Six-degree-of-freedom precise pipettor adjusting platform based on friction driving and pressure feedback

Abstract

The invention discloses a six-degree-of-freedom precise pipettor adjusting platform based on friction driving and pressure feedback, and relates to the field of laboratory equipment.The adjusting platform comprises a platform shell, a top cover fixed to the top of the platform shell and an objective table arranged on the inner side of the platform shell and used for installing a pipettor; a pitching supporting mechanism is installed on the inner side of the platform shell, and a plurality of pitching posture adjusting mechanisms are installed on the top of the top cover. The pitch attitude adjusting mechanism comprises a supporting base fixed to the top of the top cover, a friction box fixed to the top of the supporting base and a friction rod connected to the friction box in a sleeving mode. By adopting the friction driving technology, the problem of mechanical clearance of a traditional gear or a ball screw is effectively solved, and the multi-dimensional parallel platform has the advantages of low cost, low noise and high response speed, so that the multi-dimensional parallel platform can perfectly replace a traditional six-foot parallel platform, and high-precision and quick response adjustment of a pipette tip in a multi-dimensional direction is realized.

Description

Technical Field

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

[0002] As a key device in the fields of biomedicine, chemical analysis, drug development and microfluidics, the core function of the pipette is to achieve accurate aspiration and distribution of trace amounts of liquid (usually 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 the experimental data.

[0003] Especially in microfluidic chip technology, nanoliter or even picoliter liquids need to be injected into micron-scale channels or reaction chambers, which places 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 are 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 mainstream, but the core bottleneck lies in how to achieve high-precision dynamic alignment of the pipette tip with the target position, especially in complex three-dimensional space and multi-degree-of-freedom posture adjustment scenarios.

[0004] Existing pipette adjustment platforms are mostly based on three-dimensional translation stage design, which achieves position adjustment through linear motion in the X / Y / Z axis. However, such platforms can only solve the problem of translational freedom, and cannot compensate for the tilt of the gun tip due to assembly errors or external vibrations (such as pitch, yaw, and roll angle deviations). For example, during the microfluidic chip injection process, if the axis of the gun tip is not strictly parallel to the chip injection hole, it may cause liquid splashing, hole blockage, or sample volume deviation, which directly affects the repeatability of the 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 invention overcomes the shortcomings 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-mentioned purpose, 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, comprising: a platform shell, a top cover fixed on the top of the platform shell, and a stage arranged inside the platform shell for mounting a pipette; A pitch support mechanism for providing both flexible and rolling support to the loading platform is installed on the inner side of the platform shell, and a plurality of pitch attitude adjustment mechanisms are installed on the top of the top cover; The pitch attitude adjustment mechanism comprises: a support seat fixed on the top of the top cover, a friction box fixed on the top of the support seat, and a friction rod sleeved on the friction box; an active mounting box and a driven mounting box are mounted on the inner side of the friction box, and the inner sides of the active mounting box and the driven mounting box are respectively connected to an active friction wheel and a driven friction wheel through a rotating shaft; A power source for driving the active friction wheel to rotate is installed on the top of the support seat, and rubber structures are fixed to the sides of the friction driving wheel and the driven friction wheel, and are both in contact with the sides of the friction rod; an adjustment box is fixed to the side of the driven mounting box, and a gas cavity is formed between the adjustment box and the active mounting box, and a connector for an external device for monitoring the air pressure changes inside the gas cavity is installed on the side of the friction box.

[0008] In a preferred embodiment of the present invention, the bottom of the platform shell 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 loading platform, and the side of the friction rod is located inside the gas cavity; the side of the active mounting box is fixed to the inner side of the friction box, and the side of the adjustment box is slidably connected to the inner side of the friction box.

[0009] In a preferred embodiment of the present invention, it further comprises: a rotation posture adjustment mechanism; the rotation posture adjustment mechanism comprises: a ball assembly installed at the bottom end of the friction rod for reducing the friction force on the top of the loading platform, a mounting groove provided on the side of the top cover, and a first hollow cup motor fixed on the inner side of the mounting groove; a friction roller is overlapped on the top of the loading platform, and the output end of the first hollow cup motor is connected to one end of the friction roller through a mesh flexible coupling; A C-shaped plate is fixed to the side of the top cover, the top of the C-shaped plate is threadedly connected with a screw, and the bottom is fixed with a guide column; the bottom end of the screw and the top end of the guide column are rotatably connected with a pressure ring, and the sides of the screw and the guide column located between the C-shaped plate and the pressure ring are sleeved with compression springs, and the side of the pressure ring is in contact with the side of the mesh flexible coupling.

[0010] In a preferred embodiment of the present invention, the ball assembly includes: a connecting block fixed to the bottom end of the friction rod, and a plurality of contact balls rotatably connected to the bottom end of the connecting block; the bottom ends of the plurality of contact balls are in contact with the top of the loading platform.

[0011] In a preferred embodiment of the present invention, the pitch support mechanism includes: a bottom retaining frame fixed to the platform shell near the inner bottom, a plurality of bottom balls rotatably connected to the bottom retaining frame, and a plurality of support springs fixed to the top of the bottom retaining frame; the tops of the plurality of support springs overlap the bottom of the loading platform; a plurality of intermediate retaining frames are fixed to the top of the bottom retaining frame, and a plurality of middle balls are rotatably connected to the intermediate retaining frames.

[0012] In a preferred embodiment of the present invention, the friction box is detachably connected to a pressure cover on the side facing the adjustment box, a slot is provided on one side of the adjustment box, a disc spring is fixed on one side of the pressure cover, and the side of the disc spring is located on the inner side of the slot.

[0013] In a preferred embodiment of the present invention, the power source includes: a motor base fixed on the top of the support base, a second hollow cup motor installed on the top of the motor base, and a worm installed on the output end of the second hollow cup motor; a worm wheel is fixed to one end of the rotating shaft on the active friction wheel, and the side surface of the worm gear is meshed with the side surface of the worm wheel.

[0014] The present invention provides a pressure feedback control method based on any one of the above-mentioned six-degree-of-freedom precision pipette adjustment platforms, comprising the following steps: S1. Real-time monitoring of the dynamic changes of air pressure in the gas cavities of several pitch attitude adjustment mechanisms, and calculation of the lifting and lowering amount of each friction rod based on the mapping relationship between the pressure value and the displacement of the friction rod; S2, calculating the lifting amount of several friction rods based on the inverse solution algorithm of parallel mechanism kinematics to solve the current six-degree-of-freedom position parameters of the stage; S3, comparing the calculated actual position parameters of the stage with the preset target position parameters, and calculating the position error value in each degree of freedom direction; S4. According to the position error value, the power source drives the steering and speed of the active friction wheel in a closed loop, and dynamically adjusts the lifting amount of each friction rod until the error value between the actual position parameter and the target position parameter of the stage approaches zero.

[0015] In a preferred embodiment of the present invention, in step S1, the real-time monitoring of the air pressure is performed by monitoring the dynamic changes through a pressure sensor; the mapping relationship is expressed by a pressure-displacement linear relationship model calibrated in a pre-experiment, which is used to convert the air pressure change value into the actual lifting and lowering displacement of each friction rod.

[0016] In a preferred embodiment of the present invention, in step 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.

[0017] The present invention solves the defects existing in the background technology and has the following beneficial effects: (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 active friction wheel and the driven friction wheel directly contact the friction rod to transmit the power for adjusting the freedom of the stage. Combined with the rubber structure on the surface of the friction wheel, the friction force is increased when transmitting power, and the elastic material is used to compensate for slight deformation, keeping the contact surface tightly fitted, effectively avoiding the mechanical clearance problem of traditional gears or ball screws. It has the advantages of low cost, low noise and high response speed, so it can perfectly replace the traditional six-legged parallel platform and realize high-precision and fast response adjustment of the pipette tip in multi-dimensional directions.

[0018] (2) In the present invention, the first hollow cup motor, mesh flexible coupling and friction roller in the rotation attitude adjustment mechanism are combined with the coordinated pre-tightening of the screw, pressure ring, compression spring and guide column to achieve the degree of freedom adjustment of the rotation of the pipette around the axis. Compared with the reverse clearance problem of the traditional ball screw, the backlash error in the rotation adjustment is avoided through the direct transmission of rolling friction. At the same time, combined with the coordinated control of the pitch attitude adjustment mechanism, the pipette gun tip does not need to rely on the reverse adjustment of the pitch attitude of multiple devices, and only needs to rotate to directly achieve the reverse alignment of the gun tip, thereby significantly simplifying the complexity of multi-dimensional attitude adjustment and improving the motion stability and reliability in the microfluidic chip injection scenario.

[0019] (3) In the present invention, the pitch support mechanism provides flexible rolling support for the platform in multiple degrees of freedom through the cooperation of the bottom ball on the bottom retaining frame, the middle ball on the intermediate retaining frame and the support spring. When the platform pitches or yaws due to the lifting and lowering of the friction rod, the rolling contact between the ball and the retaining frame reduces the friction resistance, and the support spring absorbs the tiny displacement when the platform adjusts its posture, ensuring the overall stability and flexibility of the platform during the adjustment process, so that the platform can still maintain smooth movement when the platform changes in complex postures such as pitch and yaw, avoiding jamming or deviation caused by rigid support.

[0020] (4) In the present invention, based on the pressure feedback control of the gas cavity, the changes in the cavity air pressure caused by the lifting and lowering of the friction rod are monitored in real time, and combined with the kinematic inverse solution algorithm of the parallel mechanism, they are converted into multi-degree-of-freedom position parameters of the stage to form a closed-loop control. The position and posture deviation of the pipette tip can be corrected in real time. This active control method eliminates the hysteresis of traditional open-loop control and ensures sub-micron positioning accuracy and long-term repeatability in scenarios such as microfluidic chip injection. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art are briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative work. Figure 1 is a three-dimensional structural diagram of an adjustment platform according to Embodiment 1 of the present invention; Figure 2 is a top view of a half-section structure of a friction box according to Embodiment 1 of the present invention; Figure 3 This is a front view half-section structural diagram of the adjustment platform of Example 1 of the present invention; Figure 4 Embodiment 1 of the present invention Figure 3 The enlarged structural diagram at A in the middle; Figure 5 This is a front view half-section structural diagram of the adjustment platform of Example 2 of the present invention; Figure 6 It is embodiment 2 of the present invention Figure 5 The structure diagram at B is enlarged; In the figure: 1. platform shell; 11. top cover; 2. loading platform; 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 hollow cup motor; 42. friction roller; 43. mesh flexible coupling; 44. C-type plate; 45. screw; 46. guide column; 47. pressure ring; 48. pressure spring; 5. connecting block; 51. contact ball; 6. bottom retaining frame; 61. bottom ball; 62. support spring; 63. middle retaining frame; 64. middle ball; 7. pressure cover; 71. slot; 72. disc spring; 8. motor seat; 81. second hollow cup motor; 82. worm; 83. worm wheel. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited to the specific embodiments disclosed below.

[0024] In the description of the present application, it should be understood that the terms "first", "second", etc. are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "several" means two or more.

[0025] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood by specific circumstances.

[0026] Application Overview: In the existing technology, in order to meet the needs of high-precision pipetting, a six-degree-of-freedom adjustment platform came into being. The six-degree-of-freedom adjustment platform can achieve precise position and posture adjustment of the pipette in three-dimensional space, thereby ensuring that the pipette can accurately align with the injection hole of the microfluidic chip. Some high-end systems use a six-legged parallel platform to achieve six-degree-of-freedom adjustment through the coordinated extension and contraction of six electric struts, hydraulic or electric cylinders.

[0027] However, the applicant found that although this type of platform has high precision (up to sub-micron level), its disadvantages are also prominent: first, the structure is complex and bulky; second, it relies on high-precision ball screws or hydraulic drives, which are costly and require frequent maintenance; third, positioning errors are easily caused by mechanical clearance (such as gear meshing clearance, screw reverse backlash) when the rotational freedom is adjusted, and wear after long-term use further exacerbates the degradation of accuracy.

[0028] 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 of existing technologies in cost, accuracy and reliability, and provide efficient solutions for high-precision application scenarios such as microfluidic chips and single-cell analysis. Example 1

[0029] like Figure 1 and Figure 2As shown, a six-degree-of-freedom precision pipette adjustment platform based on friction drive and pressure feedback comprises: a platform housing 1, a top cover 11 fixed on the top of the platform housing 1, and a stage 2 arranged inside the platform housing 1 for mounting a pipette; a pitch support mechanism for providing flexibility and rolling support to the stage 2 is installed inside the platform housing 1, and a plurality of pitch attitude adjustment mechanisms are installed on the top of the top cover 11; The pitch attitude adjustment mechanism includes: a support seat 3 fixed on the top of the top cover 11, a friction box 31 fixed on the top of the support seat 3, and a friction rod 32 sleeved on the friction box 31; an active mounting box 33 and a passive mounting box 34 are installed on the inner side of the friction box 31, and the inner sides of the active mounting box 33 and the passive mounting box 34 are respectively connected to an active friction wheel 35 and a passive friction wheel 36 through a rotating shaft; a power source for driving the active friction wheel 35 to rotate is installed on the top of the support seat 3, and the sides of the friction driving wheel and the passive friction wheel 36 are fixed with rubber structures, and are both in contact with the sides of the friction rod 32; an adjustment box 37 is fixed on the side of the passive mounting box 34, and a gas cavity 38 is formed between the adjustment box 37 and the active mounting box 33, and a connector 39 for externally monitoring the air pressure change inside the gas cavity 38 is installed on the side of the friction box 31.

[0030] It should be noted that the bottom of the platform shell 1 is open, so that the pipette can be installed on the stage 2 so that the bottom can pass through the platform shell 1, ensuring the interference-free effect of 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 the sleeve surface of the friction rod 32 and the top and bottom of the friction box 31 is provided with a rubber ring 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 inner side of the friction box 31, and the side of the adjustment box 37 is slidably connected to the inner side of the friction box 31; the material of the rubber structure is nitrile, which has both high friction coefficient and wear resistance.

[0031] More specifically, there are six groups of pitch attitude adjustment mechanisms, which are evenly distributed circumferentially on the top of the top cover 11 to form six-degree-of-freedom adjustment. The active friction wheel 35 is driven to rotate by a power source, and the active friction wheel 35 converts the rotational motion into the linear lifting of the friction rod 32 through the friction force between the rubber structure and the friction rod 32. Since the driven friction wheel 36 is in contact with the side of the friction rod 32, under the action of the friction force, the driven friction wheel 36 will follow the movement of the friction rod 32, and then by controlling the rotation speed and direction of the active friction wheel 35, the force applied by the friction rod 32 on the stage 2 in the six groups of pitch attitude adjustment mechanisms can be accurately adjusted, so that the pitch, yaw and longitudinal axial adjustment of the stage 2 can be controlled. , and utilizes the pitch support mechanism to provide flexible and rolling support to the stage 2. At the same time, when the friction rod 32 is raised or lowered, its side squeezes the gas cavity 38, causing the volume of the cavity to change. An external device for monitoring the internal air pressure change of the gas cavity 38 is connected through the connector 39, and the air pressure is monitored in real time. The data is input into the control system, and the driving power source adjusts the position of the friction rod 32 to form 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 problem of traditional gears or ball screws is effectively avoided, and it has the advantages of low cost, low noise and high response speed, so it can perfectly replace the traditional six-legged parallel platform and realize high-precision and fast response adjustment of the pipette tip in multi-dimensional directions.

[0032] like Figure 3 and Figure 4 As shown, in this embodiment, the pitch support mechanism includes: a bottom retaining frame 6 fixed to the platform shell 1 near the inner bottom, a plurality of bottom balls 61 rotatably connected to the bottom retaining frame 6, and a plurality of support springs 62 fixed to the top of the bottom retaining frame 6; the tops of the plurality of support springs 62 overlap with the bottom of the loading platform 2; a plurality of intermediate retaining frames 63 are fixed to the top of the bottom retaining frame 6, and a plurality of middle balls 64 are rotatably connected to the intermediate retaining frames 63.

[0033] It should be noted that a plurality of bottom balls 61, a plurality of intermediate retaining frames 63 and a plurality of support springs 62 are evenly distributed circumferentially on the bottom retaining frame 6 to form preliminary support for the bottom of the loading platform 2; a plurality of middle balls 64 are evenly distributed in a linear array along the length direction of the intermediate retaining frame 63 to provide rolling support in the vertical direction to avoid jamming when the loading platform 2 is tilted; the stiffness coefficient of the support spring 62 is preferably 30 N / mm to ensure a balance between the reset force and the adjustment accuracy.

[0034] More specifically, when the stage 2 pitches or yaws due to the gravity of the pipette and the thrust of the friction rod 32, the support spring 62 is compressed and deformed to store elastic potential energy. When the external force is removed, the support spring 62 releases the potential energy to push the stage 2 back to the equilibrium position, providing flexible support for the stage 2. At the same time, when the stage 2 pitches, the bottom ball 61 and the middle ball 64 contact the bottom of the stage 2, and the bottom ball 61 and the middle ball 64 roll to reduce the friction between the stage 2 and the platform shell 1, so that the stage 2 can pitch smoothly, thereby providing flexible and rolling support for the stage 2, so that the stage 2 can flexibly pitch while bearing the load, and reduces the friction resistance during the movement, thereby improving the movement accuracy and stability of the pipette adjustment platform.

[0035] like Figure 2 As shown, in this embodiment, the friction box 31 is detachably connected to a pressure cover 7 on the side facing the adjustment box 37, a slot 71 is provided on one side of the adjustment box 37, a disc spring 72 is fixed on one side of the pressure cover 7, and the side of the disc spring 72 is located on the inner side of the slot 71.

[0036] It should be noted that the pressure cover 7 and the friction box 31 are connected by bolts, and the bolts are evenly distributed on the edge of the pressure cover 7 to facilitate installation and disassembly; the stiffness and deformation parameters of the disc spring 72 are selected according to the relative motion range between the adjustment box 37 and the friction box 31 and the required preload force to ensure that the disc spring 72 can provide appropriate preload force during the sliding process of the adjustment box 37.

[0037] More specifically, by detachably connecting the pressure cover 7 to one side of the friction box 31 and positioning the disc spring 72 in the slot 71 on one side of the adjustment box 37, the elastic deformation of the disc spring 72 can provide a radial preload to the driven friction wheel 36 through the adjustment box 37. The preload can be adjusted by replacing the disc spring 72, thereby achieving friction-driven lifting and lowering of the adaptively adjustable friction force and driving the six-dimensional change of the adjustment surface.

[0038] In this embodiment, the power source includes: a motor base 8 fixed to the top of the support base 3, a second hollow cup motor 81 installed on the top of the motor base 8, and a worm 82 installed at the output end of the second hollow cup motor 81; a worm wheel 83 is fixed to one end of the rotating shaft on the active friction wheel 35, and the side of the worm 82 is meshed with the side of the worm wheel 83.

[0039] More specifically, by controlling the speed and direction of the second hollow cup motor 81, the second hollow cup motor 81 drives the worm 82 to rotate, the worm 82 meshes with the worm wheel 83, and transmits the rotational motion of the motor to the active friction wheel 35. The active friction wheel 35 drives the friction rod 32 to move through the friction force, so that it provides power for the active friction wheel 35, thereby achieving the adjustment of the pitch attitude of the stage 2. At the same time, the self-locking property of the transmission of 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, thereby improving the stability and reliability of the pitch attitude adjustment. Example 2

[0040] like Figure 5 and Figure 6 As shown, this embodiment is basically the same as the embodiment 1, and the difference is that it also includes: a rotation posture adjustment mechanism; the rotation posture adjustment mechanism includes: a ball assembly installed at the bottom end of the friction rod 32 for reducing the friction force on the top of the loading platform 2, a mounting groove 4 provided on the side of the top cover 11, and a first hollow cup motor 41 fixed on the inner side of the mounting groove 4; a friction roller 42 is overlapped on the top of the loading platform 2, and the output end of the first hollow cup motor 41 is connected to one end of the friction roller 42 through a mesh flexible coupling 43; A C-shaped plate 44 is fixed to the side of the top cover 11, the top end of the C-shaped plate 44 is threadedly connected with a screw 45, and the bottom end is fixed with a guide column 46; the bottom end of the screw 45 and the top end of the guide column 46 are rotatably connected with a pressure ring 47, and the sides of the screw 45 and the guide column 46 located between the C-shaped plate 44 and the pressure ring 47 are sleeved with a compression spring 48, and the side of the pressure ring 47 is in contact with the side of the mesh flexible coupling 43.

[0041] It should be noted that the mesh flexible coupling 43 is a HUAZN brand spring coupling, made of high-quality zinc alloy and high-strength spring, with an operating temperature 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 grooves, which can increase friction, prevent idling, and eliminate noise; the cross-sectional shape of the pressure ring 47 is semicircular, and the arc surface fits the side of the mesh flexible coupling 43.

[0042] More specifically, the first hollow cup motor 41 serves as a driving component, 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 angle deviation and vibration. Since the friction roller 42 is in contact with the top of the stage 2, it can drive the stage 2 to rotate through friction force during rotation, thereby realizing the adjustment of the rotation posture 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-plate 44, driving the pressure ring 47 to move up and down, and the guide column 46 guides the movement of the pressure ring 47 to ensure that the movement direction of the pressure ring 47 is stable. The compression spring 48 is compressed or stretched under the action of the screw 45 and the guide column 46, generating a certain pressure, so that the pressure ring 47 is always tightly fitted with the side of the mesh flexible coupling 43, thereby ensuring the stability of the tension of the mesh flexible coupling 43, avoiding unstable power transmission due to vibration or looseness, improving the accuracy and reliability of the rotation posture adjustment, and avoiding the problem of machining flatness of the friction surface at the top of the worktable 2.

[0043] In this embodiment, the ball assembly includes: a connecting 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 connecting block 5; the bottom ends of the plurality of contact balls 51 are in contact with the top of the stage 2.

[0044] 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 connecting block 5 at the bottom and the contact ball 51. The contact ball 51 rolls as the stage 2 rotates, thereby converting the sliding friction into rolling friction, thereby reducing the friction between the top of the stage 2 and the bottom of the friction rod 32, avoiding rotational interference, and effectively reducing the frictional resistance of the stage 2 during rotation, improving the rotation efficiency, and reducing energy loss.

[0045] The present invention provides a pressure feedback control method for a six-degree-of-freedom precision pipette adjustment platform, comprising the following steps: S1, real-time monitoring of the dynamic changes of the air pressure in the gas cavities 38 of the six groups of pitch attitude adjustment mechanisms, and calculation of the lifting and lowering amounts of the six friction rods 32 based on the mapping relationship between the pressure value and the displacement of the friction rods 32; S2, calculating the lifting amount of the six friction rods 32 based on the inverse solution algorithm of the kinematics of the parallel mechanism to solve the current six-degree-of-freedom position parameters of the stage 2; S3, comparing the calculated actual position parameters of the stage 2 with the preset target position parameters, and calculating the position error value in each degree of freedom direction; S4. According to the position error value, the power source is closed-loop regulated to drive the steering 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 and the target position parameter of the stage 2 approaches zero.

[0046] In this embodiment, in step S1, the real-time monitoring of the air pressure is performed by monitoring the dynamic changes through a pressure sensor, wherein the model of the pressure sensor is preferably a XGZP6847A vacuum negative pressure sensor with a pressure range of 0-5 kPa.

[0047] Furthermore, for the setting of the pre-experimental calibration of the mapping relationship, the pressure-displacement linear relationship model is as follows: the initial position of the friction rod 32 is set as the reference point , the volume of the gas cavity 38 is , control the friction rod 32 with a known step length (such as μm) and record the corresponding air pressure value at each displacement point For example, when the friction rod 32 rises 1 μm, the cavity volume decreases. , the air pressure increases ; According to the experimental data, the pressure change is fitted With displacement The linear relationship is: ; Among them, the proportionality coefficient (Unit: Pa / μm), obtained by experimental calibration.

[0048] Furthermore, 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 air cavities 38 ( ); with reference pressure (the air pressure when the friction rod 32 is in the initial position) is used as a reference to calculate the air pressure change : ; Using pre-calibrated scaling factors , calculate the lifting displacement of each friction rod 32: ; in, Indicates that the friction rod 32 rises, Indicates a decrease.

[0049] Example: Assume that the friction rod 32 calibration coefficient Pa / μm, real-time monitoring of air pressure increase Pa, then its displacement is: μm; This indicates that the friction rod 32 has risen by 10 μm.

[0050] In this embodiment, in step S2, the current six-degree-of-freedom position parameters of the stage 2 are solved: first, the pipette base coordinate system and the stage 2 moving platform coordinate system are defined, and the initial positions of the six contact points on the two are determined respectively. Among them, the base coordinate system is fixed at the bottom center of the platform shell 1, and the moving platform coordinate system is aligned with the geometric center of the stage 2; when the stage 2 is displaced or rotated due to the lifting and lowering of the friction rod 32, the position of the hinge point on the moving platform changes accordingly, and the lifting amount of each friction rod 32 corresponds to the actual change value of the length of the friction rod 32; The length change of the friction rod 32 is associated with the posture parameters of the stage 2 (including X / Y / Z translation and rotation angles around three axes) through a geometric model. Assuming that the stage 2 is in a certain unknown posture, 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 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 difference 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 posture and the theoretical model.

[0051] The Newton-Raphson iteration method is used for optimization, and the guessed values ​​of the posture parameters are continuously adjusted so that the length change of the friction rod 32 calculated by the model gradually approaches the measured value.

[0052] Specifically, the initial posture is first set (such as the stage 2 is in a horizontal position and has no translation), the theoretical length change of the friction rod 32 is calculated, and the error is obtained by comparing it with the measured value. Subsequently, the adjustment direction and amplitude are determined by analyzing the sensitivity of each posture parameter (such as the translation component or the rotation angle) to the length of the friction rod 32 (i.e., the Jacobian matrix). For example, if the actual elongation of a friction rod 32 is greater than the model prediction value, the system will determine that the stage 2 may be tilted or translated in the direction of the friction rod 32, and correct the posture parameters accordingly. After multiple iterations, the error is gradually reduced, and finally the six-degree-of-freedom parameters that meet the accuracy requirements are obtained.

[0053] It should be noted that by solving the current six-degree-of-freedom position parameters of the stage 2, the actual state of the stage 2 in the six degrees of freedom can be accurately identified. Whether it is micron-level translation or millirad rotation, it can be analyzed and fed back to the control system through the algorithm. The high-precision posture solution capability enables the pipette tip to quickly align with the target hole position in scenarios such as microfluidic chip injection, avoiding liquid splashing or positioning failure due to posture deviation, and ultimately achieving sub-micron positioning accuracy and stable repeatable operation.

[0054] In this embodiment, in step S3, the rotation error needs to take into account 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: ; Similarly, calculate the errors of the yaw angle β around the Y axis and the roll angle γ around the Z axis: ; Then the angle error is limited to the interval , avoiding the confusion of error direction caused by 360° periodicity, and finally obtaining the six-degree-of-freedom error vector: ,This vector will be used as the input of step S4 to generate the control signal for driving the motor.

[0055] In this embodiment, in step S4, when the error vector is input to the controller, the controller decomposes the six-degree-of-freedom error into independent displacement adjustment amounts of each friction rod 32 according to a preset mapping relationship; for example, a certain friction rod 32 may need to rise 0.5 μm to drive the stage 2 to rotate around the X-axis, while another friction rod 32 needs to fall 0.3 μm to balance the overall posture. The control signal is then sent to the second hollow cup motor 81 that drives each friction rod 32. The direction of rotation (forward or reverse) of the motor is determined by the positive or negative sign of the adjustment amount, and the speed is proportional to the absolute value of the adjustment amount, thereby quickly and accurately driving the friction rod 32 to the target position.

[0056] In this process, the high responsiveness and low inertia characteristics of the second hollow cup motor 81 play a key role. For example, when the error is detected and the friction rod 32 needs to rise by 2 μm, the motor will rotate rapidly at a speed matching the error amplitude (such as 20 RPM / μm), and the rotational motion will be converted into the linear lifting and lowering of the friction rod 32 through the worm gear 83 and worm 82 transmission mechanism. The preload 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 gap-free characteristics of the transmission and avoids the response delay or positioning deviation caused by mechanical backlash in the traditional gear or screw system. 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 regulation. If a friction rod 32 does not fully reach the target position 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.

[0057] The above is based on the ideal embodiment of the present invention. Through the above description, it is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is limited by the attached claims rather than the above description, and it is intended to include all changes within the meaning and scope of the equivalent elements of the claims. Any figure mark in the claims should not be regarded as limiting the claims involved.

[0058] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes 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: include: A platform housing, a top cover fixed on the top of the platform housing, and a stage disposed inside the platform housing for mounting a pipette; A pitch support mechanism for providing both flexible and rolling support to the loading platform is installed on the inner side of the platform shell, and a plurality of pitch attitude adjustment mechanisms are installed on the top of the top cover; The pitch attitude adjustment mechanism comprises: a support seat fixed on the top of the top cover, a friction box fixed on the top of the support seat, and a friction rod sleeved on the friction box; an active mounting box and a driven mounting box are mounted on the inner side of the friction box, and the inner sides of the active mounting box and the driven mounting box are respectively connected to an active friction wheel and a driven friction wheel through a rotating shaft; A power source for driving the active friction wheel to rotate is installed on the top of the support seat, and rubber structures are fixed to the sides of the friction driving wheel and the driven friction wheel, and are both in contact with the sides of the friction rod; an adjustment box is fixed to the side of the driven mounting box, and a gas cavity is formed between the adjustment box and the active mounting box, and a connector for an external device for monitoring the air pressure changes inside the gas cavity is installed on the side of the friction box.

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

3. The six-degree-of-freedom precision pipette adjustment platform based on friction drive and pressure feedback according to claim 1, characterized in that: Also includes: Rotating attitude adjustment mechanism; The rotation posture adjustment mechanism comprises: a ball assembly installed at the bottom end of the friction rod for reducing the friction force on the top of the loading platform, a mounting groove provided on the side of the top cover, and a first hollow cup motor fixed inside the mounting groove; a friction roller is overlapped on the top of the loading platform, and the output end of the first hollow cup motor is connected to one end of the friction roller through a mesh flexible coupling; A C-shaped plate is fixed to the side of the top cover, the top of the C-shaped plate is threadedly connected with a screw, and the bottom is fixed with a guide column; the bottom end of the screw and the top end of the guide column are rotatably connected with a pressure ring, and the sides of the screw and the guide column located between the C-shaped plate and the pressure ring are sleeved with compression springs, and the side of the pressure ring is in contact with the side of the mesh 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 comprises: a connecting block fixed at the bottom end of the friction rod, and a plurality of contact balls rotatably connected to the bottom end of the connecting block; the bottom ends of the plurality of contact balls are in contact with the top of the loading platform.

5. The six-degree-of-freedom precision pipette adjustment platform based on friction drive and pressure feedback according to claim 1, characterized in that: The pitch support mechanism includes: a bottom retaining frame fixed to the platform shell near the inner bottom, a plurality of bottom balls rotatably connected to the bottom retaining frame, and a plurality of support springs fixed to the top of the bottom retaining frame; the tops of the plurality of support springs overlap the bottom of the loading platform; a plurality of intermediate retaining frames are fixed to the top of the bottom retaining frame, and a plurality of middle balls are rotatably connected to the intermediate retaining frames.

6. The six-degree-of-freedom precision pipette adjustment platform based on friction drive and pressure feedback according to claim 1, characterized in that: The friction box is detachably connected with a pressure cover on the side facing the adjustment box, a slot is provided on one side of the adjustment box, a disc spring is fixed on one side of the pressure cover, and the side of the disc spring is located on the inner side of the slot.

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 on the top of the support base, a second hollow cup motor installed on the top of the motor base, and a worm installed on the output end of the second hollow cup motor; a worm wheel is fixed to one end of the rotating shaft on the active friction wheel, and the side surface of the worm gear is meshed with the side surface of the worm wheel.

8. A pressure feedback control method based on the six-degree-of-freedom precision pipette adjustment platform according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1. Real-time monitoring of the dynamic changes of air pressure in the gas cavities of several pitch attitude adjustment mechanisms, and calculation of the lifting and lowering amount of each friction rod based on the mapping relationship between the pressure value and the displacement of the friction rod; S2, calculating the lifting amount of several friction rods based on the inverse solution algorithm of parallel mechanism kinematics to solve the current six-degree-of-freedom position parameters of the stage; S3, comparing the calculated actual position parameters of the stage with the preset target position parameters, and calculating the position error value in each degree of freedom direction; S4. According to the position error value, the power source drives the steering and speed of the active friction wheel in a closed loop, and dynamically adjusts the lifting amount of each friction rod until the error value between the actual position parameter and the target position parameter of the stage approaches zero.

9. The pressure feedback control method according to claim 8, characterized in that: In step S1, the real-time monitoring of the air pressure is performed by monitoring the dynamic changes through a pressure sensor; the mapping relationship is expressed by a pressure-displacement linear relationship model calibrated in a pre-experiment, which is used to convert the air pressure change value into the actual lifting and lowering displacement of each friction rod.

10. The pressure feedback control method according to claim 8, characterized in that: In step 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.

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