JP2010203907A - Scanning control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a scanning control device allowing scanning of a scanning object beyond a length of a permanent magnet. <P>SOLUTION: A coil 102 is supported by a flat spring 17, keeping a predetermined clearance from surfaces of permanent magnets 103A and 103B. In the coil 102, a current runs in a direction orthogonal to a magnetic field of the magnet 103A and the magnet 103B. If the current runs through the coil 102, an electromagnetic force is generated according to Fleming's law, allowing scanning of the coil 102. Now, if one end of the coil 102 deviates from either surface of the magnet 103A and the magnet 103B, a current supply is stopped. Then, the coil 102 moves by inertia and a resonance frequency of the flat spring 17 continues an amplitude motion, thus allowing scanning of the scanning object beyond the magnetic field of the permanent magnet. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a scanning control device that scans an electromagnetic wave such as a laser beam in a horizontal direction or a vertical direction.

  Conventionally, as a mechanism for scanning a laser beam in a horizontal direction and a vertical direction, a mechanism using a linear motor and scanning a light projecting lens and a light receiving lens in a horizontal direction and a vertical direction has been proposed (for example, Patent Documents 1 and 2). See).

  FIG. 1 is a view showing a conventional scanning mechanism. The scanning mechanism 2 includes a vertical scanning mechanism 21 and a horizontal scanning mechanism 22. The vertical scanning mechanism 21 and the horizontal scanning mechanism 22 are connected by a holder 23.

  The vertical scanning mechanism 21 includes two leaf springs 31 connected to both ends of the holder 23 in the vertical direction (Z, −Z direction). The two leaf springs 31 are fixed to the fixing member 20 so as to sandwich the holder 23 therebetween. The coil 32 is fixed in the back direction (−Y direction) of the holder 23. The fixed member 20 is provided with a magnet 33 so as to face the coil 32.

  The vertical scanning mechanism 21 generates an electromagnetic force in the vertical direction by the magnetic field of the magnet 33 by causing a current to flow through the coil 32. As a result, the holder 23 moves to a position where the generated electromagnetic force and the reaction force of the leaf spring 31 are balanced. The vertical scanning mechanism 21 can move the holder 23 to an arbitrary position by controlling the direction of the current flowing through the coil 32.

  The vertical position detection unit 34 is provided so as to face one leaf spring 31, irradiates the leaf spring 31 with light, receives light reflected from the leaf spring 31, and detects a displacement amount of the leaf spring 31. Photo sensor.

  The horizontal scanning mechanism 22 includes two plate springs 25 connected to both ends of the holder 23 in the horizontal direction (X, −X direction). A lens holder 24 is connected to the front direction (Y direction) of the two leaf springs 25. A coil 26 is fixed in the front direction of the lens holder 25. The fixed member 20 is provided with a magnet 27 so as to face the coil 26.

  The horizontal scanning mechanism 22 generates an electromagnetic force in the horizontal direction by the magnetic field of the magnet 27 by causing a current to flow through the coil 26. Thereby, the lens holder 24 moves to a position where the generated electromagnetic force and the reaction force of the leaf spring 25 are balanced. The horizontal scanning mechanism 22 can move the lens holder 24 to an arbitrary position by controlling the direction of current.

  Further, the horizontal position detector 28 is provided so as to face one of the leaf springs 25, irradiates the leaf spring 25 with light, receives light reflected from the leaf spring 25, and the amount of displacement of the leaf spring 25. It is a photo sensor that detects

  As described above, the conventional scanning mechanism scans the light projecting lens and the light receiving lens in the horizontal direction and the vertical direction using the linear motor. Since an automobile travels forward, backward, left and right on a road surface, when performing two-dimensional scanning using the above scanning mechanism for an automobile radar, a particularly wide scanning range is required in the horizontal direction. That is, it is necessary to increase the amplitude of the lens holder (scanning object).

  In order to increase the amplitude of the lens holder, the length of the magnet becomes a problem. That is, as shown in Patent Document 3 (particularly, FIG. 2 of this document), each coil can control movement only within the magnetic field of the opposing magnet. If the magnet is lengthened, the scanning range can be expanded, but the problem that the scanning mechanism becomes large occurs, and the manufacturing cost is increased by the length of the magnet.

  Patent Document 4 discloses a scanning mechanism that can obtain a large amplitude with a small current by adjusting the weight of the lens holder and the spring constant so that the scanning timing coincides with the vibration timing near the resonance point of the lens holder. Are listed. In this case, however, the lens holder cannot be scanned beyond the length of the magnet.

JP 2004-240662 A JP 2003-177348 A Japanese Patent Laid-Open No. 7-9178 JP-A-10-123252

  An object of this invention is to provide the scanning control apparatus which can scan a scanning target object more than the length of a permanent magnet.

  The scanning control device according to the present invention is arranged such that a current flows in a direction orthogonal to the magnetic fields of the first permanent magnet, the second permanent magnet, and the first permanent magnet and the second permanent magnet. A coil, an elastic body that supports the coil to move parallel to the first permanent magnet and the second permanent magnet at predetermined intervals, and detects the position of the coil And a control circuit for controlling the direction and magnitude of the current supplied to the coil, wherein the control circuit has one end of the coil from the surface of one of the permanent magnets to the other permanent magnet. When moving in the plane of the magnet, the current supplied to the coil is stopped.

  In this way, when one end of the coil moves from the surface of one of the permanent magnets to the other surface, the current is stopped, so that the scanning object moves by inertia. The amplitude motion continues at the resonance frequency of the elastic body (leaf spring) that supports the coil, and the scanning object can be scanned even if the magnetic field of the permanent magnet is exceeded.

  According to this invention, the scanning object can be scanned beyond the length of the permanent magnet.

It is a figure which shows the conventional scanning mechanism. It is an external appearance perspective view which shows the structure of the laser radar of this embodiment. It is a disassembled perspective view of each component. It is a figure explaining operation | movement of the scanning mechanism of a horizontal direction. It is the figure which showed the horizontal scanning position of the lens holder. It is the figure which showed the condition where the end of a coil remove | deviates from the surface of a magnet. It is the figure which showed the position of a coil and the time relationship of electric current supply. It is a block diagram which shows the structure of a laser radar. It is the figure which showed the case where the space | interval of a coil is shorter than the length of a magnet. It is the figure which showed the case where the space | interval of a coil is shorter than the length of a magnet. It is the figure which showed the scanning range.

  A laser radar equipped with a scanning control device of the present invention will be described below with reference to the drawings. The laser radar of this embodiment is attached to a vehicle of an automobile and is attached horizontally to the road surface. FIG. 2 is an external perspective view showing the configuration of the laser radar. FIG. 3 is an exploded perspective view in which each component of the laser radar is disassembled. In the following description, the laser beam irradiation direction is the front direction (Y direction) of the laser radar.

  As shown in FIGS. 2A and 2B, the laser radar 1 includes a linear motor 11 mounted on a fixed base 5, a light receiving unit 12 that receives a light beam pulse, and a projector that projects the light beam pulse. The light unit 13 includes a light receiving lens 14 provided on the front surface of the light receiving unit 12, a light projecting lens 15 provided on the front surface of the light projecting unit 13, a stepping motor 16, a leaf spring (elastic body) 17, and a holder 19. Yes.

  A linear motor 11, a light receiving unit 12, a light projecting unit 13, and a stepping motor 16 are fixed on the upper surface of the fixed base 5.

  The linear motor 11 and the stepping motor 16 are fixed to the center of the fixed base 5. The linear motor 11 is fixed to the front side, and the stepping motor 16 is fixed to the back side. The light receiving unit 12 is fixed in the right direction (X direction) of the stepping motor 16, and the light projecting unit 13 is attached in the left direction (−X direction). The light receiving unit 12 may be in the left direction and the light projecting unit 13 may be in the right direction.

  The light beam pulse projected by the light projecting unit 13 is condensed by the light projecting lens 15 and projected in the front direction of the laser radar 1. The light receiving lens 14 collects the light beam pulse reflected from the object existing in front of the laser radar and guides it to the light receiving unit 12. When the light receiving lens 14 and the light projecting lens 15 are moved in the horizontal direction, the projected light beam pulse is scanned in the horizontal direction. Similarly, when the light receiving lens 14 and the light projecting lens 15 are moved in the vertical direction, the received light beam pulse is scanned in the vertical direction.

  That is, the laser radar 1 projects a light beam pulse from the light projecting unit 13 onto the object at predetermined time intervals, scans the light beam pulse in a predetermined direction, and receives the light beam pulse reflected from the object. Receive light at. The laser radar 1 detects the presence / absence of an object based on the time from projecting a light beam pulse to receiving it and the scanning direction.

  The laser radar 1 of the present embodiment performs horizontal scanning with a linear motor 11 and vertical scanning with a stepping motor 16. The vertical direction may also be scanned with a linear motor.

  The stepping motor 16 has a holder 19 attached in the back direction (−Y direction) via a joint 166 attached to an end portion in the top surface direction (Z direction). When the stepping motor 16 rotates, the joint 166 moves up and down by a rotation gear (not shown), and the holder 19 moves up and down.

  Two leaf springs 17 are attached to the holder 19 at both ends in the horizontal direction (X direction and -X direction). The two leaf springs 17 are rectangular leaf springs that are thin in the horizontal direction and long in the front direction. Each of the two leaf springs 17 has a rear side end attached to the holder 19 and a front side end attached to the lens holder 104.

  The lens holder 104 is a rectangular frame in which the light receiving lens 14 and the light projecting lens 15 are fitted. Two leaf springs 17 are attached and supported at both ends of the lens holder 104 in the horizontal direction. With the lens holder 104, the light receiving lens 14 is positioned in front of the light receiving unit 12, and the light projecting lens 15 is positioned in front of the light projecting unit 13. A linear motor 11 is provided at the center of the lens holder 104.

  Therefore, when the stepping motor 16 that is a rotation motor is rotated, the lens holder 104 moves up and down, so that the lens holder 104 that is a scanning object can be scanned in the vertical direction.

  Next, the horizontal scanning mechanism will be described. As shown in FIGS. 3A and 3B, the horizontal scanning mechanism 10 includes a linear motor 11, a lens holder 104, and two leaf springs 17.

  The linear motor 11 includes an iron core 101 having a hollow structure when viewed from the side, a coil 102 attached to a central portion of the lens holder 104, and a magnet 103 which is a permanent magnet attached to the iron core 101. Become. The iron core 101 is divided into a front iron core 101A and a back iron core 101B. The central portion of the lens holder 104 is surrounded by the iron core 101A and the iron core 101B.

  The coil 102 is attached to the back side of the lens holder 104. The magnet 103 is attached to the front side of the iron core 101B. The magnet 103 is divided into a left side magnet 103A and a right side magnet 103B when viewed from above (see FIG. 4). One of the magnet 103A and the magnet 103B is the first permanent magnet of the present invention, and the other is the second permanent magnet. The magnet 103A and the magnet 103B may be adjacent to each other at the center as shown in the figure, or may be separated from each other. In the example of the figure, the coil 102 is arranged so that the left side faces the magnet 103A and the right side of the coil 102 faces the magnet 103B.

  FIG. 4A is a cross-sectional view of the linear motor 11 as viewed from above, and shows a case where no current flows through the coil 102. FIG. 5B is a view of the coil 102 and the magnet 103 as seen from the front direction of the laser radar. FIGS. 2A and 2B show an example in which the distance between the coils 102 is the same as the length of the magnet 103.

  As shown in FIGS. 1A and 1B, the coil 102 is supported by a leaf spring 17 so as to move in parallel with a predetermined distance from the surfaces of the magnet 103A and the magnet 103B. The coil 102 is supported so that a current flows in a direction orthogonal to the magnetic fields of the magnets 103A and 103B.

  In the state shown in FIG. 6A, there is no force (electromagnetic force) generated by the magnetic field generated by the magnet 103A and the magnet 103B, and the coil 102 is in the neutral position.

  Here, when a current is passed through the coil 102, an electromagnetic force as shown in FIG. That is, in the left coil 102, the electromagnetic force in accordance with Fleming's law is generated in the right direction by the front magnetic field generated by the magnet 103A and the current flowing from the front side to the back side (from the upper surface side to the lower surface side). Occurs. At the same time, in the right coil 102, the electromagnetic force in accordance with Fleming's law is applied in the right direction by the magnetic field in the back direction generated by the magnet 103B and the current flowing from the back to the front of the paper (from the lower surface side to the upper surface side). Occurs.

  Therefore, as shown in FIG. 5A, the coil 102 (the lens holder 104 that is the scanning object) moves to the right, and moves to a position where the generated electromagnetic force and the reaction force of the leaf spring 17 are balanced. On the other hand, when the direction of the current is reversed, an electromagnetic force in the left direction is generated, so that the lens holder 104 moves in the left direction as shown in FIG.

  In this way, the linear motor 11 that is a horizontal scanning mechanism can scan the coil 102 (the lens holder 104 that is the scanning object) by controlling the current that flows through the coil 102.

  Here, when the length of the magnet 103A and the magnet 103B is short, and the position where the electromagnetic force and the reaction force of the leaf spring 17 are balanced exists at a position deviating from the surfaces of the magnet 103A and the magnet 103B, it is shown in FIG. Thus, the coil 102 comes off from the surfaces of the magnet 103A and the magnet 103B.

  In this state, if a current is continuously supplied to the coil 102, an electromagnetic force opposite to the scanning direction is generated by the magnetic field generated by the right magnet 103B and the current flowing from the front side to the back side (from the upper surface side to the lower surface side) of the left coil 102. Will do.

  Therefore, in the laser radar of the present embodiment, when the coil deviates from the surface of the magnet, the supply of current is stopped as shown in FIG. That is, when the left side of the coil 102 is located in the plane of the magnet 103A and the right side of the coil 102 is located in the plane of the magnet 103B, the current supply is controlled (within a control range), and the magnets 103A and 103B are out of the plane. In such a case, the current supply is stopped (with no control range). Then, when the coil 102 deviates from the surfaces of the magnets 103 </ b> A and 103 </ b> B, the coil 102 moves due to inertia, and the amplitude motion continues at the resonance frequency of the leaf spring 17. Therefore, as shown in FIG. 3C, the lens holder 104 that is the object to be scanned can be scanned even if the magnetic fields of the magnet 103A and the magnet 103B are exceeded.

  Next, various configurations and operations of the laser radar for performing the current control will be described. FIG. 7A is a block diagram showing the configuration of the laser radar. In the figure, a laser radar 1 includes a CPU 51, an LD drive circuit 52, an LD 53, a light receiving lens 14, a light projecting lens 15, a light receiving element 54, an amplifier circuit 55, an A / D converter 56, a horizontal scanning position detecting unit 18, a horizontal scanning position detector 18. A scanning mechanism (linear motor) 11, a vertical scanning mechanism (stepping motor) 16, and a CPU 51 are provided.

  The LD drive circuit 52 controls the light emission of the LD 53 based on an instruction from the CPU 51. The light projecting unit 13 is configured by the LD driving circuit 52 and the LD 53. The light beam pulse projected by the LD 53 is projected forward of the host vehicle via the projection lens 15. The reflected light returned from the object reflected by the light beam pulse is collected by the light receiving lens 14 and received by the light receiving element 54. The light receiving element 54 outputs an analog signal corresponding to the amount of received light. The analog signal output from the light receiving element 54 is amplified by the amplifier circuit 55, converted into a digital signal by the A / D converter 56, and input to the CPU 51.

  The CPU 51 functions as a time measurement unit that measures the time from when the light beam pulse is projected to when the digital signal is input. The CPU 51 can calculate the distance to the object by measuring the time from light projection to light reception.

  On the other hand, the CPU 51 outputs a control signal for controlling the current flowing through the coil 102 to the linear motor 11 to scan the light beam pulse in the horizontal direction. Further, the pulse input of the stepping motor 16 is controlled to scan the light beam pulse in the vertical direction. The horizontal scanning position is input from the horizontal scanning position detector 18. The vertical scanning position is detected by the number of input pulses.

  The CPU 51 determines the presence / absence of an object based on the measured time from light projection to light reception, the horizontal scanning position obtained from the horizontal scanning position detection unit 18, and the vertical scanning position detected by the number of input pulses. Is detected.

  FIG. 5B is a detailed block diagram of each configuration (horizontal scanning position detection unit 18, CPU 51, and linear motor 11) for the CPU 51 to control the current of the linear motor 11. It should be noted that the comparison / determination unit 511, the arithmetic unit 512, and the switching unit 513 shown in the figure are functionally realized by the CPU 51 by software.

  As shown in FIG. 3, the horizontal scanning position detector 18 is fixed so as to face either one of the leaf springs 17. The light projecting element 181 of the horizontal scanning position detection unit 18 irradiates the leaf spring 17 with light, and the light receiving element 182 receives the reflected light from the leaf spring 17. The output value of the light receiving element 181 is amplified by the amplifier 183 and then input to the comparison / determination unit 511 of the CPU 51 as a digital value through the A / D converter 184.

  The comparison / determination unit 511 calculates the amount of displacement of the leaf spring 17 by referring to the database 501 with the input output value of the horizontal scanning position detector 18. The database 501 stores a table in which output values and displacement amounts of the light receiving elements 181 are defined in advance. Therefore, the comparison / determination unit 511 can calculate the displacement amount of the leaf spring 17, that is, the scanning position of the coil 102 from the output value of the horizontal scanning position detection unit 18. The calculated scanning position is input to the calculator 512 and the switch 513. The calculator 512 controls the current supplied to the coil 102 by the drive circuit 111 in accordance with the scanning position of the coil 102. The switch 513 switches between supply and cutoff of the control signal output from the computing unit 512 according to the scanning position of the coil 102, and controls the stop timing of the current supplied to the coil 102 by the drive circuit 111.

  FIG. 8 is a diagram showing the time relationship between the coil position and the current supply. As shown in the figure, the calculator 512 controls the current (drive current) in accordance with the resonance frequency of the coil 102 (resonance frequency of the leaf spring 17). That is, the drive circuit 111 is controlled so that an alternating current having the same frequency as the resonance frequency of the leaf spring 17 flows through the coil 102. However, current control is performed in consideration of a time lag from when the current flows through the coil 102 until the lens holder 104 actually starts moving.

  Here, the switch 513 switches between supplying and shutting off the control signal at a position where the scanning position of the coil 102 deviates from the surfaces of the magnets 103A and 103B. That is, the switch 513 stops the current supplied to the coil 102 when the scanning position of the coil 102 is about to move out of the surfaces of the magnets 103A and 103B. On the other hand, the switch 513 supplies current to the coil 102 again when the scanning position of the coil 102 is about to move from the outside of the magnets 103A and 103B to the in-plane.

  When the control as described above is performed, even if the coil is detached from the surface of the permanent magnet, it is moved by inertia, and the amplitude motion is continued at the resonance frequency of the leaf spring. Therefore, the scanning object can be scanned even when the magnetic field of the permanent magnet is exceeded, and a wide scanning range can be secured in the horizontal direction even if the length of the permanent magnet is short.

  Next, FIG. 9 shows an example in which the interval between the coils 102 is shorter than the length of the magnet 103A (or the magnet 103B). FIG. 3A is a view of the coil 102 and the magnet 103 as seen from the front direction of the laser radar. FIG. 2B is a cross-sectional view of the linear motor 11 as viewed from above. FIGS. 6A and 6B are diagrams showing a case where the coil 102 is in a neutral position.

  Here, as shown in FIG. 5B, a current flows from the front side to the back side of the paper in the left coil 102 (from the upper surface side to the lower surface side), and from the back side of the paper surface to the front side (from the lower surface side to the upper surface). When an electric current is applied toward the side), an electromagnetic force according to Fleming's law is generated in the right direction.

  Here, if a current is continuously supplied to the coil 102, the left side of the coil 102 is disengaged from the surface of the magnet 103A as shown in FIG. However, since the distance between the coils 102 is shorter than the length of the magnet 103A (or the magnet 103B), the right coil 102 exists in the plane of the magnet 103B.

  In this state, if a current is continuously supplied to the coil 102, an electromagnetic force opposite to the scanning direction is generated by a magnetic field generated by the right magnet 103B and a current flowing from the front side to the back (upper surface side to lower surface side) of the left coil 102. Will occur. Therefore, as shown in FIG. 10B, when one end of the coil 102 is out of the plane of one of the magnets and moves into the plane of the other magnet, the supply of current is stopped.

  When the interval between the coils 102 is longer than the length of the magnet 103A (or magnet 103B), one end (for example, the right side) of the coil 102 is disengaged from the in-plane of the magnet, contrary to the examples shown in FIGS. Even in this case, the other end (for example, the left side) does not come out of the plane of the magnet. In this case, the current supply may be stopped and scanning by inertia may be performed, or current may be supplied to the coil on the side still in the plane of the magnet, and scanning may be performed using the generated electromagnetic force. .

  Further, even when the magnet 103A and the magnet 103B are spaced apart from each other, similarly to the above, even if one end (for example, the right side) of the coil 102 is out of the plane of the magnet, the other end (For example, the left side) may be out of the plane of the magnet. Even in this case, the current supply may be stopped and scanning may be performed by inertia, or the current may be supplied to the coil located in the plane of the magnet and the generated electromagnetic force may be used for scanning. Good.

  Next, FIG. 11 is a diagram showing a scanning range of the laser radar. The automobile travels on the road surface in the front-rear and left-right directions, and when performing two-dimensional scanning, a high-speed and wide scanning range is required in the horizontal direction. Therefore, for example, as shown in FIG. 11, a two-dimensional scanning range of about 30 degrees in the horizontal direction and about 10 degrees in the vertical direction is set in order to detect the preceding vehicle traveling in front of the host vehicle as an object. Yes. In the present invention, a linear motor is used as a scanning mechanism. When one end of the coil moves out of the plane of one of the permanent magnets and moves into the plane of the other permanent magnet, the current is stopped and the length of the permanent magnet is reduced. The object to be scanned can be scanned even if the value exceeds. Therefore, even if the permanent magnet is downsized and the laser radar is downsized, a wide scanning range can be secured in the horizontal direction.

1-laser radar 10-horizontal scanning mechanism 11-linear motor 12-light receiving unit 13-light projecting unit 14-light receiving lens 15-light projecting lens 16-stepping motor 17-plate spring 18-horizontal scanning position detecting unit 19-holder

Claims (1)

A first permanent magnet;
A second permanent magnet;
A coil disposed so that a current flows in a direction orthogonal to the magnetic fields of the first permanent magnet and the second permanent magnet;
An elastic body that supports the coil so as to move parallel to the first permanent magnet and the surface of the second permanent magnet at a predetermined interval from each other;
Position detecting means for detecting the position of the coil;
A control circuit for controlling the direction and magnitude of the current supplied to the coil;
With
The control circuit stops the current supplied to the coil when one end of the coil moves from the surface of one of the permanent magnets to the surface of the other permanent magnet. .

Images