An electro-hydraulic hybrid power system control method based on dynamic impedance adjustment and predictive hydraulic state

Abstract

The application relates to the field of new energy vehicle and engineering machinery power control technology, and discloses an electro-hydraulic hybrid power system control method based on dynamic impedance adjustment and predicted hydraulic state, which comprises the following steps: firstly, a unified model of an electro-hydraulic system containing equivalent dynamic impedance is constructed; then, a short-term power demand change trend is predicted based on system state quantity; according to the prediction result, a target dynamic impedance and a hydraulic system target pressure state are determined in advance; finally, a coordinated closed-loop regulator taking dynamic impedance deviation as the core is designed, and the motor torque change rate and the hydraulic system flow are dynamically distributed, so that adaptive matching and coordination of the electro-hydraulic system are realized. Through prediction feedforward and dynamic impedance adjustment, the application changes the traditional passive power distribution into active dynamic characteristic coordination, effectively suppresses motor side power oscillation and hydraulic pressure fluctuation, and significantly improves the response smoothness, operation stability and energy utilization efficiency of the system under complex dynamic working conditions.

Description

Technical Field

[0001] This invention relates to the field of power control technology for new energy vehicles and construction machinery, and in particular to a control method for an electro-hydraulic hybrid power system based on dynamic impedance regulation and predictive hydraulic state. Background Technology

[0002] With increasing global demands for energy conservation, emission reduction, and green development, the application of new energy technologies in transportation and industry is deepening. Electro-hydraulic hybrid power systems, as a new type of power system that combines the high controllability and efficiency of electric drive with the high power density and strong impact resistance of hydraulic transmission, have demonstrated enormous potential in many fields with stringent power performance requirements. Their core applications are mainly concentrated in various types of construction machinery (such as hydraulic excavators, wheel loaders, and cranes), special vehicles (such as mining dump trucks and heavy-duty tractors), and other heavy-duty mobile equipment.

[0003] In these application scenarios, the working cycles of equipment are typically highly dynamic and complex. For example, when a hydraulic excavator completes a series of actions such as digging, rotating, unloading, and resetting, its load torque changes drastically within a very short time. Traditional pure internal combustion engine-driven or simple electromechanical drive systems often struggle to meet the demands of both low-speed, high-torque conditions and high-speed, light-load conditions, resulting in inefficiency and slow response. However, an electro-hydraulic hybrid system, by configuring a battery and motor as the basic power source and main regulating unit, supplemented by a hydraulic system as a power "reservoir" and instantaneous power compensation unit, can theoretically handle such complex dynamic conditions very well. The motor provides stable basic power and enables precise speed control, while the hydraulic system, utilizing its high power density and rapid energy storage and release, handles sudden, impactful high-power load demands, such as the instantaneous peak torque when the excavator bucket cuts into hard materials. This collaborative working mode aims to improve overall system efficiency, reduce fuel consumption, and enhance the smoothness of power output.

[0004] Despite the significant theoretical advantages of electro-hydraulic hybrid power systems, a series of pressing technical problems remain to be solved in practical engineering applications and operation control. These problems severely restrict the full realization of the performance and reliable operation of electro-hydraulic hybrid power systems, including:

[0005] Technical Issue 1: Dynamic Response Mismatch and Power Oscillation. The motor system (including the battery) and the hydraulic system have vastly different dynamic characteristics. The motor responds quickly but is limited by the battery's charge / discharge rate and the motor's own thermal load capacity. The hydraulic system has high power density but suffers from pressure build-up and release delays due to fluid compressibility and pipeline cavities. Under dynamic operating conditions with rapidly fluctuating loads, if a control strategy based on steady-state power distribution or simple rules is adopted, the two subsystems are highly susceptible to power "passing the buck" or "competition" phenomena due to dynamic response speed mismatch. This leads to torque oscillations and speed fluctuations in the transmission chain, severely affecting the smoothness of operation and the stability of the equipment.

[0006] Technical Issue Two: Severe Fluctuations in Hydraulic Pressure and System Shocks. Most existing control methods rely on feedback regulation of the hydraulic system based on current load demands. When faced with sudden increases or decreases in load, the controller responds passively, and the flow regulation commands from the hydraulic pump lag. This easily leads to overshoot or sudden drops in hydraulic system pressure, resulting in severe pressure fluctuations. Frequent pressure shocks not only reduce the lifespan of hydraulic components and generate noise, but may also trigger frequent opening and closing of system safety valves, leading to energy loss and further exacerbating the oscillations of the entire power system.

[0007] The third technical problem is the lack of foresight in control and the imbalance in energy distribution: Traditional feedback control is a "remedial" mechanism that cannot anticipate changes in load trends. For example, when the operator is about to perform a heavy-duty digging operation, the control system only begins to adjust the output of the motor and hydraulic system after the load torque actually acts on the system. This lag means that the system is always in a state of "catching up" with the load, making it difficult to achieve optimal energy pre-distribution. The hydraulic system cannot build up sufficient pressure reserves in advance, resulting in insufficient instantaneous compensation capability, forcing the motor to bear loads beyond its ideal working range, exacerbating the current stress on the battery and motor losses; or conversely, when the load is released, energy cannot be absorbed and stored by the hydraulic system in time, resulting in energy waste and low regenerative braking efficiency.

[0008] Technical Problem 4: Subsystem Working Boundary Conflicts and Overall Coordination Challenges: Motor systems have current, voltage, and speed limitations; batteries have charging and discharging power and state of charge limitations; hydraulic systems have pressure and flow limits. Under complex working conditions, the constraint boundaries of each subsystem may be frequently touched. Existing control strategies often lack unified coordination of these dynamic constraints, which can easily lead to one subsystem (such as the battery) prematurely limiting its output to avoid overload, while another subsystem (such as the hydraulic system) fails to compensate in time. The end result is a decrease in the overall output capacity of the system, which cannot meet the instantaneous power demand and affects the efficiency of operation.

[0009] Therefore, those skilled in the art urgently need a collaborative control method that can uniformly describe and proactively coordinate the differences in dynamic characteristics between the motor system and the hydraulic system, and can proactively guide energy distribution to ensure power output. Summary of the Invention

[0010] The core technical problem to be solved by this invention is that the existing technology lacks a coordinated control scheme that can uniformly describe and actively coordinate the differences in dynamic characteristics between the motor system and the hydraulic system, and can proactively guide energy distribution, thereby achieving smooth, efficient and stable power output under complex and rapidly changing working conditions.

[0011] To address the aforementioned core technical problems, this invention designs a control method for an electro-hydraulic hybrid power system based on dynamic impedance regulation and predictive hydraulic state. This method is not a simple optimization of existing control parameters, but rather starts from the essence of dynamic energy interaction in the system, regulating the electro-hydraulic hybrid power system based on dynamic impedance regulation and predictive hydraulic state. The method includes:

[0012] First, an "equivalent dynamic impedance" model that can uniformly characterize the dynamic response characteristics of the two power sources (electric and hydraulic) is constructed as a common benchmark for the coordinated control of the system.

[0013] Secondly, a short-term dynamic prediction mechanism for power demand torque is introduced to transform passive response into proactive contingency planning.

[0014] Then, using the forecast information, the “target dynamic impedance” and the “target pressure state” of the hydraulic system are determined proactively to match future load trends.

[0015] Finally, a closed-loop regulator was designed with dynamic impedance matching as its core and hydraulic system pressure and pressure change rate as its collaborative tracking targets. This regulator dynamically distributes the torque change rate of the motor system and the flow output of the hydraulic system, making the two subsystems behave like an adaptive "compliant" whole, smoothly responding to load changes. This effectively suppresses power oscillations and pressure shocks, and improves the dynamic performance and operational stability of the system.

[0016] The technical solution of the present invention to achieve the above objectives is a control method for an electro-hydraulic hybrid power system based on dynamic impedance regulation and predictive hydraulic state, the method comprising the following steps:

[0017] S1. Construct an electro-hydraulic hybrid power system model oriented towards dynamic impedance;

[0018] S2. Dynamically predict the torque demand based on the state variables of the electro-hydraulic hybrid power system model;

[0019] S3. Determine the target pressure parameters and equivalent dynamic impedance adjustment target of the hydraulic system based on the results of dynamic prediction;

[0020] S4. Based on the equivalent dynamic impedance adjustment target and the pressure target parameters of the hydraulic system, the motor system and the hydraulic system are coordinated and closed-loop regulated.

[0021] In S1, the electro-hydraulic hybrid power system model oriented towards dynamic impedance includes at least:

[0022] S1.1, Axial dynamics model of electro-hydraulic hybrid power system, calculation formula is:

[0023]

[0024] in, This is the system's equivalent moment of inertia. This refers to the angular acceleration of the drive shaft. Output torque for the battery / motor system; This provides the output torque for the hydraulic system. This refers to the load torque of the hybrid power system.

[0025] S1.2 The calculation rules for the power system model composed of a battery / motor combination are as follows:

[0026]

[0027] in, This is the motor current / torque conversion factor; This is the equivalent current of the power system.

[0028] S1.3, The model for the relationship between output torque and pressure in a hydraulic system, and the calculation formula is as follows:

[0029]

[0030] in, This refers to the motor torque coefficient in the hydraulic system. For hydraulic system pressure;

[0031] The pressure dynamics of the hydraulic system satisfy the following relationship:

[0032]

[0033] in, The rate of change of pressure in the hydraulic system; The equivalent bulk modulus of hydraulic oil; Equivalent hydraulic volume; This refers to the output flow rate of the hydraulic pump. It absorbs flow for the hydraulic motor.

[0034] S1.4, Equivalent dynamic impedance model of electro-hydraulic hybrid power system, its calculation formula is as follows:

[0035]

[0036] in, The equivalent dynamic impedance of the system is used to characterize the comprehensive dynamic response characteristics of the system to changes in angular velocity. This represents the angular velocity of the drive shaft.

[0037] Prioritizing the dynamic prediction of power demand torque based on system state variables in S2, the process includes the following sub-steps:

[0038] S2.1 The calculation of the rate of change of demand torque is as follows:

[0039]

[0040] in, The rate of change of required torque; The rate of change of angular acceleration; This represents the rate of change of load torque.

[0041] S2.2 Short-term forecasting model establishment, the calculation formula is as follows:

[0042]

[0043] in, For prediction time window Rate of change in domestic demand torque; The mapping function is implemented using linear / nonlinear models.

[0044] S2.3 Determination of dynamic shock risk indicators, the calculation formula is as follows:

[0045]

[0046] in, This refers to the dynamic impact strength that the system can withstand.

[0047] Preferably, in S3, the hydraulic target and the dynamic impedance target are determined based on the prediction results, specifically including the following sub-steps:

[0048] S3.1 Determination of the target equivalent dynamic impedance, the calculation formula is as follows:

[0049]

[0050] in, The reference impedance; This is the impedance adjustment coefficient.

[0051] S3.2 Calculate the target hydraulic system pressure and the rate of change of target hydraulic system pressure using the target equivalent dynamic impedance. The calculation formula is as follows:

[0052]

[0053]

[0054] in, The target hydraulic system pressure; The target hydraulic system pressure change rate.

[0055] Preferably, in S4, the electro-hydraulic coordinated closed-loop regulation based on equivalent dynamic impedance and hydraulic system pressure target parameters specifically includes the following sub-steps:

[0056] S4.1 Calculation of equivalent dynamic impedance deviation and hydraulic system pressure deviation is as follows:

[0057]

[0058] in, Equivalent dynamic impedance deviation characterizes the degree of deviation between the current dynamic characteristics of the power output of the electro-hydraulic hybrid power system and the target dynamic characteristics.

[0059] S4.2. Based on the equivalent dynamic impedance deviation and its changing trend, construct the electro-hydraulic synergistic adjustment weighting coefficient λ(t), which is calculated as follows:

[0060]

[0061] in, This is a limiting function used to... The constraint is within the interval [0,1].

[0062] S4.3 Under the influence of the aforementioned coordinated adjustment weighting coefficient λ(t), the control objective of the hydraulic system is expanded from single pressure tracking to coordinated tracking of pressure and pressure change rate. The hydraulic pump output flow control quantity of the hydraulic system is determined by the following formula:

[0063]

[0064] Where, k p k i These are the adjustment coefficients for pressure deviation and pressure change rate deviation, respectively.

[0065] S4.4. The target for the rate of change of output torque of the battery / motor system is determined based on the coordinated adjustment weighting coefficient λ(t). The calculation formula is as follows:

[0066]

[0067] S4.5. The control current of the power system is calculated based on the target output torque change rate of the battery / motor system, as follows:

[0068] .

[0069] Compared with the prior art, the technical solution disclosed in this application has the following non-obvious technical features:

[0070] First, this application introduces "equivalent dynamic impedance" as a unified dynamic coordination variable for electro-hydraulic synergy, expands and dynamically models the concept of impedance in mechanical transmission systems, and creatively proposes an "equivalent dynamic impedance" index that can comprehensively reflect the combined resistance of the motor side and the hydraulic side to changes in load angular velocity. Using this as a bridge, the traditional power / torque distribution problem is transformed into a matching and adjustment problem of the overall dynamic response characteristics of the system, realizing the coordinated description and target setting of two subsystems with different dynamic characteristics under a unified dimension.

[0071] Second, this application constructs a feedforward collaborative link of "prediction-impedance-hydraulic state", establishing a complete feedforward decision chain from "power demand prediction" to "target dynamic impedance calculation" and then to "target hydraulic pressure and pressure change rate derivation". This enables the hydraulic system to adjust to a "prepared state" that is most conducive to absorbing or releasing impact energy in advance based on the prediction of future load trends. This changes the lag situation in traditional methods where the hydraulic system can only passively follow pressure feedback, and realizes the leap from reactive control to predictive feedforward coordination.

[0072] Third, this application designs a time-varying weighted collaborative closed-loop controller based on dynamic impedance deviation, and invents an electro-hydraulic collaborative adjustment weight coefficient λ(t) with "equivalent dynamic impedance deviation" as the core feedback quantity. This coefficient is not a fixed value, but is dynamically calculated based on the degree of deviation and changing trend of the system's real-time dynamic characteristics from the target characteristics. Through λ(t), the control target of the hydraulic system is intelligently switched from single pressure tracking to weighted collaborative tracking of pressure and pressure change rate. At the same time, the torque change rate of the motor system is dynamically constrained. This design enables the controller to adaptively adjust the adjustment intensity and division of labor of the electro-hydraulic parts according to the urgency of the working conditions, which is the key to solving the problem of dynamic response matching.

[0073] Fourth, this application achieves "flexible" constraint on motor output characteristics and indirect protection of battery status. By using dynamic impedance targets to limit the rate of change of motor output torque in real time, it avoids the motor from making abrupt and large-scale torque adjustments under load disturbances. This "softened" adjustment method not only makes the power output smoother, but also indirectly smooths the charging and discharging current of the battery, reduces the transient load on the battery, and helps to extend its service life. This effect is indirectly achieved through system-level dynamic characteristic adjustment, rather than directly limiting the battery current, and is therefore not obvious.

[0074] Compared with the prior art, the present invention has the following beneficial effects:

[0075] 1. This invention can significantly improve dynamic smoothness and stability. Through dynamic impedance matching and predictive feedforward, the motor and hydraulic system achieve a coordinated response like a "soft connection", effectively suppressing torque oscillation and speed fluctuation in the transmission chain, and greatly improving the smoothness and overall stability of the system under complex dynamic conditions.

[0076] 2. This invention can effectively suppress hydraulic pressure fluctuations and system shocks. Predictive hydraulic state control enables the hydraulic system to act in advance, absorb or release energy, and avoid rapid pressure changes. Combined with the coordinated tracking of pressure and pressure change rate, it can more precisely manage the energy state in the hydraulic cavity, significantly reduce pressure shock peaks, protect hydraulic components, and reduce noise and energy loss.

[0077] 3. This invention can optimize energy distribution and system efficiency. The forward-looking control allows the system to perform more reasonable energy pre-distribution. The hydraulic system can better play its role as a power buffer, so that the motor and battery can work in the high-efficiency range more often, reducing the frequent and violent adjustment of the motor and the large current impact of the battery, thereby improving the overall energy efficiency.

[0078] 4. This invention enhances the system's adaptability and robustness to complex operating conditions. The method coordinates based on the system's global dynamic characteristics, exhibiting relatively low dependence on changes in subsystem parameters. Its inherent collaborative mechanism enables the system to maintain good control performance and strong robustness even in the face of sudden load changes and parameter perturbations.

[0079] 5. This invention extends the service life of key components; the smooth motor torque output reduces stress cycles in mechanical transmission components; it suppresses hydraulic pressure shocks and protects hydraulic components such as pumps, valves, and pipelines; the smooth battery charging and discharging process is beneficial to battery health; and it extends the service life of key components of the power system as a whole.

[0080] 6. This invention has strong engineering applicability. The entire control method has a clear structure and distinct logical hierarchy. The required state variables (such as speed, pressure, torque, etc.) are all conventionally acquired signals of the vehicle controller. The algorithm is easy to implement and calibrate in existing embedded platforms, and has good prospects for engineering application and promotion. Attached Figure Description

[0081] Figure 1 This is a flowchart of the method described in Embodiment 1 of the present invention;

[0082] Figure 2 This is a schematic diagram of the electro-hydraulic hybrid power system described in Embodiment 1 of the present invention. Detailed Implementation

[0083] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings:

[0084] Example 1;

[0085] A control method for an electro-hydraulic hybrid power system based on dynamic impedance regulation and predictive hydraulic state, such as... Figure 1 As shown, the structure of the electro-hydraulic hybrid power system involved in the implementation of this method is as follows: Figure 2 As shown, it includes the following steps:

[0086] S1. A model of an electro-hydraulic hybrid power system oriented towards dynamic impedance should include at least the following:

[0087] S1.1, Axial dynamics model of electro-hydraulic hybrid power system, the calculation formula is as follows:

[0088]

[0089] in, This is the system's equivalent moment of inertia. This refers to the angular acceleration of the drive shaft. Output torque for the battery / motor system; This provides the output torque for the hydraulic system. This refers to the load torque of the hybrid power system.

[0090] S1.2 The calculation rules for the power system model composed of a battery / motor combination are as follows:

[0091]

[0092] in, This is the motor current / torque conversion factor; This is the equivalent current of the power system.

[0093] S1.3, The model for the relationship between output torque and pressure in a hydraulic system, and the calculation formula is as follows:

[0094]

[0095] in, This refers to the motor torque coefficient in the hydraulic system. For hydraulic system pressure;

[0096] The pressure dynamics of the hydraulic system satisfy the following relationship:

[0097]

[0098] in, The rate of change of pressure in the hydraulic system; The equivalent bulk modulus of hydraulic oil; Equivalent hydraulic volume; This refers to the output flow rate of the hydraulic pump. It absorbs flow for the hydraulic motor.

[0099] S1.4, the equivalent dynamic impedance model of the electro-hydraulic hybrid power system is as follows:

[0100]

[0101] in, The equivalent dynamic impedance of the system is used to characterize the comprehensive dynamic response characteristics of the system to changes in angular velocity. This represents the angular velocity of the drive shaft.

[0102] S2. Dynamic prediction of power demand torque based on system state variables, specifically including the following sub-steps:

[0103] S2.1 The calculation of the rate of change of demand torque is as follows:

[0104]

[0105] in, The rate of change of required torque; The rate of change of angular acceleration; This represents the rate of change of load torque.

[0106] S2.2 Short-term forecasting model establishment, the calculation formula is as follows:

[0107]

[0108] in, For prediction time window Rate of change in domestic demand torque; The mapping function is implemented using linear / nonlinear models.

[0109] The short-term prediction model can use a Long Short-Term Memory (LSTM) network prediction model, and the calculation formula is as follows:

[0110]

[0111] S2.3 Determination of dynamic shock risk indicators, the calculation formula is as follows:

[0112]

[0113] in, This refers to the dynamic impact strength that the system can withstand.

[0114] S3. Determine the hydraulic target and dynamic impedance target based on the prediction results, specifically including the following sub-steps:

[0115] S3.1 Determination of the target equivalent dynamic impedance, the calculation formula is as follows:

[0116]

[0117] in, The reference impedance; This is the impedance adjustment coefficient.

[0118] S3.2 Calculate the target hydraulic system pressure and the rate of change of target hydraulic system pressure using the target equivalent dynamic impedance. The calculation formula is as follows:

[0119]

[0120]

[0121] in, The target hydraulic system pressure; The target hydraulic system pressure change rate.

[0122] S4. Electro-hydraulic coordinated closed-loop regulation based on equivalent dynamic impedance and hydraulic system pressure target parameters, specifically including the following sub-steps:

[0123] S4.1 Calculation of equivalent dynamic impedance deviation and hydraulic system pressure deviation is as follows:

[0124]

[0125] in, Equivalent dynamic impedance deviation characterizes the degree of deviation between the current dynamic characteristics of the power output of the electro-hydraulic hybrid power system and the target dynamic characteristics.

[0126] S4.2. Based on the equivalent dynamic impedance deviation and its changing trend, construct the electro-hydraulic synergistic adjustment weighting coefficient λ(t), which is calculated as follows:

[0127]

[0128] in, This is a limiting function used to... The constraint is within the interval [0,1].

[0129] S4.3 Under the influence of the aforementioned coordinated adjustment weighting coefficient λ(t), the control objective of the hydraulic system is expanded from single pressure tracking to coordinated tracking of pressure and pressure change rate. The hydraulic pump output flow control quantity of the hydraulic system is determined by the following formula:

[0130]

[0131] Where, k p ki These are the adjustment coefficients for pressure deviation and pressure change rate deviation, respectively.

[0132] S4.4. The target for the rate of change of output torque of the battery / motor system is determined based on the coordinated adjustment weighting coefficient λ(t). The calculation formula is as follows:

[0133]

[0134] S4.5. The control current of the power system is calculated based on the target output torque change rate of the battery / motor system, as follows:

[0135] .

[0136] Example 2:

[0137] An electro-hydraulic hybrid power system controller is provided for performing the steps of the method described in Embodiment 1. The controller is part of the electro-hydraulic hybrid power system (e.g., Figure 2 The core decision-making and computation unit (as shown in the structure);

[0138] The controller hardware mainly includes: a high-performance microprocessor (MCU or MPU), non-volatile program memory (such as Flash), volatile data memory (such as RAM), analog-to-digital converter (ADC) module, digital-to-analog converter (DAC) module, digital input / output (I / O) interface, and controller area network (CAN) bus communication interface, etc.

[0139] The controller's software architecture is built based on the method, and executable instructions are stored in the program memory. When the microprocessor executes these instructions, it performs the following functions:

[0140] System Status Awareness and Acquisition Module: Through the ADC module and CAN bus, it collects system status quantities in real time, including but not limited to: drive shaft angular velocity, angular acceleration, battery / motor system output torque, hydraulic system pressure, hydraulic pump output flow, hydraulic motor absorption flow, estimated or measured load torque, and parameters such as battery current, voltage, and state of charge (SOC).

[0141] Dynamic model construction and calculation module: Based on the collected state variables, the module executes step S1 online or offline. This module calculates the axial dynamic model, power system model, and hydraulic system pressure dynamic model, and calculates the equivalent dynamic impedance Z. This module provides a unified dynamic characteristic description basis for subsequent prediction and decision-making.

[0142] Power demand forecasting: Following step S2, this module first calculates the current rate of change in demand torque, then calls a built-in short-term forecasting model (e.g., based on linear extrapolation, autoregressive models, or trained LSTM neural network models) to predict the demand torque change trend within a future time window using historical state variable sequences. Simultaneously, a dynamic impact risk index can be calculated to assess the urgency of the operating condition.

[0143] Target decision: Execute step S3, receive the output of the prediction module, determine the impedance adjustment coefficient by looking up a table or calculating a formula based on the predicted demand change trend, and then calculate the target equivalent dynamic impedance; subsequently, derive the target hydraulic system pressure and the target pressure change rate based on the relationship, and thus form the system's advanced control target;

[0144] Electro-hydraulic coordinated closed-loop regulation: Executing step S4, firstly, the equivalent dynamic impedance deviation and hydraulic pressure deviation are calculated; then, based on the equivalent dynamic impedance deviation and its differential dynamics, the coordinated regulation weight coefficient λ(t) is calculated; finally, two sub-control laws are executed in parallel.

[0145] Hydraulic system control law: Based on λ(t), hydraulic pressure deviation and calculated pressure change rate deviation, calculate the output flow control command of the hydraulic pump according to the formula, and output it through DAC module or dedicated hydraulic valve drive circuit to control the proportional valve or variable mechanism of the hydraulic pump.

[0146] Motor system control law: The target output torque change rate of the battery / motor system is calculated based on λ(t), and then the target control current is calculated through the motor current-torque relationship. This instruction is sent to the motor controller (MCU) via the CAN bus, or directly through analog / PWM output, to achieve flexible adjustment of motor torque.

[0147] Through the coordinated operation of the above processes, the controller achieves dynamic impedance matching and predictive coordinated control of the electro-hydraulic hybrid power system. Its inputs are various sensor signals, and its outputs are control commands for the hydraulic pump and motor system, forming a complete closed-loop control system.

[0148] Example 3:

[0149] An electro-hydraulic hybrid vehicle, particularly a fully hydraulic excavator, comprising an electro-hydraulic hybrid system controller as described in Example 2, the fully hydraulic electro-hydraulic hybrid excavator including:

[0150] Power source and drive system: including a battery pack as the main drive source and a three-phase permanent magnet synchronous motor, with the motor output shaft connected to the main drive shaft through a reducer;

[0151] Hydraulic system: including a variable hydraulic pump driven by the main drive shaft, multiple hydraulic motors (represented as equivalent motors in the figure) that perform digging / slewing / traveling actions, hydraulic oil tank, control valve group, accumulator (optional), and pressure sensor, flow sensor, etc.

[0152] Working device and load: including boom, stick, bucket and corresponding hydraulic cylinders, which constitute a variable load torque acting on the transmission system;

[0153] It should be noted that the electro-hydraulic hybrid power system controller (i.e. the controller described in Embodiment 2), as the "brain" of the entire excavator, has its signal input terminals connected to an encoder for measuring the drive shaft speed, a pressure sensor for measuring the hydraulic system pressure, a torque sensor for measuring the motor output torque (or estimated by motor current), and the vehicle's CAN network (to acquire operating handle signals, battery status, etc.); the controller's control output terminals are connected to the torque command interface of the motor controller and the drive amplifier of the hydraulic pump proportional valve.

[0154] When the excavator is working, the operator's operating intention is converted into an electrical signal through the handle. The controller not only responds to the current operating signal, but more importantly, it executes the steps of the method described in Example 1: it continuously predicts the power demand trend in the next short period of time (as in the next operating action); based on the prediction results, it dynamically adjusts the overall "impedance" target of the system; and coordinates the control of the motor to gently change the output torque, while instructing the hydraulic pump to adjust the flow rate in advance, so that the hydraulic system pressure smoothly transitions to the target value.

[0155] For example, when heavy-duty digging is predicted, the controller will increase the target pressure of the hydraulic system in advance and instruct the hydraulic pump to increase its displacement and pressure storage in advance, while allowing the motor to gradually increase torque. In this way, when the bucket actually contacts the material, the hydraulic system has sufficient pressure reserves to provide peak torque, and the motor does not need to respond violently, thus achieving extremely smooth power output and effectively suppressing the engine speed drop, body vibration and hydraulic shock noise of traditional excavators at the moment of digging.

[0156] Therefore, the electro-hydraulic hybrid excavator provided in this embodiment, by integrating the dedicated controller based on dynamic impedance adjustment and predictive hydraulic state, significantly improves the smoothness of operation, the comfort of operation, and the energy-saving effect, while reducing the impact on hydraulic components and extending the service life of the whole machine. It should be noted that Embodiment 3 is also applicable to other types of electro-hydraulic hybrid engineering machinery or special vehicles such as wheel loaders and mining dump trucks.

[0157] The above technical solutions only embody the preferred technical solutions of the present invention. Any modifications that may be made by those skilled in the art to certain parts thereof embody the principles of the present invention and fall within the protection scope of the present invention.

Claims

1. A control method for an electro-hydraulic hybrid power system based on dynamic impedance regulation and predictive hydraulic state, characterized in that, Includes the following steps: S1. Construct an electro-hydraulic hybrid power system model oriented towards dynamic impedance; The equivalent dynamic impedance model of the electro-hydraulic hybrid power system is calculated using the following formula: ； in, The equivalent dynamic impedance of the system is used to characterize the comprehensive dynamic response characteristics of the system to changes in angular velocity. The angular velocity of the drive shaft; Output torque for the battery / motor system; This provides the output torque for the hydraulic system. This is the motor current / torque conversion factor; This represents the equivalent current of the power system. This refers to the motor torque coefficient in the hydraulic system. For hydraulic system pressure; S2. Dynamically predict the torque demand based on the state variables of the electro-hydraulic hybrid power system model; S3. Determine the target pressure parameters and equivalent dynamic impedance adjustment target of the hydraulic system based on the results of dynamic prediction; S4. Based on the equivalent dynamic impedance adjustment target and the pressure target parameters of the hydraulic system, the motor system and the hydraulic system are coordinated and closed-loop regulated. The specific process of S3 includes: S3.

1. Based on the predicted trend of power demand torque variation, the target equivalent dynamic impedance is determined as follows: ； in, As the reference impedance, The impedance adjustment coefficient is related to the predicted trend. The dynamic impact strength that the system can withstand; S3.

2. Based on the target equivalent dynamic impedance, calculate the target hydraulic system pressure and the rate of change of the target hydraulic system pressure. The calculation formula is as follows: ； ； in, For the target hydraulic system pressure, The target hydraulic system pressure change rate; This refers to the angular acceleration of the drive shaft. The specific process of S4 includes: S4.1 Calculate the deviation between the current equivalent dynamic impedance and the target equivalent dynamic impedance, as well as the deviation between the current hydraulic system pressure and the target pressure; S4.

2. Based on the equivalent dynamic impedance deviation and its changing trend, dynamically calculate the electro-hydraulic synergistic adjustment weighting coefficient. ; S4.3, using the aforementioned weighting coefficients This generates hydraulic pump output flow control commands that simultaneously track the target pressure and the rate of change of the target pressure. The hydraulic pump output flow control command is determined by the following formula: ； in, This is a flow control command for the hydraulic pump output. , These are the adjustment coefficients for pressure deviation and pressure change rate deviation, respectively. S4 further includes: S4.4, According to the weighting coefficients Constraints and determinations are made regarding the target output torque change rate of the battery / motor system; S4.

5. Calculate the control current of the power system based on the output torque change rate target.

2. The method according to claim 1, characterized in that, The electro-hydraulic hybrid power system model constructed in S1 for dynamic impedance includes at least one of the following: an axial dynamics model of the electro-hydraulic hybrid power system, a power system model composed of a battery / motor combination, a hydraulic system output torque and pressure relationship model, and an equivalent dynamic impedance model of the electro-hydraulic hybrid power system.

3. The method according to claim 1, characterized in that, The specific process of S2 includes: S2.1 Calculate the rate of change of current power demand torque; S2.2 Establish a short-term forecasting model to predict the trend of power demand torque changes within the future forecast time window; S2.

3. Based on the predicted trend information, assess the dynamic shock risk of the system.

4. The method according to claim 1, characterized in that, The formula for determining the target output torque change rate of the battery / motor system is: ,in, This represents the rate of change in required torque.

5. A controller for an electro-hydraulic hybrid power system, characterized in that, Configure steps for performing the method according to any one of claims 1 to 4.

6. An electro-hydraulic hybrid vehicle or engineering machinery, characterized in that, It includes the electro-hydraulic hybrid power system controller as described in claim 5.

Images