Perceptual driving integrated pneumatic driver and control method thereof

Abstract

The invention relates to a sensing and driving integrated pneumatic driver and a control method thereof. The driver comprises a distance detection device, a corrugated pipe elastic soft shell and a telescopic sleeve set. The corrugated pipe elastic soft shell is provided with an elastic cavity in a first telescopic direction; the telescopic sleeve set is implanted into the corrugated pipe elastic soft shell and used for restraining the corrugated pipe elastic soft shell from stretching out and drawing back in the first stretching-out and drawing-back direction. The first end of the telescopic sleeve set is connected with the first end of the corrugated pipe elastic soft shell in a matched mode. The second end of the telescopic sleeve set is connected with the second end of the corrugated pipe elastic soft shell in a matched mode. The distance detection device comprises a signal transmitting end and a signal receiving end and is used for detecting the actual length of the driver. The distance detection device is integrated in the telescopic sleeve set, the length of the pneumatic driver can be accurately controlled and dynamically adjusted in combination with the controller, and the effect of rapidly adjusting the length can be achieved in combination with the model-based controller.

Description

Technical Field

[0001] The present invention belongs to the technical field of artificial muscles. Specifically, it relates to a perception-driven integrated pneumatic actuator and its control method. Background Art

[0002] A Fluidic Elastomer Actuator (FEA) is a flexible driving device that mimics the characteristics of biological muscles. Its core principle is to generate a driving force through pressurized fluid (usually gas, sometimes also including liquid). With the ability to achieve various motion modes such as bending, stretching, contraction, and torsion, FEA provides a flexible and cost-effective driving method for bionic robots. Bionic robots that combine rigid structures with flexible actuators can reduce their dependence on high-frequency feedback control systems, and at the same time have higher motion safety and environmental adaptability, thus laying a technical foundation for diverse application scenarios.

[0003] However, to further draw on the biological paradigm of rigid-flexible collaboration to construct bionic robots, relying solely on traditional FEA is still difficult to fully meet the actual needs. This is because flexible artificial muscles not only need to have good controllability but also need to provide a sufficiently high output force to achieve natural and smooth bionic motion and at the same time adapt to the diverse requirements of complex environments. Although traditional FEA has advantages such as large deformation, multiple degrees of freedom, low stiffness, low driving pressure, and high energy density, it still has deficiencies in bearing capacity and output force. Essentially, the speed and load capacity of FEA are limited, which restricts its performance in high-load and high-response applications. Therefore, there is an urgent need to design a new type of flexible artificial muscle that can respond quickly and has a high load capacity to further break through the performance of bionic robots.

[0004] In addition to optimizing the structural design, integrating sensors to convert external stimuli into recordable feedback signals is also crucial. The addition of sensors can not only achieve precise perception of the motion state of artificial muscles but also lay the foundation for the implementation of a closed-loop control system. However, due to the diverse structural characteristics of fluidic elastomer actuators, sensor design faces many challenges such as compatibility, robustness, and easy integration. Currently, common sensing technologies include resistive, inductive, capacitive, and optoelectronic sensors, each with its own advantages and disadvantages. In contrast, optical waveguide sensors provide a better solution for improving the performance of pneumatic artificial muscles due to their unique advantages.

[0005] Optical waveguide sensors have high sensitivity and high signal-to-noise ratio, can accurately capture minute displacements and deformations, and support precise motion control; their low hysteresis characteristics and fast response capabilities meet the requirements of closed-loop control; non-contact measurement avoids mechanical wear and additional resistance, contributing to extending the system lifespan. At the same time, optical waveguide sensors are small in size and light in weight, facilitating embedding inside artificial muscles without significantly increasing the system weight. In addition, it is resistant to electromagnetic interference and suitable for applications in complex environments. Combining these advantages, optical waveguide sensors not only achieve efficient perception of artificial muscles but also significantly enhance the fast response capabilities and closed-loop control performance of bionic robots, further promoting the application of flexible artificial muscles in bionic robots. Summary of the Invention

[0006] According to a first aspect of the embodiments of the present disclosure, a perception-driven integrated pneumatic actuator is provided, including a distance detection device, a corrugated elastic soft shell, and a telescopic sleeve group;

[0007] The corrugated elastic soft shell has an elastic cavity in a first telescopic direction and has a first end and a second end opposite to each other in the first telescopic direction;

[0008] The telescopic sleeve group is implanted inside the corrugated elastic soft shell for restricting the corrugated elastic soft shell to telescopic in the first telescopic direction and has a first end and a second end opposite to each other in the first telescopic direction;

[0009] The first end of the telescopic sleeve group is mated with the first end of the corrugated elastic soft shell; the second end of the telescopic sleeve group is mated with the second end of the corrugated elastic soft shell;

[0010] The distance detection device includes a signal transmitting end and a signal receiving end; the signal transmitting end is implanted on one side of the first end of the telescopic sleeve group, and the signal receiving end is implanted on one side of the second end of the telescopic sleeve group for detecting the actual length of the corrugated elastic soft shell after telescoping.

[0011] Optionally, the telescopic sleeve group includes a large sleeve and a small sleeve nested with each other and a first limiting structure and a second limiting structure connected thereto; the outer diameter of the second limiting structure is greater than the inner diameter of the first limiting mechanism;

[0012] One end of the large sleeve is connected to the sealing cover of the elastic cavity, and the other end is connected to the first limiting structure, and the inner diameter of the first limiting structure is greater than the outer diameter of the small sleeve;

[0013] One end of the small sleeve is connected to the air inlet cover of the elastic cavity, and the other end is connected to the second limiting structure, and the outer diameter of the second limiting structure is less than the inner diameter of the large sleeve;

[0014] The signal transmitting end of the distance detection device is arranged inside the large sleeve, and the signal receiving end of the distance detection device is arranged inside the small sleeve.

[0015] Optionally, at least one slot is arranged inside the large sleeve; at least one T-shaped protrusion is arranged on the outer side of the small sleeve; each slot of the large sleeve corresponds to each T-shaped protrusion of the small sleeve one by one, and the T-shaped protrusion slides in the corresponding slot.

[0016] Optionally, a sealed dark space is formed inside the telescopic sleeve; the distance detection device is an optoelectronic sensor; the light emitter of the optoelectronic sensor serves as the signal transmitting end, and the light detector of the optoelectronic sensor serves as the signal receiving end.

[0017] Optionally, the optoelectronic sensor further includes a light emitter installation channel, the light emitter installation channel is implanted inside the small sleeve and the light emitter is implanted inside the light emitter installation channel; the light emitter installation channel is made of a material with an absorption coefficient greater than or equal to a preset coefficient threshold.

[0018] Optionally, an air inlet is provided at the first end of the elastic cavity, and the air inlet is used to insert an air inlet pipe and be hermetically connected to the air inlet pipe; the pneumatic actuator further includes a controller, an inflation valve module and a deflation valve module; the inlet of the inflation valve module is connected to a pressure pump, and the outlet of the inflation valve module is connected to the air inlet of the elastic cavity; the inlet of the deflation valve module is connected to the air inlet of the elastic cavity, and the outlet of the deflation valve module is connected to a vacuum pump; the controller is electrically connected to the inflation valve module, the deflation valve module and the distance detection device respectively;

[0019] The controller is used to adjust the air pressure inside the elastic cavity through the inflation valve module and the deflation valve module; and obtain the difference between the actual length and the expected length returned by the distance detection device; and stop adjusting the air pressure inside the elastic cavity when the difference is less than or equal to a preset difference threshold.

[0020] According to a second aspect of the embodiments of the present disclosure, a control method for a perception-driven integrated pneumatic actuator is provided, which is applicable to the pneumatic actuator according to any one of the first aspect, and the method includes:

[0021] Obtain the target length and external load of the pneumatic actuator;

[0022] Calculate the target air pressure inside the elastic cavity of the pneumatic actuator according to the target length and external load;

[0023] In response to the difference between the target air pressure and the actual air pressure being less than or equal to a preset difference threshold, stop adjusting the air pressure inside the elastic cavity of the pneumatic actuator.

[0024] Optionally, adjusting the air pressure in the elastic cavity of the pneumatic actuator according to the target length includes:

[0025] Obtaining the target maximum deflection of the annular plate in the pneumatic actuator according to the target length;

[0026] Calculating a series of maximum deflections w through a mechanical model according to the external load F and the internal cavity air pressure P at both ends of the pneumatic actuator max ;

[0027] Calculating the target air pressure of the elastic cavity of the pneumatic actuator.

[0028] Optionally, the maximum target deflection of the annular plate is expressed by the following formula:

[0029]

[0030] In the formula, L represents the length of the pneumatic actuator; n represents the number of drive units included in the pneumatic actuator; w max,t represents the maximum target deflection of each annular plate.

[0031] Optionally, the mechanical model is expressed by the following formula:

[0032]

[0033] The boundary conditions are expressed by the following formula:

[0034] When r = b, and

[0035] When r = a, M r = 0 and u = 0

[0036] The load is expressed by the following formula:

[0037]

[0038] The other variables are expressed by the following formula:

[0039]

[0040] In the formula, r represents the radial coordinate, μ represents the Poisson's ratio of the material of the pneumatic actuator, q represents the Young's modulus of the material of the pneumatic actuator, E represents the Young's modulus of the material of the pneumatic actuator, M rLet \(M\) represent the bending moment, \(u\) represent the radial displacement, \(a\) represent the inner radius of the top ring of the driving unit, \(b\) represent the inner radius of the elastic cavity, \(c\) represent the thickness of the top ring of the driving unit in the first telescopic direction, \(d\) represent the thickness of the root ring of the driving unit in the first telescopic direction, \(e\) represent the difference between the inner radius and the outer radius of the root ring of the driving unit, and \(h\) represent the thickness of the annular plate of the driving unit in the first telescopic direction.

[0041] The technical solutions provided by the embodiments of the present disclosure may include the following beneficial effects:

[0042] As can be seen from the above embodiments, the pneumatic actuator provided by the embodiments of the present disclosure can detect the actual length of the pneumatic actuator when the telescopic sleeve group is set with a distance sensor in the telescopic sleeve group, achieving the effect of accurately controlling the length of the pneumatic actuator. Moreover, in this embodiment, the distance sensor has a small influence on the weight of the pneumatic actuator, which is beneficial to reducing the weight of the robot when the pneumatic actuator is applied to the robot.

[0043] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The drawings herein are incorporated into the specification and constitute a part of the specification, showing embodiments consistent with the present disclosure and used together with the specification to explain the principles of the present disclosure.

[0045] Figure 1 is a schematic structural diagram of a perception-driven integrated pneumatic actuator shown according to an exemplary embodiment.

[0046] Figure 2 is a schematic structural diagram of a corrugated elastic soft shell connected to a bottom cover and a ventilation cover respectively shown according to an exemplary embodiment.

[0047] Figure 3 is a schematic diagram of the working principle of a sensor shown according to an exemplary embodiment.

[0048] Figure 4 is a schematic circuit diagram of a photoelectric sensor shown according to an exemplary embodiment.

[0049] Figure 5 is a simulation schematic diagram of a photoelectric sensor shown according to an exemplary embodiment.

[0050] Figure 6 is a simulation schematic diagram of the emission angle of an infrared LED shown according to an exemplary embodiment.

[0051] Figure 7 is a schematic diagram of the calibration result of a sensor shown according to an exemplary embodiment.

[0052] Figure 8 Schematic diagram of a control system of a perception-driven integrated pneumatic actuator shown according to an exemplary embodiment.

[0053] Figure 9 Block diagram of a controller of a perception-driven integrated pneumatic actuator shown according to an exemplary embodiment.

[0054] Figure 10 Schematic diagram of state division of a flow regulator shown according to an exemplary embodiment.

[0055] Figure 11 Test result of sine trajectory tracking shown according to an exemplary embodiment.

[0056] Figure 12 Test results of step trajectory tracking and anti-interference shown according to an exemplary embodiment.

[0057] Figure 13 Control flowchart of a perception-driven integrated pneumatic actuator shown according to an exemplary embodiment.

[0058] Figure 14 Flowchart of obtaining air pressure in an elastic cavity shown according to an exemplary embodiment.

[0059] Figure 15 Schematic diagram of structural composition and parametric description of a corrugated unit shown according to an exemplary embodiment.

[0060] Figure 16 Schematic diagram of force analysis of an annular plate shown according to an exemplary embodiment. Detailed implementation manners

[0061] The embodiments of the present disclosure provide a perception-driven integrated pneumatic actuator and its control method. Figure 1 Schematic diagram of a perception-driven integrated pneumatic actuator shown according to an exemplary embodiment. Refer to Figure 1 , the pneumatic actuator includes: a bellows elastic soft shell 11, a telescopic sleeve group 12, and a distance detection device 13.

[0062] In an example, the bellows elastic soft shell 11 has a first telescopic direction (such as Figure 1An elastic cavity 111 in the x-axis direction (as shown in the example), and having a first end 112 and a second end 113 opposite to each other in the first telescopic direction. Among them, the first end 112 and the second end 113 of the corrugated elastic soft shell 11 are respectively provided with a ventilation cover 21 and a bottom cover 23, that is, the ventilation cover 21, the bottom cover 23 and the corrugated elastic soft shell 11 form a sealed elastic cavity 111. The ventilation cover is provided with an air inlet 114, and the inside of the air inlet 114 can be connected to an air inlet pipe. It can be understood that the air inlet and the air inlet pipe can maintain a sealed state. Through the air inlet pipe, the elastic cavity 111 can be inflated or deflated, so as to achieve the effect of adjusting the amount of gas in the elastic cavity.

[0063] In one example, refer to Figure 2 , the ventilation cover 21 is provided with a first groove 22. The first end 112 of the corrugated elastic soft shell 11 can be inserted into the first groove 22 to achieve the effect of fixing the corrugated elastic soft shell 11 and the static seal between the two. Similarly, the bottom cover 23 is provided with a second groove 24, and the second end 113 of the corrugated elastic soft shell 11 can be inserted into the second groove 24 to achieve the effect of fixing the corrugated elastic soft shell 11 and the static seal between the two. In this way, in this example, the two ends of the corrugated elastic soft shell 11 are respectively fixed to the first groove 22 and the second groove 24, or in other words, the two ends of the corrugated elastic soft shell 11 are buckled into the grooves and are not easy to fall off, which is beneficial to the telescopic deformation of the pneumatic actuator. Moreover, the two ends of the corrugated elastic soft shell 11 are buckled into the grooves, making it easier for the ventilation cover 21, the bottom cover 23 and the corrugated elastic soft shell 11 to form a closed space, that is, the elastic cavity 111.

[0064] In one example, the telescopic sleeve group 12 includes a large sleeve 121, a small sleeve 122, a first limiting structure 123 and a second limiting structure 124. The large sleeve 121 and the small sleeve 122 are nested with each other. The telescopic sleeve group is implanted inside the corrugated elastic soft shell, used to restrict the telescopic movement of the corrugated elastic soft shell in the first telescopic direction, and having a first end and a second end opposite to each other in the first telescopic direction. The first end of the telescopic sleeve group 12 is mated with the first end of the corrugated elastic soft shell; the second end of the telescopic sleeve group is mated with the second end of the corrugated elastic soft shell. For example, in the case where the corrugated elastic soft shell 11 is provided with a ventilation cover and a bottom, one end of the large sleeve 121 is connected to the bottom cover of the elastic cavity, and the other end is connected to the first limiting structure 123. One end of the small sleeve 122 is connected to the air inlet cover of the elastic cavity 111, and the other end is connected to the second limiting structure 124.

[0065] In this example, the inner diameter of the first limiting structure 123 is larger than the outer diameter of the small sleeve 122, so that when the first limiting structure 123 is connected to the outside of the small sleeve 122, a first protruding part is formed outward. The outer diameter of the second limiting structure 124 is smaller than the inner diameter of the large sleeve 121, so that when the second limiting structure 124 is connected to the inside of the large sleeve 121, a second protruding part is formed inward.

[0066] In this example, the small sleeve 122 can slide freely along the first telescopic direction within the large sleeve 121. When the telescopic sleeve group 12 extends to its maximum length, the first protruding portion corresponding to the small sleeve 122 comes into contact with the second protruding portion corresponding to the large sleeve 121, restricting each other and preventing the large sleeve 121 and the small sleeve 122 from slipping off each other. It can be understood that the specific implementation forms of the first limiting structure 123 and the second limiting structure 124 should not be construed as a substantial limitation on the protection scope of this application; simple deformations of the first limiting structure 123 and the second limiting structure 124 still fall within the protection scope of this disclosure.

[0067] In this example, the large sleeve 121 and the small sleeve 122 can be sleeves made of carbon fiber material; choosing sleeves made of carbon fiber material has the advantages of being lighter and having a smaller friction coefficient between the sleeves, which can further improve the energy density and power density of the pneumatic actuator. The structure of the telescopic sleeve group is not limited to two sections, and can include a sleeve group with three or more sections, so as to achieve better ductility. The manufacturing material of the telescopic sleeve group can also be 3D printing materials, various metal materials, plastics, etc.

[0068] In one example, the first limiting structure 123 can be provided with at least one slot (not shown in the figure). The slot and both sides can form a T-shaped slot, and at least one T-shaped protrusion is provided on the outer side of the small sleeve 122. The slots and the T-shaped protrusions are arranged in one-to-one correspondence; moreover, the T-shaped protrusions can slide within the slots. In this way, the solution of providing slots and T-shaped protrusions in this example can reduce the contact area between the large sleeve 121 and the small sleeve 122 and reduce the friction force. Also, the solution of this example can prevent the small sleeve 122 from rotating along the first telescopic direction within the large sleeve 121, and further prevent the elastic soft shell of the corrugated pipe from rotating, which is beneficial to accurately measuring the length of the pneumatic actuator subsequently. It can be understood that the formation of the slots and the T-shaped protrusions is not limited to the T shape, and can also be V-shaped, semi-circular, triangular, serrated, etc. As long as the friction force can be reduced and rotation can be prevented, the corresponding solutions fall within the protection scope of this disclosure.

[0069] In this example, a friction-reducing layer (not shown in the figure) can be provided on the inner wall of the slot of the first limiting structure 123 and the outer wall of the T-shaped protrusion of the small sleeve 122, or rather, on the contact area between the slot of the first limiting structure 123 and the T-shaped protrusion of the small sleeve 122. The friction-reducing layer can be obtained by smoothing the surface of the contact area through methods such as grinding and polishing, and can be made of high molecular polymers, polyamides, alloy materials, etc. In this way, by providing a friction-reducing layer in this example, the friction force between the first limiting structure 123 and the small sleeve 122 can be reduced, and the friction force between the large sleeve 121 and the small sleeve 122 can be reduced, which is beneficial to improving the smoothness of telescoping.

[0070] When the air pressure in the elastic cavity changes, the length of the pneumatic actuator will change. Referring further to Figure 1 , the left figure illustrates the length L0 of the pneumatic actuator when the air pressure change is zero; when inflated, the elastic cavity 111 will extend axially (i.e., the first telescopic direction) by L under the action of air pressure, and the telescopic sleeve group 12 will passively elongate by L along with the elastic cavity 111, as shown in the right figure of Figure 1 . The design of the rigid-soft coupling between the elastic cavity 111 and the telescopic sleeve group 12 implanted therein is intended to prevent the elastic cavity 111 from buckling when an excessive load is applied axially, so that the pneumatic actuator can generate a greater axial force while maintaining axial compliance.

[0071] It can be understood that the elastic cavity 111 can have different structural forms. The elastic cavity 111 can be made of an elastic material with good stretchability, such as rubber, etc., or can be a thin shell or film structure that is prone to bending and folding. The elastic cavity 111 can have different shape characteristics, including but not limited to corrugated structures, folding / pleating structures, etc. It can be understood that the specific implementation form of the elastic cavity 111 should not be construed as a substantial limitation on the protection scope of this application. Simple deformations of the elastic cavity 111 still fall within the protection scope of this application.

[0072] It is particularly noteworthy that although the embodiments of this application are applied to pneumatic actuators, that is, driven by compressed air, it is also possible to directly use hydraulic or other driving methods for driving.

[0073] In one example, referring to Figure 2 , the distance detection device 13 includes a signal transmitting end 131 and a signal receiving end 132; the signal transmitting end 131 is implanted on one side of the first end of the telescopic sleeve group 12, and the signal receiving end 132 is implanted on one side of the second end of the telescopic sleeve group 12; or rather, the signal transmitting end 131 is implanted inside the large sleeve of the telescopic sleeve group 12, and the signal receiving end 132 is implanted inside the small sleeve of the telescopic sleeve group 12. The distance detection device 13 and the telescopic sleeve group 12 form an optical waveguide structure with air as the propagation medium. It can be understood that the signal transmitting end 131 is arranged inside the large sleeve and the signal receiving end 132 is arranged inside the small sleeve, so as to ensure that the signal emitted by the signal transmitting end 131 is incident on the signal receiving end 132 as directly as possible, reduce the stray signals formed by the reflection and refraction of the signal on the inner wall of the large sleeve and / or small sleeve, reduce the non-linearity between the transmitted signal and the received signal, and is beneficial to improving the accuracy of the received signal.

[0074] In this example, the sensor composition and signal transmission block diagram are as shown in Figure 3As shown, the signal transmitting end 131 can emit an infrared light signal to the signal receiving end 132, and the signal receiving end 132 can convert it into an electrical signal after receiving the light signal; when the installation position is fixed, the lengths of the installation position and the two ends of the corrugated flexible shell 11 are known quantities. In this way, the actual length of the corrugated flexible shell 11 after expansion and contraction can be calculated based on the calibrated distance and the electrical signal, that is, the distance detection device 13 can be used to detect the actual length of the corrugated flexible shell 11 after expansion and contraction. In this way, in this example, by arranging a distance sensor inside the telescopic sleeve group 12, the space occupation can be reduced, achieving the effect of reducing the volume of the pneumatic actuator.

[0075] In one example, the distance detection device 13 can be an infrared pair tube. At this time, a closed dark space is formed inside the telescopic sleeve group to avoid external light interference. In this example, the infrared LED serves as the signal transmitting end of the distance detection device, that is, the infrared light source, and the photosensitive triode serves as the signal receiving end of the distance detection device, that is, the photosensitive element. The dimensional change generated by the optical waveguide under the action of the actuator modulates the intensity of the light signal at the receiving end, thus completing the preliminary response to the input measured quantity. The modulated light signal is received by the photosensitive triode and generates a corresponding output electrical signal through photoelectric conversion. The electrical signal output by the photosensitive element can be used through an auxiliary circuit to condition the signal into a standardized electrical signal and output the standardized electrical signal. The standardized electrical signal is converted into a digital signal after being collected by the ADC module of the control board, and then filtered and signal processed in the software, and finally used by the controller of the robot system.

[0076] In one example, referring to Figure 4 , the light emitter includes an emitting diode IR LED and an emitting end resistor R LED . Among them, the first end of the emitting end resistor R LED is electrically connected to the power supply Uv, and the second end of the emitting end resistor R LED is electrically connected to the anode of the emitting diode IR LED; the cathode of the emitting diode IR LED is grounded to GND. In some examples, a switch is arranged between the power supply Uv and the emitting end resistor R LED . When the switch is switched to the conducting state, the emitting diode IR LED is in the working state and can emit light; and the power of the light intensity can be controlled through the emitting end resistor R LED . The light detection end includes a photosensitive triode PT and a receiving end resistor R PT . Among them, the first end of the receiving end resistor R PT is electrically connected to the power supply Uv, the second end of the receiving end resistor R PT is electrically connected to the first end of the photosensitive triode PT, and the second end of the photosensitive triode PT is grounded to GND. Among them, the first end of the photosensitive triode PT is electrically connected to the output end, that is, the output end can output the sensed electrical signal U s; and, the output signal U can be adjusted by adjusting the receiving-end resistor R PT Adjust the output signal U s range.

[0077] In one example, continue to refer to Figure 2 , the photoelectric sensor further includes a photodetector mounting channel 33. The photodetector mounting channel 33 is implanted inside the small sleeve 122, and the photodetector is implanted inside the photodetector mounting channel 33. In this example, the photodetector mounting channel 33 can be prepared by 3D printing technology, which can improve the preparation accuracy. And, in this example, the light emitter mounting channel 33 is made of a material with a relatively large absorption coefficient α s (such as greater than or equal to 0.6). The absorption coefficient refers to the ratio of the reflected energy to the incident energy, and the larger the value, the greater the loss of light. Its value range is between 0 and 1. In this example, the light scattered onto the inner wall can be absorbed by the photodetector mounting channel 33, and the photodetector can detect as much direct light as possible, thereby avoiding the influence of the reflected light on the detection result and reducing the nonlinearity and non-monotonicity of the emitted light and the detected light, which is beneficial to improving the accuracy of the detection result.

[0078] In one example, the photodetector mounting channel 33 can be provided with a T-shaped protrusion instead of the small sleeve 122. At this time, the T-shaped protrusion of the photodetector mounting channel 33 slides in the slot of the large sleeve, which can reduce the contact area and achieve the effect of reducing the friction force. Similarly, in this example, a friction-reducing layer (not shown in the figure) can also be provided in the contact area between the slot and the T-shaped protrusion. The friction-reducing layer can be obtained by smoothing the surface by grinding, polishing, etc. the contact area, and can be made of polymer, polyamide, alloy material, etc. In this way, in this example, by providing the friction-reducing layer, the friction force between the large sleeve and the photodetector mounting channel 33 can be reduced, and the friction force between the large sleeve 121 and the small sleeve 122 can be reduced.

[0079] In this example, a geometric optical model can be established for the photoelectric sensor, hoping to predict the response of the sensor by simulating the propagation and interaction of light. The geometric model of the photoelectric sensor includes two cylinders combined together, such as Figure 5 shown. The boundary conditions at both ends and the connection part of the two cylinders are established as disappearing. The inner walls of the two cylinders are affected by mixed diffuse reflection / specular reflection and may absorb some light; in this example, the absorption coefficient (α s is the ratio of the reflected energy to the incident energy) is used to represent the light loss during the reflection process, and the transmittance (%) is the intensity of the light received by PT.

[0080] In this example, a parameter scan is performed on the cylinder of the large sleeve, and the scan range is from 0 to 160 mm, with a step size of 5 mm. The length x2 of the cylinder of the small sleeve is set to 60 mm. The simulation effect is asFigure 6 as shown. Refer to Figure 6 , the diffuse reflection continuously reduces the transmittance, and different absorption coefficients have the least influence. The specular reflection exhibits complex behavior. At a low absorption coefficient (α s = 0.3) and a small incident angle (Φ = 15°), the transmittance detected by the photosensitive triode PT exhibits non-linear and non-monotonic behavior. As the absorption coefficient α s increases, the non-monotonic behavior gradually weakens. When keeping the absorption coefficient constant, a narrower LED emission angle is beneficial to a wider range of transmittance changes. Therefore, it is important for optimizing the response of the sensor to select a suitable mounting tube material for the light emitter and the emission angle of the emitting diode IR LED. In this example, a black nylon material with a relatively large absorption coefficient α s (such as greater than or equal to a preset coefficient threshold, and the value range of the preset coefficient threshold is [0.6, 0.9] and can be adjusted) is selected to manufacture the PT mounting tube.

[0081] In one example, Figure 7 shows the characteristic curves of light loss and displacement changing with time during the driver calibration process. In this example, the light emitter selects an infrared LED with an emission angle of 15°. The receiving-end resistor R PT in the signal receiving circuit and the transmitting-end resistor R LED in the light emitter are respectively set to 3.9 kΩ and 390 Ω. The installation channel length of the photodetector is 60 mm, and the power supply U v is 5V. It can be seen from the figure that the light loss curve shows certain non-linear characteristics with the change of displacement, but the overall trend is clear and has strong regularity. In addition, no obvious hysteresis phenomenon is observed between the light loss and the displacement, indicating that the sensing system has high repeatability and stability during the dynamic response process. To construct a mathematical relationship model between the light loss (calculated according to formula (1)) and the displacement x1, a 6th-order polynomial can be used to fit the calibration data, taking into account both the fitting accuracy and the computational complexity. Specifically, a low-order polynomial cannot fully describe the complex non-linear behavior of the sensor and is prone to significant fitting errors; while a high-order polynomial may slightly improve the fitting accuracy, but there is a risk of overfitting and significantly increases the computational amount, which is not conducive to the real-time application of the sensor.

[0082]

[0083] In this example, since the response is non-linear, the sensitivity of the sensor decreases as the displacement increases. It can be seen that within the working range of the actuator, as the actuator extends, the fitting error shows a gradually increasing trend. After calculation, the maximum absolute error of the actuator is 1.7 m, which is 1.6% of the full scale. At the same time, the average absolute error of the actuator is 0.4 mm, corresponding to 0.4% of the full scale. This result indicates that the optical waveguide sensor has successfully achieved millimeter-level position sensing ability in the designed fluid elastomer actuator, especially reaching sub-millimeter-level measurement accuracy in the small displacement range. Although the accuracy decreases under extreme displacement conditions, indicating that there is still room for optimization in the full scale range, the current accuracy performance can already meet the closed-loop control requirements of the flexible actuator.

[0084] Based on the above pneumatic actuator and sensor, the embodiments of the present disclosure further provide a perception-driven integrated pneumatic actuator control system and control method.

[0085] In one example, the actuator control system is shown in Figure 8 , and includes a controller 71, an inflation valve module 72, a deflation valve module 73, a pressure detection device 74, and a distance detection device in the telescopic sleeve group 12, that is, an optical waveguide structure. The inlet of the inflation valve module 72 is connected to the positive pressure gas storage tank, and the outlet of the inflation valve module 72 is connected to the inlet of the elastic cavity; the inlet of the deflation valve module 73 is connected to the inlet of the elastic cavity, and the outlet of the deflation valve module 73 is connected to the vacuum gas storage tank; the controller is electrically connected to the inflation valve module 72, the deflation valve module 73, the pressure detection device 74, and the distance detection device 13 respectively. The controller 71 is used to adjust the gas volume in the elastic cavity through the inflation valve module 72 and the deflation valve module 73; it can be understood that when the gas volume in the elastic cavity changes, the bellows elastic soft shell 11 expands or contracts to drive the small sleeve of the telescopic sleeve group 12 to slide, and finally the pneumatic actuator becomes longer or shorter. The controller 71 is also used to obtain the difference between the actual length and the expected length returned by the distance detection device 13; and when the difference is less than or equal to the preset difference threshold, stop adjusting the gas volume in the elastic cavity to achieve position closed-loop control. The controller 71 is also used to obtain the difference between the actual pressure and the expected pressure returned by the pressure detection device 74; and when the difference is less than or equal to the preset difference threshold, stop adjusting the air pressure in the elastic cavity to achieve air pressure closed-loop control.

[0086] In one example, the source pressure of the positive pressure gas storage tank is set to 400 kPa, and the exhaust pressure of the negative pressure gas storage tank is set to -80 kPa.

[0087] See Figure 9, the controller 71 can be implemented using a cascade PID controller, which can send control signals to the drivers of the inflation valve module and the discharge valve module for regulating the flow rate of each regulating valve. By reasonably designing and optimizing the parameters of each level of the controller, this method can effectively improve the dynamic response performance of the system, reduce the oscillation phenomenon, and enhance the stability and accuracy of control. The core of the controller consists of a position regulator, a speed regulator, and a flow regulator, which combines with an optical waveguide position sensor to provide a position feedback signal with high signal-to-noise ratio to achieve closed-loop control of the driver position.

[0088] The position feedback of the position regulator is provided by the optical waveguide position sensor. The actual position x of the driver actual is compared with the reference position x ref to generate a position deviation e outer = x ref - x actual . Then, PID regulation is performed on this position deviation signal to output a target speed command v ref .

[0089]

[0090] The speed feedback value of the speed regulator is calculated from the first-order difference of the position feedback signal. The speed regulator performs PI regulation on the deviation e ref between the target speed command v actual and the speed feedback value v inner to generate a flow control command u.

[0091]

[0092] The flow regulator adjusts the valve opening degrees of the intake valve group and the exhaust valve group according to the output command u of the speed regulator, that is, u i and u o . The control state division of the flow regulator is as shown in Figure 10 . The horizontal direction represents the control command u, which is continuously distributed from negative to positive. The vertical direction represents the valve opening degree, where the upper half represents the intake valve opening degree and the lower half represents the exhaust valve opening degree. The flow regulator divides the driver into five states according to u: rapid exhaust, slow exhaust, hold, slow intake, and rapid intake. When slowly exhausting or intaking, the valve opening degrees u i and u o are obtained through simple proportional mapping according to the flow characteristics of the flow valve. In other states, u i and u o are fixed.

[0093] The control laws for the five state intervals are set as follows:

[0094] 1. When u < s1, the driver is in the rapid exhaust state

[0095]

[0096] 2. When s1 ≤ u ≤ s2, the driver is in the slow air release state

[0097]

[0098] 3. When s2 < u < s3, the driver is in the dead zone

[0099]

[0100] 4. When s3 ≤ u ≤ s4, the driver is in the slow air intake state

[0101]

[0102] 5. When s4 < u, the driver is in the fast air intake state

[0103]

[0104] See Figure 11 , the test results of the driver tracking the sine trajectory, where the frequency of the target trajectory is 0.5 Hz and the amplitude is 50% of the stroke. The feedback trajectory is highly consistent with the true trajectory, verifying the measurement accuracy of the optical waveguide displacement sensor. The MAE compared with the true value is 0.38 mm, and the RMSE is 0.46 mm. In addition, the feedback value and the true value can generally closely follow the change trend of the target value, indicating that the closed-loop control system has good tracking performance. The error curve shows periodic fluctuations within the sine period and reaches the error peak at about 1.25 s, approximately -7.6 mm. During the entire control experiment period, the MAE of the system is 3.77 mm, and the RMSE is 4.22 mm. In addition, the dynamic adjustment of the duty cycles of the inflation valve and the deflation valve illustrates the adaptability and effectiveness of the control strategy for real-time position adjustment under different pressure differences.

[0105] See Figure 12 , the results of the multi-step displacement tracking and disturbance robustness test of the driver. In the multi-step displacement tracking experiment, the average response time for multiple steps is 0.244 s, and the average error is 1.244 mm. In the disturbance robustness test, the target position can be set to 60 mm, and a random axial disturbance is manually introduced, and this process is repeated five times. The average settling time of the system is 0.49 s, and the steady-state MAE is 1.06 mm. The system can be observed to be stable after these disturbances.

[0106] Based on the above pneumatic driver, the embodiment of the present disclosure also provides a control method for a perception-driven integrated pneumatic driver. See Figure 13 , including steps 131 to 133.

[0107] In step 131, obtain the target length and external load of the pneumatic actuator.

[0108] In step 132, calculate the target air pressure in the elastic cavity of the pneumatic actuator according to the target length and external load.

[0109] In step 132, in response to the difference between the target air pressure and the actual air pressure being less than or equal to a preset difference threshold, stop adjusting the air pressure in the elastic cavity of the pneumatic actuator.

[0110] In this step, the controller of the pneumatic actuator needs to calculate the target air pressure P according to the target length L and the external load F t , see Figure 14 , including steps 141 to 143.

[0111] In step 141, obtain the target maximum deflection of the annular plate in the pneumatic actuator according to the target length.

[0112] In this example, the corrugated elastic soft shell is divided into multiple drive units. See Figure 15 , each drive unit can be divided into five connected parts, from top to bottom in sequence: root ring, annular plate, top ring, annular plate, and root ring. Among them, the inner radius of the top ring is a, the inner radius of the root ring is b, the thickness of the top ring in the first telescopic direction is c, the thickness of the root ring in the first telescopic direction is d, the difference between the inner radius and the outer radius of the root ring of the drive unit and the difference between the inner radius and the outer radius of the top ring are e, and the thickness of the annular plate in the first telescopic direction is h.

[0113] When the pneumatic actuator includes n corrugated units, the maximum deflection of the ring plate as shown in formula (9) can be obtained.

[0114]

[0115] In step 142, according to the external load F and the internal cavity air pressure P at both ends of the pneumatic actuator, calculate a series of maximum deflections w through a mechanical model max .

[0116] In this example, assume that the material is a linear elastic material, its Young's modulus is E, and the Poisson's ratio is μ; and assume that the root ring and the top ring have no deformation when pressurized, only the annular plate deforms; and the telescopic sleeve has no resistance in the telescopic direction.

[0117] See Figure 16, the force analysis of the driving unit is carried out. For the deflection of the axisymmetric annular plate, the polar coordinate form of the von Karman equation is used, and the variables of this equation are the radial coordinate r and the angular coordinate θ. The stress and deflection w are shown in Equation (10).

[0118]

[0119] where,

[0120]

[0121] In addition, the radial displacement u, the radial boundary force N r , the bending moment M r and the shear force Q r can be calculated by Formulas (12) to (15), which are expressed as functions of the deflection w and the stress .

[0122]

[0123] Under the action of the internal cavity pressure P and the external load F, the load q in Equation (10) is expressed as follows:

[0124]

[0125] To solve Equation (10), the corresponding boundary conditions also need to be determined. Considering the boundary conditions at the inner edge (r = b) and the outer edge (r = a) of the annular plate, they satisfy the following relationships:

[0126] i. When r = b, the inner edge cannot rotate freely and can move radially.

[0127]

[0128] ii. When r = a, the outer edge can rotate freely but cannot move radially.

[0129] M r = 0, u = 0 (18)

[0130] The bvp5c solver in MATLAB is used to solve this boundary value problem. Before applying bvp5c to solve the BVP, the second-order ordinary differential equation, that is, Equation (10), needs to be transformed into a first-order ODE system. This is because the solver requires the input to be a first-order differential equation. Specifically, the system of equations should be rewritten to describe w(r) and the first derivative dw / dr and The system. Then, the boundary conditions and loads are substituted into the bvp5c solver, which can numerically solve these first-order derivatives over the interval [b, a]. After obtaining the solutions of the first-order derivatives, we can obtain the deflection w and stress distributions over the entire interval.

[0131] The above mechanical model can be expressed as w = f(P, F, r, a, b, h, E, μ). Since the maximum deflection occurs at the inner edge of the annular plate, that is, the value of the deflection w when r = b, we have:

[0132] w max = w| r＝b (19)

[0133] In step 143, the target air pressure of the elastic cavity of the pneumatic actuator is calculated.

[0134] In this step, when w max reaches w max,t , the internal air pressure of the elastic cavity is the target air pressure P t , and this value can be obtained by linearly interpolating [w max , P] at w max,t .

[0135] In step 133, in response to the difference between the target air pressure and the actual air pressure being less than or equal to a preset difference threshold, stop adjusting the air pressure in the elastic cavity of the pneumatic actuator.

[0136] In this step, the controller can obtain the difference between the target air pressure and the actual air pressure, and then compare the size of the above difference with the preset difference threshold. When the above difference is less than or equal to the preset difference threshold, it is determined that the length of the pneumatic actuator meets the requirements. At this time, the inflation valve module and the deflation valve module can be controlled to stop working, thereby stopping the adjustment of the air pressure in the elastic cavity of the pneumatic actuator, and the effect of adjusting the length can be quickly achieved. After the controller stops adjusting the air pressure, more precise length control can be achieved by controlling the amount of gas in the fine-tuning elastic body.

Claims

1. A sensor-driven integrated pneumatic actuator, characterized in that: It includes a distance detection device, a bellows elastic soft shell and a telescopic sleeve group; The bellows elastic soft shell has an elastic cavity in a first telescopic direction, and has a first end and a second end opposite to each other in the first telescopic direction; The telescopic sleeve assembly is implanted in the bellows elastic soft shell, and is used to constrain the bellows elastic soft shell to telescope in the first telescopic direction, and has a first end and a second end opposite to each other in the first telescopic direction; The first end of the telescopic sleeve assembly is matched with the first end of the bellows elastic soft shell; the second end of the telescopic sleeve assembly is matched with the second end of the bellows elastic soft shell; The distance detection device includes a signal transmitting end and a signal receiving end; the signal transmitting end is implanted on one side of the first end of the telescopic sleeve group, and the signal receiving end is implanted on one side of the second end of the telescopic sleeve group, and is used to detect the actual length of the first end and the second end of the bellows elastic soft shell after expansion and contraction.

2. The pneumatic actuator according to claim 1, characterized in that The telescopic sleeve assembly comprises a large sleeve and a small sleeve which are nested with each other, and a first limiting structure and a second limiting structure connected thereto; the outer diameter of the second limiting structure is greater than the inner diameter of the first limiting structure; One end of the large sleeve is connected to the sealing cover of the elastic cavity, and the other end is connected to the first limiting structure, and the inner diameter of the first limiting structure is larger than the outer diameter of the small sleeve; One end of the small sleeve is connected to the air inlet cover of the elastic cavity, and the other end is connected to the second limiting structure, and the outer diameter of the second limiting structure is smaller than the inner diameter of the large sleeve; The signal transmitting end of the distance detecting device is arranged inside the large sleeve, and the signal receiving end of the distance detecting device is arranged inside the small sleeve.

3. The pneumatic actuator according to claim 2, characterized in that At least one slot is arranged inside the large sleeve; at least one T-shaped protrusion is arranged outside the small sleeve; each slot of the large sleeve corresponds to each T-shaped protrusion of the small sleeve, and the T-shaped protrusion slides in the corresponding slot.

4. The pneumatic actuator according to any one of claims 1 to 3, characterized in that: The interior of the telescopic sleeve forms a sealed dark space; the distance detection device is a photoelectric sensor; the light transmitter of the photoelectric sensor serves as the signal transmitting end, and the light detector of the photoelectric sensor serves as the signal receiving end.

5. The pneumatic actuator according to claim 4, characterized in that The photoelectric sensor also includes a light detector installation channel, the light detector installation channel is implanted in the small sleeve and the light emitter is implanted in the light emitter installation channel; the light emitter installation channel is made of a material with an absorption coefficient greater than or equal to a preset coefficient threshold.

6. The pneumatic actuator according to claim 1, characterized in that The first end of the elastic cavity is provided with an air inlet, and the air inlet is used to insert an air inlet pipe and is sealed and connected to the air inlet pipe; the pneumatic driver also includes a controller, an inflation valve module and an air release valve module; the inlet of the inflation valve module is connected to a positive pressure source, and the outlet of the inflation valve module is connected to the air inlet of the elastic cavity; the inlet of the air release valve module is connected to the air inlet of the elastic cavity, and the outlet of the air release valve module is connected to a negative pressure source; the controller is electrically connected to the inflation valve module, the air release valve module and the distance detection device respectively; The controller is used to adjust the amount of gas in the elastic cavity through the inflation valve module and the deflation valve module; and obtain the difference between the actual length and the expected length returned by the distance detection device; When the difference is less than or equal to a preset difference threshold, the adjustment of the gas volume in the elastic cavity is stopped.

7. A control method for a pneumatic actuator with integrated sensing and driving, characterized in that: Applicable to the pneumatic driver according to any one of claims 1 to 6, the method comprising: obtaining a target length and an external load of the pneumatic actuator; Calculating a target air pressure in the elastic cavity of the pneumatic actuator according to the target length and the external load; In response to the difference between the target air pressure and the actual air pressure being less than or equal to a preset difference threshold, the air pressure in the elastic cavity of the pneumatic driver is stopped from being adjusted.

8. The control method according to claim 7, characterized in that: Adjusting the air pressure in the elastic cavity of the pneumatic actuator according to the target length includes: Obtaining a target maximum deflection of the annular plate in the pneumatic actuator according to the target length; According to the external load F at both ends of the pneumatic actuator and the internal air pressure P, a series of maximum deflections w are calculated by the mechanical model. max ; Calculate the target air pressure for the pneumatic actuator's elastic cavity.

9. The control method according to claim 8, characterized in that: The target maximum deflection is expressed by the following formula: Wherein, L represents the length of the pneumatic drive; n represents the number of drive units included in the pneumatic drive; w max,t Represents the maximum target deflection of each annular plate.

10. The control method according to claim 8, characterized in that: The mechanical model w=f(P, F, r, a, b, h, E, μ) is expressed by the following formula: The boundary conditions are expressed as follows: When r = b, and When r = a, M r =0 and u=0 The load is expressed as follows: Other variables are expressed as follows: Where r represents the radial coordinate, μ represents the Poisson's ratio of the material of the pneumatic actuator, E represents the Young's modulus of the material of the pneumatic actuator, and M r represents the bending moment, u represents the radial displacement, a represents the inner radius of the top ring of the driving unit, b represents the inner radius of the elastic cavity, c represents the thickness of the top ring of the driving unit in the first telescopic direction, d represents the thickness of the root ring of the driving unit in the first telescopic direction, e represents the difference between the inner radius and the outer radius of the root ring of the driving unit, and h represents the thickness of the annular plate of the driving unit in the first telescopic direction.

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