A method and system for controlling the rotation speed of an electric vehicle range extender, and an electric vehicle

Abstract

This invention provides a method, control system, and electric vehicle for controlling the speed of an electric vehicle range extender. A basic simulation model of the range extender speed control system is built using the backstepping method. By setting the injection timing, intake parameters, ignition advance angle, and load torque, and increasing the range extender speed by a step, the output speed is recorded and a fast Fourier transform is performed to obtain the engine torque ripple model. Based on this, repetitive controller parameters and an FIR filter are designed. This method can significantly reduce range extender speed fluctuations, is simple to design, reduces controller design costs, and solves the problem of large and difficult-to-control range extender speed fluctuations. It is applicable to the field of range extender speed control.

Description

Technical Field

[0001] This invention relates to the field of electric vehicle range extender control, specifically to an electric vehicle range extender speed control method, a control system, and an electric vehicle. Background Technology

[0002] Electric vehicles, with their advantages of high energy efficiency, zero emissions, and low noise, are gaining increasing attention in the face of the dual energy and environmental crises the world is currently facing, and have made significant progress in recent years. However, pure electric vehicles have disadvantages such as difficulty in obtaining payment, short driving range, and slow charging, so consumers tend to buy hybrid vehicles. Range-extended electric vehicles (REEVs), with their single drive mode (using only the electric motor for all times), linear acceleration, and inherent elimination of the possibility of jerking during drive mode switching, along with their simple system architecture and lower cost, have also won the favor of consumers.

[0003] The range extender, mainly composed of an engine and a generator, is a core component of range-extended electric vehicles. Range extenders typically use engines with small displacement and few cylinders, resulting in poor vibration performance and increased speed fluctuations. These speed fluctuations significantly impact the lifespan, vibration, noise, and efficiency of the range extender's shaft system and connecting components, and consequently affect the vehicle's stability and ride comfort. Currently, range extender systems still exhibit significant speed fluctuations, primarily manifested as torque fluctuations in steady-state operation and transient torque fluctuations during operating mode switching. These large torque fluctuations cause speed fluctuations in the range extender system, thus affecting the vehicle's NVH performance. Therefore, research on the torsional vibration characteristics of range extenders and the control of speed fluctuations are of great importance.

[0004] Current research on range extenders by scholars both domestically and internationally mainly focuses on structural design and layout, dynamic modeling and model development, energy management and efficiency optimization, and overall vibration characteristics analysis. However, research on range extender speed fluctuations is scarce. Regarding range extender speed control, previous studies have only focused on the control of the engine itself. The engine is a complex and highly nonlinear system. Its intake system, fuel system, crankshaft, load system, and other actuators all exhibit certain hysteresis characteristics, with torque response times on the order of seconds. Furthermore, the engine in a range extender has fewer cylinders and greater vibration, making direct control of engine speed more difficult.

[0005] Therefore, in view of the vibration characteristics of the range extender, it is urgent to develop a range extender speed control method to avoid excessive fluctuations in the range extender speed and ensure vehicle stability and overall vehicle comfort. Summary of the Invention

[0006] The main objective of this invention is to provide a method for controlling the speed of an electric vehicle range extender, so as to solve the problem that large speed fluctuations of the range extender in the prior art affect the smoothness of the vehicle.

[0007] This objective is achieved through the following technical solution:

[0008] A method for controlling the speed of an electric vehicle range extender includes the following steps:

[0009] S1. Establish the dynamic model of the range extender and the simulation model of the range extender speed control system. Use the output torque of the motor as the control quantity of the speed control system, and give the desired speed of the speed control system. Record the output speed of the range extender simulation model at each desired speed.

[0010] S2. Using the data recorded in step S1, perform a fast Fourier transform on the output speed of the range extender dynamic model to obtain the engine torque ripple model that causes speed fluctuations.

[0011] S3. Design of a repetitive controller for the engine torque ripple model;

[0012] S4. Apply the repeating controller from step S3 to the controller of the range extender speed control system to reduce the speed fluctuation of the range extender.

[0013] Furthermore, the specific process of step S1 is as follows:

[0014] S11. Establish the dynamic model of the range extender, and at the same time use the backstepping method to build a simulation model of the range extender speed control system, and initially realize speed tracking control.

[0015] S12. After setting the injection timing, intake parameters, ignition advance angle and load torque in the range extender simulation model, the desired speed is increased in the form of a step function, and the output speed of the range extender simulation model at each desired speed is recorded.

[0016] Furthermore, the dynamic model of the range extender established in step S11 is as follows:

[0017]

[0018] Where J is the moment of inertia of the range extender, ω is the mechanical angular velocity of the range extender, and T... m T is the output torque of the motor. e Where B is the engine output torque, and B is the coefficient of viscous friction.

[0019] Furthermore, in step S12, when the desired rotational speed is increased in the form of a step function, the change amount of the desired rotational speed is set each time, and the desired rotational speed is changed once every time interval T.

[0020] Furthermore, the specific process of step S2 is as follows:

[0021] S21. Select a portion of the range extender output speed data recorded in step S1 and perform a fast Fourier transform.

[0022] S22. Select a combination of several sine functions with different amplitudes, frequencies and phase angles as the engine torque ripple model. Based on the results of the fast Fourier transform in step S21, obtain the engine torque ripple model.

[0023] Furthermore, the specific process of step S21 is as follows: select data within the same desired speed range from the range extender output speed data recorded in step S1 and perform a fast Fourier transform.

[0024] Furthermore, the engine torque ripple model obtained in step S22 is as follows:

[0025]

[0026] Where θ is the angular position of the range extender, and T i The amplitude of each harmonic. T represents the phase angle of each harmonic. d It is a periodic function of angular position with a period of 360°.

[0027] Furthermore, the transfer function of the repetitive controller designed based on the engine torque ripple model in step S3 is as follows:

[0028]

[0029] Where k is the repetitive controller gain, Q(z) is the FIR low-pass filter, N is the ratio of the sampling frequency to the engine torque ripple signal frequency, representing the step size required for the range extender to rotate one position cycle, and N0 is the phase delay compensation of Q(z).

[0030] Furthermore, the FIR low-pass filter is designed using the Gaussian window function method.

[0031] Another object of the present invention is to provide a speed control system for an electric vehicle range extender, comprising:

[0032] Range extender simulation model; Use the range extender simulation model to perform range extender simulation.

[0033] Feedback controller, used in range extender simulation models to change the speed;

[0034] The data processor performs a fast Fourier transform on the output speed of the feedback controller to obtain the engine torque ripple model;

[0035]

[0036] Where θ is the angular position of the range extender, and T i The amplitude of each harmonic. T represents the phase angle of each harmonic. d It is a periodic function of angular position with a period of 360°;

[0037] The repetitive controller is designed based on the engine torque ripple model, and its transfer function is:

[0038]

[0039] Where k is the repetitive controller gain, Q(z) is the FIR low-pass filter, N is the ratio of the sampling frequency to the engine torque ripple signal frequency, representing the step size required for the range extender to rotate one position cycle, and N0 is the phase delay compensation of Q(z).

[0040] Another object of the present invention is to provide an electric vehicle range extender speed control device, including a memory, a processor, and a range extender control program stored in the memory and executable on the processor, the range extender control program being configured to implement the steps of the above-described electric vehicle range extender speed control method.

[0041] Another object of the present invention is to provide a storage medium storing a range extender control program, which, when executed by a processor, implements the steps of the above-described electric vehicle range extender speed control method.

[0042] Another object of the present invention is to provide an electric vehicle including the above-described electric vehicle range extender speed control system.

[0043] The beneficial effects are:

[0044] The range extender speed control method provided by this invention utilizes a backstepping method to design a simulation model of the range extender speed control system, keeping the range extender speed near the desired speed. The output speed of the range extender simulation model at each desired speed is recorded and then subjected to a Fast Fourier Transform to obtain the engine torque ripple model. A repetitive controller is then designed to reduce the range extender speed fluctuation. Compared to engines, electric motors generally use vector control, resulting in very fast torque response (in the millisecond range). Therefore, this invention utilizes motor torque to balance engine torque ripple, ensuring vehicle stability and overall vehicle comfort.

[0045] Experiments have verified that the range extender speed control method proposed in this invention can achieve excellent control results when used to control the range extender simulation model. Attached Figure Description

[0046] Figure 1 This is a flowchart of the electric vehicle range extender speed control method of the present invention;

[0047] Figure 2 This is a control structure diagram of the range extender speed control system of the present invention;

[0048] Figure 3 This is a schematic diagram of the rotational speed data collected in Embodiment 1 of the present invention;

[0049] Figure 4 This is a schematic diagram of the Fourier transform of the output rotational speed in Embodiment 1 of the present invention;

[0050] Figure 5 This is a comparison diagram of the output speed before and after the introduction of the repetitive controller in Embodiment 1 of the present invention;

[0051] Figure 6 This is a speed control diagram of the repetitive controller adjustment in Embodiment 1 of the present invention. Detailed Implementation

[0052] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The following will provide a detailed description with reference to the accompanying drawings and embodiments.

[0053] Combination Figure 1 This embodiment describes a method for controlling the speed of a range extender using a motor. The method specifically includes the following steps:

[0054] S1. Establish the dynamic model of the range extender and the simulation model of the range extender speed control system. Use the output torque of the motor as the control quantity of the speed control system, and give the desired speed of the speed control system. Record the output speed of the range extender simulation model at each desired speed.

[0055] S2. Using the data recorded in step S1, perform a fast Fourier transform on the output speed of the range extender simulation model to obtain the engine torque ripple model that causes speed fluctuations.

[0056] S3. Design of a repetitive controller for the engine torque ripple model;

[0057] S4. Apply the repeating controller from step S3 to the controller of the range extender speed control system to reduce the speed fluctuation of the range extender.

[0058] The range extender speed control method provided by this invention solves the problem of poor vibration performance of the range extender, which leads to poor speed control effect. It uses a high-precision simulation model in the software to obtain the engine torque ripple model, and then designs an accurate repeating controller, which has strong innovation and practical value.

[0059] In some other embodiments, unlike the embodiments described above, the specific process of step S1 is as follows:

[0060] S11. Establish the dynamic model of the range extender, and at the same time use the backstepping method to build a simulation model of the basic speed control system of the range extender, so as to initially realize speed tracking control.

[0061] S12. After setting the injection timing, intake parameters, ignition advance angle and load torque in the range extender simulation model, the desired speed is increased in the form of a step function, and the output speed of the range extender simulation model at each desired speed is recorded.

[0062] This implementation method builds a physical model based on the working principle of the range extender. This physical model closely resembles the real range extender system and is well-suited for analyzing engine torque ripple.

[0063] The other steps and parameters are the same as those in the above implementation method.

[0064] In other embodiments, unlike one of the embodiments described above, the dynamic model of the range extender established in step 11 is as follows:

[0065]

[0066] Where J is the moment of inertia of the range extender, ω is the mechanical angular velocity of the range extender, and T... m T is the output torque of the motor. e Where B is the engine output torque, and B is the coefficient of viscous friction.

[0067] In this embodiment, the backstepping method constructs a Lyapunov function through this dynamic model to obtain a feedback controller.

[0068] The other steps and parameters are the same as in one of the above implementation methods.

[0069] In some other embodiments, unlike one of the embodiments described above, when the desired rotational speed is increased in the form of a step function in step S12, the change amount of the desired rotational speed is set each time, and the desired rotational speed is changed once every time interval T.

[0070] The other steps and parameters are the same as in one of the above implementation methods.

[0071] In other embodiments, unlike one of the embodiments described above, the specific process of step S2 is as follows:

[0072] S21. Select a portion of the range extender output speed data recorded in step S1 and perform a fast Fourier transform.

[0073] S22. Select a combination of several sine functions with different amplitudes, frequencies and phase angles as the engine torque ripple model. Based on the results of the fast Fourier transform in step S21, obtain the engine torque ripple model.

[0074] This implementation method performs a fast Fourier transform on the simulation data to obtain the influence of harmonic content on torque ripple at different frequencies. The established engine torque ripple model is suitable for repetitive control, which only requires the signal frequency and does not need to know the signal amplitude.

[0075] The other steps and parameters are the same as in one of the above implementation methods.

[0076] In some other embodiments, unlike one of the embodiments described above, the specific process of step S21 is as follows: select data within the same desired speed range from the range extender output speed data recorded in step 1 and perform a fast Fourier transform.

[0077] For example, when the desired rotational speed is set to 1000 r / min, only data around 1000 r / min are selected for the Fast Fourier Transform.

[0078] The other steps and parameters are the same as in one of the above implementation methods.

[0079] In some other embodiments, unlike one of the embodiments described above, the engine torque ripple model obtained in step S22 is:

[0080]

[0081] Where θ is the angular position of the range extender, and T i The amplitude of each harmonic. Let T be the phase angle of each harmonic, which shows that... d It is a periodic function of angular position with a period of 360°.

[0082] In this embodiment, the amplitude of the obtained engine torque ripple model is unknown, while the frequency is known.

[0083] The other steps and parameters are the same as in one of the above implementation methods.

[0084] In other embodiments, unlike one of the embodiments described above, the transfer function of the repetitive controller designed based on the engine torque ripple model in step 3 is:

[0085]

[0086] Where k is the repetitive controller gain, Q(z) is the FIR low-pass filter, N is the ratio of the sampling frequency to the engine torque ripple signal frequency, representing the step size required for the range extender to rotate one position cycle, and N0 is the phase delay compensation of Q(z).

[0087] This implementation method designs repetitive controller parameters based on the engine torque ripple model and compensates for the phase delay N0 of the FIR low-pass filter Q(z) to suppress the speed fluctuation of the range extender.

[0088] The other steps and parameters are the same as in one of the above implementation methods.

[0089] In other embodiments, unlike one of the embodiments described above, the FIR low-pass filter is designed using the Gaussian window function method.

[0090] In this embodiment, the Gaussian window has a wide main lobe and no negative side lobes. The first side lobe attenuates to -55dB, which is beneficial for capturing more harmonic components in the feedback signal and improving the control effect.

[0091] The other steps and parameters are the same as in one of the above implementation methods.

[0092] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. The design flow of a method for controlling the speed of a range extender using a motor based on a software platform according to the present invention is as follows: Figure 1 As shown.

[0093] Example 1

[0094] This embodiment uses a range extender consisting of a four-stroke two-cylinder gasoline engine with a bore of 80.5mm, a stroke of 88.2mm, and a compression ratio of 10.5, and a surface-mounted permanent magnet synchronous motor for simulation modeling and simulation experiments.

[0095] A method for controlling the speed of a range extender using a motor based on a software platform, the method specifically includes the following steps:

[0096] S1: The working principle and basic parameters of the range extender were modeled using the system simulation software AMEsim. A co-simulation model was established using the SimuCosim module of AMEsim and the AME2SLCoSim module of Matlab / Simulink. The simulation model is as follows: Figure 2 The block diagram is shown below. After setting the injection timing, intake parameters, ignition advance angle, and load torque, a range extender simulation is performed, and input and output speed data are collected. A speed control system is designed, using the motor output torque as the control variable, so that the range extender simulation model can change speed within the allowable operating speed range. The sampling frequency is set to 1000Hz, and the recorded output speed data is shown below. Figure 3 As shown;

[0097] S2: Using the data recorded in step S1, perform a fast Fourier transform on the output speed of the range extender simulation model to obtain the engine torque ripple model that causes speed fluctuations in this example.

[0098]

[0099] In this embodiment, the amplitude of the engine torque ripple model is unknown, while the frequency is known.

[0100] The result of performing a Fourier transform on the output speed is as follows Figure 4 As shown;

[0101] S3: Design of a repetitive controller for the engine torque ripple model. The design process is as follows:

[0102] S31. Calculate the frequency of the engine torque ripple signal as ω / 2π, where ω is the angular velocity of the range extender;

[0103] S32. Design an FIR low-pass filter, using a Gaussian window as the window function, setting the filter order to 100, and the cutoff frequency to 60Hz.

[0104] S33. Compensate for the phase delay of the FIR low-pass filter, i.e., N0 is half of the filter order;

[0105] S34. Set the repetitive controller gain k to 50. The larger k is, the faster the system response.

[0106] S4: In the software platform, establish a range extender speed control system, and apply the repetitive controller parameters set in step S3 to the controller of the speed control system so that the range extender can complete the control to reduce speed fluctuations.

[0107] The obtained repetitive control parameters were applied to the controller to control the range extender in a joint simulation experiment, verifying the effectiveness of the range extender speed control. The range extender speed control effect in Example 1 is as follows: Figure 5 , Figure 6 As shown. Figure 5 The output speed curve of the range extender is shown, where only backstepping control is used from 0-10s, and repetitive control is introduced from 10-20s. Figure 5 The control effect of the speed before and after 10 seconds shows that when only the backstepping method is used, the speed fluctuation of the range extender is large and deviates significantly from the desired speed. In practical applications, this has a great impact on the performance and lifespan of the range extender. By introducing the repetitive controller proposed in this invention, the speed fluctuation is reduced by about 86.7%, and the actual output speed of the range extender quickly tracks the desired speed, meeting the requirements of practical engineering control. Figure 6 The speed control diagram for repetitive controller adjustment. From Figure 6As can be seen, the actual speed of the range extender can quickly track the desired speed, especially after the engine reaches the starting speed in a very short time (about 5s). The repetitive controller starts to adjust the output torque of the motor, and its signal response lags behind the target signal response by about 0.1s. Under the conditions of changes in desired speed and sudden load unloading (15s) and sudden load addition (25s), the speed of the range extender can quickly follow the desired speed under the action of the repetitive controller, which demonstrates the good following performance of the present invention in speed control.

[0108] The above examples of the present invention are merely illustrative of the computational model and process of the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is impossible to exhaustively list all possible implementations here. Any obvious variations or modifications derived from the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A method of controlling the speed of an electric vehicle range extender, characterized by, Includes the following steps: S1. Establish the dynamic model of the range extender and the simulation model of the range extender speed control system. Use the output torque of the motor as the control variable of the simulation model of the range extender speed control system. Given the desired speed of the simulation model of the range extender speed control system, record the output speed of the simulation model of the range extender at each desired speed. S2. Performing a Fast Fourier Transform on the output speed of the range extender dynamics model yields the engine torque ripple model that causes speed fluctuations: in, The angular position of the range extender. The amplitude of each harmonic. Let the phase angles of each harmonic be denoted as . It is a periodic function of angular position, with a position period of . ; S3. Based on the engine torque ripple model, the repetitive controller is obtained. The transfer function of the repetitive controller is: in, For the repetitive controller gain, It is an FIR low-pass filter. The ratio of the sampling frequency to the engine torque ripple signal frequency represents the step size required for the range extender to rotate one position cycle. for Phase delay compensation; S4. Use the repetitive controller for the speed control of the electric vehicle range extender; The dynamics model of the range extender is: in, The moment of inertia of the range extender. The mechanical angular velocity of the range extender. For the motor output torque, For engine output torque, It is the coefficient of viscous friction; Step S1 specifically includes the following steps: S11. Establish the dynamic model of the range extender, and at the same time use the backstepping method to build a simulation model of the range extender speed control system, and initially realize speed tracking control. S12. After setting the injection timing, intake parameters, ignition advance angle and load torque in the dynamic model of the range extender, the desired speed is increased in the form of a step function, and the output speed of the range extender simulation model at each desired speed is recorded. In step S12, when the desired rotational speed is increased in the form of a step function, the change in the desired rotational speed is set each time, at intervals of... Time will change the desired rotational speed once; Step S2 includes the following steps: S21. Select a portion of the output speed data from the range extender and perform a fast Fourier transform. S22. Select a combination of several sine functions with different amplitudes, frequencies and phase angles as the engine torque ripple model, and obtain the engine torque ripple model based on the results of the fast Fourier transform in step S21.

2. The electric vehicle range extender speed control method of claim 1, wherein, In step S3, the FIR low-pass filter is designed using the Gaussian window function method.

3. An electric vehicle range extender speed control system, characterized by, include: Range extender simulation model; Use the range extender simulation model to perform range extender simulation. Feedback controller, used in range extender simulation models to change the speed; The data processor transforms the output speed of the feedback controller by fast Fourier transform to obtain an engine torque ripple model as follows: in, The angular position of the range extender. The amplitude of each harmonic. Let the phase angles of each harmonic be denoted as . It is a periodic function of angular position, with a position period of . ; a repetitive controller designed according to an engine torque ripple model, the repetitive controller transfer function being: in, For the repetitive controller gain, It is an FIR low-pass filter. The ratio of the sampling frequency to the engine torque ripple signal frequency represents the step size required for the range extender to rotate one position cycle. for Phase delay compensation; The dynamic model of the range extender is as follows: in, The moment of inertia of the range extender. The mechanical angular velocity of the range extender. For the motor output torque, For engine output torque, It is the coefficient of viscous friction; A dynamic model of the range extender was established, and a simulation model of the range extender speed control system was built using the backstepping method to initially realize speed tracking control. After setting the injection timing, intake parameters, ignition advance angle and load torque in the dynamic model of the range extender, the desired speed is increased in the form of a step function, and the output speed of the range extender simulation model at each desired speed is recorded. When increasing the desired speed in the form of a step function, the amount of change in the desired speed is set each time, at intervals of... Time will change the desired rotational speed once; Select a portion of the output speed data from the range extender and perform a fast Fourier transform. A combination of several sine functions with different amplitudes, frequencies, and phase angles is selected as the engine torque ripple model, and the engine torque ripple model is obtained based on the results of the fast Fourier transform.

4. An electric vehicle range extender speed control device, characterized by, The device includes a memory, a processor, and a range extender control program stored in the memory and executable on the processor, the range extender control program being configured to implement the steps of the electric vehicle range extender speed control method as described in any one of claims 1 to 2.

5. A storage medium, characterized by The storage medium stores a range extender control program, which, when executed by a processor, implements the steps of the electric vehicle range extender speed control method as described in any one of claims 1 to 2.

6. An electric vehicle, characterized by Includes the electric vehicle range extender speed control system as described in claim 3.

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