Prosthetic hand multifunctional sharing control method based on touch sense

Abstract

The invention relates to the technical field of control engineering, in particular to a touch-based prosthetic hand multifunctional sharing control method, which comprises the following steps of: S1, acquiring a surface electromyogram signal of a user in real time, and identifying a motion intention of the user based on the surface electromyogram signal; s2, a finger needing to move is determined according to the movement intention of the user, the current availability of the finger needing to move is judged through fingertip touch readings, and a movable finger is determined and pre-grabbed; s3, after pre-grabbing is conducted, the movable fingers are controlled to conduct stable grabbing by calculating the grabbing force change rate of each finger at the adjacent moments; and S4, after stable grasping is carried out, the grasping power level is adjusted by executing a target activation gesture, and control over the prosthetic hand is completed. Stable grasping of the prosthetic hand, in-hand operation and one-hand multi-grasping control can be achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of control engineering, and particularly to a multi-functional shared control method for a prosthetic hand based on touch. Background Art

[0002] Due to limited hand functions and heavy control burdens, the disuse rate of prosthetic hands among amputee groups is very high, highlighting the gap between clinical applications and laboratory technologies. Therefore, shared control technology helps to provide a solution that takes into account both control burden and control accuracy for prosthetic hands. Currently, there are still different opinions on what functions should be introduced into prosthetic hand control for shared control technology, and there is a lack of a comprehensive shared control method that can adapt to diverse daily life tasks. Summary of the Invention

[0003] The purpose of the present invention is to provide a multi-functional shared control method for a prosthetic hand based on touch, which can achieve compliant grasping and stable grasping of the prosthetic hand according to real-time touch readings and preset thresholds; realize the function of a prosthetic hand with multiple grasps by autonomously judging the availability of fingers; determine an object-specific grasping force threshold based on the change rate of the grasping force at adjacent moments, and autonomously adjust the grasping force level according to the user's intention.

[0004] To achieve the above purpose, the present invention provides the following solution:

[0005] A multi-functional shared control method for a prosthetic hand based on touch, comprising:

[0006] S1. Real-time collect the surface electromyographic signals of the user, and identify the user's movement intention based on the surface electromyographic signals;

[0007] S2. Determine the fingers to be moved according to the user's movement intention, and judge the current availability of the fingers to be moved through fingertip touch readings, determine the movable fingers and perform pre-grasping;

[0008] S3. After performing the pre-grasping, control the movable fingers to perform stable grasping by calculating the change rate of the grasping force at adjacent moments of each finger;

[0009] S4. After performing the stable grasping, adjust the grasping force level by executing the target activation gesture to complete the control of the prosthetic hand.

[0010] Preferably, in S1, real-time collect the surface electromyographic signals of the user, and identify the user's movement intention based on the surface electromyographic signals, including:

[0011] Place surface electromyographic sensors on a pair of forearm antagonist muscles of the user to real-time collect the surface electromyographic signals of the user;

[0012] Filter, rectify, and normalize the surface electromyogram signal, and map the processed surface electromyogram signal to a control signal.

[0013] Preferably, mapping the processed signal to a control signal includes:

[0014]

[0015] where K is the gain coefficient, EMG(t) is the processed surface electromyogram signal, Output is the output control signal, and EMG(min) and EMG(max) are the minimum threshold and maximum threshold of the surface electromyogram signal, respectively.

[0016] Preferably, in S2, determining the current availability of the finger to be moved by the fingertip tactile reading, determining the movable finger and performing pre - grasping includes:

[0017] Real - time monitor the fingertip tactile reading of the finger to be moved and compare it with a preset tactile threshold. If it is greater than or equal to the preset tactile threshold, it is determined as an occupied finger; if it is less than the preset tactile threshold, it is determined as a movable finger;

[0018] Control the movable finger to perform the first - stage flexion movement until the fingertip tactile readings of all movable fingers reach the preset tactile threshold, and complete the pre - grasping.

[0019] Preferably, in S3, controlling the movable finger to perform stable grasping by calculating the grasping force change rate of each finger at adjacent moments includes:

[0020] After completing the pre - grasping, control all movable fingers to perform the second - stage flexion movement, and calculate the grasping force change rate of each movable finger at adjacent moments in real - time. When the grasping force change rate of the movable finger reaches the preset grasping threshold, stop the second - stage flexion movement until all movable fingers stop the second - stage flexion movement, and complete the stable grasping.

[0021] Preferably, calculating the grasping force change rate of the movable finger at adjacent moments includes:

[0022]

[0023] where β is the grasping force change rate at adjacent moments, F t is the grasping force at time t, and F t-1 is the grasping force at time t - 1.

[0024] Preferably, in S4, adjusting the grasping force level by performing the target activation gesture to complete the control of the prosthetic hand includes:

[0025] After completing the stable grasp, record the current fingertip tactile reading F i as the stable grasping force F S , at this time F i = F S ;

[0026] Adjust the grasping force level by performing the first target activation gesture, and perform the third-stage flexion movement until F i = 2·F S ;

[0027] Adjust the grasping force level by performing the second target activation gesture, and perform the extension movement until F i = F S , thus completing the in-hand operation of the prosthetic hand.

[0028] Preferably, the method further includes:

[0029] After completing the stable grasp, when the user needs to grasp another object while retaining the object in the hand, perform another grasping gesture by performing S2 - S3 to complete the stable grasp of the other object.

[0030] The beneficial effects of the present invention are as follows:

[0031] A multifunctional shared control method for a tactile-based prosthetic hand proposed by the present invention improves the operating performance and user experience of the prosthetic hand through signal processing according to fingertip tactile perception; autonomously judges the usability of fingers based on contact state analysis to achieve the multi-grasp function of a human-like hand; based on the real-time monitoring of the grasping force, enables the prosthetic hand to grasp the target object smoothly and stably, and allows the user to autonomously adjust the grasping force level to complete the in-hand operation based on stable grasp. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0033] Figure 1 It is a flowchart of a multifunctional shared control method for a tactile-based prosthetic hand according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0034] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0036] This embodiment provides a multifunctional shared control method for a prosthetic hand based on tactile sensation, such as Figure 1 As shown, including:

[0037] S1, collecting the user's surface electromyography signal in real time, and identifying the user's movement intention based on the surface electromyography signal;

[0038] S2, determining the finger to be moved according to the user's movement intention, judging the current availability of the finger to be moved by fingertip tactile readings, determining the movable finger and performing pre-grabbing;

[0039] S3, after the pre-grasping, controlling the movable fingers to perform stable grasping by calculating the gripping force change rate of each finger at adjacent moments;

[0040] S4. After the stable grasping is performed, the grasping force level is adjusted by executing a target activation gesture to complete the control of the prosthetic hand.

[0041] Specifically, this embodiment obtains the occupancy status of each finger by identifying the contact state between the finger and the object, realizes autonomous judgment of the finger availability, and completes grasp preforming and multiple grasps with one hand; by analyzing the grasping force change rate, the force interaction information between the finger and the object is obtained, and the autonomous judgment of the force closure of the grasped object and the recording of the object-specific grasping force threshold are realized; based on the autonomously recorded object-specific grasping force threshold, the grasping force is monitored in real time to realize the user's autonomous adjustment of the grasping force level, and keep the object from being damaged (when the grasping force level is increased) or the object from falling (when the grasping force level is reduced).

[0042] Among them, the method of designing a new shared control strategy includes: based on real-time fingertip tactile readings, using the threshold method to judge the finger availability and initial contact with the object; based on calculating the grip force change rate at adjacent moments, using the threshold method to determine when to achieve stable grip of the object, and simultaneously recording the current tactile readings of each finger as the object-specific stable grip force threshold; based on the object-specific stable grip force threshold, adjusting the fingertip tactile readings in real time by controlling the finger movement, and realizing autonomous adjustment of the grip force level according to the user's wishes.

[0043] Further, in S1, the real-time acquisition of the user's surface electromyogram signal and the recognition of the user's movement intention based on the surface electromyogram signal include:

[0044] Placing surface electromyogram sensors on a pair of forearm antagonist muscles of the user to acquire the user's surface electromyogram signal in real time;

[0045] Filtering, rectifying, and normalizing the surface electromyogram signal, and mapping the processed surface electromyogram signal into a control signal.

[0046] Among them, mapping the processed signal into a control signal includes:

[0047]

[0048] Among them, K is the gain coefficient, EMG(t) is the processed surface electromyogram signal, Output is the output control signal, and EMG(min) and EMG(max) are the minimum threshold and maximum threshold of the surface electromyogram signal respectively.

[0049] Specifically, in this embodiment, two surface electromyogram sensors are placed on a pair of antagonist muscles of the user's forearm to obtain real-time surface electromyogram signals. Then, a series of preprocessing operations such as filtering and rectifying the surface electromyogram signal are carried out, and it is normalized to the range of 0-1. Finally, it is linearly or non-linearly mapped to the speed of the motor to control the prosthetic hand to perform different actions.

[0050] As known, if the surface electromyogram signal collected by the sensor and preprocessed is EMG(t), the relationship between the control signal and the input surface electromyogram signal is Among them, K is the gain coefficient, which can be adjusted according to the actual situation of the user.

[0051] Further, in S2, judging the current availability of the finger to be moved through the fingertip tactile reading, determining the movable finger and performing pre-grasping includes:

[0052] Real-time monitoring the fingertip tactile reading of the finger to be moved and comparing it with a preset tactile threshold. If it is greater than or equal to the preset tactile threshold, it is determined as an occupied finger; if it is less than the preset tactile threshold, it is determined as a movable finger;

[0053] Controlling the movable finger to perform the first-stage flexion movement until the fingertip tactile readings of all movable fingers reach the preset tactile threshold to complete the pre-grasping.

[0054] Specifically, based on the user's motion intention recognized in S1, determine the finger that needs to move. By real-time monitoring the tactile readings at the fingertips and comparing them with a preset threshold, determine whether the finger is currently occupied. If the tactile reading of the i-th finger at the current time is F i (i = 1, 2…, 5), and the preset threshold is F T , when F i ≥F T , the finger is occupied and will not perform the movement; otherwise, the unoccupied finger will perform a flexion movement according to the user's intention. When the tactile degree at the fingertip of the moving finger reaches the preset threshold F T , the moving finger will stop moving. When the tactile readings of all moving fingers reach the preset threshold F T , the prosthetic hand completes the pre-grasp of the object.

[0055] Further, in S3, controlling the movable fingers to perform a stable grasp by calculating the change rate of the grasping force at adjacent moments of each finger includes:

[0056] After completing the pre-grasp, control all movable fingers to perform a second-stage flexion movement, and calculate the change rate of the grasping force at adjacent moments of each movable finger in real time. When the change rate of the grasping force at adjacent moments of the movable finger reaches the preset grasping threshold, stop the second-stage flexion movement until all movable fingers stop the second-stage flexion movement, and complete the stable grasp.

[0057] Among them, calculating the change rate of the grasping force at adjacent moments of the movable finger includes:

[0058]

[0059] Among them, β is the change rate of the grasping force at adjacent moments, F t is the grasping force at time t, and F t-1 is the grasping force at time t - 1.

[0060] Specifically, after the prosthetic hand completes the pre-grasp of the object based on the contact state recognition, all moving fingers will be reactivated and continue to perform the flexion movement. At this time, the change rate of the grasping force at adjacent moments of each finger will be calculated and compared with the preset threshold β t to determine whether the prosthetic hand has stably grasped the object. If the prosthetic hand completes the stable grasp of the object, the tactile readings of each finger at the current moment will be automatically recorded as the grasping force threshold specific to the object.

[0061] Further, in S4, adjusting the grasping force level by executing the target activation gesture and completing the control of the prosthetic hand includes:

[0062] After completing the stable grasp, the current tactile reading F at the fingertip iRecord the stable grasping force as F S , at this time F i = F S ;

[0063] Perform the third-stage flexion movement by executing the first target activation gesture until F i = 2·F S ;

[0064] Perform the extension movement by executing the second target activation gesture until F i = F S , completing the in-hand operation of the prosthetic hand.

[0065] Specifically, after the prosthetic hand completes the stable grasping of an object by calculating the change rate of the grasping force at adjacent moments of the fingers, the user's execution of a specific activation gesture will adjust the grasping force level to achieve the in-hand operation of the prosthetic hand on the object. For example, after the prosthetic hand completes the stable grasping of an object, the tactile reading of the moving finger at this time should be F i = F S , where F S is the threshold of the stable grasping force of the object obtained in S3. The user's specific activation gesture will cause the moving finger to continue the flexion movement until F i = 2·F S . On this basis, the user's execution of a specific activation gesture again will cause the moving finger to perform the extension movement until F i = F S .

[0066] Furthermore, the method further includes:

[0067] After completing the stable grasping, when the user needs to grasp another object while retaining the object in the hand, perform another grasping gesture by executing S2 - S3 to complete the stable grasping of the other object.

[0068] Specifically, after the prosthetic hand completes the stable grasping of an object, when the user wishes to grasp another object while retaining the object in the hand, the user can directly execute another grasping gesture. Based on the autonomous judgment of finger availability, the prosthetic hand will perform the operation of grasping multiple objects with one hand and repeat S2 - S3 until the stable grasping of the second object is completed.

[0069] A multifunctional sharing control method for a tactile-based prosthetic hand proposed in this embodiment improves the operation performance and user experience of the prosthetic hand through signal processing according to fingertip tactile perception; realizes the function of grasping multiple objects with one hand of a humanoid hand based on the analysis of the contact state and autonomous judgment of finger availability; realizes the compliant and stable grasping of the target object by the prosthetic hand based on the real-time monitoring of the grasping force, and allows the user to autonomously adjust the grasping force level to complete the in-hand operation based on stable grasping.

[0070] The embodiments described above are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A multifunctional shared control method for a tactile-based prosthetic hand, characterized in that, Including: S1. Real-time collect the surface electromyogram (sEMG) signals of the user, and identify the user's movement intention based on the sEMG signals; S2. Determine the fingers to be moved according to the user's movement intention, judge the current availability of the fingers to be moved through fingertip tactile readings, determine the movable fingers and perform pre-grasping; S3. After performing the pre-grasping, control the movable fingers to perform stable grasping by calculating the grasping force change rate of each finger at adjacent moments; S4. After performing the stable grasping, adjust the grasping force level by executing the target activation gesture to complete the control of the prosthetic hand.

2. The multifunctional shared control method for a tactile-based prosthetic hand according to claim 1, wherein In S1, real-time collect the surface electromyogram (sEMG) signals of the user, and identify the user's movement intention based on the sEMG signals, including: Place surface electromyogram sensors on a pair of forearm antagonist muscles of the user to real-time collect the sEMG signals of the user; Filter, rectify, and normalize the sEMG signals, and map the processed sEMG signals into control signals.

3. The multifunctional shared control method for a tactile-based prosthetic hand according to claim 2, characterized in that Mapping the processed signals into control signals includes: Where K is the gain coefficient, EMG(t) is the processed sEMG signal, Output is the output control signal, and EMG(min) and EMG(max) are the minimum threshold and maximum threshold of the sEMG signal respectively.

4. The multifunctional shared control method for a tactile-based prosthetic hand according to claim 1, characterized in that In S2, judge the current availability of the fingers to be moved through the fingertip tactile readings, determine the movable fingers and perform pre-grasping, including: Real-time monitor the fingertip tactile readings of the fingers to be moved, and compare them with the preset tactile threshold. If it is greater than or equal to the preset tactile threshold, it is determined as an occupied finger; if it is less than the preset tactile threshold, it is determined as a movable finger; Control the movable fingers to perform the first-stage flexion movement until the fingertip tactile readings of all movable fingers reach the preset tactile threshold to complete the pre-grasping.

5. The multifunctional shared control method for a tactile-based prosthetic hand according to claim 1, characterized in that In S3, control the movable fingers to perform stable grasping by calculating the grasping force change rate of each finger at adjacent moments, including: After completing the pre-grasping, control all movable fingers to perform the second-stage flexion movement, and real-time calculate the grasping force change rate of each movable finger at adjacent moments. When the grasping force change rate of the movable finger reaches the preset grasping threshold, stop the second-stage flexion movement until all movable fingers stop the second-stage flexion movement to complete the stable grasping.

6. The multifunctional shared control method of a tactile-based prosthetic hand according to claim 5, wherein Calculating the grasping force change rate of the movable finger at adjacent moments includes: Among them, β is the change rate of the grasping force at adjacent moments, F t is the grasping force at time t, F t-1 is the grasping force at time t - 1.

7. The multifunctional shared control method for a tactile-based prosthetic hand according to claim 1, characterized in that, In S4, adjust the grasping force level by executing the target activation gesture to complete the control of the prosthetic hand, including: After completing the described stable grip, record the current fingertip tactile reading F i as the stable grip force F S , at which point F i = F S ; Adjust the grip force level by performing the first target activation gesture and perform the third-stage flexion movement until F i = 2·F S ; Adjust the grasping force level by performing a second target activation gesture and perform an extension movement until F i = F S , and complete the in-hand operation of the prosthetic hand.

8. The multifunctional shared control method for a tactile-based prosthetic hand according to any one of claims 1-7, characterized in that, The method further includes: After completing the stable grasping, when the user needs to grasp another object while retaining the object in the hand, perform another grasping gesture by executing S2 - S3 to complete the stable grasping of the other object.

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