JP3572810B2 - Control device for in-vehicle satellite receiving antenna - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a control device for a vehicle-mounted satellite receiving antenna, and more particularly to tracking control of a vehicle-mounted satellite receiving antenna using a gyro sensor.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, there has been developed a device that is mounted on a mobile body such as an automobile and receives a radio wave by tracking a BS so that an on-vehicle satellite receiving antenna is always directed to a broadcasting satellite (hereinafter referred to as a BS). In general, a technology is provided in which a gyro sensor for detecting a turning state of a moving body is provided, and a vehicle-mounted satellite receiving antenna is rotationally driven based on an output from the gyro sensor.
[0003]
For example, JP-A-4-232483 discloses a configuration for driving a receiving antenna. In addition to the output from the gyro sensor, a step track that drives the receiving antenna in the direction in which the signal level increases by comparing the signal strength of the current receiving level with the signal strength of the previous receiving level by swinging the antenna by a small angle left and right. A technique for performing control also has been developed (Japanese Patent Laid-Open No. 4-336821).
[0004]
[Problems to be solved by the invention]
However, in the case where the tracking operation is performed by rotating the vehicle-mounted satellite receiving antenna based on the output (yaw rate) from the gyro sensor, the output from the gyro sensor is sampled at predetermined time intervals (for example, 5 msec), and the sampling timing is set. The drive amount of the stepping motor or the like is determined based on the detection value in the above, and this drive amount is kept constant until the next sampling timing, whereas the output from the gyro sensor changes continuously with time. . Therefore, an error occurs between the continuous value and the discrete value, and the drive amount to the stepping motor includes an error.
[0005]
FIG. 4 schematically shows a drive amount (pulse rate) to the stepping motor for representing this error with time. In FIG. 4, the horizontal axis is time, and the sampling timing is 5 msec. The vertical axis indicates the amount of drive to the stepping motor (number of pulses / sec). While the gyro output from one sampling timing to the next sampling timing changes continuously, the amount of driving for rotating the stepping motor based on this gyro output is a constant value. An error as shown by hatching in the figure occurs between the two, and this error increases as the gyro output change increases. Therefore, the errors are accumulated after the elapse of a predetermined time, and the direction of the directional beam of the antenna may greatly deviate from the direction of the satellite.
[0006]
As a method of reducing this error, a method of narrowing the sampling interval and shortening the cycle for driving and controlling the motor can be considered. However, this method requires a CPU capable of performing high-speed calculations in order to calculate the driving amount of the motor in a short time. However, such a CPU inevitably consumes a large amount of current, and therefore is not suitable for an in-vehicle device where low current consumption is particularly important. From the viewpoint of current consumption, it is desirable to use a method in which satellite tracking can be performed with high accuracy even if the sampling interval is set wide.
[0007]
SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the related art, and has as its object to perform tracking control in which a satellite receiving antenna is rotationally driven based on an output from a gyro sensor. An object of the present invention is to provide a control device of an on-vehicle satellite receiving antenna capable of suppressing an error occurring between a driving amount for rotationally driving a satellite receiving antenna and accurately tracking a satellite even when a vehicle turns at high speed. .
[0008]
[Means for Solving the Problems]
In order to achieve the above object, a first invention is a control device for directing an on-vehicle satellite receiving antenna toward a satellite, comprising: a gyro sensor for detecting a turning amount of a vehicle; A stepping motor that changes the directivity of the antenna in the azimuth direction by driving; a control unit that controls a driving amount of the step motor based on a turning amount detected by the gyro sensor; And a correcting means for correcting the driving amount based on a difference between the current turning amount and the previous turning amount.
[0009]
In order to achieve the above object, in a second aspect based on the first aspect, the correction means adds a half of a difference between a current turning amount and a previous turning amount to the current turning amount. It is characterized by the following.
[0010]
As described above, in the present invention, the driving amount for driving the step motor is corrected based on the difference between the previously detected turning amount and the current turning amount. As a correction method, a half of the difference between the current turning amount and the previous turning amount may be added to the current driving amount. As shown in FIG. 4 described above, the error between the gyro output and the driving amount of the step motor (that is, the turning amount of the receiving antenna) is indicated by a hatched portion, and this error amount is represented by the current turning amount and the previous turning amount. Is approximately equal to 1/2 of the difference value of the above. By adding this correction amount to the current step motor drive amount, it is possible to easily and reliably suppress the error.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0012]
FIG. 1 is a block diagram showing the configuration of the on-vehicle satellite receiving antenna and the tracking device according to the present embodiment. A satellite receiving antenna (BS antenna) 10 is connected to a BS tuner 14 in the vehicle cabin via a converter 12, and a satellite broadcast received by the antenna 10 is demodulated by the BS tuner 14 and output as a video output by a CRT (not shown). And so on. The antenna 10 is provided with a stepping motor 16 for changing the direction of the directivity by rotating the antenna, and the driving amount of the stepping motor 16 is determined by a control signal from a vehicle interior unit. The antenna may be of any type as long as it has a certain directivity. For example, a planar beam tilt antenna is suitable as shown in FIG. The planar beam tilt antenna is a planar antenna in which the beam of the antenna is tilted at a certain angle from the vertical direction by adjusting the phase of each element of the antenna. The directivity of this antenna is fixed in the direction shown in the figure, but since the altitude of the BS (broadcast satellite) or CS (communication satellite) is constant, the planar antenna shown in the figure is moved by the stepping motor 16. By rotating in the azimuth direction, it is possible to direct the beam of the antenna toward BS or CS even when the vehicle moves. Since such a planar antenna can be formed thin, it can be provided on the roof of a vehicle. Of course, it is also preferable to incorporate a planar antenna in the sunroof. The vehicle interior unit includes, in addition to the BS tuner 14 described above, a vibration gyro 18 for detecting a yaw rate of the vehicle, a connection unit 24 including a motor control board 20 and an A / D board 22, a control device 26, and a stepping motor. The stepping motor driver 28 drives the stepping motor 16. The received signal C / NOUT from the BS tuner 14 and the output from the vibrating gyroscope 18 are supplied to the A / D board 22 in the connection unit 24, and after being converted into digital signals, are supplied to the control device 26. The control device 26 determines the amount of rotation of the antenna 10 based on the gyro output and the received signal, and instructs the motor control board 20 in the connection unit 24.
[0013]
Specifically, this control is performed as follows. That is, after the end of the initial search operation, the antenna 10 is driven at the same amount as the yaw rate detected by the vibrating gyroscope 18 and at the opposite sign. This control is performed every predetermined sampling timing (for example, 5 msec). Then, during this control, when it is detected that the C / NOUT from the BS tuner 14 has decreased to become equal to or less than the predetermined threshold value 1, the control device 26 performs the gyro tracking and, at a predetermined time interval ( For example, the antenna 10 is swung at a predetermined angle at 100 msec), the previous reception level is compared with the current reception level, and if the reception level is increased, the antenna 10 is driven again in the same direction, and conversely, the reception level is decreased. If this is the case, the system shifts to the hybrid system that also uses so-called step track tracking in which the antenna is driven so that the reception level always increases by rotating in the opposite direction. Then, when the reception level again becomes equal to or higher than the predetermined threshold value 2 by the hybrid tracking, the antenna 10 is driven again based only on the output from the vibration gyro 18. Here, the threshold value 1 is smaller than the threshold value 2, so that the tracking characteristic has hysteresis when the reception level is between the threshold value 1 and the threshold value 2. The reason why the hysteresis characteristic is provided in this way is that, when the reception level increases due to the hybrid tracking and the threshold value 1 is reached, the gyro tracking is immediately shifted to the gyro tracking. This is because it is highly possible that the control value becomes lower than the threshold value 1 again and the control becomes unstable. When not only the gyro output but also the reception level is equal to or less than the predetermined threshold value 1 and tracking is likely to be lost, step track control for controlling the reception level to the increasing side in addition to the gyro output is also used. By doing so, satellite tracking can be performed with high accuracy.
[0014]
However, as described above, an error occurs between the actual output value of the gyro that continuously changes and the drive amount of the motor that changes stepwise determined by the control device 26 based on the gyro output. Accordingly, the control device 26 controls the antenna 10 with higher precision than before by suppressing this error simply and accurately as described below.
[0015]
FIG. 2 shows a flowchart of the error suppression processing performed by the control device 26. First, a digitized gyro output is read from the A / D board 22 in the connection unit 24 (S101). This reading is performed at a predetermined timing (5 msec). Next, the read gyro output is converted into the angular velocity of the vehicle (S102). Since the gyro output generally includes an offset error, the offset error is corrected first (S103). Although there are several possible methods for the offset error, the antenna 10 is rotated in either direction when shifting to the hybrid tracking using the step track tracking in consideration of the variation of each product and the variation of the temperature condition. It is desirable to determine whether or not the reception level increases, and to appropriately adjust the offset amount based on the direction to perform focusing. That is, if the reception level increases when the antenna 10 is rotated clockwise, this means that the antenna 10 has been rotated counterclockwise too much. Is the opposite direction to the gyro output, which means that the gyro output has output a clockwise turning amount more than the original turning amount of the vehicle. Therefore, the vibrating gyroscope 18 includes a clockwise offset error, and the correction may be made so as to eliminate the error in this direction. However, since the offset error amount is unknown, such an error correction may be repeated for each predetermined step to finally eliminate all the offset errors.
[0016]
After the offset error correction is completed, the control device 26 calculates a motor pulse rate PPS required to rotate the antenna 10 in the opposite direction at the same angular velocity based on the gyro output corrected for the offset error (S104). Since an error is included between the pulse rate PPS and the actual gyro output (actual angular velocity of the vehicle) as shown by hatching in FIG. 4, the antenna 10 was rotationally driven at the pulse rate PPS. Then, the satellite cannot be tracked accurately. Therefore, the control device 26 first calculates a difference ΔPPS between the current pulse rate PPS and the pulse rate PPS at the previous sampling timing to eliminate the error indicated by the hatched portion in FIG. It is added to the current pulse rate PPS calculated in S104. That is, for the PPS calculated based on the gyro output,
(Equation 1)
PPS1 = PPS + 1/2 · ΔPPS
To correct the current pulse rate PPS to calculate a new pulse rate PPS1 (S105). The ・ · ΔPPS in the above equation substantially corresponds to the hatched portion in FIG. 4, and by adding this amount to the current pulse rate PPS, the error indicated by the hatched portion in FIG. 4 can be almost eliminated. .
[0017]
After calculating the drive amount PPS1 to be supplied to the stepping motor 16 in this manner, the current pulse rate PPS is substituted into the immediately preceding pulse rate PPSlast for the next difference amount calculation (S106), and then calculated in S105. The stepping motor 16 is driven by the set PPS1 to rotate the antenna 10 (S107).
[0018]
FIG. 3 shows a comparison between the pulse rate when the pulse rate is corrected and the antenna 10 is rotated by driving the stepping motor 16 and the actual gyro output. By adding and correcting a half of the difference between the current pulse rate and the previous pulse rate to the current pulse rate, the pulse rate supplied to the stepping motor 16 approximates the actual gyro output. Therefore, it is understood that the antenna 10 can be tracked with higher accuracy than before.
[0019]
In the present embodiment, the gyro output correction in the hybrid system using both the gyro control and the step track control has been described. However, it goes without saying that the gyro control can be similarly used in the system using only the gyro control.
[0020]
【The invention's effect】
As described above, according to the present invention, when tracking control of the satellite receiving antenna based on the gyro sensor output, it is possible to easily and reliably calculate the actual vehicle turning amount based on the difference from the previous driving amount. Since the error can be suppressed, the tracking operation can be performed with high accuracy without causing tracking loss.
[Brief description of the drawings]
FIG. 1 is a configuration block diagram of an embodiment of the present invention.
FIG. 2 is a processing flowchart of a correction operation in the embodiment.
FIG. 3 is a graph showing a relationship between a gyro output and a pulse rate in the embodiment.
FIG. 4 is a graph showing a relationship between a gyro output and a pulse rate in a conventional technique.
FIG. 5 is a diagram showing functions and directional directions of a planar antenna.
[Explanation of symbols]
10 satellite receiving antenna (BS antenna), 12 converter, 14 BS tuner, 16 stepping motor, 18 vibration gyro, 24 connection unit, 26 controller, 28 stepping motor driver.

Claims (2)

A control device for pointing the onboard satellite receiving antenna in the direction of the satellite,
A gyro sensor for detecting a turning amount of the vehicle;
A stepping motor that changes the directional direction of the antenna in an azimuth direction by rotating the on-vehicle satellite receiving antenna,
Control means for controlling the driving amount of the step motor based on the turning amount detected by the gyro sensor,
Correction means for correcting the drive amount based on the difference between the current turn amount detected by the gyro sensor and the previous turn amount,
A control device for a vehicle-mounted satellite receiving antenna, comprising: The control device for an on-vehicle satellite receiving antenna according to claim 1,
The control device for a vehicle-mounted satellite receiving antenna, wherein the correction means adds a half of a difference between a current turning amount and a previous turning amount to the current turning amount.

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