Towards a Rapid Control Prototyping Toolbox for the Stellaris LM3S8000 Microcontrollers

Transcription

1 Preprnts of the 18th IFAC Worl Congress Towars a Rap Control Prototypng Toolbox for the Stellars LM3S8000 Mcrocontrollers Rau Duma 1), Petru Dobra 2), Mrela Trusca 3), Dorn Petreus 4) an Danel Moga 5) 1, 2, 3, 5) Automatc Control Department, 4) Apple Electroncs Department Techncal Unversty of Cluj Napoca (e-mal: 1) rau.uma@aut.utcluj.ro, 2) obra@aut.utcluj.ro, 3) mrela.trusca@aut.utcluj.ro, 4) orn.petreus@ael.utcluj.ro, 5) anel.moga@aut.utcluj.ro) Abstract: The paper presents a Rap Control Prototypng (RCP) toolbox for Matlab/Smulnk, whch s use to generate real-tme C coe for the Stellars LM3S800 famly of mcrocontrollers from Texas Instruments (TI). The toolbox, Target for Stellars LM3S800, contans Smulnk blocks, whch mplement rvers an algorthms specfc for the Stellars LM3S800 famly of mcrocontrollers. The paper presents an ongong work. For the moment the toolbox contans four lbrares: I/O rvers, Dgtal Motor Control (DMC), Controller Area Network (CAN) an LM3S8000 Target Preferences. A practcal applcaton for a Computer Numercal Controlle (CNC) machne s presente. Keywors: rap control prototypng, mcrocontroller, close-loop control, CNC machne, PID control 1. INTRODUCTION Developng controllers for applcatons (electrcal rve systems) means large expenture, when performe wth usual evelopment methos. The workloa comprses evelopment of a mathematcal moel as well as algorthm esgn an mplementaton, off-lne smulaton, an optmzaton. The whole process has to be restarte on occurrng errors or vergences, whch makes the evelopment process tme consumng an costly (Hanselman, 1996). Rap Control Prototypng (RCP) s a way out of ths stuaton, especally f the control algorthm s complex an a lot of teraton steps are necessary. Wth the great versty of applcatons, a evelopment envronment must be flexble an prove exactly the functonalty necessary for effcent problem solvng. Mathworks' Smulnk (Mathworks, 2010) software s such a graphcal moellng tool. In Fg. 2 s presente the block agram for the nformaton flow (from concept to moel) an for the ata flow (between PC an the Stellars LM3S8000 mcrocontroller) for the mplemente toolbox. RCP requres two components: a Computer Ae Control System Desgn (CACSD) software an a ecate harware, capable of runnng tasks n real-tme (Fg.1). Fg. 2. Block agram for the nformaton an ata flows for the Target for Stellars LM3S8000 RCP toolbox. Fg. 1. The general archtecture of a RCP system. CACSD tools are extensvely use to generate real tme coe automatcally. The graphcal programmng approach removes the nee to wrte software by han an allows the engneer to focus nstea on mprovng functonalty an performance. Complete system esgn s carre out wthn the smulaton envronment. Control algorthms for the LM3S8000 mcrocontrollers can be evelope usng blocks from the Target for Stellars LM3S8000 toolbox an preefne blocks from Smulnk or user efne blocks. After the valaton of the moel, coe can be generate usng Real-Tme Workshop. At the en of the coe generaton process the Coe Composer Stuo (CCS) Integrate Development Envronment (IDE) s automatcally starte, a new CCS project s create, the generate coe source fles are ae to the project, the project s comple an the bnary fle s ownloae to the Copyrght by the Internatonal Feeraton of Automatc Control (IFAC) 1965

2 Preprnts of the 18th IFAC Worl Congress target processor. The executon of the coe can be montore n real-tme usng the mplemente CAN rvers. 2. RELATED WORK In ths secton s brefly presente some of the research lterature relate to RCP. MathWork s evelope toolboxes for some wlly use targets: Motorola MPC555, Infneon C166, C2000 an C6000 DSP famles from Texas Instruments. Rebeschess (Rebeschess, 1999) evelope the MICROS toolbox for stanar 80C166 mcrcontrollers. A DSP base RCP system for engneerng eucaton an research usng as CACSD tool Matlab/Smulnk s presente n (Hercog et al., 2006). Duma an Dobra have mplemente a RCP toolbox for the Renesas M32C87 mcrocontroller (Duma et al., 2010). Mcrochp (Mcrochp, 2009) evelope a Matlab RCP toolbox for the spic33 Dgtal Sgnal Controllers (DSC), whle Kerhuel (Kerhuel, 2009) evelope a toolbox whch offers support for several Mcrochp mcrocontrollers an DSCs. base on the Eclpse open source software framework an s a fle system base moel IDE. There are comman-lne utltes that come wth CCS to create, bul an mport a CCS project. Usng these commans at the en of the coe generaton process CCS s automatcally starte, a new CCS project s create, the generate coe fles are cope nto the project rectory an the project s bul. In the fnal verson of the mplemente RCP toolbox Debug Server Scrptng (DSS) wll be use for the automate ownloa of the generate bnary fle on the target processor. 4. TARGET FOR STELLARIS LM3S8000 The Smulnk lbrary for the Stellars LM3S8000 mcrocontrollers s presente n Fg. 3. For the moment the toolbox contans four lbrares: I/O rvers, DMC, CAN an LM3S8000 Target Preferences. Natonal Instruments LabVIEW graphcal coe can be use to evelop ARM mcrocontroller embee applcatons for the Stellars LM3S88962 usng the LabVIEW Embee Moule for ARM Mcrocontrollers (Natonal Instruments, 2010). A free, open source, RCP soluton s base on Sclab/Sccos (Campbell et al., 2009) an Lnux-RTAI (Bucher et al., 2004), whch uses the processor of a general purpose computer for executng real-tme tasks. A real-tme patch s apple to the stanar Lnux kernel. A mofe verson of the Sccos coe generator, RTAI-Lab, generates har realtme coe compatble wth Lnux-RTAI. Acquston cars can be rectly ntegrate nto the Sccos scheme an nto the generate coe usng rvers prove by the COMEDI ([Come]) project. Ravn (Ravn, 2006) mplemente an aaptve control toolbox, for Sclab/Sccos, whch can be use for RCP. A target supporte n Sclab/Sccos s the Mcrochp spic DSC mcrocontroller. Duma (Duma et al., 2009) presente a system entfcaton an control RCP toolbox for Sclab/Sccos. 3. CODE COMPOSER STUDIO It s mportant for an RCP toolbox to offer support for a complete bul process. A full post-coe generaton bul process nclues: complaton of generate coe, lnkng of comple coe an runtme lbrares nto an executable program moule, ownloang the executable to target harware wth a ebugger or other utlty, ntatng executon of the ownloae program. Supportng a complete bul process s a complex task, because t nvolves nterfacng to cross-evelopment tools an utltes that are external to the Real-Tme Workshop software (Mathworks, 2008). CCS s the ntegrate evelopment envronment for TI's DSPs, mcrocontrollers an applcaton processors. CCS s Fg. 3. The Target for Stellars LM3S8000 Smulnk toolbox. The target processors for the mplemente toolbox are the Stellars LM3S8000 famly of mcrocontrollers. The Stellars famly of mcrocontrollers - the frst ARM Cortex-M3 base controllers - brngs hgh-performance 32-bt computng to cost-senstve embee mcrocontroller applcatons. The Stellars LM3S8000 seres combnes Bosch Controller Area Network (CAN) technology wth both a 10/100 Ethernet Mea Access Control (MAC) an Physcal (PHY) layer. The LM3S8000 mcrocontrollers are targete for nustral applcatons, nclung remote montorng, electronc pontof-sale machnes, test an measurement equpment, network applances an swtches, factory automaton, HVAC an bulng control, gamng equpment, moton control, mecal nstrumentaton an fre an securty. Smulnk blocks are efne by two functons: a MEX functon wrtten n the C language an a Target Language 1966

3 Preprnts of the 18th IFAC Worl Congress Compler (TLC) mplementaton. The MEX functon confgures the number of nputs/outputs ports of the block an transfers the parameters specfe n the graphcal user nterface of the block n the coe generaton process. The TLC mplementaton ntalzes the I/O evce, computes the value for the output of the block an termnates the program by settng the harware to a neutral state. For each block of the toolbox the two fles were mplemente. enable/sable through nput ports. Ths feature s useful for the control of three phase brges. In the followng sectons the lbrares of the toolbox are brefly escrbe. 5. I/O Drvers Lbrary The I/O rvers (Fg. 4) lbrary contans rvers for the I/O perpherals of the target processor. Fg. 5. Functon Block Parameters wnow of the LM3S000 PWM block. Sgnal generator n Count-Down moe, there are four events that can affect the PWM sgnal: zero, loa, match comparator A own an match comparator B own. In Count- Up/Down moe, there are two supplementary events that can affect the PWM sgnal: match comparator A up an an match comparator B up. These actons can be use to generate a par of PWM sgnals of varous postons an uty cycles, whch o or o not overlap. Fg. 4. I/O rvers lbrary. For the moment the lbrary contans two blocks, one for the generaton of PWM sgnals an one for nput capture. In the future we plan to mplement rvers for the followng perpherals of the mcrocontroller: analog to gtal converter, gtal nput, gtal output, quarature encoer nterface. In Fg. 5 s presente the Functon Block Parameters wnow for settng the parameters of the LM3S000 PWM block. The wnow contans several tabs whch are escrbe below. Tmer - n ths tab the esre PWM generator can be selecte an tmer relate optons can be specfe (Up-Down or Down count moe). The pero of the PWM sgnal can be set through the alog (f t s fxe urng program executo or through nput port (f t s varable urng program executo. Ths opton s useful because there are processes whch are controlle usng a PWM sgnal wth fxe uty cycle an a varable frequency. Output each PWM generator can generate two PWM sgnals. In ths tab one or both PWM outputs can be enable, the uty cycle of the PWM sgnals can be specfe va alog or through nput port. The PWM outputs can be Dea ban - f ea ban s enable, the secon output PWM sgnal s the nverson of the frst PWM sgnal wth a programmable elay ae between the fallng ege an the rsng ege of the PWM sgnals. Ths tab allows the specfcaton of the rsng an fallng ege elays between the two PWM sgnals. The PWM sgnals wth ea ban are use for rvng a half H brge n orer to avo a short crcut conton. Synchronzaton ths tab allows the specfcaton of the upate moe for the tmers an for the comparators use to generate the PWM sgnals; the upate moe for the PWM generators an the ea ban upate moe. ADC trgger specfes the events that generates ADC trgger. 6. CAN lbrary Controller Area Network (CAN) s a multcast, share seral bus stanar for connectng electronc control unts. CAN was specfcally esgne to be robust n electromagnetcallynosy envronments. Orgnally create for automotve purposes, t s also use n many embee control applcatons. Bt rates up to 1Mbps are possble at network lengths less than 40 meters. An mportant feature whch shoul be mplemente by an RCP toolbox s the real-tme observaton of the coe execute on the embee processor (Mathworks, 2008). One nustry stanar s the use of the CAN bus. For ths 1967

4 Preprnts of the 18th IFAC Worl Congress purpose the CAN lbrary presente n Fg. 6 was mplemente. processors. Only nteger varables are eclare, an the sngle-cycle multply nstructon an the harware ve features of Stellars mcrocontrollers are use n orer to obtan the lowest samplng rate wthout breakng the realtme constrans. For the moment the lbrary contans only a block whch mplements a PID controller wth antsaturaton. The structure of the controller s escrbe n etal below. In the fnal verson of the toolbox the DMC Lbrary wll contan blocks for three phase motor control an for BLDC motor control. More than 90% of the control loops are of PI an PID type. The reason for whch the PID controller s so wely use s ts smple structure whch has prove to be very robust wth regar to many commonly control problems. The stanar equaton of a PID controller s presente below: Fg. 6. CAN lbrary. The lbrary contans three blocks whch are use for the confguraton of the CAN moule: CAN Confgure the block specfes the CAN moule use, the operatng moe an the bau rate. CAN Transmt the block confgures the slot of a CAN moule for the transmsson of a message wth a certan entfer. CAN Receve the block confgures the slot of a CAN moule for the recepton of a message wth a certan entfer. 7. Dgtal Motor Control Lbrary The DMC lbrary (Fg. 7) contans blocks whch mplement gtal motor control algorthms. 1 u( t) K t p ( t) ( ) T T 0 ( t) t where ( t) ysp( t) t) s the error sgnal, y sp s the set pont an y s the output of the process. The screte equatons use for the mplementaton of the PID algorthm are escrbe below: P( K ( y ( ) p sp D( D( n 1) ( y( n 1) ) (1) v( P( I( D( I( n 1) I( ( y ( ) ( u( v( ) sp where T T Nh, K T N T Nh K T T an t Ts Tt p s. p t, Equatons (1) were use for TLC mplementaton of the LM3S8000 PID block. For the PID controller the followng parameters have to be chosen: K p, proportonal gan; T, ntegraton tme; T, ervatve tme; β, fracton of comman sgnal; N, hgh frequency lmter of ervatve acton; u mn, mnmum saturaton value; u max, maxmum saturaton value; an T s, samplng tme. The block has two nput ports: the reference an the feeback sgnal an one output: the comman sgnal for the controlle process. 8. APPLICATION EXAMPLE Fg. 7. DMC lbrary. The mplemente algorthms are optmze for the LM3S8000 mcrocontrollers, whch are fxe pont In orer to test the mplemente toolbox a practcal applcaton for a Computer Numercal Controlle (CNC) machne was mplemente. The stepper motors of an ol CNC machne are replace wth Brushless Drect Current (BLDC) motors, n orer to obtan hgher postonng accuracy. For BLDC motor control, three PWM sgnals an three actvaton sgnals are neee. Unlke a DC motor, the 1968

5 Preprnts of the 18th IFAC Worl Congress BLDC motor must be commutate electroncally. In orer to smplfy the control of the BLDC motor, a control logc crcut was mplemente. Usng ths control logc crcut, a BLDC motor can be controlle smlarly to a DC motor. A sngle PWM sgnal an a sngle feeback sgnal are neee. The escrpton of the control logc crcut s out of the scope of ths paper. A Stellars LM3S8962 Ethernet+CAN evaluaton kt, equppe wth a LM3S8962 mcrocontroller s use as target processor. The motor whch s controlle s a Hurst-Emerson BLDC motor ([Emerson]). In orer to communcate between the embee processor an the PC, an USB to CAN converter prouce by Systec-Electronc ([SystecElectronc]) s use. The test setup s presente n Fg. 8. control algorthm mplements a cascae control topology. For the poston loop a PI controller s use an for the spee loop a P controller s use. The parameters of the controllers are compute usng the metho ntrouce by Kessler (Kessler, 1958). The poston reference s a rectangular sgnal, whch s apple on the reference port of a LM3S8000 PID bock. The output of the poston controller sets the reference of the spee controller. The spee controller computes the uty cycle of the PWM sgnal whch s use for the control of the BLDC motor of the axs of the CNC machne. A confguraton LM3S8000 CAN Confgure block s ae to the moel. It oes not connect to any other blocks, but stans alone to confgure the selecte CAN moule.the reference poston, the measure poston an the spee are concatenate nto an array an are sent over the CAN bus usng a LM3S8000 CAN Transmt block. A target preference block has to be ae to the moel. The LM3S8000 Target block oes not connect to any other blocks, but stans alone to set the target preferences for the moel. After the valaton of the moel the coe generaton process s nvoke, an the generate executable fle s ownloae to the LM3S8962 processor The postonng of the axs of the CNC machne s shown n Fg. 10 an the spee n Fg CONCLUSIONS CNC axs LM3S8000 Evaluaton Kt USB-CAN Converter Drver Control Logc Fg. 8. The test setup. The close loop Smulnk moel for the control of an axs of the CNC machne s presente n Fg. 9. The moel of the A contrbuton of the paper s the mplementaton of a RCP toolbox for the Stellars LM3S8000 famly of mcrocontrollers, usng as CACSD tool Matlab/Smulnk. Untl now, for these mcrocontrollers there was not a RCP toolbox. The RCP approach removes the nee to wrte software by han an allows the engneer to focus nstea on mprovng the performance of the control algorthm. Fg. 9 Smulnk block agram for the control of an axs of the CNC machne. 1969

6 Preprnts of the 18th IFAC Worl Congress Socal Fun through Sectoral Operatonal Program Human Resources Fg. 10. The postng of the axs of the CNC machne. Fg. 11. Spee profle of the axs of the CNC machne. In our opnon, the Traget for Stellars LM3S8000 RCP toolbox has some avantages over the coe generaton soluton offere by NI. Frst, the toolbox s targete for all the mcrocontrollers of the LM3S8000 famly of ARM mcrocontrollers, whle n LabVew only the LM3S8962 mcrocontroller s supporte. Secon, the evelope RCP toolbox s ecate for the LM3S8000 processors, whch makes the graphcal programmng approach much easer than n LabVew, whch offers support for several ARM mcrocontrollers, among whch the Stellars LM3S8962 mcrocontroller. The Stellars mcrocontrollers are sute for motor control an communcaton applcatons because moton plus connectvty s possble only wth a etermnstc archtecture lke ARM Cortex-M3. In the selecton of the target processor t s recommene to choose a wely avalable evaluaton boar. The LM3S8962 Ethernet+CAN Evaluaton Kt use n the practcal applcaton presente s such an evaluaton boar. ACKNOWLEDGMENT Ths paper was supporte by the project Progress an evelopment through post-octoral research an nnovaton n engneerng an apple scences PRDE - Contract no. POSDRU/89/1.5/S/57083", project co-fune from European REFERENCES Bucher, R., Dozo L. an Mantegazza P. (2004). Rap control prototypng wth Sclab/Sccos an Lnux RTAI. Sclab Conference. Campbell, S. L., Chanceler, J.-P., an Nkoukhah, R. (2009). Moelng an smulaton n Sclab/Sccos wth SccosLab 4.4, Sprnger. Duma, R., Dobra, P., Trusca, M., Dumtrache, D., an Sta, I. V. (2009). Rap control prototypng eucatonal toolbox for Sclab/Sccos, n Proc. of European Control Conference 2009, pp Duma, R., Trusca, M., an Dobra, P. (2010). BLDC Motor Control usng Rap Control Prototypng, n Journal of Control Engneerng an Apple Informatcs, vol. 12, nr. 1. Hanselman, H. (1996). Automotve control: from concept to experment to prouct, Proc. IEEE Internatonal Symposum on Computer-Ae Control System Desgn, pp , Sept Hercog, D., Curkovc, M., an Jezernk, K. (2006). DSP Base Rap Control Prototypng Systems for Engneerng Eucaton an Research, Proceengs of the 2006 IEEE Conference on computer Ae Control Systems Desgn, Munch, Germany, October 4-6. Kerhuel, L. (2009). Smulnk - Embee Target for PIC. Kessler, C. (1958) Das symmetrche optmum. Regelungstetechnk, 6, , Mathworks (2008), Real-Tme Workshop Embee Coer 5 Developng Embee Targets. Mathworks (2010), Smulnk user s gue. Mcrochp (2009), MATLAB/Smulnk evce blocksets for spic DSCs. Natonal Instruments (2010). Gettng starte wth the NI LabVIEW embee moule for ARM mcrocontrollers. Ravn, O. (2006). Aaptve control usng the aaptve toolbox-tat for Sclab/Sccos, 14th IFAC Symposum on System Ientfcaton, Newcastle, Australa. Rebeschess, S. (1999). MIRCOS- mcrocontroller-base real tme control system toolbox for use wth Matlab/Smulnk. Proc. IEEE Int. Symp.Computer Ae Control System Desgn, pp ([Come]) Come. URL ([Emerson]) Emerson. URL ([SystecElectronc]) SystecElectronc. URL