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GPA.cpp
- Committer:
- altb
- Date:
- 2018-04-03
- Revision:
- 0:78ca29b4c49e
- Child:
- 3:769ce5f06d3e
File content as of revision 0:78ca29b4c49e:
/* GPA: frequency point wise gain and phase analyser to measure the frequency respone of dynamical system hint: the measurements should only be perfomed in closed loop assumption: the system is at the desired steady state of interest when the measurment starts exc(2) C: controller | P: plant v exc(1) --> o ->| C |--->o------->| P |----------> out ^ | | | --> inp | exc: excitation signal (E) | | inp: input plant (U) -------------------------------- out: output plant (Y) instantiate option 1: GPA(float fMin, float fMax, int NfexcDes, int NperMin, int NmeasMin, float Ts, float Aexc0, float Aexc1) fMin: minimal desired frequency that should be measured in Hz fMax: maximal desired frequency that should be measured in Hz NfexcDes: number of logarithmic equaly spaced frequency points NperMin: minimal number of periods that are used for each frequency point NmeasMin: maximal number of samples that are used for each frequency point Ts: sampling time Aexc0: excitation amplitude at fMin Aexc1: excitation amplitude at fMax hints: the amplitude drops with 1/fexc, if you're using Axc1 = Aexc0/fMax the d/dt exc = const., this is recommended if your controller does not have a rolloff. if a desired frequency point is not measured try to increase Nmeas. pseudo code for a closed loop measurement with a proportional controller Kp: float inp = "measurement of inputsignal"; float out = "mesurement of outputsignal"; float exc = myGPA(inp, out); float off = "desired steady state off the system"; excitation input at (1): inp = Kp*(exc + off - out); excitation input at (2): inp = Kp*(off - out) + exc; usage: exc = myGPA(inp, out) does update the internal states of the gpa at the timestep k and returns the excitation signal for the timestep k+1. the results are plotted to a terminal (putty) over serial cennection and look as follows: ----------------------------------------------------------------------------------------- fexc[Hz] |Gyu| ang(Gyu) |Gye| ang(Gye) |E| |U| |Y| ----------------------------------------------------------------------------------------- 7.01e-01 1.08e+01 -7.45e-02 1.08e+01 -7.38e-02 9.99e-01 9.99e-01 1.08e+01 in matlab you can use: dataNucleo = [... insert measurement data here ...]; g = frd(dataNucleo(:,2).*exp(1i*dataNucleo(:,3)), dataNucleo(:,1), Ts, 'Units', 'Hz'); gcl = frd(dataNucleo(:,4).*exp(1i*dataNucleo(:,5)), dataNucleo(:,1), Ts, 'Units', 'Hz'); if you're evaluating more than one measurement which contain equal frequency points try: dataNucleo = [dataNucleo1; dataNucleo2]; [~, ind] = unique(dataNucleo(:,1),'stable'); dataNucleo = dataNucleo(ind,:); autor: M.E. Peter */ #include "GPA.h" #include "mbed.h" #include "math.h" #define pi 3.1415927f using namespace std; GPA::GPA(float fMin, float fMax, int NfexcDes, int NperMin, int NmeasMin, float Ts, float Aexc0, float Aexc1) { this->NfexcDes = NfexcDes; this->NperMin = NperMin; this->NmeasMin = NmeasMin; this->Ts = Ts; // calculate logarithmic spaced frequency points fexcDes = (float*)malloc(NfexcDes*sizeof(float)); fexcDesLogspace(fMin, fMax, NfexcDes); // calculate coefficients for decreasing amplitude (1/fexc) this->aAexcDes = (Aexc1 - Aexc0)/(1.0f/fexcDes[NfexcDes-1] - 1.0f/fexcDes[0]); this->bAexcDes = Aexc0 - aAexcDes/fexcDes[0]; fnyq = 1/2.0f/Ts; pi2 = 2.0f*pi; pi2Ts = pi2*Ts; piDiv2 = pi/2.0f; sU = (float*)malloc(3*sizeof(float)); sY = (float*)malloc(3*sizeof(float)); reset(); } GPA::~GPA() {} void GPA::reset() { Nmeas = 0; Nper = 0; fexc = 0.0f; fexcPast = 0.0f; ii = 1; // iterating through desired frequency points jj = 1; // iterating through measurement points w.r.t. reachable frequency scaleG = 0.0f; cr = 0.0f; ci = 0.0f; for(int i = 0; i < 3; i++) { sU[i] = 0.0f; sY[i] = 0.0f; } sinarg = 0.0f; NmeasTotal = 0; Aexc = 0.0f; pi2Tsfexc = 0.0f; } float GPA::update(float inp, float out) { // a new frequency point has been reached if(jj == 1) { // get a new unique frequency point while(fexc == fexcPast) { // measurement finished if(ii > NfexcDes) { return 0.0f; } calcGPAmeasPara(fexcDes[ii - 1]); // secure fexc is not higher or equal to nyquist frequency if(fexc >= fnyq) { fexc = fexcPast; } // no frequency found if(fexc == fexcPast) { ii += 1; } else { Aexc = aAexcDes/fexc + bAexcDes; pi2Tsfexc = pi2Ts*fexc; } } fexcPast = fexc; // filter scaling scaleG = 1.0f/sqrt((float)Nmeas); // filter coefficients cr = cos(pi2Tsfexc); ci = sin(pi2Tsfexc); // filter storage for(int i = 0; i < 3; i++) { sU[i] = 0.0f; sY[i] = 0.0f; } } // filter step for signal su sU[0] = scaleG*inp + 2.0f*cr*sU[1] - sU[2]; sU[2] = sU[1]; sU[1] = sU[0]; // filter step for signal sy sY[0] = scaleG*out + 2.0f*cr*sY[1] - sY[2]; sY[2] = sY[1]; sY[1] = sY[0]; // measurement of frequencypoint is finished if(jj == Nmeas) { jj = 1; ii += 1; // calculate the one point dft float Ureal = 2.0f*scaleG*(cr*sU[1] - sU[2]); float Uimag = 2.0f*scaleG*ci*sU[1]; float Yreal = 2.0f*scaleG*(cr*sY[1] - sY[2]); float Yimag = 2.0f*scaleG*ci*sY[1]; // calculate magnitude and angle float Umag = sqrt(Ureal*Ureal + Uimag*Uimag); float Ymag = sqrt(Yreal*Yreal + Yimag*Yimag); float absGyu = Ymag/Umag; float angGyu = atan2(Yimag, Yreal) - atan2(Uimag, Ureal); float absGye = Ymag/Aexc; float angGye = (atan2(Yimag, Yreal) + piDiv2); // user info if(ii == 1) { printLine(); printf(" fexc[Hz] |Gyu| ang(Gyu) |Gye| ang(Gye) |E| |U| |Y|\r\n"); printLine(); } printf("%11.2e %10.2e %10.2e %10.2e %10.2e %10.2e %10.2e %10.2e\r\n", fexc, absGyu, angGyu, absGye, angGye, Aexc, Umag, Ymag); } else { jj += 1; } sinarg = fmod(sinarg + pi2Tsfexc, pi2); NmeasTotal += 1; return Aexc*sin(sinarg); } void GPA::fexcDesLogspace(float fMin, float fMax, int NfexcDes) { // calculate logarithmic spaced frequency points float Gain = log10(fMax/fMin)/((float)NfexcDes - 1.0f); float expon = 0.0f; for(int i = 0; i < NfexcDes; i++) { fexcDes[i] = fMin*pow(10.0f, expon); expon += Gain; } } void GPA::calcGPAmeasPara(float fexcDes_i) { // Nmeas has to be an integer Nper = NperMin; Nmeas = (int)floor((float)Nper/fexcDes_i/Ts + 0.5f); // secure that the minimal number of measurements is fullfilled int Ndelta = NmeasMin - Nmeas; if(Ndelta > 0) { Nper = (int)ceil((float)NmeasMin*fexcDes_i*Ts); Nmeas = (int)floor((float)Nper/fexcDes_i/Ts + 0.5f); } // evaluating reachable frequency fexc = (float)Nper/(float)Nmeas/Ts; } void GPA::printLine() { printf("-----------------------------------------------------------------------------------------\r\n"); } void GPA::printGPAfexcDes() { printLine(); for(int i = 0; i < NfexcDes; i++) { printf("%9.4f\r\n", fexcDes[i]); } } void GPA::printGPAmeasPara() { printLine(); printf(" fexcDes[Hz] fexc[Hz] Aexc Nmeas Nper\r\n"); printLine(); for(int i = 0; i < NfexcDes; i++) { calcGPAmeasPara(fexcDes[i]); if(fexc == fexcPast || fexc >= fnyq) { fexc = 0.0f; Nmeas = 0; Nper = 0; Aexc = 0; } else { Aexc = aAexcDes/fexc + bAexcDes; fexcPast = fexc; } NmeasTotal += Nmeas; printf("%12.2e %9.2e %10.2e %7i %6i \r\n", fexcDes[i], fexc, Aexc, Nmeas, Nper); } printGPAmeasTime(); reset(); } void GPA::printGPAmeasTime() { printLine(); printf(" number of data points: %9i\r\n", NmeasTotal); printf(" measurment time in sec: %9.2f\r\n", (float)NmeasTotal*Ts); }