Control method and system for limiting maximum speed of gas tractor

Abstract

The invention belongs to the technical field of gas tractors, and particularly relates to a control method and system for limiting the maximum speed of a gas tractor, and the method comprises the following steps: a vehicle control unit receives the real vehicle speed sent by an instrument from a CAN bus, and filters the real vehicle speed; when the vehicle speed of the real vehicle is larger than the intervention vehicle speed, the speed-limiting torque is calculated through an improved PID closed-loop control method, and the speed-limiting torque is the non-zero torque for maintaining the gas tractor to run at the highest vehicle speed; the speed limit torque, the accelerator pedal torque, and the cruise torque are compared, an output torque is determined, and the output torque is sent from the CAN bus to the gas engine. Smooth output and stable transition of torque of the gas tractor in a full-accelerator acceleration scene, a cruise scene, a flat road, an uphill road, a downhill road and other road conditions are guaranteed, and the problems of post-processing high temperature and engine fire caused by direct torque withdrawal after the gas tractor reaches the highest speed are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of gas tractor, and particularly relates to a control method and system for limiting the maximum speed of a gas tractor. BACKGROUND

[0002] Since this year, the sales of gas tractors have increased sharply, and the main reasons include: the reduction of operating costs caused by the difference between oil and gas, the reduction of carbon deposition caused by the full combustion of natural gas, the improvement of safety caused by the high ignition point, and the fact that card friends do not need to worry about gas stealing. However, the promotion of gas tractors also needs to follow strict regulatory standards.

[0003] According to the requirements of "JT / T 1178.2-2019 Safety Technical Conditions for Operating Truck Part 2: Towing Vehicles and Trailers", the maximum speed of a towing vehicle without an electronic brake system (EBS) and without disc brakes on all wheels of the steering axle should be limited to below 90Km / h.

[0004] At present, many gas tractors directly reduce the engine torque to zero torque or intervene in advance to reduce the torque to zero torque to achieve speed limiting after reaching the speed limit. Both of these methods will cause the gas tractor to be unable to burn equivalent, that is, air and gas cannot be uniformly mixed in the theoretical proportion before participating in combustion, thereby causing the risk of excessive temperature of the aftertreatment and engine misfire. SUMMARY

[0005] Based on the technical problems existing in the background art, the present application provides a control method and system for limiting the maximum speed of a gas tractor.

[0006] The control method for limiting the maximum speed of a gas tractor provided by the present application comprises the following steps:

[0007] Step one, the vehicle control unit receives the real vehicle speed sent by the instrument from the CAN bus and performs filtering operation;

[0008] Step two, the vehicle control unit compares the filtered real vehicle speed with the preset intervention speed:

[0009] If the real vehicle speed > intervention speed, start the speed limiting control and enter the torque adjustment stage in step three;

[0010] If the real vehicle speed > maximum limit speed, send an overspeed alarm signal from the CAN bus to the instrument;

[0011] Step three, calculate the speed limiting torque by the PID closed loop control method;

[0012] Step four, compare the speed limiting torque, the throttle pedal torque and the cruise torque to determine the output torque, and send the output torque from the CAN bus to the gas engine.

[0013] Further, the intervention vehicle speed is less than the highest limit vehicle speed.

[0014] Further, in step three, the speed limit torque is calculated by the improved PID closed-loop control method, including proportional torque, integral torque and differential torque, the upper limit of the integral torque is T max-torque , and the lower limit of the integral torque is zero torque. max-torque

[0015] Further, in step four, the output torque is obtained by comparing the speed limit torque, the throttle pedal torque and the cruise torque.

[0016] Further, in step one, the instrument calculates the vehicle speed according to the pulse signal of the vehicle speed sensor.

[0017] Further, in step two, the overspeed alarm signal is used to light the overspeed alarm indicator of the instrument and trigger the buzzer alarm.

[0018] Further, in the full throttle scene:

[0019] If the actual vehicle speed is less than or equal to the intervention vehicle speed and the road is flat, the speed limit torque is T max-torque , i.e. the maximum torque of the gas engine;

[0020] If the actual vehicle speed is greater than the intervention vehicle speed and the road is flat, the speed limit torque is smoothly decreased from T max-torque to the torque for maintaining the gas traction vehicle to travel at the highest limit speed;

[0021] If the actual vehicle speed is greater than the highest limit speed and the road is downhill, the speed limit torque is slowly decreased from the torque for maintaining the gas traction vehicle to travel at the highest limit speed to zero torque;

[0022] If the actual vehicle speed is less than or equal to the highest limit speed and the road is uphill, the speed limit torque is smoothly increased from zero torque to the torque for maintaining the gas traction vehicle to travel at the highest limit speed.

[0023] The system for limiting the highest speed of a gas traction vehicle provided by the application comprises:

[0024] an instrument, a vehicle control unit and a gas engine;

[0025] The instrument is responsible for calculating the vehicle speed according to the pulse signal of the vehicle speed sensor.

[0026] The vehicle control unit is responsible for receiving the vehicle speed signal sent by the instrument from the CAN bus, sending the overspeed alarm prompt to the instrument from the CAN bus, calculating the speed limit torque, the throttle pedal torque and the cruise torque, comparing the speed limit torque, the throttle pedal torque and the cruise torque, and sending the output torque to the gas engine from the CAN bus. ​

[0027] The gas engine is responsible for executing the output torque sent by the vehicle control unit from the CAN bus.

[0028] The beneficial effects in the present application are:

[0029] 1. Through the improved PID closed-loop control method, torque smooth output and smooth transition are realized in full throttle acceleration scene, cruise scene and road conditions such as flat road, uphill and downhill, avoiding the problem of high temperature of aftertreatment and engine misfire caused by direct torque withdrawal after the gas tractor reaches the highest vehicle speed, which not only meets the regulatory requirements of the highest vehicle speed, but also improves the driving experience and safety. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 A flowchart of a control method for limiting the highest vehicle speed of a gas tractor is proposed in the present application;

[0031] Figure 2 A schematic diagram of a control system for limiting the highest vehicle speed of a gas tractor is proposed in the present application;

[0032] Figure 3 A speed-limiting torque curve diagram of the control method for limiting the highest vehicle speed of a gas tractor under full throttle is proposed in the present application. DETAILED DESCRIPTION

[0033] Example 1: Refer to Figures 1-2 A control method for limiting the highest vehicle speed of a gas tractor, comprising the following steps:

[0034] Step one, the vehicle control unit receives the real vehicle speed sent by the instrument from the CAN bus, and filters the received vehicle speed real vehicle speed signal;

[0035] Step two, the vehicle control unit compares the filtered real vehicle speed with the preset intervention vehicle speed:

[0036] If the real vehicle speed is greater than the intervention vehicle speed, start the speed-limiting control and enter the torque adjustment stage in step three; avoid sudden braking adjustment near the speed limit by intervening in advance;

[0037] If the real vehicle speed is greater than the highest limit speed, send an overspeed alarm signal from the CAN bus to the instrument;

[0038] Step three, calculate the speed-limiting torque through the PID closed-loop control method;

[0039] Step four, compare the speed-limiting torque, the throttle pedal torque and the cruise torque to determine the output torque, and send the output torque from the CAN bus to the gas engine.

[0040] In the present application, the intervention vehicle speed is less than the highest limit speed.

[0041] In the step three, the speed limit torque is calculated by the improved PID closed loop control method, including proportional torque, integral torque and differential torque, the upper limit of the integral torque is T max-torque , T max-torque is the maximum torque of the gas engine, avoiding the integral torque accumulating to infinity, the lower limit of the integral torque is zero torque, avoiding the integral torque reducing to infinity;

[0042] It should be noted that: the speed limit torque = proportional torque T p + integral torque T i + differential torque T d .

[0043] The calculation logic of each item is based on the speed deviation e, and the speed deviation = the highest limit speed - the actual vehicle speed; the calculation formula of each item is: T p = K p ×e, wherein K p is a set value which can be obtained according to multiple experiments; T i = K i ×∫e(t)dt, and 0≤T i ≤T max-torque , wherein K i is a set value which can be obtained according to multiple experiments; T d = K d ×(d e / d t ), wherein K d is a set value which can be obtained according to multiple experiments.

[0044] In the step four, the output torque is obtained by comparing the speed limit torque, the throttle pedal torque and the cruise torque.

[0045] It should be noted that: the obtaining method is to compare the maximum value of the throttle pedal torque and the cruise torque first, and the power demand of the driver's active acceleration or cruise setting is preferentially met; then the maximum value is compared with the speed limit torque to obtain the minimum value, and the speed limit torque is capped to ensure that the output torque does not exceed the allowed value of maintaining the highest limit speed, thereby fundamentally limiting the speed.

[0046] In the step one, the instrument calculates the vehicle speed according to the pulse signal of the vehicle speed sensor.

[0047] In the step two, the overspeed alarm signal is used to light the overspeed alarm indicator of the instrument and trigger the buzzer alarm.

[0048] A system for limiting the highest speed of a gas tractor, comprising:

[0049] Instrument, vehicle control unit and gas engine;

[0050] The instrument is responsible for calculating the vehicle speed according to the pulse signal of the vehicle speed sensor;

[0051] The vehicle control unit is responsible for receiving the vehicle speed signal sent by the instrument from the CAN bus, sending the overspeed warning prompt to the instrument from the CAN bus, calculating the speed limit torque, the throttle pedal torque and the cruise torque, comparing the speed limit torque, the throttle pedal torque and the cruise torque, and sending the output torque to the gas engine from the CAN bus;

[0052] The gas engine is responsible for executing the output torque sent by the vehicle control unit from the CAN bus.

[0053] Embodiment 2: based on embodiment 1, wherein Figure 3 The speed limit torque curve under full throttle provided by the embodiment of the present application is shown in the figure, which is the torque change under three working condition scenes of flat road, downhill and uphill in turn;

[0054] The 0-t1 time period represents that the real vehicle speed is less than or equal to the intervention vehicle speed, and is a flat road, and the speed limit torque is T max-torque , that is, the maximum torque of the gas engine, that is, no intervention during normal acceleration;

[0055] The t1-t2 time period represents that the real vehicle speed is greater than the intervention vehicle speed, and is a flat road, and the speed limit torque is smoothly decreased from T max-torque to the torque for maintaining the gas traction vehicle to travel at the highest limit speed, and the adjustment is made in advance to avoid sudden drop;

[0056] The t2-t3 time period represents that the real vehicle speed is greater than the highest limit speed, and is a downhill, and the speed limit torque is slowly decreased from the torque for maintaining the gas traction vehicle to travel at the highest limit speed to zero torque, and the vehicle is easy to accelerate when downhill, and is limited by zero torque, but the slow decrease avoids impact;

[0057] The t3-t4 time period represents that the real vehicle speed is less than or equal to the highest limit speed, and is an uphill, and the speed limit torque is smoothly increased from zero torque to the torque for maintaining the gas traction vehicle to travel at the highest limit speed, and the power is needed when uphill, and the torque is increased to ensure that the vehicle speed is not lower than the highest limit speed, and the smooth transition avoids jerk.

[0058] The above is only the preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can make equivalent replacement or change according to the technical scheme and the inventive concept of the present application within the technical range disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A control method of limiting the maximum vehicle speed of a gas tractor, characterized by, The method comprises the following steps: Step one, the vehicle control unit receives the real vehicle speed sent by the instrument from the CAN bus and performs filtering operation; Step two, the vehicle control unit compares the filtered real vehicle speed with the preset intervention vehicle speed: If the real vehicle speed > intervention vehicle speed, start the speed limit control and enter the torque adjustment stage in step three; If the real vehicle speed > the highest limit speed, send the overspeed alarm signal from the CAN bus to the instrument; Step three, calculate the speed limit torque by the PID closed loop control method; Step four, compare the speed limit torque, the throttle pedal torque and the cruise torque to determine the output torque and send the output torque from the CAN bus to the gas engine.

2. The control method of limiting the maximum speed of a gas tractor according to claim 1, characterized by, The intervention vehicle speed is less than the highest limit speed.

3. The control method of limiting the maximum speed of a gas tractor according to claim 1, characterized in that, In step three, the limited speed torque is calculated by the improved PID closed loop control method, including proportional torque, integral torque and differential torque, the upper limit of integral torque is T max-torque , T max-torque is the maximum torque of the gas engine, and the lower limit of integral torque is zero torque.

4. The control method of limiting the maximum speed of a gas tractor according to claim 1, characterized in that, In step four, the output torque is the torque obtained after comparing the speed limit torque, the throttle pedal torque and the cruise torque.

5. The control method of limiting the maximum speed of a gas tractor according to claim 1, wherein, In step one, the instrument calculates the vehicle speed according to the pulse signal of the vehicle speed sensor.

6. The control method of limiting the maximum speed of a gas tractor according to claim 1, wherein In step two, the overspeed alarm signal is used to light the overspeed alarm indicator and trigger the buzzer alarm of the instrument.

7. The control method of limiting the maximum speed of a gas tractor according to any one of claims 1 to 6, characterized in that, In the full throttle scenario: If the actual vehicle speed is less than or equal to the intervention vehicle speed and the road is flat, the speed-limiting torque is T max-torque That is, the maximum torque of the gas engine If the actual vehicle speed > the intervention vehicle speed, and it is a flat road, the speed limit torque is reduced from T max-torque Smoothly down to the torque that maintains the gas traction vehicle to travel at the highest limit speed.

8. The control method of limiting the maximum speed of a gas tractor according to any one of claims 1 to 6, characterized in that, In the full throttle scenario, if the real vehicle speed > the highest limit speed and it is downhill, the speed limit torque slowly decreases from the torque that maintains the gas traction vehicle to travel at the highest limit speed to zero torque.

9. The control method of limiting the maximum speed of a gas tractor according to any one of claims 1 to 6, characterized in that, In the full throttle scenario, if the real vehicle speed ≤ the highest limit speed and it is uphill, the speed limit torque smoothly rises from zero torque to the torque that maintains the gas traction vehicle to travel at the highest limit speed.

10. A system for limiting the maximum speed of a gas-powered towing vehicle according to the control method for limiting the maximum speed of a gas-powered towing vehicle according to any one of claims 1 to 6, characterized by, The method comprises: The instrument, the vehicle control unit and the gas engine; The instrument is responsible for calculating the vehicle speed according to the pulse signal of the vehicle speed sensor; The vehicle control unit is responsible for receiving the vehicle speed signal sent by the instrument from the CAN bus, sending the overspeed alarm prompt from the CAN bus to the instrument, calculating the speed limit torque, the throttle pedal torque and the cruise torque, comparing the speed limit torque, the throttle pedal torque and the cruise torque, and sending the output torque from the CAN bus to the gas engine; The gas engine is responsible for executing the output torque sent by the vehicle control unit from the CAN bus.

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