performed that is different from that for the course desired by the driver. This is also undesirable.
In contrast, a type of vehicle travel controller taught herein sets a target vehicle speed with respect to the road ahead of the vehicle, and the actual vehicle speed is controlled to become the target vehicle speed. When branching of the road ahead of the vehicle position is detected, after primary speed reduction control during a first deceleration, secondary speed reduction control at a second deceleration higher than the first deceleration is performed with respect to the road having the lowest target vehicle speed among the preset target speeds for the various possible roads. Accordingly, when one of the branching roads is a road with a lower target vehicle speed, such as a curve, while the other branching road is a straight road that does not require speed reduction control, it is possible to prevent the performance of rapid speed reduction control that would make the driver feel uneasy even when the vehicle travels on the straight road after branching. This embodiment and other embodiments of the invention are described with reference to the drawing figures.
Controller 4 is composed of a microcomputer, memory and other peripheral parts, and it performs control of the travel of the vehicle, typically using software stored in memory and operable to perform the functions herein described. More specifically, based on the vehicle position and node information from navigation system 1, controller 4 computes the curvature radius of the curve, and the target vehicle speed for each node is set based on the curvature radius of each node and the preset lateral acceleration. Also, the target deceleration at each node is computed based on the actual vehicle speed computed based on the target vehicle speed for each node and the measurement of the wheel speed. Then, the minimum value is searched from among the target decelerations of the various nodes, and the node as the control object and the target deceleration are set while the target vehicle speed instruction value is computed for reaching the target vehicle speed for the node as the control object.
When navigation system 1 detects that there is a branching road on the road where the vehicle is traveling, controller 4 judges whether the target vehicle speed instruction value has changed. Based on the judgment result, controller 4 computes the speed reduction control quantity for reaching the target vehicle speed instruction value and outputs the quantity to a speed reduction controller 5. Also, controller 4 judges whether there is a branching road ahead of the vehicle by judging whether there is branching information in the information about nodes ahead of the vehicle acquired from navigation system 1. The information about various nodes acquired from navigation system 1 contains a branching number. If the branching number is 0, it is judged that the road is a single road free of branching. If the branching number is 1 or more, it is judged that there are two or more branch roads ahead of the vehicle.
In another embodiment of the disclosure, a camera can be used to take pictures ahead of the vehicle, and road branching is detected by processing the pictures taken. Alternatively, or in addition thereto, radar or the like is used to detect objects ahead of the vehicle, and road branching is detected based on the detection results.
Speed reduction controller 5 makes use of engine controller 5_1 and brake controller 5_2 to perform automatic braking of the vehicle according to the speed reduction control quantity sent from controller 4.
In order to perform the operations described, controller 4 has control blocks, or parts, 4_1 to 4_14 formed in the microcomputer software format. Navigation information processing part 4_1 computes the curvature radius and curvature direction at each node based on the node information acquired from navigation system 1. Target vehicle speed computing part 4_2 sets the target vehicle speed at each node based on the curvature radius at the node. Target deceleration computing part 4_3 computes the target deceleration for meeting the target vehicle speed at each node ahead of the vehicle based on the target vehicle speed at the node and the actual vehicle speed. Target deceleration computing part 4_3 searches for the node with the lowest target vehicle speed among the target vehicle speeds preset for the various roads, and then outputs the lowest target deceleration.
Target vehicle speed instruction value computing part 4_4 computes the target vehicle speed instruction value obtained by adding a limiter of the deceleration variation based on the lowest target deceleration. Branching road detecting part 4_5 detects branching of the road ahead of the vehicle based on the node information acquired from navigation system 1. Target vehicle speed instruction value change permission judgment part 4_6 judges whether the target vehicle speed instruction value is to be changed based on the branching information for the node ahead of the vehicle. Target vehicle speed instruction value changing part 4_7 changes the target vehicle speed instruction value when change in the target vehicle speed instruction value is permitted. Target vehicle speed instruction part 4_8 outputs the vehicle speed instruction value changed based on the branching information or outputs the vehicle speed instruction value that is unchanged.
Vehicle speed setting part 4_9 sets the vehicle speed so as to achieve constant speed traveling based on the operation of the various switches 3 and the actual vehicle speed. For example, when the SET switch is operated while the adaptive cruise control (ACC) main switch among switches 3 is ON, the actual vehicle speed in this case is taken as the set vehicle speed, and the vehicle travels at the constant speed of the set vehicle speed.
Vehicle speed instruction value computing part 4_10 selects the target vehicle speed instruction value or the set vehicle speed, whichever is lower, and outputs it as the vehicle speed instruction value. Vehicle speed servo computing part 4_11 computes the target acceleration/deceleration for reaching the vehicle speed instruction value and outputs it.
Torque allocation control computing part 4_12 determines the allocation of engine torque and brake torque corresponding to the target acceleration/deceleration and outputs the allocation to engine torque computing part 4_13 and brake hydraulic pressure computing part 4_14. According to the allocated engine torque, engine torque computing part 4_13 computes the gear setting of the automatic transmission, the throttle opening and other engine control instruction values and outputs them to engine controller 5 —1 and transmission controller 5_3. On the other hand, brake hydraulic pressure computing part 4_14 computes the brake hydraulic pressure according to the allocated brake torque and outputs it to brake controller 5_2. Engine controller 5_1 controls the throttle opening and air intake system, etc., of engine 6. Transmission controller 5_3 controls the gear setting of automatic transmission 7. Brake controller 5_2 controls the brake hydraulic pressure of friction brake 8, etc.
In step 2 navigation system 1 detects whether the target is set and the vehicle is being guided. If the vehicle is being guided a flag for route guidance, flg_route_guide, is set (=1) as shown in FIG, 3. In addition, the priority status of the route is detected. For example, when the route with a general road is given priority, the flag for general road priority, flg_general_route, is set (=1). On the other hand, when the route with a toll highway is given priority, the flag for toll highway priority, flg_highway_route, is set (=1). Here, in the case of the flag for general road priority, flg_general_route=1, the flag for toll highway priority, flg_highway_route, is set at 0, and when the flag for toll highway priority flg_highway_route=1, the flag for general road priority, flg_general_route, is set at 0.
Returning now to
V=(Vw1+Vw2)/2 (1)
Also, when ABS control or another system using the vehicle speed is turned ON, the actual vehicle speed (estimated vehicle speed) used in that system can be adopted.
In step 4 a judgment is made on which road will be taken by the vehicle at the branching point based on the node information acquired from navigation system 1. For example, as shown in
Returning now to
In step 6 the controller 4 computes the target vehicle speed at each node. More specifically, assuming the lateral acceleration Yg* at each node to be 0.3 G, the target vehicle speed Vrj at each node can be computed based on the lateral acceleration Yg* and curvature radius Rj as follows:
Vrj
2
=Yg* ·|Rj| (2)
According to equation (2), the larger the curvature radius Rj, the higher the target vehicle speed Vrj. Also, a value set by the driver can be used as the lateral acceleration Yg* at each node. Also, setting the target vehicle speed with respect to each node is shown in this embodiment as an example. A scheme can also be adopted in which equidistant interpolation points are arranged on the road that passes the various nodes, and the target vehicle speed is computed at the interpolation points.
In step 7 the controller 4 calculates the target deceleration at each node. The target deceleration Xgsj at each node is computed from actual vehicle speed V, target vehicle speed Vrj at each node and distance Lj between the current position and each node such that:
Xgsj=(V2−Vrj2)/(2·Lj)=(V2−Yg*·|Rj|)/(2·Lj) (3)
In equation (3), the sign for target deceleration Xgsj is positive on the speed reducing side. In this way, target deceleration Xgsj is computed from actual vehicle speed V, target vehicle speed Vrj and distance Lj from the current vehicle position to each node. The lower the target vehicle speed Vrj, the smaller the curvature radius Rj is, or the smaller the distance Lj, the higher the target deceleration Xgsj is. Also, in this example, the distance to each node is used as distance Lj in equation (3). However, a scheme can also be adopted in which equidistant interpolation points are arranged on the road that passes through the various nodes, and the target deceleration is computed at each interpolation point using the distance to the interpolation point.
In step 8, in order to determine the node as the control object from the target deceleration at the various nodes, the lowest target deceleration is detected using the following equation:
Xgs—min=min{Xgsj}; wherein (4)
The minimum value of the target deceleration Xgs_min is then used in step 9, in which the target vehicle speed instruction value Vrr with the limiter of the variation in the deceleration added to it is computed using the following equation:
Vrr=f{Xgs_min}·t; wherein (5)
t represents time; and
In step 10 the branching number Branchj for the various nodes Nj is read from the various node information, and a judgment is made on whether a change in the target vehicle speed instruction value is permitted based on the flag for route guidance, flg_route_guide, the flag for a general road being given priority, flg_general_route, the flag for a toll highway being given priority, flg_highway_route, and whether the predicted route is set.
For example, as shown in
In this described example, whether a target vehicle speed instruction value change is permitted is set depending on whether the vehicle is in the route guidance state. However, a scheme can also be adopted in which whether the target vehicle speed instruction value can be changed is set corresponding to the state of the branching road ahead of the vehicle. For example, irrespective of the value of the flag indicating route setting, flg_route_set_on, the information pertaining to the road state at the branching, such as branching road types, type of link, road width, number of lanes, etc., is read. Then, as shown in
Also, when it is judged that the lane where the vehicle is traveling is the lane with branching, the flag can be set for target vehicle speed instruction value change permission, flag_control_chg (=1). For example, when the vehicle is traveling in the left-hand lane (or the right-hand lane) on a highway, the flag can be set for target vehicle speed instruction value change permission, flag_control_chg (=1), each time there is an exit from the highway or a branching road to a service area. In addition, the branching road can also be selected as the object of speed reduction control based on the angle (branching angle) of the branching road with respect to the lane where the vehicle is traveling. For example, a road with a branching angle smaller than a prescribed value (±60°) is defined as a branching road where the vehicle may well possibly enter. As a result, a road with a branching angle at the crossing point of ±90° is not taken as a branching road.
In the above-described example, the target vehicle speed instruction value change permission flag is set irrespective of the value of the route prediction flag. However, a scheme can also be adopted wherein when the flag indicating route setting, flg_route_set_on=1, that is, when route prediction operates, and route prediction causes one road from among the branching roads to be set as the predicted route, as described with reference to
Returning again to
As shown in
Here, for example, the control quantity in secondary speed reduction control outputs the target vehicle speed instruction value such that it can reach the target vehicle speed, computed from the lateral acceleration set value and the curvature radius, at the same location as in normal operation. Also, when primary speed reduction control is performed, the flag for the primary speed reduction control operation, flg_control_fst, is set (=1), and when secondary speed reduction control is performed, the flag for secondary speed reduction control operation, flg_control_snd, is set (=1).
Referring again to
Next, as shown in
According to step 14 shown in
Referring again to
In the following, a method for effecting gentle speed reduction control primary speed reduction control) and the threshold for effecting slightly greater speed reduction control (secondary speed reduction control) according to an embodiment of the disclosure is explained. In addition, a method for changing the target vehicle speed instruction value by means of driver intervention and a method for changing warning activated by changing the target vehicle speed instruction value according to another embodiment of the disclosure are explained.
When the flag for target vehicle speed instruction value change permission, flag_control_chg, is set (=1), the maximum value of the target deceleration is reduced when the target vehicle speed instruction value is computed. For example, as shown in
When the flag for target vehicle speed instruction value change permission, flag_control_chg, is set (=1), the lateral acceleration set value Yg* may be high. That is, when the flag flag_control _chg is set (=1), for example, the lateral acceleration set value may be changed from 0.25 G to 0.35 G. Then, when set vehicle speed Vset actual vehicle speed V, as target vehicle speed instruction value Vrr becomes lower than set vehicle speed Vset, both the flag for speed reduction control operation, flg_control, and the flag for primary speed reduction control operation, flg_control_fst, are set (=1). Then, primary speed reduction control is turned ON with a timing slower than that in conventional control. In this way, it is possible to delay the primary speed reduction control ON start timing relative to the timing for performing normal speed reduction control (or to have the same timing).
When the flag for target vehicle speed instruction value change permission, flag_control_chg, is set (=1), the speed reduction control can be performed by means of brake control using the friction brake or by means of a downshift by the automatic transmission or torque-down (throttle shut-off or the like) of the engine.
In the following, the threshold for performing secondary speed reduction control after primary speed reduction control according to an embodiment of the disclosure is explained.
As shown in
Alternatively, a scheme can also be adopted in which secondary speed reduction control is turned ON after traveling for a prescribed time after primary speed reduction control was turned ON. In this way, by using a prescribed elapsed time since primary speed reduction control was turned ON as the threshold for turning ON secondary speed reduction control, it is possible to perform speed reduction such that the driver does not notice the speed reduction. Then, speed reduction is performed with secondary speed reduction control to reach the target vehicle speed with respect to the curve ahead of the vehicle.
In the following, a method for changing the target vehicle speed instruction value is explained with respect to intervention by the driver, such as operation of the accelerator by the driver. As shown in
When the driver steps on the accelerator during speed reduction control, and then releases it, and the curve ahead of the vehicle has not been passed, the vehicle is decelerated to the set vehicle speed if the actual vehicle speed is higher than the set vehicle speed. In contrast, the vehicle speed when the accelerator is released is taken as the target vehicle speed instruction value if the actual vehicle speed is lower than the set vehicle speed. That is, speed reduction control is terminated at the time that the accelerator is operated, and the vehicle then runs at a constant speed equal to the target vehicle speed instruction value. Another scheme can also be adopted whereby speed reduction control is terminated when the driver operates the accelerator, but when the difference between the target vehicle speed computed from the lateral acceleration set value and the curvature radius and the target vehicle speed instruction value exceeds a prescribed value when the accelerator is released, the target vehicle speed instruction value is changed so that speed reduction control is turned ON. In addition, a scheme can also be adopted in which the primary speed reduction control is not started if the driver has already operated the accelerator before entering speed reduction control.
In this way, by terminating speed reduction control upon operation of the accelerator by the driver, it is possible to reduce driver uneasiness when inappropriate speed reduction control is performed. Also, the target vehicle speed instruction value rises to the set vehicle speed corresponding to the accelerator operation by the driver, and then the target vehicle speed instruction value is taken to be the vehicle speed when the accelerator is released. As a result, the vehicle can run at a constant speed, and it is possible to prevent the speed reduction control operation.
As another example, besides accelerator operation by the driver, the driver can operate switches. In the following, the method is explained for changing the target vehicle speed instruction value with respect to such switch operation by the driver. As shown in
In this embodiment the set vehicle speed is increased when the RES switch is pressed. However, in other embodiments a scheme can also be adopted in which when, for example, the speed reduction control ON flag is set, the target vehicle speed instruction value is changed to become the set vehicle speed without a change in the set vehicle speed. More specifically, when the set vehicle speed is at 80 km/h, the speed reduction control is turned ON, and when the driver presses the RES switch, the set vehicle speed is kept as is at 80 km/h while the target vehicle speed instruction value is gradually changed to the set vehicle speed, that is, 80 km/h.
In this way, as speed reduction control is terminated due to operation of a switch by the driver, it is possible to reduce driver uneasiness when inappropriate speed reduction control is turned ON. Also, when the driver presses the switch, the set vehicle speed is not changed and the target vehicle speed instruction value is taken as the set vehicle speed, or the set vehicle speed is increased by 1 setting, so that the vehicle is accelerated to the set vehicle speed before speed reduction or to the newly set vehicle speed.
In the following, a method is explained for changing a warning activated when a target vehicle speed instruction value change is permitted. As shown in
In this example, the warning is issued as an announcement from a speaker of navigation system 1. However, it can also be issued by a buzzer, a meter display, a navigation screen display, a heads-up display, or any other form that can provide the warning information to the driver.
A scheme can also be adopted in which while primary speed reduction control is performed, the message “Branching ahead” is announced. In this way, while primary speed reduction control is performed, a warning of “Branching ahead” or the like is announced so that the driver can easily handle a situation in which inappropriate speed reduction control is turned ON. In a conventional travel controller, because a warning is issued when primary speed reduction control is turned ON, it is difficult for the driver to determine which curve ahead requires deceleration. In the present embodiment the warning of “Curve ahead” is announced before secondary speed reduction control, so that it is possible to avoid possible driver confusion due to too early a warning.
As explained above, according to certain embodiments, when a branching road ahead of the vehicle is detected by the navigation system, and speed reduction control is turned ON, by performing primary speed reduction control such that the driver does not notice it, it is still possible to avoid a warning or inappropriate speed reduction control that makes the driver notice it even when the vehicle enters a route different from the predicted route, and it is possible to travel with the traffic flow without a significant drop in the vehicle speed. On the other hand, when the vehicle follows the predicted route, it is possible by means of secondary speed reduction control to reduce the vehicle speed to the target vehicle speed as it passes the branching road so that the operation assisting effect can be realized with high reliability. In addition, because speed reduction control is terminated due to driver intervention, it is possible to alleviate driver unease due to inappropriate speed reduction control.
Also, according to certain embodiments, a warning is issued after the start of primary speed reduction control. As a result, the driver can easily handle a situation in which inappropriate speed reduction control is turned ON. In addition, because the warning is issued after the start of secondary speed reduction control, the warning is issued at an appropriate location.
Also, in embodiments described herein, the precondition is that speed reduction control is performed when branching of the road ahead of the vehicle is detected while traveling according to the preset vehicle speed. However, the present invention is not limited to this. For example, a scheme can also be adopted in which speed reduction control is performed while the driver operates of the accelerator. In this case, the requested driving torque corresponding to the accelerator operation by the driver can be reflected in the speed reduction control.
Also, in the speed reduction control described herein, the operation is performed with respect to the curve ahead of the vehicle. However, the present invention is not limited to this. For example, it can also be adopted for speed reduction control for a restricted speed corresponding to the specific road type, or school zone, slope, or other area where the vehicle should travel slowly.
In addition, the branching is not limited to situations with two branching roads. The present invention can also be adopted in a situation in which there are three or more branching roads. That is, stepwise speed reduction control consisting of primary speed reduction control and secondary speed reduction control can be performed for the road among the various branching roads with the lowest target vehicle speed (that is, the road with the highest target deceleration).
Accordingly, the above-described embodiments have been described in order to allow easy understanding of the invention and do not limit the invention. On the contrary, the invention is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims, which scope is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structure as is permitted under the law.
Number | Date | Country | Kind |
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2006-209747 | Aug 2006 | JP | national |
2007-168900 | Jun 2007 | JP | national |