Add actuator and sensor delays. Fixes #1004

PiperOrigin-RevId: 866478839
Change-Id: Id21a6da0f98454c8fa39ea5af8a5e213d6eae497

include/mujoco/mjspec.h

@@ -698,6 +698,9 @@ typedef struct mjsActuator_ {      // actuator specification
 
   // other
   int group;                       // group
+  int nsample;                     // number of samples in history buffer
+  int interp;                      // interpolation order (0=ZOH, 1=linear, 2=cubic)
+  double delay;                    // delay time in seconds; 0: no delay
   mjDoubleVec* userdata;           // user data
   mjsPlugin plugin;                // actuator plugin
   mjString* info;                  // message appended to compiler errors
@@ -724,6 +727,12 @@ typedef struct mjsSensor_ {        // sensor specification
   double cutoff;                   // cutoff for real and positive datatypes
   double noise;                    // noise stdev
 
+  // history buffer
+  int nsample;                     // number of samples in history buffer
+  int interp;                      // interpolation order (0=ZOH, 1=linear, 2=cubic)
+  double delay;                    // delay time in seconds
+  double interval[2];              // [period, time_prev] in seconds
+
   // other
   mjDoubleVec* userdata;           // user data
   mjsPlugin plugin;                // sensor plugin