DSP控制无刷直流电机例程BLDC3_1中pid_reg3.h有些问题请教各位大佬

#ifndef __PIDREG3_H__
#define __PIDREG3_H__

typedef struct {  _iq  Ref;      // Input: Reference input
      _iq  Fdb;      // Input: Feedback input
      _iq  Err;    // Variable: Error
      _iq  Kp;    // Parameter: Proportional gain
      _iq  Up;    // Variable: Proportional output
      _iq  Ui;    // Variable: Integral output
      _iq  Ud;    // Variable: Derivative output  
      _iq  OutPreSat;   // Variable: Pre-saturated output
      _iq  OutMax;      // Parameter: Maximum output
      _iq  OutMin;      // Parameter: Minimum output
      _iq  Out;      // Output: PID output
      _iq  SatErr;   // Variable: Saturated difference
      _iq  Ki;       // Parameter: Integral gain
      _iq  Kc;        // Parameter: Integral correction gain
      _iq  Kd;           // Parameter: Derivative gain
      _iq  Up1;          // History: Previous proportional output
        void  (*calc)();    // Pointer to calculation function
     } PIDREG3;            

typedef PIDREG3 *PIDREG3_handle;
/*-----------------------------------------------------------------------------
Default initalizer for the PIDREG3 object.
-----------------------------------------------------------------------------*/                    
#define PIDREG3_DEFAULTS { 0, \
                           0, \
                           0, \
                           _IQ(1.3), \
                           0, \
                           0, \
                           0, \
                           0, \
                           _IQ(1), \
                           _IQ(-1), \
                           0, \
                           0, \
                           _IQ(0.02), \
                           _IQ(0.5), \
                           _IQ(1.05), \
                           0, \
                   (void (*)(Uint32))pid_reg3_calc }

/*------------------------------------------------------------------------------
Prototypes for the functions in PIDREG3.C
------------------------------------------------------------------------------*/
void pid_reg3_calc(PIDREG3_handle);

#endif // __PIDREG3_H__

大佬们，我有几个问题如下：

1：_iq  Fdb和_IQ(1.3)这类的语句是什么意思呢，我知道是IQMATH里定义的奈何百度了几天都不清楚，头文件IQmath.h里几千行语句看到我眼花缭乱，头大如斗=.=；

2：(void (*)(Uint32))pid_reg3_calc请问大佬们这句是什么意思呢；

3：PIDREG3_DEFAULTS为什么这样定义呢？每行之间的   \    是什么作用呢？

谢谢各位大佬的帮助，小弟在此拜谢！！！