Having implemented a nested PID controller using fixed-point arithmetic in an FPGA, I can tell you that fixed-point is a pain in the ass, and you only use it wh

Having implemented a nested PID controller using fixed-point arithmetic in an FPGA, I can tell you that fixed-point is a pain in the ass, and you only use it when floating-point is too slow, too large (in terms of on-chip resources), or consumes too much power, or when you really need to control the precision going into and out of an arithmetic operation.