CN110744577A

CN110744577A - Manipulator for controlling clamping deformation

Info

Publication number: CN110744577A
Application number: CN201911037133.5A
Authority: CN
Inventors: 雷华; 鲁阳
Original assignee: Zhejiang University ZJU
Current assignee: Zhejiang University ZJU
Priority date: 2019-10-29
Filing date: 2019-10-29
Publication date: 2020-02-04
Anticipated expiration: 2039-10-29
Also published as: CN110744577B

Abstract

The invention discloses a manipulator for controlling clamping deformation, which is used for a robot. The device consists of a frame, a coding screw rod, a clamp holder, a driver and a digital controller. The coding screw rod consists of a micrometer screw rod and a three-state coder, and the three-state coder comprises a fluted disc and four pairs of cantilever beam sensors. The gripper comprises two gripper arms. The coding screw rod and the clamper form a force-deformation-displacement composite sensing mechanism which is arranged on the frame and connected with the driver. When the device works, the digital controller controls the driver and the coding screw rod to rotate, the holder clamps an object, the composite sensing mechanism and the digital controller interactively transmit measurement and control signals, the clamping force and the distance between clamping points are measured in real time, and the deformation of the object is controlled.

Description

Manipulator for controlling clamping deformation

Technical Field

The design is a manipulator for controlling clamping deformation, and is used for industrial robots.

Background

The manipulator is a front-end operation mechanism of various robots including a large amount of automatic production, processing and detection equipment in the industrial field, and has the basic functions of picking and placing, namely grabbing, transferring and releasing objects. In the process of taking and placing, the clamping force of the manipulator to the object needs to be controlled. For many applications it is also desirable to control the deformation of the object caused by the clamping force and to achieve sufficient control accuracy. However, a robot having such a capability has been lacking so far.

Disclosure of Invention

The purpose of this design is to provide a manipulator of control centre gripping deformation for industrial robot. The manipulator clamps an object in a flexible mode, realizes measurement, measurement and control of clamping deformation through measurement, measurement and control of clamping force and clamping point distance, and can meet the requirements of common industrial measurement on load resolution and deformation resolution.

The manipulator of this design comprises frame, coding lead screw, driver, holder and digital control ware.

The structure of the frame comprises a rectangular substrate, a coupler, a left bearing support plate, a right bearing support plate and a U-shaped guide limiting groove, wherein the coupler is positioned below the substrate and used for connecting a robot arm, the left bearing support plate and the right bearing support plate are respectively positioned on the left side and the right side above the substrate, and the U-shaped guide limiting groove is positioned on the upper surface of the substrate. The left bearing support plate is embedded with a left bearing, the right bearing support plate is embedded with a right bearing, the two bearings are in coaxial positions, and the axis of the two bearings is parallel to the axis of the U-shaped guide limiting groove.

The coding screw rod consists of a micrometer screw rod and a three-state coder.

The micrometer screw rod is a double-thread step shaft, and the structure of the micrometer screw rod is divided into five sections of I-II, II-III, III-IV and IV-V, V-VI from left to right. The section I-II is an optical axis, the section II-III is a left-handed thread shaft, the section III-IV is a raised step shaft, the section IV-V is a right-handed thread shaft, and the section V-VI is also an optical axis. The length, lead and external diameter of the two thread sections are equal. The micrometer screw rod is arranged on the frame through the matching of the section I-II optical axis and the left bearing and the matching of the section V-VI optical axis and the right bearing, the section I-II optical axis extends to the left side of the left bearing support plate, and the section V-VI optical axis extends to the right side of the right bearing support plate.

The tri-state encoder consists of a fluted disc, a sensor bracket, a left upper cantilever beam sensor, a right upper cantilever beam sensor, a left lower cantilever beam sensor and a right lower cantilever beam sensor. The fluted disc is a disc with circular arc teeth distributed on the periphery and is fixed on the V-VI section optical axis of the micrometer screw rodAnd the number of the circular arc teeth is integral multiple of 4. The sensor bracket is a rectangular frame and is fixed at the upper right of the base plate of the frame, and the fluted disc is surrounded in the middle. The four sides of the sensor support are sequentially provided with a rectangular through hole and a threaded hole, wherein the axis of the rectangular through hole is parallel to the plane of the support and is vertical to the side of the support, and the threaded hole is vertically communicated with the rectangular through hole. The four cantilever beam sensors are the same in shape and size, the elastic bodies are uniform-section elastic beams or variable-section elastic beams, the roots of the four elastic beams are respectively matched with the four rectangular through holes of the sensor support, and the four cantilever beam sensors are fixed on the inner walls of the four sides of the sensor support by utilizing pressing force generated by screwing the set screws into the threaded holes. Four elastic beams are respectively stuck with a single-axis resistance strain gauge R along the axial direction of the beams at the positions close to the roots₅,R₆]、[R₇,R₈]、[R₉,R₁₀]And [ R ]₁₁,R₁₂]A left triangular ridge, an upper triangular ridge, a right triangular ridge and a lower triangular ridge are respectively machined on one side, which faces the fluted disc, near the free end. The four elastic beams are all pre-deformed by a certain amount, the tops of the four triangular convex edges are respectively kept in contact with the circular arc teeth on the periphery of the fluted disc by elastic pressure generated by pre-deformation, and the positions of contact points are determined according to the following conditions:

a. the longitudinal symmetry line of the fluted disc passes through the centers of the arc teeth right above and the arc teeth right below, and the horizontal symmetry line of the fluted disc passes through the centers of the arc teeth at the leftmost end and the arc teeth at the rightmost end.

b. At the moment, the left triangular ridge is positioned on the horizontal symmetry line of the fluted disc and is contacted with the vertex of the leftmost circular arc tooth. The right triangular ridge is positioned on the horizontal symmetry line of the fluted disc and the upper side of the rightmost circular arc tooth and is opposite to the valley bottom between the two adjacent circular arc teeth. The upper triangular ridge and the lower triangular ridge are both positioned on the right side of the longitudinal symmetry line of the fluted disc and are respectively contacted with the right side of the arc teeth right above and the right side of the arc teeth right below. H is used for distance from left triangular ridge to longitudinal symmetric line of fluted disc_maxThe distance from the right triangular ridge to the longitudinal symmetry line of the fluted disc is represented by h_minShowing the distance from the contact point of the upper triangular ridge and the right upper arc tooth to the horizontal symmetry line of the fluted disc and the lower triangular ridgeThe distances from the contact points of the ridge and the arc teeth under the ridge to the horizontal symmetry line of the fluted disc are equal, and the distance from the contact points of the ridge and the arc teeth under the ridge to the horizontal symmetry line of the fluted disc is h_midAnd (4) showing. h is_midAnd h_minAnd h_maxThere is a relationship represented by formula (1):

h_min、h_midand h_maxCollectively called the characteristic height, where h_minIs the minimum feature height, h_midIs the average feature height, h_maxIs the maximum feature height.

The driver is arranged on the left side of the left bearing support plate and is connected with the optical axis of the section I-II of the micrometer screw rod.

The clamp holder is composed of a left clamping arm and a right clamping arm, the two cantilever type elastic beam sensors are respectively connected with shaft sleeves at fixed ends, the materials, the shapes and the sizes are the same, a left limiting guide rod and a right limiting guide rod are respectively embedded at the bottoms of the two shaft sleeves, chucks are installed on the left side and the right side of the free end of the elastic beam, a left-handed transmission nut is embedded in the middle of the shaft sleeve of the left clamping arm, and a right-handed transmission nut is embedded in the middle of the shaft sleeve of the right clamping arm. The left clamping arm is matched with a left-handed threaded shaft of the micrometer screw rod through a left-handed transmission nut and is installed on the micrometer screw rod through a left-handed limiting guide rod and a U-shaped guiding limiting groove. The right clamping arm is matched with a right-handed threaded shaft of the micrometer screw rod through a right-handed transmission nut and is installed on the micrometer screw rod through a right limiting guide rod and a U-shaped guiding limiting groove. The two clamping arms are vertically upward and are in symmetrical positions. The two limiting guide rods are matched with the U-shaped guiding limiting groove to ensure that the two clamping arms cannot rotate around the axis of the micrometer screw rod. When the micrometer screw rod rotates, the two clamping arms are driven to move oppositely or reversely along the axis direction of the micrometer screw rod. The elastic beam of the clamp has two basic structural forms:

a) the fish hook-shaped folding beam structurally comprises a long arm a-c section, a folding joint a-d section and a short arm d-e section, wherein the cross sections of the three sections are all rectangular, the section c is a fixed end of the folding beam, and the a-d section is a rigid joint.

b) The structure of the straight beam is divided into a section a-b and a section b-c from top to bottom, the height H of the section a-b is larger than the height H of the section b-c, the section c is a fixed end of the beam, and the section a is a free end of the beam.

A single-axis resistance strain gauge R is attached to the left side and the right side of the elastic beam of the left clamping arm along the beam axis direction at the section b-c₂And R₁The elastic beam of the right clamping arm is pasted with a single-axis resistance strain gauge R along the beam axis direction at the left side and the right side of the section b-c₃And R₄。

The clamping head of the clamping device has three types of surface contact, line contact and point contact, and is selected according to the use requirement. The clamping head of the fishhook-shaped folding beam is arranged at the section e of the section d-e of the short arm. The chucks of the straight beam are arranged on the left side and the right side of the free end a. The distance between the left and right chucks, i.e. the distance between the clamping points, is indicated by s.

The purpose of using the fishhook-shaped folding beam is to design the holder according to the zero-corner condition of the chuck. The zero-rotation-angle condition of the chuck is as follows: the angle of rotation of the cartridge remains zero when the line of action of the clamping force of the fishhook-shaped fold beam coincides with the line of intersection of the longitudinal plane of symmetry of the beam (the x-y plane in figure 1) and the cross-section e. This condition can be achieved by coordinating the structural dimensions of the beam sections. For example, the widths b of the sections of the folded beam are equal, as shown in fig. 1; the sections b-c are of equal height to the sections d-e, i.e. h₁＝h₂H; the height H of the section a-b is more than or equal to 5H, so the section can be regarded as a rigid body. The length L of the a-c segment is the length L of the b-c segment ₁5 times of (i), i.e. L is 5L₁. According to the bending theory, under the condition of small linear elastic deformation, the relation formula can be obtained:

in the formula (2), l₂Is the length of the d-e segment. If L, l₁And l₂When the formula (2) is satisfied, the rotation angle of the cross section e is equal to zero, and the rotation angles of the left clamping surface and the right clamping surface in fig. 1 are also equal to zero, that is, the zero rotation angle condition is satisfied.

The digital controller is a microcomputer system with a strain signal acquisition-conditioning circuit, a driver control circuit and measurement software. The measurement software is obtained by programming according to the following measurement method idea.

The coding screw rod is a relatively independent component with relatively independent functions and is used for tracking and measuring the relative displacement of the two clamping arms. The coding screw rod works in the following way:

1) adjusting the zero position of a measuring circuit of the tri-state encoder: resistance strain gauge R₅,R₆]、[R₇,R₈]、[R₉,R₁₀]、[R₁₁,R₁₂]The digital controllers are respectively connected in a half-bridge mode. The digital controller controls the driver to drive the coding screw rod to rotate, and the strain readings of four half-bridge circuits

A continuous periodic variation occurs, the period of variation being denoted by T. Each time the toothed disc rotates by one tooth, i.e. one period T,

respectively completing one cycle. Tracking observations

When changing over to

To a minimum value epsilon_rminWhen the gear disc stops rotating, the resistance strain gauge R in the digital controller is adjusted₅,R₆]The balance circuit of the bridge is arranged so that

Repeating the above operations in sequence

Take the minimum value epsilon_rminTime, adjust the resistance strain gauge [ R ]₇,R₈]、[R₉,R₁₀]And [ R ]₁₁,R₁₂]The balance circuit of the bridge is arranged so thatAfter the zero adjustment of the four half-bridge circuits is completed, the fluted disc is rotated, and then

Are all at a minimum value of 0 and a maximum value of epsilon_rmaxThe minimum value of 0 corresponds to the position of the left triangular ridge or the upper triangular ridge or the right triangular ridge or the lower triangular ridge opposite to the valley bottom between two adjacent circular arc teeth, namely the minimum characteristic height h_minMaximum value epsilon_rmaxCorresponding to one of the four triangular ridges being in point contact with the tip of the circular arc, i.e. corresponding to the maximum feature height h_max. The method for adjusting the zero position of the measuring circuit of the tri-state encoder is called a zero position four-step adjusting method.

2) And determining the relation between the strain reading and the rotation state of the fluted disc: after the zero adjustment of the measuring circuit of the three-state encoder is completed, the numbers 1, 0 and 1/2 are respectively used for representing strain reading

Maximum value of (e)_rmaxMinimum 0 and mean 0.5 epsilon_rmax. Number 1 and maximum feature height h_maxCorrespondingly, a full value is defined. Number 0 and minimum feature height h_minAnd correspondingly, a value of zero is defined. Number 1/2 and average feature height h_midCorrespondingly, the median value is defined. Full, zero, and median values are collectively defined as strain readings

The tri-state encoded value of (1) is referred to as a tri-state value for short. When the fluted disc rotates, the three state values 0, 1/2 and 1 change circularly according to the period T. The cyclic variation of the three-state values is used to determine the rotation state, i.e. the rotation direction and the rotation angle, of the toothed disc. There are four different combinations of tristate values, as shown in table 1:

TABLE 1 Strain readings

Tri-state value combination of

TABLE 2 Change of tri-state values 0, 1/2, 1 during clockwise rotation of the toothed disc during each cycle T.

"↓" in the table means an increase in the three-state value, and "↓" means a decrease in the three-state value

TABLE 3 change of tri-state values 0, 1/2, 1 during counterclockwise rotation of the toothed disc during each period T.

Any one of the three-state value combinations shown in table 1 is selected as a starting point for determining the rotation state of the toothed disc, and for the sake of clarity, three-state value combination 1 is selected, so that the toothed disc rotates clockwise by one tooth, and the three-state values complete a cycle of a period T as shown in table 2. The tri-state values complete a cycle of one period T as shown in table 3 for every tooth rotated by the gear plate in the counter-clockwise direction. In tables 2 and 3, the period T is divided into four 1/4 sub-periods, with four strain readings during each 1/4 sub-period

The eight rows ① to ⑧, which are different from each other in pairs, have uniqueness, wherein each row of data uniquely represents a specific rotation state of the toothed disc, for example, the row of data numbered ③ represents and only represents that the toothed disc rotates clockwise for a third 1/4 period within a period T, i.e., 0.5T to 0.75T, the row of data numbered ⑤The toothed disc is shown and only shown rotated counterclockwise through the first 1/4 cycles, i.e., 0 to 0.25T, within one cycle T. And the strain reading is matched with the three-state value to monitor the rotation state of the fluted disc.

3) Measuring the relative displacement of the clamping arm: the rotation of the micrometer screw rod is controlled by a digital controller, the two clamping arms are adjusted to a certain designated position or any position on the micrometer screw rod, the position is recorded as the displacement original point of the two clamping arms, and the position of the fluted disc at the moment is recorded as the fluted disc zero position. The fluted disc is enabled to rotate from the fluted disc zero position, and the two clamping arms move oppositely or reversely from the displacement original point. The relative displacement of the two gripper arms is represented by S, which is defined as the origin-dependent displacement, and S is calculated by equation (3):

in the formula (3), t represents the lead of the micrometer screw, N_cIndicating the number of teeth of the toothed disc, n_z,sRepresenting the cumulative number of teeth, n, rotated clockwise by the toothed disc from its zero position_z,nRepresenting the cumulative number of teeth, n, rotated by the toothed disc counterclockwise from its zero position_z,sAnd n_z,nTaking a constant positive value. n is_zRepresents n_z,sAnd n_z,nThe difference is defined as the number of active rotating teeth. n is_z,s、n_z,nAnd n_zAlso known as the tooth disc rotation parameter. n is_zAnd S is the number of generations. When the fluted disc rotates clockwise, the two clamping arms move reversely, n_zAnd S are all "+". When the fluted disc rotates anticlockwise, the two clamping arms move oppositely, n_zAnd the symbols of S are "-".

The mechanical arm of the design is connected with a mechanical arm of the robot through the coupler 2, and works under the control of the mechanical arm and a numerical controller, and the using method of the mechanical arm comprises the following steps:

1) the measuring line is connected. Resistance strain gauge R₁、R₂、R₃、R₄The circuit is connected with a digital controller in a full-bridge mode, and the circuit is used for sensing and measuring the clamping force F and the clamping point spacing s. When measuring F, the strain reading measured by the digital controller is epsilon_rfRepresents; measurings time, the strain reading measured by the digital controller is epsilon_rdAnd (4) showing.

2) And (5) calibrating the force measuring system. The force here refers to the clamping force F. A standard load sensor or a standard force ring is generally adopted as a force value standard device. During calibration, the digital controller controls the clamper to clamp the standard load sensor or the standard force measuring ring and apply a set of standard force F to the clamping arm₁，F₂，…，F_N，(F₁＜F₂＜…，＜F_N(ii) a N is a positive integer not less than 2), and is recorded by a numerical controller and F₁，F₂，…，F_NCorresponding strain reading

Then is provided with

For calibration, force F and strain reading ε_rfThe force F is calculated by equation (4):

in the formula (4), A₁And B₁Is a constant, calculated according to equations (5) and (6), respectively:

in the formulae (5) and (6), N represents the ordinal number of the standard force, F_iForce values representing different ordinal standard forces,

is represented by the formula_iCorresponding strain readings, i.e. calibration numbers

3) And (5) calibrating a length measuring system. The length here refers to the nip point spacing s. A standard caliper gauge and a standard thickness gauge are generally adopted as the length standard. The standard diameter gauge is a group of standard cylinders with different diameters and is used for a line contact type chuck and a surface contact type chuck. The standard thickness gauge is a group of standard thickness block gauges with different thicknesses, and is used for point contact type chucks, and can also be used for line contact type chucks and surface contact type chucks. The thickness value of each standard cylinder or standard block gauge is sequentially expressed by d₀，d₁，d₂…，d_nIs represented by d₀＜d₁＜d₂,...,＜d_nN represents the number of standard cylinders or standard block gauges, and n is more than or equal to 2 and less than or equal to 10 generally. d₀，d₁，d₂，…，d_nAlso denoted the corresponding standard cylinder or standard block gauge. The calibration method will be described by taking a point contact type chuck as an example. And using a standard thickness gauge as an etalon. The calibration procedure is divided into four steps: first, read for strain_rdPresetting an initial value

Can take values in the range of 10 mu epsilon to 40 mu epsilon; second, get the standard block gauge₀The digital controller controls the clamper to clamp d₀When reading strain

When the fluted disc is in zero position, the current position of the fluted disc is recorded as the displacement original point; third step, with d₁，d₂…，d_nBy replacing d in turn₀Repeating the second step and recording the strain readingThe fourth step is to

For calibration, reading by length s and strainε_rdThe length s is calculated by equation (7):

in the formula (7), A₂And B₂Is a constant, calculated using equations (8) and (9), respectively:

in the formulae (8) and (9), n represents the number of gauge blocks, d_iRepresent thickness values of different standard thickness gauges,

is represented by_iCorresponding strain readings, i.e. calibration numbers

Equations (4) and (7) are derived using a linear fit method.

4) And (5) clamping and measuring. The method of measuring the length of a rigid object will be described. The measuring procedure is divided into three steps: firstly, adjusting the position of a manipulator and the distance s between clamping arms to ensure that s is greater than the length m of an object, and the object enters a clamping space; secondly, controlling the driver to rotate to enable the two clamping arms to move oppositely to clamp the object, and reading epsilon when the strain_rdObtaining

Any or a specified value epsilon of the range_rdxWhen it is, record_rdxCorresponding to epsilon_rdxStrain reading of_rfAnd a dependent origin shift S; in a third step,. epsilon._rfSubstituted by formula (4) with_rdxAnd S is formula (10):

equation (4) gives the clamping force F to which the object is subjected, and equation (10) gives the length m of the object.

The length and the deformation of the deformed object are measured and divided into two situations of integral deformation and local indentation deformation.

The overall deformation is illustrated by way of example with a compression spring. The measuring procedure is divided into three steps: first, a strain reading is set

As starting points for the measurement, for example, setSecondly, controlling the gripper to hold the object to enable the strain reading

Take notes of

And the origin-dependent point shift S corresponding thereto₀Calculating the initial length s of the object according to equation (11)₀：

Thirdly, increasing the clamping force F, and tracking and recording F and strain reading epsilon_rdAnd calculating the length of the object according to the equation (12) by relying on the origin point displacement S:

calculating the deformation v of the object in real time according to the formula (13):

by using the measurement software, a force-deformation relation curve, namely an F-v curve, can be drawn.

The local press-fitting deformation is described by taking a rubber parallelepiped as an example, and a point contact type chuck is used. The measuring procedure is divided into three steps: first, a strain reading is set

As starting points for the measurement, for example, set

Secondly, controlling the gripper to grip the object to enable the two gripping thimbles to contact the object, and reading when the strain is read

When it is needed, record

And the origin-dependent point shift S corresponding thereto^*(ii) a Thirdly, increasing the clamping force F, pressing the two clamping thimbles into the object, tracking and recording F and strain reading epsilon_rdAnd calculating the penetration depth δ according to equation (14) based on the origin point displacement S:

using the measurement software, a force-indentation depth relationship curve, i.e., an F-delta curve, can be plotted.

In the clamping measurement, F, ν, δ, S and S can be used as control parameters, so that control in different modes is realized.

Compared with the existing manipulator, the design has the following characteristics:

1. and (3) controlling the clamping force by using a coding screw rod and clamp holder combined mechanism, and measuring the distance between the clamping points. The mechanical arm of the design is a force-deformation-displacement composite sensing mechanism consisting of a coding screw rod and a clamp holder, the mechanism is matched with a driver and a numerical controller to realize closed-loop control and measurement of clamping force, clamping point distance and clamping deformation, and the control mode comprises force (F) control, displacement (S, s) control and deformation (v and delta) control. The measuring software can give out force-deformation relation curves, such as F-v curves and F-delta curves.

2. The grip has flexible properties. The manipulator of this design grasps the object in a flexible manner, i.e. the gripper grasps the object with an elastic force and the gripping force variation is controlled by the numerical controller.

3. The measurement has flexible properties. When the manipulator clamps a rigid object, if the fluted disc is controlled to rotate at a small angle, the strain reading epsilon is realized_rdContinuously changing, it can be seen that although ε_rdAnd the origin-dependent displacement S are both changing, but the length value m given by equation (10) remains unchanged. The phenomenon is called 'flexible equal differential output', is a characteristic property of a force-deformation-displacement composite sensing mechanism consisting of the coding screw rod and the clamp holder, and is a principle basis for measuring the distance s between the clamping points. Varying epsilon within a certain range_rdThe measured length m remains constant and is different by_rdThe values correspond to different clamping forces. Therefore, the algorithm design of the measurement software can utilize the output property of the flexibility equal difference according to different operation objects and measurement requirements.

4. The design range of the clamping force and the measurement and control precision thereof is wider. The value range of the clamping force and the measurement resolution of the clamping force of the mechanical arm are mainly determined by the structural form, the size and the material property of the elastic beam used by the clamp holder, so that the design flexibility is very high, for example, the clamp holder with the force value range of 0-10N and the resolution of less than 0.1N can be designed, and the clamp holder with the force value range of 10-5000N and the resolution of less than 1N can also be designed.

5. The design range of the adjustment of the distance between the clamping points is wider. The adjusting range of the distance between the clamping points of the manipulator mainly depends on the moving distance of the two clamping arms. The required adjustment range of the distance between the clamping points can be obtained by selecting a micrometer screw rod with a proper length for the coding screw rod-clamp combined mechanism, for example, 0-20 mm, 0-100 mm and 50-500 mm.

6. The resolution of the nip point spacing measurement can reach a moderate level of the mechanical industry length measurement. The manipulator of this design, its grip point interval measurement resolution is decided by holder and two aspects of factor of code lead screw. The design range of the displacement resolution of the two is basically the same and is 0.1-10 mu m.

Drawings

FIG. 1 is a front view of a robot configuration diagram of the present design;

FIG. 2 is a right side view of the robot configuration sketch of the present design;

FIG. 3 is a schematic view of a straight beam type clamp and a three-form collet, where (a) is a straight beam type clamp and a point contact type conical collet, (b) is a line contact type clamping firmware, and (c) is a line contact type V-shaped collet;

FIG. 4 is a schematic diagram of a tristate encoder architecture;

FIG. 5 is a schematic diagram of a tri-state encoder measurement circuit in which (a) a resistive strain gauge [ R ]₅,R₆]Half-bridge diagram, (b) resistance strain gauge [ R ]₇,R₈]Half-bridge diagram, (c) resistance strain gauge [ R ]₉,R₁₀]Half-bridge diagram, (d) resistance strain gauge [ R ]₁₁,R₁₂]A half-bridge diagram;

FIG. 6 is a schematic diagram of a gripper measurement circuit;

in the figure: 1. the device comprises a frame, 2, a driver, 3, a left bearing support plate, 4, a micrometer screw rod, 5, a left bearing, 6, a U-shaped guide limit groove, 7, a left limit guide rod, 8, a left rotation transmission nut, 9, a right rotation transmission nut, 10, a right limit guide rod, 11, a right bearing, 12, a right bearing support plate, 13, a left clamping arm, 14, a right clamping arm, 15, a left clamping surface, 16, a right clamping surface, 17, a sensor support, 18, a right upper cantilever beam sensor, 19, a fluted disc, 20, a circular arc tooth, 21, a left lower cantilever beam sensor, 22, a right lower cantilever beam sensor, 23, a coupler, 24, a left triangular ridge, 25, a left upper cantilever beam sensor, 26, an upper triangular ridge, 27, a right triangular ridge, 28, a lower triangular ridge, 29, a rectangular through hole, 30, a threaded hole, 31, a set screw, 32, a first clamping ejector pin, 33 and a second clamping ejector pin, 34. a third clamping thimble, 35, a fourth clamping thimble, 36, a first clamping blade block, 37, a second clamping blade block, 38, a first V-shaped clamp, 39, a second V-shaped clamp, TE., a tri-state encoder, w.

Detailed Description

The design is further explained below with reference to the drawings.

Referring to fig. 1-6, the present design is a robot that controls gripping deformation. The manipulator consists of a frame 1, a coding screw rod, a driver 2, a clamp holder and a digital controller.

The structure of the frame 1 comprises a rectangular substrate, a coupler 23 which is positioned below the substrate and is used for connecting a robot arm, a left bearing support plate 3 positioned on the left side above the substrate, a right bearing support plate 12 positioned on the right side above the substrate, and a U-shaped guide limiting groove 6 positioned on the upper surface of the substrate. The left bearing support plate 3 is embedded with a left bearing 5, the right bearing support plate 12 is embedded with a right bearing 11, the two bearings are in coaxial positions, and the axis is parallel to the axis of the U-shaped guide limiting groove 6.

The coding screw rod consists of a micrometer screw rod 4 and a three-state coder TE.

The micrometer screw rod 4 is a double-thread step shaft, and the structure of the micrometer screw rod is divided into five sections of I-II, II-III, III-IV and IV-V, V-VI from left to right. The section I-II is an optical axis, the section II-III is a left-handed thread shaft, the section III-IV is a raised step shaft, the section IV-V is a right-handed thread shaft, and the section V-VI is also an optical axis. The length, the lead and the outer diameter of the two thread sections are equal, and the outer diameter is larger than the diameter of the two optical axes. The micrometer screw rod 4 is arranged on the frame 1 through the matching of the section I-II optical axis and the left bearing 5 and the matching of the section V-VI optical axis and the right bearing 11, the section I-II optical axis extends to the left side of the left bearing support plate 3, and the section V-VI optical axis extends to the right side of the right bearing support plate 12. The left end face of the section II-III threaded shaft is in sliding fit with the right end face of the left bearing 5, the right end face of the section IV-V threaded shaft is in sliding fit with the left end face of the right bearing 11, and the two matching pairs prevent the micrometer screw rod 4 from moving left and right.

The tri-state encoder TE is composed of a sensor bracket 17, a fluted disc 19, an upper left cantilever beam sensor 25, an upper right cantilever beam sensor 18, a lower left cantilever beam sensor 21, and a lower right cantilever beam sensor 22. The sensor support 17 may be a rectangular frame, and four sides of the frame are sequentially provided with a rectangular through hole 29 and a threaded hole 30, wherein the axis of the rectangular through hole is parallel to the plane of the frame and is vertical to the side of the frame, and the threaded hole is vertically communicated with the rectangular through hole 29. The fluted disc 19 is a disk with equal thickness and the periphery of which is distributed with arc teeth 20, the arc teeth 20 can be made by embedding steel balls or cutting. The number of circular arc teeth 20 is an integer multiple of 4, for example 180, 500. The four cantilever beam sensors have the same shape and size, the elastic bodies are uniform-section elastic beams or variable-section elastic beams, the roots of the four elastic beams are respectively matched with the four rectangular through holes 29 of the sensor bracket 17, and the four elastic beams are respectively fixed on the inner walls of the four sides of the sensor bracket 17 by utilizing the pressing force generated by screwing the set screws 31 into the threaded holes 30. Four elastic beams are respectively stuck with a single-axis resistance strain gauge R along the axial direction of the beams at the positions close to the roots₅,R₆]、[R₇,R₈]、[R₉,R₁₀]And [ R ]₁₁,R₁₂]A left triangular ridge 24, an upper triangular ridge 26, a right triangular ridge 27 and a lower triangular ridge 28 are respectively machined on the side facing the fluted disc 19 near the free end. The four elastic beams have a certain amount of pre-deformation, the elastic pressure generated by the pre-deformation makes the tops of the four triangular convex edges respectively keep contact with the circular arc teeth 20 on the periphery of the fluted disc 19, and the positions of the contact points are determined according to the following conditions:

a. it is assumed that the longitudinal symmetry line of the toothed disc 19 passes through the centers of the right upper circular arc teeth 20 and the right lower circular arc teeth 20, and the horizontal symmetry line of the toothed disc 19 passes through the centers of the leftmost circular arc teeth 20 and the rightmost circular arc teeth 20.

b. At this time, the left triangular ridge 24 is located on the horizontal symmetry line of the toothed disc 19 and contacts the apex of the leftmost circular tooth 20. The right triangular ridge 27 is located on the upper side of the horizontal symmetry line of the fluted disc 19 and the rightmost circular arc tooth 20 and is just aligned with the valley bottom between two adjacent circular arc teeth 20. The upper triangular ridge 26 and the lower triangular ridge 28 are located on the right side of the longitudinal symmetry line of the fluted disc 19 and are respectively in contact with the right side of the right upper circular arc tooth 20 and the right side of the right lower circular arc tooth 20. Distance h between the left triangular ridge 24 and the longitudinal symmetry line of the toothed disc 19_maxThe distance h from the right triangular ridge 27 to the longitudinal symmetry line of the toothed disk 19 is shown_minIt is shown that the distance from the contact point of the upper triangular ridge 26 with the right-above circular arc tooth 20 to the horizontal symmetry line of the toothed disc 19 is equal to the distance from the contact point of the lower triangular ridge 28 with the right-below circular arc tooth 20 to the horizontal symmetry line of the toothed disc 19, both of which are defined by h_midAnd (4) showing. h is_midAnd h_minAnd h_maxBetween areA relationship represented by formula (1):

The fluted disc 19 is coaxially fixed on the V-VI section optical axis of the micrometer screw rod 4. The sensor support 17 is fixed on the upper right of the base plate of the frame 1 and encloses the toothed disc 19 in the middle.

The driver 2 is used for driving the coding screw rod to rotate and can adopt a stepping motor. The driver 2 is arranged on the left side of the left bearing support plate 3 and is connected with the I-II section optical axis of the micrometer screw rod 4 through a coupler (not shown in the figure).

The clamp holder is composed of a left clamping arm 13 and a right clamping arm 14, the two are cantilever type elastic beam sensors of which the fixed ends are connected with shaft sleeves, the materials, the shapes and the sizes are the same, the bottoms of the two shaft sleeves are respectively embedded with a left limiting guide rod 7 and a right limiting guide rod 10, the left side and the right side of the free end of the elastic beam can be provided with a chuck, the middle part of the shaft sleeve of the left clamping arm 13 is embedded with a left-handed transmission nut 8, and the middle part of the shaft sleeve of the right clamping arm 14 is embedded with a right-handed transmission. The left clamping arm 13 is matched with a left-handed threaded shaft of the micrometer screw rod 4 through a left-handed transmission nut 8 and is arranged on the micrometer screw rod 4 through the matching of the left limiting guide rod 7 and the U-shaped guiding limiting groove 6. The right clamping arm 14 is matched with a right-handed threaded shaft of the micrometer screw rod 4 through a right-handed transmission nut 9 and is arranged on the micrometer screw rod 4 through the matching of a right limiting guide rod 10 and the U-shaped guiding limiting groove 6. The two clamping arms are vertically upward and are in symmetrical positions. The two limiting guide rods are matched with the U-shaped guiding limiting groove 6, so that the two clamping arms cannot rotate around the axis of the micrometer screw rod 4. When the micrometer screw rod 4 rotates, the two clamping arms are driven to move oppositely or reversely along the axis direction of the micrometer screw rod 4. The two transmission nuts and the micrometer screw rod 4 are matched in pairs to adopt clearance elimination measures so as to meet two requirements: firstly, theoretically, when the rotation direction of the micrometer screw rod 4 is changed, the micrometer screw rod can drive the two transmission nuts to change the moving direction without delay; and secondly, the rotational freedom of the axes of the two transmission nuts in the x-y plane is zero. The elastic beam of the clamp has two basic structural forms:

a) the fishhook-shaped folding beam structurally comprises a long arm a-c section, a folding joint a-d section and a short arm d-e section, wherein the cross sections of the three sections are all rectangular, and the section c is a fixed end of the folding beam; the cross-sectional dimension of the sections a-d is much larger than the cross-sectional dimensions of the sections a-c and d-e, so that the sections can be regarded as rigid nodes of the folded beam. The structure of the long arm a-c section is divided into a-b section and a b-c section from top to bottom, the height H of the a-b section is greater than the height H of the b-c section₁. The section d-e of the short arm is a beam with equal section. The heights of the sections a-c of the long arm, the sections a-d of the turning joint and the sections d-e of the short arm can be equal or unequal.

b) The structure of the straight beam is divided into a section a-b and a section b-c from top to bottom, the height H of the section a-b is larger than the height H of the section b-c, the cross sections of the section a-b and the section b-c are both rectangular, the section c is a fixed end of the beam, and the section a is a free end of the beam.

A single-axis resistance strain gauge R is attached to the left side and the right side of the elastic beam of the left clamping arm 13 along the beam axis direction at the section b-c₂And R₁The elastic beam of the right clamping arm 14 is pasted with a single-axis resistance strain gauge R along the beam axis direction at the left side and the right side of the section b-c₃And R₄。

The clamping head of the clamping device has three types of surface contact, line contact and point contact, and is selected according to the use requirement. The jaws of the fishhook-shaped fold are arranged at the section e of the short arm d-e, for example the left gripping surface 15 on the left gripping arm 13 and the right gripping surface 16 on the right gripping arm 14 in fig. 1, which constitute a pair of surface contact type jaws. The straight beam chucks are arranged on the left and right sides of the free end a, such as a first clamping thimble 32 on the left clamping arm 13 and a second clamping thimble 33 on the right clamping arm 14 in fig. 3(a), which form a pair of point contact type chucks; the third clamping thimble 34 and the fourth clamping thimble 35 form a pair of point contact type chucks which support outwards; the first holding-edge block 36 and the second holding-edge block 37 in fig. 3(b) constitute a pair of line contact type chucks; the first V-clip 38 and the second V-clip 39 in fig. 3(c) are also line contact type clips. The distance between the left and right chucks, i.e. the distance between the clamping points, is indicated by s.

When the clamp adopts the fishhook-shaped folding beam, the clamp is designed according to the zero-corner condition of the clamp. The width b of each section of the fish-hook-shaped folding beam is equal, as shown in figure 1; the sections b-c are of equal height to the sections d-e, i.e. h₁＝h₂H; the height H of the section a-b is more than or equal to 5H, so the section can be regarded as a rigid body. The length L of the a-c segment is the length L of the b-c segment ₁5 times of (i), i.e. L is 5L₁. According to the bending theory, under the condition of small linear elastic deformation, the relation formula can be obtained:

in the formula (2), l₂Is the length of the d-e segment. If L, l₁And l₂When equation (2) is satisfied, the rotation angle of the cross section e is equal to zero, and the rotation angles of the left clamping surface 15 and the right clamping surface 16 in fig. 1 are also equal to zero, that is, the zero rotation angle condition is satisfied.

The digital controller (not shown in the figure) is a microcomputer system with a strain signal acquisition-conditioning circuit, a driver control circuit and measurement software. The digital controller is generally integrated with the control system of the robot, and can also be arranged separately.

The coding screw rod is used for tracking and measuring the relative displacement of the two clamping arms, and the working mode is as follows:

1) adjusting the zero position of a measuring circuit of the tri-state encoder: resistance strain gauge R₅,R₆]、[R₇,R₈]、[R₉,R₁₀]、[R₁₁,R₁₂]The digital controllers are respectively connected in a half-bridge mode, the driver 2 is controlled to drive the coding screw rod to rotate, and the strain readings of four half-bridge circuitsA continuous periodic variation occurs, the period of variation being denoted by T. The toothed disc 19 rotates one tooth at a time, i.e. one period T,

respectively completing one cycle. Tracking observations

When changing over to

To a minimum value epsilon_rminWhen the rotation of the fluted disc 19 is stopped, the resistance strain gauge R in the digital controller is adjusted₅,R₆]The balance circuit of the bridge is arranged so that

Repeating the above operations in sequence

Take the minimum value epsilon_rminTime, adjust the resistance strain gauge [ R ]₇,R₈]、[R₉,R₁₀]And [ R ]₁₁,R₁₂]The balance circuit of the bridge is arranged so that

After the zero adjustment of the four half-bridge circuits is completed, the fluted disc 19 is rotated again, and then

Are all at a minimum value of 0 and a maximum value of epsilon_rmaxThe minimum value 0 corresponds to the position of the left triangular ridge 24 or the upper triangular ridge 26 or the right triangular ridge 27 or the lower triangular ridge 28 opposite to the valley bottom between two adjacent circular-arc teeth 20, i.e. corresponds to the minimum characteristic height h_minMaximum value epsilon_rmaxCorresponding to one of the four triangular ridges being in contact with the apex of the circular tooth 20, i.e. corresponding to the maximum characteristic height h_max. The method for adjusting the zero position of the TE measuring circuit of the tri-state encoder is called a zero position four-step adjusting method.

2) And determining the relation between the strain reading and the rotation state of the fluted disc: after the zero adjustment of the TE measuring circuit of the three-state encoder is completed, the numbers 1, 0 and 1/2 are respectively used for representing strain reading

The tri-state encoded value of (1) is referred to as a tri-state value for short. When the toothed disk 19 rotates, the tristate values 0, 1/2, 1 change cyclically with a period T. The cyclical variation of the three state values is used to determine the rotational state of toothed disc 19, i.e. the rotational direction and rotational angle of toothed disc 22. There are a total of four different combinations of tristate values, as shown in table 1:

TABLE 1 Strain readings

Tri-state value combination of

TABLE 2 Change of tri-state values 0, 1/2, 1 during clockwise rotation of the toothed disc 22 during each cycle T.

TABLE 3 Change of tri-state values 0, 1/2, 1 during counterclockwise rotation of the toothed disc 22 during each cycle T.

A combination of three values is selected from table 1 as a starting point for determining the rotational state of the toothed disc, and for clarity, combination 1 is selected such that for each clockwise rotation of toothed disc 19 by one tooth, the three values complete a cycle of one period T as shown in table 2. The tri-state values complete a cycle of one period T as shown in table 3 for each counterclockwise rotation of the toothed disc 19 by one tooth. In tables 2 and 3, the period T is divided into four 1/4 sub-periods, with four strain readings during each 1/4 sub-period

The eight rows of data numbered ① - ⑧, which are different from each other in pairs and unique in that each row of data uniquely represents a specific rotation state of the toothed disc, for example, the row of data numbered ③ represents and only represents that the toothed disc 19 rotates clockwise for the third 1/4 period of a period T, i.e., the row of data numbered 0.5T-0.75T- ⑤ represents and only represents that the toothed disc 19 rotates counterclockwise for the first 1/4 period of a period T, i.e., the strain readings continuously changing from 0 to 0.25T cooperate with the tri-state values to monitor the rotation state of the toothed disc 19.

3) Measuring the relative displacement of the two clamping arms: the micrometer screw rod 4 is controlled by a digital controller to rotate, the two clamping arms are adjusted to a certain designated position or any position on the micrometer screw rod 4, the position is recorded as the displacement original point of the two clamping arms, and the position of the fluted disc 19 at the moment is recorded as the fluted disc zero position. The fluted disc 19 is rotated from the fluted disc zero position, and the two clamping arms move oppositely or reversely from the displacement original point. The relative displacement of the two gripper arms is represented by S, which is defined as the origin-dependent displacement, and S is calculated by equation (3):

in the formula (3), t represents the lead of the micrometer screw 4, N_cIndicating the number of teeth, n, of the toothed disc 19_z,sRepresenting the cumulative number of teeth turned clockwise by the toothed disc 19 from its zero position, n_z,nIndicating that the toothed disc 19 has accumulated counterclockwise from its zero positionCounting the number of teeth turned, n_z,sAnd n_z,nTaking a constant positive value. n is_zRepresents n_z,sAnd n_z,nThe difference is defined as the number of active rotating teeth. n is_z,s、n_z,nAnd n_zAlso known as the tooth disc rotation parameter. n is_zAnd S is the number of generations. When the gear 19 rotates clockwise, the two holding arms move in opposite directions, n_zAnd S are all "+". When the fluted disc 19 rotates anticlockwise, the two clamping arms move oppositely, n_zAnd the symbols of S are "-".

The manipulator of this design passes through shaft coupling 23 and is connected with the arm of robot, works under the arm and the control of numerical controller, and its application method includes the following step:

1) the measuring line is connected. Resistance strain gauge R₁、R₂、R₃、R₄The digital controller is connected in a full-bridge mode, and the circuit is used for sensing and measuring the clamping force F and the clamping point distance s. When measuring F, the strain reading measured by the digital controller is epsilon_rfRepresents; when measuring s, the strain reading measured by the digital controller is epsilon_rdAnd (4) showing.

2) And (5) calibrating the force measuring system. The force refers to the clamping force F. The calibration method will be described by taking the surface contact type chuck shown in fig. 1 as an example. A standard load sensor or a force measuring ring is used as a force value standard device, and when the standard load sensor or the force measuring ring is calibrated, a numerical controller controls a left clamping surface 15 and a right clamping surface 16 of a clamp holder to clamp the standard load sensor or the force measuring ring, and a group of standard forces F are applied to a clamping arm₁，F₂，…，F_N，(F₁＜F₂＜…，＜F_N(ii) a N is a positive integer not less than 2, the value range is determined according to requirements, for example, 2 is more than or equal to N is less than or equal to 10), and the value range is recorded by a digital controller and F₁，F₂，…，F_NCorresponding strain reading

Then is provided with

During calibration, the elastic beam is under the standard force F_NThe maximum stress generated by the action must not exceed the proportional limit of the material used for the beam.

3) And (5) calibrating a length measuring system. The length here refers to the nip point spacing s. First, a length standard is selected according to the type of the chuck, and a standard diameter gauge and a standard thickness gauge are commonly used length standards. The standard diameter gauge is a group of standard cylinders with different diameters and is used for a line contact type chuck and a surface contact type chuck. The standard thickness gauge is a group of standard thickness block gauges with different thicknesses, and is used for point contact type chucks, and can also be used for line contact type chucks and surface contact type chucks. The thickness value of each standard cylinder or standard block gauge is sequentially expressed by d₀，d₁，d₂…，d_nIs represented by d₀＜d₁＜d₂,...,＜d_nN denotes the number of standard cylinders or standard block gauges, in generalN is 2. ltoreq. n.ltoreq.10 (for example, n is 7). d₀，d₁，d₂，…，d_nAlso denoted the corresponding standard cylinder or standard block gauge. The calibration method will be described by taking the point contact type chuck shown in fig. 3(a) as an example. And (3) taking a standard thickness gauge as a standard device, wherein the thickness value of the standard block gauge meets the condition: when the deflection lambda of the elastic beam of the clamp at the section e is d_n-d₀The maximum stress of the beam does not exceed the proportional limit of the materials used. The calibration procedure is divided into four steps: first, read for strain_rdPresetting an initial value

Can take values in the range of 10 mu epsilon to 40 mu epsilon, for example

Second, get the standard block gauge₀The digital controller controls the movement of the clamper to make the first and second clamping pins 32 and 33 clamp d₀When reading strain

When the two clamping arms move, recording the current positions of the two clamping arms as displacement original points, and recording the current position of the fluted disc 19 as a fluted disc zero position; thirdly, using a standard block gauge d₁，d₂…，d_nBy replacing d in turn₀Repeating the second step to record corresponding strain readings

The fourth step is to

For calibration, reading e according to the length s and strain_rdThe length s is calculated by equation (7):

in the formula (7), A₂And B₂Is a constant, isCalculated using equations (8) and (9), respectively:

is represented by_iCorresponding strain readings, i.e. calibration numbers

Equations (4) and (7) are derived using a linear fit method. When the force measuring system calibration and the length measuring system calibration are carried out, positioning devices can be respectively designed for the force value standard device and the length standard device, so that the standard devices can be conveniently installed.

4) And (5) clamping and measuring. The method for measuring the length of a rigid object is illustrated by way of example in fig. 1. The measuring procedure is divided into three steps: firstly, adjusting the position of a manipulator and the distance s between two clamping surfaces to ensure that s is greater than the length m of an object W, and the object W enters the middle position of the two clamping surfaces; secondly, the driver 2 is controlled to rotate, so that the two clamping arms move oppositely to clamp the object W, and when the strain reading epsilon is read_rdObtaining

equation (4) gives the clamping force F to which the object W is subjected, and equation (10) gives the length m of the object W.

The overall modification is described by way of example in fig. 3 (d). The object W is a compression spring, and the measuring procedure is divided into three steps: first, a strain reading is set

As starting points for the measurement, for example, set

Secondly, controlling the gripper to hold the object W to enable the strain reading

Take notes of

And the origin-dependent point shift S corresponding thereto₀Calculating the initial length s of the object W according to equation (11)₀：

Thirdly, increasing the clamping force F, and tracking and recording F and strain reading epsilon_rdAnd calculating the length of the object W in real time according to the formula (12) by depending on the displacement S of the origin:

and (3) calculating the deformation v of the object W in real time according to the formula (13):

The local press-in deformation is illustrated in FIG. 3(a). The object W is a rubber regular hexahedron, and the measuring procedure is divided into three steps: first, a strain reading is set

As starting points for the measurement, for example, set

Secondly, controlling the gripper to grip the object to enable the two gripping thimbles to contact the object W, and reading when the strain is read

When it is needed, recordAnd the origin-dependent point shift S corresponding thereto^*(ii) a Thirdly, increasing the clamping force F, and tracking and recording F and strain reading epsilon_rdAnd calculating an approximate value of the penetration depth δ according to equation (14) depending on the origin point displacement S:

Claims

1. A manipulator for controlling clamping deformation; the device is characterized by consisting of a rack (1), a coding screw rod, a driver (2), a clamp holder and a digital controller;

the structure of the frame (1) comprises a rectangular substrate, a coupling (23) fixed below the substrate and used for connecting a robot arm, a left bearing support plate (3) fixedly arranged on the left side above the substrate, a right bearing support plate (12) fixedly arranged on the right side above the substrate, and a U-shaped guide limiting groove (6) arranged on the upper surface of the substrate; a left bearing (5) is embedded on the left bearing support plate (3), a right bearing (11) is embedded on the right bearing support plate (12), the two bearings are in coaxial positions, and the axis is parallel to the axis of the U-shaped guide limiting groove (6);

the coding screw rod consists of a micrometer screw rod (4) and a three-state encoder (TE);

the structure of the micrometer screw rod (4) is divided into five sections of I-II, II-III, III-IV and IV-V, V-VI from left to right; the section I-II is an optical axis, the section II-III is a left-handed thread shaft, the section III-IV is a raised step shaft, the section IV-V is a right-handed thread shaft, and the section V-VI is also an optical axis; the micrometer screw rod (4) is arranged on the frame (1) through the matching of the section I-II optical axis and the left bearing (5) and the matching of the section V-VI optical axis and the right bearing (11), the section I-II optical axis extends out to the left side of the left bearing support plate (3), and the section V-VI optical axis extends out to the right side of the right bearing support plate (12);

the tri-state encoder (TE) consists of a fluted disc (19), a sensor bracket (17), a left upper cantilever beam sensor (25), a right upper cantilever beam sensor (18), a left lower cantilever beam sensor (21) and a right lower cantilever beam sensor (22); the fluted disc (19) is a disc with a plurality of circular arc teeth (20) uniformly distributed on the circumference, and is coaxially fixed on the V-VI section optical axis of the micrometer screw rod (4), and the number of teeth of the fluted disc (19) is integral multiple of 4; the sensor bracket (17) is a rectangular frame, is fixed at the upper right of the base plate of the frame (1), and encloses the fluted disc (19) in the middle; left upper, right lower, left lower, right upper cantilever beam sensors (25, 22, 21, 18) are respectively fixed on the inner walls of the upper, lower, left and right sides of the sensor bracket (1), and resistance strain gauges (R) are respectively stuck at the positions close to the beam root along the beam axis direction₅,R₆]、[R₇,R₈]、[R₁₁,R₁₂]And [ R ]₉,R₁₀]A left triangular ridge (24), a right triangular ridge (27), a lower triangular ridge (28) and an upper triangular ridge (26) are respectively machined on one side of the free end of the beam, which faces the fluted disc (19); the four cantilever beam sensors have a certain amount of pre-deformation, the elastic pressure generated by the pre-deformation enables the crests of the four triangular convex ridges to respectively keep contact with the circular arc teeth (20) on the periphery of the fluted disc (19), and the specific positions of contact points are determined according to the following conditions:

a. the longitudinal symmetry line of the fluted disc (19) passes through the centers of the arc teeth right above and the arc teeth right below, and the horizontal symmetry line of the fluted disc (19) passes through the centers of the arc teeth at the leftmost end and the arc teeth at the rightmost end;

b. at the moment, the left triangular ridge (24) is positioned on the horizontal symmetrical line of the fluted disc (19) and is contacted with the vertex of the circular arc tooth at the leftmost end; the right triangular ridge (27) is positioned on the horizontal symmetry line of the fluted disc (19) and the upper side of the rightmost circular arc tooth and just aligns with the valley bottom between two adjacent circular arc teeth (20); the upper triangular ridge (26) and the lower triangular ridge (28) are both positioned on the right side of the longitudinal symmetry line of the fluted disc (19) and are respectively contacted with the right side of the arc teeth right above and the right side of the arc teeth right below; the distance h from the left triangular ridge (24) to the longitudinal symmetrical line of the fluted disc (19)_maxThe distance h from the right triangular ridge (27) to the longitudinal symmetry line of the toothed disc (19) is shown_minThe distance from the contact point of the upper triangular ridge (26) and the right upper arc tooth to the horizontal symmetry line of the fluted disc (19) is equal to the distance from the contact point of the lower triangular ridge (28) and the right lower arc tooth to the horizontal symmetry line of the fluted disc (19), and the distances are both h_midRepresents; h is_midAnd h_minAnd h_maxThere is a relationship represented by formula (1):

h_min、h_midand h_maxCollectively called the characteristic height, where h_minIs the minimum feature height, h_midIs the average feature height, h_maxIs the maximum feature height;

the driver (2) is used for driving the coding screw rod to rotate, and the driver (2) is arranged on the left side of the left bearing support plate (3) and is connected with the optical axis of the section I-II of the micrometer screw rod (4);

the clamp holder consists of a left clamping arm (13) and a right clamping arm (14), the two are cantilever type elastic beam sensors with fixed ends provided with shaft sleeves, the materials, the shapes and the sizes are the same, the bottoms of the two shaft sleeves are respectively embedded with a left limiting guide rod (7) and a right limiting guide rod (10), the left clamping arm (13) is embedded with a left-handed transmission nut (8) in the middle of the shaft sleeve, and the right clamping arm (14) is embedded with a right-handed transmission nut (9) in the middle of the shaft sleeve; the left clamping arm (13) is matched with a left-handed threaded shaft of the micrometer screw rod (4) through a left-handed transmission nut (8) and is arranged on the micrometer screw rod (4) through the matching of a left limiting guide rod (7) and a U-shaped guiding limiting groove (6); the right clamping arm (14) is matched with a right-handed threaded shaft of the micrometer screw rod (4) through a right-handed transmission nut (9), and the right limiting guide rod (10) is matched with the U-shaped guiding limiting groove (6) and is arranged on the micrometer screw rod (4); the two clamping arms are vertically upward and are in symmetrical positions; when the micrometer screw rod (4) rotates, the two clamping arms are driven to move oppositely or reversely along the axis direction of the micrometer screw rod (4); the left and right sides of the free end of the elastic beam of the clamping arm are provided with clamping heads, and the elastic beam of the clamping device comprises two basic structural forms:

a) the fish hook-shaped folding beam structurally comprises a long arm a-c section, a folding section a-d section and a short arm d-e section which are fixedly connected, wherein the section c is a fixed end of the folding beam, and the a-d section is a rigid node of the folding beam; the structure of the long arm a-c section is divided into a-b section and a b-c section from top to bottom, the height H of the a-b section is greater than the height H of the b-c section₁(ii) a The section d-e of the short arm is a beam with equal section;

b) the structure of the straight beam is divided into a section a-b and a section b-c from top to bottom, the height H of the section a-b is greater than the height H of the section b-c, the section c is a fixed end of the beam, and the section a is a free end of the beam;

the elastic beam of the left clamping arm (13) is pasted with a resistance strain gauge R along the beam axis direction at the left side and the right side of the b-c section₂And R₁The elastic beam of the right clamping arm (14) is pasted with a resistance strain gauge R along the beam axis direction at the left side and the right side of the section b-c₃And R₄；

The clamping head of the clamping device has three types of surface contact, line contact and point contact; the chuck of the fishhook-shaped folding beam is arranged on the section e of the section d-e of the short arm and meets the zero-turning-angle condition; the zero rotation angle condition means that: when the action line of the clamping force is superposed with the intersection line of the longitudinal symmetrical surface of the folding beam and the cross section e, the corner of the cross section e and the corner of the chuck are both zero; the chucks of the straight beam are arranged on the left side and the right side of the free end a;

the digital controller is a microcomputer system with a strain signal acquisition-conditioning circuit and a driver control circuit, and can obtain a measurement result.

2. The manipulator of claim 1, wherein the code screw is used for tracking and measuring the relative displacement of the two clamping arms, and the operation mode is as follows:

1) adjusting the zero position of a measuring circuit of the tri-state encoder: resistance strain gauge R of circuit₅,R₆]、[R₇,R₈]、[R₉,R₁₀]And [ R ]₁₁,R₁₂]Respectively connecting the digital controllers in a half-bridge mode; the digital controller controls the driver (2) to drive the coding screw rod to rotate, and the strain readings of the four half-bridge circuits

The continuous periodic change is generated, and the change period is represented by T; the toothed disk (19) rotates by one tooth, namely a period T,respectively completing a cycle; tracking observationsWhen changing over to

To a minimum value epsilon_rminWhen the rotation of the fluted disc (19) is stopped, the resistance strain gauge (R) in the digital controller is adjusted₅,R₆]The balance circuit of the bridge is arranged so that

Repeating the above operations in sequence

After the zero adjustment of the four half-bridge circuits is completed, the fluted disc (19) is rotated, and thenAre all at a minimum value of 0 and a maximum value of epsilon_rmaxThe minimum value 0 corresponds to the valley bottom position of one of the four triangular ridges which is just opposite to the position between two adjacent circular arc teeth (20), namely the minimum characteristic height h_minMaximum value epsilon_rmaxCorresponding to one of the four triangular ridges being in contact with the vertex of the circular-arc tooth (20), i.e. corresponding to the maximum characteristic height h_max(ii) a A method for adjusting the zero position of a three-state encoder (TE) measuring circuit is called a zero position four-step adjusting method;

2) and determining the relation between the strain reading and the rotation state of the fluted disc: after the zero adjustment of the measuring circuit of the three-state encoder (TE) is completed, the numbers 1, 0 and 1/2 are respectively used for representing the strain reading

Maximum value of (e)_rmaxMinimum 0 and mean 0.5 epsilon_rmax(ii) a Number 1 and maximum feature height h_maxCorrespondingly, defining as a full value; number 0 and minimum feature height h_minCorrespondingly, a value of zero is defined; number 1/2 and average feature height h_midCorrespondingly, defining the median value; full, zero, and median values are collectively defined as strain readings

The tri-state encoding value of (1) is called tri-state value for short; when the fluted disc (19) rotates, the three-state values 0, 1/2 and 1 change circularly according to the period T; the cyclic change of the three-state values is used for determining the rotation state, namely the rotation direction and the rotation angle, of the fluted disc (19);

3) measuring the relative displacement of the two clamping arms: controlling the rotation of the micrometer screw rod (4) by a digital controller, adjusting the two clamping arms to a certain designated position or any position on the micrometer screw rod (4), recording the position as the displacement original points of the two clamping arms, and recording the position of the fluted disc (19) as the fluted disc zero position; the fluted disc (19) starts to rotate from the fluted disc zero position, and the two clamping arms move oppositely or reversely from the displacement origin; the relative displacement of the two gripper arms is represented by S, which is defined as the origin-dependent displacement, and S is calculated by equation (3):

in the formula (3), t represents the lead of the micrometer screw (4), N_cDenotes the number of teeth, n, of the toothed disc (19)_z,sRepresenting the cumulative number of teeth turned clockwise by the toothed disc (19) from its zero position, n_z,nRepresenting the cumulative number of teeth turned by the toothed disc (19) in the counter-clockwise direction from its zero position, n_z,sAnd n_z,nTaking a positive value constantly; n is_zRepresents n_z,sAnd n_z,nThe difference, defined as the number of active rotating teeth; n is_z,s、n_z,nAnd n_zAlso known as the tooth disc rotation parameter; n is_zAnd S is the number of generations; when the fluted disc (19) rotates clockwise, the two clamping arms move reversely, n_zAnd the symbols of S are both "+"; when the fluted disc (19) rotates anticlockwise, the two clamping arms move oppositely, n_zAnd the symbols of S are "-".

3. The manipulator for controlling clamping deformation as claimed in claim 1, wherein the manipulator is connected with a mechanical arm of the robot through a coupling (23), and works under the control of the mechanical arm and a numerical controller, and the use method is as follows:

1) measuring line connection; resistance strain gauge R₁、R₂、R₃、R₄The circuit is connected with a digital controller in a full-bridge mode, and is used for sensing and measuring the clamping force F and the clamping point spacing s; when measuring F, the strain reading measured by the digital controller is epsilon_rfRepresents; when measuring s, the strain reading measured by the digital controller is epsilon_rdRepresents;

2) calibrating a force measuring system; calibrating the force measuring system by adopting a force value standard; the numerical controller controls the clamp force value standard device of the clamp holder to apply a group of standard forces F to the clamping arm₁，F₂，…，F_NIn which F is₁＜F₂＜…，＜F_NN is a positive integer not less than 2, and is represented by₁，F₂，…，F_NCorresponding strain reading

To be provided with

For calibration, force F and strain reading ε_rfIs equation (4), calculates F:

representation and force F_iCorresponding strain readings, i.e. calibration numbers

3) Calibrating a length measuring system; calibrating the length measuring system by adopting a length standard device; the standard device comprises a standard diameter gauge and a standard thickness gauge, wherein the standard diameter gauge is a group of standard cylinders with different diameters, and the standard thickness gauge is a group of standard thickness block gauges with different thicknesses; the standard length values of the standard are sequentially used as d₀，d₁，d₂，…，d_nIs represented by d₀＜d₁＜d₂,...,＜d_nN represents the number of standard cylinders or standard block gauges; the calibration procedure is divided into four steps: first, read for strain_rdPresetting an initial value

The value is within the range of 10 mu epsilon-30 mu epsilon; second, take d from the standard₀Controlling the clamper holding d₀When reading strainWhen the position of the clamping arm is not changed, the current position of the fluted disc (19) is recorded as the displacement original point; third step, with d₁，d₂…，d_nBy replacing d in turn₀Repeating the second step and recording the corresponding strain reading

The fourth step is to

For the calibration number, the length is calculated according to (7), namely the clamping point spacing s:

in the formulae (8) and (9), n represents the number of etalons, d_iIndicating the standard length of the different standards,is represented by_iCorresponding strain readings, i.e. calibration numbers

4) Clamping and measuring; the measuring procedure of the length of the rigid object is divided into three steps: firstly, adjusting the position of a manipulator and the distance s between two chucks to ensure that s is greater than the length m of an object (W) and the object (W) enters a clamping space; in a second step, the drive (2) is controlled to rotate, so that the gripper grips the object (W) when the strain is read_rdObtaining

equation (4) gives the clamping force F to which the object (W) is subjected, and equation (10) gives the length m of the object (W);

the length and the deformation of a deformed object are measured and divided into two situations of integral deformation and local indentation deformation:

the measuring procedure of the overall deformation of the object comprises three steps: first, a strain reading is set

As a measureA quantity starting point; in a second step, the gripper is controlled to grip the object (W) so that the strain reading is takenTake notes of

And the origin-dependent point shift S corresponding thereto₀Calculating the initial length s of the object (W) according to equation (11)₀：

Thirdly, increasing the clamping force F, and tracking and recording F and strain reading epsilon_rdAnd calculating the length of the object (W) in real time according to the formula (12) by depending on the origin point displacement S:

and (2) calculating the deformation v of the object (W) in real time according to the formula (13):

the local indentation deformation measuring program is divided into three steps: first, a strain reading is set

As a measurement starting point; secondly, controlling the gripper to grip the object so that the two gripping pins contact the object (W) when the strain is read

When it is needed, record

And the origin-dependent point shift S corresponding thereto^*(ii) a Thirdly, increasing the clamping force F, and tracking and recording F and FVariable reading epsilon_rdAnd calculating an approximate value of the penetration depth δ according to equation (14) depending on the origin point displacement S: