Closed-loop control motor-driven ball screw reciprocating pump and control method

Abstract

The application relates to the technical field of reciprocating pump control, in particular to a closed-loop control motor-driven ball screw reciprocating pump and a control method, which mainly comprises that a pressure sensor is connected to the outlet of the liquid end module; the pressure sensor, a motor controller, a rotary transformer and a position sensor are electrically connected with a central controller; the central controller is used for outputting a control signal for rotating the driving motor to the motor controller; and the motor controller is used for controlling the driving motor to operate. The above scheme removes the brake, avoids the disadvantages caused by the brake, and in the prior art, the wear of the brake pad and the inertia problem of the brake can make the brake system impossible to be implemented in the industry of the reciprocating pump. In the application, the central controller is used for digitally and accurately controlling the speed, position and thrust of the reciprocating pump device, so that the ball screw reciprocating pump with the structure can be used in the industry.

Description

Technical Field

[0001] This invention relates to the field of equipment control technology, and more specifically, to a closed-loop control method for a motor-driven ball screw reciprocating pump. Background Technology

[0002] Traditional reciprocating pumps use a crank-connecting rod structure to drive a piston or plunger, achieving reciprocating motion through several strokes. Existing technology has improved this by using the rotational motion of an electric motor to achieve the reciprocating motion of a lead screw. Specifically, referring to CN112503153A, a device and method for achieving reciprocating motion of a fracturing pump through the rotation of a lead screw and nut is described. The device includes a brake B, gear B, gear C, lead screw and nut B, a motor, and lead screw B. Gear C is connected to the power output end of the motor and meshes with gear B. The lead screw and nut B are fitted onto the lead screw and nut B, and the brake B cooperates with the lead screw and nut B. This device achieves the reciprocating motion of the fracturing pump through the rotation of the lead screw and nut. This solution reduces the rotational inertia during commutation, resulting in less commutation impact when driving at a constant speed.

[0003] In practice, the above scheme decelerates the vehicle by braking and then reverses the rotation. However, this method is difficult to implement in actual use because, under conditions of high inertia and high speed, the analog-controlled brake is difficult to accurately control the movement position. In addition, the brake inevitably experiences wear and heat due to friction, which increases the failure rate and requires regular maintenance. Furthermore, the brake structure is too bulky and occupies a large space. It also has a certain response time during operation, i.e., a delay. Since the reciprocating pump requires repeated starting and stopping of the brake, it puts a heavy burden on the mechanical device and accumulates a large positional deviation. Summary of the Invention

[0004] The purpose of this invention is to provide a closed-loop control method for a motor-driven ball screw reciprocating pump to solve the above-mentioned problems in the prior art.

[0005] This invention is achieved through the following technical solution:

[0006] In a first aspect, a closed-loop controlled motor-driven ball screw reciprocating pump includes several sets of drive modules connected to a hydraulic end module. Each drive module includes a position sensor, a central controller, a power unit, and a transmission unit. The power unit is connected to the hydraulic end module through the transmission unit and is used to drive the transmission unit to perform reciprocating motion. A pressure sensor is connected to the outlet of the hydraulic end module, and the position sensor is used to collect the position data of the transmission unit.

[0007] The power unit includes a motor controller, a gear set, a drive motor, a ball screw, and a rotary transformer. The pressure sensor, motor controller, rotary transformer, and position sensor are electrically connected to the central controller. The central controller outputs a control signal to the motor controller to rotate the drive motor. The motor controller controls the operation of the drive motor. The drive motor is connected to the ball screw via the gear set, and one end of the ball screw is connected to the transmission unit.

[0008] Preferably, the gear set includes a first gear, a second gear, and two third gears. The first gear is connected to the output end of the drive motor and meshes with the second gear. The second gear is rotatably connected to the bearing housing via a rotating shaft and meshes with only one of the third gears. The two third gears are meshed together.

[0009] The ball screw includes a screw rod, a screw rod nut, and balls. The third gear is fixedly connected to the screw rod nut. The screw rod is located inside the screw rod nut. A threaded raceway is provided inside the screw rod nut. The balls are arranged in the threaded raceway. The screw rod nut drives the screw rod to perform linear reciprocating motion through the balls, converting the rotational motion of the motor into the linear reciprocating motion of the screw rod.

[0010] Preferably, the transmission unit includes a plunger sleeve and a plunger, one end of the plunger being connected to the lead screw, and the other end being located within the plunger sleeve and moving.

[0011] Secondly, the present invention also provides a closed-loop control method for a motor-driven ball screw reciprocating pump, comprising the aforementioned closed-loop control method for a motor-driven ball screw reciprocating pump, wherein the central controller is used to output a control signal to the motor controller to rotate the drive motor, comprising:

[0012] After obtaining the power-on signal of the device, the lead screw on the same side in each group of drive modules is set as the target lead screw, the position data of the target lead screw is obtained, and the position difference threshold and error threshold between adjacent target lead screws are set.

[0013] Based on position data, position difference threshold and error threshold, it is determined whether the position difference condition between the two target lead screws is met. If the position difference condition is met, the target displacement is obtained to calculate the motor speed, and the calculated motor speed value is sent to the motor controller of each drive motor.

[0014] If the position difference condition is not met, the adjustment value is obtained, one of the target lead screws of the drive module is selected as the reference lead screw, and the motor controller is output a control signal to adjust the position of other lead screws based on the adjustment value.

[0015] Preferably, the calculation of motor speed includes:

[0016]

[0017] In the formula, This refers to the displacement of a single pump unit. The total displacement of the system. Where is the plunger radius. Let be the lead of the lead screw. Where m is the motor speed, and m is the number of lead screw assemblies. This represents the transmission ratio of the gear set.

[0018] In the formula, The target displacement of the pump, Where is the plunger radius. Let be the lead of the lead screw. The number of strokes per minute. This refers to the motor speed. This represents the transmission ratio of the gear set.

[0019] Preferred options also include:

[0020] The current real-time speed of the motor is obtained by using a rotary transformer, and the current displacement of the hydraulic end module is obtained at the same time. The difference between the current displacement and the target displacement is calculated.

[0021] The motor speed for the next cycle is calculated based on the difference.

[0022] Preferably, the drive motor is provided in i groups, and the calculation of the speed of the i groups of motors includes:

[0023] When i=1:

[0024]

[0025] When i is greater than 1:

[0026] When the i-th group of motors is in the acceleration or constant speed phase:

[0027]

[0028] When the i-th group of motors is in the deceleration phase:

[0029]

[0030] in, ;

[0031] In the formula, , … Let be the rotational speed of the first to the i-th drive motor in the next cycle. , … For each reciprocating motion, the predicted velocity value of the current position in the position-velocity control mode. The reference parameter for speed adjustment, Let be the position difference threshold between the target lead screw and the reference lead screw in the i-th group. Let be the position difference between the first target lead screw and the i-th target lead screw. , … Let be the proportional gain of the PID control for the first to the ith drive motor. This represents the difference between the rotational speed in the k-th cycle and the target rotational speed. The integral gain for the first drive motor PID control. The sampling period is the time interval between two output calculations by the controller. For the position data of the i-th lead screw, The position data of the reference lead screw. The current number of operating cycles of the reference leadscrew. Let i be the current number of operating cycles of the i-th leadscrew. This represents the total stroke of a single end of the leadscrew.

[0032] Preferred options also include:

[0033] The first pump pressure of the hydraulic end module is obtained through the pressure sensor, the torque value of the motor is obtained through the motor controller, and the theoretical second pump pressure is calculated based on the torque value.

[0034] Set a safe pump pressure threshold, obtain a first difference based on the first pump pressure and the safe pump pressure threshold, and obtain a second difference based on the second pump pressure and the safe pump pressure threshold;

[0035] Several judgment thresholds are set, and the current diagnosis result is output based on the first difference, the second difference, and several judgment thresholds.

[0036] Preferably, the step of outputting the current diagnostic result through a first difference, a second difference, and several judgment thresholds includes:

[0037] Set the first pump pressure threshold, the second pump pressure threshold, and the third pump pressure threshold;

[0038] Determine whether there is a first difference greater than or equal to the third pump pressure threshold, or a second difference greater than or equal to the third pump pressure threshold. If so, send a control signal for emergency system shutdown.

[0039] If not, determine whether there is a first difference greater than or equal to the second pump pressure threshold, or whether the second difference is greater than or equal to the second pump pressure threshold. If so, then issue a deceleration constant pressure control signal.

[0040] If not, determine whether there is a first difference greater than or equal to the second pump pressure threshold, or a second difference greater than or equal to the second pump pressure threshold. If yes, send an alarm signal; otherwise, the system operates normally.

[0041] Preferably, the control signal output by the motor controller based on the adjustment value to adjust the position of other lead screws includes:

[0042] After the positions of the remaining lead screws are adjusted, the position data of the target lead screw on the same side is acquired again to obtain the position difference data. If the position difference condition is met, the target displacement is acquired to calculate the motor speed. If the position difference condition is not met within the operating cycle or preset time period, a fault signal is sent to the central controller.

[0043] The technical solution of the present invention has at least the following advantages and beneficial effects:

[0044] The structure provided by this invention mainly includes a pressure sensor connected to the outlet of the hydraulic end module; the pressure sensor, motor controller, rotary transformer, and position sensor are electrically connected to the central controller. The central controller outputs a control signal to the motor controller to rotate the drive motor, and the motor controller controls the operation of the drive motor. This solution eliminates the need for brakes, avoiding the drawbacks associated with them. In existing technologies, issues such as brake pad wear and braking inertia make braking systems unusable in the industrial application of reciprocating pumps. However, this invention achieves industrial application of this type of ball screw reciprocating pump by using a central controller for fully digital and precise control of the speed, position, and thrust of the reciprocating pump. Attached Figure Description

[0045] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0046] Figure 1 This is a schematic diagram of the system structure of the present invention;

[0047] Figure 2 This is a schematic diagram of the control flow of the central controller of the present invention;

[0048] Figure 3 This is a schematic diagram of the power unit of the present invention;

[0049] Figure 4 This is a schematic diagram of the plunger sleeve of the present invention;

[0050] Figure 5 This is a schematic diagram of the overall structure of the present invention.

[0051] Icons: 1-Drive motor, 2-Resolver, 3-Lead screw, 4-Ball bearing, 5-Lead screw nut, 6-Third gear, 7-Second gear, 8-First gear, 9-Plunger, 10-Plunger sleeve, 11-Hydraulic end module, 12-Power unit. Detailed Implementation

[0052] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0053] The module division in this application is a logical division. In actual application, there may be other division methods. For example, multiple modules may be combined into or integrated into another system, or some features may be ignored or not executed.

[0054] In addition, the connection, coupling or communication in this application can be a direct connection, coupling or communication between related objects, or an indirect connection, coupling or communication through other devices. Furthermore, the connection, coupling or communication between objects can be electrical or other similar forms, and no limitation is made in this application.

[0055] Please refer to Figures 1-5 This invention provides a closed-loop controlled motor-driven ball screw reciprocating pump, comprising several sets of drive modules connected to a hydraulic end module 11. Each drive module includes a position sensor, a central controller, a power unit 12, and a transmission unit. The power unit 12 is connected to the hydraulic end module 11 via the transmission unit and is used to drive the transmission unit to perform reciprocating motion. A pressure sensor is connected to the outlet of the hydraulic end module 11. The position sensor is used to collect the position data of the transmission unit. The position sensor is mounted on the transmission unit and can be mounted on a plunger to measure the movement distance of the plunger.

[0056] The hydraulic end module includes conventional structures such as a cylinder body and cylinder liner, an intake valve and an exhaust valve, and a sealing device, which will not be described in detail in this embodiment.

[0057] The power unit 12 includes a motor controller, a gear set, a drive motor 1, a ball screw, and a rotary transformer 2. The pressure sensor, motor controller, rotary transformer 2, and position sensor are electrically connected to the central controller. The central controller is used to output a control signal to the motor controller to rotate the drive motor 1. The motor controller is used to control the operation of the drive motor 1. The drive motor 1 is connected to the lead screw 3 through the gear set. One end of the lead screw 3 is connected to the transmission unit.

[0058] Specifically, the central controller reads data from various sensors, reads the parameters of the three drive motors 1 and their controllers, sends control commands to the three motor controllers, calculates the speed and position of the lead screw and the motor, and performs other related logic and data processing.

[0059] Rotary transformer 2: Coaxially mounted on the motor shaft, used for reading the motor position and calculating the motor speed.

[0060] Motor controller: The motor controller is mainly used to control the position, torque, speed and acceleration of the drive motor 1, receive control commands from the central controller, and at the same time feed back relevant parameters of the motor controller body (such as temperature, faults, etc.) and the speed, position and torque of the drive motor 1.

[0061] Position sensor: used for lead screw position correction and safe travel protection, and feeds back to the central controller. One sensor is configured for each group of lead screws.

[0062] Pressure sensor: Used to detect the liquid pressure at the output terminal of a reciprocating pump.

[0063] The structure provided by this invention mainly includes a pressure sensor connected to the outlet of the hydraulic end module 11; the pressure sensor, motor controller, rotary transformer 2, and position sensor are electrically connected to the central controller, which outputs a control signal to rotate the drive motor 1 to the motor controller, which controls the operation of the drive motor 1. This solution eliminates the need for brakes, avoiding the drawbacks associated with them. In existing technologies, both brake pad wear and braking inertia make braking systems unusable in the industrial application of reciprocating pumps. However, this invention achieves industrial application of this type of ball screw reciprocating pump by using a central controller for fully digital and precise control of the speed, position, and thrust of the reciprocating pump.

[0064] In one exemplary embodiment of the present invention, the gear set includes a first gear 8, a second gear 7, and two third gears 6. The first gear 8 is connected to the output end of the drive motor 1 and meshes with the second gear 7. The second gear 7 is rotatably connected to a bearing seat via a rotating shaft and meshes with only one of the third gears 6. The two third gears 6 are meshed together.

[0065] The ball screw includes a screw 3, a screw nut 5, and balls 4. A third gear 6 is fixedly connected to the screw nut 5. The screw 3 is located inside the screw nut 5. The screw nut 5 has a threaded raceway. The screw nut 5 drives the screw 3 to perform linear reciprocating motion through the balls 4, converting the rotational motion of the drive motor 1 into the linear reciprocating motion of the screw 3.

[0066] In one exemplary embodiment of the present invention, the transmission unit includes a plunger sleeve 10 and a plunger 9, one end of the plunger 9 is connected to the lead screw 3, and the other end is located within the plunger sleeve 10 and moves.

[0067] In use, the two third gears 6 form a pair that rotate in both directions, thereby driving the plunger 9 to perform reciprocating pumping work; the reciprocating pump is operated by converting the rotational motion of the drive motor 1 into the linear reciprocating motion of the lead screw 3 through this device.

[0068] Secondly, the present invention also provides a closed-loop control method for a motor-driven ball screw reciprocating pump, comprising the aforementioned closed-loop control method for a motor-driven ball screw reciprocating pump, wherein the central controller is used to output a control signal to the motor controller to rotate the drive motor, comprising:

[0069] S101: After obtaining the power-on signal of the device, set the lead screw on the same side in each group of drive modules as the target lead screw, obtain the position data of the target lead screw, and set the position difference threshold and error threshold between adjacent target lead screws;

[0070] Understandably, in the same drive module, there are two sets of lead screws. When comparing and calculating the position difference, the lead screw on the same side is used. For example, the position data of the lead screw located on the left side of the same drive module is used for subsequent calculations.

[0071] S102: Based on position data, position difference threshold and error threshold, determine whether the position difference condition is met between the two target lead screws. If the position difference condition is met, obtain the target displacement to calculate the motor speed and send the calculated motor speed value to the motor controller of each drive motor.

[0072] Specifically, the lead screw in the first drive module is set as the reference lead screw to determine whether other lead screws meet the position difference condition;

[0073] Secondly, the current position conversion: Since the lead screw reciprocates, there are the same position points in both directions. For ease of understanding and calculation: Assume that when the motor rotates clockwise, the lead screw position is 0->L; when the motor rotates counterclockwise, the lead screw position is L->2L. L is the total stroke of a single end of the lead screw.

[0074]

[0075] In the formula, Let be the positional difference between the i-th target lead screw and the reference lead screw. For the position data of the i-th lead screw, The position data of the reference lead screw. Let the position difference threshold between the target lead screw and the reference lead screw in the i-th group be denoted as . The current number of operating cycles of the reference leadscrew. Let i be the current number of operating cycles of the i-th leadscrew. This represents the total stroke of a single end of the leadscrew.

[0076] when If the error is less than or equal to the error threshold, the output meets the position difference condition; otherwise, it does not meet the position difference condition.

[0077] S103: If the position difference condition is not met, obtain the adjustment value, select one of the target lead screws of the drive module as the reference lead screw, and output a control signal to the motor controller to adjust the position of other lead screws based on the adjustment value.

[0078] Specifically, the central controller sends the calculated positions to be adjusted for lead screw groups #2 and #3, as well as the preset motor speed (e.g., 20 rpm), to drive motor controllers #2 and #3 respectively.

[0079] After receiving the control command, the #2 and #3 drive motor controllers control the drive motors to run at preset motor speeds to their respective target positions.

[0080] Each cycle, drive motor controllers #2 and #3 check whether their respective motors are in position. If they are, they send a feedback command to the central controller, which then checks the lead screw position again. If the lead screw position is correct, the next layer of logic control is initiated.

[0081] If the No. 2 drive motor controller and the No. 3 drive motor controller fail to reach the target position within the preset time limit (e.g., 30000ms), an over-fault is sent, and the fault is simultaneously transmitted to the central controller.

[0082] In one exemplary embodiment of the present invention, the calculation of motor speed includes:

[0083]

[0084] In the formula, This refers to the displacement of a single pump unit. The total displacement of the system. Where is the plunger radius. Let be the lead of the lead screw. Where m is the motor speed, and m is the number of lead screw assemblies. This represents the transmission ratio of the gear set.

[0085] Preferred options also include:

[0086] The current real-time speed of the motor is obtained by a rotary transformer, and the current displacement of the hydraulic end module is also obtained at the same time. The difference between the current displacement and the target displacement is calculated. The current displacement of the hydraulic end module can be calculated by the current speed of the motor or obtained by a sensor.

[0087] The motor speed for the next cycle is calculated based on the difference.

[0088] In one exemplary embodiment of the present invention, the drive motor is provided with i groups, and the calculation of the speed of the i groups of motors includes:

[0089] When i=1:

[0090]

[0091] When i is greater than 1:

[0092] When the i-th group of motors is in the acceleration or constant speed phase:

[0093]

[0094] When the i-th group of motors is in the deceleration phase:

[0095]

[0096] in, ;

[0097] It should be noted that the calculation of absolute values ​​has been removed here. The purpose is that positive and negative values ​​represent whether the speed is ahead or behind, which is related to the PID control of the speed mentioned above.

[0098] In the formula, , … Let be the rotational speed of the first to the i-th drive motor in the next cycle. , … For each reciprocating motion, the predicted velocity value of the current position in the position-velocity control mode, where the position-velocity control mode is the corresponding data collected from historical data. The reference parameter for speed adjustment, Let be the position difference threshold between the target lead screw and the reference lead screw in the i-th group. Let be the positional difference between the i-th target lead screw and the reference lead screw. , … Let be the proportional gain of the PID control for the first to the ith drive motor. This represents the difference between the rotational speed in the k-th cycle and the target rotational speed. The integral gain for the first drive motor PID control. The sampling period is the time interval between two output calculations by the controller. For the position data of the i-th lead screw, The position data of the reference lead screw. The current number of operating cycles of the reference leadscrew. Let i be the current number of operating cycles of the i-th leadscrew. This represents the total stroke of a single end of the leadscrew.

[0099] An exemplary embodiment of the present invention further includes:

[0100] The first pump pressure of the hydraulic end module is obtained through the pressure sensor, the torque value of the motor is obtained through the motor controller, and the theoretical second pump pressure is calculated based on the torque value.

[0101] Set a safe pump pressure threshold, obtain a first difference based on the first pump pressure and the safe pump pressure threshold, and obtain a second difference based on the second pump pressure and the safe pump pressure threshold;

[0102] Several judgment thresholds are set, and the current diagnosis result is output based on the first difference, the second difference, and several judgment thresholds.

[0103] Specifically, the step of outputting the current diagnostic result through the first difference, the second difference, and several judgment thresholds includes:

[0104] Set the first pump pressure threshold, the second pump pressure threshold, and the third pump pressure threshold;

[0105] Determine whether there is a first difference greater than or equal to the third pump pressure threshold, or a second difference greater than or equal to the third pump pressure threshold. If so, send a control signal for emergency system shutdown.

[0106] If not, determine whether there is a first difference greater than or equal to the second pump pressure threshold, or whether the second difference is greater than or equal to the second pump pressure threshold. If so, then issue a deceleration constant pressure control signal.

[0107] If not, determine whether there is a first difference greater than or equal to the second pump pressure threshold, or a second difference greater than or equal to the second pump pressure threshold. If yes, send an alarm signal; otherwise, the system operates normally.

[0108] In addition, the control signals output by the motor controller based on the adjustment value to adjust the position of other lead screws include:

[0109] After the positions of the remaining lead screws are adjusted, the position data of the target lead screw on the same side is acquired again to obtain the position difference data. If the position difference condition is met, the target displacement is acquired to calculate the motor speed. If the position difference condition is not met within the operating cycle or preset time period, a fault signal is sent to the central controller.

[0110] The closed-loop control system provided by this invention mainly consists of a central controller, a motor controller, a drive motor, a rotary transformer, a position sensor, and a pressure sensor. The pressure sensor acquires the initial pump pressure of the current hydraulic module. The central controller issues commands for speed, acceleration, torque, and position, as well as real-time calculation and correction commands. The motor controller executes the commands from the central controller and controls the drive motor, providing feedback on the execution results. The drive motor executes the commands from the motor controller and operates. The rotary transformer is coaxial with the drive motor, providing real-time feedback on the drive motor's speed, acceleration, and rotational position. The position sensor accurately detects and provides feedback on the starting position of the lead screw. The central controller and the motor controller, based on the feedback from the rotary transformer and position sensor, perform real-time calculations and corrections to form a closed-loop control, ensuring stable overall operation, balanced pressure, and smooth commutation of the reciprocating pump.

[0111] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0112] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. This computer software product, stored in a storage medium, includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0113] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A closed-loop control method for a motor-driven ball screw reciprocating pump, characterized in that, The central controller, which outputs control signals to the motor controller to cause the drive motor to rotate, includes: After obtaining the power-on signal of the device, the lead screw on the same side in each group of drive modules is set as the target lead screw, the position data of the target lead screw is obtained, and the position difference threshold and error threshold between adjacent target lead screws are set. Based on position data, position difference threshold and error threshold, it is determined whether the position difference condition between the two target lead screws is met. If the position difference condition is met, the target displacement is obtained to calculate the motor speed, and the calculated motor speed value is sent to the motor controller of each drive motor. If the position difference condition is not met, the adjustment value is obtained, one of the target lead screws of the drive module is selected as the reference lead screw, and the motor controller is output with a control signal to adjust the position of other lead screws based on the adjustment value; The drive motor is configured with group i. The calculation of the speed of group i motors includes: When i=1: When i is greater than 1: When the i-th group of motors is in the acceleration or constant speed phase: When the i-th group of motors is in the deceleration phase: in, ; In the formula, , … Let be the rotational speed of the first to the i-th drive motor in the next cycle. , … For each reciprocating motion, the predicted velocity value for the current position in the historical data. The reference parameter for speed adjustment, Let be the position difference threshold between the target lead screw and the reference lead screw in the i-th group. Let be the positional difference between the i-th target lead screw and the reference lead screw. , … Let be the proportional gain of the PID control for the first to the ith drive motor. This represents the difference between the rotational speed in the k-th cycle and the target rotational speed. The integral gain for the first drive motor PID control. The sampling period is the time interval between two output calculations by the controller. For the position data of the i-th lead screw, The position data of the reference lead screw. The current number of operating cycles of the reference leadscrew. Let i be the current number of operating cycles of the i-th leadscrew. This represents the total stroke of a single end of the leadscrew.

2. The closed-loop control method for a reciprocating pump driven by a ball screw according to any one of claims 1, characterized in that, The calculation of motor speed includes: In the formula, This refers to the displacement of a single pump unit. The total displacement of the system. Where is the plunger radius. Let be the lead of the lead screw. Where m is the motor speed, and m is the number of lead screw assemblies. This represents the transmission ratio of the gear set.

3. A closed-loop control method for a reciprocating pump driven by a ball screw according to any one of claims 2, characterized in that, Also includes: The current real-time speed of the motor is obtained by using a rotary transformer, and the current displacement of the hydraulic end module is obtained at the same time. The difference between the current displacement and the target displacement is calculated. The motor speed for the next cycle is calculated based on the difference.

4. A closed-loop control method for a reciprocating pump driven by a ball screw according to any one of claims 3, characterized in that, Also includes: The first pump pressure of the hydraulic end module is obtained through the pressure sensor, the torque value of all motors is obtained through the motor controller, and the theoretical second pump pressure is calculated based on the torque value. Set a safe pump pressure threshold, obtain a first difference based on the first pump pressure and the safe pump pressure threshold, and obtain a second difference based on the second pump pressure and the safe pump pressure threshold; Several judgment thresholds are set, and the current diagnosis result is output based on the first difference, the second difference, and several judgment thresholds.

5. A closed-loop control method for a reciprocating pump driven by a ball screw according to any one of claims 4, characterized in that, The step of outputting the current diagnostic result through the first difference, the second difference, and several judgment thresholds includes: Set the first pump pressure threshold, the second pump pressure threshold, and the third pump pressure threshold; Determine whether there is a first difference greater than or equal to the third pump pressure threshold, or a second difference greater than or equal to the third pump pressure threshold. If so, send a control signal for emergency system shutdown. If not, determine whether there is a first difference greater than or equal to the second pump pressure threshold, or whether the second difference is greater than or equal to the second pump pressure threshold. If so, then issue a deceleration constant pressure control signal. If not, determine whether there is a first difference greater than or equal to the second pump pressure threshold, or a second difference greater than or equal to the second pump pressure threshold. If yes, send an alarm signal; otherwise, the system operates normally.

6. The closed-loop control method for a reciprocating pump driven by a ball screw according to claim 1, characterized in that, The control signal output by the motor controller based on the adjustment value to adjust the position of other lead screws includes: After the positions of the remaining lead screws are adjusted, the position data of the target lead screw on the same side is acquired again to obtain the position difference data. If the position difference condition is met, the target displacement is acquired to calculate the motor speed. If the position difference condition is not met within the operating cycle or preset time period, a fault signal is sent to the central controller.

7. A closed-loop controlled motor-driven ball screw reciprocating pump, used to execute the closed-loop controlled motor-driven ball screw reciprocating pump control method according to claim 1, comprising a plurality of drive modules connected to a hydraulic end module, characterized in that, The drive module includes a position sensor, a central controller, a power unit, and a transmission unit. The power unit is connected to the hydraulic end module through the transmission unit. The power unit is used to drive the transmission unit to perform reciprocating motion. A pressure sensor is connected to the outlet of the hydraulic end module. The position sensor is used to collect the position data of the transmission unit. The power unit includes a motor controller, a gear set, a drive motor, a ball screw, and a rotary transformer. The pressure sensor, motor controller, rotary transformer, and position sensor are electrically connected to the central controller. The central controller outputs a control signal to the motor controller to rotate the drive motor. The motor controller controls the operation of the drive motor. The drive motor is connected to the ball screw via the gear set, and one end of the ball screw is connected to the transmission unit.

8. A closed-loop controlled motor-driven ball screw reciprocating pump according to claim 7, characterized in that, The gear set includes a first gear, a second gear, and two third gears. The first gear is connected to the output end of the drive motor and meshes with the second gear. The second gear is rotatably connected to the bearing housing via a rotating shaft and meshes with only one of the third gears. The two third gears are meshed together. The ball screw includes a screw rod, a screw rod nut, and balls. The third gear is fixedly connected to the screw rod nut. The screw rod is located inside the screw rod nut. A threaded raceway is provided inside the screw rod nut. The balls are arranged in the threaded raceway. The screw rod nut drives the screw rod to perform reciprocating linear motion through the balls, converting the rotational motion of the drive motor into the linear reciprocating motion of the screw rod.

9. A closed-loop controlled motor-driven ball screw reciprocating pump according to claim 8, characterized in that, The transmission unit includes a plunger sleeve and a plunger. One end of the plunger is connected to the lead screw, and the other end moves within the plunger sleeve.

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