CN113331825A - Real-time RULA evaluation method in virtual reality - Google Patents

Abstract

The invention provides a real-time RULA evaluation method in virtual reality, which comprises the steps of collecting action frames, establishing a space coordinate system based on the action frames, extracting joint point coordinates based on the space coordinate system, and acquiring each limb vector based on the joint point coordinates; acquiring a main sagittal plane and a correction sagittal plane based on the joint point coordinates and the coordinate axis in the space coordinate system; acquiring main scores of all limbs and corrected scores of all limbs based on the vectors of all limbs, the main sagittal plane and the corrected sagittal plane; and obtaining total scores of all the limbs based on the main scores of all the limbs and the corrected scores of all the limbs, and obtaining the RULA scores of the human body postures through the RULA worksheet based on the total scores of all the limbs. The RULA evaluation method provided by the invention realizes quick, real-time and accurate evaluation of human-computer work efficiency.

Description

A real-time evaluation method of RULA in virtual reality

technical field

The invention relates to the technical field of artificial machine effect evaluation, in particular to a RULA real-time evaluation method in virtual reality.

Background technique

Ergonomic design is of great significance to industrial production, product quality, production cost, and worker safety. It is urgent to consider human factors in industrial product design. The traditional ergonomic evaluation method is that engineers use the Digital Human Model (DHM) in CAM software to evaluate the ergonomics of assembly design. However, CAM software is less efficient, less accurate, and lacks real-time performance. Engineers need to adjust the DHM's limbs, vision, etc., and make a large number of key frames, which is very complex and cumbersome, and lacks realism and immersion. Therefore, it is urgent to improve the ergonomic evaluation method based on DHM, and to improve the rapidity, real-time and accuracy of evaluation through virtual reality technology.

Among the ergonomic evaluation methods of DHM, the RULA rapid upper limb analysis model is a commonly used ergonomic evaluation method. In the field of machinery industry, the evaluation of ergonomics is mainly achieved by subjective observation or estimation of the angle of human joints in pictures or videos, which requires inviting experts in this field to spend a lot of time on posture analysis, and cannot achieve the ergonomics of the RULA model. Fast, real-time and accurate evaluation of ergonomics.

SUMMARY OF THE INVENTION

In order to solve the problem that the existing RULA model existing in the above-mentioned prior art cannot be evaluated quickly, in real time and accurately, the present invention provides a RULA real-time evaluation method in virtual reality, including:

collecting action frames, establishing a space coordinate system based on the action frames, extracting joint point coordinates based on the space coordinate system, and acquiring each limb vector based on the joint point coordinates;

Obtaining the main sagittal plane and the corrected sagittal plane based on the joint point coordinates and the coordinate axes in the space coordinate system;

Project each limb vector into the main sagittal plane to obtain the main projection vector of each limb vector, and obtain the main angle of each limb vector on the main sagittal plane according to the main projection vector; Describe the main angle of each limb and obtain the main score of each limb;

Project each limb vector into the modified sagittal plane, obtain the modified projection vector of each limb vector, and obtain the modified angle of the limb vector on the modified sagittal plane according to the modified projection vector; , get the corrected score of each limb;

Based on the main score of each limb and the modified score of each limb, the total score of each limb is obtained, and based on the total score of each limb, the RULA score of the human body posture is obtained through the RULA worksheet.

Preferably, the joint point coordinates include tail vertebra coordinates, neck coordinates, head coordinates, left shoulder coordinates, right shoulder coordinates, left elbow coordinates, right elbow coordinates, left wrist coordinates, right wrist coordinates, left hand coordinates, right hand coordinates, Left hip coordinates, right hip coordinates, and shoulder coordinates.

Preferably, each limb vector includes a torso vector, a neck vector, a right upper arm vector, a left upper arm vector, a right forearm vector, a left forearm vector, a right wrist vector and a left wrist vector.

Preferably, the specific steps of obtaining the main sagittal plane include:

Based on the coordinates of the shoulder vertebra, the coordinates of the left shoulder, and the coordinates of the right shoulder, the main sagittal plane is obtained, wherein the coordinates of the shoulder vertebra are located on the main sagittal plane, and the vector from the coordinates of the left shoulder to the coordinates of the right shoulder is the main vector The normal vector of the plane.

Preferably, the modified sagittal plane includes a first modified sagittal plane, a second modified sagittal plane, and a third modified sagittal plane;

The first corrected sagittal plane is used to calculate the corrected score of trunk torsion and the corrected score of neck torsion based on the vectors of each limb;

the second corrected sagittal plane is used to calculate the corrected score of the scoliosis of the trunk based on the vectors of each limb;

The third corrected sagittal plane is used to calculate the corrected score of the scoliosis of the neck, the corrected score of the scoliosis of the upper arm, and the corrected score of the scoliosis of the forearm based on the vectors of each limb.

Preferably, the specific steps of obtaining the first corrected sagittal plane include:

The first modified sagittal plane is obtained based on the x-axis and the y-axis in the space coordinate system, wherein the x-axis and the y-axis in the space coordinate system are located on the first modified sagittal plane.

Preferably, the specific step of obtaining the second corrected sagittal plane includes:

The second modified sagittal plane is obtained based on the coordinates of the left hip, the right hip, and the coordinate axes in the space coordinate system, wherein the left hip coordinates and the right hip coordinates are located on the second modified sagittal plane, and the space The y-axis in the coordinate system is parallel to the second modified sagittal plane.

Preferably, the specific step of obtaining the third corrected sagittal plane includes:

The third modified sagittal plane is obtained based on the torso vector, left shoulder coordinates, and right shoulder coordinates, wherein the torso vector is located on the third modified sagittal plane, and points from the left shoulder coordinates to the right shoulder coordinates The vector obtained by the cross product of the vector and the torso vector is the normal vector of the third modified sagittal plane.

Preferably, the specific steps of obtaining the principal score of each limb include:

Calculate the projection vector of each limb vector on the normal vector of the main sagittal plane, calculate the main projection vector of each limb vector on the main sagittal plane through the projection vector, and then calculate the main projection of each limb vector by calculating The included angle between the vectors is used to obtain the main angle of each limb vector. By matching the corresponding score of the main angle in the RULA worksheet, the main score of each limb is obtained.

Preferably, the specific steps for obtaining the correction score of each limb based on the correction angle are:

Based on the correction angle, the posture factor at the current correction angle is obtained, and the correction score of each limb is obtained by matching the correction score corresponding to the posture factor in the RULA worksheet.

Compared with the prior art, the present invention has the following effects:

In the present invention, the RULA of the test posture can be obtained by constructing the main sagittal plane, correcting the sagittal plane, projecting the limb vector into each sagittal plane, then calculating the angle of the projected vector, and combining with the RULA worksheet to determine the score. Score, does not need manual data collection and analysis, avoids the complexity of manual operation, greatly reduces the time to determine the RULA score of the test posture, and avoids the subjectivity of manual judgment, greatly increasing the RULA score determination The accuracy of the RULA model has been achieved quickly, real-time and accurate evaluation of the ergonomics of the RULA model.

Description of drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings required in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some of the present invention. In the embodiments, for those of ordinary skill in the art, other drawings can also be obtained according to these drawings without creative labor.

1 is a schematic flowchart of a method provided by an embodiment of the present invention;

2 is a schematic diagram of a main sagittal plane provided by an embodiment of the present invention;

3 is a schematic diagram of a first corrected sagittal plane provided by an embodiment of the present invention;

4 is a schematic diagram of a second modified sagittal plane provided by an embodiment of the present invention;

5 is a schematic diagram of a third modified sagittal plane provided by an embodiment of the present invention;

FIG. 6 is a diagram for evaluating the revised scores of the upper arm, forearm, and wrist provided by an embodiment of the present invention;

FIG. 7 is an evaluation diagram of correction scores of the neck and torso according to an embodiment of the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

In order to solve the problems in the prior art that the ergonomics of the RULA model cannot be achieved quickly, in real time, and accurately, the present invention provides the following solutions:

As shown in Figure 1, the present invention provides a RULA real-time evaluation method in virtual reality, comprising:

collecting action frames, establishing a space coordinate system based on the action frames, extracting joint point coordinates based on the space coordinate system, and acquiring each limb vector based on the joint point coordinates;

The present invention uses Vive HMD, Kinect v2 and LeapMotion as human body motion capture devices. During the test process, each action frame is collected, and at the same time, the position of the test person's joint points in the action frame is collected. The coordinate system, in the space coordinate system, collects the joint point coordinates corresponding to the joint point based on the joint point position.

The joint points include tail vertebra, neck, head, left shoulder, left elbow, left wrist, left hand, right shoulder, right elbow, right wrist, right hand, left hip, right hip and shoulder vertebra, and the corresponding joint point coordinates include: Coccyx j ₀ , neck j ₂ , head j ₃ , left shoulder j ₄ , left elbow j ₅ , left wrist j ₆ , left hand j ₇ , right shoulder j ₈ , right elbow j ₉ , right wrist j ₁₀ , right hand j ₁₁ , left hip j ₁₂ , right hip j ₁₆ and shoulder vertebra j ₂₀ .

The limb vectors include a trunk vector v _truck , a neck vector v _neck , a right upper arm vector v _rua , a left upper arm vector v _lua , a right forearm vector v _rla , a left forearm vector v _lla , a right wrist vector v _rw and a left wrist vector v _lw .

The relationship between the limb vector and the joint point coordinate is shown in Table 1 below:

Table 1

Based on the joint point coordinates and the coordinate axes in the space coordinate system, obtain the main sagittal plane and the corrected sagittal plane:

As shown in FIG. 2 , based on the coordinates of the shoulder vertebra, the coordinates of the left shoulder, and the coordinates of the right shoulder, the main sagittal plane is obtained, wherein the shoulder vertebra coordinate j ₂₀ is located on the main sagittal plane, and points from the left shoulder coordinate j ₄ to the The vector of the right shoulder coordinate j ₈ is the shoulder vector v _rs-ls , v _rs-ls =j ₄ -j ₈ , and the shoulder vector v _rs-ls is the normal vector of the main sagittal plane.

As shown in FIGS. 3-5 , the modified sagittal plane includes a first modified sagittal plane, a second modified sagittal plane, and a third modified sagittal plane; the first modified sagittal plane is used for The vector of each limb is used to calculate the correction score of trunk torsion and the correction score of neck torsion; the second correction sagittal plane is used to calculate the correction score of side bending of the trunk based on the vector of each limb; the third correction The sagittal plane is used to calculate the corrected score of neck scoliosis, the corrected score of upper arm scoliosis, and the corrected score of forearm scoliosis based on the vector of each limb. in,

The first modified sagittal plane is obtained based on the x-axis and the y-axis in the space coordinate system, wherein the x-axis and the y-axis in the space coordinate system are located on the first modified sagittal plane.

The second modified sagittal plane is obtained based on the coordinates of the left hip, the right hip, and the coordinate axes in the space coordinate system, wherein the left hip coordinates and the right hip coordinates are located on the second modified sagittal plane, and the space The y-axis in the coordinate system is parallel to the second modified sagittal plane.

The third modified sagittal plane is obtained based on the torso vector, left shoulder coordinates, and right shoulder coordinates, wherein the torso vector is located on the third modified sagittal plane, and points from the left shoulder coordinates to the right shoulder coordinates The vector obtained by the cross product of the vector and the torso vector is the normal vector of the third modified sagittal plane.

Then, project each limb vector into the main sagittal plane to obtain the main projection vector of each limb vector, and obtain the main angle of each limb of the limb vector on the main sagittal plane according to the main projection vector; Describe the main angle of each limb and obtain the main score of each limb;

The specific steps for obtaining the principal score of each limb include:

Calculate the projection vector of each limb vector on the normal vector of the main sagittal plane, calculate the main projection vector of each limb vector on the main sagittal plane through the projection vector, and then calculate the main projection of each limb vector by calculating The included angle between the vectors is used to obtain the main angle of each limb vector. By matching the corresponding score of the main angle in the RULA worksheet, the main score of each limb is obtained.

The projection vector of the trunk vector v _truck on the direction of the unit normal vector n _rl of the sagittal plane S is v _rl-truck , where v _rl-truck = n _rl · v _truck · n _rl

Further, the projection vector of the trunk vector v _truck on the sagittal plane S is v' _truck , where v' _truck = v _truck -n _rl · v _truck · n _rl

The calculation method of the main projection vector of the other limb vectors on the main sagittal plane is the same as that of the torso vector, that is, the neck vector v _neck , the right upper arm vector v _rua , the left upper arm vector v _lua , the right forearm vector v _lua , the left forearm vector The main projection vectors of v _lla on the main sagittal plane S are v' _truck , v' _rua , v' _lua , v' _rla , v' _lla ,

in:

v' _neck =v _neck -n _rl v _neck n _rl v' _rua =v _rua -n _rl v _rua n _rl v' _lua =v _lua -n _rl v _lua n _rl v' _rla =v _rla -n _rl · v _rla · n _rl v' _lla = v _lla -n _rl · v _lla · n _rl .

通过RULA工作表对躯干主角度进行判断，得到躯干主分值。Calculate the trunk principal score, the angle between the projection vector v' _truck of the trunk vector v _truck on the sagittal plane S and the y-axis n _y of the world coordinate system is the trunk principal angle θ _truck , where

The main angle of the trunk is judged by the RULA worksheet, and the main score of the trunk is obtained.

To calculate the principal score of the neck, the curvature of the neck is relative to the trunk, so the angle between the principal projection vector v' _neck of the neck and the principal projection vector v' _truck of the trunk is calculated as the principal neck angle θ _neck , where,

The neck posture feature is divided into two situations: forward tilt and backward tilt, so first judge whether the neck is forward or backward. The main projection vector v' _neck of the neck is vertical on the main sagittal plane and the vector direction is the test person The angle between the face orientation vector H _z and the torso vector v _truck is θ _neckjudge , where,

则颈部前倾；若

则颈部后仰。like

the neck is tilted forward; if

The neck is tilted back.

The main angle of the trunk was judged by the RULA worksheet, and the main score of the neck was obtained. If the neck is tilted backward, the neck principal score is 4; if the neck is tilted forward, the corresponding neck principal score S' _{neck is obtained according to the neck angle θ neck .}

Calculate the upper arm principal score S' _upperarm , the forward or backward tilt of the upper arm is relative to the trunk, therefore, the projection of the upper arm vector v _upperarm on the sagittal plane S, the projection vector v' _upperarm and the trunk vector v _truck on the sagittal plane S projection The angle between the vectors v' _truck is the upper arm forward or backward tilt angle θ _upperarm .

The upper arm is divided into the left upper arm and the right upper arm, and the main score of the upper arm takes the larger value of the left upper arm score and the right upper arm score. The angle between the main projection vector v' _lua of the left upper arm vector v _lua on the sagittal plane S and the vector v' _truck is the left upper arm main angle θ _lua , where,

In the same way, the main angle θ _rua of the upper right arm can be obtained

The calculation of the principal score of the upper arm needs to be discussed in two cases, anteversion and retroversion. However, when θ _lua or θ _rua is greater than 45°, the score difference between the anteversion and retroversion of the upper arm will appear.

The body orientation of the virtual human is the vector obtained by the cross product of the torso vector and the shoulder vector. The vector v _ls-rs from the left shoulder j ₄ to the right shoulder j ₈ is v _ls-rs =j ₈ -j ₄ , and the virtual human body orientation is v _bd where v _bd =v _truck ×v _ls-rs

Calculate the angle θ _{upperarmjudge} between the virtual human body orientation v _bd and the sum of the upper arm vector v _upperarm and the trunk vector v _truck v _uat (v _uat =v _upperarm +v _truck ) to judge, θ _{upperarmjudge} is shown in the following formula.

则上臂后倾；若

则上臂前倾。like

The upper arm is tilted backward; if

The upper arm leans forward.

The main angle θ _upperarm of the upper arm is judged through the RULA worksheet, and the main score S' _upperarm of the upper arm is obtained.

Left forearm main angle θ _lla and right forearm main angle θ _rla and forearm main score S' _lowerarm calculation

The forward tilt of the forearm is relative to the trunk, so the forearm angle θ _lowerarm is the clip between the projection vector v' _lowerarm of the forearm vector v _lowerarm on the sagittal plane S and the projection vector v' _truck of the trunk vector v _truck on the sagittal plane S. horn.

The forearm is divided into the left forearm and the right forearm, and the forearm score takes the larger of the left forearm principal score and the right forearm principal score.

The angle θ _lla between the projection vector v' _lla of the left forearm vector v _lla on the sagittal plane S and the vector v' _truck , where:

In the same way, the main angle θ _rla of the right forearm can be obtained,

Judging the main angle θ _lowerarm of the forearm through the RULA worksheet to obtain the main score S' _lowerarm of the forearm.

Left wrist main angle θ _lw and right wrist main angle θ _rw and wrist main score S' _wrist calculation

The curvature of the wrist is relative to the forearm, so the wrist angle θ _wrist is the angle between the wrist vector v _wrist and the forearm vector v _lowerarm .

The wrist is divided into a left wrist and a right wrist, and the principal score of the wrist is the larger of the principal score of the left wrist and the principal score of the right wrist.

The angle between the left wrist vector v _lw and the left forearm vector v _lla is θ _leftwrist , where,

In the same way, the main angle θ _rw of the right wrist can be obtained, where:

The main wrist angle θ _wrist is judged by the RULA worksheet, and the main wrist score S' _wrist is obtained.

Project each limb vector into the modified sagittal plane, obtain the modified projection vector of each limb vector, and obtain the modified angle of the limb vector on the modified sagittal plane according to the modified projection vector; , get the corrected score of each limb;

The specific steps of obtaining the correction angle of the limb vector on the correction sagittal plane include: obtaining the posture factor under the current correction angle based on the correction angle, as shown in Figures 6-7, by matching the posture factor in RULA. Corresponding correction points in the worksheet, get correction points for each limb.

Torso torsion correction score calculation.

According to the RULA worksheet, the trunk correction score is determined by whether the trunk is twisted or not, and whether the trunk is side-curved. If the trunk is twisted but not sideways, or the trunk is sideways but not twisted, the trunk correction score S" _truck is 1 point; if the trunk is twisted and sideways, the trunk correction score S" _truck is 2 points; Torsion is also not sideways, and the trunk correction score S” _truck is 0 points.

Among them, the sagittal plane S _xoz is the projected sagittal plane calculated by the torsion of the torso, and its normal vector is the y-axis _ny of the world coordinate system; the shoulder vector v _ls-rs is the vector from the left shoulder j ₄ to the right shoulder j ₈ , that is, v _ls-rs =j ₈ -j ₄ ; the hip vector v _lh-rh is the vector of the left hip j ₁₂ pointing to the right hip j ₁₆ , ie v _lh-rh =j ₁₆ -j ₁₂ . If the torso is twisted, the projection vector v” _ls-rs of the shoulder vector v _ls-rs on the sagittal plane S _xoz and the projection vector v” _lh -rh of the hip vector v _lh-rh on the sagittal plane S _xoz If it is not parallel, its included angle is θ _trucktwist (torso twist correction angle).

The projection vectors of the shoulder vector v _ls-rs and the hip vector v _lh-rh on the first modified sagittal plane S _xoz are v” _ls-rs , v” _lh-rh , where: v” _ls-rs =v _ls-rs -n _y v _ls-rs n _y , v” _lh-rh =v _lh-rh -n _y v _lh-rh n _y

So the trunk twist correction angle θ _trucktwist :

认为躯干扭转；若

认为躯干未扭转。Set the threshold value to 20° for θ _trucktwist , then if

The trunk is considered to be twisted; if

The torso is considered untwisted.

Trunk scoliosis calculation, wherein, the second modified sagittal plane S _hy is the projected sagittal plane calculated for trunk scoliosis, and the unit normal vector of the second modified sagittal plane S _hy is

If the trunk is bent sideways, the included angle θ _truckbend (torso side bending correction angle) between the projection vector v” _truck of the trunk vector v _truck on the second corrected sagittal plane S _hy and the y-axis _ny of the world coordinate system is not zero.

The projection vector v” _truck of the trunk vector v _truck on the sagittal plane S _hy is as follows:

So the trunk torsion correction angle θ _truckbend is as follows:

认为躯干侧弯；若

认为躯干未侧弯。Set a threshold value of 20° for θ _truckbend , then if

The trunk is considered scoliosis; if

The torso is considered uncurved.

Neck correction score calculation:

According to the RULA worksheet, the neck correction score is determined by whether the neck is twisted or not, and whether the neck is scoliated or not. If the neck is twisted but not sideways, or the neck is sideways but not twisted, the neck correction score S” _neck is 1 point; if the neck is twisted and the neck is sideways, the neck correction score S” _neck is scored as 2 points; if the neck is not twisted and laterally bent, the neck correction score S” _neck is scored as 0 points.

neck twist judgment

Calculation of neck torsion: Among them, the first modified sagittal plane S _xoz is the projection sagittal plane for the calculation of neck torsion. The main projection vector v' _neck of the neck is vertical on the main sagittal plane and the vector direction is the vector H _z of the test person's connecting orientation and the virtual human body orientation vector v _bd are respectively projected to the first modified sagittal plane S _xoz to obtain The vector H” _z and the vector v” _bd , if the neck is twisted, the vector H” _z and the vector v” _bd are not parallel, and the included angle is θ _necktwist (the neck twist correction angle).

The projection vector H” _z of the vector H _z on the sagittal plane S _xoz , where: H” _z =H _z -n _y ·H _z · _ny

The projection vector v” _bd of v _bd on the sagittal plane S _xoz , v” _bd = v _bd -n _y · v _bd · n _y

Therefore, the neck twist judgment angle θ _necktwist is shown in the following formula.

认为颈部扭转；若

认为颈部未扭转。Set the threshold for θ _necktwist to 20°, then if

The neck is considered to be twisted; if

The neck is considered untwisted.

Neck Scoliosis Calculation

Wherein, the third modified sagittal plane S _tr-bd is the projected sagittal plane calculated by the neck scoliosis, and its normal vector is the virtual human body facing v _bd . The neck curvature correction angle θ _neckbend is the included angle between the projection vector v” _neck of the neck vector v _neck on the sagittal plane Str _-bd and the trunk vector v _truck .

The projection vector v” _neck of the neck vector v _neck on the sagittal plane S _tr-bd , where:

Therefore, the neck scoliosis judgment angle θ _neckbend is shown in the following formula.

认为颈部侧弯；若

认为颈部未侧弯。Set the threshold for θ _neckbend to 20°, then if

The neck is considered scoliosis; if

Consider that the neck is not scoliated.

Upper Arm Correction Score

According to the RULA worksheet, the upper arm correction score is determined by whether the shoulder is raised or not and whether the upper arm is abducted or not. If the shoulder is raised but the upper arm is not abducted, or the upper arm is abducted but the shoulder is not raised, the upper arm correction score S” _upperarm is 1 point; if the upper arm is abducted and the shoulder is raised, the upper arm correction score S” _upperarm is 2 points; if the upper arm is not abducted and the shoulder is not raised, the upper arm correction score S” _upperarm is 0 points.

shoulder lift calculation

Shoulder lifts are divided into right shoulder lifts and left shoulder lifts. If the right shoulder is lifted up, the angle _θrs-upp between the projection vector v” _rs of the right shoulder vector v _rs on the third modified sagittal plane _Str-bd and the trunk vector v _truck ) is less than 90°. Similarly, if the left shoulder is lifted up, the angle θ _ls-upp between the projection vector v” _ls of the left shoulder on the sagittal plane S _tr-bd and the trunk vector v _truck less than 90°. The right shoulder vector v _rs is v _rs =j ₈ -j ₂₀ ; the left shoulder vector v _ls is v _ls =j ₄ -j ₂₀ .

The projection vector v” _ls of the left shoulder vector v _ls on the sagittal plane _Str-bd is shown in the following formula.

Therefore, the left shoulder lift judgment angle θ _ls-upp is shown in the following formula.

Similarly, the right shoulder uplift judgment angle θ _rs-upp can be obtained, as shown in the following formula.

或

则给上臂修正分值增加1分，否则不用修正上臂分值。Set the threshold to 20°, if the

or

Then add 1 point to the upper arm correction score, otherwise the upper arm score does not need to be corrected.

Upper arm abduction calculation

Upper arm abduction is divided into right upper arm abduction and left upper arm abduction. If the right upper arm is abducted, the projection vector v” _rua of the right upper arm vector v _rua on the sagittal plane S _tr-bd is not parallel to the trunk vector v _truck , and the included angle is θ _rua-ex (judgment angle of right upper arm abduction) Similarly, if the left upper arm is abducted, the projection vector v” _lua of the left upper arm on the sagittal plane S _tr-bd is not parallel to the torso vector v _truck , and its included angle is θ _lua-ex (the left upper arm abduction judgment angle ).

The projection vector v” _rua of the right upper arm vector v _rua on the third modified sagittal plane _Str-bd is shown in the following formula.

Then the right upper arm abduction judgment angle θ _rua-ex is shown in the following formula.

Similarly, the left upper arm abduction judgment angle θ _lua-ex can be obtained, as shown in the following formula.

或

则给上臂修正分值增加1分。Set the threshold to 20°, if there is

or

Then add 1 point to the upper arm correction score.

Forearm Correction Score

According to the RULA worksheet, the forearm correction score is determined by whether the forearm is placed on the other side of the midline of the body, or whether the forearm is placed on the outside of the body. If the forearm is placed on the other side of the body midline or on the outside of the body, the modified forearm score S” _lowerarm is 1 point; otherwise the modified forearm score S” _lowerarm is 0 point.

Forearm on the outside of the body

The third modified sagittal plane S _tr-bd is the projected sagittal plane calculated when the forearm is placed outside the body. The forearm placed on the outside of the body is divided into the right forearm placed on the outside of the body and the left forearm placed on the outside of the body. If the right forearm is placed on the outside of the body, the projection vector v” _rla of the right forearm vector v _rla on the third modified sagittal plane S _tr-bd is not parallel to the trunk vector v _truck , and the included angle is θ _rla-ex (the right forearm Place it on the outside of the body to determine the angle). Similarly, if the left forearm is placed on the outside of the body, the projection vector v” _lla of the left forearm vector v _lla on the sagittal plane S _tr-bd is not parallel to the trunk vector v _truck , and the included angle is It is θ _lla-ex (the left forearm is placed outside the body to judge the angle).

The projection vector v” _rla of the right forearm vector v _rla on the sagittal plane Str _-bd is shown below.

Therefore, the right forearm is placed outside the body to judge the angle θ _rla-ex as shown in the following formula.

In the same way, the left forearm can be placed outside the body to judge the angle θ _lla-ex , as shown in the following formula.

或

认为前臂置于身体另一侧，否则认为前臂未置于身体另一侧。Set the threshold to 20°, then if

or

The forearm is considered to be on the other side of the body, otherwise the forearm is considered not to be on the other side of the body.

The forearm is placed on the other side of the midline of the body

If the left forearm is placed on the other side of the midline of the body, then the projection of the vector v _rs- l _w on the vector v _rs-ss The modular length of the vector v” _rs-lw is less than the modular length of the vector v _rs-ss |v” _{rs- lw} | (the left forearm is placed on the other side of the body midline to judge the length of the mold), that is, |v” _rs-lw |<| _vrs-ss |. Wherein, _{vrs - lw} is the distance from the right shoulder j8 to the left wrist j6 The vector, ie v _rs-lw =j ₆ -j ₈ ; is the vector of v _rs-ss from the right shoulder j ₈ to the shoulder vertebra j ₂₀ , that is, v _rs-ss =j ₂₀ -j ₈ .

Therefore, the left forearm is placed on the other side of the midline of the body to determine the modulo length |v” _rs-lw | as shown in the following formula.

Similarly, the right forearm can be placed on the other side of the midline of the body to determine the length of the mold |v” _ls-rw |, as shown in the following formula.

So, if |v” _rs-lw |<|v _rs-ss |, or |v” _{ls -rw} | placed on the other side of the midline of the body.

Based on the main score of each limb and the modified score of each limb, the total score of each limb is obtained, and based on the total score of each limb, score matching is performed through the RULA worksheet to obtain the RULA score of the human body posture.

Through the above process, the trunk main score S' _truck , the neck main score S' _neck , the upper arm main score S' _upperarm , the forearm main score S' _lowerarm , and the wrist main score S' _wrist are obtained; The criterion calculation formula is used to obtain the corrected score of trunk S” _truck , the corrected score of neck S” _neck , the corrected score of upper arm S” _upperarm , and the corrected score of forearm S” _lowerarm . The wrist score S _wrist is the same as the wrist main score S' _wrist , the trunk score S _truck , the neck part S _neck , the upper arm score S _upperarm , and the forearm score S _lowerarm need to be revised, which are the main scores of each limb of the human body. The sum of the value and the corresponding correction score, as shown in the following formula.

S _truck = S' _truck + S” _truck

S _neck =S' _neck +S" _neck

S _upperarm =S' _upperarm +S” _upperarm

S _lowerarm =S' _lowerarm +S" _lowerarm

Through the above calculation, the main score and modified score of each limb RULA are determined from Figure 6 and Figure 7, and then calculated by the above formula to obtain the total score of each limb RULA, by looking up the A table and B table in the RULA worksheet, Then a muscle assessment, i.e. if the position is held still for more than one minute or if the pose is repeated more than four times in one minute, add 1 to the total score, and a force and load assessment, i.e. no resistance or intermittent loads of less than 2kg or The total score of resistance remains unchanged, the total score of intermittent load or resistance of 2-10kg is increased by 1, the total score of static load or periodic load of 2-10kg is increased by 2, and the total score of static load greater than 10kg, repetitive load or impact, Add 3 to the total score of the transient load, obtain the C component value and D component value based on the above evaluation, and finally check the C table to obtain the RULA score. According to the RULA score obtained from the C table, the posture is divided into four levels for evaluation:

(1) 1-2 points: The pose is not held or repeated for a long time is acceptable.

(2) 3-4 points: The posture needs to be studied and changed after a long period of time.

(3) 5-6 points: The posture needs to be studied and changed after a period of time.

(4) 7 points: The posture needs to be studied and changed immediately.

Among them, Table A, Table B and Table C are shown in Table 2, Table 3 and Table 4.

Table 2

table 3

Table 4

Compared with the prior art, the present invention has the following effects:

In the present invention, the RULA of the test posture can be obtained by constructing the main sagittal plane, correcting the sagittal plane, projecting the limb vector into each sagittal plane, then calculating the angle of the projected vector, and combining with the RULA worksheet to determine the score. The score does not require manual analysis, which avoids the complexity of manual judgment, greatly reduces the time for judging the RULA score of the test posture, and avoids the subjectivity of manual judgment, which greatly increases the accuracy of RULA score judgment. Fast, real-time and accurate evaluation of the ergonomics of the RULA model is achieved.

The foregoing has shown and described the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above-mentioned embodiments, and the descriptions in the above-mentioned embodiments and the description are only to illustrate the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have Various changes and modifications fall within the scope of the claimed invention. The claimed scope of the present invention is defined by the appended claims and their equivalents.

Claims (10)

1. A real-time RULA evaluation method in virtual reality is characterized by comprising the following steps:

acquiring an action frame, establishing a space coordinate system based on the action frame, extracting joint point coordinates based on the space coordinate system, and acquiring each limb vector based on the joint point coordinates;

acquiring a main sagittal plane and a correction sagittal plane based on the joint point coordinates and the coordinate axis in the space coordinate system;

projecting each limb vector to the main sagittal plane to obtain a main projection vector of each limb vector, and obtaining each limb main angle of each limb vector on the main sagittal plane according to the main projection vector; acquiring main scores of all limbs based on the main angles of all limbs;

projecting each limb vector to the correction sagittal plane to obtain the correction projection vector of each limb vector, and obtaining the correction angle of the limb vector on the correction sagittal plane according to the correction projection vector; obtaining correction scores of all limbs based on the correction angles;

and obtaining total scores of all the limbs based on the main scores of all the limbs and the corrected scores of all the limbs, and obtaining the RULA scores of the human body postures through the RULA worksheet based on the total scores of all the limbs.

2. The real-time RULA evaluation method in virtual reality according to claim 1, wherein:

the joint point coordinates comprise caudal vertebra coordinates, neck coordinates, head coordinates, left shoulder coordinates, right shoulder coordinates, left elbow coordinates, right elbow coordinates, left wrist coordinates, right wrist coordinates, left hand coordinates, right hand coordinates, left hip coordinates, right hip coordinates and shoulder vertebra coordinates.

3. The real-time RULA evaluation method in virtual reality according to claim 2, wherein:

each limb vector comprises a body vector, a neck vector, a right upper arm vector, a left upper arm vector, a right front arm vector, a left front arm vector, a right wrist vector and a left wrist vector.

4. The real-time RULA evaluation method in virtual reality according to claim 2, wherein:

the specific steps for obtaining the main sagittal plane include:

and acquiring a main sagittal plane based on a shoulder vertebra coordinate, a left shoulder coordinate and a right shoulder coordinate, wherein the shoulder vertebra coordinate is positioned on the main sagittal plane, and a vector pointing to the right shoulder coordinate from the left shoulder coordinate is a normal vector of the main sagittal plane.

5. The real-time RULA evaluation method in virtual reality according to claim 3, wherein:

the modified sagittal planes comprise a first modified sagittal plane, a second modified sagittal plane and a third modified sagittal plane;

the first correction sagittal plane is used for calculating a body torsion correction score and a neck torsion correction score based on each limb vector;

the second correction sagittal plane is used for calculating a lateral bending correction score of the trunk based on each limb vector;

and the third correction sagittal plane is used for calculating a neck lateral bending correction score, an upper arm lateral bending correction score and a forearm lateral bending correction score based on the limb vectors.

6. The real-time RULA evaluation method in virtual reality according to claim 5, wherein:

the specific step of obtaining the first modified sagittal plane includes:

and acquiring the first modified sagittal plane based on an x axis and a y axis in the space coordinate system, wherein the x axis and the y axis in the space coordinate system are positioned on the first modified sagittal plane.

7. The real-time RULA evaluation method in virtual reality according to claim 5, wherein:

the specific step of obtaining the second modified sagittal plane includes:

and acquiring the second correction sagittal plane based on the left hip coordinate, the right hip coordinate and the coordinate axis in the space coordinate system, wherein the left hip coordinate and the right hip coordinate are positioned on the second correction sagittal plane, and the y axis in the space coordinate system is parallel to the second correction sagittal plane.

8. The real-time RULA evaluation method in virtual reality according to claim 5, wherein:

the specific step of obtaining the third modified sagittal plane includes:

and acquiring the third correction sagittal plane based on the trunk vector, the left shoulder coordinate and the right shoulder coordinate, wherein the trunk vector is positioned on the third correction sagittal plane, and a vector pointing to the right shoulder coordinate from the left shoulder coordinate and a vector cross-multiplied by the trunk vector are normal vectors of the third correction sagittal plane.

9. The real-time RULA evaluation method in virtual reality according to claim 1, wherein:

the specific steps for obtaining the main score of each limb comprise:

calculating projection vectors of all the limb vectors on a normal vector of the main sagittal plane, calculating main projection vectors of all the limb vectors on the main sagittal plane through the projection vectors, then calculating included angles among the main projection vectors of all the limb vectors to obtain main angles of all the limb vectors, and matching corresponding scores of the main angles in an RULA working table to obtain main scores of all the limbs.

10. The real-time RULA evaluation method in virtual reality according to claim 1, wherein:

the specific steps of obtaining the correction score of each limb based on the correction angle are as follows:

and acquiring the posture factors under the current correction angle based on the correction angle, and obtaining the correction score of each limb by matching the corresponding correction score of the posture factors in the RULA working table.

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