Motor control method for emergency loading condition of power split type hybrid vehicle

Abstract

The invention relates to the technical field of hybrid power vehicle control, and particularly discloses a motor control method for a power split type hybrid power vehicle under an emergency loading working condition, after a vehicle control unit recognizes that the vehicle is switched from a single-motor pure electric mode to a hybrid power mode, for a motor MG1, if the rotating speed of the motor MG1 is reduced to be smaller than-50 rpm, an improved I / F control strategy is adopted, and the speed of the motor MG1 is reduced to be smaller than-50 rpm; after the rotating speed of the motor MG1 is increased to be larger than 50 rpm, the improved I / F is switched back to the maximum torque current ratio control strategy, and the engine continues to be dragged to the target rotating speed; for the motor MG2, an adaptive sliding-mode observer is adopted to observe the extended counter electromotive force, an orthogonalization phase-locked loop is combined to extract rotor position and rotating speed information from the extended counter electromotive force, and meanwhile, the resistance, inductance and flux linkage of the motor MG2 are identified on line through least square method parameter identification with a forgetting factor and are fed back to the sliding-mode observer in real time. Therefore, the full-speed-domain stable operation of the motor in the process of converting the pure electric mode to the hybrid driving mode of the power split type hybrid vehicle is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hybrid vehicle control, in particular to a motor control method for power split hybrid vehicle in emergency loading condition. BACKGROUND

[0002] For a vehicle using power split hybrid power, when the driver steps on the accelerator or climbs a steep slope, the demand for power of the vehicle increases rapidly, at this time, it is difficult to provide enough power relying on the battery-motor energy alone, and the engine needs to intervene in power driving and respond quickly, which will be referred to as "emergency loading condition" hereinafter. At present, in the field of motor control research, some scholars have tried to integrate the sliding mode observer and the maximum torque current ratio control into a complete vector control strategy for controlling the motor. This strategy can significantly reduce the cost and perform well in the simulation of motor driving vehicle conditions, but it is not completely suitable for the emergency loading condition of power split hybrid vehicles. Because in this condition, the demand for power of the vehicle increases rapidly, and needs to switch from single motor pure electric mode to hybrid power driving mode, and there are two problems in the mode conversion process: on the one hand, the motor MG1 faces the transient problem of positive and negative rotation switching in the low speed domain. Specifically, during mode switching, the motor MG1 needs to gradually reduce the speed to zero from the negative rotation state, and then switch to positive rotation to drag the engine to reach the target speed. However, the maximum torque current ratio control, as a steady-state current distribution optimization strategy, does not consider the transient demand of speed zero crossing, which will cause the positive and negative rotation switching time of MG1 to be prolonged. On the other hand, the motor MG2 also has the transient problem of unstable torque output during mode switching, that is, the instantaneous sharp increase of load, current, demand speed and demand torque of the motor MG2 during mode switching will cause the sharp change of its operating condition and environmental condition, so that the parameters such as inductance, flux linkage and resistance change, resulting in inaccurate estimation of the motor rotor position by the traditional sliding mode observer. The inaccurate estimation of the rotor position can easily distort the control current waveform in the maximum torque current ratio vector control strategy, and then cause the fluctuation of the output torque, which poses a serious challenge to the stability of the torque output of the motor MG2 during mode switching. SUMMARY

[0003] The present application aims to solve at least one of the above-mentioned technical problems, and provides a motor control method for power split hybrid vehicle in emergency loading condition, to realize the smooth running of the motor in the full speed domain during the conversion of the power split hybrid vehicle from pure electric mode to hybrid driving mode.

[0004] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows: a motor control method for power split hybrid vehicle in emergency loading condition, when the vehicle controller identifies that the vehicle is switched from single motor pure electric mode to hybrid power mode,

[0005] For motor MG1, when the motor MG1 controller MCU1 receives the instruction to switch to the hybrid drive mode, if the motor MG1 speed drops to less than -50 rpm, the improved I / F control strategy is adopted, which adopts the virtual d * The phase relationship of the two coordinate systems is not adjusted when the motor MG1 switches between forward rotation and reverse rotation, so that the motor MG1 can switch from reverse rotation to forward rotation and output a forward torque to drive the engine. When the motor MG1 speed rises to more than 50 rpm, the improved I / F is switched back to the maximum torque current ratio control strategy to continue driving the engine to the target speed;

[0006] For motor MG2, when the motor MG2 controller MCU2 receives the instruction to switch to the hybrid drive mode, the adaptive sliding mode observer is used to observe the extended back-EMF, and the quadrature phase-locked loop is used to extract the rotor position and speed information of the extended back-EMF, to provide the accurate rotor position θ r and electrical angular velocity ω e for the maximum torque current ratio control vector control strategy, to realize accurate decoupling of dq-axis currents, and to use least squares method with forgetting factor parameter identification to online identify the resistance, inductance and flux of the motor MG2, and to feedback to the sliding mode observer in real time.

[0007] Preferably, the improved I / F control generates a speed given signal w e * and d * axis current given signal In the real coordinate system, the relationship between the q-axis current i q and the virtual synchronous coordinate system d * axis current is:

[0008]

[0009] In the formula, θ L is the phase difference between the real synchronous coordinate system and the virtual synchronous coordinate system;

[0010] The supplementary angle of θ L is defined as the power angle δ of the improved I / F control, and The electromagnetic torque of the motor is:

[0011]

[0012] In the formula, P n is the number of pole pairs of the motor; ψ f is the permanent magnet flux.

[0013] Preferably, the identification algorithm of the parameter identification of the recursive least square method with forgetting factor is as follows:

[0014]

[0015] The parameter identification by the least square method with forgetting factor can accelerate the convergence speed. The voltage transient equation of the IPMSM is discretized as follows:

[0016]

[0017] The identification model relationship is as follows:

[0018]

[0019] Taking the same as the output quantity, we have

[0020]

[0021] The least square expression of the system is as follows:

[0022]

[0023] Taking

[0024]

[0025] Introducing the forgetting factor λ and 0 < λ < 1, we have

[0026]

[0027] Preferably, the adaptive sliding mode observer adopts the hyperbolic tangent function h(s) with smooth continuous characteristics instead of the sign function sgn(s), and the expression is as follows:

[0028]

[0029] The sliding mode surface function is defined as The adaptive feedback gain η related to the electric angular velocity is η = |ω e | + ζ, wherein ζ is a non-zero small constant,

[0030] The adaptive sliding mode observer at this time is as follows:

[0031]

[0032] In the formula, The observed values of the stator currents of the α and β axes are i α and i β The control inputs of the observer are u d Ld is the d-axis inductance, L q Lq is the q-axis inductance, and R is the stator resistance.

[0033] The sliding mode control law and back-EMF observation are:

[0034]

[0035] The back-EMF and motor speed adaptive law are designed as:

[0036]

[0037] wherein, are the estimated values of back-EMF and electrical angular velocity respectively; l is the observer coefficient;

[0038] The error equation is:

[0039]

[0040] wherein, are the back-EMF errors respectively; is the electrical angular velocity error.

[0041] In the preferred orthogonal PLL, let The function of error ΔE is:

[0042]

[0043] The closed-loop transfer function is:

[0044]

[0045] wherein, K p is the proportional gain coefficient, K i is the integral gain coefficient;

[0046] The transfer function of the second-order system is:

[0047]

[0048] wherein, ω n is the undamped natural frequency, and ξ is the damping.

[0049] In the preferred improved I / F control strategy and maximum torque current ratio control strategy switching, a linear weighting function is used to realize the change of angle θ and ω, and the estimation equation is:

[0050]

[0051] wherein, p is the weighting factor.

[50150] is the switching speed interval, and its function is:

[0052]

[0053] Preferably, the vehicle controller recognizes that the vehicle is in a rapid loading condition and there is no brake pedal signal input, and when the battery SOC is lower than a preset power threshold of 30%; or the accelerator pedal opening is greater than 60%; or the vehicle speed reaches a preset speed threshold of 40km / h and the total power required by the vehicle is greater than the preset power threshold, which is 80% of the maximum power of motor MG2, it switches from single-motor pure electric mode to hybrid power mode.

[0054] The beneficial effect is that compared with the prior art, the motor control method of a power split hybrid vehicle under rapid loading conditions adopts an improved I / F control, and the motor has the same initial state under forward and reverse conditions, that is, the real dq coordinate system and the virtual d * q * The coordinate systems are in phase with each other, so there is no need to adjust the phase relationship and d of the two coordinate systems when the motor speed passes through zero. * q * The motor's low-speed forward and reverse rotation can be controlled by simply setting the shaft current, and the entire process is smooth and stable. At the same time, the sliding mode observer is improved using an adaptive algorithm and least squares parameter identification with a forgetting factor. Parameter identification is introduced to reduce the impact of changes in parameters such as resistance, inductance, and flux on the adaptive sliding mode observer. The adaptive algorithm also reduces the impact of motor speed on the accuracy of extended back-EMF observation during mode switching. Finally, an orthogonalized phase-locked loop is used to accurately extract rotor position and speed information from the extended back-EMF, providing the precise rotor position θ required for the maximum torque current ratio vector control strategy. r and electrical angular velocity ω e This can achieve precise decoupling of the dq axis currents, improve the quality of the control current, and further improve the smoothness of the torque output of the motor MG2 during mode switching. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] The specific embodiments of the present invention are further described in detail below with reference to the accompanying drawings, wherein:

[0056] Figure 1 A schematic diagram of the power system structure of a power-split hybrid vehicle in the prior art;

[0057] Figure 2 A schematic diagram of the control system architecture of a power-split hybrid vehicle in the prior art;

[0058] Figure 3 This is the improved I / F control structure diagram adopted in this application;

[0059] Figure 4 This is the control structure diagram of the improved adaptive sliding mode observer used in this application;

[0060] Figure 5A structure diagram of a conventional phase-locked loop (PLL);

[0061] Figure 6 A structure diagram of a quadrature phase-locked loop (PLL) used in the present application;

[0062] Figure 7 A mind map of an improved motor control strategy used in the present application. DETAILED DESCRIPTION

[0063] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0064] It should be noted that when a component is referred to as being "fixed" to another component, it can be directly on the other component or there can be intervening components. When a component is referred to as being "connected" to another component, it can be directly connected to the other component or there can be intervening components. When a component is referred to as being "disposed on" another component, it can be directly disposed on the other component or there can be intervening components. When a component is referred to as being "disposed in the middle", it is not only disposed in the middle position, but also disposed in the range defined by the middle. The terms "vertical", "horizontal", "left", "right", and similar terms used herein are for illustrative purposes only.

[0065] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0066] As shown in Figure 1 and Figure 2 are respectively a structure schematic diagram of a power split type hybrid vehicle power system in the prior art and a vehicle control system architecture schematic diagram of a power split type hybrid vehicle in the prior art, wherein, Figure 1The reference signs in the drawings are shown as follows: 1 - engine, 2 - brake CB (Central Brake), 3 - front planetary gear ring, 4 - front planetary gear carrier, 6 - motor MG1, 7 - motor MG2, 8 - rear planetary gear ring, 9 - rear planetary gear carrier, 10 - rear planetary gear sun gear, 11 - output shaft, 12 - reducer, 13 - tire. The motor control method adopted in the present application is mainly applied to Figure 2 The position outlined by the dashed line in the figure.

[0067] In the motor control method for power split hybrid vehicle in emergency load working condition disclosed in the present application, when the vehicle controller identifies that the vehicle is switched from single motor pure electric mode to hybrid mode,

[0068] For motor MG1, when the motor MG1 controller MCU1 receives the instruction to switch to hybrid driving mode, if the motor MG1 speed is less than -50 rpm, the improved I / F control strategy is adopted, which uses the virtual d * The phase relationship of the two coordinate systems is not adjusted when the motor MG1 is switched from reverse rotation to forward rotation, so as to realize the switching of the motor MG1 from reverse rotation to forward rotation and output the forward torque to drive the engine. When the motor MG1 speed rises to more than 50 rpm, the improved I / F is switched back to the maximum torque current ratio control strategy to continue to drive the engine to the target speed;

[0069] For motor MG2, when the motor MG2 controller MCU2 receives the instruction to switch to hybrid driving mode, the adaptive sliding mode observer is used to observe the extended back electromotive force, and the orthogonal phase-locked loop is used to extract the rotor position and speed information of the extended back electromotive force, so as to provide the accurate rotor position θ r And electrical angular velocity ω e For the accurate decoupling of dq axis current, the least square method with forgetting factor is used for online identification of the resistance, inductance and flux linkage of the motor MG2, and real-time feedback to the sliding mode observer.

[0070] In a specific embodiment, when the vehicle control unit (VCU) identifies that the vehicle is in a rapid load working condition and there is no brake pedal signal input, it will make a judgment on whether to switch from the dual-motor pure electric mode to the hybrid mode according to the current vehicle speed, accelerator pedal position, battery state of charge (SOC), and total power demand of the vehicle, etc. Specifically, when the battery SOC is lower than the preset power threshold of 30%; or the throttle pedal opening is greater than 60%; or the vehicle speed reaches the preset speed threshold of 40 km / h and the total power demand of the vehicle is greater than the power preset threshold, which is 80% of the maximum power of motor MG2, the vehicle switches from the single-motor pure electric mode to the hybrid mode. At the same time, the VCU combines the feedback information of the motor controller 1 (MCU1) of motor MG1, the motor controller 2 (MCU2) of motor MG2, and the ECU to calculate the engine target speed, engine starting torque, engine starting judgment, MG1 starting engine target torque, MG1 target speed, and MG2 target speed and torque according to the preset program, and transmits them to MCU1, MCU2, and ECU respectively. MCU2 controls the output of motor MG2, MCU1 controls the output of motor MG1, and ECU controls the power output of the engine. The control process of MCU1 and MCU2 in the process of switching from the single-motor pure electric mode to the hybrid drive mode will be introduced below.

[0071] After receiving the signal of starting the engine from the VCU, MCU1 needs to control motor MG1 to quickly reduce the speed from reverse rotation to zero and switch to forward rotation to drag the engine. When the speed of motor MG1 drops below -50 rpm, it will switch to the improved I / F control, which can take full advantage of the two advantages of the improved I / F control in forward and reverse rotation conditions, i.e. the same initial state and no need to adjust the phase of the two coordinate systems when the speed crosses zero, to realize the rapid reverse start of motor MG1, and quickly increase the speed according to the target torque and speed signal to output the positive torque required to start the engine. When the speed rises above 50 rpm, it switches back to the maximum torque current ratio control strategy to continue outputting positive torque to drag the engine to the target speed, thereby meeting the set requirements of the engine target economic torque. After the engine speed approaches the target economic speed, if motor MG1 does not need to participate in hybrid driving, its torque and current will gradually decrease to zero, and the output torque of motor MG1 will turn from zero to negative under the drive of the engine, and stabilize at a certain negative value when the engine reaches the optimal working condition. At this time, the motor is in a generating state. If motor MG1 needs to participate in hybrid driving, it will output driving torque together with the engine under the maximum torque current ratio vector control strategy.

[0072] In addition, after receiving the target rotating speed, target torque and mode switching instruction of the VCU, the MCU2 controls the motor MG2 by using an improved sliding mode observer, in which an adaptive sliding mode observer is used to accurately observe the extended back electromotive force, and a quadrature phase locked loop is used to accurately extract the rotor position and rotating speed information of the extended back electromotive force, so as to provide the accurate rotor position θ r and the electrical angular velocity ω e for the maximum torque current ratio vector control strategy, so as to realize the accurate decoupling of the dq-axis currents and reduce the pulsation of the output torque. Meanwhile, the least square method with a forgetting factor is used for online identification of the motor parameters such as resistance, inductance and flux linkage, and the parameters are fed back to the adaptive sliding mode observer in real time, so as to reduce the influence of parameter changes on the adaptive sliding mode observer, improve the observation accuracy during mode switching, and further improve the stability of the torque output of the motor MG2 during mode switching.

[0073] The motor control method mainly improves the low-speed transient control of the rapid switching of the motor MG1 and the transient output control of the torque pulsation during the mode switching of the motor MG2. Figure 3

[0074] In the power split hybrid vehicle, the working responsibilities of the motor MG1 include starting the engine, charging the battery and participating in driving in the dual-motor pure electric driving and hybrid driving. During the process of switching from the single-motor pure electric driving mode to the hybrid driving mode, in the single-motor pure electric driving mode, the MG2 drives the vehicle, and the MG1 reversely rotates (the rotating speed is negative) due to the stationary planetary carrier. After the motor MG1 controller MCU1 receives the instruction of switching to the hybrid driving mode, the MCU1 needs to control the motor MG1 to rapidly reduce the rotating speed from the reverse rotation to zero and switch to the forward rotation to drag the engine. When the rotating speed of the motor MG1 is reduced to below -50 rpm, the improved I / F control is used, which can rapidly and smoothly complete the zero-crossing of the rotating speed, switch from the reverse rotation to the forward rotation and output the forward torque to drag the engine, and when the rotating speed is increased to above 50 rpm, the original maximum torque current ratio control strategy is switched back to continue to drag the engine to the target rotating speed.

[0075] Considering the special working condition requirement of the rapid switching of the forward and reverse rotations of the motor MG1 of the power split hybrid vehicle at low speed, the improved I / F control based on the given d * axis (virtual d-axis) current is used, which can meet the special working condition requirement of the motor MG1, realize the switching from the reverse rotation to the forward rotation and preliminarily output the engine starting torque. As shown in Figure 4

[0076] ​​Figure 4 The improved I / F control in the system generates a speed setting signal by I / F control. and d * Shaft current given signal (The given current is generally about 20% of the rated current.) In the real coordinate system, the q-axis current i q Synchronous with virtual coordinate system d * Shaft current The relationship between them is:

[0077]

[0078] Where θ L is the phase difference between the real synchronous coordinate system and the virtual synchronous coordinate system.

[0079] Define θ L The complementary angle of is the power angle δ of the improved I / F control, and At this time, the electromagnetic torque of the built-in permanent magnet synchronous motor is:

[0080]

[0081] Where, P n is the number of pole pairs of the motor; ψ f is the permanent magnet flux.

[0082] In addition, when the improved I / F control is used, the motor has the same initial state in forward and reverse rotation conditions, that is, the real dq coordinate system and the virtual d * q * The phase of the coordinate system coincides. Therefore, when the motor speed passes through zero, there is no need to adjust the phase relationship and d * q * The given shaft current can realize the forward and reverse control of the motor at low speed, and the whole process is smooth and stable.

[0083] There is a torque output unstable transient problem when the motor MG2 mode switches. That is, during the transient response process of starting the engine when switching from single motor drive mode to hybrid drive mode, the motor MG2 not only needs to output torque to drive the vehicle, but also needs to play the role of output torque compensation. Therefore, the torque of the motor MG2 needs to first increase to compensate for the reduced driving torque of the motor MG1 and the negative impact generated before the engine is ignited, and then decrease to compensate for the positive impact generated after the engine is ignited. It can be seen that during this transient response process, the load, current, required speed and required torque of the motor MG2 will increase dramatically. This will cause the operating conditions and environmental conditions of the motor MG2 to change dramatically, causing the inductance, flux linkage, resistance and other parameters to also change, resulting in inaccurate rotor position estimation by the system. Inaccurate rotor position estimation can easily distort the control current waveform in the maximum torque current ratio vector control strategy, and then cause the output torque to fluctuate. Suppression of torque fluctuations, improvement of torque output stability and improvement of control current accuracy all depend on accurate rotor position and speed information, and this information is contained in the extended back electromotive force. Therefore, in order to improve the accuracy of the rotor position and speed information of the motor MG2 in the transient state, the motor vector control system needs to rely on a high-precision rotor position θ r and electrical angular velocity ω e To achieve accurate decoupling of dq-axis currents to meet the special control requirements of suppressing torque pulsation, the improved adaptive sliding mode observer is used to optimize the transient control of the motor MG2 during mode switching.

[0084] The traditional sliding mode not only has a high degree of dependence on motor parameters, but also has a high-frequency chattering problem, which causes the back electromotive force (BEMF) estimation value to contain a large number of harmonic components, resulting in a significant increase in position estimation error. This causes distortion of the current waveform in the maximum torque current ratio vector control, which in turn causes the output torque to fluctuate. Therefore, an improved adaptive sliding mode observer is used. This strategy uses an adaptive algorithm and a least squares method with a forgetting factor to identify parameters to improve the sliding mode observer. That is, parameter identification is used to reduce the impact of changes in resistance, inductance and flux linkage on the adaptive sliding mode observer; the adaptive algorithm is used to reduce the impact of motor speed on the observation accuracy of the extended back electromotive force during mode switching; and finally, the quadrature phase-locked loop is used to accurately extract the rotor position and speed information from the extended back electromotive force, providing the vector control strategy with the accurate rotor position θ r and electrical angular velocity ω e To achieve accurate decoupling of dq-axis currents, improve the quality of control currents, and thus improve the smoothness of the torque output of the motor MG2 during mode switching.

[0085] The structure diagram of the improved adaptive sliding mode observer used in the present application is shown in Figure 5 , and specifically:

[0086] (1) The identification algorithm of forgetting factor recursive least square parameter identification is as follows:

[0087]

[0088] The least square method with forgetting factor is used for parameter identification to accelerate the convergence speed. The voltage transient equation of the IPMSM is discretized as follows:

[0089]

[0090] The identification model relationship is as follows:

[0091]

[0092] Taking it as the output quantity, we have

[0093]

[0094] The least square expression of the system is as follows:

[0095]

[0096] Taking

[0097]

[0098] The forgetting factor λ is introduced and 0 < λ < 1, and we have

[0099]

[0100] (2) The adaptive sliding mode observer uses the hyperbolic tangent function h(s) with smooth continuous characteristics instead of the sign function sgn(s), and its expression is as follows:

[0101]

[0102] In this way, not only the back electromotive force participates in the estimation of the adaptive algorithm, but also the feedback of the electrical angular velocity makes the estimated back electromotive force curve smoother.

[0103] The sliding mode surface function is defined as The adaptive feedback gain η related to the electrical angular velocity is η = |ω e | + ζ, where ζ is a non-zero small constant.

[0104] The adaptive sliding mode observer at this time is as follows:

[0105]

[0106] In the formula, are the observed values of the stator currents of the α and β axes, respectively; u α , uβ is the control input of the observer; L d is the d-axis inductance, L q is the q-axis inductance, R is the stator resistance.

[0107] The sliding mode control law and back EMF observation are as follows:

[0108]

[0109] The back EMF and motor speed adaptive law is designed as:

[0110]

[0111] where, are the estimated values of back EMF and electrical angular velocity, respectively; l is the observer coefficient.

[0112] The error equation is:

[0113]

[0114] where, are the back EMF errors, respectively; is the electrical angular velocity error.

[0115] To verify the stability of the adaptive sliding mode observer, the Lyapunov function is defined as

[0116]

[0117] The derivative of the above equation is taken, and equation (14) is substituted to obtain:

[0118]

[0119] Since h > max{|E α |,|E β |} = ω e ψ f , when h can take ψ f , l > 0, the Lyapunov stability is satisfied. As can be seen from equation (12), when ξ is small enough, The change of the electrical angular velocity has little effect on the back EMF amplitude F αβ , which improves the observation accuracy.

[0120] When the sign function is used as the switching function in the traditional sliding mode observer (SMO), high-frequency chattering occurs, which makes the estimated back electromotive force (BEMF) contain a large number of harmonic components. This not only directly introduces torque harmonics, but also causes rotor position estimation deviation, affecting torque output accuracy. Specifically, since the back electromotive force is proportional to the speed, when the back electromotive force contains 5th, 7th, etc. harmonic, the estimated speed calculated according to the formula also contains the same harmonic, causing the periodic fluctuation of the term related to the speed in the torque formula (such as i q ∝ω), which causes torque pulsation at the same frequency; at the same time, the harmonic component distorts the input signal of the arctangent function, causing periodic jumps in position estimation, and the position error Δθ makes the angle between the current vector and the flux linkage vector deviate from the 90° optimal value expected in vector control, resulting in torque loss. At the same time, the traditional phase-locked loop (PLL) will produce a position error of ±180° electrical angle error when the motor is reversed, further increasing torque loss.

[0121] The adaptive sliding mode observer uses the hyperbolic tangent function (tanh) instead of the sign function. This type of function has continuous and differentiable characteristics, avoiding the discrete jumps of the sign function, and can significantly weaken the chattering, making the estimated back electromotive force waveform closer to the sine wave and reducing the source of torque pulsation. At the same time, the introduction of parameter identification and adaptive algorithm reduces the influence of resistance, inductance, flux linkage, and motor speed on the adaptive sliding mode observer. Finally, since the quadrature phase-locked loop has significant phase tracking characteristics, excellent anti-interference performance, and fast dynamic response capability, the quadrature phase-locked loop is used to monitor and capture the phase change of the input signal in real time, providing an accurate phase reference signal for the field-oriented control strategy, thereby improving the smoothness of the torque output of the motor MG2 during mode switching.

[0122] Therefore, compared with the traditional sliding mode observer, the improved adaptive sliding mode observer used in the present application has the following advantages: first, the extended back electromotive force is involved in the adaptive algorithm estimation, and the feedback of the electrical angular velocity makes the estimated back electromotive force curve smoother; second, the least squares parameter identification with a forgetting factor is introduced to provide real-time feedback to the adaptive sliding mode observer, reducing the influence of parameter changes such as resistance, inductance, and flux linkage on the adaptive sliding mode observer; third, when the traditional SMO is used, the change of the electrical angular velocity will affect the amplitude of the back electromotive force, affecting the accuracy of the extracted rotor position. The adaptive sliding mode observer extracts rotor position and speed information from the F αβ with constant amplitude observation through the adaptive algorithm, thereby reducing the influence of motor speed on the observation accuracy of the extended back electromotive force during mode switching and improving the estimation accuracy.

[0123] To weaken the influence of the sliding mode chattering, the orthogonal PLL is introduced to further improve the position θ e The estimation accuracy. The traditional PLL is shown in Figure 6 p is the proportional gain coefficient, K i is the integral gain coefficient.

[0124] Assume When , it is considered that holds (actually when , the sin function is monotonically increasing, which will not affect normal work), according to Figure 6 The following relationship is obtained:

[0125]

[0126] The running frequency of the PLL is set to be greater than the system sampling frequency, and when the motor is rotating forward, the nonlinear dynamic equation of the PLL is:

[0127]

[0128] When the motor is rotating in the opposite direction, the angle error will be positive and negative. If the PI controller parameters in the PLL are unchanged, the nonlinear dynamic equation of the PLL becomes:

[0129]

[0130] Obviously, the dynamic equations of the motor rotating forward and backward are different. Therefore, when the PI controller parameters in the PLL are constant, the rotor position will have an error of 180° when the traditional PLL switches the rotating direction. Therefore, the traditional PLL model is not suitable for the power split type hybrid power system which needs to rotate forward and backward.

[0131] To solve the above problems, the orthogonal PLL adopted by the application is shown in Figure 7 Based on formula (17) after normalization, the error ΔE can be derived:

[0132]

[0133] The new closed-loop transfer function is:

[0134]

[0135] For the new second-order system transfer function:

[0136]

[0137] In the formula, ω n is the undamped natural frequency, and ξ is the damping.​

[0138] Compared with the traditional PLL, the normalized quadrature PLL avoids the participation of the counter electromotive force amplitude E, and does not affect the error signal ΔE when the motor steering changes suddenly, so the same set of PI parameters can meet the demand of the motor forward rotation and the demand of the reverse rotation, and is more suitable for the power split hybrid power system which needs to operate frequently in the forward and reverse directions.

[0139] Finally, in order to reasonably design the smooth switching between the improved I / F control strategy and the maximum torque current ratio control strategy, a suitable switching function needs to be designed. A linear weighting function is used to realize the change of the angle θ and ω, and the estimation equation is:

[0140]

[0141] In the formula, p is a weighting factor.

[50150] is taken as the switching speed interval, and the function is:

[0142]

[0143] The above examples are only used to illustrate the technical solutions of the present application and not to limit it, any modification or equivalent replacement within the spirit and scope of the present application should be covered within the scope of the technical solutions of the present application.

Claims

1. A motor control method for a power-split hybrid vehicle under a rapid loading condition, characterized in that: When the vehicle controller recognizes that the vehicle switches from single-motor pure electric mode to hybrid mode, For the motor MG1, when the motor MG1 controller MCU1 receives the instruction to switch to the hybrid drive mode, when the motor MG1 speed drops to less than -50rpm, the improved I / F control strategy is adopted. This strategy adopts the virtual d * The shaft current setting method eliminates the need to adjust the phase relationship between the two coordinate systems when switching between forward and reverse rotation of the motor MG1, so that the motor MG1 can switch from reverse to forward rotation and output positive torque to drive the engine. When the speed of the motor MG1 rises to more than 50rpm, the improved I / F switches back to the maximum torque-current ratio control strategy to continue to drive the engine to the target speed. For motor MG2, when the motor controller MCU2 receives the command to switch to the hybrid drive mode, it uses an adaptive sliding mode observer to observe the extended back electromotive force and combines it with an orthogonal phase-locked loop to extract the rotor position and speed information from the extended back electromotive force, providing the precise rotor position θ required for the maximum torque current ratio vector control strategy. r and electrical angular velocity ω e , in order to achieve accurate decoupling of the dq axis currents. At the same time, the resistance, inductance and flux linkage of the motor MG2 are identified online using the least squares parameter identification method with forgetting factor, and the parameters are fed back to the sliding mode observer in real time.

2. The motor control method for a power-split hybrid vehicle under a rapid loading condition according to claim 1, characterized in that: The improved I / F control generates a speed setting signal from the conventional I / F control and d * Shaft current given signal In the real coordinate system, the q-axis current i q Synchronous with virtual coordinate system d * Shaft current The relationship between them is: Where θ L is the phase difference between the real synchronous coordinate system and the virtual synchronous coordinate system; Define θ L The complementary angle of is the power angle δ of the improved I / F control, and The electromagnetic torque of the motor is: Where, P n is the number of pole pairs of the motor; ψ f is the permanent magnet flux.

3. The motor control method for a power-split hybrid vehicle under a rapid loading condition according to claim 1, characterized in that: The identification algorithm of the forgetting factor recursive least squares parameter identification is as follows: Using the least square method with forgetting factor for parameter identification can accelerate the convergence speed. Discretizing the voltage transient equation of IPMSM is: Identify model relationships: Take it as the output Then the least squares expression of the system is: Pick Introducing the forgetting factor λ and 0<λ<1, we get:

4. The motor control method for a power-split hybrid vehicle under a rapid loading condition according to claim 1, characterized in that: The adaptive sliding mode observer uses the hyperbolic tangent function h(s) with smooth and continuous characteristics to replace the sign function sgn(s), and its expression is: The sliding surface function is defined as The adaptive feedback gain η related to the electrical angular velocity is η=|ω e |+ζ, where ζ is a small nonzero constant. The adaptive sliding mode observer at this time is: Where, are the stator current observation values ​​of α and β axes respectively; u α 、u β is the control input of the observer; L d is the d-axis inductance, L q is the q-axis inductance, and R is the stator resistance. The sliding mode control law and back EMF observation value are as follows: At this time, the adaptive law of back electromotive force and motor speed is designed as: Where, are the estimated values ​​of back electromotive force and electric angular velocity respectively; l is the observer coefficient; At this time, the error equation is: Where, are back electromotive force errors respectively; is the electrical angular velocity error.

5. The motor control method for a power-split hybrid vehicle under a rapid loading condition according to claim 1, characterized in that: In the orthogonalized phase-locked loop PLL, let Then the function of error ΔE is: The closed-loop transfer function is: Where K p is the proportional gain coefficient, K i is the integral gain coefficient; The transfer function of the second-order system is: Where, ω n is the undamped natural frequency and ξ is the damping.

6. The motor control method for a power-split hybrid vehicle under a rapid loading condition according to claim 1, characterized in that: When the improved I / F control strategy switches to the maximum torque current ratio control strategy, a linear weighting function is used to achieve the change of angles θ and ω, and its estimation equation is: Where p is the weighting factor. Taking [50150] as the switching speed range, its function is:

7. The motor control method for a power-split hybrid vehicle under a rapid loading condition according to claim 1, characterized in that: The vehicle controller recognizes that the vehicle is in a rapid loading condition and there is no brake pedal signal input, and when the battery SOC is lower than the preset power threshold of 30%; or the accelerator pedal opening is greater than 60%; or the vehicle speed reaches the preset speed threshold of 40km / h and the total power required by the vehicle is greater than the preset power threshold, which is 80% of the maximum power of motor MG2, it switches from single-motor pure electric mode to hybrid mode.

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