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通过视频图像的实时变化调整云台,使设备对准靶板假目标,在设备的码盘上读出当前靶板相对设备的方位角并记录,从而确定当前位置下靶板假目标的大致方位角。但是,人工布设的靶板法线方向与系统设备视线方向无法做到完全一致,因此需要对靶板进行参数解算,计算靶板的法向角,用其方位分量和俯仰分量数据修正靶板假目标的朝向。另外,还需要测量靶板与系统设备的距离,为干扰空域评估提供数据。靶板目标参数解算是依据透视投影[9-10]原理,其解算流程如图2所示。
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在对假目标干扰空域进行评估的过程中,干扰距离是非常重要的一个指标。激光发射机发射激光干扰信号至漫反射板假目标上,激光干扰信号通过漫反射假目标反射后的能量随着反射方向与漫反射板假目标法线方向夹角的增大而呈余弦衰减。当在某一角度下反射能量衰减到与导引头最小可接收功率相同时,此时的距离即为干扰距离。可以通过漫反射板的反射模型以及对应天气的大气散射模型画出散射激光所充斥的空间,如图3所示。图中,
${\varphi _p}$ 为漫反射板假目标相对于设备法向角的俯仰分量,${\theta _i}$ 为入射光与漫反射板法线的夹角,${\theta _{rp}}$ 为漫反射板的法线和激光制导武器来袭方向夹角的俯仰分量,$\theta $ 为激光制导武器来袭方向与地面的夹角(威胁角)。干扰空域的边界由干扰距离的大小所决定,可由以下公式计算[11]:
$$ R = \sqrt {\dfrac{{{E_{{t}}}{\tau _{{t}}}{\tau _{{r}}}\rho \cos {\theta _r}}}{{\pi {E_r}}}{{\rm{e}}^{ - {u_a}(R + {R_1})}}} $$ (1) 式中:
${E_{\rm{t}}}$ 为干扰激光单个脉冲能量;${\tau _{\rm{t}}}$ 为激光干扰源发射光学系统的透过率;${\tau _{{r}}}$ 为导引头接收系统的透过率;$\;\rho $ 为漫反射假目标的半球反射率;${\theta _r}$ 为反射光与漫反射板法线的夹角;${E_{{r}}}$ 为导引头接收的激光能量密度阈值;${u_{{a}}}$ 为大气的衰减常数;$R$ 为干扰距离;${R_1}$ 为干扰激光器与漫反射板之间的距离。 -
此次激光诱偏假目标系统实验中使用的是1.064 μm的激光,在传输过程中,大气衰减系数[12]
${u_{{a}}}$ 为:$$ {u_{\rm{a}}} = \left( {\frac{{3.912}}{{{V_m}}}} \right){\left( {\frac{{0.55}}{{1.06}}} \right)^q} $$ (2) 式中:
${V_m}$ 为大气能见度,km;q为与大气能见度有关的参数,q的取值如下:$$ q = \left\{ {\begin{array}{*{20}{l}} {\begin{array}{*{20}{l}} {0,\begin{array}{*{20}{c}} {}&{}&{}&{\begin{array}{*{20}{c}} {}&{{V_m} \leqslant 0.5\;{\rm{km}}} \end{array}} \end{array}} \\ {{V_m} - 0.5,\begin{array}{*{20}{c}} {}&{0.5\;{\rm{km}} < {V_m} \leqslant 1\;{\rm{km}}}&{} \end{array}} \end{array}} \\ {0.585V_m^{\frac{1}{3}}\begin{array}{*{20}{c}} ,&{1\;{\rm{km}} < {V_m} \leqslant 6\;{\rm{km}}}&{} \end{array}} \\ {1.36,\begin{array}{*{20}{c}} {}&{}&{\begin{array}{*{20}{c}} {6\;{\rm{km}} < {V_m} \leqslant 50\;{\rm{km}}}&{} \end{array}}&{} \end{array}} \\ {1.6,\begin{array}{*{20}{c}} {}&{\begin{array}{*{20}{c}} {}&{} \end{array}}&{{V_m} > 50\;{\rm{km}}}&{} \end{array}} \end{array}} \right. $$ (3) -
根据有效干扰距离计算公式可以得出漫反射板法线方向最大干扰距离计算公式为:
$$ {R_{\max }} = \sqrt {\dfrac{{{E_{{t}}}{\tau _{{t}}}{\tau _{{r}}}\rho }}{{\pi {E_r}}}{{\rm{e}}^{ - {u_a}({R_{\max }} + {R_1})}}} $$ (4) 设系统接收光学系统透过率与导引头接收系统透过率相同,结合系统测量数据可以得到设备与假目标距离L和设备接收能量密度E的公式(5),其中
$\varphi $ 为假目标相对系统设备的法向角。$$ L = \sqrt {\dfrac{{{E_{{t}}}{\tau _{{t}}}{\tau _{{r}}}\rho \cos \varphi }}{{\pi {E_{}}}}{{\rm{e}}^{ - {u_a}(L + {R_1})}}} $$ (5) 结合公式(4)和(5)可以得出最大干扰距离Rmax与此系统所测量数据的公式(6)为:
$$ {R_{\max }} = L\sqrt {\dfrac{{E{{\rm e}^{ - {\mu _a}{R_{\max }}}}}}{{{E_r}{{\rm e}^{ - {\mu _a}L}}\cos \varphi }}} $$ (6) 根据公式(1)可得出不同
${\theta _r}$ 下的干扰距离的公式(7)为:$$R=L \sqrt{\frac{E {\rm e}^{-\mu_{a} R} \cos \theta_{r}}{E_{r} {\rm e}^{-\mu_{a} L} \cos \varphi}}$$ (7) 反射角
${\theta _r}$ 在空间中存在方位角分量${\theta _{ra}}$ 和俯仰角分量${\theta _{rp}}$ 。其中${\theta _{ra}}$ 的取值范围为假目标正向所对应的半球空间,即[0°,180°]。${\theta _{rp}}$ 取值为:$${\theta _{rp}} = \left\{ {\begin{array}{*{20}{c}} {\theta - {\theta _i},\begin{array}{*{20}{c}} {\theta \geqslant } \end{array}{\theta _i}} \\ {\begin{array}{*{20}{c}} {\theta _i} - \theta, \end{array}\begin{array}{*{20}{c}} \end{array}\begin{array}{*{20}{c}}{\theta < {\theta _i}} \end{array}} \end{array}} \right.$$ (8) 假设激光与地面平行入射到假目标上,则此时入射角
${\theta _i}$ 与$ {\varphi _p} $ 相等,公式(8)可以由公式(9)表示:$${\theta _{rp}} = \left\{ {\begin{array}{*{20}{c}} {\theta - {\varphi _p},\begin{array}{*{20}{c}} {\theta \geqslant } \end{array}{\varphi _p}} \\ {\begin{array}{*{20}{c}} {\varphi _p}- \theta , \end{array}\begin{array}{*{20}{c}} \end{array}\begin{array}{*{20}{c}} {\theta < {\varphi _p}} \end{array}} \end{array}} \right.$$ (9) 由此可以得出不同威胁角和漫反射板倾角下的激光干扰空域,由公式(10)表示:
$$R=L \sqrt{\frac{E {\rm e}^{-\mu_{a}(R-L)} \cos \left(\theta-\varphi_{p}\right) \cos \theta_{r a}}{E_{r} \cos \varphi}}$$ (10) 如已知单个漫反射板假目标相对设备法向角的俯仰分量,就可以得到其在不同威胁角下、不同方位上的干扰距离,不同方位距离数据合成单个假目标的干扰空域,多个假目标干扰空域合成得到多假目标干扰空域态势图。
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干扰空域评估实验需要用到激光目标指示模拟器、漫反射板假目标和干扰空域评估系统等设备,具体实验示意图如图4所示。
实验步骤如下:
(1)将3个漫反射板按照一定距离和方位摆放在干扰空域评估系统的0°,120°,240°三个方向上,由激光目标指示模拟器发射模拟“干扰激光”,照射在其中一个漫反射板假目标上。
(2)利用干扰空域评估系统设备上的观瞄望远镜来瞄准目标,通过调整云台方位旋钮和俯仰旋钮控制干扰空域评估系统设备对准目标,读出此时云台上码盘的方位角数据。
(3)通过评估系统设备对当前位置下的反射激光能量密度进行测量,通过对视频图像中靶板图像进行解算得到靶板距离和法向角方位分量、俯仰分量,再结合码盘方位角数据对漫反射板假目标的朝向进行精确修正。
(4)根据上一步所采集到的数据和干扰空域评估模型,对单个假目标干扰空域进行评估。
(5)重复以上步骤,对其他两块漫反射板假目标用不同功率的激光进行照射,对剩余假目标干扰空域进行评估。用不同功率干扰激光进行照射的目的是验证不同接收激光功率对假目标干扰空域大小的影响。在对整个布站区域的单个假目标测完之后,可以得到整个区域内所有假目标干扰空域的态势图。
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实验中首先对三个方向上的反射能量密度进行测量,每一个方向上经过测量计算得到20组能量密度数据,最后计算每个方向上的能量密度平均值,得到的测量计算结果如表1所示。
表 1 激光能量密度测量结果
Table 1. Laser energy density measurement results
Number Energy value in the 0°/J·mm−2 Energy value in the 120°/J·mm−2 Energy value in the 240°/J·mm−2 1 2.79×10−13 2.24×10−13 4.20×10−13 2 2.77×10−13 2.23×10−13 4.15×10−13 3 2.75×10−13 2.22×10−13 4.15×10−13 4 2.75×10−13 2.20×10−13 4.14×10−13 5 2.72×10−13 2.20×10−13 4.14×10−13 6 2.72×10−13 2.19×10−13 4.11×10−13 7 2.72×10−13 2.18×10−13 4.11×10−13 8 2.71×10−13 2.18×10−13 4.10×10−13 9 2.71×10−13 2.18×10−13 4.08×10−13 10 2.71×10−13 2.18×10−13 4.08×10−13 11 2.71×10−13 2.17×10−13 4.07×10−13 12 2.69×10−13 2.16×10−13 4.07×10−13 13 2.68×10−13 2.15×10−13 4.06×10−13 14 2.68×10−13 2.15×10−13 4.06×10−13 15 2.67×10−13 2.15×10−13 4.06×10−13 16 2.66×10−13 2.14×10−13 4.04×10−13 17 2.65×10−13 2.14×10−13 4.04×10−13 18 2.65×10−13 2.12×10−13 4.04×10−13 19 2.64×10−13 2.12×10−13 4.02×10−13 20 2.64×10−13 2.10×10−13 4.02×10−13 Average 2.70×10−13 2.17×10−13 4.08×10−13 -
分别对三个方向上的靶板进行图像采集和参数解算,得到靶板的距离L和法向角
$\varphi $ 等参数,图像采集及参数解算结果如图5和表2所示。表 2 靶板参数解算结果
Table 2. Result of target board parameter calculation
Azimuth/(°) Distance of target board L/m Normal angle azimuth component ${\varphi _a}$/(°) Normal angle pitch component ${\varphi _p}$/(°) 0 143.072 0.4 18.4 120 142.643 0.4 19.4 240 143.072 0.2 19.0 结果显示,系统能够正确识别靶板目标并对其参数进行解算。其中,0°方向上的靶板目标与测试系统设备距离为143.072 m,靶板的法向角方位分量为0.4°、俯仰分量为18.4°;120°方向上的靶板目标与测试系统设备距离为142.643 m,靶板的法向角方位分量为0.4°,俯仰分量为19.4°;240°方向上的靶板目标与测试系统设备距离为143.072 m,靶板的法向角方位分量为0.2°,俯仰分量为19.0°。由于三块靶板的法向角方位分量较小,为方便计算,靶板的法向角
$\varphi $ 近似取为${\varphi _p}$ 。 -
根据3.2.1及3.2.2节所测量和解算的数据,对三个方向的假目标进行干扰空域评估。假设气象条件为一般,能见度为15 km,导引头所接收的能量密度阈值为1.0×10−15 J/mm2,分别得到三个方向假目标的干扰空域态势图。态势图给出了20°、45°和70°威胁角下的干扰空域,如图6(a)~(c)所示。漫反射板实际的干扰空域应是一个近似半球空间,图6所绘制的干扰空域是三个威胁角平面下截取的干扰范围。在完成对三个单目标干扰空域评估后,通过空间合成可完成对三个目标联合布站干扰空域的评估,如图6(d)所示。
态势图结果显示,三个方向的靶板在45°威胁角下的干扰最大距离分别为2045.6 m、1860.4 m和2470.0 m,可见单个目标的干扰空域大小与系统接收能量有关,接收能量越强,干扰距离越大。由于文中实验使用的激光目标指示器功率较小,因此假目标的干扰空域较小,在实际应用中假目标干扰空域的范围会随干扰激光功率的增加而增大。三个靶板的法向角俯仰分量最大为19°,均不超过20°,比较同一个靶板在不同威胁角下的干扰空域可以看出,当威胁角与靶板法向角俯仰分量的角度差越大,即武器来袭方向与漫反射板的法线方向夹角越大时,靶板的干扰空域越小。因此,当武器来袭方向与靶板的法线方向相同时,靶板的干扰效果最好,干扰空域可以达到最大。多目标干扰空域合成可以实现对整个防区内的假目标干扰态势的评估。
Research on the technique of interference airspace evaluation of laser angle deception false targets
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摘要: 针对目前激光角度欺骗干扰效果评估中存在的实时性差、可视化程度不高等问题,构建了激光角度欺骗假目标干扰空域评估系统。首先依据透视投影原理求解漫反射板假目标的距离及姿态参数,然后通过分析漫反射板假目标的干扰机理,以干扰距离为基础,推导出了漫反射板假目标干扰空域评估模型,最后依托系统设计了相关实验。实验中,分别对相对设备0°、120°和240°三个方向上布设的漫反射板用不同功率激光进行照射,然后用评估系统设备对三个漫反射板进行参数测量,最终得到系统接收的能量密度平均值分别2.70×10−13 J/mm2, 2.17×10−13 J/mm2和4.08×10−13 J/mm2,通过假目标干扰空域评估模型计算出在45°威胁角下的干扰最大距离分别为2045.6 m、1860.4 m和2470.0 m。最终分析了干扰空域大小与武器威胁角的关系,得到在20°、45°和70°威胁角下的假目标干扰空域的态势图。实验结果表明:在实验条件下,漫反射板假目标的干扰空域范围随系统接收能量增大而增大;武器来袭方向与漫反射板法线方向夹角越小,漫反射板假目标的干扰空域越大。以干扰距离作为评价指标,对漫反射板假目标干扰空域进行评估,可为假目标干扰效果评估提供技术支持。Abstract: Aiming at the problems of lack of instantaneity and low visualization in laser angle deception interference evaluation, the evaluation system for the airspace interference of false targets of laser angle deception interference was constructed. Firstly, the distance and attitude parameters of the false target of the diffuse reflector were calculated according to the principle of perspective projection, and then the interference mechanism of the false target of the diffuse reflector was analyzed and based on the interference distance, the airspace evaluation model of the false target interference of the diffuse reflector was derived. Finally, experiments were designed relied on the system. In the experiment, the diffuse reflector installed in the direction of 0°, 120° and 240° of the equipment was irradiated by lasers with different powers. Then the evaluation system equipment was used to measure the parameters of the three diffuse reflectors, and the average energy density received by the system were 2.70×10−13 J/mm2, 2.17×10−13 J/mm2 and 4.08×10−13 J/mm2 respectively. The maximum interference distance under 45° threat angle were 2045.6 m, 1860.4 m and 2470.0 m, respectively. Finally, the relationship between the size of the jamming airspace and the threat angle of the weapon was analyzed, and the situation maps of the interference airspace of the false target under the threat angles of 20°, 45° and 70° were obtained. The experimental results show that, under the experimental conditions, the interference airspace range of the false target increases with the increase of the energy received by the system. The smaller the angle between the attack direction of the weapon and the normal direction of the diffuse reflector, the greater the interference airspace. Taking the interference distance as the evaluation index, the interference airspace of the diffuse reflector false target is evaluated, which can provide technical support for the interference effect evaluation of false target.
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表 1 激光能量密度测量结果
Table 1. Laser energy density measurement results
Number Energy value in the 0°/J·mm−2 Energy value in the 120°/J·mm−2 Energy value in the 240°/J·mm−2 1 2.79×10−13 2.24×10−13 4.20×10−13 2 2.77×10−13 2.23×10−13 4.15×10−13 3 2.75×10−13 2.22×10−13 4.15×10−13 4 2.75×10−13 2.20×10−13 4.14×10−13 5 2.72×10−13 2.20×10−13 4.14×10−13 6 2.72×10−13 2.19×10−13 4.11×10−13 7 2.72×10−13 2.18×10−13 4.11×10−13 8 2.71×10−13 2.18×10−13 4.10×10−13 9 2.71×10−13 2.18×10−13 4.08×10−13 10 2.71×10−13 2.18×10−13 4.08×10−13 11 2.71×10−13 2.17×10−13 4.07×10−13 12 2.69×10−13 2.16×10−13 4.07×10−13 13 2.68×10−13 2.15×10−13 4.06×10−13 14 2.68×10−13 2.15×10−13 4.06×10−13 15 2.67×10−13 2.15×10−13 4.06×10−13 16 2.66×10−13 2.14×10−13 4.04×10−13 17 2.65×10−13 2.14×10−13 4.04×10−13 18 2.65×10−13 2.12×10−13 4.04×10−13 19 2.64×10−13 2.12×10−13 4.02×10−13 20 2.64×10−13 2.10×10−13 4.02×10−13 Average 2.70×10−13 2.17×10−13 4.08×10−13 表 2 靶板参数解算结果
Table 2. Result of target board parameter calculation
Azimuth/(°) Distance of target board L/m Normal angle azimuth component ${\varphi _a}$ /(°)Normal angle pitch component ${\varphi _p}$ /(°)0 143.072 0.4 18.4 120 142.643 0.4 19.4 240 143.072 0.2 19.0 -
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