CN106153331A - The measurement apparatus vibrated based on the flexible doublejointed mechanical arm of machine vision and method - Google Patents

Abstract

The invention discloses a kind of measurement apparatus and the method for flexible doublejointed mechanical arm vibration based on machine vision.This device includes doublejointed flexible mechanical arm, CCD camera, camera fixing device, absolute value encoder, multiple LED and PC.Absolute value encoder is installed on rotary electric machine, and LED is placed on two armed lever tail ends, and CCD camera is placed at middle joint, and the output port of CCD camera and encoder is connected with PC.Camera fixing device makes camera lens direction be in the angular bisector direction of the angle that two-arm bar is formed, and each two field picture of CCD camera detection and the real time positioning data of encoder are sent to PC；Through PC process, when this movement position is static compared with facula position, obtains the vibration displacement of light source, and then analyze mechanical arm vibration performance.The present invention can not contact, do not measure two-arm vibration of bar feature with not changing measured object vibration characteristics, conveniently compares and research, can be widely used.

Description

The measurement apparatus vibrated based on the flexible doublejointed mechanical arm of machine vision and method

Technical field:

The present invention relates to the measuring method of flexible doublejointed mechanical arm vibration, particularly a kind of flexibility based on machine vision The measurement apparatus of doublejointed mechanical arm vibration and method.

Background technology:

Multi-joint mechanical arm, also referred to as articulated robot be modal industrial robot in current industrial circle form it One.It is suitable for the machine automatization equalization of many industrial circles, such as, automatically assemble, spray paint, carry, the work such as welding.This The modal damping of class flexible structure is little, is once acted on by certain exciting force, and it significantly vibrates last very long. This not only can affect the work of structure, also by making structure produce too early fatigue rupture, affects the service life of structure, or causes The damage of structure Instrumental.It is thus desirable to measurement and the vibration suppressing this type of flexible structure.

In prior art, the vibration measurement of flexible joint mechanical arm mainly has employing piezoelectric patches, acceierometer sensor, angle Rate gyroscope sensor, photoelectrical position sensor (Position Sensitive Detector) and fiber-optic grating sensor Methods such as (Fiber Grating Sensor): because multiple links such as signal amplification, filtering can cause signal during piezoelectric patches measurement Postponing and delayed phase, measuring speed is slow, be limited in scope；Acceierometer sensor and angular rate gyroscope sensor are quick to noise Sense, there is the problems such as sluggish and warm drift affects its precision；The measurement scope of photoelectrical position sensor is less, structure is complicated, operation Difficulty is big, calculating process is loaded down with trivial details and cost intensive；The topmost problem of fiber-optic grating sensor is the demodulation of transducing signal, due to Fiber grating is more fragile, is very easy to destroy in harsh environments, so that could use after it is packaged, Packaging technology and safeguard measure structure are complicated.

Content of the invention:

It is an object of the invention to provide a kind of simple in construction, stable performance, the flexibility based on machine vision being convenient for measuring The measurement apparatus of doublejointed mechanical arm vibration and method, it is achieved noncontact, real-time one-shot measurement accurately obtain machine at two simultaneously The vibration performance of mechanical arm.

The technical solution realizing the object of the invention is, a kind of flexible doublejointed mechanical arm vibration based on machine vision Measurement apparatus and method, this device includes doublejointed flexible mechanical arm, CCD camera, camera fixing device, absolute encoder Device, multiple LED and PC, diarticular armed lever rotary electric machine is installed absolute value encoder, and the output of encoder End is connected with PC, and LED is placed on two armed lever tail ends, and CCD camera is placed on the joint between two mechanical arm armed levers, and CCD camera is configured with camera lens, and the output port of CCD camera is connected with PC.When camera fixing device ensures camera lens direction Carving and being at the angular bisector of the angle that two-arm bar is formed, CCD camera can measure two armed lever tail end LED vibrations simultaneously Each two field picture, and be sent to PC；The real time data of encoder reaches PC and enters the motion of row operation positioning mechanical arm Position；PC processes image, with this movement position obtain compared with facula position when static vibration displacement at LED and The parameter of the flexible doublejointed mechanical arm structural low-frequency vibration of reflection.

Measuring method based on the flexible doublejointed mechanical arm vibration of machine vision, it is characterised in that step is as follows:

Entire image is divided into two by the 1st step: the LED position in the image of each frame according to CCD camera collection The corresponding subregion of armed lever tail end LED, and determine the upper corresponding light source collection position in each region；

2nd step: according to the camera image data of incoming PC, determine the barycenter position of each light source hot spot in image coordinate system Put；

3rd step: gather data, localization machine mechanical arm movement angle, the barycenter position that the 2nd step is gathered according to absolute value encoder Put corresponding movement angle data this moment and be recorded in PC；

4th step: according to the facula mass center position gathering under the conditions of different vibration measurings, quiet with under now manipulator motion position Only facula mass center position is processed, and obtains horizontal displacement Δ x and vertical displacement delta y of two corresponding LED；

5th step: according to the parameter of CCD camera, from image coordinate, the vertical position of world coordinate system is tied to two LED Move transformation factor K_x, horizontal transformation factor K_yDemarcate；

6th step: the water that horizontal displacement Δ x according to each LED in image, vertical displacement delta y and the 5th step are demarcated Flat transformation factor K_x, vertical transitions factor K_y, obtain the real standard displacement x of each LED, actual vertical displacement y；

7th step: the actual displacement obtaining according to the 6th step, draws out the position curve of each LED, to each LED The displacement of luminous tube carries out Fast Fourier Transform (FFT), obtains first-order modal frequency and the second order mode of flexible doublejointed mechanical arm vibration State frequency.

The present invention compared with the prior art, has a following remarkable advantage: (1) based on machine vision detection method not only more Intuitively, more easily obtain the low-frequency vibration information of flexible mechanical arm, and whole device is by the detection behaviour to LED Work is simple, it is convenient to implement, measurement noise is little.(2) using absolute value encoder localization machine mechanical arm position, noiseproof feature is strong, number According to reliability high.(3) special construction for mechanical arm, places can change nyctitropic CCD camera with motion at joint, can It to be detected simultaneously by two LED light sources of two mechanical arm armed lever tail ends, is greatly simplified apparatus structure, cost-effective.(4) In the case of not changing the vibration performance of measured object, follow the tracks of light source by machine vision, detect the dynamic displacement of flexible structure, There is noncontact, measurement wide ranges, the advantage such as vibration characteristics not changing measured object.

Brief description:

Fig. 1 is the structural representation of the measurement apparatus based on the flexible doublejointed mechanical arm vibration of machine vision for the present invention；

Fig. 2 is camera fixing device simplified schematic diagram；

Fig. 3 is graphical analysis sketch；

Detailed description of the invention:

The present invention is described in further detail with detailed description of the invention below in conjunction with the accompanying drawings.

The present invention uses method the shaking by the mechanical arm tail end illuminating source of collection different motion position of machine vision Dynamic displacement realizes the device and method that low frequency modal is analyzed.

As it is shown in figure 1, include that doublejointed is flexible based on the measurement apparatus of the flexible doublejointed mechanical arm vibration of machine vision Mechanical arm the 1st, CCD camera the 2nd, camera fixing device the 3rd, absolute value encoder the 4th, multiple LED 5 and PC 6；Described flexibility Doublejointed mechanical arm 1, diarticular armed lever rotary electric machine is installed absolute value encoder 4, and the output of encoder and PC 6 Connecting, LED 5 is placed on 1 liang of armed lever tail end of doublejointed flexible mechanical arm, and CCD camera 2 is placed between two mechanical arm armed levers Joint on, and CCD camera is configured with camera lens, and the output port of CCD camera 2 is connected with PC 6.As in figure 2 it is shown, described camera Fixing device, forms a diamond structure with doublejointed flexible mechanical arm two-arm bar, and diagonal uses retractable material as CCD phase Machine support, support can be according to manipulator motion position change direction, and CCD camera is on cornerwise support of diamond structure, Ensure that the CCD camera lens direction moment is in the angular bisector direction of the angle that two-arm bar is formed.

Based on the measuring method of the flexible doublejointed mechanical arm vibration of machine vision, step is as follows:

Entire image is divided into by the 1st step: LED 5 position in the image of each frame according to CCD camera 2 collection The two corresponding subregions of armed lever tail end LED 5, and determine the upper corresponding light source collection position in each region；

2nd step: according to the camera image data of incoming PC 6, determine the barycenter of each light source hot spot in image coordinate system Position；

3rd step: gather data, localization machine mechanical arm movement angle, the barycenter that the 2nd step is gathered according to absolute value encoder 4 The corresponding movement angle data this moment in position are recorded in PC 6；

As it is shown on figure 3, during the work of electric machine rotation driving mechanical arm, in motor, absolute value encoder 4 records rotational angle, Being α to the rotational angle of armed lever 1, the rotational angle of armed lever 2 is that (direction is initial level direction and revolves counterclockwise 180 ° of-β Turn), the slewing area of α, β is 90 °, 0 ° ＜ β ＞ of 0 ° of ＜ α ＞ 90 °, for two armed levers when (α, β) in image coordinate system Projected position is:

$Y_{1(\mathrm{\α},\mathrm{\β})}=l_{1}sin\frac{(\mathrm{\α}+\mathrm{\β})}{2},Y_{2(\mathrm{\α},\mathrm{\β})}=-l_{2}sin\frac{(\mathrm{\α}+\mathrm{\β})}{2}---\left(1\right)$

Y in formula_{1 (α, β)}, Y_{2 (α, β)}It is respectively armed lever 1 and y-axis coordinate position in the image coordinate system of (α, β) position for the armed lever 2 Put, l₁,l₂For being arranged on the distance of LED 5 to CCD camera 2 camera lens of 1 liang of armed lever tail end of doublejointed flexible mechanical arm.

X-axis direction non-displacement when static, so obtaining static friction and when mechanical arm is in (α, β) position, armed lever is the 1st, On armed lever 2, light source coordinate in CCD camera 2 image coordinate system is:

${(X_1,Y_1)}_{(\mathrm{\α},\mathrm{\β})}=(0,l_{1}sin\frac{(\mathrm{\α}+\mathrm{\β})}{2}),{(X_2,Y_2)}_{(\mathrm{\α},\mathrm{\β})}=(0,-l_{2}sin\frac{(\mathrm{\α}+\mathrm{\β})}{2})---\left(2\right)$

4th step: according to the facula mass center position gathering under the conditions of different vibration measurings, with now doublejointed flexible mechanical arm 1 machine Static facula mass center position under mechanical arm movement position is processed, and obtains the horizontal displacement Δ x of two corresponding LED 5 With vertical displacement delta y, specifically comprise the following steps that

According to the 1st step, the 2nd step detecting step and Fig. 3, under (α, β) position, this two field picture of CCD camera record Obtain the centroid position of light source on armed lever the 1st, armed lever 2 on image coordinate system through computing:

(X₁,Y₁)′_(α,β)=(x₁,y₁), (X₂,Y₂)′_(α,β)=(x₂,y₂) (3)

And then obtain the displacement in two armed lever glazing sources in image coordinate system:

${\mathrm{\Δx}}_1=x_1,{\mathrm{\Δy}}_1=y_1-l_{1}sin\frac{(\mathrm{\α}+\mathrm{\β})}{2}---\left(4\right)$

${\mathrm{\Δx}}_2=x_2,{\mathrm{\Δy}}_2=y_2+l_{2}sin\frac{(\mathrm{\α}+\mathrm{\β})}{2}---\left(5\right)$

Δ x in formula₁,Δy₁, Δ x₂,Δy₂It is respectively the horizontal displacement in two armed lever image coordinate systems and vertical displacement.

5th step: according to the parameter of CCD camera 2, from image coordinate, world coordinate system is tied to two LED 5 vertical Shift transformation factor K_x, horizontal transformation factor K_yDemarcate, specifically comprise the following steps that

Set up coordinate system: as a example by the armed lever of the top of flexible doublejointed mechanical arm 1, with armed lever tail end LED 5 Placement location O_WFor initial point, the direction pointing to camera 2 when armed lever is static is Z axis, sets up world coordinate system O_W-W_WX_WY_WZ_W；With CCD The photocentre O of camera 2_CFor initial point.The angle bisection of the angle that camera lens direction, i.e. doublejointed flexible mechanical arm 1 two-arm bar are formed Line direction is that Z axis sets up image coordinate system O_C-W_CX_CY_CZ_C；

Image coordinate system O_C-W_CX_CY_CZ_CIn horizontal displacement, vertical displacement to world coordinate system O_W-W_WX_WY_WZ_WConversion Relation is:

X=K_xΔ x, y=K_yΔy (6)

$K_x=1,K_y=\frac{1}{cos\left(\frac{\mathrm{\α}+\mathrm{\β}}{2}\right)}---\left(7\right)$

Wherein Δ x, Δ y are horizontal displacement and vertical displacement in image coordinate system, and x, y are actual in world coordinate system Horizontal displacement and vertical displacement, K_x K_yIt is tied to the horizontal displacement transformation factor of world coordinate system for image coordinate and vertical displacement becomes Change the factor.

6th step: horizontal displacement Δ x according to each LED 5 in image, vertical displacement delta y and the 5th step are demarcated Horizontal transformation factor K_x, vertical transitions factor K_y, obtain the real standard displacement x of each LED, actual vertical displacement y, Specifically comprise the following steps that

Composite type (4), formula (5) and formula (7) obtain:

Real standard displacement and the actual vertical displacement of light source on armed lever 1 is:

x₁=K_xΔx₁=x₁ (8)

$y_1=K_y{\mathrm{\Δy}}_1=\frac{1}{cos\left(\frac{\mathrm{\α}+\mathrm{\β}}{2}\right)}\[y_1-l_{1}sin\frac{(\mathrm{\α}+\mathrm{\β})}{2}\]---\left(9\right)$

Real standard displacement and the actual vertical displacement of light source on armed lever 2 is:

x₂=K_xΔx₂=x₂ (10)

$y_2=K_y{\mathrm{\Δy}}_2=\frac{1}{cos\left(\frac{\mathrm{\α}+\mathrm{\β}}{2}\right)}\[y_2+l_{2}sin\frac{(\mathrm{\α}+\mathrm{\β})}{2}\]---\left(11\right)$

7th step: the actual displacement obtaining according to the 6th step, draws out the position curve of each LED 5, to each The displacement of LED 5 carries out Fast Fourier Transform (FFT), obtain flexible doublejointed mechanical arm 1 vibration first-order modal frequency and Second-order modal frequency.Specifically comprise the following steps that

Repeatedly measuring diverse location is (α₁, β₁)、(α₂, β₂) ... wait the armed lever tail end light source displacements of location point, it is entered Row Fast Fourier Transform (FFT), obtains first-order modal frequency and the second-order modal frequency of flexible 1 liang of armed lever of doublejointed mechanical arm.

In sum, the machine vision vibration measurement device constructed by method that the present invention proposes, can be for doublejointed Mechanical arm special construction, uses absolute value encoder positioning, it is achieved that vibration at a CCD camera measurement two.The method has The plurality of advantages such as noncontact, the vibration characteristics not changing measured object, device is simple, the degree of accuracy is high.

Claims (5)

1. the measurement apparatus vibrated based on the flexible doublejointed mechanical arm of machine vision, including doublejointed flexible mechanical arm (1), it is characterised in that: this device also includes CCD camera (2), camera fixing device (3), absolute value encoder (4), multiple LED Luminous tube (5) and PC (6), described flexible doublejointed mechanical arm (1), two armed lever tail ends arrange LED (5), joint Placing camera fixing device (3), CCD camera (2) is fixed on device and is configured with camera lens, and two joint arranges absolute value encoder (4), CCD camera (2) is connected with PC (6) with the output port of absolute value encoder (4).

2. the measurement apparatus of the flexible doublejointed mechanical arm vibration based on machine vision according to claim 1, its feature Being: described camera fixing device (3), forming a diamond structure with doublejointed flexible mechanical arm (1) two-arm bar, diagonal uses Retractable material is as CCD camera (2) support, and support can be according to manipulator motion position change direction, and CCD camera (2) is in On cornerwise support of diamond structure, it is ensured that the angle that CCD camera (2) the lens direction moment is in the angle that two-arm bar is formed is put down Separated time direction.

3. the measuring method based on the flexible doublejointed mechanical arm vibration of machine vision, it is characterised in that step is as follows:

Entire image is divided into by the 1st step: LED (5) position in the image of each frame gathering according to CCD camera (2) The two corresponding subregions of armed lever tail end LED (5), and determine that the upper corresponding light source in each region gathers position；

2nd step: according to the camera image data of incoming PC (6), determine the barycenter position of each light source hot spot in image coordinate system Put；

3rd step: gather data, localization machine mechanical arm movement angle, the barycenter position that the 2nd step is gathered according to absolute value encoder (4) Put corresponding movement angle data this moment and be recorded in PC (6)；

4th step: quiet according under hot spot centroid position, with now manipulator motion position when gathering vibration under the conditions of different vibration measurings Only facula mass center position is processed, and obtains horizontal displacement Δ x and vertical displacement delta y of two corresponding LED (5)；

5th step: according to the parameter of CCD camera (2), from image coordinate, world coordinate system is tied to two LED (5) vertical Shift transformation factor K_x, horizontal transformation factor K_yDemarcate；

6th step: the water that horizontal displacement Δ x according to each LED (5) in image, vertical displacement delta y and the 5th step are demarcated Flat transformation factor K_x, vertical transitions factor K_y, obtain the real standard displacement x of each LED (5), actual vertical displacement y；

7th step: the actual displacement obtaining according to the 6th step, draws out the position curve of each LED (5), to each LED The displacement of luminous tube (5) carries out Fast Fourier Transform (FFT), obtains the first-order modal frequency and two of flexible doublejointed mechanical arm vibration Rank model frequency.

4. the measuring method of the flexible doublejointed mechanical arm vibration based on machine vision according to claim 3, its feature It is, described in the 3rd step, gather data, localization machine mechanical arm movement angle, the matter that the 2nd step is gathered according to absolute value encoder (4) The corresponding movement angle data this moment in heart position are recorded in PC (6), specifically comprise the following steps that

By encoder (4) obtain flexible (1) two armed lever of doublejointed mechanical arm rotated counterclockwise by angle α with respect to the horizontal plane with 180 ° of-β, and 90 °, 0 ° ＜ β ＞ of 0 ° of ＜ α ＞ 90 °, projected position in image coordinate system for two armed levers now is:

$Y{1}_{\mathrm{\α},\mathrm{\β}}=l_{1}sin\frac{(\mathrm{\α}+\mathrm{\β})}{2},Y{2}_{\mathrm{\α},\mathrm{\β}}=l_{2}sin\frac{(\mathrm{\α}+\mathrm{\β})}{2}---\left(1\right)$

Y1 in formula_{α, β}, Y2_{α, β}For flexible position in image coordinate system for doublejointed mechanical arm (1) two armed lever, l₁,l₂For being arranged on The LED (5) of two armed lever tail ends is to the distance of camera lens.

5. the measuring method of the flexible doublejointed mechanical arm vibration based on machine vision according to claim 3, its feature It is, the 5th step: according to the parameter of CCD camera (2), from image coordinate, world coordinate system water is tied to two LED (5) Prosposition moves transformation factor Kx, and vertical displacement transformation factor Ky demarcates, and specifically comprises the following steps that

Set up coordinate system: as a example by the armed lever of the top of flexible doublejointed mechanical arm (1), with armed lever tail end LED (5) Placement location O_WFor initial point, the direction pointing to camera when armed lever is static is Z axis, sets up world coordinate system；With CO_W-W_WX_WY_WZ_WCD The photocentre O of camera (2)_CFor initial point.Camera lens direction, the angle of the angle that i.e. flexible doublejointed mechanical arm (1) two-arm bar is formed Bisector direction is that Z axis sets up image coordinate system O_C-W_CX_CY_CZ_C,

Image coordinate system O_C-W_CX_CY_CZ_CIn horizontal displacement, vertical displacement to world coordinate system O_W-W_WX_WY_WZ_WTransformation relation For:

X=K_xΔ x, y=K_yΔy (2)

$K_x=1,K_y=\frac{1}{cos\left(\frac{\mathrm{\α}+\mathrm{\β}}{2}\right)}---\left(3\right)$

Δ x in formula, Δ y are horizontal displacement and vertical displacement in image coordinate system, and x, y are level actual in world coordinate system Displacement and vertical displacement, K_x K_yFor image coordinate be tied to the horizontal displacement transformation factor of world coordinate system and vertical displacement conversion because of Son.