Development and construction if a novel parallel manipulator with a degree of freedom of five (PENTAPOD)

High rigidity and good dynamic properties predestine handling devices with parallel kinematic structures, also known as PKM (Parallel Kinematics Manipulator), for solving a large number of practical handling tasks. For rotationally symmetric production tasks - e. g. drilling or milling - the rotation around the normal axis to the platform is unnecessary. The relatively unexplored PKMs with a degree of freedom of five are more suitable here, not least for cost and control reasons. Figure 1 shows a promising PKM for both manufacturing and positioning tasks.

As part of this research work, a novel parallel manipulator with a degree of freedom of five (PENTAPOD) was developed, designed and built at the Institute of Mechanism Theory, Machine Dynamics and Robotics (Figure 1).

Figure 2 shows the result of a systematic classification of all parallel kinematic structures with a degree of freedom of five. For predefined requirements, suitable structures are selected and compared with respect to the design of the achievable working area, the required installation space and the structural rigidity (Fig. 3) [1,2]. For this purpose, solutions of the inverse kinematic (IKP) and dynamic (IDP) problem were worked out[3,4]. Based on this, the prototype of a parallel manipulator was designed and built with a degree of freedom of five. The parallel manipulator has the structure "1UPU-4UPS" and consists of five single driven kinematic chains (legs) connecting the base and the platform. Four legs are identical and have the structure UPS, with a universal joint (U for Universal) on the base, a driven push joint (P for Prismatic) to connect the lower and upper legs and a ball joint (S for Spherical) on the platform. The fifth leg is distinguished from the others by a universal joint on the platform [3].

For control and regulation, the flexible environment xPC Target from Mathworks is used. Various control and regulation concepts for PARAROB5-01 have been tested under this environment. To reduce the dynamic errors, a force feedforward under Matlab/Simulink is implemented. A position control of the drives to compensate for the deviation between the real system and the dynamic model is designed [3].

[1] Mbarek, T.; Barmann, I.; Corves, B.: Parallel Structures with Five Degrees of Freedom: Systematic Classsification and Determination of Workspace. In Mechatronics & Robotics' 04, Aachen-Germany, September 13-15,2004, pp. 990-996.

[2] Mbarek, T.; Nefzi, M.; Corves, B.: Kinematic Analysis and Workspace Determination of a Parallel Manipulator with Five Degrees of Freedom. In Computational Kinematics CK2005, Cassino, Italy, May 4-6,2005

[3] Mbarek, T.; Nefzi, M.; Corves, B.: Prototype development and construction of a novel parallel manipulator with a degree of freedom of five. In: VDI Reports No. 1892,2005.

[4] Mbarek, T.; M. Nefzi; B. Corves: Kinematic Analysis and Workspace Determination of a Five-DOF Parallel Manipulator. To appear in: Mechanism and Machine Theory (MMT 40-133)