Stepping limitation proportional-integral algorithm for creep control of pure electric vehicle

Abstract

The invention relates to the technical field of integral algorithms, in particular to a stepping limit proportional integral algorithm for creep control of a pure electric vehicle, which comprises the following steps: S1, not applying any control acting force within 1.01 seconds after creep enabling; s2, setting a proportional parameter P and an integral parameter I of a discrete PI algorithm; s3, the modification amount yd (k) of the expected automobile speed is set, and the expected automobile speed is a function changing along with time; and S4, discrete PI calculation is carried out, and discrete PI output u (k) is carried out. According to the step limit proportional-integral algorithm for creep control of the pure electric vehicle, overshoot of the expected vehicle speed modification amount is not prone to occurring, and creep control is more stable; and PI parameter adjustment requirements can be reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of integral algorithms, and in particular to a step-limited proportional integral algorithm for creep control of pure electric vehicles. Background Art

[0002] With the continuous progress of society, pure electric vehicles have gradually replaced fuel vehicles and become a popular means of transportation for people nowadays. In the field of pure electric vehicles, the commonly used control method is the discrete proportional integral algorithm (discrete PI), and the principle of this algorithm is simple and easy to implement:

[0003]

[0004] In the formula: T and k respectively represent the sampling period and sampling sequence number of the vehicle controller; e(k) represents the difference between the expected quantity y d (k) (such as the expected vehicle speed) and the vehicle output quantity y(k) (such as the actual vehicle speed); u o (k) represents the preliminary output of the algorithm in the k-th period; u(k) represents the output of the algorithm in the k-th period and is also the input of the actuator (such as the drive motor, gearbox shift lever); k p 、k i respectively represent the parameters of the proportional and integral links in the PI algorithm; a and b respectively represent the upper and lower limits of the output quantity of the vehicle controller.

[0005] Later, through continuous research and development by people, the step PI control was developed. The improvement compared to the traditional PI lies in that: the control system does not directly respond to the overall expected quantity but makes the modification quantity y d (k) of the expected quantity gradually approach the expected quantity, and this modification quantity is preferably a constant. For vehicle creep control, the target vehicle speed is relatively stable, so this algorithm can be applied. After applying this algorithm, the stability of vehicle creep is improved while the rapidity is inhibited. However, creep control has low requirements for rapidity and high requirements for stability, so the step integral separation type PI is an effective method for controlling vehicle creep. The following is an example of this improvement point in a formula. In the formula, R represents the overall expected quantity, that is, the creep target vehicle speed, and r represents the step size of the modification quantity of the expected quantity:

[0006]

[0007] The traditional step PI has good rapidity but poor stability. Creep has low requirements for rapidity but high requirements for stability, so the parameters of the traditional step PI need to be adjusted well. The above traditional PI lacks a means of adjusting the step quantity k, so the modification quantity y d (k) of the expected quantity may overshoot, which is not conducive to the control of creep. Summary of the Invention

[0008] The technical problem to be solved by the present invention is: to solve the problems existing in the above background technology, a stepped limit proportional integral algorithm for creep control of pure electric vehicles is provided, which can prevent the overshoot of the expected vehicle speed modification amount and make the creep control more stable; it can also reduce the requirements for PI parameter adjustment.

[0009] The technical solution adopted by the present invention to solve its technical problems is: a stepped limit proportional integral algorithm for creep control of pure electric vehicles, including the following steps: S1. Within 1.01 seconds after creep enabling, no control force is applied; S2. Set the proportional parameter P and integral parameter I of the discrete PI algorithm; S3. Set the modification amount y d (k) of the expected vehicle speed of the vehicle, and the expected vehicle speed is a function that changes with time; S4. Perform discrete PI calculation, and the discrete PI outputs u(k), where y(k) is the actual vehicle speed:

[0010] Further, in the above technical solution, the S3 includes four stages:

[0011] The first stage: y d (k) increases rapidly:

[0012] Solve the following inequality, where k represents the sampling sequence number and is also the unknown positive integer to be solved, r represents the step unit, and R represents the set vehicle speed. In this case, R is taken as 5 km / h and r is taken as 0.25;

[0013]

[0014] After obtaining the sequence of k, take the maximum value k 1 from it, then y d in the first stage is expressed as follows:

[0015]

[0016] The second stage: y d (k) increases uniformly:

[0017] Solve the following inequality group, where k is an unknown positive integer;

[0018]

[0019] After obtaining the sequence of k, take the maximum value k 2 from it, then y d in the second stage is shown as follows:

[0020] y d (k)-y d (k - 1) = k 1 - 1(k1 <k ≤ k 2 )

[0021] The third stage: y d (k) continues to increase uniformly, but the increasing speed decreases;

[0022] Solve the following system of inequalities, where k is an unknown positive integer;

[0023]

[0024] After obtaining the sequence of k, take the maximum value k from it 3 , then the y in the third stage d (k) is as follows:

[0025] y d (k) - y d (k - 1) = 1 (k 2 <k ≤ k 3 )

[0026] The fourth stage: y d (k) remains unchanged. In this stage, y d (k) is as follows:

[0027] y d (k) - y d (k - 1) = 0 (k > k 3 )

[0028] In summary, the y d (k) set in the third step is as shown in the following formula:

[0029]

[0030] Furthermore, in the above solution, when the pure electric vehicle creep is not enabled, all quantities in this method are 0.

[0031] Furthermore, in the above technical solution, when the vehicle in S2 is in the forward gear, the proportional parameter is 2 and the integral parameter is 0.2.

[0032] Furthermore, in the above technical solution, when the vehicle in S2 is in the reverse gear, the proportional parameter is 1 and the integral parameter is 0.1.

[0033] The beneficial effect produced by the technical solution of this application is: a step limit proportional integral algorithm for pure electric vehicle creep control can make the modification amount of the desired vehicle speed not prone to overshoot, and the creep control is more stable; it can also reduce the requirements for PI parameter adjustment. Description of the Drawings

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required for the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only some embodiments recorded in this application. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can also be obtained based on these drawings.

[0035] Figure 1 It is the image display of yd(k) in the present invention;

[0036] Appendix Figure 1 In the abscissa is time, and the ordinate is the modified amount yd(k) of the desired vehicle speed.

[0037] Figure 2 It is the schematic diagram of the step flow of this method during creep enabling in the present invention. Detailed implementation manners

[0038] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0039] See Figure 1 And Figure 2 Shown is a step limit proportional integral algorithm for creep control of a pure electric vehicle, including the following steps: S1. Within 1.01 seconds after creep enabling, no control force is applied; S2. Set the proportional parameter P and integral parameter I of the discrete PI algorithm; S3. Set the modified amount y d (k) of the desired vehicle speed of the vehicle, and this desired vehicle speed is a function of time; S4. Perform discrete PI calculation, and the discrete PI outputs u(k), where y(k) is the actual vehicle speed:

[0040] Among them, S3 includes four stages:

[0041] The first stage: y d (k) increases rapidly:

[0042] Solve the following inequality, where k represents the sampling sequence number and is also the unknown positive integer to be solved, r represents the step unit, and R represents the set vehicle speed. In this case, R takes a value of 5 km / h and r takes a value of 0.25;

[0043]

[0044] After obtaining the sequence of k, take the maximum value k 1 from it, then y in the first stage d(k) is expressed as follows:

[0045]

[0046] The second stage: y d (k) increases uniformly:

[0047] Solve the following system of inequalities, where k is an unknown positive integer;

[0048]

[0049] After obtaining the sequence of k, take the maximum value k from it 2 , then y in the second stage d (k) is as follows:

[0050] y d (k) - y d (k - 1) = k 1 -1(k 1 < k ≤ k 2 )

[0051] The third stage: y d (k) continues to increase uniformly, but the increasing speed decreases;

[0052] Solve the following system of inequalities, where k is an unknown positive integer;

[0053]

[0054] After obtaining the sequence of k, take the maximum value k from it 3 , then y in the third stage d (k) is as follows:

[0055] y d (k) - y d (k - 1) = 1(k 2 < k ≤ k 3 )

[0056] The fourth stage: y d (k) remains unchanged. In this stage, y d (k) is as follows:

[0057] y d (k) - y d (k - 1) = 0(k > k 3 )

[0058] In summary, y d (k) set in the third step is as shown in the following formula:

[0059]

[0060] When the creep function of the pure electric vehicle is not enabled, all the quantities in this method are 0. When the vehicle is in the forward gear in 2, the proportional parameter is 2 and the integral parameter is 0.2. When the vehicle is in the reverse gear in S2, the proportional parameter is 1 and the integral parameter is 0.1.

[0061] This application has the following advantages compared with the traditional step PI: the stability has been greatly improved, the requirements for PI parameter adjustment have been reduced; the overshoot of the expected vehicle speed modification amount is not likely to occur.

[0062] The above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, making equivalent substitutions or changes, should be covered within the protection scope of the present invention.

Claims

1. A step-limited proportional-integral algorithm for pure electric vehicle creep control, characterized in that: The method comprises the following steps: S1, within 1.01 seconds after creeping, no control force is applied; S2, the proportional parameter P and the integral parameter I of the discrete PI algorithm are set; S3, the modification amount y of the desired vehicle speed is set d (k), the expected vehicle speed is a function that changes with time; S4, perform discrete PI calculation, and the discrete PI outputs u(k), where y(k) represents the actual vehicle speed: 。 2. A step-limited proportional-integral algorithm for creep control of a pure electric vehicle as claimed in claim 1, characterized in that: The S3 described includes four stages: Phase 1: y d (k) Accelerated increase: Solve the following inequality, where k represents the sampling number and is also the unknown positive integer, r represents the step unit, and R represents the set speed. In this case, R is 5 km / h and r is 0.25; After solving the sequence of k, take the maximum value k1 from it, then the y of the first stage d (k) is expressed as follows: Phase 2: y d (k) Uniform increase: Solve the following system of inequalities, where k is an unknown positive integer; After solving the sequence of k, take the maximum value k2 from it, then the y of the second stage d (k) is as follows: y d (k)-y d (k-1)=k1-1(k1 <k≤k2) Stage 3: y d (k) Continue to increase at a constant speed, but the rate of increase decreases; Solve the following system of inequalities, where k is an unknown positive integer; After solving the sequence of k, take the maximum value k3 from it, then the y of the third stage is d (k) is as follows: y d (k)-y d (k-1)=1(k2<k≤k3) Stage 4: y d (k) remains unchanged, at this stage y d (k) is as follows: y d (k)-y d (k-1)=0(k>k3) In summary, the y set in the third step d (k) is shown in the following formula:

3. A step-limited proportional-integral algorithm for creep control of a pure electric vehicle as claimed in claim 1, characterized in that: When the pure electric vehicle creep is not enabled, all quantities in this method are 0.

4. A step-limited proportional-integral algorithm for creep control of a pure electric vehicle as claimed in claim 1, characterized in that: When the vehicle is in the forward gear in S2, the proportional parameter is 2 and the integral parameter is 0.

2.

5. A step-limited proportional-integral algorithm for creep control of a pure electric vehicle as claimed in claim 1, characterized in that: When the vehicle is in reverse gear in S2, the proportional parameter is 1 and the integral parameter is 0.1.

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