A pump displacement control method and system based on PWM duty cycle regulation

Abstract

This invention proposes a pump displacement control method and system based on PWM duty cycle adjustment, belonging to the technical field of pump displacement control. The pump controller is used to adjust the displacement. After receiving a target displacement command, it controls the pump. The TIM port of the pump controller chip is configured in PWM mode. The target value of the PID algorithm is determined based on the pump's pressure cut-off mode, constant power regulation mode, and electro-proportional regulation mode. Combined with the PID controller, PID control is performed, adjusting the PWM duty cycle. The PWM duty cycle increment triggers the opening of the electro-proportional valve, finding suitable PID control parameters. This allows the pump to flexibly switch between pressure cut-off mode, constant power regulation mode, and electro-proportional regulation mode, controlling the pump displacement, improving pump efficiency, saving costs, and integrating the pump into a mechatronics system, laying the foundation for intelligent products in digital transformation.

Description

Technical Field

[0001] This invention relates to the technical field of pump displacement control, and more specifically, to a pump displacement control method and system based on PWM duty cycle adjustment. Background Technology

[0002] Pump systems have very important applications in many key fields such as aerospace, military weapons, scientific research, and engineering machinery. As the core component of pump systems, pumps occupy an important position.

[0003] Pump operating control modes include pressure cut-off mode, constant power regulation mode, and electro-proportional regulation mode. However, in each mode, the pump displacement control is inflexible. Currently, most traditional hydraulic pumps control their displacement by changing the piston stroke using a swashplate mechanism. For example, a straight-shaft axial piston pump is disclosed in the prior art. This piston pump includes a pump shaft, a swashplate, pistons, a cylinder block, and a distributor plate. The piston pump adopts a through-shaft drive. The swashplate, cylinder block, and distributor plate are mounted on the pump shaft. The cylinder block has an odd number of piston holes evenly distributed along the circumference, parallel to the pump shaft. Each piston hole contains a piston that can slide freely within it. However, because the swashplate position is difficult to control, this type of pump has low volumetric and mechanical efficiency, resulting in energy loss.

[0004] Therefore, how to achieve flexible adjustment of pump displacement is an urgent problem to be solved. Summary of the Invention

[0005] To address the challenge of flexibly adjusting and controlling pump displacement, this invention proposes a pump displacement control method and system based on PWM duty cycle adjustment. This method allows for flexible switching between different operating modes, improving pump efficiency and saving costs. Furthermore, it integrates the pump into a mechatronics system, laying the foundation for intelligent products undergoing digital transformation.

[0006] To achieve the above-mentioned technical effects, the technical solution of the present invention is as follows:

[0007] A pump displacement control method based on PWM duty cycle adjustment, the method comprising the following steps:

[0008] S1. The pump controller receives the target displacement and configures the PWM mode of the pump controller chip. Combined with the pressure and current displacement information, it begins control processing.

[0009] S2. Determine if the pump meets the pressure cut-off condition. If yes, the pump enters the pressure cut-off mode, the target value of the PID algorithm is determined, and step S4 is executed; otherwise, step S3 is executed.

[0010] S3. Determine whether the pump meets the constant power condition. If yes, the pump enters the constant power regulation mode, determines the target value of the PID algorithm, and executes step S4; otherwise, the pump enters the electro-proportional regulation mode, determines the target value of the PID algorithm, and executes step S4.

[0011] S4. Use the PID algorithm to adjust the PWM duty cycle, and control the pump displacement by controlling the PWM duty cycle.

[0012] In this technical solution, the pump controller is used to adjust the displacement. After receiving the command for the target displacement, it controls the pump. The chip's TIM port is configured in PWM mode. The target value of the PID algorithm is determined when the pump enters the pressure cut-off mode, constant power regulation mode, and electro-proportional regulation mode. Combined with the PID controller, PID control is performed. The PID controller adjusts the PID control according to a certain period, continuously based on the difference between the target value and the actual value. After PID control adjustment, the pump's output displacement reaches the target value. Based on the current pressure and torque, the pump switches between pressure cut-off mode, constant power regulation mode, and electro-proportional regulation mode to control the pump displacement and improve the pump's working efficiency.

[0013] Preferably, in step S1, the chip model used by the pump controller is selected, and the TIM port corresponding to that chip model is configured in PWM mode. The duty cycle and frequency of the PWM can be changed by configuring the counter register of the TIM channel through the program, thus achieving the purpose of changing the output PWM duty cycle through the program.

[0014] Preferably, in step S2, the current pressure value of the pump is collected and set as Pa, and the cut-off pressure is set as Pc. When Pa≥Pc, the pump meets the pressure cut-off condition.

[0015] Preferably, when the pump enters the pressure cut-off mode, the pump's current pressure Pa is not less than the cut-off pressure P. cutoff The linear equation that the pump reduces its displacement to zero at a pressure of 2 MPa is:

[0016] PumA=(1-(Pa-P cutoff ) / 2)*PumC

[0017] Where PumA represents the target displacement and PumC represents the power displacement; the target displacement PumA is the target value of the PID algorithm.

[0018] Preferably, the pump's limiting torque is set to T1, the target displacement is PumA, the current pressure at the pump outlet is Pa, and the current displacement is PumB. The pump enters constant power mode to satisfy the following:

[0019] (Pump outlet pressure × target displacement) / (20 × Pi) ≤ beta

[0020] Where beta is the target torque; based on this formula, the target torque T2 for entering the constant power mode is derived according to the target displacement PumA and the current pressure Pa; based on the set limit torque T1 and the current pressure Pa, the power displacement PumC in the constant power mode is derived in reverse; when T2≥T1, the pump meets the constant power condition and starts to enter the constant power regulation mode, and the power displacement PumC is the target value of the PID algorithm.

[0021] Preferably, when T2 < T1, the pump exits the constant power regulation mode and enters the electric proportional regulation mode within a set exit time period.

[0022] Preferably, when the pump enters the electro-proportional control mode, the larger the valve core opening of the electro-proportional valve, the larger the pump displacement, and the larger the swing angle amplitude of the pump's tilt sensor. Based on the pump's analog pressure input, the sampled value Value of the tilt sensor is obtained. The pressure P is acquired by the pressure sensor, satisfying the following:

[0023] P = (I-4) * 3.588;

[0024] Where I represents the sampling current, and if I is less than 4mA, then the value of P is 0;

[0025] Tilt sensors have voltage-type output and current-type output. The voltage-type output range is 0 to 5V, and the current-type output range is 4 to 20mA.

[0026] When the pump's tilt sensor has a voltage output, the pump's current real-time displacement is:

[0027] Pump = (4.383 - Value) * 51.351

[0028] When the pump's tilt sensor is a current-type output, the pump's current real-time displacement is:

[0029] Pump = (17.89 - Value) * 15.2 + 10, where the current real-time pump displacement Pump is used as the target value for the PID algorithm.

[0030] Preferably, when adjusting the PWM duty cycle using the PID algorithm, the adjustment process incorporates a PID controller, an electro-proportional valve, a tilt sensor, and the target value of the PID algorithm. The sampled value of the tilt sensor is compared with the target displacement PumA to obtain the displacement error. The displacement error is input to the PID controller, and the output value of the PID controller is assigned to the TIM port of the chip used by the pump controller, outputting the PWM duty cycle increment. The PWM duty cycle increment serves as the input to the electro-proportional valve. The higher the PWM duty cycle, the larger the valve core opening of the electro-proportional valve, the larger the pump displacement, and the larger the tilt angle amplitude of the tilt sensor. The PID controller adjusts the PID control according to a certain cycle, continuously based on the difference between the target value and the actual value. After PID control adjustment, the pump's output displacement reaches the target value. Based on the current pressure and torque, the system switches between pressure cut-off mode, constant power adjustment mode, and electro-proportional adjustment mode.

[0031] Preferably, the PID controller is a variable speed integral PID controller.

[0032] A pump displacement control system based on PWM duty cycle regulation, the system comprising:

[0033] The system includes a pump controller, tilt sensor, pressure sensor, and electro-proportional valve. The pump controller is a digital pump module with an integrated PID controller. It receives the target displacement from the vehicle controller or host computer for displacement control and uses a specific chip with its TIM port configured in PWM mode. The tilt sensor performs voltage and current sampling, and the pressure sensor collects the pump pressure. The digital pump module collects information from the tilt and pressure sensors and combines it with the PID controller for PID control, adjusting the PWM duty cycle. The change in the PWM duty cycle adjusts the opening of the electro-proportional valve, allowing the pump to switch between pressure cut-off mode, constant power regulation mode, and electro-proportional regulation mode to control the pump displacement.

[0034] The digital pump module includes: an MCU, a power management module, a CAN module, a power output module, and an analog input module. The MCU is the main controller, the power management module supplies power to the MCU, CAN module, power output module, and analog input module, the CAN module is used to send and receive CAN data and transmit it to the MCU, the MCU sends control signals to the power output module, and the power output module performs PWM output, and the analog input module sends the acquired tilt sensor and pressure sensor signal data to the MCU, which then performs signal data analysis.

[0035] Compared with the prior art, the beneficial effects of the technical solution of the present invention are:

[0036] This invention proposes a pump displacement control method and system based on PWM duty cycle adjustment. The method utilizes a pump controller to issue the target pump displacement and configures the TIM port of the pump controller chip to PWM mode. The target value of the PID algorithm is determined when the pump enters pressure cut-off mode, constant power regulation mode, and electro-proportional regulation mode. Combined with a PID controller, PID control is performed by adjusting the PWM duty cycle. The increment of the PWM duty cycle triggers the opening of the electro-proportional valve, finding suitable PID control parameters. This allows the pump to flexibly switch between pressure cut-off mode, constant power regulation mode, and electro-proportional regulation mode, controlling the pump displacement and improving pump efficiency. Attached Figure Description

[0037] Figure 1 This is a flowchart illustrating the pump displacement control method based on PWM duty cycle adjustment proposed in Embodiment 1 of the present invention.

[0038] Figure 2 This is a schematic diagram illustrating the principle of PWM generation proposed in Embodiment 1 of the present invention;

[0039] Figure 3 A flowchart illustrating the implementation of the PID algorithm proposed in Embodiment 1 of the present invention;

[0040] Figure 4 This is a schematic diagram illustrating the pump displacement control method based on PWM duty cycle adjustment proposed in Embodiment 3 of the present invention under the first type of PID parameters.

[0041] Figure 5 This is a schematic diagram illustrating the pump displacement control method based on PWM duty cycle adjustment proposed in Embodiment 3 of the present invention under the second type of PID parameters.

[0042] Figure 6 This is a schematic diagram illustrating the pump displacement control method based on PWM duty cycle adjustment proposed in Embodiment 3 of the present invention under the third type of PID parameters.

[0043] Figure 7 This is a schematic diagram illustrating a tracking experiment of the target displacement and the actual value when the PID controller is activated, as proposed in Embodiment 3 of the present invention.

[0044] Figure 8 This is a schematic diagram illustrating another tracking experiment of the target displacement and the actual value when the PID controller is activated, as proposed in Embodiment 3 of the present invention.

[0045] Figure 9 This is a schematic diagram of the pump reversal curve for constant power regulation proposed in Embodiment 3 of the present invention;

[0046] Figure 10This is a schematic diagram of the constant power regulation mode curve proposed in Embodiment 3 of the present invention;

[0047] Figure 11 This represents the commutation curve of the mechanical open-loop pump proposed in Embodiment 3 of the present invention. Detailed Implementation

[0048] The accompanying drawings are for illustrative purposes only and should not be construed as limiting the scope of this patent.

[0049] To better illustrate this embodiment, some parts of the accompanying drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions;

[0050] It is understandable to those skilled in the art that some well-known details may be omitted from the accompanying drawings.

[0051] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0052] The positional relationships depicted in the accompanying drawings are for illustrative purposes only and should not be construed as limiting this patent.

[0053] Example 1

[0054] like Figure 1 As shown, this embodiment proposes a pump displacement control method based on PWM duty cycle adjustment. See [link to relevant documentation]. Figure 1 The method includes the following steps:

[0055] S1. The pump controller receives the target displacement and configures the PWM mode of the pump controller chip. Combined with the pressure and current displacement information, it begins control processing.

[0056] S2. Determine if the pump meets the pressure cut-off condition. If yes, the pump enters the pressure cut-off mode, the target value of the PID algorithm is determined, and step S4 is executed; otherwise, step S3 is executed.

[0057] S3. Determine whether the pump meets the constant power condition. If yes, the pump enters the constant power regulation mode, determines the target value of the PID algorithm, and executes step S4; otherwise, the pump enters the electro-proportional regulation mode, determines the target value of the PID algorithm, and executes step S4.

[0058] S4. Use the PID algorithm to adjust the PWM duty cycle, and control the pump displacement by controlling the PWM duty cycle.

[0059] Overall, the pump controller is used to adjust the displacement. After receiving the command of the target displacement (including the pump truck controller sending the command of the target displacement through the bus; or using the host computer to send the target displacement on the computer), it controls the pump, and configures the TIM port of the pump controller chip into the PWM mode. When the pump enters the pressure cut-off mode, constant power regulation mode, and electro-hydraulic proportional regulation mode, the target value of the PID algorithm is determined, and PID control is carried out in combination with the PID controller to adjust the PWM duty cycle. The PWM duty cycle increment triggers the opening of the electro-hydraulic proportional valve, and the appropriate PID control parameters are found to enable the pump to flexibly switch between the pressure cut-off mode, constant power regulation mode, and electro-hydraulic proportional regulation mode, control the pump displacement, and improve the working efficiency of the pump.

[0060] In step S1, in this embodiment, the selected chip model of the pump controller is the STM32G491VET6 chip. By configuring the corresponding TIM port of this chip into the PWM mode and sending a control command to the power output module, the PWM wave can be output. The duty cycle and frequency of the PWM can be changed by configuring the counter register of the TIM channel through the program, that is, the purpose of changing the output PWM duty cycle through the program is achieved.

[0061] Figure 2 It shows the schematic diagram of the principle of PWM formation; assume that the timer works in the up-counting PWM mode, and when CNT < CCRx, output 0, and when CNT >= CCRx, output 1. Then, the above PWM schematic diagram can be obtained: when the CNT value is less than CCRx, the IO outputs a low level (0), when the CNT value is greater than or equal to CCRx, the IO outputs a high level (1), and when the CNT reaches the ARR value, it resets to zero and then counts up again, cycling in turn. By changing the value of CCRx, the duty cycle of the PWM output can be changed, and by changing the value of ARR, the frequency of the PWM output can be changed. This is the principle of PWM output.

[0062] In this embodiment, for step S2, the current pressure value of the pump is collected through the electronic pressure gauge, set as Pa, and the cut-off pressure is set as Pc. When Pa ≥ Pc, the pump meets the pressure cut-off condition.

[0063] When the pump enters the pressure cut-off mode, the current pressure Pa of the pump is not less than the cut-off pressure P cutoff , the pump reduces the displacement to zero within a pressure of 2 MPa. The linear formula satisfied by the process of the pump reducing the displacement to zero within a pressure of 2 MPa is:

[0064] PumA = (1 - (Pa - P cutoff ) / 2) * PumC

[0065] Where PumA represents the target displacement and PumC represents the power displacement; the target displacement PumA is the target value of the PID algorithm.

[0066] For constant power regulation mode:

[0067] Set the pump's limiting torque to T1, target displacement PumA, current pump outlet pressure to Pa, and current displacement to PumB. The pump enters constant power mode to satisfy the following conditions:

[0068] (Pump outlet pressure × target displacement) / (20 × Pi) ≤ beta

[0069] Where beta is the target torque; based on this formula, the target torque T2 for entering the constant power mode is derived according to the target displacement PumA and the current pressure Pa; based on the set limit torque T1 and the current pressure Pa, the power displacement PumC in the constant power mode is derived in reverse; when T2≥T1, the pump meets the constant power condition and starts to enter the constant power regulation mode, and the power displacement PumC is the target value of the PID algorithm.

[0070] When T2 < T1, the pump exits the constant power regulation mode and enters the electro-proportional regulation mode or directly enters the electro-proportional regulation mode within a set exit time period.

[0071] Electro-proportional adjustment mode:

[0072] When the pump enters the electro-proportional control mode, the larger the valve opening of the electro-proportional valve, the larger the pump displacement, and the larger the swing angle amplitude of the pump's tilt sensor. Based on the pump's analog pressure input, the sampled value Value of the tilt sensor is obtained. The pressure P is acquired by the pressure sensor, satisfying the following:

[0073] P = (I-4) * 3.588;

[0074] Where I represents the sampling current, and if I is less than 4mA, then the value of P is 0;

[0075] Tilt sensors have voltage-type output and current-type output. The voltage-type output range is 0 to 5V, and the current-type output range is 4 to 20mA.

[0076] When the pump's tilt sensor has a voltage output, the pump's current real-time displacement is:

[0077] Pump = (4.383 - Value) * 51.351

[0078] When the pump's tilt sensor is a current-type output, the pump's current real-time displacement is:

[0079] Pump = (17.89 - Value) * 15.2 + 10, where the current real-time pump displacement Pump is used as the target value for the PID algorithm.

[0080] See Figure 3 When adjusting the PWM duty cycle using the PID algorithm, the adjustment process incorporates a PID controller, an electro-proportional valve, a tilt sensor, and the target value of the PID algorithm. The sampled value from the tilt sensor is compared with the target displacement PumA to obtain the displacement error. This displacement error is input to the PID controller, and the output value of the PID controller is assigned to the TIM port of the chip used in the pump controller, outputting the PWM duty cycle increment. This PWM duty cycle increment serves as the input to the electro-proportional valve. A higher PWM duty cycle results in a larger valve opening, a larger pump displacement, and a larger tilt angle amplitude from the tilt sensor. After PID control adjustment, the pump's output displacement reaches the target value. Based on the current pressure and torque, the system switches between pressure cut-off mode, constant power regulation mode, and electro-proportional regulation mode. In this embodiment, the PID controller is a variable speed integral PID controller.

[0081] Example 2

[0082] This embodiment proposes a pump displacement control system based on PWM duty cycle adjustment. The system includes a pump controller, a tilt sensor, a pressure sensor, and an electro-proportional valve. The pump controller uses a digital pump module with an integrated PID controller. The pump controller receives the target displacement from the vehicle controller or a host computer and performs displacement control. It uses a specific type of chip, and the chip's TIM port is configured in PWM mode. The tilt sensor performs voltage and current sampling, and the pressure sensor collects the pump pressure. The digital pump module collects the information from the tilt sensor and pressure sensor, and combines it with the PID controller for PID control, adjusting the PWM duty cycle. The change in the PWM duty cycle adjusts the opening of the electro-proportional valve, allowing the pump to switch between pressure cut-off mode, constant power regulation mode, and electro-proportional regulation mode to control the pump displacement.

[0083] The digital pump module includes: MCU, power management module, CAN module, power output module, and analog input module. The MCU is the main controller. The power management module supplies power to the MCU, CAN module, power output module, and analog input module. The CAN module is used to send and receive CAN data and transmit it to the MCU. The MCU sends control signals to the power output module, which then performs PWM output. The analog input module sends the acquired tilt sensor and pressure sensor signal data to the MCU, which then performs signal data analysis.

[0084] Example 3

[0085] Based on the method proposed in Example 1 and the system proposed in Example 2, this example takes the verification of three control modes (pressure cut-off mode, constant power regulation mode, and electric proportional regulation mode) as its starting point to find suitable PID control parameters. The selected materials include a digital pump module, a CAN card, an adjustable power supply, wires, and an oil pump stand (Sany Laboratory). Table 1 shows the basic parameter settings. The digital pump module collects sensor information, processes the data, and then adjusts the proportional valve current by controlling PWM to achieve the purpose of controlling the pumping displacement.

[0086] Table 1

[0087]

[0088] Table 2 shows the parameter settings for constant power mode.

[0089] Table 2

[0090]

[0091] The experimental steps are as follows: Under electro-proportional regulation, the PWM duty cycle is changed, and the data changes of the angle sensor are collected; the oil pump pressure is changed through the test bench, and different control modes are switched to verify the feasibility of switching between constant power mode and pressure cut-off mode; under electro-proportional regulation, a suitable PID control parameter is found. Figure 4 The PID control parameters are: P: 0.025, I: 7, D: 0. This is the pump displacement adjustment curve, and the curve parameters are:

[0092] Steady-state value ys = 99 ml / r; overshoot σ = 61.6%; rise time tr = 150 ms; settling time ts = 2.8 s;

[0093] Theoretical formula for calculating steady-state error:

[0094] A:=Kp*(1+α*Ts / Ti+Td / Ts);

[0095] B:=Kp*(1+2*Td / Ts);

[0096] C:=Kp*Td / Ts;

[0097] Δ=(A-B+C)*e;

[0098] Where Kp is the P value multiplied by 100, α = 1; Ts = 1; Δ is the minimum increment under steady state, e is the steady state error; Δ is the duty cycle in this system, and the minimum increment of the duty cycle value is 1;

[0099] After simplifying the formula, we get:

[0100] Δ=(Kp / Ti)*e;

[0101] After substituting the PID parameters, 1 = (2.5 / 7) * e -> e = 2.8 ml / r;

[0102] Therefore, the theoretical steady-state error is 2.8 ml / r, and the actual error is 100 - 99 = 1 ml / r; from Figure 4 It can be seen that the actual error is smaller than the theoretical error because adding the penultimate increment will make the minimum increment less than 1.

[0103] Figure 5 This is a pump displacement adjustment curve with PID control parameters: P: 0.019, I: 7, D: 0. The curve parameters are:

[0104] Steady-state value ys = 99 ml / r; overshoot σ = 38.4%; rise time tr = 180 ms; settling time ts = 1.25 s;

[0105] Theoretical formula for calculating steady-state error:

[0106] A:=Kp*(1+α*Ts / Ti+Td / Ts);

[0107] B:=Kp*(1+2*Td / Ts);

[0108] C:=Kp*Td / Ts;

[0109] △=(A-B+C)*e;

[0110] Where Kp is the P value multiplied by 100, α = 1; Ts = 1; Δ is the minimum increment under steady state, e is the steady state error; Δ is the duty cycle in this system, and the minimum increment of the duty cycle value is 1;

[0111] After simplifying the formula, we get:

[0112] △=(Kp / Ti)*e;

[0113] After substituting the PID parameters, 1 = (1.9 / 7) * e -> e = 3.68 ml / r;

[0114] Therefore, the theoretical steady-state error is 3.68 ml / r, and the actual error is 100 - 99 = 1 ml / r; combined with Figure 5 It can be seen that the actual error is smaller than the theoretical error because adding the penultimate increment makes the minimum increment less than 1. In summary, a larger P value results in a faster response speed but also a larger overshoot; a larger I value results in greater stability but also affects the steady-state error.

[0115] Figure 6 This is a pump displacement adjustment curve with PID control parameters: P: 0.015, I: 8, D: 0. The curve parameters are:

[0116] Steady-state value ys = 98.6 ml / r; overshoot σ = 22.7%; rise time tr = 200 ms; settling time ts = 900 ms;

[0117] Theoretical formula for calculating steady-state error:

[0118] A:=Kp*(1+α*Ts / Ti+Td / Ts);

[0119] B:=Kp*(1+2*Td / Ts);

[0120] C:=Kp*Td / Ts;

[0121] Δ=(A-B+C)*e;

[0122] Where Kp is the P value multiplied by 100, α = 1; Ts = 1; Δ is the minimum increment under steady state, e is the steady state error; Δ is the duty cycle increment under this system, and the minimum increment of the duty cycle value is 1;

[0123] Simplifying the formula, we get: Δ=(Kp / Ti)*e; Substituting the PID parameters, we get 1=(1.5 / 8)*e->

[0124] e = 5.3 ml / r; therefore, the theoretical steady-state error is 5.3 ml / r, and the actual error is 100 - 98.6 = 1.4 ml / r; combined with Figure 2 It can be seen that the actual error is smaller than the theoretical error because adding the penultimate increment makes the minimum increment less than 1. In summary, a larger P value results in a faster response speed but also a larger overshoot; a larger I value results in greater stability but also affects the steady-state error. The controller issues the target displacement every 200ms, and the PID calculation cycle is 10ms. Figure 7 It follows the curve. Figure 8 It is the second type of follow curve, by Figure 7 and Figure 8 It is known that the controller's output cycle is 200ms and the PID calculation cycle is 10ms. At this time, there is more time to adjust, so we can consider appropriately increasing the P value and decreasing the I value to reduce the response time and steady-state error.

[0125] Figure 9 To apply the method proposed in this application to vehicle pumps, the pump reversing curve with constant power regulation is shown; such as Figure 9 As shown, when the vehicle pump reverses direction, the pressure drops sharply and then recovers within 800ms. This vehicle condition affects the constant power regulation mode: In this mode, the target displacement uses the power displacement derived from the pressure. The sudden drop in pressure will cause the power displacement to surge. To resolve this fluctuation caused by reversal, an exit time is added to the constant power regulation mode. During this time, the current displacement is locked to prevent the displacement from fluctuating too much with pressure. Figure 10This is the constant power regulation mode curve. Figure 11 For the commutation curve of a mechanical open-loop pump, this control strategy is equivalent to performing a pressure filter in constant power mode to eliminate the impact of a sudden pressure drop caused by commutation.

[0126] The embodiments described are merely examples to clearly illustrate the present invention and are not intended to limit the implementation of the invention. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively describe all possible implementations. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A pump displacement control method based on PWM duty cycle adjustment, characterized in that, The method includes the following steps: S1. The pump controller receives the target displacement and configures the PWM mode of the pump controller chip. Combined with the pressure and current displacement information, it begins control processing. S2. Determine if the pump meets the pressure cut-off condition. If yes, the pump enters the pressure cut-off mode, the target value of the PID algorithm is determined, and step S4 is executed; otherwise, step S3 is executed. In S2, the current pressure value at the pump outlet is collected and denoted as Pa, and the cut-off pressure is denoted as P. cutoff When Pa≥P cutoff At that time, the pump meets the pressure cut-off condition; S3. Determine if the pump meets the constant power condition. If so, the pump enters the constant power regulation mode, determines the target value of the PID algorithm, and when the pump enters the pressure cut-off mode, the current pressure Pa at the pump outlet is not less than the cut-off pressure P. cutoff The linear equation that the pump reduces its displacement to zero at a pressure of 2 MPa is: PumA=(1-(Pa-P cutoff ) / 2)*PumC Where PumA represents the target displacement and PumC represents the power displacement; the target displacement PumA is the target value of the PID algorithm, and step S4 is executed; otherwise, the pump enters the electro-proportional control mode, the target value of the PID algorithm is determined, and step S4 is executed. In S3, the pump's limiting torque is set to T1, the target displacement is PumA, the current pressure at the pump outlet is Pa, and the current displacement is PumB. The pump enters constant power mode to satisfy the following: (Current pump outlet pressure × target displacement) / (20 × Pi) ≤ beta Where beta is the target torque; based on this formula, the target torque T2 for entering the constant power mode is derived according to the target displacement PumA and the current pressure Pa at the pump outlet; based on the set limit torque T1 and the current pressure Pa at the pump outlet, the power displacement PumC in the constant power mode is derived in reverse; when T2≥T1, the pump meets the constant power condition and starts to enter the constant power regulation mode, and the power displacement PumC is the target value of the PID algorithm. S4. Use the PID algorithm to adjust the PWM duty cycle, and control the pump displacement by controlling the PWM duty cycle.

2. The pump displacement control method based on PWM duty cycle adjustment according to claim 1, characterized in that, In step S1, the chip model used by the pump controller is selected, and the TIM port corresponding to the chip model is configured to PWM mode.

3. The pump displacement control method based on PWM duty cycle adjustment according to claim 1, characterized in that, When T2 < T1, the pump exits the constant power regulation mode and enters the electro-proportional regulation mode within a set exit time period.

4. The pump displacement control method based on PWM duty cycle adjustment according to claim 1, characterized in that, When the pump enters the electro-proportional control mode, the larger the valve opening of the electro-proportional valve, the larger the pump displacement, and the larger the swing angle amplitude of the pump's tilt sensor. Based on the pump's analog pressure input, the sampled value Value of the tilt sensor is obtained. The pressure P is acquired by the pressure sensor, satisfying the following: P = (I - 4) * 3.588; Where I represents the sampling current, and if I is less than 4mA, then the value of P is 0; Tilt sensors have voltage-type output and current-type output. The voltage-type output range is 0~5V, and the current-type output range is 4~20mA. When the pump's tilt sensor has a voltage output, the pump's current real-time displacement is: Pump = (4.383 - Value) * 51.351 When the pump's tilt sensor is a current-type output, the pump's current real-time displacement is: Pump=(17.89-Value)*15.2+10.

5. The pump displacement control method based on PWM duty cycle adjustment according to claim 1 or 4, characterized in that, When adjusting the PWM duty cycle using the PID algorithm, the adjustment process involves a PID controller, an electro-proportional valve, a tilt sensor, and the target value of the PID algorithm. After the tilt sensor's sampled value is acquired, the real-time pump displacement is calculated. The real-time displacement is compared with the target displacement PumA to obtain the displacement error. This displacement error is input to the PID controller, and the PID controller's output value is assigned to the TIM port of the chip used in the pump controller, outputting the PWM duty cycle change. The PWM duty cycle change serves as the input to the electro-proportional valve. The higher the PWM duty cycle, the larger the valve core opening of the electro-proportional valve, resulting in a larger pump displacement and a larger tilt angle amplitude of the tilt sensor. The PID controller's PID control adjustment is performed periodically, continuously based on the difference between the target value and the actual value. After PID control adjustment, the pump's output displacement reaches the target value. Based on the current pressure and torque at the pump outlet, the system switches between pressure cut-off mode, constant power regulation mode, and electro-proportional regulation mode.

6. The pump displacement control method based on PWM duty cycle adjustment according to claim 5, characterized in that, The PID controller is a variable speed integral PID controller.

7. A pump displacement control system based on PWM duty cycle adjustment, characterized in that, The system is used to implement the pump displacement control method according to claim 1, including: The system includes a pump controller, tilt sensor, pressure sensor, and electro-proportional valve. The pump controller is a digital pump module with an integrated PID controller. It receives the target displacement from the vehicle controller or host computer for displacement control and uses a specific chip with its TIM port configured in PWM mode. The tilt sensor performs voltage and current sampling, and the pressure sensor collects the pump pressure. The digital pump module collects information from the tilt and pressure sensors and combines it with the PID controller for PID control. This adjusts the PWM duty cycle, and the change in the PWM duty cycle adjusts the opening of the electro-proportional valve, allowing the pump to switch between pressure cut-off mode, constant power regulation mode, and electro-proportional regulation mode to control the pump displacement. The digital pump module includes: an MCU, a power management module, a CAN module, a power output module, and an analog input module. The MCU is the main controller, the power management module supplies power to the MCU, CAN module, power output module, and analog input module, the CAN module is used to send and receive CAN data and transmit it to the MCU, the MCU sends control signals to the power output module, and the power output module performs PWM output, and the analog input module sends the acquired tilt sensor and pressure sensor signal data to the MCU, which then performs signal data analysis.

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