Commercial semi-trailer electric drive strategy and power distribution method and system

Abstract

The application discloses a kind of commercial semitrailer electric drive strategy and power distribution method and system, comprising the following steps: establishing the multi-body dynamics model of commercial semitrailer;According to vehicle speed and pedal opening, respectively establish different working modes, reduce energy consumption while providing power;According to the gear information of vehicle model, clutch engagement information and transmission torque, the output torque of engine at a time before gear shifting is judged, the desired motor torque signal is obtained, the improved compensation sliding film control algorithm is used, and the actual motor torque is obtained;Actual motor torque is input to the intermediate shaft of semitrailer as additional power input;Actual speed is fed back to driver model to realize closed-loop control.The superiority of the method is that the power mechanism of traditional commercial semitrailer is not changed, the driving comfort and vehicle power performance are greatly improved by installing motor, in addition, the motor can also act as a retarder to ensure safety on 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 provides an electric drive strategy and power distribution method and system for commercial semi-trailers. Background Art

[0002] The fundamental function of a modern powertrain is to transmit torque to the road-tire interface. To ensure proper vehicle operation, the engine and transmission must be carefully designed. However, the heavy weight of traditional commercial semi-trailers can exaggerate speed and torque discontinuities during gear shifts, impacting driving quality and reducing comfort.

[0003] Commercial semi-trailers with added motors are no longer traditional fuel vehicles, but hybrid vehicles, and 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 under steady-state conditions to improve the energy efficiency of the entire 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, neural network control methods, fuzzy control methods, genetic algorithms, adaptive algorithms, etc. have all been effectively applied. They are effective in improving the performance of the entire vehicle and improving the adaptability of hybrid vehicles under different working conditions.

[0004] In existing technology, hybrid vehicles can be categorized as series hybrid vehicles, parallel hybrid vehicles, and series-parallel hybrid vehicles based on the arrangement of powertrain components in the power transmission path (Design and Optimization of Energy Management Strategies for Plug-in Hybrid Electric Vehicles, Master's Thesis at Chongqing University, Ji Yawei). Series hybrid vehicles have a simpler structure, directly powering the drive wheels through the electric motor alone, while the engine indirectly provides energy by charging the battery via a generator. Therefore, the engine can always operate in its high-efficiency range, and its drive system is similar to that of an extended-range pure electric vehicle. Parallel hybrid vehicles, powered by both the electric motor and the engine simultaneously or independently, offer a wider range of operating modes, meeting drivers' greater power demands and adapting to more complex operating conditions. Series-parallel hybrid vehicles, on the other hand, can provide power in both series and parallel configurations, offering greater adaptability. However, commercial semi-trailers are larger and require consideration of R&D costs. Summary of the Invention

[0005] The purpose of this invention is to provide an electric drive strategy and power distribution method for commercial semi-trailers. The motor is installed on the semi-trailer axle. Through power distribution, the frustration caused by the shifting process of heavy-duty commercial vehicles can be effectively reduced, and the driving comfort and smoothness can be 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 through at least one of the following technical solutions.

[0007] A commercial semi-trailer electric drive strategy and power distribution method includes 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 angle to achieve the target vehicle speed.

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

[0010] (3) Inputting the pedal opening into a multi-body dynamics model of a commercial semi-trailer, and determining the engine output torque immediately before the gear shift based on 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 shifting moment to obtain the desired motor torque signal;

[0012] (5) Taking the expected torque signal of the engine as the motor load, the improved compensating 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 an 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.

[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 and actual vehicle speeds as input, and uses PI control to obtain the signal values ​​of the accelerator and brake pedals to achieve the target vehicle speed. The driver model uses a low-pass filter function to filter the input speed difference, and uses the nominal vehicle speed to perform dimensionless processing on the input speed difference. The processed value is used to calculate the speed control variable using proportional-integral control with tracking compensation and feedforward gain. 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 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 speed, y sat 、y acc 、y bra They are anti-saturation control quantity, 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 combined drive mode: within the speed range of 0-35km / h, it is high-torque combined drive, and the motor runs at maximum power;

[0023] Small torque combined drive mode: When the speed is within 35-60 km / h, it 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 is basically running stably and the motor does not participate in driving;

[0025] In addition, within the speed ranges of the three driving modes mentioned above, the operating 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 coasting 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 respectively; F yfl 、F yfr 、F yml 、F ymr 、F yrl and F yrr are the lateral forces of the front, middle and rear wheels respectively; d f d m and d r They are the wheelbases of the front, middle and rear drive axles, L f is the distance from the front axle to the vehicle's 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 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 tires on the middle and rear axles is shown in formula (7); F zfl is the vertical force on the left front wheel, F zfr is the vertical force on the right front wheel, F zrl is the vertical force on the left rear wheel, F zrr is the vertical force on the right rear wheel, F zml is the vertical force on 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 expanded 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 Indicates that the hypersurface defined in the system state space belongs to the real number range. Solving the sliding mode surface according to the above formula gives:

[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] 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 derived from formula (11):

[0041]

[0042] in is the integral of the state variables, p is the number of motor pole pairs, ψ f is the magnetic linkage, 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, and 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 the sliding surface and state variables respectively;

[0047] In actual motor control, the sliding mode control method has the problem of high-frequency chattering. 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. The improved approach rate is:

[0048]

[0049] Where ε and k represent constants, and ε>0, k>0. The constant velocity approach term is -ε|x1|sgn(s), and the exponential approach term is ks. When the error increases, the constant velocity approach term makes the system state variable approach the sliding surface, while the exponential approach term reduces the system state variable to 0. Definition Combining equations (11) and (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 the Lyapunov function. According to the Lyapunov stability theorem, we only need to prove that Then the system is asymptotically stable, and from equations (15) and (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 can get Therefore, the system error can converge to zero 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. As can be seen from formula (16), the control rate designed using the sliding surface contains the motor parameter changes 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):

[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 linkage, 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 observation objects, and the gain feedback of the speed estimation error e1 is established. Based on formula (17), the extended disturbance observer is designed as follows:

[0062]

[0063] Where: are the estimated values ​​of electrical angular velocity and load parameter perturbation respectively; λ1, λ2, and 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 estimation error of system parameters and load torque, 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] From this we can see 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 approaches 0 asymptotically, so that the system error approaches 0, and the observed disturbance and load parameter disturbance estimate Substituting into equations (4)-(34), we can obtain:

[0070]

[0071] As can be seen from formula (16), with parameter changes and load disturbances as feedforward compensation, when the load and motor parameters change, the controller can overcome the impact of load and parameter disturbances on the system and effectively suppress the system chattering phenomenon. At the same time, the introduction of saturation function further improves the robustness of the system.

[0072] A system for implementing the aforementioned 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 desired speed and pedal opening determined by the driver module are input into the vehicle model, and the vehicle model outputs 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 desired additional torque as the motor desired torque. The motor desired 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. The vehicle uses different power distribution strategies according to different vehicle speeds.

[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, it implements the commercial semi-trailer electric drive strategy and power distribution method.

[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 to traditional sliding-film control algorithms, the improved compensatory sliding-mode control of this invention takes into account the disturbance of the motor load torque. When the torque changes suddenly, the estimated torque is smoother than the actual torque. Incorporating the estimated motor parameter changes and the load torque disturbance observed by the extended observer into the sliding-mode controller effectively reduces chatter. The motor acts as a retarder when the vehicle enters a long downhill slope, ensuring driving safety. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0081] Figure 3 2. It is a longitudinal dynamic model diagram of a semi-trailer in the embodiment;

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

[0083] Figure 5 This is a simulation diagram comparing the original longitudinal acceleration and the longitudinal acceleration of the electric-drive vehicle in the embodiment;

[0084] Figure 6 This 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 will be described in further detail below with reference to the accompanying drawings and embodiments.

[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) Based on the given working conditions, the desired vehicle speed and the actual vehicle speed, the driver's accelerator pedal and brake pedal opening size input is processed: the driver model takes the difference between the desired vehicle speed and the actual vehicle speed as input, uses PI control to obtain the signal values ​​of the accelerator pedal and the brake pedal, so as to achieve the target vehicle speed. The specific principles are shown in Equations (1) to (4). First, a low-pass filter function is used to filter the input speed difference. The input speed difference is dimensionless using the nominal vehicle speed. The processed value is used to calculate the speed control quantity using proportional integral control with tracking compensation and feedforward gain. The calculated result is anti-saturation processed so that the result range is between -1 and 1, thereby obtaining the input quantity of the brake pedal and the accelerator pedal. The parameters of the driver model include nominal vehicle speed, actual vehicle speed, proportional gain, integral gain, anti-saturation gain, vehicle 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 speed, y sat 、y acc 、y bra They are anti-saturation control quantity, accelerator pedal opening and brake pedal opening respectively.

[0090] (2) Different working modes are established according to vehicle speed and pedal opening: large torque combined drive mode, small torque combined 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 high-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, within each speed range, the operating mode is further distinguished by judging the acceleration and brake pedal: if the acceleration is less than 0 and the brake signal is 0, it enters the coasting 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 engine output torque immediately before the gear shift based on 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, where m is the mass of the tractor, m 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 respectively; F yfl 、F yfr 、F yml 、F ymr 、F yrl and F yrr are the lateral forces of the front, middle and rear wheels respectively; d f d m and d r They are the wheelbases 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 non-independent suspension, the left and right loads of the front axle are equal, and the specific size is as 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 1.5 seconds, of which the clutch disengagement time is 0.4 seconds and the clutch engagement time is 1.1 seconds. Therefore, according to the clutch state, the torque signal is maintained for 0.4 seconds during the clutch disengagement; during the clutch engagement process, the torque signal is linearly reduced to obtain the desired motor torque signal.

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

[0101] The sliding film control algorithm is used to control the torque. For common sliding mode controllers, which are mostly used in nonlinear systems, the design process mainly involves 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 means the function depends on time, 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 yields:

[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 derived from formula (11):

[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 field 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 the problem of high-frequency chattering. 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. The improved approach rate is:

[0119]

[0120] Where ε and k represent constants, and ε>0, k>0. The constant velocity approach term is -ε|x1|sgn(s), and the exponential approach term is ks. When the error increases, the constant velocity approach term makes the system state variable approach the sliding surface, while the exponential approach term reduces the system state variable to 0. Definition Combining equations (11) and (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 the Lyapunov function. According to the Lyapunov stability theorem, we only need to prove that Then the system is asymptotically stable, and from equations (15) and (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 can get Therefore, the system error can converge to zero 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. As can be seen from formula (16), the control rate designed using the sliding surface contains the motor parameter changes 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):

[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 field 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 observation objects, and the gain feedback of the speed estimation error e1 is established. Based on formula (17), the extended disturbance observer is designed as follows:

[0133]

[0134] Where: are the estimated values ​​of electrical angular velocity and load parameter perturbation respectively; λ1, λ2, and 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 estimation error of system parameters and load torque, 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] From this we can see 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 the load torque Substituting into formula (16) we can get:

[0141]

[0142] As can be seen from formula (16), with parameter changes and load disturbances as feedforward compensation, when the load and motor parameters change, the controller can overcome the impact of load and parameter disturbances on the system and effectively suppress the system chattering phenomenon. At the same time, the introduction of saturation function further improves the robustness of the system.

[0143] The sliding film control algorithm can significantly improve the vehicle's longitudinal stability. The improved compensatory sliding film control algorithm incorporates the estimated motor parameter changes and load torque disturbances observed by the extended observer into the sliding mode controller, effectively reducing jitter in the motor's torque output. This is because the sliding film control algorithm detects torque interruptions caused by clutch engagement and disengagement during gear shifts, allowing the motor to compensate for these interruptions. The introduction of the extended observer, by observing motor parameter changes, can reduce overshoot and oscillations during the motor's torque output, thereby reducing motor output instability and preventing unstable motor output from affecting the vehicle's longitudinal stability.

[0144] (6) Input the actual motor torque to the intermediate shaft of the semi-trailer 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 the actual speed of the vehicle model back to the driver model can achieve closed-loop control and complete the entire electrification process.

[0146] like Figure 5 The longitudinal acceleration comparison diagram shown in the figure shows that the amplitude range of the vehicle's longitudinal acceleration has been significantly reduced after the additional torque is added. 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. Essentially, 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, the calculated VDV represents the driver's physical perception of the degree of gear shift. The 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] To calculate the total VDV experienced by vehicle occupants, it is necessary to include acceleration in all three directions. However, since the present invention focuses on using VDV as an indicator of shift quality, it is not necessary to include vertical or lateral vibration. The VDV of the present invention is calculated using the following formula:

[0148]

[0149] where a(t) is the vehicle longitudinal acceleration, 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 electric semi-trailer vehicles. When the torque filling strategy is used, the shift quality of low gears is improved more, for example, the improvement of 2-3 gears is nearly 50%, while the improvement of high gears is less, but it can reach about 15%. Since the torque required for starting from 1st gear to 2nd gear is large, 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 does not decrease significantly.

[0150] Table 1 Vibration dose values

[0151]

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

[0153] The preferred embodiments of the present invention disclosed above are intended only to help illustrate the present invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the present invention to the specific embodiments described. Obviously, numerous modifications and variations are possible based on the contents of this specification. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, so that those skilled in the art can better understand and utilize the present invention.

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 angle to achieve the target vehicle speed. (2) Different working modes are established according to vehicle speed and pedal opening: large torque combined drive mode, small torque combined drive mode, engine single drive mode, coasting mode, and cruise mode, ensuring power supply while reducing energy consumption; (3) Inputting the pedal opening into a multi-body dynamics model of a commercial semi-trailer, and determining the engine output torque immediately before the gear shift based on 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 shifting moment to obtain the desired motor torque signal; (5) Taking the expected torque signal of the engine as the motor load, the improved compensating sliding film control algorithm is used to obtain the actual motor torque; In step (5), the improved compensatory sliding film control algorithm introduces the estimated motor parameter changes and the load torque disturbance value observed by the extended observer into the sliding mode controller to weaken the jitter of the motor torque output, thereby compensating the torque interruption caused by the clutch engagement and disengagement during the vehicle shifting process through the motor; (6) The actual motor torque is input to the intermediate shaft of the semi-trailer as an 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 and actual vehicle speeds as input, and uses PI control to obtain the signal values ​​of the accelerator and brake pedals to achieve the target vehicle speed. The driver model uses a low-pass filter function to filter the input speed difference, and uses the nominal vehicle speed to perform dimensionless processing on the input speed difference. The processed value is used to calculate the speed control variable using proportional-integral control with tracking compensation and feedforward gain. 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 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 speed, y sat 、y acc 、y bra They are anti-saturation control quantity, 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 vehicle speed and pedal opening, including: High-torque combined drive mode: within the speed range of 0-35km / h, it is high-torque combined drive, and the motor runs at maximum power; Small torque combined drive mode: When the speed is within 35-60 km / h, it 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 is basically running stably and the motor does not participate in driving; In addition, within the speed ranges of the three driving modes mentioned above, the operating 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 coasting 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 respectively; F yfl 、F yfr 、F yml 、F ymr 、F yrl and F yrr are the lateral forces of the front, middle and rear wheels respectively; d f d m and d r They are the wheelbases 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 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 tires on the middle and rear axles is shown in formula (7); F zfl is the vertical force on the left front wheel, F zfr is the vertical force on the right front wheel, F zrl is the vertical force on the left rear wheel, F zrr is the vertical force on the right rear wheel, F zml is the vertical force on 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 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 Indicates that the hypersurface defined in the system state space belongs to the real number range. Solving the sliding mode surface according to the above formula gives: in and denote the control functions on and below the hypersurface, respectively; The state variables of the permanent magnet synchronous motor are taken as: 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 derived from formula (11): in is the integral of the state variables, p is the number of motor pole pairs, ψ f is the magnetic linkage, 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 the 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, and x1 and x2 are state variables. Derivative the sliding surface function and substitute Equation (11) into it to obtain: are the integrals of the sliding surface and state variables respectively; The improved approach rate is: Where ε and k represent constants, and ε>0, k>0. The constant velocity approach term is -ε|x1|sgn(s), and the exponential approach term is ks. When the error increases, the constant velocity approach term makes the system state variable approach the sliding surface, while the exponential approach term reduces the system state variable to 0. Definition Combining equations (11) and (12), the output equation of the controller is: in is the reference current of q axis; Select the Lyapunov function: V is the Lyapunov function. According to the Lyapunov stability theorem, we only need to prove that Then the system is asymptotically stable, and from equations (15) and (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 can get Therefore, the system error can converge to zero 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.

6. The commercial semi-trailer electric drive strategy and power distribution method according to claim 5, characterized in that: The extended observer is introduced into the common sliding film control algorithm. As can be seen from formula (16), the control rate designed using the sliding surface contains the motor parameter changes and the load torque disturbance term β, and the disturbance value cannot be measured. Therefore, a disturbance observer is designed 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): 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 linkage, 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 observation objects, and the gain feedback of the speed estimation error e1 is established. Based on formula (17), the extended disturbance observer is designed as follows: Where: Then it is the estimated value of the above integral; are the estimated values ​​of electrical angular velocity and load parameter perturbation respectively; λ1, λ2, and 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 estimation error of system parameters and load torque, 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 From this we can see 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 approaches 0 asymptotically, so that the system error approaches 0, and the observed disturbance and load parameter disturbance estimate Substituting into equations (4)-(34), we can obtain: As can be seen from formula (16), with parameter changes and load disturbances as feedforward compensation, when the load and motor parameters change, the controller can overcome the impact of load and parameter disturbances on the system and effectively suppress the system chattering phenomenon. At the same time, the introduction of saturation function further improves the robustness of the system.

7. A system for implementing the commercial semi-trailer electric drive strategy and power distribution method according to any one of claims 1 to 6, 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 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.

8. The system of electric drive strategy and power distribution method for commercial semi-trailer according to claim 7, characterized in that: Engine information includes gear information, engine torque information, and clutch engagement signal.

9. A computer device, characterized in that: The invention comprises: a memory and a processor and a computer program stored in the memory, and when the computer program is executed on the processor, it implements a commercial semi-trailer electric drive strategy and power distribution method as described in any one of claims 1 to 8.

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