A six-degree-of-freedom precision pipette adjustment platform based on friction drive and pressure feedback

Abstract

The present invention discloses a six-degree-of-freedom precision pipette adjustment platform based on friction drive and pressure feedback, which relates to the field of laboratory equipment. The adjustment platform includes: a platform housing, a top cover fixed to the top of the platform housing, and a carrier table arranged inside the platform housing for installing a pipette; a pitching support mechanism is installed inside the platform housing, and a plurality of pitching attitude adjustment mechanisms are installed on the top of the top cover; the pitching attitude adjustment mechanism includes: a support seat fixed to the top of the top cover, a friction box fixed to the top of the support seat, and a friction rod sleeved on the friction box; by adopting the friction drive technology, the mechanical clearance problems of traditional gears or ball screws are effectively avoided, and it has the advantages of low cost, low noise and high response speed, so that it can perfectly replace the traditional six-legged parallel platform and realize the high-precision and fast-response adjustment of the pipette tip in multiple dimensions.

Description

Technical Field

[0001] The present invention relates to the technical field of laboratory equipment, and particularly to pipettes, specifically a six-degree-of-freedom precision pipette adjustment platform based on friction drive and pressure feedback. Background Art

[0002] As a key device in fields such as biomedical, chemical analysis, drug research and development, and microfluidic technology, the core function of a pipette is to achieve precise aspiration and dispensing of trace amounts of liquid (usually from microliters to nanoliters). In high-precision experiments such as gene sequencing, cell culture, and high-throughput screening, the positioning accuracy and repeatability of the pipette directly determine the reliability and repeatability of experimental data.

[0003] Especially in microfluidic chip technology, it is necessary to inject nanoliter or even picoliter of liquid into micron-sized channels or reaction chambers, which poses almost stringent requirements on the positioning accuracy, stability, and repeatability of the pipette. Traditional pipettes are operated manually or semi-automatically, relying on the operator's experience, and it is difficult to meet the needs of high-throughput experiments. With the popularization of automation technology, electric pipettes and multi-channel pipetting systems have gradually become the mainstream, but their core bottleneck lies in how to achieve high-precision dynamic alignment between the pipette tip and the target position, especially in complex three-dimensional spaces and multi-degree-of-freedom attitude adjustment scenarios.

[0004] Existing pipette adjustment platforms are mostly designed based on three-dimensional translation stages, and the position adjustment is achieved through linear motion in the X / Y / Z axes. However, such platforms can only solve the problem of translational degrees of freedom and cannot compensate for the tilt of the tip caused by assembly errors or external vibrations (such as pitch, yaw, and roll angle deviations). For example, during the injection process of a microfluidic chip, if the axis of the pipette tip is not strictly parallel to the injection hole of the chip, it may cause liquid splashing, hole blockage, or deviation in the added sample volume, directly affecting the repeatability of experimental results.

[0005] Therefore, it is necessary to improve the deficiencies in the prior art to solve the above problems. Summary of the Invention

[0006] The present invention overcomes the deficiencies of the prior art and provides a six-degree-of-freedom precision pipette adjustment platform based on friction drive and pressure feedback.

[0007] To achieve the above object, the technical solution adopted by the present invention is: a six-degree-of-freedom precision pipette adjustment platform based on friction drive and pressure feedback, including: a platform housing, a top cover fixed on the top of the platform housing, and a carrier for installing a pipette arranged inside the platform housing;

[0008] An elevation support mechanism for simultaneously providing flexible and rolling support to the stage is installed inside the platform housing, and a number of elevation attitude adjustment mechanisms are installed on the top of the top cover;

[0009] The elevation attitude adjustment mechanism includes: a support base fixed to the top of the top cover, a friction box fixed to the top of the support base, and a friction rod sleeved on the friction box; an active mounting box and a driven mounting box are installed inside the friction box, and an active friction wheel and a driven friction wheel are respectively rotatably connected inside the active mounting box and the driven mounting box through a rotating shaft;

[0010] A power source for driving the rotation of the active friction wheel is installed on the top of the support base, rubber structures are fixed on the sides of the friction driving wheel and the driven friction wheel, and both are in contact with the side of the friction rod; an adjustment box is fixed to the side of the driven mounting box, a gas cavity is formed between the adjustment box and the active mounting box, and a connector for externally connecting a device for monitoring the air pressure change inside the gas cavity is installed on the side of the friction box.

[0011] In a preferred embodiment of the present invention, the bottom of the platform housing is open; the cross-sectional shape of the friction rod is one of a circle or a polygon, the bottom end of the friction rod is in contact with the top of the stage, and the side of the friction rod is located inside the gas cavity; the side of the active mounting box is fixed to the inside of the friction box, and the side of the adjustment box is slidably connected to the inside of the friction box.

[0012] In a preferred embodiment of the present invention, it further includes: a rotation attitude adjustment mechanism; the rotation attitude adjustment mechanism includes: a ball component installed at the bottom end of the friction rod for reducing the friction force on the top of the stage, a mounting groove opened on the side of the top cover, and a first hollow cup motor fixed inside the mounting groove; a friction roller is lapped on the top of the stage, and the output end of the first hollow cup motor is connected to one end of the friction roller through a mesh flexible coupling;

[0013] A C-shaped plate is fixed to the side of the top cover, a screw is threadedly connected to the top end of the C-shaped plate, and a guide post is fixed to the bottom end; the bottom end of the screw and the top end of the guide post are both rotatably connected to a pressing ring, compression springs are sleeved on the sides of the screw and the guide post between the C-shaped plate and the pressing ring, and the side of the pressing ring is in contact with the side of the mesh flexible coupling.

[0014] In a preferred embodiment of the present invention, the ball component includes: a connecting block fixed to the bottom end of the friction rod, and a number of contact balls rotatably connected to the bottom end of the connecting block; the bottom ends of the number of contact balls are in contact with the top of the stage.

[0015] In a preferred embodiment of the present invention, the pitching support mechanism includes: a bottom cage fixed to the inner bottom of the platform housing, a plurality of bottom balls rotatably connected to the bottom cage, and a plurality of support springs fixed to the top of the bottom cage; the tops of the plurality of support springs are lapped with the bottom of the load platform; a plurality of intermediate cages are fixed to the top of the bottom cage, and a plurality of intermediate balls are rotatably connected to the intermediate cages.

[0016] In a preferred embodiment of the present invention, a gland is detachably connected to the side of the friction box facing the adjustment box. A clamping groove is formed on one side of the adjustment box, a disc spring is fixed to one side of the gland, and the side of the disc spring is located inside the clamping groove.

[0017] In a preferred embodiment of the present invention, the power source includes: a motor base fixed to the top of the support base, a second hollow cup motor installed on the top of the motor base, and a worm installed at the output end of the second hollow cup motor; a worm gear is fixed to one end of the rotating shaft on the active friction wheel, and the side of the worm is engaged with the side of the worm gear.

[0018] The present invention provides a pressure feedback control method for a six-degree-of-freedom precision pipette adjustment platform based on any one of the above, including the following steps:

[0019] S1. Real-time monitor the dynamic changes in air pressure in the gas cavities of a plurality of pitching attitude adjustment mechanisms, and calculate the lifting amounts of the respective friction rods based on the mapping relationship between the pressure value and the displacement of the friction rod.

[0020] S2. Based on the inverse kinematics algorithm of the parallel mechanism, solve the six-degree-of-freedom position parameters of the current load platform from the lifting amounts of the plurality of friction rods.

[0021] S3. Compare the calculated actual position parameters of the load platform with the preset target position parameters, and calculate the position error values in the directions of each degree of freedom.

[0022] S4. According to the position error values, close-loop adjust the steering and speed of the power source to drive the active friction wheel, and dynamically adjust the lifting amounts of the respective friction rods until the error value between the actual position parameters of the load platform and the target position parameters approaches zero.

[0023] In a preferred embodiment of the present invention, in the step of S1, the real-time monitoring of the air pressure is performed by a pressure sensor for dynamic change monitoring; the mapping relationship is expressed by a pre-experimentally calibrated air pressure-displacement linear relationship model, which is used to convert the air pressure change value into the actual lifting displacement of each friction rod.

[0024] In a preferred embodiment of the present invention, in the step of S2, the six-degree-of-freedom position parameters include three-dimensional translation parameters of X, Y, and Z and three-dimensional rotation parameters of pitch angle, yaw angle, and roll angle.

[0025] The present invention solves the defects existing in the background art and has the following beneficial effects:

[0026] (1) The present invention provides a six-degree-of-freedom precision pipette adjustment platform based on friction drive and pressure feedback. By adopting friction drive technology, the power to adjust the degrees of freedom of the carrier stage is transmitted through the direct contact friction between the active friction wheel and the driven friction wheel on the friction rod. Combining with the rubber structure on the surface of the friction wheel, it not only increases the friction force when transmitting power but also compensates for micro deformations with elastic materials to keep the contact surface in close fit, effectively avoiding the mechanical clearance problems of traditional gears or ball screws. It has the advantages of low cost, low noise, and high response speed, and thus can perfectly replace the traditional six-legged parallel platform to achieve high-precision and fast-response adjustment of the pipette tip in multi-dimensional directions.

[0027] (2) In the present invention, by rotating the first cup motor, the reticulated flexible coupling, and the friction roller in the attitude adjustment mechanism, combined with the cooperative pre-tightening of the screw, the pressure ring, the compression spring, and the guide post, the adjustment of the degree of freedom of the pipette to rotate around the axis can be achieved. Compared with the reverse clearance problem of traditional ball screws, through the direct transmission of rolling friction, the dead zone error in rotational adjustment is avoided. At the same time, combined with the cooperative control of the pitch attitude adjustment mechanism, the pipette tip does not need to rely on the reverse adjustment of multiple devices to adjust the pitch attitude. It only needs to rotate to directly achieve the reverse alignment of the tip, thus significantly simplifying the complexity of multi-dimensional attitude adjustment and improving the motion stability and reliability in the microfluidic chip injection scenario.

[0028] (3) In the present invention, the pitch support mechanism provides flexible rolling support for the carrier stage under multiple degrees of freedom through the cooperation of the bottom balls on the bottom cage, the middle balls on the middle cage, and the support spring. When the carrier stage pitches or yaws due to the lifting of the friction rod, the rolling contact between the balls and the cage reduces the frictional resistance, and the support spring absorbs the micro displacements during the attitude adjustment of the carrier stage to ensure the overall stability and flexibility of the platform during the adjustment process, so that the carrier stage can still maintain smooth movement during complex attitude changes such as pitching and yawing, avoiding jamming or offset caused by rigid support.

[0029] (4) In the present invention, based on the pressure feedback control of the gas cavity, by monitoring in real time the change in the air pressure in the cavity caused by the lifting of the friction rod, combined with the inverse kinematic algorithm of the parallel mechanism, it is converted into the multi-degree-of-freedom position parameters of the stage, forming a closed-loop control, which can correct in real time the position and attitude deviation of the pipette tip. Furthermore, this active control method abandons the lag of the traditional open-loop control and ensures the sub-micron positioning accuracy and long-term repeatability in scenarios such as microfluidic chip sample injection. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments recorded in the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings;

[0031] Figure 1 It is a three-dimensional structure diagram of the adjustment platform in Embodiment 1 of the present invention;

[0032] Figure 2 It is a top-view semi-sectional structure diagram of the friction box in Embodiment 1 of the present invention;

[0033] Figure 3 It is a front-view semi-sectional structure diagram of the adjustment platform in Embodiment 1 of the present invention;

[0034] Figure 4 It is in Embodiment 1 of the present invention Figure 3 Enlarged structure diagram at position A;

[0035] Figure 5 It is a front-view semi-sectional structure diagram of the adjustment platform in Embodiment 2 of the present invention;

[0036] Figure 6 It is in Embodiment 2 of the present invention Figure 5 Enlarged structure diagram at position B;

[0037] In the figure: 1. Platform housing; 11. Top cover; 2. Stage; 3. Support seat; 31. Friction box; 32. Friction rod; 33. Active mounting box; 34. Driven mounting box; 35. Active friction wheel; 36. Driven friction wheel; 37. Adjustment box; 38. Gas cavity; 39. Connector; 4. Mounting groove; 41. First cup-shaped hollow motor; 42. Friction roller; 43. Mesh flexible coupling; 44. C-shaped plate; 45. Screw; 46. Guide post; 47. Pressure ring; 48. Pressure spring; 5. Connecting block; 51. Contact ball; 6. Bottom cage; 61. Bottom ball; 62. Support spring; 63. Intermediate cage; 64. Middle ball; 7. Pressure cover; 71. Card slot; 72. Disc spring; 8. Motor base; 81. Second cup-shaped hollow motor; 82. Worm; 83. Worm gear. Detailed implementation manners

[0038] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0039] In the following description, many specific details are set forth in order to fully understand the present invention. However, the present invention can also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited by the specific embodiments disclosed below.

[0040] In the description of the present application, it should be understood that the terms "first", "second", etc. are only used for descriptive purposes, and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Therefore, the features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, the meaning of "several" is two or more.

[0041] In the description of the present application, it should be noted that unless otherwise clearly specified and limited, the terms "installed", "connected", "connected" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected, or indirectly connected through an intermediate medium, and it may be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood through specific situations.

[0042] Application overview:

[0043] In the prior art, in order to meet the requirements of high-precision pipetting, a six-degree-of-freedom adjustment platform came into being. The six-degree-of-freedom adjustment platform can realize the precise position and attitude adjustment of the pipette in three-dimensional space, so as to ensure that the pipette can accurately align with the injection hole of the microfluidic chip. Some high-end systems adopt a six-legged parallel platform, and realize six-degree-of-freedom adjustment through the coordinated expansion and contraction of six electric struts, hydraulic or electric cylinders.

[0044] However, the applicant found that although such platforms have high precision (up to the sub-micron level), their disadvantages are also prominent: First, the structure is complex and the volume is large; second, it relies on high-precision ball screws or hydraulic drives, with high costs and frequent maintenance; third, positioning errors are likely to occur due to mechanical clearances (such as gear meshing clearances, lead screw backlash) during the adjustment of the rotational degree of freedom, and the accuracy deterioration is further aggravated by wear after long-term use.

[0045] In order to overcome the shortcomings of traditional six-degree-of-freedom adjustment platforms, the present invention proposes a six-degree-of-freedom precision pipette adjustment platform based on friction drive and pressure feedback, aiming to break through the bottlenecks in cost, precision, and reliability of the existing technology and provide an efficient solution for high-precision application scenarios such as microfluidic chips and single-cell analysis. Example 1

[0046] As Figure 1 and Figure 2 shown, a six-degree-of-freedom precision pipette adjustment platform based on friction drive and pressure feedback includes: a platform housing 1, a top cover 11 fixed to the top of the platform housing 1, and a stage 2 provided inside the platform housing 1 for installing a pipette; an elevation support mechanism for providing both flexible and rolling support to the stage 2 is installed inside the platform housing 1, and a number of elevation attitude adjustment mechanisms are installed on the top of the top cover 11;

[0047] The elevation attitude adjustment mechanism includes: a support base 3 fixed to the top of the top cover 11, a friction box 31 fixed to the top of the support base 3, and a friction rod 32 sleeved on the friction box 31; an active mounting box 33 and a driven mounting box 34 are installed inside the friction box 31, and an active friction wheel 35 and a driven friction wheel 36 are respectively rotatably connected to the inside of the active mounting box 33 and the driven mounting box 34 through a rotating shaft; a power source for driving the rotation of the active friction wheel 35 is installed on the top of the support base 3, rubber structures are fixed to the sides of the friction drive wheel and the driven friction wheel 36, and both are in contact with the side of the friction rod 32; an adjustment box 37 is fixed to the side of the driven mounting box 34, a gas cavity 38 is formed between the adjustment box 37 and the active mounting box 33, and a connector 39 for externally connecting a device for monitoring the change in air pressure inside the gas cavity 38 is installed on the side of the friction box 31.

[0048] It should be noted that the bottom of the platform housing 1 is open, so that the pipette can be installed on the stage 2 and the bottom can penetrate the platform housing 1 to ensure the non-interference effect at the bottom of the pipette tip; the cross-sectional shape of the friction rod 32 is one of a circle or a polygon, preferably a circle. The bottom end of the friction rod 32 contacts the top of the stage 2, the side of the friction rod 32 is located inside the gas cavity 38, and rubber rings are provided on the socket surfaces of the top and bottom of the friction rod 32 and the friction box 31 to ensure the sealing of the gas cavity 38 and prevent gas leakage from affecting the accuracy of air pressure monitoring; the side of the active mounting box 33 is fixed to the inside of the friction box 31, and the side of the adjustment box 37 is slidably connected to the inside of the friction box 31; the material of the rubber structure is nitrile, taking into account both high friction coefficient and wear resistance.

[0049] More specifically, the number of pitch attitude adjustment mechanisms is six groups, which are circumferentially and evenly distributed on the top of the top cover 11 to form six-degree-of-freedom adjustment. By driving the rotation of the active friction wheel 35 by a power source, the active friction wheel 35 converts the rotational motion into the linear lifting of the friction rod 32 through the frictional force between the rubber structure and the friction rod 32. Since the driven friction wheel 36 is in contact with the side surface of the friction rod 32, under the action of the frictional force, the driven friction wheel 36 will follow the movement of the friction rod 32. Furthermore, by controlling the rotation speed and direction of the active friction wheel 35, the acting force exerted by the friction rod 32 on the stage 2 in the six groups of pitch attitude adjustment mechanisms can be precisely adjusted, enabling it to control the pitch, yaw, and longitudinal axial adjustment of the stage 2. The pitch support mechanism provides flexible and rolling support to the stage 2. At the same time, when the friction rod 32 moves up and down, its side squeezes the gas cavity 38, resulting in a change in the cavity volume. By connecting the monitoring device for the internal air pressure change of the gas cavity 38 through the connector 39, the air pressure is monitored in real time, and the data is input into the control system to drive the power source to adjust the position of the friction rod 32, forming a closed-loop adjustment to ensure the stability and accuracy of the pitch attitude adjustment. Furthermore, by adopting the friction drive technology, the mechanical clearance problems of traditional gears or ball screws are effectively avoided, with the advantages of low cost, low noise, and high response speed, thus being able to perfectly replace the traditional six-legged parallel platform and achieve high-precision and fast-response adjustment of the pipette tip in multiple dimensions.

[0050] As Figure 3 and Figure 4 shown, in this embodiment, the pitch support mechanism includes: a bottom cage 6 fixed to the inner bottom of the platform housing 1, a plurality of bottom balls 61 rotatably connected to the bottom cage 6, and a plurality of support springs 62 fixed to the top of the bottom cage 6; the tops of the plurality of support springs 62 are lapped with the bottom of the stage 2; a plurality of intermediate cages 63 are fixed to the top of the bottom cage 6, and a plurality of middle balls 64 are rotatably connected to the intermediate cages 63.

[0051] It should be noted that the plurality of bottom balls 61, the plurality of intermediate cages 63, and the plurality of support springs 62 are all circumferentially and evenly distributed on the bottom cage 6 to form a preliminary support for the bottom of the stage 2. The plurality of middle balls 64 are evenly distributed in a linear array along the length direction of the intermediate cage 63 to provide rolling support in the vertical direction and avoid jamming when the stage 2 tilts; the stiffness coefficient of the support spring 62 is preferably 30 N / mm to ensure the balance between the reset force and the adjustment accuracy.

[0052] More specifically, when the stage 2 pitches or yaws under the gravity of the pipette and the thrust of the friction rod 32, the support spring 62 is compressed and deformed, storing elastic potential energy. When the external force is removed, the support spring 62 releases the potential energy, pushing the stage 2 back to the equilibrium position, providing a flexible support for the stage 2. At the same time, when the stage 2 pitches, when the bottom ball 61 and the middle ball 64 contact the bottom of the stage 2, the bottom ball 61 and the middle ball 64 roll, reducing the friction between the stage 2 and the platform housing 1, enabling the stage 2 to smoothly pitch, thereby providing a flexible and rolling support for the stage 2. When the stage 2 bears a load, it can flexibly pitch, and the friction resistance during the movement is reduced, improving the movement accuracy and stability of the pipette adjustment platform.

[0053] As Figure 2 shown, in this embodiment, a gland 7 is detachably connected to the side of the friction box 31 facing the adjustment box 37. A clamping groove 71 is provided on one side of the adjustment box 37. One side of the gland 7 is fixed with a disc spring 72, and the side of the disc spring 72 is located inside the clamping groove 71.

[0054] It should be noted that the gland 7 and the friction box 31 are connected by bolts, and the bolts are evenly distributed on the edge of the gland 7, which is convenient for installation and disassembly. The stiffness and deformation parameters of the disc spring 72 are selected according to the relative movement range between the adjustment box 37 and the friction box 31 and the required pre-tightening force to ensure that the disc spring 72 can provide an appropriate pre-tightening force during the sliding process of the adjustment box 37.

[0055] More specifically, by detachably connecting the gland 7 to one side of the friction box 31 and placing the disc spring 72 in the clamping groove 71 on one side of the adjustment box 37, the elastic deformation of the disc spring 72 can provide a pre-tightening force in the radial direction of the driven friction wheel 36 through the adjustment box 37. This pre-tightening force can be adjusted by replacing the disc spring 72, realizing friction-driven lifting with adjustable self-adaptive friction, driving the six-dimensional movement of the adjustment surface.

[0056] In this embodiment, the power source includes: a motor base 8 fixed on the top of the support base 3, a second cup-shaped hollow motor 81 installed on the top of the motor base 8, and a worm 82 installed at the output end of the second cup-shaped hollow motor 81; one end of the rotating shaft on the active friction wheel 35 is fixed with a worm gear 83, and the side of the worm 82 meshes with the side of the worm gear 83.

[0057] More specifically, by controlling the rotation speed and direction of the second coreless motor 81, the second coreless motor 81 drives the worm 82 to rotate. The worm 82 meshes with the worm wheel 83, transmitting the rotational motion of the motor to the driving friction wheel 35. The driving friction wheel 35 drives the friction rod 32 to move through friction, enabling the friction rod 32 to provide power for the driving friction wheel 35, thereby achieving the adjustment of the pitching attitude of the stage 2. At the same time, the self-locking property of the transmission between the worm 82 and the worm wheel 83 can ensure that the friction rod 32 can maintain a stable position when the motor stops rotating, improving the stability and reliability of the pitching attitude adjustment. Embodiment 2

[0058] As Figure 5 and Figure 6 shown, this embodiment is basically the same as Embodiment 1, except that it further includes: a rotational attitude adjustment mechanism; the rotational attitude adjustment mechanism includes: a ball component installed at the bottom end of the friction rod 32 for reducing the friction force on the top of the stage 2, an installation groove 4 opened on the side surface of the top cover 11, and a first coreless motor 41 fixed inside the installation groove 4; a friction roller 42 is lapped on the top of the stage 2, and the output end of the first coreless motor 41 is connected to one end of the friction roller 42 through a mesh flexible coupling 43;

[0059] A C-shaped plate 44 is fixed to the side surface of the top cover 11. A screw 45 is threadedly connected to the top end of the C-shaped plate 44, and a guide post 46 is fixed to the bottom end. The bottom end of the screw 45 and the top end of the guide post 46 are both rotatably connected to a pressure ring 47. Compression springs 48 are sleeved on the side surfaces of the screw 45 and the guide post 46 located between the C-shaped plate 44 and the pressure ring 47. The side surface of the pressure ring 47 is in contact with the side surface of the mesh flexible coupling 43.

[0060] It should be noted that the mesh flexible coupling 43 is a spring coupling of the HUAZN brand, made of high-quality zinc alloy and high-strength springs, with an operating temperature range of -35 °C to 80 °C; the friction surface of the friction roller 42 is made of wear-resistant rubber material and has anti-slip patterns, which can increase the friction force, prevent idling, and also reduce noise; the cross-sectional shape of the pressure ring 47 is semi-circular, and the arc surface is in contact with the side surface of the mesh flexible coupling 43.

[0061] More specifically, the first hollow cup motor 41 serves as a driving member, and its output end drives the friction roller 42 to rotate through a mesh flexible coupling 43. The mesh flexible coupling 43 transmits power and allows a certain angular deviation and vibration. Since the friction roller 42 contacts the top of the stage 2, it can drive the stage 2 to rotate through friction during rotation, thereby realizing the adjustment of the rotation attitude of the stage 2. When it is necessary to adjust the tension of the mesh flexible coupling 43, by rotating the screw 45, the screw 45 moves up and down on the C-shaped plate 44, driving the pressure ring 47 to move up and down. The guide post 46 guides the movement of the pressure ring 47 to ensure the stability of the moving direction of the pressure ring 47. The compression spring 48 is compressed or stretched under the action of the screw 45 and the guide post 46 to generate a certain pressure, so that the pressure ring 47 is always in close contact with the side surface of the mesh flexible coupling 43, thereby ensuring the stability of the tension of the mesh flexible coupling 43, avoiding unstable power transmission caused by vibration or loosening, improving the accuracy and reliability of the rotation attitude adjustment, and avoiding the problem of the machining flatness of the friction surface at the top of the stage 2.

[0062] In this embodiment, the ball assembly includes: a connection block 5 fixed to the bottom end of the friction rod 32, and a plurality of contact balls 51 rotatably connected to the bottom end of the connection block 5; the bottom ends of the plurality of contact balls 51 contact the top of the stage 2.

[0063] More specifically, when the stage 2 rotates, the friction rod 32 in contact with the top of the stage 2 contacts the top of the stage 2 through the connection block 5 and the contact balls 51 at the bottom end. The contact balls 51 will roll as the stage 2 rotates, thereby converting sliding friction into rolling friction, reducing the friction between the top of the stage 2 and the bottom end of the friction rod 32, avoiding rotational interference, effectively reducing the frictional resistance when the stage 2 rotates, improving the rotation efficiency, and reducing energy loss.

[0064] The present invention provides a pressure feedback control method for a six-degree-of-freedom precision pipette adjustment platform, including the following steps:

[0065] S1. Real-time monitor the dynamic change of the air pressure in the gas cavity 38 of the six pitching attitude adjustment mechanisms, and calculate the lifting amounts of the six friction rods 32 based on the mapping relationship between the pressure value and the displacement of the friction rod 32;

[0066] S2. Based on the inverse kinematic algorithm of the parallel mechanism, solve the six-degree-of-freedom position parameters of the current stage 2 from the lifting amounts of the six friction rods 32;

[0067] S3. Compare the calculated actual position parameters of the stage 2 with the preset target position parameters, and calculate the position error values in the directions of each degree of freedom;

[0068] S4. According to the position error value, the power source of the closed-loop regulation is used to drive the rotation direction and speed of the active friction wheel 35, and the lifting amount of each friction rod 32 is dynamically adjusted until the error value between the actual position parameter of the stage 2 and the target position parameter approaches zero.

[0069] In this embodiment, in the step of S1, the real-time monitoring of the air pressure is carried out by a pressure sensor for dynamic change monitoring. Among them, the model of the pressure sensor is preferably XGZP6847A vacuum negative pressure sensor, and the pressure range is 0 - 5 kPa.

[0070] Further, for the pre-experiment calibration of the mapping relationship, the setting of the air pressure-displacement linear relationship model: taking the initial position of the friction rod 32 as the reference point , the volume of the gas cavity 38 is , control the friction rod 32 to lift and lower at a known step size (such as μm), and record the air pressure value corresponding to each displacement point , for example: when the friction rod 32 rises by 1 μm, the cavity volume shrinks , and the air pressure rises ;

[0071] According to the experimental data, fit the linear relationship between the air pressure change and the displacement :

[0072] ;

[0073] Among them, the proportional coefficient (unit: Pa / μm) is obtained by experimental calibration.

[0074] Further, for the calculation of the lifting amount of the six friction rods 32: synchronously collect the real-time air pressure values of the corresponding six gas cavities 38 ( ); taking the reference air pressure (the air pressure when the friction rod 32 is in the initial position) as a reference, calculate the air pressure change amount :

[0075] ;

[0076] Using the pre-calibrated proportional coefficient , calculate the lifting displacement amount of each friction rod 32:

[0077] ;

[0078] Among them, indicates that the friction rod 32 rises, indicates that it descends.

[0079] Example:

[0080] Suppose the calibration coefficient of a certain friction rod 32 is Pa / μm, and it is monitored in real time that the air pressure rises by Pa, then its displacement is:

[0081] μm;

[0082] It means that the friction rod 32 has risen by 10 μm.

[0083] In this embodiment, in the step of S2, for the calculation of the current six-degree-of-freedom position parameters of the stage 2: First, define the pipette base coordinate system and the moving platform coordinate system of the stage 2, and determine the initial positions of six contact points on both of them respectively. Among them, the base coordinate system is fixed at the center of the bottom of the platform housing 1, and the moving platform coordinate system is aligned with the geometric center of the stage 2; when the stage 2 moves or rotates due to the lifting of the friction rod 32, the positions of the hinge points on the moving platform change accordingly, and the lifting amount of each friction rod 32 corresponds to the actual change value of the length of the friction rod 32;

[0084] And through the geometric model, the length change of the friction rod 32 is associated with the pose parameters of the stage 2 (including X / Y / Z translations and rotation angles around three axes). Suppose when the stage 2 is in a certain unknown pose, the position of each hinge point on the moving platform relative to the base can be represented by a translation vector and a rotation matrix. The rotation matrix is constructed by Euler angles (such as the angles around the X, Y, and Z axes), and the translation vector directly describes the displacement of the center of the stage 2. By calculating the coordinate differences of each friction rod 32 in the base and moving platform coordinate systems and combining the measured length change of the friction rod 32, a set of nonlinear equations can be established to describe the deviation between the actual pose and the theoretical model.

[0085] The Newton-Raphson iteration method is used for optimization. By continuously adjusting the guessed values of the pose parameters, the length change of the friction rod 32 calculated by the model gradually approaches the measured value.

[0086] Specifically, first set the initial pose (such as the stage 2 is in a horizontal position and there is no translation), calculate the theoretical length change of the friction rod 32 at this time, and compare it with the measured value to obtain the error. Subsequently, by analyzing the sensitivity of each pose parameter (such as the translation component or the rotation angle) to the length of the friction rod 32 (i.e., the Jacobian matrix), determine the adjustment direction and amplitude. For example, if the actual elongation of a certain friction rod 32 is greater than the value predicted by the model, the system will judge that the stage 2 may tilt or translate in the direction of this friction rod 32, and accordingly correct the pose parameters. After multiple iterations, the error gradually decreases, and finally the six-degree-of-freedom parameters that meet the accuracy requirements are obtained.

[0087] It should be noted that by calculating the current six - degree - of - freedom position parameters of the stage 2, the actual state of the stage 2 in six degrees of freedom can be accurately identified. Whether it is micron - level translation or milliradian - level rotation, it can be analyzed by the algorithm and fed back to the control system. Furthermore, the high - precision pose calculation ability enables the pipette tip to quickly align with the target hole in scenarios such as microfluidic chip injection, avoiding liquid splashing or positioning failure caused by attitude deviation, and finally achieving sub - micron - level positioning accuracy and stable repetitive operation.

[0088] In this embodiment, in the step of S3, the rotational error needs to consider the periodicity of the angle (for example, 0° is equivalent to 360°). Taking the pitch angle α around the X - axis as an example, the error calculation needs to correct the angle - wrapping problem:

[0089] ;

[0090] Similarly, calculate the errors of the yaw angle β around the Y - axis and the roll angle γ around the Z - axis:

[0091] ;

[0092] Furthermore, limit the angular error within the interval , avoiding the confusion of error directions caused by the 360° periodicity, and finally obtaining the six - degree - of - freedom error vector: , which will be used as the input of step S4 to generate the control signal for the drive motor.

[0093] In this embodiment, in the step of S4, when the error vector is input to the controller, the controller decomposes the six - degree - of - freedom error into independent displacement adjustment amounts for each friction rod 32 according to the preset mapping relationship; for example, a certain friction rod 32 may need to rise by 0.5 μm to drive the stage 2 to rotate around the X - axis, while another friction rod 32 needs to descend by 0.3 μm to balance the overall attitude. The control signal is then sent to the second cup - shaped hollow motor 81 that drives each friction rod 32. The rotation direction (forward or reverse) of the motor is determined by the positive or negative sign of the adjustment amount, and the rotational speed is proportional to the absolute value of the adjustment amount, so as to quickly and accurately drive the friction rod 32 to the target position.

[0094] During this process, the high responsiveness and low inertia characteristics of the second cup-shaped motor 81 play a crucial role. For example, when it is detected that the error requires the friction rod 32 to rise by 2 μm, the motor will rotate quickly at a speed (such as 20 RPM / μm) that matches the error amplitude, and convert the rotational motion into the linear lifting and lowering of the friction rod 32 through the worm gear 83 and worm 82 transmission mechanism. The pre-tightening force design between the friction wheel and the friction rod 32 (such as the dynamic adjustment of the compression spring 48 and the disc spring 72) ensures the backlash-free characteristic of the transmission, avoiding the response delay or positioning deviation caused by mechanical backlash in traditional gear or lead screw systems. At the same time, the pressure sensor in step S1 continuously monitors the actual displacement of the friction rod 32, and feeds back the data to the control system in real time to form a closed-loop adjustment. If a certain friction rod 32 does not reach the target position completely due to external interference, the system will immediately detect the remaining error and start a new round of adjustment until the errors in all degrees of freedom are eliminated.

[0095] Based on the ideal embodiments of the present invention as inspiration, through the above description, for those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention. Any reference signs in the claims should not be regarded as limiting the claims involved.

[0096] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A six-degree-of-freedom precision pipette adjustment platform based on friction drive and pressure feedback, characterized in that Comprising: A platform housing, a top cover fixed to the top of the platform housing, and a stage provided inside the platform housing for mounting a pipette; An elevation support mechanism for simultaneously providing flexible and rolling support to the stage is installed inside the platform housing, and a number of elevation attitude adjustment mechanisms are installed on the top of the top cover; The elevation attitude adjustment mechanism includes: a support base fixed to the top of the top cover, a friction box fixed to the top of the support base, and a friction rod sleeved on the friction box; an active mounting box and a driven mounting box are installed inside the friction box, and an active friction wheel and a driven friction wheel are respectively rotatably connected inside the active mounting box and the driven mounting box through a rotating shaft; A power source for driving the rotation of the active friction wheel is installed on the top of the support base, rubber structures are fixed on the sides of the friction drive wheel and the driven friction wheel, and both are in contact with the side of the friction rod; an adjustment box is fixed to the side of the driven mounting box, a gas cavity is formed between the adjustment box and the active mounting box, and a connector for externally connecting a device for monitoring the air pressure change inside the gas cavity is installed on the side of the friction box.

2. The six-degree-of-freedom precision pipette adjustment platform based on friction drive and pressure feedback according to claim 1, characterized in that: The bottom of the platform housing is open; the cross-sectional shape of the friction rod is one of a circle or a polygon, the bottom end of the friction rod contacts the top of the stage, and the side of the friction rod is located inside the gas cavity; the side of the active mounting box is fixed to the inside of the friction box, and the side of the adjustment box is slidably connected to the inside of the friction box.

3. A six-degree-of-freedom precision pipette adjustment platform based on friction drive and pressure feedback according to claim 1, characterized in that: Also comprising: A rotational attitude adjustment mechanism; The rotational attitude adjustment mechanism includes: a ball assembly installed at the bottom end of the friction rod for reducing the friction force on the top of the stage, a mounting groove opened on the side of the top cover, and a first hollow cup motor fixed to the inside of the mounting groove; a friction roller is lapped on the top of the stage, and the output end of the first hollow cup motor is connected to one end of the friction roller through a net-shaped flexible coupling; A C-shaped plate is fixed to the side of the top cover, a screw is threadedly connected to the top end of the C-shaped plate, and a guide post is fixed to the bottom end; a pressure ring is rotatably connected to the bottom end of the screw and the top end of the guide post, compression springs are sleeved on the sides of the screw and the guide post between the C-shaped plate and the pressure ring, and the side of the pressure ring is in contact with the side of the net-shaped flexible coupling.

4. The six-degree-of-freedom precision pipette adjustment platform based on friction drive and pressure feedback according to claim 3, characterized in that: The ball assembly includes: a connection block fixed to the bottom end of the friction rod, and a number of contact balls rotatably connected to the bottom end of the connection block; the bottom ends of the number of contact balls contact the top of the stage.

5. A six-degree-of-freedom precision pipette adjustment platform based on friction drive and pressure feedback according to claim 1, characterized in that: The elevation support mechanism includes: a bottom retainer fixed to the inner bottom of the platform housing near the bottom, a number of bottom balls rotatably connected to the bottom retainer, and a number of support springs fixed to the top of the bottom retainer; the tops of the number of support springs are lapped with the bottom of the stage; a number of intermediate retainers are fixed to the top of the bottom retainer, and a number of intermediate balls are rotatably connected to the intermediate retainers.

6. The six-degree-of-freedom precision pipette adjustment platform based on friction drive and pressure feedback according to claim 1, characterized in that: A gland is detachably connected to the side of the friction box facing the adjustment box. A clamping groove is formed on one side of the adjustment box. A disc spring is fixed to one side of the gland, and the side of the disc spring is located inside the clamping groove.

7. The six-degree-of-freedom precision pipette adjustment platform based on friction drive and pressure feedback according to claim 1, characterized in that: The power source includes: a motor base fixed to the top of the support base, a second hollow cup motor installed on the top of the motor base, and a worm installed at the output end of the second hollow cup motor; one end of the rotating shaft on the active friction wheel is fixed with a worm gear, and the side of the worm is meshed with the side of the worm gear.

8. A pressure feedback control method for a six-degree-of-freedom precision pipette adjustment platform according to any one of claims 1-7, characterized in that, It includes the following steps: S1. Dynamically monitor the dynamic changes of the air pressure in the gas cavities of a number of pitch attitude adjustment mechanisms in real time, and calculate the lifting amounts of the respective friction rods based on the mapping relationship between the pressure value and the displacement of the friction rods. S2. Based on the inverse kinematics algorithm of the parallel mechanism, solve the current six-degree-of-freedom position parameters of the load platform from the lifting amounts of the number of friction rods. S3. Compare the actually calculated position parameters of the load platform with the preset target position parameters, and calculate the position error values in the directions of each degree of freedom. S4. According to the position error values, closed-loop adjust the rotation direction and speed of the power source driving the active friction wheel, and dynamically adjust the lifting amounts of the respective friction rods until the error value between the actually calculated position parameters of the load platform and the target position parameters approaches zero.

9. The pressure feedback control method according to claim 8, wherein: In the step of S1, the real-time monitoring of the air pressure is carried out by a pressure sensor for dynamic change monitoring; the mapping relationship is expressed by a pre-experimentally calibrated air pressure-displacement linear relationship model, which is used to convert the air pressure change value into the actual lifting displacement amount of each friction rod.

10. The pressure feedback control method according to claim 8, wherein: In the step of S2, the six-degree-of-freedom position parameters include three-dimensional translation parameters of X, Y, and Z and three-dimensional rotation parameters of pitch angle, yaw angle, and roll angle.

Images