阅读说明：本技术 一种新型激光雷达探测时序控制系统 (Novel laser radar detection time sequence control system ) 是由 周国清 李伟豪 周祥 林港超 李先行 于 2021-06-29 设计创作，主要内容包括：本发明公开了一种新型机载激光雷达探测时序控制系统。该系统采用控制模块的STM32控制器作为门控信号发生器,控制激光模块的激光器和探测模块的PMT,通过调节门控信号的幅值、频率、周期以及占空比等参数,实现系统的时序控制,进而使得探测系统避免接收过强的水面回波信号。另外,该系统结合PMT可调增益技术,放大水底的微弱回波信号。在实际测量中,使用STM32代替传统的信号发生器,降低系统功耗,减轻载重。通过实验证明,该方法真实有效,实验结果显示该方法能够将水底信号最少放大6倍。(The invention discloses a novel airborne laser radar detection time sequence control system. The system adopts the STM32 controller of the control module as a gating signal generator, controls the laser of the laser module and the PMT of the detection module, realizes the time sequence control of the system by adjusting the amplitude, the frequency, the period, the duty ratio and other parameters of the gating signal, and further ensures that the detection system avoids receiving the over-strong water surface echo signal. In addition, the system combines the PMT adjustable gain technology to amplify weak echo signals at the water bottom. In practical measurement, STM32 is used to replace the traditional signal generator, so that the system power consumption is reduced, and the load is lightened. Experiments prove that the method is real and effective, and the experimental results show that the method can amplify the water bottom signals by 6 times at least.)

1. A novel laser radar detection time sequence control system is characterized in that the time sequence control system is composed of a laser module, a control module, a detection module and a power supply module; through host computer programming program instruction, write in control module's STM32 controller for the STM32 controller sends the pulse trigger signal who has specific chronogenesis as the gate control signal of PMT, and then the operating condition of gate control PMT in the control detection module, and STM32 also controls the laser of laser module and opens and stop simultaneously, accomplishes the chronogenesis synchronization.

2. The novel laser radar detection timing control system according to claim 1, wherein a laser of the laser module is used as an external trigger, and an STM32 controller is used for sending a corresponding instruction of the laser to control the laser, so that the laser is directly turned on and off, and parameters such as laser pulse width, repetition frequency and energy are adjusted.

3. The novel laser radar detection timing control system according to claim 1, wherein an STM32 controller of the control module replaces a traditional signal generator to send out a pulse trigger signal to serve as a gating signal of a gating PMT, so that the start and stop of the gating PMT are controlled according to a set timing sequence; specifically, the values of corresponding parameters of the gating signals are adjusted through upper computer programming, and the pulse width, repetition frequency, period, duty ratio and the like of the gating signals can be adjusted.

4. The system according to claim 1, wherein the detector PMT of the detection module has a gating function, and the operating state of the gating PMT has a specific timing relationship with an externally input gating signal, and whether the gating PMT is turned on or off depends on the characteristics of the gating signal.

5. The system according to claim 1, wherein the gated PMT in the detection module is turned on after the laser enters the water during the actual measurement, so as to avoid receiving too strong water surface signals, adjust the gain of the PMT, amplify weak water bottom signals, and simultaneously achieve real-time debugging of the start and end of the test point, and echo reception and observation in any time period.

Technical Field

The invention relates to the technical field of laser radars, in particular to a technology for a detection system to receive underwater echo signals in stages according to a set time sequence in laser radar water depth measurement, which can avoid the interference of over-strong water surface signals, simultaneously enlarge weak underwater signals and facilitate the acquisition of signals by an acquisition module.

Background

Airborne laser radar is widely applied to measuring the water depth of inland waters and shallow water coasts, and because the topography under water is more complicated, the water depth change is great to water particles have the decay to laser energy, and water also has the absorption to laser, finally leads to submarine echo signal to be less strong. When enlargiing the signal through the module of enlargiing, the surface of water signal is too strong and seriously influences submarine signal again, consequently, is used for detecting system with high-efficient, accurate gate control technique and gain technique, and to the whole sequential control of detecting system, observe and receive submarine signal have the significance.

Over the past few decades, the use of lidar to measure land, water, wind and atmosphere has become an important tool. For the waveform processing aspect, the software method can be summarized as: a Gaussian decomposition method, a wiener filter deconvolution method, a peak detection method, an average square error function method, a quadrilateral fitting method and the like; the hardware method can be summarized as follows: polarization compression, gating techniques, etc. In these methods, many models are complex, data processing is cumbersome, and the like, and the specific problems are as follows:

1) most software models aim at land echo signals, and underwater echo signals are not easy to extract and separate;

2) the polarization compression of the hardware module only compresses the large dynamic range of the echo signal and cannot completely eliminate the influence of the water surface signal on the water bottom signal;

3) few gating technologies appearing before are immature, the system design is complex, the power consumption is high, only real-time debugging of the start and the end of a test point can be realized, and the problem that underwater echo signals are weak and difficult to observe and collect is not solved.

The invention discloses a novel laser radar detection time sequence control system, which can effectively avoid the reception of water surface signals and amplify weak underwater signals.

Disclosure of Invention

The invention discloses a novel laser radar detection time sequence control system, which has the following implementation principle and technical scheme.

The principle of the invention is as follows: an STM32 controller is used as a time schedule controller designed by the whole system, and a gate control signal is sent by the controller to act on a gate control type PMT in a detection module, so that the detection module receives a target return laser signal according to the designed time schedule, and the reception of a water surface signal is avoided; in addition, the system combines PMT voltage control gain technology, under the prerequisite of avoiding too strong surface of water signal reception, enlargies faint submarine echo signal, makes things convenient for acquisition module to gather follow-up submarine signal more easily. In the working process, after the laser emits laser to a target, the controller performs time sequence control on the detection part, and after the PMT converts an optical signal into an electric signal, the voltage waveform is finally output through matching 50 omega impedance.

In order to achieve the above purpose, the technical scheme of the invention is as follows:

a novel laser radar detection time sequence control system integrates a laser module, a detection module, a control module and a power supply module with lines. Through host computer programming program instruction, write in control module's STM32 controller for the STM32 controller sends the pulse trigger signal who has specific chronogenesis as the gate control signal of PMT, and then the operating condition of gate control PMT in the control detection module, and STM32 also controls the laser of laser module and opens and stop simultaneously, accomplishes the chronogenesis synchronization.

The laser of the laser module is used as an external trigger. And an STM32 controller is used for sending corresponding instructions of the laser to control the laser, so that the on and off of the laser and the adjustment of parameters such as laser pulse width, repetition frequency, energy and the like are directly realized.

The STM32 controller of the control module replaces a traditional signal generator to send out pulse trigger signals to serve as gating signals of the gating PMT, and therefore starting and stopping of the gating PMT are controlled according to the set time sequence. Specifically, the values of corresponding parameters of the gating signals are adjusted through upper computer programming, and the pulse width, repetition frequency, period, duty ratio and the like of the gating signals can be adjusted.

The detector PMT of the detection module has a gating function, and the working state of the gating PMT has a specific time sequence relation with a gating signal input from the outside, and whether the gating PMT is started or not depends on the characteristics of the gating signal.

In actual measurement, the gated PMT in the detection module is started after laser water enters, so that an over-strong water surface signal is prevented from being received, the gain of the PMT is adjusted, a weak water bottom signal is amplified, and meanwhile, real-time debugging of starting and ending of a test point and echo receiving and observation in any time period are realized.

The invention has the beneficial effects that: a novel laser radar detection time sequence control system is disclosed, which comprises a laser module, a control module, a detection module and a power module. The system can finish the random regulation and control and observable of the laser radar test starting point and the laser radar test ending point, avoid receiving water surface signals, amplify weak underwater echo signals, facilitate the acquisition of subsequent echo signals, reduce the power consumption of a gate control module and reduce the load.

Drawings

FIG. 1 shows a novel timing control system flow for laser radar detection

FIG. 2 is a graph showing the relationship between the start/stop state and the gating signal of the NN-type gated PMT

FIG. 3 graph of NN-gated PMT output signal

FIG. 4 Integrated laboratory experiment

FIG. 5 Controless PMT receive Signal

FIG. 6 shows PMT receiving signal with controller

FIG. 7 outdoor Whole experiment

FIG. 8 is a waveform diagram of 300-1300mW without pump power of controller

FIG. 9 is a waveform diagram of 1300mW with the controller pump power 300-

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, preferred embodiments are described below in detail with reference to the accompanying drawings.

Example (b):

s1, system construction is explained by combining the figure 1.

The laser module, the detection module, the control module and the power supply module are integrated by wires. The laser module adopts a VENUS-M series 532nm pulse laser, the output average power is up to 2W, the working pulse width is 1ns-100ns adjustable, the repetition frequency is 500Hz-500kHz adjustable, and experimental parameters are convenient to adjust. The detection module adopts H11526-20 type PMT as the detector of the detection module, the change of the working state of the NN type PMT has certain time delay with a gate control signal, the rising time is 8ns, the time delay is 80ns, the NN type PMT works and closes under the condition of giving the gate control signal, the specific working start-stop state and the working time period depend on the pulse width, the repetition frequency and the like of the given gate control signal, and the detection module has higher gain to 532nm laser. Control module adopts STM32F103ZET6 control panel as the controller, including host computer programming, burns into STM32 control panel, utilizes the internal clock doubling of frequency to amplify the signal, prescales, and the counter counts, and outside is interrupted, outputs the PWM pulse signal as gating signal. The power supply module is used for supplying 12V and 15V power to the whole system.

And S2, the description is given by combining the figures 2 and 3 to adopt a control module STM32 controller as a time schedule controller of the whole system to set parameters such as relevant parameters of the laser and pulse width, repetition frequency, period and the like of the gating signals.

The pulse width of the gate control signal is set as follows. The analysis is carried out by combining theory, and the conditions that the underwater channel of the laser radar detection system avoids receiving the water surface echo signal and only receives the water bottom echo signal are as follows: the STM32 controller sends out a gate control signal while sending out a laser opening instruction, provides the gate control signal for the PMT to make the PMT in a closed state, and cuts off the gate control signal after the laser reaches the water surface to make the PMT in a normal working condition. Therefore, the system has a limit on the flying height of the airplane, namely, the flying height is larger than the distance of laser emission in the rising time and the delay time of the PMT, and the distance is set as h₁Delay time of t₁Rise time of t₂The fall time is t₃The speed of light is set to be c, the laser scanning angle is theta, the flying height is h, and the distance from the laser emitting port to the water surface is S. So the following relationship exists:

h₁＝c(t₁+t₂) (1)

and needs to satisfy:

h＞h₁ (2)

from the trigonometric function:

setting the time from the emission of laser to the reception of the water surface echo signal as t, then:

setting the distance from the water surface to the water bottom of a measuring point to be l, and setting the time from the laser emission to the reception of the underwater echo signal to be T, then:

according to the formulas (5) and (6), when l is greater than 0, T is greater than T, and the pulse width of the gating signal is set to be T_GFrom the above analysis, it follows:

② the gating signal output is as follows. And (3) carrying out relevant configuration on a universal timer 3 in the controller, automatically changing the equivalent of an automatic loader arr and a pre-frequency-dividing coefficient psc, and adjusting the frequency and the duty ratio of an output pulse signal. The concrete configuration is as follows: initializing and enabling a timer 3 clock, a GPIO (general purpose input/output) and an AFIO multiplexing functional module clock; initializing GPIO, setting a PA7 pin as a multiplexing output push-pull output mode, and outputting the speed of 50 MHz; initializing a timing function, setting arr and psc, setting a clock to be divided into 0, and setting a timer to count up; the PWM mode of timer channel 2 is initialized, timer pulse width modulation is selected to be mode 2, and the output enables are compared.

After the timer configuration is completed, the values of arr and psc are adjusted and modified according to formula (7) to adjust the output signal frequency and duty ratio of the PWM.

Wherein f is the frequency of the output pulse of the controller, T_clkThe inherent clock frequency of the timer inside the controller, arr is the auto-loading value and psc is the pre-division coefficient.

S3, the laboratory experiment is described with reference to fig. 4, 5 and 6.

The whole indoor experimental device is shown in fig. 4 and comprises a LiDAR system, a power supply, an oscilloscope, an acrylic material water tank, a plane mirror and a black baffle. Firstly, a gate control function is not used, so that the PMT normally receives signals, and the waveform is shown in FIG. 5; a gating function was then added and the parameters were adjusted so that the gating signal duty cycle was 80% and the gated PMT was turned off 80% of the time in each cycle, the waveform being shown in fig. 6.

From the analysis it is possible to obtain: 1. as is obvious from fig. 5, the water surface echo signal is much larger than the water bottom echo signal, the time difference between the two signals is 19.897ns, the inherent length of the water tank is 3m, the experimental data is true and effective, and the error is about 1 ns; 2. as is evident from fig. 6, there is no signal; 3. the method can control the start and stop of the PMT according to a given time sequence, so that whether the detection module receives signals or not is controlled, and the method is feasible.

S4, the outdoor experiment will be described with reference to fig. 7, 8 and 9.

The experiment was conducted in a corridor of a teaching building, and the whole experimental setup, as shown in fig. 7, included a LiDAR system, a power supply, an oscilloscope, a plane mirror, and a black water bucket. Firstly, a gate control function is not used, so that the PMT normally receives signals, and the waveform is shown in FIG. 8; then, a gate control function is added, parameters are adjusted to enable the PMT to be started after the laser enters water, and meanwhile, the PMT gain is adjusted, wherein the waveform is shown in figure 9.

The conclusion is as follows: 1. as can be obtained from fig. 8, the water surface signal is much larger than the water bottom signal, and as the laser pumping power is increased from 300mw to 1300mw, the amplitude of the water bottom signal is continuously increased, and there is no obvious saturation tendency; 2. as can be seen from fig. 9, after the controller is added and the gain is adjusted, the water bottom signal amplitude can be amplified without receiving the water surface signal, and the water bottom signal can be amplified by at least 6 times by adjusting the control voltage under the premise that the gain is large and the waveform is not distorted, the amplification effect depends on the strength of the signal, and the weaker signal is amplified by a larger amplification factor.

According to the indoor and outdoor experiments, the laser radar detection time sequence control system realizes the random regulation and control and observation of the starting point and the ending point of the laser radar test, can avoid the reception of water surface signals, amplifies weak underwater signals, is beneficial to subsequent waveform acquisition and the like, and proves the correctness and the feasibility of the novel laser radar detection time sequence control system disclosed by the invention.

The above embodiments are merely illustrative, and not restrictive, and those skilled in the relevant art can make various changes and modifications without departing from the spirit and scope of the invention. Therefore, all equivalent technical solutions also belong to the scope of the present invention, and the protection scope of the present invention should be defined by the claims. The technical contents not described in detail in the present invention are all known techniques.