3 phase BLDC sinusoidal drive using PWM controller and/or DSP?
A single UC1825 is not capable of driving a 3 phase motor. 
You could perhaps build a controller with 3 * UC1825, with one for each phase of the BLDC. However the complexity of using such an solution would seem hardly worth the efforts.

I'd suggest you read this great application note from TI using an MSP430 to generate the PWM signals as a starting point.
How you proceed will depend on whether you have Hall Effect sensors on your current motors, or are constrained to build a sensorless driver solution.  

You would definitely be better purchasing a BLDC integrated servo to simplify your task.
I'd recommend you look at Teknic's Clearpath-SDSK servo as a potential plug in replacement for your BLDC motors. This gives you a simple Step/Dir interface and would relieve you of much work designing your own solution.