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Festival. In this day, girls will throw a sewing needle into a bowl full of water 。s time for the wild fruits to ripe. The picturesque Arxan in Autumn is indeed a fairyland only exists in a dream that satisfies all your fantasies. If it rains heavily on Saturday night, some elderly Chinese will say it is because Zhinu, or the Weaving Maid, is crying on the day she met her husband Niulang, or the Cowherd, on the Milky Way. Most Chinese remember being told this romantic tragedy when they were children on Qixi, or the Seventh Night Festival, which falls on the seventh day of the seventh lunar month, which is usually in early August. This year it falls on Saturday, August 2. Folklore Story As the story goes, once there was a cowherd, Niulang, who lived 28 with his elder brother and sisterinlaw. But she disliked and abused him, and the boy was forced to leave home with only an old cow for pany. The cow, however, was a former god who had violated imperial rules and was sent to earth in bovine form. One day the cow led Niulang to a lake where fairies took a bath on earth. Among them was Zhinu, the most beautiful fairy and a skilled seamstress. The two fell in love at first sight and were soon married. They had a son and daughter and their happy life was held up as an example for hundreds of years in China. Yet in the eyes of the Jade Emperor, the Supreme Deity in Taoism, marriage between a mortal and fairy was strictly forbidden. He ordered the heaven troop to catch Zhinu back. Niulang grew desperate when he discovered Zhinu had been taken back to heaven. Driven by Niulang39。 ll wait in the line for one hour to get a ticket, and another two hours at the site, to only see a tiny bit of the place due to the crowds. Last year, 428 million tourists traveled in China over the weeklong holiday in October. Traveling during this period is a matter that needs thorough preparation. If you are short on time to plan the uping Golden Week it may not be a bad idea to avoid some of the most crowded places for now. There is always a place so fascinating that everyone yearns for. Arxan is a place like this. The beauty of Arxan is everlasting regardless of the changing of four seasons. Bestowed by nature, its spectacular seasonal landscape and mountains are just beyond word. Arxan is a crucial destination for the remended travelling route, China Inner Mongolia Arxan — Hailar — Manzhouli. It is also the joint of the four prairies across the SinoMongolian border, where people gravitate towards the exotic atmosphere mixed with Chinese, Russian, and Mongolia elements. As a historic site for the Yitian Battle, Arxan still embodies the spirit of Genghis Khan. Walking into Arxan, you will be amazed by a kaleidoscope of geous colors all the year round the Spring azaleas blooming red in the snow, the Summer sea wavering blue in the breeze, the Autumn leaves painted in yellow covering volcanic traces, and the Winter woods shining white on the vast alpine snowscape. Hinggan League Arxan city is situated in the far eastern area of Inner Mongolia Autonomous Region. Its full name Haren Arxan means hot holy water in the Mongolian language. Arxan is a tourism city in the northern frontier with a blend of large forest, grand prairies, vast snowfield, heaven lake cluster, thermium, as well as volcanic cluster. It is a rare and unique ecotourism base filled with healthy sunshine, clean air and unspoiled green. Nestled close to the country39?;叵胝麄€論文的寫作過程,雖有不易,卻讓我除卻浮躁,經(jīng)歷了思考和啟示,也更加深切地體會了科研的艱難與不易,因此倍感珍惜。同時也感謝這篇論文所涉及到的各位學者。本論文從選題到完成,幾易其稿,每一步都是在26 徐老師的指導下完成的,傾注了大量的心血,在此向我的指導教師徐坤老師表示深切的謝意與祝福! 本論文的完成也離不開物理與電子工程系其他各位老師、同學和朋友的關心與幫助。四年來,徐老師淵博的專業(yè)知識,嚴謹?shù)闹螌W態(tài)度,精益求精的工作作風,誨人不倦的高尚師德,樸實無華、平易近人的人格魅力對我影響深遠。值此畢業(yè)論文完成之際,我謹向所有關心、愛護、幫助我的人們表示最誠摯 的感謝與最美好的祝愿。 參考文獻 [1] 唐蘇亞 .我國電動自行車產(chǎn)業(yè)的發(fā)展現(xiàn)狀 [J].電機技術 ,2021(2): 3943. [2] 顧軍民 .基于 MSP430的電動車穩(wěn)壓充電器研制 [D].江蘇 :江蘇大學 ,2021. [3] 顧銘 .無刷直流電機控制系統(tǒng)設計 [D].大連 :大連理工大學 ,2021. [4] 萬文斌 ,劉瑞芳 .基于直流無刷電機的電動車智能驅動系統(tǒng)設計 [J].儀表技術 ,2021(3): 79. [5] 姜書政 ,王桂海 .基于 AT89S52單片機的電機控制系統(tǒng)設計 [J].現(xiàn)代電子技術 ,2021,33(7): 3840. 25 [6] 魏昌洲 .基于 DSP的交流變頻調(diào)速系統(tǒng)研究 [D].南京 :南京航空航天大學 ,2021. [7] 郭崇軍 ,李琦 ,洪權 ,許強 .基于 C8051的無刷直流電機控制系統(tǒng) [J].機電工程 ,2021,24(9): 3638. [8] 駱嬌 .基于 AVR 單片機的電動自行車控制系統(tǒng)研究 [D].大連 :大連理工大學 ,2021. [9] 葛榮 ,張邦武 .電動自行車控制器的設計與實現(xiàn) [J].南通職業(yè)大學學報 ,2021,19(2): 3539. 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[18] 康世斌 .自行車低成本直流無刷電機控制器研究 [D].上海 :同濟大學 ,2021. 致 謝 歲月如梭,轉眼間四年的大學生活即將結束,站在畢業(yè)的門檻上,回首往昔,奮斗和辛勞成為絲絲的記憶,甜美與歡笑也都塵埃落定。閉環(huán)控制的理論及方法已非常成熟,但是測速電機的成本卻影響了閉環(huán)方法在直流無刷電機控制器上的應用,而以反電動勢檢測法為主的低成本速度檢測方法目前尚在性能上與測速電機方法有較大差異。將直流無刷電機控制器全數(shù)字化,是比較有 前景的研究方向。數(shù)字化設計具有參數(shù)修改方便、減小系統(tǒng)對器件性能依賴、提高工作效率和便于實現(xiàn)多種功能等優(yōu)點。 ( 2) 系統(tǒng)全數(shù)字化設計。力矩的抖動對電動車的使用者會產(chǎn)生一定程度的不適感,不利于提高用戶對產(chǎn)品的人性化的需求。 由于時間以及水平有限, 本 設計 提出的解決方案, 也 存在一些 缺點 和 未 深入 分析探討 的地方。 針對原有直流無刷電機控制器電流采樣的快速性、準確性問題, 設計出合理的電流采樣保持電路。增加了多種保護功能,使電動車的可靠性大大提高,而且更加人性化。 5. 展望 本 設計 對電動自行車用無刷直流電動機控制器的各個方面進行了 分析 探討 ,經(jīng)過分24 析驗證能夠較好地解決目前直流無刷電動機控制器存在的一些問題 。 綜上所述, 該設計方案具有實際可行性,達到了預期要求,運行平穩(wěn)可靠。 圖 19 堵轉保護相電流波形 通過波形圖可以看出,在電機發(fā)生堵轉時,相電流迅速增大,此時保護程序啟動,使輸出 PWM 波占空比迅速減小,從而相電流減小,保護電機不至于損毀。 23 圖 18 柔性電子剎車效果圖 電動機在正常運行中,受到外力不能正常 運轉或者電子換相異常,會導致相電流迅速增大,對電機造成不可修復的損傷。在沒有使用機械剎車的情況下只使用柔性電子剎車,如圖 18 所示為柔性電子剎車效果圖。結果與預期目標符合??梢钥闯鲭妱榆噭倖愚D速較低時,電機轉矩迅速增大。當軟啟動結束, PWM 波形正常。如圖 16所示為 PWM 波形。 4. 結果與分析 本設計從理論分析、硬件電路設計、軟件設計和系統(tǒng)總體調(diào)試等方面考慮, 逐步實現(xiàn)了控制器所要完成的各項功能。在調(diào)試過程中,能夠很容易找到錯誤位置。當系統(tǒng)受到外界突發(fā)干擾時,軟