CN111062161B - Large-tension high-stability light and small constant force device - Google Patents
Large-tension high-stability light and small constant force device Download PDFInfo
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Abstract
The invention discloses a large-tension high-stability light and small constant force device which comprises a bounding box and at least one constant force unit. The bounding box includes box body and roof, is equipped with out rope hole and fixed pulley on the roof. Each constant force unit comprises a nonlinear spring, a sliding block, a sliding rod, a spiral spring and an adjusting nut. Two ends of the sliding rod are fixedly connected with the surrounding box bottom plate and the surrounding box top plate respectively; one end of the nonlinear spring is fixed with the surrounding box bottom plate, and the other end of the nonlinear spring is hinged with the sliding block; the sliding block is arranged on the sliding rod and can slide up and down along the sliding rod; one end of the spiral spring is connected with the sliding block, and the other end of the spiral spring is connected with the adjusting nut; the adjusting nut is screwed with the thread on the upper part of the sliding rod. The constant force device can basically keep constant output load (tensile force) along with the increase of deformation, has the advantages of large output force, constant load, high energy storage density, small volume, small friction loss and the like, and can be widely applied to the fields of machinery, electronics, instruments, spaceflight, medical treatment and the like, such as vibration isolation devices, balance mechanisms, motor brush holders, weightlessness simulation devices and the like.
Description
Technical Field
The invention relates to the technical field of constant force devices, in particular to a large-tension high-stability light and small constant force device.
Background
The existing constant force device is usually a thin-wall constant force spring, but in practical engineering application, the constant force spring is found to have the following problems: the output force is not constant; the thin-wall reed is easy to be unstable; the shrinking process is not in a linear direction.
In recent years, scholars at home and abroad are dedicated to research constant force institutions. The constant force mechanism scheme based on the PRBM model can realize constant force output by optimizing a rigid connecting rod and an elastic element. The main-auxiliary constant-force spring support and hanger scheme adopts a pair of auxiliary springs and a swinging knife-shaped cam to cut and complement a force-displacement triangular characteristic curve of a main spring during compression into a rectangle, and the force provided by a mechanism is constant in the whole process. However, in general, the force output by the constant force mechanism schemes is not large, and the displacement stroke corresponding to the constant force is not long; unreliability, heavy weight and non-smoothness due to complex mechanisms; some solutions require the input of an initial force. These disadvantages limit the engineering application of the constant force mechanism solution.
Disclosure of Invention
The invention aims to provide a light and small constant force device with high tension, high stability and small size aiming at the defects of the prior art. The technical scheme adopted by the invention is as follows:
the utility model provides a light small-size constant force device of high stability of big tension, includes bounding box and at least one constant force unit, and the bounding box includes box body and roof, is equipped with out rope hole and fixed pulley on the roof, and the constant force unit includes nonlinear spring, slider, slide bar, coil spring, adjusting nut etc.. The two ends of the sliding rod are provided with internal thread holes which are connected with the surrounding box bottom plate and the top plate through bolts, the lower part of the sliding rod is smooth, the middle part of the sliding rod is provided with a limiting bulge, and the upper part of the sliding rod is provided with external threads; one end of the nonlinear spring is fixed with the surrounding box bottom plate, and the other end of the nonlinear spring is hinged with the sliding block; the sliding block is arranged on the sliding rod and can slide up and down along the smooth section of the sliding rod; the spiral spring is sleeved outside the sliding rod, one end of the spiral spring is connected with the sliding block, and the other end of the spiral spring is connected with the adjusting nut; the adjusting nut is matched with the external thread on the upper part of the sliding rod, and the length of the spiral spring can be changed by changing the position of the adjusting nut on the thread of the sliding rod.
The technical methodIn the case of the constant force unit, a combined spring scheme can be adopted, as shown in fig. 1, and the system mainly comprises a coil spring with positive stiffness and a nonlinear spring with negative stiffness. The load displacement curve of the coil spring is shown in fig. 2(a), and has a positive structural stiffness k. The load displacement curve of the nonlinear spring is shown in fig. 2(b), wherein the ab segment is a positive stiffness segment, and the bc segment is a negative stiffness segment. The load displacement curve of the combined structure is shown in fig. 2(c), and when the negative stiffness of the bc section of the nonlinear spring is designed to be-k, the load displacement curve of the combined structure has a constant force section de. When the pre-adjusting force FaWhen applied to a coil spring, the load-displacement curve translates, as shown in fig. 2 (d). If the design of the non-linear spring is kept constant, the load-displacement curve of the final assembled structure is as shown in FIG. 2 (f). So that it is possible to apply a pre-adjusting force FaTo adjust the output constant force of the constant force unit.
In the above technical solution, the nonlinear spring is represented by a spline curve, and the spline curve form of the nonlinear spring is designed by an optimization theory, and the design method is as follows:
1) establishing a nonlinear spring form optimization design model
In order to design an optimal nonlinear spring form, so that the nonlinear spring has a target load-displacement curve meeting the design requirements of constant force and displacement stroke, the actual load-displacement curve needs to be close to the target load-displacement curve as much as possible, and therefore discrete points on a plurality of target load-displacement curves are selected to establish an optimized objective function as follows: min (SFE + DP)
Wherein the content of the first and second substances,
the form function deviation SFE of a non-linear spring is expressed as:
wherein N is the number of discrete points on the load-displacement curve; when the spring is not flexed, FspringFor the actual applied load, when the spring is flexed, FspringCritical load for buckling, fiFor the relative deviation of two load-displacement curves at each discrete point；
The displacement penalty function DP is:
in the formula dspringFor the actual displacement stroke, dminFor a predetermined minimum displacement stroke, WdispThe weight coefficient can be set according to the requirement;
optimizing variables: the optimized variables for the nonlinear spring form optimization include: coordinates (x) of several control points of a spline curvei,yi) Constraint condition (one end is fixed and the other end is hinged), and the inner thickness h of the spring surface1Thickness h outside the dough2And the like.
The constraint conditions mainly comprise that the design space of the nonlinear spring, the value ranges of the in-plane thickness and the out-of-plane thickness of the spring and the maximum stress meet the strength requirement:
0≤xi≤X,0≤yi≤Y
0＜h1≤h1max
0＜h2≤h2max
σmax＜[σ]
in the formula (x)i,yi) As coordinates of control points of the B-spline curve, h1Is the spring in-plane thickness sum h2Out-of-plane thickness, X, Y, optimization design space, h1max,h2maxMaximum values of in-plane thickness and out-of-plane thickness, [ sigma ] respectively]Is the yield stress of the spring material.
2) Adopting GA algorithm to combine with non-linear finite element software ANSYS to complete optimization design
Establishing a plurality of groups of random design variable initial values, wherein each group of design variables represents a design scheme, mapping the design variables to a finite element model of the spring, carrying out nonlinear finite element analysis on each design scheme, carrying out mechanical property evaluation, checking a termination standard if an evaluation result meets the design requirement, generating new design variables to establish a new spring design scheme if the evaluation result does not meet the design requirement, carrying out new optimization iteration, and finally determining the optimal design scheme of the nonlinear spring.
The positive stiffness of the spiral spring is determined by the negative stiffness of the nonlinear spring, and the numerical value of the negative stiffness of the nonlinear spring is obtained by fitting from a load-displacement curve corresponding to the optimal form.
In addition, the length of the spiral spring can be changed by changing the screwing position of the adjusting nut on the thread of the sliding rod, and further the pre-adjusting force F of the spiral spring is changedaThe effect of changing the output constant force of the constant force unit is achieved.
In addition, the direction of the pulling force rope can be changed and the pulling force can be kept unchanged through the fixed pulley on the top plate of the bounding box, so that the constant force device can output constant force within the range of +/-45 degrees.
The large-tension high-stability light small constant force device can output a plurality of constant forces in a given design space, has large constant force value and good stability, and has long corresponding displacement stroke of the constant force section compared with the existing constant force device. The large-tension high-stability light small-size constant force device can be widely applied to the fields of machinery, electronics, instruments, aerospace, medical treatment and the like, such as vibration isolation devices, balance mechanisms, motor brush holders, weightlessness simulation devices and the like.
Drawings
FIG. 1 is a schematic view of a combination spring arrangement;
FIG. 2 is a combination spring scheme operating principle;
FIG. 3 is a non-linear spring design;
FIG. 4 is a graph of non-linear spring actual and target load-displacement;
FIG. 5 is a non-linear spring design flow;
FIG. 6 is a non-linear spring load displacement curve of an example;
FIG. 7 is an example optimized load-displacement curve;
FIG. 8 is a spline curve optimized in an example;
FIG. 9 is an example nonlinear spring finite element model;
FIG. 10 is a configuration and stress distribution at maximum displacement of a nonlinear spring;
FIG. 11 is the combined structure after the addition of linear springs;
FIG. 12 is a load-displacement curve of a composite structure
FIG. 13 is a schematic diagram of a specific structure of a bounding box body;
FIG. 14 is a schematic view of the enclosure top plate being connected to a tension cord;
FIG. 15 is a schematic view of a central shaft configuration;
FIG. 16 is a schematic view of a specific structure of a slider;
fig. 17 is a schematic view of an example non-linear spring constant force device assembly.
In the figure: 1. the adjustable spring comprises an adjusting nut, 2 positive stiffness linear springs, 3 limiting protrusions, 4 tensile rope joints, 5 sliding blocks, 6 hinged ends, 7 negative stiffness nonlinear springs, 8 fixed ends, 9 tensile ropes, 10 bounding box top plates and 11 fixed pulleys.
Detailed Description
The principles and technical solutions of the present invention are further explained below with reference to the drawings.
1. The design principle on which the invention is based
In order to obtain a specified load displacement curve (including output force magnitude and compensation displacement stroke), a combined spring scheme can be adopted by the constant force unit, such as fig. 1, and the system mainly comprises a positive-stiffness spiral spring and a negative-stiffness nonlinear spring. The load displacement curve of the coil spring is shown in fig. 2(a), and has a positive structural stiffness k. The load displacement curve of the nonlinear spring is shown in fig. 2(b), wherein the ab segment is a positive stiffness segment, and the bc segment is a negative stiffness segment. The load displacement curve of the combined structure is shown in fig. 2(c), and when the negative stiffness of the bc section of the nonlinear spring is designed to be-k, the load displacement curve of the combined structure has a constant force section de. When the pre-adjusting force FaWhen applied to a linear spring, the load-displacement curve translates, as shown in fig. 2 (d). If the design of the non-linear spring is guaranteedIf the load displacement curve is constant, the load displacement curve of the final combined structure is shown in fig. 2 (f). So that it is possible to apply a pre-adjusting force FaTo adjust the output constant force of the constant force unit.
The design scheme of the nonlinear spring with negative stiffness is shown in figure 3, the nonlinear spring can be regarded as a plane curved beam model, one end of the nonlinear spring is fixed on a bottom plate of a surrounding box of a constant force device, and the other end of the nonlinear spring is a constant force output point. The plane curved beam is a slender component, has stronger geometric non-linear characteristics, and can provide a very long effective working stroke corresponding to a constant force section. The shape of the plane curved beam can be described by a spline curve, such as a Bezier curve, a B-spline curve and a Nubers curve. Such as using B-spline curves for parametric morphological topology of nonlinear springs. The middle circle is the load input point, the black point is the fixed point, and the middle circle point and the gray point are both the shape control points. For a B-spline curve, several control points determine the shape of the curve, and as the control points move within the design space, the shape of the curve is continuously adjusted to the new control polygon shape. Thus repositioning of the control points changes the geometry of the planar curved beam and also changes the non-linear characteristics of the non-linear spring, thereby changing the load-displacement curve of the spring.
Establishing a form optimization design model of the nonlinear spring, taking the control point coordinates and the section size of a B spline curve of the plane curved beam as optimization variables, taking a load-displacement curve as an optimization target, and obtaining an optimal scheme of the form of the nonlinear spring under certain constraint conditions, thereby realizing a preset load-displacement curve.
2. Form optimization design of nonlinear spring
2.1 morphological optimization mathematical model
1) Optimizing an objective function
The goal of the form optimization is to design the form of the nonlinear spring such that it has a target load-displacement curve as the solid line in fig. 4, while meeting the design requirements of constant force magnitude and displacement travel. The dashed line in the figure represents the actual load-displacement curve of one non-linear spring sample during optimization. During the optimization, each spring sample is subjected to the same load. In order to design an optimal spring formIt is desirable that the actual load-displacement curve (dashed line) approximates the target load-displacement curve (solid line) as closely as possible. Since the optimization objective cannot be established based on the overall deviation of the two load-displacement curves, the optimization objective function is established based on a plurality of discrete points (such as points a-D in the figure). At each discrete point, the relative deviation of the two load-displacement curves is fi。
The form function deviation of a nonlinear spring can be expressed as:
wherein N is the number of discrete points on the load-displacement curve; when the spring is not flexed, FspringFor the actual applied load, when the spring is flexed, FspringThe buckling critical load.
In order to achieve a predetermined constant force step displacement travel dspringThe optimization objective function includes a displacement penalty function DP and a weight coefficient W thereofdisp：
In the formula dspringFor the actual displacement stroke, dminIs a predetermined minimum displacement stroke.
The overall optimization objective function is therefore:
min(SFE+DP)
2) optimizing variables
The optimized variables for the nonlinear spring form optimization include: coordinates (x) of control points of B-spline curvei,yi) Constraint condition (one end is fixed and the other end is hinged), and the inner thickness h of the spring surface1Thickness h outside the dough2And the like.
3) Constraint conditions
The constraint conditions mainly comprise the design space of the nonlinear spring, the value ranges of the in-plane thickness and the out-of-plane thickness of the spring and the requirement that the maximum stress meets the strength.
0≤xi≤X,0≤yi≤Y
0＜h1≤h1max
0＜h2≤h2max
σmax＜[σ]
In the formula, X and Y are optimized design space, h1max,h2maxMaximum values of in-plane thickness and out-of-plane thickness, [ sigma ] respectively]Is the yield stress of the spring material.
In summary, the form optimization mathematical model of the nonlinear spring is as follows:
X＝[xi,yi,h1,h2]
minf(X)＝SFE+DP
s.t.0≤xi≤X,0≤yi≤Y
0＜h1≤h1max
0＜h2≤h2max
σmax＜[σ]
2.2 form optimization design flow
The form optimization design flow of the nonlinear spring is shown in figure 5. Firstly, establishing a nonlinear spring form optimization design model, determining multiple optimization targets such as a specified load-displacement curve and the lightest weight, and determining the upper and lower limit ranges of nonlinear spring design variables such as working space, geometric dimension, material parameters, strength and the like. If an accurate optimization parameter value range is specified, the design specification can be selected to be reduced, and the efficiency of the optimization design process is improved. And then, adopting a GA algorithm to combine with non-linear finite element software ANSYS to complete optimization design, creating a plurality of groups of random design variable initial values, wherein each group of design variables represents a design scheme, mapping the design variables to a finite element model of the spring, and carrying out non-linear finite element analysis on each design scheme to evaluate the mechanical property. If the evaluation result meets the design requirements, the termination criteria are checked. If the design requirements are not met, new design variables are generated to create a new spring design solution and new optimization iterations are performed. Finally, the optimal design scheme of the nonlinear spring is determined, and the optimal design scheme can be selected and expanded to better match the specified load-displacement curve.
The morphological optimization design results are illustrated by way of example
And (4) performing shape optimization design of the nonlinear spring according to the theory and the software tool. The load-displacement curve of a non-linear spring requires a curve as shown in fig. 6: the force corresponding to the force peak point B is 30N, and the displacement value is 15 mm; the force at the force valley point C corresponds to a force of 10N and a displacement value of 45 mm. The spring optimization design space is as follows: the x direction: 0-30 mm; the y direction: 0-80 mm. The spring material is titanium alloy, the elastic modulus is 115E3 MPa, the Poisson ratio is 0.33, and the density is 4500Kg/m3The yield strength was 800 MPa. The spring is characterized by a B spline curve, and has 7 control points, wherein the first control point is fixedly supported, and the other end restrains X-direction displacement. The constraints of in-plane thickness are 0.4-2mm and out-of-plane thickness is 5.0 mm.
Through the form optimization design, an optimal load-displacement curve is obtained as shown in fig. 7. The analysis result shows that the load-displacement curve is superior to the design requirement.
The B-spline curve obtained by optimization is shown in FIG. 8, and the coordinates of the control points of the B-spline curve are shown in Table 1. The corresponding nonlinear spring finite element model is shown in fig. 9.
TABLE 1B spline Curve control Point coordinates
| Control point numbering | X coordinate (mm) | Y coordinate (mm) |
| 1 | 0.00 | 0.00 |
| 2 | 2.423 | -2466 |
| 3 | 12.953 | -40.165 |
| 4 | 15.426 | -51.584 |
| 5 | 2.875 | -76.251 |
| 6 | 30.000 | -2.733 |
The configuration of the nonlinear spring when the nonlinear spring generates the maximum displacement is shown in figure 10, the maximum stress in the deformed spring is smaller than the yield stress of the material, and the structure is safe.
A y-direction linear spring with positive stiffness added to the right end of the nonlinear spring, as shown in fig. 11, has a linear spring stiffness of 0.686N/mm, as determined from the load-displacement curve of the nonlinear spring of fig. 7. The linear spring was simulated in ANSYS software using a COMBIN39 cell, the load-displacement curve of which is defined in table 2. The upper end of the linear spring is fixed, and the lower end of the linear spring is connected with the nonlinear spring. The load-displacement curve data of the linear spring are shown in the table.
TABLE 2 load-Displacement curves for Linear springs
| Displacement (mm) | Load (N) |
| 0 | 0 |
| 15 | 10.285 |
| 45 | 30.856 |
| 130 | 89.139 |
And (3) carrying out static analysis on the combined structure to obtain a load-displacement curve as shown in figure 12, namely the final load-displacement curve of the constant force device.
From the load-displacement analysis results, when the displacement increased to 13.7mm, the load was 40N; when the displacement continues to increase, the load decreases and enters a constant-force section; when the displacement is increased to 34mm, the load reaches the lowest value of the constant force section, namely 40.4N; when the displacement was increased to 45mm, the load was 42.2N. The change amplitude of the constant force section is 5 percent <10 percent, and each index meets the design requirements that the constant force value is 40N and the displacement stroke is 15mm-45 mm.
3. Constant force device component structure
The entire constant force device can be composed of a bounding box and 4 constant force units. The bounding box comprises a box body and a top plate, wherein a bottom plate of the box body is fixedly connected with one end of the nonlinear spring and is also fixedly connected with the sliding rod, so that the whole constant force device is supported and protected, as shown in fig. 13.
In order to ensure that the slide bar is stable and does not incline, the upper part of the slide bar is provided with an internal thread hole which is fixed with the top plate of the bounding box by a bolt. In addition, 8 rope outlet holes and 8 fixed pulleys are arranged at the upper part of the top plate. One end of the tension rope is connected with the semicircular hole on the sliding block, and the other end of the tension rope passes through the rope outlet hole of the top plate, bypasses the pulley on the top plate of the outer packing box and is finally combined into one rope. Through the pulley, the direction of the pulling force rope can be changed and the magnitude of the pulling force is kept unchanged, so that the constant force device can output the constant force within the range of +/-45 degrees, as shown in fig. 14.
Each constant force unit comprises a nonlinear spring, a spiral spring, an adjusting nut, a sliding block and a sliding rod. The two ends of the sliding rod are provided with internal thread holes which are respectively fixed with the surrounding box bottom plate and the top plate by bolts. The lower part is smooth, which provides support for the up-and-down sliding of the sliding block; the middle part of the sliding rod is provided with a limiting bulge to protect the constant tension device and prevent the hinged end of the nonlinear spring from excessively large displacement, and when the sliding block moves to the moment, the sliding block is limited, so that when the displacement change exceeds the range of the constant force section, the constant force device has large output force to carry out self protection; the upper part of the sliding rod is provided with external threads which are screwed with the adjusting nut. As shown in fig. 15. The spiral spring is sleeved on the whole sliding rod, the lower end of the spiral spring is fixed with the sliding block, the upper end of the spiral spring is fixed with the adjusting nut, and specifically, a through hole in the center of the sliding block is matched with the sliding rod and slides up and down along the sliding rod; the sliding block is matched with one end of the nonlinear spring, and the sliding block and one end of the nonlinear spring are hinged through a pin; in addition, the sliding block is fixedly connected with one end of the spiral spring; the upper end of the sliding block is provided with a semicircular hole for connecting with a tension rope, as shown in fig. 16.
The whole large-tension high-stability light and small constant-force device is assembled as shown in fig. 17.
Claims (7)
1. A large-tension high-stability light and small constant-force device is characterized by comprising an enclosure and at least one constant-force unit; the surrounding box comprises a box body and a top plate, and the top plate is provided with a rope outlet hole and a fixed pulley; each constant force unit comprises a nonlinear spring, a sliding block, a sliding rod, a spiral spring and an adjusting nut; the two ends of the sliding rod are provided with internal thread holes which are connected with the surrounding box bottom plate and the top plate through bolts, the lower part of the sliding rod is smooth, the middle part of the sliding rod is provided with a limiting bulge, and the upper part of the sliding rod is provided with external threads; one end of the nonlinear spring is fixed with the surrounding box bottom plate, and the other end of the nonlinear spring is hinged with the sliding block; the sliding block is arranged on the sliding rod and can slide up and down along the smooth section of the sliding rod; the spiral spring is sleeved outside the sliding rod, one end of the spiral spring is connected with the sliding block, and the other end of the spiral spring is connected with the adjusting nut; the adjusting nut is matched with the external thread on the upper part of the sliding rod, and the length of the spiral spring can be changed by changing the position of the adjusting nut on the thread of the sliding rod.
2. A high tension, high stability, light weight and small constant force apparatus as claimed in claim 1, wherein the load displacement curve of said coil spring has a positive structural stiffness k; the nonlinear spring has negative stiffness, an ab section in a load displacement curve of the nonlinear spring is a positive stiffness section, and a bc section is a negative stiffness section; in the load displacement curve of the structure formed by combining the spiral spring and the nonlinear spring, when the negative stiffness of the bc section of the nonlinear spring is designed to be-k, the load displacement curve of the structure formed by combining the spiral spring and the nonlinear spring has a constant force section de; when the pre-adjusting force FaThe load-displacement curve of a helical spring is translated by applying a pre-adjusting force F if the design of the non-linear spring is kept constantaTo adjust the output constant force of the constant force unit.
3. The large tension high stability light weight and small constant force device according to claim 1, wherein said non-linear spring is a curved beam structure whose form can be expressed by a spline curve, said spline curve being a Bezier curve, a B-spline curve, or a Nubers curve.
4. The large-tension high-stability light and small constant force device according to claim 1, wherein the spline curve form of the nonlinear spring is designed by using an optimization theory, and the design method is as follows:
1) establishing a nonlinear spring form optimization design model
In order to design an optimal form of the nonlinear spring, so that the nonlinear spring has a target load-displacement curve meeting the design requirements of constant force and displacement stroke, the actual load-displacement curve needs to be as close to the target load-displacement curve as possible, and therefore discrete points on a plurality of target load-displacement curves are selected to establish an optimized objective function as follows:
min(SFE+DP)
wherein the content of the first and second substances,
the form function deviation SFE of the nonlinear spring load-displacement curve is expressed as:
wherein N is the number of discrete points on the load-displacement curve; when the spring is not flexed, FspringFor the actual applied load, when the spring is flexed, FspringCritical load for buckling, fiRelative deviation of the two load-displacement curves at each discrete point;
the displacement penalty function DP is:
in the formula dspringFor the actual displacement stroke, dminFor a predetermined minimum displacement stroke, WdispThe weight coefficient can be set according to the requirement;
optimizing variables: the optimized variables for the nonlinear spring form optimization include: coordinates (x) of several control points of a spline curvei,yi) Inner thickness h of spring plane1Thickness h outside the dough2；
Constraint conditions are as follows: the strength requirement is met mainly by the design space of the nonlinear spring, the value ranges of the in-plane thickness and the out-of-plane thickness of the spring and the maximum stress:
0≤xi≤X,0≤yi≤Y
0＜h1≤h1max
0＜h2≤h2max
σmax＜[σ]
in the formula (x)i,yi) As coordinates of control points of the B-spline curve, h1Is the spring in-plane thickness sum h2Out-of-plane thickness, X, Y, optimization design space, h1max,h2maxMaximum values of in-plane thickness and out-of-plane thickness, [ sigma ] respectively]Is the yield stress of the spring material;
2) adopting GA algorithm to combine with non-linear finite element software ANSYS to complete optimization design
Establishing a plurality of groups of random design variable initial values, wherein each group of design variables represents a design scheme, mapping the design variables to a finite element model of the nonlinear spring, carrying out nonlinear finite element analysis on each design scheme, carrying out load-displacement curve mechanical property evaluation, checking a termination standard if an evaluation result meets the design requirement, generating new design variables to establish a new nonlinear spring design scheme if the evaluation result does not meet the design requirement, carrying out new optimization iteration, and finally determining the optimal form design scheme of the nonlinear spring.
5. A high-tension high-stability light and small constant force device as claimed in claim 1, wherein the positive stiffness of the coil spring is determined by the negative stiffness of the non-linear spring, and the negative stiffness value of the non-linear spring is obtained by fitting the load-displacement curve corresponding to the optimal form.
6. A high-tension high-stability light and small constant force device as claimed in claim 1, wherein the length of the coil spring is changed by changing the screwing position of the adjusting nut on the screw thread of the slide rod, and the pre-adjusting force F of the coil spring is further changedaThe effect of changing the output constant force of the constant force unit is achieved.
7. A large-tension high-stability light and small constant-force device as claimed in claim 1, wherein one end of the pulling force rope is connected with the sliding block, the other end of the pulling force rope passes through the rope outlet hole of the top plate and goes around the fixed pulley on the top plate of the bounding box, the pulling force direction of the pulling force rope can be changed through the fixed pulley, the pulling force can be kept unchanged, and therefore the constant-force device can output constant force within the range of +/-45 degrees.
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