Patent Grant
10384716
This application is based on and claims the benefit of priority from earlier Japanese Patent Application No. 2016-162802 filed Aug. 23, 2016, the description of which is incorporated herein by reference.
Technical Field
The present disclosure relates to a driving aid control apparatus.
Related Art
A driving aid apparatus disclosed in Japanese Patent Application Laid-Open Publication No. 2012-20652 includes a steering actuator and a steering control ECU. The steering actuator causes a steering device to generate an assistive torque to assist a driver's steering force. The steering control ECU is capable of performing feedforward control to control the assistive torque so that the vehicle can turn in accordance with a curvature of a lane in which the vehicle is traveling, and capable of performing feedback control to control the assistive torque so that the vehicle can approach a center line of a lane in which the vehicle is traveling. The steering control ECU determines whether or not the vehicle is changing lanes. If the vehicle is not changing lanes, the steering control ECU uses the assistive torque of the feedforward control. When the vehicle is changing lanes, the steering control ECU uses the assistive torque of the feedforward control and the assistive torque of the feedback control.
In a situation where the vehicle is traveling in a lane, a driver of the vehicle fine tunes a steering angle to keep straight-ahead driving or keep driving in a straight line. This may cause an oscillatory change in the travel direction of the vehicle. Such an oscillatory change in the travel direction of the vehicle may cause an oscillatory change in curvature information detected by the driving aid apparatus. The oscillatory change in the curvature information may in turn cause an oscillatory change in the assistive torque set by the feedforward control based on the curvature information. This can prevent stabilization of the vehicle behavior.
In view of the above, driving aid control apparatuses that can stabilize driving aid control are desired.
The present disclosure provides an apparatus for performing driving aid control to cause a travel trajectory of a mobile object to follow a setpoint trajectory by transmitting a control command value to a yaw moment controller capable of controlling a yaw moment of the mobile object. The apparatus includes: a first control command value calculator configured to calculate a first control command value used to calculate the control command value; a straight-driving stabilizing compensator configured to, when the mobile object is driving straight, calculate a first control command compensation value by decreasing the first control command value, a second control command value calculator configured to calculate a second control command value used to calculate the control command value; and a third control command value calculator configured to calculate the final control command value based on the first control command compensation value and the second control command value.
With the above configuration, calculation of the first control command value by decreasing the first control command value can provide a first control command compensation value with oscillation suppressed as compared with the first control command value. Therefore, when the mobile object is driving straight, the final control command value is calculated based on the first control command compensation value with oscillation suppressed as compared with the first control command value. That is, the oscillation of the first control command value is less likely to affect the final control command value, which can improve stability of the driving aid control.
Hereinafter, an exemplary embodiment of the present disclosure will be described in detail with reference to the accompanying drawings, in which like reference numerals refer to like or similar elements regardless of reference numerals and a duplicated description thereof will be omitted.
A driving aid control apparatus according to one embodiment will now be described with reference to the drawings. The driving aid control apparatus is used in a driving aid system that performs driving aid control to cause a travel trajectory of a vehicle to follow a setpoint trajectory.
As shown in
The driving environment detector 20 detects a position of the vehicle, a road shape ahead of the vehicle, and others. The driving environment detector 20 includes a GNSS receiver 21 and a camera 22. The GNSS receiver 21 receives navigation signals from a plurality of satellites constituting a global navigation satellite system (GNSS), and outputs the received navigation signals to the driving aid ECU 50. The camera 22 outputs to the driving aid ECU 50 a signal corresponding to image data acquired by imaging ahead of the vehicle.
The map database 30 is a database of information, such as latitudes and longitudes of roads and various facilities. Information about road shapes and lanes of roads are also registered in the map database 30. The information about the lanes includes locations and types of the lane lines or lane boundaries. The map database 30 may be dedicated to the driving aid system 10 or may be a database commonly used in a car navigation device mounted in the vehicle.
The vehicle state quantity detector 40 detects various state quantities of the vehicle. The vehicle state quantity detector 40 includes a vehicle speed sensor 41 and a yaw rate sensor 42. The vehicle speed sensor 41 detects a travel speed of the vehicle based on a rotational speed of the wheel and outputs a signal corresponding to the detected travel speed to the driving aid ECU 50. The yaw rate sensor 42 detects a yaw rate that is a rate of change of a yaw angle over time and outputs a signal corresponding to the yaw rate to the driving aid ECU 50.
The driving aid ECU 50 is configured as a microcomputer or the like that incorporates therein a central processing unit (CPU) (not shown), a read-only memory (ROM) (not shown), a random access memory (RAM) (not shown). The CPU performs driving aid control processing to cause a travel trajectory of the vehicle to follow a setpoint trajectory. The ROM stores programs and data necessary for the driving aid control. The RAM transiently stores results of the CPU.
The driving aid ECU 50 loads output signals from the GNSS receiver 21 and the camera 22. The driving aid ECU 50 acquires information of a latitude φ and longitude λ corresponding to a current position of the vehicle based on the output signals from the GNSS receiver 21. The driving aid ECU 50 acquires image data I based on the output signal from the camera 22. The driving aid ECU 50 acquires map data M from the map database 30. The driving aid ECU 50 sets a setpoint trajectory La of the vehicle based on the acquired information from the GNSS receiver 21, the camera 22, and the map database 30.
The driving aid ECU 50 further loads output signals from the vehicle speed sensor 41 and the yaw rate sensor 42. The driving aid ECU 50 acquires information of a travel speed V and a yaw rate Y of the vehicle based on the output signals from the vehicle speed sensor 41 and the yaw rate sensor 42.
Based on the setpoint trajectory La, the travel speed V and the yaw rate Y, the driving aid ECU 50 calculates a steering angle command value δ for causing the actual travel trajectory of the vehicle to follow the setpoint trajectory La. The steering angle command value δ is a target steering angle.
The driving aid ECU 50 is communicatively connected to the steering angle controller 60 via an onboard network 70. The driving aid ECU 50 transmits via the onboard network 70 information of the steering angle command value δ to the steering angle controller 60, thereby performing the driving aid control to cause the travel trajectory of the vehicle to follow the setpoint trajectory.
The steering angle controller 60 is capable of controlling the steering angle of the vehicle. An electrically-powered steering device that applies an assistive torque to a steering shaft to thereby assist the driver of the vehicle in steering may be used as the steering angle controller 60. The steering angle controller 60 receives the steering angle command value δ from the driving aid ECU 50 via the onboard network 70, and performs steering angle feedback control to cause an actual steering angle to follow the steering angle command value δ. In the present embodiment, the steering angle controller 60 serves as a yaw moment controller capable of controlling a yaw moment of the vehicle.
The driving aid control to be performed in the driving aid ECU 50 will now be described in more detail.
As shown in
The current position detector 51 receives information, such as a latitude φ and longitude λ corresponding to a current position of the vehicle, map data M, and image data I. The current position detector 51 detects a current position Pc of the vehicle based on the received information. More specifically, the latitude φ and longitude λ represent an absolute position on the map data M. The current position detector 51 translates the absolute position of the vehicle represented by the latitude φ and longitude λ on the map data M to a position in a vehicle's fixed coordinate system to acquire a relative positional relationship between each lane registered in the map data M and the vehicle. In addition, the current position detector 51 image-processes the image data in an appropriate manner to detect a position of a lane ahead of the vehicle, thereby acquiring a relative positional relationship between the lane and the vehicle. The current position detector 51 uses at least one of the relative positional relationship between the lane and the vehicle acquired from the map data M and the relative positional relationship between the lane and the vehicle acquired from the image data I to detect a current position Pc of the vehicle. Subsequent processing will be performed using the vehicle's fixed coordinate system.
The setpoint trajectory setter 52 receives information, such as the current position Pc of the vehicle detected by the current position detector 51, the map data M and the image data I. The setpoint trajectory setter 52 sets a setpoint trajectory La based on the received information. For example, the setpoint trajectory setter 52 detects positions of lane lines that demarcate the lane that the vehicle is traveling in based on the map data M and the image data I, and sets a setpoint trajectory La to a center line between the two-lane lines.
The first control command value calculator 53 receives information, such as the current position Pc of the vehicle detected by the current position detector 51, the setpoint trajectory La set by the setpoint trajectory setter 52, the travel speed V and yaw rate Y of the vehicle. Based on the received information, the first control command value calculator 53 calculates a first steering angle command value δ1 by performing feedforward control based on a future target position Pc* on the setpoint trajectory La. In the present embodiment, the first steering angle command value δ1 corresponds to a first control command value, and the feedforward control corresponds to target-position following control. The following control method may be used as the target-position following control.
As shown in
The first control command value calculator 53 calculates a travel trajectory F that allows the vehicle to approach the target position Pc* from the current position Pc and calculates a target curvature pa of the calculated travel trajectory F. Subsequently, the first control command value calculator 53 calculates a first steering angle command value δ1 to achieve the target curvature pa according to equations based on a two-wheel model of a vehicle.
More specifically, the first control command value calculator 53 calculates a first steering angle command value δ1 according to the following equations (f1)-(f3):
In the equations (f1)-(f3), J is a yaw moment of inertia of the vehicle, Kf is front-wheel cornering power, Kr is rear-wheel cornering power, Lf is a distance between a vehicle center of gravity and a front-wheel axis, and Lr is a distance between a vehicle center of gravity and a rear-wheel axis. These parameters are prestored in the ROM of the driving aid ECU 50.
As shown in
More specifically, the straight-driving stabilizing compensator 54 calculates the gain Kdgn according to the following equation (f4):
In the equation (f4), δth is a steering angle threshold. An amplitude of oscillatory change in the first steering angle command value δ1 that is unwanted when the vehicle is driving straight is measured in advance by experiments or the like, and the steering angle threshold δth is set to a value of the amplitude.
According to the equation (f4), the straight-driving stabilizing compensator 54 sets the gain Kdgn to a smaller one of one and a square of (δ1/δth). That is, as shown in
Based on the gain Kdgn calculated according to the equation (f4) and the first steering angle command value δ1, the straight-driving stabilizing compensator 54 calculates a first steering angle command compensation value δ11 according to the following equation (f5):
δ11=Kdgn×δ1 (f5)
As shown in
As shown in
The adder 57 adds the first steering angle command compensation value δ11 calculated by the straight-driving stabilizing compensator 54 and the second steering angle command value δ2 calculated by the second control command value calculator 56 to calculate a final steering angle command value δ. The driving aid ECU 50 transmits the steering angle command value δ calculated by the adder 57 to the steering angle controller 60. In the present embodiment, the adder 57 serves as a third control command value calculator.
Processing to calculate the steering angle command value δ to be performed in the driving aid ECU 50 will now be described with reference to
As shown in
In step S14, the driving aid ECU 50 performs setpoint-trajectory following control as the feedback control to calculate a second steering angle command value δ2. More specifically, the driving aid ECU 50 calculates a lateral error ΔH based on information, such as the current position Pc detected by the current position detector 51 and the setpoint trajectory La set by the setpoint trajectory setter 52, and then performs the integral control based on the lateral error ΔH to thereby calculate a second steering angle command value δ2.
In step S15, the driving aid ECU 50 adds the first steering angle command compensation value δ11 and the second steering angle command value δ2 to calculate a final steering angle command value δ. In step S16, the driving aid ECU 50 transmits the steering angle command value δ to the steering angle controller 60.
In the driving aid ECU 50, the current position detector 51 executes the operation of step 10. The setpoint trajectory setter 52 executes the operation of step 11. The first control command value calculator 53 executes the operation of step S12. The straight-driving stabilizing compensator 54 executes the operation of step S13. The second control command value calculator 55 executes the operation of step S14. The adder 57 executes the operation of step S15.
Operations of the driving aid system 10 will now be described with reference to
When the vehicle is driving straight, the driving aid ECU 50 adjusts finely the steering angle for the driver of the vehicle to keep the vehicle driving straight, which may cause disturbances. As indicated by the dashed-two dotted line in
Even when the first steering angle command value δ1 oscillates during straight driving of the vehicle, the driving aid ECU 50 of the present embodiment, as shown in
In addition, when the vehicle is turning, the first steering angle command value δ1 exceeds the steering angle threshold δth. As shown in
The final steering angle command value δ is set to a sum of the first steering angle command value δ1 and the second steering angle command value δ2. Therefore, even if the first steering angle command compensation value δ11 is set to almost zero by the straight-driving stabilizing compensator 54, the setpoint-trajectory following control based on the second steering angle command value δ2 is performed. That is, in the presence of an error between the current position Pc of the vehicle and the setpoint trajectory La, the feedback control works to reduce such an error, which allows the position of the vehicle to follow the setpoint trajectory La. Therefore, deviation of the position of the vehicle from the setpoint trajectory La can be prevented.
The driving aid ECU 50 of the present embodiment described as above can provide the following advantages (1) to (5).
(1) When the vehicle is driving straight, the driving aid ECU 50 decreases the first steering angle command value δ1 to thereby calculate the first steering angle command compensation value δ11. The driving aid ECU 50 calculates the final steering angle command value δ based on the first steering angle command compensation value δ11 and the second steering angle command value δ2. With this configuration, even if an oscillatory change in the first steering angle command value δ1 occurs due to a disturbance, such an oscillatory change in the first steering angle command value δ1 is less likely to affect the final steering angle command value δ, which can improve stability of the driving aid control.
(2) If the first steering angle command value δ1 is equal to or greater than the steering angle threshold δth, the straight-driving stabilizing straight-driving stabilizing compensator 54 directly outputs the first steering angle command value δ1 as the first steering angle command compensation value δ11. If the first steering angle command value δ1 is less than the steering angle threshold δth, the straight-driving stabilizing compensator 54 decreases the first steering angle command value δ1 to output it as the first steering angle command compensation value δ11. With this configuration, if the first steering angle command value δ1 is equal to or greater than the steering angle threshold δth, that is, when the vehicle is turning, the target-position following control based on the first steering angle command value δ1 is reliably performed, which can inhibit driving aid control responsiveness lowering during turning of the vehicle.
(3) The straight-driving stabilizing compensator 54 calculates the gain Kdgn based on a ratio of the first steering angle command value δ1 to the first steering angle threshold δth, and calculates the first steering angle command compensation value δ11 by multiplying the first steering angle command value δ1 by the gain Kdgn. With this configuration, the first steering angle command compensation value δ11 can be decreased significantly after the vehicle has entered a straight road from a curve. This is because the gain Kdgn decreases as the first steering angle command value δ1 decreases due to the vehicle having passed the curve and entered the straight road. Therefore, the first steering angle command value δ1 can be decreased during straight driving of the vehicle without determining whether or not the vehicle is driving straight.
(4) The straight-driving stabilizing compensator 54 sets the gain Kdgn to a smaller one of one and a square of the ratio of the first steering angle command value δ1 to the steering angle threshold δth. With this configuration, when the gain Kdgn is set to a square of the ratio of the first steering angle command value δ1 to the steering angle threshold δth, the first steering angle command compensation value δ11 decreases with decreasing ratio of the first steering angle command value δ1 to the steering angle threshold δth. This can more reliably inhibit oscillation of the first steering angle command compensation value δ11, which can further improve the driving aid control stability.
(5) The first control command value calculator 53 calculates a first steering angle command value δ1 by performing feedforward control based on a future target position Pc* on a setpoint trajectory La. The second control command value calculator 56 calculates a second steering angle command value δ2 by performing feedback control based on a lateral error ΔH that is an error between a current position Pc of the vehicle and the setpoint trajectory La. In such a driving aid ECU 50 configured to perform the feedforward control and the feedback control in combination, oscillation of the feedforward control that may occur during straight driving of the vehicle is likely to adversely affect the vehicle behavior. Therefore, the above configuration is advantageous to inhibit the oscillation.
Modifications
There will now be described some modifications that may be devised without departing from the spirit and scope of the present disclosure.
(M1) Methods used by the current position detector 51 to detect the current position Pc of the vehicle may be changed as appropriate. For example, the current position detector 51 may detect the current position Pc of the vehicle based on lane lines detected by the laser radar device or the millimeter-wave radar. The current position detector 51 may estimate a current position Pc of the vehicle based on dead reckoning based on a travel speed V detected by the travel speed sensor 41 and a yaw rate Y detected by the yaw rate sensor 42. The current position detector 51 may estimate a current position Pc of the vehicle based on a combination of various vehicle state quantities, such as the image data I, a travel speed V, a yaw rate Y, an acceleration, a steering angle, and a slip angle.
(M2) The method of the target-position following control performed by the first control command value calculator 53 may be changed as appropriate. For example, the first control command value calculator 53 may calculate the first steering angle command value δ1 using a look-ahead model, a primary predictive model, a secondary predictive model or the like. The look-ahead model is a control method based on a lateral error between the setpoint trajectory La and a point of regard that is located at a predetermined distance from the current position Pc in the travel direction of the vehicle. The primary predictive model and the secondary predictive model are control methods based on a future lateral error that is an error between the setpoint trajectory La and a predictive position of the vehicle after a predetermined period of time has elapsed and is calculated based on predefined vehicle state quantities. In the primary predictive model, a linear expression with the vehicle state quantities as variables is used, where the linear expression represents a relationship between a predicted position of the vehicle and the vehicle state quantities. In the secondary predictive model, a quadratic expression with the vehicle state quantities as variables is used, where the quadratic expression represents a relationship between a predicted position of the vehicle and the vehicle state quantities.
(M3) The straight-driving stabilizing compensator 54 may be configured to determine whether or not the vehicle is driving straight based on vehicle state quantities, such as a steering angle and yaw rate Y of the vehicle, and if it is determined that the vehicle is driving straight, decrease the first steering angle command value δ1. That is, the straight-driving stabilizing compensator 54 may include a determiner configured to determine whether or not the vehicle is driving straight.
(M4) The straight-driving stabilizing compensator 54 may use a value of an nth order function, logarithm function, or exponential function of the ratio of the first steering angle command value δ1 to the steering angle threshold δth, as the gain Kdgn.
(M5) The straight-driving stabilizing compensator 54 may decrease the second steering angle command value δ2 instead of the first steering angle command value δ1.
(M6) Methods used by the driving aid ECU 50 to detect the travel speed V and the yaw rate Y may be changed as appropriate. For example, the driving aid ECU 50 may detect the travel speed V using a GNSS speedometer. Alternatively, the driving aid ECU 50 may detect the travel speed V based on an absolute speed acquired from the image data I of the camera 22. The driving aid ECU 50 may detect the yaw rate Y based on a speed difference between the left and right wheels.
(M7) Methods used by the setpoint trajectory setter 52 to set the setpoint trajectory La may be changed as appropriate. For example, to support a lane change, the setpoint trajectory setter 52 may set the setpoint trajectory La to cross a lane line between different lanes. The setpoint trajectory setter 52 may detect an obstacle to travel of the vehicle based on the current position Pc, the map data M, and the image data I, and may set the setpoint trajectory La that can avoid the obstacle. The setpoint trajectory setter 52 may calculate a plurality of setpoint trajectory La candidates and then select one of the plurality of setpoint trajectory La candidates as a setpoint trajectory La to be traveled.
(M8) In the embodiment described above, the map database 30 used in the driving aid system 10 is a database mounted in a vehicle. Alternatively, the map database 30 may be a map database that is registered in and downloaded from a server.
(M9) The steering angle controller 60 is a device to correct the travel trajectory of the vehicle by generating a yaw moment applied to the vehicle. Such a device is not limited to the steering angle controller 60. Instead of using the steering angle controller 60, a device may be used that is configured to change the distribution of driving or braking forces to the wheels of the vehicle to thereby generate a yaw moment applied to the vehicle.
(M10) Alternatively, the driving aid ECU 50 may calculate an arbitrary control command value that allows a steering angle of the vehicle to be controlled. Such a control command value may include a control command value of assistive torque to be applied from a motor to a steering shaft. In addition, types of the first and second control command values respectively calculated by the first control command value calculator 53 and the second control command value calculator 55 may be changed depending on a type of control command value calculated by the driving aid ECU 50.
(M11) In the embodiment described above, the driving aid ECU 50 is applied to every automobile. Alternatively, the driving aid ECU 50 configured as above may be applied to any other type of vehicle, such as a motorcycle or a bicycle.
(M12) The means and/or functions provided by the driving aid ECU 50 can be provided by software stored in a non-transitory computer-readable storage medium and a computer executing it, software only, hardware only, or a combination thereof. For example, when the driving aid ECU 50 is provided by an electronic circuit which is hardware, it can be provided by a digital circuit including a number of logic circuits or an analog circuit.
(M13) The embodiments of the present disclosure have been described with reference to specific examples. However, the disclosure is not limited to those specific examples. Any design modification applied to such specific examples by a person skilled in the art is encompassed in the scope of the present disclosure, as long as it has the features of the present disclosure. Each element included in each of the above-mentioned specific examples, as well as the arrangement, are not limited to those illustrated in the specific examples and may be arbitrarily changed.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2016-162802 | Aug 2016 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 20170122749 | Urano | May 2017 | A1 |
| 20170228159 | Tanaka | Aug 2017 | A1 |
| Number | Date | Country |
|---|---|---|
| 2012-020652 | Feb 2012 | JP |
| 2013-212838 | Oct 2013 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20180057053 A1 | Mar 2018 | US |
