Underground tunnel experience education system

Abstract

The present invention relates to an underground utility tunnel experience education system, characterized by comprising: a Head Mounted Display (HMD); a motion platform configured to enable the simulation of the underground utility tunnel through 4-degrees of freedom (4-DOF) driving including pitch, roll, heave, and surge; a motion sensor that recognizes motion data including the 3D posture and position of the user; and a control PC that transmits virtual reality content generated through the modeling of the underground utility tunnel to the HMD to visualize the virtual reality content through the HMD, and controls the 4-DOF driving of the motion platform based on the motion data recognized by the motion sensor.

Description

Technology Field

[0001] The present invention relates to an underground utility tunnel experience education system. Background Technology

[0003] As cities today become more complex in size and function, the majority of urban infrastructure is buried beneath roads in facilities known as underground utility tunnels. An underground utility tunnel refers to a facility that manages various types of urban infrastructure (electricity, telecommunications, water and sewage systems, gas, etc.) by consolidating them into a single underground passage. This approach offers several advantages: instead of burying these facilities individually, sharing a single tunnel increases efficiency in installation and maintenance, enhances urban aesthetics, and reduces ground subsidence and traffic congestion. In particular, underground utility tunnels are considered critical infrastructure in areas undergoing advanced urbanization or large-scale development, and are regarded as an essential element for sustainable urban development.

[0004] However, the aging of underground utility tunnels leads to a deterioration in durability—resulting in condensation and corrosion of internal facilities due to inadequate ventilation and humidity control—which in turn causes fires. Furthermore, the loss of communication networks and power cables can paralyze the entire city and cause significant economic disruption. To prevent this, relevant agencies have codified design standards and regular maintenance guidelines for underground utility tunnels into law to supervise and manage them. Nevertheless, fires frequently occur in underground utility tunnels and infrastructure facilities due to condensation and corrosion, resulting in substantial economic losses and inconvenience for residents.

[0005] The background technology of the present invention is disclosed in Korean Published Patent Application No. 10-2024-0086850 (June 19, 2024). The problem to be solved

[0007] The objective of the present invention is to provide an underground utility tunnel experience education system and method capable of providing realistic underground utility tunnel experience education in a virtual reality environment. means of solving the problem

[0009] An underground utility tunnel experience education system according to one embodiment of the present invention includes: a Head Mounted Display (HMD); a motion platform configured to enable the simulation of the underground utility tunnel through 4-degrees of freedom (4-DOF) driving including pitch, roll, heave, and surge; a motion sensor that recognizes motion data including the 3D posture and position of the user; and a control PC that transmits virtual reality content generated through the modeling of the underground utility tunnel to the HMD to visualize the virtual reality content through the HMD, and controls the 4-DOF driving of the motion platform based on the motion data recognized by the motion sensor. Effects of the invention

[0011] According to the present invention, by applying a 4-DOF motion platform to enhance immersion, it is possible to provide digital twin-based underground utility tunnel virtual training content that allows the user to have a realistic experience of the underground utility tunnel and to quickly respond to fires and perform facility maintenance.

[0012] According to the present invention, by using a motion capture sensor to track the walking direction and speed of the user and precisely controlling the speed and direction of the treadmill so that it is naturally positioned in the center within the motion platform, it is possible to provide an underground utility tunnel experience education platform that allows the user to experience comfortably without inducing motion sickness. Brief explanation of the drawing

[0014] FIG. 1 is a configuration diagram of an underground utility tunnel experience education system according to one embodiment of the present invention. Figure 2 is a drawing showing the structure of the vertical drop device of Figure 1. Figure 3 is a diagram showing the structure of the motion base of Figure 1. Figure 4 is a diagram showing the upper drive unit structure of the motion base of Figure 1. FIGS. 5 to 8 are drawings illustrating a method for reducing cyber sickness in one embodiment of the present invention. Specific details for implementing the invention

[0015] Embodiments according to the present invention are described below. In this process, the thickness of lines or the size of components shown in the drawings may be exaggerated for clarity and convenience of explanation. Furthermore, the terms described below are defined considering their functions in the present invention, and these may vary depending on the intention or convention of the user or operator. Therefore, the definitions of these terms should be based on the content throughout this specification.

[0016] Embodiments of the present invention are described below with reference to the attached drawings so that those skilled in the art can easily implement them. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein. Furthermore, in order to clearly explain the present invention in the drawings, parts unrelated to the explanation have been omitted, and similar parts throughout the specification are denoted by similar reference numerals.

[0017] Throughout the specification, when a part is described as "including" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0018] The implementations described herein may be implemented, for example, as methods or processes, devices, software programs, data streams, or signals. Even if discussed only in the context of a single form of implementation (e.g., discussed only as a method), the implementation of the discussed features may also be implemented in other forms (e.g., devices or programs). Devices may be implemented in appropriate hardware, software, and firmware, etc. Methods may be implemented in devices such as processors, which generally refer to processing devices including, for example, computers, microprocessors, integrated circuits, or programmable logic devices.

[0020] Although research on high-speed fire prediction, detection, and response has been conducted to minimize disasters within underground utility tunnels, the poor environmental conditions—such as high humidity and outdated ventilation facilities—have led to frequent equipment failures. Consequently, depending on the size and length of the tunnel, personnel generally enter the underground tunnel at least once a week to conduct direct patrols and repairs. However, working in narrow passages can not only place psychological pressure on patrolmen but also cause sleep deprivation, stress, depression, and various types of cancer due to the high electromagnetic fields from extra-high voltage power cables installed within the tunnel. Therefore, inexperienced workers may suffer fatal harm from prolonged exposure to the tunnel environment. To avoid such prolonged exposure, the development of a digital twin-based virtual training platform for underground utility tunnels that mimics reality is necessary.

[0021] Recently, research has been conducted on immersive virtual training experiences that provide opportunities to experience guided risk awareness along with immediate feedback to improve safety management in dangerous sites such as construction. In these recent studies, training systems were built using 360-degree panoramic images and videos to reproduce the complex and dangerous elements of construction sites as accurately as possible. However, providing various construction sites solely through 360-degree panoramic images and videos not only fails to reproduce the sense of the site in an immersive manner but also raises concerns that it may cause virtual sickness by triggering vergence-accommodation conflict (VAC).

[0022] 3-DOF (Degree of Freedom) motion platforms and HMDs (Head Mounted Displays) have been used to reduce virtual sickness caused by the mismatch between visual and vestibular senses in virtual reality. Consequently, while visual and physical movements are synchronized, there is a problem in that the user's physical movements are not reflected. Therefore, it is necessary to develop a complex and highly accurate system for human behavior by tracking signals through an HMD.

[0023] Furthermore, there is a case where a system was developed that provides an immersive virtual reality experience using a treadmill and a new optimization technique based on a modified GAN model. However, since the system did not track and incorporate the user's location and pose, meaningful learning effects were observed only when moving at low speeds. Therefore, a virtual training platform utilizing a motion platform can prevent the induction of virtual motion sickness caused by sensory conflict with the virtual environment by considering both the user's location tracking and the motion platform's pose.

[0024] The performance of motion simulation is a key factor in developing realistic VR training platforms. To date, most motion platforms have adopted hexapod motion systems capable of easily utilizing 6 degrees of freedom. However, since these systems operate only within a limited range of motion within a structured space and cannot simulate walking, running, or other forms of movement, they significantly reduce immersion and realism when used in VR applications such as physical rehabilitation and sports training.

[0025] In this invention, a 4-DOF motion platform is applied to enhance immersion, thereby providing digital twin-based underground utility tunnel virtual training content that allows users to have a realistic experience of an underground utility tunnel and to quickly respond to fires and perform facility maintenance. Furthermore, this invention provides an underground utility tunnel experience education platform that allows users to comfortably experience the tunnel without inducing motion sickness by using an Azure Kinect DK motion capture sensor to track the user's walking direction and speed, and by precisely controlling the speed and direction of the treadmill so that it is naturally positioned in the center of the motion platform.

[0027] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0028] FIG. 1 is a configuration diagram of an underground utility tunnel experience education system according to one embodiment of the present invention.

[0029] Referring to FIG. 1, an underground utility tunnel experience education system (100) according to one embodiment of the present invention may be configured to include a control PC (110), an HMD (120), a motion sensor (130), and a 4-DOF motion platform (140).

[0030] Virtual reality content for underground utility tunnels for experiential education can be designed to resemble actual utility tunnels by modeling the actual utility tunnels using high-precision LiDAR and allowing users to experience various facilities within the tunnels, such as communication lines, power lines, and water supply lines (general water supply, industrial water supply), in order to meet the purpose of experiential education.

[0031] When the underground utility tunnel experience education system (100) is booted, virtual reality content installed on the control PC (110) is visualized on the HMD (120), and the motion sensor (130) can recognize the 3D posture and position of the user (101) in real time.

[0032] The motion detector (130) can acquire joint position information of the user (101) as motion data using a model-based feature point method and an Azure Kinect DK, which is a TOF-based motion recognition sensor. To this end, the motion detector (130) can acquire joint position coordinate information of the user by tracking a skeleton composed of 25 joints in the human body in real time, and can recognize motion in real time while walking centered on the base of the spine of the tracked joint skeleton and apply it to underground tunnel virtual training content (virtual reality content).

[0033] The motion sensor (130) determines the direction and speed of the motion base (142) based on the forward direction and speed of the user (101) relative to the base of the spine, and the control PC (110) can control the user (101) so that they do not fall out of the motion platform (140) and are always positioned in the center based on the direction and speed of the surge determined by the motion sensor (130).

[0034] The motion base (142) and the control PC (110) can be wired connected via UDP (User Datagram Protocol) communication, and the vertical drop device (141) and the control PC (110) can be wired connected via USB (Universal Serial Bus) communication. The motion base (142) can perform simulations by precisely synchronizing with respect to the terrain (angle of inclination with respect to the x and y axes, drop, etc.) within the virtual underground utility tunnel in the virtual reality content. Thus, the user (101) can receive realistic (realistic) underground utility tunnel experience education within a limited space.

[0035] The motion platform (140) is composed of a vertical drop device (141) and a motion base (142), and the controllers of these two devices (141, 142) can each operate independently. The vertical drop device (141) can perform a heave using four pneumatic cylinders (210) as shown in FIG. 2 to provide the user with an experience similar to a real fall.

[0036] Referring to FIG. 2, each cylinder (210) can be connected to an individual 5 / 2 solenoid valve (220), and the valve (220) receives an electrical signal from the controller (230) and, together with it, receives air from the compressor (150), thereby controlling the flow of air to cause the plate of the vertical drop device (141) to rise or fall. At this time, the operating speed of each cylinder (210) is about 1.5 m / s, and since the stroke length of each cylinder (210) used in the experiment is 30 cm, it can be almost similar to the speed of a person in a stationary state free fall (about 0.25 seconds).

[0037] The motion base (142) has a total of 4 degrees of freedom (Roll, Pitch, Heave, Surge) and can operate by being divided into a top driving part and a bottom driving part as shown in FIG. 3.

[0038] The lower drive unit can have three rotational and movement degrees of freedom (Roll, Pitch, Heave) by operating three drive devices (A, B, C). Each drive device (A, B, C) may consist of a motor (Servo motor), a shaft, a lifting link, and a device for fixing parts.

[0039] The lifting links of the driving devices (A, B) may be installed in the same direction, and the lifting link of the driving device (C) may be installed in the opposite direction to the lifting links of the driving devices (A, B). The three lifting links of the driving devices (A, B, C) may be connected to the upper driving unit. At this time, the axial coupling direction between the lifting link of the driving device (C) and the upper driving unit may be perpendicular to the axial coupling direction between the lifting link of the driving devices (A, B) and the upper driving unit.

[0040] That is, the shaft connected between the lifting link of the drive unit (C) and the upper drive unit can be in a direction parallel to the shaft. Through such a configuration of the drive units (A, B, C), the lower drive unit can perform Pitch, Roll, and Heave.

[0041] The upper drive unit is configured as a treadmill structure as shown in FIG. 4, consisting of a motor (Servo Motor), a rubber belt, and a walking pad, and can perform surge of the motion base (142). The upper drive unit may include two rubber belts and one walking pad to implement smooth motion drive, thereby providing the user (101) with a realistic and smooth walking experience in the VR space.

[0042] In this embodiment, all motors used in the motion base (142) are Delta ECMA-C10807ES and can be controlled by a motion card (PCI-DMC-F02) with a PCI interface. The operating speed of the motion base (142) can be determined by the specifications of the motor and the number of threads on the shaft. Since the rotational speed of the motor used in the implementation of the motion base (142) is 5,000 r / min and the number of threads on the motor is 20, the time required for the rising link to operate can be 0.24 seconds.

[0043] The ideal operating speed of Pitch is ±41.7° / s, but due to the increased weight of the user (101) and the upper drive unit (treadmill), the motor speed and acceleration decrease, and the final angular speed can be measured as ±35° / s. The angular speed can be estimated by utilizing the motor speed obtained through the motion card's SDK.

[0044] The operating range of the vertical drop device (141) may be 300 mm depending on the stroke length of the cylinder (see "210" in FIG. 2), and the heave operating range of the motion base (142) may be 200 mm depending on the height of the rising link shown in FIG. 3. Also, since the distance between the fixed axes of the driving devices (A, B) and driving device (C) in FIG. 3 is 1,150 mm and the distance between the driving device (A) and the driving device (B) is 800 mm, the driving ranges of Roll and Pitch may be ±14° and ±10°, respectively.

[0045] The user (101) wears an HMD (120) to experience the underground utility tunnel virtual reality content, in which case the underground utility tunnel is a facility consisting of a straight-line tunnel. The user (101) walks through the underground utility tunnel in a straight-line direction in virtual reality, and can experience it while walking on a 4-DOF motion base (142). The 4-DOF motion base (142) can provide feedback on the control speed so that the user (101) is placed in the center position of the motion base (142) based on motion data acquired through the motion sensor (130) of the Azure Kinect DK.

[0046] A treadmill on a motion plate can provide the function for an immersive virtual reality experience that interacts through walking. However, there are stability constraints on the user (101) walking freely within the limited space of the motion base (142). In the present invention, based on motion data acquired through a motion detector (motion capture sensor), the maximum range of activity guaranteed to prevent the user (101) from leaving the motion base (142) can be identified.

[0047] Motion data acquisition can be performed by an Azure Kinect DK, which is an example of a motion sensor (130). The Azure Kinect DK can estimate the walking speed of the user (101) by capturing the pelvis base coordinates in real time from the 25 joint position coordinates of the user's skeleton (101) in a wide field of view mode of 120° * 120°. The control PC (110) can ensure the safety of the user's interaction by estimating the user's (101) walking speed as a position change value based on the motion data and controlling the driving speed of the motion base (142) so that the user (101) is always positioned in the center of the motion base (142).

[0048] However, in a virtual reality environment based on an HMD (120), the user (101) may experience cyber sickness, such as discomfort, nausea, paleness, vomiting, and headaches, due to sensory conflict. In real space, since body movements occur together with visual stimuli, the user (101) feels sensations through the resultant force between inertial force and physical force. However, in virtual reality, there are no actual body movements or physical stimuli, only visual stimuli. Therefore, even with the same visual stimuli, there is a clear discrepancy between the resultant force felt in real space and the resultant force felt in virtual reality, and cyber sickness is induced by this transference illusion.

[0049] In the present invention, acceleration control techniques for visual and kinesthetic senses can be applied to reduce such cyber sickness. In the proposed system (100), regarding limiting walking speed, a motion recognition-based simulator operation standard value (e.g., average 1.4 m / s) can be set based on the average walking speed according to gender and age group.

[0050] FIG. 5 shows positional variables for setting a walking safety range for speed control of the upper drive unit treadmill. As shown in FIG. 5, when the maximum length of the treadmill of the motion plate is S0 and the driving speed is V, the actual walking speed of the user (101) is V P The stride period can be defined as T, the walking danger zone at both ends of the motion base (142) as D, and the safety range from the center position of the treadmill of the motion plate as r.

[0051] In the present invention, a formula for controlling the user (101) walking on the treadmill to be positioned in the center can be defined and solved as shown in FIG. 6. In order to determine the walking range to ensure the stability of the user (101) on a treadmill moving back and forth along the X-axis, the walking danger zone at both ends of the treadmill can be expressed as in the formula (1) for D. A positive sign indicates the front direction relative to the user (101).

[0052] In formula (1), the walking risk section D is the walking speed V of the user (101). P Wow, single stride period T P It can be defined as being shorter than the distance traveled. Equation (2) represents the threshold length of the walking risk zone D. The distance r in Equation (3) is the distance obtained from the Azure Kinect DK, which is the motion detector (130), where S0 is the distance measured based on the pelvis coordinates of the user (101) standing at the center position of the motion base (142), and S is the distance measured by moving one step. p It is defined as follows. Formula (4) is the minimum unit critical distance r driven by the motion base (142) at speed V p When moving for a stride period, the motion base (142) V p It operates at a speed of 0. If it does not meet the critical distance condition for starting operation, the motion base (142) stops operating at a speed of 0.

[0053] Formula (5) can apply a constant average speed when operating the motion base (142) based solely on the position coordinates of the user. Formula (5) is the control speed V of the motion base (142). fixed It represents the average speed V of men and women in their 20s to 50s. avgThe safety range can be specified by fixing the speed at 1.4 m / s. Equation (6) can be defined as the driving walking safety control distance R. According to Equation (6), if the walking danger zone threshold length D0 and the bottom length r are subtracted from the center (L / 2) of the motion base (142), the walking safety range R of the user is obtained. fixed It can be calculated as shown in the following formula (7). Formula (7) represents the walking safety range R of the user in a special case when a constant average speed is applied. fixed It represents.

[0054] The motion base speed control algorithm proposed in the present invention can control the driving speed V of the motion plate treadmill by reflecting the distance of the user from the central position of the motion plate treadmill, which is obtained by Azure Kinect, as the threshold distance r for starting the motion base (142) drive, as shown in FIG. 7. However, as an alternative method, the walking speed V of the user can be controlled by supplementing it as in Equation (8) of FIG. 6. p can be assumed for time t. The experiencer's walking speed V p is one stride T p It follows approximately half the period of the sine function. In this case, V max represents the maximum speed during the swing phase of the gait when the user moves with one stride. V p and V max If the difference between them is small, the maximum speed in the swing phase of the walking experience can be calculated by Equation (9).

[0055] FIG. 8 shows a table of velocity V(r,t) and walking safety control distance R for the user, with respect to the critical distance r and t at which the motion plate treadmill begins to operate. Based on the above velocity and walking safety control distance, according to the present invention, the walking safety distance decreases as the user is closer to the motion sensor (130), but by reflecting the swing phase in the gait, the acceleration is reflected more in the operation of the motion base (142) than in a system where the average speed is applied, thereby obtaining the effect of reducing virtual motion sickness.

[0057] The device described above may be implemented as a hardware component, a software component, and / or a combination of a hardware component and a software component. For example, the device and components described in the embodiments may be implemented using one or more general-purpose or special-purpose computers, such as, for example, a processor, a controller, an arithmetic logic unit (ALU), a digital signal processor, a microcomputer, a field programmable array (FPA), a programmable logic unit (PLU), a microprocessor, or any other device capable of executing and responding to instructions. The processing unit may execute an operating system (OS) and one or more software applications executed on the operating system. Additionally, the processing unit may access, store, manipulate, process, and generate data in response to the execution of the software. For ease of understanding, the processing unit may be described as being used as a single unit, but those skilled in the art will understand that the processing unit may include multiple processing elements and / or multiple types of processing elements. For example, the processing unit may include multiple processors or one processor and one controller. In addition, other processing configurations, such as parallel processors, are also possible.

[0058] Software may include a computer program, code, instructions, or a combination of one or more of these, and may configure a processing unit to operate as desired or instruct the processing unit independently or collectively. Software and / or data may be stored in a storage medium, such as memory, to be interpreted by the processing unit or to provide instructions or data to the processing unit.

[0060] Although the present invention has been described with reference to embodiments illustrated in the drawings, this is merely illustrative, and those skilled in the art will understand that various modifications and equivalent alternative embodiments are possible therefrom. Accordingly, the technical scope of protection of the present invention should be determined by the following claims. Explanation of the symbols

[0062] 100: Underground Utility Tunnel Experience Education System 110: Control PC 120: HMD 130: Motion detector 140: Motion Platform 141: Vertical Drop Device 142: Motion Base 150: Compressor 210: Cylinder 220: Solenoid valve 230: Controller

Claims

Claim 1 An underground utility tunnel experience education system characterized by comprising: a Head Mounted Display (HMD); a motion platform configured to enable the simulation of the underground utility tunnel through 4-degrees of freedom (4-DOF) driving including pitch, roll, heave, and surge; a motion sensor that recognizes motion data including the 3D posture and position of a user; and a control PC that transmits virtual reality content generated through the modeling of the underground utility tunnel to the HMD to visualize the virtual reality content through the HMD, and controls the 4-DOF driving of the motion platform based on the motion data recognized by the motion sensor.

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