Updates from Tony.

src/FDM/LaRCsim/c172_aero.c

@@ -239,14 +239,15 @@ void aero( SCALAR dt, int Initialize ) {
   {  Weight=1500; }
   
   
-  if(Dx_cg > 0.5586)
+  if(Dx_cg > 0.43)
-  {  Dx_cg = 0.5586; }
+  {  Dx_cg = 0.43; }
-  else if(Dx_cg < -0.4655)
+  else if(Dx_cg < -0.6)
-  {  Dx_cg = -0.4655; }
+  {  Dx_cg = -0.6; }
   
-  Cg=Dx_cg/cbar +0.25;
+  Cg=0.25 - Dx_cg/cbar;
   
   Dz_cg=Zcg*cbar;
+  Dy_cg=0;
   
 
   if(Flap_handle < flap_ind[0])

src/FDM/LaRCsim/c172_aero.h

@@ -66,10 +66,13 @@
 
   
   SCALAR elevator, aileron, rudder;
+
   
   SCALAR Flap_Position;
-  /* float Flap_Handle; */
+ 
   int Flaps_In_Transit;
   
+
+
 #endif
 

src/FDM/LaRCsim/c172_gear.c

@@ -36,8 +36,8 @@
 
 $Header$
 $Log$
-Revision 1.11  1999/11/15 22:54:07  curt
+Revision 1.12  1999/12/08 18:48:55  curt
-Updates from Tony, mostly to landing gear.
+Updates from Tony.
 
 
 ----------------------------------------------------------------------------
@@ -113,28 +113,31 @@ clear3( DATA v[] )
 gear()
 {
 char rcsid[] = "$Id$";
-char gear_strings[3][12]={"nose","right main", "left main"};
+#define NUM_WHEELS 4
+char gear_strings[NUM_WHEELS][12]={"nose","right main", "left main", "tail skid"};
   /*
    * Aircraft specific initializations and data goes here
    */
    
-#define NUM_WHEELS 3
 
     static int num_wheels = NUM_WHEELS;		    /* number of wheels  */
-    static DATA d_wheel_rp_body_v[NUM_WHEELS][3] =  /* X, Y, Z locations */
+    static DATA d_wheel_rp_body_v[NUM_WHEELS][3] =  /* X, Y, Z locations,full extension */
     {
-	{ 5,  0., 7.0 },				/*nose*/ /* in feet */
+	{  3.91,  0.,   6.67 },		   /*nose*/ /* in feet */
-	{ -2.0,  3.6, 6.5 },        /*right main*/
+	{ -1.47,  3.58, 6.71 },        /*right main*/
-	{ -2.0, -3.6, 6.5 }         /*left main*/ 
+	{ -1.47, -3.58, 6.71 },        /*left main*/ 
+	{ -15.67, 0, 2.42 }            /*tail skid */
     };
+	static DATA gear_travel[NUM_WHEELS] = /*in Z-axis*/
+	{ -0.5, 2.5, 2.5, 0};
     static DATA spring_constant[NUM_WHEELS] =	    /* springiness, lbs/ft */
-	{ 1500., 5000., 5000. };
+	{ 1200., 900., 900., 10000. };
     static DATA spring_damping[NUM_WHEELS] =	    /* damping, lbs/ft/sec */
-	{ 1000.,  1500.,  1500. };		
+	{ 200.,  300., 300., 400. };	
     static DATA percent_brake[NUM_WHEELS] =	    /* percent applied braking */
-	{ 0.,  0.,  0. };			    /* 0 = none, 1 = full */
+	{ 0.,  0.,  0., 0. };			    /* 0 = none, 1 = full */
     static DATA caster_angle_rad[NUM_WHEELS] =	    /* steerable tires - in */
-	{ 0., 0., 0.};				    /* radians, +CW */	
+	{ 0., 0., 0., 0};				    /* radians, +CW */	
   /*
    * End of aircraft specific code
    */
@@ -159,9 +162,10 @@ char gear_strings[3][12]={"nose","right main", "left main"};
      */
   
   
-    static DATA sliding_mu   = 0.5;	
+    static int it_rolls[NUM_WHEELS] = { 1,1,1,0};	
-    static DATA rolling_mu   = 0.01;	
+	static DATA sliding_mu[NUM_WHEELS] = { 0.5, 0.5, 0.5, 0.3};	
-    static DATA max_brake_mu = 0.6;	
+    static DATA rolling_mu[NUM_WHEELS] = { 0.01, 0.01, 0.01, 0.0}; 	
+    static DATA max_brake_mu[NUM_WHEELS] ={ 0.0, 0.6, 0.6, 0.0};	
     static DATA max_mu	     = 0.8;	
     static DATA bkout_v	     = 0.1;
     static DATA skid_v       = 1.0;
@@ -172,9 +176,12 @@ char gear_strings[3][12]={"nose","right main", "left main"};
     DATA d_wheel_cg_body_v[3];		/* wheel offset from cg,  X-Y-Z	*/
     DATA d_wheel_cg_local_v[3];		/* wheel offset from cg,  N-E-D	*/
     DATA d_wheel_rwy_local_v[3];	/* wheel offset from rwy, N-E-U */
+	DATA v_wheel_cg_local_v[3];    /*wheel velocity rel to cg N-E-D*/
     DATA v_wheel_body_v[3];		/* wheel velocity,	  X-Y-Z	*/
     DATA v_wheel_local_v[3];		/* wheel velocity,	  N-E-D	*/
     DATA f_wheel_local_v[3];		/* wheel reaction force,  N-E-D	*/
+	DATA altitude_local_v[3];       /*altitude vector in local (N-E-D) i.e. (0,0,h)*/
+	DATA altitude_body_v[3];        /*altitude vector in body (X,Y,Z)*/
     DATA temp3a[3], temp3b[3], tempF[3], tempM[3];	
     DATA reaction_normal_force;		/* wheel normal (to rwy) force	*/
     DATA cos_wheel_hdg_angle, sin_wheel_hdg_angle;	/* temp storage */
@@ -207,17 +214,24 @@ char gear_strings[3][12]={"nose","right main", "left main"};
     {
 		/* printf("%s:\n",gear_strings[i]); */
 
+
+
 		/*========================================*/
 		/* Calculate wheel position w.r.t. runway */
 		/*========================================*/
 
-	    	/* First calculate wheel location w.r.t. cg in body (X-Y-Z) axes... */
+		
+		/* printf("\thgcg: %g, theta: %g,phi: %g\n",D_cg_above_rwy,Theta*RAD_TO_DEG,Phi*RAD_TO_DEG); */
+
+		
+			/* First calculate wheel location w.r.t. cg in body (X-Y-Z) axes... */
 
 		sub3( d_wheel_rp_body_v[i], D_cg_rp_body_v, d_wheel_cg_body_v );
 
 	    	/* then converting to local (North-East-Down) axes... */
 
 		multtrans3x3by3( T_local_to_body_m,  d_wheel_cg_body_v, d_wheel_cg_local_v );
+		
 
 	    	/* Runway axes correction - third element is Altitude, not (-)Z... */
 
@@ -241,11 +255,11 @@ char gear_strings[3][12]={"nose","right main", "left main"};
 
 	    	/* transform into local axes */
 
-		multtrans3x3by3( T_local_to_body_m, temp3a, temp3b );
+		multtrans3x3by3( T_local_to_body_m, temp3a,v_wheel_cg_local_v );
 
 	    	/* plus contribution due to cg velocities */
 
-		add3( temp3b, V_local_rel_ground_v, v_wheel_local_v );
+		add3( v_wheel_cg_local_v, V_local_rel_ground_v, v_wheel_local_v );
 
 		clear3(f_wheel_local_v);
 		reaction_normal_force=0;
@@ -271,25 +285,36 @@ char gear_strings[3][12]={"nose","right main", "left main"};
 					 + v_wheel_local_v[1]*sin_wheel_hdg_angle;
 			v_wheel_sideward = v_wheel_local_v[1]*cos_wheel_hdg_angle
 					 - v_wheel_local_v[0]*sin_wheel_hdg_angle;
-
+			
+	            
 	    	/* Calculate normal load force (simple spring constant) */
 
 	    	reaction_normal_force = 0.;
-
+        
-	    	reaction_normal_force = spring_constant[i]*HEIGHT_AGL_WHEEL
+	    	reaction_normal_force = spring_constant[i]*d_wheel_rwy_local_v[2]
 					  - v_wheel_local_v[2]*spring_damping[i];
+			/* printf("\treaction_normal_force: %g\n",reaction_normal_force); */
+
 	    	if (reaction_normal_force > 0.) reaction_normal_force = 0.;
 			/* to prevent damping component from swamping spring component */
 
 
 	    	/* Calculate friction coefficients */
 
-			forward_mu = (max_brake_mu - rolling_mu)*percent_brake[i] + rolling_mu;
+			if(it_rolls[i])
-			abs_v_wheel_sideward = sqrt(v_wheel_sideward*v_wheel_sideward);
+			{
-			sideward_mu = sliding_mu;
+			   forward_mu = (max_brake_mu[i] - rolling_mu[i])*percent_brake[i] + rolling_mu[i];
-			if (abs_v_wheel_sideward < skid_v) 
+			   abs_v_wheel_sideward = sqrt(v_wheel_sideward*v_wheel_sideward);
-	    		sideward_mu = (abs_v_wheel_sideward - bkout_v)*beta_mu;
+			   sideward_mu = sliding_mu[i];
-			if (abs_v_wheel_sideward < bkout_v) sideward_mu = 0.;
+			   if (abs_v_wheel_sideward < skid_v) 
+	    		   sideward_mu = (abs_v_wheel_sideward - bkout_v)*beta_mu;
+			   if (abs_v_wheel_sideward < bkout_v) sideward_mu = 0.;
+			}
+			else
+			{
+				forward_mu=sliding_mu[i];
+				sideward_mu=sliding_mu[i];
+			}	   
 
 	    		/* Calculate foreward and sideward reaction forces */
 
@@ -324,8 +349,9 @@ char gear_strings[3][12]={"nose","right main", "left main"};
 
 
 
-		/* printf("\tN: %g,dZrwy: %g\n",reaction_normal_force,HEIGHT_AGL_WHEEL);
+		/* printf("\tN: %g,dZrwy: %g dZdotrwy: %g\n",reaction_normal_force,HEIGHT_AGL_WHEEL,v_wheel_cg_local_v[2]); */
-		printf("\tFxgear: %g Fygear: %g, Fzgear: %g\n",F_X_gear,F_Y_gear,F_Z_gear);
+
+		/*printf("\tFxgear: %g Fygear: %g, Fzgear: %g\n",F_X_gear,F_Y_gear,F_Z_gear);
 		printf("\tMgear: %g, Lgear: %g, Ngear: %g\n\n",M_m_gear,M_l_gear,M_n_gear); */
 
 

src/FDM/LaRCsim/c172_init.c

@@ -73,7 +73,11 @@ void model_init( void ) {
   I_zz=1967;
   I_xz=0;
 
+
   Flap_Position=Flap_handle;
   Flaps_In_Transit=0;
+
+
+  
   
 }

src/FDM/LaRCsim/c172_main.c

@@ -38,9 +38,6 @@
 #include <stdio.h>
 #include <string.h>
 
-
-
-
 void do_trims(int kmax,FILE *out,InitialConditions IC)
 {
 	int bad_trim=0,i,j;
@@ -216,14 +213,77 @@ int fgLaRCsimInit(double dt) {
     return(1);
 }
 
-
+int wave_stats(float *var,float *var_rate,int N,FILE *out)
+{	
+	int Nc,i,Nmaxima;
+	float varmax,slope,intercept,time,ld,zeta,omegad,omegan;
+	float varmaxima[100],vm_times[100];
+	/*adjust N so that any constant slope region at the end is cut off */
+	i=N;
+	while((fabs(var_rate[N]-var_rate[i]) < 0.1) && (i >= 0))
+	{ 
+       i--;
+	}
+	Nc=N-i;
+	slope=(var[N]-var[Nc])/(N*0.01 - Nc*0.01);
+	intercept=var[N]-slope*N*0.01;
+	printf("\tRotating constant decay out of data using:\n");
+	printf("\tslope: %g, intercept: %g\n",slope,intercept);	
+	printf("\tUsing first %d points for dynamic response analysis\n",Nc);
+	varmax=0;
+	Nmaxima=0;i=0;
+	while((i <= Nc) && (i <= 801))
+	{
+		
+		fprintf(out,"%g\t%g",i*0.01,var[i]);
+		var[i]-=slope*i*0.01+intercept;
+		/* printf("%g\n",var[i]); */
+        fprintf(out,"\t%g\n",var[i]);
+		if(var[i] > varmax)
+	    {
+		   varmax=var[i];
+		   time=i*0.01;
+		   
+		}   
+	    if((var[i-1]*var[i] < 0) && (var[i] > 0))
+		{
+		   varmaxima[Nmaxima]=varmax;
+		   vm_times[Nmaxima]=time;
+		   printf("\t%6.2f: %8.4f\n",vm_times[Nmaxima],varmaxima[Nmaxima]);
+		   varmax=0;Nmaxima++;
+		   
+		}   
+		
+		i++;
+    }	  			
+	varmaxima[Nmaxima]=varmax;
+    vm_times[Nmaxima]=time;
+    Nmaxima++;
+	if(Nmaxima > 2)
+	{
+	  ld=log(varmaxima[1]/varmaxima[2]);   //logarithmic decrement
+	  zeta=ld/sqrt(4*PI*PI +ld*ld);        //damping ratio
+	  omegad=1/(vm_times[2]-vm_times[1]);  //damped natural frequency Hz
+	  if(zeta < 1)
+	  {
+	  	omegan=omegad/sqrt(1-zeta*zeta);   //natural frequency Hz
+	  }	
+	  printf("\tDamping Ratio: %g\n",zeta);
+	  printf("\tDamped Freqency: %g Hz\n\tNatural Freqency: %g Hz\n",omegad,omegan);
+	}
+	else
+	  printf("\tNot enough points to take log decrement\n");  
+/* 	printf("w: %g, u: %g, q: %g\n",W_body,U_body,Q_body);
+ */
+	return 1;
+}	
 
 // Run an iteration of the EOM (equations of motion)
 int main(int argc, char *argv[]) {
     
 	
 	double save_alt = 0.0;
-    int multiloop=1,k=0,i,j;
+    int multiloop=1,k=0,i,j,touchdown,N;
 	double time=0,elev_trim,elev_trim_save,elevator,speed,cmcl;
 	FILE *out;
 	double hgain,hdiffgain,herr,herrprev,herr_diff,htarget;
@@ -232,7 +292,8 @@ int main(int argc, char *argv[]) {
     SCALAR *control[7];
 	SCALAR *state[7];
 	float old_state,effectiveness,tol,delta_state,lctrim;
-	float newcm,lastcm,cmalpha;
+	float newcm,lastcm,cmalpha,td_vspeed,td_time,stop_time;
+	float h[801],hdot[801],altmin,lastAlt,theta[800],theta_dot[800];
 	
     if(argc < 6)
 	{
@@ -252,31 +313,92 @@ int main(int argc, char *argv[]) {
 	IC.beta=0;
 	IC.theta=strtod(argv[3],NULL);
 	IC.use_gamma_tmg=0;
-	IC.phi=strtod(argv[4],NULL);
+	IC.phi=0;
 	IC.psi=0;
 	IC.weight=2400;
 	IC.cg=0.25;
-	IC.flap_handle=0;
+	IC.flap_handle=30;
 	IC.long_control=0;
 	IC.rudder_pedal=0;
     
-	printf("IC.vc: %g\n",IC.vc);
+	
 	ls_ForceAltitude(IC.altitude);  
     fgLaRCsimInit(0.01);
 	setIC(IC);
+	printf("Dx_cg: %g\n",Dx_cg);
+	V_down=strtod(argv[4],NULL);;
 	ls_loop(0,-1);
-	printf("\nAltitude: %g\n\n",Altitude);
+	i=0;time=0;
-	i=0;
+	IC.long_control=0;
-	while(i <= 1) 
+	altmin=Altitude;
+    printf("\tAltitude: %g, Theta: %g, V_down: %g\n\n",Altitude,Theta*RAD_TO_DEG,V_down);
+    
+	printf("%12s %10s %10s\n","Alpha (deg)","Alpha","Drag");
+	for(i=-5;i<=22;i++)
+	{
+		IC.alpha=i;
+		setIC(IC);
+		ls_loop(0,-1);
+		printf("%12f %10f %10f\n",Alpha*RAD_TO_DEG,Alpha,cd);
+	}	
+		
+	
+	
+	
+	/*out=fopen("drop.out","w");
+	N=800;touchdown=0;
+	
+	while(i <= N) 
 	{ 
-	  if(i > 0)
+	  ls_update(1);
-	     Brake_pct=1;
+	  printf("\tAltitude: %g, Theta: %g, V_down: %g\n\n",D_cg_above_rwy,Theta*RAD_TO_DEG,V_down);
-	  ls_update(1); 
+	  fprintf(out,"%g\t%g\t%g\t%g\t%g\t%g\n",time,D_cg_above_rwy,Theta*RAD_TO_DEG,V_down,F_Z_gear/1000.0,V_rel_ground);
-	  printf("\tAltitude: %g, Theta: %g, Phi: %g\n\n",Altitude,Theta*RAD_TO_DEG,Phi*RAD_TO_DEG);
+	  h[i]=D_cg_above_rwy;hdot[i]=V_down;
+	  theta[i]=Theta; theta_dot[i]=Theta_dot;
+	  if(D_cg_above_rwy < altmin)
+	  	altmin=D_cg_above_rwy;
+	  if((F_Z_gear < -10) && (! touchdown))
+	  {
+	  	 	touchdown=1;
+			td_vspeed=V_down;
+			td_time=time;
+	  }
+	  time+=0.01; 	
 	  i++; 
 	}
-	printf("w: %g, u: %g, q: %g\n",W_body,U_body,Q_body);
+	while(V_rel_ground > 1)
-    
+	{
+		if(Brake_pct < 1)
+		{
+		   Brake_pct+=0.02;
+		}   
+		ls_update(1);
+		time=i*0.01;
+	    fprintf(out,"%g\t%g\t%g\t%g\t%g\t%g\n",time,D_cg_above_rwy,Theta*RAD_TO_DEG,V_down,F_Z_gear/1000.0,V_rel_ground);
+		i++;
+    }
+	stop_time=time;
+    while((time-stop_time) < 5.0)
+	{
+		ls_update(1);
+		time=i*0.01;
+	    fprintf(out,"%g\t%g\t%g\t%g\t%g\t%g\n",time,D_cg_above_rwy,Theta*RAD_TO_DEG,V_down,F_Z_gear/1000.0,V_rel_ground);
+		i++;
+	}		
+	fclose(out);
+	
+	printf("Min Altitude: %g, Final Alitutde: %g, Delta: %g\n",altmin, h[N],  D_cg_above_rwy-altmin);
+	printf("Vertical Speed at touchdown: %g, Time at touchdown: %g\n",td_vspeed,td_time);
+    printf("\nAltitude response:\n");
+	out=fopen("alt.out","w");
+	wave_stats(h,hdot,N,out);
+	fclose(out);
+	out=fopen("theta.out","w");
+	printf("\nPitch Attitude response:\n");
+	wave_stats(theta,theta_dot,N,out);
+    fclose(out);*/
+
+
 
 	/*printf("Flap_handle: %g, Flap_Position: %g\n",Flap_handle,Flap_Position);
 	printf("k: %d, %g knots, %g lbs, %g %%MAC\n",k,V_calibrated_kts,Weight,Cg);