docs: function( dt ){
  
              if ( dt === true ){
                  // force sleep
                  this.asleep = true;
  
              } else if ( dt === false ){
                  // force wakup
                  this.asleep = false;
                  this._sleepMeanK = 0;
                  this._sleepAngPosMean = 0;
                  this._sleepAngPosVariance = 0;
                  this._sleepPosMean.zero();
                  this._sleepPosVariance.zero();
                  this.sleepIdleTime = 0;
  
              } else if ( dt && !this.asleep ) {
  
                  this.sleepCheck( dt );
              }
  
              return this.asleep;
          }