Energy management method and system based on slope and load estimation

Abstract

An energy management method based on slope and load estimation. The method comprises: on the basis of a dynamic slope and a dynamic load of a vehicle, determining a compensation torque output coefficient; in a driving state, determining a compensation torque on the basis of the difference between a rated driving torque and a peak driving torque of the vehicle, and the compensation torque output coefficient, and adding the rated driving torque to the compensation torque to obtain an output driving torque, wherein in the driving state, when the vehicle is in a no-load state under a flat-road condition or a downhill operating condition, the compensation torque output coefficient is 0; and in a coasting braking state, determining a compensation torque on the basis of the difference between a rated braking torque and a peak braking torque of the vehicle, and the compensation torque output coefficient, and adding the rated braking torque to the compensation torque to obtain an output braking torque, wherein in the coasting braking state, when the vehicle is in a no-load state under the flat-road condition or an uphill operating condition, the compensation torque output coefficient is 0. Further provided is an energy management system based on slope and load estimation. The method and system improve the control precision and control effect of energy management.

Description

An energy management method and system based on slope and load estimation Technical Field

[0001] This invention belongs to the field of new energy vehicle technology, specifically relating to an energy management method and system based on slope and load estimation. Background Technology

[0002] During vehicle operation, the gradient and load conditions frequently change, significantly impacting the vehicle's braking performance and handling stability. Therefore, real-time and accurate gradient and load data, integrated for vehicle energy distribution and management, would significantly improve vehicle control and provide crucial information for autonomous driving assistance decisions, green driving, and automatic transmission shift control, ultimately achieving safe, economical, and comfortable driving. However, current solutions for new energy vehicles only manage energy based on gradient or load conditions, failing to address how to integrate these information for comprehensive vehicle energy management. This results in low energy management control accuracy and poor vehicle control performance. Summary of the Invention

[0003] The purpose of this invention is to provide an energy management method and system based on slope and load estimation, in order to solve the problems of low energy management control accuracy and poor vehicle control effect caused by existing energy management methods.

[0004] To address the aforementioned technical problems, this invention provides an energy management method based on slope and load estimation, comprising:

[0005] The compensation torque output coefficient is determined based on the vehicle's dynamic gradient and dynamic load.

[0006] In driving mode, the compensation torque is determined based on the difference between the rated driving torque and the vehicle's peak driving torque, and the compensation torque output coefficient. The rated driving torque and the compensation torque are added together to obtain the output driving torque. In driving mode, when the vehicle is in a flat road unloaded or downhill unloaded condition, the compensation torque output coefficient is 0.

[0007] Under coasting braking conditions, the compensation torque is determined based on the difference between the rated braking torque and the vehicle's peak braking torque, and the compensation torque output coefficient. The rated braking torque and the compensation torque are then added together to obtain the output braking torque. Under coasting braking conditions, when the vehicle is in a flat, unloaded condition or an uphill, unloaded condition, the compensation torque output coefficient is 0.

[0008] Furthermore, the compensation torque output coefficient is determined by the dynamic load coefficient and the dynamic slope coefficient; the dynamic slope coefficient is calculated based on the vehicle's dynamic slope and the vehicle's maximum design gradeability, and the larger the absolute value of the dynamic slope, the larger the dynamic slope coefficient; the dynamic load coefficient is calculated based on the vehicle's dynamic load, the vehicle's curb weight and the vehicle's maximum design gross weight, and the larger the dynamic load, the larger the dynamic load coefficient.

[0009] Furthermore, in driving mode, the compensation torque output coefficient is positive when going uphill and negative when going downhill and not unloaded; in coasting braking mode, the compensation torque output coefficient is positive when going downhill and negative when going uphill and not unloaded.

[0010] Furthermore, the compensation torque output coefficient is determined by looking up a table of compensation torque output coefficients corresponding to the dynamic load coefficient and dynamic slope coefficient. The table includes a driving state table and a coasting braking state table, which are obtained based on actual vehicle calibration.

[0011] Furthermore, the actual vehicle calibration method involves providing the vehicle with different driving torques or braking torques under different loads and gradients, respectively, in both the driving state and the coasting braking state. When the vehicle acceleration corresponding to the driving torque or braking torque is the same as the vehicle's acceleration when unloaded on a flat road, the compensation torque output coefficient corresponding to the driving torque or braking torque is used as the calibration value.

[0012] Furthermore, the method for calculating the dynamic slope includes determining the acceleration formula in the vehicle's driving direction based on the acceleration components of the vehicle's longitudinal acceleration and gravitational acceleration along the slope, combined with the acceleration component of the vehicle's centrifugal acceleration in the driving direction during the turning process, and then using a Kalman filter to obtain the optimal estimate of the road slope, and using the optimal estimate as the dynamic slope at the current moment.

[0013] Furthermore, the formula for the acceleration in the direction of vehicle travel is: a Xsens = dv / dt + g*sinθ + d*ω 2

[0014] Among them, a Xsens ω is the acceleration in the direction of vehicle travel, v is the vehicle speed, t is time, g is the gravitational acceleration, θ is the dynamic slope, d is the distance of the gyroscope from the rear axle, and ω is the yaw rate of the vehicle.

[0015] Furthermore, the method for calculating the dynamic load includes establishing a longitudinal dynamics model of the vehicle regarding the dynamic load and dynamic slope, substituting the calculated dynamic slope at the current moment into the longitudinal dynamics model of the vehicle, and then solving the longitudinal dynamics model of the vehicle to obtain the dynamic load at the current moment.

[0016] Furthermore, the longitudinal dynamics model of the vehicle is as follows:

[0017] Among them, F x The longitudinal driving force is m, and the dynamic load is m. v is the longitudinal acceleration of the vehicle. x Let C be the longitudinal velocity of the vehicle, ρ be the air density, and C be the... d denoted as drag coefficient, A as windward area, g as gravitational acceleration, θ as dynamic slope, and f as road rolling resistance coefficient.

[0018] The beneficial effects of the above technical solution are as follows: This invention is an improved invention. It determines the compensation torque output coefficient required by the vehicle under the current slope and load conditions based on the obtained dynamic slope and dynamic load of the vehicle. The output torque corresponding to the driving state or coasting braking state is calculated based on the coefficient. That is, the vehicle's energy management is optimized in real time by integrating the vehicle's dynamic load and dynamic slope, which improves the accuracy and effect of energy management control, and can avoid energy waste caused by excessive compensation. It also improves the vehicle's economy while taking into account the vehicle's power performance.

[0019] To address the aforementioned technical problems, the present invention also provides an energy management system based on slope and load estimation, including a controller for implementing the energy management method based on slope and load estimation described above.

[0020] The beneficial effects of the above technical solution are as follows: This invention is an improved invention. It determines the compensation torque output coefficient required by the vehicle under the current slope and load conditions based on the obtained dynamic slope and dynamic load of the vehicle. The output torque corresponding to the driving state or coasting braking state is calculated based on the coefficient. That is, the vehicle's energy management is optimized in real time by integrating the vehicle's dynamic load and dynamic slope, which improves the accuracy and effect of energy management control, and can avoid energy waste caused by excessive compensation. It also improves the vehicle's economy while taking into account the vehicle's power performance. Attached Figure Description

[0021] Figure 1 is a flowchart of the energy management method based on slope and load estimation according to an embodiment of the present invention;

[0022] Figure 2 is a force analysis diagram of vehicle slope motion according to an embodiment of the system of the present invention;

[0023] Figure 3 is a diagram showing the centrifugal acceleration analysis of a vehicle turning according to an embodiment of the system of the present invention. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the present invention clearer, the specific embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0025] This invention determines the required compensation torque output coefficient of the vehicle under the current slope and load conditions based on the obtained dynamic slope and dynamic load of the vehicle. The output torque corresponding to the driving state or coasting braking state is calculated based on the coefficient. In other words, the vehicle's energy management is optimized in real time by integrating the vehicle's dynamic load and dynamic slope, which improves the accuracy and effect of energy management control, and can avoid energy waste caused by excessive compensation, thus improving the vehicle's economy while taking into account the vehicle's power performance.

[0026] System Implementation Examples

[0027] This invention provides an energy management system based on slope and load estimation, applicable to new energy vehicles, including an acceleration sensor, an angular acceleration sensor, a vehicle speed sensor, and a controller. In this embodiment, a gyroscope is used as both an acceleration sensor and an angular velocity sensor. The vehicle's driving slope is estimated in real time based on the gyroscope's three-axis acceleration and angular velocity information. Preferably, to improve control efficiency, the gyroscope is integrated into the controller, which is the vehicle control unit (VCU). The controller acquires vehicle information such as acceleration signals, angular velocity signals, vehicle speed signals, and vehicle driving force, and calculates the output torque to implement an energy management method based on slope and load estimation. In other embodiments, a separate controller can be configured to interact with the collected information, calculate the output torque, and then send a request to the VCU. The implementation principle of this method is shown in Figure 1, and will be explained in detail below.

[0028] 1. Determine the compensation torque output coefficient under different working conditions based on the vehicle's dynamic slope and dynamic load.

[0029] Specifically, the vehicle operating conditions are divided based on the real-time calculated dynamic load and dynamic slope to determine the vehicle's load state and the slope state of the road it is traveling on.

[0030] 1) Determine the vehicle load status: Vehicle dynamic load coefficient ρ m When ρ is 0, it indicates that the vehicle is unloaded. m A value of 100% indicates that the vehicle is fully loaded. The formula for calculating the vehicle dynamic load factor is:

[0031] Where, ρ m ρ is the dynamic load factor, m is the dynamic load, m1 is the vehicle curb weight, and m2 is the vehicle's maximum design gross weight. m When ρ is 0, it indicates that the vehicle is unloaded. m A value of 100% indicates that the vehicle is fully loaded.

[0032] 2) Determine the road slope status of the vehicle: When the dynamic slope -2% ≤ θ ≤ 2%, it means that the vehicle is currently on a flat road; when θ > 2%, it means that the vehicle is currently on an uphill road; when θ < -2%, it means that the vehicle is currently on a downhill road.

[0033] In this embodiment, the compensation torque output coefficient is determined based on the dynamic load coefficient and the dynamic slope coefficient. The formula for calculating the vehicle's dynamic slope coefficient is as follows:

[0034] Where, ρ θ Here, θ represents the vehicle's dynamic gradient coefficient, θ is the dynamic gradient, and θ1 is the vehicle's maximum design gradeability. The larger the absolute value of the dynamic gradient, the larger the dynamic gradient coefficient.

[0035] The corresponding compensation torque output coefficient is determined based on the vehicle's dynamic gradient and dynamic load, including the compensation torque output coefficient ρ under driving conditions. Drive =f1(ρ m ,ρ θ and the compensation torque output coefficient ρ under coasting braking conditions Brake =f2(ρ m ,ρ θ The compensation torque output coefficient is determined by referring to tables of compensation torque output coefficients corresponding to dynamic load coefficients and dynamic gradient coefficients. These tables include tables for driving state and coasting / braking state, obtained from actual vehicle calibration. The actual vehicle calibration method involves providing the vehicle with different driving torques or braking torques for different loads and gradients under both driving and coasting / braking states. When the vehicle acceleration corresponding to the driving torque or braking torque is the same as the vehicle's acceleration when unloaded on a flat road, the compensation torque output coefficient corresponding to that driving torque or braking torque is used as the calibration value. The compensation torque output coefficient corresponding to the driving torque is the ratio between the driving torque and the driving torque when the vehicle is unloaded on a flat road with the same acceleration; similarly, the compensation torque output coefficient corresponding to the braking torque is the ratio between the braking torque and the braking torque when the vehicle is unloaded on a flat road with the same acceleration.

[0036] 2. Energy management control is performed based on the combined slope and load, and the output torque is calculated.

[0037] In driving mode, the compensation torque is determined based on the difference between the rated driving torque and the vehicle's peak driving torque, and the compensation torque output coefficient. The rated driving torque and the compensation torque are then added together to obtain the output driving torque. In coasting braking mode, the compensation torque is determined based on the difference between the rated braking torque and the vehicle's peak braking torque, and the compensation torque output coefficient. The rated braking torque and the compensation torque are then added together to obtain the output braking torque.

[0038] In driving mode, the vehicle's final output driving torque T DriveThe calculation formula is: T Drive =T Drive_n +ρ Drive *(T Drive_max -T Drive_n )

[0039] Among them, T Drive_n T is the vehicle's rated drive torque. Drive_max This represents the vehicle's peak drive torque. ρ represents the torque during uphill driving. Drive When ρ is positive, it indicates that the slope is not unloaded. Drive It is a negative value. This coefficient increases with the increase of the dynamic load coefficient and the dynamic slope coefficient when going uphill; that is, the compensation torque gradually increases with the increase of load and uphill slope. When the vehicle is in a flat road unloaded or downhill unloaded condition, ρ Drive When the value is 0, the final output drive torque of the vehicle is the vehicle's rated drive torque.

[0040] Under coasting braking conditions, the vehicle's final output braking torque T Brake The calculation formula is: T Brake =T Brake_n +ρ Brake *(T Brake_max -T Brake_n )

[0041] Among them, T Brake_n T is the vehicle's rated braking torque. Brake_max This represents the vehicle's peak braking torque. ρ is the torque applied when going downhill. Brake When ρ is positive, it indicates that the load is not unloaded when going uphill. Brake It is a negative value. ρ Brake The compensation torque increases with the increase of the dynamic load coefficient and the decrease of the dynamic gradient coefficient when going downhill; that is, the compensation torque gradually increases with the increase of the absolute value of the load and the downhill gradient. When the vehicle is in a flat, unloaded condition or in an uphill, unloaded condition, ρ... Brake When the value is 0, the final output braking torque of the vehicle is the vehicle's rated braking torque.

[0042] The dynamic slope and dynamic load in this invention can be calculated according to existing technology. As a preferred embodiment, this invention also considers the influence of centrifugal acceleration during turning when calculating the dynamic slope. The calculation method is as follows:

[0043] As shown in Figure 2, when a vehicle is dynamically traveling on a slope and is not turning, the acceleration in the vehicle's direction of travel measured by the gyroscope is the sum of the vehicle's longitudinal acceleration and the component of gravitational acceleration along the slope. The kinematic formula is as follows: a Xsens =a veh +g*sinθ a veh =dv / dt

[0044] Among them, a Xsensa is the acceleration in the vehicle's direction of travel measured by the gyroscope sensor. veh Let v be the vehicle's longitudinal acceleration, t be the vehicle speed, and g be the time.

[0045] As shown in Figure 3, the acceleration in the direction of travel during turning is also affected by centrifugal acceleration. Based on the yaw acceleration formula, the corrected acceleration component of centrifugal acceleration in the direction of travel during vehicle turning is obtained: a XQ / a Q =d / ra Q =v 2 / r

[0046] Among them, a XQ Let a be the acceleration component of centrifugal acceleration in the direction of travel. Q Let d be the vehicle's centrifugal acceleration, d be the distance between the gyroscope and the rear axle, r be the vehicle's turning radius, and ω be the vehicle's yaw rate.

[0047] Therefore, the formula for the acceleration of a vehicle in the direction of travel when turning is: a Xsens = dv / dt + g*sinθ + d*ω 2

[0048] The above formula simplifies to the following system equation. Since the slope changes slowly relative to the controller's operating cycle during actual operation, the derivative of the road slope with respect to time is assumed to be 0:

[0049] After discretization:

[0050] Define the system state variable x(k) as: x(k) = [v(k)θ(k)] T

[0051] The system state equations can be transformed into matrix form using x(k)=Ax(k-1)+BU(k)+w(k):

[0052] in: For system parameters, For the control matrix, Let w(k) be the system control quantity at time k, and w(k) be the system process noise.

[0053] In actual operation, the vehicle speed can be obtained by a vehicle speed sensor or calculated from the output shaft rotation speed. Therefore, the vehicle speed is chosen as the observation quantity, i.e., Z(k) = v(k), where v(k) is the vehicle speed at time k. The system observation equation is: Z(k) = Hx(k) + V(k)

[0054] Where H is the system measurement coefficient, H = [1 0], and V(k) is the system measurement noise.

[0055] Using a Kalman filter, that is, estimating the optimal value of the road slope at the current moment in real time according to the Kalman filtering principle, and using the optimal estimate as the dynamic slope at the current moment, the specific process is as follows:

[0056] 1) Input initial estimates: x(k-1|k-1), P(k-1|k-1);

[0057] 2) State prediction: x(k|k-1)=Ax(k-1|k-1)+BU(k), P(k|k-1)=AP(k-1|k-1)A T +Q;

[0058] 3) Measurement update: Update the estimated value based on the measured value.

[0059] The optimal estimate x(k|k) is calculated as follows: x(k|k)=x(k|k-1)+K(k)[Z(k)-Hx(k|k-1)]

[0060] The formula for calculating the Kalman gain K(k) is:

[0061] The update formula for the error covariance is: P(k|k)=[IK(k)H]P(k|k-1)

[0062] Where P is the error covariance of the filter, Q is the process noise covariance matrix, and R is the measurement noise covariance matrix.

[0063] 4) Output the optimal estimate x(k|k) at time k. Based on x(k|k) and the corresponding vehicle speed, determine the optimal estimate of the road slope at time k and use it as the dynamic slope at time k.

[0064] Based on the real-time dynamic slope obtained above, a longitudinal dynamic model of the vehicle regarding dynamic load and dynamic slope is established. Then, based on this longitudinal dynamic model, the dynamic load at the current moment is solved using the least squares method with a forgetting factor. The specific process is as follows:

[0065] Establish a longitudinal dynamics model for the vehicle:

[0066] Among them, F x The longitudinal driving force is m, and the dynamic load is m. v is the longitudinal acceleration of the vehicle. x Let C be the longitudinal velocity of the vehicle, ρ be the air density, and C be the... dWhere A is the drag coefficient, f is the frontal area, and f is the rolling resistance coefficient of the road surface. The longitudinal driving force can be calculated from the actual output torque of the power system, the longitudinal acceleration of the vehicle can be measured by a gyroscope sensor, and the longitudinal speed of the vehicle can be calculated from a vehicle speed sensor or the driveshaft speed.

[0067] Since the dynamic gradient under vehicle operating conditions has been estimated in real time and the vehicle speed can be observed in real time, the dynamic model is transformed into:

[0068] in, D represents the observation. ε represents the system noise. This represents the vehicle dynamic load to be estimated. Using the least squares formula with a forgetting factor, the estimated value at the previous time k-1 can be corrected using the observation at the current time k, thus obtaining the estimated value of the vehicle dynamic load. The least squares formula with a forgetting factor is:

[0069] Where L is the least squares gain, P′ is the error covariance, and λ is the forgetting factor.

[0070] Method Implementation Examples

[0071] This invention provides an energy management method based on slope and load estimation. The specific implementation process of this method has been described in detail in the system embodiment and will not be repeated here.

[0072] This invention integrates vehicle dynamic load and dynamic slope to optimize vehicle energy management in real time, improving the accuracy and effectiveness of energy management control, and avoiding energy waste caused by excessive compensation. It balances vehicle power performance with improved vehicle economy. When calculating dynamic slope, the longitudinal acceleration of the vehicle is corrected based on the centrifugal acceleration during the turning process, improving the adaptability and accuracy of slope calculation. Based on the real-time calculated dynamic slope and vehicle dynamic equations, the real-time load is calculated using the least squares method with a forgetting factor, simplifying the calculation steps while improving calculation accuracy.

Claims

1. An energy management method based on slope and load estimation, characterized in that, include: The compensation torque output coefficient is determined based on the vehicle's dynamic gradient and dynamic load. In driving mode, the compensation torque is determined based on the difference between the rated driving torque and the vehicle's peak driving torque, and the compensation torque output coefficient. The rated driving torque and the compensation torque are then added together to obtain the output driving torque. When the vehicle is in a driving state and is unloaded on a flat road or in a downhill condition, the compensation torque output coefficient is 0. Under coasting braking conditions, the compensation torque is determined based on the difference between the rated braking torque and the vehicle's peak braking torque, and the compensation torque output coefficient. The rated braking torque and the compensation torque are then added together to obtain the output braking torque. When the vehicle is in a flat, unloaded state or an uphill, unloaded state under coasting braking conditions, the compensation torque output coefficient is 0.

2. The energy management method based on slope and load estimation according to claim 1, characterized in that, The compensation torque output coefficient is determined by the dynamic load coefficient and the dynamic slope coefficient. The dynamic slope coefficient is calculated based on the vehicle's dynamic slope and the vehicle's maximum design gradeability. The larger the absolute value of the dynamic slope, the larger the dynamic slope coefficient. The dynamic load coefficient is calculated based on the vehicle's dynamic load, vehicle curb weight, and vehicle's maximum design gross weight. The larger the dynamic load, the larger the dynamic load coefficient.

3. The energy management method based on slope and load estimation according to claim 2, characterized in that, In driving mode, the compensation torque output coefficient is positive when going uphill and negative when going downhill and not unloaded; in coasting braking mode, the compensation torque output coefficient is positive when going downhill and negative when going uphill and not unloaded.

4. The energy management method based on slope and load estimation according to claim 2, characterized in that, The compensation torque output coefficient is determined by looking up a table of compensation torque output coefficients corresponding to the dynamic load coefficient and dynamic slope coefficient. The table includes a driving state table and a coasting braking state table, which are obtained based on the actual vehicle calibration.

5. The energy management method based on slope and load estimation according to claim 4, characterized in that, The actual vehicle calibration method is as follows: under the vehicle driving state and the coasting braking state, different driving torques or braking torques are provided to the vehicle for different loads and slopes. When the vehicle acceleration corresponding to the driving torque or braking torque is the same as the vehicle acceleration when it is unloaded on a flat road, the compensation torque output coefficient corresponding to the driving torque or braking torque is used as the calibration value.

6. The energy management method based on slope and load estimation according to claim 1, characterized in that, The method for calculating the dynamic slope includes determining the acceleration formula in the vehicle's driving direction based on the acceleration components of the vehicle's longitudinal acceleration and gravitational acceleration along the slope, combined with the acceleration component of the vehicle's centrifugal acceleration in the driving direction during the turning process, and then using a Kalman filter to obtain the optimal estimate of the road slope, and using the optimal estimate as the dynamic slope at the current moment.

7. The energy management method based on slope and load estimation according to claim 6, characterized in that, The formula for the acceleration in the direction of vehicle travel is: a Xsens = dv / dt + g*sinθ + d*ω 2 Among them, a Xsens ω is the acceleration in the direction of vehicle travel, v is the vehicle speed, t is time, g is the gravitational acceleration, θ is the dynamic slope, d is the distance of the gyroscope from the rear axle, and ω is the yaw rate of the vehicle.

8. The energy management method based on slope and load estimation according to claim 6, characterized in that, The method for calculating the dynamic load includes establishing a longitudinal dynamics model of the vehicle regarding the dynamic load and dynamic slope, substituting the calculated dynamic slope at the current moment into the longitudinal dynamics model of the vehicle, and then solving the longitudinal dynamics model of the vehicle to obtain the dynamic load at the current moment.

9. The energy management method based on slope and load estimation according to claim 8, characterized in that, The longitudinal dynamics model of the vehicle is as follows: Among them, F x The longitudinal driving force is m, and the dynamic load is m. v is the longitudinal acceleration of the vehicle. x Let C be the longitudinal velocity of the vehicle, ρ be the air density, and C be the... d denoted as drag coefficient, A as windward area, g as gravitational acceleration, θ as dynamic slope, and f as road rolling resistance coefficient.

10. An energy management system based on slope and load estimation, comprising a controller, characterized in that, The controller is used to implement the energy management method based on slope and load estimation as described in any one of claims 1-9.

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