林輝, 戴志勇,2, 陳曉雷, 李兵強(qiáng), 呂帥帥
(1.西北工業(yè)大學(xué) 自動(dòng)化學(xué)院,陜西,西安 710129;2.西安電子科技大學(xué) 機(jī)電工程學(xué)院,陜西,西安 710071)
電動(dòng)負(fù)載模擬器反演終端滑??刂?/p>
林輝1, 戴志勇1,2, 陳曉雷1, 李兵強(qiáng)1, 呂帥帥1
(1.西北工業(yè)大學(xué) 自動(dòng)化學(xué)院,陜西,西安 710129;2.西安電子科技大學(xué) 機(jī)電工程學(xué)院,陜西,西安 710071)
電動(dòng)負(fù)載模擬器存在高階非線性、參數(shù)時(shí)變以及多余力矩?cái)_動(dòng),常規(guī)控制算法難以得到理想控制效果. 本文提出一種反演設(shè)計(jì)的終端滑??刂撇呗? 采用反演控制的思想,將加載系統(tǒng)劃分為3個(gè)子系統(tǒng),設(shè)計(jì)終端滑??刂坡桑⒁氲屯V波器顯著降低抖振,使跟蹤誤差在有限時(shí)間內(nèi)收斂到0. 利用Lyapunov方法證明閉環(huán)系統(tǒng)的漸進(jìn)穩(wěn)定性及有限時(shí)間收斂特性,實(shí)驗(yàn)結(jié)果表明所提出控制策略的有效性,與常規(guī)前饋反饋控制相比,加載控制精度有顯著提升.
電動(dòng)負(fù)載模擬器;反演控制;終端滑模控制;永磁同步電機(jī);多余力矩
飛行器在不同飛行條件下,其舵面/翼面等運(yùn)動(dòng)機(jī)構(gòu)會(huì)承受瞬時(shí)變化的負(fù)載力矩. 負(fù)載模擬器可在地面半物理仿真中復(fù)現(xiàn)飛行環(huán)境中作動(dòng)機(jī)構(gòu)所承受的鉸鏈力矩,檢測(cè)試件在接近真實(shí)載荷下的性能,是進(jìn)行舵機(jī)性能測(cè)試的重要設(shè)備,對(duì)縮短飛行器研發(fā)周期有著舉足輕重的作用[1]. 隨著電力電子技術(shù)的發(fā)展,以伺服電機(jī)為驅(qū)動(dòng)機(jī)構(gòu)的電動(dòng)負(fù)載模擬器(electric dynamic load simulator,EDLS)得到較廣泛的研究. EDLS是典型的被動(dòng)式加載系統(tǒng),亟待解決的問(wèn)題是實(shí)現(xiàn)對(duì)多余力矩的有效抑制[2],現(xiàn)有控制策略包括前饋補(bǔ)償[3]、神經(jīng)網(wǎng)絡(luò)自適應(yīng)補(bǔ)償[4]、模糊自適應(yīng)PID控制[5]等. 李成功等[3]根據(jù)結(jié)構(gòu)不變性原理設(shè)計(jì)位置前饋補(bǔ)償器對(duì)多余力矩進(jìn)行抑制,該方法的不足之處在于需要系統(tǒng)精確逆模型,而實(shí)際系統(tǒng)存在未知非線性及參數(shù)時(shí)變等問(wèn)題,難以達(dá)到理想的控制效果. 沈東凱等[4]設(shè)計(jì)前饋小腦模型補(bǔ)償算法并應(yīng)用圖表法進(jìn)行尋優(yōu),試圖最大限度地消除多余力矩,在特定加載條件下取得較好的控制效果,該算法不足之處在于神經(jīng)網(wǎng)絡(luò)參數(shù)整定較繁復(fù),對(duì)于較短暫的加載過(guò)程,神經(jīng)網(wǎng)絡(luò)難以保證收斂到全局最優(yōu)解. 倪志盛等[5]采用模糊自適應(yīng)PID方法實(shí)現(xiàn)加載力矩控制,相對(duì)常規(guī)PID控制而言精度有所提升,但在動(dòng)態(tài)加載工況下精度不夠理想.
分析可知,實(shí)現(xiàn)高精度的力矩加載控制,依賴于對(duì)加載力矩的精密測(cè)量以及對(duì)干擾力矩的有效抑制,此外,控制設(shè)計(jì)中必須考慮驅(qū)動(dòng)機(jī)構(gòu)及傳動(dòng)機(jī)構(gòu)中的非線性因素. 表貼式永磁同步電機(jī)(surface permanent magnet synchronous motors, SPMSM)具有轉(zhuǎn)矩脈動(dòng)小、調(diào)速范圍寬等優(yōu)勢(shì),適用于作為EDLS的驅(qū)動(dòng)機(jī)構(gòu),然而SPMSM本身具有非線性強(qiáng)耦合特點(diǎn),此外傳動(dòng)機(jī)構(gòu)中不可避免存在摩擦、齒隙非線性等復(fù)雜因素,使得EDLS具有高階非線性特性. 現(xiàn)有文獻(xiàn)均采用基于線性模型的前饋反饋控制結(jié)構(gòu),不足之處在于忽略了系統(tǒng)中的非線性因素,系統(tǒng)逆模型較難精確建立,難以實(shí)現(xiàn)對(duì)多余力矩的精確補(bǔ)償.
針對(duì)電動(dòng)負(fù)載模擬器的特點(diǎn),提出一種基于反演設(shè)計(jì)的終端滑模控制(terminal sliding mode control, TSMC)策略,將電動(dòng)負(fù)載模擬器分為3個(gè)子系統(tǒng)進(jìn)行控制設(shè)計(jì),采用TSMC方法設(shè)計(jì)虛擬控制量,反向遞推得到交直軸電流控制律,并對(duì)控制切換項(xiàng)采用低通濾波的方法,極大程度地降低滑模抖振問(wèn)題. 應(yīng)用Lyapunov方法證明閉環(huán)系統(tǒng)的漸進(jìn)穩(wěn)定及有限時(shí)間的收斂特性.
電動(dòng)負(fù)載模擬器結(jié)構(gòu)如圖1所示,由伺服電機(jī)、減速機(jī)構(gòu)、光電編碼器、力矩傳感器、加載試件等構(gòu)成. SPMSM作為EDLS的驅(qū)動(dòng)元件,通過(guò)聯(lián)軸器與力矩傳感器、減速器、加載試件相連. 減速機(jī)構(gòu)及傳動(dòng)機(jī)構(gòu)作為執(zhí)行元件,轉(zhuǎn)矩傳感器實(shí)時(shí)測(cè)量傳動(dòng)機(jī)構(gòu)上的加載力矩,構(gòu)成力矩反饋回路.
SPMSM在d-q坐標(biāo)系下的電壓、機(jī)械和轉(zhuǎn)矩方程為
(1)
式中:ud、uq、id、iq分別為SPMSM直軸、交軸的電壓、電流;φf(shuō)、Rs、Ls分別為永磁體磁鏈、定子電阻、等效直軸交軸電感;Te為電磁轉(zhuǎn)矩;TL為負(fù)載轉(zhuǎn)矩;ωr為軸系機(jī)械轉(zhuǎn)速;T0為由摩擦、慣性等非線性因素引起的未知非線性力矩;np為SPMSM的極對(duì)數(shù);B為阻尼系數(shù);J為軸系的轉(zhuǎn)動(dòng)慣量.
根據(jù)胡克定律,傳感器的數(shù)學(xué)模型為
(2)
式中:KG為剛度系數(shù);τ為傳動(dòng)機(jī)構(gòu)減速比;θ為EDLS的角度輸出;θf(wàn)為被加載對(duì)象的角度. 對(duì)式(2)求導(dǎo)并考慮測(cè)量誤差及未建模動(dòng)態(tài),與參數(shù)不確定因素疊加視為復(fù)合干擾項(xiàng),可得轉(zhuǎn)矩的變化率為
(3)
式中:ωf為被加載對(duì)象的角速度;d1為干擾項(xiàng).
電流環(huán)動(dòng)態(tài)特性與電磁轉(zhuǎn)矩直接相關(guān),是衡量加載系統(tǒng)性能的關(guān)鍵指標(biāo). 隨著SPMSM運(yùn)行中繞組溫度的變化,電磁特性將發(fā)生改變,如電阻、電感等參數(shù)會(huì)有較大的變動(dòng),因此將模型誤差及未建模動(dòng)態(tài)視為未知干擾. 定義狀態(tài)變量
x=[TLωriqid]T,
聯(lián)立式(1)(3)可得SPMSM驅(qū)動(dòng)的EDLS數(shù)學(xué)模型為
(4)
式中:y為系統(tǒng)輸出;uq、ud為控制量;di(i=1~4)為建模誤差及未建模動(dòng)態(tài).
2.1 負(fù)載轉(zhuǎn)矩子系統(tǒng)設(shè)計(jì)
(5)
(6)
由式(6)可計(jì)算
(7)
(8)
(9)
則有
(10)
由式(10)可知滑模面有限時(shí)間內(nèi)可達(dá)[7],隨后系統(tǒng)可在有限時(shí)間內(nèi),任意初始條件z1(0)≠0下沿滑模面運(yùn)動(dòng)到z1=0.
2.2 SPMSM機(jī)械子系統(tǒng)設(shè)計(jì)
(11)
式中c2為正實(shí)數(shù),0<α2<1.
(12)
(13)
(14)
有
(15)
2.3 SPMSM電氣子系統(tǒng)設(shè)計(jì)
(16)
(17)
式中:c3、c4為正實(shí)數(shù),0<α3,α4<1.
設(shè)計(jì)交軸電壓uq為
(18)
設(shè)uqsw(0)=0,T3、η3為正實(shí)數(shù).
設(shè)計(jì)直軸電壓ud為
(19)
設(shè)udsw(0)=0,T4、η4為正實(shí)數(shù). 可知uq、ud為連續(xù)量,消除了常規(guī)滑模控制存在的抖振.
2.4 穩(wěn)定性分析
首先給出穩(wěn)定性分析需要的引理.
引理1 若a1,a2,…,an皆為正實(shí)數(shù),δ∈(0,2),則下列不等式成立[7]
(20)
引理2 若連續(xù)可微Lyapunov函數(shù)V(t)滿足如下不等式[8]
(21)
式中:α,β>0,0<γ<1,則V(t)可在有限時(shí)間內(nèi)收斂到0點(diǎn).
定理1 對(duì)式(4)所示EDLS系統(tǒng),虛擬控制量設(shè)計(jì)如式(6)(12),采用式(18)(19)所示電流控制律,若滿足假設(shè)1~2,取適當(dāng)?shù)幕C鎱?shù)αi、ci及控制器參數(shù)kdi、kTi、ηi、κi(i=1~4),則滑模面si有限時(shí)間內(nèi)可達(dá),跟蹤誤差隨后在有限時(shí)間內(nèi)收斂為0.
證明 選取整體系統(tǒng)的控制Lyapunov函數(shù)為
(22)
對(duì)式(22)求微分得
(23)
(24)
(25)
由引理2可知V(t)為有限時(shí)間收斂,結(jié)合終端滑模面性質(zhì),可知跟蹤誤差隨后在有限時(shí)間收斂為0. 與文獻(xiàn)[6]相比,本文算法在切換設(shè)計(jì)中增加線性項(xiàng),保留了線性滑模在遠(yuǎn)離平衡點(diǎn)時(shí)指數(shù)收斂的優(yōu)點(diǎn),縮短了系統(tǒng)到達(dá)滑模面的時(shí)間.
在自行設(shè)計(jì)的負(fù)載模擬器平臺(tái)上進(jìn)行力矩加載試驗(yàn),驗(yàn)證控制策略的有效性. 被加載舵機(jī)的驅(qū)動(dòng)電機(jī)及力矩加載電機(jī)使用相同參數(shù)的SPMSM. 額定轉(zhuǎn)矩為4.77 N·m,黏滯系數(shù)B為0.003 N·m/rad/s,磁極對(duì)數(shù)np為5,轉(zhuǎn)子磁鏈φf(shuō)為0.050 3 Wb,轉(zhuǎn)動(dòng)慣量J為2.5 g·m2,定子電阻Rs為0.43 Ω,繞組電感Ls為1.7 mH,直流母線電壓Vdc為300 V. 剛度系數(shù)KG為6 kN·m/rad,傳動(dòng)機(jī)構(gòu)減速比τ為50.
針對(duì)永磁同步電機(jī)驅(qū)動(dòng)的電動(dòng)負(fù)載模擬器存在的多余力矩、參數(shù)時(shí)變及未知擾動(dòng),基于反演控制思想設(shè)計(jì)終端滑??刂破?,并對(duì)切換控制項(xiàng)采用低通濾波,得到平滑的電流控制律. 分析了影響力矩加載精度及誤差收斂時(shí)間的若干因素. 實(shí)驗(yàn)結(jié)果表明,與前饋反饋型復(fù)合控制相比,誤差收斂速度顯著縮短,力矩加載控制精度及閉環(huán)系統(tǒng)魯棒性顯著提高.
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(責(zé)任編輯:李兵)
Backstepping Terminal Sliding-Mode Control for Electric Dynamic Load Simulator
LIN Hui1, DAI Zhi-yong1,2, CHEN Xiao-lei1, LI Bing-qiang1, Lü Shuai-shuai1
(1.School of Automation, Northwestern Polytechnical University, Xi’an ,Shaanxi 710129, China;2.School of Mechanical and Electrical Engineering, Xidian University, Xi’an, Shaanxi 710071, China)
Owing to the interfere of higher order nonlinearity, parameters variability and surplus torque in electric dynamic load simulator(EDLS), it is hard to obtain satisfactory results by the traditional compensation algorithm. To overcome the deficiencies of the conventional control scheme for EDLS, a chattering free terminal sliding mode control scheme based on backstepping design was proposed. The EDLS model was divided into three subsystems and the control law was designed using chattering free terminal sliding mode to make the load tracking error converged to zero within finite time, which the switching control term was softened to be a smooth signal by a low-pass filter. Through Lyapunov stability analysis, it is shown that the control strategy guarantees the asymptotic stability and a finite time convergence of the closed-loop system. The experimental results show the effectiveness of the proposed control scheme. Compared with the traditional feedforward and feedback control strategy, the accuracy of the load torque tracking is improved significantly.
electrical dynamic load simulator; backstepping control; terminal sliding mode control; permanent magnet synchronous motors; surplus torque
2015-07-30
國(guó)家自然科學(xué)基金資助項(xiàng)目(51407143);國(guó)家教育部高等學(xué)校博士學(xué)科點(diǎn)專項(xiàng)科研基金資助課題(20136102120049);陜西省自然科學(xué)基礎(chǔ)研究計(jì)劃資助項(xiàng)目(2014JQ7264);陜西省微特電機(jī)及驅(qū)動(dòng)技術(shù)重點(diǎn)實(shí)驗(yàn)室開(kāi)放基金資助項(xiàng)目(2013SSJ1002);中央高?;究蒲袠I(yè)務(wù)費(fèi)專項(xiàng)資金資助項(xiàng)目(3102014JCQ01066)
林輝(1957—),男,教授,博士生導(dǎo)師,E-mail:linhui@nwpu.edu.cn.
戴志勇(1987—),男,博士生,E-mail:daizhiyong_nwpu@hotmail.com.
TP 273
A
1001-0645(2016)12-1259-05
10.15918/j.tbit1001-0645.2016.12.010