A collision warning system for highway guardrail

Abstract

The present invention discloses a collision alarm system for highway guardrails, comprising: a sensing optical fiber installed on the guardrail of the highway; an optical time domain reflectometer connected to the sensing optical fiber, used to detect the position information of the sensing optical fiber loss; a monitoring device connected to the optical time domain reflectometer, receiving the position information of the sensing optical fiber loss, and displaying the guardrail position information corresponding to the position information of the sensing optical fiber loss on a highway map; and a plurality of portable alarm devices connected to the monitoring device, receiving the guardrail position information corresponding to the position information of the sensing optical fiber loss. The present invention detects the position information of the sensing optical fiber loss set on the highway guardrail through the optical time domain reflectometer, and the monitoring device converts the position information of the sensing optical fiber loss into the corresponding guardrail position information, displays it, and sends it to a plurality of portable alarm devices, thereby realizing automatic detection of guardrail damage and intelligent alarm, and improving the work efficiency of the staff.

Description

Technical Field

[0001] The present invention belongs to the technical field of online monitoring and detection of highway guardrails, and more specifically, relates to a collision alarm system for highway guardrails. Background Art

[0002] The total mileage of China's expressways has reached 143,000 kilometers (as of the end of 2018), ranking first in the world. For safety reasons, expressways need to be equipped with fences and guardrails. These are one of the basic safety facilities for the normal operation of expressways. During the operation of expressways, accidents occur every day, and damage to fences and guardrails also occurs frequently. At present, the damage control of guardrails is mainly achieved through two ways: first, on-site confirmation based on traffic accident reports, and second, manual inspection. In the former, drivers will only report traffic accidents unless there are serious traffic accidents or collisions between two or more vehicles. If a single vehicle collides and scratches a guardrail or guardrail, it is often not reported, and it can only rely on manual inspection, but this method is time-consuming and labor-intensive, and the workload is large. The guardrails of expressways are the guardian of the lives of residents around the highway and the majority of drivers. Timely detection of the damage of the guardrails and timely repair are also our guarantee and protection of life. Therefore, it is particularly important to be able to detect the damage of the guardrails in time and accurately locate the location.

[0003] Therefore, a technology is needed to realize intelligent detection of highway guardrail damage. Summary of the invention

[0004] The purpose of the present invention is to provide a highway guardrail collision alarm system capable of intelligently detecting damage to highway guardrails.

[0005] In order to achieve the above-mentioned purpose, the present invention provides a collision alarm system for a highway guardrail, comprising: a sensing optical fiber, which is installed on the guardrail of the highway; an optical time domain reflectometer, which is connected to the sensing optical fiber and is used to detect position information of loss of the sensing optical fiber; a monitoring device, which is connected to the optical time domain reflectometer, receives the position information of loss of the sensing optical fiber, and displays the guardrail position information corresponding to the position information of loss of the sensing optical fiber on a highway map; and a plurality of portable alarm devices, which are connected to the monitoring device and receive the guardrail position information corresponding to the position information of loss of the sensing optical fiber.

[0006] Optionally, the sensing optical fiber is bonded, bound or magnetically attracted to an existing guardrail on the highway.

[0007] Optionally, when the guardrail panel is newly built, the sensing optical fiber is installed at a reserved installation position of the newly built guardrail panel.

[0008] Optionally, the optical time domain reflectometer and monitoring equipment are arranged in a toll station or a relay station.

[0009] Optionally, the optical time domain reflectometer includes a low-resolution point sampling working state and a high-resolution point sampling working state.

[0010] Optionally, when the optical time domain reflectometer detects that the loss of the sensing optical fiber is greater than a preset threshold in the low-resolution point sampling working state, the high-resolution point sampling working state is turned on to obtain the position information of the optical fiber loss.

[0011] Optionally, the optical time domain reflectometer utilizes backscattered light generated when light propagates in the sensing optical fiber to obtain attenuation information and detect the loss of the sensing optical fiber.

[0012] Optionally, the low-resolution point sampling working state and the high-resolution point sampling working state are adjusted according to season and time.

[0013] Optionally, the portable alarm device is connected to the monitoring device via wireless communication and performs two-way communication.

[0014] Optionally, the optical time domain reflectometer compares the optical fiber information detected in the current time period with the optical fiber information obtained in the previous time period, and obtains the optical fiber loss information according to the comparison result, and the interval time between the current time period and the previous time period is a preset time period.

[0015] Optionally, the optical fiber is arranged as a ring wiring according to the length, and a dual wavelength filtering method or an optical switch is used to switch the output port.

[0016] The beneficial effects of the present invention are as follows: the highway guardrail collision alarm system of the present invention sets the sensing optical fiber on the guardrail of the highway, detects the position information of the sensing optical fiber loss by optical time domain reflectometer, and sends it to the monitoring equipment. The monitoring equipment converts the position information of the sensing optical fiber loss into the corresponding damaged guardrail position information and displays it, and sends it to multiple portable alarm devices, so as to remind the highway maintenance personnel or the staff closer to the site to arrange the inspection and maintenance reasonably, realize the automatic detection and intelligent alarm of the guardrail damage, and the staff can timely feedback the maintenance status through the terminal, thereby improving the work efficiency of the staff.

[0017] The present invention has other features and advantages, which will be apparent from or will be described in detail in the accompanying drawings and the following specific embodiments incorporated herein, which together serve to explain the specific principles of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The above and other purposes, features and advantages of the present invention will become more apparent by describing the exemplary embodiments of the present invention in more detail in conjunction with the accompanying drawings. In the exemplary embodiments of the present invention, the same reference numerals generally represent the same components.

[0019] Figure 1 A structural block diagram of a highway guardrail collision warning system according to an embodiment of the present invention is shown.

[0020] Figure 2 A structural block diagram of a highway guardrail collision warning system according to yet another embodiment of the present invention is shown.

[0021] Figure 3 The diagram shows a ring-shaped connection mode of the sensing optical fiber of the highway guardrail collision warning system according to an embodiment of the present invention.

[0022] Figure 4 A diagram showing the location of the sensing optical fiber of a highway guardrail collision warning system according to an embodiment of the present invention is shown.

[0023] Description of reference numerals:

[0024] 1. Sensing optical fiber; 2. Optical time domain reflectometer; 3. Monitoring equipment; 4. Portable alarm equipment; 5. Guardrail; 6. Fixed point; 7. Monitoring center module; 8. Power supply module; 9. Communication module; 10. Electric-controlled optical switch; 11. Loop 1 port; 12. Loop 2 port. DETAILED DESCRIPTION

[0025] The preferred embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the preferred embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to make the present invention more thorough and complete, and to fully convey the scope of the present invention to those skilled in the art.

[0026] The present invention provides a collision alarm system for a highway guardrail, comprising: a sensing optical fiber, the sensing optical fiber is installed on the guardrail of the highway; an optical time domain reflectometer, the optical time domain reflectometer is connected to the sensing optical fiber, and is used to detect position information of loss of the sensing optical fiber; a monitoring device, the monitoring device is connected to the optical time domain reflectometer, receives position information of loss of the sensing optical fiber, and displays guardrail position information corresponding to the position information of loss of the sensing optical fiber on a highway map; and a plurality of portable alarm devices, the plurality of portable alarm devices are all connected to the monitoring device, and receive guardrail position information corresponding to the position information of loss of the sensing optical fiber.

[0027] Optical fibers are distributed on both sides of the highway. Each side can be used as a single route, or the optical fibers on both sides of the road can be connected into a loop for simultaneous monitoring. In particular, loop monitoring can use light sources of different wavelengths at both ends of the input and output, add filters before the detector for monitoring, or alternately select the input port through an optical switch at the input end, which has the advantage of having one breakpoint without affecting other locations.

[0028] Specifically, the sensing optical fiber is set on the guardrail board of the highway. The sensing optical fiber of the guardrail board on one side of the highway can be used as a reference alone, or the sensing optical fibers on the guardrail boards on both sides of the highway can be connected into a loop for monitoring. Considering that the damage to the guardrail board is often caused by high-intensity collision, an optical time domain reflectometer (OTDR) is used to monitor the loss of the sensing optical fiber. The loss of the sensing optical fiber caused by the collision with the guardrail board is used to determine whether there is a scratch on the fence. When the optical time domain reflectometer detects that the sensing optical fiber has loss, the specific location information of the loss is determined, and the specific location information of the loss is sent to the monitoring device. The monitoring device converts the specific location information of the loss into the specific location information of the guardrail board on the highway. The monitoring device receives the location information of the sensing optical fiber loss detected by the optical time domain reflectometer, displays the location information on the highway map and marks it, so that the staff can obtain the damage information of the guardrail board in time. After the staff arrives at the site for confirmation or repair, they can feedback the situation through the terminal and cancel the damage mark, which improves the work efficiency of the staff.

[0029] The portable alarm device is equipped with a satellite positioning module. The monitoring device compares the real-time location information of the portable alarm device with the location information of the damaged guardrail board based on the real-time location information of the portable alarm device. Through comparison, the specific location information of the corresponding guardrail board is sent to the portable alarm device closest to the damaged guardrail board. After receiving the alarm information, the carrier of the portable alarm device can confirm and send the confirmation information to the monitoring device through the portable alarm device. After receiving the information, the monitoring device displays it to remind the existing staff to check it, so that the staff can arrange their work reasonably. The portable alarm device can also feedback the on-site situation and maintenance situation to the monitoring device. If there is no reply from the carrier of the portable alarm device, the monitoring point closest to the damaged location should immediately send a vehicle to check and repair it.

[0030] In one example, after confirmation by the nearest portable alarm device, navigation is automatically started to guide the carrier of the portable alarm device to the specific location where the guardrail is damaged.

[0031] Before using the alarm system, the optical fiber length will be matched with the road position, especially the position of key landmarks near the road. The monitoring equipment in the background receives the location information of the sensing optical fiber loss detected by the optical time domain reflectometer, and determines the nearby landmark information corresponding to the location. Finally, the nearby landmark information will be provided on the highway map showing the accident location, which is convenient for the handling personnel to quickly find the fault point.

[0032] In the future application of smart highways, when a serious accident occurs, the system will have the function of broadcasting warnings to nearby vehicles, requesting nearby vehicles to take photos through the driving monitor, and determining through evidence collection whether a tow truck, police car or ambulance is needed.

[0033] According to an exemplary embodiment, the highway guardrail collision alarm system sets a sensor fiber on the guardrail of the highway, detects the position information of the sensor fiber loss through an optical time domain reflectometer, and sends it to a monitoring device. The monitoring device converts the position information of the sensor fiber loss into corresponding damaged guardrail position information, displays it, marks it, and sends it to multiple portable alarm devices to remind highway maintenance personnel or staff close to the site to arrange inspection and maintenance reasonably, thereby realizing automatic detection of guardrail damage and intelligent alarm. After the staff arrives at the site for confirmation or repair, they can feedback the situation through the terminal and cancel the damage mark, thereby improving the work efficiency of the staff.

[0034] As an optional solution, the collision alarm system of the highway guardrail also includes a monitoring center module, which is connected to the monitoring equipment. The monitoring center module determines the degree of damage to the highway guardrail according to the degree of change in optical fiber loss.

[0035] The monitoring center module is connected to the monitoring equipment. The monitoring center intelligently determines the level of damage to the front end based on the degree of change in optical fiber loss. Different levels correspond to different linkage plans. The emergency plans are divided into (1) the highest level plan: notify relevant departments, such as the public security fire 120 ambulance to go to the accident site at the same time for emergency rescue and emergency accident handling; (2) medium-level plan: maintenance personnel immediately go to the scene to check; (3) low-level plan: suspected guardrail damage or minor scratches, no immediate processing is required. After the mobile terminal staff arrives at the scene of the latter two plans, they can redefine the event level based on the on-site information collected by the mobile terminal and transmit it back to the monitoring center and the command emergency hall to proceed to the next step.

[0036] As an optional solution, the optical time domain reflectometer compares the optical fiber information detected in the current period with the optical fiber information obtained in the previous period, and obtains the optical fiber loss information according to the comparison result. The interval time between the current period and the previous period is a preset period.

[0037] Specifically, the optical time domain reflectometer compares the optical fiber information detected in the current time period with the optical fiber loss information obtained in the previous time period, obtains the additional optical fiber loss information based on the comparison result, and determines whether the optical fiber is lost based on the additional optical fiber loss information. The preset time period can be set through software.

[0038] As an option, the sensing fiber is glued, bonded or magnetically attached to an existing guardrail on the highway.

[0039] Specifically, a single or multiple sensing optical fibers are attached to the guardrail of the highway, and fixed points are set on the guardrail. The sensing optical fibers can be connected to the fixed points of the existing guardrail by bonding, binding or magnetic attraction, without changing the existing guardrail, and the installation is convenient.

[0040] As an optional solution, when the guardrail panel is newly built, the sensing optical fiber is set at a reserved installation position of the newly built guardrail panel.

[0041] Specifically, the sensing optical fiber is installed on the newly built guardrail by burying it in a reserved installation position.

[0042] As an optional solution, the optical time domain reflectometer and monitoring equipment are set up in the toll station or relay station.

[0043] Specifically, the optical time domain reflectometer and monitoring equipment can be placed at toll booths, highway service stations, or other designated locations on highways. If the distance between toll booths is too long, relay stations can be set up on both sides of the road for monitoring. In particular, if the monitoring distance is too long, a relay station can be set up under the highway bridge and equipped with wind power, electricity, and solar power supply devices and 5G equipment. The 5G signal is connected to the cloud and then transmitted back to the designated monitoring center through the cloud.

[0044] As an optional solution, the optical time domain reflectometer includes a low-resolution point sampling working state and a high-resolution point sampling working state.

[0045] Specifically, for long-term monitoring, the optical time domain reflectometer can be set in two working states: a low-resolution sampling point (LS) working state and a high-resolution sampling point (HS) working state.

[0046] As an optional solution, when the optical time domain reflectometer detects that the loss of the sensing optical fiber is greater than a preset threshold in the low-resolution point sampling working state, the high-resolution point sampling working state is turned on to obtain the position information of the optical fiber loss.

[0047] Specifically, the optical time domain reflectometer includes a low-resolution sampling point (LS) working state and a high-resolution sampling point (HS) working state. When long-term monitoring is performed, the optical time domain reflectometer is first set to the low-resolution sampling point (LS) working state. After the loss of the sensing optical fiber is detected, it is set to the high-resolution sampling point (HS) working state. The more accurate specific location information of the sensing optical fiber loss obtained through the high-resolution sampling point (HS) working state is sent to the monitoring device. The monitoring device confirms the direction of travel of the vehicle according to the specific location, and sends warning information to the highway exit in this driving direction according to the direction of travel. According to the distance of each exit from the scratch accident, the time to arrive at the exit is estimated according to the speed limit, and the suspicious vehicle is photographed and evidence is collected through the camera at the exit. At the same time, a vehicle is dispatched from the nearest monitoring point to collect evidence on the spot.

[0048] As an alternative, an optical time domain reflectometer uses backscattered light generated when light propagates in a sensing optical fiber to obtain attenuation information and detect the loss of the sensing optical fiber.

[0049] Specifically, the light emitted by the optical time domain reflectometer will be scattered when propagating in the sensing optical fiber. If there is a break or damage in the sensing optical fiber, Fresnel reflection or enhanced back-scattering will be generated. The strength of the reflection or scattering is proportional to the optical power passing through the point, reflecting the attenuation of the optical fiber point. Therefore, the breakpoint position of the sensing optical fiber, that is, the position information of the loss, is determined based on the scattered light transmitted back by reflection. It can also be said that the damage of the guardrail is determined based on the abnormal change of the optical signal at the collision point.

[0050] As an optional solution, the low-resolution point collection working state and the high-resolution point collection working state are adjusted according to season and time.

[0051] Specifically, the standards of the high-resolution sampling (HS) working state and the low-resolution sampling (LS) working state used as reference need to be adjusted in different seasons and time periods, that is, they can be adjusted according to the season and time, and the overall loss changes of the line can be judged as loss changes caused by climate change.

[0052] As an optional solution, the portable alarm device is connected to the monitoring device via wireless communication and performs two-way communication.

[0053] Specifically, the portable alarm device communicates with the monitoring device through 4G or 5G, which is convenient and fast, and can communicate in both directions.

[0054] Specifically, the optical fiber is arranged in a ring wiring according to the length, and a dual-wavelength filtering method or an optical switch is used to switch the output port.

[0055] Specifically, the optical fiber can be set to a ring wiring according to the length, using dual wavelength filtering, or switching the output port with an optical switch to ensure that the entire process is still monitored in the event of a breakpoint.

[0056] Example

[0057] Figure 1 A structural block diagram of a highway guardrail collision warning system according to an embodiment of the present invention is shown. Figure 2 A structural block diagram of a highway guardrail collision warning system according to yet another embodiment of the present invention is shown. Figure 3 The diagram shows a ring-shaped connection mode of the sensing optical fiber of the highway guardrail collision warning system according to an embodiment of the present invention. Figure 4 A diagram showing the location of the sensing optical fiber of a highway guardrail collision warning system according to an embodiment of the present invention is shown.

[0058] Combination Figure 1 , Figure 2 , Figure 3 and Figure 4 As shown, the collision alarm system of the highway guardrail comprises: a sensing optical fiber 1, which is installed on the guardrail 5 of the highway; an optical time domain reflectometer 2, which is connected to the sensing optical fiber 1 and is used to detect the position information of the loss of the sensing optical fiber 1; a monitoring device 3, which is connected to the optical time domain reflectometer 2, receives the position information of the loss of the sensing optical fiber 1, and displays the position information of the guardrail 5 corresponding to the position information of the loss of the sensing optical fiber 1 on the highway map; and a plurality of portable alarm devices 4, which are all connected to the monitoring device 3 and receive the position information of the guardrail 5 corresponding to the position information of the loss of the sensing optical fiber 1.

[0059] The sensing optical fiber 1 is bonded, bound or magnetically attracted to a fixing point 6 of an existing guardrail 5 on the highway.

[0060] When the guardrail board 5 is newly built, the sensing optical fiber 1 is installed at a reserved installation position of the newly built guardrail board 5 .

[0061] The optical time domain reflectometer 2 and the monitoring device 3 are arranged in a toll station or a relay station.

[0062] The optical time domain reflectometer 2 includes a low-resolution point sampling working state and a high-resolution point sampling working state.

[0063] When the optical time domain reflectometer 2 detects that the loss of the sensing optical fiber 1 is greater than a preset threshold in the low-resolution point sampling working state, the high-resolution point sampling working state is turned on to obtain the position information of the optical fiber loss.

[0064] The optical time domain reflectometer 2 utilizes the backscattered light generated when the light propagates in the sensing optical fiber 1 to obtain the attenuation information and detect the loss of the sensing optical fiber 1 .

[0065] Among them, the low-resolution point collection working status and the high-resolution point collection working status are adjusted according to the season and time.

[0066] The portable alarm device 4 is connected to the monitoring device 3 via wireless communication and performs two-way communication.

[0067] The optical time domain reflectometer compares the optical fiber information detected in the current period with the optical fiber information obtained in the previous period, and obtains the optical fiber loss information according to the comparison result. The interval time between the current period and the previous period is the preset period.

[0068] The collision alarm system of the highway guardrail also includes a monitoring center module 7, which is connected to the monitoring device 3. The monitoring center module 7 determines the degree of damage to the highway guardrail according to the degree of change in optical fiber loss.

[0069] The optical fiber is arranged in a ring wiring according to the length, and a dual-wavelength filtering method or an optical switch is used to switch the output port.

[0070] Figure 1 The connection structure of the highway guardrail collision alarm system is suitable for placing the monitoring equipment at highway toll stations or service centers. Figure 2 The connection structure of the highway guardrail collision alarm system is suitable for monitoring equipment placed in a newly built monitoring station in the highway section. It needs to have an optional solar or wind power supply module 8 and a communication module 9. The optical time domain reflectometer 2 sends data to the monitoring device 3 through the communication module 9. According to the geographical location of the equipment, the power supply module 8 can use solar energy or wind energy, and the communication module 9 can use 5G or network cables. The portable alarm device 4 can be a mobile phone, which has the function of feeding back information to the monitoring device 3.

[0071] Figure 3 In the example, the sensing optical fiber 1 is connected as a loop, and an electric-controlled optical switch 10 with one-to-two paths is connected behind the optical time domain reflectometer 2. According to the state of the electric-controlled optical switch 10, the output light of the optical time domain reflectometer 2 can be selectively used to enter the loop 1 port 11 or the loop 2 port 12. When the electric-controlled optical switch 10 is in working state 1, the light of the optical time domain reflectometer 2 enters the loop 1 port 11, and the light monitors the entire optical fiber loop along the loop. When the optical time domain reflectometer 2 detects a breakpoint in the loop, it switches back and forth through the optical switch, which plays a role in temporarily monitoring the entire process.

[0072] The working process of the collision alarm system of the highway guardrail is as follows: the optical time domain reflectometer 2 detects the attenuation signal of the light in the sensing optical fiber 1 in the low-resolution sampling point working state. When the signal attenuation becomes stronger, it changes to the high-resolution sampling point working state to re-detect and obtain the specific position information of the sensing optical fiber loss 1. The optical time domain reflectometer 2 transmits the specific position information of the sensing optical fiber 1 loss to the monitoring device 3. The monitoring device 3 converts the position information of the sensing optical fiber 1 loss into the corresponding guardrail 5 position information, that is, the specific position information on the highway, and displays the specific position information on the highway. Since the monitoring device 3 is placed at the toll station Or in a relay station, when the monitoring device 3 displays the specific location information on the highway, an alarm will be issued to remind the staff in the toll station that the guardrail 5 is faulty and to check and maintain it. At the same time, the monitoring device 3 sends the specific location information on the highway to the portable alarm device 4. After the staff carrying the portable alarm device 4 receives the alarm information, they check the alarm information. When a staff member is close to the specific location information on the highway and it is convenient to check it, the staff member sends convenient information to the monitoring device 3 through the portable alarm device 4. After receiving the information, the monitoring device 3 displays it, and the staff at the toll station knows that relevant staff have gone to check it.

[0073] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A collision warning system for highway guardrails, It is characterized in that include: A sensing optical fiber, wherein the sensing optical fiber is installed on a guardrail plate of a highway; An optical time domain reflectometer, which is connected to the sensing optical fiber and is used to detect position information of loss of the sensing optical fiber; A monitoring device, the monitoring device is connected to the optical time domain reflectometer, receives the position information of the sensing optical fiber loss, and displays the guardrail position information corresponding to the position information of the sensing optical fiber loss on a highway map; A plurality of portable alarm devices, each of which is connected to the monitoring device and receives guardrail position information corresponding to the position information of the sensing optical fiber loss; The optical time domain reflectometer includes a low-resolution point sampling working state and a high-resolution point sampling working state, and the low-resolution point sampling working state and the high-resolution point sampling working state are adjusted according to season and time; When the optical time domain reflectometer detects that the loss of the sensing optical fiber is greater than a preset threshold in the low-resolution point sampling working state, the high-resolution point sampling working state is turned on to obtain the position information of the optical fiber loss; The sensing optical fiber is arranged in a ring wiring according to the length, and a dual-wavelength filtering method or an optical switch is used to switch the output port.

2. The collision warning system for highway guardrail according to claim 1, It is characterized in that The sensing optical fiber is bonded, bound or magnetically attracted to an existing guardrail plate on the highway.

3. The collision warning system for highway guardrail according to claim 2, It is characterized in that When the guardrail panel is newly built, the sensing optical fiber is installed at a reserved installation position of the newly built guardrail panel.

4. The collision warning system for highway guardrail according to claim 1, It is characterized in that The optical time domain reflectometer and monitoring equipment are arranged in a toll station or a relay station.

5. The collision warning system for highway guardrail according to claim 1, It is characterized in that The optical time domain reflectometer utilizes the backscattered light generated when the light propagates in the sensing optical fiber to obtain attenuation information and detect the loss of the sensing optical fiber.

6. The collision warning system for highway guardrail according to claim 1, It is characterized in that The portable alarm device is connected to the monitoring device via wireless communication and performs two-way communication.

7. The collision warning system for highway guardrail according to claim 1, It is characterized in that The optical time domain reflectometer compares the optical fiber information detected in the current period with the optical fiber information obtained in the previous period, and obtains the optical fiber loss information according to the comparison result. The interval time between the current period and the previous period is the preset period.

Images