嵌入式導論課件3Modelvehicle

LIAOYong(Alan)Introductionto

EmbeddedSystems

Chapter3ModelVehicleControlSystem

1OUTLINEThereisamodelvehicle4cartwheels;2motors:Oneissteeringengine(130sBrushlessmotor)thatisusedtocontrolthefronttwocartwheels;theotherisspeedmotor(BrushlessESC(ElectronicSpeedController))thatisusedtodrivethereartwocartwheels;1batter;1freescale5213card(MCF5213);1ultrasonicsensor(SRF05);1LCD(LCD1602).YourmissionDrivethemodelvehicletogoaheadwhilekeepsitatagivendistance(50cm)

fromawall.

1OUTLINE1OUTLINERequirementsDetect(Acquire)thecurrentdistancefromthewallinrealtimebytheultrasonicsensor;DisplaythedetecteddistancebytheLCD;Drivethesteeringengineandspeedmotortocontrolthemodelvehicletogoaheadwhilekeepsitat50cm

fromthewall;YourprogramrunsonthetopofuC/OSⅡ;Codewarrior,C&Assemblelanguage.Howtodothis?2Problem(P1)P1:Howtodetectthedistanceinreal-time?Velocityofultrasonicis340meter/s;Distance=(

*340m/s)/2;Howtogetthe

TimeDuration?TimeDuration3Problem(P2),(P3),(P4)P2:HowtodrivethesteeringenginetoturnLeft/Right?Givenaturningangle,Howtoimplementthe“turning”command?P3:Howtodeterminetheturningangleineachadjustment?P4:Howtoorganizeanddesignthesoftwarearchitectureonthetopofuc/OSII?DFD(DataFlowDiagram)Taskstructure4ImplementtheabovedesignonthetopofuC/OSⅡ

Taskmanagement:OSTaskCreate()

MailBox:OSMBoxCreate()OSMBoxPost()OSMBoxPend()

Synchronize:OSSemCreate()OSSemPost()OSSemPend()

Mutex:OSMutexCreate()OSMutexPost()OSMutexPend()Interrupt:OSVectSet()............APIsprovidedbytheuC/OSⅡ?4ImplementtheabovedesignonthetopofuC/OSⅡMCF_GPIO_PORTDD&=~Trig//producea20uspulse

TestTimeSum=Gettime[1]-Gettime[0]//CalculatethedistanceInterfacesforultrasonicOSSpeeddown()OSSpeedup()OSTurnLeft()OSTurnRight()InterfacesforPWMLCDWcmd()//DeterminethepositionontheLCD

LCDWdata()//DisplaythegiveninformationLCDShowChar()//DisplaythedetecteddistanceInterfacesforLCD5Howtodesignamoreperfectcontrolsystem?Moresensors(Agroupofphotoelectricsensors)MoretasksPerfectcontrolalgorithmOptimizeyourprogramResponsibility,StabilityOthercontrolapplications……Q&ATestTimeSum=(GetTime[1]-GetTime[0])Time

Duration=F(TestTimeSum)ScanCalculatethedistance(TestDst),accordingtotheoriginaldata(GetTime[0],GetTime[1])fromGPT)Calculatethedistanceerror(ScanResult),accordingtotheincreasingPID(Proportion,Integral,Differential)controlalgorithmCarAdjusttheturningangleofthesteeringengine,accordingtotheScanResultandagivenadjustmentpolicySendtheadjustmentcommandstothesteeringengineShowGOSetpointr(t):Theset-pointofthedesireddistance(50cm)

c(t):Thedetecteddistance(TestDst)Where:e(k),e(k-1),e(k-2)aresuccessiveerrorsof3times.

?(u)isthecontrolleroutput,alsotheadjustmentamountofthedistance.e(t)=r(t)-c(t),Where:PIDisalinearcontrolPcontrol:Improvetheresponsibilitywhenerrorhappens.Icontrol:Eliminatetheresidualerror(AfterthePcontrol,ifthecontrolledTestDstdoesnotreturntosetpoint,thereexistsaerrorbetweenthesetpointandthevaluethathasbeenadjustedbythePcontrol).Dcontrol:Decreasethedynamicerror.Theadjustmentisbasedontheerrorvariationrateoftheprevious3periods.Thusthestabilityisimproved.PWM:Pulse-WidthModulor

TherelationbetweentheturningangleandDutyratio(turningangle--Pulsewidth--

Dutyratio)(PulsewidthofPWM)TurninganglePWMPulsethePeriodis20msDutyratio=0o1.57.5%DIRCT*(1000-75)AnglePulsewidthDutyRatioParameterofPWM-45o1.05.0%DIRCT*(1000-50)45o2.010.0%DIRCT*(1000-100)18o1.78.5%DIRCT*(1000-8