JP2008189053A - Steering support device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steering support device restraining interference of steering wheel returning control and supporting control concerning steering. <P>SOLUTION: This steering support device 1 is furnished with a steering wheel returning means 3 to give steering torque in a neutral point direction of a steering wheel when there is no steering wheel operation by a driver and a travelling support means 2 to give the steering torque so that one's own vehicle comes to be in a target travelling state. It is characteristically possible to make the steering torque to be given by at least one of the steering wheel returning means 3 and the travelling support means 2 variable in giving the steering torque by the steering wheel returning means 3 and giving the steering torque by the travelling support means 2. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a steering assist device that performs steering wheel return control and assist control related to steering.

  In recent years, various devices (such as a lane keeping support device and a lane departure prevention device) for assisting the driver in steering have been developed in order to reduce the burden on the steering operation of the driver. For example, in the lane keeping assist device, a white line is detected from a captured image obtained by imaging the front of the vehicle, and a steering torque is output to the steering mechanism by driving the steering actuator so that the vehicle travels in the center of the lane composed of the white lines on the left and right sides. To do.

In addition, a steering wheel return device has been developed that smoothly returns the steering wheel to a neutral point when there is no steering input by the driver after the steering wheel has been steered (see Patent Document 1). For example, the steering wheel return device detects the steering input by the driver and also detects the steering angle of the steering wheel, and steers to return to the neutral point when there is no steering operation by the driver and the steering angle deviates from the neutral point. The actuator is driven to output a steering torque to the steering mechanism.
Japanese Patent Publication No. 2-40537 JP 2003-26028 A JP 2001-233227 A JP 2001-48033 A JP 2000-142441 A

  When the lane keeping assist device and the steering wheel return device are mounted on the vehicle, the steering actuator such as an electric power steering device is shared as the steering actuator, and the steering actuator requires the steering torque and the steering wheel return control. Steering torque is output to each steering mechanism. In such a vehicle, when the driver is not operating the steering wheel, the lane keeping assist control and the steering wheel return control may operate simultaneously. In this case, the required steering torque by the lane keeping support control and the required steering torque by the steering wheel return control are simultaneously output by the common steering actuator, so the lane keeping support control and the steering wheel return control interfere. For this reason, the output steering torque output by the steering actuator may be excessive or insufficient with respect to the required steering torque for the lane keeping assist control, and the vehicle may shift from the center of the lane.

  Therefore, an object of the present invention is to provide a steering assist device that suppresses interference between steering wheel return control and assist control related to steering.

  The steering assist device according to the present invention provides a steering wheel return means for applying a steering torque toward the neutral point of the steering wheel when there is no steering operation by the driver, and the steering torque is applied so that the host vehicle is in a target running state. When the steering torque is applied by the steering wheel returning means and the steering torque is applied by the driving assistance means, the steering assistance device is provided by at least one of the steering wheel returning means and the driving assistance means. The steering torque is variable.

  In this steering assist device, when there is no steering operation by the driver after steering by the steering wheel return means, steering torque in the neutral point direction of the steering wheel is applied to the steering mechanism, and the steering wheel is returned to the neutral point. Further, in the steering assist device, steering torque is applied by the travel assist means (for example, the lane keeping assist means, the lane departure prevention assist means) so that the host vehicle is in the target travel state, and the host vehicle is driven to the target. State. In particular, in the steering assist device, when the control by the steering wheel returning means is activated and the control by the traveling assistance means is activated, the control by the steering wheel returning means and the control by the traveling assistance means are not interfered with each other. The steering torque applied by at least one means is changed. As described above, in the steering assist device, when the steering wheel returning means and the travel assist means perform control simultaneously, by changing at least one of the required steering torques of the two means, an appropriate steering torque as the steering assist is obtained. Can be output, and interference of each control by the two means can be suppressed.

  In the steering assist device according to the present invention, when the steering torque is applied by the steering wheel return means and the steering torque is applied by the travel support means, the gain for the steering torque applied by at least one of the steering wheel return means and the travel support means. It is good also as a structure which changes. In this steering assist device, the steering torque to be easily applied can be made variable by changing the gain with respect to the steering torque.

  In the steering assist device according to the present invention, when the steering torque is applied by the handle return means and the steering torque is applied by the travel support means, the steering wheel is output so that the output steering torque becomes the steering torque requested by the travel support means. It is preferable that the steering torque applied by at least one of the return means and the travel support means is variable. In this steering assist device, by setting the steering torque output to the steering mechanism to the steering torque requested by the control by the travel assist means, the host vehicle that is prioritized as the steering assist can be brought into the target travel state.

  The present invention can suppress interference between the steering wheel return control and the driving support control even when the steering wheel return control and the driving support control related to steering are operated simultaneously.

  Hereinafter, embodiments of a steering assist device according to the present invention will be described with reference to the drawings.

  In the present embodiment, the steering assist device according to the present invention is applied to a steering assist system including a lane keeping assist device and an electric power steering device. The electric power steering apparatus according to the present embodiment has a steering wheel return function and an arbitration function in addition to the power steering function, and applies a steering torque to the steering mechanism by a steering actuator. The lane keeping assist device according to the present embodiment has a lane keeping assist function, and applies steering torque to the steering mechanism using the steering actuator of the electric power steering device. In the present embodiment, the steering wheel return function of the electric power steering device corresponds to the steering wheel return means described in the claims, and the lane keeping support function of the lane keeping support device is the driving assistance described in the claims. Corresponds to means.

  With reference to FIG. 1, the steering assistance system 1 is demonstrated. FIG. 1 is a configuration diagram of a steering assist system (lane keeping assist device, electric power steering device) according to the present embodiment.

  The steering assist system 1 provides steering assistance to the driver in order to reduce the burden of the driver's steering operation. In the steering assist system 1, when there is a steering operation by the driver, the steering operation by the driver is reduced by the power steering function, and even when there is no steering operation by the driver, the lane keeping support function, the steering wheel return function, and the arbitration function are used. Steer. For this purpose, the steering assist system 1 includes a lane keeping assist device 2 and an electric power steering device 3.

  The lane keeping assist device 2 will be described. The lane keeping assist device 2 applies steering torque to the steering mechanism using the electric power steering device 3 so that the host vehicle travels in the center of the lane. For this purpose, the lane keeping assist device 2 includes a lane detection sensor 10, a vehicle speed sensor 11, and a lane keeping assist ECU [Electronic Control Unit] 30, and uses the electric power steering device 3 as an output.

  The lane detection sensor 10 includes a camera and an image processing device. The camera is a camera that images the front of the host vehicle, and includes an image sensor such as a CCD (Charge coupled device) or a CMOS (Complementary Metal Oxide Semiconductor). The camera is attached in front of the host vehicle so that its optical axis direction coincides with the traveling direction of the vehicle. The camera captures an image of a road ahead of the host vehicle and transmits the captured image data as an image signal to the image processing apparatus. In the image processing apparatus, an image signal is received at regular intervals, and a pair of white lines indicating a lane in which the vehicle is traveling is recognized from captured image data of the image signal. In the image processing apparatus, the lane width and the line passing through the center of the pair of white lines (that is, the center line of the lane) are calculated from the recognized pair of white lines. Further, the image processing apparatus calculates the radius (curve radius) of the center line of the lane, and calculates the curvature from the curve radius. Further, the image processing apparatus calculates the vehicle orientation (yaw angle) with respect to the white line and the vehicle center position (offset) with respect to the lane center line. Then, the image processing apparatus transmits the recognized pair of white line information and each calculated information to the lane keeping assist ECU 30 as a lane signal.

  The vehicle speed sensor 11 is a sensor that detects the vehicle speed of the host vehicle. The vehicle speed sensor 11 detects the vehicle speed of the host vehicle, and transmits the detected vehicle speed to the lane keeping assist ECU 30 as a vehicle speed signal. Further, the vehicle speed sensor 11 also transmits a vehicle speed signal to the EPS (Electronic Power Steering) ECU 31 of the electric power steering device 3.

  The lane keeping support ECU 30 includes a CPU [Central Processing Unit], a ROM [Read Only Memory], a RAM [Random Access Memory], and the like, and comprehensively controls the lane keeping support device 2. The lane keeping assist ECU 30 receives a lane signal from the lane detection sensor 10 and a vehicle speed reception from the vehicle speed sensor 11 at regular intervals. The lane keeping assist ECU 30 operates the lane keeping assist control when the lane keeping assist device 2 is activated by an operation by the driver. When the lane keeping assist control is activated, the lane keeping assist ECU 30 uses the control map or the like based on various information (curvature, yaw angle, offset) indicated in the lane signal and the vehicle speed indicated in the vehicle speed signal. The required steering torque T1 necessary for traveling so that the center line coincides with the center line of the lane is set. The lane keeping assist ECU 30 transmits a lane keeping assist control signal indicating the required steering torque T1 to the EPS ECU 31.

  The electric power steering device 3 will be described. The electric power steering device 3 applies steering torque to the steering mechanism in order to reduce steering operation by the driver. The electric power steering device 3 applies steering torque to the steering mechanism in order to smoothly return the steering wheel to the neutral point when there is no steering wheel operation by the driver after steering. Furthermore, the electric power steering device 3 adjusts the steering torque applied by the lane keeping assist control and the steering wheel return control. For this purpose, the electric power steering apparatus 3 includes a vehicle speed sensor 11, a steering torque sensor 12, a steering angle sensor 13, a steering actuator 20, and an EPS ECU 31.

  The steering torque sensor 12 is a sensor that detects the steering torque input from the steering wheel. The steering torque sensor 12 detects the steering torque, and transmits the detected steering torque to the EPS ECU 31 as a steering torque signal. The steering angle sensor 13 is a sensor that detects the steering angle of the steering wheel. The steering angle sensor 13 detects the steering angle, and transmits the detected steering angle to the EPS ECU 31 as a steering angle signal.

  The steering actuator 20 includes a motor and a speed reduction mechanism, and transmits a rotational driving force by the motor to a steering mechanism (rack, pinion, column, etc.) via the speed reduction mechanism, and applies a steering torque to the steering mechanism. The motor is supplied with a control current from the EPS ECU 31 and is driven to rotate in accordance with the control current.

  The EPS ECU 31 includes a CPU, a ROM, a RAM, a motor drive circuit, and the like, and comprehensively controls the electric power steering device 3. The EPS ECU 31 receives the vehicle speed from the vehicle speed sensor 11, the steering torque signal from the steering torque sensor 12, and the steering angle signal from the steering angle sensor 13 at regular intervals. Further, the EPS ECU 31 receives a lane keeping support control signal from the lane keeping assist ECU 30. The EPS ECU 31 performs power steering control, steering wheel return control, and arbitration control, and controls the steering actuator 20 so that the steering torque set in each control is obtained.

  The power steering control will be described. In the EPS ECU 31, when there is a steering operation by the driver (when the steering torque indicated by the steering torque signal is equal to or greater than a threshold value), the power steering control is activated. When the power steering control is activated, the EPS ECU 31 sets the assist steering torque using a control map or the like based on the steering torque indicated by the steering torque signal and the vehicle speed indicated by the vehicle speed signal. Then, the EPS ECU 31 sets a target current necessary for applying the assist steering torque, and supplies a control current to the motor of the steering actuator 20 so as to be the target current.

  The handle return control will be described. In the EPS ECU 31, when there is no steering operation by the driver (when the steering torque indicated by the steering torque signal is less than the threshold value) and when the steering angle is other than the neutral point (the steering angle indicated by the steering angle signal is not 0). ), Handle return control is activated. When the steering wheel return control is activated, the EPS ECU 31 is required to smoothly return the steering angle to the neutral point using a control map or the like based on the steering angle indicated by the steering angle signal and the vehicle speed indicated by the vehicle speed signal. The required steering torque T2 is set.

  Arbitration control will be described. When the lane keeping assist device 2 is activated, the lane keeping assist control and the steering wheel return control are simultaneously activated, and the required steering torque T1 and the required steering torque T2 may be set together. In this case, if the steering actuator 20 is controlled using (the required steering torque T1 + the required steering torque T2) as the target steering torque T, the steering torque required for the lane keeping assist control is not output to the steering mechanism. As a result, the host vehicle deviates from the lane, and appropriate lane maintenance support cannot be performed.

  Therefore, even when the required steering torque T1 and the required steering torque T2 are both set, the target steering torque T needs to be set as the required steering torque T1. Therefore, in order to change the required steering torque of at least one of the required steering torque T1 and the required steering torque T2, the gain K1 is set for the required steering torque T1, the gain K2 is set for the required steering torque T2, Target steering torque T = K1 × T1 + K2 × T2 (1). Further, in order to cause the host vehicle to travel in the center of the lane, the target steering torque T in equation (1) is set as the required steering torque T1, and T1 = K1 × T1 + K2 × T2 (2). When this equation (2) is transformed, K2 / (1-K1) = T1 / T2 (3). By selecting an arbitrary set of real numbers of K1 and K2 that satisfy this equation (3), even when the lane keeping assist control and the steering wheel return control are operating simultaneously, the host vehicle is driven in the center of the lane. be able to. As for the set of real numbers of K1 and K2, a set of real numbers of K1 and K2 with respect to the value of T1 / T2 may be obtained in advance and held in a map or the like.

  The EPS ECU 31 always operates arbitration control, and performs a torque gain variable flag setting process and a target steering torque setting process. First, the EPS ECU 31 determines whether the lane keeping assist control is operating and the steering wheel return control is operating. For example, when the required steering torque T1 is set, it is determined that the lane keeping assist control is activated, and when the required steering torque T2 is set, it is determined that the steering wheel return control is activated. When the lane keeping assist control is operating and the steering wheel return control is operating, the EPS ECU 31 sets the torque gain variable flag to ON. On the other hand, when at least one of the lane keeping assist control and the steering wheel return control is not operating, the EPS ECU 31 sets the torque gain variable flag to OFF. The torque gain variable flag is a flag indicating whether or not it is necessary to change the required steering torques T1 and T2 by setting the gains K1 and K2 by simultaneously operating the lane keeping assist control and the steering wheel return control. In this case, it is necessary to change, and in the case of OFF, there is no need to change.

  Next, the EPS ECU 31 determines whether or not the torque gain variable flag is ON. When the torque gain variable flag is ON (when the lane keeping assist control and the steering wheel return control are simultaneously operated), the EPS ECU 31 uses the required steering torques T1 and T2, and K2 / (1-K1) = T1. Gains K1 and K2 that satisfy / T2 are set. Then, the EPS ECU 31 calculates the target steering torque T = K1 × T1 + K2 × T2 using the set gains K1, K2 and the required steering torques T1, T2. When the torque gain variable flag is OFF (when the lane keeping assist control and the steering wheel return control are not simultaneously operated), the EPS ECU 31 requests the required steering torque as the target steering torque T when only the lane keeping assist control is actuated. When T1 is set, the required steering torque T2 is set as the target steering torque T when only the steering wheel return control is operating, and 0 is set as the target steering torque T when both controls are not operating. Then, the EPS ECU 31 sets a target current necessary for applying the target steering torque T, and supplies a control current to the motor of the steering actuator 20 so as to be the target current.

  When a predetermined torque is set as the assist steering torque and the target steering torque, the target steering torque may be set to 0 in order to give priority to the steering operation by the driver, or the target steering torque may be set to a predetermined value. The gain may be multiplied, and the multiplied value (added torque) may be added to the assist steering torque to obtain the corrected assist steering torque. The additional torque is a relatively small torque that assists the steering operation by the driver.

  With reference to FIG. 1, the operation | movement in the steering assistance system 1 is demonstrated. In particular, the torque gain variable flag setting process and the target steering torque setting process by the arbitration control in the EPS ECU 31 will be described with reference to the flowcharts of FIGS. FIG. 2 is a flowchart showing a flow of a torque gain variable flag setting process in the EPS ECU of FIG. FIG. 3 is a flowchart showing a flow of a target steering torque setting process in the EPS ECU of FIG.

  The lane detection sensor 10 images a road ahead of the host vehicle with a camera. Then, the lane detection sensor 10 recognizes a pair of white lines from the captured image by the image processing device, and determines from the pair of white lines the lane width, the lane center line, the curve radius and curvature of the lane center line, the yaw angle, and the lane center line. The vehicle offset is calculated, and the information on the pair of white lines and the calculated information are transmitted as lane signals to the lane keeping assist ECU 30. The vehicle speed sensor 11 detects the vehicle speed of the host vehicle, and transmits vehicle speed information as a vehicle speed signal to the lane keeping assist ECU 30 and the EPS ECU 31. The steering torque sensor 12 detects the steering torque input from the steering wheel, and transmits the steering torque information to the EPS ECU 31 as a steering torque signal. The steering angle sensor 13 detects the steering angle of the steering wheel and transmits the steering angle information to the EPS ECU 31 as a steering angle signal.

  The EPS ECU 31 receives a vehicle speed signal, a steering torque signal, and a steering angle signal at regular intervals. When there is a steering wheel operation by the driver, the power steering control is activated, and the EPS ECU 31 sets the assist steering torque based on the steering torque and the vehicle speed. Then, the EPS ECU 31 sets a target current necessary for generating the assist steering torque, and supplies a control current to the steering actuator 20 so as to be the target current. In the steering actuator 20, the motor is rotationally driven according to the control current, and this rotational driving force is output to the steering mechanism via the speed reduction mechanism. As a result, an assist torque corresponding to the driver's steering torque and vehicle speed is applied to the steering mechanism, and the driver's steering operation is reduced.

  Further, when there is no steering wheel operation by the driver and the steering wheel steering angle is other than the neutral point, the steering wheel return control is activated, and the EPS ECU 31 smoothly returns the steering angle to the neutral point based on the steering angle and the vehicle speed. Is set to the required steering torque T2.

  When the lane keeping assist device 2 is activated by the driver, the lane keeping assist control is activated, and the lane keeping assist ECU 30 receives a lane signal and a vehicle speed signal at regular intervals. The lane keeping assist ECU 30 sets the required steering torque T1 necessary for the host vehicle to travel in the center of the lane based on the curvature, the yaw angle, the offset, and the vehicle speed, and the requested steering torque T1 is set to the lane keeping assist control. The signal is transmitted to the EPS ECU 31 as a signal.

  The EPS ECU 31 determines whether the lane keeping assist control is operating and the steering wheel return control is operating at regular time intervals (S10). When it is determined that the determination condition of S10 is satisfied, the EPS ECU 31 sets the torque gain variable flag to ON (S11). On the other hand, if it is determined that the determination condition of S10 is not satisfied, the EPS ECU 31 sets the torque gain variable flag to OFF (S12).

  Then, the EPS ECU 31 determines whether or not the torque gain variable flag is ON (S20). If it is determined in S20 that the torque gain variable flag is ON, the EPS ECU 31 uses the required steering torque T1 for the lane keeping assist control and the required steering torque T2 for the steering wheel return control, and K2 / (1-K1) = T1. Gains K1 and K2 that satisfy / T2 are set (S21). Then, the EPS ECU 31 calculates K1 × T1 + K2 × T2 using the required steering torques T1, T2 and the gains K1, K2, and sets the calculated value as the target steering torque T (S22).

  If it is determined in S20 that the torque gain variable flag is OFF, the EPS ECU 31 determines whether or not the lane keeping assist control is activated (S23). When it is determined in S23 that the lane keeping assist control is activated, the EPS ECU 31 sets the required steering torque T1 for the lane keeping assist control as the target steering torque T (S24).

  If it is determined in S23 that the lane keeping assist control is not activated, the EPS ECU 31 determines whether the steering wheel return control is activated (S25). If the steering wheel return control is determined to be activated in S25, the EPS ECU 31 sets the required steering torque T2 for the steering wheel return control as the target steering torque T (S26).

  If it is determined in S25 that the steering wheel return control is not activated, the EPS ECU 31 sets 0 as the target steering torque T (S27).

  Then, the EPS ECU 31 sets a target current necessary for generating the target steering torque T, and supplies a control current to the steering actuator 20 so as to be the target current. In the steering actuator 20, the motor is rotationally driven according to the control current, and this rotational driving force is output to the steering mechanism via the speed reduction mechanism. As a result, when only the lane keeping assist control is operating or when the lane keeping assist control and the steering wheel return control are simultaneously operating, the vehicle travels so that the center line of the host vehicle coincides with the center line of the lane. Necessary steering torque is applied, and the host vehicle travels in the center of the lane. Further, when only the steering wheel return control is operating, a steering torque is applied to the steering mechanism in the neutral point direction, and the steering wheel returns smoothly to the neutral point.

  According to the steering support system 1, even when the lane keeping support control and the steering wheel return control are simultaneously operated, the steering torque necessary for the lane keeping support can be output to the steering mechanism, and appropriate lane keeping support is performed. Can do. Thus, it is possible to prevent the lane keeping support control and the steering wheel return control from interfering with each other, and the lane keeping support can be preferentially performed. Furthermore, in the steering assist system 1, when the lane keeping assist control and the steering wheel return control are simultaneously activated, the required steering torques of the two controls are easily changed to optimum values by setting the gains K1 and K2. be able to.

  As mentioned above, although embodiment which concerns on this invention was described, this invention is implemented in various forms, without being limited to the said embodiment.

  For example, although the present embodiment is applied to a steering support system that performs lane keeping support, the present invention can also be applied to other steering support such as lane departure prevention, parking support, and automatic travel.

  In this embodiment, the present invention is applied to a steering mechanism having an electric power steering device, and the electric power steering device is used to apply steering torque by lane keeping assist control or steering wheel return control. As long as a steering actuator or the like is provided, the present invention can be applied to other steering mechanisms such as a steering mechanism having a hydraulic power steering device or a steering mechanism having no power steering device.

  In this embodiment, the lane keeping support function is performed by the lane keeping support ECU and the steering wheel return function and the arbitration function are performed by the EPS ECU. However, all the functions may be performed by one ECU. Alternatively, the handle return mechanism and the arbitration mechanism may be configured by separate ECUs.

  In the present embodiment, the required steering torque for the lane keeping assist control and the required steering torque for the steering wheel return control are made variable by changing the gain. However, the required steering torque is made variable by another method. It is good. In particular, when the lane keeping assist control and the steering wheel return control are simultaneously operated, the required steering torque for the steering wheel return control may be simply set to zero.

It is a lineblock diagram of a steering support system (lane maintenance support device, electric power steering device) concerning this embodiment. 3 is a flowchart showing a flow of a torque gain variable flag setting process in the EPS ECU of FIG. 1. 2 is a flowchart showing a flow of target steering torque setting processing in the EPS ECU of FIG. 1.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Steering assistance system, 2 ... Lane maintenance assistance apparatus, 3 ... Electric power steering apparatus, 10 ... Lane detection sensor, 11 ... Vehicle speed sensor, 12 ... Steering torque sensor, 13 ... Steering angle sensor, 20 ... Steering actuator, 30 ... ECU for lane keeping support, 31 ... ECU for EPS

Claims (3)

Steering support comprising steering wheel return means for applying steering torque in the neutral point direction of the steering wheel when there is no steering operation by the driver, and driving support means for applying steering torque so that the host vehicle is in a target driving state A device,
When the steering torque is applied by the steering wheel return means and the steering torque is applied by the travel support means, the steering torque applied by at least one of the steering wheel return means and the travel support means is variable. A steering assist device.   When the steering torque is applied by the steering wheel return means and the steering torque is applied by the travel support means, a gain for the steering torque applied by at least one of the steering wheel return means and the travel support means is changed. The steering assist device according to claim 1.   When the steering torque is applied by the steering wheel return means and the steering torque is applied by the travel support means, the steering wheel return means and the travel support so that the output steering torque becomes the steering torque required by the travel support means. The steering assist device according to claim 1 or 2, wherein the steering torque applied by at least one of the means is variable.

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