SCARA

About: SCARA is a(n) research topic. Over the lifetime, 1430 publication(s) have been published within this topic receiving 12561 citation(s). The topic is also known as: Selective Compliance Articulated Robot Arm & SCARA.

Type synthesis of 3T1R 4-DOF parallel manipulators based on screw theory

Abstract: 3T1R four-degrees-of-freedom (DOF) parallel manipulators (3T1R-PMs) are the parallel counterparts of the 4-DOF SCARA serial robots. In a 3T1R-PM, the moving platform can generate 3T1R motion (also called Schonflies motion), which refers to a rotation about any axis with a given direction in conjunction with 3-DOF translations. A method is proposed for the type synthesis of 3T1R-PMs based on screw theory. The wrench systems of a 3T1R parallel kinematic chain (3T1R-PKC) and its legs are first analyzed. A general procedure is then proposed for the type synthesis of 3T1R-PMs. The type synthesis of legs for 3T1R-PKCs, the type synthesis of 3T1R-PKCs, as well as the selection of actuated joints of 3T1R-PMs, are dealt with in sequence. 3T1R-PKCs with and without inactive joints are synthesized. The phenomenon of dependent joint groups in a 3T1R-PKC is revealed for the first time. Several 3T1R-PMs with identical type of legs are obtained.

Kinematic-Parameter Identification for Serial-Robot Calibration Based on POE Formula

Abstract: This paper presents a generic error model, which is based on the product of exponentials (POEs) formula, for serial-robot calibration. The identifiability of parameters in this error model was analyzed. The analysis shows the following: 1) Errors in all joint twists are identifiable. 2) The joint zero-position errors and the initial transformation errors cannot be identified when they are involved in the same error model. With either or neither of them, three practicable error models were obtained. The joint zero-position errors are identifiable when the following condition is satisfied: Coordinates of joint twists are linearly independent. 3) The maximum number of identifiable parameters is 6n + 6 for an n-degree-of-freedom (DOF) generic serial robot. Simulation results show the following: 1) The maximum number of identifiable parameters is 6r + 3t + 6, where r is the number of revolute joints, and t is the number of prismatic joints. 2) All the kinematic parameters of the selective compliant assembly robot arm (SCARA) robot and programmable universal machine for assembly (PUMA) 560 robots were identified by using the three error models, respectively. The error model based on the POE formula can be a complete, minimal, and continuous kinematic model for serial-robot calibration.

Dynamic hybrid position/Force control of robot manipulators--Controller design and experiment

Abstract: An approach to designing controllers for dynamic hybrid position/force control of robot manipulators is presented, and preliminary experimental results are given. Dynamic hybrid control is an extension of an approach proposed by M.H. Raibert and J.J. Craig (1981) to the case where the full manipulator dynamics is taken into consideration and the end-effector constraint is explicitly given by the constraint hypersurfaces. This design method consists of two steps. The first step is the linearization of the manipulator dynamics by nonlinear state feedback. Formulation of the constraint by the constraint hypersurfaces plays an essential role in establishing the linearizing law. The second step is the design of position and force controllers for the linearized model using the concept of two-degrees-of-freedom servocontroller. The merit of this servocontroller is that it can take account of both the command response and the robustness of the controllers to modeling errors and disturbances. Preliminary experiments using a SCARA robot show the validity of the approach. >

Methods and apparatus for extending the reach of a dual scara robot linkage

Abstract: Methods and apparatus are provided for the use of a dual Selective Compliant Assembly Robot Arm (SCARA) robot. In some embodiments two SCARAs are provided, each including an elbow joint, wherein the two SCARAs are vertically stacked such that one SCARA is a first arm and the other SCARA is a second arm, and wherein the second arm is adapted to support a first substrate, and the first arm is adapted to extend to a full length when the second arm supports the first substrate, and wherein the first substrate supported by the second arm is coplanar with the elbow joint of the first arm, and the second arm is further adapted to move concurrently in parallel (and/or in a coordinated fashion) with the first arm a sufficient amount to avoid interference between the first substrate and the elbow joint of the first arm. Numerous other embodiments are provided.

Dynamic identification of robots with power model

Abstract: This paper presents a new approach to identify the minimum dynamic parameters of robots using least squares techniques (LS) and a power model. Theoretical analysis is carried out from a filtering point of view and clearly shows the superiority of the power model over the energy one and over the dynamic identification model which has been used to carry out a classical ordinary LS estimation and a new weighted LS estimation. These results are checked from comparing experimental identification of the dynamic parameters of a planar SCARA prototype robot.