pid.h Source File

00001 #ifndef PID_H
00002 #define PID_H
00003 
00004 /*
00005    pid.h
00006 
00007    Decls for PID control law data structure and class
00008 
00009    Modification history:
00010 
00011    6-Jul-2001  FMP removed decls for the useless functions pidGetCycleTime(),
00012    pidGetGains().
00013     7-Nov-2000 WPS added lastSetPoint_was_set flag.
00014    13-Jul-2000 WPS added some hacks surrounded by THROWAWAY_CUMULATIVE_ERROR_ON_SIGN_CHANGES and SMOOTH_D_FACTOR
00015    13-Mar-2000 WPS added unused attribute to pid_h to avoid 'defined but not used' compiler warning.
00016    24-Feb-2000  FMP added deadband
00017    18-Aug-1998  FMP took out reverse gains, added bias
00018    5-Jun-1998   FMP added reverse gains
00019    14-Apr-1998  FMP added backlash
00020    18-Dec-1997  FMP took out C++ interface
00021    19-Nov-1997  FMP added ff2
00022    16-Oct-1997  FMP changed vf, af to ff0, ff1
00023    15-Aug-1997  FMP added maxError
00024    01-Aug-1997  FMP added lastOutput to PID_STRUCT; added pidReset()
00025    24-Apr-1997  FMP added pidIniLoad(); removed inifile
00026    17-Apr-1997  FMP split into C/C++ sections
00027 */
00028 
00029 /* ident tag */
00030 #ifndef __GNUC__
00031 #ifndef __attribute__
00032 #define __attribute__(x)
00033 #endif
00034 #endif
00035 
00036 /* Uncomment these lines if you like these mathematically impure effects. */
00037 /* #define  SMOOTH_D_FACTOR */
00038 /* #define THROWAWAY_CUMULATIVE_ERROR_ON_SIGN_CHANGES */
00039 
00040 static char __attribute__((unused)) pid_h[] = "$Id: pid.h,v 1.6 2001/07/06 21:50:05 proctor Exp $";
00041 
00042 typedef struct
00043 {
00044   double p;                     /* proportional gain, volts/unit */
00045   double i;                     /* integral gain, volts/unit */
00046   double d;                     /* derivative gain, volts/unit per sec */
00047   double ff0;                   /* 0th order feedforward, volts/unit */
00048   double ff1;                   /* 1st order feedforward, volts/unit/sec */
00049   double ff2;                   /* 2nd order feedforward, volts/unit/sec^2 */
00050   double backlash;              /* backlash */
00051   double bias;                  /* bias for gravity comp, for example */
00052   double maxError;              /* ceiling for cumError */
00053   double deadband;              /* delta below which error is deemed to be 0 */
00054   double cycleTime;             /* copy of arg to setCycleTime() */
00055   double error;                 /* error this cycle */
00056   double lastError;             /* last error computed */
00057   double lastSetpoint;          /* last setpoint received */
00058   double lastOutput;            /* last value output */
00059   double lastSetpointDot;       /* delta setpoint / delta t */
00060   double cumError;              /* cumulative error, all cycles */
00061   int configured;               /* configure flags */
00062 #ifdef SMOOTH_D_FACTOR
00063 #define MAX_ERROR_WINDOW 4
00064   double oldErrors[MAX_ERROR_WINDOW]; /* This is a ring buffer that stores the
00065                                          last MAX_ERROR_WINDOW errors. */
00066   double errorWindowFactors[MAX_ERROR_WINDOW];/* Weights to use in smoothing
00067                                                  error factors. */
00068   int errorIndex; /* Index into the oldErrors ring buffer. */
00069 #endif
00070   int lastSetpoint_was_set; /* true when lastSetpoint is valid. */
00071 
00072 } PID_STRUCT;
00073 
00074 extern int pidInit(PID_STRUCT * pid);
00075 extern int pidReset(PID_STRUCT * pid);
00076 extern int pidSetCycleTime(PID_STRUCT * pid, double seconds);
00077 extern int pidSetGains(PID_STRUCT * pid, PID_STRUCT parameters);
00078 extern double pidRunCycle(PID_STRUCT * pid, double sample, double setpoint);
00079 extern int pidIniLoad(PID_STRUCT * pid, const char * filename);
00080 
00081 #endif /* PID_H */