A cable compliance control method for a scoliosis correction exoskeleton

Abstract

A kind of cable compliance control method of scoliosis orthosis exoskeleton, it includes: patient wears exoskeleton;Motor is started after wearing is completed, starts to provide tension, reaches the preset level by PD algorithm control motor and obtains the position data of the encoder detected on the motor when the tension of cable is zero;If cable tension always remains in the preset level fluctuation range, when exoskeleton receives external force or the motion generated by wearer, causes the tension of cable to exceed the preset level fluctuation range, the rotational speed of motor is controlled by admittance control algorithm and PD algorithm, so that the tension of cable returns to the preset level fluctuation range;Corrective work is finished, and motor is reversed to rotate and relax cable, and power self-driven tensioning module stops working.The present application can make exoskeleton can continuously provide correction force, while, when suddenly encountering external force or wearer motion, it can make cable tension return to preset level with lower impedance, and realize compliance control.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of rehabilitation, and particularly relates to a cable compliance control method of an exoskeleton for correcting scoliosis. BACKGROUND

[0002] Scoliosis in adolescents is a common spinal disease that occurs in the adolescent population. Scoliosis is characterized by three-dimensional structural deformity of the spine, including abnormal arrangement of spinal vertebrae in the coronal, sagittal and axial planes. In recent years, the incidence of scoliosis in the adolescent population in China has shown an upward trend. If scoliosis is not effectively intervened and treated in time, the scoliosis angle of the patient will gradually increase, causing deformation of the torso and thorax, and further causing respiratory and cardiopulmonary dysfunction, spinal cord and spinal nerve damage, etc.

[0003] Currently, orthopedic braces used in clinical practice can be divided into two categories: rigid braces and flexible braces. The rigid brace is worn for a long time, which compresses the chest cavity and affects breathing when worn, and the wearer has difficulty moving. Adolescents grow rapidly, and rigid braces not only restrict the growth of adolescents, but also need to be frequently replaced as the patient's body size changes. Studies have shown that the corrective force applied by some rigid braces decreases during use. The correction effect of flexible braces is not good, and it is difficult to correct patients with severe scoliosis.

[0004] Exoskeleton robots directly interact with the human body, and the movement feedback of the human body will affect the controlled variables, which may lead to system instability, so the safe interaction between the exoskeleton robot and the human body is the key to the design of the exoskeleton robot.

[0005] CN115429516A discloses a scoliosis control system and method, which determines the optimal force application point based on dynamic three-dimensional kinematic data generated at multiple skeletal key points on the patient's body through the force application point determination module; determines the motion state of the human body based on the real-time acquired human body acceleration signal through the human body motion state detection module; determines the optimal application force under the constraint of the human body motion state based on the Hueter-Volkmann law by taking the application force at the optimal force application point as an optimization parameter through the force value optimization module; and drives the force application module to apply the corresponding optimal orthopedic application force at the optimal force application point position through the driving module to achieve spinal correction. The main purpose is to stimulate the active contraction of the paraspinal muscles of the patient, increase muscle strength, and solve the problem of iatrogenic muscle atrophy. SUMMARY

[0006] The present application provides a cable compliance control method of an exoskeleton for correcting scoliosis to overcome the prior art. The method enables the exoskeleton to continuously provide a corrective force while allowing the cable tension to return to a preset level with lower impedance when sudden external forces or wearer movements are encountered, achieving compliance control.

[0007] A cable compliance control method of a scoliosis correction exoskeleton comprises:

[0008] S1, the patient wears the exoskeleton

[0009] The power self-driven tensioning module of the exoskeleton comprises a motor, a wire winding tensioning module A and a wire winding tensioning module B; the wire winding tensioning module A and the wire winding tensioning module B are structurally identical and arranged in series; the motor is fixed on the lower fixed module; the wire winding tensioning module A comprises a module housing A, a one-way bearing A and a volute spring A; the module housing A is provided with an outer groove, a cable is wound on the outer groove; the outer ring of the one-way bearing A and the volute spring A are arranged in the inner cavity of the module housing A respectively; the output shaft of the motor is connected with the inner ring of the one-way bearing A and the inner end of the volute spring A respectively; and the outer end of the volute spring A is connected with the inner wall of the module housing A.

[0010] The cable is arranged as follows: one end of the cable is fixed on the outer groove of the module housing B; the correction wire is wound on the outer groove of the module housing A in sequence through the pulley F, the wire pipe B, the pulley B, the pulley A, the wire pipe A, the pulley E, the pulley H, the wire pipe C, the pulley C, the pulley D and the wire pipe D; and the other end of the cable is fixed on the outer groove of the module housing A; the pulley A and the pulley E are rotatably arranged on the rear side and the front side of the upper fixed module 1 respectively; the pulley B and the pulley C are coaxially arranged and rotatably arranged on the rear side of the middle fixed module; the pulley F and the pulley H are coaxially arranged and rotatably arranged on the front side of the middle fixed module; the pulley D is rotatably arranged on the rear side of the lower fixed module; the wire pipe A is fixedly connected on the side of the upper fixed module; the wire pipe B and the wire pipe C are fixedly connected on the side of the middle fixed module; and the wire pipe D is fixedly connected on the side of the lower fixed module.

[0011] The motor, the wire winding tensioning module A and the wire winding tensioning module B are respectively provided with an encoder;

[0012] S2, after wearing, the motor is started to provide tension; the motor is controlled by a PD algorithm to make the cable tension reach a preset level, and the position data of the encoder on the motor when the cable tension reaches the preset level is obtained;

[0013] S3, if the cable 7 tension always remains in the preset level fluctuation range, the motor stops rotating; when the exoskeleton receives external force or the wearer produces movement, causing the cable tension to exceed the preset level fluctuation range, the motor speed is controlled by the admittance control algorithm and the PD algorithm, so that the cable tension returns to the preset level fluctuation range again;

[0014] S4, the correction work is completed, the motor is reversely rotated to relax the cable, and the power self-driven tensioning module stops working.

[0015] The beneficial effects of the present application compared to the prior art are:

[0016] The present application aims at the clinical demand for scoliosis correction, and designs a control algorithm which can continuously provide appropriate correction force and compensate for disturbances. The present application controls the motor through a PD algorithm to make the cable tension reach a preset level; when the system is disturbed by the human body, the impedance of the exoskeleton system is reduced through an admittance algorithm. The present application can continuously provide correction force for the exoskeleton, and when external force or wearer movement is suddenly encountered, the cable tension can be returned to the preset level with low impedance to realize soft control.

[0017] The technical solutions of the present application will be further described below in combination with the drawings and embodiments: BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 The flowchart of the cable soft control method of the present application;

[0019] Figure 2 The perspective view of the scoliosis correction exoskeleton combined with the method of the present application;

[0020] Figure 3 The front view of the exoskeleton;

[0021] Figure 4 The perspective view of the power self-driving tensioning module;

[0022] Figure 5 The exploded view of the wire winding tensioning module;

[0023] Figure 6 The flowchart of the admittance control algorithm;

[0024] Figure 7 The schematic diagram of the driving system. DETAILED DESCRIPTION

[0025] The embodiments of the technical solutions of the present application will be described in detail below in combination with the drawings. Unless otherwise specified, the technical terms or scientific terms used in the present application should be understood as the usual meanings understood by the skilled in the art to which the present application belongs.

[0026] Specific embodiment one: combined with Figures 2-3 It is explained that the active exoskeleton for scoliosis correction based on the cable soft control method comprises: a fixed module worn on the trunk part, which comprises an upper fixed module 1, a middle fixed module 2 and a lower fixed module 3;

[0027] A bionic spine module 5 is used to connect adjacent fixed modules to realize forward and backward flexion, lateral bending and rotation movement following the human spine;

[0028] The self-driven tensioning module 4 is arranged on the lower fixing module 3 to drive the corrective wire 7 and, through the threading tube group sleeved on the corrective wire 7, act on the sides of the upper fixing module 1, the middle fixing module 2 and the lower fixing module 3 to apply corrective force to the torso.

[0029] The active exoskeleton for correcting scoliosis provided in this embodiment has an upper fixation module 1 positioned under the armpit and a power-driven tensioning module 4 fixed to a lower fixation module 3 at the waist. During wear, when the wearer is standing still, the motor rotates to control the tension of the cable 7, which applies corrective force to the upper, middle, and lower fixation modules through a side conduit.

[0030] Specific implementation method two: such as Figures 1-5 As shown, the cable compliance control method for the scoliosis correction exoskeleton based on the above-described embodiment one includes:

[0031] S1, The patient wears an exoskeleton

[0032] The exoskeleton's self-driven tensioning module 4 includes a motor 401, a wire-winding tensioning module A403, and a wire-winding tensioning module B404. The wire-winding tensioning module A403 and the wire-winding tensioning module B404 have the same structure and are connected in series. The motor 401 is fixed on the lower fixing module 3. The wire-winding tensioning module A403 includes a module housing A4031, a one-way bearing A4032, and a spiral spring A4033. The module housing A4031 has an outer wheel groove on which a cable 7 is wound. The outer ring of the one-way bearing A4032 and the spiral spring A4033 are respectively arranged in the inner cavity of the module housing A4031. The output shaft of the motor 401 is connected to the inner ring of the one-way bearing A4032 and the inner end of the spiral spring A4033, respectively. The outer end of the spiral spring A4033 is connected to the inner wall of the module housing A4031.

[0033] The wire tensioning module B404 includes a module housing B4041, a one-way bearing B4042, and a spiral spring B4043. The module housing B4041 has an outer groove on which a straightening wire 7 is wound. The outer ring of the one-way bearing B4042 and the spiral spring B4043 are respectively arranged in the inner cavity of the module housing B4041. The output shaft of the motor 401 is connected to the inner ring of the one-way bearing B4042 and the drive module 402 respectively. The inner end of the spiral spring B4043 is connected to the drive module 402, and the outer end of the spiral spring B4043 is connected to the inner wall of the module housing B4041.

[0034] The cable 7 is arranged as follows: one end of the cable 7 is fixed on the outer groove of the module shell B4041, the correction wire 7 goes out from the module shell B4041, passes through the pulley F806, the threading pipe B902, the pulley B802, the pulley A801, the threading pipe A901, the pulley E805, the pulley H807, the threading pipe C903, the pulley C803, the pulley D804 and the threading pipe D904 in turn, and is wound on the outer groove of the module shell A4031, the other end of the cable 7 is fixed on the outer groove of the module shell A4031, the pulley A801 and the pulley E805 are rotatably arranged on the rear side and the front side of the upper fixed module 1 respectively, the pulley B802 and the pulley C803 are coaxially arranged and rotatably arranged on the rear side of the middle fixed module 2, the pulley F806 and the pulley H807 are coaxially arranged and rotatably arranged on the front side of the middle fixed module 2, the pulley D804 is rotatably arranged on the rear side of the lower fixed module 3, the threading pipe A901 is fixedly connected to the side of the upper fixed module 1, the threading pipe B902 and the threading pipe C903 are fixedly connected to the side of the middle fixed module 2, and the threading pipe D904 is fixedly connected to the side of the lower fixed module 3;

[0035] The motor 401, the wire winding tensioning module A403 and the wire winding tensioning module B404 are respectively provided with an encoder;

[0036] S2, after wearing, the motor 401 is started to provide tension, the motor 401 is controlled by the PD algorithm to make the tension of the cable 7 reach a preset level (a preset value), and the position data l0 of the encoder on the motor 401 when the tension of the cable 7 reaches the preset level is obtained;

[0037] S3, if the tension of the cable 7 always remains in the preset level fluctuation range, the motor stops rotating, when the exoskeleton receives external force or the wearer produces movement, the tension of the cable 7 exceeds the preset level fluctuation range, the motor 401 is controlled by the admittance control algorithm and the PD algorithm to control the rotating speed, so that the tension of the cable 7 returns to the preset level fluctuation range again;

[0038] S4, the correction work is finished, the motor is reversely rotated to relax the cable 7, and the power self-driving tensioning module 4 stops working.

[0039] The compliant control method of the embodiment is based on the combination of the admittance control algorithm and the PD control algorithm, the interaction between the human body and the exoskeleton is received through the change data of the tension sensor, so that the motor is controlled to rotate to cope with the interference with small impedance, and the compliant control is realized; the admittance control algorithm establishes an equation between the total force F ext and the expected position x d , and the PD control algorithm controls the rotating speed of the motor, so that the actual position x converges to x d as soon as possible.

[0040] Further, as shown in Figure 6

[0041] The admittance control algorithm in step S3 is:

[0042] Wherein, F ext is the external force received by the exoskeleton or the force exerted on the exoskeleton by the wearer due to movement, for example, the external force F ext is calculated by the change amount of the tension sensor, the tension sensor is connected at any section of the cable 7, M d , D d , P d are respectively preset inertia coefficient, damping coefficient and stiffness coefficient, F f represents the total friction generated by the cable, x0 represents the initial position of the motor rotation, x d represents the desired rotation position of the motor.

[0043] The PD algorithm in steps S2 and S3 is: x(t) = K p ·e(t) + K d ·de(t) / dt;

[0044] Wherein, K p and K d are respectively preset proportional coefficient and differential coefficient, x(t) represents the actual position of the motor rotation, e(t) is the deviation curve of the set value and the actual value with time.

[0045] In step 2, for example, the motor 401 rotates forward at a certain speed until the cable 7 is in close contact with the exoskeleton and starts to provide tension. After the wearing is completed in step S4, the motor 401 reversely rotates to loosen the cable 7 so that the wearer can take off the exoskeleton.

[0046] The cable tension is brought to the vicinity of the preset value based on the PD algorithm, wherein the k p value and the k d value of the PD algorithm are set to values suitable for the wearer's movement through the optimization algorithm.

[0047] Further, as shown in Figure 7 , the system in which the motor 401 is connected in series with the volute spring can be regarded as a set of elastic drivers (SFA), and the dynamic equation of the elastic driver (SEA) suitable for the exoskeleton system is established; the dynamic equation of the driving system composed of the motor and the volute spring (the dynamic equation is established according to the motor displacement, the displacement of the wire tensioning module and the properties of the volute spring) is:

[0048]

[0049] F1 = k​s (x1-x2)

[0050] Wherein, x1 is the motor displacement, which is directly obtained by coupling the encoder (such as absolute encoder) on the motor, x2 is the displacement of the wire winding tension module A403 or the wire winding tension module B404, which is directly obtained by coupling the encoder (such as absolute encoder) on the tension device, k s is the elastic coefficient of the spiral spring, b1 is the damping coefficient between the motor and the wire winding tension module A403 or the wire winding tension module B404, f l is the friction force generated by the wire winding tension module where the cable is located, F1 is the cable tension, and m1 represents the equivalent mass of the driving system.

[0051] Since x1 and x2 are displacement data, the data obtained by coupling the encoder on the motor is obtained by integration, and the value may accumulate errors and become inaccurate with the increase of the use time. Therefore, F1 is not only calculated by the formula F1=k s (x1-x2), but also corrected according to the data of the tension sensor in series on the cable 7.

[0052] Therefore, x1=l0+∫w1(t)r1dt;

[0053] x2=∫w2(t)r2dt;

[0054] Wherein, w1(t) represents the angular velocity obtained by the encoder on the motor, w2(t) represents the angular velocity obtained by the encoder on the wire winding tension module, r1=r2 represents the equivalent outer diameter of the module shell, and l0 represents the position data of the encoder on the motor 401 when the tension of the cable 7 reaches the preset level.

[0055] Based on the above control method, the exoskeleton can continuously provide a correction force, and when suddenly encountering an external force or when the wearer moves, the cable tension can be returned to the preset level with lower impedance.

[0056] The present application has been disclosed in the preferred embodiment as above, however, it is not used to limit the present application, any person skilled in the art can make some changes or modifications to the equivalent embodiments of the equivalent changes within the scope of the technical solutions of the present application, which still belong to the scope of the technical solutions of the present application.

Claims

1. An exoskeleton for correcting scoliosis, characterized in that: The exoskeleton includes a fixation module worn on the torso, a bionic spine module (5), and a power-driven tensioning module (4); the fixation module includes an upper fixation module (1), a middle fixation module (2), and a lower fixation module (3), the bionic spine module (5) is connected to the adjacent fixation module, and the power-driven tensioning module (4) is arranged on the lower fixation module (3); The self-driven tensioning module (4) includes a motor (401), a wire winding tensioning module A (403), and a wire winding tensioning module B (404); the wire winding tensioning module A (403) and the wire winding tensioning module B (404) have the same structure and are connected in series; the motor (401) is fixed on the lower fixing module (3), and the wire winding tensioning module A (403) includes a module housing A (4031), a one-way bearing A (4032), and a spiral spring A (4033). 33), the module housing A (4031) has an outer wheel groove, and a cable (7) is wound on the outer wheel groove. The outer ring of the one-way bearing A (4032) and the spiral spring A (4033) are respectively arranged in the inner cavity of the module housing A (4031). The output shaft of the motor (401) is connected to the inner ring of the one-way bearing A (4032) and the inner end of the spiral spring A (4033) respectively. The outer end of the spiral spring A (4033) is connected to the inner wall of the module housing A (4031). The cable (7) is arranged as follows: one end of the cable (7) is fixed on the outer groove of the module housing B (4041). The straightening wire (7) starts from the module housing B (4041), passes through pulley F (806), conduit B (902), pulley B (802), pulley A (801), conduit A (901), pulley E (805), pulley H (807), conduit C (903), pulley C (803), pulley D (804) and conduit D (904) in sequence, and then wraps around the outer groove of the module housing A (4031). The other end of the cable (7) is fixed on the outer groove of the module housing A (4031). The pulley A (801) and the conduit D (904) are connected to the module housing B (4031). Wheel E (805) is rotatably mounted on the rear and front sides of the upper fixing module (1), pulley B (802) and pulley C (803) are coaxially mounted and rotatably mounted on the rear side of the middle fixing module (2), pulley F (806) and pulley H (807) are coaxially mounted and rotatably mounted on the front side of the middle fixing module (2), pulley D (804) is rotatably mounted on the rear side of the lower fixing module (3), conduit A (901) is fixed to the side of the upper fixing module (1), conduit B (902) and conduit C (903) are fixed to the side of the middle fixing module (2), and conduit D (904) is fixed to the side of the lower fixing module (3); The motor (401), the wire winding tension module A (403), and the wire winding tension module B (404) are each equipped with an encoder; The exoskeleton's cables achieve compliance control through the following steps: S1. After the device is worn, start the motor (401) to provide tension. Control the motor (401) through the PD algorithm to make the tension of the cable (7) reach the preset level, and obtain the position data detected by the encoder on the motor (401) when the tension of the cable (7) reaches the preset level. S2. If the tension of the cable (7) remains within the preset horizontal fluctuation range, the motor will stop rotating. When the exoskeleton is subjected to external force and the tension of the cable (7) exceeds the preset horizontal fluctuation range, the speed of the motor (401) will be controlled by the admittance control algorithm and the PD algorithm to make the tension of the cable (7) return to the preset horizontal fluctuation range. S3. When the work is finished, the motor rotates in the opposite direction to loosen the cable (7), and the self-driven tensioning module (4) stops working.

2. The scoliosis correction exoskeleton according to claim 1, characterized in that: The admittance control algorithm in step S3 is as follows: Among them, F ext M represents the external force acting on the exoskeleton. d D d P d These are the preset inertia coefficient, damping coefficient, and stiffness coefficient, respectively, F f The x represents the total frictional force generated by the cable, and x0 represents the initial position of the motor rotation. d This indicates the desired rotational position of the motor.

3. The exoskeleton for correcting scoliosis according to claim 1, characterized in that: The PD algorithm in step S2 is: x(t) = K p ·e(t)+K d ·de(t) / dt; Among them, K p and K d These are the preset proportional coefficient and differential coefficient, respectively. x(t) represents the actual position of the motor rotation, and e(t) is the curve of the deviation between the set value and the actual value over time.

4. The exoskeleton for correcting scoliosis according to claim 1, characterized in that: The dynamic equations of the drive system consisting of a motor and a spiral spring are as follows: F1=k s (x1-x2); Where x1 is the motor displacement, x2 is the displacement of the wire tensioning module A (403) or the wire tensioning module B (404), and k s b1 is the spring constant of the spiral spring, b1 is the damping coefficient between the motor and the winding tension module A (403) or the winding tension module B (404), and f is the damping coefficient. l F1 represents the frictional force generated by the winding tension module where the cable is located, F1 represents the cable tension, and m1 represents the equivalent mass of the drive system.

5. The scoliosis correction exoskeleton according to claim 4, characterized in that: x1 = l0 + ∫w1(t)r1dt; x2=∫w2(t)r2dt; Where w1(t) represents the angular velocity obtained by the encoder on the motor, w2(t) represents the angular velocity obtained by the encoder on the winding tension module, r1=r2 represents the equivalent outer diameter of the module shell, and l0 represents the position data detected by the encoder on the motor (401) when the tension of the cable (7) reaches the preset level.

6. The scoliosis correction exoskeleton according to claim 1, characterized in that: The encoder is an absolute encoder.

7. The scoliosis correction exoskeleton according to claim 2, characterized in that: A tension / compression sensor is connected at any point on the cable (7), F ext It is obtained from the change in tension and compression sensors.

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