CN113177310A - Mechanical arm holding method based on human body comfort - Google Patents

Mechanical arm holding method based on human body comfort Download PDF

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CN113177310A
CN113177310A CN202110445913.4A CN202110445913A CN113177310A CN 113177310 A CN113177310 A CN 113177310A CN 202110445913 A CN202110445913 A CN 202110445913A CN 113177310 A CN113177310 A CN 113177310A
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human body
joint
track
arm
mass
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CN113177310B (en
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李兵
刘飞
黄海林
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Shenzhen Graduate School Harbin Institute of Technology
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Shenzhen Graduate School Harbin Institute of Technology
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    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F30/00—Computer-aided design [CAD]
    • G06F30/20—Design optimisation, verification or simulation
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61G—TRANSPORT, PERSONAL CONVEYANCES, OR ACCOMMODATION SPECIALLY ADAPTED FOR PATIENTS OR DISABLED PERSONS; OPERATING TABLES OR CHAIRS; CHAIRS FOR DENTISTRY; FUNERAL DEVICES
    • A61G7/00—Beds specially adapted for nursing; Devices for lifting patients or disabled persons
    • A61G7/10—Devices for lifting patients or disabled persons, e.g. special adaptations of hoists thereto
    • A61G7/1049—Attachment, suspending or supporting means for patients
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61G—TRANSPORT, PERSONAL CONVEYANCES, OR ACCOMMODATION SPECIALLY ADAPTED FOR PATIENTS OR DISABLED PERSONS; OPERATING TABLES OR CHAIRS; CHAIRS FOR DENTISTRY; FUNERAL DEVICES
    • A61G7/00—Beds specially adapted for nursing; Devices for lifting patients or disabled persons
    • A61G7/10—Devices for lifting patients or disabled persons, e.g. special adaptations of hoists thereto
    • A61G7/1049—Attachment, suspending or supporting means for patients
    • A61G7/1061—Yokes
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61G—TRANSPORT, PERSONAL CONVEYANCES, OR ACCOMMODATION SPECIALLY ADAPTED FOR PATIENTS OR DISABLED PERSONS; OPERATING TABLES OR CHAIRS; CHAIRS FOR DENTISTRY; FUNERAL DEVICES
    • A61G7/00—Beds specially adapted for nursing; Devices for lifting patients or disabled persons
    • A61G7/10—Devices for lifting patients or disabled persons, e.g. special adaptations of hoists thereto
    • A61G7/1073—Parts, details or accessories
    • A61G7/1082—Rests specially adapted for
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61G—TRANSPORT, PERSONAL CONVEYANCES, OR ACCOMMODATION SPECIALLY ADAPTED FOR PATIENTS OR DISABLED PERSONS; OPERATING TABLES OR CHAIRS; CHAIRS FOR DENTISTRY; FUNERAL DEVICES
    • A61G2203/00—General characteristics of devices
    • A61G2203/70—General characteristics of devices with special adaptations, e.g. for safety or comfort
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F2119/00—Details relating to the type or aim of the analysis or the optimisation
    • G06F2119/14—Force analysis or force optimisation, e.g. static or dynamic forces

Abstract

The invention provides a mechanical arm holding method based on human body comfort level, which comprises the steps of establishing a human body dynamic model, and obtaining human body posture data and data of a contact posture of a mechanical arm and a human body under the optimal comfort level after optimization solution; then establishing an expected track of the mechanical arm according to the human body posture data and the data of the contact posture of the mechanical arm and the human body, and adjusting the human body posture; the invention can enable the human body to finally form a comfortable holding posture, and the experience feeling is better.

Description

Mechanical arm holding method based on human body comfort
Technical Field
The invention relates to a mechanical arm holding method based on human body comfort.
Background
Medical staff often need to move bedridden nursing objects from a ward to other places such as a toilet, a bathroom or an examination department, and the like, the transfer of the nursed objects between a sickbed and a wheelchair is the most frequent, the most tedious, the most physical and the most accident-prone typical and basic task, and the scene conversion process involves a plurality of changes and transitions of the body postures of the nursed objects.
In the aspects of intelligent control and human-computer interaction, in order to smoothly complete the nursing task of holding up and stably moving a nursed person, unsafe conditions such as overlarge stress or slipping caused by uncomfortable postures of the nursed person in the operation process need to be avoided; therefore, the method is provided, and on the basis of comfort evaluation, the holding posture of the mechanical arm which enables the human body to be comfortable is calculated by analyzing the relation between the stress and the posture of the human body and establishing a corresponding mathematical model.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a mechanical arm holding method based on human body comfort level so as to improve the human body comfort level.
In order to achieve the purpose, the invention provides a mechanical arm holding method based on human body comfort, which comprises the following steps of:
step one, establishing a human body dynamic model
Providing two mechanical arms, wherein one mechanical arm is used as a supporting arm and acts on the lower limbs of the human body to support the lower limbs of the human body, and the other mechanical arm is used as an adjusting arm and acts on the trunk of the human body to adjust the posture of the human body;
the human body is equivalent to four connecting rods which are respectively connected through knee joints, hip joints and neck joints, the relative mass and the mass center position of the four connecting rods are respectively obtained, and then a gravity balance equation and a moment balance equation when the mechanical arm holds the human body are obtained;
obtaining human body posture data and data of the contact posture of the mechanical arm and the human body under the optimal comfort level according to the established human body dynamics model;
step two, the posture of the supporting arm is kept unchanged in the process of holding the person, and a fixed coordinate system o is established by adjusting the central position of the shoulder joint of the armm-xmymzmA human body coordinate system o is established at the center of the hip joint of the embraced human bodyh-xhyhzhBased on the position translation relationship between the human body coordinate system and the fixed coordinate system, a transformation matrix can be obtained:
Figure BDA0003036842820000021
wherein p ish(dx,dy,dz) The coordinate value of the central point of the hip joint in a fixed coordinate system depends on the size of the human body and the contact position of the mechanical arm and the human body;
step three, taking the supporting arm as a reference to obtain phPoint in a fixed coordinate system om-xmymzmAnd during the human posture adjustment process, phPoint in a fixed coordinate system om-xmymzmThe middle is kept unchanged;
keeping contact lines of the supporting arm and the adjusting arm with the human body in a horizontal state all the time in the process of holding the person, keeping the relative position of the motion track of the adjusting arm in contact with the human body unchanged, and adjusting the posture of the human body to be in the optimal comfort level through the adjusting arm;
wherein the motion track of the adjusting arm is an arc segment which takes the hip joint as the circle center and the length between the contact point of the adjusting arm and the human body and the hip joint as the radius, and the arc segment is obtained at oh-xhyhzhCoordinates under a coordinate system;
step five, according to the obtained conversion matrix ohPoint in a fixed coordinate system om-xmymzmAnd the arc segment is at oh-xhyhzhThe coordinate under the coordinate system is calculated to obtain the position of the adjusting arm at om-xmymzmAnd coordinates of the track point under the coordinate system are the expected track equation of the adjusting arm.
As another specific embodiment of the present invention, further comprising: step six, calculating the optimized track of the expected track in the Cartesian space through kinematic calculation, wherein the optimized track and the expected track are at the characteristic point piAnd pi+1The positions are overlapped;
establishing a chord height error model of the optimized track and the expected track, and calculating a track error fpAnd:
when f ispIf the desired accuracy is not satisfied, the feature point p is setiAnd pi+1Inserting new characteristic points at the middle point of the track, and modifying the optimized track and the chord height error model until fpWhen the desired accuracy is met.
As another specific embodiment of the present invention, further comprising: seventhly, optimizing the track of the joint of the adjusting arm;
selecting characteristic points on the expected track of the Cartesian space, obtaining corresponding joint angles by solving inverse kinematics, and establishing a joint track node sequence;
b spline interpolation is carried out on the joint track node sequence to obtain joint track curve characteristics;
and taking the motion stability and the running time of the mechanical arm as optimization targets, adding kinematics and time constraints, establishing a multi-target joint track optimization model, solving through an optimization algorithm, and judging the advantages and disadvantages of particles according to the optimization algorithm to obtain an optimal joint track node sequence.
As another specific embodiment of the invention, the method further comprises the following steps: step eight, optimizing the track of the tail end of the adjusting arm;
according to the error between the expected track and the joint optimization track, a track error model is constructed, and the quality of the joint track optimization model solution is verified;
if the joint optimization track meets the track error model precision, the cooperative optimization is finished, otherwise, a new characteristic point is inserted, the joint track is optimized again until the joint optimization track meets the track error model precision, and at the moment, the tail end track of the adjusting arm and the joint track meet mixed constraint.
As another specific embodiment of the present invention, the method for determining the relative mass of the four-bar linkage in the step one comprises: respectively calculating the relative mass of each connecting rod based on the mass of the human body, the relative mass distribution of human body links and the percentage of the relative mass in the whole mass of the human body;
the method for solving the centroid position of the four-bar linkage in the first step comprises the following steps: and respectively calculating the mass center position of each connecting rod based on the relative position of the mass center of each connecting rod and the percentage of the size of the upper part of the mass center of each connecting rod in the total length of the link.
As another embodiment of the present invention, the stepThe gravity balance equation obtained in one is: fn+Fr+G＝0；
Wherein Fn＝[Fn1,Fn2]The human body is subjected to positive pressure at the contact position of thighs, trunk and mechanical arms Fr＝[Fr1,Fr2]The human body is subjected to the friction force at the contact position of the thighs, the trunk and the mechanical arm, and G is the gravity of the human body;
the moment balance equation obtained in the first step is as follows: mo+τ＝0；
Wherein
Figure BDA0003036842820000041
External moment for external force, τ ═ τ1,τ2,τ3]The internal joint torque generated by human muscle at knee joint, hip joint and neck joint.
As another specific embodiment of the present invention, in the step one, based on the contact force between the human body and the mechanical arm and the acting force exerted on the human body by the moment in the joint, a human body comfort function is defined to calculate the optimal comfort:
CHB＝f(Fn1,Fr1,Fn2,Fr2,τ1,τ2,τ3)；
wherein Fn1The human body is subjected to positive pressure at the contact positions of the thighs, the trunk and the supporting arms Fn2The human body is subjected to positive pressure at the contact positions of thighs, trunk and adjusting arms Fr1Is the friction force of the human body at the contact position of the thigh and the supporting arm, tau1For moment of neck joint, τ2For moment of hip joint, τ3Knee joint moment;
wherein the smaller the value of CHB, the more comfortable the human body feels;
based on neck joint moment tau1And knee joint moment tau3Are respectively related to the neck joint angle and the knee joint angle, adapt to the posture of being held up according to the self adjustment of the human body, and modify the human comfort function into:
CHB＝f(Fn1,Fr1,Fn2,Fr2,τ2)；
further conversion is as follows:
Figure BDA0003036842820000051
wherein wi(i is 1, 2, 3, 4, 5) weight factors set for each item, respectively;
Fn max＝Fr max＝0.5mhg，mhthe weight of the human body is half of the self gravity of the human body;
τ2 maxthe maximum value of the moment of the hip joint is when the human body lies on the supporting arm and the adjusting arm.
As another specific embodiment of the present invention, the first step is performed by using a state vector q ═ a2f a3f θ1 θ2 θ3θ4]TRepresenting a human body posture;
wherein a is2f＝l2f/L2，a3f＝l3f/L3，l2fThe distance between the contact point of the supporting arm and the thigh and the hip joint is L1The angular position is theta1Length between knee joint and hip joint is L2The angular position is theta2，l3fAdjusting the distance between the contact point of the arm and the trunk and the hip joint, wherein the length between the neck joint and the hip joint is L3The angular position is theta3Length above neck joint is L4The angular position is theta4；
A here2fDetermining the contact pose of the supporting arm with the human body, a3fDetermining the contact pose of the adjusting arm and the human body, theta1、θ2、θ3、θ4The prone position of the human body is determined.
As another specific embodiment of the present invention, in step one, the gravity balance equation can be expressed as:
Figure BDA0003036842820000052
the moment balance equation can be expressed as:
Figure BDA0003036842820000053
wherein the content of the first and second substances,
Figure BDA0003036842820000054
respectively the mass center position of the four connecting rods;
e1、e2、e3、e4is a set scale factor;
m1,m2,m3,m4the mass of each four-bar linkage, i.e. the mass below the knee joint, is m1Mass between knee joint and hip joint is m2Mass between neck and hip joints m3Mass m above the cervical joint4；
F is obtained by solving according to the gravity balance equation and the moment balance equationn1、Fr1、Fn2、Fr2And τ2The relationship between them is:
Figure BDA0003036842820000061
wherein b is L2cosθ2-l1ccosθ1，c＝L3cosθ3+l4ccosθ4；
As another specific embodiment of the present invention, in step one, the following constraints are defined to solve the human comfort:
(I) based on the human body movement in the holding process as the bending movement, the moment of the hip joint is set as:
τ2∈[0.72mh,2.0mh]Nm
(II) setting the range of the joint angle as follows based on the actual lying posture of the human body:
Figure BDA0003036842820000062
(III) based on the limitation of human body muscles to the rotation range of hip joint, theta is required to be satisfied2-θ3＞270°；
Combining human body link size data (L) under constraint conditions (I), (II) and (III)1,L2,L3,L4) And mass m of human bodyhAnd solving to obtain the human body comfort level.
The invention has the following beneficial effects:
according to the invention, the human body posture data of the human body under the optimal comfort level and the data of the contact posture of the mechanical arm and the human body are obtained based on the human body comfort level, the tracks of the supporting arm and the mechanical arm are planned according to the data, the human body posture is adjusted, the human body finally forms a comfortable holding posture, and the experience feeling is better.
The present invention will be described in further detail with reference to the accompanying drawings.
Drawings
FIG. 1 is a schematic illustration of a hugging process of the present invention;
FIG. 2 is a kinetic model of a human body being embraced by the present invention;
FIG. 3 is a schematic diagram of the present invention showing the adjustment arm adjusting the trajectory of the body posture;
FIG. 4 is a schematic diagram of a fixed coordinate system established by the present invention;
fig. 5 is a schematic diagram of the string height error of the desired trajectory and the feeding trajectory of the present invention;
FIG. 6 is a schematic flow chart of the collaborative optimization of the trajectory of a hugger in accordance with the present invention;
fig. 7 is a flow chart diagram of the person embracing method of the present invention.
Detailed Description
In order that the above objects, features and advantages of the present invention can be more clearly understood, a more particular description of the invention will be rendered by reference to the appended drawings. It should be noted that the embodiments and features of the embodiments of the present application may be combined with each other without conflict.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, however, the present invention may be practiced in other ways than those specifically described herein, and therefore the scope of the present invention is not limited to the specific embodiments disclosed below.
In the process of holding a person by the mechanical arm, human muscles pull human joints under the action of the force of the mechanical arm to adjust the posture of the human body, so that the posture of the human body follows the track motion of the mechanical arm, as shown in fig. 1. In the whole holding process, the feeling of human body comfort mainly comes from the degree of muscle pulling force. Since human musculoskeletal system is a rather complicated motion system, it is difficult to establish muscle model and obtain human muscle strength value. Considering that the human muscle and the torque in the joint have a mapping relation:
τH＝Dm×nfn (1)
wherein D is a muscle arm matrix, and m and n are the number of joints and muscles respectively.
Thus, the comfort of the human body can be evaluated by the intra-articular moment generated by the muscles.
Based on this, the present embodiment provides a robot arm holding method based on human comfort, as shown in fig. 7, the robot arm holding method includes:
establishing a human body dynamics model
Providing a support Arm-1 to act on the lower limbs of the human body so as to support the lower limbs of the human body, providing an adjusting Arm-2 to act on the trunk of the human body so as to adjust the posture of the human body, and enabling the human body to be equivalent to four connecting rods which are respectively connected through a knee joint, a hip joint and a neck joint;
as shown in FIG. 2, the length below the knee joint is L1The angular position is theta1Length between knee joint and hip joint is L2The angular position is theta2Length between neck joint and hip joint is L3The angular position is theta3Length above neck joint is L4The angular position is theta4；
According to relative mass distribution and relative position of mass centers of male human body links given in GB/T17245-1998 adult human body mass center, the relative mass distribution refers to the percentage of mass of each link in the whole mass of the human body, and the relative position of mass centers refers to the percentage of upper size of mass centers of each link in the total length of the joint, as shown in the following table:
Figure BDA0003036842820000081
Figure BDA0003036842820000091
suppose the human body mass is mhFrom table 1, column 2, one can see:
L1(the foot and lower leg link below the knee joint) has a mass m1＝10.3％mh；
L2(femoral segment between Knee and hip) Mass m2＝28.38％mh；
L3(arm, trunk link between neck and hip) mass m3＝52.69％mh；
L4(neck link above neck joint) mass m4＝8.62％mh；
The centroid position (L) of the bar member of each link is calculated from column 3 of the above table1c,L2c,L3c,L4c) Respectively as follows:
Figure BDA0003036842820000092
the nursing and carrying process of the body to be nursed has the following acting forces:
each link of the human body is subject to gravity: g ═ m1,m2,m3,m4]g；
The human body is subjected to positive pressure F at the contact position of the thigh, the trunk and the mechanical armn＝[Fn1,Fn2]In which F isn1The human body is subjected to positive pressure at the contact positions of the thighs, the trunk and the supporting arms Fn2The human body is subjected to positive pressure at the contact positions of thighs, a trunk and the adjusting arms;
the human body is subjected to the friction force F at the contact position of the thigh, the trunk and the mechanical armr＝[Fr1,Fr2]In which F isr1The human body is subjected to the friction force at the contact position of the thigh and the supporting arm, Fr2The friction force of the contact position of the trunk and the adjusting arm is applied to the human body;
external moment produced by external force
Figure BDA0003036842820000093
And
the internal moment tau ═ in the joint generated by human muscle1,τ2,τ3]。
Wherein tau is1For moment of neck joint, τ2For moment of hip joint, τ3Knee joint moment;
the steady human body of holding up of arm, then arm power and human gravity keep balance have:
Fn+Fr+ G ═ 0, i.e.:
Figure BDA0003036842820000101
the moment of acting force produced in the human body keeps balance with the moment in the human joint, and the moment of acting force has:
Mo+ τ is 0, i.e.:
Figure BDA0003036842820000102
establishing a human comfort function
The human comfort level is related to the contact force between the human body and the mechanical arm and the moment in the joint, and a human comfort level function can be defined as follows:
CHB＝f(Fn1,Fr1,Fn2,Fr2,τ1,τ2,τ3) (5)
the smaller the CHB (comfort of human body) value, the more comfortable the human body feels. Relative to an individual, the sizes of all links of a human body and the positions of the gravity centers of all links in the link are determined, and the neck joint moment tau1And knee joint moment tau3Adjusted by the human body to suit the posture of being held up in relation to the neck joint angle and the knee joint angle, respectively, thereby correcting (5) to
CHB＝f(Fn1,Fr1,Fn2,Fr2,τ2) (6)
Further conversion is as follows:
Figure BDA0003036842820000103
wherein wi(i is 1, 2, 3, 4, 5) weight factors set for each item, respectively;
Fn max＝Fr max＝0.5mhg，mhthe weight of the human body is half of the self gravity of the human body;
τ2 maxmaximum value of the moment of the hip joint, in particular, tau, for a human body lying flat on the support and adjustment arms2 max＝max{(m1g(l1c+L2)+m2gl2c),(m3gl3c+m4g(l4c+L3))}；
Muscle strength tests and questionnaire surveys show that when the position of the arm of the mechanical arm is adjusted, the comfortable sensation of the human body is mainly focused on the sliding friction of the human body, the moment of the hip joint and the oppressive sensation of the back; therefore, according to the influence degree of each item on the comfort of the human body, we apply the weight factors w of the formula (7)iRespectively setting as follows: w is a1＝1.5，w2＝10，w3＝2.5，w4＝10，w5＝5。
Human comfort function optimization solutionSolution (II)
By state vector q ═ a2f a3f θ1 θ2 θ3 θ4]TIndicating the posture of the human body,/2fDistance between the contact point of the supporting arm and the thigh and the hip joint3fAdjusting the distance between the contact point of the arm and the trunk and the hip joint, as shown in fig. 2, the optimization problem can be simplified as follows: solving q, min (CHB), solving by collating the formulas (3) and (4) to obtain Fn1、Fr1、Fn2、Fr2And τ2The relationship between them is:
Figure BDA0003036842820000111
wherein b is L2cosθ2-l1ccosθ1，c＝L3cosθ3+l4ccosθ4；
A research paper published in the periodical Chinese general medicine indicates that the muscle group muscle force characteristic research of the hip joint surrounding of the chronic lumbago patient (the author: Wangnan et al, No. 22, P2705-2708, No. 8.2019) shows that when a human body tests the supine position constant-speed flexion and extension movement, the torque value ranges of the hip joint extension and flexion of the lumbago patient under the action of the muscle force group are respectively as follows:
[1.17mh,2.66mh]Nm、[0.72mh,2.0mh]Nm；
the hip joint extension and flexion moment value ranges of the patients with non-lumbago are respectively as follows:
[1.44mh,2.79mh]Nm、[0.67mh,2.17mh]Nm。
in the embodiment, the human body movement is taken as bending movement in the process of holding a person by the mechanical arm, so that the constraint condition (I) of the hip joint moment is set as follows:
τ2∈[0.72mh,2.0mh]Nm
considering that the joints of the human body have a certain angle range, the range of the joint angle constraint condition (II) can be reasonably set as follows:
Figure BDA0003036842820000121
on the other hand, the hip angle θ is taken in consideration of the limitation of the human muscle on the hip rotation range, i.e., the hip rotation may cause the nearby muscles to form a squeezeh> 90 °, i.e. the constraint (iii) is:
θ2-θ3＞270°
substituting the formula (8) into the human body comfort function, giving the human body weight mhAnd human body link size data (L)1,L2,L3,L4) Under the constraint conditions (I), (II) and (III), the comfort level of the human body can be solved by adopting an intelligent optimization algorithm such as particle swarm and the like.
Trajectory planning for a robotic arm
The human body balance needs to be kept in the process of adjusting the human-holding posture of the mechanical arm, and the human body is kept in a relatively comfortable state. The human body is used as the load of the mechanical arm, the moving track of the mechanical arm has great influence on the comfort of the human body, and the track planning of the posture adjusting arm needs to be researched. As described above, two mechanical arms are provided for carrying out the holding operation, and one of the mechanical arms is provided as a supporting arm which supports the lower limbs of the human body without adjusting the posture; the mechanical arm in contact with the human body is set as the posture adjusting arm to adjust the posture of the human body, so that the human body finally forms a comfortable holding posture and has reliable safety.
Equation of expected trajectory
As shown in fig. 3 and 4, the posture of the supporting arm is kept unchanged in the process of holding a person, and a fixed coordinate system o is established by adjusting the central position of the shoulder joint fixed platform of the armm-xmymzmWherein z ismPointing in the end direction, y, along the axis of the adjustment armmDownwards in the direction of gravity, xmDetermined by the right hand rule;
establishing a human body coordinate system o at the center of hip joint of the embraced human bodyh-xhyhzh，xhyhIs a sagittal plane of a human body, yhDownwards in the direction of gravity, xhPoint to the contact point of the mechanical arm with the human body, zhDetermined by the right hand rule.
Based on the position translation relationship between the human body coordinate system and the fixed coordinate system, a transformation matrix can be obtained:
Figure BDA0003036842820000131
wherein p ish(dx,dy,dz) The coordinate value of the central point of the hip joint in a fixed coordinate system depends on the size of the human body and the contact position of the adjusting arm and the human body;
the posture of the support arm is kept unchanged in the process of holding the person, and the support arm is used as a reference to determine ohPoint in a fixed coordinate system om-xmymzmThe positions in (a) are:
Figure BDA0003036842820000132
wherein the content of the first and second substances,
Figure BDA0003036842820000133
the upper arm of the supporting arm forms an included angle with the horizontal direction, dmThe distance between the supporting arm and the center point of the fixed platform of the shoulder joint of the adjusting arm; in the process of holding posture adjustmenthIn a fixed coordinate system om-xmymzmIs kept unchanged.
In order to keep the human body in a relatively comfortable state during the contact between the mechanical arm and the human body, the contact line between the mechanical arm and the human body should be kept in a horizontal state in the holding state of the mechanical arm, as shown in fig. 4.
In order to avoid friction between the mechanical arm and the human body, the mechanical arm and the human body should not slide relatively, that is, the motion track of the mechanical arm should ensure that the relative position of the mechanical arm contacting with the human body is kept unchanged. As shown in fig. 5Setting the starting point of the track as the contact point p between the adjusting arm and the human body when the posture adjustment starts1The track end point is the contact point p between the adjusting arm and the human body after the posture adjustment is finished4The motion track of the adjusting arm is the length l between the contact point (the contact point between the adjusting arm and the human body) and the hip joint point by taking the hip joint as the center of circle3fIs a circular arc segment of radius
Figure BDA0003036842820000141
At oh-xhyhzhUnder the coordinate system, the coordinates of the circular arc point can be expressed as:
Figure BDA0003036842820000142
according to (9), (10) and (11), the compound represented by formula (I) can be obtainedm-xmymzmCoordinates of the track point under the coordinate system are the expected track equation of the adjusting arm:
Figure BDA0003036842820000143
chord height error model
And after planning the joint track, obtaining the optimized track in the Cartesian space through kinematic calculation.
The optimized track and the expected track are coincident at the position of the characteristic point, errors can exist at other positions, and a chord height error model of the optimized track and the expected track is shown in figure 5 and is at the characteristic point piAnd pi+1Track segment between, pdAnd paRespectively for the desired trajectory and the optimized trajectory to pipi+1Point of maximum link distance, qdAnd q isaAre respectively a drop foot; face pipdpi+1And face pipapi+1The included angle therebetween is alpha. The error model between the desired trajectory and the optimized trajectory is defined as:
fp＝(1+λ)|papd| (13)
wherein
Figure BDA0003036842820000144
Figure BDA0003036842820000145
The number of the characteristic points of the track has important influence on the track precision by calculating the track error fpDifference from desired accuracy (e.g. desired accuracy may be set to 1mm), if fpIf the desired accuracy is not satisfied, the feature point p is setiAnd pi+1Inserting a new feature point at the middle point of the middle track; then calculating an optimized track to obtain a new track error fp。
And repeating the steps until the track error meets the expected precision.
Joint trajectory optimization
As shown in fig. 6, selecting feature points on the cartesian space expected trajectory, obtaining corresponding joint angles by solving a kinematic inverse solution, and establishing a joint trajectory node sequence;
b spline interpolation is carried out on the joint track node sequence to obtain joint track curve characteristics;
and taking the motion stability and the running time of the mechanical arm as optimization targets, adding kinematics and time constraints, establishing a multi-target joint track optimization model, solving through a PSO algorithm, and judging the advantages and disadvantages of particles according to the solution to obtain an optimal joint track node sequence.
Optimization of end trajectories
As shown in fig. 6, a trajectory error model is constructed according to the error between the expected trajectory and the joint optimization trajectory, and the quality of the joint trajectory optimization model solution is verified;
if the joint optimization track meets the track error model precision, the cooperative optimization is finished, otherwise, a new characteristic point is inserted, the joint track is optimized again until the joint optimization track meets the track error model precision, and at the moment, the tail end track of the adjusting arm and the joint track meet mixed constraint.
Finally, the operation of holding a person is carried out through the mechanical arm on the basis of meeting the comfort level of the human body.
Although the present invention has been described with reference to the preferred embodiments, it is not intended to limit the scope of the invention. It will be appreciated by those skilled in the art that changes may be made without departing from the scope of the invention, and it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

Claims (10)

1. A mechanical arm holding method based on human body comfort comprises the following steps:
step one, establishing a human body dynamic model
Providing two mechanical arms, wherein one mechanical arm is used as a supporting arm and acts on the lower limbs of the human body to support the lower limbs of the human body, and the other mechanical arm is used as an adjusting arm and acts on the trunk of the human body to adjust the posture of the human body;
the human body is equivalent to four connecting rods which are respectively connected through knee joints, hip joints and neck joints, the relative mass and the mass center position of the four connecting rods are respectively obtained, and then a gravity balance equation and a moment balance equation when the mechanical arm holds the human body are obtained;
obtaining human body posture data and data of the contact posture of the mechanical arm and the human body under the optimal comfort level according to the established human body dynamics model;
step two, the posture of the supporting arm is kept unchanged in the process of holding the person, and a fixed coordinate system o is established by adjusting the central position of the shoulder joint of the armm-xmymzmA human body coordinate system o is established at the center of the hip joint of the embraced human bodyh-xhyhzhBased on the position translation relationship between the human body coordinate system and the fixed coordinate system, a transformation matrix can be obtained:
Figure FDA0003036842810000011
wherein p ish(dx,dy,dz) The coordinate value of the central point of the hip joint in a fixed coordinate system depends on the size of the human body and the contact position of the mechanical arm and the human body;
step three, taking the supporting arm as a reference to obtain phPoint in a fixed coordinate system om-xmymzmAnd during the human posture adjustment process, phPoint in a fixed coordinate system om-xmymzmThe middle is kept unchanged;
keeping contact lines of the supporting arm and the adjusting arm with the human body in a horizontal state all the time in the process of holding the person, keeping the relative position of the motion track of the adjusting arm in contact with the human body unchanged, and adjusting the posture of the human body to be in the optimal comfort level through the adjusting arm;
wherein the motion track of the adjusting arm is an arc segment which takes the hip joint as the circle center and the length between the contact point of the adjusting arm and the human body and the hip joint as the radius, and the arc segment is obtained at oh-xhyhzhCoordinates under a coordinate system;
step five, according to the obtained conversion matrix ohPoint in a fixed coordinate system om-xmymzmAnd the arc segment is at oh-xhyhzhThe coordinate under the coordinate system is calculated to obtain the position of the adjusting arm at om-xmymzmAnd coordinates of the track point under the coordinate system are the expected track equation of the adjusting arm.
2. The robot arm embracing method based on human body comfort of claim 1,
further comprising: step six, calculating the optimized track of the expected track in the Cartesian space through kinematic calculation, wherein the optimized track and the expected track are at the characteristic point piAnd pi+1The positions are overlapped;
establishing a chord height error model of the optimized track and the expected track, and calculating a track error fpAnd:
when f ispWhen the desired accuracy is not met, the system may,then at the feature point piAnd pi+1Inserting new characteristic points at the middle point of the track, and modifying the optimized track and the chord height error model until fpWhen the desired accuracy is met.
3. The robot arm embracing method based on human body comfort of claim 2,
further comprising: seventhly, optimizing the track of the joint of the adjusting arm;
selecting characteristic points on the expected track of the Cartesian space, obtaining corresponding joint angles by solving inverse kinematics, and establishing a joint track node sequence;
b spline interpolation is carried out on the joint track node sequence to obtain joint track curve characteristics;
and taking the motion stability and the running time of the mechanical arm as optimization targets, adding kinematics and time constraints, establishing a multi-target joint track optimization model, solving through an optimization algorithm, and judging the advantages and disadvantages of particles according to the optimization algorithm to obtain an optimal joint track node sequence.
4. The robot arm embracing method based on human body comfort of claim 3,
further comprising: step eight, optimizing the track of the tail end of the adjusting arm;
according to the error between the expected track and the joint optimization track, a track error model is constructed, and the quality of the joint track optimization model solution is verified;
if the joint optimization track meets the track error model precision, the cooperative optimization is finished, otherwise, a new characteristic point is inserted, the joint track is optimized again until the joint optimization track meets the track error model precision, and at the moment, the tail end track of the adjusting arm and the joint track meet mixed constraint.
5. The robot arm embracing method based on human body comfort of claim 1,
the method for calculating the relative mass of the four-bar linkage in the first step comprises the following steps: respectively calculating the relative mass of each connecting rod based on the mass of the human body, the relative mass distribution of human body links and the percentage of the relative mass in the whole mass of the human body;
the method for solving the centroid position of the four-bar linkage in the first step comprises the following steps: and respectively calculating the mass center position of each connecting rod based on the relative position of the mass center of each connecting rod and the percentage of the size of the upper part of the mass center of each connecting rod in the total length of the link.
6. The robot arm embracing method based on human body comfort of claim 1,
the gravity balance equation obtained in the first step is as follows: fn+Fr+G＝0；
Wherein Fn＝[Fn1,Fn2]The human body is subjected to positive pressure at the contact position of thighs, trunk and mechanical arms Fr＝[Fr1,Fr2]The human body is subjected to the friction force at the contact position of the thighs, the trunk and the mechanical arm, and G is the gravity of the human body;
the moment balance equation obtained in the first step is as follows: mo+τ＝0；
Wherein
Figure FDA0003036842810000031
External moment for external force, τ ═ τ1,τ2,τ3]The internal joint torque generated by human muscle at knee joint, hip joint and neck joint.
7. The robot arm embracing method based on human body comfort of claim 6,
in the first step, a human body comfort function is defined to calculate the optimal comfort degree based on the contact force between the human body and the mechanical arm and the acting force exerted on the human body by the moment in the joint:
CHB＝f(Fn1,Fr1,Fn2,Fr2,τ1,τ2,τ3)；
wherein Fn1The human body is subjected to positive pressure at the contact positions of the thighs, the trunk and the supporting arms Fn2For the human body to be suffered from the thigh, the trunk and the adjusting armPositive pressure at the contact position, Fr1Is the friction force of the human body at the contact position of the thigh and the supporting arm, tau1For moment of neck joint, τ2For moment of hip joint, τ3Knee joint moment;
wherein the smaller the value of CHB, the more comfortable the human body feels;
based on neck joint moment tau1And knee joint moment tau3Are respectively related to the neck joint angle and the knee joint angle, adapt to the posture of being held up according to the self adjustment of the human body, and modify the human comfort function into:
CHB＝f(Fn1,Fr1,Fn2,Fr2,τ2)；
further conversion is as follows:
Figure FDA0003036842810000041
wherein wi(i is 1, 2, 3, 4, 5) weight factors set for each item, respectively;
Fn max＝Fr max＝0.5mhg，mhthe weight of the human body is half of the self gravity of the human body;
τ2 maxthe maximum value of the moment of the hip joint is when the human body lies on the supporting arm and the adjusting arm.
8. The robot arm embracing method based on human comfort of claim 7,
in step one, a state vector q ═ a is passed2f a3f θ1 θ2 θ3 θ4]TRepresenting a human body posture;
wherein a is2f＝l2f/L2，a3f＝l3f/L3，l2fThe distance between the contact point of the supporting arm and the thigh and the hip joint is L1The angular position is theta1Length between knee joint and hip joint is L2CornerDegree position of theta2，l3fAdjusting the distance between the contact point of the arm and the trunk and the hip joint, wherein the length between the neck joint and the hip joint is L3The angular position is theta3Length above neck joint is L4The angular position is theta4；
A here2fDetermining the contact pose of the supporting arm with the human body, a3fDetermining the contact pose of the adjusting arm and the human body, theta1、θ2、θ3、θ4The prone position of the human body is determined.
9. The robot arm embracing method based on human comfort of claim 8,
in step one, the gravity balance equation can be expressed as:
Figure FDA0003036842810000051
the moment balance equation can be expressed as:
Figure FDA0003036842810000052
wherein the content of the first and second substances,
Figure FDA0003036842810000053
respectively the mass center position of the four connecting rods;
e1、e2、e3、e4is a set scale factor;
m1,m2,m3,m4the mass of each four-bar linkage, i.e. the mass below the knee joint, is m1Mass between knee joint and hip joint is m2Mass between neck and hip joints m3Mass m above the cervical joint4；
F is obtained by solving according to the gravity balance equation and the moment balance equationn1、Fr1、Fn2、Fr2And τ2The relationship between them is:
Figure FDA0003036842810000054
wherein b is L2 cosθ2-l1c cosθ1，c＝L3cosθ3+l4ccosθ4。
10. The robot arm embracing method based on human comfort of claim 9,
in the first step, the following constraint conditions are defined to solve the human comfort:
(I) based on the human body movement in the holding process as the bending movement, the moment of the hip joint is set as: tau is2∈[0.72mh,2.0mh]Nm
(II) setting the range of the joint angle as follows based on the actual lying posture of the human body:
Figure FDA0003036842810000061
(III) based on the limitation of human body muscles to the rotation range of hip joint, theta is required to be satisfied2-θ3＞270°；
Combining human body link size data (L) under constraint conditions (I), (II) and (III)1,L2,L3,L4) And mass m of human bodyhAnd solving to obtain the human body comfort level.
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