A commercial vehicle OBD controller

Abstract

The present invention discloses an OBD controller for commercial vehicles. It includes an OBD diagnostic data management module, which is used to obtain vehicle information and OBD data from a vehicle controller, receive the ready state and fault information of the SCR, and respond to the corresponding OBD diagnostic data to the diagnostic tool according to the received OBD diagnostic request when an activation signal is received; a diagnostic ready state management module, which is used to obtain vehicle information after the vehicle is powered on, judge the ready state of the SCR according to the vehicle information, and send the judgment result to the OBD diagnostic data management module; a diagnostic message routing module, which is used to parse the diagnostic ID message received from the OBD port, and send an activation signal to the OBD diagnostic data management module when the parsing result is a request for OBD data; an OBD fault management module, which is used to determine the fault information according to the fault diagnosis message, and send the fault information to the OBD diagnostic data management module. The present invention can uniformly manage the OBD data and faults of the whole vehicle and obtain complete OBD data.

Description

Technical Field

[0001] The invention belongs to the technical field of automobiles, and in particular relates to an OBD controller for commercial vehicles. Background Art

[0002] Limited by the vehicle system architecture, the current OBD system architecture of commercial vehicles is mostly a distributed architecture, and the OBD data is distributed in multiple controllers. For example, the accelerator pedal is connected to the VCU controller, the engine is responsible for fuel-related data, and the post-processing system is processed by the post-processing controller.

[0003] The existing OBD system architecture has the following disadvantages:

[0004] 1. OBD-related data is distributed in multiple controllers, and the general social OBD detection tool can only read OBD data from a single controller, resulting in some OBD data being unable to be read completely during OBD detection.

[0005] 2. Unable to obtain the ready status. Since some diagnostic ready functions require specific working conditions to meet the diagnostic conditions and complete the ready status diagnosis, new cars and user cars may not be able to complete the OBD test items during annual inspections due to ready status issues or incomplete OBD data. Summary of the invention

[0006] The purpose of the present invention is to solve the deficiencies of the above-mentioned background technology and provide an OBD controller for commercial vehicles.

[0007] The technical solution adopted by the present invention is: a commercial vehicle OBD controller, comprising

[0008] An OBD diagnostic data management module, used to obtain vehicle information and OBD data from the vehicle controller, receive the ready state and fault information of the SCR, and respond to the diagnostic tool with corresponding OBD diagnostic data according to the received OBD diagnostic request when receiving an activation signal, wherein the OBD diagnostic data is any one or more of the vehicle information, OBD data, the ready state of the SCR, and the fault information;

[0009] The diagnostic readiness status management module is used to obtain vehicle information after the vehicle is powered on, determine the readiness status of the SCR based on the vehicle information, and send the determination result to the OBD diagnostic data management module;

[0010] The diagnostic message routing module is used to parse the diagnostic ID message received from the OBD port, and send an activation signal to the OBD diagnostic data management module when the parsing result is a request for OBD data;

[0011] The OBD fault management module is used to determine the fault information according to the fault diagnosis message and send the fault information to the OBD diagnostic data management module.

[0012] Furthermore, when an activation signal is received, if no OBD diagnostic request is received through the OBD port within a set time, the diagnostic tool is considered offline and the current OBD diagnostic data response function is exited until an OBD diagnostic request is received through the OBD port again.

[0013] Furthermore, after the vehicle is powered off, the OBD diagnostic data management module updates and stores the currently acquired vehicle information, OBD data, the ready state of the received SCR and the fault information.

[0014] Furthermore, the fault information includes a fault code, a fault level, and static OBD data of the entire vehicle.

[0015] Furthermore, the vehicle information includes any one or more of the vehicle's total mileage, the engine's total operating time, the vehicle's operating conditions, and the vehicle's fault conditions.

[0016] Further, the process of determining the ready state of the SCR according to the vehicle information includes:

[0017] When the total mileage of the vehicle is less than the set mileage and the total engine running time is less than the set time,

[0018] If there is no vehicle fault, the SCR readiness state is set to the ready state, and the SCR readiness state diagnostic factor is set to 1;

[0019] If a vehicle fault occurs, the SCR's ready state is set to a not-ready state, waiting for the fault to be rectified; after the fault is rectified, the SCR's ready state is set to a ready state, and the SCR's ready state diagnostic factor is cleared.

[0020] Further, the process of judging the SCR ready state according to the vehicle information includes: when the total mileage of the vehicle is greater than or equal to the set mileage or the total engine running time is greater than or equal to the set time,

[0021] If there is no vehicle fault, the SCR readiness status is determined based on the vehicle operating conditions;

[0022] If a vehicle fault occurs, the SCR's ready state is set to not ready and the fault is waiting to be rectified. After the fault is rectified, the SCR's ready state is determined based on the vehicle's operating conditions and the SCR's ready state diagnostic factor is cleared.

[0023] Further, the process of judging the SCR readiness state according to the vehicle operating condition is as follows: determining whether the normal diagnostic readiness state judgment condition is met according to the vehicle operating parameters,

[0024] If the normal diagnostic readiness judgment condition is not met, and the current SCR readiness diagnosis factor is greater than the set factor, the SCR readiness state is set to the ready state, and the SCR readiness diagnosis factor is updated according to the total vehicle mileage and the total engine running time;

[0025] If the normal diagnostic readiness judgment condition is not met, and the current SCR readiness diagnosis factor is equal to the set factor, the SCR readiness state is set to the unready state, and the SCR readiness diagnosis factor is cleared;

[0026] If the normal diagnostic readiness state judgment condition is not met and the current SCR readiness state diagnostic factor does not exist, the SCR readiness state is set to the not-ready state;

[0027] If the normal diagnostic ready state judgment conditions are met, the SCR ready state is set to the ready state, and the SCR ready state diagnostic factor is cleared.

[0028] Furthermore, during the driving of the vehicle, after the ready state of the SCR is set to the not-ready state, if at a certain moment it is determined that the normal diagnosis ready state judgment condition is met, the ready state of the SCR is set to the ready state.

[0029] Furthermore, when the following conditions are met at the same time, it is determined that the normal diagnostic ready state judgment condition is reached: 1) the engine speed is between 1200 and 1500 rpm; 2) the engine load is between 75% and 100%; 3) the after-treatment inlet and outlet exhaust temperatures are both higher than 250°C; 4) the NOx emission concentration is less than 20 ppm; 5) the duration reaches 20 seconds.

[0030] The beneficial effects of the present invention are:

[0031] The OBD controller of the present invention cooperates with the OBD diagnostic data management module, the diagnostic readiness status management module, the diagnostic message routing module and the OBD fault management module to uniformly manage the OBD data and faults of the entire vehicle and obtain complete OBD data, thereby avoiding the OBD detection device from interacting with only a single controller for OBD data when performing vehicle diagnosis.

[0032] The OBD diagnostic data management module of the present invention obtains vehicle information from the entire vehicle through diagnostic services, which helps to ensure the integrity of the acquired OBD data and can also judge the data to improve the validity of the OBD data.

[0033] The diagnostic readiness management module of the present invention determines the vehicle readiness state to avoid affecting the result of the vehicle OBD detection; the diagnostic message routing module can achieve network isolation and can also quickly and effectively detect the connection of the OBD detection tool to avoid the OBD detection tool directly connecting to controllers such as EECU and VCU, resulting in incomplete OBD data reading. DETAILED DESCRIPTION

[0034] The specific embodiments of the present invention are further described below. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0035] The present invention provides a commercial vehicle OBD controller, comprising

[0036] The OBD diagnostic data management module implements the ISO-27145 / SAE-J1939 and other related OBD diagnostic service functions, and is used to obtain vehicle information and OBD data from the vehicle controller, receive the SCR's ready state and fault information, and respond to the diagnostic tool with the corresponding OBD diagnostic data according to the received OBD diagnostic request when receiving the activation signal. The OBD diagnostic data is any one or more of the vehicle information, OBD data, SCR's ready state, and fault information. After the vehicle is powered off, the OBD diagnostic data management module updates the currently acquired vehicle information, OBD data, and the received SCR's ready state and fault information, and stores them after powering off.

[0037] The diagnostic readiness management module is used to obtain vehicle information after the vehicle is powered on, determine the readiness of the SCR based on the vehicle information, and send the determination result to the OBD diagnostic data management module. The vehicle information includes any one or more of the vehicle's total mileage, total engine running time, vehicle operating conditions, and vehicle fault conditions.

[0038] The diagnostic message routing module is used to parse the diagnostic ID message received from the OBD port, and send an activation signal to the OBD diagnostic data management module when the parsing result is a request for OBD data.

[0039] The OBD fault management module is used to determine the fault information according to the fault diagnosis message and send the fault information to the OBD diagnostic data management module.

[0040] The specific operation strategies of each functional module of the OBD controller of the present invention are described as follows:

[0041] OBD diagnostic data management module:

[0042] After the vehicle T15 is powered on, the vehicle information is obtained from the vehicle through the diagnostic service, including but not limited to: static information such as the vehicle VIN, CVN, CALID, and dynamic information such as vehicle speed and rotation speed.

[0043] After the engine is running, the OBD diagnostic data request function is actively activated. Through the ISO-27145 and SAE-J1939 data request services, OBD data requests are made to each node on the bus. According to the ISO-27145 and SAE-J1939 standards, combined with the actual vehicle working conditions, the rationality of the data responded by each controller is judged, the appropriate response data is selected, and the OBD data source (response controller information) is recorded. After all OBD data information (including support and non-support) is obtained, the active request function is stopped.

[0044] If an OBD diagnostic request is received through the OBD port, the OBD diagnostic data request function is activated again to periodically request OBD data from the corresponding controller and update the OBD data buffer in real time; then, according to the OBD diagnostic request, the corresponding OBD diagnostic data is responded to the diagnostic tool.

[0045] If no OBD diagnostic request is received through the OBD port within 10 consecutive seconds, the diagnostic tool is considered offline and the OBD diagnostic data request function is exited until an OBD diagnostic request is received through the OBD port again.

[0046] After the vehicle T15 is powered off, the controller records the acquired vehicle information and OBD data information source and stores them after power off.

[0047] Diagnostic Readiness Management Module:

[0048] After the vehicle T15 is powered on, vehicle information is obtained from the vehicle through the bus, including vehicle mileage, total transmitter operating time, engine / after-treatment and other emission-related system DM1 message information.

[0049] When the total mileage of the vehicle is less than the set mileage and the total engine running time is less than the set time, if there is no vehicle failure, the vehicle is regarded as a new vehicle off the production line, and the ready state of the SCR is set to the ready state, and the SCR ready state diagnostic factor is set to 1; if there is a vehicle failure, the ready state of the SCR (that is, emission-related systems and components, such as DOC, DPF, SCR, etc.) is set to the not ready state, waiting for the fault to be resolved; after the fault is resolved, the ready state of the SCR is set to the ready state, and the SCR ready state diagnostic factor is cleared, that is, when the ready state of the SCR is judged later, the SCR ready state diagnostic factor does not exist, and the SCR ready state diagnostic factor is not used as a judgment condition.

[0050] When the total mileage of the vehicle is greater than or equal to the set mileage or the total engine running time is greater than or equal to the set time, if there is no vehicle fault (corresponding OBD fault, determined by the fault information sent by the corresponding controller), the SCR ready state is judged according to the vehicle operating conditions; if a vehicle fault occurs, the SCR ready state is set to not ready state, waiting for the fault to be eliminated; after the fault is eliminated, the SCR ready state is judged according to the vehicle operating conditions, and the SCR ready state diagnostic factor is cleared at the same time.

[0051] In the above scheme, the process of judging the SCR readiness state according to the vehicle operating condition is as follows: determining whether the normal diagnostic readiness state judgment condition is met according to the vehicle operating parameters,

[0052] If the normal diagnostic ready state judgment conditions are not met, and the current SCR ready state diagnostic factor exists, and the current SCR ready state diagnostic factor is greater than the set factor, the SCR ready state is set to the ready state, and the SCR ready state diagnostic factor is updated according to the total vehicle mileage and the total engine running time; the standard for updating the SCR ready state diagnostic factor is: based on the time when the SCR ready state diagnostic factor was last updated, the total vehicle mileage increases by 5000KM and the total engine running time increases by 200 hours, the diagnostic factor is updated and the diagnostic factor is reduced by 0.1; the total vehicle mileage and the total engine running time are calculated cumulatively, that is, when the total vehicle mileage increases to 10000KM and the total engine running time increases to 400 hours based on the last update of the SCR ready state diagnostic factor, the diagnostic factor is reduced by 0.2.

[0053] If the normal diagnostic readiness judgment condition is not met, and the current SCR readiness diagnostic factor exists, and the current SCR readiness diagnostic factor is equal to the set factor, the SCR readiness state is set to the unready state, and the SCR readiness diagnostic factor is cleared;

[0054] If the normal diagnostic readiness state judgment condition is not met and the current SCR readiness state diagnostic factor does not exist, the SCR readiness state is set to the not-ready state;

[0055] If the normal diagnostic ready state judgment conditions are met, the SCR ready state is set to the ready state, and the SCR ready state diagnostic factor is cleared.

[0056] After the above-mentioned SCR readiness status diagnostic factor is cleared, it will no longer be used, that is, the next time the vehicle is started or operated, only the total vehicle mileage, total engine running time, normal diagnostic readiness status judgment and vehicle fault judgment will be performed, and the SCR readiness status diagnostic factor will no longer be used as a judgment condition.

[0057] In the above scheme, after the ready state of the SCR is set to the not-ready state, if at a certain moment it is determined that the normal diagnosis ready state judgment condition is met, the ready state of the SCR is set to the ready state.

[0058] In the above scheme, when the following conditions are met at the same time, it is determined that the normal diagnostic ready state judgment condition is reached: 1) the engine speed is between 1200 and 1500 rpm; 2) the engine load is between 75% and 100%; 3) the after-treatment inlet and outlet exhaust temperatures are both higher than 250°C; 4) the NOx emission concentration is less than 20ppm; 5) the duration reaches 20 seconds.

[0059] Diagnostic message routing module:

[0060] For diagnostic messages (such as XCP / UDS and other diagnostic protocols) received at the OBD port and other CAN channels, the message routing function between different CAN network segments is realized;

[0061] When an emission-related diagnostic ID message is received from the OBD port, the message content is judged. If the message content is not a request for OBD data, the message is routed according to normal routing rules;

[0062] When an emission-related diagnostic ID message is received from the OBD port, the message content is judged. If the message content is a request for OBD data, the diagnostic message routing function is stopped and the "OBD diagnostic data management" function is activated. The "OBD diagnostic data management" takes over the relevant message information response work.

[0063] OBD fault management module:

[0064] Receive DM1 messages from emission-related systems such as the engine and after-treatment through the bus, confirm the fault level based on the fault code, request the instrument to light up the MIL light through the specified rules, and store and eliminate the fault information; send the fault level and fault information to the OBD diagnostic data management, which sends it to the OBD diagnostic tool.

[0065] Example:

[0066] The commercial vehicle OBD system consists of an OBD controller (OCU), a vehicle control unit (VECU), an engine control unit (ECM), an after-treatment controller (ACM), and an instrument cluster (IC).

[0067] Obtain vehicle information and OBD data source:

[0068] Step 1: After the vehicle is powered on by T15, OCU initiates the OBD diagnostic service on the bus and determines whether the vehicle has VECU, EECU, ACM, and IC based on the received response;

[0069] Step 2: OCU sends OBD diagnostic data requests to VECU, EECU, and ACM respectively through OBD diagnostic service, makes comprehensive judgment on the response of each controller, and records the static information of the vehicle such as VIN, CVN, CALID, etc.

[0070] Step 3: Combine the response data from step 2 with the vehicle CAN communication data to determine the source of the OBD data and record: throttle opening (VECU), engine speed (EECU), engine torque percentage (EECU), EGP inlet temperature (ACM), NOx emission concentration (ACM), vehicle speed (IC), mileage (IC), etc.

[0071] Step 4: OCU receives the OBD diagnostic request from the diagnostic instrument from OBDCAN (OBD port 6, 14). Based on the request content, OCU feeds back the vehicle VIN, CVN, CALID, diagnostic readiness status, etc. to the diagnostic instrument, and obtains the throttle opening, engine speed, engine torque percentage, EGP inlet temperature, NOx emission concentration, vehicle speed, mileage and other data from VECU, EECU, IC respectively, and responds to the data according to the request of the diagnostic instrument.

[0072] Step 5: After detecting that the diagnostic instrument is offline, stop obtaining data such as throttle opening, engine speed, engine torque percentage, EGP inlet temperature, NOx emission concentration, vehicle speed, mileage, etc. from VECU, EECU, and IC until the diagnostic instrument is detected to be online again.

[0073] Diagnostic message routing

[0074] Step 1: OCU receives a CAN message with ID 0x18DB33F / 0x7DF from OBDCAN, confirms it is an OBD diagnosis-specific message, and enters OBD diagnosis mode;

[0075] Step 2: OCU receives a CAN message with ID 0x18DA00XX (XX is the source address, the specific value is not limited) from OBDCAN, judges the content of the message, confirms that the message content is not an OBD diagnostic message, routes the message to EECU, and routes the response message of EECU to OBDCAN.

[0076] Diagnostic Readiness Management

[0077] Step 1: After the vehicle is powered on by T15, OCU determines that the vehicle is new based on the vehicle mileage (less than 2000 km), total engine running time (less than 50 hours), and no current or historical ACM-related faults, and sets the SCR diagnostic readiness state to ready state and the SCR readiness state diagnostic factor to 1.

[0078] Step 2: When the vehicle mileage and total engine running time reach 10,000 km / 200 hours and 15,000 km / 400 hours, the OCU will judge the ACM fault information and vehicle operation records, confirm that the SCR has not reached the normal diagnostic readiness condition, and reduce the SCR readiness status diagnostic factor by 0.1 and 0.2 respectively.

[0079] Step 3: When the SCR readiness status diagnosis factor is less than or equal to 0.5, the OCU sets the SCR readiness status to not ready;

[0080] Step 4: As the vehicle is running, the OCU detects that the engine speed is between 1200 and 1500 rpm, the engine load is between 75% and 100%, and the inlet and outlet exhaust temperatures of the aftertreatment are both higher than 250°C, the NOx emission concentration is less than 20 ppm, and the duration is more than 20 seconds. It is determined that the SCR diagnostic readiness conditions are met, the SCR diagnostic readiness state is set to the ready state, and the SCR readiness state diagnostic factor is cleared.

[0081] In order to make the description of the present disclosure more detailed and complete, the above description is provided for the implementation and specific embodiments of the present invention; however, this is not the only form of implementing or using the specific embodiments of the present invention. The implementation covers the features of multiple specific embodiments and the method steps and sequences used to construct and operate these specific embodiments. However, other specific embodiments can also be used to achieve the same or equivalent functions and step sequences.

[0082] The above description includes examples of one or more embodiments. Of course, it is impossible to describe all possible combinations of components or methods for the purpose of describing the above embodiments, but it should be recognized by those skilled in the art that the various embodiments may be further combined and arranged. Therefore, the embodiments described herein are intended to cover all such changes, modifications and variations that fall within the scope of protection of the appended claims. In addition, with respect to the term "comprising" used in the specification or claims, the word is covered in a manner similar to the term "including", just as "including," is explained as a transitional word in the claims. In addition, any term "or" used in the specification of the claims is intended to mean "non-exclusive or".

[0083] The various illustrative logic blocks or units described in the embodiments of the present invention can be implemented or operated by a general-purpose processor, a digital signal processor, an application-specific integrated circuit (ASIC), a field programmable gate array or other programmable logic device, a discrete gate or transistor logic, a discrete hardware component, or any combination of the above. The general-purpose processor can be a microprocessor, and optionally, the general-purpose processor can also be any conventional processor, controller, microcontroller or state machine. The processor can also be implemented by a combination of computing devices, such as a digital signal processor and a microprocessor, a plurality of microprocessors, one or more microprocessors combined with a digital signal processor core, or any other similar configuration.

[0084] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in the field.

Claims

1. A commercial vehicle OBD controller, characterized in that: It includes an OBD diagnostic data management module, which is used to obtain vehicle information and all OBD data from the vehicle controller, receive the ready state and fault information of the SCR, and respond to the corresponding OBD diagnostic data to the diagnostic tool according to the received OBD diagnostic request when an activation signal is received, wherein the OBD diagnostic data is any one or more of the vehicle information, OBD data, the ready state of the SCR, and the fault information; The diagnostic readiness status management module is used to obtain vehicle information after the vehicle is powered on, determine the readiness status of the SCR based on the vehicle information, and send the determination result to the OBD diagnostic data management module; The diagnostic message routing module is used to parse the diagnostic ID message received from the OBD port, and send an activation signal to the OBD diagnostic data management module when the parsing result is a request for OBD data; The OBD fault management module is used to determine the fault information according to the fault diagnosis message and send the fault information to the OBD diagnostic data management module.

2. The commercial vehicle OBD controller according to claim 1, characterized in that: When an activation signal is received, if no OBD diagnostic request is received through the OBD port within a set time, the diagnostic tool is considered offline and the current OBD diagnostic data response function is exited until an OBD diagnostic request is received through the OBD port again.

3. The commercial vehicle OBD controller according to claim 1, characterized in that: After the vehicle is powered off, the OBD diagnostic data management module updates and stores the currently acquired vehicle information, OBD data, the ready state of the received SCR and the fault information.

4. The commercial vehicle OBD controller according to claim 1, characterized in that: The fault information includes fault code, fault level, and static OBD data of the vehicle.

5. The commercial vehicle OBD controller according to claim 1, characterized in that: The vehicle information includes any one or more of the vehicle's total mileage, the engine's total operating time, the vehicle's operating conditions, and the vehicle's fault conditions.

6. The commercial vehicle OBD controller according to claim 1, characterized in that: The process of judging the ready state of the SCR according to the vehicle information includes: when the total mileage of the vehicle is less than the set mileage and the total engine running time is less than the set time, if there is no vehicle fault, the ready state of the SCR is set to the ready state, and the SCR ready state diagnostic factor is set to 1; if there is a vehicle fault, the ready state of the SCR is set to the not ready state, waiting for the fault to be resolved; after the fault is resolved, the ready state of the SCR is set to the ready state, and the SCR ready state diagnostic factor is cleared.

7. The commercial vehicle OBD controller according to claim 1, characterized in that: The process of judging the ready state of the SCR based on the vehicle information includes: when the total mileage of the vehicle is greater than or equal to the set mileage or the total engine running time is greater than or equal to the set time, if there is no vehicle fault, the ready state of the SCR is judged according to the vehicle operating condition; if there is a vehicle fault, the ready state of the SCR is set to a not ready state, waiting for the fault to be resolved; after the fault is resolved, the ready state of the SCR is judged based on the vehicle operating condition, and the SCR ready state diagnostic factor is cleared at the same time.

8. The commercial vehicle OBD controller according to claim 7, characterized in that: The process of judging the SCR readiness state according to the vehicle operating condition is as follows: determining whether the normal diagnostic readiness state judgment condition is met according to the vehicle operating parameters; if the normal diagnostic readiness state judgment condition is not met and the current SCR readiness state diagnosis factor is greater than the set factor, the SCR readiness state is set to the ready state, and the SCR readiness state diagnosis factor is updated according to the total vehicle mileage and the total engine operating time; If the normal diagnostic readiness judgment condition is not met, and the current SCR readiness diagnosis factor is equal to the set factor, the SCR readiness state is set to the unready state, and the SCR readiness diagnosis factor is cleared; If the normal diagnostic readiness state judgment condition is not met and the current SCR readiness state diagnostic factor does not exist, the SCR readiness state is set to the not-ready state; If the normal diagnostic ready state judgment conditions are met, the SCR ready state is set to the ready state, and the SCR ready state diagnostic factor is cleared.

9. The commercial vehicle OBD controller according to claim 8, characterized in that: During vehicle driving, after the ready state of the SCR is set to the not-ready state, if at a certain moment it is determined that the normal diagnostic ready state judgment condition is met, the ready state of the SCR is set to the ready state.

10. The commercial vehicle OBD controller according to claim 8, characterized in that: When the following conditions are met at the same time, it is determined that the normal diagnostic readiness state judgment conditions are met: 1) the engine speed is between 1200 and 1500 rpm; 2) the engine load is between 75% and 100%; 3) the after-treatment inlet and outlet exhaust temperatures are both higher than 250°C; 4) the NOx emission concentration is less than 20ppm; 5) the duration reaches 20 seconds.