High Power Permanent Magnet DC Motor Controller
The requirement in motor control besides commutation timing, and controls for torque and direction is to decide the cost tradeoff for power losses during stall current.  


This is often 8x the rated current at full load. 
This is peak current when starting/stopping motor at full torque
Consider that 8x 18A x= 144 A implies the motor DCR = 24C/144 A = 167 mΩ
Motor losses then start at Pd=I²*DCR = 144²*167mΩ =3.5kW assuming 0 Ω bridge
Switching Bridge losses then rise with RdsOn and torque reduces.


I prefer to start with a budget of RdsOn =1% of DCR of motor then decide if that suits requirements and budget.

Thus RdsOn= &lt;=1.67mΩ and Ip=144A for x duration.