A scenario simulation system and test method for autonomous driving of intelligent connected vehicles

Abstract

The present invention relates to the field of autonomous driving test technology, and in particular to a scene simulation system for autonomous driving of intelligent connected vehicles and a test method thereof. The scene simulation system comprises: a main frame is built on a road surface base, and a shielding movable plate is provided on the main frame; a driving device is installed on the main frame, and the driving device is connected to the shielding movable plate, and the driving device is used to drive the shielding movable plate to switch between two states on the main frame; when the shielding movable plate is in a first state, the shielding movable plate is fully unfolded and covers the main frame for tunnel simulation; when the shielding movable plate is in a second state, the shielding movable plate is retracted to the main frame for elevated simulation. This application provides a shielding movable plate that can be retracted, so that a scene simulation system can switch between scenes such as tunnels, without the need for additional investment in the construction of multiple independent simulation scenes, thereby solving the problem of high scene simulation construction costs in related technologies.

Description

Technical Field

[0001] The present invention relates to the field of autonomous driving testing technology, and in particular to a scenario simulation system and a testing method for autonomous driving of an intelligent connected vehicle. Background Art

[0002] In recent years, with the rapid development of intelligent and connected vehicles (ICVs), which have gradually evolved from standalone mechanical units to intelligent and connected vehicles, automotive system security faces new and more serious challenges. To ensure the safety, comfort, agility, and intelligence of ICVs, rigorous and systematic evaluation of their functions and performance is essential before they are put into use.

[0003] To adapt to the technical characteristics of autonomous driving functions in intelligent connected vehicles (ICVs), the domestic and international automotive industries, through years of accumulated technology and experience, have reached a consensus on combining multiple testing methods, including field, road, and simulation, to verify these functions. As a key component of the automated driving function testing methodology, field testing provides corresponding test scenarios, test methods, and passing requirements. The field testing recommended in "GBT41798-2022 Field Test Methods and Requirements for Automated Driving Functions of Intelligent Connected Vehicles" serves only as part of safety verification and sets basic requirements for typical scenarios, roads, and traffic environments within the vehicle's operating range. The standards and test methods for automated driving tests conducted by various domestic companies and groups for intelligent connected vehicles also specify requirements for the conditions and environment of the automated driving test sites. Tunnels and urban elevated roads (with soundproof booths) are both important and complex test scenarios within automated driving test sites.

[0004] Currently, the relevant technologies for autonomous driving scenarios in urban elevated roads (with soundproof booths) and tunnels require each company to build real urban elevated and tunnel scenarios based on actual conditions. The tunnel scenarios are based on actual tunnel construction on public roads, and their construction costs and requirements are very high. Some companies, after applying for permission to conduct autonomous driving road tests, conduct autonomous driving tests in urban elevated and tunnel scenarios on actual public roads. Building completely according to real scenarios is costly; testing on public roads is also risky because autonomous driving vehicles are experimental products before they are launched on the market. Testing on public roads carries the risk of loss of control and poses safety hazards. Summary of the Invention

[0005] Regarding related technologies, the testing of the autonomous driving functions of intelligent connected vehicles requires simulation of tunnels and urban elevated roads, but the construction costs and requirements of the two scene simulations are very high, resulting in the problem of excessive testing investment.

[0006] In a first aspect, an embodiment of the present application provides a scenario simulation system for autonomous driving of an intelligent connected vehicle, comprising: a road surface base, a main frame, and a drive device; wherein,

[0007] a main frame, which is constructed on the road surface base and is provided with a shielding movable plate; a driving device, which is installed on the main frame and is connected to the shielding movable plate, and is used to drive the shielding movable plate to switch between two states on the main frame;

[0008] When the shielding movable plate is in the first state, the shielding movable plate is fully unfolded and covers the main frame for use in tunnel simulation;

[0009] When the shielding movable plate is in the second state, the shielding movable plate is retracted to the main frame for use in overhead simulation.

[0010] In conjunction with the first aspect, in one embodiment, the main frame includes:

[0011] A side wall frame is constructed on the road surface base, and a first guide rail for the shielding movable plate to move is provided on the side wall frame;

[0012] A top frame is built on the side wall frame, and a second guide rail for the shielding movable plate to move is installed on the top frame.

[0013] In combination with the first aspect, in one embodiment, the shielding movable plate includes:

[0014] a side wall shielding coil, which is installed on the first guide rail, and the side wall shielding coil is connected to the driving device;

[0015] a top shielding coil mounted on the second guide rail, the top shielding coil being connected to the driving device;

[0016] The driving device is used to drive the side wall shielding coil and the top shielding coil to expand or contract on the first guide rail and the second guide rail respectively.

[0017] In combination with the first aspect, in one embodiment, the driving device includes:

[0018] A side rolling curtain motor is installed on the side wall frame, and the side rolling curtain motor is connected to the side wall shielding coil;

[0019] A top drive motor is installed on the arc top of the top frame, and the top drive motor is connected to the top shielding coil.

[0020] In combination with the first aspect, in one embodiment, the shielding movable plate includes: a tin foil shielding plate or an aluminum foil modified shielding plate.

[0021] In combination with the first aspect, in one embodiment, a sound insulation board is laid on the main frame.

[0022] In combination with the first aspect, in one embodiment, a sunshade is provided on the main frame.

[0023] In combination with the first aspect, in one embodiment, the pavement base includes: a lime-improved soil subbase; a cement-stabilized gravel base layer, which is laid on the lime-improved soil subbase; a coarse-grained asphalt concrete layer, which is laid on the cement-stabilized gravel base layer; and a fine-grained modified asphalt concrete base layer, which is laid on the coarse-grained asphalt concrete layer.

[0024] In combination with the first aspect, in one embodiment, the present invention further includes: a remote control module, which is connected to the driving device signal, and the remote control module is used to drive the driving device to drive the shielding movable plate to switch between two states.

[0025] In a second aspect, an embodiment of the present application provides a testing method using any of the above scenario simulation systems, comprising:

[0026] Acquire test requirement information, and control the driving device to drive the shielding movable plate to move according to the test requirement information; wherein,

[0027] When a tunnel test requirement is obtained, the driving device is controlled to drive the shielding movable panel to be fully unfolded to cover the surface of the main frame;

[0028] When the urban elevated functional test requirements are obtained, the driving device is controlled to drive the shielding movable plate to be retracted back into the main frame.

[0029] The beneficial effects of the technical solutions provided in the embodiments of the present application include at least:

[0030] This application sets up a movable and retractable shielding movable plate, so that a scene simulation system can switch between scenes such as tunnels, without the need for additional investment in the construction of multiple independent simulation scenes, thereby solving the problem of high scene simulation construction costs in related technologies. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0032] Figure 1 A cross-sectional view of the scene simulation system in the main viewing direction in an embodiment of the present application;

[0033] Figure 2 A cross-sectional view of the scene simulation system in the embodiment of the present application from the side;

[0034] Figure 3 This is a structural diagram of the scene simulation system in an embodiment of the present application.

[0035] In the figure: 1. Pavement base; 2. Main frame; 21. Side wall frame; 211. First guide rail; 22. Top frame; 221. Second guide rail; 23. Sound insulation board; 3. Driving device; 31. Side roller shutter motor; 32. Top driving motor; 4. Shielding movable plate; 41. Side wall shielding coil; 42. Top shielding coil; 43. Reel. DETAILED DESCRIPTION

[0036] In order to enable those skilled in the art to better understand the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0037] Regarding related technologies, the testing of the autonomous driving functions of intelligent connected vehicles requires simulation of tunnels and urban elevated roads, but the construction costs and requirements of the two scene simulations are very high, resulting in the problem of excessive testing investment.

[0038] First, as Figure 1 and Figure 2 As shown, the present application provides a scenario simulation system for automatic driving of an intelligent connected vehicle, which includes: a road surface base 1, a main frame 2, and a drive device 3; wherein,

[0039] a main frame 2, which is constructed on the road base 1, and is provided with a shielding movable plate 4 on the main frame 2; a driving device 3, which is installed on the main frame 2, the driving device 3 being connected to the shielding movable plate 4, and the driving device 3 being used to drive the shielding movable plate 4 to switch between two states on the main frame 2;

[0040] When the shielding movable plate 4 is in the first state, the shielding movable plate 4 is fully unfolded and covers the main frame 2 for tunnel simulation; when the shielding movable plate 4 is in the second state, the shielding movable plate 4 is retracted to the main frame 2 for elevated simulation.

[0041] Optionally, the main frame 2 adopts a steel frame structure.

[0042] It is worth noting that the scenario simulation system for autonomous driving of intelligent connected vehicles in this application can switch between two states. In the first state, the shielding plate 4 is fully extended to cover the surface of the main steel frame 2, thereby achieving the scene shielding function. In this way, the shielding plate 4 and the road surface base 1 form a test area, simulating a real tunnel scene for scenario testing of the autonomous driving function of intelligent connected vehicles. Furthermore, in the second state, the shielding plate 4 is retracted, and the test area no longer has the signal shielding function, allowing simulation of urban elevated roads or other scenarios.

[0043] In some specific embodiments, Figure 3 As shown, the main frame 2 includes: a side wall frame 21 and a top frame 22; wherein,

[0044] The side wall frame 21 is built on the road surface base 1, and the side wall frame 21 is provided with a first guide rail 211 for moving the shielding movable plate 4; the top frame 22 is built on the side wall frame 21, and the top frame 22 is provided with a second guide rail 221 for moving the shielding movable plate 4.

[0045] In some preferred embodiments, the shielding movable plate 4 is made of shielding coiled material, which is easy to roll up and can be flexibly unfolded and retracted.

[0046] In combination with the above preferred embodiments, in some implementation methods, the shielding movable plate 4 includes: a side wall shielding coil 41 and a top shielding coil 42; wherein,

[0047] The side wall shielding coil 41 is mounted on the first guide rail 211 and is connected to the driving device 3. The top shielding coil 42 is mounted on the second guide rail 221 and is connected to the driving device 3. The driving device 3 is used to drive the side wall shielding coil 41 and the top shielding coil 42 to expand or contract on the first guide rail 211 and the second guide rail 221, respectively.

[0048] In some optional embodiments, both the sidewall shielding coil 41 and the top shielding coil 42 include a reel 43, a bearing block, and the coil. The bearing blocks are mounted at both ends of the first guide rail 211 or the second guide rail 221, and the reel 43 is mounted on the bearing blocks. The reel 43 is used to bundle the coils, and the reels 43 of the sidewall shielding coil 41 and the top shielding coil 42 are located on the sidewall frame 21 and the top frame 22, respectively.

[0049] Furthermore, the driving device 3 includes: a side roller blind motor 31 and a top driving motor 32;

[0050] The side roller shutter motor 31 is installed on the side wall frame 21 , and the side roller shutter motor 31 is connected to the side wall shielding coil 41 ; the top drive motor 32 is installed on the arc top of the top frame 22 , and the top drive motor 32 is connected to the top shielding coil 42 .

[0051] It is understood that the use of the side curtain motor 31 and the top drive motor 32 to independently control the side wall shielding coil 41 and the top shielding coil 42 improves the efficiency and speed of scene switching. On the other hand, testers can also change the test scene according to test needs to meet different test requirements.

[0052] In some preferred embodiments, the top frame 22 is an arc-shaped structure, and two sets of top drive motors 32 and top shielding coils 42 are provided on the top of the top frame 22. The reels 43 of the two top shielding coils 42 are both provided at the top, and the coils are unfolded from the top of the top frame 22 to both sides to complete the complete coverage of the top frame 22.

[0053] In some optional embodiments, the shielding movable plate 4 includes: a tin foil shielding plate or an aluminum foil modified shielding plate.

[0054] It is understood that the shielding movable plate 4 can be made of improved flexibility and durability. Furthermore, in order to meet the different shielding capabilities required by autonomous driving, different shielding coils can be selected to achieve multi-adaptive functions.

[0055] Furthermore, in order to simulate an urban elevated road, auxiliary facilities are provided on the main frame 2. Specifically, the auxiliary facilities include a sound insulation board 23 and a sunshade board provided on the main frame 2.

[0056] It should be noted that this application only simulates the urban elevated test through the sound insulation board 23 and the sunshade. Testers can simulate other types of test areas by setting up different auxiliary facilities.

[0057] In some optional embodiments, in order to better simulate the actual scene, the pavement base 1 of the present application is an asphalt concrete pavement. Specifically, the pavement base 1 includes: a lime-improved soil subbase, a cement-stabilized crushed stone subbase, a coarse-grained asphalt concrete layer, and a fine-grained modified asphalt concrete base layer; wherein,

[0058] A cement-stabilized crushed stone base layer is laid on the lime-improved soil subbase layer; a coarse-grained asphalt concrete layer is laid on the cement-stabilized crushed stone base layer; and a fine-grained modified asphalt concrete base layer is laid on the coarse-grained asphalt concrete layer.

[0059] Some preferred embodiments further include: a remote control module, which is connected to the driving device 3 by signal, and the remote control module is used to drive the driving device 3 to drive the shielding movable plate 4 to switch between two states.

[0060] It is understood that during testing, based on the needs of the intelligent connected autonomous driving test scenario, the remote control module can be used to select the tunnel scenario adapter function. The control motor of the drive device 3 will then unroll the shielding coil, realizing the shielding function of the autonomous driving tunnel scenario. This will then allow the autonomous driving test tunnel scenario to be tested. Alternatively, the remote control module can be used to select the city elevated road adapter function. The drive device 3 will then reel in the shielding coil, realizing the simulated city elevated road scenario of the autonomous driving test, thus allowing the autonomous driving test city elevated road scenario to be tested.

[0061] Furthermore, the present application provides a specific embodiment of a method for manufacturing the above-mentioned scenario simulation system for autonomous driving of an intelligent connected vehicle, which comprises the following steps:

[0062] Step S1: constructing a main frame 2 of a tunnel / urban elevated road. The main frame 2 is made into a height of 5 m, a width of 10 m, and a length of 100 m.

[0063] In some specific embodiments, as shown in the figure, the main frame 2 includes: a side wall frame 21 and a top frame 22; wherein,

[0064] The side wall frame 21 is built on the road surface base 1, and the side wall frame 21 is provided with a first guide rail 211 for moving the shielding movable plate 4; the top frame 22 is built on the side wall frame 21, and the top frame 22 is provided with a second guide rail 221 for moving the shielding movable plate 4.

[0065] Step S2: Complete the construction and maintenance of the pavement base 1.

[0066] Specifically, the pavement base 1 includes: a lime-modified soil subbase, a cement-stabilized crushed stone subbase, a coarse-grained asphalt concrete layer, and a fine-grained modified asphalt concrete base layer; wherein,

[0067] A cement-stabilized crushed stone base layer is laid on the lime-improved soil subbase layer; a coarse-grained asphalt concrete layer is laid on the cement-stabilized crushed stone base layer; and a fine-grained modified asphalt concrete base layer is laid on the coarse-grained asphalt concrete layer.

[0068] Furthermore, the multi-layered pavement base 1 comprises: a first layer of 5 cm of fine-grained modified asphalt concrete. The asphalt material shall be road petroleum asphalt and shall comply with Table 4.2.1-2 <Technical Requirements for Road Petroleum Asphalt> of the "Technical Specifications for Highway Asphalt Pavement Construction" (JTG F40-2004), with the asphalt grade selected being AH-70. Fine aggregate: The fine aggregate for the asphalt surface layer may be natural sand, machine-made sand, or stone chips, and their specifications shall comply with Table 4.9.3 "Specifications for Natural Sand for Asphalt Mixtures" and Table 4.9.4 of JTG F40-2004, respectively. The second layer is 8 cm of coarse-grained asphalt concrete (AC-25c). The asphalt material shall be road petroleum asphalt and shall comply with Table 4.2.1-2 <Technical Requirements for Road Petroleum Asphalt> of the "Technical Specifications for Highway Asphalt Pavement Construction" (JTG F40-2004), with the asphalt grade selected being AH-70. Coarse aggregate: The particle size specifications of coarse aggregate should be selected in accordance with Table 4.8.3, "Specifications for Coarse Aggregates for Asphalt Mixtures," of JTG F40-2004. The quality of coarse aggregate should comply with Table 4.8.2, "Technical Requirements for Coarse Aggregates for Asphalt Mixtures," of JTG F40-2004. The third layer should be a 20cm thick base layer of 5% cement-stabilized crushed stone. Use 32.5R Portland cement. The unconfined compressive strength of the cement-stabilized crushed stone (dense skeleton type) at 7 days must be ≥3.0 MPa, and the compaction level must be ≥98%. The fourth layer should be a 20cm thick base layer of 4% cement-stabilized crushed stone. Use 32.5R Portland cement. The unconfined compressive strength of the cement-stabilized crushed stone (dense skeleton type) at 7 days must be ≥3.0 MPa, and the compaction level must be ≥98%. The fifth layer should be a 40cm thick subbase layer of 8% lime-amended soil.

[0069] Step S3: Install auxiliary facilities on the main frame 2 of the steel structure.

[0070] Specifically, the auxiliary facilities include sunshades, sound insulation panels 23 (or other devices providing sound barriers).

[0071] Step S4, install the drive device 3 and the shielding movable plate 4 in the form of a coil on the main frame 2; if the autonomous driving test needs to be tested in an urban elevated scene, the drive device 3 will roll up the shielding coil of the shielding movable plate 4 (similar to a roller shutter structure). If the autonomous driving test needs to be tested in a tunnel scene, the shielding coil of the shielding movable plate 4 is spread out to fully cover the main frame 2 through the drive device 3 to achieve the shielding function of the scene. Among them, the shielding coil can be made of modified tin foil or aluminum foil with improved flexibility and good durability. At the same time, different shielding coils can be selected according to the shielding capability required by the autonomous driving. In order to achieve multi-adaptability functions.

[0072] In a second aspect, the present application provides a testing method using the scenario simulation system as described in any one of the above embodiments, comprising:

[0073] Acquire test requirement information, and control the driving device 3 to drive the shielding movable plate 4 to move according to the test requirement information; when the tunnel test requirement is obtained, control the driving device 3 to drive the shielding movable plate 4 to unfold to cover the surface of the main frame 2; when the urban elevated function test requirement is obtained, control the driving device 3 to drive the shielding movable plate 4 to retract into the main frame 2.

[0074] It is worth noting that by selecting the tunnel adaptation function via the remote control module, the drive device 3 will unroll the shielding coil, realizing the shielding function of the autonomous driving tunnel scene. This allows for autonomous driving tunnel scene testing. By selecting the city elevated road adaptation function via the remote control module, the drive device will reel in the shielding coil, realizing the simulated city elevated road scene, allowing for autonomous driving city elevated road scene testing.

[0075] In summary, this application sets a movable and retractable shielding movable plate so that a scene simulation system can switch between scenes such as tunnels, without the need for additional investment in the construction of multiple independent simulation scenes, thereby solving the problem of high scene simulation construction costs in related technologies. Furthermore, this application can quickly and efficiently produce urban elevated / tunnel scenes for autonomous driving. In addition, the scene simulation system of this application has multiple applicability and can meet the switching of various autonomous driving test scenarios through a remote control module; the construction cost is cheaper than the form of fully building a formal tunnel (reinforced concrete + earthwork cover). It has a wide range of applicability, and different shielding materials can be replaced according to different shielding signal requirements to meet the test needs of different shielding signals.

[0076] In the description of this application, it should be noted that the terms "upper" and "lower" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application. Unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be internal communication between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to the specific circumstances.

[0077] It should be noted that, in this application, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprising a ..." does not exclude the presence of other identical elements in the process, method, article or device comprising the element.

[0078] The foregoing is merely a list of specific embodiments of the present application, intended to enable those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application is not limited to the embodiments shown herein, but is intended to conform to the broadest scope consistent with the principles and novel features of the present application.

Claims

1. A scenario simulation system for autonomous driving of intelligent connected vehicles, characterized in that: include: Pavement base (1); A main frame (2) is built on the road surface base (1), and a shielding movable plate (4) is provided on the main frame (2); a driving device (3) mounted on the main frame (2), the driving device (3) being connected to the shielding movable plate (4), and the driving device (3) being used to drive the shielding movable plate (4) to switch between two states on the main frame (2); When the shielding movable plate (4) is in the first state, the shielding movable plate (4) is fully unfolded and covers the main frame (2) for use in tunnel simulation; When the shielding movable plate (4) is in the second state, the shielding movable plate (4) is retracted to the main frame (2) for use in overhead simulation.

2. The scene simulation system according to claim 1, wherein: The main frame (2) comprises: A side wall frame (21) is built on the road surface base (1), and a first guide rail (211) for the shielding movable plate (4) to move is provided on the side wall frame (21); A top frame (22) is built on the side wall frame (21), and a second guide rail (221) for the shielding movable plate (4) to move is installed on the top frame (22).

3. The scenario simulation system according to claim 2, wherein: The shielding movable plate (4) comprises: A side wall shielding coil (41) is mounted on the first guide rail (211), and the side wall shielding coil (41) is connected to the driving device (3); A top shielding coil (42) is mounted on the second guide rail (221), and the top shielding coil (42) is connected to the driving device (3); The driving device (3) is used to drive the side wall shielding coil (41) and the top shielding coil (42) to expand or contract on the first guide rail (211) and the second guide rail (221) respectively.

4. The scenario simulation system according to claim 3, wherein: The driving device (3) comprises: A side rolling curtain motor (31) is mounted on the side wall frame (21), and the side rolling curtain motor (31) is connected to the side wall shielding coil (41); A top drive motor (32) is installed on the arc top of the top frame (22), and the top drive motor (32) is connected to the top shielding coil (42).

5. The scene simulation system according to claim 1, wherein: The shielding movable plate (4) comprises: a tin foil shielding plate or an aluminum foil modified shielding plate.

6. The scene simulation system according to claim 1, wherein: A sound insulation board (23) is laid on the main frame (2).

7. The scenario simulation system according to claim 1, wherein: A sunshade is provided on the main frame (2).

8. The scene simulation system according to claim 1, wherein: The road surface base (1) comprises: lime-amended soil subbase; a cement-stabilized crushed stone base layer, which is laid on the lime-improved soil subbase; a coarse-grained asphalt concrete layer, which is laid on the cement-stabilized crushed stone base; The fine-grained modified asphalt concrete base layer is laid on the coarse-grained asphalt concrete layer.

9. The scenario simulation system according to claim 1, wherein: Also includes: A remote control module is connected to the drive device (3) via a signal, and the remote control module is used to drive the drive device (3) to drive the shielding movable plate (4) to switch between two states.

10. A testing method using the scenario simulation system according to claim 1, characterized in that: include: Acquiring test requirement information, and controlling a driving device (3) to drive a shielding movable plate (4) to move according to the test requirement information; wherein, When a tunnel test requirement is obtained, the driving device (3) is controlled to drive the shielding movable plate (4) to fully unfold so as to cover the surface of the main frame (2); When the urban elevated functional test requirements are obtained, the driving device (3) is controlled to drive the shielding movable plate (4) to retract into the main frame (2).

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