Ultramicro peristaltic pump system

Abstract

The invention belongs to the technical field of pumps, and provides an ultramicro peristaltic pump system which comprises a motion conversion mechanism, a linear actuator, a linear displacement sensor and a peristaltic pump head. The motion conversion mechanism is configured to be driven to convert rotary motion into linear motion to be output; the linear actuator is driven by the motion conversion mechanism to realize linear reciprocating motion; the linear displacement sensor is parallel to the motion direction of the linear actuator and is used for measuring the absolute linear position of the linear actuator; and the peristaltic pump head is mounted on the linear actuator and is used for controlling a pump pipe to form a continuously propelled compression wave so as to realize pumping of fluid. According to the invention, high-precision and pulseless driving of the fluid is realized.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of pumps, and relates to a perfusion pump system, in particular to an ultramicro peristaltic pump system. BACKGROUND

[0002] In the application background of ultramicro fluid dispensing, the existing peristaltic pump technology based on rotary encoder control, although mature in macro fluid delivery, exposes the following four fundamental and difficult-to-overcome technical defects when pursuing nanoliter-level precision, repeatability and dynamic control capability:

[0003] 1. Indirectness of control and error accumulation effect

[0004] Problem description: The control closed loop of the traditional scheme is established on the motor shaft, and the controller accurately knows "how many degrees the motor has rotated", but the actual position of the final execution end, i.e. the pump head pressure roller, is "guessed". There is a long mechanical transmission chain (reduction gear box, shaft coupling, pump head mounting structure, etc.) between the motor and the pressure roller. The machining tolerance, assembly error, running vibration and thermal expansion and contraction of each link are continuously accumulated in this chain, finally resulting in a significant and unpredictable deviation between the actual movement of the pump head pressure roller and the theoretical calculation value. In nanoliter dispensing, this small deviation is enough to cause a huge failure of the dispensing volume.

[0005] 2. Fatal influence of mechanical backstroke error

[0006] Problem description: When the "dispensing-backsuction" action needs to be performed to prevent dripping, the motor needs to be reversely rotated. Due to the inevitable gap (i.e. backstroke error or backlash) between the teeth of the reduction gear box, the slight reverse rotation of the motor will not be immediately transmitted to the pump head, but will first "idle" in the gear gap. The existence of this "idle stroke" makes it impossible to perform an accurate backsuction action. As a result, either the backsuction is insufficient, resulting in dripping, volume error and cross contamination, or the backsuction is excessive, sucking in air bubbles, which has a disastrous impact on subsequent dispensing.

[0007] 3. Limited volume resolution and inherent pulsation

[0008] Problem description: The minimum dispensable volume of the system is limited by the minimum stepping angle of the driving motor (such as a stepper motor) and the number of pulses per revolution (PPR) of the rotary encoder. This physical resolution is fixed and cannot be infinitely improved. For example, a high-resolution system may have a minimum driving unit corresponding to 10 nanoliters, so it can never accurately dispense a volume of 3 nanoliters. In addition, the discontinuity of motor rotation (stepping) and the periodic rolling of the pump head pressure roller together cause the pulsation of the output fluid. At the micro level, this pulsation seriously interferes with the laminar flow state in the microfluidic chip, affecting the stability of biochemical reactions.

[0009] 4. Poor dynamic response and single control mode

[0010] Problem description: Due to the existence of long transmission chain and large moment of inertia, the traditional peristaltic pump system has a delay in response to control instructions, and it is difficult to quickly and accurately perform complex speed change or start-stop tasks. Its control mode is usually single "constant speed delivery", which cannot be programmed to achieve advanced fluid operations, such as dynamically adjusting the flow rate according to sensor feedback, or generating a specific flow waveform, which greatly limits its application in advanced automated experimental processes.

[0011] In summary, developing an ultra-micro dispensing system is a key direction to break through the bottleneck of existing technology. SUMMARY

[0012] In order to overcome the shortcomings of the prior art, an ultra-micro peristaltic pump system is provided, which realizes high-precision and pulse-free driving of fluid through innovative mechatronic design.

[0013] An ultra-micro peristaltic pump system includes a motion conversion mechanism, a linear actuator, a linear displacement sensor, and a peristaltic pump head;

[0014] The motion conversion mechanism is configured to be driven to convert rotary motion into linear motion output;

[0015] The linear actuator is driven by the motion conversion mechanism to realize linear reciprocating movement;

[0016] The linear displacement sensor is arranged in parallel with the motion direction of the linear actuator and is used to measure the absolute linear position of the linear actuator;

[0017] The peristaltic pump head is installed on the linear actuator and is used to control the pump tube to form a continuous advancing compression wave and realize fluid pumping.

[0018] Further, the motion conversion mechanism includes a cam, a follower, a movable rod, and a spring; the cam is driven to rotate, the cam is in contact with the follower, the follower is connected with the movable rod, and the spring is arranged on the follower; the rotation of the cam and the restoring force of the spring can drive the movable rod to move linearly.

[0019] Further, the linear displacement sensor is a linear grating ruler.

[0020] Further, the peristaltic pump head is a wedge cam.

[0021] Further, the motion conversion mechanism is driven by a servo motor.

[0022] The beneficial effects of the present application compared with the prior art are:

[0023] 1. By converting the rotational motion of the peristaltic pump into linear motion, and detecting the displacement of the linear motion using a linear grating ruler, the grating ruler can better reflect the pump's motion and has higher monitoring accuracy, thus improving the accuracy of the pump's flow control.

[0024] 2. Submicron-level drive control: This solution uses a linear grating ruler to achieve submicron-level displacement control of the linear actuator. This tiny linear displacement has a more direct and precise correspondence with the tiny volume change of the compressed pump tube.

[0025] 3. Eliminate the influence of backlash error: During use, the system can completely compensate for the backlash error of the mechanical transmission chain through the closed-loop feedback of the grating ruler, ensuring that the "push stroke" allocated each time is absolutely accurate, which is something that traditional semi-closed-loop rotary encoders cannot do.

[0026] 4. Precise distribution mode: Linear drive can achieve very complex motion patterns, such as "forward 5 micrometers, pause for 10 milliseconds, retreat 0.5 micrometers (decompression)", to achieve drip-free precise distribution.

[0027] The present invention will be further described below with reference to the accompanying drawings and embodiments: Attached Figure Description

[0028] Figure 1 This is a perspective view of the ultra-micro peristaltic pump system of the present invention;

[0029] Figure 2 This is a side view of the ultra-micro peristaltic pump system of the present invention;

[0030] Figure 3 A schematic diagram of the mechanism for the New Year's Day transition;

[0031] Figure 4 This is a schematic diagram showing the connection between the slider and the wedge cam.

[0032] Figure 5 Diagram showing the contact state between the pump pipe and the wedge-shaped cam when the pump pipe is arranged at an angle;

[0033] Figure 6 This diagram illustrates the state of the pump being pumped by a wedge-shaped cam when the pump pipe is arranged at an angle. Detailed Implementation

[0034] The embodiments of the technical solutions of this application will now be described in detail with reference to the accompanying drawings. Unless otherwise stated, the technical or scientific terms used in this application have the ordinary meanings understood by those skilled in the art.

[0035] Example 1, Reference Figure 1 and Figure 2The ultramicro peristaltic pump system of the embodiment comprises a motion conversion mechanism 1, a linear actuator 2, a linear displacement sensor 3 and a peristaltic pump head 4.

[0036] The motion conversion mechanism 1 is configured to be driven to convert rotary motion into linear motion output.

[0037] A high-response servo motor is used as the driving source. Compared with a stepper motor, the servo motor is controlled in a closed loop by an encoder, runs very smoothly, has no step loss problem, can provide high dynamic response and accurate torque control.

[0038] The high-speed rotary motion of the servo motor is converted by the motion conversion mechanism 1 into smooth and gap-free linear reciprocating motion of the linear actuator 2.

[0039] Referring to Figure 3 The motion conversion mechanism 1 comprises a cam 11, a follower 12, a movable rod 13 and a spring 14. The cam 11 is rotatably driven by the servo motor 8, the cam 11 is in contact with the follower 12, the follower 12 is connected with the movable rod 13, the movable rod 13 is slidably arranged on the base 7, the spring 14 is arranged between the follower 12 and the base 7 and abuts against the base 7, the spring 14 is sleeved on the movable rod 13, and the rotation of the cam 11 and the restoring force of the spring 14 can drive the movable rod 13 to move linearly.

[0040] The servo motor 8 drives the cam 11 to rotate, the cam 11 rotates to the maximum point, the follower 12 is driven to move linearly, at this time the spring 14 is compressed, the cam 11 continues to rotate to disengage from the follower 12, at this time the spring 14 resets, and drives the follower 12 and the movable rod 13 to retreat under the action of the restoring force, and the fluid is pumped during the retreat process.

[0041] The linear actuator 2 adopts a slider or a slide, which is installed at the end of the movable rod 13 and serves as the final operation execution member.

[0042] The linear displacement sensor 3 adopts a linear grating ruler, which is located directly above the pump pipe 5 and is installed on the base 7. A high-resolution absolute linear grating ruler is used, the ruler scale is fixed on the base 7 and is arranged in parallel with the movement direction of the slider or slide, and the reading head is fixed on the slider and moves synchronously with the slider. The grating ruler can measure the absolute linear position of the slider relative to the base in real time and non-contact, and the resolution can reach 0.1 microns or even higher.

[0043] Referring to Figure 4The peristaltic pump head 4 is a wedge-shaped cam, installed on one side of the bottom of the slider or slide table (the inlet pipe has a wedge-shaped cam, the outlet pipe does not), used to control the pump pipe 5 to form a continuously advancing compression wave, realizing the pumping of fluid. In use, the pump pipe 5 is arranged at an angle under the support of the fixed seat, forming a wedge-shaped structure with the wedge-shaped cam. The wedge-shaped cam mainly consists of a wedge-shaped element and a fixed wheel, with the fixed wheel installed at the lower end of the wedge-shaped element. Figure 1 , 5 and Figure 6 The servo motor 8 drives the cam 11 to rotate. When the cam 11 rotates to its maximum point, it drives the follower 12 to move linearly, and the slider or slide table moves linearly along the path. The wedge cam disengages and releases the pump tube 5. At the same time, the spring 14 is compressed, and the cam 11 continues to rotate and disengage from the follower 12. At this time, the spring 14 returns to its original position, and under the action of the restoring force, it drives the follower 12 and the movable rod 13 to retract. The slider moves along the path... Figure 5 and Figure 6 The arrow moves linearly in the direction of motion, and the surface of the wedge cam 4 will press down the pump tube 5 smoothly in sequence, forming a continuously advancing compression wave, thereby realizing the pumping of fluid. The liquid moves from the inlet to the outlet.

[0044] This embodiment proposes an improved filling pump structure that converts the rotational motion of a peristaltic pump into linear motion and detects the displacement of this linear motion using a grating ruler. Since the grating ruler better reflects the pump's movement, it offers higher monitoring accuracy and improves the accuracy of flow control. In applications requiring extremely low flow rates, such as nanoliters (nL) or even picoliters (pL), traditional peristaltic pumps achieve this by controlling minute rotational angles, but this is susceptible to issues such as motor stepping errors and gear backlash. This embodiment achieves sub-micron level displacement control of the linear actuator.

[0045] Example 2: The peristaltic pump system in this example also integrates a controller with advanced motion control algorithms. As the system's brain, it connects to the host computer, servo motor driver, and linear encoder to achieve signal feedback.

[0046] The complete closed-loop control process, with the following specific steps:

[0047] Step 1: Command Parsing and Trajectory Planning. The user sets a target flow rate, such as "100 nL / min", through the host computer software. After receiving this command, the controller 6 first parses it into a speed command for the slider 2, such as "0.1 mm / min", based on the mechanical design parameters of the pump head (e.g., the pumping volume corresponding to each 1 mm movement of the slider 2). Subsequently, the controller internally generates a precise, time-driven target position trajectory curve P_target(t).

[0048] Second step: real-time position feedback, in every control cycle of the system (usually with a frequency of thousands of hertz, i.e. thousands of times per second), the linear grating ruler 3 will accurately measure the current actual position P_actual of the slider and feed back this high-precision data to the servo control core in real time.

[0049] Third step: the dynamic error calculation controller compares the target position P_target at the current time with the feedback actual position P_actual, and calculates the extremely small position error Error = P_target - P_actual.

[0050] Fourth step: PID algorithm and command correction, the position error will be input into an optimized PID (proportional-integral-derivative) control algorithm. The algorithm will calculate an optimal compensation command according to the size, duration and trend of the error.

[0051] If P_actual lags behind P_target (i.e. the movement is slow), the controller will immediately increase the drive voltage / current given to the servo motor to make it accelerate to catch up.

[0052] If P_actual is ahead of P_target (i.e. the movement is too fast), the controller will reduce the drive output or even apply a reverse braking force to make it slow down and wait.

[0053] Fifth step: command execution and cycle, the corrected drive command is sent to the servo driver, and the motor accurately executes it to drive the slider to move towards the target position. Immediately, the system enters the next control cycle and repeats steps two to five.

[0054] The linear grating ruler closed-loop control-based ultra-micro dispensing system proposed in Embodiment 2 perfectly solves all the defects of the prior art by fundamentally changing the position of the sensor and the control logic:

[0055] 1. Full closed-loop direct position control, eliminating error accumulation

[0056] Technical advantage: The high-precision linear grating ruler is directly installed in the linear actuator area to achieve full closed-loop direct measurement of the position of the execution end. The controller no longer cares about “how many the motor has rotated”, but about “where the actual linear position of the slider is”. No matter how the transmission chain deforms, vibrates or has tolerances, the servo controller will force the motor to make real-time compensation to ensure that the position of the slider closely tracks the target curve at any time with sub-micron accuracy. This breaks the chain of error accumulation and establishes the shortest and most reliable path from the control command to the final mechanical movement.

[0057] 2. Real-time return stroke error compensation, perfect "zero-droplet" return

[0058] Technical advantage: When the controller issues a reverse return stroke command (e.g. 0.5 micron back), the linear encoder will immediately detect the "slider not moving" phenomenon due to the existence of gear backlash. The servo system will instantly identify this as a huge position error and immediately increase the motor torque to eliminate the backlash at high speed until the actual position feedback from the encoder matches the target position. The mechanical return stroke error is actively and completely compensated by the controller in real time. This enables the system to accurately perform the micron-level return stroke action required after nanoliter dispensing with extremely high repeatability, thereby achieving perfect "zero-droplet" and "zero-bubble" dispensing.

[0059] 3. Infinite theoretical resolution, smooth and pulse-free flow

[0060] Technical advantage: The volumetric resolution of the system depends only on the resolution of the linear encoder. With commercially available 0.1 micron or even higher resolution encoders, the system can achieve theoretically infinite fine displacement control. This makes it possible to dispense picoliter (pL) or even femtoliter (fL) volumes at the drive level. More importantly, the servo system based on continuous position feedback for smooth PID adjustment, converts the stepping motion or rotational pulsation of the motor into highly smooth and stable linear advancement on the linear slider, thereby greatly suppressing flow pulsation and providing high-quality stable laminar flow for microfluidic chip applications.

[0061] 4. High dynamic response and programmability, advanced fluid manipulation

[0062] Technical advantage: Based on high-speed servo controller and linear encoder direct feedback, the system has high dynamic response capability. Users can freely program complex "displacement-time" curves like writing code to achieve various advanced fluid manipulation functions: for example, "push-pull" type pulsatile delivery for handling high-viscosity liquids; gentle "trapezoidal" acceleration-deceleration curves for cell screening; and complex waveforms for precise control of instantaneous flow ratio for drug mixing. This application upgrades peristaltic pumps from a simple delivery tool to a multifunctional, software-defined "flow waveform generator".

[0063] Through this uninterrupted high-speed closed-loop cycle of "planning-measuring-comparing-correcting" thousands of times per second, the application ensures that the actual motion trajectory of the linear actuator can unconditionally and mandatorily reproduce the target trajectory curve planned inside the controller with sub-micron accuracy. Any disturbance from the outside, such as changes in mechanical friction, slight vibrations, or even thermal expansion and contraction of the ball screw itself, will be immediately identified as a position error and dynamically compensated and eliminated by the servo system within milliseconds. This fundamentally guarantees the long-term stability and accuracy of the flow output.

[0064] The application has been disclosed above with preferred embodiments, but is not intended to limit the application. Any person skilled in the art can make minor changes or modifications to the above disclosed structures and technical contents without departing from the scope of the application, and equivalent embodiments with equivalent changes are also included in the scope of the application.

Claims

1. An ultra-micro peristaltic pump system, characterized by: The motion conversion mechanism (1), the linear actuator (2), the linear displacement sensor (3) and the peristaltic pump head (4) are included. The motion conversion mechanism (1) is configured to be driven to convert rotary motion into linear motion output. The linear actuator (2) is driven by the motion conversion mechanism to realize linear reciprocating movement. The linear displacement sensor (3) is arranged in parallel with the motion direction of the linear actuator (2) and is used to measure the absolute position of the linear actuator (2). The peristaltic pump head (4) is installed on the linear actuator (2) and is used to control the pump tube (5) to form a continuous compression wave to realize fluid pumping.

2. The ultra-micro peristaltic pump system according to claim 1, wherein: The motion conversion mechanism (1) includes a cam (11), a follower (12), a movable rod (13) and a spring (14). The cam (11) is driven to rotate, the cam (11) is in contact with the follower (12), the follower (12) is connected with the movable rod (13), the spring (14) is arranged on the follower (12), and the rotation of the cam (11) and the restoring force of the spring (14) can drive the movable rod (13) to move linearly.

3. The ultra-micro peristaltic pump system according to claim 1, wherein: The linear actuator (2) is a slider.

4. The ultra-micro peristaltic pump system according to claim 1, wherein: The linear displacement sensor (3) is a linear grating ruler.

5. The ultra-micro peristaltic pump system according to claim 1, wherein: The peristaltic pump head (4) is a wedge cam.

6. The ultra-micro peristaltic pump system of claim 1, wherein: The motion conversion mechanism (1) is driven by a servo motor (8).

7. The ultra-micro peristaltic pump system according to claim 6, wherein: A controller (6) is further included, which is connected with an upper computer, a servo motor driver and a signal feedback of the linear grating ruler.

Images