Variable stiffness driver based on isosceles trapezoid flexible hinge double variable stiffness mode

Abstract

The invention provides a variable stiffness driver based on an isosceles trapezoid flexible hinge double variable stiffness mode, which comprises an elastic force transmission mechanism and a stiffness modulation mechanism, and is characterized in that the elastic force transmission mechanism comprises an output shaft, a force transmission input component, a plurality of groups of force transmission connecting rods and an isosceles trapezoid flexible hinge; the outer side ends of the two side waists of the isosceles trapezoid flexible hinge are hinged to the output shaft and the force transmission connecting rod respectively, the inner side ends of the two side waists of the isosceles trapezoid flexible hinge are hinged to the force transmission input component and the rigidity modulation mechanism respectively, and the two side waists of the isosceles trapezoid flexible hinge are made of plate springs capable of being elastically bent and reset. Compared with a linear spring, large elastic energy storage can be achieved in a small space at an acting force point, and meanwhile, compared with a single-plate spring, low-rigidity driving can be achieved in the small space. The rigidity modulation mechanism is composed of four sets of same rigidity-variable mechanisms, and the rigidity is modulated based on two rigidity-variable modes. On the whole, the variable-stiffness driver is designed to be small in size while the large-stiffness range and the high-stiffness speed are guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of medical devices, and in particular to a variable stiffness driver based on an isosceles trapezoidal flexible hinge with double variable stiffness. Background Art

[0002] The demand for rehabilitation training is increasing with the aging population, and the number of patients suffering from lower limb motor dysfunction due to age, disease, and muscle deterioration is increasing. With long-term, scientific treatment and rehabilitation training, patients can gradually regain the ability to walk. However, traditional manual rehabilitation training requires high standards from rehabilitation therapists and lacks accurate data recording and evaluation. Rehabilitation robots are gaining popularity due to their excellent stability and repeatability, as well as their ability to monitor and evaluate data in real time.

[0003] Traditional rehabilitation robots primarily utilize rigid structures and lack inherent flexibility. During movement, human joints cannot align with the robot's joints in real time, and collisions and impacts can easily cause secondary injuries to the patient. Therefore, scientists have designed an elastic actuator: an elastic element is inserted between the motor and the load to achieve compliant actuation and protect the patient. However, due to the fixed stiffness of the elastic element, it cannot simultaneously achieve fast response speed and low mechanical impedance, making it unsuitable for various rehabilitation modes, such as high-precision passive training and highly compliant active training.

[0004] To overcome the problem of constant stiffness in elastic actuators, scientists have designed a new variable-stiffness actuator. By adding a variable-stiffness mechanism and then using an additional motor to control the stiffness of the variable-stiffness elastic actuator, different performance requirements can be met by varying the stiffness. However, the actual variable stiffness range of current variable-stiffness elastic actuators is limited because the variable-stiffness mechanism is affected by space. In addition, the motor travels too long to modulate the stiffness from minimum to maximum, resulting in a slow stiffness change that cannot meet actual requirements. Finally, the elastic elements of variable-stiffness elastic actuators mostly use linear springs and leaf springs. Leaf springs need to be very long to ensure the minimum stiffness value, and linear springs are usually perpendicular to the connecting rod, making them less compact.

[0005] Based on this, this case came into being. Summary of the Invention

[0006] (1) Technical problems solved

[0007] In response to the shortcomings of the existing technology, the present invention provides a variable stiffness driver based on an isosceles trapezoidal flexible hinge with a dual variable stiffness method. The variable stiffness range is increased by integrating two variable stiffness principles. At the same time, the traditional structural design is changed, and multiple groups of variable stiffness mechanisms are used in parallel to increase the effective stroke of the variable stiffness motor movement and the speed of the variable stiffness driver. In addition, an isosceles trapezoidal flexible hinge is used instead of a spring and a leaf spring, which has sufficient elastic energy storage capacity while effectively reducing the size of the driver.

[0008] (2) Technical solution

[0009] To achieve the above objectives, the present invention is implemented through the following technical solutions: a variable stiffness driver based on the dual variable stiffness method of an isosceles trapezoidal flexible hinge, including an elastic force transmission mechanism and a stiffness modulation mechanism, the elastic force transmission mechanism includes an output shaft, a force transmission input component and several groups of force transmission connecting rods, an isosceles trapezoidal flexible hinge, the outer ends of the waists on both sides of the isosceles trapezoidal flexible hinge are respectively hinged to the output shaft and the force transmission connecting rod, the inner ends of the waists on both sides of the isosceles trapezoidal flexible hinge are respectively hinged to the force transmission input component and the stiffness modulation mechanism, and the stiffness modulation mechanism is used to adjust the angles of the waists on both sides of the isosceles trapezoidal flexible hinge.

[0010] Preferably, the force input component includes a fixed disk and a force input wire wheel, and the force input wire wheel is fixed on the fixed disk.

[0011] Preferably, the isosceles trapezoidal flexible hinge is composed of a bottom link and side waist link 1 and side waist link 2. One end of the side waist link 1 and one end of the bottom link are hinged on the output shaft, one end of the side waist link 2 and one end of the bottom link are hinged on the force transmission link, the other end of the side waist link 1 is hinged on the fixed plate, and the stiffness modulation mechanism is used to adjust the other end of the side waist link 2.

[0012] Preferably, the stiffness modulation mechanism includes a rear cam, a front cam, a transmission plate, a lever, a fulcrum shaft, and a swing arm. The front cam is pivotally connected to a fixed plate, and the transmission plate is fixed to the fixed plate. The rear cam, the front cam, and the transmission plate are respectively provided with a plurality of groups of rear wheel guide grooves, front wheel guide grooves, and transmission plate guide grooves, the number of which is the same as that of isosceles trapezoidal flexible hinges. The rear wheel guide grooves, the front wheel guide grooves, and the transmission plate guide grooves are gradually opened from the inside to the outside. The force transmission connecting rod includes a force transmission slide rail and a slider slidably adapted on the force transmission slide rail. One of the side waist connecting rods The end and one end of the bottom link are hinged on the slider together, the lever is arranged in the middle of the bottom link, and one end of the swing arm is coaxially hinged on the hinge part of the side waist link and the bottom link. The lever and the swing arm are provided with a lever slide groove and a swing arm slide groove along their length direction, the fulcrum shaft is hinged to the inner end part of the force transmission slide rail, and the upper and lower sections are slidably adapted in the rear wheel guide groove, the lever slide groove, the swing arm slide groove, and the transmission plate guide groove; the end of the side waist link 2 away from the slider is provided with a guide shaft, and the guide shaft is slidably adapted on the front wheel guide groove and the transmission plate guide groove.

[0013] Preferably, the stiffness modulation mechanism further comprises an adjustment shaft coaxially connected to the front cam, and the adjustment shaft is provided with an adjustment wire fixing hole for fixing the adjustment wire.

[0014] Preferably, the isosceles trapezoidal flexible hinges are provided in four groups, and the four groups of isosceles trapezoidal flexible hinges are arranged at equal angles in the circumference.

[0015] Preferably, the force input wire wheel is driven to rotate by an external wire driving source.

[0016] (3) Beneficial effects

[0017] The present invention provides a variable stiffness driver based on an isosceles trapezoidal flexible hinge with double variable stiffness.

[0018] It has the following beneficial effects:

[0019] This variable stiffness actuator utilizes an isosceles trapezoidal flexure hinge with dual variable stiffness. The hinge's sides are made of leaf springs, which are elastically bendable and repositionable. Compared to linear springs, this design allows for high elastic energy storage within a small space at the point of application. Furthermore, by combining leaf spring deformation with hinge rotation, low stiffness is achieved. Compared to a single leaf spring, this design allows for low-stiffness actuation within a small space. This achieves a variable stiffness actuator while maintaining excellent performance while maintaining a compact design and low mass.

[0020] 2. This variable stiffness actuator, based on an isosceles trapezoidal flexible hinge with dual variable stiffness, achieves a wide stiffness range through the integration of a two-stage stiffness modulation mechanism, achieving a variable stiffness range of 0 to 4071 Nm / rad. This makes it suitable for rehabilitation training for a wider range of patients with varying degrees of recovery. The low-stiffness mode offers improved safety and compliance, while the high-stiffness mode offers improved trajectory accuracy. Four sets of variable stiffness mechanisms are designed to be symmetrically distributed. These mechanisms simultaneously control the movement of the four pivot axes within the working stroke, allowing all four mechanisms to operate simultaneously when modulating stiffness. This increases stiffness variation efficiency and achieves a higher stiffness variation speed, enabling modulation from minimum to maximum stiffness in 0.1 seconds. This allows for timely stiffness modulation to meet performance requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is the overall external axonometric view of the present invention;

[0022] Figure 2 is a schematic diagram of a stripping output shaft of the present invention;

[0023] Figure 3 Schematic diagram of the stripping force input wire wheel of the present invention;

[0024] Figure 4 This is a design diagram of the stiffness model principle of the isosceles trapezoidal flexible hinge of the present invention.

[0025] In the figure: 1 output shaft, 2 force transmission connecting rod, 21 force transmission slide rail, 22 slider, 3 isosceles trapezoidal flexible hinge, 31 bottom side connecting rod, 32 side waist connecting rod 1, 33 side waist connecting rod 2, 4 force transmission input component, 41 fixed plate, 42 force transmission input wire wheel, 51 rear cam, 52 rear wheel guide groove, 53 lever, 54 fulcrum shaft, 55 lever slide groove, 56 swing arm, 57 swing arm slide groove, 58 front cam, 59 transmission plate, 60 front wheel guide groove, 61 transmission plate guide groove, 62 guide shaft, 63 adjustment shaft, 64 adjustment wire fixing hole. DETAILED DESCRIPTION

[0026] The embodiment of the present invention provides a variable stiffness driver based on an isosceles trapezoidal flexible hinge with double variable stiffness, such as Figure 1-3 As shown, the elastic force transmission mechanism and stiffness modulation mechanism 5 are included. The elastic force transmission mechanism includes an output shaft 1, a force transmission input member 4, several groups of force transmission connecting rods 2, and an isosceles trapezoidal flexible hinge 3. It is used to transmit the driving force to the output shaft through the elastic element, thereby achieving flexible drive and improving the compliance and safety of human interaction.

[0027] In this embodiment, four groups of isosceles trapezoidal flexible hinges 3 are provided, and the four groups of isosceles trapezoidal flexible hinges 3 are arranged at equal angles in a circumferential direction.

[0028] The isosceles trapezoidal flexible hinge 3 serves as an elastic element. The outer ends of the two waists of the isosceles trapezoidal flexible hinge 3 are hinged to the output shaft 1 and the force transmission link 2, respectively. The inner ends of the two waists of the isosceles trapezoidal flexible hinge 3 are hinged to the force transmission input member 4 and the stiffness modulation mechanism, respectively. The stiffness modulation mechanism 5 is used to adjust the angle of the two waists of the isosceles trapezoidal flexible hinge 3.

[0029] The waists of the isosceles trapezoidal flexible hinge 3 are made of leaf springs that are elastically bendable and repositionable. Compared to linear springs, this allows for high elastic energy storage within a small space at the point of application. Furthermore, by combining leaf spring deformation with hinge rotation, low stiffness is achieved. Compared to a single leaf spring, low-stiffness actuation can be achieved within a small space. This enables a variable-stiffness actuator to maintain excellent performance while achieving a compact and lightweight design.

[0030] The elastic force transmission mechanism adopts a variable transmission ratio force transmission mechanism to transmit force. The force input component 4 transmits the force to the fulcrum and the isosceles trapezoidal flexible hinge 3 through the force transmission connecting rod 2, and then finally returns to the output shaft 1. This design changes the variable transmission ratio arrangement structure. By designing the output-elastic force-fulcrum configuration, the elastic element is changed from the traditional design of placing it at the axis to moving the elastic element to the outside. At the same time, four groups of variable stiffness mechanisms are designed to be symmetrically distributed. The mechanism is used to simultaneously control the movement of the four fulcrum axes in the working stroke so that the four groups of mechanisms work simultaneously when the mechanism modulates the stiffness, thereby increasing the stiffness variable efficiency and significantly improving the stiffness variable speed.

[0031] like Figure 1 As shown, the force input component 4 includes a fixed disk 41 and a force input wire wheel 42. The force input wire wheel 42 is fixed on the fixed disk 41 and is used to connect to an external wire drive source. The force input wire wheel 42 realizes remote transmission through an external wire rope.

[0032] like Figure 3 As shown, the isosceles trapezoidal flexible hinge 3 is composed of a bottom link 31, a side waist link 1 32, and a side waist link 2 33. One end of the side waist link 1 32 and one end of the bottom link 31 are hinged on the output shaft 1, one end of the side waist link 2 33 and one end of the bottom link 31 are hinged on the force transmission link 2, and the other end of the side waist link 1 32 is hinged on the fixed plate 41. The stiffness modulation mechanism 5 is used to adjust the other end of the side waist link 2 33.

[0033] like Figure 2-3As shown, the stiffness modulation mechanism 5 includes a rear cam 51, a front cam 58, a transmission plate 59, a lever 53, a fulcrum shaft 54, and a swing arm 56. The front cam 58 is pivotally connected to the fixed plate 41, and the transmission plate 59 is fixed to the fixed plate 41. The rear cam 51, the front cam 58, and the transmission plate 59 are respectively provided with a number of rear wheel guide grooves 52, front wheel guide grooves 60, and transmission plate guide grooves 61, the number of which is consistent with the isosceles trapezoidal flexible hinge 3. The rear wheel guide grooves 52, the front wheel guide grooves 60, and the transmission plate guide grooves 61 are arranged to gradually open from the inside to the outside. The force transmission link 2 includes a force transmission slide rail 21 and a slider 22 slidably adapted on the force transmission slide rail 21. One of the side waist links 33 The end is hinged to the slider 22 together with one end of the bottom link 31, the lever 53 is arranged in the middle of the bottom link 31, and one end of the swing arm 56 is coaxially hinged to the hinge part of the side waist link 32 and the bottom link 31. The lever 53 and the swing arm 56 are provided with a lever slide groove 55 and a swing arm slide groove 57 along their length direction. The fulcrum shaft 54 ​​is hinged to the inner end part of the force transmission slide rail 21, and the upper and lower sections are slidably adapted in the rear wheel guide groove 52, the lever slide groove 55, the swing arm slide groove 57, and the transmission plate guide groove 61; a guide shaft 62 is provided at the end of the side waist link 2 33 away from the slider 22, and the guide shaft 62 is slidably adapted in the front wheel guide groove 60 and the transmission plate guide groove 61.

[0034] The stiffness modulation mechanism 5 can realize the overall stiffness modulation of the driver. The variable stiffness principle adopts a two-stage composite design of variable transmission ratio type and variable flexible hinge stiffness type. Specifically, the principle design of the composite two-stage variable stiffness is reflected by performing mechanical analysis of the two variable stiffness models respectively. Figure 4 As shown in a, the stiffness model of the isosceles trapezoidal flexible hinge is established as shown in the following formula:

[0035]

[0036] The stiffness k1 of the isosceles trapezoidal flexure hinge is affected by the trapezoid's smaller base e. The modeling principle is that the deformation of the leaf spring side link drives the relative rotation of the upper and lower trapezoidal base links. Changing the length of the lower base influences the output rotation around the link hinge, thereby affecting the actual deformation of the side link 31, 33 during the link rotation process. The variable flexure hinge stiffness model works by the front cam 58 driving the second side link 33 to rotate around the link hinge point, achieving a change in the trapezoidal shape and, consequently, a change in the stiffness of the overall elastic element.

[0037] Likewise, Figure 4 As shown in Figure 2, a stiffness model with variable transmission ratio is established, as shown in the following formula:

[0038]

[0039] It can be seen that the single variable transmission ratio stiffness k2 is affected by the force arm ratio l1 / l2. The modeling principle is that the elastic element and the output end are at both ends of the lever 53. Due to the three-force equilibrium convergence theorem, the elastic force and the fulcrum force are equal to the output force. By moving the position of the fulcrum shaft 54 ​​in the lever slot 55, the force arm at both ends from the fulcrum shaft 54 ​​is changed, and the fulcrum force and the elastic force are interchangeable. According to Hooke's theorem, the deformation of the elastic element is affected by the elastic force. The principle of variable transmission ratio and variable stiffness is that the fulcrum shaft 54 ​​can move in the lever slot 55 as a fulcrum. The position of the fulcrum shaft 54 ​​in the lever slot 55 is changed by the rear cam 51 to achieve variable transmission ratio and variable stiffness. At the same time, the front cam 58 drives the side waist link 2 33 to rotate around the link hinge point to achieve a trapezoidal shape change, thereby changing the stiffness of the elastic element as a whole.

[0040] like Figure 1 As shown, the stiffness modulation mechanism 5 also includes an adjustment shaft 63 coaxially connected to the front cam 58. The adjustment shaft 63 is provided with an adjustment wire fixing hole 64 for securing an adjustment wire. The adjustment wire drives the rotation of the adjustment shaft 63, the front cam 58, and the rear cam 51. The front and rear cams are connected to the central rotating shaft via a keyway structure, enabling synchronous rotation of the front and rear cams and driving displacement within the optical axis slot. This achieves a two-stage stiffness variation method: variable transmission ratio + variable flexible hinge stiffness, effectively increasing the range of stiffness variation.

[0041] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A variable stiffness actuator based on an isosceles trapezoidal flexible hinge with dual variable stiffness, characterized by: The invention comprises an elastic force transmission mechanism and a stiffness modulation mechanism (5), wherein the elastic force transmission mechanism comprises an output shaft (1), a force transmission input member (4), a plurality of force transmission connecting rods (2), and an isosceles trapezoidal flexible hinge (3), wherein the outer ends of the waists on both sides of the isosceles trapezoidal flexible hinge (3) are respectively hinged to the output shaft (1) and the force transmission connecting rod (2), and the inner ends of the waists on both sides of the isosceles trapezoidal flexible hinge (3) are respectively hinged to the force transmission input member (4) and the stiffness modulation mechanism, and the stiffness modulation mechanism (5) is used to adjust the angles of the waists on both sides of the isosceles trapezoidal flexible hinge (3).

2. The variable stiffness actuator based on the isosceles trapezoidal flexible hinge with double variable stiffness according to claim 1, characterized in that: The force input component (4) comprises a fixed disk (41) and a force input wire wheel (42), and the force input wire wheel (42) is fixed on the fixed disk (41).

3. The variable stiffness actuator based on the isosceles trapezoidal flexible hinge with double variable stiffness according to claim 2, characterized in that: The isosceles trapezoidal flexible hinge (3) is composed of a bottom link (31), a side waist link (32), and a side waist link (33). One end of the side waist link (32) and one end of the bottom link (31) are hinged together on the output shaft (1). One end of the side waist link (33) and one end of the bottom link (31) are hinged together on the force transmission link (2). The other end of the side waist link (32) is hinged on the fixed plate (41). The stiffness modulation mechanism (5) is used to adjust the other end of the side waist link (33).

4. The variable stiffness actuator based on the isosceles trapezoidal flexible hinge with double variable stiffness according to claim 3, characterized in that: The stiffness modulation mechanism (5) includes a rear cam (51), a front cam (58), a transmission plate (59), a lever (53), a fulcrum shaft (54), and a swing arm (56). The front cam (58) is pivotally connected to a fixed plate (41), and the transmission plate (59) is fixed to the fixed plate (41). The rear cam (51), the front cam (58), and the transmission plate (59) are respectively provided with a plurality of groups of rear wheel guide grooves (52), front wheel guide grooves (60), and transmission plate guide grooves (61) whose numbers are consistent with the isosceles trapezoidal flexible hinge (3). The rear wheel guide grooves (52), the front wheel guide grooves (60), and the transmission plate guide grooves (61) are arranged to gradually open from the inside to the outside. The force transmission connecting rod (2) includes a force transmission slide rail (21) and a slider (22) slidably adapted on the force transmission slide rail (21). The side waist connecting rod 2 (33) One end of the lever (53) and one end of the bottom link (31) are hinged on the slider (22), the lever (53) is arranged in the middle of the bottom link (31), one end of the swing arm (56) is coaxially hinged on the hinge part of the side waist link (32) and the bottom link (31), the lever (53) and the swing arm (56) are provided with a lever sliding groove (55) and a swing arm sliding groove (57) along their length direction, the fulcrum shaft (54) is hinged on the inner end of the force transmission slide rail (21), and the upper and lower sections are slidably adapted in the rear wheel guide groove (52), the lever sliding groove (55), the swing arm sliding groove (57), and the transmission plate guide groove (61); the end of the side waist link (33) away from the slider (22) is provided with a guide shaft (62), and the guide shaft (62) is slidably adapted in the front wheel guide groove (60) and the transmission plate guide groove (61).

5. The variable stiffness actuator based on the isosceles trapezoidal flexible hinge with double variable stiffness according to claim 4, characterized in that: The stiffness modulation mechanism (5) further comprises an adjustment shaft (63) coaxially connected to the front cam (58), and an adjustment wire fixing hole (64) for fixing the adjustment wire is provided on the adjustment shaft (63).

6. The variable stiffness actuator based on the isosceles trapezoidal flexible hinge with double variable stiffness according to claim 1, characterized in that: The isosceles trapezoidal flexible hinges (3) are provided in four groups in total, and the four groups of isosceles trapezoidal flexible hinges (3) are arranged at equal angles in the circumferential direction.

7. The variable stiffness actuator based on the isosceles trapezoidal flexible hinge with double variable stiffness according to claim 2, characterized in that: The force input wire wheel (42) is driven to rotate by an external wire driving source.

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