In this paper a multi－variable fuzzy positional control system has been designed to control the position of the AC server motor and the controlled object Is digital AC serve motor made by Panasonic. Also an Interface card has been designed based on PCI Bus protocol In order to control motor．In this paper another main Job is programming device driver under Windows98 platform using VtoolsD．
Firstly，by moving and circumrotating coordinate switching the complex model of tri－phase AC aosynchronism motor to Magnetization－Torque two axeses，The physical model of AC color Is transformed model of DC motor approximately，It is convenience to control the motor．Analyzing principle of fuzzy control system and part of correlation production provide the foundation for Introducing decoupling theorem on a multi－Input and multi－output fuzzy system Into this paper．By decomposing the whole system Into two sub－control systems， a fuzzy control system has been designed to control AC motor．The experiments about the designed system has shown that it can make the system run stably and reach at the control requirements.
Secondly，on the base of designing hardware circuit to implement measuring the signal of angle displacement of motor accurately，a Interface card has been designed．From the point of view of software and hardware have gone Into particular PCI configuration space and configuration mechanism and have put forward a convenient and shortcut method to operate PCI configuration space．We can find specifically PCI device and then read or write all of the configuration space only using Input／output command．
Finally，the paper also has Introduced the virtual world of Windows and how to map the logical address to physical address In protected mode and the Interrupt mechanism of protected mode，then the paper has illustrated that it is necessary to write virtual device driver （VxD） In order to access hardware device from the third level． That is the device driver Is a medium for program to access hardware device．
After all that the paper has gone into particular how to write device driver under Windows98 platform using VtoolsD consequently finished the whole development of the software and set up with a friendly Interface of man—machine．
Keywords： multi－variable； fuzzy control； AC serve motor； PCI Bus； device driver
