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Ultra-fast escape maneuver of an octopus-inspired robot

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2015 Bioinspir. Biomim. 10 016016

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PAPER

Ultra-fast escape maneuver of an octopus-inspired robot

G D Weymouth 1,V Subramaniam 2and M S Triantafyllou 3

1Southampton Marine and Maritime Institute,University of Southampton,Southampton SO171BJ,UK

2Centre for Environmental Sensing and Modeling,Singapore MIT Alliance for Research and Technology,Singapore 138062,Singapore 3

Center for Ocean Engineering,Massachusetts Institute of Technology,Cambridge MA 02139,USA

E-mail:G.D.Weymouth@https://www.wendangku.net/doc/4516711582.html,

Keywords:high speed manuevers,drag reduction,energy ef ?ciency,shape change

Abstract

We design and test an octopus-inspired ?exible hull robot that demonstrates outstanding fast-starting performance.The robot is hyper-in ?ated with water,and then rapidly de ?ates to expel the ?uid so as to power the escape https://www.wendangku.net/doc/4516711582.html,ing this robot we verify for the ?rst time in laboratory testing that rapid size-change can substantially reduce separation in bluff bodies traveling several body lengths,and recover ?uid energy which can be employed to improve the propulsive performance.The robot is found to experience speeds over ten body lengths per second,exceeding that of a similarly propelled optimally streamlined rigid rocket.The peak net thrust force on the robot is more than 2.6times that on an optimal rigid body performing the same maneuver,experimentally demonstrating large energy recovery and enabling acceleration greater than 14body lengths per second squared.Finally,over 53%of the available energy is converted into payload kinetic energy,a performance that exceeds the esti-mated energy conversion ef ?ciency of fast-starting ?sh.The Reynolds number based on ?nal speed and robot length is ≈Re 700000.We use the experimental data to establish a fundamental de ?ation scaling parameter σ*which characterizes the mechanisms of ?ow control via shape change.Based on this scaling parameter,we ?nd that the fast-starting performance improves with increasing size.

1.Introduction

The cephalopods,such as the octopus,cuttle ?sh,and squid,undergo large-scale body and volume changes during escape maneuvers.For example,the octopus ?rst hyper-in ?ates its mantle cavity ?lling it with water,which it then rapidly expels in the form of a propelling jet (Huffard 2006,Wells 1990,Pack-ard 1969),accelerating it up to high speed (?gure 1(a)).Expelling a large mass of water at lower speed imparts maximum momentum for a given energy expenditure since momentum scales linearly with speed and mass,while energy scales linearly with mass but quadratically with speed.Hence the in ?ation before the onset of the maneuver must be large,increasing the body ’s lateral dimension substantially.As a result,the normally streamlined mantle becomes quite bluff.Flow around a similarly shaped rigid body geometry would incur large energy penalties in the form of ?ow separation and added mass resistance.However,the ?exible,rapidly de ?ating mantle com-pletely alters the dynamics of the ?ow,inducing

unsteady ?ow control mechanisms such as separation elimination and ?uid energy recovery.

Unsteady ?ow control is an active area of research,especially in relation to animal behavior (Daniel 1984,Kanso et al 2005,Childress et al 2011,Moored et al 2012),and unsteady propulsion mechanisms involving rapid shape-change offer intriguing possibi-lities to overcome the maneuvering limitations of standard rigid underwater vehicles.The importance of shape-change is exempli ?ed by considering the ?uid kinetic energy associated with the body ’s added mass.While added mass is ?xed for a rigid vessel and the added mass force opposes acceleration,a shrinking body has a diminishing added mass,and can therefore see a net ?ow of energy into the body.To quote from Spagnolie and Shelley (2009),who studied a shape-changing body,‘while a reduced virtual mass gives a reduced acceleration reaction,a reducing virtual mass can generate a boost in velocity ’.Such a boost is observed in jelly ?sh even during the ‘rest ’phase of their propulsion cycle,indicating energy recapture (Gemmell et al 2013

RECEIVED

10July 2014

REVISED

24October 2014

ACCEPTED FOR PUBLICATION

9January 2015

PUBLISHED

2February 2015

?2015IOP Publishing Ltd

This recovery mechanism is especially important to the ultimate speed and ef?ciency of shrinking bod-ies performing fast-start maneuvers.Weymouth and Triantafyllou(2013)demonstrated that the irrota-tional energy initially imparted to the?uid by an accel-erating body can be recovered by size reduction to increase the propulsive thrust later in the maneuver.In other words,while the added-mass is essentially addi-tional payload for a rigid accelerating body,a shrink-ing body effectively turns the added mass into additional propellant.A remarkable consequence is that a shrinking rocket in a heavy inviscid?uid accel-erates up to speeds greater than it could achieve in the vacuum of space.

The amount of irrotational kinetic energy recovery that can be achieved in a viscous?uid is determined by the evolution of the boundary layer vorticity at the external surface of the body as it undergoes large deformations.If this vorticity is shed into the wake the kinetic energy will be lost to the?uid instead of being recovered by the body,hence severely reducing the escape speed of the animal.Weymouth and Trianta-fyllou(2012)used viscous simulations to demonstrate that if a body very rapidly undergoes a prescribed shape change,as in the case of the octopus,then the boundary layer does not shed.Instead,it remains mostly attached to the body,and the total circulation decreases through vorticity annihilation.

A simple kinematic parameter,the shape-change numberΞ,can be used to characterize the relative speed of the size change

Ξ=W

,(1)

where W is the rate at which the cross-stream diameter

of the body decreases and U is the forward velocity of

the body.Weymouth and Triantafyllou(2013)

showed that an initially spherical shrinking body of

length L that accelerates from rest with constant

acceleration a has an ultimate shape change number of

Ξ=W aL

2,and that the larger the value ofΞthe

better the performance of the shrinking body.Speci?-

cally,simulations up to Reynolds number Re=1000

showed that moderate separation reduction and

energy recovery requiredΞ>132.

However,the purely kinematic parameterΞis

incapable of fully characterizing the physics of the

boundary layer evolution.For a self-propelled body

simulated in Weymouth and Triantafyllou(2013)

with a maximum Reynolds number

Re20000but a small value ofΞ≈144,it

was found that separation was practically absent and

energy recovery remarkably high.This demonstrated

that Reynolds number is also a signi?cant parameter

but the speci?c dependence was not resolved.Limita-

tions in the simulation also left unresolved questions

concerning the energetics and the feasibility of physi-

cally implementing a propulsion-system based on

rapid size-change.

In this paper we apply and extend the concepts

derived in previous work to design and test a de?atable

?exible hull robot inspired by the octopus.The initi-

ally bluff robot demonstrates remarkable fast-starting

performance through separation elimination and?ow

energy recovery.We use the results to investigate the

principal physical mechanisms involved and derive a

single fundamental parameter capable of characteriz-

ing the?ow around de?ating bodies.

2.Design of an octopus-inspired robot

To test the ability of shape-change to reduce separation

and recover?uid energy in experiments required the

design of the novel underwater robot shown in

?gure1(b).The octopus-inspired robot consists of a

rigid neutrally buoyant skeleton with an elastic mem-

brane stretched around it to form the outer hull.As

with the mantle of the octopus,this membrane can be

in?ated,giving it an initially bluff shape and storing

suf?cient energy to power its escape.The fully de?ated

hull shape is approximately a5:1ellipsoid,and is

suf?ciently streamlined to allow the body to coast

dozens of body lengths.

The rigid skeleton was three-dimensional(3D)-

printed in a single piece out of polycarbonate

(?gure2).This structure has large openings to reduce

frictional losses from the?uid as it is pushed through

the robot when the membrane de?ates.The length of

the membrane-covered section is=

L27cm to match

the in?ated diameter of the commercially available

synthetic rubber balloons.As the skeleton is neutrally

buoyant and the membrane is?lled with water,the

Figure1.Biological and biologically inspired jet-propelled escape.(a)Octopus using jet propulsion to escape from threat at high speed.Image captured from video courtesy of Dr Roger Hanlon of the Marine Biology Laboratory,Woods Hole.(b)This propulsion mode inspired the design of a simple jetting robot using a3D printed polycarbonate model and covered by an elastic membrane made of synthetic rubber.

robot is neutrally buoyant throughout the maneuver.The volume of the robot when fully de ?ated is 1030cm 3,and so the ‘payload ’mass accelerated by the maneuver is =m 1.03kg f .

The tail of the skeleton is ?tted with a convex jet nozzle and a set of four NACA 0012?ns for directional stability instead of the trailing arms of the octopus,hence avoiding interactions with the propelling jet (?gure 3).The aperture area =A 15cm J 2was chosen as a compromise between the need to have a large aperture to increase the ?ow rate and the requirement to have a small area that ?ts the ultimate (de ?ated)shape.

3.Open-water testing methodology

The simple but effective design above does not require

any moving parts or energy storage other than the stretching membrane and enables self-propelled open water fast-start tests to be performed.In these tests,the robot is slowly in ?ated by ?lling it with pressurized water from a rigid mount which was ?tted with a pressure sensor (?gure 4).The robot was ?lled until the diameter of the membrane reached L 0.6giving a pressure difference inside and outside the membrane of 4.45kPa .In this condition,the membrane has a surface area of 0.1m 2.The strain in the membrane is highly localized,but the overall strain relative to the fully de ?ated shape is ?=0.94.Thus the effective modulus is only 4.77kPa .In ?ation past this point typically led to membrane failure.

3.1.Measurement and image processing method Once in ?ated,the robot is released from the mount allowing it to accelerate forward in open water under its own power.The resulting fast-start maneuver performance is measured using high-speed cameras at 150frames/second.Figure 5shows the rapid accelera-tion and de ?ation of the shrinking robot from a self-propelled run.

Each frame of the high-speed video is analyzed separately,and a sample of the process is depicted in

?gure 6.The algorithm applies a threshold to the image followed by edge detection and morphological operations.The end result is an image with the robot isolated from the background.The length scale in each image is calibrated based on the known dimensions of the rigid skeleton.From this the position of the mem-brane outline is established to a resolution of ±0.9mm ,corresponding to the average size of one pixel in the image.The outline is numerically inte-grated to give the instantaneous volume V and center of mass enclosed by the ?exible hull assuming the membrane to be axisymmetric about the robot ’s major axis.Differentiating the location of the center of mass between snapshots gives the instantaneous velo-city U .We ?nd that the measurement error of the membrane tracking method is averaged out in the volume integration,resulting in consistent and noise free measurements of the robot volume and mass.In contrast,the ?nite differencing introduces numerical noise,which we ?lter by ?tting a smoothing spline to data from four test runs.

4.Results of self-propelled robot tests

Qualitatively we see from,?gure 5that the robot moves slowly in the ?rst 0.5s ,but the boost in speed achieved at the end of the maneuver is clearly visible,with the robot displacing the membrane length L between the frames at 0.9and 1.0s.The ?nal streamlined shape allows the robot to maintain fairly high speed,similar to the de ?ated form of escaping cephalopods.

The velocity history presented in ?gure 7(a)quan-ti ?es these observations.The robot achieves peak velo-city U above ?L 10s 1(body lengths per second)or ?2.7m s 1at =t 0.95s ,after which the robot slows down as it coasts.The acceleration is fairly constant during the jetting period,with a peak value of ?L 14s 2or ?3.8m s 2.The peak velocity gives a maximum Rey-nolds number of 729000,well above the value of 20000explored numerically,and consistent with the values experienced by fast moving marine animals (Daniel 1984).The value of Ξ=W U ave max is approxi-mately 1/24.

Figure 7(b)shows that the mass m of the robot decreases from the initial size of 3.65kg down to the payload mass when the membrane comes in contact with the rigid skeleton.At the end of the maneuver,the membrane is less stiff and in contact with the struts of the rigid structure leading to a ‘starved horse ’effect and the observed dip and recovery in the robot mass at =t 1s .The mass decreases at a rate near ?3kg s 1through most of the jetting period.

4.1.Force analysis and ef ?ciency

To extend this analysis,the ?ltered values of U and m are used to compute the net force on the robot

Σ=F mU

˙and the jet force =F mU ˙J J ,where Figure 2.Dimensions and shape of internal skeleton of the robot,3D printed using polycarbonate.The length of the membrane-covered section is =L 27cm ,and a 5:1ellipse is drawn on the background for reference.

=U V

A ˙J 4

3J is the jet momentum velocity.F J is a conservative estimate of the jet momentum ?ux as it assumes a parabolic pro ?le,a uniform pro ?le pro-duces 33%less thrust for the same mass ?ow rate,but it neglects any additional forces on the nozzle.Addi-tional thrust can be produced by a pressure impulse in jet ?ow (Krueger and Gharib 2005,Krieg and Moh-seni 2013),but these forces are strongest for pulsed jets and were not observed to be signi ?cant in the previous numerical work comparing shrinking and rigid bodies (Weymouth and Triantafyllou 2013).The proximity of the ?lling mount early in the maneuver does induce a pressure force on the nozzle,and so the F J model is only used after =t 0.2s .

Figure 7(c)shows that the instantaneous net force on the body is remarkably high,peaking at 130%of the force provided by the jet.For comparison,?gure 7(c)also shows a conservative estimate of the forces that would be experienced by a rigid 5:1prolate body made to follow the same kinematics experienced by the robot.A 5:1ellipsoid is a nearly optimal streamlined form for steady forward motion (Hoerner 1965)but the drag and reactive forces on a rigid ellipsoid would still reduce the net force by 50%at =t 0.6s .There-fore,the net force on the shrinking robot is 2.6times that of an optimal rigid body at =t 0.6s ,and the

relative improvement is even greater later in the maneuver.

Finally,we compute the kinetic energy of the pay-load =m U KE f 1

22and the integrated power (total

work)supplied by the jet ∫Δ=P t mU t ˙d 12

J 2.We use the ?nal payload mass =m 1.03kg f instead of the instantaneous mass to avoid crediting the robot for accelerating propellant that it ejects later in the man-euver.The ratio the payload kinetic energy and the work done by the jet gives the hydrodynamic energy

Lip to secure Diameter = 42 mm

elastic membrane DETAIL:B SCALE 1:5

isometric view of the tail of the robot showing the large openings and the dimensions pretensioned along the length and fastened to the skeleton at the rim indicated.(b)acheive stable open-water motion of the robot.

Figure 4.The robot is ?lled with pressurized water (dyed red in this image for contrast)from a rigid mount,hyper-in ?ating the balloon to take on a bluff body shape.The initial in ?ated diameter is L 0.6for every test.

Figure 5.Filmstrip of the octopus-inspired robot as it jets and shrinks in the self-propelled fast-start maneuver.The time delay between images is 0.1s.

ef ?ciency of the robot in accelerating its payload up to speed.The large energy recovery powered thrust of the shrinking body enables a correspondingly large energy ef ?ciency with a peak of 53%during the fast-start maneuver.

5.Physical mechanisms exploited by size-reducing bodies

We next address the physical mechanisms of separa-tion reduction and energy recovery to establish general

rules for their application to other situations of shape-changing bodies.The key factors are the strong velocity component normal to the body surface and the large pressure gradients generated by the rapid shrinking.

A simpli ?ed potential ?ow model of the ?ow around translating and shrinking sphere demonstrates these factors.The potential in spherical coordinates (θψr ,,)is:

?θ=?+?U r R r WR r 2cos 2,

(2)

322

????where R is the instantaneous radius of the sphere,

=W R

2˙is the rate of change of the radius.Taking the gradient of the unsteady potential at r =R gives the velocity on the surface of the sphere

?θ=

??=+u r U W

cos 2

,(3)

r ?θθ=

??=θu r U 11

sin ,(4)

showing that the radial component of velocity matches

the required normal condition on the shrinking sphere.

The unsteady Bernoulli equation gives the pres-sure on the surface of the sphere as ρθρθ=

++p U UW

Ra 916cos 2322

cos ,(5)

2??????where =a U

˙as before and we have dropped the terms that are uniform on the surface (W 2,WR

˙)as they do not contribute to the tangential pressure gradient or to the net force.The ?rst term in (5)is the pressure due to the forward speed of the body,proportional to ρU 2.The second term is due to the rate of change of the body ’s size and speed,proportional to ρUW and ρRa ,respectively.From (5)we see that Ξ=W U expresses the magnitude of the pressure induced by shrinking and translating relative to the pressure induced purely by translation.

Large negative values of W cause low pressure at the front of the body and high pressure at the back.The integrated effect of this pressure is a forward thrust force completely separate from any decrease in the quasi-steady drag caused by the reduced cross stream area.As discussed in the introduction,this thrust force is the result of the transfers ?uid kinetic

energy =T m U a 1

22back into the body,as the added mass m a decreases with the size R .The magnitude of this force is:

Figure 6.Each frame of the high speed camera data (a)was processed using thresholding (b),and edge detection algorithms (c),to determine the instantaneous centroid and outline of the robot (d),which thereby determine the robot kinematics and dynamics.

Figure 7.Data analysis from four self-propelled runs.(a)Velocity measurements (gray points)show that the robot achieves peak velocity U greater than ?L 10s 1in less than a second.(b)The mass m of the robot (gray points)decreases as the body shrinks,ejecting

?uid at a rate =??m

˙3kg s 1.The blue lines in (a),(b)are the average performance values using a smoothing spline.(c)The peak net thrust force ΣF is 30%greater than the thrust provided by the jet F J .The gray line shows a conservative estimate of the net force on a streamlined body with the shape of a 5:1spheroid (=m m 10a ,C D =0.05(Hoerner 1965))under the same conditions.(d)The high thrust enables 53%of the integrated jet power ΔP t to be converted into payload kinetic energy KE.

=??()

F t

m U m

U m a d

d ˙,(6)

a a a where m

˙a depends linearly on the shrinking rate W .Equation (6)demonstrates that when the body is bluff and moving slowly early in the maneuver,the force is negative as energy is transferred into the ?uid.How-ever,later in the maneuver this energy can be recovered by a body that is shrinking and moving quickly.This accounts for the slow start but rapid ?nish observed in the octopus robot results.

5.1.Separation reduction at high Reynolds number The recovery of ?uid kinetic energy is perfect within irrotational ?ow,but in viscous ?uids the added mass-induced thrust depends critically on simultaneous separation reduction to avoid irrecoverable energy loss to the wake in the form of large vortical structures.Numerical simulations of shrinking circular cylinders in (Weymouth and Triantafyllou 2012)demonstrated that the negative pressure gradient due to W in (5)generates a sheet of opposite sign vorticity on the surface of the body,starting from the rear and moving up towards the 90°point.At the same time,the normal velocity on the wall induced by shrinking advects the previously formed boundary layer vorticity towards the body surface,causing it to come in contact with the newly developed layer of opposite-sign vorticity,resulting in partial vorticity annihilation.This is similar to the vorticity annihilation noted by Kambe (1986)in the case of two shear layers of opposite vorticity forced to collide.

This mechanism of vorticity control depends on W overcoming the rate of diffusion and separation in the boundary layer.To estimate the required rate of shape change it is insightful to compare a shrinking deformable body to the application of suction on a rigid body boundary layer (Choi et al 2008).Both pro-cesses induce velocity normal to the body surface (as seen in (3)),although shrinking induces it without actual mass-?ow through the membrane.As shown in the study of a porous circular cylinder of diameter D placed in cross-?ow U (Pankhurst et al 1953),employ-ing a uniform suction with velocity w o causes delayed separation and decreased drag when the suction coef-?cient,π=C Dw UD ()q o ,exceeds a theoretical value estimated by Prandtl as π=C 4.35Re q and by Pre-ston (1948)as π=C 3.214Re q .For example,for =C Re 14q the drag coef ?cient is reduced from a value of 0.90without suction to a value of 0.69;and for =C Re 42q the drag coef ?cient is measured to be 0.01.

Returning to the de ?ating robot problem,the ana-logy with applying suction can be used to de ?ne equivalent controlling parameters,particularly in view of the circulation reduction noted above for the case of a shrinking cylinder.Through the use of the Mangler transform (Mangler 1948,Schlichting and Ger-sten 2000),3D axisymmetric boundary layers can be

reduced to planar ones hence we de ?ne a de ?ation scal-ing parameter ,σ*,which is analogous to the suction scaling parameter of a cylinder:

σ=

V AU

*˙Re ,

(7)

where A is the frontal area,and V

˙is the rate of change of the volume of the body,which is proportional to the average normal velocity on the surface,and therefore typically to W .The de ?ation scaling parameter σ*therefore provides an instantaneous value that accounts for the effects of the shape-change number as well as the Reynolds number,hence replacing the parameter Ξin predicting separation control.We estimate the theoretical threshold value of σ*for separation delay on a sphere as:

σπ

>* 2.41(8)

following the methodology of Preston (1948).

We can test the predictive power of this parameter using the previous and current results.In Weymouth and Triantafyllou (2013)Ξ=132was found to result in moderate separation because the average Re during the maneuver was 500,giving a low value of σ=* 1.85.In contrast,in the simulation of the rocket fast-start maneuver we observed good boundary layer control and energy recovery despite the small value of Ξ≈144because the higher Re (peaking at 20000)results in σ>*9throughout the maneuver.

The value of σ*for the de ?ating robot is adequate to effectively control the ?ow and recover the ?uid kinetic energy.The minimum value of σ*occurs at around =t 0.5s ,while the robot is still fairly bluff (the area is =A 170cm 2)but has accelerated up to fairly high speed (=?U 135cm s 1).The de ?ation rate of the

volume =?V

˙3000cm s 31therefore gives σ=77min *for the robot escape maneuver.This minimum value is well above the threshold,enabling separation control and added-mass energy recovery and leading to the remarkably high measured net force shown in ?gure 7(c).

6.Conclusions

We designed and tested a ?exible hull in ?atable robot that exhibits outstanding fast-starting performance,emulating the function of an escaping octopus for the amount of power available,reaching ?nal speeds in excess of 10body lengths per second in less than a second,and converting 53%of the energy to kinetic energy.

We note that the energetics of the self-propelled robot are particularly important,as powering unsteady maneuvers can be the limiting factor in the operational life of self-powered underwater vehicles.The overall ef ?ciency of energy conversion at 53%is at least as high as the best in fast-starting ?sh (Frith and Blake 1995);and the robot achieves speeds matching

those of fast squid(Neumeister et al2000).While the top accelerations for fast-starting?sh are reported at 40to120?

m s2,they must be scaled with the amount of energy available for the maneuver(Gazzola et al2012,Domenici and Blake1997).In our experi-ments the extensibility and ultimate strength of the commercially available membrane we used placed an upper limit on the initial internal pressure,δ=

p 4.45kPa,and therefore on the initial energy of the robot and the force from the propelling jet.How-ever,the de?ation rate W determines how ef?ciently the energy is recaptured,and this is largely determined by the geometry for freely accelerating bodies.In addi-tion,the form of the parameterσ*shows that as the Reynolds number increases the required threshold de?ation rate decreases,making?ow control even more feasible.Therefore,for a given robot design and higher available energy,the ef?ciency is expected to remain near the(high)level found in these experi-ments,and an increase in membrane stiffness will enable man-made vehicles to rival the acceleration of their biological inspirations.

Acknowledgments

The authors wish to acknowledge support from the Singapore-MIT Alliance for Research and Technology through the CENSAM program,and from the MIT Sea Grant program.We also thank Joshua C Born for assisting with data acquisition during his internship and Roger Hanlon for valuable discussions and videos regarding cephalopod propulsion.

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(完整版)助动词用法及练习

be动词，情态动词，助动词do/does的用法区别及练习助动词，顾名思义就是帮助动词完成疑问及否定的，本身没有什么含义。主要的助动词有be,do,will,have等，其用法详述如下：一、⑴由连系动词am，is，are构成的句子：变一般疑问句时把am，is，are提到句子的前面，句尾用问号即可。变否定句时直接在am，is，are后面加not即可。例如：肯定句:He is a student. 一般疑问句: Is he a student? 否定句: He is not a student. 画线提问: 对he提问: Who is a student? 对a student 提问: What is he? (2)was 是am,is的过去式，were是are的过去式，若句子中有以上两词时，变疑问句及否定句方法与（1）相同。二、(1) 由情态动词can, may,will ，shall等构成的句子: 变一般疑问句时把can, may,will ，shall提到句子的前面,句尾用问号即可.变否定句时直接在can,may,后面加not即可. 例如: 肯定句: She can swim. 一般疑问句: Can she swim? 否定句: She can not swim. 画线提问: 对she提问: Who can swim? 对swim提问: What can she do? （2）could,might,would,should是can,may,will,shall的过去式，若句子中有以上两词时，变疑问句及否定句方法与（1）相同。三、（1）由行为动词构成的句子: 需要加助词do或does. 变一般疑问句时把do/does放在句子前面. 变否定句时把don’t/doesn’t放在动词的前面。要注意观察动词的形式并对号入座。一般疑问句和否定句的动词三单式都要变回原型。 play-----do plays-----does 例如: 肯定句: They play football after school. He plays football after school. 一般疑问句: Do they play football after school? Does he play football after school? 否定句: They don't (do not) play football after school. He doesn’t’ play football after school. 画线提问: 对they/he提问: Who plays football after school? 对play football提问: What do they do after school? What does he do after school? 对after school提问: When do they play football? When does he play football? （2）did是do和did的过去式，变一般疑问句时把did放在句子前面. 变否定句时把didn’t 放在动词的前面, 要注意观察动词的形式并对号入座。一般疑问句和否定句的动词都要变回原型。

suggest用法

suggest [原句] Tom, can you suggest any good books for my project? (P12) [点拨] suggest作及物动词，在这里表示“建议；提议”。其常用搭配有： a. suggest sth Let me suggest this one. It’s an excellent watch, it looks good, and it only costs $50. 让我向您建议这个。这是一块非常好的手表，看起来美观，而且只卖五十美元。 They were wondering where to hold the party and I suggested the Italian restaurant near the station. 他们不知道到哪里举行宴会，我提议了车站附近的意大利餐馆。 I’d suggest a visit to the Summer Palace. 我建议去颐和园参观。 b. suggest doing sth I suggestgoing to the park on Sunday. 我建议周日去公园。 My husband suggested eating out tonight to celebrate my birthday. 我丈夫建议今晚出去吃饭给我庆生。 c. suggest (that) sb (should) do sth I suggest that we wait a while before we make any decision. 我建议在做任何决定之前先等一会儿。 I suggest you give her a ring before you call on her. 我建议你拜访她之前先给她打个电话。 [拓展] (1) suggest可以表示“暗示；意味着”。如： His smile suggested that he was very happy. 他的微笑暗示了他非常高兴。 Are you suggesting that I look fat in these trousers? 你是在暗示我穿这条裤子显胖吗？ His behaviour suggested a lack of interest in what we were doing. 他的举止意味着他对我们正在做的事缺乏兴趣。 (2) suggestion是其名词形式，意为“建议；提议”，常用于make a suggestion结构。如：She made some very helpful suggestions but her boss rejected them all. 她提出了几个非常有用的建议，但是她的老板把它们全给否决了。 [即学即练]补全句子。 (1) 我建议我们把这些学生分成四组。 I suggest that _____________________. (2)我不知道今天晚上穿什么。你有什么建议吗？ I don’t know what to wear tonight. Have you got_____________? (3)他面色苍白，说明他身体不好。 His pale face ____________________. (4) 你能推荐个人做这份工作吗？ Can you ________________ for this job?

助动词的用法

助动词在英语学习当中作了解，不需要重点把握，但是助动词也是很好理解的，希望回答能够帮到你。 1.助动词：Be 助动词不能作述语动词,要与本动词一起构成动词片语,表示时态、语态等。 1. BE作为本动词表示状态或客观存在等意思。 Your house is bigger and nicer than mine. 你的房子比我的又大又好。 2. BE+不定词连用,表示约定、义务、命令等未来的动作或状态。 I am to go abroad on business tomorrow. 明天我要去外国出公差。表示未来的安排。 The meeting is to be held as scheduled. 会议将按原计划召开。表示计划好的安排。 You are not to bark at my friend. 你不许对我的朋友叫。表示命令或要求。 3. BE+现在分词构成各种进行时态。 Who are you talking to? 你在和谁说话？ I am talking to my dog. 我在和我的狗说话。 4. BE+过去分词构成被动语态。 That means I will be promoted as scheduled. 这就意味着我将要按原计划得到提升。 2. dare和used to 作为情态助动词的dare一般只能用于疑问句或否定句中,dare+原形动词表示敢。

I dare not say it is ugly. 我不敢说它丑。 How dare you say so? 你怎么敢这么说？ dare也可以作本动词,用于肯定句,后面要接带to的不定词;主词若是第三人称单数,简单现在式时,dare要变为dares。 You, you dare to talk to me like this! 你、你竟敢这样和我讲话！ used to+原形动词表示过去的习惯或状态,而现在已经不存在了。 You're not what you used to be. 你不是以前的你了。 used to构成疑问句时有两种形式。即used + 主词+ to + 其他成份？；Did + 主词+ use to+ 其他成份。 How used I to be? 我以前什么样？ How did you use to be? 你以前什么样？ used to构成否定句时有两种形式，即used not to和didn't use to。 You didn't use to say things like this. You used not to say things like this. 你以前不会说这样的话的。 be used to表示习惯于,其中used是形容词,to是介系词,后接名词、代名词或动名词等,可用于不同的时态。 You're used to hearing words of praise. 你是听好话听惯了。 3. 助动词：Do 1. DO作为助动词时的时态、人称和数的变化与它作为本动词相同,有do, does, did三种形式。 Yes, it seems he doesn't really want to have a haircut.

动名词的用法详解

动名词的用法详解今天给大家带来动名词的用法详解，我们一起来学习吧，下面就和大家分享，来欣赏一下吧。英语语法：动名词的用法详解动名词因同时拥有动词和名词两者的特点而拥有及其丰富的用法，熟练的掌握这些用法不仅可以使口语表达更地道生动，也能在写作中增分添彩。动名词主要有四种用法，做主语，作宾语，作表语，作定语，每种用法下又分小类别，是一个非常复杂庞大的系统，学习者们往往会理不清脉络，今天就为大家带来动名词的用法讲解。一.作主语 1.直接位于句首 eg.Swimming is a good sport in summer. 2.用it作形式主语，把动名词(真实主语)置于句尾作后置主语。 eg.It is no use telling him not to worry.

.mportant，essential，necessary等形容词不能用于上述结构。 3.用于“There be”结构中 eg.There is no saying when hell come. 4.动名词的复合结构作主语: 当动名词有自己的逻辑主语时，常可以在前面加上一个名词或代词的所有格，构成动名词的复合结构,动名词疑问句通常使用这种结构做主语 eg.Their coming to help was a great encouragement to us. Does your saying that mean anything to him? 二.作宾语 1.作动词的宾语某些动词后出现非限定性动词时只能用动名词作宾语，不能用不定式。不定式通常指某种特定的动作，但动名词表示泛指，常见的此类动词有： admit,appreciate,excuse,stand,advise,allow,permit,avoid,consider,e njoy,finish,give up,cannot help,imagine,include,keep,understand,keepon,mind,report,risk,mis s,put off,delay,practise,resist,suggest,depend on,think about,set about,succeed in,worry about,burst out,insist on,feel like,be used

suggest用法归纳

关于suggest用法及常见错点的归纳陕西延川中学：刘富祥【摘要】：动词suggest有两层含义,可表示“建议,提议”或“暗示,表明”。后接名词、动名词、含疑问词的不定式或从句。作“提议,建议”讲时,宾语从句要用虚拟语气。但不能接不定式或复合宾语。下面分述如下: 一、它的用法。二、常见的错误。【关键词】：不定式动名词复合宾语虚拟语气用法宾语从句建议提议错点 (一)动词suggest有如下一些用法: 一、有“建议”的意思。advise、propose也有此意，请比较它们用法的异同：（1）都可接名词做宾语 She suggested/advised/proposed an early start.她建议早一点出发。 We suggested/advised/proposed a visit to the museum the next day. 我们建议明天去参观博物馆。（2)都可接动名词做宾语 I suggested/advised/proposed putting off the sports meets. 我建议将运动会延期。 They suggested/advised/proposed waiting until the proper time. 他们建议(我们)等到恰当的时机才行动。（3)都可接that宾语从句，that从句用should+动词原形，should可以省略。 She suggested/advised/proposed that the class meeting (should)not be held on Saturday.她建议班会不要在星期六举行。 We suggested/advised/proposed that he (should) go and make an apology to his teacher.我们建议他去向老师道歉。（4)advise可接动词不定式复合宾语，propose可接不定式做宾语。 I advised him to give up the foolish idea.=I suggested/proposed his/him giving up the foolish idea.我建议他放弃那愚蠢的念头。(suggest和propose在口语里可接动

助动词的用法

助动词协助主要动词构成谓语动词词组的词叫助动词（Auxiliary Verb）。被协助的动词称作主要动词（Main Verb）。构成时态和语态。助动词是语法功能词，自身没有词义，不可单独使用，它没有对应的汉译，例如：He doesn't like English. 他不喜欢英语。（does是助动词，无词义；like是主要动词，有词义) 最常用的助动词有：be, have, do, shall, will, should, would 他们表示时态，语态，构成疑问句与否定副词not合用，加强语气助动词半助动词 2 半助动词功能介绍在功能上介乎主动词和助动词之间的一类结构，称为半助动词。常见的半助动词有be about to, be due to, be going to, be likely to, be meant to, be obliged to, be supposed to, be willing to, have to, seem to, be unable to, be unwilling to等。......情态助动词情态助动词1.情态助动词包括will(would), shall(should), can(could), may(might), must, need, dare, ought to, used to, had better后接原形不定词。2.情态助动词不受主语的人称和数的限制。3.两个情态助动词不能连用。中文:他将能够及时完成此事。(误)He will can finish it i...... 3 基本助动词基本助动词基本助动词只有三个：be, do, have, 他们没有词汇意义，只有语法作用，如协助构成进行体，完成体，被动态，否定句，疑问句等。例如He is giving a lecture. 他在作报告He has made a plan. 他已经订了计划The small animals are kept in the cages. 小动物都关在笼子里。助动词协助主要动词完成以下功用 a. 表示时态，例如： He is singing. 他在唱歌。 He has got married. 他已结婚。 b. 表示语态，例如： He was sent to England. 他被派往英国。 c. 构成疑问句，例如： Do you like college life? 你喜欢大学生活吗？ Did you study English before you came here? 你来这儿之前学过英语吗？ d. 与否定副词not合用，构成否定句，例如： I don't like him. 我不喜欢他。 e. 加强语气，例如： Do come to the party tomorrow evening. 明天晚上一定来参加晚会。 He did know that. 他的确知道那件事。 3）最常用的助动词有：be, have, do, shall, will, should, would 4 具体用法 have的用法一、have作助动词形式主要变化形式：have，has，had 动名词/现在分词：having 1）have +过去分词，构成完成时态，例： He has left for London.他已去了伦敦。

英语单词惯用法集锦解析

英语单词惯用法集锦习惯接动词不定式的动词（V to inf) adore(vi极喜欢) dread （vt.不愿做，厌恶）plan 计划 afford（+to,vt有条件，能承担）endeavour （vt，竭力做到，试图或力图）prefer（vt.宁可；宁愿(选择)；更喜欢）agree 同意endure(忍受.cannot ~ to) prepare准备 aim (vi[口语]打算：) engage (vi.保证，担保；) presume(vt.冒昧；敢于[用于第一人称时为客套话]：) appear (vi.似乎；显得) essay(vt.尝试，试图) pretend(vt.自命；自称；敢于；妄为) apply （申请）expect（期望，希望）proceed（开始，着手，）arrange （vi.做安排，(事先)筹划）fail （vt.未做…；疏忽)promise(许诺，保证做 ask （要求）forget （vt. 忘记）purpose （vt.决心，打算） beg （vt.正式场合的礼貌用语]请(原谅)，请(允许)：I beg to differ.恕我不能赞同）guarantee（保证，担保）refuse（拒绝）bear 承受，忍受hate（[口语]不喜欢；不愿意；）regret （vt. 抱歉；遗憾）begin help （有助于，促进）remember（记住） bother （vi.通常用于否定句]麻烦，费心）hesitate（vi.犹豫；有疑虑，不愿）scheme（策划做）care （vt.想要；希望；欲望[后接不定式，常用于否定、疑问及条件句中]）hope （vt.希望，盼望，期待）seek（vt.谋求，图谋[后接不定式]） cease （停止; 不再(做某事)[正式] intend （打算；想要）seem（似乎，好像[后接不定式或从句]；觉得像是，以为[ choose （意愿；选定；决定）itch start开始claim （vt. 主张；断言；宣称） continue （继续）like 喜欢swear（vt.起誓保证；立誓要做(或遵守） dare （vt.敢，敢于，勇于，胆敢）long（vi.渴望；热望；极想） decline（vt.拒绝，拒不(做、进入、考虑等) manage（设法完成某事）threaten（vt.威胁，恐吓，恫吓）deign （屈尊做）mean（有意[不用进行时）trouble（vi.费心，费神；麻烦）demand（vi.要求，请求：）need （需要）try（设法做） deserve (应得) neglect (疏忽) undertake(承诺,答应，保证) desire （希望渴望）offer（表示愿意(做某事)，自愿；）venture（冒险(做某事））determine（vi.决心，决意，决定，）omit （疏忽，忘记）want 想要 die （誓死做）pine （渴望）wish （希望）习惯接“疑问词+动词不定式”的动词（有时也包括VN wh-+to do) advise 建议explain 解释perceive 觉察，发觉 answer 答复find 得知，察觉persuade 说服，劝说；使某人相信 ask 询问，问forget 忘记phone 打电话 assure 保证guess 臆测，猜度pray 祈祷 beg 请求，恳求hear 小心聆听（法庭案件）promise 允诺 conceive 想象，设想imagine 以为，假象remember记得 consider 考虑，思考indicate 暗示remind 提醒，使想起 convince 使相信inform告知通知instruct告知，教导 see 看看，考虑，注意decide 解决，决定know 学得，得知 show 给人解释；示范；叙述；discover发现；知道learn 得知，获悉 signal以信号表示doubt 怀疑，不相信look 察看；检查；探明 strike 使想起；使突然想到；使认为suggest 提议，建议tell 显示，表明；看出，晓得；warn 警告，告诫think 想出；记忆，回忆；想出，明白wonder 纳闷，想知道 wire 打电报telegraph 打电报习惯接动名词的动词（包括v+one’s/one+v+ing) acknowledge 认知，承认…之事实escape免除，避免omit疏忽，忽略 admit 承认，供认excuse 原谅overlook 放任，宽容，忽视adore （非正式）极为喜欢fancy 构想，幻想，想想postpone 延期，搁置 advise 劝告，建议finish完成prefer较喜欢 appreciate 为…表示感激(或感谢)forbid 不许，禁止prevent预防 avoid 逃避forget 忘记prohibit 禁止，妨碍

使用suggest的常见错点

使用suggest的常见错点一、误用不定式作宾语要表示汉语的“建议做某事”，英语通常用suggest doing sth，而不能用suggest to do sth。如：他建议坐飞机去，可我认为这样花费太大。正：He suggested going by plane, but I thought it would cost too much. 误：He suggested to go by plane, but I thought it would cost too much. 汤姆建议把房子卖了，但是安表示反对。正：Tom suggested selling the house but Ann was against it. 正：Tom suggested to sell the house but Ann was against it. 二、汉语通常说“建议某人做某事”，但英语习惯上不能说suggest sb to do sth，而说suggest sb’s [sb]doing sth。也就是说，suggest 后不仅不接不定式，而且也不接不定式的复合结构。如：他建议我们早点动身。正：He suggested that we leave earlier. 误：He suggested us to leave earlier.

当然，我们也可以用后接that 从句的形式来表达此意思(注意谓语用“should+动词原形”这样的虚拟语气形式)。如： I suggest that we (should) have lunch right now. 我建议我们现在就吃午饭。 He suggests that we should all go to see the film. 他建议我们都去看电影。比较以下同义表达：他建议他们在没有听到事实真相之前什么都别说。正：He suggested (should) not saying anything till they heard the facts. 正：He suggested saying nothing about it till they heard the facts. 正：He suggested that they shouldn’t say anything till they heard the facts. 三、混用其后宾语从句的语气 suggest 后接宾语从句时，从谓语既可用陈述语气，也可用虚拟语气，其区别与suggest所表示的意思有关： 1. 若suggest 表示“建议”，则其后接的that 从

小学英语助动词用法归纳

助动词（Auxiliary Verb）：协助主要动词构成谓语动词词组的词。自身没有词义，不可单独使用。主要动词（Main Verb）：是被协助的动词，构成时态和语态。 He doesn't like English. 他不喜欢英语。（doesn't是助动词，无词义；like是主要动词，有词义) 最常用的助动词有：be, have, do, shall, will, should, would 等。基本助动词只有三个：be, do, have 他们没有词汇意义，只有语法作用，如协助构成进行时，完成时，被动态，否定句，疑问句等。一、be 动词的用法既可作系动词，又可作助动词，做助动词有人称和数的变化，第一人称用am,第二人称及复数用are,第三人称及单数用is，am,is 过去式

为was, are的过去式为were,它与现在分词构成进行时态和过去分词一起构成被动语态。 a. 表示时态be+doing（现在分词）表示现在进行的动作 He is singing. 他正在唱歌。 b. 表示语态be+done(过去分词）表被动语态 He was sent to England. 他被派往英国。 c. be+to do（动词不定式）表示计划安排命令。 We are to plant trees next week. 下周我们将要去植树。 You are to explain this 。对此你要做出解释。二、do的用法 Do主要帮助实意动词构成否定和疑问句，后跟动词原形，有时放在实意动词前起强调作用，还可代替前文出现的动词，避免重复。Do 有人称和数的变化，第一、二人称及复数用do，第三人称及单数用does，过去式为did。 1）构成一般疑问句。DO +主语+动词原形+其他 I like singing 变为疑问句为Do you like singing ? 2）do + not 构成否定句。主语+do +not +动词原形。 I do not want to be criticized.我不想挨批评。 He doesn't like to study.他不想学习。 Many students didn’t know the importance of English before.过去好多学生不知道英语的重要性. 3)构成否定祈使句。

高考英语动名词用法详解(21页)

高考英语动名词用法详解 I.动名词具有名词和动词的特征，可以带有自己的宾语和状语。动名词可以作主语、表语、宾语和定语。 1、作主语表示比较抽象，或者泛指习惯性的动作，或表示说话者对所述动作有过经验或多次做过。 Swimming is my favorite sport. Collecting information is very important to business man. Reading books makes one wise. 读书使人明智。Listening, speaking, reading and writing are the important things you must do in learning a foreign language. 注：动名词做主语，有时先用it作形式主语，把动名词置于句末。这种用法以下句型中常用。

It’s no use / no good / useless / not any use /not any good + (sb’s) doing… It’s no use watching too much TV. It’s no good talking to him. It’s no use crying over spilt milk.(覆水难收） It is a waste of time + doing … It's a waste of time trying to talk to her when she is in a bad mood. It is fun + doing … It is fun playing with children. 和孩子们一起玩真好 2、作表语仅限于表示工作、任务等抽象名词表示主语的内涵。 Her job is teaching. What I hate most is being laughed at. Teaching is learning. 教学相长。 3、作宾语表示一般的、抽象的、经常性的行为。 I couldn’t risk missing that train. They went on walking and never stopped talking. 他们继续走，

动词suggest 的用法

动词suggest的用法: 一、有"建议"的意思.advise，propose 也有此义,请比较它们用法的异同: 1) 都可接名词作宾语 She suggested / advised / proposed an early start. 她建议早一点出发. We suggested / advised / proposed a visit to the museum the next day. 我们建议明天去参观博物馆. 2) 都可接动名词作宾语 I suggested / advised / proposed putting off the sports meet. 我建议将运动会延期. They suggested / advised / proposed waiting until the proper time. 他们建议(我们)等到恰当的时机才行动. 3) 都可接that 宾语从句,that从句用should+动词原形,should可以省略. She suggested / advised / proposed that the class meeting (should) not be held on Saturday. 她建议班会不要在星期六举行. We suggested / advised / proposed that he (should) go and make an apology to his teacher. 我们建议他去向老师道歉. 4) advise 可接动词不定式复合宾语,propose 可接不定式作宾语. I advised him to give up the foolish idea. = I suggested / proposed his / him giving up the foolish idea. 我建议他放弃那愚蠢的念头.(suggest和propose在口语里可接动名词的复合宾语). We proposed to start early. = We proposed starting early. 我们建议早一点出发.(接不定式不用suggest和advise) 二、有"提出"的意思.如: He suggested a different plan to his boss. 他向老板提出了一个不同的计划. Xiao Wang suggested a way to solve the problem. 小王提出了一个解决这个问题的办法. 三、有"暗示、表明"的意思.其主语往往是事物,而不是人. 1)接名词或动名词作宾语. The simple house suggested a modest income. 这座简朴的房子表明(房主的)收入并不高. Her pale face suggested bad health. 她脸色苍白,看来身体不好. The thought of summer suggests swimming. 一想到夏天就使人们联想到游泳. 2)接宾语从句,从句用陈述语气.如: The decision suggested that he might bring his family. 这个决定表明他可以把家属带来. The expression on his face suggested that he was very angry. 他脸上的表情表明他很生气. 四、在主语从句It is suggested that... 及名词suggestion 后面表示具体建议的表语从句、同位语从句都应用should+动词原形,should可以省略.如: It was suggested that we (should) give a performance at the party. 人们建议我们在晚会上表演节目. His suggestion was that the debts (should) be paid off first. 他的建议是先把债务还清. The doctors made a suggestion that the new hospital (should) not be set up on the hill. 医生们建议不要把新医院建在山上.

助动词的用法大全

助动词的用法大全助动词的形式与作用 1)英语常用的助动词(auxiliary verb)有shall，will，should，would，be，have，do等。助动词一般无词义，不能单独作谓语动词。助动词在句中的作用，在于帮助构成各种时态、语态、语气、否定和疑问结构等。如：China has entered a great new era. 中国已进入了一个伟大的新时期。(帮助构成完成时态) Some boys are playing on the grass. 一些男孩正在草地上玩。 (帮助构成进行时态) Mother is written by Gorky. 《母亲》是高尔基写的。 (帮助构成被动语态) We Shall have the football match if it does not rain.如果不下雨，我们就赛足球。(帮助构成将来时态和否定结构) Do you see my point? 你明白我的意思吗?(帮助构成疑问结构) [注]在否定结构中，not须放在助动词后面。 2)助动词加not一般都有简略式，用于口语中。如： is not-isn't would not--wouldn't are not--aren't [B:nt] have not--haven't was not -- wasn't has not--hasn't were not-- weren't [wE:nt] had not--hadn't shall not--shan't [FB:nt] do not--don't [dEunt] will not--won't [wEunt] does not--doesn't

助动词用法归纳小学

助动词用法归纳小学 -CAL-FENGHAI-(2020YEAR-YICAI)_JINGBIAN

式为was, are的过去式为were,它与现在分词构成进行时态和过去分词一起构成被动语态。 a. 表示时态 be+doing（现在分词）表示现在进行的动作 He is singing. 他正在唱歌。 b. 表示语态 be+done(过去分词）表被动语态 He was sent to England. 他被派往英国。 c. be+to do（动词不定式）表示计划安排命令。 We are to plant trees next week. 下周我们将要去植树。 You are to explain this 。对此你要做出解释。二、do的用法 Do主要帮助实意动词构成否定和疑问句，后跟动词原形，有时放在实意动词前起强调作用，还可代替前文出现的动词，避免重复。Do 有人称和数的变化，第一、二人称及复数用do，第三人称及单数用does，过去式为did。 1）构成一般疑问句。 DO +主语+动词原形 +其他 I like singing 变为疑问句为 Do you like singing 2）do + not 构成否定句。主语+do +not +动词原形。 I do not want to be criticized.我不想挨批评。 He doesn't like to study.他不想学习。 Many students didn’t know the importance of English before. 过去好多学生不知道英语的重要性.

suggest用法总结及易混词比较

1. suggest+ 名词/代词或suggest+名词/代词to+人，但不能说suggest sb sth ,即不能加双宾做宾语Eg：We suggest him the plan (Χ) We suggest the plan to him(√) 2. suggest+doing sth Eg：He suggested going out for a walk. 注意：suggest 不可以加不定式，所以上面的句子不可以这样写： He suggested to go out for a walk.(Χ) 3. suggest +(that )+主语+(should) do+sth 其中的should 可以省略 eg: He suggested that you should go there tomorrow. =He suggested you go there tomorrow. 注意：suggest 不可以加不定式的复合结构 He suggested you to go there tomorrow. X 4. it is suggested that +主语+(should )do sth eg: It is suggested that the work (should) be finished at once.马上 5. suggestion做主语时，其后的表语从句也用这个结构即： The suggestion is that +主语+should +do sth eg: His suggestion is that I should leave for Beijing immediately. 6.suggest 表示“暗示或表明”之意，注意此时做主语时后面的表语从句用陈述语气 eg: Her yawn suggested that she was sleepy. 她哈欠连天表明她困了。一、有“建议”的意思。advise、propose也有此意，请比较它们用法的异同： 1)都可接名词做宾语 She suggested/advised/proposed an early start.她建议早一点出发。 We suggested/advised/proposed a visit to the museum the next day.我们建议明天去参观博物馆。 2)都可接动名词做宾语 I suggested/advised/proposed putting off the sports meet.我建议将运动会延期。 They suggested/advised/proposed waiting until the proper time.他们建议(我们)等到恰当的时机才行动。 3)都可接that宾语从句，that从句用should+动词原形，should可以省略。 She suggested/advised/proposed that the class meeting (should) not be held on Saturday.她建议班会不要在星期六举行。 We suggested/advised/proposed that he (should) go and make an apology to his teacher.我们建议他去向老师道歉。 4)advise可接动词不定式复合宾语，propose可接不定式做宾语

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