A control strategy for determining the timing of cutting out the tractor engine

Abstract

The present invention provides a control strategy for determining the timing of cutting out the engine of a tractor, which calculates the benefits and costs after the engine is cut out, and then determines whether the engine should be cut out, thereby achieving a good energy-saving effect. For a tractor that can obtain the slope information ahead in advance, it combines the historical power demand of the tractor and the slope resistance prediction in the future period of time, calculates the benefits and costs after the engine is cut out, and then determines whether the engine should be cut out.

Description

Technical Field

[0001] The present invention relates to the technical field of tractor power control, and in particular to a control strategy for determining a tractor engine cut-out timing. Background Art

[0002] Tractors are the main type of high-speed freight. Reducing the fuel consumption of tractors has important economic benefits and is also conducive to reducing emissions. When the vehicle does not need the engine to output power, it is an effective way to reduce the fuel consumption of tractors to cut out the engine as soon as possible to reduce the energy lost by its reverse braking. A typical scenario where the engine does not need to output power is that the driver releases the accelerator to coast, and then for a long period of time, the driver does not step on the accelerator or steps on the accelerator very lightly. The vehicle does not need power during the whole process, or for hybrid vehicles, the motor can be used to output power. The way to cut out the engine in the prior art is to separate the clutch or put the gearbox in neutral. However, affected by the driver's operating habits and actual road conditions, the engine drive requirements of the vehicle are usually complex and changeable. It is very likely that the vehicle does not need engine drive in the previous short period of time, but it will be driven again soon afterwards. Improper control of the engine cut-out will cause the engine power to be frequently cut out and cut in, which will increase fuel consumption. Summary of the invention

[0003] In view of the above problems, the present invention provides a control strategy for determining the timing of cutting out the tractor engine, which calculates the benefits and costs after the engine is cut out, and then determines whether the engine should be cut out, thereby achieving good energy-saving effects.

[0004] A control strategy for determining when to cut out an engine of a tractor, characterized in that: for a tractor that can obtain the slope information ahead in advance, the strategy combines the historical power demand of the tractor and the slope resistance prediction in the future to calculate the benefits and costs after the engine is cut out, and then determines whether the engine should be cut out.

[0005] The specific steps are as follows:

[0006] a Calculate the power loss P of the engine when the vehicle does not need driving force at the current speed. Power loss = engine friction torque * engine speed. Both engine friction torque and engine speed signals can be obtained from the message broadcast by the engine to the CAN bus. P = T fric ω;

[0007] b. Calculate the energy E consumed when the engine is cut out and then cut in again at the current engine speed. The consumed energy = the rotational kinetic energy of the engine inertia corresponding to the current speed - the rotational kinetic energy corresponding to the speed after cutting out.

[0008] c Combining steps a and b, the appropriate time for the engine to be cut out is when there is no need for the engine to be cut in again within the next t time, and the cumulative loss of the engine not being cut out within t time is greater than the energy required for the engine to be cut in again, that is,

[0009] d Combined with the current vehicle speed v, the appropriate time for the engine to cut out is: within the following S distance, there is no need for the engine to cut in again, that is,

[0010] e Real-time statistics of historical power demand, divide the vehicle speed into several speed segments at certain intervals, and count the average throttle opening pedal_now on flat roads in each speed segment;

[0011] Considering the driving characteristics of the tractor, it usually maintains a constant speed or small speed fluctuations over a relatively long distance. Therefore, within the distance S ahead, the tractor will maintain the speed section corresponding to the current speed. According to the average throttle opening corresponding to the speed section, the expected power source demand torque Tpedal on the flat road within the distance S behind the vehicle is calculated;

[0012] g assumes that the vehicle can obtain the slope values ​​of several positions in front of S_pre in advance. Then, when S_pre ≥ S, the slope value within the distance S in front of the vehicle can be obtained, and the maximum value is taken as the maximum slope within the distance S, recorded as Amax. Combined with the vehicle weight M, the maximum slope resistance within the distance S can be calculated. The torque required by the power source to overcome this part of the slope resistance is Tslope:

[0013] T slope =MgrA max / i

[0014] Where g is the acceleration due to gravity, r is the wheel radius, and i is the transmission ratio from the vehicle to the power source;

[0015] h Combine steps e and g to calculate the maximum torque Tmax expected to be required by the power source within the distance S ahead:

[0016] T max =T pedal +T slope ;

[0017] iFor conventional engine vehicles, if Tmax≤0, it means that within the distance S ahead, it is expected that the engine output power is not needed, and the current engine should be cut out; for hybrid vehicles, if Tmax does not exceed the torque that the motor can provide, it is expected that the engine output power is not needed, and the engine should be cut out;

[0018] When S_pre < S, since the slope resistance cannot be fully predicted, it is considered that the engine should not be cut out.

[0019] It is further characterized in that:

[0020] In step e, when counting the average throttle opening on flat roads for each vehicle speed segment, when the ramp sensor detects that the current road is flat, record the vehicle speed and throttle opening at this time. According to the vehicle speed segment corresponding to this vehicle speed, re-average this throttle opening and the average throttle opening before the corresponding vehicle speed segment. It uses a moving weighted average, taking t_ave as the time interval for the moving average. Based on the throttle opening pedal_raw within the current sampling time dt and the previous average opening pedal_last, calculate the new average opening pedal_now:

[0021]

[0022] After adopting the present invention, it can reasonably determine the engine cut-out timing of the tractor, thereby effectively reducing fuel consumption; and with the continuous development of tractor technology, more and more tractors that can obtain the slope information ahead are emerging, and this strategy can be widely applied to such tractors. Detailed implementation method

[0023] A control strategy for determining the engine cut-out timing of a tractor: For a tractor that can obtain the slope information ahead in advance, in combination with the historical power demand situation of the tractor and the prediction of the slope resistance within a certain period of time in the future, calculate the benefits and costs after the engine is cut out, and then determine whether the engine should be cut out.

[0024] The specific steps are as follows:

[0025] a Calculate the power loss P when the engine is not cut out when the whole vehicle does not require driving force at the current vehicle speed.

[0026] b Calculate the energy E required when the engine is cut out and then re-cut in at the current engine speed.

[0027] c Combining the above two steps, the appropriate timing for the engine to cut out is that within the subsequent t time, there is no need for the engine to re-cut in, and the cumulative loss of the engine not being cut out within the t time is greater than or equal to the energy required for the engine to re-cut in, that is

[0028] d Combining the current vehicle speed v, the appropriate timing for the engine to cut out is: within the subsequent S distance, there is no need for the engine to re-cut in, that is

[0029] e Real-time statistics of historical power demand, divide the vehicle speed into several speed segments at certain intervals. In specific implementation, the speed segments are divided into 6 speed segments of 0-20kmph, 20-40kmph, 40-60kmph, 60-80kmph, 80-100kmph, and above 100kmph at 20kmph intervals, and the average throttle opening on a flat road in each speed segment is counted; in specific implementation, when the ramp sensor detects that the current road is flat, the vehicle speed and throttle opening at this time are recorded, and according to the speed segment corresponding to the vehicle speed at this time, the throttle opening and the average throttle opening before the corresponding speed segment are averaged again, which adopts moving weighted average, takes t_ave as the time interval of moving average, and calculates the new average opening pedal_now according to the throttle opening pedal_raw within the current sampling time dt and the previous average opening pedal_last:

[0030]

[0031] Considering the driving characteristics of the tractor, it usually maintains a constant speed or small speed fluctuations over a relatively long distance. Therefore, within the distance S ahead, the tractor will maintain the speed section corresponding to the current speed. According to the average throttle opening corresponding to the speed section, the expected power source demand torque Tpedal on the flat road within the distance S behind the vehicle is calculated.

[0032] T pedal =f(pedal_now), where f represents the throttle characteristics of the power source;

[0033] g assumes that the vehicle can obtain the slope values ​​of several positions in front of S_pre in advance. Then, when S_pre ≥ S, the slope value within the distance S in front of the vehicle can be obtained, and the maximum value is taken as the maximum slope within the distance S, recorded as Amax. Combined with the vehicle weight M, the maximum slope resistance within the distance S can be calculated. The torque required by the power source to overcome this part of the slope resistance is Tslope:

[0034] T slope =MgrA max / i

[0035] Where g is the acceleration due to gravity, r is the wheel radius, and i is the transmission ratio from the vehicle to the power source;

[0036] h Combine steps e and g to calculate the maximum torque Tmax expected to be required by the power source within the distance S ahead:

[0037] T max =T pedal +T slope ;

[0038] i For a conventional engine vehicle, if Tmax ≤ 0, it means that within the distance S ahead, it is expected that no engine power output is required, and the current engine should be disengaged; for a hybrid vehicle, if Tmax does not exceed the torque that the motor can provide, it is expected that no engine power output is required, and the engine should be disengaged.

[0039] j When S_pre < S, since the slope resistance cannot be fully predicted, it is considered that the engine should not be disengaged.

[0040] The beneficial effects are as follows. It proposes a quantitative criterion for determining the engine disengagement timing: whether engine power output is required within the distance S ahead; it also proposes a method that can predict and calculate the required torque of the power source of the tractor within a certain distance on a flat road in the future; it also proposes a method that can combine the pre-acquired slope resistance to predict and calculate the required torque of the power source of the tractor within a certain distance in the future. In summary, it can reasonably determine the engine disengagement timing of the tractor, thereby effectively reducing fuel consumption; and with the continuous development of tractor technology, more and more tractors that can obtain the slope information ahead are emerging, and this strategy can be widely applied to such tractors.

[0041] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, it is intended to embrace all changes that fall within the meaning and scope of the equivalent elements of the claims within the present invention.

[0042] In addition, it should be understood that although this specification is described according to the embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A control strategy for determining when to cut out the tractor engine, characterized in that: For a tractor that can obtain slope information ahead in advance, it calculates the benefits and costs after the engine is cut out by combining the historical power demand situation of the tractor and the prediction of ramp resistance within a certain period in the future, and then determines whether the engine should be cut out; The specific steps are as follows: aCalculate the power loss P when the engine is not cut out and the vehicle does not need driving force at the current speed. Power loss = engine friction torque * engine speed. Both engine friction torque and engine speed can be obtained from the message broadcast by the engine to the CAN bus. P = T fric ω; b. Calculate the energy E consumed when the engine is cut out and then cut in again at the current engine speed. The consumed energy = the rotational kinetic energy of the engine inertia corresponding to the current speed - the rotational kinetic energy corresponding to the speed after cutting out. c Combining steps a and b, the appropriate time for the engine to be cut out is when there is no need for the engine to be cut in again within the next t time, and the cumulative loss of the engine not being cut out within t time is greater than the energy required for the engine to be cut in again, that is, d Combined with the current vehicle speed v, the appropriate time for the engine to cut out is: within the following distance S, there is no need for the engine to cut in again, that is, e Statistically record the historical power demand situation in real time. Divide the vehicle speed into several speed segments at a certain interval, and statistically record the average throttle opening pedal_now on flat roads for each speed segment; f Considering the driving characteristics of the tractor, it usually maintains a constant speed or has a small speed fluctuation over a relatively long distance. Therefore, it is assumed that within the distance S ahead, the tractor will remain in the speed segment corresponding to the current vehicle speed. According to the average throttle opening corresponding to this speed segment, calculate the expected power source demand torque Tpedal of the vehicle on flat roads within the subsequent distance S; g Assume that the vehicle can obtain the slope values at several positions within S_pre ahead. In the case of S_pre≥S, the slope values within the distance S ahead of the vehicle can be obtained. Take the maximum value among them as the maximum slope within the distance S, denoted as Amax. Combining the vehicle weight M, the maximum ramp resistance within the distance S can be calculated. The torque required for the power source to overcome this part of the ramp resistance is Tslope: T slope =MgrA max / i In the formula, g is the acceleration due to gravity, r is the wheel radius, and i is the transmission ratio from the whole vehicle to the power source; h Combine steps e and g to calculate the maximum torque Tmax expected to be demanded by the power source within the distance S ahead; T max =T pedal +T slope ; i For a conventional engine vehicle, if Tmax≤0, it means that within the distance S ahead, it is expected that the engine does not need to output power, and the current engine should be cut out; for a hybrid vehicle, if Tmax does not exceed the torque that the motor can provide, it is expected that the engine does not need to output power, and the engine should be cut out; j When S_pre < S, since the ramp resistance cannot be fully predicted, it is considered that the engine should not be cut out.

2. A control strategy for determining the timing of cutting out the tractor engine as claimed in claim 1, characterized in that: In step e, when statistically recording the average throttle opening on flat roads for each speed segment, when the ramp sensor detects that it is currently on a flat road, record the current vehicle speed and throttle opening. According to the speed segment corresponding to this vehicle speed, re-average this throttle opening and the average throttle opening before the corresponding speed segment. It uses a moving weighted average. Take t_ave as the time interval for the moving average. According to the throttle opening pedal_raw within the current sampling time dt and the previous average opening pedal_last, calculate the new average opening pedal_now

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