Adjustable fully compliant constant force guide device, its design method and adjustment

Abstract

The invention relates to an adjustable, fully flexible guide device with constant force, which enables the adjustment of a force operating point by changing the preload of flexible elements, an associated method for adjusting the device for a given force and for dimensioning the flexible elements of the guide device. The adjustable, fully compliant, constant-force guide device has a wide range of applications, including metrology, weighing technology, precision engineering, nanofabrication, biomedical engineering, sports and rehabilitation equipment, the automotive industry, and robotics.

Description

Field of the invention

[0001] The invention relates to an adjustable, fully flexible guide device with constant force, which enables the adjustment of a force operating point by changing the preload of flexible elements, an associated method for adjusting the device for a given force and for dimensioning the flexible elements of the guide device.

[0002] The adjustable, fully compliant, constant-force guide device has a wide range of applications, including metrology, weighing technology, precision engineering, nanofabrication, biomedical engineering, sports and rehabilitation equipment, the automotive industry, and robotics. State of the art

[0003] The compliant guide devices with constant force known from the state of the art exhibit a large movement for a small force change around a force operating point; thus, a small force change ΔF causes a large position change, i.e., a large displacement difference Δs. Their advantages include the elimination of the need for lubrication, no wear and no play, i.e., the elimination of undesirable backlash, as well as the possibility of miniaturization and very easy scalability. Furthermore, such devices are passive devices, which means that no additional control with sensors and actuators is required to ensure a constant force. This makes such devices cost-effective and easy to install [1].

[0004] Two variants for the design of fully compliant guide devices with constant force are known from the state of the art. In the first variant, a constant force is achieved by optimizing the shape of the compliant elements. A constant force is achieved by varying the cross-section, curvature, and material along the length of the element [2, 3]. Due to its complex structure, this variant is susceptible to production errors, which affect the quality of the device. Furthermore, adjustment of the force operating point is not possible with this variant.

[0005] In the second variant of the device, the constant force is achieved by combining compliant elements with positive and negative stiffnesses. These are designed so that the different stiffnesses of the elements balance each other out, creating a region with a constant force [4, 5]. Thus, the device has a stiffness, defined as the difference quotient ΔF / Δs (F - force, s - displacement), of zero and achieves a constant force over the considered range of motion Δs. By using a spring as a compliant element with positive stiffness (ΔF / Δs > 0), the force operating point can be adjusted based on the spring preload [6]. A disadvantage of this variant is that several different elements are required, which must be coordinated with each other. In addition, there is the problem that a classic spring in the device makes scalability (miniaturization) difficult or even impossible.While using compliant elements as springs can ensure a certain degree of miniaturization, this would result in a complex shape. Thus, this variant has similar disadvantages to the first one. Both variants require significant development effort to achieve a certain constant force for a given application.

[0006] The influence of the connection angle, length, and cross-section of the beam elements of a complex beam mechanism on its stiffness has already been investigated in the literature [7]. However, the results of these investigations only focus on a specific, fixed force operating point. Further investigations into the dependence of the parameters were not conducted, thus precluding application to an adjustable guide device with an adjustable force operating point.

[0007] Based on a literature search, [8] and [9] are the only sources known to the applicants that utilize the bending behavior under different clamping conditions to adjust the force operating point for a region with a constant force. In patent US11047458B1 [8], the area moment of inertia along the bending axis is changed by torsion to adjust the force operating point. To ensure movement in one plane, this method requires a rigid external frame. Thus, the device is not a purely flexible device. The means for adjusting the force operating point are located on the mechanism and are moved with it, resulting in higher energy consumption. This requires several components, which increases assembly effort and costs. In [9], the interaction of the angles of two elements relative to the direction of movement is used to adjust the force operating point.Not only the angle but also the length of an element must be adjusted at various points. This requires several flexible elements, each of which is individually controlled and coordinated with each other. This increases the potential for error and the control / regulation effort. Furthermore, the use of multiple elements leads to a more complex structure. The guide elements and the elements to be adjusted are functionally separate and are separate components.

[0008] The disadvantages of the adjustable compliant guide devices known from the prior art can be summarized as follows: The guide devices have complex shapes and structures, and their design requires complex and time-consuming design processes, which makes easy scalability difficult, particularly because of the presence of rigid body elements. None of the devices has the means to adjust the force operating point in such a way that the guide elements and the elements to be adjusted are the same component. Furthermore, the known devices require several different compliant components that must be precisely coordinated with one another. Object of the invention

[0009] The object of the present invention is to provide a guide device that overcomes the disadvantages of the adjustable guide devices known from the prior art. The object also includes the provision of a method for designing and adjusting such a guide device. Solution to the task

[0010] The object of the invention is achieved by an adjustable, fully flexible guide device for guiding a table with the features specified in claim 1. Advantageous embodiments of the guide device are disclosed in subclaims 2 to 12. Furthermore, the object of the invention is achieved by a method for designing and adjusting such a guide device according to claim 13.

[0011] The term "stage" is to be interpreted broadly in this application. It encompasses any platform that is movable in one spatial direction (x), i.e., linearly; in two spatial directions (x, y), i.e., in a plane; or in three spatial directions (x, y, z), i.e., in three-dimensional space. This includes, for example, xy translation stages (xy stages), which allow precise positioning in the nm range in a plane.

[0012] As is common in the present technical field, compliant elements are also referred to in this application as beams or beam elements. Short description of the drawings Fig. 1 - Front view of a guide device with a rectangular cross-section table to be guided with mirrored flexible elements Fig. 2 - Top view of the guide device with the table to be guided with rectangular cross-section with mirrored flexible elements Fig. 3 - Top view of a guide device with a table to be guided with triangular cross-section with mirrored flexible elements Fig. 4 - Top view of a guide device with a table to be guided with a round cross-section with mirrored flexible elements Fig. 5 - Front view of a guide device with a rectangular cross-section table to be guided with flexible elements attached below the table Fig. 6 - Top view of the guide device with the table to be guided with a rectangular cross-section and flexible elements attached below the table Fig. 7 - Front view of a guide device with a rectangular cross-section table for zero-force applications Fig. 8 - Front view of a guide device with a table to be guided with a rectangular cross-section with a slight angular deviation φ of the guide device from the guide direction Fig. 9 - Characteristic curve of the guide device with slight angular deviation φ from the guide direction Fig. 10 - Front view of a guide device with a table to be guided with a rectangular cross-section with an angle of inclination ζ of the frame relative to the direction orthogonal to the guide direction Fig. 11 - Front view of a guide device with a table to be guided with a rectangular cross-section with movable fastening point of the flexible elements parallel to the guide direction Fig. 12 - Basic design of the adjustable fully flexible guide device with constant force (free on one side, with a straight flexible element) Fig. 13 - Basic design of the adjustable, fully compliant guide device with constant force (clamped, smaller force operating point) Fig. 14 - Basic design of the adjustable, fully compliant guide device with constant force (clamped, larger force operating point) Fig. 15 - Rectangular cross-section of a flexible element Fig. 16 - Round cross-section of a flexible element Fig. 17 - Characteristic curve for minimum and maximum force operating point Fig. 18 - Flowchart of the procedure for dimensioning the compliant elements and determining their number for the adjustable, fully compliant, constant force guide device Detailed description of the solution

[0013] The invention is explained in detail below using the drawings described above.

[0014] The basic idea of ​​the fully compliant, constant-force guide device considered here is the use of simple, preferably straight, compliant elements with a constant cross-section. The constant force is achieved by utilizing the preload of the compliant elements by adjusting the connection distance to the table and the connection angle to the frame, taking into account the dimensions of the compliant elements.

[0015] The fully compliant guide device with constant force according to the invention comprises one or more flexible elements with a constant cross-section. The guide device obtains its function solely through the flexibility of these elements, which is why it is referred to as a fully compliant guide device. These elements are preferably constructed in a similar manner and are suitable for guiding a table. The elements are preferably manufactured straight, but are used in the clamped state in the guide device and generally assume a curved shape. The use of straight, flexible elements has the advantage that a guide device equipped with such straight elements is simple and cost-effective to manufacture and particularly easy to dimension, as explained in detail in exemplary embodiments 1 and 2.The flexible elements can also be designed pre-bent, but the dimensioning of the guide device is then much more complicated and requires an additional adjustment of the parameters connection angle β and connection distance p, which results in an additional calculation effort for each radius of curvature (see example 3).

[0016] If several flexible elements are used, they are preferably arranged in parallel in groups. The flexible elements are each firmly connected to the table to be guided at one end. Flexible elements are firmly connected to the table on at least two sides of the table. Each flexible element is thus firmly connected to the table to be guided at one end. The end of the flexible element is perpendicular to the side of the table, so that the connection is orthogonal to the guide direction of the table. The other end of the element is connected to the frame at a connection distance p from the table, measured orthogonal to the guide direction. This connection is designed such that a connection angle β is created between the frame and the tangent to the end of the flexible element.The parameters p and β are adjustable by providing a mechanism on the frame for each flexible element. This mechanism consists of sliding and rotating joints with actuators or is designed as a mechanism, preferably with only a single actuator. This mechanism connects the flexible element to the frame and ensures the adjustment of a characteristic curve of the guide device by changing the connection distance to the table and the connection angle to the frame. The characteristic curve of the guide device with constant force describes the relationship between the travel s of the table and the force F in the same direction; it is therefore a force-displacement characteristic curve. The adjustment of the characteristic curve can also take place during operation of the guide device, e.g., when objects of different weights are placed on the table. The dimensions of the flexible elements determine the movement and force working range of the guide device.The connection distance and connection angle determine the force operating point. Depending on the selected dimensions of the compliant elements, the force operating point can range from nano-newtons to kilo-newtons, making the device suitable for applications such as force compensation, force limitation, and force measurement in both nanofabrication and robotics.

[0017] The characteristic curve of a guide device with constant force typically consists of three regions. In the first region, the curve rises; in the next region, a constant force is established, forming a plateau; and in the last region, the curve rises again. In the middle of the second, almost horizontal region, the plateau, is the point with the force value, which is referred to as the force operating point. This lies in the middle of the travel range with a nearly constant force curve, which is the travel range for the constant force, referred to as the range of motion. The range of motion therefore extends across the plateau.

[0018] If the connection distance p is smaller than the length of the flexible element and the connection angle β # π, the flexible element will bend, which preloads the flexible element. Reducing the connection angle β and / or increasing the connection distance p increases the stiffness of the flexible element and thus of the entire guide device. By correctly selecting the connection distance p and the connection angle β, deformations can be found that result in a region of zero stiffness, i.e., a stiffness ΔF / Δs = 0, and thus a constant force distribution.

[0019] Likewise, a suitable connection angle can be found for different connection distances, resulting in a range of motion in which the stiffness is zero. Smaller connection distances result in greater curvatures of the flexible element. Thus, larger forces are required in the guide direction to move the flexible elements in the guide direction. This also increases the force operating point. Thus, it is possible to adjust the force operating point by changing the connection distance and the connection angle without changing the dimensions of the flexible element.

[0020] The fully compliant, constant-force guide device can contain a varying number of compliant elements. If only one element is used, additional frictionless or low-friction guidance of the table is required. Two or more elements are attached to the table in such a way that all reaction forces and moments cancel each other out in all directions orthogonal to the guide direction. This is achieved as follows: If the compliant elements are attached to two sides of the table, an arrangement should be chosen that results from a mirror image or from rotating the elements through an angle of 180° around an axis parallel to the guide direction. The elements can also be attached to three, four, or more sides / areas of the table and in groups. Here, too, the positions of the elements for each side / area of ​​the table should be grouped, e.g.by reflection or by rotation around the axis parallel to the guide direction at an angle of 360° / m, where m is the number of sides / areas on the table. The term "area" here refers to tables that do not have straight sides, e.g., round or elliptical tables or sections of one side of a table. Possible arrangements are shown in . Fig. 1 to Fig. 4. Here, Fig. 1 shows the front view of a guide device with six flexible elements 3. The elements 3 form two groups of three elements 3 each, which are attached at one end in a mirror-symmetrical manner to two opposite sides of a rectangular table 4 to be guided. The second end of the flexible elements 3 is each connected to a section of a frame 2. This connection is realized using a means 8, which is movable along the respective section of the frame 2. The sections of the frame 2 are also positioned in a mirror-symmetrical manner on both sides of the table 4, without being directly connected to it. On each side, three sections of the frame 2 are positioned parallel to each other at a distance 6. The position of the means 8 sets a connection distance p and a connection angle β, thereby adjusting the stiffness of the flexible elements 3.The table 4 can be moved with a constant force F within a range of motion between the stops 5a and 5b. By shifting the means 8, the connection distance p and the connection angle β, and thus the rigidity of the flexible elements 3, can be changed, allowing the magnitude of the constant force F, i.e., the force operating point of the guide device, to be adjusted. This will be explained in more detail in Example 1. Fig. 2, Fig. 3 and Fig. 4 show the guide device from above for rectangular, triangular and round tables 4. In these, an additional force is realized by an object 10 positioned on the table 4. It is also possible to mount the elements 3 below the table 4. This leads to smaller dimensions of the flexible guide device. Such an arrangement is shown in Fig. 5 from the front and in Fig. 6 from above. In the view from above ( Fig. 6), the table 4 is indicated only by two side edges. This reveals two groups of four flexible elements 3 located below the table 4, which are connected to two opposite sides of the table 4. In Fig. 5 the elements of a group are hidden. In Fig. 6, the sections of the frame 2 are covered by the flexible elements 3.

[0021] If the flexible elements are mirrored with respect to the plane orthogonal to the guide direction and all elements are additionally preloaded in the guide direction up to the force working point, a guide with zero force F is achieved with a negligible weight of the table or with additional compensation of its weight. Null realized (F Null = 0). Such an embodiment is shown in Fig. 7. The elements 3 connected to the left side of the table 4 exert a force F on the table 4. The elements 3 connected to the right side of the table 4 exert an oppositely directed but equal force -F on the table 4, so that a force F Null = 0 results. Table 4 can thus be moved force-free in the guide direction. The weight of the table is negligible if the connection distance is not distorted by more than 5%. Compensation for the table weight can be achieved by orienting the guide direction of the table horizontally, whereby additional low-friction guidance of the table, for example, by means of a mechanism that can move almost horizontally, is necessary.

[0022] Preferably, the guide direction should be parallel to gravity, with the frame horizontal. A slight deviation ±φ of the table (5%) from the guide direction, which should be orthogonal to the frame (or of the frame from the horizontal position), as shown in Fig. 8, is permissible, especially if the groups of flexible elements are arranged on opposite sides / areas of the table. In this case, the inaccuracies in the characteristic curves of opposing elements cancel each other out, resulting in the desired characteristic curve with constant force. This is also shown by the force-displacement diagram in Fig. 9. The halved sum of the force-displacement relationship with the positive deviation +φ and the force-displacement relationship with the negative deviation -φ is almost identical to the force-displacement relationship without deviation (φ = 0). Thus, the adjustable, fully compliant guide device with constant force is invariant with respect to a slight inclination of the frame.

[0023] If an additional angle ζ is set for the frame, as in Fig. 10, the range of motion receives a proportional angle ζ d to the force axis in the force-displacement diagram Fig. 17. This changes the force-displacement relationship within the range of motion. With a suitable choice, the behavior with the constant force can be improved across the entire force range, resulting in a smaller force deviation within the range of motion. A similar effect can also be achieved if the means 8 for adjusting the connection distance p and angle β has an additional distance 9 that can be adjusted in the vertical direction, as shown in Fig. 11. This allows the position of the range of motion in the force-displacement diagram Fig. 17 can be moved left or right.

[0024] To avoid exceeding the range of motion, stops can be used to mechanically limit the range of motion. In the arrangement according to Fig. 1, the stops 5a and 5b limit the upper and lower ranges of motion, respectively. This ensures that the permissible elongations of preloaded flexible elements are not exceeded. List of reference symbols and formula symbols 1 parallel guide 2 frames 3 Flexible element 4 tables 5 characters 6 Distance between sections of the frame 7 Range of motion 8 remedies 9 Distance of the frame to the base position 10 objects 11 Force working point p connection distance β connection angle L beam length h beam height b Bar width R beam radius E Elastic modulus σ allowable stress F force operating point F min minimum force operating point F max maximum force operating point F̃ dimensionless force constant I z Area moment of inertia of z-axis I y Area moment of inertia of y-axis r radius of curvature n number of bars M̃ dimensionless moment constant ζ Angle of the frame ζ d angle proportional to ζ φ Deviation of the table from the guide direction Σ halved sum Example 1

[0025] In Fig. 12 to Fig. 14 shows a flexible element 3. This element is connected on one side to a table 4 to be guided, which is supported by an additional frictionless parallel guide 1. The element is connected to the table 4 in a direction orthogonal to the guide direction. On the other side, it is connected to the frame 2 via a means 8 for adjusting the connection distance and angle. The frame 2 is positioned orthogonal to the guide direction.

[0026] The preferred connection distance p lies in the range p ∈ [0.5 L; 0.85 L], where L is the length of the flexible element. The parallel guide should preferably be selected with negligible friction. Friction-free guidance without additional friction-free parallel guide can be achieved, for example, by a symmetrical design of the flexible elements. This cancels out forces orthogonal to the direction of movement and moments acting on table 4. The relationships (F1), (F2), (F4), and (F7) are represented by polynomials. It is not excluded that other forms of mathematical relationships exist between the parameters, as long as similar values ​​result for the parameters involved. All calculation methods are given in SI units. Quantities marked with a tilde are dimensionless.

[0027] For the guide device under consideration, for each connection distance p there is a connection angle β at which the guidance with constant force occurs. Fig. 13 is a flexible element for a small force working point 11 (see Fig. 17) and in Fig. 14 for a large force operating point 11. The connection distance p and the connection angle β must have a relationship that can be described by the following polynomial: β(p)=a1L2p2+a2Lp+a3

[0028] The polynomial coefficients are preferably in the intervals: a1 ∈ [1.98; 2.52]; a2 ∈ [-0.12; 0.6]; a3 ∈ [-0.14; 0.098]. Polynomial coefficients of a1 = 2.248; a2 = 0.2363; a3 = -0.0223 are particularly preferred.

[0029] The range of motion 7 begins at the same level as the connection point of the flexible element 2 on the frame, measured orthogonally to the guide direction. Outside the range of motion, increased stiffness occurs. The characteristic curves are for a maximum F max and a minimal F min Force working point in Fig. 17. The maximum force operating point F max preferably less than 2.3 times the minimum force operating point F min Between the curves shown, the force operating point F can be adjusted by adjusting the connection distance p and the connection angle β. The force operating point F and the connection distance p are subject to a relationship that can be represented in polynomial form: p(F)=b1LF˜2FminF2+b2LF˜FminF+b3L

[0030] The polynomial coefficients preferably lie in the intervals b1 ∈ [0.00029; 0.00048]; b2 ∈ [-0.048; -0.043]; b3 ∈ [1.14; 1.17] . Polynomial coefficients of b1 = 0.000385; b2 = -0.04547; b3 = 1.156 are particularly preferred.

[0031] For a maximum connection distance p of 0.85 times the length L, the force constant F̃ preferably lies in the range F̃ ∈ [7.0525; 7.2171] with a particularly preferred value of F̃ = 7.08105. Each different maximum connection distance corresponds to a different force constant.

[0032] In order to maintain a constant force within the range of motion 7, the length L of the flexible element should be significantly longer than the range of motion 7, preferably as follows: L≥10.15⋅Range of motion 7

[0033] To prevent bending outside the considered plane, the area moment of inertia I zof the cross-section of the element around the axis parallel to the guide direction must be significantly smaller than the area moment of inertia I y around the orthogonal axis. In addition, the cross-sectional dimensions should be significantly smaller, preferably ten times smaller, than the length and the radius of curvature r of the loaded flexible element (slenderness condition). For rectangular or round cross-sections, the y- and z-axes are in Fig. 15 or Fig. 16. The maximum radius of curvature r is subject to the following relationship: r(F˜)=c1LFmaxF˜4Fmin+c2LFmaxF˜3Fmin+c3LFmaxF˜2Fmin+c4LFmaxF˜Fmin+c5L.

[0034] The polynomial coefficients are preferably in the intervals: c1 ∈ [7,45 * 10 -06 ; 1.053 * 10 -05 ]; c2 ∈ [-0.00061; -0.00045]; c3 ∈ [0.01; 0.014]; c4 ∈ [-0.15; -0.12]; c5 ∈ [0.75; 0.81] . Polynomial coefficients of c1 = 8.993e ​​are particularly preferred. -06; c2 = -0.0005298 ; c3 = 0.01219; c4 = -0.136; c5 = 0.7778 .

[0035] The following relationship is used to determine the cross-sectional dimensions for an area of ​​force working points 11: Iz=FminL2F˜En

[0036] Here, E is the elastic modulus of the material of the flexible element and n is the number of elements attached in parallel to table 4.

[0037] At high force operating points with short lengths of flexible elements, conflicts with the slenderness condition may occur. In this case, the number n of flexible elements can be increased. It must be noted that the flexible elements are loaded in parallel. The higher number of elements reduces their cross-sectional dimensions and thus the area moment of inertia. When arranging the flexible elements, the bending of the beams must be taken into account. The connections to frame 2 should therefore have at least a preferred distance 6, see Fig. 1, of 0.35 times the length of the flexible element in the direction of movement.

[0038] In order to guarantee pure elastic deformation, the following must also apply to a rectangular or round cross-section: h2≤σLM˜E or R≤σLM˜E

[0039] Where σ is the allowable stress of the material, h is the height of the cross section or R is the radius of a round cross section, s. Fig. 15 or Fig. 16, and M̃ results from M˜(F˜)=d1FmaxF˜2Fmin+d2FmaxF˜Fmin+d3

[0040] The polynomial coefficients preferably lie in the intervals: d1 ∈ [-0.011; -0.0098]; d2 ∈ [0.58; 0.61]; d3 ∈ [0.093; 0.2]. Polynomial coefficients of d1 = -0.01025; d2 = 0.5952; d3 = 0.1428 are particularly preferred.

[0041] Using relationships (F3) to (F7), a method can be defined that allows the dimensions and number of the compliant elements to be determined. These make up the adjustable, fully compliant guide device with constant force. Such a method is described in Fig. 18 is shown schematically using a flow chart. The input for the development of the guide device is the range for the force operating points F ∈ [Fmin ; F max] , i.e. the force working range, which should be greater than zero, the movement range 7, which should be greater than zero, the number n ∈ ℕ of the flexible elements and the elastic modulus E as well as the permissible stress σ of the material of the flexible elements. Using these values, the length L of the elements according to (F3), the dimensionless moment constant M̃ according to (F7), the maximum radius of curvature r according to (F4) and the maximum value for h or R according to (F6) are determined. The inputs and the desired values ​​can be freely selected. The order of the determinations should then only be followed to the extent that the parameters required in the relationships are calculated first. In this way, the cross-sectional dimensions can be determined using the area moment of inertia I zaccording to (F5). The slenderness conditions are then checked. If these are not met and it turns out that the parameter h or R is too large, it is reduced; otherwise, the number n of elements is increased. If the slenderness conditions are met with the determined cross-sectional dimensions, they can be accepted.

[0042] The procedure for setting the force operating point 11 consists in determining the connection distance p(F) according to (F2) and the connection angle β(p) according to (F1). Any beam can be used as a flexible element as long as it meets the slenderness conditions, has a constant cross-section over its length L, and does not exceed the allowable stresses σ during deformation. The cross-sectional dimensions of flexible elements, their length L, as well as the elastic modulus E and allowable stresses σ are then known. By rearranging (F5), the minimum force operating point F can be determined. min The maximum force operating point F max results from (F6) with (F7), the slenderness conditions taking into account (F4) and the preferred force working range F min < F max < 2.3F min. During application of the adjustable constant force compliant guide device, the connection distance and the connection angle can also be adjusted according to (F2) and (F1) to set a desired force operating point 11. Example 2

[0043] A typical cross-section of flexible elements is rectangular. In particular, a cross-section with a width b that is significantly greater than the height h of a flexible element fulfills the requirements for deformation in a plane and leads to the linear guide movement of the table. The calculation formulas for the width b and height h are derived from the calculation formulas (F5) and (F6) for the area moment of inertia and the elastic limit of motion: h≤2σLM˜E b=12FminL2F˜Eh3n

[0044] To meet the slimming conditions, the following should preferably be met: h≤r10;h≤L10 b≤r10; b≤L10

[0045] As in Example 1, the number of elements can be increased to meet the slenderness requirements. Example 3

[0046] By using pre-bent, compliant elements, the maximum stress in the element can be reduced within the range of motion. The compliant element should preferably have a curvature similar to that of a straight element with the same dimensions in the pre-loaded state, which corresponds to the desired force operating point. To reduce deviations from the constant force characteristic curve, the radius of curvature and / or at least one parameter setting (connection angle β, connection distance p) must be adjusted. For significantly deviating curvatures, an adjustable constant force can no longer be guaranteed. Advantages of the invention • Elimination of lubrication • no wear and play • easy scalability • no regulation necessary • simple beam shape, thus easier production and assembly • Similar flexible elements can be used simultaneously as guide elements and adjustable elements • low sources of production errors • Simple and quick design of the device using simple calculation formulas • adaptable to changing environmental conditions • versatile areas of application Industrial applicability

[0047] The adjustable, fully compliant, constant-force guide device has a wide range of applications: metrology, weighing technology, precision engineering, nanofabrication, biomedical engineering, sports and rehabilitation equipment, automotive industry, robotics, etc.

[0048] One example of the application of a constant-force guide device is gravitational compensation. Here, the device is designed so that the force operating point of the table to be moved (even with an object) is at the value of its gravity. Thus, the compliant elements are preloaded by the table's gravity, and the potential energy is added to the system by the table's gravity. Moving the table within the specified range of motion then requires hardly any energy. This is ideal for use in nanopositioning machines. Since the objects to be moved on the table can have different weights, a device is required that can be adjusted to different force operating points. This is achieved by adjusting the connection distance and the connection angle using a suitable tool.

[0049] The adjustable, fully compliant guide device can also be used to determine the weight of an object. An object is placed on the table, then all compliant elements are adjusted (connection distance and angle) until the force operating point is reached. By reading the adjustment and position of the table with the object, the weight of the object can be determined. This means that the guide device can also be used in weighing technology.

[0050] Another application is force limitation. To avoid injuring people or damaging objects, it is important in robotics or medical technology not to exceed a maximum force within a specified range of motion. The required constant force between a work object guided by the guide device and the person or object being processed can vary depending on the application and can be adjusted using this device.

[0051] Furthermore, the fully compliant guide device with constant force can be used in sports and rehabilitation equipment. To load muscles with the same force over a given range of motion, a compliant guide device with constant force is required. The adjustable force working point also allows for adaptation to different training forces. Cited literature [1] Howell, Larry L.; Magleby, Spencer P.; Olsen, Brian M. (2013): Handbook of Compliant Mechanisms. S. 6. DOI: 10.1002 / 9781118516485. [2] Rahman, Minhaz Ur; Zhou, Hong (2014): Design of Constant Force Compliant Mechanisms. In: INTERNATIONAL JOURNAL OF ENGINEER-ING RESEARCH & TECHNOLOGY (IJERT) 3 (7), S. 14-19. DOI: 10.17577 / IJERTV3IS070028. [3] Radaelli, G.; Herder, J. L. (2017): Gravity balanced compliant shell mechanisms. In: International Journal of Solids and Structures 118-119, S. 78-88. DOI: 10.1016 / j.ijsolstr.2017.04.021. [4] Tong, Zongdi; Zhang, Xiaozhi; Wang, Guangwei (2023): Automatic Optimization for Compliant Constant Force Mechanisms. In: Actuators 12(2) (61). DOI: 10.3390 / act12020061. [5] Hoetmer, Karin; Woo, Geoffrey; Kim, Charles; Herder, Just (2010): Negative Stiffness Building Blocks for Statically Balanced Compliant Mechanisms: Design and Testing. In: Journal of Mechanisms and Robotics 2 (4), Artikel 041007. DOI: 10.1115 / 1.4002247. [6] Wu, Yi-Syuan; Lan, Chao-Chieh (2014): Linear Variable-Stiffness Mechanisms Based on Preloaded Curved Beams. In: Journal of Mechanical Design 136 (12), Artikel 122302. DOI: 10.1115 / 1.4028705. [7] Tong, Zongdi; Zhang, Xiaozhi; Wang, Guangwei (2023): Automatic Optimization for Compliant Constant Force Mechanisms. In: Actuators 12(2) (61). DOI: 10.3390 / act12020061. [8] Hasara, Steven Lawrence; Lusk, Craig Perry (2019): Load-adjustable constant-force mechanisms. Veröffentlichungsnr: US11047458B1. [9] Tolman, Kyler A.; Merriam, Ezekiel G.; Howell, Larry L. (2016): Compliant constant-force linear-motion mechanism. In: Mechanism and Machine Theory 106, pp. 68-79. DOI: 10.1016 / j.mechmachttheory.2016.08.009. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] US 11047458B1

[0007] Cited non-patent literature

[0000] Howell, Larry L.; Magleby, Spencer P.; Olsen, Brian M. (2013): Handbook of Compliant Mechanisms. P. 6. DOI: 10.1002 / 9781118516485

[0051] Rahman, Minhaz Ur; Zhou, Hong (2014): Design of Constant Force Compliant Mechanisms. In: INTERNATIONAL JOURNAL OF ENGINEER-ING RESEARCH & TECHNOLOGY (IJERT) 3 (7), S. 14-19. DOI: 10.17577 / IJERTV3IS070028

[0051] Radaelli, G.; Herder, J. L. (2017): Gravity balanced compliant shell mechanisms. In: International Journal of Solids and Structures 118-119, S. 78-88. DOI: 10.1016 / j.ijsolstr.2017.04.021

[0051] Tong, Zongdi; Zhang, Xiaozhi; Wang, Guangwei (2023): Automatic Optimization for Compliant Constant Force Mechanisms. In: Actuators 12(2) (61). DOI: 10.3390 / act12020061

[0051] Hoetmer, Karin; Woo, Geoffrey; Kim, Charles; Herder, Just (2010): Negative Stiffness Building Blocks for Statically Balanced Compliant Mechanisms: Design and Testing. In: Journal of Mechanisms and Robotics 2 (4), Artikel 041007. DOI: 10.1115 / 1.4002247

[0051] Wu, Yi-Syuan; Lan, Chao-Chieh (2014): Linear Variable-Stiffness Mechanisms Based on Preloaded Curved Beams. In: Journal of Mechanical Design 136 (12), Artikel 122302. DOI: 10.1115 / 1.4028705

[0051] Hasara, Steven Lawrence; Lusk, Craig Perry (2019): Load-adjustable constant-force mechanisms. Veröffentlichungsnr: US11047458B1

[0051] Tolman, Kyler A.; Merriam, Ezekiel G.; Howell, Larry L. (2016): Compliant constant-force linear-motion mechanism. In: Mechanism and Machine Theory 106, S. 68-79. DOI: 10.1016 / j.mechmachtheory.2016.08.009

[0051]

Claims

[1] Adjustable fully flexible guide device for guiding a table (4) with constant force along a guide direction in a movement range (7), comprising a frame (2), at least one flexible element (3), at least one means (8) for adjusting a prestress state of the at least one flexible element (3), characterized by that one end of the at least one flexible element (3) can be connected to the table (4) orthogonally to its guide direction and the other end of the at least one flexible element (3) is connected to the frame (2) via the means (8), so that with the help of the means (8) a connection distance p to the table (4) and a connection angle β to the frame (2) can be adjusted, whereby a prestress state of the at least one flexible element (3) and a force working point (11) of the guide device can be adjusted. [2] Guide device according to claim 1 characterized bythat the frame can be positioned orthogonally to the guide direction of the table (4). [3] Guide device according to claim 1 or 2, characterized by that it has one or more flexible prestressed elements (3) for connection to one side of the table (4) and an additional parallel guide (1) for the table (4). [4] Guide device according to claim 1 or 2, characterized by that it has several flexible prestressed elements (3) which are arranged in such a way that all reaction forces and moments cancel each other out in all directions which are orthogonal to the guide direction. [5] Guide device according to claim 1, characterized by that several flexible elements (3) are arranged in groups in at least two groups, wherein the flexible elements (3) of each group have in total the same cross-sectional area and are arranged either mirrored or rotationally symmetrically. [6] Guide device according to claim 5, characterized by that a force-free guidance is achieved by at least two groups of flexible elements (3) prestressed up to the force working point (11), which are mirrored with respect to a plane orthogonal to the guidance direction. [7] Guide device according to claim 5, characterized by that a slight angular deviation φ of the guide direction from the orthogonality to the frame (2) is compensated by the groups of flexible elements (3) being able to be arranged on opposite sides of the table (4). [8] Guide device according to claim 5, characterized by that the frame (2) can be tilted by an additional angle ζ relative to its horizontal position, whereby the range of motion (7) of the table (4) is tilted proportionally to the angle ζ and a smaller force deviation in the range of motion is achieved. [9] Guide device according to claim 5, characterized bythat the means (8) for adjusting the connection distance p and the connection angle β additionally has a distance (9) from the frame (2) which can be adjusted in the vertical direction, whereby the position of the movement area (7) of the table (4) can be displaced with constant force along the guide direction. [10] Guide device according to one of claims 1 to 5, characterized by that it can be connected to a table (4) with small or negligible mass, so that the frame (2) can be positioned in any orientation in space. [11] Guide device according to one of claims 1 to 10, characterized by that it has mechanical stops (5a, 5b) in order not to exceed a predetermined range of movement (7) for the table (4). [12] Guide device according to one of claims 1 to 11, characterized by that the flexible elements (3) are straight in the non-prestressed state. [13] Method for dimensioning and adjusting a guide device according to claim 12, characterized by following steps: a) Dimensioning of the flexible elements and determining their number by specifying a force range of a force working point using the formulas (F3) to (F7): L≥10.15⋅Range of motion 7 r=c1LFmaxF˜4Fmin+c2LFmaxF˜3Fmin+c3LFmaxF˜2Fmin+c4LFmaxF˜Fmin+c5L IZ=FminL2F˜En h2≤σLM˜E or R≤σLM˜E M˜=d1FmaxF˜2Fmin+d2FmaxF˜Fmin+d3 b) Adjustment of the flexible elements before or during use of the guide device by changing the connection angle β and the connection distance p according to formulas (F1) and (F2): β=a1L2p2+a2Lp+a3 p=b1LF˜FminF2+b2LF˜Fmin+b3L whereby each force operating point from the specified force range can be set. [14] Table (4) equipped with a guide device according to one of claims 1 to 12. [15] Use of the guide device according to one of claims 1 to 12 and / or the table (4) according to claim 14 for moving the table (4) with an optional object (10) located on the table (4) with constant force for gravitational compensation, for force limitation, in nanopositioning machines, in force measuring and weighing technology for determining mass, in robot and gripper technology, in medical technology and for force adjustment in sports and rehabilitation equipment.

Images