initialization error could not locate OCI dll
2011-06-28 10:27
转载自分享
最终编辑xmuhot
装完ODAC,使用PL/SQL连接数据库出现
initialization error could not locate OCI dll
【原因】
装ODAC时,其实安装了Oracle Client 11g,此时Oracle的环境变量被修改,PL/SQL里的Oracle home和oci library也被修改,所以读不到对应的tnsnames文件和oci.dll。
【解决方案】
打开PL/SQL,进入tools-->preferences,如下界面所示。配置Oracle Home和OCI library。OK!!
感官动词和使役动词 默认分类2010-05-28 23:14:26 阅读46 评论0 字号:大中小订阅 使役动词,比如let make have就是3个比较重要的 have sb to do 没有这个用法的 只有have sb doing.听凭某人做某事 have sb do 让某人做某事 have sth done 让某事被完成(就是让别人做) 另外: 使役动词 1.使役动词是表示使、令、让、帮、叫等意义的不完全及物动词,主要有make(使,令), let(让), help(帮助), have(叫)等。 2.使役动词后接受词,再接原形不定词作受词补语。 He made me laugh. 他使我发笑。 I let him go. 我让他走开。 I helped him repair the car. 我帮他修理汽车。 Please have him come here. 请叫他到这里来。 3.使役动词还可以接过去分词作受词补语。 I have my hair cut every month. 我每个月理发。 4.使役动词的被动语态的受词补语用不定词,不用原形不定词。 (主)He made me laugh. 他使我笑了。 (被)I was made to laugh by him. 我被他逗笑了。 使役动词有以下用法: a. have somebody do sth让某人去做某事 ??i had him arrange for a car. b. have somebody doing sth.让某人持续做某事。 ??he had us laughing all through lunch. 注意:用于否定名时,表示“允许” i won't have you running around in the house. 我不允许你在家里到处乱跑。 ******** 小议“使役动词”的用法 1. have sb do 让某人干某事 e.g:What would you have me do? have sb/sth doing 让某人或某事处于某种状态,听任 e.g: I won't have women working in our company. The two cheats had the light burning all night long. have sth done 让别人干某事,遭受到 e.g:you 'd better have your teeth pulled out. He had his pocket picked. notes: "done"这个动作不是主语发出来的。 2.make sb do sth 让某人干某事 e.g:They made me repeat the story. What makes the grass grow?
感官动词 1.see, hear, listen to, watch, notice等词,后接宾语,再接省略to的动词不定式或ing形式。前者表全过程,后者表正在进行。句中有频率词时,以上的词也常跟动词原形。 注释:省略to的动词不定式--to do是动词不定式,省略了to,剩下do,其形式和动词原形是一样的,但说法不同。 see sb do sth 看到某人做了某事 see sb doing sth 看到某人在做某事 hear sb do sth 听到某人做了某事 hear sb doing sth 听到某人在做某事 以此类推... I heard someone knocking at the door when I fell asleep. (我入睡时有人正敲门,强调当时正在敲门) I heard someone knock at the door three times. (听到有人敲门的全过程) I often watch my classmates play volleyball after school. (此处有频率词often) (了解)若以上词用于被动语态,须将省略的to还原: see sb do sth----sb be seen to do sth hear sb do sth----sb be seen to do sth 以此类推... We saw him go into the restaurant. → He was seen to go into the restaurant. I hear the boy cry every day. → The boy is heard to cry every day. 2.感官动词look, sound, smell, taste, feel可当系动词,后接形容词。 He looks angry. His explanation sounds reasonable. The cakes smell nice.
英语中感官动词的用法 一、感官动词 1、感官动词(及物动词)有:see/notice/look at/watch/observe/listen to/hear/feel(Vt)/taste(Vt)/smell(Vt) 2、连缀动词(含感官不及物动词) be/get/become/feel/look/sound/smell/taste/keep/stay/seem/ appear/grow/turn/prove/remain/go/run 二、具体用法: 1、see, hear, smell, taste, feel,这五个动词均可作连系动词,后面接形容词作表语,说明主语所处的状态。其意思分别为"看/听/闻/尝/摸起来……"。除look之外,其它几个动词的主语往往是物,而不是人。 例如:These flowers smell very sweet.这些花闻起来很香。 The tomatoes feel very soft.这些西红柿摸起来很软。 2、这些动词后面也可接介词like短语,like后面常用名词。 例如:Her idea sounds like fun.她的主意听起来很有趣。 3、这五个感官动词也可作实义动词,除look(当"看起来……"讲时)只能作不及物动词外,其余四个既可作及物动词也可作不及物动词,此时作为实义动词讲时其主语一般为人。 例如:She smelt the meat.她闻了闻那块肉。 I felt in my pocket for cigarettes.我用手在口袋里摸香烟。 4、taste, smell作不及物动词时,可用于"t aste / smell + of +名词"结构,意为"有……味道/气味"。 例如:The air in the room smells of earth.房间里的空气有股泥土味。 5、它们(sound除外)可以直接作名词,与have或take构成短语。 例如:May I have a taste of the mooncakes?我可以尝一口这月饼吗?taste有品位、味道的意思。 例如:I don’t like the taste of the garlic.我不喜欢大蒜的味道。 She dresses in poor taste.她穿着没有品位。 look有外观,特色的意思,例:The place has a European look.此地具有欧洲特色。 feel有感觉,感受的意思,watch有手表,观察的意思。例:My watch is expensive.我的手表很贵。 6、其中look, sound, feel还能构成"look / sound / feel + as if +从句"结构,意为"看起来/听起来/感觉好像……"。 例如:It looks as if our class is going to win.看来我们班好像要获胜了。 7、感官动词+do与+doing的区别: see, watch, observe, notice, look at, hear, listen to, smell, taste, feel + do表示动作的完整性,真实性;+doing 表示动作的连续性,进行性。 I saw him work in the garden yesterday.昨天我看见他在花园里干活了。(强调"我看见了"
1.感官动词用法之一:see, hear, listen to, watch, notice等词,后接宾语,再接动词原形或ing形式。前者表全过程,后者表正在进行。句中有频率词时,以上的词也常跟动词原形。 I heard someone knocking at the door when I fell asleep. (我入睡时有人正敲门) I heard someone knock at the door three times. (听的是全过程) I often watch my classmates play volleyball after school.(此处有频率词often) 若以上词用于被动语态,后面原有动词原形改为带to不定式: We saw him go into the restaurant. →He was seen to go into the restaurant. I hear the boy cry every day. →The boy is heard to cry every day. 2.感官动词用法之二:look, sound, smell, taste, feel可当系动词,后接形容词: He looks angry. It sounds good. The flowers smell beautiful. The sweets taste sweet. The silk feels soft. I felt tired. They all looked tired. 这些动词都不用于被动语态。如:The sweets are tasted sweet.是个病句。注意:如果加介词like,则后不可接形容词,而接名词或代词:
感官动词的概念和相关考点 1、什么是感官动词? 听觉:listen to、hear 视觉:look at、seem、watch 嗅觉:smell 触觉:feel、touch 味觉:taste 2、感官动词如何正确使用? Tom drove his car away. →I saw him drive away. (全过程) 用法一:somebody did sth + I saw this I saw somebody do something. Tom was waiting for the bus. →I saw Tom waiting for the bus. (看不到全过程) 用法二:somebody was doing sth + I saw this I saw somebody doing something 练习: 一、句子翻译 1. I didn,t hear you come in. 2. I suddenly felt sth touch me on the shoulder. 3. I could hear it raining. 4. Listen to the birds singing. 5. Can you smell sth burning? 6. I found Sue in my room reading my letters. 二、灵活运用 1. I saw Ann waiting for the bus. 2. I saw Dave and Helen playing tenins. 3. I saw Clair having her meal. 三、选择最佳选项 1. Did anybody see the accident (happen/happening)? 2. We listen to the old man (tell/telling) his story from beginning to the end. 3. Listen! Can you hear a baby (cry/crying)? 4.—Why did you turn around suddenly? — I heard someone (call/calling) my name. 5. We watched the two men (open/opening) a window and (climb/climbing) through it into house. 6. When we got there, we found our cat (sleep/sleeping) on the table. 四、感官动词的被动语态 Oh,the milk is tasted strange.
先静下心来看几篇技术报告,可以是几个人一起看,边看边讨论,大致了解智能车制作的过程及所要完成的任务。 看完报告之后,对智能车也有了大概的了解,其实总结起来,要完成的任务也很简单,即输入模块——控制——输出。 (1)输入模块:各种传感器(光电,电磁,摄像头),原理不同,但功能都一样,都是用来采集赛道的信息。这里面就包含各种传感器的原理,选用,传感器电路的连接,还有传感器的安装、传感器的抗干扰等等需要大家去解决的问题。 (2)控制模块:传感器得到了我们想要的信息,进行相应的AD转换后,就把它输入到单片机中,单片机负责对信息的处理,如除噪,筛选合适的点等等,然后对不同的赛道信息做出相应的控制,这也是智能车制作过程中最为艰难的过程,要想出一个可行而又高效的算法,确实不是一件容易的事。这里面就涉及到单片机的知识、C语言知识和一定的控制算法,有时为了更直观地动态控制,还得加入串口发送和接收程序等等。 (3)输出模块:好的算法,只有通过实验证明才能算是真正的好算法。经过分析控制,单片机做出了相应的判断,就得把控制信号输出给电机(控制速度)和舵机(控制方向),所以就得对电机和舵机模块进行学习和掌握,还有实现精确有效地控制,又得加入闭环控制,PID算法。 明确了任务后,也有了较为清晰的控制思路,接下来就着手弄懂每一个模块。虽然看似简单,但实现起来非常得不容易,这里面要求掌握电路的知识,基本的机械硬件结构知识和单片机、编程等计算机知识。最最困难的是,在做的过程中会遇到很多想得到以及想不到的事情发生,一定得细心地发现问题,并想办法解决这些问题。 兴趣是首要的,除此之外,一定要花充足的时间和精力在上面,毕竟,有付出就会有收获,最后要明确分工和规划好进度。
我们学过了五个与人的感觉有关的动词,它们是look,sound,smel l,taste,feel,我们可称之为“感官”动词。它们的用法有着许多相同点,但也有不同之处,现就此作一小结。 一、这五个动词均可作连系动词,后面接形容词作表语,说明主语所处的状态。其意思分别为“看/听/闻/尝/摸起来……”。除loo k之外,其它几个动词的主语往往是物,而不是人。例如:These flowers smell very sweet. 这些花闻起来很香。 The tomatoes feel very soft. 这些西红柿摸起来很软。 The music sounds beautiful. 二、这些动词后面也可接介词like短语,like后面常用名词。例如: Her idea sounds like fun. 她的主意听起来很有趣。 He looks like his father. 三、这五个感官动词也可作实义动词,除look(当“看起来……”讲时)只能作不及物动词外,其余四个既可作及物动词也可作不及物动词,其主语通常是人。例如: She smelt the meat. 她闻了闻那块肉。
I felt in my pocket for cigarettes. 我用手在口袋里摸香烟。 He tasted the soup and added some salt. Miss Wang asked us to look at the blackboard. 四、taste,smell作不及物动词时,可用于“taste / smell + of + 名词”结构,意为“有……味道 / 气味”。例如: The air in the room smells of earth. 房间里的空气有股泥土味。 The bread taste of sugar. 五、它们(sound除外)可以直接作名词,与have或take构成短语。例如: May I have a taste of the mooncakes?我可以尝一口这月饼吗? May I have a look at your photo? 六、其中look,sound,feel还能构成“look / sound / feel + as if +从句”结构,意为“看起来/听起来/ 感觉好像……”。例如:
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在基础英语写作中往往有学生对谓语的选用有一定困惑,其中就有一类特殊的动词:感官动词。今天就由来为大家把其用法进行一下总结: (A)感官动词(及物动词)有: see/notice/look at/watch/observe/listen to/hear/feel(Vt)/taste(Vt)/smell(Vt) (B)连缀动词(含感官不及物动词) be/get/become/feel/look/sound/smell/taste/keep/stay/seem/ appear/grow/turn/prove/remain/go/run 一、see, hear, feel, watch, look,这五个动词均可作 连系动词,后面接形容词作表语,说明主语所处的状态。其意思分别为"看/听/闻/尝/摸起来……" look之外,其它几个动词的主语往往是物,而不是人。 例如: These flowers smell very sweet.这些花闻起来很香。 The tomatoes feel very soft.这些西红柿摸起来很软。 二、这些动词后面也可接介词like短语,like后面常用名词。 例如: Her idea sounds like fun.她的主意听起来很有趣。 三、这五个感官动词也可作实义动词,除look(当"看起来……"讲时)只能作不及物动词外,其余四个既可作及物动词也可作不及物动词,此时作为实义动词讲时其主语一般为人。(和1有区别) 例如: She smelt the meat.她闻了闻那块肉。 I felt in my pocket for cigarettes.我用手在口袋里摸香烟。 四、taste, smell作不及物动词时,可用于"taste / smell + of +名词"结构,意为"有……味道/气味"。 例如: The air in the room smells of earth.房间里的空气有股泥土味。 五、它们(sound除外)可以直接作名词,与have或take构成短语。 例如: May I have a taste of the mooncakes?我可以尝一口这月饼吗? taste有品位,味道的意思 例:I don't like the taste of the garlic. 我不喜欢大蒜的味道。 She dresses in poor taste.她穿着没有品位。 look有外观,特色的意思 例:The place has a European look.此地具有欧洲特色。 feel有感觉,感受的意思 watch有手表,观察的意思 例:My watch is expensive.我的手表很贵。 六、其中look, sound, feel还能构成"look / sound / feel + as if +从句"结构,意为"看起来/听起来/感觉好像……"。 例如:
感官动词表示人的感官动作,可作完全及物动词或不完全及物动词,例如:see/look/watch/notice/observe, hear/listen to, taste, smell, feel/touch. 一、感官动词经常和情态动词can 连用,例如: hear: Can you hear that? 你能听到吗? see: I can't see much. 我看不太清楚。 feel: I can feel the baby moving inside me. 我能感觉到婴儿在我体内移动。 二、感官动词用于进行时,表明主语或感知者集中在一个特别的对象上,是一种自愿的动作,常见的有listen to, look at, touch, smell 和taste,例如: listen to: He is listening to the radio. 他正在听收音机。 look at: They are looking at the picture. 他们正在看这幅画。 touch: She is touching her cat. 她正在抚摸她的猫。 smell: She is smelling the flowers. 她在闻花。 taste:
We are tasting champagne. 我们正在品尝香槟。 并不是所有的感官动词都可以用进行时,例如: 误:She was hearing a noise. 误:He was seeing a woman in the rain. 但当hear 在表达一种经历时,可以用进行时;see 在表达与人见面或是约会,可以用进行时,等等,例如: hearing: She was always hearing voices in her head. 她脑子里总有声音。 seeing: She is seeing the doctor. 她正在看医生。 He was seeing another woman. 他在和另一个女人约会。 三、感官动词的特殊用法 1、感官动词+ 宾语+ 不带to 不定式,例如: We heard you leave. 我们听见你走了。 解析:此句强调的重点是“We heard". I saw her go. 我看见她走了。 解析:此句强调的重点是"I saw" . 2、感官动词 + 宾语 + 动名词,例如: We heard you leaving. 我们听见你走了。 解析:此句强调的重点是“you leaving",相当于 We heard you when you
“感官”动词用法小结 我们学过了五个与人的感觉有关的动词,它们就是look,sound,smell,ta ste,feel,我们可称之为“感官”动词。它们的用法有着许多相同点,但也有不同之处,现就此作一小结。 一、这五个动词均可作连系动词,后面接形容词作表语,说明主语所处的状态。其意思分别为“瞧/听/闻/尝/摸起来……”。除look之外,其它几个动词的主语往往就是物,而不就是人。例如: These flowers smell very sweet、这些花闻起来很香。 The tomatoes feel very soft、这些西红柿摸起来很软。 The music sounds beautiful、 二、这些动词后面也可接介词like短语,like后面常用名词。例如: Her idea sounds like fun、她的主意听起来很有趣。 He looks like his father、 三、这五个感官动词也可作实义动词,除look(当“瞧起来……”讲时)只能作不及物动词外,其余四个既可作及物动词也可作不及物动词,其主语通常就是人。例如: She smelt the meat、她闻了闻那块肉。
I felt in my pocket for cigarettes、我用手在口袋里摸香烟。 He tasted the soup and added some salt、 Miss Wang asked us to look at the blackboard、 四、taste,smell作不及物动词时,可用于“taste / smell + of + 名词”结构,意为“有……味道/ 气味”。例如: The air in the room smells of earth、房间里的空气有股泥土味。The bread taste of sugar、 五、它们(sound除外)可以直接作名词,与have或take构成短语。例如: May I have a taste of the mooncakes?我可以尝一口这月饼不?May I have a look at your photo? 六、其中look,sound,feel还能构成“look / sound / feel + as if +从句”结构,意为“瞧起来/听起来/ 感觉好像……”。例如: It looks as if our class is going to win、瞧来好像我们班要获胜了It sounds as if the rain is very heavy、
英语中感官动词的用法 二、具体用法: 1、see, hear, smell, taste, feel,这五个动词均可作连系动词,后面接形容词作表语,说明主语所处的状态。其意思分别为"看/听/闻/尝/摸起来……"。除look之外,其它几个动词的主语往往是物,而不是人。 例如:These flowers smell very sweet.这些花闻起来很香。 The tomatoes feel very soft.这些西红柿摸起来很软。 2、这些动词后面也可接介词like短语,like后面常用名词。 例如:Her idea sounds like fun.她的主意听起来很有趣。 3、这五个感官动词也可作实义动词,除look(当"看起来……"讲时)只能作不及物动词外,其余四个既可作及物动词也可作不及物动词,此时作为实义动词讲时其主语一般为人。 例如:She smelt the meat.她闻了闻那块肉。 I felt in my pocket for cigarettes.我用手在口袋里摸香烟。 4、taste, smell作不及物动词时,可用于"t aste / smell + of +名词"结构,意为"有……味道/气味"。 例如:The air in the room smells of earth.房间里的空气有股泥土味。 5、它们(sound除外)可以直接作名词,与have或take构成短语。 例如:May I have a taste of the mooncakes?我可以尝一口这月饼吗?taste有品位、味道的意思。 例如:I don’t like the taste of the garlic.我不喜欢大蒜的味道。 She dresses in poor taste.她穿着没有品位。 look有外观,特色的意思,例:The place has a European look.此地具有欧洲特色。 feel有感觉,感受的意思,watch有手表,观察的意思。例:My watch is expensive.我的手表很贵。 6、其中look, sound, feel还能构成"look / sound / feel + as if +从句"结构,意为"看起来/听起来/感觉好像……"。 例如:It looks as if our class is going to win.看来我们班好像要获胜了。 7、感官动词+do与+doing的区别: see, watch, observe, notice, look at, hear, listen to, smell, taste, feel + do表示动作的完整性,真实性;+doing 表示动作的连续性,进行性。 I saw him work in the garden yesterday.昨天我看见他在花园里干活了。(强调"我看见了"这个事实) I saw him working in the garden yesterday.昨天我见他正在花园里干活。(强调"我见他正干活"这个动作)
感官动词的用法 1.see, hear, listen to, watch, notice等词,后接宾语,再接省略to的动词不定式或ing形式。前者表全过程,后者表正在进行。句中有频率词时,以上的词也常跟动词原形。 注释:省略to的动词不定式--to do是动词不定式,省略了to,剩下do,其形式和动词原形是一样的,但说法不同。 see sb do sth 看到某人做了某事 see sb doing sth 看到某人在做某事 hear sb do sth 听到某人做了某事 hear sb doing sth 听到某人在做某事 以此类推... I heard someone knocking at the door when I fell asleep. (我入睡时有人正敲门,强调当时正在敲门) I heard someone knock at the door three times. (听到有人敲门的全过程) I often watch my classmates play volleyball after school. (此处有频率词often) (了解)若以上词用于被动语态,须将省略的to还原: see sb do sth----sb be seen to do sth hear sb do sth----sb be seen to do sth 以此类推... We saw him go into the restaurant. → He was seen to go into the restaurant. I hear the boy cry every day. → The boy is heard to cry every day. 2.感官动词look, sound, smell, taste, feel可当系动词,后接形容词。 He looks angry. His explanation sounds reasonable. The cakes smell nice.
感官动词用法 (A)感官动词(及物)有: see/notice/look_at/watch/notice/observe/listen_to/hear/feel(Vt)/taste(Vt)/smell(Vt) (B)连缀动词(含感官不及物) be/get/become/feel/look/sound/smell/taste/keep/stay/seem/ appear/grow/turn/prove/remain/go/run 一、see, hear, feel, watch, look,这五个动词均可作连系动词,后面接形容词作表语,说明主语所处的状态。其意思分别为"看/听/闻/尝/摸起来……"。除look之外,其它几个动词的主语往往是物,而不是人。例如: These flowers smell very sweet.这些花闻起来很香。 The tomatoes feel very soft.这些西红柿摸起来很软。 二、这些动词后面也可接介词like短语,like后面常用名词。例如: Her idea sounds like fun.她的主意听起来很有趣。 三、这五个感官动词也可作实义动词,除look(当"看起来……"讲时)只能作不及物动词外,其余四个既可作及物动词也可作不及物动词,其主语通常是人。例如: She smelt the meat.她闻了闻那块肉。 I felt in my pocket for cigarettes.我用手在口袋里摸香烟。 四、taste, smell作不及物动词时,可用于"taste / smell + of +名词"结构,意为"有……味道/气味"。例如: The air in the room smells of earth.房间里的空气有股泥土味。 五、它们(sound除外)可以直接作名词,与have或take构成短语。例如: May I have a taste of the mooncakes?我可以尝一口这月饼吗? 六、其中look, sound, feel还能构成"look / sound / feel + as if +从句"结构,意为"看起来/听起来/感觉好像……"。例如: It looks as if our class is going to win.看来好像我们班要获胜了 1. 在表示生理感觉的动词后的不定式不带to。这类词有:
first 感官动词 1、感官动词(及物动词)有:see/notice/look at/watch/observe/listen to/hear/feel(Vt)/taste(Vt)/smell(Vt) 2、连缀动词(含感官不及物动词) be/get/become/feel/look/sound/smell/taste/keep/stay/seem/ appear/grow/turn/prove/remain/go/run 二、具体用法: 1、see, hear, smell, taste, feel,这五个动词均可作连系动词,后面接形容词作表语,说明主语所处的状态。其意思分别为"看/听/闻/尝/摸起来……"。除look 之外,其它几个动词的主语往往是物,而不是人。 例如:These flowers smell very sweet.这些花闻起来很香。 The tomatoes feel very soft.这些西红柿摸起来很软。 2、这些动词后面也可接介词like 短语,like 后面常用名词。 例如:Her idea sounds like fun.她的主意听起来很有趣。 3、这五个感官动词也可作实义动词,除look(当"看起来……"讲时)只能作不及物动词外,其余四个既可作及物动词也可作不及物动词,此时作为实义动词讲时其主语一般为人。 例如:She smelt the meat.她闻了闻那块肉。 I felt in my pocket for cigarettes.我用手在口袋里摸香烟。 4、taste, smell 作不及物动词时,可用于"taste / smell + of +名词"结构,意为"有……味道/气味"。 例如:The air in the room smells of earth.房间里的空气有股泥土味。 5、它们(sound 除外)可以直接作名词,与have 或take 构成短语。 例如:May I have a taste of the mooncakes?我可以尝一口这月饼吗?taste 有品位、味道的意思。 例如:I don’t like the taste of the garlic. 我不喜欢大蒜的味道。 She dresses in poor taste.她穿着没有品位。 look 有外观,特色的意思,例:The place has a European look.此地具有欧洲特色。 feel 有感觉,感受的意思,watch 有手表,观察的意思。例:My watch is expensive.我的手表很贵。 6、其中look, sound, feel 还能构成"look / sound / feel + as if +从句"结构,意为"看起来/听起来/感觉好像……"。 例如:It looks as if our class is going to win.看来我们班好像要获胜了。 7、感官动词+do 与+doing 的区别: see, watch, observe, notice, look at, hear, listen to, smell, taste, feel + do 表示动作的完整性,真实性;+doing 表示动作的连续性,进行性。 I saw him work in the garden yesterday. 昨天我看见他在花园里干活了。(强调"我看见了"这个事实)
飞思卡尔智能车入门指南 概述 智能车巡线是一个半实时随动系统。系统不断传感前方赛道的信息,根据赛道偏转情况计算前轮转向角度,再配合后轮的动力,达到巡线的目的。如下图: 该系统主要涉及知识领域有:单片机、传感器、电机、舵机、电路等,附带着涉及到一些调试手段知识。以下就从这几方面简要介绍。 速度控制 给电机加一个恒定的电压,电机最终会以某个恒定速度转动。适当增加电压,电机速度会加快,最终稳定在一个更快的速度。故调节电机所加电压即可调节电机转速。由于单片机是数字电路,只能控制电压为“有”或“无”,于是我们让电压在“有”和“无”之间反复跳动,那么电压的有效值在电池电压到0之间可连续变化。实际加载在电机上的电压是一个方波,方波的高电平时间长度比方波周期为占空比,占空比越高电压的有效值越高。100%占空比相当于电池直接接在电机上,0%占空比相当于断路,0~100%相当于降压。 单片机普通输出口只能提供小电流的信号电,无法给电机提供功率,故使用MOS管。用单片机的信号控制MOS管的通断,起到开关的作用。开关串联在电池与电机之间,即可给电机提供功率。 单片机方波信号的频率一般在K的数量级(1000Hz)。假设现在给电机50%占空比的方波,信号频率为1K,电机以某个恒定速度转动。适当改变信号周期会发现电机转速略有变化。信号频率很小(例如几十赫兹)或者很大(例如几兆赫兹)时,电机转速会较慢,在某个适中的值时速度达到最大值。此时电机能量转化效率最高。此时固定信号频率不变,改变信号占空比,电机转速和占空比基本成正比。 若以恒定占空比驱动电机,在负载发生变化时,电机速度也会发生变化。若希望电机负载变化而电机仍能匀速转动,应采用闭环控制。给电机安装速度传感器(例如:光电编码器),每隔固定的时间检测光电编码器旋转的圈数(例如:每10ms检测一次光电编码器在过去的10ms内旋转了多少圈),该圈数即可换算成速度。当发现实际转速比目标转速慢时,适当增
“感官”动词用法小结 主要的感官动词有:look,sound,smell,taste,feel 一、这五个动词后面接形容词作表语,说明主语所处的状态。其意思分别为“看/听/闻/尝/摸起来……”。除look之外,其它几个动词的主语往往是物,而不是人。例如: These flowers smell very sweet. 这些花闻起来很香。 The tomatoes feel very soft. 这些西红柿摸起来很软。 The music sounds beautiful. 这首歌听起来很动听。 用法的感官动词还有:hear, notice, watch, listen (to) 习题 ( )1.Don’t eat that meat. It smells______. A.dirty B.delicious C.bad ( ) 2. In the Science Museum, the children felt _____ to see so many ______ things. A.surprised; amazed B. surprising; amazing C. surprising; amazed D. surprised; amazing ( )3.I am eating cookies. Do you want to______one?
A.tastes B.taste C.tasting ( )4.Look! The butterflies are flying here and there. They look very______. A.beautiful B.beautifully C.beauty ( )5.That’s a good idea! It sounds______. A.interested B.interesting C.interest ( )6.Birthday cake is ready now, and it______nice.Would you like some? A.smells B.feels C.sounds ( )7.Oh, the vegetables have too much sugar.They taste______. A.salty B.hot C.sweet ( ) 8. ----Have you ever heard the song Welcome to Beijing? ---Yes, it _______ nice. A. hears B. sounds C. looks D. Listens ( ) 9. The girl's voice sounds_____. Maybe she can become a good singer when she grows up. A. sweet B. sweetly C. beautifully ( )10.The table______ very smooth.(光滑的) A looks B turns C feels D smells ( ) 11. Grandma, you must feel ________ after cleaning the house. Let’s take a rest. A. tired B. well C. good D. angry