The rotation accuracy evaluation methods for the high-speed spindle of machining robots
High speed machining robots is designed for a number of high speed machining applications, the precision of which is one of the essential features. To increase precision of the robots, the study of accuracy evaluation methods is important. First, according to the demands for robots, key information of high-speed spindle of machining robots is determined, then it will be extracted by sensors and data acquisition card. Second, four different evaluating methods are introduced to assess the rotation accuracy, the results respectively solved by which are compared in detail. Furthermore, the particle swarm algorithm based on simulated annealing (SA-PSO) is introduced and theory analysis about the impact of simulated annealing factor is carried on to provide basis for giving the parameter better value. Finally, through the contrast between the evaluation results obtained by the proposed method and other optimization methods, the availability and precision of the SA-PSO is verified.
A methodology for joint stiffness identification of serial robots
This paper presents a new methodology for joint stiffness identification of serial robots. This methodology aims at evaluating all joint stiffness values responsible for both translational and rotational displacements of the robot end-effector subject to an external wrench (force and torque). The links of the robot are supposed to be quite stiffer than the joints and not known as it is usually the case with industrial serial robots. The robustness of the identification method and the sensitivity of the results to measurement errors and number of experimental tests are also analyzed. The Kuka KR240-2 robot is used as an illustrative example through the paper.
Law as Palimpsest: Conceptualizing Contingency in Judicial Opinions (forthcoming 2009)
Metaphors create conceptualizations, and for decades legal academics have employed metaphors to shape understandings of legal problems. But no metaphor in current use successfully conceptualizes the contingency of judicial opinions and the complexity of the relationship between opinions and precedent. This Article seeks to fill this void by introducing a new metaphor, the palimpsest, into the realm of legal analysis. A palimpsest is a writing surface that can be cleared away for reuse, like a personal blackboard. What distinguishes a palimpsest from other writing surfaces is that its removed contents do not disappear, but remain, obscured yet recoverable: A writing on a palimpsest never goes away. This Article argues that thinking of judicial opinions as being part of a shared, ever-evolving palimpsest underscores the fact that they are ultimately contingent and serves as a reminder of the multiple levels of interconnectedness between them and the cases they cite. Precedents—like the underlayers of a palimpsest—never go away, and they inform and shape the application of opinions in ways far more significant than simply serving as points of reference. A palimpsestic approach to understanding judicial decisionmaking also helps to explain why even the oldest, most reviled cases remain part of our national psyche—like underlayers of a palimpsest, they can never truly disappear, and their continued presence forces us to grapple with their existence. Finally, considering judicial opinions as part of a shared palimpsest reminds us that even the most troubling opinion is ultimately contingent, its application subject to reexamination and revision by future courts and future generations. Just as such an opinion replaces its precedents, it too will one day be replaced, like each of a palimpsest’s layers. 2 Law as Palimpsest [Vol. __:__ Law as Palimpsest: Conceptualizing Contingency in Judicial Opinions