ZERO PHASE ERROR TRACKING CONTROLLERS WITH OPTIMAL GAIN CHARACTERISTICS

Recently, a digital feedforward controller, called a Zero Phase Error Tracking Controller (ZPETC), has been proposed. In this controller, th e overall frequency response between the desired output and the contro lled output exhibits zero phase shift for all frequencies by using a f ew steps of the future desired output data. In this paper, two extensi ons of ZPETCs are proposed: a ZPETC with deadbeat tracking performance and an L2-Optimal ZPETC. These ZPETCs can provide the overall control system with not only the above phase property but also the excellent tracking performance for a desired output and the superior gain proper ty, respectively. Moreover, a ZPETC with both the excellent tracking p erformance for a step-type and ramp-type desired output and the superi or gain property, called an L2-Optimal ZPETC with deadbeat tracking pe rformance, is presented.