WO2020093577A1 - 一种直升机载激光雷达激光扫描姿态角稳定方法与装置 - Google Patents

一种直升机载激光雷达激光扫描姿态角稳定方法与装置 Download PDF

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Publication number
WO2020093577A1
WO2020093577A1 PCT/CN2018/126005 CN2018126005W WO2020093577A1 WO 2020093577 A1 WO2020093577 A1 WO 2020093577A1 CN 2018126005 W CN2018126005 W CN 2018126005W WO 2020093577 A1 WO2020093577 A1 WO 2020093577A1
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Prior art keywords
axis
laser
mirror
rotation
center
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PCT/CN2018/126005
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English (en)
French (fr)
Inventor
王建军
范媛媛
苗松
乔建委
许文硕
王志勇
白崇岳
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山东理工大学
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Priority to ZA2019/02540A priority Critical patent/ZA201902540B/en
Publication of WO2020093577A1 publication Critical patent/WO2020093577A1/zh

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
    • G01S17/88—Lidar systems specially adapted for specific applications
    • G01S17/89—Lidar systems specially adapted for specific applications for mapping or imaging
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
    • G01S7/481—Constructional features, e.g. arrangements of optical elements
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
    • G01S7/491—Details of non-pulse systems
    • G01S7/493—Extracting wanted echo signals
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A90/00—Technologies having an indirect contribution to adaptation to climate change
    • Y02A90/10—Information and communication technologies [ICT] supporting adaptation to climate change, e.g. for weather forecasting or climate simulation

Definitions

  • Helicopters are widely used as lidar load platforms.
  • the helicopter is flexible in flight and can be hovered in the air.
  • the maximum speed can reach 300km / h.
  • the flight altitude ranges from several meters to 6000m from the ground. It can achieve vertical take-off and landing on a small field without taking off and landing runways. These characteristics make it the most suitable for carrying LiDAR.
  • Models. Helicopters have some high-speed rotating moving parts such as rotors and tail rotors. These parts will produce violent vibrations during operation, resulting in high vibration and noise during helicopter flight. These shortcomings make the helicopter's flight trajectory more complicated than fixed-wing aircraft, and the attitude angle disturbance of its airborne platform is more obvious and complicated. There are both low-frequency fluctuations and high-frequency vibrations.
  • the goal of airborne LiDAR's attitude angle compensation is to quickly correct the spatial direction of the laser pulse beam rather than the spatial direction of the entire device. Therefore, it is difficult for the airborne lidar to achieve a satisfactory attitude angle compensation effect for a general-purpose stable platform .
  • the MEMS gyroscope is installed on the scanning mirror to obtain real-time measurement values of the three attitude angles of the scanning mirror relative to the local reference coordinate system. Therefore, by controlling the spatial orientation of the scanning mirror normal, the laser scanning direction of the scanning mirror can be directed to the desired Spatial orientation.
  • two screw stepper motors are used to control the scanning mirror to rotate around the x-axis (rolling angle rotation axis) and the y-axis (pitch angle rotation axis) in a linear push mode.
  • the method and device for stabilizing the laser scanning attitude angle of a helicopter-borne lidar proposed by the present application is characterized by that it can realize an airborne LiDAR laser scanning attitude stabilization system, including a laser scanning attitude angle stabilizing device (1) and a laser gyroscope ( 2).
  • the laser scanning attitude angle stabilization device (1) includes a mechanical transmission part and an attitude angle stabilization device controller.
  • the reference coordinate system is XYZ-o, where the X direction is the direction of the aircraft's advance, Z is the vertical downward direction, and Y is the right direction of the aircraft.
  • Half of the value, and the z-axis reverse rotation is the same magnitude as the yaw angle measurement value of the airborne platform (5), so that the spatial direction of the laser beam emitted after being reflected by the laser mirror (101) is not affected by the machine The impact of the three-dimensional attitude angle of the carrier platform (5).
  • the laser mirror (101) also needs to realize the laser scanning function.
  • control movement of the laser mirror (101) is the superposition of three control signals, one is the scanning and swinging movement around the x axis to realize the two-dimensional scanning of the laser; the second is the real-time change of the three-dimensional attitude angle of the airborne platform (5) Compensate the movement; third is the normal direction of the laser mirror (101) to realize the real-time tracking movement of the space dynamic target.
  • the z-axis is the same as the rotation axis of the yaw angle, and the center column (107) is driven to rotate by the z-axis stepper motor (112) fixed on the mounting base (114), and then driven
  • the laser mirror (101) rotates around the z axis.
  • the rotation of the laser mirror (101) around the x and y axes adopts the screw and the anti-backlash screw nut (119) of the X-axis screw stepper motor (108) and the Y-axis screw stepper motor (109), respectively
  • the mechanism drives the linear slider (118) to move up and down; the rotation of the laser mirror (101) around the z-axis is directly driven by a z-axis stepper motor (112).
  • the screw stepping motor is to replace the rotating shaft of the stepping motor with a longer screw, and add an internal thread slider that can be driven by external force on the screw, and the internal thread is engaged with the screw. So as to achieve the purpose of linear movement of the slider along the axial direction.
  • the screw nut is a mechanical subdivision structure, which can achieve different control accuracy by controlling the pitch of the thread.
  • the Y-axis screw stepper motor (109) is fixedly installed in the motor bracket (104), and the anti-backlash screw nut (119) installed on the screw is fixedly connected with the linear motion slider (118) installed on it.
  • the linear slider (118) is connected to the screw hole end of the ball head universal bearing (103) through a small screw rod protruding from the front side, and the small screw rod extending from the other end of the ball head universal bearing (103) is cross-shaped
  • the screw holes of the mirror support rod (102) are connected, so that when the Y-axis screw stepper motor (109) rotates, it can sequentially drive the anti-backlash screw nut (119), the straight-moving slider (118), the ball The head universal bearing (103), the cross-shaped mirror support rod (102) and the laser mirror (101) rotate around the X axis.
  • the optical axis extends vertically on both sides of the linear motion slider (118), and the optical axis is tightly connected to the inner ring of the miniature bearing, and the outer ring of the miniature bearing is placed in the track groove on the side of the motor bracket (104).
  • the constraint can eliminate the linear motion slider (118) rotating with the radial direction of the screw under the action of friction resistance, so that it only moves linearly along the axis of the screw, and the rolling contact between the miniature bearing and the track groove wall is reduced.
  • the frictional resistance of the track groove to the linear motion slider (118) is increased.
  • a longitudinal deflection hinge (116) is installed at the bottom center of the motor bracket (104), and the longitudinal deflection hinge (116) is connected to the axial deflection hinge (110).
  • the axial deflection hinge (110) has a certain damping and spring restoring force, when the laser mirror (101) is perpendicular to the central column (107), the motor bracket (104) can be maintained parallel to the central column; and when the screw When the stepping motor pushes the laser mirror to rotate, the motor bracket (104) can be slightly deflected in the rotation direction of the two hinges according to the geometric constraints of the device.
  • the center column chassis (115) is tightly connected with the center column (107) through an interference fit.
  • a weight block (117) of the same quality as the Y-axis screw stepper motor (109) is installed to realize the laser mirror ( 101) Dynamic and static balance during rotation.
  • the relevant structure and working mode of the X-axis screw stepper motor (108) are the same as the Y-axis screw stepper motor (109).
  • the central column (107) is designed in the shape of a stepped shaft, which is divided into four stages, and the four parts are arranged in descending order of their diameters: the first part serves as the central support shaft of the entire laser mirror (101), and The magnetic steel concave spherical body (106) is fastened and welded; the second part forms an interference fit with the center hole of the center column chassis (115), and uses the interference friction bonding force to make the center column (107) and the center column chassis (115) ) become one; the third part is installed on the miniature ball bearing (111) in the central hole of the mounting base (114), the stepped shaft and the inner ring of the miniature ball bearing (111) are fitted with interference fit; the fourth part passes through The miniature ball bearing (111) is connected to the rotation axis of the z-axis stepping motor (112) through a coupling to realize the rotation drive around the z-axis.
  • the mounting base (114) has a square shape, and support columns (113) are added to the four corners of each
  • px1 is the center of rotation of the ball joint bearing (103) on the x-axis
  • px2 is the center of rotation of the longitudinal deflection hinge (116) on the x-axis
  • px3 is x The center of motion of the linearly moving slider (118) on the shaft.
  • px1 ' is the spatial position of the center of rotation of the ball head universal bearing (103) on the x-axis when the rotation angle of the laser mirror (101) is ⁇
  • px3' is the rotation angle of the laser mirror (101) when it is ⁇ , that is, x
  • ⁇ 1 is the slight inclination angle of the motor bracket (104) on which the x-axis screw stepper motor (108) is mounted relative to the vertical direction.
  • the laser mirror (101) rotates around both the x-axis and the y-axis
  • the laser mirror (101) first rotates around the x-axis by an angle ⁇ , and then rotates around the y-axis
  • the linear motion slider (118) on the x-axis screw stepper motor (109) moves ⁇ x
  • the linear motion slider (118) on the y-axis screw stepper motor (109) moves ⁇ y
  • the corresponding relationship between the moving distance of the linear slider (118) on the two screws and the two rotation angles of the laser mirror (101) is analyzed.
  • Py1 be the center of rotation of the ball joint bearing (103) on the y axis
  • py2 be the center of rotation of the longitudinal deflection hinge (116) on the y axis
  • py3 be the center of motion of the linear motion slider (118) on the y axis point.
  • the connection between py1 and py3 is always parallel to the y-axis direction, and the connection between py1 and py3 is always perpendicular to the connection between py2 and py3.
  • the connection between px2 and px3 around the point px2 only has a slight rotation parallel to the x-axis direction, and there is no slight rotation along the direction parallel to the y-axis.
  • This is the two-axis motor bracket (104) brought by controlling the movement of the Y-axis screw stepper motor (109) and then the movement of the X-axis screw stepper motor (108) when the laser mirror (101) rotates around both axes. )
  • the rotation of the laser mirror (101) around the z-axis is relatively independent, as long as the rotation of the z-axis stepper motor is controlled, it will not cause a coupling effect on the rotation around the x-axis and y-axis.
  • the three-dimensional rotation angle of the laser mirror (101) is a combination of three kinds of movements.
  • One is the swing scanning angle around the x-axis, which is set to ⁇ ; the other is the three-dimensional attitude angle change of the airborne platform
  • the compensations are The third is to allow the normal direction of the laser mirror (101) to point to any direction in space.
  • equations (5) and (6) the corresponding screw linear movement slider displacements ⁇ x and ⁇ y, and the rotation control angle ( ⁇ e - ⁇ ) around the z axis can be obtained.
  • the controller of the attitude angle stabilization device adopts an embedded control system, and there are three original moving parts to be controlled: an x-axis screw stepper motor (108), a y-axis screw stepper motor (109) and a z-axis stepper Motor (112); There are six external information to be received: three attitude angles of airborne platform (5), namely roll angle, pitch angle and yaw angle; three attitude angles of laser reflector (101).
  • the control system software program of the attitude stabilization device controller includes: (1) Start the boot program: complete the establishment of the abnormal interrupt vector table, turn off the watchdog timer, system clock initialization, general input / output interface (GPIO) initialization 2. Initialization and interrupt initialization of each PWM timer; (2) I 2 C data acquisition program: When the attitude angle stabilization device starts to work, first judge the running status of the three stepper motors.
  • the I 2 C interface is configured as the main receiving mode to receive the three-axis attitude angle data measured by the laser gyroscope (2) and the MEMS gyroscope (4); (3) the motor Rotation step solution program: the step angle of the selected screw stepper motor is 1.8 °, then the motor needs 200 steps to complete 360 ° rotation, and the lead of the screw is 5.08mm, then the motor anti-backlash nut The motion step length is 0.0254mm, and the rotation angle control resolution of the laser mirror (101) is 0.029 °.
  • the rotation angle control resolution of the laser mirror can be halved, which is 0.0145 °;
  • Motor running program the rotation of the three stepper motors is driven by three sets of GPIO pins to control its stepper motor driver, the direction of the x-axis screw stepper motor (108) is controlled by the level signal provided by GPG3, and the rotation angle is The pulse signal provided by GPE11 is controlled; the direction of the y-axis screw stepper motor (109) is controlled by the level signal provided by GPG5, and the rotation angle is controlled by the pulse signal provided by GPE12; the direction of the z-axis stepper motor (112) is controlled by GPG6 Level signal control provided, rotation angle provided by GPE13 pulse Signal control.
  • Fig. 1 is a schematic diagram of stabilization of laser scanning attitude angle achieved by helicopter LiDAR.
  • Figure 2 is a composition diagram of the airborne LiDAR attitude stabilization system.
  • Fig. 3 is a mechanical configuration diagram of a laser scanning posture angle stabilizing device (1).
  • FIG. 4 is a diagram of the related structure of the laser mirror (101).
  • FIG. 5 is a structural diagram of a screw stepper motor drive mechanism.
  • Fig. 6 is a structural view of the z-axis driving of the central column (107).
  • FIG. 7 is an analysis diagram of the control principle of the laser mirror (101) rotating only around the Y axis.
  • Fig. 8 is an analysis diagram of the control principle of the rotation of the laser mirror (101) around the X axis and the Y axis.
  • FIG. 9 is a schematic diagram of a control system structure of a controller of an attitude stabilization device.
  • Fig. 10 is a flowchart of the control system program of the controller of the attitude stabilization device.
  • Fig. 1 is a schematic diagram of stabilization of laser scanning attitude angle that can be achieved by helicopter LiDAR.
  • the laser pulse emitter (3) is consolidated with the airborne platform (5), and the laser emission direction is directed to the geometric center of the laser reflector (101) and is directed to the ground to be measured.
  • the base of the laser mirror (101) is consolidated with the airborne platform (5), and the laser mirror (101) reflects the laser pulse beam at a fixed angle, so that the laser pulse beam points in a certain spatial direction.
  • the laser radar it is usually desired that the exit direction of the laser pulse beam remains unchanged, but the attitude angle of the airborne platform (5) changes at any time, causing the exit direction of the laser pulse to deviate from the desired direction.
  • XYZ-O is a Cartesian coordinate system
  • the X direction is the direction of flight
  • the Z direction is vertically downward
  • the Y direction is perpendicular to X and Z, and meets the right-hand rule.
  • the airborne platform (5) has a clockwise elevation angle 2 ⁇ around the Y axis
  • the direction of the emitted laser is offset, so if you want to keep the exit direction unchanged, you need to turn the laser mirror (101) counterclockwise to the airborne platform (5) Half of the pitch angle, ⁇ .
  • the method for rolling angle compensation is the same.
  • the laser beam (101) can be reversely rotated by half of the value of the corresponding attitude angle, so that the angle of the emitted light can be corrected to the ideal case without disturbance of the attitude angle.
  • the disturbance of the yaw angle of the airborne platform (5) only rotates the direction of the laser exit angle around the z-axis without changing its exit angle, so when the yaw angle of the airborne platform (5) has a rotation angle, only Turn the scanning mirror in the reverse direction at the same angle as the yaw angle.
  • FIG 2 shows the composition of the airborne LiDAR attitude stabilization system. It can realize the airborne LiDAR laser scanning attitude angle stabilization system, including laser scanning attitude angle stabilization device (1), laser gyroscope (2), laser pulse transmitter (3), MEMS gyroscope (4) and airborne platform (5 ).
  • the laser scanning attitude angle stabilization device (1) includes a mechanical transmission part and an attitude angle stabilization device controller.
  • the reference coordinate system is XYZ-o, where the X direction is the direction of the aircraft's advance, Z is the vertical downward direction, and Y is the right direction of the aircraft.
  • the coordinate origin o is the laser scanning optical center, that is, the rotation center of the laser mirror (101), that is, the laser pulse reflection point of the laser mirror (101).
  • the laser pulse transmitter (3) is consolidated with the airborne platform (5), and the laser emission direction is directed to the center of the laser reflector (101) and directed to the ground to be measured.
  • a laser gyroscope (2) is used to detect the attitude angle change of the airborne platform (5) in real time, and the laser reflector (101) is controlled to rotate accordingly to stabilize the exit direction of the laser scanning.
  • the MEMS gyroscope (4) is mounted on the back of the laser mirror (101), and is configured to measure the actual three-dimensional attitude angle of the laser mirror (101).
  • Half of the value, and the z-axis reverse rotation is the same magnitude as the yaw angle measurement value of the airborne platform (5), so that the spatial direction of the laser beam emitted after being reflected by the laser mirror (101) is not affected by the machine The impact of the three-dimensional attitude angle of the carrier platform (5).
  • the laser mirror (101) also needs to realize the laser scanning function.
  • control movement of the laser mirror (101) is the superposition of three control signals, one is the scanning and swinging movement around the x axis to realize the two-dimensional scanning of the laser; the second is the real-time change of the three-dimensional attitude angle of the airborne platform (5) Compensate the movement; third is the normal direction of the laser mirror (101) to realize the real-time tracking movement of the space dynamic target.
  • Fig. 3 is a mechanical structure diagram of a laser scanning attitude angle stabilizing device (1).
  • the mechanical transmission part of the laser scanning attitude stabilization device (1) includes: a laser reflector (101), a cross-shaped mirror support rod (102), a ball head universal bearing (103), a motor bracket (104), and a slotted stainless steel small Hemisphere (105), magnetic steel concave sphere (106), center post (107), x-axis screw stepper motor (108), y-axis screw stepper motor (109), axial deflection hinge (110) , Miniature ball bearing (111), z-axis stepper motor (112), support column (113), mounting base (114), center column chassis (115), longitudinal deflection hinge (116), counterweight (117), Straight-moving slider (118), anti-backlash screw nut (119).
  • the laser mirror (101) can realize three-axis rotation, and the coordinate origin o of the reference coordinate system XYZ-o is the symmetric center of the laser mirror (101), that is, the rotation center of the laser mirror and the laser pulse reflection point.
  • the mirror symmetry center of the laser reflecting mirror (101) coincides with the rotation center of the laser reflecting mirror (101), and its spatial position is fixed by the central post (107).
  • the x-axis and y-axis of the two directions of the laser mirror (101) perpendicular to each other are the rotation axis of the roll angle (x-axis) and the pitch angle (y-axis) of the airborne platform, which can be stepped by the x-axis screw
  • the feed motor (108) and the y-axis screw stepper motor (109) drive the laser mirror (101) to rotate around the y-axis and x-axis, respectively.
  • the center column (107) can rotate around the z-axis.
  • the z-axis is the same as the rotation axis of the yaw angle, and the center column (107) is driven to rotate by the z-axis stepper motor (112) fixed on the mounting base (114), and then driven
  • the laser mirror (101) rotates around the z axis.
  • the center of the mirror surface of the laser mirror (101) and the midpoint of the four sides of the mirror surface are control points that constrain the rotation direction of the mirror space.
  • Four linear motion slides (118) are connected by ball joint universal bearings (103). Rolling bearings are installed at both ends of the four linear motion sliders (118), which can move up and down along the track grooves of the four motor brackets (104), respectively.
  • the X-axis screw stepper motor (108) and the Y-axis screw stepper motor (109), two straight-moving sliders are installed in the two motor brackets (104) connected in the positive direction of the x-axis and the y-axis, respectively 118) Installed on the screws of the X-axis screw stepper motor (108) and the Y-axis screw stepper motor (109) through anti-backlash screw nuts (119), driven by the screws of the two stepper motors
  • the linear motion slider (118) performs a linear motion up and down, driving the laser mirror (101) to rotate around the x-axis and the y-axis.
  • a weight block (117) is installed, which is configured to satisfy the static and dynamic balance when the laser mirror (101) rotates around three axes.
  • the center upright (107) and the center upright chassis (115) are tightly connected to maintain a vertical relationship.
  • the lower stepped shaft of the center column (107) passes through the miniature ball bearing (111) and is connected with the z-axis stepper motor (112) through a coupling. When the z-axis stepper motor (112) rotates, it can drive the central column (107) to rotate.
  • the four motor brackets (104) are fixedly connected with the four longitudinal deflection hinges (116), respectively, so that the four motor brackets (104) can realize slight deflection along the direction of the corresponding side perpendicular to the connected laser mirror (101).
  • the four longitudinal deflection hinges (116) are connected with the four axial deflection hinges (110), respectively, so that the four motor brackets (104) can be slightly parallel to the corresponding side direction of the connected laser mirror (101) deflection.
  • the received echo signal is strong enough, it can be recorded correctly.
  • the echo signals that can be received by the mirror surface are weaker, and the size of the laser mirror (101) needs to be increased to reflect as many echo signals as possible.
  • the size of the scanning mirror is severely limited.
  • the structural characteristics of the laser scanning posture angle stabilizing device (1) can satisfy the installation of a larger-size laser mirror (101) and keep the device volume and mass smaller.
  • the specific size of the laser mirror (101) used in this device is 100mm ⁇ 100mm ⁇ 2mm.
  • FIG. 4 is a related structural diagram of the laser mirror (101).
  • the laser mirror (101) is mounted on a cross-shaped mirror support rod (102).
  • the four rod ends of the cross-shaped mirror support rod (102) are a square joint with a threaded hole, which can be connected to a ball head universal bearing
  • the screw end of (103) is connected.
  • the threaded hole end of the ball head universal bearing (103) is connected to the screw end of the linear motion slider (118), and the linear motion slider (118) is consolidated with the anti-backlash screw nut (119) and passes through the wire
  • the bar stepper motor drives up and down.
  • the cross-shaped mirror support rod (102) is fixedly connected with a slotted stainless steel small hemisphere (105).
  • the slotted stainless steel small hemisphere (105) is a small steel ball part cut from a solid steel ball with a diameter of 30 mm at a distance of 2 mm from the center of the ball, and is processed on the cutting plane with the center of the cross-shaped mirror support rod (102)
  • the cross-shaped grooves of the same size so that the cross-shaped mirror support rod (102) can be firmly embedded in the center of the slotted stainless steel small hemisphere (105), and firmly bonded.
  • a magnetic steel concave spherical body (106) made of a magnetic steel material is tightly connected with the central column (107).
  • the slotted stainless steel small hemisphere (105) and the magnetic steel concave sphere (106) are tightly attracted by the magnetic field force, and the contact surface of the two is polished to a mirror precision, and lubricating oil can be applied in three-dimensional space No relative displacement occurs, only spherical sliding contact is formed.
  • two isolated parts, slotted stainless steel small hemisphere (105) and magnetic steel concave spherical body (106) can be combined into a magnetic universal motion bearing structure.
  • the laser mirror (101) is pasted on the cross-shaped mirror support rod (102)
  • the center of the laser reflection of the laser mirror (101) will coincide with the center of the slotted stainless steel hemisphere (105), so that the center of rotation when the laser mirror (101) rotates can be fixed.
  • the scanning center point of the outgoing laser pulse beam also remains unchanged.
  • FIG. 5 is a structural diagram of a screw stepper motor drive mechanism.
  • the rotation of the laser mirror (101) around the x and y axes uses the screw and anti-backlash screw nut (119) mechanisms of the X-axis screw stepper motor (108) and the Y-axis screw stepper motor (109),
  • the linear motion slider (118) is driven to move up and down; the rotation of the laser mirror (101) around the z-axis is directly driven by a z-axis stepper motor (112).
  • the screw stepping motor is to replace the rotating shaft of the stepping motor with a longer screw, and add an internal thread slider that can be driven by external force on the screw, and the internal thread is engaged with the screw. So as to achieve the purpose of linear movement of the slider along the axial direction.
  • the screw nut is a mechanical subdivision structure, which can achieve different control accuracy by controlling the pitch of the thread.
  • the Y-axis screw stepper motor (109) is fixedly installed in the motor bracket (104), and the anti-backlash screw nut (119) installed on the screw is fixedly connected with the linear motion slider (118) installed on it.
  • the linear slider (118) is connected to the screw hole end of the ball head universal bearing (103) through a small screw rod protruding from the front side, and the small screw rod extending from the other end of the ball head universal bearing (103) is cross-shaped
  • the screw holes of the mirror support rod (102) are connected, so that when the Y-axis screw stepper motor (109) rotates, it can sequentially drive the anti-backlash screw nut (119), the straight-moving slider (118), the ball The head universal bearing (103), the cross-shaped mirror support rod (102) and the laser mirror (101) rotate around the X axis.
  • the optical axis extends vertically on both sides of the linear motion slider (118), and the optical axis is tightly connected to the inner ring of the miniature bearing, and the outer ring of the miniature bearing is placed in the track groove on the side of the motor bracket (104).
  • the constraint can eliminate the linear motion slider (118) rotating with the radial direction of the screw under the action of friction resistance, so that it only moves linearly along the axis of the screw, and the rolling contact between the miniature bearing and the track groove wall is reduced.
  • the frictional resistance of the track groove to the linear motion slider (118) is increased.
  • a longitudinal deflection hinge (116) is installed at the bottom center of the motor bracket (104), and the longitudinal deflection hinge (116) is connected to the axial deflection hinge (110).
  • the axial deflection hinge (110) has a certain damping and spring restoring force, when the laser mirror (101) is perpendicular to the central column (107), the motor bracket (104) can be maintained parallel to the central column; and when the screw When the stepping motor pushes the laser mirror to rotate, the motor bracket (104) can be slightly deflected in the rotation direction of the two hinges according to the geometric constraints of the device.
  • the center column chassis (115) is tightly connected with the center column (107) through an interference fit.
  • a weight block (117) of the same quality as the Y-axis screw stepper motor (109) is installed to realize the laser mirror ( 101) Dynamic and static balance during rotation.
  • the relevant structure and working mode of the X-axis screw stepper motor (108) are the same as the Y-axis screw stepper motor (109).
  • Fig. 6 is a structural diagram of the z-axis driving of the central column (107).
  • the central column (107) is designed in the shape of a stepped shaft, which is divided into four stages, and these four parts are arranged in descending order of their diameters: the first part serves as the central support shaft of the entire laser mirror (101), and the magnetic steel
  • the concave spherical body (106) is fastened and welded; the second part forms an interference fit with the center hole of the center column chassis (115), and uses the interference friction binding force to make the center column (107) and the center column chassis (115) become Integral;
  • the third part is installed on the miniature ball bearing (111) in the center hole of the mounting base (114), the stepped shaft and the inner ring of the miniature ball bearing (111) are fitted with interference fit; the fourth part passes through the miniature ball
  • the bearing (111) is connected to the rotating shaft of the z-axis stepping motor (112) through a coupling to realize the rotational driving around the z-axis
  • FIG. 7 is an analysis diagram of the control principle of the laser mirror (101) rotating only around the Y axis.
  • the laser mirror (101) only rotates around a single axis of the x-axis or y-axis, such as rotating around the y-axis, it is assumed that when the X-axis screw stepper motor (108) rotates, the linear motion on the screw
  • the laser mirror (101) rotates around the y-axis by an angle of ⁇ .
  • px1 is the center of rotation of the ball joint bearing (103) on the x-axis
  • px2 is the center of rotation of the longitudinal deflection hinge (116) on the x-axis
  • px3 is x The center of motion of the linearly moving slider (118) on the shaft.
  • px1 ' is the spatial position of the center of rotation of the ball head universal bearing (103) on the x-axis when the rotation angle of the laser mirror (101) is ⁇
  • px3' is the rotation angle of the laser mirror (101) when it is ⁇ , that is, x
  • ⁇ 1 is the slight inclination angle of the motor bracket (104) on which the x-axis screw stepper motor (108) is mounted relative to the vertical direction.
  • Fig. 8 is an analysis diagram of the control principle of the laser mirror (101) rotating around the X axis and the Y axis.
  • the laser mirror (101) rotates around both the x-axis and the y-axis, for example, the laser mirror (101) first rotates around the x-axis by an angle ⁇ , and then rotates around the y-axis
  • the linear motion slider (118) on the x-axis screw stepper motor (109) moves ⁇ x
  • the linear motion slider (118) on the y-axis screw stepper motor (109) moves ⁇ y
  • the corresponding relationship between the moving distance of the linear slider (118) on the two screws and the two rotation angles of the laser mirror (101) is analyzed.
  • Py1 be the center of rotation of the ball joint bearing (103) on the y axis
  • py2 be the center of rotation of the longitudinal deflection hinge (116) on the y axis
  • py3 be the center of motion of the linear motion slider (118) on the y axis point.
  • the connection between py1 and py3 is always parallel to the y-axis direction, and the connection between py1 and py3 is always perpendicular to the connection between py2 and py3.
  • the connection between px2 and px3 around the point px2 only has a slight rotation parallel to the x-axis direction, and there is no slight rotation along the direction parallel to the y-axis.
  • This is the two-axis motor bracket (104) brought by controlling the movement of the Y-axis screw stepper motor (109) and then the movement of the X-axis screw stepper motor (108) when the laser mirror (101) rotates around both axes. )
  • the rotation of the laser mirror (101) around the z-axis is relatively independent, as long as the z-axis stepper motor is controlled to rotate, and will not cause a coupling effect on the rotation around the x-axis and y-axis.
  • the three-dimensional rotation angle of the laser mirror (101) is a combination of three kinds of movements. One is the swing scanning angle around the x-axis, which is set to ⁇ ; the other is the three-dimensional attitude angle change of the airborne platform
  • the compensations are The third is to allow the normal direction of the laser mirror (101) to point to any direction in space. Let the three posture angles of the normal direction of the desired laser mirror (101) relative to the initial posture position be Then the total rotation angle of the laser mirror (101) about the x-axis is ( ⁇ - ⁇ / 2 + ⁇ e ), and the total rotation angle about the y-axis is The total rotation angle around the z-axis is ( ⁇ e - ⁇ ). According to equations (5) and (6), the corresponding screw linear movement slider displacements ⁇ x and ⁇ y, and the rotation control angle ( ⁇ e - ⁇ ) around the z axis can be obtained.
  • FIG. 9 is a schematic diagram of the control system structure of the controller of the attitude stabilization device.
  • the controller of the attitude angle stabilization device adopts an embedded control system, and there are three original moving parts to be controlled: an x-axis screw stepper motor (108), a y-axis screw stepper motor (109) and a z-axis stepper motor ( 112); There are six external information to be received: three attitude angles of the airborne platform (5), namely roll angle, pitch angle and yaw angle; three attitude angles of the laser reflector (101).
  • Fig. 10 is a flowchart of the control system program of the controller of the attitude stabilization device.
  • the control system software program of the attitude angle stabilization device controller includes: (1) Start boot program: complete the establishment of the abnormal interrupt vector table, turn off the watchdog timer, system clock initialization, general input / output interface (GPIO) initialization, each PWM timer initialization and interrupt initialization, etc .; (2) I 2 C data acquisition program: When the attitude angle stabilization device starts to work, first judge the running status of the three stepper motors.
  • the I2C interface is configured as the main receiving mode to receive the three-axis attitude angle data measured by the laser gyroscope (2) and the MEMS gyroscope (4); (3) the motor rotation step Numerical solution program: the step angle of the selected screw stepper motor is 1.8 °, then the motor needs 200 steps to complete the 360 ° rotation, and the screw lead is 5.08mm, then the motor anti-backlash nut movement step The length is 0.0254mm, and the resolution of the rotation angle control of the laser mirror (101) is 0.029 °.
  • the rotation of the three stepper motors is driven by three sets of GPIO pins to control its stepper motor driver.
  • the direction of the x-axis screw stepper motor (108) is controlled by the level signal provided by GPG3, and the rotation angle is provided by GPE11.
  • the pulse signal control of the y-axis screw stepper motor (109) is controlled by the level signal provided by GPG5, and the rotation angle is controlled by the pulse signal provided by GPE12;
  • the z-axis stepper motor (112) is provided by GPG6 Level signal control, pulse signal provided by GPE13 Number control.

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Abstract

一种直升机载激光雷达激光扫描姿态角稳定方法与装置，激光反射镜（101）的旋转采用推转结构，可有效增大激光反射镜（101）尺寸并减小装置的体积和质量。激光反射镜（101）安装在磁性万向球轴承上并以球心为旋转中心摆动扫描，激光脉冲在激光反射镜（101）的旋转中心反射。机载平台（5）姿态角变化时，采用两个丝杆步进电机（108，109）以直线推动方式控制激光反射镜（101）绕x轴与y轴反向转动滚动角和俯仰角的一半进行补偿；采用z轴步进电机（112）驱动激光反射镜（101）绕z轴反向转动偏航角幅值进行补偿，使激光扫描中心的空间指向不受平台姿态角变化影响。机载平台（5）安装激光陀螺仪（2），激光反射镜（101）上安装MEMS陀螺仪（4），通过比较两者姿态角测量值，控制激光反射镜（101）的法线指向期望空间方位，实现对动态目标的实时跟踪扫描。

Description

一种直升机载激光雷达激光扫描姿态角稳定方法与装置
相关申请的交叉引用
本申请要求于2018年11月07日提交中国专利局的申请号为201811315591.6、名称为“一种直升机载激光雷达激光扫描姿态角稳定方法与装置”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请涉及直升机载激光雷达高精度激光扫描技术，如何消除机载平台的姿态角低频波动和高频振动对激光点云的影响，提出了一种激光扫描时可保持姿态角稳定的方法与装置。
背景技术
机载激光雷达(LiDAR)作为对地测绘设备，可快速精确地采集被测地形的大规模激光点云，生成被测地形的数字表面模型(DSM)。数字表面模型作为数字化描述地形信息的基础，其精度对后续科学研究和应用产生重要影响。因此，如何有效提升机载LiDAR点云数据所生成的DSM精度，具有重要的现实意义。
直升机作为激光雷达的载荷平台，得到了广泛应用。直升机飞行灵活，可空中悬停，最高时速可达300km/h，飞行高度从距离地面数米至6000m高空，可实现无需起降跑道的小场地垂直起降，这些特点使其成为最适合搭载LiDAR的机种。直升机具有旋翼和尾桨等一些高速旋转的动部件，这些部件工作时会产生剧烈振动，导致直升机飞行时振动和噪声较高。这些缺点使直升机的飞行轨迹与固定翼飞机相比更为复杂，其机载平台的姿态角扰动更加明显和复杂，既有低频波动，又有高频振动，因而对安装在机载平台上的激光雷达工作会产生严重影响。复杂的姿态角扰动将使机载LiDAR发射出的激光脉冲束的出射空间角度发生变化，导致所获得的被测地形激光点云分布极不均匀。激光点云密度较低处生成的DSM精度恶化，无法清晰描述被测地形在该区域的细节信息。因此，为有效提高DSM精度，需要切实解决直升机载荷平台的姿态角复杂变化对激光扫描带来的不利影响。
为解决此问题，国内外常用的方法是制作稳定平台以达到隔离负载与载荷平台的目的。近年来，稳定平台方面的研究文献很多，稳定平台技术也已经相当成熟，但大部分的研究都局限于对维持设备整体姿态角稳定的通用稳定平台。通用稳定平台主要用于消除载体姿态角振动对需要精确定位的设备仪器的影响，能适应各种载体，如汽车、飞机和舰船等。而对于实时性要求更高的机载LiDAR，通用稳定平台由于其残余姿态角误差仍较大，故补偿效果较差。机载LiDAR的姿态角补偿目标是快速矫正激光脉冲束的出射空间方向而非整个设备的空间方向定位，因此，通用稳定平台对于机载激光雷达而言，难以实现令人满意 的姿态角补偿效果。
目前国内外在机载LiDAR姿态角补偿方面也进行了一定程度的研究，如Gat在专利中提出了一种用于机载或星载平台上推帚式、相框式相机以及激光扫描仪的通用姿态角光学装置；徐立军、王建军等在专利ZL201010183492.4和ZL201010180527.9中分别提出一种用于机载激光雷达俯仰角偏差实时补偿的方法与装置和一种用于机载激光雷达滚转角偏差实时补偿的方法与装置，但仅限于对单个姿态角的稳定补偿。一些世界主流的LiDAR生产厂家也已经开始关注研究适合机载LiDAR系统搭载的姿态角光学补偿装置，如徕卡公司和Optech公司的两款产品中加入了一种滚转角补偿方法。综上所述，对于机载LiDAR的激光扫描姿态角稳定方法将成为激光雷达产品重要的研究方向。
发明内容
为了实现在直升机载激光雷达激光扫描时不受机载平台姿态角复杂变化的影响，本申请提出了一种专用于直升机载LiDAR的激光扫描姿态角稳定方法与装置。设计时，主要考虑了以下几个方面的因素：(1)由于机载激光雷达测量距离远，激光扫描镜的面积要设计得足够大，以有效收集激光回波信号；(2)直升机载荷平台的姿态角变化复杂，既有阵风与湍流引起的低频大幅度姿态角波动，又有直升机的发动机与旋转机构的高频姿态角振动，因此，要求激光扫描对姿态角的补偿控制有较大带宽，以实现快速控制响应，补偿高频姿态角振动；(3)可同时实现对三个姿态角的稳定与补偿；(4)由于作为机载设备安装，稳定装置的体积要小，重量要轻。因此，经过分析比较，设计的直升机载激光雷达激光扫描姿态角稳定装置有别于通用的三轴转动式稳定平台，而是采用推转结构，能够同时实现三轴姿态角复杂振动的实时补偿，扫描镜较大，并且装置有体积小和质量轻的优点。在扫描镜上安装了MEMS陀螺仪，可获得扫描镜相对于当地参考坐标系的三个姿态角实时测量值，因此可通过控制扫描镜法线的空间方位，使扫描镜的激光扫描方向指向期望的空间方位。另外，当直升机载荷平台的姿态角有变化时，采用了两个丝杆步进电机以直线推动形式控制扫描镜绕x轴(滚动角转轴)与y轴(俯仰角转轴)反向转动一定的角度来补偿滚动角和俯仰角扰动；采用z轴步进电机驱动扫描镜绕z轴反向转动一定角度来补偿偏航角扰动，使激光扫描与出射方向不受机载平台姿态角的变化影响，始终期望指向。此姿态角稳定方法也非常适合于激光对动态目标的跟踪扫描，虽然飞机载荷平台的姿态角在不断地变化，但激光扫描中心的空间指向可始终不变，或者可实时控制指向动态目标的任意空间方位。
本申请提出的一种直升机载激光雷达激光扫描姿态角稳定方法与装置，其特征在于，可实现机载LiDAR激光扫描姿态角稳定系统，包括激光扫描姿态角稳定装置(1)、激光陀螺仪(2)、激光脉冲发射器(3)、MEMS陀螺仪(4)和机载平台(5)。激光扫描姿态角稳定装置(1)包括机械传动部分和姿态角稳定装置控制器。参考坐标系为XYZ-o，其中X 方向为飞机的前进方向，Z为垂直向下方向，Y为飞机的正右方向。坐标原点o为激光扫描光学中心，即激光反射镜(101)的转动中心，亦即激光反射镜(101)的激光脉冲反射点。激光脉冲发射器(3)与机载平台(5)固结，激光出射方向指向激光反射镜(101)中心并射向被测地面。采用激光陀螺仪(2)实时测出机载平台(5)的姿态角变化，并控制激光反射镜(101)进行相应转动，以稳定激光扫描的出射空间方向不变。另外，将MEMS陀螺仪(4)安装在激光反射镜(101)的背面，配置成测量激光反射镜(101)的实际三维姿态角。
其中，通过比较所述激光陀螺仪(2)和所述MEMS陀螺仪(4)的测量值，获得两者角度差，可控制激光反射镜(101)的中心法线指向任意期望的空间方位上，对动态和静态目标进行激光跟踪扫描和探测。另一方面，当机载平台(5)有三维姿态角变化时，控制激光反射镜(101)的x轴和y轴分别反向转动机载平台(5)的滚动角和俯仰角测量值幅值的一半，而z轴反向转动与机载平台(5)的偏航角测量值相同的幅值，从而可使经激光反射镜(101)反射后出射的激光束的空间指向不受机载平台(5)的三维姿态角变化影响。同时，激光反射镜(101)还要实现激光扫描功能。因此，激光反射镜(101)的控制运动是三个控制信号的叠加，一是绕x轴的扫描摆动运动，实现激光二维扫描；二是对机载平台(5)三维姿态角变化的实时补偿运动；三是激光反射镜(101)法线指向实现对空间动态目标的实时跟踪运动。
其中，激光扫描姿态角稳定装置(1)的机械传动部分包括：激光反射镜(101)，十字形镜面支撑杆(102)，球头万向轴承(103)，电机支架(104)，开槽不锈钢小半球体(105)，磁性钢凹球面体(106)，中心立柱(107)，x轴丝杆步进电机(108)，y轴丝杆步进电机(109)，轴向偏转铰链(110)，微型滚珠轴承(111)，z轴步进电机(112)，支撑立柱(113)，安装底座(114)，中心立柱底盘(115)，纵向偏转铰链(116)，配重块(117)，直动滑块(118)，消隙丝杠螺母(119)。所述激光反射镜(101)可实现三轴转动，参考坐标系XYZ-o的坐标原点o为激光反射镜(101)的对称中心，亦即激光反射镜的转动中心及激光脉冲反射点。激光反射镜(101)的镜面对称中心与激光反射镜(101)的旋转中心重合，由中心立柱(107)固定其空间位置。激光反射镜(101)两个互相垂直边的两个方向x轴和y轴，分别为机载平台的滚转角(x轴)和俯仰角(y轴)的旋转轴，可由x轴丝杆步进电机(108)和y轴丝杆步进电机(109)分别驱动激光反射镜(101)绕y轴和x轴转动。中心立柱(107)可绕z轴转动，z轴与偏航角的旋转轴相同，由固定在安装底座(114)上的z轴步进电机(112)驱动中心立柱(107)旋转，进而带动激光反射镜(101)绕z轴转动。
其中，激光反射镜(101)的镜面中心和镜面四边中点为约束镜面空间转动方位的控制点。通过球头万向轴承(103)连接四个直动滑块(118)。四个直动滑块(118)两端安装 了滚动轴承，可分别沿四个电机支架(104)的轨道槽上下移动。在x轴和y轴正方向上相连的两个电机支架(104)中分别安装了X轴丝杠步进电机(108)和Y轴丝杠步进电机(109)，两个直动滑块(118)分别通过消隙丝杠螺母(119)安装在X轴丝杠步进电机(108)和Y轴丝杠步进电机(109)的丝杠上，由两个步进电机的丝杠驱动直动滑块(118)进行上下的直线运动，驱动激光反射镜(101)绕x轴和y轴的转动。在另外两个电机支架(104)上，安装了配重块(117)，配置成满足激光反射镜(101)绕三轴转动时的静和动平衡。中心立柱(107)与中心立柱底盘(115)紧固连接，保持垂直关系。中心立柱(107)的下部阶梯轴穿过微型滚珠轴承(111)，与z轴步进电机(112)通过联轴器连接。当z轴步进电机(112)转动时，可驱动中心立柱(107)旋转。四个电机支架(104)分别与四个纵向偏转铰链(116)固定连接，可实现四个电机支架(104)沿着垂直于所连接激光反射镜(101)的对应边方向的微小偏转。同时，四个纵向偏转铰链(116)分别与四个轴向偏转铰链(110)连接，可实现四个电机支架(104)沿着平行于所连接激光反射镜(101)的对应边方向的微小偏转。
其中，所述激光扫描姿态角稳定装置(1)的本身结构特点，可满足安装较大尺寸的激光反射镜(101)并保持较小的装置体积和质量。采用的激光反射镜(101)的具体尺寸为100mm×100mm×2mm。
其中，激光反射镜(101)安装在十字形镜面支撑杆(102)上，所述十字形镜面支撑杆(102)的四个杆端为一个带有螺纹孔的方形接头，可与球头万向轴承(103)的螺杆端相连。继而所述球头万向轴承(103)的螺纹孔端与直动滑块(118)的螺杆端相连，而直动滑块(118)与消隙丝杠螺母(119)固结，通过丝杠步进电机驱动上下移动。所述十字形镜面支撑杆(102)与一个开槽不锈钢小半球体(105)相固连。开槽不锈钢小半球体(105)是将一个直径30mm的实心钢球在偏离球心2mm处所切下来的小半钢球部分，并在切平面上加工出与十字形镜面支撑杆(102)的中心尺寸相同的十字形凹槽，从而可将十字形镜面支撑杆(102)牢固嵌入开槽不锈钢小半球体(105)中心处，并紧固粘接。将激光反射镜(101)粘贴在十字形镜面支撑杆(102)上，这样就可确保激光反射镜(101)的旋转中心与开槽不锈钢小半球体(105)的球心相重合。采用一个磁性钢材料制作的磁性钢凹球面体(106)与中心立柱(107)紧固连接。所述开槽不锈钢小半球体(105)与所述磁性钢凹球面体(106)依靠磁场力紧紧吸住，二者接触表面均打磨成镜面精度，并涂抹润滑油，可在三维空间内不会发生相对位移，只形成球面滑动接触。通过磁力吸引作用，可将开槽不锈钢小半球体(105)和磁性钢凹球面体(106)两个孤立的零件组合成一个磁性万向运动轴承结构。同时，由于激光反射镜(101)的厚度为2mm，正好等于开槽不锈钢小半球体(105)偏离球点的距离，故激光反射镜(101)粘贴在十字形镜面支撑杆(102)上后，激 光反射镜(101)的激光反射中心点将与开槽不锈钢小半球体(105)的球心重合，从而激光反射镜(101)转动时的旋转中心可固定不变。当激光脉冲在激光反射镜(101)的旋转中心进行反射时，出射激光脉冲束的扫描中心点也保持不变。
其中，激光反射镜(101)绕x和y轴的转动分别采用X轴丝杠步进电机(108)和Y轴丝杠步进电机(109)的丝杆与消隙丝杠螺母(119)机构，驱动直动滑块(118)上下运动；激光反射镜(101)绕z轴的转动采用z轴步进电机(112)直接驱动。丝杆步进电机为将步进电机的旋转轴替换为一段较长的丝杆，并在丝杆上外加一个可以利用外力驱动的内螺纹滑块，通过内螺纹与丝杆之间形成啮合，从而达到滑块沿轴向直线移动的目的。丝杆螺母是一种机械细分结构，可以通过控制螺纹的螺距达到不同的控制精度。Y轴丝杠步进电机(109)固定安装在电机支架(104)中，丝杆上安装的消隙丝杠螺母(119)与加装在其上的直动滑块(118)固定连接，直动滑块(118)通过前侧面伸出的小螺杆与球头万向轴承(103)的螺孔端连接，而球头万向轴承(103)的另一端伸出的小螺杆与十字形镜面支撑杆(102)的杆端螺孔连接，因此，当Y轴丝杆步进电机(109)旋转时，可依次带动消隙丝杠螺母(119)、直动滑块(118)、球头万向轴承(103)、十字形镜面支撑杆(102)和激光反射镜(101)绕X轴转动。在直动滑块(118)的两侧面垂直伸出光轴，光轴与微型轴承内圈紧固相连，微型轴承的外圈则放置于电机支架(104)侧面的轨道槽中，依靠轨道槽的约束可消除直动滑块(118)在摩擦阻力作用下随丝杆的径向旋转，使其只沿丝杆的轴向直线移动，并且微型轴承与轨道槽壁之间形成滚动接触，减小了轨道槽对直动滑块(118)的摩擦阻力。在电机支架(104)底部中心安装纵向偏转铰链(116)，纵向偏转铰链(116)与轴向偏转铰链(110)相连。所述轴向偏转铰链(110)具有一定的阻尼和弹簧恢复力，当激光反射镜(101)垂直于中心立柱(107)时，可维持电机支架(104)与中心立柱平行；而当丝杆步进电机推动激光反射镜旋转时，可根据装置的几何结构约束使电机支架(104)在两个铰链转动方向上产生微小偏转。中心立柱底盘(115)通过过盈配合与中心立柱(107)紧固连接。在与Y轴丝杠步进电机(109)相对方向上的电机支架(104)中，安装与Y轴丝杠步进电机(109)等质量的配重块(117)，实现激光反射镜(101)转动时的动和静平衡。关于X轴丝杠步进电机(108)的相关结构和工作方式，与Y轴丝杠步进电机(109)相同。
其中，中心立柱(107)被设计为阶梯轴的形状，共分为四个阶段，这四个部分按其直径大小的降序排列：第一部分作为整个激光反射镜(101)的中心支撑轴，与磁性钢凹球面体(106)紧固焊接；第二部分与中心立柱底盘(115)的中心孔间形成过盈配合，利用过盈摩擦结合力，使中心立柱(107)与中心立柱底盘(115)成为一体；第三部分安装在安装底座(114)中心孔中的微型滚珠轴承(111)上，阶梯轴与微型滚珠轴承(111)的内圈 过盈配合装配在一起；第四部分穿过微型滚珠轴承(111)，通过联轴器与z轴步进电机(112)的旋转轴相连，实现绕z轴的转动驱动。安装底座(114)为方形，分别在其四个角上加装支撑立柱(113)，可进一步与机载平台(5)相固联。
其中，当激光反射镜(101)只绕x轴或y轴两轴中的单个轴旋转时，如绕y轴转动，设当X轴丝杠步进电机(108)转动使丝杠上的直动滑块(118)中心点移动了△x距离时，此时激光反射镜(101)绕y轴转动了θ角。设点o是激光反射镜(101)的对称中心，px1是x轴上球头万向轴承(103)的转动中心，px2是x轴上纵向偏转铰链(116)的转动中心点，px3是x轴上直动滑块(118)的运动中心点。px1’是当激光反射镜(101)转动角为θ时x轴上球头万向轴承(103)转动中心的空间位置，px3’是当激光反射镜(101)转动角θ时，亦即x轴上直动滑块(118)上下移动△x距离后的运动中心点。θ 1为安装x轴丝杠步进电机(108)的电机支架(104)相对于垂直方向的微小倾斜角。由Px1’和Px2两点之间的距离，根据勾股定理，可建立丝杠上的直动滑块(118)移动量△x与激光反射镜(101)的旋转角度θ之间的关系：
2r 1(r 1+r 2)(1-cosθ)-2r 1d 1sinθ＝Δx 2-2d 1·Δx         (1)
解得：
Figure PCTCN2018126005-appb-000001
当r1＝7，r2＝3.7，d1＝14时，
Figure PCTCN2018126005-appb-000002
Figure PCTCN2018126005-appb-000003
其中，当激光反射镜(101)绕x轴和y轴两个轴旋转时，例如，激光反射镜(101)首先绕x轴转动一个角度ω，然后再绕y轴转动
Figure PCTCN2018126005-appb-000004
设此时x轴丝杆步进电机(109)上的直动滑块(118)移动△x，而y轴丝杆步进电机(109)上的直动滑块(118)移动△y，分析两个丝杠上的直动滑块(118)的移动距离与激光反射镜(101)的两个转角之间的对应关系。设Py1是y轴上球头万向轴承(103)的转动中心点，py2是y轴上纵向偏转铰链(116)的转动中心点，py3是y轴上直动滑块(118)的运动中心点。激光反射镜(101)绕两轴的转动过程中，py1与py3连线始终平行于y轴方向，py1与py3的连线始终垂直于py2与py3的连线，此时，py2与py3连线绕点py2既有沿着平行于y轴方向的微小转动，又有沿 着平行于x轴方向的微小转动。而对于x轴，px2与px3连线绕点px2只有沿着平行于x轴方向的微小转动，而在沿着平行于y轴的方向上没有微小转动。这是激光反射镜(101)绕两轴都转动时、先控制Y轴丝杆步进电机(109)移动再控制X轴丝杆步进电机(108)移动带来的两轴电机支架(104)的中心轴倾斜角的不同之处。因此，在结构设计上，在py2处要有一个围绕y轴方向转动的轴向偏转铰链(110)，同时有能绕沿着平行于x轴方向转动的纵向偏转铰链(116)。而在px2处，只要有一个绕沿着x轴方向转动的纵向偏转铰链(116)即可，其轴上的轴向偏转铰链(110)可以锁死在铅锤方向上而不用转动。
Figure PCTCN2018126005-appb-000005
Figure PCTCN2018126005-appb-000006
即X和Y轴步进电机丝杠上的直动滑块(118)的两个位移与激光反射镜(101)的绕X和Y轴两个转角之间建立了一一对应关系。
其中，激光反射镜(101)绕z轴的转动相对独立，只要控制z轴步进电机转动即可，不会造成对绕x轴和y轴转动的耦合效应。
其中，激光反射镜(101)的三维转动角是三种运动的合成，一是绕x轴的摆动扫描角，设为θ；二是对机载平台三维姿态角变化
Figure PCTCN2018126005-appb-000007
的补偿，分别为
Figure PCTCN2018126005-appb-000008
三是让激光反射镜(101)的法线方向能指向空间任意指向，设期望的激光反射镜(101)的法线方向相对于初始姿态位置的三个姿态角为
Figure PCTCN2018126005-appb-000009
则激光反射镜(101)绕x轴的总转动角度为(θ-ω/2+ω e)，绕y轴的总转动角度为
Figure PCTCN2018126005-appb-000010
绕z轴的总转动角度为(γ e-γ)。根据式(5)和(6)，可得相应的丝杠直动滑块位移△x和△y，以及绕z轴的转动控制角度(γ e-γ)。
其中，姿态角稳定装置控制器采用嵌入式控制系统，需操控的原动件共三个：x轴丝杆步进电机(108)、y轴丝杆步进电机(109)和z轴步进电机(112)；需接收的外部信息共有六个：机载平台(5)的三个姿态角，即滚转角、俯仰角和偏航角；激光反射镜(101)的三个姿态角。利用嵌入式系统s3c2440接收激光陀螺仪(2)和MEMS陀螺仪(4)采集到的六个瞬时姿态角信息；根据设定的激光扫描摆动角度、激光反射镜(101)法线指向的目标空间方位以及当前的六个姿态角信息，计算出△x、△y和绕z轴的转动角度(γ e-γ)，获得各轴上步进电机的转动步数；最后，利用输出接口分别控制3个步进电机驱动器，驱动激光反射镜(101)旋转至指定的三个转动角度。
其中，姿态角稳定装置控制器的控制系统软件程序包括：(1)启动引导程序：完成异常中断向量表的建立，关闭看门狗定时器、系统时钟初始化、通用输入/输出接口(GPIO)初始化、各PWM定时器初始化和中断初始化等工作；(2)I 2C数据采集程序：当姿态角稳定装置开始工作后，首先判断三个步进电机的运行状态。若三个步进电机均处于停转状态， 则将I 2C接口配置为主接收模式，接收激光陀螺仪(2)与MEMS陀螺仪(4)测量的三轴姿态角数据；(3)电机转动步数解算程序：所选用的丝杆步进电机的步距角为1.8°，则该电机完成360°的转动需要200步运动，丝杆导程为5.08mm，则该电机消隙螺母运动步长为0.0254mm，激光反射镜(101)的转角控制分辨率为0.029°，当采用单双拍控制时，可将激光反射镜的转角控制分辨率减半，即0.0145°；(4)电机运行程序：三个步进电机的转动由三组GPIO引脚控制其步进电机驱动器进行驱动，x轴丝杆步进电机(108)的转向由GPG3提供的电平信号控制，旋转角度由GPE11提供的脉冲信号控制；y轴丝杆步进电机(109)的转向由GPG5提供的电平信号控制，旋转角度由GPE12提供的脉冲信号控制；z轴步进电机(112)的转向由GPG6提供的电平信号控制，旋转角度由GPE13提供的脉冲信号控制。
附图说明
图1是直升机载LiDAR可实现激光扫描姿态角稳定原理图。
图2是机载LiDAR姿态角稳定系统组成图。
图3是激光扫描姿态角稳定装置(1)的机械结构图。
图4是激光反射镜(101)的关联结构图。
图5是丝杆步进电机驱动机构结构图。
图6是中心立柱(107)的z轴驱动结构图。
图7是激光反射镜(101)只绕Y轴转动的控制原理分析图。
图8是激光反射镜(101)绕X轴和Y轴转动的控制原理分析图。
图9是姿态角稳定装置控制器的控制系统结构示意图。
图10是姿态角稳定装置控制器的控制系统程序流程图。
具体实施方式
以下结合附图对本申请专利实施例作进一步详细描述。
图1为直升机载LiDAR可实现激光扫描姿态角稳定原理图。激光脉冲发射器(3)与机载平台(5)固结，激光出射方向指向激光反射镜(101)的几何中心并射向被测地面。激光反射镜(101)的底座与机载平台(5)固结，激光反射镜(101)以一个固定角反射激光脉冲束，使激光脉冲束指向一定的空间方向。激光雷达工作时，通常希望激光脉冲束的出射空间方向保持不变，但机载平台(5)的姿态角却随时在变化，造成激光脉冲的出射方向偏离期望的方向。XYZ-O为笛卡尔坐标系，X方向是飞行前进方向，Z方向垂直向下，Y方向与X和Z垂直，并满足右手规则。当机载平台(5)绕Y轴有一个顺时针方向的俯仰角2α时，出射激光方向偏移，故如果要保持出射方向不变，需将激光反射镜(101)逆时针转动机载平台(5)俯仰角的一半，即α。对于滚动角的补偿，方法相同。因此，在俯 仰角和滚转角方向上，可以通过将激光反射镜(101)逆向旋转对应姿态角数值的一半，即可将出射光线角度更正至无姿态角扰动的理想情况下。而机载平台(5)偏航角的扰动仅将激光出射角的方向绕z轴旋转，而并未改变其出射角度，故当机载平台(5)的偏航角有一个转角，只需将扫描镜反向转动与偏航角相同的角度。
图2为机载LiDAR姿态角稳定系统组成图。可实现机载LiDAR激光扫描姿态角稳定系统，包括激光扫描姿态角稳定装置(1)、激光陀螺仪(2)、激光脉冲发射器(3)、MEMS陀螺仪(4)和机载平台(5)。激光扫描姿态角稳定装置(1)包括机械传动部分和姿态角稳定装置控制器。参考坐标系为XYZ-o，其中X方向为飞机的前进方向，Z为垂直向下方向，Y为飞机的正右方向。坐标原点o为激光扫描光学中心，即激光反射镜(101)的转动中心，亦即激光反射镜(101)的激光脉冲反射点。激光脉冲发射器(3)与机载平台(5)固结，激光出射方向指向激光反射镜(101)中心并射向被测地面。采用激光陀螺仪(2)实时测出机载平台(5)的姿态角变化，并控制激光反射镜(101)进行相应转动，以稳定激光扫描的出射空间方向不变。另外，将MEMS陀螺仪(4)安装在激光反射镜(101)的背面，配置成测量激光反射镜(101)的实际三维姿态角。通过比较所述激光陀螺仪(2)和所述MEMS陀螺仪(4)的测量值，获得两者角度差，可控制激光反射镜(101)的中心法线指向任意期望的空间方位上，对动态和静态目标进行激光跟踪扫描和探测。另一方面，当机载平台(5)有三维姿态角变化时，控制激光反射镜(101)的x轴和y轴分别反向转动机载平台(5)的滚动角和俯仰角测量值幅值的一半，而z轴反向转动与机载平台(5)的偏航角测量值相同的幅值，从而可使经激光反射镜(101)反射后出射的激光束的空间指向不受机载平台(5)的三维姿态角变化影响。同时，激光反射镜(101)还要实现激光扫描功能。因此，激光反射镜(101)的控制运动是三个控制信号的叠加，一是绕x轴的扫描摆动运动，实现激光二维扫描；二是对机载平台(5)三维姿态角变化的实时补偿运动；三是激光反射镜(101)法线指向实现对空间动态目标的实时跟踪运动。
图3为激光扫描姿态角稳定装置(1)的机械结构图。激光扫描姿态角稳定装置(1)的机械传动部分包括：激光反射镜(101)，十字形镜面支撑杆(102)，球头万向轴承(103)，电机支架(104)，开槽不锈钢小半球体(105)，磁性钢凹球面体(106)，中心立柱(107)，x轴丝杆步进电机(108)，y轴丝杆步进电机(109)，轴向偏转铰链(110)，微型滚珠轴承(111)，z轴步进电机(112)，支撑立柱(113)，安装底座(114)，中心立柱底盘(115)，纵向偏转铰链(116)，配重块(117)，直动滑块(118)，消隙丝杠螺母(119)。所述激光反射镜(101)可实现三轴转动，参考坐标系XYZ-o的坐标原点o为激光反射镜(101)的对称中心，亦即激光反射镜的转动中心及激光脉冲反射点。激光反射镜(101)的镜面对称中心与激光反射镜(101)的旋转中心重合，由中心立柱(107)固定其空间位置。激光反 射镜(101)两个互相垂直边的两个方向x轴和y轴，分别为机载平台的滚转角(x轴)和俯仰角(y轴)的旋转轴，可由x轴丝杆步进电机(108)和y轴丝杆步进电机(109)分别驱动激光反射镜(101)绕y轴和x轴转动。中心立柱(107)可绕z轴转动，z轴与偏航角的旋转轴相同，由固定在安装底座(114)上的z轴步进电机(112)驱动中心立柱(107)旋转，进而带动激光反射镜(101)绕z轴转动。
激光反射镜(101)的镜面中心和镜面四边中点为约束镜面空间转动方位的控制点。通过球头万向轴承(103)连接四个直动滑块(118)。四个直动滑块(118)两端安装了滚动轴承，可分别沿四个电机支架(104)的轨道槽上下移动。在x轴和y轴正方向上相连的两个电机支架(104)中分别安装了X轴丝杠步进电机(108)和Y轴丝杠步进电机(109)，两个直动滑块(118)分别通过消隙丝杠螺母(119)安装在X轴丝杠步进电机(108)和Y轴丝杠步进电机(109)的丝杠上，由两个步进电机的丝杠驱动直动滑块(118)进行上下的直线运动，驱动激光反射镜(101)绕x轴和y轴的转动。在另外两个电机支架(104)上，安装了配重块(117)，配置成满足激光反射镜(101)绕三轴转动时的静和动平衡。中心立柱(107)与中心立柱底盘(115)紧固连接，保持垂直关系。中心立柱(107)的下部阶梯轴穿过微型滚珠轴承(111)，与z轴步进电机(112)通过联轴器连接。当z轴步进电机(112)转动时，可驱动中心立柱(107)旋转。四个电机支架(104)分别与四个纵向偏转铰链(116)固定连接，可实现四个电机支架(104)沿着垂直于所连接激光反射镜(101)的对应边方向的微小偏转。同时，四个纵向偏转铰链(116)分别与四个轴向偏转铰链(110)连接，可实现四个电机支架(104)沿着平行于所连接激光反射镜(101)的对应边方向的微小偏转。
对于机载LiDAR，只有当接收到的回波信号足够强时，才能进行正确记录。随着探测距离的增大，能被镜面接收到的回波信号就较弱，需要增大激光反射镜(101)的尺寸来反射尽可能多的回波信号。传统姿态角稳定平台采用三轴转动平台的结构中，扫描镜的尺寸严重受限。而所述激光扫描姿态角稳定装置(1)的本身结构特点，可满足安装较大尺寸的激光反射镜(101)并保持较小的装置体积和质量。本装置中采用的激光反射镜(101)的具体尺寸为100mm×100mm×2mm。
图4为激光反射镜(101)的关联结构图。激光反射镜(101)安装在十字形镜面支撑杆(102)上，所述十字形镜面支撑杆(102)的四个杆端为一个带有螺纹孔的方形接头，可与球头万向轴承(103)的螺杆端相连。继而所述球头万向轴承(103)的螺纹孔端与直动滑块(118)的螺杆端相连，而直动滑块(118)与消隙丝杠螺母(119)固结，通过丝杠步进电机驱动上下移动。所述十字形镜面支撑杆(102)与一个开槽不锈钢小半球体(105)相固连。开槽不锈钢小半球体(105)是将一个直径30mm的实心钢球在偏离球心2mm处 所切下来的小半钢球部分，并在切平面上加工出与十字形镜面支撑杆(102)的中心尺寸相同的十字形凹槽，从而可将十字形镜面支撑杆(102)牢固嵌入开槽不锈钢小半球体(105)中心处，并紧固粘接。将激光反射镜(101)粘贴在十字形镜面支撑杆(102)上，这样就可确保激光反射镜(101)的旋转中心与开槽不锈钢小半球体(105)的球心相重合。采用一个磁性钢材料制作的磁性钢凹球面体(106)与中心立柱(107)紧固连接。所述开槽不锈钢小半球体(105)与所述磁性钢凹球面体(106)依靠磁场力紧紧吸住，二者接触表面均打磨成镜面精度，并涂抹润滑油，可在三维空间内不会发生相对位移，只形成球面滑动接触。通过磁力吸引作用，可将开槽不锈钢小半球体(105)和磁性钢凹球面体(106)两个孤立的零件组合成一个磁性万向运动轴承结构。同时，由于激光反射镜(101)的厚度为2mm，正好等于开槽不锈钢小半球体(105)偏离球点的距离，故激光反射镜(101)粘贴在十字形镜面支撑杆(102)上后，激光反射镜(101)的激光反射中心点将与开槽不锈钢小半球体(105)的球心重合，从而激光反射镜(101)转动时的旋转中心可固定不变。当激光脉冲在激光反射镜(101)的旋转中心进行反射时，出射激光脉冲束的扫描中心点也保持不变。
图5为丝杆步进电机驱动机构结构图。激光反射镜(101)绕x和y轴的转动分别采用X轴丝杠步进电机(108)和Y轴丝杠步进电机(109)的丝杆与消隙丝杠螺母(119)机构，驱动直动滑块(118)上下运动；激光反射镜(101)绕z轴的转动采用z轴步进电机(112)直接驱动。丝杆步进电机为将步进电机的旋转轴替换为一段较长的丝杆，并在丝杆上外加一个可以利用外力驱动的内螺纹滑块，通过内螺纹与丝杆之间形成啮合，从而达到滑块沿轴向直线移动的目的。丝杆螺母是一种机械细分结构，可以通过控制螺纹的螺距达到不同的控制精度。Y轴丝杠步进电机(109)固定安装在电机支架(104)中，丝杆上安装的消隙丝杠螺母(119)与加装在其上的直动滑块(118)固定连接，直动滑块(118)通过前侧面伸出的小螺杆与球头万向轴承(103)的螺孔端连接，而球头万向轴承(103)的另一端伸出的小螺杆与十字形镜面支撑杆(102)的杆端螺孔连接，因此，当Y轴丝杆步进电机(109)旋转时，可依次带动消隙丝杠螺母(119)、直动滑块(118)、球头万向轴承(103)、十字形镜面支撑杆(102)和激光反射镜(101)绕X轴转动。在直动滑块(118)的两侧面垂直伸出光轴，光轴与微型轴承内圈紧固相连，微型轴承的外圈则放置于电机支架(104)侧面的轨道槽中，依靠轨道槽的约束可消除直动滑块(118)在摩擦阻力作用下随丝杆的径向旋转，使其只沿丝杆的轴向直线移动，并且微型轴承与轨道槽壁之间形成滚动接触，减小了轨道槽对直动滑块(118)的摩擦阻力。在电机支架(104)底部中心安装纵向偏转铰链(116)，纵向偏转铰链(116)与轴向偏转铰链(110)相连。所述轴向偏转铰链(110)具有一定的阻尼和弹簧恢复力，当激光反射镜(101)垂直于中心立柱(107)时，可维持 电机支架(104)与中心立柱平行；而当丝杆步进电机推动激光反射镜旋转时，可根据装置的几何结构约束使电机支架(104)在两个铰链转动方向上产生微小偏转。中心立柱底盘(115)通过过盈配合与中心立柱(107)紧固连接。在与Y轴丝杠步进电机(109)相对方向上的电机支架(104)中，安装与Y轴丝杠步进电机(109)等质量的配重块(117)，实现激光反射镜(101)转动时的动和静平衡。关于X轴丝杠步进电机(108)的相关结构和工作方式，与Y轴丝杠步进电机(109)相同。
图6为中心立柱(107)的z轴驱动结构图。中心立柱(107)被设计为阶梯轴的形状，共分为四个阶段，这四个部分按其直径大小的降序排列：第一部分作为整个激光反射镜(101)的中心支撑轴，与磁性钢凹球面体(106)紧固焊接；第二部分与中心立柱底盘(115)的中心孔间形成过盈配合，利用过盈摩擦结合力，使中心立柱(107)与中心立柱底盘(115)成为一体；第三部分安装在安装底座(114)中心孔中的微型滚珠轴承(111)上，阶梯轴与微型滚珠轴承(111)的内圈过盈配合装配在一起；第四部分穿过微型滚珠轴承(111)，通过联轴器与z轴步进电机(112)的旋转轴相连，实现绕z轴的转动驱动。安装底座(114)为方形，分别在其四个角上加装支撑立柱(113)，可进一步与机载平台(5)相固联。
图7为激光反射镜(101)只绕Y轴转动的控制原理分析图。当激光反射镜(101)只绕x轴或y轴两轴中的单个轴旋转时，如绕y轴转动，设当X轴丝杠步进电机(108)转动使丝杠上的直动滑块(118)中心点移动了△x距离时，此时激光反射镜(101)绕y轴转动了θ角。设点o是激光反射镜(101)的对称中心，px1是x轴上球头万向轴承(103)的转动中心，px2是x轴上纵向偏转铰链(116)的转动中心点，px3是x轴上直动滑块(118)的运动中心点。px1’是当激光反射镜(101)转动角为θ时x轴上球头万向轴承(103)转动中心的空间位置，px3’是当激光反射镜(101)转动角θ时，亦即x轴上直动滑块(118)上下移动△x距离后的运动中心点。θ 1为安装x轴丝杠步进电机(108)的电机支架(104)相对于垂直方向的微小倾斜角。由Px1’和Px2两点之间的距离，根据勾股定理，可建立丝杠上的直动滑块(118)移动量△x与激光反射镜(101)的旋转角度θ之间的关系：
2r 1(r 1+r 2)(1-cosθ)-2r 1d 1sinθ＝Δx 2-2d 1·Δx          (1)
解得：
Figure PCTCN2018126005-appb-000011
当r1＝7，r2＝3.7，d1＝14时，
Figure PCTCN2018126005-appb-000012
Figure PCTCN2018126005-appb-000013
图8为激光反射镜(101)绕X轴和Y轴转动的控制原理分析图。当激光反射镜(101)绕x轴和y轴两个轴旋转时，例如，激光反射镜(101)首先绕x轴转动一个角度ω，然后再绕y轴转动
Figure PCTCN2018126005-appb-000014
设此时x轴丝杆步进电机(109)上的直动滑块(118)移动△x，而y轴丝杆步进电机(109)上的直动滑块(118)移动△y，分析两个丝杠上的直动滑块(118)的移动距离与激光反射镜(101)的两个转角之间的对应关系。设Py1是y轴上球头万向轴承(103)的转动中心点，py2是y轴上纵向偏转铰链(116)的转动中心点，py3是y轴上直动滑块(118)的运动中心点。激光反射镜(101)绕两轴的转动过程中，py1与py3连线始终平行于y轴方向，py1与py3的连线始终垂直于py2与py3的连线，此时，py2与py3连线绕点py2既有沿着平行于y轴方向的微小转动，又有沿着平行于x轴方向的微小转动。而对于x轴，px2与px3连线绕点px2只有沿着平行于x轴方向的微小转动，而在沿着平行于y轴的方向上没有微小转动。这是激光反射镜(101)绕两轴都转动时、先控制Y轴丝杆步进电机(109)移动再控制X轴丝杆步进电机(108)移动带来的两轴电机支架(104)的中心轴倾斜角的不同之处。因此，在结构设计上，在py2处要有一个围绕y轴方向转动的轴向偏转铰链(110)，同时有能绕沿着平行于x轴方向转动的纵向偏转铰链(116)。而在px2处，只要有一个绕沿着x轴方向转动的纵向偏转铰链(116)即可，其轴上的轴向偏转铰链(110)可以锁死在铅锤方向上而不用转动。
Figure PCTCN2018126005-appb-000015
Figure PCTCN2018126005-appb-000016
即X和Y轴步进电机丝杠上的直动滑块(118)的两个位移与激光反射镜(101)的绕X和Y轴两个转角之间建立了一一对应关系。
激光反射镜(101)绕z轴的转动相对独立，只要控制z轴步进电机转动即可，不会造成对绕x轴和y轴转动的耦合效应。
激光反射镜(101)的三维转动角是三种运动的合成，一是绕x轴的摆动扫描角，设为θ；二是对机载平台三维姿态角变化
Figure PCTCN2018126005-appb-000017
的补偿，分别为
Figure PCTCN2018126005-appb-000018
三是让激光反射镜(101)的法线方向能指向空间任意指向，设期望的激光反射镜(101)的法线方向相对于初始姿态位置的三个姿态角为
Figure PCTCN2018126005-appb-000019
则激光反射镜(101)绕x轴的总转动角度为(θ-ω/2+ω e)，绕y轴的总转动角度为
Figure PCTCN2018126005-appb-000020
绕z轴的总转动角度为(γ e-γ)。 根据式(5)和(6)，可得相应的丝杠直动滑块位移△x和△y，以及绕z轴的转动控制角度(γ e-γ)。
图9为姿态角稳定装置控制器的控制系统结构示意图。姿态角稳定装置控制器采用嵌入式控制系统，需操控的原动件共三个：x轴丝杆步进电机(108)、y轴丝杆步进电机(109)和z轴步进电机(112)；需接收的外部信息共有六个：机载平台(5)的三个姿态角，即滚转角、俯仰角和偏航角；激光反射镜(101)的三个姿态角。利用嵌入式系统s3c2440接收激光陀螺仪(2)和MEMS陀螺仪(4)采集到的六个瞬时姿态角信息；根据设定的激光扫描摆动角度、激光反射镜(101)法线指向的目标空间方位以及当前的六个姿态角信息，计算出△x、△y和绕z轴的转动角度(γ e-γ)，获得各轴上步进电机的转动步数；最后，利用输出接口分别控制3个步进电机驱动器，驱动激光反射镜(101)旋转至指定的三个转动角度。
图10为姿态角稳定装置控制器的控制系统程序流程图。姿态角稳定装置控制器的控制系统软件程序包括：(1)启动引导程序:完成异常中断向量表的建立，关闭看门狗定时器、系统时钟初始化、通用输入/输出接口(GPIO)初始化、各PWM定时器初始化和中断初始化等工作；(2)I 2C数据采集程序：当姿态角稳定装置开始工作后，首先判断三个步进电机的运行状态。若三个步进电机均处于停转状态，则将I2C接口配置为主接收模式，接收激光陀螺仪(2)与MEMS陀螺仪(4)测量的三轴姿态角数据；(3)电机转动步数解算程序：所选用的丝杆步进电机的步距角为1.8°，则该电机完成360°的转动需要200步运动，丝杆导程为5.08mm，则该电机消隙螺母运动步长为0.0254mm，激光反射镜(101)的转角控制分辨率为0.029°，当采用单双拍控制时，可将激光反射镜的转角控制分辨率减半，即0.0145°；(4)电机运行程序：三个步进电机的转动由三组GPIO引脚控制其步进电机驱动器进行驱动，x轴丝杆步进电机(108)的转向由GPG3提供的电平信号控制，旋转角度由GPE11提供的脉冲信号控制；y轴丝杆步进电机(109)的转向由GPG5提供的电平信号控制，旋转角度由GPE12提供的脉冲信号控制；z轴步进电机(112)的转向由GPG6提供的电平信号控制，旋转角度由GPE13提供的脉冲信号控制。
以上对本申请及其具体实施方式的描述，并不局限于此，附图中所示仅是本申请的实施方式之一。在不脱离本申请创造宗旨的情况下，不经创造地设计出与该技术方案类似的结构或实施例，均属本申请保护范围。

Claims (7)

  1. 一种直升机载激光雷达激光扫描姿态角稳定方法与装置，其特征在于，能实现机载LiDAR激光扫描的姿态角稳定系统，包括激光扫描姿态角稳定装置(1)、激光陀螺仪(2)、激光脉冲发射器(3)、MEMS陀螺仪(4)和机载平台(5)；激光扫描姿态角稳定装置(1)包括机械传动部分和姿态角稳定装置控制器；采用所述激光陀螺仪(2)实时测出所述机载平台(5)的姿态角变化，并控制所述激光扫描姿态角稳定装置(1)的机械传动部分中的激光反射镜(101)进行相应转动，以稳定激光扫描中心的出射空间方位不变；所述MEMS陀螺仪(4)安装在所述激光反射镜(101)的背面，测量所述激光反射镜(101)的三维姿态角；通过比较所述激光陀螺仪(2)和所述MEMS陀螺仪(4)的测量值，获得两者角度差，能控制所述激光反射镜(101)的中心法线指向任意期望的空间方位，对动态和静态目标进行激光跟踪扫描探测；当所述机载平台(5)有三维姿态角变化时，控制所述激光反射镜(101)的x轴和y轴分别反向转动所述机载平台(5)的滚动角和俯仰角测量值幅值的一半，而z轴反向转动与所述机载平台(5)的偏航角测量值相同的幅值，从而能使经所述激光反射镜(101)反射后出射的激光束的空间指向不受所述机载平台(5)的三维姿态角变化影响；所述激光反射镜(101)绕x轴摆动，实现激光扫描功能；所述激光反射镜(101)的控制运动是三个控制信号的叠加，一是绕x轴的摆动扫描运动，实现激光二维扫描；二是对所述机载平台(5)三维姿态角变化的实时补偿运动；三是控制所述激光反射镜(101)法线指向，实现对空间动态目标的实时跟踪运动。
  2. 按照权利要求1所述的一种直升机载激光雷达激光扫描姿态角稳定方法与装置，其特征在于，所述激光扫描姿态角稳定装置(1)的机械传动部分包括：激光反射镜(101)，十字形镜面支撑杆(102)，球头万向轴承(103)，电机支架(104)，开槽不锈钢小半球体(105)，磁性钢凹球面体(106)，中心立柱(107)，x轴丝杆步进电机(108)，y轴丝杆步进电机(109)，轴向偏转铰链(110)，微型滚珠轴承(111)，z轴步进电机(112)，支撑立柱(113)，安装底座(114)，中心立柱底盘(115)，纵向偏转铰链(116)，配重块(117)，直动滑块(118)，消隙丝杠螺母(119)；所述激光反射镜(101)能实现三轴转动，所述激光反射镜(101)的镜面对称中心与其旋转中心重合，由所述中心立柱(107)固定其空间位置；所述激光反射镜(101)两个互相垂直边的两个方向x轴和y轴，分别为机载平台的滚转角和俯仰角的旋转轴，能由所述x轴丝杆步进电机(108)和所述y轴丝杆步进电机(109)分别驱动所述激光反射镜(101)绕y轴和x轴转动；所述中心立柱(107)能绕z轴转动，z轴与偏航 角的旋转轴相同，由固定在所述安装底座(114)上的所述z轴步进电机(112)驱动所述中心立柱(107)旋转，进而带动所述激光反射镜(101)绕z轴转动。
  3. 按照权利要求1和2所述的一种直升机载激光雷达激光扫描姿态角稳定方法与装置，其特征在于，所述激光反射镜(101)的镜面中心和镜面四边中点为约束镜面空间转动方位的控制点；通过所述球头万向轴承(103)连接四个所述直动滑块(118)；四个所述直动滑块(118)两端安装了滚动轴承，能分别沿四个所述电机支架(104)的轨道槽上下移动；在x轴和y轴正方向上相连的两个所述电机支架(104)中分别安装所述X轴丝杠步进电机(108)和所述Y轴丝杠步进电机(109)，两个所述直动滑块(118)分别通过所述消隙丝杠螺母(119)安装在所述X轴丝杠步进电机(108)和所述Y轴丝杠步进电机(109)的丝杠上，由两个步进电机的丝杠驱动所述直动滑块(118)进行上下直线运动，驱动所述激光反射镜(101)绕x轴和y轴的转动；在另外两个所述电机支架(104)上，安装了所述配重块(117)，配置成满足所述激光反射镜(101)绕三轴转动时的静和动平衡；所述中心立柱(107)的下部阶梯轴穿过所述微型滚珠轴承(111)，与所述z轴步进电机(112)通过联轴器连接；四个所述电机支架(104)分别与四个所述纵向偏转铰链(116)固定连接，能实现四个所述电机支架(104)沿着垂直于所连接所述激光反射镜(101)的对应边方向的微小偏转；同时，四个所述纵向偏转铰链(116)分别与四个所述轴向偏转铰链(110)连接，能实现四个所述电机支架(104)沿着平行于所连接所述激光反射镜(101)的对应边方向的微小偏转。
  4. 按照权利要求1和2所述的一种直升机载激光雷达激光扫描姿态角稳定方法与装置，其特征在于，所述激光扫描姿态角稳定装置(1)的本身结构特点，能满足安装较大尺寸的所述激光反射镜(101)并保持较小的装置体积和质量；采用的所述激光反射镜(101)的具体尺寸为100mm×100mm×2mm；所述激光反射镜(101)安装在所述十字形镜面支撑杆(102)上，所述十字形镜面支撑杆(102)的四个杆端为带有螺纹孔的方形接头，能与所述球头万向轴承(103)的螺杆端相连；所述球头万向轴承(103)的螺纹孔端与所述直动滑块(118)的螺杆端相连，而所述直动滑块(118)与所述消隙丝杠螺母(119)紧固连结，通过丝杠步进电机驱动而上下移动；所述十字形镜面支撑杆(102)与所述开槽不锈钢小半球体(105)相紧固连结；所述开槽不锈钢小半球体(105)是将一个直径30mm的实心钢球在偏离球心2mm处所切下来的小半钢球部分，并在切平面上加工出与所述十字形镜面支撑杆(102)的中心尺寸相同的十字形凹槽，从而能将所述十字形镜面支撑杆(102)牢固嵌入所述开槽不锈钢小半球体(105)中心处；将所述激光反射镜(101)粘贴在所述十字形镜面支撑杆(102)上，这样就 能确保所述激光反射镜(101)的旋转中心与所述开槽不锈钢小半球体(105)的球心相重合；采用一个磁性钢材料制作的所述磁性钢凹球面体(106)与所述中心立柱(107)紧固连接；所述开槽不锈钢小半球体(105)与所述磁性钢凹球面体(106)依靠磁场力紧紧吸住，二者接触表面均打磨成镜面精度，并涂抹润滑油，在三维空间内不会发生相对位移，只形成球面滑动接触；通过磁力吸引作用，能将所述开槽不锈钢小半球体(105)和所述磁性钢凹球面体(106)两个元件组合成一个磁性万向球轴承结构；所述激光反射镜(101)的厚度为2mm，正好等于所述开槽不锈钢小半球体(105)切面偏离球点的距离，故所述激光反射镜(101)粘贴在所述十字形镜面支撑杆(102)上后，所述激光反射镜(101)的激光反射中心点与所述开槽不锈钢小半球体(105)的球心重合，从而所述激光反射镜(101)转动时的旋转中心固定不变；激光脉冲在所述激光反射镜(101)的旋转中心进行反射，出射激光脉冲束的扫描中心点保持不变。
  5. 按照权利要求1和3所述的一种直升机载激光雷达激光扫描姿态角稳定方法与装置，其特征在于，在所述直动滑块(118)的两侧面垂直伸出光轴，光轴与一个微型轴承的内圈紧固相连，微型轴承的外圈则放置于所述电机支架(104)侧面的轨道槽中，依靠轨道槽的约束能消除所述直动滑块(118)在摩擦阻力作用下随丝杆的径向旋转，使其只沿丝杆的轴向直线移动，并且此微型轴承与轨道槽壁之间形成滚动接触，减小了轨道槽对所述直动滑块(118)的摩擦阻力；所述轴向偏转铰链(110)具有一定的阻尼和弹簧恢复力，当所述激光反射镜(101)垂直于所述中心立柱(107)时，能维持所述电机支架(104)与所述中心立柱平行；而当丝杆步进电机推动激光反射镜旋转时，根据所述激光扫描姿态角稳定装置(1)的几何结构约束将使所述电机支架(104)在所述纵向偏转铰链(116)和所述轴向偏转铰链(110)转动方向上产生微小偏转。
  6. 按照权利要求1和2所述的一种直升机载激光雷达激光扫描姿态角稳定方法与装置，其特征在于，当所述激光反射镜(101)绕x轴和y轴两个轴旋转时，例如，所述激光反射镜(101)首先绕x轴转动一个角度ω，然后再绕y轴转动
    Figure PCTCN2018126005-appb-100001
    设此时所述x轴丝杆步进电机(109)上的所述直动滑块(118)移动△x，而所述y轴丝杆步进电机(109)上的直动滑块(118)移动△y，能建立两个丝杠上的所述直动滑块(118)的移动距离与所述激光反射镜(101)的两个转角之间的对应关系；设点o是所述激光反射镜(101)的对称中心，px1是x轴上所述球头万向轴承(103)的转动中心，px2是x轴上所述纵向偏转铰链(116)的转动中心点，px3是x轴上所述直动滑块(118)的运动中心点；设Py1是y轴上所述球头万向轴承(103)的转动中心点，py2是y轴上所述纵向偏转铰链(116)的转动中心点，py3是y轴上所述直动滑块(118)的运动中心点；所述激光反射镜(101)绕两轴的转动过程中，py1与py3连线始终平行于y 轴方向，py1与py3的连线始终垂直于py2与py3的连线，此时，py2与py3连线绕点py2既有沿着平行于y轴方向的微小转动，又有沿着平行于x轴方向的微小转动；而对于x轴，px2与px3连线绕点px2只有沿着平行于x轴方向的微小转动，而在沿着平行于y轴的方向上没有微小转动；所述激光反射镜(101)绕z轴的转动相对独立，只要控制z轴步进电机转动即可，不会造成所述激光反射镜(101)对绕x轴和y轴转动的耦合效应。
  7. 按照权利要求2和6所述的一种直升机载激光雷达激光扫描姿态角稳定方法与装置，其特征在于，所述激光反射镜(101)的三维转动角是三种运动的合成，一是绕x轴的摆动扫描角，设为θ；二是对机载平台三维姿态角变化(ω，
    Figure PCTCN2018126005-appb-100002
    γ)的补偿，分别为(-ω/2，
    Figure PCTCN2018126005-appb-100003
    -γ)，负号表示反向转动；三是使所述激光反射镜(101)的法线方向指向空间任意方位，设期望的所述激光反射镜(101)的法线方向相对于所述机载平台(5)初始位置的三个姿态角为(ω e，
    Figure PCTCN2018126005-appb-100004
    γ e)，则所述激光反射镜(101)绕x轴的总转动角度为(θ-ω/2+ω e)，绕y轴的总转动角度为
    Figure PCTCN2018126005-appb-100005
    绕z轴的总转动角度为(γ e-γ)；根据所述激光扫描姿态角稳定装置(1)的机械运动约束关系，可得所述x轴丝杆步进电机(109)上的直动滑块位移△x和所述x轴丝杆步进电机(108)上的直动滑块位移△y，以及所述z轴步进电机(112)绕z轴的转动控制角度(γ e-γ)。
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CN112298056A (zh) * 2020-10-12 2021-02-02 长春通视光电技术有限公司 一种车载雷达俯仰角度摆动机构
CN112298056B (zh) * 2020-10-12 2024-03-15 长春通视光电技术股份有限公司 一种车载雷达俯仰角度摆动机构
CN114739559B (zh) * 2021-03-08 2023-06-27 石家庄铁道大学 用于轮轨力及钢轨中性轴测试位置的定位组件、工艺
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CN114593736A (zh) * 2022-01-27 2022-06-07 中南大学 一种摆扫式卫星的地理定位方法、定位误差分析方法及其系统
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CN115854907A (zh) * 2022-03-04 2023-03-28 江汉大学 一种封头内表面形状公差的测量装置
CN114966889A (zh) * 2022-05-24 2022-08-30 中国科学院西安光学精密机械研究所 一种机载稳定平台稳定精度检测装置及其测试方法
CN114966889B (zh) * 2022-05-24 2024-04-12 中国科学院西安光学精密机械研究所 一种机载稳定平台稳定精度检测装置及其测试方法
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