Rotational speed fluctuation amount control method, device and automobile
By adjusting the motor's starting torque in stages, the problem of transmission system knocking and vehicle vibration caused by large speed fluctuations during engine start-stop in hybrid electric vehicles has been solved, resulting in a more stable starting process and improved noise levels.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- GUANGZHOU AUTOMOBILE GROUP CO LTD
- Filing Date
- 2023-05-16
- Publication Date
- 2026-07-14
AI Technical Summary
The engine speed of hybrid vehicles fluctuates greatly during start-stop, causing knocking in the transmission system and vibration of the whole vehicle. Existing closed-loop control is lagging and unstable.
By adjusting the motor's starting torque in stages, including the torque action in the first to fourth stages, and adjusting the torque slope and duration according to the characteristics of the motor and engine, the speed fluctuations caused by cylinder pressure changes during engine dragging are offset.
It reduces the speed fluctuation on both sides of the torsional damper, improving starting noise and overall vehicle stability.
Smart Images
Figure CN118991726B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of hybrid vehicle control, and more particularly to a method, device, and vehicle for controlling speed fluctuation. Background Technology
[0002] Hybrid electric vehicles (HEVs) are characterized by frequent engine start-stop cycles. During these cycles, the engine speed fluctuates significantly. HEVs typically use a starter motor within the transmission, which then uses a torsional damper to reverse-drive the engine for starting. Due to the vibration isolation requirements of engine-driven operation, the torsional damper usually has relatively low torsional stiffness. When using dampers with low torsional stiffness, the reverse-drive speed fluctuation control process involves the torsional damper's resonant speed range. In this resonant speed range, due to the relatively large inertia, the speed fluctuations on both sides of the flywheel are significant. These large speed fluctuations can cause knocking in the transmission system clearances and lead to vehicle vibration. If a centrifugal pendulum shock absorber is used, knocking from the centrifugal pendulum shock absorber will also occur.
[0003] In existing technologies, closed-loop control is achieved by using the difference between the starter motor speed and the engine speed, followed by PI (proportional integral controller) adjustment of the driving torque to complete the starting and driving process. However, this method has a lag; closed-loop control only begins after the speed difference is established. The control process is affected by various system factors (such as changes in the resistance model and the initial engine position), resulting in large and unstable speed fluctuations. This speed difference is a key factor causing knocking noises in the transmission system during starting, or knocking noises from the vibration damper matched with the centrifugal pendulum vibration absorber during starting. Summary of the Invention
[0004] Therefore, it is necessary to provide a method, device, and automobile for controlling the speed fluctuation of the motor during the starting and driving process, so as to improve the speed fluctuation of the motor and reduce starting noise.
[0005] A method for controlling speed fluctuation includes:
[0006] After the engine start command is issued, the motor drives the engine:
[0007] Apply a first-stage torque to the motor until the first starting torque is reached; the duration of the first stage is the first duration.
[0008] A second stage of torque is applied to the motor: the first starting torque is increased by the first starting torque slope to obtain a second starting torque;
[0009] A third stage of torque is applied to the motor: if the motor speed is greater than a preset motor speed threshold and the engine speed rise gradient is less than zero, the second starting torque is increased by a second starting torque slope until the maximum starting torque is reached; the second starting torque slope is greater than the first starting torque slope.
[0010] A fourth stage of torque is applied to the motor: if the motor speed is detected to have reached the target speed, the maximum starting torque is reduced.
[0011] A speed fluctuation control device, comprising:
[0012] The start-up drag module is used to drive the engine by a motor after the engine start command is issued;
[0013] The start-up drag module includes:
[0014] The first torque control unit is used to apply a first stage of torque to the motor until the first starting torque is reached; the duration of the first stage is a first duration.
[0015] The second torque control unit is used to apply a second stage of torque to the motor: increasing the first starting torque with a first starting torque slope to obtain a second starting torque;
[0016] The third torque control unit is used to apply a third stage of torque to the motor: if the motor speed is greater than a preset motor speed threshold and the engine speed rise gradient is less than zero, the second starting torque is increased by a second starting torque slope until the maximum starting torque is reached; the second starting torque slope is greater than the first starting torque slope.
[0017] The fourth torque control unit is used to apply a fourth stage of torque to the motor: if the motor speed is detected to have reached the target speed, the maximum starting torque is reduced.
[0018] An automobile includes an electronic control unit for executing any of the above-described speed fluctuation control methods.
[0019] The aforementioned speed fluctuation control method, device, and vehicle adjust the motor's starting torque in stages based on the characteristics of the motor, engine, and torsional damper. By correcting the starting torque, the speed fluctuation of the motor caused by cylinder pressure changes during engine operation can be offset, thereby reducing the fluctuation on both sides of the torsional damper and significantly reducing the speed fluctuation of the motor. This invention can improve the speed fluctuation of the motor during startup and reduce startup noise. Attached Figure Description
[0020] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0021] Figure 1 This is a flowchart illustrating a speed fluctuation control method according to an embodiment of the present invention;
[0022] Figure 2 This is a speed-torque-time curve in one embodiment of the present invention;
[0023] Figure 3 This is a schematic diagram of a speed fluctuation control device in one embodiment of the present invention;
[0024] Figure 4 This is a schematic diagram of a computer device according to an embodiment of the present invention. Detailed Implementation
[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0026] In one embodiment, such as Figure 1 As shown, the speed fluctuation control method provided in this embodiment includes the following steps S10-S50.
[0027] S10. After the engine start command is issued, the motor drives the engine.
[0028] Understandably, between the issuance of the engine start command and the engine starting, the electric motor provides the initial torque, which drives the engine to rotate through the torsional damper, thereby helping the engine start faster.
[0029] S20. Apply a first-stage torque to the motor until the first starting torque is reached; the duration of the first stage is the first duration.
[0030] Understandably, after the vehicle controller issues the engine start command, the motor controller (a type of electronic control unit) applies a first-stage torque to the motor until the first starting torque is reached. Here, the duration of this first stage is called the first duration. That is, the starting torque applied to the motor increases from 0 Nm to the first starting torque over the first duration. In the first stage, the motor torque can increase linearly to reach the first starting torque. Setting the first starting torque and the first duration here eliminates drivetrain backlash during the starting process. The first starting torque can be represented by T1.
[0031] S30. Apply a second stage of torque to the motor: increase the first starting torque with the first starting torque slope to obtain a second starting torque.
[0032] Understandably, the initial starting torque slope can be set according to actual needs. Here, the setting of the initial starting torque slope needs to consider how to reasonably increase engine speed. If the initial starting torque slope is too small, the motor speed will increase slowly, resulting in a slower rate of engine speed increase. If the initial starting torque slope is too large, it will limit the motor's subsequent adjustment capabilities, making it impossible to further adjust the starting torque slope. The second starting torque can be represented by T2. Therefore, the second starting torque T2 = T1 + a * t2, where a is the initial starting torque slope and t2 is the duration of the second stage.
[0033] S40. Apply a third stage of torque to the motor: if the motor speed is greater than a preset motor speed threshold and the engine speed rise gradient is less than zero, then increase the second starting torque with a second starting torque slope until the maximum starting torque is reached; the second starting torque slope is greater than the first starting torque slope.
[0034] Understandably, the preset motor speed threshold can be set according to actual needs, such as the lower limit of the resonance speed range. In the third stage, if the motor speed is greater than the preset motor speed threshold and the engine speed rise gradient is less than zero, it is necessary to quickly increase the motor speed to reduce resonance between the motor and the torsional damper. Therefore, a larger second starting torque slope can be used to increase the second starting torque until the maximum starting torque is reached. The second starting torque slope can be set according to actual needs.
[0035] After reaching the maximum starting torque, the starting torque is kept constant, the motor speed is increased, and S50 continues to apply the fourth stage of torque to the motor: if the motor speed is detected to have reached the target speed, the maximum starting torque is reduced.
[0036] Understandably, in the fourth stage, if the motor speed is detected to have reached the target speed, the engine can begin ignition. After the engine begins ignition, the maximum starting torque needs to be reduced to prevent the engine speed from surging too high under the combined effects of starting torque and ignition torque.
[0037] This embodiment adjusts the motor's starting torque in stages based on the characteristics of the motor, engine, and torsional damper. By correcting the starting torque, the fluctuations in motor speed caused by cylinder pressure changes during engine operation can be offset, thereby reducing the fluctuations on both sides of the torsional damper and significantly reducing motor speed fluctuations. This embodiment can improve the amount of motor speed fluctuations during startup and reduce startup noise.
[0038] like Figure 2 As shown, Figure 2 This is an example of a speed-torque-time curve. The left axis represents speed in rpm, the right axis represents torque in Nm, and the bottom axis represents time in seconds. L1 represents the speed-time curve, and L2 represents the torque-time curve. In the first stage, the applied torque increases to the motor within a first time period, reaching the first starting torque T1, at which point the motor speed begins to increase. In the second stage, the starting torque increases with the slope of the first starting torque, resulting in the second starting torque T2, at which point the motor speed also increases. In the third stage, the starting torque increases with the slope of the second starting torque, resulting in the third starting torque T3, and reaches the maximum starting torque T. max At this point, the motor speed has passed through the resonant speed range [N1, N2]. In the fourth stage, the motor speed reaches the target speed N3, and the engine starts and ignites; at this time, the maximum starting torque T... max It begins to decrease linearly, while the rotational speed continues to increase.
[0039] Optionally, the first starting torque includes 40 Nm to 50 Nm, and the first duration includes 150 ms to 250 ms.
[0040] Understandably, the initial starting torque can be determined after tuning based on the actual performance of the vehicle's engine. The purpose of setting the initial duration is to compensate for drivetrain backlash. If the initial duration is too short, the starting torque will rise too quickly, causing a shock. In some examples, the initial starting torque includes 45 Nm, and the initial duration includes 200 ms.
[0041] It's important to note that the initial starting torque and initial start-up duration can vary between different vehicle models. This difference is primarily due to inconsistencies in engine drag torque. Furthermore, even for the same vehicle model, variations in ambient temperature (mainly engine temperature) can lead to differences in engine drag torque, causing changes in both the initial starting torque and initial start-up duration.
[0042] Optionally, before step S20, the application of a first-stage torque to the motor until the first starting torque is reached further includes:
[0043] S21. Obtain the peak value of the engine anti-drag cylinder pressure resistance;
[0044] S22. Determine the first starting torque based on the peak value of the engine anti-drag cylinder pressure resistance.
[0045] Understandably, the setting of the initial starting torque needs to take into account the engine drag torque. If the initial starting torque is set too high, exceeding the peak value of the engine's anti-drag cylinder pressure resistance, it will cause engine speed fluctuations after dragging, which is detrimental to subsequent closed-loop control. If the initial starting torque is set too low, it can only eliminate gear backlash in the drivetrain, but cannot eliminate the rotational backlash of flexible damping elements (dual-mass flywheel or torsional damper) in the drivetrain, which can easily generate vibration or noise. Therefore, the initial starting torque can be set to a specified torque value less than the peak value of the engine's anti-drag cylinder pressure resistance, such as 3Nm to 8Nm, preferably 5Nm.
[0046] Optionally, the first starting torque slope includes: less than or equal to 250 Nm / s.
[0047] Understandably, the initial starting torque slope can be set according to actual needs. Here, the setting of the initial starting torque slope needs to consider how to reasonably increase engine speed. If the initial starting torque slope is too small, the motor speed will increase slowly, resulting in a slower rate of engine speed increase. If the initial starting torque slope is too large, it will limit the motor's subsequent adjustment capabilities, making further adjustment of the starting torque slope impossible. In one example, the initial starting torque slope includes: less than or equal to 250 Nm / s.
[0048] Optionally, the second starting torque slope includes 1250 Nm / s.
[0049] Understandably, the second starting torque slope needs to be greater than the first starting torque slope to ensure that the motor speed can increase rapidly, allowing the motor speed to quickly move out of the resonant speed range of the torsional damper. In some examples, the second starting torque slope can be set to 1250 Nm / s.
[0050] Optionally, before step S40, i.e., before the step of increasing the second starting torque by the second starting torque slope until the maximum starting torque is reached when the motor speed is greater than a preset motor speed threshold and the engine speed rise gradient is less than zero, the method further includes:
[0051] S41. Obtain the torsional stiffness of the torsional damper, the first equivalent moment of inertia of the torsional damper on the engine side, and the second equivalent moment of inertia of the torsional damper on the motor side; the torsional damper is disposed between the engine and the motor;
[0052] S42. Determine the preset motor speed threshold based on the torsional stiffness, the first equivalent moment of inertia, and the second equivalent moment of inertia.
[0053] Understandably, the preset motor speed threshold can be calculated using the following formula:
[0054]
[0055] Where n1 is the preset motor speed threshold;
[0056] K is the torsional stiffness of the torsional damper;
[0057] J1 is the first equivalent moment of inertia on the engine side of the torsional damper;
[0058] J2 is the second equivalent moment of inertia on the motor side of the torsional damper;
[0059] Q is a constant term, which can be set according to actual needs.
[0060] In some examples, Q = 2 * 60 (representing 120 rpm). The constant term Q represents a speed before reaching resonance speed during the engine speed increase process, which can allow the motor to enter the third stage of torque action earlier.
[0061] Optionally, the maximum starting torque includes 130 Nm.
[0062] Understandably, the maximum starting torque is related to the motor's driving and starting performance. The maximum starting torque generally varies between different vehicle models. In one example, the maximum starting torque includes 130 Nm.
[0063] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.
[0064] In one embodiment, a speed fluctuation control device is provided, which corresponds one-to-one with the speed fluctuation control method described in the above embodiments. For example... Figure 3 As shown, the speed fluctuation control device includes a start-up drive module 10, which comprises a first torque control unit 110, a second torque control unit 120, a third torque control unit 130, and a fourth torque control unit 140. Detailed descriptions of each functional module are as follows:
[0065] The start-up drag module 10 is used to drive the engine by a motor after the engine start command is issued;
[0066] The start-up drag module 10 includes:
[0067] The first torque control unit 110 is used to apply a first stage of torque to the motor until a first starting torque is reached; the duration of the first stage is a first duration.
[0068] The second torque control unit 120 is used to apply a second stage of torque to the motor: increasing the first starting torque with a first starting torque slope to obtain a second starting torque;
[0069] The third torque control unit 130 is used to apply a third stage of torque to the motor: if the speed of the motor is greater than a preset motor speed threshold and the speed increase gradient of the engine is less than zero, the second starting torque is increased by a second starting torque slope until the maximum starting torque is reached; the second starting torque slope is greater than the first starting torque slope.
[0070] The fourth torque control unit 140 is used to apply a fourth stage of torque to the motor: if the motor speed is detected to have reached the target speed, the maximum starting torque is reduced.
[0071] Optionally, the first starting torque includes 40 Nm to 50 Nm, and the first duration includes 150 ms to 250 ms.
[0072] Optionally, the first starting torque includes 45 Nm, and the first duration includes 200 ms.
[0073] Optionally, the speed fluctuation control device further includes a module for determining a first starting torque, the module for determining the first starting torque including:
[0074] An engine resistance acquisition unit is used to acquire the peak value of the engine's anti-drag cylinder pressure resistance.
[0075] A first starting torque calculation unit is used to determine the first starting torque based on the peak value of the engine anti-drag cylinder pressure resistance.
[0076] Optionally, the first starting torque slope includes: less than or equal to 250 Nm / s.
[0077] Optionally, the second starting torque slope includes 1250 Nm / s.
[0078] Optionally, the speed fluctuation control device further includes a speed threshold determination module, the speed threshold determination module comprising:
[0079] A torsional parameter acquisition unit is used to acquire the torsional stiffness of the torsional damper, the first equivalent moment of inertia of the torsional damper on the engine side, and the second equivalent moment of inertia of the torsional damper on the motor side; the torsional damper is disposed between the engine and the motor;
[0080] A speed threshold determination unit is used to determine the preset motor speed threshold based on the torsional stiffness, the first equivalent moment of inertia, and the second equivalent moment of inertia.
[0081] Optionally, the maximum starting torque includes 130 Nm.
[0082] Specific limitations regarding the speed fluctuation control device can be found in the limitations of the speed fluctuation control method described above, and will not be repeated here. Each module in the aforementioned speed fluctuation control device can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in or independent of the processor in a computer device in hardware form, or stored in the memory of a computer device in software form, so that the processor can call and execute the corresponding operations of each module.
[0083] In one embodiment, an automobile is provided, including an electronic control unit for executing any of the above-described speed fluctuation control methods.
[0084] In one embodiment, a computer device is provided, which may be a terminal, and its internal structure diagram may be as follows: Figure 4 As shown, the computer device includes a processor, memory, network interface, display screen, and input device connected via a system bus. The processor provides computing and control capabilities. The memory includes a readable storage medium and internal memory. The non-volatile storage medium stores the operating system and computer-readable instructions. The internal memory provides an environment for the operation of the operating system and computer-readable instructions in the readable storage medium. The network interface is used to communicate with an external server via a network connection. When the computer-readable instructions are executed by the processor, they implement a speed fluctuation control method. The readable storage medium provided in this embodiment includes both non-volatile and volatile readable storage media.
[0085] In one embodiment, a computer device is provided, including a memory, a processor, and computer-readable instructions stored in the memory and executable on the processor, wherein the processor performs the following steps when executing the computer-readable instructions:
[0086] After the engine start command is issued, the motor drives the engine:
[0087] Apply a first-stage torque to the motor until the first starting torque is reached; the duration of the first stage is the first duration.
[0088] A second stage of torque is applied to the motor: the first starting torque is increased by the first starting torque slope to obtain a second starting torque;
[0089] A third stage of torque is applied to the motor: if the motor speed is greater than a preset motor speed threshold and the engine speed rise gradient is less than zero, the second starting torque is increased by a second starting torque slope until the maximum starting torque is reached; the second starting torque slope is greater than the first starting torque slope.
[0090] A fourth stage of torque is applied to the motor: if the motor speed is detected to have reached the target speed, the maximum starting torque is reduced.
[0091] In one embodiment, one or more computer-readable storage media storing computer-readable instructions are provided. The readable storage media provided in this embodiment include non-volatile readable storage media and volatile readable storage media. The readable storage media stores computer-readable instructions, which, when executed by one or more processors, perform the following steps:
[0092] After the engine start command is issued, the motor drives the engine:
[0093] Apply a first-stage torque to the motor until the first starting torque is reached; the duration of the first stage is the first duration.
[0094] A second stage of torque is applied to the motor: the first starting torque is increased by the first starting torque slope to obtain a second starting torque;
[0095] A third stage of torque is applied to the motor: if the motor speed is greater than a preset motor speed threshold and the engine speed rise gradient is less than zero, the second starting torque is increased by a second starting torque slope until the maximum starting torque is reached; the second starting torque slope is greater than the first starting torque slope.
[0096] A fourth stage of torque is applied to the motor: if the motor speed is detected to have reached the target speed, the maximum starting torque is reduced.
[0097] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by instructing related hardware with computer-readable instructions. These computer-readable instructions can be stored in a non-volatile readable storage medium or a volatile readable storage medium. When executed, these computer-readable instructions can include the processes of the embodiments of the above methods. Any references to memory, storage, databases, or other media used in the embodiments provided in this application can include non-volatile and / or volatile memory. Non-volatile memory may include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or flash memory. Volatile memory may include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in a variety of forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), dual data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link DRAM (SLDRAM), RAMbus direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM).
[0098] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is used as an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above.
[0099] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.
Claims
1. A method for controlling speed fluctuation, characterized in that, include: After the engine start command is issued, the motor drives the engine: Apply the first stage of torque to the motor until the first starting torque is reached; The duration of the first phase is the first duration; A second stage of torque is applied to the motor: the first starting torque is increased by the first starting torque slope to obtain a second starting torque; A third stage of torque is applied to the motor: if the motor speed is greater than a preset motor speed threshold and the engine speed rise gradient is less than zero, the second starting torque is increased by a second starting torque slope until the maximum starting torque is reached; the second starting torque slope is greater than the first starting torque slope. A fourth stage of torque is applied to the motor: if the motor speed is detected to reach the target speed, the engine is started and ignited, and after the engine starts ignition, the maximum starting torque is reduced.
2. The speed fluctuation control method as described in claim 1, characterized in that, The first starting torque includes 40Nm~50Nm, and the first duration includes 150ms~250ms.
3. The speed fluctuation control method as described in claim 2, characterized in that, The first starting torque includes 45 Nm, and the first duration includes 200 ms.
4. The speed fluctuation control method as described in claim 1, characterized in that, The process of applying a first-stage torque to the motor until the first starting torque is reached also includes: Obtain the peak value of the engine's anti-cylinder drag; The first starting torque is determined based on the peak value of the engine anti-drag cylinder pressure resistance.
5. The speed fluctuation control method as described in claim 1, characterized in that, The first starting torque slope includes: less than or equal to 250 Nm / s.
6. The speed fluctuation control method as described in claim 1, characterized in that, The second starting torque slope includes 1250 Nm / s.
7. The speed fluctuation control method as described in claim 1, characterized in that, If the motor speed is greater than a preset motor speed threshold and the engine speed increase gradient is less than zero, then the second starting torque is increased by a second starting torque slope until the maximum starting torque is reached, further comprising: The torsional stiffness of the torsional damper, the first equivalent moment of inertia of the torsional damper on the engine side, and the second equivalent moment of inertia of the torsional damper on the motor side are obtained; the torsional damper is disposed between the engine and the motor; The preset motor speed threshold is determined based on the torsional stiffness, the first equivalent moment of inertia, and the second equivalent moment of inertia.
8. The speed fluctuation control method as described in claim 1, characterized in that, The maximum starting torque includes 130 Nm.
9. A speed fluctuation control device, characterized in that, include: The start-up drag module is used to drive the engine by a motor after the engine start command is issued; The start-up drag module includes: The first torque control unit is used to apply a first stage of torque to the motor until the first starting torque is reached; the duration of the first stage is a first duration. The second torque control unit is used to apply a second stage of torque to the motor: increasing the first starting torque with a first starting torque slope to obtain a second starting torque; The third torque control unit is used to apply a third stage of torque to the motor: if the motor speed is greater than a preset motor speed threshold and the engine speed rise gradient is less than zero, the second starting torque is increased by a second starting torque slope until the maximum starting torque is reached; the second starting torque slope is greater than the first starting torque slope. The fourth torque control unit is used to apply a fourth stage of torque to the motor: if the motor speed is detected to have reached the target speed, the engine is started and ignited, and after the engine starts and ignites, the maximum starting torque is reduced.
10. A car, characterized in that, It includes an electronic control unit for performing the speed fluctuation control method as described in any one of claims 1 to 8.