Locked Anti-Phase Servo

[ifsercon]

Hi
I want to build a Locked Anti-Phase Servo with brushed DC Motor
with dual power supply( +/- 24v for DC motor , 2 isolated 12v for driving).

For testing I'll use a 20 KHz 555 PWM Generator.
Opto are 2x HCPL 2630 not PC817.
MOSFET will have diodes augmentation and big VDSS(... and rdson)
I could not find something useful on Internet so I have a question:
- how should motor current be read for start/stall conditions?

Please tell me any idea or links about this type of circuit
Sorry for my english...

Florin