It can be controlled by the PWM technique to give proper commutations so that two of the three phases are with on states and the remaining one is with floating state.

you can control BDPM using field orientation (vector control) technique with either a space vector modulation (SVM) or Pulse width Modulation (PWM)

The following thesis may be useful for you

http://webfiles.portal.chalmers.se/et/MSc/BaldurssonStefanMSc.pdf

Thanks for your response is it possible open loop bldc torque and speed control at lower speeds  (1500 rpm) ?

At my lab I am doing an experiment on  bldc  open loop speed control. 

at no load and full load speed control motor will getting heated.  

At the output terminal I am observed  output  waveform are given bellow.