CN110018073A - A kind of On-line Estimation method for elastic actuator elastomer rigidity of connecting - Google Patents
A kind of On-line Estimation method for elastic actuator elastomer rigidity of connecting Download PDFInfo
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- CN110018073A CN110018073A CN201910277291.1A CN201910277291A CN110018073A CN 110018073 A CN110018073 A CN 110018073A CN 201910277291 A CN201910277291 A CN 201910277291A CN 110018073 A CN110018073 A CN 110018073A
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Abstract
A kind of On-line Estimation method for elastic actuator elastomer rigidity of connecting, including elastic actuator (SEA) of connecting come into operation before to moment of friction model parameter offline identification method and after coming into operation to elastomer rigidity On-line Estimation method.Before SEA comes into operation, when unloaded stable operation, the torque of motor output is completely used for overcoming harmonic speed reducer moment of friction；Accurate loading moment is calculated by galvanometer, as the estimation to moment of friction；It is assumed that the moment of friction of harmonic speed reducer and Coulomb friction, viscous friction, revolving speed square and it is related with absolute angle, and provide corresponding polynomial function；The unknown parameter of polynomial function is estimated by system identifying method, establishes the model of harmonic speed reducer moment of friction.After SEA comes into operation, output loading torque is accurately estimated by electric current, deducts the moment of friction of harmonic speed reducer, obtains the true torque that SEA elastomer is subject to, and with Kalman filter, corrects elastomer rigidity.
Description
Technical field
The invention belongs to elastic Actuator technique field of connecting, be related to a kind of elastic actuator elastomer rigidity of connecting
Line estimation method more particularly to a kind of the online of elastic actuator elastomer rigidity of connecting for considering harmonic speed reducer moment of friction
Estimation method.
Background technique
Elastic actuator (Serial Elastic Actuator, SEA) of connecting introduces bullet in traditional rigid actuator
Property body, have many advantages, such as low noise power control and anti-shock loading, joint of robot flexibility and environmental suitability can be enhanced.
SEA adapts to load variation complicated state often using elastomer deformation as the basis of power control, converts position control for Torque Control
System greatly improves power and controls precision.However this power prosecutor formula excessively relies on accurate mechanical modeling and bullet to elastomer
The stability of property body rigidity.The rigidity of elastomer (such as long-term reuses, high temperature, high is born because of extreme load or environmental factor
Carry etc.) change, the torque estimated can have very big error.
Carnegie Mellon University Steven Ford proposes the rigidity of the torque correction elastomer using current estimation, still
This method does not account for the frictional force of system, so that the torque of current estimation is very inaccurate, it is difficult to it is rigid to reach calibration elastomer
The purpose of degree.
In the case where load variation is very complicated, current estimation torque deviation is very big.Moreover, indefinite in system friction
In the case where, it is difficult accurately to estimate torque.Service type joint of robot mostly uses harmonic speed reducer, and friction model is complicated, makes electricity
Stream estimation torque is more difficult.Gandhi proposes the frictional behavior identification and compensation method of harmonic speed reducer, including harmonic wave subtracts
Frictional force relevant to speed and position in fast device.Tutle proposes that the frictional behavior of harmonic speed reducer during operation is divided into
Coulomb friction, viscous friction, friction relevant to position and resonance friction, and friction model is described with cubic polynomial.
The rigidity of SEA elastomer is because of extreme load or environmental factor (such as long-term reuse, high temperature, high load) hair
Changing, there is an urgent need to can be realized the method for the elastic actuator elastomer rigidity of On-line Estimation series connection.However as previously mentioned, by
Current estimation torque is very inaccurate, harmonic speed reducer moment of friction on-line measurement is very complicated when in the presence of frictional force is disregarded etc.
Technical problem, the prior art cannot still provide the On-line Estimation method for elastic actuator elastomer rigidity of connecting.
Summary of the invention
In order to solve the problems in the existing technology, for the rigidity of SEA elastomer because extreme load or environment because
When element (such as a long time reuse, high temperature, high load) changes, disregards frictional force current estimation torque it is very inaccurate,
The problems such as moment of friction on-line measurement of harmonic speed reducer is very complicated, the present invention provide a kind of elastic actuator (Serial of series connection
Elastic Actuator, SEA) elastomer rigidity On-line Estimation method.This method includes two stages: SEA comes into operation
Before to moment of friction model parameter offline identification method；SEA come into operation after to elastomer rigidity On-line Estimation method.
The characteristics of this method: before SEA comes into operation, when unloaded stable operation, the torque of motor output is completely used for overcoming
Harmonic speed reducer moment of friction.Accurate loading moment is calculated by galvanometer, as the estimation to moment of friction.It is assumed that harmonic wave subtracts
The moment of friction of fast device and Coulomb friction, viscous friction, revolving speed square and it is related with absolute angle, and provide corresponding more
Item formula function.The unknown parameter of polynomial function is estimated by system identifying method, establishes the mould of harmonic speed reducer moment of friction
Type.After SEA comes into operation, output loading torque is accurately estimated by electric current, therefrom deducts the moment of friction of harmonic speed reducer, it can
Elastomer rigidity can be corrected with Kalman filter by obtaining the true torque that SEA elastomer is subject to.Reach in very fast fortune
In the case that dynamic, load changes greatly, the accurate purpose for estimating actuator output torque.
Method of the invention is achieved by the following technical programs:
A kind of On-line Estimation method for elastic actuator elastomer rigidity of connecting, which is characterized in that this method includes following
Step:
(1) before elastic actuator of connecting comes into operation, harmonic speed reducer moment of friction model is established, to moment of friction
Model parameter carries out off-line identification；
(2) after elastic actuator of connecting comes into operation, consider the harmonic speed reducer moment of friction that step (1) obtains,
On-line Estimation is carried out to elastomer rigidity.
Technical solution of the present invention is described in detail below.
(1) to moment of friction model parameter off-line identification before SEA comes into operation
Before SEA comes into operation, need to recognize the moment of friction model parameter of its harmonic speed reducer, parameter is extremely
Less include constant term (Coulomb friction), the first order (viscous friction) of angular speed, angle trigonometric function item coefficient, according to essence
Degree requirement may also need the quadratic term even high-order term of angular speed.Such as harmonic speed reducer moment of friction Wherein a, b, c, d are parameter to be identified,For harmonic speed reducer output end revolving speed, θ is that harmonic speed reducer is defeated
Outlet absolute angular position.In view of the complexity of harmonic speed reducer moment of friction, only in angular speed section appropriateInterior identified parameters.
Identification experiment is T in zero loadl=0 or TlIt is carried out under conditions of capable of accurately measuring, makes angular accelerationIt is zero, that is, turns
SpeedSize and Orientation is constant, to eliminate the torque loss of rotary inertiaInfluence, electric current is all used to overcome friction at this time
Power, by current of electric ImCalculate moment of friction Tf.The process of identification is as follows.
With certain revolving speed gradient, each revolving speed within the scope of 0 to maximum (top) speedUnder constant a period of time, and when taking this section
Moment of friction of the average value of interior moment of friction as the revolving speed, draws moment of friction and rotation speed relation figure, due to friction
Torque and absolute angular position θ meet trigonometric function relationship, so being averaged latter csin θ is 0.Curve rubs in low-speed stage
Wiping torque can reduce with the increase moment of friction of revolving speed, and at the high speed stage, moment of friction increases with revolving speed and increased, and increase
The trend added becomes slowly, substantially parabolically.Within the scope of the identical parabola of high speed periodical trend, one section of revolving speed area is taken
BetweenQuadratic fit is carried out to moment of friction on the section, fitting parameter a, b, d is obtained and falls into a trap as controller
Calculate the parameter of moment of friction.
Due to moment of friction component csin θ relevant to Angle Position and revolving speedIt is unrelated, in order to reduce accidental error, takeIn N number of revolving speedUnder each revolving speed after a period of stabilisation, the relationship of moment of friction Yu Angle Position θ is obtained
Figure, passes through Sine-Fitting and removes magnitude shift amount, obtain sinusoidal magnitude value ci, it is averagedObtain moment of friction
The identification result of model parameter.
(2) to elastomer rigidity On-line Estimation after SEA comes into operation
Set the initial stiffness k of SEA elastomer0, it is very accurate not need.Setting initial variance P, process noise Q, measurement are made an uproar
Sound R.
In SEA operation, synchronous detection harmonic speed reducer exports revolving speedOutput angle θ, elastomer deformation θs, motor electricity
Flow Im。
Work as angular speed?In range, angular accelerationAnd elastomer deformation change rateLess than certain
When value, by current of electric ImCalculate the friction torque T of harmonic speed reducerf, the calculated torque of electric current is subtracted out moment of friction, obtains
To corresponding loading moment T at this timel.Into Kalman filtering process:
Under normal circumstances, ktThat is the On-line Estimation result of elastomer rigidity.Work as angular speedDo not existRange
Interior or angular accelerationOr elastomer deformation change rateWhen greater than certain value, terminate Kalman filtering iteration, with karr
The rigidity k of graceful filtering final outputtAs newest elastomer rigidity.
By above method, can with on-line calibration elastomer rigidity, effectively reduce because extreme load or environment because
Torque evaluated error caused by element changes enhances the stability, control precision and the adaptability to complexity variation of system
Detailed description of the invention
Fig. 1 is elastomer rigidity On-line Estimation method flow diagram of the invention.
Fig. 2 is elastic actuator configurations schematic diagram of connecting.
Fig. 3 is moment of friction and rotation speed relation figure.
Fig. 4 is moment of friction and Angle Position relational graph.
Fig. 5 is current estimation M curve figure.
Appended drawing reference: 1- motor driver, 2- motor, 3- harmonic speed reducer, 4- input angle encoder, 5- elastomer,
6- output angle encoder, 7- dynamic force moment sensor, 8- single-chip microcontroller, 9- host computer.
Specific embodiment
The present invention is described in further detail with reference to the accompanying drawing.
Elastomer rigidity On-line Estimation method flow of the invention is as shown in Figure 1.
The elastic actuator configurations of series connection of the present invention are as shown in Fig. 2, be driven by motor device 1, motor 2, harmonic reduction
Device 3, input angle encoder 4, elastomer 5, output angle encoder 6, dynamic force moment sensor 7, single-chip microcontroller 8, host computer 9.
Single-chip microcontroller 8 be used as system master controller, to motor driver 1 send voltage signal with control motor 2 revolving speed and
Torque.
Single-chip microcontroller 8 acquires the pulse signal of input angle encoder 4 and output angle encoder 6, resolves as angle, θ1With
θ2, thus obtain the deformation quantity θ of elastomers=θ2-θ1, retarder output end absolute angular position θ=θ1, the output end revolving speed of retarder
It is obtained by Angle Position derivationThe deformation quantity change rate of elastomerBy the deformation quantity θ of elastomersTime derivation is obtained.
Single-chip microcontroller 8 acquires the analog voltage signal that dynamic torque sensor 7 exports, and is converted to corresponding moment values, as output end
True value, be used for moment of friction identification of Model Parameters.
Host computer 9 acquires current of electric I by motor driver 1m, and by electric current ImLow-pass filtering is to reduce high-frequency noise
Interference.Host computer 9 receives the relevant data of angle and torque sensor data that single-chip microcontroller 8 uploads, and carries out to data corresponding
Processing.
Before SEA comes into operation, need to carry out parameter identification to the moment of friction model of harmonic speed reducer.Identification is completed
Afterwards, the parameter for needing to recognize by 7 Duis of dynamic torque sensor carries out Accuracy Verification.Specific identification process and result are as follows:
Recognize parameter relevant to revolving speed: with certain revolving speed gradient, each invariablenes turning speed within the scope of 0.2~2.5rad/s
For a period of time, and moment of friction of the average value of moment of friction in this time as the revolving speed is taken, obtains friction shown in Fig. 3
Torque and rotation speed relation figure.Find out in low-speed stage ω < 0.4rad/s from Fig. 3 curve as the increase moment of friction of revolving speed subtracts
Small, in ω > 0.4rad/s, moment of friction increases with revolving speed and is increased, and increased trend becomes slowly, substantially parabolically.It takes
The consistent parabola section of variation tendencyIn the range to moment of friction with secondary letter
Number carries out least square fitting, obtains fitting parameter a=0.236, b=0.766, d=- 0.204, and rub as calculating in single-chip microcontroller 8
Wipe the program parameter of torque.
It recognizes parameter relevant to angle: in the previous step in determining revolving speed section [0.8,2.2] rad/s, taking N=
5 tachometer values { 1,1.2,1.4,1.6,1.8 } under each revolving speed after a period of stabilisation obtain 5 and are similar to Fig. 4 friction
The relational graph of torque and Angle Position θ carries out least square fitting with SIN function and obtains parameter ci={0.118,0.110,
}, 0.109,0.112,0.113 it is averagedUsing parameter c as calculating moment of friction in controller
Parameter.
Verify the accuracy of identified parameters: when single-chip microcontroller 8 controls motor driver 1, motor 2 is with revolving speedIn 1rad/s and
Neighbouring range of speeds rotation, applies the load end of SEA and changes more slow torque, and the torque T of application is passed by dynamic torque
Sensor measures, and measures real-time Angle Position θ, current of electric ImWith the revolving speed of retarderWith step in summary of the invention (2) according to reality
Parameter a, b, c, the d for testing identification calculate theoretical torque Tl, the true torque T of dynamic torque sensor 7 is compared, is obtained shown in Fig. 5
Current estimation M curve figure, it can be seen that calculated ideal torque and true torque meet fine, therefore demonstrate
The accuracy of identified parameters.
After harmonic speed reducer moment of friction model parameter is recognized and is arranged, commencement of commercial operation state is made it into, is transported
During row, 8 real-time monitoring of single-chip microcontroller and calculating current Im, harmonic speed reducer angular speed is calculated by angular encoderAngle
AccelerationElastomer deformation θs, retarder absolute angle θ.
Work as angular speedPositioned at section [0.8,2.2] rad/s of above-mentioned identification, angular accelerationDeformation change rateWhen (deformation change rate setting limit), into Kalman filtering on-line calibration program, with angular speedAngle Position θ
Calculate the moment of friction T of harmonic speed reducerf, T is subtracted out in motor output torquefAfterwards, the loading moment T exportedl, Kalman
Filtering is with TlElastomer rigidity k is updated, it is anti-as torque ring to calculate output end moment for updated rigidity combination Hooke's law
Feedback.
Work as angular speedNot in section [0.8, the 2.2] rad/s or angular acceleration of above-mentioned identificationOr deformation becomes
RateWhen do not enter Kalman filtering on-line calibration program, i.e., do not update the estimated value to elastomer rigidity, directly
It connects using Hooke's law and calculates output end moment as torque ring feedback.
The foregoing is only a preferred embodiment of the present invention, but scope of protection of the present invention is not limited thereto,
Within the technical scope of the present disclosure, any changes or substitutions that can be easily thought of by anyone skilled in the art,
It should be covered by the protection scope of the present invention.Therefore, protection scope of the present invention should be with the protection model of claims
Subject to enclosing.
Claims (7)
1. a kind of On-line Estimation method for elastic actuator elastomer rigidity of connecting, which is characterized in that this method includes following step
It is rapid:
(1) before elastic actuator of connecting comes into operation, harmonic speed reducer moment of friction model is established, to moment of friction model
Parameter carries out off-line identification；
(2) after elastic actuator of connecting comes into operation, the harmonic speed reducer moment of friction that step (1) obtains is considered, to bullet
Property body rigidity carry out On-line Estimation.
2. On-line Estimation method according to claim 1, which is characterized in that step establishes moment of friction model in (1)
Method is: the moment of friction of harmonic speed reducer is described as a polynomial function, including at least constant term, angular speed it is primary
The trigonometric function item of item and angle.
3. On-line Estimation method according to claim 2, which is characterized in that description moment of friction is multinomial in step (1)
Formula function further includes the quadratic term, cubic term and high-order term of angular speed.
4. On-line Estimation method according to claim 1, which is characterized in that step establishes moment of friction model in (1)
Method is: the moment of friction of harmonic speed reducer is expressed asWherein, a, b, c, d are to be identified
Parameter, θ andRespectively harmonic speed reducer output end angle and angular speed；Measure θ andAnd its corresponding moment of friction Tf, pass through
System identifying method estimates the value of a, b, c, d, obtains moment of friction model.
5. On-line Estimation method according to claim 4, which is characterized in that keep revolving speed in step (1)It is constant, it is believed that
Angular acceleration is 0, and the moment of inertia of entire actuator is 0, and current of electric consumption is completely used for overcoming the friction of harmonic speed reducer
Torque；It detects current of electric and estimates moment of friction Tf, synchronous to detect harmonic speed reducer output end angle, θ and angular speedRealization pair
The identification of moment of friction model parameter a, b, c, d.
6. On-line Estimation method according to claim 1, which is characterized in that carried out in step (2) to elastomer rigidity
The method of line estimation is: when connecting elastic actuator operation, synchronous detection harmonic speed reducer exports revolving speedOutput angle θ,
Elastomer deformation θs, current of electric Im；
Work as angular speed?In range, angular accelerationAnd elastomer deformation change rateWhen less than setting value, by
Current of electric ImCalculate the friction torque T of harmonic speed reducerf, will be according to the calculated friction torque T of electric currentfDeduction step (1)
Moment of friction out obtains corresponding loading moment T at this timel, into Kalman filtering process, obtain the online of elastomer rigidity
Estimated result；
Work as angular speedDo not existIn range, angular accelerationOr elastomer deformation change rateWhen being greater than the set value,
Terminate Kalman filtering iteration, using the rigidity of Kalman filtering final output as newest elastomer rigidity.
7. On-line Estimation method according to claim 6, which is characterized in that the Kalman filtering process is as follows:
(a) elastomer rigidity is predicted
(b) variance is predicted
(c) kalman gain is calculated:
(d) elastomer rigidity k is updatedt:
(e) variance P is updatedt:
(f) current time updated rigidity ktWith variance PtInitial stiffness k as Kalman filtering iteration next timet-1The side and
Poor Pt-1, repeat (a)~(e) the step of.
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| CN2019102623207 | 2019-04-02 | ||
| CN201910262320 | 2019-04-02 |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112014217A (en) * | 2020-09-08 | 2020-12-01 | 湖南省力宇燃气动力有限公司 | Elastomer stiffness determination method |
| CN112847365A (en) * | 2021-01-07 | 2021-05-28 | 西安电子科技大学 | Torque estimation method |
| CN114964593A (en) * | 2022-06-21 | 2022-08-30 | 郑州安杰莱智能科技有限公司 | Current torque conversion method and device and rehabilitation robot |
-
2019
- 2019-04-08 CN CN201910277291.1A patent/CN110018073A/en not_active Withdrawn
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112014217A (en) * | 2020-09-08 | 2020-12-01 | 湖南省力宇燃气动力有限公司 | Elastomer stiffness determination method |
| CN112847365A (en) * | 2021-01-07 | 2021-05-28 | 西安电子科技大学 | Torque estimation method |
| CN112847365B (en) * | 2021-01-07 | 2022-08-02 | 西安电子科技大学 | Torque estimation method |
| CN114964593A (en) * | 2022-06-21 | 2022-08-30 | 郑州安杰莱智能科技有限公司 | Current torque conversion method and device and rehabilitation robot |
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