How to implement ion acceleration and deceleration in stepper motor?
One define max acceleration,g and max velocity,v based on step rate and motor torque and load. 


g and v max must be discovered by trial and error with max loads for given pulley size, step rate steps /rev ,  voltage,current , and thus torque which declines with velocity.


I used a constant g max and constant v max for both directions to reach up to v= 1m/s in x or y=0.5m with no load on 8mm pulleys using 12V on NEMA17 2A for an XY Gantry.


but I used both an STM Gcode board and then switched to an UNO with CNC shield and GCode Panel(free) for WIndows with full steps. THe software did all the calculations.
it was the best for my application. Pulse step rate was 100kHz max 1us for Fwd/Reverse.