Asymmetric pneumatic flexible gripper and its grasping control method combined with visual feedback

Abstract

This invention discloses an asymmetric pneumatic flexible gripper and its gripping control method combined with visual feedback. The asymmetric pneumatic flexible gripper includes: a fixed part, three pneumatic grippers, and an inflation / deflation device; the first and second pneumatic grippers are arranged side-by-side at the first end of the fixed part, and the third pneumatic gripper is arranged at the second end of the fixed part; each pneumatic gripper includes a rigid cavity with one open side and an elastic membrane sealing the open side, forming a flexible chamber; the size of the first and second pneumatic grippers is smaller than that of the third pneumatic gripper; the elastic membranes of the first and second pneumatic grippers and the elastic membrane of the third pneumatic gripper are arranged opposite to each other; the inflation / deflation device is connected to the flexible chamber of each pneumatic gripper through an air pipe and adjusts the inflation / deflation of each flexible chamber, causing the elastic membrane to expand towards the opposite side, forming a gripping point for the target object. This invention uses an asymmetric layout of flexible grippers to create a more enveloping contact interface, which can effectively grip irregular workpieces.

Description

Technical Field

[0001] This invention belongs to the field of robot control technology, specifically relating to an asymmetric pneumatic flexible gripper and its grasping control method combined with visual feedback. Background Technology

[0002] With the rapid development of automation technology, robotic grasping tasks are becoming increasingly frequent and complex in industrial production, warehousing and logistics, and service robots. Traditional industrial robot gripping devices mostly use rigid grippers. Although these grippers are structurally stable and have strong holding force, when handling irregularly shaped, fragile, delicate, or soft objects (such as fruits, thin electronic components, or irregularly shaped workpieces), rigid contact can easily cause surface damage or structural destruction. Furthermore, rigid grippers have low tolerance for dimensional deviations, often requiring custom-made fixtures for specific shapes, lacking versatility. It is worth noting that when dealing with objects with a shifted center of gravity or irregular shapes, traditional symmetrical two-finger grippers often struggle to achieve precise envelopment due to limited contact points, easily leading to unstable gripping or even workpiece slippage. Summary of the Invention

[0003] This invention provides an asymmetric pneumatic flexible gripper and a gripping control method combined with visual feedback. The flexible gripper with an asymmetric layout creates a more enveloping contact interface, effectively solving the problem of poor gripping robustness of traditional two-finger grippers when handling irregular workpieces.

[0004] To achieve the above technical objectives, the present invention adopts the following technical solution:

[0005] An asymmetric pneumatic flexible gripper includes: a fixing part, a first pneumatic gripper, a second pneumatic gripper, a third pneumatic gripper, and an air filling and suction device; the fixing part includes two opposing ends, the first and second pneumatic grippers are arranged side by side at the first end of the fixing part, and the third pneumatic gripper is arranged at the second end of the fixing part.

[0006] Each pneumatic gripper includes a rigid cavity with one open side and an elastic membrane sealing the open side to form a flexible chamber; the flexible chambers of the first and second pneumatic grippers are the same size and smaller than the flexible chamber of the third pneumatic gripper; the elastic membranes of the first and second pneumatic grippers and the elastic membrane of the third pneumatic gripper are arranged opposite to each other.

[0007] The inflation / inflation device is connected to the flexible chamber of each pneumatic gripper via an air tube, and the inflation / deflation of each flexible chamber is adjusted so that the elastic membrane expands toward the opposite side, and the top end forms the gripping point of the target object.

[0008] Furthermore, the two ends of the fixing part are respectively provided with spring-shaped supports with a spiral structure in the middle, and the top of the spring-shaped supports is used to support and fix the pneumatic gripper.

[0009] Furthermore, the inflation / inhalation device includes a microcontroller, a relay, a solenoid valve, an air pump, and an air tube;

[0010] The first end of the trachea is connected to the flexible chamber, and the second end is connected to the air pump via a solenoid valve.

[0011] The microcontroller is connected to the solenoid valve via a relay to control the opening and closing of the solenoid valve.

[0012] Furthermore, the inflation / inhalation device is configured with three relays, three solenoid valves, and three air tubes, so as to independently control the air pressure of each flexible chamber.

[0013] Furthermore, the asymmetric pneumatic flexible gripper also includes a depth camera for acquiring the deformation of all pneumatic gripper elastic membranes and the depth information of the target object;

[0014] The microcontroller controls the inflation / deflation status of the air pump and the on / off state of the solenoid valve based on the data collected by the depth camera.

[0015] A grasping control method for the aforementioned asymmetric pneumatic flexible gripper combined with visual feedback includes:

[0016] S1. Establish a mapping function between the expansion length and the inflation amount for each elastic membrane;

[0017] S2. Obtain the rectangular candidate frame of the target object, adjust the flexible gripper downwards to be above the target object and the two pneumatic grippers at both ends to be at the same height as the target object, and the axis is perpendicular to the long side of the candidate frame; the axis of the flexible gripper refers to the line connecting the centers of the two ends of the fixed part.

[0018] S3. Based on the mapping function established in S1, the short side length of the candidate box, and the initial opening distance of the flexible gripper, calculate the target inflation volume of each flexible chamber and the target expansion length of the corresponding elastic membrane.

[0019] S4. The inflation and suction device inflates each flexible chamber according to the target inflation volume and monitors the actual expansion length of each elastic membrane in real time.

[0020] S5. The PID control algorithm is adopted, and the inflation volume of each flexible chamber is adjusted according to the actual expansion length and target expansion length of each elastic membrane, so that each elastic membrane expands to its target expansion length.

[0021] Furthermore, let the first The target expansion length of the elastic membrane of each pneumatic gripper is The actual expansion length is Then, the expansion deviation is calculated as follows: The inflation volume of the corresponding flexible chamber is adjusted using a PID control algorithm, as expressed as:

[0022] ;

[0023] In the formula, , , These are the proportional coefficient, integral coefficient, and derivative coefficient in the PID control algorithm; The first step in the PID control process The incremental adjustment value of the inflation volume at each control moment. This indicates the current control moment in the PID control process. This represents the index of the discrete control moment in the PID control process; j=0 indicates the initial moment of the PID control process. and The elastic membrane of the pneumatic gripper is in the first... , The expansion deviation at each control moment;

[0024] if , If the allowable error threshold for expansion deviation is set, the inflation / inflation device continues to inflate the flexible chamber. Then the inflation / inflation device controls the deflation of the flexible chamber; if If so, the current air pressure will be maintained.

[0025] Furthermore, step S4 also includes: real-time monitoring of the target object's center of gravity coordinates. When the target object is detected to have slipped, i.e., the center of gravity shifts. When the preset compression depth has been reached, stop inflating each flexible chamber and maintain the current state or depressurize each flexible chamber according to the preset amount; among which, This is the offset threshold. and The target object at the current time Moment and the previous moment The coordinates of the centroid.

[0026] Furthermore, S3 calculates the target inflation volume of each flexible chamber and the target expansion length of the corresponding elastic membrane, specifically: based on the preset initial opening distance. And the length of the short side of the candidate box for visual recognition. A symmetrical expansion strategy is employed to calculate the uniform target expansion length for each pressure gripper. :

[0027] ;

[0028] In the formula, This represents the initial opening distance of the flexible gripper. is the length of the shorter side of the candidate box. This is a pre-set allowance factor based on the material's deformation coefficient;

[0029] Call the independent inverse mapping functions of the first, second, and third air pressure grippers to calculate the corresponding target inflation volume:

[0030] ;

[0031] ;

[0032] ;

[0033] In the formula, These are the target inflation volumes for the flexible chambers of the first, second, and third air pressure grippers, respectively. These are the inverse mapping functions of the elastic membrane expansion length and inflation volume of the first, second, and third air pressure grippers, respectively.

[0034] Furthermore, the inflation volume of each flexible chamber Inflation times with a fixed duration Measurements were taken; the expansion lengths of each elastic membrane were constructed. With inflation volume mapping function Represented as:

[0035] ;

[0036] In the formula, To accumulate the number of inflations, For the first The expansion length of the elastic membrane of each pneumatic gripper With inflation volume The mapping function, For mapping functions The One fitting coefficient, The number of fitting coefficients. ; This refers to the amount of air inflated each time. This refers to the duration of each inflation.

[0037] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0038] The asymmetric pneumatic flexible gripper provided by this invention overcomes the technical bottleneck of traditional symmetrical two-finger grippers, which suffer from inaccurate gripping and easy slippage due to limited contact points when facing irregularly shaped or offset workpieces, through an asymmetric bubble gripper layout (a combination of a large bubble gripper on one side and two small grippers on the other). By constructing an isosceles triangular contact interface, it significantly improves the wrapping and gripping robustness of irregularly shaped and non-geometric objects. By setting helical spring supports and arc-shaped rigid cavities inside the gripper, this invention enhances the overall structural rigidity and reset capability of the gripper while maintaining the advantages of flexible gripping, ensuring stability under heavy loads. In addition, this invention integrates a depth camera into the gripper fixing part, achieving a deep fusion of visual perception and pneumatic drive. Utilizing real-time acquired depth information and elastic membrane deformation feedback, it can autonomously generate the optimal gripping point and dynamically optimize the gripping path, completely changing the "blind gripping" state of traditional flexible grippers and greatly improving the repeatability and intelligence level of gripping. Finally, the elastic membrane is connected to the inflation and suction system through a sealed air passage. With the help of an algorithm, the air pressure is precisely adjusted to ensure that the gripping force is delicate and controllable, which can effectively protect fragile or precision workpieces from damage. Attached Figure Description

[0039] Figure 1 This is an assembly diagram of the asymmetric pneumatic flexible gripper described in an embodiment of the present invention;

[0040] Figure 2 This is an exploded schematic diagram of the two symmetrically arranged first and second pneumatic grippers described in an embodiment of the present invention;

[0041] Figure 3 This is an exploded view of the third pneumatic gripper described in an embodiment of the present invention;

[0042] Figure 4 This is a schematic diagram of the air-inhalation device according to an embodiment of the present invention;

[0043] Figure 5 This is the Y-shaped force-bearing topology described in the embodiments of the present invention;

[0044] Figure 6 This is a schematic diagram of the overall gripping action of the gripper as described in an embodiment of the present invention;

[0045] Figure 7 This is a schematic diagram of the target object grasping control method according to an embodiment of the present invention.

[0046] Reference numerals: 10-First pneumatic gripper, 11-Rigid cavity of the first pneumatic gripper, 12-Elastic membrane of the first pneumatic gripper, 13-Nested pressing component of the first pneumatic gripper, 20-Second pneumatic gripper, 21-Rigid cavity of the second pneumatic gripper, 22-Elastic membrane of the second pneumatic gripper, 23-Nested pressing component of the second pneumatic gripper, 30-Third pneumatic gripper, 31-Rigid cavity of the third pneumatic gripper, 32-Elastic membrane of the third pneumatic gripper, 33-Nested pressing component of the third pneumatic gripper, 40-Fixing part, 41-Spring-shaped support, 50-Inflation / Inhalation device, 51-Microcontroller, 52-Relay, 53-Solenoid valve, 54-Air pump, 55-External power supply, 56-Air tube, 60-Depth camera, 70-Target object. Detailed Implementation

[0047] The embodiments of the present invention will be described in detail below. These embodiments are based on the technical solutions of the present invention and provide detailed implementation methods and specific operation processes to further explain the technical solutions of the present invention.

[0048] Example 1

[0049] This embodiment provides an asymmetric pneumatic flexible gripper, such as Figure 1-3 As shown, it includes: a fixing part 40, a first pneumatic gripper 10, a second pneumatic gripper 20, a third pneumatic gripper 30, an air filling and suction device 50, and a depth camera 60.

[0050] The fixing part 40 includes two opposing ends. The first pneumatic gripper 10 and the second pneumatic gripper 20 are arranged side by side at the first end of the fixing part 40, and the third pneumatic gripper 30 is arranged at the second end of the fixing part 40. Specifically, the two ends of the fixing part 40 are respectively provided with spring-shaped supports 41 with a spiral structure in the middle. On the one hand, the top of the spring-shaped support 41 is used to support and fix the first pneumatic gripper 10, the second pneumatic gripper 20 and the third pneumatic gripper 30. On the other hand, it can be used to provide multi-directional displacement compensation during the gripping of the target object 70, and assist the elastic membranes 12 of the first pneumatic gripper, 22 of the second pneumatic gripper and 32 of the third pneumatic gripper to reset after gripping and releasing.

[0051] Each pneumatic gripper includes a rigid cavity with one open side and an elastic membrane sealing the open side. The flexible chambers of the first pneumatic gripper 10 and the second pneumatic gripper 20 are the same size, but smaller than the flexible chamber of the third pneumatic gripper 30.

[0052] The openings of the rigid cavity 11 of the first pneumatic gripper, the rigid cavity 21 of the second pneumatic gripper, and the rigid cavity 31 of the third pneumatic gripper are arranged opposite to each other. That is, the elastic membranes 12 of the first pneumatic gripper, the elastic membranes 22 of the second pneumatic gripper, and the elastic membranes 32 of the third pneumatic gripper are also arranged opposite to each other.

[0053] like Figure 4 As shown, the inflation / inhalation device 50 includes a microcontroller 51, a relay 52, a solenoid valve 53, an air pump 54, an external power supply 55, and an air tube 56. The external power supply 55 provides power to the entire inflation / inhalation device. The first end of the air tube 56 is connected to the flexible chamber, and the second end is connected to the air pump 54 through the solenoid valve 53. The microcontroller 51 is connected to the solenoid valve 53 through the relay 52 to control the on / off state of the solenoid valve 53. In a more preferred embodiment, the inflation / inhalation device 50 has three relays 52, three solenoid valves 53, and three air tubes 56, respectively, to independently control the air pressure of each flexible chamber and adjust the deformation degree, i.e., the expansion length, of the elastic membrane 12 of the first air pressure gripper, the elastic membrane 22 of the second air pressure gripper, and the elastic membrane 32 of the third air pressure gripper.

[0054] In this embodiment, the asymmetric pneumatic flexible gripper has an air inlet / outlet device 50 that connects to the flexible chambers of the first pneumatic gripper 10, the second pneumatic gripper 20, and the third pneumatic gripper 30 via an air pipe 56. This device adjusts the inflation / deflation of each flexible chamber. Under sufficient air pressure, the elastic membranes 12, 22, and 32 of the first, second, and third pneumatic grippers deform and expand towards their opposite sides, forming a Y-shaped force-bearing topology in space. This achieves clamping of the target object 70 and enables optimal envelope alignment along the long axis of irregularly shaped workpieces (i.e., the target object). Figure 5 , Figure 6 As shown.

[0055] To achieve automated gripping control of the asymmetric pneumatic flexible gripper in this embodiment, a depth camera 60 collects the deformation of the elastic membrane 12 of the first pneumatic gripper, the elastic membrane 22 of the second pneumatic gripper, and the elastic membrane 32 of the third pneumatic gripper, as well as the depth information of the target object 70. Then, the microcontroller 51 intelligently controls the inflation / deflation status of the air pump 54 and the on / off state of the solenoid valve 53 based on the data collected by the depth camera 60. The method for intelligent control to achieve gripping is detailed in Embodiment 3.

[0056] Example 2

[0057] This embodiment 2 provides a more detailed explanation of the connection relationships between the components of the asymmetric pneumatic flexible gripper in embodiment 1.

[0058] The rigid cavity 11 of the first pneumatic gripper, the rigid cavity 21 of the second pneumatic gripper, and the rigid cavity 31 of the third pneumatic gripper adopt an arc-shaped support as a forming skeleton, and the bottom is provided with a hole for the air pipe 56 to pass through.

[0059] The spring-like support 41 is helical, with its lower end nested within the end of the fixing part 40 and its upper end supporting the rigid cavity. This helical spring structure provides nonlinear stiffness feedback at the moment of grasping contact, effectively absorbing impact energy.

[0060] The elastic membrane 12 of the first pneumatic gripper is fixed to the open edge of the rigid cavity 11 of the first pneumatic gripper by the nested pressing component 13 of the first pneumatic gripper, as well as by screws and glue. The elastic membrane 22 of the second pneumatic gripper is fixed to the open edge of the rigid cavity 21 of the second pneumatic gripper by the nested pressing component 23 of the second pneumatic gripper, as well as by screws and glue. The elastic membrane 32 of the third pneumatic gripper is fixed to the open edge of the rigid cavity 31 of the third pneumatic gripper by the nested pressing component 33 of the third pneumatic gripper, as well as by screws and glue, to ensure that the flexible chamber maintains good airtightness when the inflation pressure is high.

[0061] The main body of the flexible gripper adopts an asymmetrical spatial layout. At one end are two symmetrically arranged small-sized first pneumatic grippers 10 and 20, and at the other end is a large-sized third pneumatic gripper 30. This layout creates a triangular contact interface in physical space. The asymmetrical structural design aims to solve the problem of workpiece slippage caused by the offset of the workpiece's center of gravity through the differentiated force distribution between the third pneumatic gripper 30 and the small-sized first and second pneumatic grippers 10 and 20.

[0062] The first pneumatic gripper 10, the second pneumatic gripper 20, and the third pneumatic gripper 30 are all integrally molded using high-strength photosensitive resin material through industrial-grade 3D printing technology, ensuring the dimensional stability and fatigue resistance of the structural components when subjected to high-pressure gas expansion. The rigid cavity 11 of the arc-shaped first pneumatic gripper, the rigid cavity 21 of the second pneumatic gripper, the rigid cavity 31 of the third pneumatic gripper, and the spring-shaped support 41 possess excellent axial flexibility and radial deformation resistance. The spring-shaped support 41 achieves a precise fit between the gripper-fixed nested component and the fixing part 40, and is locked in place with high-performance structural adhesive, ensuring the reliability of the mechanical connection.

[0063] The elastic membrane is made of a high-performance modified silicone rubber superelastic film. This material has extremely high elongation, low hysteresis effect, and excellent tear resistance, ensuring consistent physical properties under multiple inflation and deflation cycles. Furthermore, the elastic membranes 12, 22, and 32 of the first, second, and third pneumatic grippers are secured to the edges of the rigid cavities 11, 21, and 31 of the first, second, and third pneumatic grippers, respectively, by nesting pressing components 13, 23, and 33, and high-precision screws. A dedicated sealing layer further ensures a full circumferential seal, maintaining extremely high chamber airtightness even under high-pressure conditions.

[0064] The fixing part 40 and the depth camera fixing part are also made of high-toughness engineering nylon material through additive manufacturing, which has extremely high structural rigidity and shock absorption performance. The fixing part 40 serves as the central mounting base of the entire end effector and interfaces with the robot end effector through a modular standard interface, which not only reduces the overall weight burden of the system, but also significantly improves the environmental adaptability of the structural components.

[0065] The inflation / inflation device 50 is integrated outside the fixing part 40. The air pipe 56 passes through holes at the bottom of the rigid cavities 11, 21, and 31 of the first, second, and third pneumatic grippers into the internal flexible chamber. Employing high-precision additive manufacturing technology, precise airflow channels are pre-installed inside the rigid cavities 11, 21, and 31 of the first, second, and third pneumatic grippers, further simplifying the assembly process. This combination of internal flow channel design and sealing curing process effectively prevents gas leakage during reciprocating expansion, improving the efficiency of fluid dynamics transmission.

[0066] The depth camera 60 is mounted to one end of the depth camera fixing part via a precision positioning pin, and the other end of the depth camera fixing part is connected to the fixing part 40. Furthermore, the optical axis center of the depth camera 60, through a structured offset design, always covers the geometric working area enclosed by the first pneumatic gripper 10, the second pneumatic gripper 20, and the third pneumatic gripper 30. This integrated layout ensures a rigid connection between the sensor and the actuator, effectively avoiding dimensional deviations during movement and providing accurate data input for visual feedback.

[0067] The microcontroller 51, acting as the logic control core, drives the relay 52 to independently control the on / off state of the solenoid valve 53. When the air pump 54 starts, compressed air is distributed to each flexible chamber via the solenoid valve 53. By changing the hydrostatic pressure inside the elastic diaphragm, precise control of the geometric deformation of the elastic diaphragm is achieved, thereby completing the stable envelopment and gripping of irregularly shaped parts.

[0068] Example 3

[0069] This embodiment provides a grasping control method for an asymmetric pneumatic flexible gripper combined with visual feedback, such as... Figure 7 As shown, it includes:

[0070] S1. Establish a mapping function between the expansion length and the inflation amount for each elastic membrane.

[0071] In this embodiment, a fixed duration is used. Inflation is performed cyclically for each inflation cycle, therefore the inflation volume of each flexible chamber is... It can be done for a fixed duration each time. Number of inflations Measurements were performed to construct the expansion length of each elastic membrane. With inflation volume mapping function Represented as:

[0072] ;

[0073] In the formula, To accumulate the number of inflations, For the first The expansion length of the elastic membrane of each pneumatic gripper With inflation volume The mapping function, For mapping functions The One fitting coefficient, The number of fitting coefficients. ; This refers to the amount of air inflated each time. This refers to the duration of each inflation.

[0074] In the specific process of constructing the mapping function, the fitting coefficients of each mapping function are determined. In this embodiment, the method for determining the fitting coefficients includes: first, controlling the flexible chamber to be in an initial relaxed state and performing depth zeroing, and then, for a fixed duration... The system performs cyclic inflation for each inflation cycle, and uses a depth camera to record the length of the elastic membrane protrusion during each inflation cycle. The higher-order polynomial mapping function is obtained by fitting using the least squares method. The fitting coefficients in .

[0075] S2. Obtain the rectangular candidate frame of the target object, adjust the flexible gripper downwards to be above the target object and the two pneumatic grippers at both ends to be at the same height as the target object, and the axis is perpendicular to the long side of the candidate frame; the axis of the flexible gripper refers to the line connecting the centers of the two ends of the fixed part.

[0076] In this embodiment, a pre-trained deep neural network (SOFT-GG-CNN) is used to obtain rectangular grasping candidate boxes. Additionally, visual feedback is used to adjust the robotic arm's pose, ensuring the initial opening distance formed by the first, second, and third pneumatic grippers is achieved. The geometric center is aligned with the geometric center of the workpiece; at the same time, the flexible gripper is adjusted so that its axis is perpendicular to the long side of the candidate frame.

[0077] S3. Based on the mapping function established in S1, the short side length of the candidate box, and the initial opening distance of the flexible gripper, calculate the target inflation volume of each flexible chamber and the target expansion length of the corresponding elastic membrane.

[0078] Specifically, based on the preset initial opening distance and the length of the short side of the candidate box obtained by visual recognition A symmetrical expansion strategy is employed to calculate the uniform target expansion length for each pressure gripper. :

[0079] ;

[0080] In the formula, This represents the initial opening distance of the flexible gripper. The length of the short side of the candidate box (the width of the target work area). The gripping allowance factor, which is preset based on the material deformation coefficient, can offset the nonlinear stiffness change of the elastic membrane flexible material at the moment of contact with the workpiece, ensuring that a stable envelope extrusion is formed at the moment of contact.

[0081] Call the independent inverse mapping functions of the first, second, and third air pressure grippers to calculate the corresponding target inflation volume:

[0082] ;

[0083] ;

[0084] ;

[0085] In the formula, These are the target inflation volumes for the flexible chambers of the first, second, and third air pressure grippers, respectively. These are the inverse mapping functions of the elastic membrane expansion length and inflation volume of the first, second, and third air pressure grippers, respectively.

[0086] S4. The inflation device inflates each flexible chamber according to the target inflation volume and monitors the actual expansion length of each elastic membrane in real time.

[0087] In this embodiment, a depth camera is used to acquire depth images of each elastic membrane, and existing image recognition technology is used to extract the deformation features of the elastic membrane to obtain the expansion length of the elastic membrane relative to the initial relaxed state. This embodiment does not elaborate on the implementation principle of this monitoring.

[0088] S5. The PID control algorithm is adopted, and the inflation volume of each flexible chamber is adjusted according to the actual expansion length and target expansion length of each elastic membrane, so that each elastic membrane expands to its target expansion length.

[0089] Let the first The target expansion length of the elastic membrane of each pneumatic gripper is In step S4, the actual expansion length of the elastic membrane was monitored to be... Then, the expansion deviation is calculated as follows: The inflation volume of each flexible chamber is dynamically fine-tuned using a PID control algorithm.

[0090] ;

[0091] In the formula, , , These are the proportional coefficient, integral coefficient, and derivative coefficient in the PID control algorithm; This represents the first step in the PID control process. The incremental adjustment value of inflation volume at each control moment. This indicates the current control moment in the PID control process. Indices representing the discrete control moments in the PID control process; This indicates the initial moment of the PID control process.

[0092] Among them, the proportional term It can respond instantly to insufficient deformation and is the main driving force for inflating the solenoid valve; integral term By accumulating the deviations from each sampling cycle, the static residuals caused by gas path damping or minute leaks are eliminated, ensuring that the capture tends towards the target steady state; differential term This is achieved by monitoring the rate of change of the deviation. Predict the slippage trend of the target workpiece (i.e., the offset of the center of gravity). It also provides damping compensation to suppress system oscillations.

[0093] If expansion deviation , If the allowable error threshold for expansion deviation is set, the inflation / inflation device continues to inflate the flexible chamber. Then the inflation / inflation device controls the deflation of the flexible chamber; if This indicates that the current grasping state is stable, so stop the inflation or deflation operation and maintain the current air pressure state.

[0094] During the grasping and control of the target object, the target object maintains geometric torque balance: .in, Based on each flexible chamber Number of inflations and the actual expansion length of its elastic membrane The estimated output force vector ensures that the center of the grasping force always coincides with the visual centroid. It refers to the first The vector from the expansion vertex of the elastic membrane of the pneumatic gripper to the center of gravity of the target object. This strategy ensures that the center of the gripping force coincides with the center of mass of the workpiece obtained from visual feedback during the dynamic process, achieving stable and adaptive gripping of irregularly shaped workpieces.

[0095] In flexible contact mechanics, when workpiece slippage is detected, continuing to execute the inflation command will cause a nonlinear and dramatic increase in the stiffness of the elastic membrane and a larger contact curvature, easily triggering a wedge effect that repels the workpiece. Therefore, in a more preferred embodiment, step S4 further includes: real-time monitoring of the center of gravity coordinates of the target object. When the target object is detected to have slipped, i.e., the center of gravity shifts. When the elastic membrane is squeezed to a preset depth by an object, the inflation of each flexible chamber is stopped, and the current state is maintained or the pressure of each flexible chamber is released according to a preset amount. The purpose is to instantly reduce the stiffness of the elastic membrane, increase the adaptive wrapping area of ​​the elastic membrane on the shape of the target workpiece, and use compliance to enhance static friction to suppress slippage. This is the offset threshold.

[0096] The compression depth can be calculated in real time visually by monitoring images with a depth camera. When the interference distance (the virtual overlap between the elastic membrane and the object) reaches the preset grasping margin factor... When the physical length reaches a certain threshold, it is determined that the preset extrusion depth threshold has been reached.

[0097] The above embodiments are preferred embodiments of this application. Those skilled in the art can make various changes or improvements based on them. Without departing from the overall concept of this application, these changes or improvements should fall within the scope of protection claimed in this application.

Claims

1. A grasping control method combining asymmetric pneumatic flexible gripper with visual feedback, characterized in that, The asymmetric pneumatic flexible gripper includes: a fixing part, a first pneumatic gripper, a second pneumatic gripper, a third pneumatic gripper, and an air filling and suction device; the fixing part includes two opposing ends, the first and second pneumatic grippers are arranged side by side at the first end of the fixing part, and the third pneumatic gripper is arranged at the second end of the fixing part. Each pneumatic gripper includes a rigid cavity with one open side and an elastic membrane sealing the open side to form a flexible chamber; the flexible chambers of the first and second pneumatic grippers are the same size and smaller than the flexible chamber of the third pneumatic gripper; the elastic membranes of the first and second pneumatic grippers and the elastic membrane of the third pneumatic gripper are arranged opposite to each other. The inflation / inflation device is connected to the flexible chamber of each pneumatic gripper through an air pipe, and the inflation / deflation of each flexible chamber is adjusted so that the elastic membrane expands toward the opposite side, and the top end forms the clamping point of the target object. The capture control method includes: S1. Establish a mapping function between the expansion length and the inflation amount for each elastic membrane; S2. Obtain the rectangular candidate frame of the target object, adjust the flexible gripper downwards to be above the target object and the two pneumatic grippers at both ends to be at the same height as the target object, and the axis is perpendicular to the long side of the candidate frame; the axis of the flexible gripper refers to the line connecting the centers of the two ends of the fixed part. S3. Based on the mapping function established in S1, the short side length of the candidate box, and the initial opening distance of the flexible gripper, calculate the target inflation volume of each flexible chamber and the target expansion length of the corresponding elastic membrane. S3 calculates the target inflation volume of each flexible chamber and the target expansion length of the corresponding elastic membrane. Specifically, it calculates the target inflation volume based on the preset initial opening distance. And the short side length of the candidate box for visual recognition A symmetrical expansion strategy is employed to calculate the uniform target expansion length for each pressure gripper. : ； In the formula, This represents the initial opening distance of the flexible gripper. is the length of the shorter side of the candidate box. This is a pre-set allowance factor based on the material's deformation coefficient; Call the independent inverse mapping functions of the first, second, and third air pressure grippers to calculate the corresponding target inflation volume: ； ； ； In the formula, These are the target inflation volumes for the flexible chambers of the first, second, and third air pressure grippers, respectively. These are the inverse mapping functions of the elastic membrane expansion length and inflation volume of the first, second, and third air pressure grippers, respectively. Inflation volume of each flexible chamber Inflation times with a fixed duration Measure the expansion length of each elastic membrane; construct the expansion length of each elastic membrane. With inflation volume mapping function Represented as: ； In the formula, To accumulate the number of inflations, For the first The expansion length of the elastic membrane of each pneumatic gripper With inflation volume The mapping function, For mapping functions The One fitting coefficient, The number of fitting coefficients. ; This refers to the amount of air inflated each time. The duration of each inflation; S4. The inflation and suction device inflates each flexible chamber according to the target inflation volume and monitors the actual expansion length of each elastic membrane in real time. S5. Employs a PID control algorithm, and adjusts the control based on the individual elastic membranes. The actual expansion length and target expansion length are used to adjust the inflation volume of each flexible chamber so that each elastic membrane expands to its target expansion length.

2. The grasping control method incorporating visual feedback according to claim 1, characterized in that, Let the first The target expansion length of the elastic membrane of each pneumatic gripper is The actual expansion length is Then, the expansion deviation is calculated as follows: The inflation volume of the corresponding flexible chamber is adjusted using a PID control algorithm, expressed as: ； In the formula, , , These are the proportional coefficient, integral coefficient, and derivative coefficient in the PID control algorithm; This represents the first step in the PID control process. The incremental adjustment value of inflation volume at each control moment. This indicates the current control moment in the PID control process. This represents the index of the discrete control moment in the PID control process; j=0 indicates the initial moment of the PID control process. and The elastic membrane of the pneumatic gripper is in the first... , The expansion deviation at each control moment; if , If the allowable error threshold for expansion deviation is set, the inflation / inflation device continues to inflate the flexible chamber. Then the inflation / inflation device controls the deflation of the flexible chamber; if If so, the current air pressure will be maintained.

3. The grasping control method incorporating visual feedback according to claim 1, characterized in that, Step S4 also includes: real-time monitoring of the target object's center of gravity coordinates. When the target object is detected to have slipped, i.e., the center of gravity shifts. When the preset compression depth has been reached, stop inflating each flexible chamber and maintain the current state or depressurize each flexible chamber according to the preset amount; among which, This is the offset threshold. and The target object at the current time Moment and the previous moment The coordinates of the centroid.

4. The grasping control method incorporating visual feedback according to claim 1, characterized in that, Both ends of the fixing part are respectively provided with spring-shaped supports with a spiral structure in the middle, and the top of the spring-shaped supports is used to support and fix the pneumatic gripper.

5. The grasping control method incorporating visual feedback according to claim 1, characterized in that, The inflation / inhalation device includes a microcontroller, a relay, a solenoid valve, an air pump, and an air tube; The first end of the trachea is connected to the flexible chamber, and the second end is connected to the air pump via a solenoid valve. The microcontroller is connected to the solenoid valve via a relay to control the opening and closing of the solenoid valve.

6. The grasping control method incorporating visual feedback according to claim 5, characterized in that, The inflation / inflation device is configured with three relays, three solenoid valves, and three air tubes, so as to independently control the air pressure of each flexible chamber.

7. The grasping control method incorporating visual feedback according to claim 5, characterized in that, It also includes a depth camera, used to collect the deformation of all the pneumatic gripper elastic membranes and the depth information of the target object; The microcontroller controls the inflation / deflation status of the air pump and the on / off state of the solenoid valve based on the data collected by the depth camera.

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