Electronically controlled braking systems and driverless wide-body vehicles

Abstract

The present invention provides an electric control braking system and an unmanned wide-body vehicle, the electric control braking system comprising a front electric proportional relay valve, a middle and rear electric proportional relay valve and a two-position three-way solenoid valve; the front electric proportional relay valve and the middle and rear electric proportional relay valve are connected to an air reservoir and a front brake air chamber, and are used to inflate the corresponding brake air chamber with a corresponding air pressure through the air reservoir when a brake current signal is received, and release the air in the corresponding brake air chamber when a release current signal is received; the two-position three-way solenoid valve is connected to an air reservoir and a parking relay valve, and is used to control the parking relay valve to exhaust the parking air chamber when a parking command is received, and inflate the parking relay valve through the air reservoir when a parking release command is received, so that the parking relay valve inflates the parking air chamber. The present invention can realize autonomous braking, parking and emergency braking of an unmanned wide-body vehicle, or accept braking, parking and emergency braking control from a remote end.

Description

Technical Field

[0001] The present invention relates to the field of unmanned wide-body vehicles, and in particular to an electric control braking system and an unmanned wide-body vehicle. Background Art

[0002] In response to the current problems of low production efficiency and frequent safety accidents in mining areas, mining areas tend to use unmanned wide-body vehicles for operations. The current unmanned driving system for mining lacks effective electronically controlled autonomous braking solutions and electronically controlled autonomous parking solutions. Summary of the invention

[0003] In view of the above problems, the present invention provides an electric control braking system and an unmanned wide-body vehicle to achieve autonomous braking, parking and emergency braking of the unmanned wide-body vehicle, or accept autonomous braking, parking and emergency braking control from a remote end.

[0004] In order to achieve the above object, the present invention adopts the following technical solution:

[0005] An electric control brake system comprises a front electric proportional relay valve, a middle and rear electric proportional relay valve and a two-position three-way solenoid valve;

[0006] The front electric proportional relay valve is connected to the air reservoir and the front brake air chamber, and is used to inflate the front brake air chamber with corresponding air pressure through the air reservoir when receiving a brake current signal, and release the air in the front brake air chamber when receiving a release current signal;

[0007] The middle and rear electric proportional relay valve is connected to the air reservoir and the middle and rear brake air chamber, and is used to inflate the middle and rear brake air chamber with a corresponding air pressure through the air reservoir when a brake current signal is received, and release the air in the middle and rear brake air chamber when a release current signal is received;

[0008] The two-position three-way solenoid valve is connected to the air reservoir and the parking relay valve, and is used to control the parking relay valve to exhaust the parking air chamber when a parking command is received, and to inflate the parking relay valve through the air reservoir when a parking release command is received, so that the parking relay valve can inflate the parking air chamber.

[0009] Preferably, in the electronically controlled braking system, the front electric proportional relay valve and the middle and rear electric proportional relay valve are also connected to the brake foot valve to receive the control signal of the brake foot valve, and to inflate the front brake air chamber and the middle and rear brake air chamber with an air pressure corresponding to the control signal through the air reservoir.

[0010] Preferably, the electric control braking system further includes a vehicle controller;

[0011] The vehicle controller is connected to the front electric proportional relay valve and the middle and rear electric proportional relay valves, and is used to generate a braking current signal according to a current driving speed and a target speed.

[0012] Preferably, in the electric control braking system, the vehicle controller is also used to send a braking current signal when it is determined that the difference between the current driving speed and the target speed is greater than a preset value, and to send a release current signal to the front electric proportional relay valve and the middle and rear electric proportional relay valve after the current driving speed is equal to the target speed.

[0013] Preferably, in the electric control braking system, the current value of the release current signal is zero.

[0014] Preferably, in the electric control braking system, the two-position three-way solenoid valve comprises an air inlet, an air outlet and an exhaust port;

[0015] The air inlet is used to be connected to the air storage cylinder;

[0016] The air outlet is used to be connected to the parking relay valve.

[0017] Preferably, in the electronically controlled braking system, when the parking command is received, the air inlet is closed, the exhaust port and the air outlet are opened, and the exhaust port is connected to the air outlet, so that the parking relay valve exhausts the parking air chamber.

[0018] Preferably, in the electronically controlled braking system, when the parking release command is received, the exhaust port is closed, the air inlet and the air outlet are opened, and the air inlet is connected to the air outlet, so that the air tank inflates the parking relay valve and the parking air chamber.

[0019] Preferably, in the electric control braking system, the two-position three-way solenoid valve is also connected to a parking switch to receive a control signal of the parking switch to perform a parking operation or a parking release operation.

[0020] An unmanned wide-body vehicle comprises the above-mentioned electric control braking system.

[0021] The present invention provides an electronically controlled braking system, which comprises a front electric proportional relay valve, a middle and rear electric proportional relay valve and a two-position three-way solenoid valve; the front electric proportional relay valve is connected to an air reservoir and a front brake air chamber, and is used for inflating the front brake air chamber with a corresponding air pressure through the air reservoir when a braking current signal is received, and releasing the air in the front brake air chamber when a release current signal is received; the middle and rear electric proportional relay valve is connected to an air reservoir and a middle and rear brake air chamber, and is used for inflating the middle and rear brake air chamber with a corresponding air pressure through the air reservoir when a braking current signal is received, and releasing the air in the middle and rear brake air chamber when a release current signal is received; the two-position three-way solenoid valve is connected to an air reservoir and a parking relay valve, and is used for controlling the parking relay valve to exhaust the parking air chamber when a parking command is received, and inflating the parking relay valve through the air reservoir when a parking release command is received. The electric control braking system of the present invention, by arranging an electric proportional relay valve and a two-position three-way solenoid valve in the mining vehicle, can perform braking and parking operations of the mining vehicle by means of an electric control braking signal, thereby realizing autonomous braking, parking and emergency braking of the unmanned wide-body vehicle, or accepting braking, parking and emergency braking control from a remote end.

[0022] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solution of the present invention, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope of protection of the present invention. In each of the drawings, similar components are numbered similarly.

[0024] Figure 1 is a schematic structural diagram of an electric control braking system provided by Embodiment 1 of the present invention;

[0025] Figure 2 is a schematic diagram of a current-air pressure characteristic curve provided in Example 1 of the present invention;

[0026] Figure 3 is a schematic structural diagram of another electric control braking system provided in Example 1 of the present invention;

[0027] Figure 4 is a schematic structural diagram of an electric control braking system provided by Embodiment 2 of the present invention;

[0028] Figure 5 It is a schematic diagram of the structure of an electric control braking system provided in Example 3 of the present invention. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0030] The components of the embodiments of the present invention generally described and shown in the drawings herein may be arranged and designed in a variety of different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0031] Hereinafter, the terms "including", "having" and their cognates, which may be used in various embodiments of the present invention, are intended only to indicate specific features, numbers, steps, operations, elements, components or combinations of the foregoing items, and should not be understood as first excluding the existence of one or more other features, numbers, steps, operations, elements, components or combinations of the foregoing items or adding the possibility of one or more features, numbers, steps, operations, elements, components or combinations of the foregoing items.

[0032] Furthermore, the terms “first”, “second”, “third”, etc. are merely used for distinguishing descriptions and are not to be understood as indicating or implying relative importance.

[0033] Unless otherwise defined, all terms (including technical terms and scientific terms) used herein have the same meanings as those generally understood by those skilled in the art to which the various embodiments of the present invention belong. The terms (such as those defined in generally used dictionaries) will be interpreted as having the same meanings as the contextual meanings in the relevant technical field and will not be interpreted as having idealized meanings or overly formal meanings unless clearly defined in the various embodiments of the present invention.

[0034] Example 1

[0035] Figure 1 It is a structural schematic diagram of an electric control braking system provided in Example 1 of the present invention.

[0036] The electric control brake system 100 includes a front electric proportional relay valve 110 connected to the air reservoir 101 and the front brake air chamber 102, a middle and rear electric proportional relay valve 120 connected to the air reservoir 101 and the middle and rear brake air chamber 103, and a two-position three-way solenoid valve 130 connected to the air reservoir 101 and the parking relay valve 104;

[0037] In the embodiment of the present invention, the wide-body mining vehicle generally adopts the traditional pneumatic brake. In order to realize the unmanned driving mode of the mining vehicle, that is, to build the mining vehicle into an unmanned wide-body vehicle, an electric proportional relay valve can be added to the original manual braking pneumatic brake system to realize the electric signal control. Specifically, in the traditional pneumatic brake system, the front axle service brake includes an air reservoir 101, a brake foot valve and a front brake air chamber 102. When braking, the high-pressure air in the air reservoir 101 is input into the front brake air chamber 102 at a certain proportion of pressure by triggering the foot valve, thereby generating a braking force. When the brake is released, the high-pressure air in the front brake air chamber 102 is released.

[0038] In an embodiment of the present invention, a front electric proportional relay valve 110 can be added to the original pneumatic brake system. The front electric proportional relay valve 110 is directly connected to the air reservoir 101 and the front brake air chamber 102. After receiving a braking command, the high-pressure air in the air reservoir 101 can be input into the front brake air chamber 102, thereby generating a braking force. The braking command is generated by an upper-level controller of the unmanned wide-body vehicle. Specifically, it is usually a current signal. After receiving the current signal, the front electric proportional relay valve 110 can input air of corresponding pressure into the front brake air chamber 102 according to the current value of the current signal. The current-air pressure characteristic curve of the front electric proportional relay valve 110 can be shown as follows. Figure 2 shown. Figure 2 This is only one of the current-pressure characteristic curves provided in this application. Other current-pressure characteristic curves may be provided according to the system current range of the unmanned wide-body vehicle and the upper limit of the pressure of the front brake air chamber 102. This is not limited here. Moreover, when the current value is lower than 375mA, the pressure value output by the front electric proportional relay valve 110 is zero, that is, the current signal with a current value lower than 375mA may be used as a release current signal for releasing the braking force.

[0039] The front electric proportional relay valve 110 is used to inflate the front brake air chamber 102 with corresponding air pressure through the air reservoir 101 when receiving a brake current signal, and release the air in the front brake air chamber 102 when receiving a release current signal;

[0040] In an embodiment of the invention, a plurality of air cylinders 101 may be provided simultaneously in an unmanned wide-body vehicle, the air in the air cylinder 101 being air processed by an air compressor and having a certain air pressure. After being connected to the front electric proportional relay valve 110, the front electric proportional relay valve 110 can input the gas in the air cylinder 101 into the front brake air chamber 102 by controlling the connection with the front brake air chamber 102, and the air pressure can also be controlled during the input process, and the upper limit of the air pressure is the air pressure value in the air cylinder 101.

[0041] The middle and rear electric proportional relay valve 120 is used to inflate the middle and rear brake air chamber 103 with corresponding air pressure through the air reservoir 101 when receiving a brake current signal, and release the air in the middle and rear brake air chamber 103 when receiving a release current signal;

[0042] Similarly, in a traditional pneumatic brake system, a mechanical relay valve is also provided between the middle and rear brake air chamber 103 and the air reservoir 101. The main function of the mechanical relay valve is to control the input of high-pressure air into the brake air chamber at a certain pressure ratio and to accelerate the action of the gas.

[0043] In an embodiment of the present invention, the mechanical relay valve can be replaced by a center-rear electric proportional relay valve 120, which is directly connected to the air reservoir 101 and the center-rear brake air chamber 103. After receiving a braking command, the high-pressure air in the air reservoir 101 can be input into the center-rear brake air chamber 103, thereby generating a braking force. The braking command is generated by an upper-level controller of the unmanned wide-body vehicle, specifically, it can be a current signal, and after receiving the current signal, the center-rear electric proportional relay valve 120 can input air of corresponding pressure into the center-rear brake air chamber 103 according to the current value of the current signal. The current-air pressure characteristic curve of the center-rear electric proportional relay valve 120 can also be as shown below. Figure 2 When the current value is lower than 375 mA, the air pressure value output by the middle and rear electric proportional relay valve 120 is zero, that is, the current signal with a current value lower than 375 mA can be used as a release current signal to release the braking force of the middle and rear brake air chamber 103 .

[0044] In the embodiment of the present invention, the front electric proportional relay valve 110 and the middle and rear electric proportional relay valve 120 can be connected to the same air reservoir 101 to transmit the gas in the air reservoir 101 to the front brake air chamber 102 and the middle and rear brake air chamber 103. However, in order to further improve the braking efficiency, two air reservoirs 101 can be provided in the unmanned wide-body vehicle and respectively connected to the front electric proportional relay valve 110 and the middle and rear electric proportional relay valve 120. In addition, the front electric proportional relay valve 110 and the middle and rear electric proportional relay valve 120 can simultaneously receive the braking current signal of the same current value to perform simultaneous braking control, or can receive the braking current signal of different current values, so as to perform different braking modes according to different scenarios, which is not limited here.

[0045] The two-position three-way solenoid valve 130 is used to control the parking relay valve 104 to exhaust the parking air chamber when receiving a parking command, and to inflate the parking relay valve 104 through the air reservoir 101 when receiving a parking release command, so that the parking relay valve 104 can inflate the parking air chamber.

[0046] In a conventional pneumatic brake system, when parking, a user triggers the parking manual valve, which controls the parking relay valve 104 to discharge the gas in the parking air chamber, and then generates a parking force. When parking is released, a user triggers the parking manual valve, which controls the parking relay valve 104 to fill the gas in the air reservoir 101 into the parking air chamber, thereby releasing the parking force.

[0047] In the embodiment of the present invention, a two-position three-way solenoid valve 130 is added between the gas reservoir 101 and the parking air chamber, so as to achieve the purpose of electronically controlled parking. When receiving a parking command or an emergency braking command, the two-position three-way solenoid valve 130 can discharge the gas in the parking air chamber, thereby generating a parking force.

[0048] In the embodiment of the present invention, by providing an electric proportional relay valve and a two-position three-way solenoid valve in the mining vehicle, the braking and parking operations of the mining vehicle can be performed by means of electrical control, thereby realizing unmanned driving of the mining vehicle, allowing the unmanned wide-body vehicle to perform autonomous braking and parking, or accept braking control and parking control from a remote end.

[0049] Figure 3 It is a schematic structural diagram of another electric control braking system provided in Example 1 of the present invention.

[0050] In the embodiment of the present invention, the front electric proportional relay valve 110 and the middle and rear electric proportional relay valve 120 are also connected to the brake foot valve 105 to receive the control signal of the brake foot valve 105, and to inflate the front brake air chamber 102 and the middle and rear brake air chamber 103 with the air pressure corresponding to the control signal through the air reservoir 101. That is, the unmanned wide-body vehicle still retains the mechanical brake foot valve 105, so that when the unmanned wide-body vehicle enters the manual driving mode, the driver can control the electric proportional relay valve through the brake foot valve 105, and the brake foot valve 105 can generate a current value signal, for example, after the driver steps on the brake foot valve 105, the brake foot valve 105 can generate a current signal of a corresponding current value according to the degree of stepping and send it to the front electric proportional relay valve 110 and the middle and rear electric proportional relay valve 120, so as to control the electric proportional relay valve to input the brake gas into the brake air chamber. In addition, the electric proportional relay valve can also retain the mechanical part of the relay valve. In the manual driving mode, the driver controls the triggering of the brake foot valve 105 by stepping on the brake pedal to achieve air pressure control of the electric proportional relay valve, thereby controlling the electric proportional relay valve to input brake gas into the brake air chamber.

[0051] In the embodiment of the present invention, the two-position three-way solenoid valve 130 is also connected to the parking switch 106 to receive the control signal of the parking switch 106 to perform parking operation or parking release operation. That is, the unmanned wide-body vehicle also retains the mechanical parking switch 106, such as a parking manual valve, which can control the two-position three-way solenoid valve 130 to perform parking or release operation through a current signal.

[0052] Example 2

[0053] Figure 4 It is a structural schematic diagram of an electric control braking system provided in Example 2 of the present invention.

[0054] The electric control brake system 200 includes a front electric proportional relay valve 210 connected to the air reservoir and the front brake air chamber, a middle and rear electric proportional relay valve 220 connected to the air reservoir and the middle and rear brake air chamber, and a two-position three-way solenoid valve 230 connected to the air reservoir and the parking relay valve;

[0055] The front electric proportional relay valve 210 is used to inflate the front brake air chamber with corresponding air pressure through the air reservoir when receiving a brake current signal, and release the air in the front brake air chamber when receiving a release current signal;

[0056] The middle and rear electric proportional relay valve 220 is used to inflate the middle and rear brake air chamber with corresponding air pressure through the air reservoir when receiving a brake current signal, and release the air in the middle and rear brake air chamber when receiving a release current signal;

[0057] The two-position three-way solenoid valve 230 is used to control the parking relay valve to exhaust the parking air chamber when receiving a parking command, and to inflate the parking relay valve through an air reservoir when receiving a parking release command.

[0058] The electric control braking system 200 further includes a vehicle controller 240;

[0059] The vehicle controller 240 is connected to the front electric proportional relay valve 210 and the middle and rear electric proportional relay valves 220 and is used to generate a braking current signal according to a current driving speed and a target speed.

[0060] In the embodiment of the present invention, the vehicle controller 240 is electrically connected to the upper controller of the unmanned wide-body vehicle, and is electrically connected to the front electric proportional relay valve 210 and the middle and rear electric proportional relay valve 220, so as to receive the target speed of the unmanned wide-body vehicle sent by the upper controller, and detect the current driving speed of the unmanned wide-body vehicle through sensors, and judge whether to perform braking or parking operation according to the target speed and the driving speed. When braking operation is required, a corresponding current signal can be generated to the front electric proportional relay valve 210 and the middle and rear electric proportional relay valve 220 to perform braking operation. In addition, the vehicle controller 240 can also be connected to the two-position three-way solenoid valve 230, and when parking operation is required, a current signal can also be generated to the two-position three-way solenoid valve 230 to perform parking operation.

[0061] The vehicle controller 240 is also used to send a braking current signal when it is determined that the difference between the current driving speed and the target speed is greater than a preset value, and to send a release current signal to the front electric proportional relay valve 210 and the middle and rear electric proportional relay valve 220 after the current driving speed is equal to the target speed.

[0062] In the embodiment of the present invention, the vehicle controller 240 can also monitor the current driving speed and the target speed through sensors. When the current driving speed is detected to be equal to the target speed during braking, a release current signal can be immediately sent to the front electric proportional relay valve 210 and the middle and rear electric proportional relay valve 220 to release the braking operation and avoid excessive braking, which affects the driving speed of the unmanned wide-body vehicle. The current value of the release current signal is zero.

[0063] Example 3

[0064] Figure 5 It is a schematic diagram of the structure of an electric control braking system provided in Example 3 of the present invention.

[0065] The electric control brake system 300 includes a front electric proportional relay valve 310 connected to the air reservoir 301 and the front brake air chamber 302, a middle and rear electric proportional relay valve 320 connected to the air reservoir 301 and the middle and rear brake air chamber 303, and a two-position three-way solenoid valve 330 connected to the air reservoir 301 and the parking relay valve 304;

[0066] The front electric proportional relay valve 310 is used to inflate the front brake air chamber 302 with corresponding air pressure through the air reservoir 301 when receiving a brake current signal, and release the air in the front brake air chamber 302 when receiving a release current signal;

[0067] The middle and rear electric proportional relay valve 320 is used to inflate the middle and rear brake air chamber 303 with corresponding air pressure through the air reservoir 301 when receiving a brake current signal, and release the air in the middle and rear brake air chamber 303 when receiving a release current signal;

[0068] The two-position three-way solenoid valve 330 is used to control the parking relay valve 304 to exhaust the parking air chamber when receiving a parking command, and to inflate the parking relay valve 304 through the air reservoir 301 when receiving a parking release command.

[0069] The two-position three-way solenoid valve 330 includes an air inlet 331, an air outlet 332 and an exhaust port 333;

[0070] The air inlet 331 is used to connect to the air storage cylinder 301;

[0071] The air outlet 332 is configured to be connected to the parking relay valve 304 .

[0072] When the parking instruction is received, the air inlet 331 is closed, the exhaust port 333 and the air outlet 332 are opened, and the exhaust port 333 is connected with the air outlet 332 , so that the parking relay valve 304 exhausts the parking air chamber.

[0073] When the parking release command is received, the exhaust port 333 is closed, the air inlet 331 and the air outlet 332 are opened, and the air inlet 331 is connected to the air outlet 332 so that the air reservoir 301 inflates the parking relay valve 304 and the parking air chamber.

[0074] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. An electronically controlled braking system, characterized in that: The electric control braking system is used for unmanned wide-body vehicles, and the electric control braking system includes a front electric proportional relay valve, a middle and rear electric proportional relay valve, and a two-position three-way solenoid valve; The front electric proportional relay valve is connected to the air reservoir and the front brake air chamber, and is used to inflate the front brake air chamber with corresponding air pressure through the air reservoir when receiving a brake current signal, and release the air in the front brake air chamber when receiving a release current signal; The middle and rear electric proportional relay valve is connected to the air reservoir and the middle and rear brake air chamber, and is used to inflate the middle and rear brake air chamber with a corresponding air pressure through the air reservoir when a brake current signal is received, and release the air in the middle and rear brake air chamber when a release current signal is received; The two-position three-way solenoid valve is connected to the air reservoir and the parking relay valve, and is used to control the parking relay valve to exhaust the parking air chamber when receiving a parking command, and to inflate the parking relay valve through the air reservoir when receiving a parking release command, so that the parking relay valve inflates the parking air chamber. When the two-position three-way solenoid valve receives an emergency brake command, the two-position three-way solenoid valve discharges the gas in the parking air chamber; The front electric proportional relay valve and the middle and rear electric proportional relay valve are also connected to the brake foot valve to receive the control signal of the brake foot valve, and to inflate the front brake air chamber and the middle and rear brake air chamber with the air pressure corresponding to the control signal through the air reservoir; Among them, the front electric proportional relay valve and the middle and rear electric proportional relay valve can receive braking current signals with different current values ​​and perform different braking modes according to different scenarios.

2. The electronically controlled braking system according to claim 1, characterized in that: Also includes vehicle controller; The vehicle controller is connected to the front electric proportional relay valve and the middle and rear electric proportional relay valves, and is used to generate a braking current signal according to a current driving speed and a target speed.

3. The electronically controlled braking system according to claim 2, characterized in that: The vehicle controller is also used to send a braking current signal when it is determined that the difference between the current driving speed and the target speed is greater than a preset value, and to send a release current signal to the front electric proportional relay valve and the middle and rear electric proportional relay valve after the current driving speed is equal to the target speed.

4. The electronically controlled braking system according to claim 3, characterized in that: The current value of the release current signal is zero.

5. The electronically controlled braking system according to claim 1, characterized in that: The two-position three-way solenoid valve comprises an air inlet, an air outlet and an exhaust port; The air inlet is used to be connected to the air storage cylinder; The air outlet is used to be connected to the parking relay valve.

6. The electronically controlled braking system according to claim 5, characterized in that: When the parking instruction is received, the air inlet is closed, the exhaust port and the air outlet are opened, and the exhaust port is connected with the air outlet, so that the parking relay valve exhausts the parking air chamber.

7. The electronically controlled braking system according to claim 5, characterized in that: When the parking release command is received, the exhaust port is closed, the air inlet and the air outlet are opened, and the air inlet is connected to the air outlet, so that the air reservoir inflates the parking relay valve and the parking air chamber.

8. The electronically controlled braking system according to claim 1, characterized in that: The two-position three-way solenoid valve is also connected to the parking switch to receive a control signal of the parking switch to perform a parking operation or a parking release operation.

9. An unmanned wide-body vehicle, characterized in that: The invention comprises the electronically controlled braking system as claimed in any one of claims 1 to 8.

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