Differential compliant gripper with multi-modal sensing and zero-power locking and control method

Abstract

The application provides a differential compliant gripper with multi-modal perception and zero-power locking and a control method, relates to the technical field of robot end effectors and compliant control, and comprises a mechanical transmission assembly, a power and clutch assembly, a multi-modal perception skin assembly and a computing power and measurement and control assembly; a differential drive assembly is embedded to drive an external sleeve rack to drive a bionic finger claw unit to move, a multi-modal perception skin assembly is combined to acquire a contact state, a pressure distribution, a micro-vibration signal and a transmission capacitance signal, a computing power and measurement and control assembly is combined to control the power and clutch assembly to switch between a transmission state, a differential release state and a locking state, differential compliant grasping and zero-power locking and holding of irregular, fragile and soft and hard target objects are realized, and the problems that the existing gripper cannot simultaneously consider differential compliant grasping, stable clamping and low-energy consumption locking and holding when grasping irregular, fragile and soft and hard target objects are solved.

Description

Technical Field

[0001] This invention relates to the field of robot end effectors and compliant control technology, specifically to a differential compliant gripper with multimodal sensing and zero-power locking and a control method. Background Technology

[0002] With the development of flexible manufacturing, automation in fresh agricultural products, and medical biochemical testing, robots need to frequently grasp extremely fragile, irregularly shaped objects with varying degrees of hardness and softness, such as soft plastic parts, small ceramic parts, and thin-walled glass test tubes. The actual operational capabilities of a robot highly depend on the grasping performance of its end effector. The adaptive capability, compliant buffering characteristics, and force control precision of the gripper directly determine the success rate and operational safety of grasping irregular, fragile, and soft materials, and are key factors restricting the flexible and intelligent operation of robots.

[0003] Existing mechanical grippers still have significant shortcomings when grasping the aforementioned target objects. Traditional single-drive multi-finger grippers often employ rigid linkages or simple gear and rack transmission structures. When grasping irregular objects, if one finger touches a protruding part of the target object first and is obstructed, the entire transmission chain and drive motor are easily forced to lock, making it difficult to continue adaptive envelope grasping of the target object. At the same time, traditional position control methods are prone to crushing or even destroying soft or fragile target objects due to excessive local gripping force.

[0004] For target objects of varying hardness, existing grippers struggle to simultaneously provide both compliant protection and stable clamping. Insufficient clamping force can easily lead to slippage, while excessive clamping force may cause localized deformation or damage to the target object. Therefore, existing grippers still fall short of meeting the requirements for gripping adaptability, clamping stability, and force safety in complex operational scenarios when dealing with irregular, fragile, and varying hardness target objects.

[0005] Furthermore, existing adaptive differential compensation mechanisms typically require significant lateral or longitudinal swing space, resulting in poor overall structural compactness and making them unsuitable for complex scenarios such as densely packed structures and narrow workstations. Existing series elastic actuators often require the drive motor to continuously output torque while maintaining the gripping state, easily leading to motor overheating and increased power consumption. Meanwhile, traditional flexible actuators generally lack high-frequency multimodal sensing capabilities for actual contact force, internal elastic deformation, and deep material characteristics of the target object, making it difficult to effectively regulate complex gripping processes through closed-loop control.

[0006] Therefore, it is still necessary to provide a gripper with differential speed compliant grasping and zero-power locking capabilities to adapt to the grasping needs of irregular, fragile and soft / hard target objects, thereby improving grasping adaptability and clamping stability in complex scenarios. Summary of the Invention

[0007] This invention provides a differential compliant gripper and control method with multimodal sensing and zero-power locking. Through the coordinated cooperation of mechanical transmission components, power and clutch components, multimodal sensing skin components, and computing and measurement and control components, it solves the problem that existing grippers are difficult to balance differential compliant gripping, stable clamping, and low-power locking when grasping irregular, fragile, and soft or hard target objects.

[0008] In view of the above problems, the technical solution proposed by the present invention is as follows:

[0009] A differential compliant gripper with multimodal sensing and zero-power locking, comprising:

[0010] The mechanical transmission component includes an embedded differential drive component, an external sleeve rack, and a bionic finger and claw unit. The embedded differential drive component cooperates with the external sleeve rack to drive the external sleeve rack to move. The external sleeve rack is connected to the bionic finger and claw unit in a transmission connection.

[0011] The power and clutch assembly is connected to the mechanical transmission assembly and is used to drive the mechanical transmission assembly to move and control the mechanical transmission assembly to switch between the transmission state and the locking state.

[0012] A multimodal sensing skin component is mounted on the bionic claw unit and communicates with the computing and measurement and control components to sense the contact state between the bionic claw unit and the target object.

[0013] The computing and control components are connected to the power and clutch components and the multimodal sensing skin component, respectively. They control the power and clutch components based on the sensory information from the multimodal sensing skin component, enabling the mechanical transmission component to drive the bionic gripper unit to perform differential compliant grasping and zero-power locking. Compliant grasping means that after the gripper contacts the target object, it can adaptively adjust the gripping force according to the shape, stiffness, and contact resistance of the target object through the synergistic action of the embedded differential drive component and the series buffer spring, thereby achieving stable envelope grasping while avoiding excessive local pressure. Zero-power locking means that after the gripping force reaches a preset stable condition, the gripper mechanically locks the embedded transmission rack and the external sleeve rack through a bistable electromagnetic clutch. While maintaining the target object's gripping state, the power supply to the main drive motor is cut off or reduced, so that the gripping state is mainly maintained by mechanical locking rather than continuous electric drive.

[0014] To better realize the technical solution of the present invention, the following technical measures were also adopted.

[0015] Furthermore, the embedded differential drive assembly includes a base, an embedded transmission rack, and a series buffer spring. The base is provided with a central main gear, the embedded transmission rack is slidably disposed in the cavity inside the outer sleeve rack, the series buffer spring is abutted between the embedded transmission rack and the outer sleeve rack, the central main gear meshes with the embedded transmission rack, and the outer sleeve rack meshes with the finger joint gear of the bionic finger and claw unit through the joint drive tooth groove.

[0016] Furthermore, the bionic finger and claw unit includes a finger bone body, the root of which is connected to a finger joint gear via a connecting ear. The finger joint gear meshes with the joint drive groove of the outer sleeve rack to make the finger bone body rotate relative to the base.

[0017] Furthermore, the multimodal sensing skin component includes a flexible circuit board, a pressure-sensitive sensor array, a high-frequency micro-vibration sensor, a biomimetic corrugated skin, and a transfinger transmissive capacitor plate. The flexible circuit board is disposed on the biomimetic finger unit, and the pressure-sensitive sensor array, the high-frequency micro-vibration sensor, and the transfinger transmissive capacitor plate are all connected to the flexible circuit board. The biomimetic corrugated skin covers the outside of the pressure-sensitive sensor array.

[0018] Furthermore, the trans-finger transmission capacitor plates are disposed on two bionic claw units arranged opposite each other to form a trans-finger transmission capacitor detection structure when grasping a target object; the pressure-sensitive sensor array is used to acquire contact pressure distribution information, and the high-frequency micro-vibration sensor is used to acquire micro-vibration signals during the contact process. The micro-vibration signal is defined as the signal acquired by the high-frequency micro-vibration sensor to characterize the micro-vibration changes during the contact between the bionic claw unit and the target object, which originates from the friction, slippage and local elastic response of the target object surface.

[0019] Furthermore, the power and clutch assembly includes a main drive motor and a bistable electromagnetic clutch. The main drive motor is mounted on a base, and its output shaft is connected to a central main gear. The bistable electromagnetic clutch includes a miniature electromagnet mounted on an outer sleeve rack, and its output shaft is connected to a push rod pin. The push rod pin selectively engages with a locking groove on the embedded transmission rack to switch between a locked state and a differential release state between the embedded differential drive assembly and the outer sleeve rack.

[0020] Furthermore, the computing and measurement and control components include a drive-side encoder, a load-side encoder, and a main controller. The drive-side encoder is located at the main drive motor or at a position that moves synchronously with the central main gear, and is used to detect the drive displacement information on the power input side. The load-side encoder is located at the finger joint gear of the bionic finger and claw unit or at a position that moves synchronously with it, and is used to detect the actual displacement information on the output side of the bionic finger and claw unit. The main controller is communicatively connected to the drive-side encoder, the load-side encoder, the power and clutch components, and the multimodal sensing skin components.

[0021] Furthermore, the main controller is used to determine the deformation of the series buffer spring and the actual gripping force based on the detection difference between the drive-side encoder and the load-side encoder, and to control the power and clutch components to perform drive, differential release, locking and reset actions based on at least one of the contact pressure distribution information, micro-vibration signal and cross-finger transmission capacitance signal obtained by the multimodal sensing skin component.

[0022] A control method for a differential compliant gripper with multimodal sensing and zero-power locking includes:

[0023] The control power and clutch components drive the mechanical transmission components to move, so that the bionic claw unit can perform a transmission and closing action to approach the target object;

[0024] The contact state between the bionic claw unit and the target object is detected by a multimodal sensing skin component;

[0025] After detecting the contact state, the control power and clutch components switch the embedded differential drive component and the external sleeve rack from the locked linkage transmission state to the differential release state, so that relative motion is generated between the embedded differential drive component and the external sleeve rack and a compliant gripping force is formed through the series buffer spring.

[0026] The driving displacement information and actual displacement information are obtained through computing power and measurement and control components, and the actual gripping force is determined.

[0027] When the actual gripping force meets the preset locking conditions, the control power and clutch components cause the mechanical transmission components to enter the locking state, so as to achieve zero-power locking and gripping of the target object.

[0028] Furthermore, the computing power and measurement and control components adjust the driving timing, differential release timing, locking timing, or gripping force control parameters of the power and clutch components based on at least one of the contact pressure distribution information obtained by the pressure-sensitive sensor array, the micro-vibration signal obtained by the high-frequency micro-vibration sensor, and the transmission capacitance signal obtained by the cross-finger transmission capacitor plate.

[0029] Compared with the prior art, the beneficial effects of the present invention are:

[0030] 1. By cooperating with the embedded differential drive component, external sleeve rack and pinion unit in the mechanical transmission assembly, the gripper can achieve differential smooth gripping according to the contact state of the target object during the gripping process. This effectively improves the problems of unilateral obstruction, transmission lock-up and difficulty in achieving adaptive envelope when gripping irregularly shaped target objects by existing grippers, thereby improving the gripper's adaptability to gripping irregular target objects.

[0031] 2. By setting a series buffer spring between the embedded transmission rack and the external sleeve rack, and combining the power and clutch components to control the switching between the transmission and locking states of the mechanical transmission components, the gripper can form a compliant gripping force after contacting the target object, thereby reducing the local squeezing force on fragile or soft target objects, reducing the risk of damage to the target object during the gripping process, and improving the stable gripping ability of target objects of varying hardness.

[0032] 3. By setting up a multimodal sensing skin component and a computing and measurement and control component connected to it, it is possible to acquire at least one of the pressure distribution information, micro-vibration signal and transmission capacitance signal during the contact process of the target object, and control the action of the power and clutch components accordingly, thereby improving the gripper's comprehensive perception ability of contact state, friction state and material characteristics, improving the problem of insufficient closed-loop perception of existing grippers, and improving the grasping control accuracy and stability.

[0033] 4. By selectively engaging the bistable electromagnetic clutch with the locking groove on the embedded transmission rack, the mechanical transmission component can enter a locking state after the gripping condition is met, achieving zero-power locking and holding of the target object. This avoids the increased power consumption and motor overheating problems caused by the existing grippers relying on the continuous power supply of the drive motor to maintain the gripping force for a long time, thus improving the energy efficiency and continuous operation reliability of the system.

[0034] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the positional relationship structure of the differential compliant gripper mechanical transmission assembly disclosed in an embodiment of the present invention;

[0036] Figure 2 This is a schematic diagram of the positional relationship of the mechanical transmission assembly after removing the embedded differential drive assembly, as disclosed in an embodiment of the present invention.

[0037] Figure 3 This is a schematic diagram of the positional structure of the embedded differential drive component disclosed in an embodiment of the present invention;

[0038] Figure 4 This is a structural diagram of the differential compliant gripper disclosed in an embodiment of the present invention;

[0039] Figure 5 The flow chart of the differential compliant gripper control method disclosed in the embodiments of the present invention. Figure 1 ;

[0040] Figure 6The flow chart of the differential compliant gripper control method disclosed in the embodiments of the present invention. Figure 2 .

[0041] Reference numerals: 10. Mechanical transmission component; 11. Base; 12. Central main gear; 13. Embedded transmission rack; 131. Locking groove; 14. External sleeve rack; 141. Cavity; 142. Joint drive tooth groove; 15. Series buffer spring; 16. Bionic finger claw unit; 161. Finger bone body; 162. Finger joint gear; 163. Connecting ear; 20. Power and clutch component; 21. Main drive motor; 22. Servo driver; 23. Bistable electromagnetic clutch; 231. Miniature electromagnet; 232. Push rod pin; 30. Multimodal sensing skin component; 31. Flexible circuit board; 32. Pressure-sensitive sensor array; 33. High-frequency micro-vibration sensor; 34. Bionic corrugated skin; 35. Cross-finger transmissive capacitor plate; 40. Computing power and measurement and control component; 41. Drive-side encoder; 42. Load-side encoder; 43. Main controller. Detailed Implementation

[0042] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0043] This embodiment provides a differential compliant gripper with multimodal sensing and zero-power locking, and a control method thereof. This differential compliant gripper is designed for grasping irregular, fragile, and varying-hardness target objects, employing an overall configuration where a mechanical transmission component 10, a power and clutch component 20, a multimodal sensing skin component 30, and a computing and control component 40 work collaboratively. Specifically, the mechanical transmission component 10 converts power input into gripper movement, forming the basis for differential compliant gripping through the relative motion between the embedded differential drive component and the external sleeve rack 14; the power and clutch component 20 provides the main driving force and controls the mechanical transmission component 10 to switch between transmission, differential release, and locking states; the multimodal sensing skin component 30 senses the contact state, friction state, and dielectric characteristics of the target object between the bionic gripper unit 16 and the target object; and the computing and control component 40 receives sensing and displacement information and controls the power and clutch component 20.

[0044] like Figures 1-3As shown, in this embodiment, the mechanical transmission assembly 10 includes an embedded differential drive assembly, an external sleeve rack 14, and a bionic claw unit 16. The embedded differential drive assembly cooperates with the external sleeve rack 14 to drive the external sleeve rack 14 to move, and the external sleeve rack 14 is drive-connected to the bionic claw unit 16. The embedded differential drive assembly includes a base 11, an embedded transmission rack 13, and a series buffer spring 15. A central main gear 12 is provided on the base 11, and the central main gear 12 meshes with the embedded transmission rack 13. A cavity 141 is formed inside the external sleeve rack 14, and the embedded transmission rack 13 is slidably disposed in the cavity 141. The series buffer spring 15 abuts between the embedded transmission rack 13 and the external sleeve rack 14, so that when the embedded transmission rack 13 moves relative to the external sleeve rack 14, it can compress the series buffer spring 15 and form a compliant gripping force.

[0045] like Figure 4 As shown, the power and clutch assembly 20 includes a main drive motor 21, a servo driver 22, and a bistable electromagnetic clutch 23. The main drive motor 21 is mounted on the base 11, and its output shaft is connected to the central main gear 12. The servo driver 22 is used to control the start, stop, direction, speed, and output torque of the main drive motor 21. The bistable electromagnetic clutch 23 includes a miniature electromagnet 231 and a push rod pin 232. The push rod pin 232 selectively engages with the locking groove 131 on the embedded transmission rack 13, allowing the embedded differential drive assembly and the external sleeve rack 14 to switch between a locked state and a differential release state. The multimodal sensing skin assembly 30 is mounted on the bionic finger unit 16. The computing power and measurement and control assembly 40 is communicatively connected to the multimodal sensing skin assembly 30 and the power and clutch assembly 20, respectively, thereby forming a closed-loop control system for contact sensing, displacement measurement, force calculation, clutch switching, and low-power holding.

[0046] The following is a detailed explanation using specific embodiments.

[0047] Example 1, this is the core example. The differential compliant gripper adopts a two- or four-finger opposing arrangement structure, suitable for gripping soft plastic parts, small ceramic parts, thin-walled glass test tubes, and irregularly shaped fruits and vegetables. The base 11 can be made of aluminum alloy, hard anodized aluminum, stainless steel, or carbon fiber reinforced composite material, preferably using machined aluminum alloy parts to balance structural rigidity, weight, and machining accuracy. The base 11 can be tubular, box-shaped, or frame-shaped.

[0048] The central main gear 12 is housed within the base 11 and coaxially connected to the output shaft of the main drive motor 21. The central main gear 12 can be made of stainless steel, powder metallurgy steel, carburized steel, or engineering plastic gears, preferably a positive displacement metal gear with a module of 0.4 to 1.2. To balance load-bearing capacity and compactness, the central main gear 12 can have a module of 0.8, 15 teeth, and a pitch circle diameter of 12 mm. An embedded transmission rack 13 can mesh with each of the opposite sides of the central main gear 12, so that when the central main gear 12 rotates in one direction, the two embedded transmission racks 13 translate in opposite directions, thereby driving the oppositely positioned bionic claw units 16 to either close towards the grasping center or open away from the grasping center.

[0049] Regarding the relationship between the knuckle rotation angle and the stroke of the outer sleeve rack 14, this embodiment can use the following calculation method to determine the shortest linear displacement of the outer sleeve rack 14. Set the initial finger opening angle to 15 degrees, the full-load closing angle to 175 degrees, and the effective working angle to 160 degrees; select a module of 0.8 and a number of teeth of 15 for the central main gear 12 or the knuckle gear 162, then the pitch circle diameter is: In the formula, The pitch circle diameter ranges from 6 mm to 12 mm, preferably 12 mm. The gear module ranges from 0.4 to 1.2, preferably 0.8. The number of teeth ranges from 10 to 30, with 15 being the preferred number.

[0050] The shortest linear displacement required for the external sleeve rack 14 to complete the full-range gripping is: In the formula, The shortest linear displacement of the outer sleeve rack 14 ranges from 8 mm to 30 mm, preferably 16.76 mm; The effective working angle is in the range of 90 degrees to 180 degrees, preferably 180 degrees. It is the pitch circle diameter.

[0051] Substituting the above preferred values, we get: .

[0052] The embedded transmission rack 13 can be made of hardened stainless steel, tempered steel, or surface-nitrided steel. The outer sleeve rack 14 can be made of aluminum alloy, stainless steel, or a low-friction engineering plastic composite structure, with a cavity 141 extending along its length inside. The cross-sectional shape of the cavity 141 is adapted to the embedded transmission rack 13, and a polytetrafluoroethylene bushing, ball guide, or self-lubricating coating can be provided between them to reduce relative sliding resistance. After the embedded transmission rack 13 extends into the cavity 141 of the outer sleeve rack 14, when the push rod pin 232 is inserted into the locking groove 131, the embedded transmission rack 13 and the outer sleeve rack 14 form a rigid linkage; when the push rod pin 232 disengages from the locking groove 131, the embedded transmission rack 13 can continue to slide in the cavity 141, while the outer sleeve rack 14 stops due to the obstruction of the target object. The relative displacement between the two compresses the series buffer spring 15. It should be noted that the cavity 141 can restrict the series buffer spring 15 and the embedded transmission rack 13 to move only in their axial direction within its cavity.

[0053] The series buffer spring 15 is preferably a compression spring made of piano wire, stainless steel spring steel, or fatigue-resistant alloy steel wire. In this embodiment, the series buffer spring 15 is preloaded and set in the cavity 141 of the outer sleeve rack 14, with one end abutting against the embedded transmission rack 13 and the other end abutting against the inner wall or end limiting surface of the outer sleeve rack 14. The preload ensures that the push rod pin 232 maintains continuous contact force at the moment of release, avoiding a force gap when switching from rigid transmission to differential release.

[0054] The stiffness of the series buffer spring 15 can be determined based on the single-finger safe clamping force and the maximum differential stroke. Assuming the maximum safe thrust for single-finger non-destructive clamping is 15 Newtons and the maximum differential decoupling deformation is 16.67 mm, the spring stiffness is: In the formula, The series buffer spring has a stiffness of 15. For single-finger safety clamping thrust; This is a differential decoupling form variable.

[0055] The outer sleeve rack 14 has a joint drive tooth groove 142 on its outer side. The bionic finger claw unit 16 includes a phalanx body 161, a finger joint gear 162, and a connecting ear 163. The connecting ear 163 is located at the root of the phalanx body 161 and is fixedly connected to or integrally formed with the finger joint gear 162. The connecting ear 163 can be a double-ear structure, with a coaxial hole between the two ears to allow it to be hinged to the base 11 or a joint support portion on the base 11 via a pin. The finger joint gear 162 meshes with the joint drive tooth groove 142 of the outer sleeve rack 14, converting the linear motion of the outer sleeve rack 14 into the swinging motion of the phalanx body 161 relative to the base 11. A copper sleeve, an oil-impregnated bearing, or a polyoxymethylene bushing can be provided at the pin to reduce wear.

[0056] In the power and clutch assembly 20, the main drive motor 21 can be a brushless DC motor, a coreless motor, or a small servo motor. The servo driver 22 is connected to the main drive motor 21 and is used to output three-phase drive current or pulse width modulation drive signal. The output shaft of the main drive motor 21 is connected to the central main gear 12. The connection method can be key connection, clamp connection, spline connection, interference fit connection, or screw clamping connection. The servo driver 22 is communicatively connected to the main controller 43.

[0057] A bistable electromagnetic clutch 23 is mounted on the outer sleeve rack 14, preferably on the side wall of the outer sleeve rack 14, allowing the push rod pin 232 to extend into the cavity 141 in a direction perpendicular to the sliding direction of the embedded transmission rack 13. The miniature electromagnet 231 can be a bistable electromagnet with a permanent magnet holding structure. The push rod pin 232 can be made of stainless steel or hardened steel, and its end can be tapered, cylindrical, or spherical. A locking groove 131 is provided on the embedded transmission rack 13 and can be a hole, slot, or toothed recess arranged at intervals along the length direction. When the push rod pin 232 is inserted into the locking groove 131, the embedded transmission rack 13 and the outer sleeve rack 14 are locked in a synchronous motion state; when the push rod pin 232 is disengaged from the locking groove 131, the embedded transmission rack 13 can slide relative to the outer sleeve rack 14, forming a differential release state.

[0058] A multimodal sensing skin component 30 is disposed on the contact surface of the bionic finger unit 16. The flexible circuit board 31 can be a polyimide flexible circuit board. The pressure-sensitive sensing array 32 can be constructed using cross-matrix electrodes and pressure-sensitive conductive rubber, with an array size ranging from 4×4 to 64×64, and a single tactile pixel side length ranging from 0.5 mm to 5 mm. The high-frequency micro-vibration sensor 33 can be a triaxial accelerometer or a microelectromechanical vibration sensor. The bionic corrugated skin 34 can be made of silicone, thermoplastic polyurethane, or liquid silicone rubber, with periodic corrugated ridges formed on its surface. Cross-finger transmissive capacitor plates 35 are disposed on two oppositely arranged bionic finger units 16, and can be made of copper foil, silver paste printed electrodes, or a flexible transparent conductive film, with one serving as the excitation plate and the other as the receiving plate.

[0059] The node voltage output by the pressure-sensitive sensor array 32 can be converted into a pressure matrix. The node pressure conversion formula is:

[0060]

[0061] In the formula, It refers to the first OK, The pressure values ​​of each tactile pixel. This refers to the reference voltage. This refers to the sampling voltage of that node. This refers to the sampling voltage divider resistor, A refers to the single-node contact area, and C refers to the piezoresistive sensitivity coefficient of the pressure-sensitive rubber.

[0062] The main controller 43 can further perform convolutional feature extraction on the pressure matrix. The formula for calculating the topological features can be expressed as:

[0063]

[0064] In the formula, This refers to the output topological feature pixel values, where P refers to the input pressure matrix. It means The convolution kernel weight matrix.

[0065] Furthermore, the sharpness gradient magnitude of each pixel is calculated. :

[0066]

[0067] In the formula, and These refer to the partial derivatives of the pressure gradient in the horizontal and vertical directions, respectively.

[0068] When the local pressure peak exceeds the preset heavy pressure threshold and the neighborhood sharpness gradient amplitude exceeds the sharpness threshold, the main controller 43 determines that a sharp local contact has occurred at the corresponding position and sends a release pulse to the corresponding bistable electromagnetic clutch 23, causing the push rod pin 232 to disengage from the locking groove 131. When the pressure pixels are distributed in a discrete spot pattern and the spatial variance is greater than the roughness threshold, it can be determined that the surface has high roughness; when the pressure pixels are distributed in a continuous elliptical pattern with smooth edges, it can be determined that the contact surface is relatively smooth.

[0069] A high-frequency micro-vibration sensor 33 is used to collect the mechanical vibrations generated when the biomimetic corrugated skin 34 slides slightly against the target object. The main controller 43 controls the servo driver 22 to cause the main drive motor 21 to output micro-vibration movements with an amplitude of 0.1 mm to 1 mm and a frequency of 5 Hz to 50 Hz, preferably with an amplitude of 0.5 mm and a typical frequency of 20 Hz. The collected vibration signals are subjected to a fast Fourier transform to obtain their frequency domain characteristics.

[0070]

[0071] In the formula, This refers to the characteristics of the frequency domain signal after conversion. This refers to the mechanical high-frequency oscillation timing signal acquired by the high-frequency micro-vibration sensor 33 (IMU). It refers to frequency. It refers to time.

[0072] The main controller 43 can estimate the static friction coefficient based on the energy ratio between the high-frequency band and the low-frequency band.

[0073] Based on the frequency domain analysis results, the estimated static friction coefficient of the target object is determined. The main controller 43 uses high-frequency bands (such as...) Energy integral With low-frequency energy The relative ratio is used to calculate and output the estimated static friction coefficient of the target object. The formula for calculating the estimated static friction coefficient is:

[0074]

[0075] in, to It refers to the high-frequency band that characterizes the friction of rough textures. to It refers to the low-frequency band. It refers to the frictional force mapping constant obtained through calibration experiments.

[0076] The computing and measurement control component 40 includes a drive-side encoder 41, a load-side encoder 42, and a main controller 43. The drive-side encoder 41 is located at the main drive motor 21 or at a position that moves synchronously with the central main gear 12, and can be an absolute magnetic encoder, photoelectric encoder, or Hall effect encoder. The load-side encoder 42 is located at the knuckle gear 162 of the bionic finger-paw unit 16 or at a position that moves synchronously with it, and is used to detect the actual displacement information on the output side of the bionic finger-paw unit 16. The main controller 43 can be a microcontroller with a floating-point unit, a digital signal processor, or an embedded processor.

[0077] The drive-side encoder 41 measures the displacement on the power input side, and the load-side encoder 42 measures the actual displacement on the output side. The spring deformation and actual contact force corresponding to each bionic claw unit 16 can be expressed as:

[0078]

[0079] In the formula, For the first The spring deformation corresponding to each bionic claw unit 16; The input-side displacement is calculated by the drive-side encoder 41; Output-side displacement calculated by the load-side encoder 42; The time of adoption.

[0080]

[0081] In the formula, For the first The actual grasping force applied by the bionic claw unit 16; The series buffer spring has a stiffness of 15.

[0082] The main controller 43 can also construct a second-order impedance control model, enabling the main drive motor 21 to simulate a spring-damped system during the compliant phase:

[0083]

[0084] In the formula, This refers to the virtual inertial mass of the system. This refers to the system's damping parameters. This refers to the virtual stiffness parameters of the system. This refers to the closed position of the target. This refers to the current actual location. and These refer to actual velocity and actual acceleration, respectively. It refers to the actual spring contact force calculated from the difference of the dual absolute encoder.

[0085] Based on the estimated static friction coefficient, the virtual stiffness and target holding force can be corrected:

[0086]

[0087] In the formula, This is the corrected virtual stiffness; As a reference virtual stiffness; This is the stiffness attenuation coefficient; This is an estimated value for the static friction coefficient.

[0088]

[0089] In the formula, For the purpose of maintaining the target; To prevent detachment and ensure the base retains its strength; This is the anti-slip compensation constant; This is an estimated value for the static friction coefficient.

[0090] When the actual gripping force reaches the target holding force and remains stable, for example, when the force fluctuation is less than five percent of the target holding force for 0.2 to 1 second, the main controller 43 sends a locking pulse to the bistable electromagnetic clutch 23, causing the push rod pin 232 to insert into the locking slot 131, locking the embedded transmission rack 13 with the outer sleeve rack 14. Subsequently, the main controller 43 reduces or cuts off the power supply to the main drive motor 21 through the servo driver 22, so that the gripper maintains the gripping state by mechanical locking.

[0091] The transconducting capacitive electrode 35 is used for deep material sensing. After steady-state grasping, the main controller 43 applies AC excitation to one transconducting capacitive electrode 35 and acquires the response signal of the other transconducting capacitive electrode 35 to obtain the real-time equivalent capacitance. Simultaneously, the main controller 43 calculates the distance between the two electrodes based on the encoder position information and estimates the effective contact area based on the area of ​​the pressure-activated pixels in the pressure-sensitive sensor array 32. The relative permittivity of the target object can be expressed as:

[0092]

[0093] In the formula, The relative permittivity of the target object; This is the real-time equivalent capacitance; The distance between the two transmissive capacitor plates is 35. It is the vacuum permittivity; This refers to the effective dielectric bonding area.

[0094] like Figures 1-6 As shown, the working process of this embodiment is as follows: In the initial state, the push rod pin 232 is inserted into the locking groove 131, the embedded transmission rack 13 and the outer sleeve rack 14 are rigidly linked, and the series buffer spring 15 maintains pre-compression but does not undergo major working compression. After receiving the grasping command, the main controller 43 controls the main drive motor 21 to rotate through the servo driver 22. The main drive motor 21 drives the central main gear 12 to rotate, the central main gear 12 drives the embedded transmission rack 13 to translate, the embedded transmission rack 13 drives the outer sleeve rack 14 to translate synchronously, and the outer sleeve rack 14 drives the finger joint gear 162 to rotate through the joint drive tooth groove 142, so that the finger bone body 161 closes relative to the base 11. When one side of the bionic claw unit 16 first contacts the target object, the multimodal sensing skin component 30 detects the contact pressure distribution, the main controller 43 determines that the corresponding side has reached the contact threshold, and controls the corresponding side bistable electromagnetic clutch 23 to release. Upon release, the outer sleeve rack 14 slows down or stops due to obstruction by the target object, while the inner transmission rack 13 continues to move and compresses the series buffer spring 15, thereby creating a compliant gripping force. The uncontacted bionic claw unit 16 can continue to maintain its transmission engagement until it contacts the target object and enters the same differential release process. In this way, the protrusions of irregular target objects will not cause the overall transmission to lock up, and the grippers can form an adaptive envelope to the target object.

[0095] In this embodiment, the bionic finger and claw assembly consists of at least two bionic finger and claw units 16. The two bionic finger and claw units 16 can be divided into two groups and respectively arranged on both sides of the mechanical transmission assembly 10 to form a symmetrical grasping structure. Each bionic finger and claw unit 16 includes a phalanx body 161, a knuckle gear 162, and a connecting ear 163. The connecting ear 163 is disposed at the root of the phalanx body 161 and can be configured as a double-ear connection structure. The two ears are arranged opposite each other along the same plane and have coaxial hinge holes. The connecting ear 163 is used to form a hinge support with the base 11 or the joint support part disposed on the base 11 through a pin, so that the phalanx body 161 can rotate relative to the base 11. The knuckle gear 162 is disposed at the root of the phalanx body 161 and is fixedly connected to or integrally formed with the connecting ear 163. The knuckle gear 162 meshes with the joint drive tooth groove 142 of the outer sleeve rack 14. When the outer sleeve rack 14 moves in a linear direction, the joint drive tooth groove 142 drives the knuckle gear 162 to rotate, which in turn drives the phalanx body 161 to open or close relative to the base 11 through the connecting ear 163, thereby realizing the envelope grasping of the target object. It should be noted that the bionic claw assembly is used to represent the grasping execution structure formed by the combination of multiple bionic claw units 16, and the bionic claw unit 16 is used to represent one of the independent claw execution units; the connecting ear 163 is used to form the hinge support of the phalanx body 161 relative to the base 11. The knuckle gear 162 and the connecting ear 163 are fixedly connected or integrally formed, and do not form a hinge pair with relative rotation.

[0096] Example 2 is an extended application scenario example. The differential compliant gripper can be used in various environments such as precision gripping in laboratories, fresh food sorting, industrial assembly, and medical biochemical testing. For different application environments, the dimensions of the base 11, the power of the main drive motor 21, the stiffness of the series buffer spring 15, the sensitivity of the multimodal sensing skin component 30, and the control parameters of the main controller 43 can be adapted.

[0097] In laboratory or medical biochemical testing scenarios, the target object may be a thin-walled glass test tube, a plastic centrifuge tube, a flexible sample container, or a small ceramic device. In this case, the biomimetic corrugated skin 34 is preferably made of silicone material with a Shore hardness of 20 to 40 to reduce localized stress upon contact. The pixel pitch of the pressure-sensitive sensing array 32 can be set to 0.5 mm to 2 mm to improve the contact resolution of small target objects. The transfinite-finger transmissive capacitor plate 35 can be made of a small-area flexible copper foil electrode, and the excitation frequency can be set to 50 kHz to 200 kHz to distinguish between empty tubes, liquid-filled tubes, or sample containers with different dielectric properties.

[0098] In fresh produce sorting scenarios, the target object may be fruit, vegetables, or soft-packaged food. In this case, the bionic claw unit 16 can adopt a relatively long finger bone body 161. The main controller 43 can use the relative permittivity obtained by the transconductance capacitor plate 35 across the fingers to identify the internal water content or hollow state. When the relative permittivity is significantly lower than the empirical range for a target of the same size, a rejection or re-inspection signal can be output. This process does not require additional damage to the target object and is suitable for continuous sorting.

[0099] In industrial assembly scenarios, the target object may be an irregularly shaped metal part, a plastic shell, a ceramic part, or a composite material part. For parts with large differences in surface roughness, the main controller 43 can rely more on the high-frequency micro-vibration sensor 33 to estimate the friction state and adjust the target holding force accordingly to prevent the workpiece from slipping during handling.

[0100] In the aforementioned different application scenarios, the basic connection relationships of the mechanical transmission component 10, the power and clutch component 20, the multimodal sensing skin component 30, and the computing power and measurement and control component 40 remain unchanged. By changing the size, material, stiffness, motor power, sampling rate, and control threshold, the same core technology solution can be extended to micro-scale precision grasping, flexible fresh food sorting, and industrial-scale stable grasping scenarios.

[0101] One of the key technical features of this invention is the embedded differential structure formed by the embedded differential drive component and the external sleeve rack 14. In this structure, the embedded transmission rack 13 does not simply push the bionic claw unit 16, but is slidably disposed within the cavity 141 of the external sleeve rack 14. When the push rod pin 232 is locked, the embedded transmission rack 13 and the external sleeve rack 14 move synchronously, enabling rapid transmission and engagement; when the push rod pin 232 is released, the external sleeve rack 14 can stop after contacting the target object, while the embedded transmission rack 13 continues to slide within the cavity 141 and compresses the series buffer spring 15, converting the rigid displacement of the main drive motor 21 into elastic potential energy. This structure uses the relative displacement inside the sleeve to replace the external swing arm type differential compensation, which can reduce the lateral expansion space and make the gripper more suitable for narrow work positions.

[0102] Another key technical feature of this invention is the closed-loop control formed between the multimodal sensing skin component 30 and the computing and measurement control component 40. The pressure-sensitive sensor array 32 provides the contact pressure distribution, the high-frequency micro-vibration sensor 33 provides micro-slippage and surface friction states, and the trans-finger transmission capacitor plate 35 provides dielectric characteristics. The main controller 43 does not determine the grasping state based solely on a single pressure threshold, but rather combines pressure, vibration, capacitance, and displacement information to control the power and clutch component 20. In this way, the gripper can promptly release the corresponding side structure at the moment of contact to protect the target object, and can also enter a locked state after the grasping is stable, avoiding continuous electric drive holding.

[0103] The zero-power locking mechanism in this embodiment of the invention is not simply a power outage, but rather utilizes the mechanical engagement between the push rod pin 232 and the locking groove 131 to withstand the elastic potential energy of the series buffer spring 15. When the actual gripping force meets the preset locking conditions, the push rod pin 232 inserts into the locking groove 131, causing the embedded transmission rack 13 and the outer sleeve rack 14 to re-establish a locking relationship. Thereafter, even if the main drive motor 21 reduces or cuts off its power supply, the clamping force generated by the series buffer spring 15 is maintained by the mechanical structure. This structure, which combines locking, energy retention, and drive unloading, enables the gripper to reduce heat generation and power consumption while maintaining stable clamping.

[0104] It should be noted that the specific models and specifications of the main drive motor 21, servo driver 22, miniature electromagnet 231, pressure-sensitive sensor array 32, high-frequency micro-vibration sensor 33, transfinite transmission capacitor plate 35, drive-side encoder 41, load-side encoder 42, and main controller 43 need to be selected and determined according to the actual specifications of the device. The specific selection calculation method adopts the existing technology in this field, so it will not be described in detail.

[0105] The power supply and principles of the main drive motor 21, servo driver 22, miniature electromagnet 231, pressure-sensitive sensor array 32, high-frequency micro-vibration sensor 33, trans-finger transmission capacitor plate 35, drive-side encoder 41, load-side encoder 42, and main controller 43 are clear to those skilled in the art and will not be described in detail here.

[0106] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A differential compliant gripper with multimodal sensing and zero-power locking, characterized in that, include: The mechanical transmission assembly (10) includes an embedded differential drive assembly, an external sleeve rack (14) and a bionic claw unit (16). The embedded differential drive assembly cooperates with the external sleeve rack (14) to drive the external sleeve rack (14) to move. The external sleeve rack (14) is connected to the bionic claw unit (16) in a transmission connection. The power and clutch assembly (20) is driven to the mechanical transmission assembly (10) and is used to drive the mechanical transmission assembly (10) to move and control the mechanical transmission assembly (10) to switch between the transmission state and the lock state. A multimodal sensing skin component (30) is disposed on the bionic claw unit (16) and is communicatively connected to the computing and measurement and control component (40) for sensing the contact state between the bionic claw unit (16) and the target object; The computing and measurement and control component (40) is connected to the power and clutch component (20) and the multimodal sensing skin component (30) respectively. It is used to control the action of the power and clutch component (20) according to the sensing information of the multimodal sensing skin component (30) so that the mechanical transmission component (10) drives the bionic claw unit (16) to perform differential compliant grasping and zero power consumption locking.

2. The differential compliant gripper according to claim 1, characterized in that: The embedded differential drive assembly includes a base (11), an embedded transmission rack (13), and a series buffer spring (15). The base (11) is provided with a central main gear (12). The embedded transmission rack (13) is slidably disposed in the cavity (141) inside the outer sleeve rack (14). The series buffer spring (15) is abutted between the embedded transmission rack (13) and the outer sleeve rack (14). The central main gear (12) meshes with the embedded transmission rack (13). The outer sleeve rack (14) meshes with the finger joint gear (162) of the bionic finger and claw unit (16) through the joint drive tooth groove (142).

3. The differential compliant gripper according to claim 1, characterized in that: The bionic finger and claw unit (16) includes a finger bone body (161), the root of which is connected to a finger joint gear (162) via a connecting ear (163). The finger joint gear (162) meshes with the joint drive groove (142) of the outer sleeve rack (14) to make the finger bone body (161) rotate relative to the base (11).

4. The differential compliant gripper according to claim 1, characterized in that: The multimodal sensing skin component (30) includes a flexible circuit board (31), a pressure-sensitive sensor array (32), a high-frequency micro-vibration sensor (33), a bionic corrugated skin (34), and a trans-finger transmissive capacitor plate (35). The flexible circuit board (31) is disposed on the bionic finger unit (16). The pressure-sensitive sensor array (32), the high-frequency micro-vibration sensor (33), and the trans-finger transmissive capacitor plate (35) are all connected to the flexible circuit board (31). The bionic corrugated skin (34) covers the outside of the pressure-sensitive sensor array (32).

5. The differential compliant gripper according to claim 4, characterized in that: Cross-finger transmission capacitor plates (35) are disposed on two bionic claw units (16) arranged opposite to each other to form a cross-finger transmission capacitor detection structure when grasping a target object; pressure-sensitive sensor array (32) is used to acquire contact pressure distribution information, and high-frequency micro-vibration sensor (33) is used to acquire micro-vibration signals during the contact process.

6. The differential compliant gripper according to claim 2, characterized in that: The power and clutch assembly (20) includes a main drive motor (21) and a bistable electromagnetic clutch (23). The main drive motor (21) is mounted on a base (11) and its output shaft is connected to a central main gear (12). The bistable electromagnetic clutch (23) includes a miniature electromagnet (231) mounted on an outer sleeve rack (14) and its output shaft is connected to a push rod pin (232). The push rod pin (232) selectively engages with a locking groove (131) on an embedded transmission rack (13) to switch between a locked state and a differential release state between the embedded differential drive assembly and the outer sleeve rack (14).

7. The differential compliant gripper according to claim 1, characterized in that: The computing and measurement and control component (40) includes a drive-side encoder (41), a load-side encoder (42), and a main controller (43). The drive-side encoder (41) is located at the position of the main drive motor (21) or the position of synchronous movement with the central main gear (12) to detect the drive displacement information on the power input side. The load-side encoder (42) is located at the finger joint gear (162) of the bionic finger and claw unit (16) or the position of synchronous movement with it to detect the actual displacement information on the output side of the bionic finger and claw unit (16). The main controller (43) is connected to the drive-side encoder (41), the load-side encoder (42), the power and clutch component (20), and the multimodal sensing skin component (30) respectively.

8. The differential compliant gripper according to claim 7, characterized in that: The main controller (43) is used to determine the deformation and actual gripping force of the series buffer spring (15) based on the detection difference between the drive-side encoder (41) and the load-side encoder (42), and to control the power and clutch assembly (20) to perform drive, differential release, locking and reset actions based on at least one of the contact pressure distribution information, micro-vibration signal and cross-finger transmission capacitance signal obtained by the multimodal sensing skin assembly (30).

9. A control method for a differential compliant gripper with multimodal sensing and zero-power locking as described in any one of claims 1 to 8, characterized in that, include: The control power and clutch assembly (20) drives the mechanical transmission assembly (10) to move, so that the bionic claw unit (16) performs a transmission closing action to approach the target object; The contact state between the bionic claw unit (16) and the target object is detected by the multimodal sensing skin component (30); After the contact state is detected, the control power and clutch assembly (20) switches the embedded differential drive assembly and the external sleeve rack (14) from the locked linkage transmission state to the differential release state, so that relative motion is generated between the embedded differential drive assembly and the external sleeve rack (14) and a compliant gripping force is formed through the series buffer spring (15). The driving displacement information and actual displacement information are obtained through the computing power and measurement and control components (40), and the actual gripping force is determined. When the actual gripping force meets the preset locking conditions, the control power and clutch assembly (20) causes the mechanical transmission assembly (10) to enter the locking state, so as to achieve zero-power locking gripping of the target object.

10. The control method according to claim 9, characterized in that: The computing power and measurement and control component (40) adjusts the driving timing, differential release timing, locking timing or gripping force control parameters of the power and clutch component (20) based on at least one of the contact pressure distribution information obtained by the pressure-sensitive sensor array (32), the micro-vibration signal obtained by the high-frequency micro-vibration sensor (33), and the transmission capacitance signal obtained by the cross-finger transmission capacitor plate (35).

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