Tandem power generation control method for extended-range light commercial vehicle

Abstract

The invention discloses a series power generation control method for an extended-range light commercial vehicle, and the method comprises the steps: 1, obtaining the driving information of the vehicle through a CAN bus, and the driving information comprises the driving speed, driving force, driving acceleration and the like of the vehicle; estimating the mass of the vehicle by using a recursive least square method with a forgetting factor; 2, grading the estimated vehicles according to mass ranges, wherein the vehicles are divided into low loads, medium loads, high loads and the like; 3, selecting different power generation modes according to the identified quality grade, the current vehicle speed and the SOC of the battery; 4 series power generation modes are mainly divided into a fixed-point low gear, a fixed-point middle gear, a fixed-point high gear and a power following mode, the power generation power of an engine does not depend on the power requirement of a driver after mass recognition, and the power following mode is adopted for power generation only when the vehicle is in a high load and the electric quantity is too low; and 5, after the working point of series power generation is determined, control is conducted according to the target working rotating speed and torque of the engine, the rotating speed of the engine is adjusted and controlled through PID, the rotating speed of the engine is adjusted through the torque of the generator, the difference between the actual rotating speed of the engine and the target rotating speed can be controlled within 100 rmp, the economical performance of the vehicle can be improved, and the vehicle safety is improved. And the vehicle always works in a high-efficiency area.

Description

Technical Field

[0001] The present application relates to the technical field of extended-range light commercial vehicles, and in particular to a method for controlling series power generation of extended-range light commercial vehicles. Background Art

[0002] At present, traditional light commercial vehicles have high fuel consumption and high vehicle use costs, and the range problem of pure electric light commercial vehicles is difficult to completely solve in a short period of time. Extended-range light commercial vehicles can not only reduce fuel consumption, but also solve consumers' range anxiety. In order to improve the economic performance of extended-range light commercial vehicles, the rationality of the control method for series power generation is crucial.

[0003] Reasonable engine start-stop control and the selection of the series power generation working point are one of the key factors that determine the economic performance of extended-range light commercial vehicles. The large load variation range of commercial vehicles poses a great challenge to the energy management control of hybrid vehicles, so it is necessary to estimate the vehicle load and accurately control the power generation according to the load size, which can improve the rationality and accuracy of vehicle energy management control. Summary of the invention

[0004] In order to overcome the shortcomings of low load identification accuracy of existing commercial vehicles and low power generation efficiency of range extenders due to load changes, the present invention proposes a series power generation control method for extended-range light commercial vehicles based on load identification. According to the vehicle's driving information, the vehicle load is estimated by using the vehicle dynamics formula and the least squares method with a forgetting factor, and the vehicle load is graded. The series power generation working point is selected according to the load level, the battery SOC and the vehicle speed, so that the engine can work at the high efficiency point for a long time, improve the system efficiency and effectively reduce fuel consumption. Because the engine working point is relatively fixed and the speed fluctuation is small, the NVH performance of the vehicle can be further improved.

[0005] The technical solution adopted by the present invention to solve the technical problem is to propose a series power generation control method for an extended-range light commercial vehicle based on load identification, comprising the following steps:

[0006] Step 1: Collect basic parameters of the vehicle, including wind resistance coefficient, frontal area, rolling radius, rolling resistance coefficient, etc. Collect driving parameter information of the vehicle in real time, obtain the current driving speed, wheel end driving force, ramp angle calculated by VCU and other signals from the CAN bus, and calculate the longitudinal acceleration a of the vehicle by differential processing of the vehicle speed. c The acceleration is calculated using the following formula:

[0007]

[0008] Longitudinal acceleration a cAfter the above calculation, low-pass filtering is performed to obtain the filtered acceleration value. In the above formula, △t is 0.1s, v k is the vehicle speed at time k, in km / h;

[0009] Step 2: Estimate the mass of the vehicle using the least squares method with a forgetting factor based on the vehicle driving information data obtained in step 1; calibrate and adjust the forgetting factor based on the mass estimated at the previous moment, and the model estimated using the recursive least squares method is:

[0010]

[0011] Where F tw The driving force of the vehicle minus the wind resistance, a eq is the equivalent acceleration, m is the vehicle mass to be estimated, α is the slope angle, T tq is the torque output by the driving motor, f is the rolling resistance coefficient, C d is the drag coefficient, A is the frontal area of ​​the vehicle, i0 is the reduction ratio of the rear axle of the vehicle, i g The corresponding speed ratio of the gearbox, η t is the total efficiency of the vehicle's powertrain, r is the tire rolling radius, and v is the vehicle's speed.

[0012] The recursive format of the least squares method is as follows:

[0013]

[0014] K(k)=P(k-1)a eq (k)×(λ(k)+a eq T (k)P(k-1)a eq (k)) -1

[0015]

[0016] In the formula is the quality of identification at k-1 moment, is the quality of recognition at time k, λ(k) is the forgetting factor, K(k) is the gain coefficient, P(k) is the error covariance, λ(k) is the forgetting factor, and I is the unit matrix.

[0017] Step 3: Classify the load according to the vehicle mass estimated in step 2. The unladen vehicle's curb mass is 3300kg. Therefore, when the estimated mass is less than 3500kg, the vehicle load is low load; when the estimated mass is greater than 3500kg and less than 5500kg, the vehicle load is medium load; and when the estimated mass is greater than 5500kg, it is high load.

[0018] Step 4: The judgment of engine start and stop takes into account the vehicle load level, battery SOC, vehicle speed, and the driver's required torque. When the accelerator pedal is greater than 80% for 2s, it directly enters the extended range mode. When the accelerator pedal is less than 80%, refer to the vehicle load level obtained in step 3, and consider the vehicle speed and battery SOC size to determine the working mode of the whole vehicle. The working modes mainly include EV mode and extended range mode. The extended range working mode is also the series power generation mode.

[0019] Step 5: Correct the actual SOC of the battery according to the load level. When the load is low, the SOC correction factor is 1.1, when the load is medium, the correction factor is 1, and when the load is high, the correction factor of the battery is 0.9. The actual SOC of the battery is multiplied by the correction factor to obtain the equivalent SOC of the battery.

[0020] When the battery equivalent SOC is lower than 18%, regardless of the vehicle speed and load conditions, the vehicle directly enters the extended-range mode when the engine is started for a long time.

[0021] When the equivalent SOC is between 18% and 40%, the vehicle enters the extended-range mode when the speed is higher than 40km / h, and enters the EV mode when the speed is lower than 30km / h. At other speeds, the vehicle maintains the operating mode of the previous moment.

[0022] When the equivalent SOC is greater than 40% and the vehicle speed is less than 40km / h, the vehicle is in EV mode and the engine does not start. When the equivalent SOC is less than 40% and the vehicle speed is higher than 50km / h, the vehicle enters extended range mode and the engine starts. At other speeds, the vehicle maintains the previous working mode.

[0023] Step 6: When the extended-range operation mode is determined, the engine operating point is further determined, and the engine operating point is controlled in multiple gears according to the load level and the SOC.

[0024] When the vehicle is under low load, refer to the current SOC of the vehicle. If the SOC is greater than 40%, select the optimal power generation point 1, that is, the fixed point low gear for power generation. When the vehicle is under low load, the SOC is less than 40%, select the optimal power generation point 2, that is, the fixed point mid-range for power generation.

[0025] When the vehicle is under medium load, refer to the current SOC of the vehicle. If the SOC is greater than 40%, select the optimal power generation point 2, that is, the fixed mid-range power generation. If the SOC is less than 40%, select the optimal power generation point 3, that is, the fixed high-range power generation.

[0026] When the vehicle is under high load, if the SOC is greater than 40% and less than 60%, the optimal power generation point 3 is selected, that is, the fixed high-speed power generation is carried out; if the SOC is greater than 60%, the optimal power generation point 2 is selected, that is, the fixed mid-speed power generation is carried out; if the SOC is less than 40%, in order to prevent the battery SOC from decreasing too quickly, the demand power following series power generation method is adopted. The demand power following is the power generation power required by the engine according to the driving demand power divided by the efficiency.

[0027] To prevent the power generation point from jumping back and forth, the transition from the current power generation level to another power generation level requires a delay of 3s.

[0028] Step 7, the selection of the power generation point 1 is mainly based on the coupling of the universal characteristic data of the engine and the universal characteristic data of the ISG generator to calculate the most efficient optimal power generation 1.

[0029] The optimal power generation point 2 is to select the most efficient engine operating point which is 15kw higher than the power generation point 1.

[0030] The optimal power generation point 3 is to select the most efficient engine operating point which is 15kW higher than the power generation point 2.

[0031] The power-following power generation method is to obtain the power required by the engine based on the power demanded by the vehicle's wheel end divided by the transmission efficiency. The amount of power generated depends on the size of the power demanded by the wheel end, which changes with the driver's accelerator pedal, but also takes into account the limitations of the vehicle's NVH performance.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] 1. The load identification-based series power generation control method for extended-range light commercial vehicles proposed in the present invention can accurately estimate the vehicle load, and then determine the start and stop of the engine and the selection of the working point according to the battery SOC and the vehicle speed. The formulation of a reasonable power generation strategy can greatly improve the working efficiency of the system. The regular series power generation strategy can not only improve the calculation efficiency, but also has higher control robustness.

[0034] 2. Based on the identified vehicle load mass, the present invention has formulated three gears of engine power generation points, which can ensure that the engine operates at a high efficiency point. Under high load and low power conditions, or under extremely low power conditions, the vehicle's series power generation control is a power following method, which can ensure that the battery's SOC remains within a reasonable range, prevent the battery from being overcharged and over-discharged, and also increase the battery's service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic diagram of the control process of series power generation of the extended-range light commercial vehicle in the present invention;

[0036] Figure 2 It is a flow chart of the selection strategy of different power generation points for series power generation in the present invention;

[0037] Figure 3 It is the engine universal data diagram and the fixed-point power generation working point schematic diagram; DETAILED DESCRIPTION

[0038] In this embodiment, a method for controlling the series power generation of an extended-range light commercial vehicle is applied to the energy management control of the extended-range light commercial vehicle. In the specific implementation, the method can identify the vehicle load and formulate a reasonable engine power generation strategy, so that the system has higher working efficiency and higher control robustness. The control process is as follows Figure 1 The specific steps include:

[0039] Step 1: Collect basic parameters of the vehicle, including wind resistance coefficient, frontal area, rolling radius, rolling resistance coefficient, etc. Collect driving parameter information of the vehicle in real time, obtain the current driving speed of the vehicle, the driving force of the wheel end, the ramp angle calculated by the VCU, etc. from the CAN bus, and calculate the longitudinal acceleration a of the vehicle by differential processing of the vehicle speed. c . Use the following formula to calculate the longitudinal acceleration.

[0040]

[0041] After the above calculation, the longitudinal acceleration is low-pass filtered to obtain the filtered acceleration value. In the above formula, △t time is 0.1s; v k is the vehicle speed at time k, in km / h.

[0042] Step 2: According to the vehicle driving information obtained in step 1, the mass of the vehicle is estimated using the least squares method with a forgetting factor; the model estimated using the recursive least squares method is as follows:

[0043]

[0044] Where F tw is the force obtained by subtracting wind resistance from the driving force, a eq is the equivalent acceleration, m is the mass to be estimated, α is the slope angle value, T tq is the torque output by the driving motor, f is the rolling resistance coefficient, C d is the drag coefficient, A is the frontal area of ​​the vehicle, i0 is the reduction ratio of the rear axle of the vehicle, i g The corresponding speed ratio of the gearbox, η t is the total efficiency of the vehicle's powertrain, r is the tire rolling radius, and v is the vehicle's speed.

[0045] Recursive calculation using the least squares method.

[0046]

[0047] K(k)=P(k-1)a eq (k)×(λ(k)+a eq T (k)P(k-1)a eq (k)) -1

[0048]

[0049] In the formula is the quality of identification at k-1 moment, is the quality of recognition at time k, λ(k) is the forgetting factor, K(k) is the gain coefficient, P(k) is the error covariance, and I is the unit matrix;

[0050] Step 3: Classify the vehicle load according to the vehicle mass estimated in step 2. The unloaded vehicle has a curb mass of 3300 kg. Therefore, when the estimated mass is less than 3500 kg, the vehicle load is low load. When the estimated mass is greater than 3500 kg and less than 5500 kg, the vehicle load is medium load. When the estimated mass is greater than 5500 kg, the vehicle load is high load.

[0051] Step 4: Under the premise that the engine and battery are not faulty, the judgment of engine start and stop takes into account the vehicle's load level, battery SOC, vehicle speed, and the driver's required torque. When the accelerator pedal is greater than 80% for 2s, it directly enters the extended range mode. When the accelerator pedal is less than 80%, the load level obtained in step 3, as well as the vehicle speed and battery SOC, is used to determine the vehicle's operating mode;

[0052] Step 5: Correct the actual SOC of the battery according to the load level of the vehicle. When the load is low, the correction factor is 1.1, when the load is medium, the correction factor is 1, and when the load is high, the correction factor of the battery is 0.9. The actual SOC of the battery is multiplied by the correction factor to obtain the equivalent SOC value of the battery;

[0053] When the battery's equivalent SOC is lower than 18%, regardless of vehicle speed and load, the vehicle will directly enter the hybrid range-extended mode if the engine is started for a long time.

[0054] When the equivalent SOC is between 18% and 40%, the vehicle enters the extended range mode when the speed is higher than 40km / h, and the vehicle enters the EV mode when the speed is lower than 30km / h. At other speeds, the vehicle maintains the previous working mode.

[0055] When the equivalent SOC is greater than 40% and the vehicle speed is less than 40km / h, the vehicle is in EV mode and the engine is not started. When the SOC is lower than 40% and the vehicle speed is higher than 50km / h, the vehicle enters the extended range mode and the engine starts. The other SOC and vehicle speed conditions remain the same as the previous working mode.

[0056] Step 6: When the vehicle's operating mode is determined to be the extended-range mode, the engine operating point needs to be further determined. The engine operating point is controlled in multiple gears according to the load level and the SOC.

[0057] When the vehicle is under low load, refer to the actual SOC of the battery. If the actual SOC is greater than 40%, select the optimal power generation point 1, that is, the fixed point low gear for power generation. When the vehicle is under low load, the actual SOC is less than 40%, select the optimal power generation point 2, that is, the fixed point mid-range for power generation.

[0058] When the vehicle is under medium load, refer to the actual SOC of the battery. If the SOC is greater than 40%, select the optimal power generation point 2, that is, the fixed mid-range power generation. If the SOC is less than 40%, select the optimal power generation point 3, that is, the fixed high-range power generation.

[0059] When the vehicle is under high load, if the SOC is greater than 40% and less than 60%, the optimal power generation point 3 is selected, that is, the fixed high-speed power generation is carried out. If the SOC is greater than 60%, the optimal power generation point 2 is selected, that is, the fixed mid-speed power generation is carried out. If the SOC is less than 40%, in order to prevent the battery SOC from dropping too quickly, the power following series power generation method is adopted.

[0060] In order to prevent the series power generation working point from jumping back and forth, after the conditions for transitioning from the current power generation level to another power generation level are met, a delay of 3 seconds is required before entering the next power generation level.

[0061] Step 7, the selection of the power generation point 1 is mainly based on the coupling calculation of the universal characteristic data of the engine and the universal characteristic data of the ISG generator, the engine efficiency and the power generation efficiency are multiplied, and the optimal power generation 1 with the highest efficiency is found and calculated.

[0062] The optimal power generation point 2 is to select the most efficient engine operating point which is 15kw higher than the power generation point 1.

[0063] The optimal power generation point 3 is to select the most efficient engine operating point which is 15kW higher than the power generation point 2.

[0064] The power-following power generation method is to obtain the power required by the engine based on the power demanded by the vehicle's wheel end divided by the transmission efficiency. The amount of power generated depends on the size of the power demanded by the wheel end, which changes with the driver's accelerator pedal, while also taking into account the limitations of the vehicle's NVH performance.

[0065] Figure 2 The selection strategy for the series power generation point under different vehicle loads and SOCs is as follows:

[0066] Step 1: Obtain vehicle load level information according to the mass estimation module.

[0067] Step 2: Refer to the vehicle load level and divide the load level into high load, medium load and low load;

[0068] Step 3: When the vehicle is under low load, refer to the actual SOC of the battery and take 40% as the critical value for judging high and low SOC. If the battery SOC is greater than 40%, it can be regarded as high SOC, and if it is less than 40%, it is in low SOC state.

[0069] If the actual SOC is greater than 40%, the optimal power generation point 1 is selected, that is, the fixed point low gear is used for power generation. When the vehicle is under low load and the actual SOC is less than 40%, the optimal power generation point 2 is selected, that is, the fixed point mid gear is used for power generation.

[0070] When the vehicle is under medium load, refer to the actual SOC of the battery. If the SOC is greater than 40%, select the optimal power generation point 2, that is, the fixed mid-range power generation. If the SOC is less than 40%, select the optimal power generation point 3, that is, the fixed high-range power generation.

[0071] When the vehicle is under high load, if the SOC is greater than 40% and less than 60%, the optimal power generation point 3 is selected, that is, the fixed high-speed power generation is carried out. If the SOC is greater than 60%, the optimal power generation point 2 is selected, that is, the fixed mid-speed power generation is carried out. If the SOC is less than 40%, in order to prevent the battery SOC from dropping too quickly, the power following series power generation method is adopted.

[0072] Step 4: To prevent the series power generation points from jumping back and forth, after the conditions for the current power generation level to transition to another power generation level are met, a delay of 3 seconds is required before entering the next power generation level.

[0073] Step 5, determine the fixed low-speed power generation point. According to the universal characteristic data of the engine and the universal characteristic data of the generator, the engine efficiency and the power generation efficiency are multiplied to calculate the three working points with the highest comprehensive efficiency after coupling. The optimal working point 1 of the engine is (2654, 132), that is, the fixed low-speed. On the basis of the optimal working point 1, 15kW is added to get the optimal working point 2 (3500, 134), that is, the fixed mid-speed. On the basis of the optimal working point 2, 15kW is added to get the optimal working point 3 (4050, 153), that is, the fixed high-speed. Figure 3 shown.

[0074] Step 6. If the current load is high and the SOC is low, the engine power generation method will be based on the driver's demand power. The engine power generation will follow the driver's demand. The required power generation can be obtained by dividing the current driving demand power by the system transfer efficiency. The target speed and torque of the engine are determined based on the required power generation. The engine speed is controlled by PID regulation, and the engine speed is adjusted by the torque of the generator to control it within the target speed range. In addition to meeting the driver's power needs, the power generation power can also charge the battery with the remaining power to prevent the battery SOC from dropping too quickly. The above applicable conditions are normal temperature conditions, and the impact of battery temperature on the maximum allowable charging and discharging power of the battery is not considered.

Claims

1. A method for controlling series power generation of an extended-range light commercial vehicle based on load identification, characterized in that: include: Step 1: By collecting the basic parameters of the vehicle, including drag coefficient, frontal area, rolling radius, rolling resistance coefficient, etc., and collecting the driving parameter information of the vehicle in real time, the current driving speed of the vehicle, wheel-end driving force, ramp angle calculated by VCU and other signals are obtained from the CAN bus, and the longitudinal acceleration a of the vehicle is calculated by differential processing of the vehicle speed. c , use the following formula to calculate the acceleration method: Longitudinal acceleration a c After the above calculation, low-pass filtering is performed to obtain the filtered acceleration value. In the above formula, △t is 0.1s, v k is the vehicle speed at time k, in km / h; Step 2: Estimate the mass of the vehicle using the least squares method with a forgetting factor based on the vehicle driving information data obtained in step 1; calibrate and adjust the forgetting factor based on the mass estimated at the previous moment, and the model estimated using the recursive least squares method is: Among them, F tw The driving force of the vehicle minus the wind resistance, a eq is the equivalent acceleration, m is the vehicle mass to be estimated, α is the slope angle, T tq is the torque output by the driving motor, f is the rolling resistance coefficient, C d is the drag coefficient, A is the frontal area of ​​the vehicle, i0 is the reduction ratio of the rear axle of the vehicle, i g The corresponding speed ratio of the gearbox, η t is the total efficiency of the vehicle transmission system, r is the tire rolling radius, and v is the vehicle speed; The recursive format of the least squares method is as follows: K(k)=P(k-1)a eq (k)×(λ(k)+a eq T (k)P(k-1)a eq (k)) -1 In the formula is the quality of recognition at k-1 moment, is the quality of recognition at time k, λ(k) is the forgetting factor, K(k) is the gain coefficient, P(k) is the error covariance, λ(k) is the forgetting factor, and I is the unit matrix; Step 3: Classify the load according to the vehicle mass estimated in step 2. The unloaded vehicle has a curb mass of 3300 kg. Therefore, when the estimated mass is less than 3500 kg, the vehicle load is low load. When the estimated mass is greater than 3500 kg and less than 5500 kg, the vehicle load is medium load. When the estimated mass is greater than 5500 kg, the vehicle load is high load. Step 4: The judgment of engine start and stop takes into account the vehicle load level, battery SOC, vehicle speed, and the driver's required torque. When the accelerator pedal is greater than 80% for 2s, it directly enters the extended-range mode. When the accelerator pedal is less than 80%, refer to the vehicle load level obtained in step 3, and consider the vehicle speed and battery SOC size to determine the working mode of the whole vehicle. The working modes mainly include EV mode and extended-range mode. The extended-range working mode is also the series power generation mode. Step 5: Correct the actual SOC of the battery according to the load level. When the load is low, the SOC correction factor is 1.1, when the load is medium, the correction factor is 1, and when the load is high, the correction factor of the battery is 0.

9. The actual SOC of the battery is multiplied by the correction factor to obtain the equivalent SOC of the battery; When the battery equivalent SOC is lower than 18%, regardless of the vehicle speed and load conditions, the vehicle will directly enter the extended range mode if the engine is started for a long time; When the equivalent SOC is between 18% and 40%, the vehicle enters the extended range mode when the speed is higher than 40km / h, and the vehicle enters the EV mode when the speed is lower than 30km / h. At other speeds, the vehicle maintains the previous working mode. When the equivalent SOC is greater than 40% and the vehicle speed is less than 40km / h, the vehicle is in EV mode and the engine does not start. When the equivalent SOC is less than 40% and the vehicle speed is higher than 50km / h, the vehicle enters the extended range mode and the engine starts. At other speeds, the vehicle maintains the previous working mode state; Step 6: When the extended-range working mode is determined, the engine working point is further determined. The engine working point is controlled in multiple gears according to the load level and SOC: When the vehicle is under low load, refer to the current SOC of the vehicle. If the SOC is greater than 40%, select the optimal power generation point 1, that is, the fixed point low gear for power generation. When the vehicle is under low load, the SOC is less than 40%, select the optimal power generation point 2, that is, the fixed point mid-range for power generation; When the vehicle is under medium load, refer to the current SOC of the vehicle. If the SOC is greater than 40%, select the optimal power generation point 2, that is, the fixed point mid-range power generation. If the SOC is less than 40%, select the optimal power generation point 3, that is, the fixed point high-range power generation. When the vehicle is under high load, if the SOC is greater than 40% and less than 60%, the optimal power generation point 3 is selected, that is, the fixed high-speed is used for power generation. If the SOC is greater than 60%, the optimal power generation point 2 is selected, that is, the fixed mid-speed is used for power generation. If the SOC is less than 40%, in order to prevent the battery SOC from decreasing too quickly, the demand power following series power generation method is adopted. The demand power following is the power generation power required by the engine according to the driving demand power divided by the efficiency. To prevent the power generation point from jumping back and forth, the transition from the current power generation level to another power generation level needs to be delayed by 3s; Step 7, the selection of the power generation point 1 is mainly based on the coupling of the universal characteristic data of the engine and the universal characteristic data of the ISG generator, and the most efficient optimal power generation 1 is calculated; The optimal power generation point 2 is to select the most efficient engine operating point which is 15kw higher than the power generation point 1; The optimal power generation point 3 is to select the most efficient engine operating point which is 15kW higher than the power generation point 2; The power-following power generation method is to obtain the power required by the engine based on the power demanded by the vehicle's wheel end divided by the transmission efficiency. The amount of power generated depends on the size of the power demanded by the wheel end, which changes with the driver's accelerator pedal, but also takes into account the limitations of the vehicle's NVH performance.

2. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that: When the processor executes the computer program, the steps of the method according to claim 1 are implemented.

3. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to claim 1 are implemented.

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