Commercial semitrailer electric drive strategy and power distribution method and system

Abstract

The invention discloses a commercial semitrailer electric drive strategy and a power distribution method and system. The method comprises the following steps that a multi-body dynamic model of a commercial semitrailer is established; according to the vehicle speed and the pedal opening degree, different working modes are established, power is provided, and meanwhile energy consumption is reduced; according to gear information of a vehicle model, clutch engagement information and gearbox torque, the output torque of an engine at the moment before gear shifting is judged, an expected motor torque signal is obtained, and the actual motor torque is obtained through an improved compensation sliding mode control algorithm; actual motor torque is input to an intermediate shaft of the semitrailer to serve as additional power input; the actual speed is fed back to the driver model, and closed-loop control is achieved. The method has the advantages that a power mechanism of a traditional commercial semitrailer is not changed, the driving comfort and the power performance of the semitrailer are greatly improved by additionally arranging the motor, and in addition, the motor can also serve as a retarder to guarantee the safety on a long downhill road surface.

Description

Technical Field

[0001] The present invention belongs to the technical field of electric drive strategy and power distribution for commercial semi-trailers, and specifically relates to an electric drive strategy and power distribution method and system for commercial semi-trailers. Background Art

[0002] The basic function of a modern powertrain is to transfer torque to the road-tire interface. In order to ensure the normal driving of the vehicle, the engine and transmission need to be designed. However, for traditional commercial semi-trailers, due to their large weight, the vehicle will amplify the speed and torque discontinuity during the gear shifting process, thus affecting the driving quality and reducing driving comfort.

[0003] Commercial semi-trailers with motors added are no longer traditional fuel vehicles, but hybrid vehicles. The main research content of hybrid vehicle control technology involves many aspects: system integration technology, energy management technology, power coordination technology, motor control technology, engine control technology, etc. Among them, energy management technology mainly studies the energy distribution strategy between the engine and the motor of the vehicle under steady-state conditions to improve the energy efficiency of the whole vehicle and reduce energy consumption and emissions while ensuring power; the vehicle coordination system mainly studies the driving ability and comfort of the vehicle, including the coordinated control of hybrid vehicle mode switching, the coordinated control of mechanical braking and electric braking, and the coordinated control of automatic transmissions. With the increasing maturity of hardware technology, the requirements for control technology are gradually increasing. For example, there are effective examples of neural network control methods, fuzzy control methods, genetic algorithms, adaptive algorithms, etc., which are effective in improving the performance of the whole vehicle and improving the adaptability of hybrid vehicles under different working conditions.

[0004] In the prior art, hybrid vehicles can be divided into series hybrid vehicles, parallel hybrid vehicles, and series-parallel hybrid vehicles according to the arrangement of power system components in the power transmission path (Design and Optimization of Energy Management Strategy for Plug-in Hybrid Vehicles, Master's Degree Thesis of Chongqing University, Ji Yawei). The structure of series hybrid vehicles is relatively simple. They only directly provide power to the drive wheels through the motor, while the engine charges the battery through the generator to provide energy indirectly. Therefore, the engine can always work in the high-efficiency area, and its drive system is similar to that of extended-range pure electric vehicles. Parallel hybrid vehicles are powered by motors and engines simultaneously or separately, with more working mode options, which can meet the driver's greater power requirements and adapt to more complex operating conditions. Series-parallel hybrid vehicles can provide power in both series and parallel modes, and have stronger adaptability. However, commercial semi-trailers have a larger body and need to consider R&D costs. Summary of the invention

[0005] The purpose of the present invention is to provide an electric drive strategy and power distribution method for a commercial semi-trailer. The motor is installed on the axle of the semi-trailer. Through power distribution, the frustration generated by the heavy-duty commercial vehicle during the gear shifting process is effectively reduced, and the driving comfort and smoothness are improved. The motor can also apply reverse torque to act as a retarder to ensure the safety of vehicle driving.

[0006] The present invention is achieved by at least one of the following technical solutions.

[0007] A commercial semi-trailer electric drive strategy and power distribution method, comprising the following steps:

[0008] (1) The driver model uses the speed difference between the desired vehicle speed and the actual vehicle speed as input and uses PI control to obtain the driver's pedal opening to achieve the target vehicle speed.

[0009] (2) Different working modes are established according to vehicle speed and pedal opening: large torque joint drive mode, small torque joint drive mode, engine single drive mode, coasting mode, and cruise mode, ensuring power is provided while reducing energy consumption;

[0010] (3) Inputting the pedal opening into the multi-body dynamics model of the commercial semi-trailer, and judging the output torque of the engine at the moment before the gear shift according to the gear position information, clutch engagement information, and transmission torque of the multi-body dynamics model of the commercial semi-trailer;

[0011] (4) Extending the torque signal at each gear shifting moment to obtain a desired motor torque signal;

[0012] (5) Taking the expected torque signal of the engine as the motor load, an improved compensatory sliding film control algorithm is used to obtain the actual motor torque;

[0013] (6) The actual motor torque is input to the intermediate shaft of the semi-trailer as additional power input, and the actual speed is fed back to the driver model to achieve closed-loop control and complete the entire electrification process.

[0014] Furthermore, the parameters of the driver model include the nominal vehicle speed v nom , actual vehicle speed v ref , proportional gain K p , integral gain K i , Anti-saturation gain K aw , vehicle speed feedforward gain K ff and the slope feedforward gain K g ;

[0015] The driver model uses the speed difference between the desired speed and the actual speed of the vehicle as input, and uses PI control to obtain the signal values ​​of the accelerator pedal and the brake pedal to achieve the target speed. The driver model uses a low-pass filter function to filter the input speed difference, and uses the nominal speed to perform dimensionless processing on the input speed difference. The processed value is used to calculate the speed control amount using proportional integral control with tracking compensation and feedforward gain. The calculated result is anti-saturated so that the result ranges from -1 to 1, thereby obtaining the input amount of the brake pedal and the accelerator pedal. The specific formula is as follows:

[0016]

[0017]

[0018] e ref =v ref -v (3)

[0019]

[0020] H(f) is the response function, τ err is the low-pass filter coefficient, y is the speed control value, e ref is the difference between the speed control amount and the anti-saturation control amount, e out is the speed difference, θ is the slope angle, v is the actual vehicle speed, y sat ,y acc ,y bra They are anti-saturation control amount, accelerator pedal opening and brake pedal opening respectively.

[0021] Furthermore, in step (2), different working modes are established according to the vehicle speed and the pedal opening, including:

[0022] High-torque joint drive mode: The speed is within 0-35km / h, which is high-torque joint drive, and the motor runs at maximum power;

[0023] Small torque combined drive mode: The speed is within 35-60km / h, which is small torque combined drive, and the motor power is set to 75% of the rated power;

[0024] Engine-only driving mode: When the speed is greater than 60km / h, the vehicle basically runs stably and the motor does not participate in the driving;

[0025] In addition, within the speed range of the above three driving modes, the working modes are further distinguished by judging the acceleration and brake pedals:

[0026] If the acceleration is less than 0 and the brake signal is 0, the vehicle enters the gliding mode, otherwise, it enters the braking mode.

[0027] If the acceleration is equal to 0, the vehicle is in cruise mode.

[0028] Furthermore, the multi-body dynamics model of the commercial semi-trailer in step (3) is:

[0029]

[0030] Where m is the mass of the tractor, m T is the mass of the trailer, I ψ is the vehicle yaw stiffness, δ w is the front wheel steering angle, a x 、a y are longitudinal and lateral accelerations, v x and v y are longitudinal and lateral speeds respectively; F xfl 、F xfr 、F xml 、F xmr 、F xrl and F xrr are the longitudinal forces of the front, middle and rear wheels; F yfl 、F yfr 、F yml 、F ymr 、F yrl and F yrr are the lateral forces of the front, middle and rear wheels; d f ,d m and d r are the track widths of the front, middle and rear drive axles, L f is the distance from the front axle to the vehicle equivalent center,

[0031] L fm is the wheelbase from the front axle to the middle axle, L mr is the wheelbase from the middle bridge to the rear bridge, ψ is the yaw angle, is the yaw angular velocity, I is the moment of inertia; since the front axle adopts a non-independent suspension, the left and right loads of the front axle are equal, and the specific size is shown in formula (6); the vertical load of the tire on the middle and rear axles is as shown in formula (7); F zfl is the vertical force of the left front wheel, F zfr is the vertical force on the right front wheel, F zrl is the vertical force of the left rear wheel, F zrr is the vertical force on the right rear wheel, F zml is the vertical force of the left middle wheel, F zmr is the vertical force of the right middle wheel, L a L is the distance from the center of the 2nd and 3rd axles of the tractor to the traction saddle. b It is the distance from the center of the third axis to the traction saddle.

[0032] Furthermore, in step (5), the improved compensatory sliding film control algorithm introduces the estimated motor parameter changes and the disturbance value of the load torque observed by the extended observer into the sliding mode controller to weaken the jitter of the motor torque output, thereby compensating for the torque interruption caused by the engagement and disengagement of the clutch during the vehicle shifting process through the motor.

[0033] Furthermore, in step (5), the sliding film control algorithm is used to control the torque. First, the function expression of the sliding surface is determined as follows:

[0034] s(x,t),s∈R m (9);

[0035] Where s(x,t) is the hypersurface defined in the system state space, x is the coordinate of the variable in the state space, and t indicates that the sliding surface depends on time; s∈R m It means that the hypersurface defined in the system state space belongs to the real number range. According to the above formula, the sliding surface is solved to obtain:

[0036]

[0037] in and denote the control functions on and below the hypersurface, respectively;

[0038] The state variables of the permanent magnet synchronous motor are taken as:

[0039]

[0040] In the formula, x1 and x2 are the state variables of the system respectively, and the integral of x1 is taken as the second state variable of the system, ω ref is the target speed, ω m is the motor output speed, combined with formula (10), and the derivative of formula (11) is obtained:

[0041]

[0042] in is the integral of the state variables, p is the number of motor pole pairs, ψ f is the magnetic flux, B is the viscous friction coefficient, J is the moment of inertia, β represents the disturbance value caused by the load torque and parameters, i q is the electric current on the q axis, is the integral of the motor output speed, It is the integration of the disturbance value caused by load torque and parameters.

[0043] The sliding surface function of the system is defined as:

[0044] s=cx1+x2 (13); Where s represents the sliding surface, c is the coefficient, x1 and x2 are state variables. Derivative the sliding surface function and substitute equation (11) into it to obtain:

[0045]

[0046] are the integrals of sliding surface and state variables respectively;

[0047] In actual motor control, the sliding mode control method has high-frequency chattering problems, so it is necessary to select a suitable exponential approach rate to effectively reduce the sliding mode chattering. Therefore, in order to improve the performance of the system, an improved approach rate will be introduced, and the improved approach rate is:

[0048]

[0049] Where ε and k represent constants, and ε>0, k>0. The constant-speed approach term is -ε|x1|sgn(s), and the exponential approach term is ks. When the error increases, the constant-speed approach term makes the system state variable approach the sliding surface, and at the same time, the exponential approach term reduces the system state variable to 0. Definition Combining equation (11) and equation (12), the output equation of the controller is:

[0050]

[0051] in is the reference current of q axis;

[0052] Select the Lyapunov function:

[0053]

[0054] V is a Lyapunov function. According to the Lyapunov stability theorem, we only need to prove Then the system is asymptotically stable, and from equation (15) and equation (17) we can get:

[0055]

[0056] In the formula represents the function integral, ε>0, k>0 and sgn(s)s>0, where sgn(s) is the sign function; thus we have Therefore, the system error can converge to 0 in a limited time, making the system stable. At the same time, using the saturation function sat(A,δ) instead of sgn(A) can effectively suppress chattering and further improve the robustness of the system. The saturation function sat(A,δ) equation is selected as follows:

[0057]

[0058] Where A is the input signal and δ is the saturation threshold, i.e. the limiting amplitude.

[0059] Furthermore, an extended observer is introduced into the common sliding film control algorithm. It can be seen from formula (16) that the control rate designed by using the sliding surface contains the motor parameter change and the load torque disturbance term β, and the disturbance value cannot be measured. Therefore, the present invention designs a disturbance observer to estimate the disturbance of the motor output. In the actual motor speed control system, the permanent magnet synchronous motor system parameter disturbance changes slowly, and the first-order derivative of the disturbance can be approximated to 0. Then, the system state space equation is established by formula (10) to obtain:

[0060]

[0061] Where Y is the output equation of the state space equation, is the integral of the state variables, p is the number of motor pole pairs, ψ f is the magnetic flux, B is the viscous friction coefficient, J is the moment of inertia, β represents the disturbance value caused by the load torque and parameters, i q is the electric current on the q axis, is the integral of the motor output speed, is the integral of the disturbance value caused by the load torque and parameters, is the estimated value of the above integral; m , β are the observed objects, and the gain feedback of the speed estimation error e1 is established. Among them, the extended disturbance observer is designed based on formula (17):

[0062]

[0063] Where: are the estimated value of electrical angular velocity and the estimated value of load parameter perturbation respectively; λ1, λ2, η are positive real numbers; the error equation of the extended observer is obtained from equations (20) and (21) as follows:

[0064]

[0065] Where: represents the speed estimation error, represents the system parameter and load torque estimation error, are the integrals of the speed and load torque estimation errors respectively, and the error state equation of the extended observer is expressed as:

[0066]

[0067] Where: is the error integral

[0068]

[0069] It can be seen that by configuring Located in the left half plane, that is, the pole is located in the left half plane of the state space plane, so that the error e asymptotically approaches 0, so that the system error approaches 0, and the observed disturbance and load parameter disturbance estimate Substituting into equation (4)-(34) we can get:

[0070]

[0071] It can be seen from formula (16) that by taking parameter changes and load disturbances as feedforward compensation, when the load and motor parameters change, the controller can overcome the influence of load and parameter disturbances on the system and effectively suppress the chattering phenomenon of the system. At the same time, the saturation function is introduced to further improve the robustness of the system.

[0072] A system for implementing the commercial semi-trailer electric drive strategy and power distribution method includes a vehicle model module, a motor module, a torque calculation module, a power distribution module, and a driver module. The expected speed and pedal opening determined by the driver module are input into the vehicle model, and the vehicle model outputs the actual vehicle speed and engine information. The actual vehicle speed and engine information output by the vehicle model are input into the torque calculation module to obtain the expected additional torque as the motor expected torque. The motor expected torque is input into the motor module, and the motor then outputs the actual torque to the vehicle model to improve the longitudinal stability of the vehicle. According to different vehicle speeds, the vehicle uses different power distribution strategies.

[0073] Furthermore, the engine information includes gear information, engine torque information, and clutch engagement signal.

[0074] A computer device comprises: a memory and a processor and a computer program stored in the memory. When the computer program is executed on the processor, the commercial semi-trailer electric drive strategy and power distribution method are implemented.

[0075] Compared with the prior art, the present invention has the following beneficial effects:

[0076] 1) The method of the present invention can reduce the longitudinal acceleration amplitude fluctuation by 15-50% without changing the tractor structure;

[0077] 2) The method of the present invention can improve the dynamic characteristics of the vehicle;

[0078] 3) Compared with the traditional sliding film control algorithm, the improved compensatory sliding film control of the present invention takes into account the disturbance value of the motor load torque: when the torque changes suddenly, the estimated torque can be smoother than the actual torque; introducing the estimated motor parameter changes and the disturbance value of the load torque observed by the extended observer into the sliding mode controller can effectively weaken the vibration. The motor used acts as a retarder when the vehicle enters a long downhill road to ensure driving safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0079] Figure 1 This is a flow chart of an electric drive strategy and a power distribution method for a commercial semi-trailer according to an embodiment of the present invention;

[0080] Figure 2 is a diagram of the lateral dynamics model of a semitrailer in the embodiment;

[0081] Figure 3 is a longitudinal dynamics model diagram of a semitrailer in an embodiment;

[0082] Figure 4 is a flow chart of the power distribution method in the embodiment;

[0083] Figure 5 : is a simulation diagram comparing the original longitudinal acceleration and the longitudinal acceleration of the vehicle after electrification in the embodiment;

[0084] Figure 6 It is a simulation diagram comparing the expected vehicle speed, original vehicle speed, and electrified vehicle speed in the embodiment. DETAILED DESCRIPTION

[0085] The present invention is further described in detail below with reference to the accompanying drawings.

[0086] like Figure 1 , Figure 2 As shown, a commercial semi-trailer electric drive strategy and power distribution method of this embodiment includes the following steps:

[0087] (1) According to the given working conditions, the expected speed and the actual speed of the vehicle, the driver's accelerator pedal and brake pedal opening size input are processed: the driver model takes the difference between the expected speed and the actual speed as input, and uses PI control to obtain the signal values ​​of the accelerator pedal and the brake pedal, so as to achieve the target speed. The specific principles are as follows (1)-(4). First, use a low-pass filter function to filter the input speed difference. Use the nominal speed to make the input speed difference dimensionless. The processed value is used with proportional integral control with tracking compensation and feedforward gain to calculate the speed control quantity, and the calculated result is anti-saturation processed so that the result range is between -1 and 1, thereby obtaining the input of the brake pedal and the accelerator pedal. The parameters of the driver model include nominal speed, actual speed, proportional gain, integral gain, anti-saturation gain, speed feedforward gain and slope feedforward gain.

[0088]

[0089] H(f) is the response function, τ err is the low-pass filter coefficient, y is the speed control value, e ref is the difference between the speed control amount and the anti-saturation control amount, e out is the speed difference, θ is the slope angle, v is the actual vehicle speed, y sat ,y acc ,y bra They are anti-saturation control amount, accelerator pedal opening and brake pedal opening respectively.

[0090] (2) Different working modes are established according to vehicle speed and pedal opening: large torque joint drive mode, small torque joint drive mode, engine single drive mode, coasting mode, and cruise mode, ensuring power supply while reducing energy consumption;

[0091] As an example, Figure 4 The power distribution strategy of the vehicle is to divide different working modes by setting different speed ranges:

[0092] The speed is within 0-35km / h, it is a large torque combined drive, and the motor runs at maximum power.

[0093] The speed is 35-60km / h, it is a small torque combined drive, and the motor power is set to 75% of the rated power.

[0094] When the speed is greater than 60km / h, the vehicle is basically running stably and the motor can choose not to participate in the driving.

[0095] In addition, in each speed range, the working mode is further distinguished by judging the acceleration and brake pedal: if the acceleration is less than 0 and the brake signal brake is 0, it enters the gliding mode, otherwise, it enters the braking mode; if the acceleration is equal to 0, the vehicle is in cruise mode.

[0096] (3) Input the pedal opening size into the multi-body dynamics model of the commercial semi-trailer, and determine the output torque of the engine at the moment before the gear shift according to the gear information, clutch engagement information, and transmission torque of the multi-body dynamics model of the commercial semi-trailer; the multi-body dynamics model of the commercial semi-trailer is:

[0097]

[0098] Establish a Figure 2 , Figure 3 The three-degree-of-freedom tractor model is T is the mass of the trailer, I ψis the vehicle yaw stiffness, δ w is the front wheel steering angle, a x 、a y are longitudinal and lateral accelerations, v x and v y are longitudinal and lateral speeds respectively; F xfl 、F xfr 、F xml 、F xmr 、F xrl and F xrr are the longitudinal forces of the front, middle and rear wheels; F yfl 、F yfr 、F yml 、F ymr 、F yrl and F yrr are the lateral forces of the front, middle and rear wheels; d f ,d m and d r are the track widths of the front, middle and rear drive axles, L f is the distance from the front axle to the equivalent center of the vehicle, L fm is the wheelbase from the front axle to the middle axle, L mr is the wheelbase from the middle bridge to the rear bridge, ψ is the yaw angle, is the yaw angular velocity, I is the moment of inertia; since the front axle adopts non-independent suspension, the left and right loads of the front axle are equal, and the specific size is shown in formula (6); the vertical load of the tire on the middle and rear axles is as shown in formula (7)

[0099] (4) The torque signal at each shifting moment is extended; as an embodiment, the engine shifting time is set to 1.5s, of which the clutch disconnection time is 0.4s; the clutch engagement time is 1.1s. Therefore, according to the clutch state, the torque signal is maintained for 0.4s during clutch disconnection; during the clutch engagement process, the torque signal is linearly reduced to obtain the desired motor torque signal.

[0100] (5) Taking the expected torque signal as the motor load, the improved compensatory sliding film control algorithm is used to obtain the actual motor torque;

[0101] Use the sliding film control algorithm to control the torque. For common sliding mode controllers: they are mostly used in nonlinear systems. The design process mainly focuses on the selection of sliding surface functions and sliding film gains. The purpose is to improve the convergence speed while preventing jitter caused by excessive gain. The general expression of nonlinear systems is:

[0102]

[0103] Among them, x∈R and u∈R represent the state variables and control variables of the control system respectively. is the integral of the state variable, f is the function of the state equation, t indicates that the function depends on time, and R is a real number

[0104] First, determine the function expression of the sliding surface as;

[0105] s(x,t),s∈R m (9);

[0106] where s(x,t) is the hypersurface defined in the system state space, s∈R m This indicates that it is within the range of real numbers. Solving the sliding surface according to the above formula gives:

[0107]

[0108] in and denote the control functions on and below the hypersurface, respectively.

[0109] The state variables of the permanent magnet synchronous motor are taken as:

[0110]

[0111] Where x1 and x2 are the state variables of the system, and the integral of x1 is taken as the second state variable of the system, ω ref is the target speed, ω m is the motor output speed, combined with formula (10), and the derivative of formula (11) is obtained:

[0112]

[0113] in is the integral of the state variables, p is the number of motor pole pairs, ψ f is the magnetic flux, B is the viscous friction coefficient, J is the moment of inertia, β represents the disturbance value caused by the load torque and parameters, iq is the electric current on the q axis, is the integral of the motor output speed, It is the integration of the disturbance value caused by load torque and parameters.

[0114] The sliding surface function of the system is defined as:

[0115] s=cx1+x2(13); where s represents the sliding surface, c is the coefficient, and x1 and x2 are state variables. Derivative the sliding surface function and substitute equation (11) into it to obtain:

[0116]

[0117] are the integrals of the sliding surface and the state variables, respectively.

[0118] In actual motor control, the sliding mode control method has high-frequency chattering problems, so it is necessary to select a suitable exponential approach rate to effectively reduce the sliding mode chattering. Therefore, in order to improve the performance of the system, an improved approach rate will be introduced, and the improved approach rate is:

[0119]

[0120] Where ε and k represent constants, and ε>0, k>0. The constant-speed approach term is -ε|x1|sgn(s), and the exponential approach term is ks. When the error increases, the constant-speed approach term makes the system state variable approach the sliding surface, and at the same time, the exponential approach term reduces the system state variable to 0. Definition Combining equation (11) and equation (12), the output equation of the controller is:

[0121]

[0122] in is the reference current of the q axis

[0123] Select the Lyapunov function:

[0124]

[0125] V is a Lyapunov function. According to the Lyapunov stability theorem, we only need to prove Then the system is asymptotically stable, and from equation (15) and equation (17) we can get:

[0126]

[0127] In the formula represents the function integral, ε>0, k>0 and sgn(s)s>0, where sgn(s) is the sign function; thus we have Therefore, the system error can converge to 0 in a limited time, making the system stable. At the same time, using the saturation function sat(A,δ) instead of sgn(A) can effectively suppress chattering and further improve the robustness of the system. The saturation function sat(A,δ) equation is selected as follows:

[0128]

[0129] Where A is the input signal and δ is the saturation threshold, i.e. the limiting amplitude.

[0130] The extended observer is introduced into the common sliding film control algorithm. It can be seen from formula (16) that the control rate designed by using the sliding surface contains the motor parameter change and the load torque disturbance term β, and the disturbance value cannot be measured. Therefore, the present invention designs a disturbance observer to estimate the disturbance of the motor output. In the actual motor speed control system, the permanent magnet synchronous motor system parameter disturbance changes slowly, and the first-order derivative of the disturbance can be approximated to 0. Then, the system state space equation is established by formula (10) to obtain:

[0131]

[0132] Where Y is the output equation of the state space equation, is the integral of the state variables, p is the number of motor pole pairs, ψ f is the magnetic flux, B is the viscous friction coefficient, J is the moment of inertia, β represents the disturbance value caused by the load torque and parameters, iq is the electric current on the q axis, is the integral of the motor output speed, is the integral of the disturbance value caused by the load torque and parameters; m , β are the observed objects, and the gain feedback of the speed estimation error e1 is established. Among them, the extended disturbance observer is designed based on formula (17):

[0133]

[0134] Where: are the estimated value of electrical angular velocity and the estimated value of load parameter perturbation respectively; λ1, λ2, η are positive real numbers. The error equation of the extended observer is obtained from equations (20) and (21) as follows:

[0135]

[0136] Where: represents the speed estimation error, represents the system parameter and load torque estimation error, are the integrals of the speed and load torque estimation errors, respectively. Therefore, the error state equation of the extended observer can be expressed as:

[0137]

[0138] Where:

[0139]

[0140] It can be seen that by configuring Located in the left half plane, the error e can be asymptotically approached to 0, which makes the system error approach 0. The perturbation value of the observed disturbance and load torque Substituting into formula (16) we can get:

[0141]

[0142] It can be seen from formula (16) that by taking parameter changes and load disturbances as feedforward compensation, when the load and motor parameters change, the controller can overcome the influence of load and parameter disturbances on the system and effectively suppress the chattering phenomenon of the system. At the same time, the saturation function is introduced to further improve the robustness of the system.

[0143] The sliding film control algorithm can significantly improve the longitudinal stability of the vehicle, and the improved compensatory sliding film control algorithm introduces the estimated motor parameter changes and load torque disturbance values ​​observed by the extended observer into the sliding mode controller, which can better weaken the jitter of the motor torque output. The specific reason is that through the sliding film control algorithm, the torque interruption caused by the clutch engagement and disengagement during the vehicle shifting process can be obtained, so that the interrupted torque can be compensated by the motor; and the introduction of the extended observer can reduce the overshoot and oscillation in the motor torque output process by observing the changes in the motor parameters, thereby reducing the instability of the motor output and preventing the unstable output of the motor from affecting the longitudinal stability of the vehicle.

[0144] (6) Input the actual motor torque to the intermediate shaft of the semitrailer as additional power input, and observe the speed fluctuation and longitudinal acceleration amplitude of the vehicle after the additional power input;

[0145] The actual speed is fed back to the driver model. Since the difference between the actual speed and the expected speed is used as the input of the driver model, feeding back the actual speed of the vehicle model to the driver model can achieve closed-loop control and complete the entire electrification process.

[0146] like Figure 5 As shown in the longitudinal acceleration comparison diagram, after adding the additional torque, the amplitude range of the vehicle's longitudinal acceleration has been significantly reduced. In order to quantify the longitudinal stability of the vehicle, the vibration dose value (VDV) is used to quantify the human body's response to vibration. In essence, it is the fourth power integral of the acceleration signal after bandpass filtering during the gear shift process. When this technique is applied to the longitudinal acceleration data collected during the gear shift of the transmission, the calculated VDV represents the driver's physical perception of the degree of gear shift. VDV is obtained from the appropriately filtered vehicle acceleration signal, as shown in formula (26). Since the acceleration signal is bandpass filtered, the resulting number is independent of other acceleration events.

[0147] In order to calculate the total VDV to which the vehicle occupants are subjected, it is necessary to include acceleration calculations in three directions. However, since the focus of the present invention is to use VDV as an indicator of shift quality, it is not necessary to include vertical or lateral vibrations. The VDV of the present invention is calculated as follows:

[0148]

[0149] where a(t) is the longitudinal acceleration of the vehicle, The fourth power integral of the bandpass filtered acceleration signal during the gear shift process. t0 is the time when the gear shift starts, t f is the time at the end of the gear shift. VDV is used to improve comfort. Since VDV is time-dependent, it is used as a comparison tool to analyze the VDV generated by a single gear shift test scenario with a duration of 1.5s. The results are shown in Table 1, which demonstrates how VDV changes with gear shifting in traditional semi-trailer vehicles and electrified semi-trailer vehicles. When the torque filling strategy is used, the shift quality of low gears is improved more, for example, 2-3 gears are improved by nearly 50%, while the improvement of high gears is less, but it can reach about 15%. Starting from 1st gear to 2nd gear requires a large torque for starting. Considering the power limitation of the motor and the stability of the vehicle, the starting torque cannot be fully provided by the motor, so the value of VDV has not decreased significantly.

[0150] Table 1 Vibration dose values

[0151]

[0152] like Figure 6 As shown, after adding the additional torque, the speed fluctuation of the vehicle is significantly reduced, and the followability with the expected speed becomes better, that is, the dynamic performance is significantly improved.

[0153] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well.

Claims

1. A commercial semi-trailer electric drive strategy and power distribution method, characterized in that: The following steps are involved: (1) The driver model uses the speed difference between the desired vehicle speed and the actual vehicle speed as input and uses PI control to obtain the driver's pedal opening to achieve the target vehicle speed. (2) Different working modes are established according to vehicle speed and pedal opening: large torque joint drive mode, small torque joint drive mode, engine single drive mode, coasting mode, and cruise mode, ensuring power is provided while reducing energy consumption; (3) Inputting the pedal opening into the multi-body dynamics model of the commercial semi-trailer, and judging the output torque of the engine at the moment before the gear shift according to the gear position information, clutch engagement information, and transmission torque of the multi-body dynamics model of the commercial semi-trailer; (4) Extending the torque signal at each gear shifting moment to obtain a desired motor torque signal; (5) Taking the expected torque signal of the engine as the motor load, an improved compensatory sliding film control algorithm is used to obtain the actual motor torque; (6) The actual motor torque is input to the intermediate shaft of the semi-trailer as additional power input, and the actual speed is fed back to the driver model to achieve closed-loop control and complete the entire electric drive process.

2. The commercial semi-trailer electric drive strategy and power distribution method according to claim 1, characterized in that: The parameters of the driver model include the nominal vehicle speed v nom , actual vehicle speed v ref , proportional gain K p , integral gain K i , Anti-saturation gain K aw , vehicle speed feedforward gain K ff and the slope feedforward gain K g ; The driver model uses the speed difference between the desired speed and the actual speed of the vehicle as input, and uses PI control to obtain the signal values ​​of the accelerator pedal and the brake pedal to achieve the target speed. The driver model uses a low-pass filter function to filter the input speed difference, and uses the nominal speed to perform dimensionless processing on the input speed difference. The processed value is used to calculate the speed control amount using proportional integral control with tracking compensation and feedforward gain. The calculated result is anti-saturated so that the result ranges from -1 to 1, thereby obtaining the input amount of the brake pedal and the accelerator pedal. The specific formula is as follows: yes ref =v ref -v(3) H(f) is the response function, τ err is the low-pass filter coefficient, y is the speed control value, e ref is the difference between the speed control amount and the anti-saturation control amount, e out is the speed difference, θ is the slope angle, v is the actual vehicle speed, y sat ,y acc ,y bra They are anti-saturation control amount, accelerator pedal opening and brake pedal opening respectively.

3. The commercial semi-trailer electric drive strategy and power distribution method according to claim 1, characterized in that: In step (2), different working modes are established according to the vehicle speed and the pedal opening, including: High-torque joint drive mode: The speed is within 0-35km / h, which is high-torque joint drive, and the motor runs at maximum power; Small torque combined drive mode: The speed is within 35-60km / h, which is small torque combined drive, and the motor power is set to 75% of the rated power; Engine-only driving mode: When the speed is greater than 60km / h, the vehicle basically runs stably and the motor does not participate in the driving; In addition, within the speed range of the above three driving modes, the working modes are further distinguished by judging the acceleration and brake pedals: If the acceleration is less than 0 and the brake signal is 0, the vehicle enters the gliding mode, otherwise, it enters the braking mode. If the acceleration is equal to 0, the vehicle is in cruise mode.

4. The commercial semi-trailer electric drive strategy and power distribution method according to claim 1, characterized in that: Step (3) The multi-body dynamics model of the commercial semi-trailer is: Where m is the mass of the tractor, m T is the mass of the trailer, I ψ is the vehicle yaw stiffness, δ w is the front wheel steering angle, a x 、a y are longitudinal and lateral accelerations, v x and v y are longitudinal and lateral speeds respectively; F xfl 、F xfr 、F xml 、F xmr 、F xrl and F xrr are the longitudinal forces of the front, middle and rear wheels; F yfl 、F yfr 、F yml 、F ymr 、F yrl and F yrr are the lateral forces of the front, middle and rear wheels; d f d m and d r are the track widths of the front, middle and rear drive axles, L f is the distance from the front axle to the vehicle equivalent center, L fm is the wheelbase from the front axle to the middle axle, L mr is the wheelbase from the middle bridge to the rear bridge, ψ is the yaw angle, is the yaw angular velocity, I is the moment of inertia; since the front axle adopts a non-independent suspension, the left and right loads of the front axle are equal, and the specific size is shown in formula (6); the vertical load of the tire on the middle and rear axles is as shown in formula (7); F zfl is the vertical force of the left front wheel, F zfr is the vertical force on the right front wheel, F zrl is the vertical force of the left rear wheel, F zrr is the vertical force of the right rear wheel, F zml is the vertical force of the left middle wheel, F zmr is the vertical force of the right middle wheel, L a L is the distance from the center of the 2nd and 3rd axles of the tractor to the traction saddle. b It is the distance from the center of the third axis to the traction saddle.

5. The commercial semi-trailer electric drive strategy and power distribution method according to claim 1, characterized in that: In step (5), the improved compensatory sliding film control algorithm introduces the estimated motor parameter changes and the disturbance value of the load torque observed by the extended observer into the sliding mode controller to weaken the jitter of the motor torque output, thereby compensating for the torque interruption caused by the engagement and disengagement of the clutch during the vehicle shifting process through the motor.

6. The commercial semi-trailer electric drive strategy and power distribution method according to claim 1, characterized in that: In step (5), the sliding film control algorithm is used to control the torque. First, the function expression of the sliding surface is determined as follows: s(x,t),s∈R m (9); Where s(x,t) is the hypersurface defined in the system state space, x is the coordinate of the variable in the state space, and t indicates that the sliding surface depends on time; s∈R m It means that the hypersurface defined in the system state space belongs to the real number range. According to the above formula, the sliding surface is solved to obtain: in and denote the control functions on and below the hypersurface, respectively; The state variables of the permanent magnet synchronous motor are taken as: In the formula, x1 and x2 are the state variables of the system respectively, and the integral of x1 is taken as the second state variable of the system, ω ref is the target speed, ω m is the motor output speed, combined with formula (10), and the derivative of formula (11) is obtained: in is the integral of the state variables, p is the number of motor pole pairs, ψ f is the magnetic flux, B is the viscous friction coefficient, J is the moment of inertia, β represents the disturbance value caused by the load torque and parameters, i q is the electric current on the q axis, is the integral of the motor output speed, It is the integral of the disturbance value caused by load torque and parameters; The sliding surface function of the system is defined as: s=cx1+x2(13); where s represents the sliding surface, c is the coefficient, x1 and x2 are state variables; take the derivative of the sliding surface function and substitute equation (11) into it to obtain: are the integrals of sliding surface and state variables respectively; The improved approach rate is: Where ε and k represent constants, and ε>0, k>0. The constant-speed approach term is -ε|x1|sgn(s), and the exponential approach term is ks. When the error increases, the constant-speed approach term makes the system state variable approach the sliding surface, and at the same time, the exponential approach term reduces the system state variable to 0. Definition Combining equation (11) and equation (12), the output equation of the controller is: in is the reference current of q axis; Select the Lyapunov function: V is a Lyapunov function. According to the Lyapunov stability theorem, we only need to prove Then the system is asymptotically stable, and from equation (15) and equation (17) we can get: In the formula represents the function integral, ε>0, k>0 and sgn(s)s>0, where sgn(s) is the sign function; thus we have Therefore, the system error can converge to 0 in a limited time, making the system stable. At the same time, using the saturation function sat(A,δ) instead of sgn(A) can effectively suppress chattering and further improve the robustness of the system. The saturation function sat(A,δ) equation is selected as follows: Where A is the input signal and δ is the saturation threshold, i.e. the limiting amplitude.

7. The commercial semi-trailer electric drive strategy and power distribution method according to claim 6, characterized in that: The extended observer is introduced into the common sliding film control algorithm. It can be seen from formula (16) that the control rate designed by using the sliding surface contains the motor parameter change and the load torque disturbance term β, and the disturbance value cannot be measured. Therefore, the present invention designs a disturbance observer to estimate the disturbance of the motor output. In the actual motor speed control system, the permanent magnet synchronous motor system parameter disturbance changes slowly, and the first-order derivative of the disturbance can be approximated to 0. Then, the system state space equation is established by formula (10) to obtain: Where Y is the output equation of the state space equation, is the integral of the state variables, p is the number of motor pole pairs, ψ f is the magnetic flux, B is the viscous friction coefficient, J is the moment of inertia, β represents the disturbance value caused by the load torque and parameters, i q is the electric current on the q axis, is the integral of the motor output speed, is the integral of the disturbance value caused by the load torque and parameters, is the estimated value of the above integral; m , β are the observed objects, and the gain feedback of the speed estimation error e1 is established. Among them, the extended disturbance observer is designed based on formula (17): Where: is the estimated value of the above integral; are the estimated value of electrical angular velocity and the estimated value of load parameter perturbation respectively; λ1, λ2, η are positive real numbers; the error equation of the extended observer is obtained from equations (20) and (21) as follows: Where: represents the speed estimation error, represents the system parameter and load torque estimation error, are the integrals of the speed and load torque estimation errors respectively, and the error state equation of the extended observer is expressed as: Where: is the error integral It can be seen that by configuring Located in the left half plane, that is, the pole is located in the left half plane of the state space plane, so that the error e asymptotically approaches 0, so that the system error approaches 0, and the observed disturbance and load parameter disturbance estimate Substituting into equation (4)-(34) we can get: It can be seen from formula (16) that by taking parameter changes and load disturbances as feedforward compensation, when the load and motor parameters change, the controller can overcome the influence of load and parameter disturbances on the system and effectively suppress the chattering phenomenon of the system. At the same time, the saturation function is introduced to further improve the robustness of the system.

8. A system for realizing the commercial semi-trailer electric drive strategy and power distribution method according to any one of claims 1 to 7, characterized in that: It includes a vehicle model module, a motor module, a torque calculation module, a power distribution module, and a driver module. The expected speed and pedal opening determined by the driver module are input into the vehicle model. The vehicle model outputs the actual vehicle speed and engine information. The actual vehicle speed and engine information output by the vehicle model are input into the torque calculation module to obtain the expected additional torque as the expected torque of the motor. The expected torque of the motor is input into the motor module, and the motor outputs the actual torque to the vehicle model to improve the longitudinal stability of the vehicle. According to different vehicle speeds, the vehicle uses different power distribution strategies.

9. The system of commercial semi-trailer electric drive strategy and power distribution method according to claim 8, characterized in that: The engine information includes gear position information, engine torque information, and clutch engagement signal.

10. A computer device, characterized in that: The invention comprises: a memory and a processor and a computer program stored in the memory. When the computer program is executed on the processor, an electric drive strategy and a power distribution method for a commercial semi-trailer as described in any one of claims 1 to 7 are implemented.

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