何 杰,朱金光,羅錫文,張智剛,胡 煉,高 陽
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電動方向盤插秧機轉(zhuǎn)向控制系統(tǒng)設(shè)計
何 杰1,朱金光2※,羅錫文1,張智剛1,胡 煉1,高 陽2
(1. 華南農(nóng)業(yè)大學(xué)南方農(nóng)業(yè)機械與裝備關(guān)鍵技術(shù)教育部重點實驗室,廣州 510642; 2. 雷沃重工股份有限公司,濰坊 261200)
電動方向盤作為農(nóng)機導(dǎo)航系統(tǒng)的轉(zhuǎn)向執(zhí)行機構(gòu)在中小型旱地拖拉機上已有應(yīng)用,但在水田農(nóng)業(yè)機械等轉(zhuǎn)向阻力大的農(nóng)機上的適應(yīng)性尚有待研究。該文以井關(guān)PZ-60型水稻插秧機為平臺,采用電動方向盤作為轉(zhuǎn)向執(zhí)行機構(gòu),對插秧機自動轉(zhuǎn)向控制進行了研究。構(gòu)建了插秧機轉(zhuǎn)向機構(gòu)的系統(tǒng)模型,采用系統(tǒng)辨識試驗獲得了系統(tǒng)模型參數(shù)。設(shè)計了基于PID的嵌套轉(zhuǎn)向控制算法,采用Simulink仿真模型驗證了算法的可行性。分別進行了幅值10°的正弦波、水田小角度轉(zhuǎn)向(直線行駛跟蹤)和水田大角度轉(zhuǎn)向(調(diào)頭)控制性能試驗,試驗結(jié)果表明:插秧機正弦波轉(zhuǎn)向跟蹤平均絕對誤差為0.301 5°,平均延時0.3 s;在泥底層平坦和不平坦的水田中直線行駛時的轉(zhuǎn)向角跟蹤平均絕對誤差分別為0.354°和0.663°,平均延遲時間均為0.6 s,角度跟蹤偏差最大分別為1.4°和3.6°,深泥腳轉(zhuǎn)向阻力大時有1.4 s的控制滯后;插秧機以28°轉(zhuǎn)向角調(diào)頭時調(diào)節(jié)時間為2.5 s,穩(wěn)態(tài)誤差為0.6%。研究表明,電動方向盤轉(zhuǎn)向系統(tǒng)具有較好的動態(tài)響應(yīng)和控制穩(wěn)定性,適用于插秧機作業(yè)的自動轉(zhuǎn)向控制,滿足插秧機自動導(dǎo)航作業(yè)要求。
農(nóng)業(yè)機械;導(dǎo)航;控制;電動方向盤;水稻插秧機;轉(zhuǎn)向控制;嵌套算法;系統(tǒng)辨識
農(nóng)業(yè)機械導(dǎo)航技術(shù)是智能農(nóng)機的重要技術(shù)之一[1-2]。自動轉(zhuǎn)向控制是實現(xiàn)農(nóng)業(yè)機械自動導(dǎo)航控制的基礎(chǔ),是導(dǎo)航系統(tǒng)中的關(guān)鍵執(zhí)行環(huán)節(jié)[3],其控制性能和適應(yīng)性直接影響導(dǎo)航控制的實際效果[4]。
常見的自動轉(zhuǎn)向控制方法包括電控液壓控制方法、電機控制方法和線控轉(zhuǎn)向控制方法[5-10],農(nóng)業(yè)機械上常采用前2種方法。電控液壓轉(zhuǎn)向系統(tǒng)主要由液壓泵、電控比例轉(zhuǎn)向閥和轉(zhuǎn)向控制器等部分組成,其優(yōu)點是控制功率大,響應(yīng)快;缺點是后裝改造困難[11-13]。目前,中大功率導(dǎo)航拖拉機主要采用電控液壓轉(zhuǎn)向系統(tǒng)[14]。電機控制轉(zhuǎn)向系統(tǒng)采用直流電機或步進電機作為轉(zhuǎn)向驅(qū)動,對農(nóng)業(yè)機械的轉(zhuǎn)向機構(gòu)進行改造,實現(xiàn)自動控制。電機控制轉(zhuǎn)向系統(tǒng)的主要優(yōu)點是對農(nóng)業(yè)機械轉(zhuǎn)向系統(tǒng)改動小,缺點是手動自動切換離合機構(gòu)復(fù)雜,傳動機構(gòu)安裝精度要求較高,且對不同車型適應(yīng)性較差[15-17]。約翰迪爾、拓普康、聯(lián)適和華測等公司對電機控制轉(zhuǎn)向系統(tǒng)進行了改進和優(yōu)化,推出了安裝在方向盤上或直接取代原方向盤的電機(簡稱電動方向盤),其傳動機構(gòu)緊湊,安裝簡單,具有手動自動切換功能,適合對農(nóng)業(yè)機械轉(zhuǎn)向機構(gòu)進行自動控制改造[18-19]。相比于電控液壓轉(zhuǎn)向系統(tǒng),電動方向盤的缺點是:1)因為是間接控制轉(zhuǎn)向,響應(yīng)需要更高頻的控制;2)控制精度受農(nóng)機轉(zhuǎn)向系統(tǒng)的自由行程和轉(zhuǎn)向器間隙等因素的影響較大;3)轉(zhuǎn)向力矩小,是否適用于水田機械等轉(zhuǎn)向阻力大的農(nóng)機尚有待研究。
本文以井關(guān)PZ-60型水稻插秧機為試驗平臺,采用電動方向盤對轉(zhuǎn)向機構(gòu)進行改造,以實現(xiàn)轉(zhuǎn)向自動控制;根據(jù)自動導(dǎo)航插秧機水田作業(yè)時轉(zhuǎn)向控制阻力大且多變的特點,建立轉(zhuǎn)向機構(gòu)的系統(tǒng)模型,設(shè)計一種帶死區(qū)的嵌套控制算法,通過Simulink仿真和田間試驗研究插秧機電動方向盤自動轉(zhuǎn)向控制在水田作業(yè)環(huán)境下的適用性。
井關(guān)PZ-60型水稻插秧機采用整體式液壓助力轉(zhuǎn)向系統(tǒng),難以實現(xiàn)電控液壓自動轉(zhuǎn)向設(shè)計。本文采用上海聯(lián)適導(dǎo)航技術(shù)有限公司生產(chǎn)的電動方向盤替換原插秧機的方向盤的方式進行改造。電動方向盤的主要參數(shù)如表1所示,安裝結(jié)構(gòu)如圖1所示。
表1 電動方向盤主要參數(shù)
1.方向盤 2.固定螺釘 3.花鍵套 4.圓柱形電機 5.轉(zhuǎn)向柱 6.固定支架 7.轉(zhuǎn)向軸固定筒 1.Steering wheel 2.Fixing screw 3.Spline sleeve 4.Cylindrical motor 5.Steering shaft 6.Fixation apparatus 7.Steering shaft fixing cylinder
電動方向盤的結(jié)構(gòu)分為固定部分和轉(zhuǎn)動部分,固定部分是圓柱形電機定子部分,通過固定支架安裝在插秧機的轉(zhuǎn)向軸固定筒上;轉(zhuǎn)動部分包括電機的轉(zhuǎn)子、方向盤以及花鍵套,其中花鍵套上部通過螺釘固定在轉(zhuǎn)子上,下端通過齒輪嚙合連接到插秧機的轉(zhuǎn)向柱上。
車輪轉(zhuǎn)角測量是自動導(dǎo)航系統(tǒng)轉(zhuǎn)向單元的重要組成部分,是影響轉(zhuǎn)向控制性能的重要環(huán)節(jié),也是影響導(dǎo)航精度的重要因素[20-22]。常用的車輪轉(zhuǎn)角測量方法有角度傳感器直接測量法、位移式間接轉(zhuǎn)角測量法、四連桿式間接轉(zhuǎn)角測量法以及陀螺儀間接測量法4種[23-27]。本文采用美國BEI公司的DUNCAN9360型號角度傳感器(12位霍爾式位置傳感器,具有2160°分辨率和±0.5%的線性度)間接測量方式獲取插秧機前輪轉(zhuǎn)角。
BEI角度傳感器安裝在插秧機的前輪轉(zhuǎn)向柱旋轉(zhuǎn)中心上方,如圖2所示。通過支撐板固定在機架上;BEI傳感器的旋轉(zhuǎn)軸通過支架連接在前輪上,間接測量前輪旋轉(zhuǎn)的角度。
1.前輪轉(zhuǎn)向柱 2.固定支撐板 3.BEI角度傳感器 4.支架 5.前輪
采用STW-2612型運動控制器作為轉(zhuǎn)向控制器[28],以實現(xiàn)與導(dǎo)航控制器通信、電動方向盤控制和輪角信息采集等功能。轉(zhuǎn)向系統(tǒng)控制框圖如圖3所示。STW-2612運動控制器具備2路CAN總線,26路輸入資源,配置靈活,使用方便;具有高防護等級、小體積、高集成度、高響應(yīng)速度等優(yōu)點,適用于農(nóng)田環(huán)境作業(yè)的農(nóng)業(yè)機械的轉(zhuǎn)向控制。
注:θ、v分別為目標(biāo)角度和目標(biāo)速度,由外部輸入;CAN為CAN總線,AI為模擬量輸入,θ2為傳感器測量得到的轉(zhuǎn)向輪角度,Δθ、Δv分別為角度控制量和速度控制量,vf為電機反饋的轉(zhuǎn)速。下同。
轉(zhuǎn)向控制器通過CAN總線獲得由導(dǎo)航控制器發(fā)送的目標(biāo)角度和目標(biāo)速度,通過轉(zhuǎn)向控制器運算和決策,得到電動方向盤的角度控制量Δ和速度控制量Δ,進行插秧機前輪轉(zhuǎn)向控制。電動方向盤自帶轉(zhuǎn)速傳感器,測量得到的轉(zhuǎn)速v經(jīng)RS232總線傳送至轉(zhuǎn)向控制器;同時,BEI角度傳感器測量插秧機前輪轉(zhuǎn)向角度,信號輸入至轉(zhuǎn)向控制器的AI通道,獲得實際轉(zhuǎn)向角度2;轉(zhuǎn)向控制器將采集的前輪轉(zhuǎn)向角度2和轉(zhuǎn)速v經(jīng)CAN總線送至導(dǎo)航控制器,形成嵌套閉環(huán)控制系統(tǒng)。
轉(zhuǎn)向系統(tǒng)模型如圖4所示。根據(jù)文獻[29-30],插秧機的轉(zhuǎn)向機構(gòu)(含電動方向盤及液壓驅(qū)動部分)可看成一階慣性環(huán)節(jié)和純積分環(huán)節(jié)的組合,其傳遞函數(shù)如下
式中k為插秧機轉(zhuǎn)向系的增益;τ為插秧機轉(zhuǎn)向系的時間常數(shù)。
注:v為電動方向盤的目標(biāo)速度,rad?s-1;v1為電動方向盤測量速度,rad?s-1;δ為插秧機前輪轉(zhuǎn)向的偏轉(zhuǎn)角度,(°)。
模型參數(shù)值可以通過辨識試驗測定。為此,先進行辨識試驗,架起插秧機前輪,使插秧機處于空載狀態(tài),施加脈沖控制信號控制插秧機前輪向左旋轉(zhuǎn)28°(限定插秧機最大轉(zhuǎn)角為[-28°,28°]),重復(fù)多次,獲取階躍響應(yīng)。同樣,獲取插秧機前輪向右旋轉(zhuǎn)28°的階躍響應(yīng)曲。采用MATLAB的System Identification工具箱,選擇傳遞函數(shù)估計模型進行辨識,結(jié)果如圖5所示。插秧機左右轉(zhuǎn)向階躍響應(yīng)模型最佳適配系數(shù)(best fits)分別為91.07%和90.12%,表明辨識結(jié)果能準(zhǔn)確反映插秧機轉(zhuǎn)向階躍特性。
通過MATLAB辨識得出模型參數(shù)k=28.02,轉(zhuǎn)向系模型參數(shù)τ=1.339,轉(zhuǎn)向系統(tǒng)的傳遞函數(shù)為
設(shè)計帶死區(qū)的嵌套控制算法,以實現(xiàn)在阻力大、黏附力大的水田環(huán)境下插秧機的轉(zhuǎn)向控制。
2.2.1 嵌套控制
嵌套控制回路是一種常見的控制結(jié)構(gòu)。本文設(shè)計嵌套PID控制方法以實現(xiàn)電動方向盤的內(nèi)環(huán)速度控制和外環(huán)角度控制,如圖6所示。
圖6 轉(zhuǎn)向控制系統(tǒng)總體結(jié)構(gòu)圖
1)內(nèi)環(huán)速度控制。如圖6所示,由位置式PID算法可得
式中K、K、K為速度PID控制的比例、積分和微分環(huán)節(jié)的系數(shù)。e為當(dāng)前速度誤差,e1為-1時刻的速度誤差,∑e代表e以及之前的偏差的累積和(其中為1,2,….,)。
2)外環(huán)角度控制。角度環(huán)位于速度環(huán)的外層,負(fù)責(zé)保持轉(zhuǎn)向系位置,角度誤差為速度環(huán)提供速度要求。本文采用增量式PID前饋方法設(shè)計角度環(huán)的控制。
式中K、K、K為角度PID控制的比例、積分和微分環(huán)節(jié)的系數(shù)。e為當(dāng)前角度誤差,e1為-1時刻的角度誤差,e2為-2時刻的角度誤差。
2.2.2 控制死區(qū)
由于插秧機轉(zhuǎn)向系統(tǒng)中各環(huán)節(jié)中存在間隙和自由行程等問題,導(dǎo)致PID控制算法在某一輸出控制量下電動方向盤旋轉(zhuǎn)但不能驅(qū)動插秧機前輪轉(zhuǎn)動。為實現(xiàn)準(zhǔn)確穩(wěn)定的控制,減少電動方向盤的頻繁調(diào)節(jié),參考文獻[31],本文設(shè)定了死區(qū)雙閾值,限定方向盤電機在閾值范圍內(nèi)不動作,認(rèn)為PID算法執(zhí)行已經(jīng)到達目標(biāo)值。死區(qū)閾值的設(shè)置,一定程度上降低了控制的精度,但是提高了控制的穩(wěn)定性,減少了電機在目標(biāo)值附近的振蕩。通過多次試驗取均值,確定了輪角控制死區(qū)的閾值,輪角順時針0.25°、逆時針0.3°以內(nèi)為死區(qū)。
對上述插秧機轉(zhuǎn)向系統(tǒng)模型以及嵌套PID控制器,采用MATLAB的Simulink工具建立插秧機的轉(zhuǎn)向控制系統(tǒng)仿真框圖,如圖7所示。
圖7 轉(zhuǎn)向控制系統(tǒng)仿真框圖
控制死區(qū)中起始死區(qū)(start of dead zone)設(shè)為0.25°,中止死區(qū)(end of dead zone)設(shè)為0.3°;內(nèi)環(huán)速度PID參數(shù)和外環(huán)角度PID參數(shù)采用MATLAB的PID Tuner工具箱自動進行調(diào)試,具體參數(shù)如表2所示。
表2 轉(zhuǎn)向控制系統(tǒng)PID參數(shù)
注:KKK分別為比例、積分和微分環(huán)節(jié)的系數(shù)。
Note:K, KandKare proportional, integral and differential coefficients, respectively.
設(shè)計的電動方向盤作為插秧機導(dǎo)航的轉(zhuǎn)向驅(qū)動,航向角偏差多為小角度范圍調(diào)節(jié)[32],設(shè)定目標(biāo)航向為10°,采用周期為20 s的方波信號和正弦波作為測試信號,仿真結(jié)果如圖8所示。
a.方波仿真b.正弦波仿真 a. Square wave simulationb. Sincove wave simulation
圖8a中方波信號跟蹤時系統(tǒng)最大超調(diào)為9.3%,死區(qū)控制效果良好,正負(fù)最大值在[9.75°, 10°]和[-10°, -9.7°]區(qū)間,可認(rèn)為系統(tǒng)達到了目標(biāo)值。圖8b中正弦轉(zhuǎn)向信號跟蹤延遲0.1 s,調(diào)節(jié)時間約0.1 s,轉(zhuǎn)向控制系統(tǒng)對正弦波信號跟蹤性能較好。仿真試驗結(jié)果表明,設(shè)計的控制系統(tǒng)具有較好的動態(tài)和穩(wěn)態(tài)響應(yīng),能夠為自動導(dǎo)航插秧機田間作業(yè)轉(zhuǎn)向控制提供理論基礎(chǔ)。
為驗證電動方向盤轉(zhuǎn)向控制系統(tǒng)在水田作業(yè)機械上的適用性,在井關(guān)PZ-60型水稻插秧機平臺上集成電動方向盤和導(dǎo)航控制系統(tǒng)(包括雙天線差分系統(tǒng)、導(dǎo)航控制器和轉(zhuǎn)向控制系統(tǒng))進行試驗,如圖9所示。其中,導(dǎo)航控制器為試驗提供目標(biāo)角度和目標(biāo)速度,試驗數(shù)據(jù)由轉(zhuǎn)向控制器采集。
圖9 水稻插秧機轉(zhuǎn)向控制試驗平臺
根據(jù)水稻插秧機作業(yè)時轉(zhuǎn)向的特點,安排了3種試驗:
1)正弦波轉(zhuǎn)向跟蹤試驗:由于插秧機正常作業(yè)時轉(zhuǎn)向一般不會跳變,故采用正弦波信號在水泥路面考察電動方向盤的轉(zhuǎn)向跟蹤特性;
2)小角度控制性能試驗:在水田環(huán)境中(泥底層平坦水田和不平坦水田2種情況)控制插秧機自動導(dǎo)航直線行駛,通過轉(zhuǎn)向目標(biāo)角度跟蹤效果,考察轉(zhuǎn)向控制系統(tǒng)的小角度控制性能;
3)大角度控制性能試驗:控制插秧機在田頭自動調(diào)頭,考察電動方向盤大角度轉(zhuǎn)向控制的性能。
正弦波轉(zhuǎn)向跟蹤試驗時,將插秧機置于空曠水泥路面,通過導(dǎo)航控制器給出信號頻率為0.05 Hz,角度幅值為 10°的正弦波進行電動方向盤的轉(zhuǎn)向跟蹤響應(yīng)特性試驗;水田轉(zhuǎn)向性能試驗時,在導(dǎo)航控制系統(tǒng)上預(yù)先規(guī)劃插秧機的直線路徑,直線距離約40 m。插秧機從起始點開始進行直線行駛,同時記錄轉(zhuǎn)向控制目標(biāo)角度和反饋角度等試驗數(shù)據(jù)。
根據(jù)試驗設(shè)計,插秧機以正弦波路徑行駛約40 s,試驗結(jié)果如圖10所示。正弦波跟蹤試驗結(jié)果表明:電動方向盤轉(zhuǎn)向控制系統(tǒng)可以很好地跟蹤控制信號,在峰值±10°附近稍有振蕩,最大跟蹤誤差為2.9°,平均絕對跟蹤誤差為0.301 5°,平均延時0.3 s,說明本文設(shè)計的基于電動方向盤的轉(zhuǎn)向控制系統(tǒng)具有較好的動態(tài)響應(yīng)和控制穩(wěn)定性。
圖10 前輪轉(zhuǎn)角正弦波跟蹤試驗結(jié)果 Fig.10 Front wheel steering angle sine wave tracking test result
在華南農(nóng)業(yè)大學(xué)增城試驗基地選擇一塊泥底層平坦(泥腳深約20 cm)和一塊泥底層坑洼不平、泥腳較深(深約40 cm)的水田,控制插秧機在2塊水田環(huán)境中以0.6 m/s的速度進行直線自動導(dǎo)航轉(zhuǎn)向目標(biāo)角度跟蹤試驗,如圖 11所示。
注:插秧機前進速度為0.6 m·s-1。
3.3.1 泥底層平坦的水田試驗
試驗開始時將插秧機從偏離起始點約0.4 m處開始行駛,測試轉(zhuǎn)向系統(tǒng)的上線跟蹤能力。試驗結(jié)果如圖12a、12b所示,在橫向偏差為0.4 m時,轉(zhuǎn)向控制系統(tǒng)延時0.6 s后以11°轉(zhuǎn)向角度開始上線,電動方向盤執(zhí)行10°輪角轉(zhuǎn)向耗時0.5 s;上線后跟蹤角度絕對值平均誤差約為0.354°,角度跟蹤偏差最大為1.4°。試驗結(jié)果表明,在工況較好的水田環(huán)境中,基于電動方向盤的轉(zhuǎn)向控制系統(tǒng)能很好地執(zhí)行控制指令,穩(wěn)定快速地驅(qū)動插秧機上線,過程平順振蕩小,控制穩(wěn)定性和控制精度良好。
圖12 泥底層平坦和不平坦水田中插秧機小角度轉(zhuǎn)向試驗結(jié)果 Fig.12 Small angle steering test results of transplanter in flat and uneven paddy field
3.3.2 泥底層不平坦的水田試驗
試驗開始時控制插秧機從起始點(泥腳深約40 cm)開始進行自動行駛。試驗結(jié)果如圖12c、12d所示,插秧機在深泥腳坑洼處角度跟蹤偏差最大為3.6°,響應(yīng)延遲時間為1.4 s,輪角平均跟蹤絕對誤差為0.663°,平均延遲時間為0.6 s。試驗結(jié)果分析表明,在淤泥阻力大時,電動方向盤轉(zhuǎn)向控制響應(yīng)稍有遲滯,隨著控制量持續(xù)增大,控制力矩增加,插秧機前輪開始執(zhí)行轉(zhuǎn)向動作,最終控制插秧機穩(wěn)定地跟蹤目標(biāo),表明本文設(shè)計的基于電動方向盤的轉(zhuǎn)向系統(tǒng)滿足插秧機水田轉(zhuǎn)向的力矩需求。
為考察電動方向盤大角度轉(zhuǎn)向控制的性能,在泥底層平坦的水田中,控制插秧機在地頭自動調(diào)頭轉(zhuǎn)向。試驗結(jié)果如圖13所示,插秧機調(diào)頭時,輪角跟蹤有約0.6 s的延遲;執(zhí)行至最大轉(zhuǎn)向角(插秧機最大轉(zhuǎn)向角度設(shè)計為±28°),調(diào)節(jié)時間為2.5 s,穩(wěn)定后僅有微小超調(diào)與波動,穩(wěn)態(tài)誤差為0.6%。試驗結(jié)果表明,大角度轉(zhuǎn)向時,電動方向盤轉(zhuǎn)向控制快速穩(wěn)定,基本無超調(diào)和振蕩現(xiàn)象。
圖13 插秧機調(diào)頭試驗結(jié)果
本文以井關(guān)PZ-60型水稻插秧機為平臺,根據(jù)自動導(dǎo)航插秧機水田作業(yè)轉(zhuǎn)向控制的特點,設(shè)計了電動方向盤轉(zhuǎn)向控制系統(tǒng);構(gòu)建了轉(zhuǎn)向系統(tǒng)的二階系統(tǒng)模型,采用MATLAB的System Identification 工具箱辨識出模型參數(shù),插秧機左右轉(zhuǎn)向模型最佳適配系數(shù)分別為91.07%和90.12%。
1)設(shè)計了帶死區(qū)的嵌套控制算法,并構(gòu)建了Simulink仿真模型,方波和正弦波仿真試驗結(jié)果表明:控制系統(tǒng)轉(zhuǎn)向信號跟蹤延遲0.1 s,調(diào)節(jié)時間約0.1 s,具有較好的動態(tài)和穩(wěn)態(tài)性能,驗證了控制算法的可行性。
2)分別進行了水泥路面轉(zhuǎn)向跟蹤(幅值10°的正弦波)、水田小角度轉(zhuǎn)向(直線行駛跟蹤)和水田大角度轉(zhuǎn)向(調(diào)頭轉(zhuǎn)向)系統(tǒng)性能試驗,結(jié)果表明,插秧機正弦波轉(zhuǎn)向角跟蹤平均絕對誤差為0.301 5°,平均延時0.3 s,轉(zhuǎn)向控制系統(tǒng)能很好地跟蹤控制信號;泥底層平坦與不平坦的水田中直線行駛時轉(zhuǎn)向輪角跟蹤的平均絕對誤差分別為0.354°和0.663°,平均延遲時間均為0.6 s,角度跟蹤偏差最大為1.4°和3.6°,深泥腳轉(zhuǎn)向阻力大時有1.4 s的控制滯后;插秧機在水田環(huán)境中調(diào)頭轉(zhuǎn)向時,執(zhí)行28°轉(zhuǎn)向角的調(diào)節(jié)時間為2.5 s,穩(wěn)定后僅有微小超調(diào)與波動,穩(wěn)態(tài)誤差為0.6%。3種不同的插秧機轉(zhuǎn)向試驗結(jié)果表明,基于電動方向盤的轉(zhuǎn)向控制系統(tǒng)具有良好的動態(tài)響應(yīng)和控制穩(wěn)定性,適用于插秧機水田作業(yè)的自動轉(zhuǎn)向控制,滿足自動導(dǎo)航插秧機轉(zhuǎn)向控制要求。
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Design of steering control system for rice transplanter equipped with steering wheel-like motor
He Jie1, Zhu Jinguang2※, Luo Xiwen1, Zhang Zhigang1, Hu Lian1, Gao Yang2
(1.,,,510642,; 2..,,261200,
The steering wheel-like motor has been used as steering control mechanism for agricultural machinery navigation systems integrated in small and medium-sized dryland tractors, but it’s adaptability for large-power paddy agricultural machinery or other agricultural machinery with large steering damping remains to be studied. Taking Iseki PZ-60 rice transplanter as the research objective, the steering control system based on steering wheel-like motor is designed in accordance with the steering control characteristic of the automatic navigation rice transplanter working in paddy field. The steering system is composed of steering wheel-like motor, steering controller and wheel angle sensor. The steering system model based on system in series with first-order inertia and integral system is identified in Matlab. First a step signal is applied to the front wheels while the transplanter is lift and with no-load, then the step responses of the steering angle are obtained for 28° to left and 28° right; Afterwards, the model parametersare identified by the MATLAB System Identification toolbox, which turns out that the best fit coefficient of the model (best fits) are 91.07% and 90.12%. A nested control algorithm with dead zone is designed. The inner loop of the algorithm is a PID speed control loop, and the outer loop is an incremental PID angle control loop. Given the control disturbance generated by the gap, free stroke and other nonlinearity in the steering system, the disturbance is regarded as the control dead zone, whose threshold have been tested and integrated into the control algorithm. Simulation del of the system is constructed by MATLAB/Simulink, and the simulation tests are carried out by using square wave and sine wave signals. The results show that tracking delay and adjustment time of the simulated model are about 0.1 s and 0.1 s respectively which indicates that the control system has a good steady-state performance. In other words, the feasibility of the control algorithm is verified. In order to verify the practical performance and control accuracy of the steering control system, the automatic navigation transplanter (including dual antenna differential GNSS system, the navigation controller and the steering control system mentioned above) is adopted to test in the Zengcheng Experimental Base of South China Agricultural University. Three verification tests are carried out on the developed automatic navigating transplanter. The steering signals to be performed in paddy field are sinusoid with amplitude of 10°, small-angle for testing tracking straight line and wide-angle for testing turning round. The results illustrate that the average absolute error (AAE) of sinusoidal signal tracking is 0.301 5° and average delay is 0.3 s; the AAE of straight-line tracking in paddy field conducted on flat and uneven bottom layer are 0.354° and 0.663° respectively, and maximum error of which are 1.4° and 3.6°, respectively with presence of 0.6 s delay; the delay goes up to 1.4 s when transplanter are driven into area with relatively deep mud; the settling time and steady-state error are 2.5 s and 0.6% respectively during the process of tracking a turning signal with 28° steering angle. Three experiments illustrate that the steering system developed for the rice transplanter based on the steering wheel-like motor has good dynamic response and control stability which can be applied to the automatic steering control of the rice transplanter in paddy fields and satisfies operation requirements of automatic navigation for rice transplanter.
agriculture machinery; navigation; control; steering wheel-like motor; rice transplanter; steering control; nested control algorithm; system identification
2019-01-06
2019-02-25
國家重點研發(fā)計劃項目(2017YFD0700404);廣東省科技計劃項目(2016B020205003)
何杰,實驗師,博士生,主要從事農(nóng)業(yè)機械導(dǎo)航研究。Email:hooget@scau.edu.cn
朱金光,研究員,主要從事智能農(nóng)業(yè)裝備研究。Email:zhujinguang@lovol.com
10.11975/j.issn.1002-6819.2019.06.002
S24;S237
A
1002-6819(2019)-06-0010-08
何 杰,朱金光,羅錫文,張智剛,胡 煉,高 陽. 電動方向盤插秧機轉(zhuǎn)向控制系統(tǒng)設(shè)計[J]. 農(nóng)業(yè)工程學(xué)報,2019,35(6):10-17. doi:10.11975/j.issn.1002-6819.2019.06.002 http://www.tcsae.org
He Jie, Zhu Jinguang, Luo Xiwen, Zhang Zhigang, Hu Lian, Gao Yang. Design of steering control system for rice transplanter equipped with steering wheel-like motor[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2019, 35(6): 10-17. (in Chinese with English abstract) doi:10.11975/j.issn.1002-6819.2019.06.002 http://www.tcsae.org