**5. Experiments**

As shown in Fig. 2, the actual experiment platform is a 2-DOF parallel manipulator with redundant actuation designed by Googol Tech. Ltd. in Shenzhen, China. It is equipped with three permanent magnet synchronous servo motors with harmonic gear drives. The active joint angles are measured with absolute optical-electrical encoders. The nonlinear dynamic controllers and the friction compensation method are programmed with the Visual C++, and the algorithms run on a Pentium III CPU at 733MHz. with the sampling period 2ms.

Fig. 2. The prototype of the 2-DOF parallel manipulator with redundant actuation
