Two-finger flexible clamp holder with clamping force and friction coefficient cooperatively regulated and controlled

Abstract

The invention provides a two-finger flexible clamp holder with clamping force and friction coefficient cooperatively regulated and controlled. Microtexture profile curves of two friction surfaces, used for clamping, of the two-finger flexible clamp holder are composed of two cosine waves with different amplitudes and the same wavelength; different radial forces are applied to a clamped object, and the purpose of cooperatively adjusting the friction coefficient is achieved through the change of the total contact area of the friction surface and the clamped object. When the two-finger flexible clamp holder applies different radial forces, the total contact area of the friction surface and a clamped object also changes, the friction coefficient is cooperatively adjusted, the two technical requirements of skid resistance and damage prevention can be met at the same time, the two-finger flexible clamp holder adapts to different clamped objects, and the clamping performance is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of clamping devices, and more particularly, to a two-finger flexible gripper with coordinated regulation of clamping force and friction coefficient. Background Art

[0002] Robotics has gained great popularity and has the potential to achieve countless outstanding tasks. Manipulation plays a key role in the field of robotics and constitutes an emerging and complex field. In modern times, a variety of materials, actuators, and manufacturing technologies have been adopted to develop grippers. In previous studies, robotic grippers can be roughly divided into two main categories: rigid types and flexible grippers.

[0003] As a key component of the robotic end effector, flexible grippers are widely used in industrial automation, medical surgery, logistics sorting, and other fields, especially suitable for grasping fragile, soft, or irregularly shaped objects (such as food, precision electronic components, soft tissues, etc.). However, traditional flexible grippers mostly rely on the friction characteristics of the material itself or a preset clamping force mode, and the friction coefficient cannot be dynamically adjusted, resulting in limited adaptability to object shapes and materials and difficulty in balancing the two requirements of anti-slip and anti-damage. For example, when grasping smooth, wet, or highly elastic objects, if the friction coefficient is low, it is easy to slip due to insufficient friction force, and the clamping force needs to be increased, but this is likely to cause damage to the object. Such flexible grippers are preferably used with a high friction coefficient; but for objects with a fragile surface, a friction surface with a high friction coefficient is likely to cause scratches and damage to the object.

[0004] With the development of intelligent processing technology, equipment tends to be integrated with multiple functions and needs to clamp a variety of objects. Currently, it is usually necessary to stop the machine to replace the gripper to adapt to different objects, which not only reduces the operation efficiency but also hardly meets the technical requirements of intelligent recognition and adaptive processing. Therefore, there is an urgent need to develop a flexible gripper with the function of adjustable friction coefficient. In addition, if the friction coefficient can be accurately regulated, the clamping performance can be significantly improved, but the current related technical solutions are not yet mature. Summary of the Invention

[0005] To overcome the deficiencies in the prior art, the purpose of the present invention is to provide a two-finger flexible gripper with coordinated regulation of clamping force and friction coefficient; when applying different radial forces, the total contact area between the friction surface and the clamping object also changes, coordinately adjusting the friction coefficient, which can simultaneously meet the two technical requirements of anti-slip and anti-damage, adapt to different clamping objects, and improve the clamping performance.

[0006] To achieve the above object, the present invention is realized through the following technical solutions: A two-finger flexible gripper for synergistically regulating the clamping force and the friction coefficient. The two friction surfaces for clamping of the two-finger flexible gripper have a micro-texture profile curve composed of two cosine waves with different amplitudes and the same wavelength; so as to realize applying different radial forces to the clamping object, and achieving the purpose of synergistically adjusting the friction coefficient through the change of the total contact area between the friction surface and the clamping object.

[0007] Preferably, the micro-texture profile curve of the friction surface is obtained by the following method:

[0008] Establish a model between the cosine wave profile and the friction coefficient; according to the model between the cosine wave profile and the friction coefficient, obtain the friction coefficient curves corresponding to multiple groups of micro-texture profile curve parameters;

[0009] According to the friction performance requirements of the clamping object, select the friction coefficient curve, and then obtain the corresponding micro-texture profile curve parameters. The micro-texture profile curve of the friction surface is expressed as z(x):

[0010] z(x) = m(x)·A1 cos(w0x)

[0011]

[0012] Wherein, A1 and A2 are the amplitudes of the two cosine waves respectively; w0 represents the angular frequency, m(x) is a modulation function; k1 = A2 / A1, and k1>1; N = n1 / n2; n1 and n2 are the numbers of the wave peaks of the two cosine waves within one period respectively; x represents the spatial coordinate position.

[0013] Preferably, establishing the model between the cosine wave profile and the friction coefficient means including the following steps:

[0014] S1. Calculate the curvature radii R1 and R2, and the deformation depths δ1 and δ2 of the two cosine waves at the wave peaks respectively;

[0015] S2. Set the contact half-widths a1 and a2 at the wave peaks of the two cosine waves respectively, and the contact area A τ1 and A τ2 ;

[0016] S3. Set the condition for judging whether the contact of the cosine wave peak with amplitude A1 is reached during the contact process with the clamping object;

[0017] S4. Use numerical methods to solve the contact load distribution during the contact process; when the wave peaks of the two cosine waves are both in contact, the load P is distributed between the wave peaks of the two amplitudes, and is solved according to the following equations:

[0018]

[0019] Among them, P1 and P2 are the load forces borne by a single micro-protrusion of two cosine waves respectively; l0 is the line contact length; E is the elastic modulus of the friction surface material;

[0020] The total contact area is expressed as: A cont = 2l0(n2·δ2 + n1·δ1);

[0021] During the contact process, the frictional force is expressed as: F = σA cont ;

[0022] Among them, σ is the friction strength;

[0023] The coefficient of friction is expressed as:

[0024] Preferably, the step S1 refers to:

[0025] In the micro-texture profile curve of the friction surface, the two cosine waves are respectively expressed as:

[0026]

[0027] Among them, λ is the wavelength of the two cosine waves;

[0028] Calculate the curvature radii R1 and R2, and the deformation depths δ1 and δ2 at the wave crests of the two cosine waves respectively:

[0029]

[0030] Preferably, the step S2 refers to:

[0031] Set the contact half-widths a1 and a2 at the peaks of the two cosine waves respectively as:

[0032]

[0033] The contact areas A τ1 and A τ2 at the peaks of the two cosine waves are:

[0034]

[0035] Preferably, in the step S3, the condition for judging whether the contact with the clamping object reaches the peak contact of the cosine wave with amplitude A1 is set as:

[0036] δ2 ≥ A2 - A1.

[0037] Preferably, the friction surface refers to a friction surface made of an elastic material.

[0038] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0039] 1. The two-finger flexible gripper of the present invention can change the total contact area between the friction surface and the gripping object while applying different radial forces, and cooperatively adjust the friction coefficient, which can simultaneously meet the two technical requirements of anti-slip and anti-damage, adapt to different gripping objects, and improve the gripping performance.

[0040] 2. Based on the mapping relationship between the cosine wave profile and the friction coefficient, the present invention realizes the prediction and control of the friction performance; according to the friction performance requirements of the gripping object, the target friction coefficient curve can be adaptively selected, and the micro-texture profile curve parameters of the friction surface can be set accordingly; there is a clear mapping relationship between the micro-textured friction surface and the load, which significantly improves the control accuracy and reliability of the flexible gripper during the gripping operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 is a schematic structural diagram of the two-finger flexible gripper for cooperative regulation of the gripping force and the friction coefficient of the present invention;

[0042] Figure 2 is a schematic structural diagram of the friction surface of the two-finger flexible gripper for cooperative regulation of the gripping force and the friction coefficient of the present invention;

[0043] Figure 3 is Figure 2 the sectional view taken along A-A in DETAILED DESCRIPTION OF THE INVENTION

[0044] The present invention will be further described in detail below in conjunction with the drawings and the specific embodiments.

[0045] Embodiment

[0046] As Figures 1 to 3 shown, in this embodiment, a two-finger flexible gripper for cooperative regulation of the gripping force and the friction coefficient, the two friction surfaces for gripping of the two-finger flexible gripper, the micro-texture profile curve is composed of two cosine waves with different amplitudes and the same wavelength; so as to realize applying different radial forces to the gripping object, and through the change of the total contact area between the friction surface and the gripping object, and further achieve the purpose of cooperatively adjusting the friction coefficient. The friction surface is uneven; when the applied radial force is small, the cosine wave with a large amplitude is higher, and it contacts the gripping object first, the contact surface is smaller, and the friction coefficient is smaller. When the applied radial force is large, both the cosine wave with a large amplitude and the cosine wave with a small amplitude will contact the gripping object, the contact surface is larger, and the friction coefficient is also larger.

[0047] The friction surface is made of an elastic material, for example, PDMS (polydimethylsiloxane) is used.

[0048] The micro-texture profile curve of the friction surface is obtained by the following method:

[0049] Establish a model between the cosine wave profile and the friction coefficient. Specifically, it includes the following steps:

[0050] S1. In the micro-texture profile curve of the friction surface, the two cosine waves are respectively expressed as:

[0051]

[0052] where λ is the wavelength of the two cosine waves; A1 and A2 are the amplitudes of the two cosine waves, and A1 > A2, so as to achieve different numbers of wave peaks contacted under different loads;

[0053] Calculate the curvature radii R1 and R2, and the deformation depths δ1 and δ2 at the wave peaks of the two cosine waves respectively:

[0054]

[0055] where P1 and P2 are the load forces borne by a single micro-protrusion of the two cosine waves respectively; l0 is the line contact length; E is the elastic modulus of the friction surface material.

[0056] S2. Set the contact half-widths a1 and a2 at the peaks of the two cosine waves respectively, and the contact area A τ1 and A τ2 :

[0057]

[0058] S3. Set the condition for judging whether the contact condition of the cosine wave peak with amplitude A1 is reached during the contact process with the clamping object as:

[0059] δ2 ≥ A2 - A1.

[0060] S4. Use numerical methods to solve the contact load distribution during the contact process; when the peaks of both cosine waves are in contact, the load P is distributed between the peaks of the two amplitudes and solved according to the following equations:

[0061]

[0062] where P1 and P2 are the load forces borne by a single micro-protrusion of the two cosine waves respectively; l0 is the line contact length; E is the elastic modulus of the friction surface material;

[0063] The total contact area is expressed as: A cont = 2l0(n2·δ2 + n1·δ1);

[0064] where n1 and n2 are the numbers of wave peaks of the two cosine waves in one period respectively;

[0065] During the contact process, the frictional force is expressed as: F = σA cont ;

[0066] where σ is the friction strength;

[0067] The friction coefficient is expressed as:

[0068] According to the model between the cosine wave profile and the friction coefficient, friction coefficient curves corresponding to multiple groups of micro-texture profile curve parameters are obtained;

[0069] According to the requirements of the gripping object for the friction performance, a friction coefficient curve is selected, and then the corresponding micro-texture profile curve parameters are obtained. The micro-texture profile curve of the friction surface is represented by z(x) as:

[0070] z(x) = m(x)·A1 cos(w0x)

[0071]

[0072] where A1 cos(w0x) is the basic cosine wave; w0 represents the angular frequency, m(x) is the modulation function; k1 = A2 / A1, and k1>1; N = n1 / n2; x represents the spatial coordinate position.

[0073] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A two-finger flexible gripper with coordinated regulation of clamping force and friction coefficient, characterized in that: The two friction surfaces for clamping of the two-finger flexible gripper, the micro-texture profile curve is composed of two cosine waves with different amplitudes and the same wavelength; so as to apply different radial forces to the clamping object, and through the change of the total contact area between the friction surface and the clamping object, and then achieve the purpose of synergistically adjusting the friction coefficient.

2. The two-finger flexible gripper with coordinated regulation of clamping force and friction coefficient according to claim 1, characterized in that: The micro-texture profile curve of the friction surface is obtained by the following method: Establish a model between the cosine wave profile and the friction coefficient; according to the model between the cosine wave profile and the friction coefficient, obtain the friction coefficient curves corresponding to multiple groups of micro-texture profile curve parameters; According to the friction performance requirements of the clamping object, select the friction coefficient curve, and then obtain the corresponding micro-texture profile curve parameters. The micro-texture profile curve of the friction surface is expressed as z(x): z(x) = m(x)·A1cos(w0x) where A1 and A2 are the amplitudes of two cosine waves respectively; w0 represents the angular frequency, m(x) is the modulation function; k1 = A2 / A1, and k1 > 1; N = n1 / n2; n1 and n2 are the numbers of the wave peaks of the two cosine waves within one period respectively; x represents the spatial coordinate position.

3. The two-finger flexible gripper with coordinated regulation of clamping force and friction coefficient according to claim 2, wherein: The establishment of the model between the cosine wave profile and the friction coefficient refers to the following steps: S1. Calculate the curvature radii R1 and R2 at the wave peaks of the two cosine waves, and the deformation depths δ1 and δ2 respectively; S2. Set the contact half-widths a1 and a2 at the peaks of the two cosine waves, and the contact areas A τ1 and A τ2 ; S3. Set the condition for judging whether the contact with the peak of the cosine wave with amplitude A1 is reached during the contact process with the clamping object; S4. Use numerical methods to solve the contact load distribution during the contact process; when the peaks of both cosine waves are in contact, the load P is distributed between the peaks of the two amplitude waves, and is solved according to the following equations: Where P1 and P2 are the load forces borne by a single micro-protrusion of the two cosine waves respectively; l0 is the line contact length; E is the elastic modulus of the friction surface material; The total contact area is expressed as: A cont = 2l0(n2·δ2 + n1·δ1); During the contact process, the frictional force is expressed as: F = σA cont ; Where σ is the friction strength; The coefficient of friction is expressed as:

4. The two-finger flexible gripper with coordinated regulation of clamping force and friction coefficient according to claim 3, wherein: The step S1 refers to: In the micro-texture profile curve of the friction surface, the two cosine waves are respectively expressed as: Where λ is the wavelength of the two cosine waves; Calculate the curvature radii R1 and R2 at the wave peaks of the two cosine waves, and the deformation depths δ1 and δ2 respectively:

5. The two-finger flexible gripper with coordinated regulation of clamping force and friction coefficient according to claim 3, wherein: The step S2 refers to: Set the contact half-widths a1 and a2 at the peaks of the two cosine waves respectively as: The contact area A at the peaks of the two cosine waves τ1 and A τ2 is as follows:

6. The two-finger flexible gripper with coordinated regulation of clamping force and friction coefficient according to claim 3, wherein: In the step S3, the condition for judging whether the contact with the peak of the cosine wave with amplitude A1 is reached during the contact process with the clamping object is set as: δ2≥A2 - A1.

7. The two-finger flexible gripper with coordinated regulation of clamping force and friction coefficient according to claim 1, wherein: The friction surface refers to a friction surface made of an elastic material.

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