Browsing by Author "Altuzarra, Oscar"
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Item Motion pattern analysis of parallel kinematic machines: A case study(2009-04) Altuzarra, Oscar; Martín, Yon San; Amezua, Enrique; Hernández, Alfonso; Centros PRE-FUSION TECNALIA - (FORMER)This paper looks at the "five-axis machines" for machining operations. These machines have five (or six at maximum) degrees of freedom (dof). The output motion must have at least three translational and two rotational dof. This output motion pattern can be obtained with different structural topologies: serial, parallel, hybrid and with serial and/or parallel manipulators working in co-operation. The latter allows higher motion ranges in rotational and translational dof. Moreover, it provides a good stiffness, a highly valued requisite in applications like machining. Manipulators of this type are characterized by their kinematics to be integrated in the CNC, which requires the study of the relative motion between their modules. This motion is usually complex, and in certain cases presents kinematic relations not evident. This work presents a methodology to solve the motion pattern out of the direct and inverse kinematics of the relative motion between the modules of which the manipulator is composed. On the one hand, the spindle is mounted on a parallel module. On the other hand, the working table is mounted on a serial module. This methodology was applied to the Hermes parallel manipulator in combination with rotary and linear tables. As a result, a series of considerations regarding other possible combinations between modules was made and a new machine is proposed.Item Parallel kinematics for machine tools(Springer London, 2009) Altuzarra, Oscar; Hernández, Alfonso; San Martín, Yon; Larrañaga, Josu; Centros PRE-FUSION TECNALIA - (FORMER); ROBOTICA_AUTOMAParallel kinematics is a branch of mechanics that focusses on manipulators formed by closed kinematic chains, i.e., mechanisms that have an endeffector joined to the fixed frame by several limbs. Such a kinematic structure provides some advantages regarding stiffness, acceleration and weight, but has some drawbacks due to mechanical complexity and limited workspaces. In the field of machining, there have been several applications of such mechanisms to machine tools. Earlier designs based on hexapods did not fulfil expectations but new topologies are promising. In this chapter, there is first a description of the evolution of parallel kinematics in the manufacturing industry. Second, the authors expose a design methodology giving some hints on the main problems to overcome. Third, there is a study on calibration processes that can be applied to these machines. And, at the end, there is a description of control issues.