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On the modelling of actuator dynamics and the computation of prescribed trajectories

On the modelling of actuator dynamics and the computation

of prescribed trajectories

B.Fox a ,L.S.Jennings b ,A.Y.Zomaya

a,*

Department of Electrical and Electronic Engineering,Parallel Computing Research Laboratory,The University of Western Australia,

Perth,WA 6907,Australia

Centre of Applied Dynamics and Optimization,The University of Western Australia,Perth,WA 6907,Australia

Received 10January 2001;accepted 9January 2002

Abstract

The dynamics of actuator mechanisms is presented using a multibody modelling approach to concisely express the structure of the system equations.The Lagrange equations are used to obtain the Newton–Euler equations to which constraint equations are augmented to form a system of di?erential algebraic equations.The di?erential algebraic equations are cast as ordinary di?erential equations and computed using the numerical integrator LSODAR of Petzold and Hindmarsh.Constraint compliance is investigated to ensure the accuracy of the results.Animation of an excavator and wheel loader system is presented and graphs of constraint forces show the nature of the actuator dynamics involved in maintaining speci?ed bucket trajectories.The model is general in nature and caters for arbitrary mechanism con-nectivity and physical properties.ó2002Elsevier Science Ltd.All rights reserved.

Keywords:Actuator;Contact forces;Di?erential algebraic equations;Lagrange’s equations;Multibody dynamics;Multibody modelling;Nonlinear dynamics;Newton–Euler equations;Numerical computation;Ordinary di?erential equations;Robotics

1.Introduction

Modelling and control of mechanical dynamics has been researched substantially by many scientists.Review papers of Simeon et al.[17],Stewart [19]and Udwadia and Kalaba [20]provide a useful insight into the general mathematical structure that may be employed in con-struction and computation of systems of equations.For a more independent body ?ne detail approach,kine-matic and dynamic analyses of robotics have been em-ployed to study both planar and spatial systems.Examples of excavator dynamics in digging operations

using a robotics approach may be found in [10,11,21].Texts such as Craig [5]and Zomaya [24]provide theory and examples of the kinematics,dynamics and control used in robotics.Control for excavator digging opera-tions has been pursued in [11,18,22].

Here the authors choose to pursue an approach using ordinary di?erential equations together with augmented constraint equations to bypass the robotics details,and show that the structure of typical mechanisms usually analysed using kinematics and dynamics of robotics,may be observed through a study of more general multibody dynamics.The typical robotics approach involves:(1)the Denavit–Hartenberg procedure,(2)the general homo-geneous transform,(3)rotational and translational ve-locities and accelerations and (4)inertia forces and moments of the bodies.The Denavit–Hartenberg pro-cedure of assigning the consecutive links with the ap-propriate parameters and then progressing to obtain the di?erence equations for velocity and acceleration is ex-plained in [5,24],and will not be discussed

here.

Corresponding author.Present address:School of Infor-mation Technologies,The University of Sydney,Madsen Building F09,Sydney,NSW 2006,Australia.

E-mail addresses:budfox@https://www.wendangku.net/doc/5b256936.html,.au (B.Fox),les@https://www.wendangku.net/doc/5b256936.html,.au (L.S.Jennings),zomaya@https://www.wendangku.net/doc/5b256936.html,.au (A.Y.Zomaya).

It is shown in[11]that the Newton–Euler equations may be used to concisely express the dynamics of the excavator as a second order linear di?erential equation in the unknown joint angles,where the right hand side of the system involves the system forces.The approach in this paper shows how the Lagrange equations are used to construct the Newton–Euler equations through gen-eral computational dynamics procedures of Nikravesh [12]and Shabana[16],and to which constraint equations may be augmented to form a di?erential algebraic equation representing the system dynamics.This method allows the structure and connectivity of the multibody system to be presented in a very readable form,and computation of a di?erential algebraic equation or an ordinary di?erential equation su?ces to obtain the un-known generalized coordinates and system forces and torques.Control of the digging operation is not per-formed explicitly,but rather bucket trajectories are speci?ed as constraint equations and are adjoined to the system being computed.

The rest of the paper is divided as follows.Section2 shows how the body kinetic energy is substituted into the Lagrange equations to form the Newton–Euler di?erential equations of motion to which constraint equations may be augmented.Section3discusses the properties of the DAE representing the mechanical systems and shows how it may be converted to an ODE by di?erentiation of the constraint equations.Section4 shows the constraint equations and contact force model used in the multibody modelling of two mechanical digging systems.Section5discusses the system anima-tion,force graphs and results concerning the trajectory prescribed systems and?nally Section6provides a summary of the research.

2.Multibody system equations

The system equations for the actuator vehicle mech-anisms,are derived using body kinetic energy and the Lagrange equations of motion;some of the following material shares the ideas of Shabana[16],and may also be found in[9].

The generalized coordinates of the i th body in a planar multibody system of NB bodies are,

q i ?R x;i;R y;i;h i

??T

:e2:1T

The position vector of an arbitrary point on body i measured with respect to the global coordinate system is r i?R itA i u i;e2:2T

where R i is the global position vector of the origin of body i, u i is the local position vector of a point on body i,the rotation matrix of the body through an angle h i is A i?

cos h iàsin h i

sin h i cos h i

;e2:3T

its derivative d A i=d h i is written as A h;i for convenience, and hence the time derivative of Eq.(2.2)is

_r i?_R itA h;i u i_h i:e2:4TThe kinetic energy of the body is

T i?

V i

q i_r T

_r i d V i;e2:5Tand on substitution of Eq.(2.4)in Eq.(2.5)one obtains T i?

_q T

M i_q

:e2:6TThe mass matrix of the body is

M i?

m RR;i m R h

m h R

m hh;i

;e2:7Twhere the matrix entries are as follows:

m RR;i?

V i

q i I d V i?m i I;e2:8T

which involves the body mass m i,the inertia coupling of the translation and rotation of the body is

m R h;i?m T

h R;i

?A h;i

V i

q i u i d V i;e2:9T

and vanishes if centroidal coordinate systems are used, and the mass moment of inertia is

m hh;i?

V i

q i u T

u i d V i:e2:10TThe kinetic energy of body i may then be written as

T i?

_R T

m RR;i_R it

m hh;i_h2

;e2:11T

and substituting this expression into the kinetic-energy form of the Lagrange equations(derived using varia-tional calculus),that is

d t

o T i

o_q i

o T i

o q i

?Q T

;e2:12T

and di?erentiating,yields the Newton–Euler equations of motion for body i

m RR;i0

0m hh;i

!€

R i

€h

R i

h i

:e2:13TThe complete system may be written as

M€q?Q?Q

tQ c;e2:14Twhere the force vector Q is composed of the externally

applied forces Q

and the NC constraint forces

606 B.Fox et al./Computers and Structures80(2002)605–614

Q c ?àC T q k ;

e2:15T

and the common joint forces and torques are repre-sented by the Lagrange multipliers k .The constraint equations of the multibody system are C eq ;t T?0;

e2:16T

and repeated di?erentiation with respect to time gives C q €

q ?Q d ?àeC q _q Tq _q à2C q t _q àC tt :e2:17T

Augmenting the system equations Eq.(2.14)with Eq.

(2.17)one obtains the complete system of 3NB tNC equations in 3NB tNC unknowns,M C T q C q 0

!€q k !?

Q e Q d !

:e2:18T3.Di?erential algebraic equations

Di?erential algebraic equations or DAEs,are di?er-ential equations with imposed algebraic constraints and

are discussed thoroughly in [2],which clari?es the nu-merical and computational methods for both ODEs and DAEs.Ascher and Petzold [1]and Byrne and Schiesser [4],study the numerical methods of ODEs,DAEs and PDEs.Brenan et al.[3],Petzold [13],and Petzold and Hindmarsh [14],discuss computer code for numerical computation of ODEs and DAEs,and ?nally mechani-cal dynamics problems are explored by Petzold et al.[15],Simeon et al.[17]and Yen and Petzold [23].A DAE may be of the form F e_x

;x ;t T?0;e3:1T

where x ?q ;_q ;l eT,_l ?k and _v ?€q .The constrained

mechanical systems studied here are represented by the equation I 000M o C o q T 000264375

_q _v _l 2435?f eq ;t T?v Q e C eq ;t T2435:e3:2TThe leading matrix,however,is singular so di?erentia-tion of the third equation in the system,given by Eq.

(3.2),with respect to time twice,results in I 000M o C

T 0o C 0

264375_q _v _l 2435?f eq ;_q ;t T?f eq ;v ;t T:e3:3TThe leading matrix of Eq.(3.3)is nonsingular provided that the constraint jacobian o C =o q ?C q is of full rank for all time.

The de?nition of the index of a DAE is:

De?nition.For general DAE systems of the form F _x

;x ;t eT?0,the index along a solution x et Tis the minimum number of di?erentiations of the system which

would be required to solve for _x

uniquely in terms of x and t (i.e.,to de?ne an ODE for x )Ascher and Petzold [2].

Two di?erentiations of Eq.(3.2)and the di?erentia-tion involved in the substitution of _l

?k yields the un-derlying ODE of Eq.(3.3).Hence the original system Eq.(3.2)is considered as an index three DAE.

The construction and computation of the mechanical system is performed by the authors’software Multibody System and the ODE software LSODAR (Livermore Solver of Ordinary Di?erential Equations with Auto-matic Method Switching for sti?and nonsti?problems with Root-?nding)of Petzold and Hindmarsh [14];this also computes the integral l t eT?R t

0k s eTd s .The Lag-range multipliers k are obtained by di?erentiating l et T.However,Ascher and Petzold [2],and Brenan et al.[3],discuss the numerical problems associated with con-straint equation di?erentiation,and indicate that the constraints may not be satis?ed as the integration pro-gresses.Since di?erentiation has been performed to convert the DAE into the underlying ODE,a check of constraint compliance as shown by Eq.(3.4)C eq ;t Tk àC eq ;0Tk ?0

e3:4T

is required throughout the computation.The Di?eren-tial-Algebraic System Solver,DASSL,described in [2]

does not require conversion of the DAE to the ODE,instead,direct computation of the DAE is performed.

4.Multibody system modelling

The actuator systems studied involve an excavator and a wheel loader,and are shown in the simulation of Section 5.The modelling of these systems requires:(1)de?ning constraint equations as functions of the generalized coordinates q and time t ,representing the connectivity of the system and the desired bucket tra-jectories,and (2)constructing a contact force model between the wheels and the ground for the wheel loader example.

4.1.Constraint forces and torques

The authors’software Multibody System ,computes the generalized constraint forces and torques Q c of the bodies in the system.These may be related to the forces and torques acting at the joints of the bodies.Shabana [16]indicates that the Lagrange multipliers

k ?àF

!;e4:1T

B.Fox et al./Computers and Structures 80(2002)605–614607

involve the common joint connectivity force F between two bodies,and the constraint moment M .The vector of reaction forces is opposite in sign to Eq.(4.1)and is equipollent to the generalized reaction force which acts at the origin of the local coordinate system of the body concerned and is given by

Q c ;i ?F

M teA i u P ;i ?F Ták !

e4:2a T

and the moment is supplemented by the cross product of

the position vector of the revolute joint with respect to the new coordinate system and the original force.This may be reorganised as

Q c ;i ?I 0 u T p ;i A T

h ;i 1 !F

M !

;e4:2b Tsince

eA i u p ;i Th ?F i

ák ? u T p ;i A T

h ;i F :

e4:3T

To illustrate the above,consider a two body system with

one body ?xed to the ground and the second free to rotate about a revolute joint connecting the bodies.The free-body-diagram of such a system is shown in Fig.1.The explicit equations of motion in the generalized co-ordinates for both bodies are as follows:Body 1

m 1€R

x 1?F x 1;2tF x 2;1?0;e4:4a T

m 1€R

y 1?F y 1;2tF y 2;1?0;e4:4b TJ 1€h 1?M 1?0:e4:4c T

Body 2m 2€R

x 2?F x 1;2;e4:5a T

m 2€R

y 2?F y 1;2tm 2g ;e4:5b T

J 2€h 2?F x 1;2

l 22sin h 2àF y 1;2l 2

cos h 2tM 2:e4:5c T

The constraint equations for this system are

C q ;t eT?R x 1

R y 1h 1R x 1àR x 2tcos h 2eTl 2R y 1àR y 2tsin h 2eTl 2

66666643

777

?0:e4:6T

On construction of Eq.(2.18)and comparison with Eqs.

(4.4a)–(4.4c)and (4.5a)–(4.5c),one ?nds that k 1?k 2?k 3?0,k 4?F x 1;2and k 5?F y 1;2,where F d i ;j denotes the force in direction d ,of body i on body j .The generalized constraint forces

are

Q c ?àC T q k ?àF x 1;2

àF y 1;20F x 1;2F y 1;2

F x 1;2sin h 2l 2àF y 1;2cos h 2l 2

66666643

7777775;e4:7T

and on comparison with Eqs.(4.4a)–(4.4c)and (4.5a)–(4.5c),it is clear how the Lagrange multipliers rep-resenting the joint constraint forces and torques are related to the generalized body constraint forces and torques Q c .

4.2.Constraint equations

The constraint equations involve:(1)?xed body constraints,(2)revolute joints,(3)prismatic joints,and (4)prescribed trajectories.The ?xed body constraints of a body i are represented as

C q i ;t eT?R i tc i

h i tc i t1 !?0;e4:8T

the revolute joint constraints between a body i and its adjoining body j are

C q ;t eT?R i h tA i u p i àR j àA j u p j i

?0;e4:9Twhere R i is the global position vector of the origin of the coordinate system of body i ,A i is the rotation matrix, u p i is the local position vector of the revolute joint pin p common to both body i and body j ,and c i are arbitrary constants.The prismatic joint constraints may be ob-tained using the following diagram (Fig.2);for more details see Shabana [16].

The constraint equations for the prismatic joint are

C q ;t eT?v T j ár p ij

h i àh j !?0;e4:10T

where the vector v j is measured with respect to the global coordinate system,hence

v j ?A j v j ?A j

!;e4:11T

and the global position vector connecting the points p i and p j may be written as r p ij ?R i àR j ??.The prescribed trajectories of the excavator and wheel loader buckets are as follows.The excavator bucket trajectory is

C q ;t eT?R x i àa cos p t àátb R y i àc 1

h i àc 22435?0;e4:12Twhere a is the bucket reach in the x -direction,and b is the half way point of reach for the bucket.The arbitrary constants c 1and c 2specify the height and angular ori-entation of the bucket.The wheel loader bucket trajec-tory is similarly de?ned as follows:

C q ;t eT?R x i àc 1R y i ta cos p 4

t àá

tb h i àc 2

243

5?0:e4:13T4.3.Contact force model

The contact force model used for the wheel loader system de?nes the contact dynamics of the wheel-axis sets with the ground as shown in Fig.3.

It is similar to that used for the caterpillar track-ground model studied in [6],and employs a spring-damper element between points p i and p j ,the former residing on the most penetrated part of the wheel and the latter on the ground.The magnitude of this force,see [7]for further details,is F c ij ?k d ij tc d ij _d

ij ;e4:14T

where k and c are the spring and damping coe?cients

respectively and the amount of penetration is given by d ij ?R y ;i àR y ;j àr :

e4:15T

The virtual work due to a force with magnitude F c ij

d W?F c

r p

o r p ij

o r p

d q

;e4:16aT

d W?Q T

i d q

tQ T

d q

;e4:16bT

where

i ?

R;i

Q h;i

?F c

u T

p i

A T

h;i

p ij

r p

e4:16cT

and

j ?

R;j

Q h;j

?àF c

u T

p j

A T

h;j

p ij

r p

:e4:16dT

The position vector written in the global coordinate system is

r p

ij ?r p

àr p

?R itA i u p

àR jàA j u p

;e4:17T

where

u p

i ?

r cos3p

àh i

àá

r sin3p

àh i

àá

and u p

R i;xàR j;x

e4:18T

The generalized force vectors Q

i and Q

are included

in the external force vector Q

e ,and one may then

complete the construction of Eq.(3.2)and compute the system over the desired time interval.5.Results

The excavator and wheel loader simulations were run over four seconds with bucket trajectory constraints governing the https://www.wendangku.net/doc/5b256936.html,putation was performed by the integrator LSODAR,of Petzold and Hindmarsh[14], using absolute and relative error tolerance parame-ters ATOL and RTOL respectively,set to10à6.The time step size h was set to10à3,and4000iterations were required to complete the simulation.The constraint compliance norm shown in Eq.(3.4),grew to no more than10à5for both studies,so the di?erentiation of the constraint equations appears acceptable in this approach to the modelling of the dynamics using prescribed tra-jectories.

The Livermore Solver of Ordinary Di?erential Equations with Automatic Method Switching for sti?and non-sti?problems with Root?nding(LSODAR)[14], adjusts the method order when the dynamics of the problem change rapidly.Provided the forces and torques governing the system are continuous and su?ciently di?erentiable,the order of the integration scheme will increase,and hence generate solution trajectories of the user-de?ned accuracy.The absolute and relative error tolerance parameters,and other input/output integra-tion parameters may be de?ned at each time point for which solution trajectories are sought.The integrator employs forward prediction and backward correction in an e?ort to‘follow’the appropriate solution trajectories, rejecting those that

diverge.

The animation of both the excavator and wheel loader systems is presented in Fig.4,and shows bucket motion and connected mechanism behaviour.This mechanism,including the main boom,arm,links and hydraulic actuators,moves according to the governing bucket constraint equations(4.12)and(4.13).The hy-draulic actuators supplying torques to various bodies are modelled to incorporate revolute and prismatic joints as given by Eqs.(4.9)–(4.11).It may be observed that the excavator bucket has constant vertical position and orientation,and similarly the wheel loader bucket is ?xed in the x-direction and has constant orientation; motion is permitted in the x-and y-direction only,for the excavator and loader bucket systems respectively. One will note that oscillations are absent in the bucket graphs as these are prescribed analytically and the si-nusoidal nature of these trajectories is expected given the form of the constraint equations.

Slides are captured at one-second time intervals over a duration of four seconds,and may be compared with

the generalized forces and torques graphs,Q

c ?àC T

of Figs.5and6.The graphs in Fig.5appear to be

smoother than those in Fig.6,which have an oscillatory

nature.This is due to the fact that the excavator is

constrained to be?xed to the ground in the absence of a

track-ground contact model,whereas the loader has a

wheel–ground contact force model as described in Sec-

tion4.3,and represented by Eqs.(4.14)and(4.15).The

oscillations here are propagated throughout the system

dynamics.Only two seconds of damped oscillatory

motion is shown in the graphs of Fig.6,although four

seconds of animation are shown in Fig.4.This is for

clarity reasons,so that the oscillatory behaviour is

suitably spread out to be observed.Oscillations after the

?rst two seconds in Fig.6are small due to the damping

involved in the contact force model.

One will notice that the rate of change of torque for all bodies in the excavator system is zero at approxi-

mately half way through the simulation.This is a result

of the bucket moving the bodies of the connected

mechanism in one direction prior to the half-way

point,and then in another direction after this point.

For

example,the main boom moves upwards then down-wards,as a result of its indirect connection to the bucket as shown in the animation of Fig.4.Similarly for the wheel loader simulation,the rate of change of torque tends to zero at the half-way point(two seconds of simulation)as a result of the bucket constraint(see Eq.(4.13))forcing a change in the derivative in the gener-alized coordinate graphs(not shown).These torques are the required torques to satisfy the imposed driving constraint.

From the body constraint forces and torques Q

,one may obtain the joint forces and torques as described

Section4.1,through the aid of Fig.1and Eqs.(4.1), (4.2a),(4.2b),(4.3),(4.4a)–(4.4c),(4.5a)–(4.5c),(4.6), (4.7).Hence from the prescribed bucket trajectories,it is possible to obtain the generalized body and joint constraint forces and torques of connected mechanisms, including hydraulic actuators,in an inverse-type ap-proach.6.Conclusions

A multibody system approach is used to model the dynamics of excavator digging operations normally conducive to the study of kinematics and dynamics of robotics work.The kinetic energy of the i th body in the system is substituted into the Lagrange equations

arrive at the Newton–Euler equations of motion for the multibody system.Constraint equations de?ning the connectivity of the system and the speci?ed bucket tra-jectory constraints are augmented to the system equa-tions to form a di?erential algebraic equation.This index3DAE is then cast as an ODE through di?eren-tiation of the constraint equations,and integrated using the ODE integrator LSODAR of Petzold and Hindmarsh [14].Constraint compliance is tested and it is found that di?erentiation of the constraint equations used in the DAE to ODE conversion method is su?ciently accurate. System simulation is shown in Section5and one notices the oscillatory dynamics of the wheel loader example is due to the wheel–ground contact force model employed in this study.One may conclude that the multibody dynamics approach yields a structured set of equations that are quite readable and actuator forces can be ob-tained by computing the Lagrange multipliers k and

hence the constraint forces Q

c .Finally,the model used

here is general and caters for machines of di?ering connectivity and physical properties.

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614 B.Fox et al./Computers and Structures80(2002)605–614

on the contrary的解析

On the contrary Onthecontrary, I have not yet begun. 正好相反，我还没有开始。 https://www.wendangku.net/doc/5b256936.html, Onthecontrary, the instructions have been damaged. 反之，则说明已经损坏。 https://www.wendangku.net/doc/5b256936.html, Onthecontrary, I understand all too well. 恰恰相反，我很清楚 https://www.wendangku.net/doc/5b256936.html, Onthecontrary, I think this is good. ⑴我反而觉得这是好事。 https://www.wendangku.net/doc/5b256936.html, Onthecontrary, I have tons of things to do 正相反，我有一大堆事要做 Provided by jukuu Is likely onthecontrary I in works for you 反倒像是我在为你们工作 https://www.wendangku.net/doc/5b256936.html, Onthecontrary, or to buy the first good. 反之还是先买的好。 https://www.wendangku.net/doc/5b256936.html, Onthecontrary, it is typically american. 相反，这正是典型的美国风格。 222.35.143.196 Onthecontrary, very exciting.

恰恰相反，非常刺激。 https://www.wendangku.net/doc/5b256936.html, But onthecontrary, lazy. 却恰恰相反，懒洋洋的。 https://www.wendangku.net/doc/5b256936.html, Onthecontrary, I hate it! 恰恰相反，我不喜欢！ https://www.wendangku.net/doc/5b256936.html, Onthecontrary, the club gathers every month. 相反，俱乐部每个月都聚会。 https://www.wendangku.net/doc/5b256936.html, Onthecontrary, I'm going to work harder. 我反而将更努力工作。 https://www.wendangku.net/doc/5b256936.html, Onthecontrary, his demeanor is easy and nonchalant. 相反，他的举止轻松而无动于衷。 https://www.wendangku.net/doc/5b256936.html, Too much nutrition onthecontrary can not be absorbed through skin. 太过营养了反而皮肤吸收不了. https://www.wendangku.net/doc/5b256936.html, Onthecontrary, I would wish for it no other way. 正相反，我正希望这样 Provided by jukuu Onthecontrary most likely pathological. 反之很有可能是病理性的。 https://www.wendangku.net/doc/5b256936.html, Onthecontrary, it will appear clumsy. 反之，就会显得粗笨。 https://www.wendangku.net/doc/5b256936.html,

英语造句

一般过去式时间状语：yesterday just now (刚刚) the day before three days ag0 a week ago in 1880 last month last year 1. I was in the classroom yesterday. I was not in the classroom yesterday. Were you in the classroom yesterday. 2. They went to see the film the day before. Did they go to see the film the day before. They did go to see the film the day before. 3. The man beat his wife yesterday. The man didn’t beat his wife yesterday. 4. I was a high student three years ago. 5. She became a teacher in 2009. 6. They began to study english a week ago 7. My mother brought a book from Canada last year. 8.My parents build a house to me four years ago . 9.He was husband ago. She was a cooker last mouth. My father was in the Xinjiang half a year ago. 10.My grandfather was a famer six years ago. 11.He burned in 1991

学生造句--Unit 1

●I wonder if it’s because I have been at school for so long that I’ve grown so crazy about going home. ●It is because she wasn’t well that she fell far behind her classmates this semester. ●I can well remember that there was a time when I took it for granted that friends should do everything for me. ●In order to make a difference to society, they spent almost all of their spare time in raising money for the charity. ●It’s no pleasure eating at school any longer because the food is not so tasty as that at home. ●He happened to be hit by a new idea when he was walking along the riverbank. ●I wonder if I can cope with stressful situations in life independently. ●It is because I take things for granted that I make so many mistakes. ●The treasure is so rare that a growing number of people are looking for it. ●He picks on the weak mn in order that we may pay attention to him. ●It’s no pleasure being disturbed whena I settle down to my work. ●I can well remember that when I was a child, I always made mistakes on purpose for fun. ●It’s no pleasure accompany her hanging out on the street on such a rainy day. ●I can well remember that there was a time when I threw my whole self into study in order to live up to my parents’ expectation and enter my dream university. ●I can well remember that she stuck with me all the time and helped me regain my confidence during my tough time five years ago. ●It is because he makes it a priority to study that he always gets good grades. ●I wonder if we should abandon this idea because there is no point in doing so. ●I wonder if it was because I ate ice-cream that I had an upset student this morning. ●It is because she refused to die that she became incredibly successful. ●She is so considerate that many of us turn to her for comfort. ●I can well remember that once I underestimated the power of words and hurt my friend. ●He works extremely hard in order to live up to his expectations. ●I happened to see a butterfly settle on the beautiful flower. ●It’s no pleasure making fun of others. ●It was the first time in the new semester that I had burned the midnight oil to study. ●It’s no pleasure taking everything into account when you long to have the relaxing life. ●I wonder if it was because he abandoned himself to despair that he was killed in a car accident when he was driving. ●Jack is always picking on younger children in order to show off his power. ●It is because he always burns the midnight oil that he oversleeps sometimes. ●I happened to find some pictures to do with my grandfather when I was going through the drawer. ●It was because I didn’t dare look at the failure face to face that I failed again. ●I tell my friend that failure is not scary in order that she can rebound from failure. ●I throw my whole self to study in order to pass the final exam. ●It was the first time that I had made a speech in public and enjoyed the thunder of applause. ●Alice happened to be on the street when a UFO landed right in front of her. ●It was the first time that I had kept myself open and talked sincerely with my parents. ●It was a beautiful sunny day. The weather was so comfortable that I settled myself into the

英语句子结构和造句

高中英语~词性~句子成分~语法构成第一章节：英语句子中的词性 1.名词：n. 名词是指事物的名称，在句子中主要作主语.宾语.表语.同位语。 2.形容词;adj. 形容词是指对名词进行修饰~限定~描述~的成份，主要作定语.表语.。形容词在汉语中是（的）.其标志是: ous. Al .ful .ive。. 3.动词：vt. 动词是指主语发出的一个动作，一般用来作谓语。 4.副词：adv. 副词是指表示动作发生的地点. 时间. 条件. 方式. 原因. 目的. 结果.伴随让步. 一般用来修饰动词. 形容词。副词在汉语中是（地）.其标志是：ly。 5.代词：pron. 代词是指用来代替名词的词，名词所能担任的作用，代词也同样.代词主要用来作主语. 宾语. 表语. 同位语。 6.介词：prep.介词是指表示动词和名次关系的词，例如：in on at of about with for to。其特征：

介词后的动词要用—ing形式。介词加代词时，代词要用宾格。例如：give up her（him）这种形式是正确的，而give up she（he）这种形式是错误的。 7.冠词：冠词是指修饰名词，表名词泛指或特指。冠词有a an the 。 8.叹词：叹词表示一种语气。例如：OH. Ya 等 9.连词：连词是指连接两个并列的成分，这两个并列的成分可以是两个词也可以是两个句子。例如：and but or so 。 10.数词：数词是指表示数量关系词，一般分为基数词和序数词第二章节：英语句子成分主语：动作的发出者，一般放在动词前或句首。由名词. 代词. 数词. 不定时. 动名词. 或从句充当。谓语：指主语发出来的动作，只能由动词充当，一般紧跟在主语后面。宾语：指动作的承受着，一般由代词. 名词. 数词. 不定时. 动名词. 或从句充当. 介词后面的成分也叫介词宾语。定语：只对名词起限定修饰的成分，一般由形容

六级单词解析造句记忆MNO

M A: Has the case been closed yet? B: No, the magistrate still needs to decide the outcome. magistrate n.地方行政官，地方法官，治安官 A: I am unable to read the small print in the book. B: It seems you need to magnify it. magnify vt.１．放大，扩大；２．夸大，夸张 A: That was a terrible storm. B: Indeed, but it is too early to determine the magnitude of the damage. magnitude n.１．重要性，重大；２．巨大，广大 A: A young fair maiden like you shouldn’t be single. B: That is because I am a young fair independent maiden. maiden n.少女，年轻姑娘，未婚女子 a.首次的，初次的 A: You look majestic sitting on that high chair. B: Yes, I am pretending to be the king! majestic a.雄伟的，壮丽的，庄严的，高贵的 A: Please cook me dinner now. B: Yes, your majesty, I’m at your service. majesty n.１．［Ｍ－］陛下（对帝王，王后的尊称）；２．雄伟，壮丽，庄严 A: Doctor, I traveled to Africa and I think I caught malaria. B: Did you take any medicine as a precaution? malaria n.疟疾 A: I hate you! B: Why are you so full of malice? malice n.恶意，怨恨 A: I’m afraid that the test results have come back and your lump is malignant. B: That means it’s serious, doesn’t it, doctor? malignant a.１．恶性的，致命的；２．恶意的，恶毒的 A: I’m going shopping in the mall this afternoon, want to join me? B: No, thanks, I have plans already. mall n.（由许多商店组成的）购物中心 A: That child looks very unhealthy. B: Yes, he does not have enough to eat. He is suffering from malnutrition.

base on的例句

意见应以事实为根据. 3 来自辞典例句 192. The bombers swooped ( down ) onthe air base. 轰炸机突袭空军基地. 来自辞典例句 193. He mounted their engines on a rubber base. 他把他们的发动机装在一个橡胶垫座上. 14 来自辞典例句 194. The column stands on a narrow base. 柱子竖立在狭窄的地基上. 14 来自辞典例句 195. When one stretched it, it looked like grey flakes on the carvas base. 你要是把它摊直, 看上去就象好一些灰色的粉片落在帆布底子上. 18 来自辞典例句 196. Economic growth and human well - being depend on the natural resource base that supports all living systems. 经济增长和人类的福利依赖于支持所有生命系统的自然资源. 12 1 来自辞典例句 197. The base was just a smudge onthe untouched hundred - mile coast of Manila Bay. 那基地只是马尼拉湾一百英里长安然无恙的海岸线上一个硝烟滚滚的污点. 6 来自辞典例句 198. You can't base an operation on the presumption that miracles are going to happen. 你不能把行动计划建筑在可能出现奇迹的假想基础上.

英语造句大全

英语造句大全English sentence 在句子中，更好的记忆单词！ 1、(1)、able adj. 能句子：We are able to live under the sea in the future. (2)、ability n. 能力句子：Most school care for children of different abilities. (3)、enable v. 使。。。能句子：This pass enables me to travel half-price on trains. 2、(1)、accurate adj. 精确的句子：We must have the accurate calculation. (2)、accurately adv. 精确地句子：His calculation is accurately. 3、(1)、act v. 扮演句子：He act the interesting character. （2）、actor n. 演员句子：He was a famous actor. (3)、actress n. 女演员句子：She was a famous actress. (4)、active adj. 积极的句子：He is an active boy. 4、add v. 加句子：He adds a little sugar in the milk. 5、advantage n. 优势句子：His advantage is fight. 6、age 年龄n. 句子：His age is 15. 7、amusing 娱人的adj. 句子：This story is amusing. 8、angry 生气的adj. 句子：He is angry. 9、America 美国n.

(完整版)主谓造句

主语+谓语 1. 理解主谓结构 1) The students arrived. The students arrived at the park. 2) They are listening. They are listening to the music. 3) The disaster happened. 2．体会状语的位置 1) Tom always works hard. 2) Sometimes I go to the park at weekends.. 3) The girl cries very often. 4) We seldom come here. The disaster happened to the poor family. 3. 多个状语的排列次序 1) He works. 2) He works hard. 3) He always works hard. 4) He always works hard in the company. 5) He always works hard in the company recently. 6) He always works hard in the company recently because he wants to get promoted. 4. 写作常用不及物动词 1. ache My head aches. I’m aching all over. 2. agree agree with sb. about sth. agree to do sth. 3. apologize to sb. for sth. 4. appear (at the meeting, on the screen) 5. arrive at / in 6. belong to 7. chat with sb. about sth. 8. come (to …) 9. cry 10. dance 11. depend on /upon 12. die 13. fall 14. go to … 15. graduate from 16. … happen 17. laugh 18. listen to... 19. live 20. rise 21. sit 22. smile 23. swim 24. stay (at home / in a hotel) 25. work 26. wait for 汉译英： 1.昨天我去了电影院。 2.我能用英语跟外国人自由交谈。 3.晚上7点我们到达了机场。 4.暑假就要到了。 5.现在很多老人独自居住。 6.老师同意了。 7.刚才发生了一场车祸。 8.课上我们应该认真听讲。9. 我们的态度很重要。 10. 能否成功取决于你的态度。 11. 能取得多大进步取决于你付出多少努力。 12. 这个木桶能盛多少水取决于最短的一块板子的长度。

初中英语造句

【it's time to和it's time for】 ——————这其实是一个句型,只不过后面要跟不同的东西. ——————It's time to跟的是不定式（to do）.也就是说,要跟一个动词,意思是“到做某事的时候了”.如： It's time to go home. It's time to tell him the truth. ——————It's time for 跟的是名词.也就是说,不能跟动词.如： It's time for lunch.(没必要说It's time to have lunch) It's time for class.(没必要说It's time to begin the class.) They can't wait to see you Please ask liming to study tonight. Please ask liming not to play computer games tonight. Don’t make/let me to smoke I can hear/see you dance at the stage You had better go to bed early. You had better not watch tv It’s better to go to bed early It’s best to run in the morning I am enjoy running with music. With 表伴随听音乐 I already finish studying You should keep working. You should keep on studying English Keep calm and carry on 保持冷静继续前行二战开始前英国皇家政府制造的海报名字 I have to go on studying I feel like I am flying I have to stop playing computer games and stop to go home now I forget/remember to finish my homework. I forget/remember cleaning the classroom We keep/percent/stop him from eating more chips I prefer orange to apple I prefer to walk rather than run I used to sing when I was young What’s wrong with you There have nothing to do with you I am so busy studying You are too young to na?ve I am so tired that I have to go to bed early

The Kite Runner-美句摘抄及造句

《The Kite Runner》追风筝的人--------------------------------美句摘抄 1.I can still see Hassan up on that tree, sunlight flickering through the leaves on his almost perfectly round face, a face like a Chinese doll chiseled from hardwood: his flat, broad nose and slanting, narrow eyes like bamboo leaves, eyes that looked, depending on the light, gold, green even sapphire 翻译：我依然能记得哈桑坐在树上的样子，阳光穿过叶子，照着他那浑圆的脸庞。他的脸很像木头刻成的中国娃娃，鼻子大而扁平，双眼眯斜如同竹叶，在不同光线下会显现出金色、绿色，甚至是宝石蓝。 E.g.: A shadow of disquiet flickering over his face. 2.Never told that the mirror, like shooting walnuts at the neighbor's dog, was always my idea. 翻译：从来不提镜子、用胡桃射狗其实都是我的鬼主意。E.g.:His secret died with him, for he never told anyone. 3.We would sit across from each other on a pair of high

翻译加造句

一、翻译 1. The idea of consciously seeking out a special title was new to me., but not without appeal. 让我自己挑选自己最喜欢的书籍这个有意思的想法真的对我具有吸引力。 2.I was plunged into the aching tragedy of the Holocaust, the extraordinary clash of good, represented by the one decent man, and evil. 我陷入到大屠杀悲剧的痛苦之中，一个体面的人所代表的善与恶的猛烈冲击之中。 3.I was astonished by the the great power a novel could contain. I lacked the vocabulary to translate my feelings into words. 我被这部小说所包含的巨大能量感到震惊。我无法用语言来表达我的感情（心情）。 4，make sth. long to short长话短说 5.I learned that summer that reading was not the innocent(简单的) pastime(消遣) I have assumed it to be., not a breezy, instantly forgettable escape in the hammock(吊床)，( though I’ ve enjoyed many of those too ). I discovered that a book, if it arrives at the right moment, in the proper season, will change the course of all that follows. 那年夏天，我懂得了读书不是我认为的简单的娱乐消遣，也不只是躺在吊床上，一阵风吹过就忘记的消遣。我发现如果在适宜的时间、合适的季节读一本书的话，他将能改变一个人以后的人生道路。二、词组造句 1. on purpose 特意，故意 This is especially true here, and it was ~. (这一点在这里尤其准确，并且他是故意的) 2.think up 虚构，编造，想出 She has thought up a good idea. 她想出了一个好的主意。 His story was thought up. 他的故事是编出来的。 3. in the meantime 与此同时助记：in advance 事前in the meantime 与此同时in place 适当地... In the meantime, what can you do? 在这期间您能做什么呢？ In the meantime, we may not know how it works, but we know that it works. 在此期间，我们不知道它是如何工作的，但我们知道，它的确在发挥作用。 4.as though 好像，仿佛 It sounds as though you enjoyed Great wall. 这听起来好像你喜欢长城。 5. plunge into 使陷入 He plunged the room into darkness by switching off the light. 他把灯一关，房

改写句子练习2标准答案

The effective sentences:(improve the sentences!) 1.She hopes to spend this holiday either in Shanghai or in Suzhou. 2.Showing/to show sincerity and to keep/keeping promises are the basic requirements of a real friend. 3.I want to know the space of this house and when it was built. I want to know how big this house is and when it was built. I want to know the space of this house and the building time of the house. 4.In the past ten years,Mr.Smith has been a waiter,a tour guide,and taught English. In the past ten years,Mr.Smith has been a waiter,a tour guide,and an English teacher. 5.They are sweeping the floor wearing masks. They are sweeping the floor by wearing masks. wearing masks,They are sweeping the floor. 6.the drivers are told to drive carefully on the radio. the drivers are told on the radio to drive carefully 7.I almost spent two hours on this exercises. I spent almost two hours on this exercises. 8.Checking carefully,a serious mistake was found in the design. Checking carefully,I found a serious mistake in the design.

用以下短语造句

M1 U1 一. 把下列短语填入每个句子的空白处（注意所填短语的形式变化）： add up (to) be concerned about go through set down a series of on purpose in order to according to get along with fall in love (with) join in have got to hide away face to face 1 We’ve chatted online for some time but we have never met ___________. 2 It is nearly 11 o’clock yet he is not back. His mother ____________ him. 3 The Lius ___________ hard times before liberation. 4 ____________ get a good mark I worked very hard before the exam. 5 I think the window was broken ___________ by someone. 6 You should ___________ the language points on the blackboard. They are useful. 7 They met at Tom’s party and later on ____________ with each other. 8 You can find ____________ English reading materials in the school library. 9 I am easy to be with and _____________my classmates pretty well. 10 They __________ in a small village so that they might not be found. 11 Which of the following statements is not right ____________ the above passage? 12 It’s getting dark. I ___________ be off now. 13 More than 1,000 workers ___________ the general strike last week. 14 All her earnings _____________ about 3,000 yuan per month. 二.用以下短语造句： 1.go through 2. no longer/ not… any longer 3. on purpose 4. calm… down 5. happen to 6. set down 7. wonder if 三. 翻译： 1.曾经有段时间，我对学习丧失了兴趣。（there was a time when…） 2. 这是我第一次和她交流。（It is/was the first time that …注意时态） 3.他昨天公园里遇到的是他的一个老朋友。（强调句） 4. 他是在知道真相之后才意识到错怪女儿了。（强调句） M 1 U 2 一. 把下列短语填入每个句子的空白处（注意所填短语的形式变化）： play a …role (in) because of come up such as even if play a …part (in) 1 Dujiangyan(都江堰) is still ___________in irrigation(灌溉) today. 2 That question ___________ at yesterday’s meeting. 3 Karl Marx could speak a few foreign languages, _________Russian and English. 4 You must ask for leave first __________ you have something very important. 5 The media _________ major ________ in influencing people’s opinion s. 6 _________ years of hard work she looked like a woman in her fifties. 二.用以下短语造句： 1.make (good/full) use of 2. play a(n) important role in 3. even if 4. believe it or not 5. such as 6. because of

英语造句

English sentence 1、(1)、able adj. 能句子：We are able to live under the sea in the future. (2)、ability n. 能力句子：Most school care for children of different abilities. (3)、enable v. 使。。。能句子：This pass enables me to travel half-price on trains. 2、(1)、accurate adj. 精确的句子：We must have the accurate calculation. (2)、accurately adv. 精确地句子：His calculation is accurately. 3、(1)、act v. 扮演句子：He act the interesting character.（2）、actor n. 演员句子：He was a famous actor. (3)、actress n. 女演员句子：She was a famous actress. (4)、active adj. 积极的句子：He is an active boy. 4、add v. 加句子：He adds a little sugar in the milk. 5、advantage n. 优势句子：His advantage is fight. 6、age 年龄n. 句子：His age is 15. 7、amusing 娱人的adj. 句子：This story is amusing. 8、angry 生气的adj. 句子：He is angry. 9、America 美国n. 句子：He is in America. 10、appear 出现v. He appears in this place. 11. artist 艺术家n. He is an artist. 12. attract 吸引 He attracts the dog. 13. Australia 澳大利亚 He is in Australia. 14.base 基地 She is in the base now. 15.basket 篮子 His basket is nice. 16.beautiful 美丽的 She is very beautiful. 17.begin 开始 He begins writing. 18.black 黑色的 He is black. 19.bright 明亮的 His eyes are bright. 20.good 好的 He is good at basketball. 21.British 英国人 He is British. 22.building 建造物 The building is highest in this city 23.busy 忙的 He is busy now. 24.calculate 计算 He calculates this test well. 25.Canada 加拿大 He borns in Canada. 26.care 照顾 He cared she yesterday. 27.certain 无疑的 They are certain to succeed. 28.change 改变 He changes the system. 29.chemical 化学药品