JP6614112B2 - Headlight control device - Google Patents

Description

  The present invention relates to a headlamp control device for controlling an irradiation direction variable means for changing the irradiation direction of a vehicle headlamp.

  Conventionally, depending on the control method of moving the direction of the headlight of the vehicle in the left-right direction in conjunction with the steering angle of the steering wheel or the curve of the road map stored as a map database, A control method for moving the direction left and right has been proposed.

JP 2008-1000068 A

  However, in the above-described headlamp control method, the irradiation direction of the headlamp is merely changed based on the steering angle of the vehicle or the data in the map database. Therefore, for example, even if the irradiation direction is changed according to the curve on the map based on the data of the latter map database, depending on the road width of the curve, the travel position of each vehicle may not always vary, It is assumed that the headlight irradiation direction is not appropriate.

  This invention is made | formed in view of the said situation, The objective is to provide the headlamp control apparatus which can change the irradiation direction of a headlamp more suitably.

  The headlamp control device according to claim 1, wherein the illumination angle of the headlamp (11) is derived in correspondence with the direction of the vehicle estimated at the current position of the vehicle on the road map data. It is corrected by the difference from the actual vehicle direction. For this reason, irradiation with the headlamp can be changed in a more preferable optical axis direction according to the actual direction of the vehicle.

1 is a functional block diagram schematically showing the overall configuration of a headlight control device showing an embodiment of the present invention. Flowchart showing swivel control procedure Schematic diagram for explaining derivation and correction of irradiation angle

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1, the overall system of the present embodiment includes a headlamp ECU 1 and other ECUs 2 as ECUs (Electronic Control Units) mounted on a vehicle such as a passenger car, and an own vehicle position locating device 3. It is configured.

  The headlamp ECU 1 is a headlamp control device 1 for controlling the irradiation direction of the headlights 11 arranged on the left and right on the front surface of the vehicle. That is, the headlight 11 as a headlamp irradiates irradiation light toward the front of the vehicle, and each headlight 11 has an actuator for changing the optical axis direction that is the irradiation direction. 12 is attached. Although detailed illustration is omitted, the actuator 12 includes, for example, a horizontal direction control motor 12s for changing the inclination of the optical axis in the horizontal direction and a vertical direction control motor 12t for changing the inclination of the optical axis in the vertical direction. It is configured, and the inclination of the optical axis is freely changed in the vertical direction and the horizontal direction by driving the motors 12s and 12t. For convenience of explanation, FIG. 1 shows only one component 11, 12s, 12t of the left and right headlights 11 and the motors 12s, 12t. The motors 12s and 12t correspond to irradiation direction variable means.

  The headlamp control device 1 includes a CPU 1a as a central processing unit that executes various arithmetic processes, a storage unit 1b including a ROM that stores a control program, a RAM that stores various data, and an input / output unit 1c. Has been. The headlamp control device 1 acquires various signals or various data from the own vehicle position locating device 3 or the like at the input / output unit 1c as an acquisition means, and based on the data, the actuators 12s and 12t are controlled according to the control program. To adjust the optical axis direction of the left and right headlights 11. In FIG. 1, in order to clarify each function, various ECUs such as a vehicle ECU are described as other ECUs 2 separately from the headlight control device 1, but these arithmetic processing functions are centered on one microcomputer. It can also be set as the apparatus comprised to.

  The vehicle position locating device 3 shown in FIG. 1 is a generic term for a locator, a navigation device, or the like that detects the current position of the vehicle or searches for a recommended route to a destination specified based on road map data. To do. That is, the own vehicle position locating device 3 includes a GNSS (Global Navigation Satellite Systems) receiver 31, a gyro sensor 32, an acceleration sensor 33 as a G sensor, a vehicle speed sensor 34, a dead reckoning navigation unit 35, a map matching unit 36, and a map data storage unit. 37.

  The GNSS receiver 31 receives a GPS (Global Positioning System) signal received by the GNSS antenna 31a, and obtains current position coordinates representing the current position of the vehicle based on the GPS signal (see X and Y in FIG. 3). The dead reckoning unit 35 receives the current position signal from the GNSS receiver 31, the detection signal detected by the gyro sensor 32, the vehicle speed signal output from the vehicle speed sensor 34, and the acceleration signal output from the acceleration sensor 33. Then, based on these signals, information such as the speed of the vehicle, the direction of the vehicle, and the traveling locus of the vehicle is created and stored.

  The map matching unit 36 is road map data that can specify the road network and road structure stored in the map data storage unit 37, the vehicle speed and the vehicle orientation and vehicle position information from the dead reckoning unit 35, Based on the current position signal from the GNSS receiver 31, current position data corresponding to the current position of the vehicle on the road map data is specified. The road map data includes road structure data, such as road surface slope, that is, slope data representing the slope of the road uphill or downhill, and curvature data related to the curvature of the curve on the road.

  Moreover, the acceleration sensor 33, the gyro sensor 32, and the vehicle speed sensor 34 in the own vehicle position locating device 3 output sensor signals that can specify the actual vehicle direction. Specifically, the acceleration sensor 33 outputs a detection signal that identifies the actual vertical inclination of the vehicle with respect to the horizontal plane in accordance with the road gradient on which the host vehicle is located.

  The gyro sensor 32 outputs a detection signal of the angular velocity of the rotational motion applied to the own vehicle. Based on this detection signal, it is possible to estimate the actual direction of the vehicle by calculating the direction change of the vehicle. For example, when the vehicle speed sensor 34 is constituted by two wheel speed sensors that detect the speeds of the left and right wheels in the host vehicle, the detection signal from the left wheel speed sensor 34L that detects the left wheel speed and the right wheel speed are obtained. A detection signal from the right wheel speed sensor 34R to be detected is output. From the detection signals of these sensors 34L and 34R, the actual vehicle orientation can be estimated based on the difference between the inner and outer wheels.

  The headlamp control device 1 uses data related to the inclination and direction of the vehicle output from the dead reckoning navigation unit 35 based on the signals of the sensors 32 to 34 on the vehicle position locating device 3 side. That is, for example, the headlight control device 1 is a vehicle direction specifying unit configured as a unit that specifies the actual vehicle direction or a unit that acquires the specified vehicle direction, and includes the gyro sensor 32 or two wheels. Based on the input signals of the speed sensors 34L, 34R, the actual vehicle heading data output from the dead reckoning navigation unit 35 and acquired via the input / output unit 1c is specified. As shown in FIG. 1, the headlamp control device 1 is also input with a detection signal of a steering angle sensor 21 for detecting the steering angle of the steering wheel 20 of the vehicle operated by the driver. It has become. The steering angle sensor 21 is a steering angle detection means for detecting the operation amount of the steering wheel 20 by an angle and detecting the steering angle data, that is, the data of the traveling direction of the vehicle.

  Next, deflection control in the optical axis direction of the headlight 11 by the headlamp control device 1 will be described with reference to the flowchart of FIG. In the following, for the sake of convenience, so-called swivel control for controlling deflection of the optical axis direction to the left and right will be mainly described, and vertical deflection control will be described later. The swivel control can be performed based on the steering angle data following the steering angle, but is performed based on the road map data and the current position data. In FIG. 2, the routine of the flowchart concerned is repeatedly executed by the CPU 1a of the headlamp control device 1 every 100 msec with a predetermined period of 100 msec, for example, and “S1, S2,. It shall represent a number.

  First, the CPU 1a determines whether or not the road on which the vehicle is currently traveling is a curve based on the road map data and the current position data acquired from the vehicle position locating device 3, and whether or not the vehicle on the recommended route. It is sequentially determined whether there is an entrance to the curve ahead or whether there is a branch point before the entrance to the curve (S1).

  In other words, at least one of a condition that the vehicle is running on a curve, a condition that the vehicle is guided in the direction of the curve before the curve entrance, and a condition that there is no branch point before the curve entrance. If it is determined that the condition is satisfied (S1: YES), the process proceeds to step S2. On the other hand, if it is determined that one condition is not satisfied (S1: NO), this process is ended (END).

  Further, in step S1, the CPU 1a determines whether or not the above condition is satisfied with the current vehicle position as the current position after 100 msec in accordance with the vehicle speed acquired from the own vehicle position locating device 3. The irradiation angle is derived in advance for one period in the predetermined period. Specifically, for example, assuming that the speed of the vehicle is 100 km / h, the position of the vehicle after 100 msec is estimated to deviate about 2.78 m ahead of the current position of the vehicle specified from the current position data. . Therefore, the CPU 1a enters the curve in order to determine whether or not the vehicle is running on the curve based on the vehicle speed and the current position data with reference to a position approximately 2.78 m ahead of the current position. It is assumed that the vehicle is running on a curve from the previous previous position (S1: YES).

  Furthermore, when the condition that there is no branch point before the entrance of the curve is satisfied (S1: YES), it can be determined that the own vehicle always enters the curve, so that swivel control can be performed in advance.

  In step S2, the CPU 1a derives the irradiation angle as the swivel angle of the headlight 11 based on the previous position obtained from the current position data and the road map data as the derivation means. The swivel angle is derived, for example, by collating a map or a data table (not shown) that predefines the relationship between the curvature radius R (see FIG. 3) as the curvature data at the previous position and the swivel angle. For example, the swivel angle is determined by setting the reference optical axis direction in the horizontal direction, that is, the horizontal direction of the optical axis, that is, the initial direction pointing in the front-rear direction of the vehicle, as a preset reference angle “0 (zero) degree” It is represented by the angle difference between the left and right directions.

  The derived swivel angle is corrected according to the speed of the vehicle (S3). The degree of correction in this case is prescribed in advance according to the level of speed, for example, when the speed of the vehicle is relatively high, the swivel angle is relatively large, while when the speed is relatively low The swivel angle θ is corrected to be relatively small.

  Then, the CPU 1a calculates the difference between the azimuth of the vehicle along the curvature radius R of the road and the actual azimuth of the vehicle as a correction value using the previous position as the current position (S4), and obtains it in steps S2 and S3. The swivel angle is corrected with the correction value (S5). Thus, the CPU 1a controls the horizontal direction control motor 12s so as to irradiate the front of the vehicle with the optimum swivel angle after the correction (S6).

  FIGS. 3A and 3B are explanatory views illustrating the swivel angle ΔΦ and the correction value Δθ of the swivel control. The series of steps S2 to S6 described above will be described in detail with reference to the same drawing. Here, it is assumed that the vehicles A and B shown in the figure are at the current position coordinates (X, Y). The vehicle A in FIG. 3A travels along the road radius R and points in the direction of the traveling direction corresponding to the radius of curvature R as indicated by the alternate long and short dash line L in FIG. The vehicle B represents a state in which the azimuth of the vehicle B does not follow the road radius R because the steering amount in the right direction is larger than the road radius R. In addition, the alternate long and short dash line L is directed to the tangential direction at the vehicle position in the virtual circle with the radius R.

  That is, for the vehicle A in FIG. 3A, the target swivel angle ΔΦ is calculated based on the curvature radius R acquired from the vehicle position locating device 3 and the vehicle speed (S2, S3), and the sensor. Based on the detection signals 34L and 34R, the actual direction of the vehicle A is specified. Since the direction of the actual vehicle A specified in this case is in a state where the vehicle A is traveling along the road radius R, the current position (X, Y) coincides with the direction of the vehicle A. Accordingly, in this case, the CPU 1a calculates the correction value, which is the difference Δθ between the azimuth of the vehicle A estimated at the current position (X, Y) on the road map data and the actual azimuth of the vehicle A, as 0 (zero). (S4, S5). Therefore, the CPU 1a controls the horizontal direction control motor 12s so as to change from the current optical axis angle to the optimum swivel angle ΔΦ using the optical axis angle ΔΦ with respect to the reference angle as the optimum swivel angle (S6). By this processing, the optical axis direction of the headlight 11 is changed to an angle [deg] indicated by ΔΦ in FIG. 3A, and the front of the vehicle A is irradiated with the optimum swivel angle ΔΦ.

  On the other hand, for the vehicle B in FIG. 3B, as with the vehicle A, the swivel angle ΔΦ is calculated based on the curvature radius R and the vehicle speed (S2, S3), and based on the detection signals of the sensors 34L, 34R. The direction of the actual vehicle B is specified. In this case, the CPU 1a calculates a difference Δθ between the identified actual orientation of the vehicle B and the orientation estimated at the current position (X, Y) on the road map data, that is, the orientation of the vehicle A (S4). . Further, the CPU 1a performs correction by subtracting the correction value Δθ from the swivel angle ΔΦ using the calculated difference Δθ as a correction value (S5). That is, when the swivel control from the reference angle to the right is set to the positive direction based on the road map data concerning the right turn, the difference Δθ of the vehicle B is the negative direction to the left minus the directing in the original direction. As adjusted. Therefore, the CPU 1a controls the horizontal direction control motor 12s so as to change the angle (ΔΦ−Δθ) of the optical axis with respect to the reference angle as the optimum swivel angle (S6). By this processing, the optical axis direction of the headlight 11 is changed to an angle [deg] indicated by ΔΦ−Δθ in FIG. 3B, and the front of the vehicle B is irradiated with the optimum swivel angle (ΔΦ−Δθ).

  As described above, the headlamp control device 1 having the CPU 1a has the irradiation angle ΔΦ derived as the derivation means in the road direction at the current position (X, Y) estimated based on the road map data and the current position data. The difference Δθ between the direction of the vehicle along the vehicle direction and the actual vehicle direction specified as the vehicle direction specifying means is corrected as a correction value.

  According to this, even if the irradiation angle ΔΦ of the headlight 11 is derived in correspondence with the direction of the vehicle estimated at the current position (X, Y) of the vehicle on the road map data, It is corrected by the difference Δθ from the direction. For this reason, irradiation with the headlight 11 can be changed in a more suitable optical axis direction according to the actual direction of the vehicle.

  The headlamp control device 1 specifies the actual vehicle direction based on at least one of the gyro sensor 32 and the wheel speed sensors 34L and 34R as vehicle direction specifying means.

  According to this, the headlamp control device 1 can determine the optimum swivel angle (ΔΦ−Δθ) by specifying the direction of the vehicle as the bearing and deriving and correcting the irradiation angle. Therefore, for example, even in a so-called out-in-out driving method of a vehicle, or even a relatively wide road or a road curve without a lane, it is possible to set the desired optical axis direction according to the actual driving situation. Therefore, it is possible to perform swivel control suitable also from the viewpoint of safety.

The calculation in the headlamp control device 1 is not limited to the above-described 100 msec, and may be executed at every calculation timing of a cycle shorter than 1 sec or 1 sec, for example.
As described above, the headlight control device 1 performs derivation and correction of the irradiation angle at every calculation timing of a predetermined cycle. The headlight control device 1 specifies the speed of the vehicle as speed specifying means, and 1 according to the speed. By obtaining the position of the vehicle after the cycle as the current position (X, Y), the irradiation angle is derived in advance for the one cycle. By this pre-calculation, the drive control of the horizontal direction control motor 12s can be executed earlier by the one cycle, and the control delay caused by the computation timing can be surely eliminated without changing the computation cycle. it can. The derivation of the irradiation angle performed in advance is not limited to the one period, and may be performed at an earlier timing at least for the one period, that is, before entering the curve.

(Other embodiments)
In the following, a description will be given of a point of substantial difference from the above-described embodiment regarding deflection control in which the headlamp 11 changes the optical axis direction of the headlight 11 up and down by the headlamp control device 1.

  The headlamp control device 1 detects the inclination of the vehicle by the acceleration sensor 33 and performs deflection control in the optical axis direction according to the inclination. However, the acceleration sensor 33 can detect the inclination of the vehicle with respect to the horizontal plane, but does not detect the inclination with respect to the road surface. Therefore, depending on the road structure such as a slope, the acceleration sensor 33 is set in the direction of the optical axis according to the actual road surface. There is a possibility that it may not be possible. In addition, for example, on a horizontal plane, even if it is set in the reference optical axis direction described later according to the flat road surface, on the flat road surface before the steep slope, only a part of the road surface of the front slope is illuminated for the driver. Things can happen.

  Therefore, when the headlamp control device 1 derives the illumination angle in the vertical direction of the headlight 11 as the derivation means, the inclination data included in the road map data and the illumination angle created in advance corresponding to the inclination data Refer to the table data. Here, the irradiation angle table predetermines the irradiation angle in the vertical direction so that an optimal irradiation range can be obtained according to the slope of the road surface, that is, the inclination data, so that the slope is suitably illuminated before, for example, a steep slope. The data table is stored in advance in its own storage unit 1b. Then, the headlamp control device 1 sets the corresponding irradiation angle at the current position based on the irradiation angle table and the current position data. The irradiation angle set in this way is hereinafter referred to as “irradiation angle according to the position”.

  Further, the headlamp control device 1 specifies the actual vertical inclination of the vehicle with respect to the horizontal plane based on the signal from the acceleration sensor 33 as vehicle orientation specifying means. And the headlamp control apparatus 1 corrects the irradiation angle according to the said position by making into the correction value the difference of the inclination of the road surface which inclination data represent, and the inclination of the actual vehicle up-down direction with respect to a horizontal surface.

  Here, the irradiation angle in the vertical direction of the headlight 11 is, for example, the reference optical axis direction in the vertical direction of the optical axis, that is, the angle in the initial direction in the vertical direction of the optical axis as a reference angle. It shall be expressed by angle difference. In addition, the inclination in the direction in which the nose of the vehicle is lowered is regarded as an angle in the plus direction, and the inclination in the direction in which the tail of the vehicle is lowered is regarded as an angle in the minus direction. For example, if the difference between the road slope [deg] represented by the slope data at the current position and the actual vehicle vertical slope [deg] with respect to the horizontal plane is plus 2 [deg], minus the difference so as to eliminate the difference. A correction value of 2 [deg] is calculated.

  Therefore, the CPU 1a controls the vertical direction so that the irradiation angle corresponding to the position, that is, the angle of the current optical axis with respect to the reference angle is changed to the optimal irradiation angle as an optimal irradiation angle corrected by minus 2 [deg]. The motor 12t is controlled. By this process, the optical axis direction of the headlight 11 is changed to the optimal irradiation angle in the vertical direction, and the front of the vehicle can be irradiated with the optimal irradiation angle based on the irradiation angle table even before the above-mentioned slope, and the stable irradiation range You can Further, the inclination of the vehicle with respect to the road surface changes depending on the load loaded on the vehicle, acceleration / deceleration, and the like, but appropriate deflection control in the optical axis direction can be performed regardless of the change and the road structure.

  Such deflection control can be executed together with steps S1 to S6 of the flow chat in FIG. 2, and the deflection control can be executed instead of steps S1 to S6. Therefore, in the following, for the sake of convenience, the steps related to the deflection control are represented by S1 ′ to S6 ′, and the flowcharts of S1 ′ to S6 ′ are not illustrated.

  That is, in step S1 ′, the CPU 1a determines a condition that the vehicle is traveling on an uphill or a downhill. In this case, the determination may be made by adding other conditions such as determining a plurality of conditions in the same manner as step S1 together with the conditions.

  Next, in order to derive the irradiation angle of the headlight 11, the CPU 1a obtains the tilt data based on the acquired road map data, current position data, vehicle speed, and the like, with the previous position as the current position, The irradiation angle table is collated and an irradiation angle corresponding to the position is set (S2 ′, S3 ′). Then, the CPU 1a sets, as a correction value, a difference between the inclination of the road surface represented by the inclination data, that is, the inclination of the vehicle estimated on the road surface, and the inclination of the actual vehicle in the vertical direction with respect to the horizontal plane as the current position. The corresponding vertical irradiation angle is corrected (S4 ′, S5 ′). Thereby, CPU1a controls the vertical direction control motor 12t so that the front of a vehicle may be irradiated with the optimal irradiation angle after the correction | amendment (S6 '). Thus, the control of the irradiation angle in the vertical direction also has the same effects as those of the above-described embodiment, such as the control delay caused by the calculation timing can be reliably eliminated without changing the calculation cycle.

  As described above, the headlamp control device 1 corrects the difference between the inclination data estimated at the current position based on the road map data and the current position data and the actual vertical inclination of the vehicle as correction means. As described above, the vertical irradiation angle of the headlight 11 is corrected. According to this, a stable irradiation range can be obtained, and an appropriate irradiation angle can be set even on a slope.

  In addition, regarding the accuracy of the navigation device and the road map used therefor, a device having higher map accuracy than the conventional one is provided. By incorporating such a device into the own vehicle position locating device 3, the above-mentioned device is used. By performing deflection control in the optical axis direction in the left and right directions and in the vertical direction separately or separately, it is possible to adjust the optical axis direction with high accuracy as a whole, and ensure a good irradiation range. can do.

  The present invention is not limited to the embodiments described above and shown in the drawings, and may be modified as appropriate, for example, by combining the above-described embodiments and modifications, or omitting some of the components. It can be implemented.

  For example, the road map data acquired by the headlamp control device 1 as an acquisition unit may be acquired as data provided from an external server (not shown) without being acquired from the own vehicle position locating device 3.

  The irradiation direction variable means is not limited to the motors 12s and 12t, and may be configured using various actuators. The vehicle orientation specifying means may specify the direction of the vehicle and the inclination of the vehicle based on the signal of the gyro sensor 32, or by specifying each position by mounting two GPS antennas (not shown) on the vehicle. The specifying method may be changed as appropriate, such as specifying the direction of the vehicle. The two GPS antennas are arranged at positions separated from each other in the vehicle, and the actual vehicle orientation is specified based on a positioning signal which is a GPS signal received via each antenna. Since a well-known configuration can be adopted for the specification, detailed description is omitted. The headlamp control device 1 may be configured to be able to identify the actual vehicle direction based on the positioning signal and the input signals of the sensors 32, 34L, and 34R. You may have the function to specify the said direction directly, without via the navigation part 35 grade | etc.,.

Further, the above-described “irradiation angle according to the position” may be derived by calculation by the headlamp control device 1 based on the inclination data, without being based on the irradiation angle table.
In addition, the numerical values represented by the period, the angle, and the like are not limited to the values described above, and can be changed as appropriate.

  Although the present disclosure has been described with reference to the embodiments, it is understood that the present disclosure is not limited to the embodiments and structures. The present disclosure includes various modifications and modifications within the equivalent range. In addition, various combinations and forms, as well as other combinations and forms including only one element, more or less, are within the scope and spirit of the present disclosure.

  In the drawings, 1... Headlight control device (acquisition means, vehicle orientation specifying means, derivation means, correction means, control means), 11... Headlight, 12... Irradiation direction variable means, 21.

Claims (5)

A headlamp control device (1) for controlling irradiation direction variable means (12) for changing the irradiation direction of a vehicle headlamp (11),
It is possible to acquire road map data that can identify the road network and road structure, current position data corresponding to the current position of the vehicle on the road map data, or steering angle data detected by the steering angle detection means (21). Acquisition means (1);
Vehicle orientation specifying means (1) configured as means for specifying the actual vehicle orientation, or means for acquiring the specified vehicle orientation;
Deriving means (1) for deriving an irradiation angle of the headlamp based on the road map data and the current position data acquired by the acquiring means or the steering angle data;
A correction value for a difference between the vehicle direction along the road direction at the current position estimated based on the road map data and the current position data and the actual vehicle direction specified by the vehicle direction specifying means Correction means (1) for correcting the irradiation angle derived by the derivation means;
Control means (1) for controlling the irradiation direction variable means so as to irradiate the front of the vehicle at the irradiation angle corrected by the correction means;
A headlamp control device comprising: Identification of the vehicle orientation by the vehicle orientation identification means is as follows:
Claim by specifying the actual vehicle direction based on the sensor signal of at least one of the gyro sensor (32) and the wheel speed sensor (34L, 34R) or the positioning signal received via the GPS antenna. The headlamp control device according to Item 1. The derivation means derives a right and left swivel angle of the headlamp based on the road map data and the current position data,
The correction means is derived by the derivation means using a difference between a vehicle azimuth along a road radius estimated at a current position on the road map data and the actual vehicle azimuth as a correction value. The headlamp control apparatus according to claim 1 or 2, wherein the swivel angle is corrected.   The correction means uses as a correction value the difference between the inclination data representing the inclination of the upward gradient or the downward gradient of the road estimated at the current position on the road map data and the vertical inclination of the actual vehicle. The headlamp control device according to any one of claims 1 to 3, wherein an irradiation angle in a vertical direction of the headlamp is corrected. The irradiation angle is derived and corrected at every calculation timing of a predetermined period, and includes speed specifying means (1) for specifying the speed of the vehicle,
According to the speed specified by the speed specifying means, the position of the vehicle after one cycle in the predetermined period or after that is determined as the current position, so that the irradiation angle by the deriving means in advance for at least one cycle. Is derived,
The headlamp control device according to any one of claims 1 to 4, wherein the headlamp control unit is configured to change the irradiation direction of the headlamp by the irradiation direction changing unit at least one cycle earlier.

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