Space camera ultrathin focusing mechanism

Abstract

The invention belongs to the technical field of space optical remote sensing, and particularly relates to a space camera ultrathin focusing mechanism comprising a stepping motor which is fixed on a base and drives a worm to rotate through a coupler, a worm gear is meshed with the worm, an outer cylinder is fixed with the worm gear, three spiral cam sliding grooves are machined in the cylinder wall, an inner cylinder is fixed with a camera base, and an outer cylinder is fixed with a camera base. Three vertical straight grooves are machined in the cylinder wall of the upper connecting cylinder, three guide rods penetrate through the cam sliding grooves and the straight grooves respectively, the tail ends of the guide rods are fixed to the upper connecting cylinder, and the focal plane assembly is installed on the upper connecting cylinder. Worm and gear transmission and cam driving are innovatively integrated in the same plane, vertical stacking of a traditional mechanism is avoided, and the thickness and mass of the mechanism in the optical axis direction are remarkably reduced; the position stability of the focal plane after focusing is ensured by the self-locking characteristic of the worm gear and the worm; finite element analysis shows that in a rocket launching vibration environment, the first-order inherent frequency is far higher than the launching fundamental frequency, resonance can be effectively avoided, and the dynamic rigidity meets the requirement.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of space optical remote sensing, and particularly relates to a high-precision ultra-thin focusing mechanism for a space remote sensing camera. BACKGROUND

[0002] Research has found that when a space remote sensing camera is working in orbit, the optical system of the camera will be out of focus due to temperature changes in the space environment, mechanical impact during the launch phase and other factors, thereby seriously affecting the imaging quality. In order to solve this problem, a focusing mechanism must be provided in the camera to correct the focal plane position in real time.

[0003] At present, the focusing mechanism of a space camera mainly adopts transmission forms such as a screw nut, a cam or a worm and gear. The prior art discloses a mechanism of a worm and gear and an eccentric cam, which has high precision, but its structure is still difficult to meet the increasingly stringent lightweight and miniaturization requirements of current space cameras in terms of thickness and volume. Specifically, due to the high cost of launching a rocket, the size and weight of a space load are extremely strictly limited. The traditional focusing mechanism often adopts a vertical stacked layout, resulting in a large thickness in the direction of the optical axis of the camera, occupying valuable space and being relatively heavy in weight.

[0004] Based on this, there is an urgent need in the field to develop an ultra-thin focusing mechanism that can significantly reduce the thickness and weight while ensuring high precision, high reliability and good dynamic performance, in order to effectively solve the above problems. SUMMARY

[0005] The purpose of the present application is to provide a high-precision ultra-thin focusing mechanism for a space remote sensing camera, in order to solve the problems of large volume, heavy weight and large thickness in the direction of the optical axis of the existing focusing mechanism. The focusing mechanism has high focusing precision and good self-locking and dynamic stability.

[0006] The present application is achieved by the following technical solutions: An ultra-thin focusing mechanism for a space camera, comprising a stepping motor 1, a shaft coupling 2, a worm 3, a worm gear 4, a vertical cylinder assembly 5, three guide rods 6 and a connecting cylinder; The stepping motor 1 is fixed on a base, one end of the worm 3 is matched with a bearing installed in a bearing support 9, and the other end is connected to the motor shaft of the stepping motor 1 through the shaft coupling 2; The vertical cylinder assembly 5 comprises a coaxially arranged outer cylinder 5.1 and an inner cylinder 5.2; the outer cylinder 5.1 is fixedly connected with the worm gear 4, and three evenly distributed spiral cam grooves are machined on the cylinder wall thereof; the inner cylinder 5.2 is fixedly connected with the camera base, and three vertical straight grooves are machined on the cylinder wall thereof; The connecting cylinder is composed of an upper connecting cylinder 7 and a lower connecting cylinder 8 for carrying the focal plane assembly; one end of the three guide rods 6 respectively passes through the cam sliding groove of the outer cylinder 5.1 and extends into the straight groove of the inner cylinder 5.2, and the tail end is fixed with the upper connecting cylinder 7, and the focal plane assembly is installed on the upper connecting cylinder 7.

[0007] Further, the stepped end of the worm shaft matched with the bearing is provided with a step, and the worm shaft is in interference fit with the inner ring of the bearing.

[0008] Further, the bearing support 9 is sleeved on the worm shaft, the bearing support 9 is fixed with the inner ring of the bearing through a nut, and the bearing support 9 is provided with a locking screw.

[0009] Further, the outer cylinder 5.1 is fixedly connected with the worm wheel 4 through a screw.

[0010] Further, the tail end of the guide rod 6 is fixed with the upper connecting cylinder 7 through a screw.

[0011] Further, the worm 3 has a head number Z=1, a module m=1, and a pitch circle diameter d=12mm, solid lubrication is adopted between the worm and the worm wheel, and the friction coefficient μ=0.12, so that the unwinding spiral angle β=4.76° of the worm 3 is smaller than the friction angle Φ=6.84°, and the self-locking condition is met: ; 。

[0012] Further, the upper connecting cylinder 7 and the shafting main force bearing are made of titanium alloy TC4, and the remaining structural members are made of aluminum alloy 7A09.

[0013] Further, a grating assembly is also integrated, the grating assembly comprises a grating 10 and a grating reading head 11, the grating 10 is installed on the upper connecting cylinder 7, and the grating reading head 11 is installed on the lower connecting cylinder 8, and is used for detecting the rotation angle of the worm wheel 4.

[0014] Compared with the prior art, the beneficial effects of the present application are: 1. Ultra-thin and light weight: the worm and worm gear transmission and the cam drive are innovatively integrated in the same plane, avoiding the vertical stacking of the traditional mechanism, and significantly reducing the thickness and mass of the mechanism in the optical axis direction; 2. High precision and high reliability: the worm and worm gear transmission ratio is large, and the resolution is high; the cam drive directly converts rotary motion into linear motion, the transmission chain is short, and the error link is less. The actual measurement focusing accuracy can reach ±4.5μm, which can meet the high precision requirement of the space camera. At the same time, the self-locking property of the worm and worm gear ensures the position stability of the focal plane after focusing.

[0015] 3. Excellent dynamic performance: through finite element analysis verification, the first order natural frequency of the application is as high as 221.463Hz, which is much higher than the base frequency of the carrier rocket, effectively avoiding the risk of resonance. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments will be briefly introduced as follows, and it should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0017] Figure 1 Figure 1 is a schematic diagram of the driving principle of the ultra-thin focusing mechanism of the spatial camera of the present application; Figure 2 Figure 2 is a structural schematic diagram of the vertical cylinder assembly in the present application; Figure 3 Figure 3 is a schematic diagram of the overall structure of the focusing mechanism of the present application; Figure 4 Figure 4 is a displacement change residual curve diagram; Figure 5 Figure 5 is a first order vibration mode diagram of the focusing mechanism.

[0018] In the figure, 1. stepper motor 2. coupling 3. worm 4. worm gear 5. vertical cylinder assembly 6. guide rod 7. upper connecting cylinder 8. lower connecting cylinder 9. bearing support 10. grating 11. grating reading head 5.1 outer cylinder 5.2 inner cylinder. DETAILED DESCRIPTION

[0019] The present application will be further described below in conjunction with the embodiments: The present application will be further described below in conjunction with the embodiments:

[0020] It should be noted that: similar labels and letters represent similar items in the following drawings, therefore, once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings. At the same time, in the description of the present application, the terms "first", "second" and the like are only used for differentiation and description, and cannot be understood as indicating or implying relative importance.

[0021] As Figures 1-3As shown, the ultra-thin focusing mechanism of the spatial camera of the present application comprises a step motor 1, a coupling 2, a worm 3, a worm wheel 4, a vertical cylinder assembly 5, three guide rods 6 and a connecting cylinder. Figures 1-3

[0022] The present application innovatively adopts an integrated planar layout combining worm wheel and worm with cam driving. In the present application, the cam is not a traditional, independent disc-shaped or cylindrical part, but a functional structure integrated on the vertical cylinder assembly 5. Specifically, it refers to a spiral cam slot opened on the cylinder wall of the outer cylinder 5.1. This cam mechanism is composed of the following two core elements: the driving part cam, i.e. the outer cylinder 5.1 with the cam slot. The spiral profile of the slot is the working profile of the cam. The driven part, i.e. the guide rod 6 which can slide in the slot. Its working principle is completely consistent with that of the classic cam mechanism: when the driving part (the outer cylinder) rotates, the cam profile (the spiral slot) on it forces the driven part (the guide rod 6) to produce a specific, expected linear motion.

[0023] Specifically, the coupling 2 is used to connect the motor shaft of the step motor 1 and the worm shaft, transmit torque and compensate for the slight deviation between the two shafts. The step motor 1 drives the worm 4 to rotate through the coupling 2, converts the rotary motion of the step motor 1 into the rotary motion of the worm 4, and then realizes speed reduction or steering adjustment through the worm wheel 3. The worm wheel 3 and the worm 4 are engaged to form a one-stage speed reduction transmission pair and have a self-locking function. The middle part of the worm 4 is provided with a spiral tooth surface engaged with the worm wheel 3. The rotation of the worm 4 drives the worm wheel 3 to rotate through the middle spiral tooth surface, realizing speed reduction (the transmission ratio is usually 1:10 to 1:100) and self-locking function, preventing reverse driving. The step motor 1 sends an electric pulse signal through an external controller. The external driver converts the pulse into an electric current, and according to the phase sequence, the motor rotates by a fixed angle, i.e. the step angle, thereby driving the worm 3 to rotate. The control part of the step motor 1 is a prior art and is not the content protected by the present application, and will not be described in detail.

[0024] The step motor 1 is fixed on the base, one end of the worm 3 is matched with the bearing in the bearing support 9, and the other end is connected with the motor shaft of the step motor 1 through the coupling 2. The end of the worm shaft matched with the bearing is provided with a step, which can limit the axial movement of the bearing. The worm shaft and the inner ring of the bearing are interference-fitted to ensure axial fixation and prevent axial movement. The bearing support 9 is sleeved on the worm shaft to support the rotary motion. The bearing support 9 fixes the inner ring of the bearing through a nut to limit the movement of the bearing. The worm shaft is aligned with the bearing hole in the bearing support 9. The bearing support 9 is provided with a lock screw, which can fix the inner ring of the bearing and the shaft to prevent relative rotation or axial displacement.

[0025] ​The key design of the ultra-thin focusing mechanism of the spatial camera is that the vertical cylinder assembly 5 comprises coaxially arranged outer cylinder 5.1 and inner cylinder 5.2.

[0026] The connecting cylinder is composed of the upper connecting cylinder 7 and the lower connecting cylinder 8 for carrying the focusing surface assembly. One end of the three guide rods 6 respectively passes through the cam slide groove of the outer cylinder 5.1 and extends into the straight groove of the inner cylinder 5.2, and the tail end is fixed with the upper connecting cylinder 7 through a screw, and the focusing surface assembly is installed on the upper connecting cylinder 7.

[0027] When the step motor 1 drives the worm wheel 4 to rotate, the outer cylinder 5.1 is driven to rotate synchronously. Since the guide rod 6 is constrained by the straight groove of the inner cylinder, it cannot rotate horizontally, but can only convert the horizontal rotation movement of the outer cylinder 5.1 into the accurate linear movement of the guide rod 6 and the upper connecting cylinder 7 along the optical axis direction under the drive of the cam slide groove, so as to realize focusing.

[0028] The number of heads of the worm 3 is Z=1, the module is m=1, the pitch circle diameter is d=12mm, the solid lubrication is adopted between the worm and the worm wheel, the friction coefficient is μ=0.12, so that the unwinding spiral angle β=4.76° of the worm 3 is less than the friction angle Φ=6.84°, and the self-locking condition is met. Wherein: ; .

[0029] In order to reduce the weight and match the thermal expansion coefficient of the optical element, the upper connecting cylinder 7 and the shafting main force bearing are made of titanium alloy TC4, and the remaining structural parts are made of aluminum alloy 7A09.

[0030] The spatial camera ultra-thin focusing mechanism also integrates a grating assembly. The grating assembly comprises a grating 10 and a grating reading head 11. The grating 10 is installed on the upper connecting cylinder 7, and the grating reading head 11 is installed on the lower connecting cylinder 8, which is used for detecting the rotation angle of the worm wheel 4, and realizing closed-loop control.

[0031] The space camera ultra-thin focusing mechanism of the embodiment comprises a step motor 1, a shaft coupling 2, a worm 3, a worm wheel 4, a vertical cylinder assembly 5 composed of an outer cylinder 5.1 and an inner cylinder 5.2, a guide rod 6, an upper connecting cylinder 7 and a lower connecting cylinder 8. The step motor 1 is fixed on a base and drives the worm 3 to rotate through the shaft coupling 2. The worm wheel 4 is engaged with the worm 3. The outer cylinder 5.1 is fixedly connected with the worm wheel 4 through a screw, and three evenly distributed helical cam grooves are processed on the cylinder wall thereof. The inner cylinder 5.2 is fixedly connected with the camera base, and three vertical straight grooves are processed on the cylinder wall thereof. The three guide rods 6 respectively pass through the cam grooves and the straight grooves, and the ends thereof are fixed with the upper connecting cylinder 7 through screws. A focal plane assembly is installed on the upper connecting cylinder 7.

[0032] Working process: after the focusing instruction is sent out, the step motor 1 is started, the worm 3 drives the worm wheel 4 to rotate. The outer cylinder 5.1 fixedly connected with the worm wheel 4 rotates. Since the inner cylinder 5.2 is fixed, the straight grooves thereon limit the horizontal rotation of the guide rods 6, and the guide rods 6 can only drive the upper connecting cylinder 7 and the focal plane assembly to make accurate linear motion along the optical axis direction (Z direction) under the guidance of the cam grooves, until the target focal plane position is reached. After the motor stops, the position is locked firmly by the self-locking characteristics of the worm and the worm wheel.

[0033] Materials and properties: the key components such as the upper connecting cylinder 7 and the shaft system are made of TC4 titanium alloy, and the rest of the structure is made of 7A09 aluminum alloy.

[0034] Precision verification: as shown in Figure 4 , an inductance micrometer is used to test the prototype, and the measurement interval is 0.2 mm. The data show that the focusing range is ±2.21 mm, and the calculated focusing precision is ±4.5 μm.

[0035] During the rocket launching process, there is a fundamental frequency of about 100 Hz, and the natural frequency of the focusing mechanism of the space remote sensing camera should be avoided to coincide with the fundamental frequency of the rocket launching to avoid resonance. Through the analysis of the finite element model of the focusing mechanism by NX12.0 software, the first-order vibration shape structure of the focusing mechanism is obtained, as shown in Figure 5 , the first-order natural frequency of the focusing mechanism is 221.463 Hz, and resonance does not occur.

[0036] In summary, the present application successfully realizes an ultra-thin, light, high-precision and high-reliable space camera focusing mechanism, which can be as low as 34.7894 mm in thickness through actual measurement, and is particularly suitable for advanced space remote sensing systems with extreme limitations on volume and weight.

[0037] The present application avoids the vertical stacking of the traditional mechanism by innovatively integrating the worm gear transmission and the cam drive in the same plane, significantly reduces the thickness and mass of the mechanism in the optical axis direction, and ensures the position stability of the focal plane after focusing by the self-locking characteristics of the worm gear. Finite element analysis shows that the first-order natural frequency is much higher than the launch base frequency in the rocket launch vibration environment, resonance can be effectively avoided, and the dynamic stiffness meets the requirements.

[0038] The design of the digital prototype model, the parameter setting of each material, and the selection of the measurement plane are only preferred embodiments of the present application and the technical principles applied. Those skilled in the art will understand that the present application is not limited to the specific embodiments described herein, and various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the scope of the present application. Therefore, although the present application has been described in more detail through the above embodiments, the present application is not limited to the above embodiments, and can include more other equivalent embodiments without departing from the concept of the present application, and the scope of the present application is determined by the scope of the appended claims.

Claims

1. A thin focusing mechanism for a space camera, characterized in that: It includes a stepper motor (1), a coupling (2), a worm gear (3), a worm wheel (4), a vertical cylinder assembly (5), three guide rods (6), and a connecting cylinder; The stepper motor (1) is fixed on the base, one end of the worm gear (3) is engaged with the bearing installed in the bearing support (9), and the other end is connected to the motor shaft of the stepper motor (1) through the coupling (2); The vertical cylinder assembly (5) includes an outer cylinder (5.1) and an inner cylinder (5.2) arranged coaxially; the outer cylinder (5.1) is fixedly connected to the worm gear (4), and three evenly distributed spiral cam grooves are machined on its cylinder wall; the inner cylinder (5.2) is fixedly connected to the camera base, and three vertical straight grooves are machined on its cylinder wall; The connecting cylinder consists of an upper connecting cylinder (7) and a lower connecting cylinder (8) for carrying the focal surface assembly; one end of each of the three guide rods (6) passes through the cam groove of the outer cylinder (5.1) and extends into the straight groove of the inner cylinder (5.2), and their ends are fixed to the upper connecting cylinder (7), and the focal surface assembly is installed on the upper connecting cylinder (7).

2. The ultra-thin focusing mechanism for a space camera according to claim 1, characterized in that: The worm shaft (3) that mates with the bearing has a step at its end, and the worm shaft is interference-fitted with the inner ring of the bearing.

3. The ultra-thin focusing mechanism for a space camera according to claim 2, characterized in that: The bearing support (9) is fitted onto the worm shaft. The bearing support (9) fixes the inner ring of the bearing by a nut. The bearing support (9) is provided with a set screw.

4. The ultra-thin focusing mechanism for a space camera according to claim 1, characterized in that: The outer cylinder (5.1) and the worm gear (4) are fixedly connected by screws.

5. The ultra-thin focusing mechanism for a space camera according to claim 1, characterized in that: The end of the guide rod (6) is fixed to the upper connecting cylinder (7) by screws.

6. The ultra-thin focusing mechanism for a space camera according to claim 1, characterized in that: The worm (3) has 1 thread Z, 1 module m, and 12mm pitch circle diameter d. Solid lubrication is used between the worm wheel and the worm, and the friction coefficient μ = 0.

12. This makes the unfolded helix angle β = 4.76° of the worm (3) less than the friction angle Φ = 6.84°, thus satisfying the self-locking condition. ； 。 7. The ultra-thin focusing mechanism for a space camera according to claim 1, characterized in that: The upper connecting cylinder (7) and the main load-bearing components of the shaft system are made of titanium alloy TC4, while the remaining structural components are made of aluminum alloy 7A09.

8. The ultra-thin focusing mechanism for a space camera according to claim 1, characterized in that: It also integrates a grating assembly, which includes a grating (10) and a grating reading head (11). The grating (10) is mounted on the upper connecting cylinder (7), and the grating reading head (11) is mounted on the lower connecting cylinder (8) for detecting the rotation angle of the worm gear (4).

Images