Local Control System of the Elliptically Polarized Undulator at SSRF

The Shanghai Synchrotron Radiation Facility (SSRF) is a third-generation light source with major emphasis on insertion device (ID) sources. In the storage ring there are 20 straight sections, each about six or ten meters in length, for possible insertion devices. Currently there installed three undulators and two wiggler installed in five straight sections. They were originally designed and fabricated by the Shanghai Institute of Applied Physics (SINAP). A variable polarizing undulator was constructed as the light source of the soft X-rays beamline for SSRF. This local control system consists of a Siemens PLC and a six axis Masterdrive motion controller. Four servo motors control the gap - two on the upper girder and two on the lower girder, and another two servos controls the phase - one on the upper girder outer and one on the lower girder inner. The main control system at the SSRF is experimental physics and industrial control system (EPICS). This paper will discuss in detail the design philosophy and the implementation of the Six-motor insertion device control system. This control system has been in operation for about one year.