Tham khảo tài liệu 'advances in robot kinematics - jadran lenarcic and bernard roth (eds) part 16', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | On PKM with Articulated Travelling-plate 449 has a constant direction with respect to a fixed frame the second axis is orthogonal to the first one. A detailed kinematic analysis is carried out and leads to geometrical conditions to be verified by the mechanism for proper functioning. Then a kinematic modelling illustrates the mechanism simplicity and provides a first evaluation of the machine s workspace. Finally preliminary information is given regarding practical implementation of this new architecture. General Concept The proposed machine is a 6-actuator 5-dof parallel mechanism. In Fig. 1 a joint-and-loop graph is depicted grey boxes represent actuated joints white boxes passive joints and circles express a kinematic coupling between two joints. As for Delta and H4 architectures the actuators are fixed on the base. Actuators may be rotational or linear one S-joint per chain may be replaced by U-joint to get rid of internal motions . One must notice the machine s symmetrical architecture the machine s upper and lower parts are identically made of a spatial-parallelogram and two single rods. Each single rod is connected to the spatial parallelogram . Note that in a general matter the spatial-parallelogram chains that is the P SS 2 chains only add one constraint on a mechanism 3 translations and 2 rotations remain feasible while a spatial-parallelogram made of PR RR 2R chains as done on the Orthoglide see Chablat et al. 2002 adds two constraints on the mechanism 3 translations and 1 rotation remain feasible . 450 S. Krut et al. The travelling plate is the one introduced in Krut et al. 2003 with the I4L robot while the two sub-parts shift one relatively to the other a mechanical device transforms this motion into a rotation. Two types of travelling plates exist see Fig. 3 Type 1 is made of two prismatic joints and two kinematically coupled rack-and-pinion systems. It has a symmetrical design which is good for balancing the loads among all the parts. Type 2 is .