A serial hybrid tractor idle speed adaptive control method

Abstract

The present application relates to the technical field of hybrid tractor control, and discloses a kind of idle speed adaptive control method of series hybrid tractor, comprising the following steps: step S1, indicated torque acquisition: the indicated torque of engine is acquired in real time;Step S2, minimum idle speed mapping: according to the preset indicated torque-idle speed mapping table, the minimum idle speed value corresponding to current indicated torque is obtained by interpolation operation;Step S3, power generation demand acquisition: the power generation demand speed output by power generation system is acquired;Step S4, speed taking decision: the minimum idle speed value and the power generation demand speed are taken big operation, and the operation result is used as the final set speed of engine;Wherein step S2 and step S3 have no execution order, can be executed in parallel or sequentially executed.This method can automatically adjust idle speed according to hydraulic load, without additional sensors, and considers hydraulic driving ability, energy consumption and NVH performance, with strong adaptability.

Description

Technical Field

[0001] This invention relates to the field of hybrid tractor control technology, and in particular to an adaptive idle speed control method for a series hybrid tractor. Background Technology

[0002] Series hybrid architecture, with its low energy consumption and smooth operation, is gradually being adopted in the tractor field. In this architecture, the engine does not directly drive the wheels; instead, it primarily powers a range extender to generate electricity, providing power to the main drive motor and other vehicle electrical equipment. The hydraulic system is a core component of the tractor, enabling implement lifting, steering control, and operational drive. The hydraulic pump is typically connected to the engine output shaft via a gear transmission mechanism. The engine's output speed directly determines the hydraulic pump's input speed and output flow, thus affecting the hydraulic system's response speed and driving capability. Currently, the engine speed of series hybrid tractors is mainly regulated by the vehicle's energy management system based on power generation needs. When the vehicle has no power generation requirements, the engine typically maintains a fixed idling speed.

[0003] Setting a fixed idle speed requires balancing hydraulic operation needs with energy consumption. If the idle speed setting is too low, the hydraulic pump's output flow will be limited, resulting in slow response and insufficient driving force when hydraulic drive is needed, thus affecting operating efficiency. If the idle speed setting is too high, it will cause unnecessary fuel consumption when there is no hydraulic demand, while also increasing engine noise and vibration, leading to poor overall NVH performance. Some solutions directly detect the load and adjust the speed by adding hydraulic pressure and flow sensors, but this increases hardware costs and wiring complexity. In agricultural machinery operating environments with high dust and vibration levels, the failure rate of additional sensors is even higher, limiting overall reliability. Currently, there is no low-cost, highly reliable solution in the industry that can effectively balance hydraulic drive performance with energy consumption and NVH performance.

[0004] The above background information is provided only to aid in understanding the concept and technical solution of this invention. It does not necessarily belong to the prior art of this patent application. In the absence of clear evidence that the above information was disclosed on the filing date of this patent application, the above background information should not be used to evaluate the novelty and inventiveness of this application. Summary of the Invention

[0005] The purpose of this invention is to propose an adaptive idle speed control method for a series hybrid tractor, so as to solve the technical problems of the prior art, such as the difficulty in balancing hydraulic drive performance, energy consumption, and NVH performance when the series hybrid tractor is at a fixed idle speed.

[0006] Therefore, this invention proposes an adaptive idling speed control method for a series hybrid tractor.

[0007] Preferably, the present invention may also have the following technical features:

[0008] An adaptive idle speed control method for a series hybrid tractor includes the following steps:

[0009] Step S1, Indicated Torque Acquisition: Acquire the indicated torque of the engine in real time;

[0010] Step S2, Minimum Idle Speed ​​Mapping: Based on the preset indicated torque-idle speed mapping table, the minimum idle speed value corresponding to the current indicated torque is obtained through interpolation calculation;

[0011] Step S3, Obtaining Power Generation Demand: Obtain the power generation demand speed output by the power generation system;

[0012] Step S4, Maximum Speed ​​Decision: The minimum idle speed value and the required power generation speed are used to calculate the maximum speed, and the result is used as the final set speed of the engine.

[0013] Steps S2 and S3 can be executed in any order, either in parallel or sequentially.

[0014] Preferably, between step S1 and step S2, there is also a filtering process step S1a: the indicated torque is filtered; the filtered indicated torque is input into step S2 for interpolation; the filtering time constant is calibrated according to the characteristics of the engine torque waveform.

[0015] Preferably, the filtering adopts a first-order low-pass filter, and the calibrated range of the filtering time constant is 50ms~200ms.

[0016] Preferably, in step S2, the minimum idle speed value in the indicated torque-idle speed mapping table increases synchronously with the increase of the indicated torque.

[0017] Preferably, between step S2 and step S4, there is also a step S2a, a maximum value holding process: the minimum idle speed value obtained in step S2 is input into the maximum value holder, and the minimum speed maximum value within the set holding time is output; the minimum speed maximum value is input into step S4 to participate in the up-to-down operation; the holding time is calibrated according to the duration of the hydraulic operation.

[0018] Preferably, the calibration range of the holding time is 1s to 5s.

[0019] Preferably, the holding time for continuous operation conditions such as tillage and deep loosening is taken as a larger value within the calibration range, while the holding time for short-term operation conditions such as steering and implement lifting is taken as a smaller value within the calibration range.

[0020] Preferably, between step S2a and step S4, there is also a step S2b, a slope limiting processing step: after the minimum maximum speed output by the maximum value holder is subjected to slope limiting processing, it is then input into step S4 to participate in the maximum operation; the speed change rate threshold of the slope limiting is a pre-calibrated value.

[0021] Preferably, the slope limit is set with independent rising slope threshold and falling slope threshold; the rising slope threshold ranges from 300 rpm / s to 800 rpm / s, and the falling slope threshold ranges from 200 rpm / s to 500 rpm / s.

[0022] Preferably, in step S3, the required rotational speed for power generation is calculated by the vehicle energy management system based on the SOC status of the energy storage element, the vehicle's electrical load, and the power generation efficiency characteristics of the range extender.

[0023] The beneficial effects of this invention compared to the prior art include:

[0024] 1. The control method of the present invention can indirectly identify the load state of the hydraulic system based on the engine indicated torque and automatically match the corresponding minimum idle speed value; when there is a hydraulic drive demand, the speed is increased to ensure the output flow and response speed of the hydraulic pump; when there is no hydraulic demand, the low idle speed is maintained, thereby achieving a dynamic balance between hydraulic drive performance and energy consumption and NVH performance.

[0025] 2. The control method of the present invention reuses the existing indicated torque signal of the engine throughout the process, without the need to add additional hydraulic detection sensors, resulting in low hardware costs and higher reliability in harsh operating conditions of agricultural machinery with dust and strong vibration.

[0026] 3. The control method of the present invention adopts the decision logic of taking the larger of the minimum idle speed value and the speed required for power generation. It can take into account both the power generation demand and the hydraulic drive demand without changing the core architecture of the original series hybrid system energy management. The solution has low migration and adaptation costs and strong compatibility.

[0027] 4. The control method of the present invention performs filtering preprocessing on the indicated torque, which can filter out high-frequency fluctuation components in the torque signal, avoid frequent oscillations of the idle speed setpoint caused by input signal jitter, and improve the stability of the control process.

[0028] 5. The control method of the present invention adds a maximum value holding process, which can maintain a higher idle speed during the hydraulic action interval, avoid the speed dropping rapidly after the short-term hydraulic load disappears, reduce the frequency of frequent rises and falls of engine speed, reduce mechanical wear and hydraulic shock, and at the same time ensure the response speed of subsequent hydraulic actions.

[0029] 6. The control method of the present invention adds a slope limiting processing step, which can constrain the rate of change of the idle speed setpoint, avoid sudden speed changes from impacting the engine, transmission mechanism and hydraulic system, reduce sudden vibration and noise, improve the NVH performance of the whole vehicle, and reduce the risk of component damage from impact. Attached Figure Description

[0030] Figure 1 This is a logic block diagram of a specific embodiment of the present invention. Detailed Implementation

[0031] The present invention will now be described in further detail with reference to specific embodiments and the accompanying drawings. It should be emphasized that the following description is merely exemplary and is not intended to limit the scope or application of the present invention.

[0032] Non-limiting and non-exclusive embodiments will be described with reference to the following figures, wherein the same reference numerals denote the same parts unless otherwise specifically stated.

[0033] This embodiment applies to a series hybrid tractor system, which includes an engine, a range extender unit, a main drive motor, a regional gearbox, a power distribution unit, energy storage elements, a vehicle controller, and a hydraulic system. The hydraulic pump is connected to the engine's output shaft via a gear transmission mechanism; the engine's output speed directly determines the hydraulic pump's input speed and output flow rate. In this series hybrid architecture, the engine does not directly drive the wheels; instead, the range extender unit converts mechanical energy into electrical energy to power the vehicle's drive and electrical equipment. The engine's operating speed is uniformly controlled by the vehicle controller.

[0034] This embodiment provides an adaptive idle speed control method for a series hybrid tractor, executed by the vehicle controller, such as... Figure 1 As shown, the specific steps include:

[0035] Step S1, Indicated Torque Acquisition: Acquire the indicated torque of the engine in real time;

[0036] Step S2, Minimum Idle Speed ​​Mapping: Based on the preset indicated torque-idle speed mapping table, the minimum idle speed value corresponding to the current indicated torque is obtained through interpolation calculation;

[0037] Step S3, Obtaining Power Generation Demand: Obtain the power generation demand speed output by the power generation system;

[0038] Step S4, Maximum Speed ​​Decision: The minimum idle speed value and the required power generation speed are used to calculate the maximum speed, and the result is used as the final set speed of the engine.

[0039] Steps S2 and S3 can be executed in any order, either in parallel or sequentially, and their outputs are input into step S4 for calculation.

[0040] The interpolation calculation can employ linear interpolation, a mature lookup table method in this field, capable of covering continuous operating conditions between calibration data points. Through the aforementioned control logic, the load state of the hydraulic system can be indirectly identified using the engine's existing indicated torque signal, achieving adaptive adjustment of the idle speed without the need for additional hydraulic detection sensors. When hydraulic drive is required, the engine's indicated torque increases with the hydraulic load, and the corresponding minimum idle speed value increases synchronously, ensuring that the hydraulic pump's output flow meets the drive requirements. When there is no hydraulic demand, the minimum idle speed value remains at a low level, reducing unnecessary fuel consumption and operating noise. The maximum value calculation logic ensures the priority of the vehicle's power generation needs. When the power generation demand is higher than the hydraulic idle speed demand, the power generation requirement is prioritized, preventing energy storage components from running out of power. Simultaneously, it does not alter the core energy management logic of the original series hybrid system, resulting in low cost for solution migration and adaptation.

[0041] In some examples of this embodiment, to improve the stability of the input signal, a step S1a, filtering processing, is included between step S1 and step S2: the indicated torque is filtered; the filtered indicated torque is then input into step S2 for interpolation; the filtering time constant is calibrated according to the characteristics of the engine torque waveform. During engine operation, the indicated torque will experience small, high-frequency fluctuations due to factors such as in-cylinder combustion fluctuations and transmission clearances. If the original signal is directly used for idle speed mapping, the idle speed setpoint will fluctuate frequently with the signal, affecting control smoothness and increasing the frequency of engine speed adjustment actions. Pre-processing and filtering the indicated torque signal can remove high-frequency fluctuation components from the torque signal, preventing frequent oscillations in the idle speed setpoint caused by input signal jitter, and improving the stability of the control process.

[0042] In some other examples of this embodiment, the filtering employs a first-order low-pass filter, with a time constant ranging from 50ms to 200ms. When operating conditions fluctuate significantly or torque fluctuates greatly, a larger time constant can be selected to enhance the filtering effect; conversely, when operating conditions are stable and high response speed is required, a smaller time constant can be selected to improve response speed. The implementation logic of a first-order low-pass filter is simple, with low computational load and low requirements for controller hardware performance, making it easy to deploy directly on existing vehicle controllers. The parameter range of 50ms to 200ms can cover the needs of most tractor operating scenarios, balancing filtering effect and response speed, and is convenient for calibration and debugging.

[0043] In some examples of this embodiment, in step S2, the minimum idle speed value in the indicated torque-idle speed mapping table increases synchronously with the increase of the indicated torque. The indicated torque-idle speed mapping table is pre-calibrated through bench tests and real-vehicle operation tests. During the calibration process, the engine indicated torque under different hydraulic loads and the corresponding minimum speed required to meet flow requirements are recorded, forming multiple sets of corresponding data points. The mapping logic of a positive correlation between the minimum idle speed value and the indicated torque aligns with the operating characteristics of higher hydraulic loads and higher flow requirements. The idle speed value accurately corresponds to the load requirement, ensuring that insufficient speed does not affect the hydraulic drive capability, nor does excessive speed cause energy waste.

[0044] In other examples of this embodiment, to adapt to the working conditions of intermittent hydraulic operation of tractors, a step S2a, a maximum value holding process, is included between step S2 and step S4: the minimum idle speed value obtained in step S2 is input to the maximum value holder, and the minimum maximum speed value within a set holding time is output; the minimum maximum speed value is input to step S4 for the maximum operation calculation; the holding time is calibrated according to the duration of the hydraulic operation. The operating logic of the maximum value holder is as follows: within the set holding time window, the maximum speed value within the window is continuously output; when a higher speed value appears within the window, the output value is updated; when the holding time expires and no higher speed is input within the window, the output value gradually falls back to the currently input minimum idle speed value.

[0045] During tractor field operations, hydraulic actions are often intermittent. For example, implement lifting and steering are short-term loads. If the engine speed drops immediately after the load disappears, the speed needs to be increased again for subsequent actions. This not only causes frequent speed fluctuations, accelerating wear on the engine and transmission, but also prolongs the response time of hydraulic actions, affecting the smoothness of operation. This solution uses maximum value hold processing to maintain the high idle speed corresponding to short-term hydraulic loads for a set duration, effectively adapting to the characteristics of such working conditions. Maximum value hold processing reduces the frequency of frequent engine speed fluctuations, reduces mechanical wear and hydraulic shock, and extends the service life of related components; at the same time, it maintains the response speed of the hydraulic system, ensuring that subsequent hydraulic actions can be executed quickly, improving the smoothness and efficiency of operation.

[0046] In some examples of this embodiment, the calibration range of the holding time is 1s to 5s. This range covers the intermittent cycles of most hydraulic operation actions of the tractor, providing a reference benchmark for parameter matching of different models. A clearly defined parameter range reduces the difficulty of calibration and debugging, enhances engineering feasibility, and allows for rapid adaptation to tractor models with different power ratings.

[0047] In other examples of this embodiment, the holding time for continuous operation conditions such as tillage and deep loosening is set to a larger value within the calibration range, while the holding time for short-term operation conditions such as steering and implement lifting is set to a smaller value within the calibration range. The vehicle controller can automatically match the corresponding holding time parameter according to the current operation mode. Different holding time values ​​are adopted for different operation characteristics. A larger value is used for continuous operation conditions to ensure the smoothness of the operation process, while a smaller value is used for short-term operation conditions to better take into account the energy-saving effect. The adaptability of operation conditions is stronger, and a reasonable balance between performance and energy consumption can be achieved in different operation scenarios.

[0048] In some examples of this embodiment, between steps S2a and S4, step S2b, slope limiting processing, is also included: the minimum maximum speed output by the maximum value holder is subjected to slope limiting processing before being input into step S4 for the maximum operation; the speed change rate threshold for slope limiting is a pre-calibrated value. When the rate of change corresponding to the difference between the target speed and the current speed exceeds the calibrated threshold, the speed is gradually adjusted according to the calibrated rate of change until the target speed value is reached. Slope limiting processing can constrain the rate of change of the idle speed setpoint, avoid sudden speed changes from impacting the engine, transmission mechanism, and hydraulic system, reduce sudden vibration and noise changes, improve the NVH performance of the entire vehicle, reduce the risk of component damage from impact, and improve the reliability and service life of the system.

[0049] In other examples of this embodiment, the slope limit is set with independent rising slope thresholds and falling slope thresholds; the rising slope threshold ranges from 300 rpm / s to 800 rpm / s, and the falling slope threshold ranges from 200 rpm / s to 500 rpm / s. The rising slope threshold is used during the speed increase process, and the falling slope threshold is used during the speed decrease process. The rising and falling slopes are calibrated independently to match the response requirements for speed increase and the smoothness requirements for speed decrease, respectively. Using a relatively larger slope during speed increase ensures a rapid speed response when hydraulic demand arises, avoiding hydraulic lag; using a relatively smaller slope during speed decrease improves the smoothness of the speed drop process and reduces abrupt changes in noise and vibration.

[0050] In some examples of this embodiment, in step S3, the required power generation speed is calculated by the vehicle energy management system based on the SOC status of the energy storage element, the vehicle's electrical load, and the power generation efficiency characteristics of the range extender. When the SOC of the energy storage element is lower than a set threshold, or when the vehicle's electrical load increases, the required power generation speed increases accordingly to ensure sufficient power supply; when the SOC of the energy storage element is sufficient and the vehicle's electrical load is low, the required power generation speed decreases accordingly. The required power generation speed calculated from multiple parameters can accurately match the actual power demand of the vehicle. By taking the larger value between this speed and the hydraulic idle speed demand, the vehicle's power supply can be stabilized while also considering the speed demand of the hydraulic drive, thus achieving reasonable allocation of vehicle energy.

[0051] In some examples of this embodiment, the above control method can be implemented by functional modules integrated into the vehicle controller. These functional modules include a torque acquisition module, an idle speed mapping module, a demand acquisition module, and a maximum value decision module. The torque acquisition module is used to collect the engine's indicated torque signal in real time; the idle speed mapping module has a built-in preset indicated torque-idle speed mapping table, used to output the corresponding minimum idle speed value based on the current indicated torque; the demand acquisition module is used to acquire the power generation demand speed output by the power generation system; and the maximum value decision module is used to take the maximum value between the minimum idle speed value and the power generation demand speed, and then output the final set engine speed. Each module has clear functional boundaries, can be debugged and optimized independently, and facilitates solution portability and maintenance.

[0052] Those skilled in the art will recognize that numerous variations are possible with respect to the above description, and the embodiments and figures are merely for describing one or more specific implementations.

[0053] Although exemplary embodiments of the invention have been described and illustrated, those skilled in the art will understand that various changes and substitutions can be made thereto without departing from the spirit of the invention. Furthermore, many modifications can be made to adapt specific situations to the doctrine of the invention without departing from the central concepts of the invention described herein. Therefore, the invention is not limited to the specific embodiments disclosed herein, but may include all embodiments and equivalents that fall within the scope of the invention.

Claims

1. An adaptive idle speed control method for a series hybrid tractor, characterized in that, Includes the following steps: Step S1, Indicated Torque Acquisition: Acquire the indicated torque of the engine in real time; Step S2, Minimum Idle Speed ​​Mapping: Based on the preset indicated torque-idle speed mapping table, the minimum idle speed value corresponding to the current indicated torque is obtained through interpolation calculation; Step S3, Obtaining Power Generation Demand: Obtain the power generation demand speed output by the power generation system; Step S4, Maximum Speed ​​Decision: The minimum idle speed value and the required power generation speed are used to calculate the maximum speed, and the result is used as the final set speed of the engine. Steps S2 and S3 can be executed in any order, either in parallel or sequentially.

2. The idling speed adaptive control method for a series hybrid tractor according to claim 1, characterized in that, Between step S1 and step S2, there is also a filtering process step S1a: the indicated torque is filtered; the filtered indicated torque is input into step S2 for interpolation; the filtering time constant is calibrated according to the characteristics of the engine torque waveform.

3. The idling speed adaptive control method for a series hybrid tractor according to claim 2, characterized in that, The filtering method uses a first-order low-pass filter, and the calibrated range of the filtering time constant is 50ms~200ms.

4. The idling speed adaptive control method for a series hybrid tractor according to claim 1, characterized in that, In step S2, the minimum idle speed value in the indicated torque-idle speed mapping table increases synchronously with the increase of the indicated torque.

5. The idling speed adaptive control method for a series hybrid tractor according to claim 1, characterized in that, Between step S2 and step S4, there is also a maximum value holding process step S2a: the minimum idle speed value obtained in step S2 is input into the maximum value holder, and the minimum speed maximum value within the set holding time is output; the minimum speed maximum value is input into step S4 to participate in the up-to-down operation; the holding time is calibrated according to the duration of the hydraulic operation.

6. The idling speed adaptive control method for a series hybrid tractor according to claim 5, characterized in that, The calibrated range for the holding time is 1s to 5s.

7. The idling speed adaptive control method for a series hybrid tractor according to claim 5, characterized in that, For continuous operation conditions such as tillage and deep loosening, the holding time should be a larger value within the calibration range; for short-term operation conditions such as steering and implement lifting, the holding time should be a smaller value within the calibration range.

8. The idling speed adaptive control method for a series hybrid tractor according to claim 5, characterized in that, Between steps S2a and S4, there is also a slope limiting process step S2b: after the minimum maximum speed output by the maximum value holder is subjected to slope limiting processing, it is then input into step S4 to participate in the maximum operation; the speed change rate threshold of the slope limiting is a pre-calibrated value.

9. The idling speed adaptive control method for a series hybrid tractor according to claim 8, characterized in that, The slope limits are set with independent rising slope thresholds and falling slope thresholds; the rising slope threshold ranges from 300 rpm / s to 800 rpm / s, and the falling slope threshold ranges from 200 rpm / s to 500 rpm / s.

10. The idling speed adaptive control method for a series hybrid tractor according to claim 1, characterized in that, In step S3, the required rotational speed for power generation is calculated by the vehicle energy management system based on the SOC status of the energy storage components, the vehicle's electrical load, and the power generation efficiency characteristics of the range extender.

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