Method and system for speed control of an electrically driven bulldozer

Abstract

The application discloses a speed control method and system of an electrically-driven bulldozer, and the method comprises the following steps: acquiring an actual vehicle speed of the bulldozer, inputting an actual speed difference obtained by subtracting the actual vehicle speed from a target vehicle speed into a PID controller, outputting a torque value by the PID controller, and controlling the bulldozer based on the obtained torque value; and in the calculation and processing of the PID controller, the integral part in the PID controller is controlled as follows: if the actual speed difference is greater than a first positive deviation value, the integral gain is increased; and if the actual speed difference is less than a second negative deviation value, the integral accumulation value is reduced. By adopting the technical scheme, when the soil load of the bulldozer changes greatly, the integral gain or the integral accumulation value of the integral part of the PID controller is adjusted, the control on the speed of the bulldozer is accelerated, and the stability of the operation of the bulldozer is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrically driven bulldozer control, and particularly to a speed control method and system of an electrically driven bulldozer. BACKGROUND

[0002] With the vigorous support of the state to the new energy industry in recent years and the rapid improvement of new energy technology, the traditional fuel bulldozer is subject to many restrictions due to high energy consumption, tail gas emission and other problems, so the traditional fuel bulldozer gradually develops towards an electrically driven bulldozer.

[0003] The bulldozer is mainly used for earthmoving operation in complex working conditions such as mine exploitation, farmland reclamation and road construction, so the soil load borne by the bulldozer may change dramatically during operation. In order to cope with such changes, improve operation efficiency and ensure the stability of the bulldozer, an electrically driven bulldozer needs a torque control strategy to meet different working conditions and avoid out-of-control speed.

[0004] In the prior art, a PID (Proportional-Integral-Derivative Control) controller is often used in the electric control system to make the controlled quantity tend to the target value. However, the PID controller also has certain disadvantages. Since the PID control belongs to feedback closed-loop control, the feedback control has a certain hysteresis, which means that when the soil load changes dramatically, the speed control needs a certain time, and the bulldozer is a large heavy machine, so if the speed deviation time is too long, there will be certain danger. SUMMARY

[0005] The present application provides a speed control method and system of an electrically driven bulldozer, which aims to solve the problem in the prior art that the speed control time of the bulldozer based on feedback control is too long when the soil load of the bulldozer changes dramatically.

[0006] Technical scheme: The present application provides a speed control method of an electrically driven bulldozer, comprising: obtaining the actual speed of the bulldozer, inputting the actual speed difference obtained by subtracting the target speed from the actual speed into a PID controller, outputting a torque value by the PID controller, and controlling the bulldozer based on the obtained torque value; during the calculation and processing of the PID controller, the integral part in the PID controller is controlled as follows: if the actual speed difference is greater than a first positive deviation value, the integral gain is increased; if the actual speed difference is less than a second negative deviation value, the integral accumulation value is reduced.

[0007] Specifically, if the actual speed difference is greater than the first positive deviation value and the torque value output by the PID controller is greater than the load change threshold, the integral gain is increased.

[0008] Specifically, in the working conditions of the first soil load and the second soil load, a first function curve and a second function curve between the vehicle speed and the corresponding torque of the bulldozer are obtained respectively; the first soil load is greater than the second soil load; based on the current torque of the bulldozer and the first function curve and the second function curve, a first theoretical vehicle speed and a second theoretical vehicle speed are calculated, a first theoretical speed difference is obtained by subtracting the second theoretical vehicle speed from the first theoretical vehicle speed, and the first theoretical speed difference is taken as a first positive deviation value; based on the current vehicle speed of the bulldozer and the first function curve and the second function curve, a first theoretical torque and a second theoretical torque are obtained, and the second theoretical torque is taken as a load change threshold.

[0009] Specifically, the increasing of the integral gain includes: comparing the current torque of the bulldozer with the first theoretical torque, if the current torque is greater than the first theoretical torque, the integral gain is multiplied by a first increasing coefficient; if the current torque is not greater than the first theoretical torque, the integral gain is multiplied by a second increasing coefficient; the first increasing coefficient is greater than the second increasing coefficient, and the first increasing coefficient and the second increasing coefficient are both greater than 1.

[0010] Specifically, the increasing of the integral gain includes: until the actual speed difference is not greater than the first positive deviation value or the torque value output by the PID controller is not greater than the load change threshold, the increasing of the integral gain is ended.

[0011] Specifically, if the actual speed difference is less than a second negative deviation value and the integral accumulation value is greater than 0, the integral accumulation value is reduced.

[0012] Specifically, in the working conditions of the first soil load and the second soil load, a first function curve and a second function curve between the vehicle speed and the corresponding torque of the bulldozer are obtained respectively; the first soil load is greater than the second soil load; based on the current torque of the bulldozer and the first function curve and the second function curve, a first theoretical vehicle speed and a second theoretical vehicle speed are calculated, a first theoretical speed difference is obtained by subtracting the second theoretical vehicle speed from the first theoretical vehicle speed, and the first theoretical speed difference is taken as a first positive deviation value; based on the current vehicle speed of the bulldozer and the first function curve and the second function curve, a first theoretical torque and a second theoretical torque are obtained, and the second theoretical torque is taken as a load change threshold.

[0013] Specifically, the reducing of the integral accumulation value includes: based on the current vehicle speed of the bulldozer and the first function curve and the second function curve, a first theoretical torque and a second theoretical torque are obtained; comparing the current torque of the bulldozer with the first theoretical torque, if the current torque is greater than the first theoretical torque, the integral gain is multiplied by a first reducing coefficient; if the current torque is not greater than the first theoretical torque and is greater than the second theoretical torque, the integral gain is multiplied by a second reducing coefficient; the first reducing coefficient is less than the second reducing coefficient, and the first reducing coefficient and the second reducing coefficient are both less than 1.

[0014] Specifically, the reducing the integral accumulation value comprises: until the actual speed difference is not less than the second negative deviation value or the integral accumulation value is not greater than 0, ending the reducing the integral accumulation value.

[0015] The application also provides a speed control device of an electrically driven bulldozer, comprising: a speed execution unit and a PID control unit, wherein: the speed execution unit is used for obtaining an actual vehicle speed of the bulldozer, inputting an actual speed difference obtained by subtracting the actual vehicle speed from a target vehicle speed into a PID controller, and outputting a torque value by the PID controller, and controlling the bulldozer based on the obtained torque value; and the PID control unit is used for controlling an integral part in the PID controller as follows: if the actual speed difference is greater than a first positive deviation value, increasing an integral gain; and if the actual speed difference is less than a second negative deviation value, reducing an integral accumulation value.

[0016] Beneficial effects: compared with the prior art, the application has the following remarkable advantages: when the soil load of the bulldozer changes greatly, the integral gain or the integral accumulation value of the integral part of the PID controller is adjusted, the control of the speed of the bulldozer is accelerated, and the stability of the operation of the bulldozer is improved. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 A flowchart of a speed control method of an electrically driven bulldozer provided by the application is shown in the figure.

[0018] Figure 2 A flowchart of the control of the integral part in the PID controller provided by the application is shown in the figure. DETAILED DESCRIPTION

[0019] The technical solutions of the application are further described below with reference to the drawings.

[0020] Reference Figure 1 A flowchart of a speed control method of an electrically driven bulldozer provided by the application is shown in the figure.

[0021] In the embodiment of the application, the actual vehicle speed of the bulldozer is obtained, the actual speed difference obtained by subtracting the actual vehicle speed from the target vehicle speed is input into the PID controller, the PID controller outputs a torque value, and the bulldozer is controlled based on the obtained torque value; and the integral part in the PID controller is controlled in the PID controller calculation process.

[0022] In the specific implementation, the torque value output by the PID controller can be executed by the motor of the electric bulldozer.

[0023] In specific implementations, PID controller, i.e. Proportional-Integral-Derivative controller, is a widely used feedback control mechanism in the field of automation control. By calculating the error between the set value (target value) and the actual measured value, and adjusting the control signal according to this error to minimize the error, precise control of the system is achieved. PID controller is composed of three independent parts, including proportional control, integral control and derivative control.

[0024] Proportional control adjusts the output directly proportional to the error, and the proportional gain determines the speed and intensity of the controller's response to the error. Higher proportional gain can speed up the response. Integral control accumulates past errors to eliminate steady-state error, i.e. the error that still exists after the system reaches a stable state. The integral gain affects the strength of the integral action, which helps improve control accuracy. Derivative control adjusts based on the rate of change of the error, providing predictive control to slow down the system's reaction and reduce overshoot. The derivative gain determines the strength of the derivative action, which can help smooth the controller's output.

[0025] In specific implementations, the integral part of the PID controller is mainly adjusted and controlled in the present application, mainly aiming at the integral gain and the integral accumulation value. Higher integral gain can eliminate steady-state error more quickly, but this often makes the system too sensitive, with too high adjustment amplitude and speed of the controlled variable. Lower integral gain means weaker integral action and slower correction speed of steady-state error. Integral accumulation value is a key component of the integral term in the PID controller, reflecting the accumulation of error over time. Specifically, the integral accumulation value is the sum of all past errors, which is weighted by the integral gain and used to adjust the controller's output to help eliminate steady-state error. The integral accumulation value continues to accumulate until the error between the actual output of the system and the set value is zero. Even if the error is very small, as long as it exists, the integral action will continue to increase the output until the error is completely eliminated. When the integral accumulation value is high, the controller will continue to increase the output to try to eliminate the error under the action of the gain, even if the current error is very small, which means the system needs more time to stabilize because a large amount of integral action accumulated in the past must be consumed first. When the integral accumulation value is low, the integral action is not enough to completely eliminate the error, and the system may have a steady-state error, i.e. a non-zero error in the steady state, which means that the integral action is weak and the system's response to the error is slow.

[0026] Therefore, different adjustment methods need to be applied when the bulldozer experiences different load changes.

[0027] In the embodiment of the present invention, if the actual speed difference is greater than the first positive deviation value, the integral gain is increased; if the actual speed difference is less than the second negative deviation value, the integral accumulation value is reduced.

[0028] In a specific implementation, when the actual speed difference between the target vehicle speed and the actual vehicle speed is greater than the first positive deviation value (greater than 0), it indicates that the system deviation is large at this time and the actual vehicle speed is relatively small, which means that a sudden increase in soil load may have occurred at this time. It is necessary to increase the sensitivity of the system to increase the torque change amplitude and rate, and therefore, increase the integral gain.

[0029] In a specific implementation, when the actual speed difference between the target vehicle speed and the actual vehicle speed is less than the second negative deviation value (less than 0), it also indicates that the system deviation is large at this time, but the actual vehicle speed is relatively high, which means that the soil load may have suddenly decreased at this time, and the system needs to reduce the torque output. Therefore, the integral accumulated value is reduced.

[0030] See Figure 2 , which is a flow chart of the integral part control in the PID controller provided by the present invention.

[0031] In the embodiment of the present invention, if the actual speed difference is greater than the first positive deviation value and the torque value output by the PID controller is greater than the load change threshold, the integral gain is increased.

[0032] In the specific implementation, when the actual speed difference is greater than the first positive deviation value, the torque value output by the PID controller is greater than the load change threshold, indicating that the current torque output has reached a certain level, while the actual speed difference is still large. This further indicates that due to a sudden increase in soil load, the original output torque is no longer sufficient to support the increase in bulldozer speed, and it is necessary to increase the torque change amplitude and rate by increasing the integral gain.

[0033] In the embodiment of the present invention, if the actual speed difference is less than the second negative deviation value and the integral accumulated value is greater than 0, the integral accumulated value is reduced.

[0034] In a specific implementation, when the actual speed difference is less than the second negative deviation value, the integral accumulated value is greater than 0, indicating that the bulldozer was originally processing a large soil load and continuously outputting high torque, so that the actual vehicle speed is close to the target vehicle speed, rather than braking or decelerating (the integral accumulated value part will have a value less than 0), but the actual speed is too high. This further indicates that the bulldozer may have completed the bulldozing operation by pushing the soil to a certain place, and the soil load suddenly decreased or even became 0, but the bulldozer speed did not decrease rapidly, so the accumulated value of the integral part decreased rapidly, thereby reducing the torque output by the system.

[0035] In the embodiment of the present application, under the working conditions of the first soil load and the second soil load, the first function curve and the second function curve between the vehicle speed of the bulldozer and the corresponding torque are obtained respectively; the first soil load is greater than the second soil load.

[0036] In the specific implementation, in order to further accurately calculate the first positive deviation value, the second negative deviation value and the load change threshold and other related parameters for measuring when to adjust the control of the integral part, the function curve of the relationship between the vehicle speed and the torque under a certain soil load is introduced in the present application.

[0037] In the specific implementation, the function curve can be obtained in many ways, such as sampling multiple sets of vehicle speed and torque under a certain soil load, and obtaining the corresponding function curve by fitting.

[0038] In the specific implementation, since the values calculated by the first function curve and the second function curve are used as the parameters for measuring when to adjust the control of the integral part, and the threshold value for measuring when the adjustment degree of the integral part changes, the difference between the first soil load and the second soil load needs to be reasonably arranged, and the first soil load can be set to 1.5 to 2 times the second soil load.

[0039] In the embodiment of the present application, based on the current torque of the bulldozer and the first function curve and the second function curve, the corresponding first theoretical vehicle speed and the second theoretical vehicle speed are calculated, the first theoretical speed difference is obtained by subtracting the first theoretical vehicle speed from the second theoretical vehicle speed, and the first theoretical speed difference is taken as the first positive deviation value; based on the current vehicle speed of the bulldozer and the first function curve and the second function curve, the corresponding first theoretical torque and the second theoretical torque are obtained, and the second theoretical torque is taken as the load change threshold.

[0040] In the specific implementation, the current torque of the bulldozer is the torque value output by the current PID controller. Based on the torque value and the first function curve and the second function curve, the first theoretical vehicle speed and the second theoretical vehicle speed can be calculated, which represent the vehicle speed that can be reached by the current torque value under the first soil load and the second soil load. The first theoretical speed difference is obtained by subtracting the first theoretical vehicle speed from the second theoretical vehicle speed, and the first theoretical speed difference is taken as the first positive deviation value. When the actual speed difference is greater than the first theoretical speed difference, it indicates that the soil load change exceeds the difference between the first soil load and the second soil load, indicating that a relatively severe soil load increase change occurs.

[0041] In the specific implementation, based on the current vehicle speed of the bulldozer and the first function curve and the second function curve, the corresponding first theoretical torque and the second theoretical torque can be calculated, which represent the torque value required by the actual vehicle speed of the current bulldozer under the first soil load and the second soil load. The second theoretical torque is taken as the load change threshold, which indicates that the actual soil load handled by the current bulldozer is greater than the second soil load, which is at a high level. The integral gain can be increased to increase the speed of torque increase, thereby avoiding increasing the sensitivity of the system when the soil load is not high, which can easily lead to rapid torque increase and difficult control of the vehicle speed, and cause unstable work of the bulldozer.

[0042] In the embodiment of the present application, the current torque of the bulldozer is compared with the first theoretical torque. If the current torque is greater than the first theoretical torque, the integral gain is multiplied by the first increase coefficient. If the current torque is not greater than the first theoretical torque, the integral gain is multiplied by the second increase coefficient. The first increase coefficient is greater than the second increase coefficient, and both the first increase coefficient and the second increase coefficient are greater than 1.

[0043] In the specific implementation, if the current torque is greater than the first theoretical torque, it indicates that the current torque is at a very high level, but the actual speed difference is still large, indicating that the soil load growth degree is high, so the corresponding torque increase amplitude and rate should also be matched. Therefore, the integral gain is multiplied by the first increase coefficient. When the current torque is not greater than the first theoretical torque, that is, between the second theoretical torque and the first theoretical torque, it indicates that the current torque is not high, and the torque increase amplitude and rate do not need to be increased greatly. Therefore, the integral gain is multiplied by the second increase coefficient.

[0044] In the embodiment of the present application, the integral gain is increased until the actual speed difference is not greater than the first positive deviation value, or the torque value output by the PID controller is not greater than the load change threshold.

[0045] In the embodiment of the present application, under the working conditions of the first soil load and the second soil load, the first function curve and the second function curve between the vehicle speed of the bulldozer and the corresponding torque are obtained respectively. The first soil load is greater than the second soil load. Based on the current torque of the bulldozer and the first function curve and the second function curve, the corresponding first theoretical vehicle speed and the second theoretical vehicle speed are calculated. The second theoretical speed difference is obtained by subtracting the second theoretical vehicle speed from the first theoretical vehicle speed, and the second theoretical speed difference is taken as the second negative deviation value.

[0046] In a specific implementation, accordingly, based on the torque value and the first function curve and the second function curve, the first theoretical vehicle speed and the second theoretical vehicle speed can be calculated, which characterize the vehicle speed that can be reached under the first soil load and the second soil load. The first theoretical vehicle speed is subtracted from the second theoretical vehicle speed to obtain the second theoretical speed difference, and the second theoretical speed difference is used as the first positive deviation value. When the actual speed difference is less than the second theoretical speed difference, it indicates that the change in soil load exceeds the gap between the second soil load and the first soil load, and also indicates that a more drastic change in soil load reduction has occurred.

[0047] In an embodiment of the present invention, based on the current vehicle speed of the bulldozer and the first function curve and the second function curve, the corresponding first theoretical torque and the second theoretical torque are obtained; the current torque of the bulldozer is compared with the first theoretical torque, and if the current torque is greater than the first theoretical torque, the integral gain is multiplied by the first reduction coefficient; if the current torque is not greater than the first theoretical torque and is greater than the second theoretical torque, the integral gain is multiplied by the second reduction coefficient; the first reduction coefficient is less than the second reduction coefficient, and both the first reduction coefficient and the second reduction coefficient are less than 1.

[0048] In specific implementation, similarly, if the current torque is greater than the first theoretical torque, it indicates that the current torque is already at a very high level, and at the same time the actual speed difference is large, indicating that the soil load reduction is high, but the torque output is high and the vehicle speed is fast, so the amplitude and rate of torque reduction should also match it, and the integral accumulated value is multiplied by the first reduction coefficient; when the current torque is between the second theoretical torque and the first theoretical torque, it indicates that the current torque is not very high, and there is no need to significantly reduce the amplitude and rate of torque increase to avoid the bulldozer suddenly losing torque output and causing power loss, so the integral gain is multiplied by the second reduction coefficient.

[0049] In the embodiment of the present invention, the reduction of the integral accumulated value is stopped until the actual speed difference is not less than the second negative deviation value, or the integral accumulated value is not greater than 0.

[0050] In practice, the introduction of first and second function curves corresponding to the first and second soil load standards offers the advantage of dynamically adjusting the first positive deviation value, second negative deviation value, load change threshold, first theoretical vehicle speed, second theoretical vehicle speed, first theoretical torque, and second theoretical torque—reference parameters used to determine when to begin adjusting the integral control component, as well as the reference parameters for adjusting the nodes where control intensity changes. Compared to fixed parameters, dynamically changing parameters are more adaptable to various application scenarios, enabling better selection of whether to adjust the integral component, and whether to make larger or smaller adjustments, under varying vehicle speeds, torques, and soil load variations.

[0051] The application further provides a speed control device of an electrically-driven bulldozer, comprising a speed execution unit and a PID control unit, wherein the speed execution unit is used for obtaining an actual vehicle speed of the bulldozer, inputting an actual speed difference obtained by subtracting the actual vehicle speed from a target vehicle speed into a PID controller, outputting a torque value by the PID controller, and controlling the bulldozer based on the obtained torque value; and the PID control unit is used for controlling an integral part in the PID controller as follows: if the actual speed difference is greater than a first positive deviation value, the integral gain is increased; and if the actual speed difference is less than a second negative deviation value, the integral accumulation value is decreased.

[0052] In specific implementation, the application provides a speed control device of an electrically-driven bulldozer, wherein the execution unit for executing a method, a step or a function executes the method, the step or the function, which can be referred to the speed control method of the electrically-driven bulldozer provided by the application.

Claims

1. A speed control method for an electric bulldozer, characterized in that: include: The actual speed of the bulldozer is obtained. The actual speed difference obtained by subtracting the actual speed from the target speed is input into the PID controller. The PID controller outputs a torque value, and the bulldozer is controlled based on the obtained torque value. During the PID controller calculation process, the integral part of the PID controller is controlled as follows: If the actual speed difference is greater than the first positive deviation value, the integral gain is increased; If the actual speed difference is less than the second negative deviation value, the integral accumulated value is reduced; Among them, under the working conditions of the first soil load and the second soil load, the first function curve and the second function curve between the bulldozer's vehicle speed and the corresponding torque are respectively obtained; the first soil load is greater than the second soil load; based on the current torque of the bulldozer, and the first function curve and the second function curve, the corresponding first theoretical vehicle speed and the second theoretical vehicle speed are calculated, the first theoretical vehicle speed is subtracted from the second theoretical vehicle speed to obtain a first theoretical speed difference, the first theoretical speed difference is used as a first positive deviation value, the first theoretical speed is subtracted from the second theoretical speed to obtain a second theoretical speed difference, and the second theoretical speed difference is used as a second negative deviation value.

2. The speed control method of an electric bulldozer according to claim 1, characterized in that: Control of the integral part of the PID controller, including: If the actual speed difference is greater than the first positive deviation value and the torque value output by the PID controller is greater than the load change threshold, the integral gain is increased.

3. The speed control method of an electric bulldozer according to claim 2, characterized in that: include: Based on the current speed of the bulldozer and the first function curve and the second function curve, the corresponding first theoretical torque and the second theoretical torque are obtained, and the second theoretical torque is used as the load change threshold.

4. The speed control method for an electric bulldozer according to claim 3, wherein: The above mentioned method improves the integral gain, including: The current torque of the bulldozer is compared with the first theoretical torque. If the current torque is greater than the first theoretical torque, the integral gain is multiplied by a first improvement coefficient. If the current torque is not greater than the first theoretical torque, the integral gain is multiplied by a second improvement coefficient. The first improvement coefficient is greater than the second improvement coefficient, and both the first improvement coefficient and the second improvement coefficient are greater than 1.

5. The speed control method for an electric bulldozer according to claim 4, wherein: The above mentioned method improves the integral gain, including: The integral gain is stopped from being increased until the actual speed difference is no greater than the first positive deviation value, or the torque value output by the PID controller is no greater than the load change threshold.

6. The speed control method for an electric bulldozer according to claim 1, wherein: Control of the integral part of the PID controller, including: If the actual speed difference is less than the second negative deviation value and the integral accumulated value is greater than 0, the integral accumulated value is reduced.

7. The speed control method for an electric bulldozer according to claim 6, wherein: The method of reducing the integral accumulated value includes: Based on the current speed of the bulldozer and the first function curve and the second function curve, obtaining the corresponding first theoretical torque and second theoretical torque; The current torque of the bulldozer is compared with the first theoretical torque. If the current torque is greater than the first theoretical torque, the integral gain is multiplied by the first reduction coefficient. If the current torque is not greater than the first theoretical torque but greater than the second theoretical torque, the integral gain is multiplied by the second reduction coefficient. The first reduction coefficient is less than the second reduction coefficient, and both the first reduction coefficient and the second reduction coefficient are less than 1.

8. The speed control method for an electric bulldozer according to claim 7, wherein: The method of reducing the integral accumulated value includes: When the actual speed difference is not less than the second negative deviation value, or the integral accumulated value is not greater than 0, the integral accumulated value is stopped from being reduced.

9. A speed control device for an electric bulldozer, characterized in that: include: Speed ​​execution unit and PID control unit, including: The speed execution unit is used to obtain the actual speed of the bulldozer, and input the actual speed difference obtained by subtracting the actual speed from the target speed into the PID controller, the PID controller outputs a torque value, and the bulldozer is controlled based on the obtained torque value; The PID control unit is used to control the integral part of the PID controller as follows: If the actual speed difference is greater than the first positive deviation value, the integral gain is increased; If the actual speed difference is less than the second negative deviation value, the integral accumulated value is reduced; Among them, under the working conditions of the first soil load and the second soil load, the first function curve and the second function curve between the bulldozer's vehicle speed and the corresponding torque are respectively obtained; the first soil load is greater than the second soil load; based on the current torque of the bulldozer, and the first function curve and the second function curve, the corresponding first theoretical vehicle speed and the second theoretical vehicle speed are calculated, the first theoretical vehicle speed is subtracted from the second theoretical vehicle speed to obtain a first theoretical speed difference, the first theoretical speed difference is used as a first positive deviation value, the first theoretical speed is subtracted from the second theoretical speed to obtain a second theoretical speed difference, and the second theoretical speed difference is used as a second negative deviation value.

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