Finger-shaped device based on liquid metal flexible sensor and control method thereof

Abstract

The invention discloses a finger-shaped device based on a liquid metal flexible sensor and a control method of the finger-shaped device, and relates to the technical field of intelligent robots and sensors. The device comprises a fixing module, a finger module, a sensor module, a driving rope and a driving module, the driving module, the fixing module and the finger module are sequentially connected through fixing studs, the driving module and the finger module are connected through the driving rope, and the finger module and the sensor module are fixedly connected in an adhesive mode; the finger module comprises a proximal phalanx, a middle phalanx, a distal phalanx, a first connecting piece and a second connecting piece, the proximal phalanx and the middle phalanx are connected through the first connecting piece, and the middle phalanx and the distal phalanx are connected through the second connecting piece. The bending angle and the grabbing pressure of the finger-shaped device can be measured, motion control of the finger-shaped device is achieved in combination with an admittance control strategy, development of the robot technology is promoted, and a way is laid for a robot system which is more intelligent and more sensitive in response.

Description

Technical Field

[0001] This invention relates to the field of wearable robot technology, and in particular to a finger-shaped device based on a liquid metal flexible sensor and its control method. Background Technology

[0002] In recent years, human-machine collaborative technology has accelerated the widespread adoption of robotic equipment in the industrial and medical fields. Exoskeleton finger devices, as key tools for enhancing human maneuverability, have been widely used in precision assembly, rehabilitation training, and other scenarios. However, traditional finger devices often employ underactuated structures and are limited by imperfect sensing systems, making it difficult to achieve precise grasping operations. Existing technologies typically equip each joint with potentiometer-based position sensors or strain gauge-based torque sensors, but these rigid sensing elements are bulky and have low integration, making it impossible to achieve multimodal measurements in a compact structure. This results in the device's inability to simultaneously sense joint motion and contact force information, severely restricting its adaptability in complex interactive tasks.

[0003] While strain gauge and potentiometer-based sensing solutions can partially meet basic detection needs, their rigid structures and fixed packaging make it difficult to simulate the flexibility and adaptability of human fingers. Especially when grasping irregularly shaped objects or performing delicate operations, traditional sensors struggle to simultaneously address the demands of angle detection and force feedback. Furthermore, limited by the spatial constraints and shape requirements of finger-shaped devices, current technologies have not yet resolved the core contradiction between high-density sensor integration and dynamic compliant sensing, necessitating the development of novel flexible sensing solutions to overcome the technical bottlenecks of multimodal information fusion. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to address the deficiencies mentioned in the background art by providing a finger-shaped device based on a liquid metal flexible sensor and its control method.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] A finger-shaped device based on a liquid metal flexible sensor, characterized in that:

[0007] Fixed module, finger module, sensor module, driver module;

[0008] The finger module is mounted on the fixed module, and the finger module includes a proximal phalanx, a middle phalanx, a distal phalanx, a first connector, and a second connector.

[0009] The proximal phalanx includes a first base, a first monoauricular connector, and a first mounting surface; the first monoauricular connector is disposed at the front end of the first base, and the first mounting surface is located on the upper surface of the proximal phalanx;

[0010] The middle phalanx includes a second base, a first binaural connector, a second monoaural connector, a second mounting surface, and a third mounting surface; the first binaural connector and the second monoaural connector are respectively disposed at the rear end and the front end of the second base, and are parallel to each other; the second mounting surface and the third mounting surface are located on the upper surface of the middle phalanx, one at the rear and one at the front.

[0011] The distal phalanx includes a third base, a second ear connector, a fourth mounting surface, and a fifth mounting surface; the second ear connector is disposed at the rear end of the third base; the fourth mounting surface is located on the upper surface of the distal phalanx; and the fifth mounting surface is located on the lower surface of the distal phalanx.

[0012] The first and second connecting parts have the same structure, including a drive shaft, end caps installed at both ends of the drive shaft, and a driven winding wheel fixedly installed on the drive shaft;

[0013] The first single-ear connector of the proximal phalanx in the finger module and the drive shaft of the first connector are fitted with a clearance; the first double-ear connector of the middle phalanx and the end cap of the first connector are fitted together, thereby forming a proximal interphalangeal joint; the second single-ear connector of the middle phalanx and the drive shaft of the second connector are fitted with a clearance; the second double-ear connector of the distal phalanx and the end cap of the second connector are fitted together, thereby forming a distal interphalangeal joint;

[0014] The sensor module includes a first sensor, a second sensor, and a third sensor;

[0015] The first, second, and third sensors have the same structure and are all liquid metal flexible sensors.

[0016] The lower surface of the first sensor is glued to the first mounting surface of the proximal phalanx and the second mounting surface of the middle phalanx of the finger module at both ends; the lower surface of the second sensor is glued to the third mounting surface of the middle phalanx and the fourth mounting surface of the distal phalanx of the finger module at both ends; the lower surface of the third sensor is glued to the fifth mounting surface of the distal phalanx of the finger module at both ends.

[0017] The drive module includes a motor bracket, a drive motor, a drive winding wheel, and a drive rope;

[0018] The drive motor is mounted on the fixed module via a motor bracket;

[0019] The drive rope and drive winding wheel correspond one-to-one with the driven winding wheels in the first and second connectors, and are connected in the following ways: First, one end of the drive rope is wound around its corresponding drive winding wheel, and the other end passes through the inlet hole of the corresponding proximal phalanx and then wound around the driven winding wheel of the corresponding first connector; Second, one end of the drive rope is wound around the drive winding wheel of its corresponding drive module, and the other end passes sequentially through the inlet hole of the corresponding proximal phalanx and the second base of the middle phalanx, and finally wound around the driven winding wheel of its corresponding second connector.

[0020] A finger-shaped device based on a liquid metal flexible sensor achieves precise assistance and real-time monitoring of joint movements through the coordinated design of a fixing module, a finger module, a sensor module, and a drive module. Its core lies in attaching the liquid metal flexible sensor to the surfaces of the proximal, middle, and distal phalanges of the finger bones, enabling high-precision detection of deformation signals during finger flexion and providing real-time feedback on joint posture. The drive module, through a motor, a winding wheel, and a rope transmission, combined with a dual-connector structure, achieves coordinated flexion and extension movements of the proximal and distal interphalangeal joints, enhancing grip strength while ensuring biomimetic motion. The overall device features a compact structure, high sensing sensitivity, and natural and reliable motion, and can be widely applied in rehabilitation medicine, prosthetic robots, or human-computer interaction, effectively improving the intelligence level and operational realism of finger function assistance.

[0021] A control method for a finger-shaped device based on a liquid metal flexible sensor, characterized by the following steps:

[0022] Step 1: Obtain the actual contact force F at the end of the finger-shaped device. m (t), the contact force is measured by a third sensor and subjected to bias calibration and filtering;

[0023] Step 2: Obtain the target contact force F set for the current task. t (t), wherein the target contact force is generated by the task planning module or the operation strategy module;

[0024] Step 3: Obtain the current joint angle Θ(t) = [θ1(t), θ2(t)] for each joint of the finger device. T The joint angle is measured in real time by a first sensor and a second sensor installed at the joint, where θ1(t) is the proximal interphalangeal joint angle measured by the first sensor and θ2(t) is the distal interphalangeal joint angle measured by the second sensor.

[0025] Step 4: Calculate the center position of the lower surface of the distal phalanx, i.e., the position x of the distal end of the finger-shaped device, using positive kinematics. (t) And obtain the initial equilibrium position x0 according to the system calibration;

[0026] Step 5: Calculate the force error e F (t)=F t (t)-F m (t);

[0027] Step 6: Input the force error into the admittance controller, which is based on a virtual mass-damping-stiffness model.

[0028]

[0029] The desired end position x is obtained by solving the problem. d (t); where M is the virtual mass matrix, B is the virtual damping matrix, and K is the virtual stiffness matrix. All of these matrices are design parameters. The dynamic response characteristics and steady-state error characteristics of the system can be changed by adjusting these parameters.

[0030] Step 7: Obtain the desired terminal position x from the solution. d (t) Perform inverse kinematics solution to obtain the desired joint angle Θ des (t);

[0031] Step 8: Send the desired joint angle to the low-level position servo controller of each joint motor to drive the finger device to move to the desired end position;

[0032] This control method realizes an intelligent compliant operation that integrates force feedback and position control. By collecting end-effector contact force and joint angles in real time and combining them with an admittance control model, the force error is dynamically converted into a compliant position adjustment command. This enables the finger device to adaptively adjust its gripping force and posture, achieving safe and precise operation in human-computer interaction. It effectively solves the problems of excessive force impact or unstable gripping that are prone to occur in rigid finger devices. Through the flexible adjustment of virtual mass-damping-stiffness parameters, it can match the physical characteristics and task requirements of different operating objects, significantly improving the adaptability, safety and operational realism of the device in scenarios such as rehabilitation training, prosthetic control or precision grasping. The overall method realizes the closed-loop integration of sensor-actuator-control algorithm, demonstrating the efficient application of force-position hybrid control in finger devices.

[0033] The liquid metal flexible sensor consists of a bottom substrate, a liquid metal layer, a top substrate, and several wires. The bottom substrate is made of an elastic material and has a microchannel array on its upper surface. The liquid metal layer is made of gallium-indium alloy liquid metal and fills the microchannels. The top substrate is made of an elastic material and covers the upper surface of the bottom substrate. The several wires are respectively embedded at both ends of the liquid metal layer and connected to an external circuit.

[0034] The liquid metal flexible sensor features high flexibility, high sensitivity, and stability. By employing a microchannel structure filled with gallium-indium alloy sandwiched between elastic substrates, the sensor can significantly deform with the skin or phalanx surface when the finger is bent. It sensitively reflects strain information through changes in the resistance of the liquid metal, while avoiding the problems of easy breakage and poor comfort of traditional rigid sensors. It achieves highly reliable and continuous measurement of joint angles and end-effector contact forces in finger devices, and has advantages such as fatigue resistance and good biocompatibility. It provides a key source of sensing data for precise force control and motion control of finger devices, significantly enhancing the durability of the entire system in long-term use and the safety of human-computer interaction.

[0035] The first connector has two driven winding wheels, located between the first single-ear connector and the first double-ear connector respectively; the second connector has two driven winding wheels, located between the second single-ear connector and the second double-ear connector respectively.

[0036] The arrangement of the driven winding wheels in the connectors was further defined, optimizing the spatial layout and torque transmission efficiency of the transmission structure. By placing driven winding wheels at both ends of the drive shaft of each connector, and between the single-ear and double-ear connectors, symmetrical winding and balanced force couple distribution of the drive rope were achieved, effectively avoiding off-center loading or jamming during joint movement. The effect is a significant improvement in the synchronization and stability of the distal and proximal interphalangeal joint movements, making finger flexion and extension movements smoother and more natural. It also enhances transmission accuracy and load capacity, providing crucial mechanical structural support for the finger-shaped device to achieve precise gripping and reliable force control.

[0037] The fixing module includes a base and a female buckle; the base is plate-shaped with an arc-shaped bottom surface, rectangular guide grooves corresponding to the female buckle on both sides, threaded through holes corresponding to the driving module symmetrically provided at the rear end, and threaded through holes corresponding to the finger module symmetrically provided at the front end; the female buckle passes through the corresponding rectangular guide groove on the base, and after circumferentially surrounding the base, it achieves a detachable snap-fit ​​connection with the female buckle through the male buckle.

[0038] The fixation module provides a highly adaptable, secure, and easy-to-install human body connection solution. By adopting a base design with an arc-shaped bottom and a snap-fit ​​buckle, the module can closely fit the physiological curvature of the back of the hand or forearm. The fixed position can be adjusted by a rectangular guide groove, effectively adapting to the anatomical features of different users. This significantly improves the overall wearing comfort and operational stability of the finger device, preventing displacement or loosening during exercise. At the same time, the detachable nature of the snap-fit ​​allows the device to be quickly put on or taken off, greatly enhancing its practicality and user experience in rehabilitation training or daily auxiliary use.

[0039] A control method for a finger-shaped device based on a liquid metal flexible sensor, characterized in that: the target contact force F in step 2... t (t) is a constant value or a force reference trajectory that varies with time;

[0040] The target contact force is further limited, which expands the adaptability and task diversity of the finger device control strategy. By allowing the target contact force to be set to a constant value or a time-varying trajectory, the device can perform both stable static grasping and complex dynamic operation tasks, which significantly improves the intelligence and flexibility of the finger device in different application scenarios. The time-varying force mode can simulate the speed and force changes of human hand grasping, thereby enhancing the device's adaptability to tasks and providing a more natural and safe force interaction experience in scenarios such as human-machine collaboration and prosthetic control.

[0041] The control method for a finger-shaped device based on a liquid metal flexible sensor is characterized in that: the inverse kinematics solution in step 7 is based on a two-link analytical solution and includes the following sub-steps:

[0042] 1) Calculate the square of the distance from the end to the base. Where, x d,x Indicates the desired end position x d (t) The coordinates of x along the x-axis, x d,y Indicates the desired end position x d (t) The coordinate of y along the y-axis;

[0043] 2) Calculation in Let l1 represent the expected angle between the middle and distal phalanges calculated by inverse kinematics, and l2 represent the length of the middle phalanx and the length of the distal phalanx.

[0044] 3) Calculation in, This represents the desired angle between the proximal and middle phalanges, calculated using inverse kinematics; the purpose of the admittance controller is to make e F As θ(t) approaches 0, θ1(t) approaches 0 during this process. θ2(t) approaches

[0045] The inverse kinematics solution provides a computationally efficient and real-time analytical algorithm for joint angles, ensuring the accuracy and rapid response of the finger device control. By employing a double-link geometric model and analytical solution, the desired angles of the proximal and distal interphalangeal joints are directly calculated from the desired end position, avoiding the slow convergence or computational complexity problems that may occur with numerical iterative methods. This enhances the real-time performance of the control system, enabling the finger device to quickly track the smooth trajectory output by the admittance controller and achieve high-precision force-position hybrid control. At the same time, the analytical solution form enhances the reliability of the algorithm, providing a stable and smooth motion foundation for the finger device in dynamic interactive tasks, and ensuring the safety and naturalness of human-machine collaboration.

[0046] Compared with the prior art, the present invention, employing the above technical solution, has the following technical effects:

[0047] 1. The present invention provides a finger-shaped device based on a liquid metal flexible sensor. Through the sensor module, the device can simultaneously measure the bending angle of the finger joint and the gripping pressure of the fingertip, realizing the coordinated perception of motion control and force feedback of the finger-shaped device, and overcoming the limitation of traditional rigid sensors that are difficult to achieve multimodal measurement in a compact space.

[0048] 2. The present invention provides a finger-shaped device based on a liquid metal flexible sensor. The liquid metal flexible sensor uses a flexible substrate as a carrier, which has good deformation adaptability and fit. It can bend with the finger module without affecting its performance. It is suitable for grasping operations on complex curved surfaces and irregularly shaped objects, thus improving the practicality and adaptability of the finger-shaped device in real environments.

[0049] 3. The finger-shaped device based on a liquid metal flexible sensor of the present invention enables quick disassembly and maintenance of each module through threaded connection, snap-fit ​​fixing and other methods. The drive rope is reasonably laid out, the transmission efficiency is high, and the overall structure has good scalability and maintainability.

[0050] 4. The finger-shaped device based on a liquid metal flexible sensor of the present invention can complete accurate grasping action through admittance control strategy, simulate the tactile interaction behavior of human fingers, and effectively avoid rigid collision. Attached Figure Description

[0051] Figure 1 This is a front structural diagram of the present invention;

[0052] Figure 2 This is a schematic diagram of the rear structure of the present invention;

[0053] Figure 3 This is a schematic diagram of the structure of the liquid metal flexible sensor in this invention;

[0054] Figure 4 This is a flowchart of the control method in this invention;

[0055] In the diagram, 1-fixed module, 11-base, 12-clasp, 2-finger module, 21-proximal phalanx, 211-first mounting surface, 212-first base, 213-first single-ear connector, 22-first connector, 221-end cap, 222-drive shaft, 223-driven winding wheel, 23-middle phalanx, 231-second mounting surface, 232-third mounting surface, 233-first double-ear connector, 234-second base, 235-second single-ear connector, 24-first... Two connectors, 25-distal phalanx, 251-fourth mounting surface, 252-third base, 253-fifth mounting surface, 254-second double-ear connector, 3-sensor module, 31-second sensor, 311-wire, 312-bottom substrate, 313-liquid metal layer, 314-top substrate, 32-first sensor, 33-third sensor, 4-drive rope, 5-drive module, 51-drive winding wheel, 52-drive motor, 53-motor bracket, 6-fixing stud. Detailed Implementation

[0056] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings:

[0057] This invention can be implemented in many different forms and should not be considered limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully express the scope of the invention to those skilled in the art. In the drawings, components are enlarged for clarity.

[0058] It should be understood that although the terms first, second, third, etc., may be used herein to describe various elements, components, and / or parts, these elements, components, and / or parts are not limited by these terms. These terms are merely used to distinguish elements, components, and / or parts from one another. Therefore, the first element, component, and / or part discussed below may be a second element, component, or part without departing from the teachings of this invention.

[0059] like Figure 1 and Figure 2 The finger-shaped device based on a liquid metal flexible sensor shown includes a fixing module 1, a finger module 2, a sensor module 3, M driving ropes 4, and a driving module 5, where M is a natural number greater than or equal to 1.

[0060] The fixing module 1 includes a base 11 and a male and female buckle 12;

[0061] The base 11 is plate-shaped with an arc-shaped bottom surface. It has rectangular guide grooves on both sides corresponding to the snap fastener 12, threaded through holes corresponding to the drive module 5 are symmetrically provided at the rear end, and threaded through holes corresponding to the finger module 2 are symmetrically provided at the front end.

[0062] The male and female buckles 12 pass through the corresponding rectangular guide groove on the base 11, and after circumferentially surrounding it, they achieve a detachable snap-fit ​​connection through the male buckle and the female buckle;

[0063] The finger module 2 includes a proximal phalanx 21, a middle phalanx 23, a distal phalanx 25, a first connector 22, and a second connector 24;

[0064] The first connector 22 and the second connector 24 have the same structure, each including a drive shaft 222, M driven winding wheels 223, and N end caps 221, where N is a natural number greater than or equal to 1;

[0065] The drive shaft 222 is cylindrical and has keyways at both ends; the N end caps 221 have bosses on their inner and outer circumferential surfaces, which mate with the end bosses of the drive shaft 222 and are symmetrically installed at both ends of the drive shaft 222; the M driven winding wheels 223 have keyways on their inner circumferential surfaces, which mate with the bosses of the drive shaft 222 and are symmetrically arranged on both sides of the drive shaft 222.

[0066] The proximal phalanx 21 includes a first base 212, a first single ear connector 213, and a first mounting surface 211;

[0067] The first base 212 has a plate-shaped three-dimensional structure with a rectangular plate-shaped bottom; the first single ear connector 213 is disposed at the top of the first base 212, and the symmetry plane of the first single ear connector 213 is located on the symmetry plane of the first base 212; the first mounting surface 211 is the upper surface of the proximal phalanx 21 and corresponds to the sensor module 3.

[0068] The first base 212 has threaded through holes distributed in a rectangular array at its bottom, corresponding to the base 11;

[0069] The first substrate 212 has M inlet through holes in the middle, each corresponding to a drive module 5;

[0070] The middle phalanx 23 includes a second base 234, a first double-ear connector 233, a second single-ear connector 235, a second mounting surface 231, and a third mounting surface 232;

[0071] The second base 234 is in the shape of a rectangular tube; the first double ear connector 233 and the second single ear connector 235 are disposed at both ends of the second base 234 and are parallel to each other; the second mounting surface 231 and the third mounting surface 232 are the upper surfaces of the middle phalanx 23 and correspond to the sensor module 3.

[0072] The distal phalanx 25 includes a third base 252, a second ear connector 254, a fourth mounting surface 251, and a fifth mounting surface 253;

[0073] The third base 252 is a rectangular tube with a variable cross-section; the second double ear connector 254 is disposed at the rear end of the third base 252; the fourth mounting surface 251 is the upper surface of the distal phalanx 25 and corresponds to the sensor module 3; the fifth mounting surface 253 is the lower surface of the distal phalanx 25 and corresponds to the sensor module 3.

[0074] The first single-ear connector 213 of the proximal phalanx 21 and the drive shaft 222 of the first connector 22 are fitted with a clearance; the first double-ear connector 233 of the middle phalanx 23 and the N end caps 221 of the first connector 22 are fitted together, thereby forming a proximal interphalangeal joint; the second single-ear connector 235 of the middle phalanx 23 and the drive shaft 222 of the second connector 24 are fitted with a clearance; the second double-ear connector 254 of the distal phalanx 25 and the N end caps 221 of the second connector 24 are fitted together, thereby forming a distal interphalangeal joint;

[0075] The M drive modules 5 include a motor bracket 53, a drive motor 52, and a drive winding wheel 51;

[0076] The motor bracket 53 is in the shape of a curved plate; the drive motor 52 is fixed to the side of the motor bracket 53 by bolts, and its output shaft is coaxially fixed to the drive winding wheel 51.

[0077] The bottom surface of the motor bracket 53 is provided with a threaded through hole corresponding to the base 11;

[0078] All drive ropes 4 are made of Kevlar fiber. M drive ropes 4 correspond one-to-one with M drive winding wheels 51 and M driven winding wheels 223. In one type of drive rope 4, one end of the lasso is wound around the drive winding wheel 51 of its corresponding drive module 5, and the other end passes through the inlet hole of the corresponding proximal phalanx 21 and then wound around the driven winding wheel 223 of its corresponding first connector 22. In another type of drive rope 4, one end of the lasso is wound around the drive winding wheel 51 of its corresponding drive module 5, and the other end passes through the inlet hole of its corresponding proximal phalanx 21 and the second base 234 of the middle phalanx 23 in sequence, and finally wound around the driven winding wheel 223 of its corresponding second connector 24.

[0079] The threaded through hole of the base 11 of the fixed module 1 and the threaded through hole of the motor bracket 53 of the drive module 5 are threadedly connected by a fixing stud 6; the threaded through hole of the base 11 of the fixed module 1 and the threaded through hole of the proximal phalanx 21 of the finger module 2 are threadedly connected by a fixing stud 6.

[0080] like Figure 3As shown, the sensor module 3 includes a first sensor 32, a second sensor 31, and a third sensor 33;

[0081] The first to third sensors 33 have the same structure, each including a bottom substrate 312, a liquid metal layer 313, a top substrate 314, and several wires 311;

[0082] The bottom substrate 312 is a rectangular plate made of elastic material, and its upper surface has a microchannel array with a rectangular cross-section. The liquid metal layer 313 is made of gallium indium alloy liquid metal and the microchannels are filled by microneedle injection molding. The top substrate 314 is a rectangular plate made of elastic material and covers the upper surface of the bottom substrate 312. The plurality of wires 311 are respectively embedded at both ends of the liquid metal layer 313 and connected to external circuits.

[0083] The two ends of the lower surface of the bottom substrate 312 of the first sensor 32 are respectively glued to the first mounting surface 211 of the proximal phalanx 21 and the second mounting surface 231 of the middle phalanx 23 of the finger module 2; the two ends of the lower surface of the bottom substrate 312 of the second sensor 31 are respectively glued to the third mounting surface 232 of the middle phalanx 23 and the fourth mounting surface 251 of the distal phalanx 25 of the finger module 2; the two ends of the lower surface of the bottom substrate 312 of the third sensor 33 are respectively glued to the fifth mounting surface 253 of the distal phalanx 25 of the finger module 2.

[0084] The sensor module 3 is used to measure the joint bending angle of the proximal interphalangeal joint and the distal interphalangeal joint, as well as the gripping pressure at the end of the finger device, thereby improving the sensing capability of the finger device.

[0085] M is 2, N is 2.

[0086] Figure 4 This invention proposes a control method for a dual-joint finger device based on admittance control, comprising the following steps:

[0087] 1) Obtain the actual contact force F at the end of the finger-shaped device m (t), the contact force is measured by a flexible force sensor based on liquid metal mounted on the end of the finger device, and is subjected to bias calibration and filtering;

[0088] 2) Obtain the target contact force F set for the current task. t (t), wherein the target contact force is generated by the task planning module or the operation strategy module;

[0089] 3) Obtain the current joint angle Θ(t) = [θ1(t), θ2(t)] for each joint of the finger device. TThe joint angle is measured in real time by a liquid metal sensor installed at the joint, where θ1(t) is the angle between the proximal phalanx 21 and the middle phalanx 23 measured by the first sensor 32, and θ2(t) is the angle between the middle phalanx 23 and the distal phalanx 25 measured by the second sensor 3.

[0090] 4) Calculate the center position of the lower surface of the distal phalanx 25, i.e., the distal end position x of the finger-shaped device, using positive kinematics. (t) And obtain the initial equilibrium position x0 according to the system calibration;

[0091] 5) Calculation of force error e F (t)=F t (t)-F m (t);

[0092] 6) Input the force error into the admittance controller, which is based on a virtual mass-damping-stiffness model.

[0093]

[0094] The desired end position x is obtained by solving the problem. d (t); where M is the virtual mass matrix, B is the virtual damping matrix, and K is the virtual stiffness matrix. All of these matrices are design parameters. The dynamic response characteristics and steady-state error characteristics of the system can be changed by adjusting these parameters.

[0095] 7) Obtain the desired terminal position x from the solution. d (t) Perform inverse kinematics solution to obtain the desired joint angle Θ des (t);

[0096] 8) The desired joint angle is sent to the low-level position servo controller of each joint motor to drive the finger device to move to the desired end position.

[0097] Specifically, the target contact force F t (t) is a constant value or a force reference trajectory that varies with time.

[0098] Specifically, the inverse kinematics solution in step 7) is based on the analytical solution of the two-link system and includes the following sub-steps:

[0099] 1) Calculate the square of the distance from the end to the base 1111. Where, x d,x Indicates the desired end position x d (t) The coordinates of x along the x-axis, x d,y Indicates the desired end position x d (t) The coordinate of y along the y-axis;

[0100] 2) Calculation in Let l1 represent the expected angle between the middle phalanx 23 and the distal phalanx 25 obtained through inverse kinematics calculation, and l2 represent the length of the middle phalanx 23.

[0101] 3) Calculation in, This represents the desired angle between the proximal phalanx 21 and the middle phalanx 23, calculated using inverse kinematics; the purpose of the admittance controller is to make e F As θ(t) approaches 0, θ1(t) approaches 0 during this process. θ2(t) approaches

[0102] The calculated joint angle is used as the control input command for the drive motor 52, which causes the motor to drive the finger device joint to move to the target angle.

[0103] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as herein.

[0104] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A liquid metal flexible sensor based finger device, characterized in that: a fixed module, a finger module, a sensor module, a driving module; the finger module is installed on the fixed module, and the finger module comprises a proximal phalanx, a middle phalanx, a distal phalanx, a first connecting member and a second connecting member; the proximal phalanx comprises a first base, a first single-ear connecting seat and a first mounting surface; the first single-ear connecting seat is arranged at the front end of the first base, and the first mounting surface is located on the upper surface of the proximal phalanx; the middle phalanx comprises a second base, a first double-ear connecting seat, a second single-ear connecting seat, a second mounting surface and a third mounting surface; the first double-ear connecting seat and the second single-ear connecting seat are arranged at the rear end and the front end of the second base respectively and are parallel to each other; the second mounting surface and the third mounting surface are located on the upper surface of the middle phalanx in front of and behind each other; the distal phalanx comprises a third base, a second double-ear connecting seat, a fourth mounting surface and a fifth mounting surface; the second double-ear connecting seat is arranged at the rear end of the third base; the fourth mounting surface is located on the upper surface of the distal phalanx; and the fifth mounting surface is located on the lower surface of the distal phalanx; the first connecting member and the second connecting member are identical in structure and comprise a transmission shaft, end covers installed at both ends of the transmission shaft and a driven winding wheel fixedly installed on the transmission shaft; the first single-ear connecting seat of the proximal phalanx in the finger module is clearance-fitted with the transmission shaft of the first connecting member; the first double-ear connecting seat of the middle phalanx is fitted with the end cover of the first connecting member, thereby forming a proximal interphalangeal joint; the second single-ear connecting seat of the middle phalanx is clearance-fitted with the transmission shaft of the second connecting member; and the second double-ear connecting seat of the distal phalanx is fitted with the end cover of the second connecting member, thereby forming a distal interphalangeal joint; the sensor module comprises a first sensor, a second sensor and a third sensor; the first sensor, the second sensor and the third sensor are identical in structure and are all liquid metal flexible sensors; the lower surface of the first sensor is fixedly connected to the first mounting surface of the proximal phalanx and the second mounting surface of the middle phalanx of the finger module by means of adhesive respectively at both ends; the lower surface of the second sensor is fixedly connected to the third mounting surface of the middle phalanx and the fourth mounting surface of the distal phalanx of the finger module by means of adhesive respectively at both ends; and the lower surface of the third sensor is fixedly connected to the fifth mounting surface of the distal phalanx of the finger module by means of adhesive respectively at both ends; the driving module comprises a motor support, a driving motor, a driving winding wheel and a driving rope; the driving motor is installed on the fixed module through the motor support; The driving rope and the driving winding wheel correspond to the driven winding wheel in the first and second connecting members one by one, and are connected in the following manner; that is, the first kind: one end of the driving rope is wound around the corresponding driving winding wheel, and the other end is wound around the driven winding wheel of the corresponding first connecting member after passing through the wire inlet hole of the corresponding proximal phalanx; the second kind: one end of the driving rope is wound around the driving winding wheel of the corresponding driving module, and the other end is wound around the driven winding wheel of the corresponding second connecting member after passing through the wire inlet hole of the corresponding proximal phalanx and the second base of the middle phalanx in sequence.

2. The liquid metal flexible sensor-based finger-shaped device according to claim 1, wherein: The liquid metal flexible sensor is composed of a bottom substrate, a liquid metal layer, a top substrate, and a plurality of wires; The bottom substrate is made of an elastic material, and the upper surface thereof is provided with a micro-channel array; the liquid metal layer is made of a gallium-indium alloy liquid metal and is filled in the micro-channels; the top substrate is made of an elastic material and covers the upper surface of the bottom substrate; and the plurality of wires are embedded at both ends of the liquid metal layer and connected with an external circuit.

3. The liquid metal flexible sensor-based finger-shaped device according to claim 1, wherein: The driven winding wheel of the first connecting member is two, which are located between the first single-ear connecting seat and the first double-ear connecting seat; The driven winding wheel of the second connecting member is two, which are located between the second single-ear connecting seat and the second double-ear connecting seat.

4. The liquid metal flexible sensor-based finger-shaped device according to claim 1, wherein: The fixing module comprises a base and a snap buckle; The base is plate-shaped, the bottom surface thereof is arc-shaped, both sides thereof are provided with rectangular guide grooves corresponding to the snap buckle, the rear end thereof is symmetrically provided with threaded holes corresponding to the driving module, and the front end thereof is symmetrically provided with threaded holes corresponding to the finger module; The snap buckle penetrates through the corresponding rectangular guide groove on the base, circumferentially surrounds, and then realizes detachable buckle connection through the male buckle and the female buckle. 5.The control method of a liquid metal-based flexible sensor-based finger device according to claim 1, wherein The method comprises the following steps: Step 1, acquire the actual contact force F at the end of the finger device m (t), the contact force is measured by a third sensor and processed by bias calibration and filtering; Step 2, acquire the target contact force F set by the current task t (t), the target contact force being generated by a task planning module or an operation strategy module; Step 3: Obtain the current joint angle Θ(t) = [θ1(t), θ2(t)] for each joint of the finger device. T The joint angle is measured in real time by a first sensor and a second sensor installed at the joint, where θ1(t) is the angle between the proximal phalanx and the middle phalanx measured by the first sensor, and θ2(t) is the angle between the middle phalanx and the distal phalanx measured by the second sensor. Step 4, calculate the center position of the lower surface of the current distal phalanx, i.e. the position x of the end of the finger-shaped device, by forward kinematics (t) and the initial equilibrium position x0 is obtained according to the system calibration; Step 5, calculate force error e F (t) = F t (t) - F m (t); Step 6: inputting the force error into an admittance controller, the admittance controller being based on a virtual mass-damper-stiffness model Solving the desired end position x d (t); wherein M is a virtual mass matrix, B is a virtual damping matrix, K is a virtual stiffness matrix, the matrices are design parameters, and by adjusting the parameters the dynamic response characteristics and the steady state error characteristics of the system are changed; Step 7, solve for desired end position x d (t) perform inverse kinematics to obtain desired joint angle Θ des (t); Step 8: issuing the expected joint angle to a low-level position servo controller of each joint motor to drive the finger-shaped device to move to the expected end position. 6.The control method of a liquid metal-based flexible sensor-based finger device according to claim 5, wherein: The target contact force F in step 2 t (t) is a force reference trajectory that is constant or varies over time. 7.The control method of a liquid metal-based flexible sensor-based finger device according to claim 5, wherein: The inverse kinematics solving in the step 7 is based on a double-link analytical solution, and comprises the following sub-steps: 1) Calculate the square of the distance from the end to the base where x d,x represents the desired end position x d (t) in the x-axis direction, x d,y represents the desired end position x d (t) in the y-axis direction; 2) Calculate wherein denotes the desired angle between the middle phalanx and the distal phalanx calculated by inverse kinematics, li denotes the length of the middle phalanx, and I2 denotes the length of the distal phalanx. 3) Calculate where, denotes the desired angle between the proximal and middle phalange calculated by inverse kinematics; the purpose of the admittance controller is to make e F (t) approaches 0, in the process θ1(t) approaches θ2(t) approaches

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