The traditional lumped modeling method in 2 degree of freedoms of a bi-driven high-speed ball screw system can not accurately characterize the high frequency mechanical resonance, which usually limits the dynamic performance of the system. This paper proposes a hybrid parameter modeling method for the bi-driven system. The workbench is modeled with lumped method in 3 degree of freedoms considering the physical dimension of the workbench and the installation location of the ball-nut and slider. The ball screw is modeled with a novel distributed parameter approach with the boundary conditions of the thrust bearings and coupling to describe its elastic characteristics. The ball screw model is integrated into the workbench one to construct a hybrid one, which is optimized by simulation on a typical test bed. The optimized model ignores unimportant parameters of the workbench one and reduces the order of the ball screw one. Compared with the experiment, the optimized hybrid model accurately characterizes both the workbench and ball screw resonance frequency of the bi-driven ball screw system.
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