In the area of parallel robots, the use of lower-mobility parallel manipulators for many tasks re quiring fewer than six degrees of freedom has drawn a lot of interest. This paper work focuses on the modeling and simulation of 3 - UPS (Universal - Prismatic - Spherical), 3 - RPS (Revolute - Prismatic - Spherical) and 3 - RPR Tripod Parallel Manipulator units. This tripod mechanism consists of base platform and movable platform, which are connected by means of three links or limbs. Spherical joints / revolute joints are used to connect one end of the link and the moving platform and the other end of the link is connected by universal joint to the half nut. This tripod type Parallel Manipulator is having two orientation freedoms and one translation freedom, which is actuated by means of screw pair, which in turn is operated by a stepper motor. The Parallel Manipulator is modeled and simulated by using ADAMS®. The simulation results are obtained by considering the geometrical parameters, Transmission angle of the link and Singularity of the mechanism. From the simulation results a comparative study is carried out based on torque at the joints, angular tilt, positional accuracy and performance of the parallel manipulator. © 2010 IEEE.