This module calculates the motor speed based on a rotor position measurement when the direction information is available.

Transcription

1 SPEED_FRQ Spd Calulator Basd on Rotor Angl With Dirtion Information Dsription This modul alulats th motor spd basd on a rotor position masurmnt whn th dirtion information is availabl. thta_l dir_qep SPEED_FRQ spd_frq spd_rpm Availability This IQ modul is availabl in on intrfa format: Th C intrfa vrsion Modul Proprtis Typ: Targt Indpndnt, Appliation Dpndnt Targt Dvis: x8x C Vrsion Fil Nams: spd_fr., spd_fr.h IQmath library fils for C: IQmathLib.h, IQmath.lib Itm C vrsion Commnts Cod Siz? 86 words Data RAM 0 words xdais rady No XDAIS omponnt No IALG layr not implmntd Multipl instans Ys Rntrany Ys Eah pr-initializd _iq SPEED_MEAS_QEP strutur onsums 0 words in th data mmory? Cod siz mntiond hr is th siz of th al( funtion Digital Control Systms (DCS Group Txas Instrumnts

2 C Intrfa C Intrfa Objt Dfinition Th strutur of SPEED_MEAS_QEP objt is dfind by following strutur dfinition typdf strut { _iq thta_l; /* Input: Eltrial angl */ long dir_qep; /* Input: Dirtion of rotation (Q0 */ _iq thta_old; /* History: Eltrial angl at prvious stp */ _iq spd_frq; /* Output: Spd in pr-unit */ long rpm_max; /* Paramtr: Bas spd in rpm (Q0 */ _iq ; /* Paramtr: Constant for diffrntiator (Q */ _iq ; /* Paramtr: Constant for low-pass filtr */ _iq 3; /* Paramtr: Constant for low-pass filtr */ long spd_rpm; /* Output : Spd in rpm (Q0 */ void (*al(; /* Pointr to th alulation funtion */ } SPEED_MEAS_QEP; /* Data typ ratd */ typdf SPEED_MEAS_QEP * SPEED_MEAS_QEP_handl; Itm Nam Dsription Format * Rang(Hx Inputs thta_l Eltrial angl GLOBAL_Q FFFFFFF (0 360 dgr dir_qep Dirtion of rotation Q0 0 or Outputs spd_frq Computd spd in pr-unit GLOBAL_Q FFFFFFF spd_rpm Spd in rpm Q FFFFFFF SPEED_QEP = /(fb*t Q FFFFFFF paramtr = /(+T**pi*f GLOBAL_Q FFFFFFF 3 3 = T**pi*f/(+T**pi*f GLOBAL_Q FFFFFFF rpm_max rpm_max = 0fb/p Q FFFFFFF Intrnal thta_old Eltrial angl in prvious stp GLOBAL_Q FFFFFFF (0 360 dgr * GLOBAL_Q valud btwn and 30 is dfind in th IQmathLib.h hadr fil. Spial Constants and Data typs SPEED_MEAS_QEP Th modul dfinition is ratd as a data typ. This maks it onvnint to instan an intrfa to spd alulation basd on masurd rotor angl. To rat multipl instans of th modul simply dlar variabls of typ SPEED_MEAS_QEP. SPEED_MEAS_QEP_handl Usr dfind Data typ of pointr to SPEED_MEAS_QEP modul SPEED_MEAS_QEP_DEFAULTS Strutur symboli onstant to initializ SPEED_MEAS_QEP modul. This provids th initial valus to th trminal variabls as wll as mthod pointrs. Digital Control Systms (DCS Group Txas Instrumnts

3 C Intrfa Mthods Modul Usag void spd_frq_al(speed_meas_qep_handl; This dfinition implmnts on mthod viz., th spd alulation basd on masurd rotor angl omputation funtion. Th input argumnt to this funtion is th modul handl. Instantiation Th following xampl instans two SPEED_MEAS_QEP objts SPEED_MEAS_QEP spd, spd; Initialization To Instan pr-initializd objts SPEED_MEAS_QEP spd = SPEED_MEAS_QEP_DEFAULTS; SPEED_MEAS_QEP spd = SPEED_MEAS_QEP_DEFAULTS; Invoking th omputation funtion spd.al(&spd; spd.al(&spd; Exampl Th following psudo od provids th information about th modul usag. main( { } void intrrupt priodi_intrrupt_isr( { spd.thta_l = thta; /* Pass inputs to spd */ spd.dir_qep = dir; /* Pass inputs to spd */ spd.thta_l = thta; /* Pass inputs to spd */ spd.dir_qep = dir; /* Pass inputs to spd */ spd.al(&spd; /* Call omput funtion for spd */ spd.al(&spd; /* Call omput funtion for spd */ } masurd_spd = spd.spd_frq; /* Ass th outputs of spd */ masurd_spd = spd.spd_frq; /* Ass th outputs of spd */ Digital Control Systms (DCS Group 3 Txas Instrumnts

4 Thnial Bakground Thnial Bakground Th typial wavforms of th ltrial rotor position angl from QEP nodr, θ, in both dirtions an b sn in Figur. Assuming th dirtion of rotation (dir_qep is availabl from QEP nodr. θ.0 dir_qep = θ 0.0 t t t t dir_qep = 0 tim 0 t t t t Not that θ =.0 pu = 360 dg r tim Figur : Th wavforms of rotor position in both dirtions Th diffrntiator quation of rotor position an b xprssd as follows. whr f T b ( θ (k θ (k ω ( ( k = =, f b is bas frquny (Hz and T is sampling priod (s. In Figur, thr ar two ass nd to b aountd for; th simpl as whr th angl has not wrappd around (as and whr it has wrappd around (as. And th quation ( is for as in both dirtions. As for as, th quation would b diffrnt, dpnding on th dirtion as follows: dir_qep = 0: ( k = ( θ(k + θ (k dir_qep = : k = ( + θ (k θ (k ω ( ω (3 ( Digital Control Systms (DCS Group 4 Txas Instrumnts

5 Thnial Bakground In addition, th synhronous spd in is nssary to b filtrd out by th low-pass filtr in ordr to rdu th amplifying nois gnratd by th pur diffrntiator. Th simpl st -ordr low-pass filtr is usd, thn th atual synhronous spd to b usd is th output of th low-pass filtr, ˆω, sn in following quation. Th ontinuous-tim quation of st -ordr low-pass filtr is as whr = πf dˆ ω dt = τ ( ω ωˆ τ is th low-pass filtr tim onstant (s, and f is th ut-off frquny (Hz. Using bakward approximation, thn (4 finally boms (4 whr τ τ + T =, and ω ˆ (k = ωˆ (k + ω (k (5 3 τ T =. + T 3 Nxt, Tabl shows th orrspondn of notations btwn variabls usd hr and variabls usd in th program (i.., spd_fr., spd_fr.h. Th softwar modul rquirs that both input and output variabls ar in pr unit valus. Inputs Outputs Othrs Equation Variabls θ dirtion ˆω 3 Tabl : Corrspondn of notations Program Variabls thta_l dir_qep spd_frq 3 Digital Control Systms (DCS Group 5 Txas Instrumnts