Steering control law for double-gimbal scissored-pair CMG
قانون کنترل فرمان دو حلقه قیچی جفت CMG-2020
Because control moment gyroscopes (CMGs) can generate a large torque compared to reaction wheels, they are used as actuators for attitude control of large spacecraft. However, when the number of Single-Gimbal CMG (SGCMG) units is five or less, there can be internal singularities that cannot generate torque around the desired direction. To construct a system that has no internal singularities, six or more SGCMGs are required, because an orthogonally arrayed, three scissored-pair CMG system has no internal singularities. Because CMG singularities are disruptive for attitude control, a great deal of effort has been devoted to overcoming the CMG singularity problem; the various designs include Variable-Speed CMGs (VSCMGs), Double-Gimbal CMGs (DGCMGs), and Double-Gimbal Variable- Speed CMGs (DGVSCMGs). However, these designs still have problems, such as a slow response to torque generation commands about the wheel axis in VSCMGs and DGVSCMGs, and difficulty in precise attitude tracking when perturbation torque is generated to avoid singularities. To overcome the problems of the traditional CMG configurations, this paper proposes a new CMG system configuration that we call the Double-Gimbal Scissored-pair CMG (DGSPCMG) system. Because the DGSPCMG system is a hybrid system combining a Scissored-Pair CMG and a DGCMG, the DGSPCMG system does not have internal singularities except at the origin and along the x-axis. Moreover, this system can recover from an internal singularity by null motion only, and from outer singularities (saturation singularities) by steering the scissored-pair gimbals only. Thus, generation of perturbation torque is unnecessary for recovering from singularities, and a precise attitude tracking maneuver can be more easily achieved. This paper presents a conceptual design of a DGSPCMG system and describes a steering control law for the proposed system. Furthermore, the validity of the proposed steering control law is demonstrated through numerical simulations and results of comparison experiments are shown to demonstrate the advantage of the DGSPCMG over a VSCMG.
Keywords: Scissored-pair CMG | Double gimbal CMG | Steering control law | Singularities
Singularity radius gradient-based rapid singularity-escape steering law for SGCMGs
قانون فرمان یکپارچه فرار سریع تکینگی شعاع تکینگی برای SGCMG ها-2020
In order to visualize singularity of SGCMGs in gimbal angle space, a novel continuous bounded singularity parameter--Singularity Radius, whose sign can distinctly determine singularity type, is proposed. Then a rapid singularity-escape steering law is proposed basing on gradient of Singularity Radius and residual base vector to drive the SGCMG system to neighboring singular boundary, and quickly escape elliptic singularities. Finally, simulation results on Pyramid-type and skew-type configuration demonstrate the effectiveness and rapidness of the proposed steering law.
KEYWORDS : Gaussian curvature | Rapid singularity escape | Single gimbal control | moment gyroscope | Singularity-escape steering | law | Singularity parameter| Singularity type
Classifying longevity profiles through longitudinal data mining
طبقه بندی پروفایل های طول عمر از طریق داده کاوی طولی-2019
Populational studies of human ageing often generate longitudinal datasets with high dimensionality. In order to discover knowledge in such datasets, the traditional knowledge discovery in database task needs to be adapted. In this article, we present a full knowledge discovery process that was performed on a lon- gitudinal dataset, mentioning the singularities of this process. We investigated the English Longitudinal Study of Ageing’s (ELSA’s) database, employing both semi-supervised and supervised learning techniques to determine and describe the profiles of individuals annotated with the class labels “short-lived”and “long-lived”who participated in the study. We report on the data preprocessing, the clustering task of finding the best sets of representatives of the profiles of each class, and the use of supervised learning to describe these profiles and perform a longitudinal classification on the dataset to investigate how consis- tently the unlabelled records would fit into the classes. The results show that several aspects are used to discriminate the individuals between the longevity profiles. Those aspects include economic, social and health-related attributes. The findings have pointed towards a need to further investigate the relation- ships between the different aspects, especially those related to physical health and wellbeing, and how they affect the lifespan of an individual. Furthermore, our methodology and the adopted procedures can be applied to any other data mining applications for longitudinal studies of ageing.
Keywords: Machine learning | Longitudinal data | Cluster analysis | Ageing studies
Inverse models and robust parametric-step neuro-control of a Humanoid Robot
مدل های معکوس و کنترل عصبی پارامتریک قوی یک ربات انسان نما-2017
In this paper we present advances on the work done on the development of the AH1N2 humanoid robot at the Automatic Control Department of the Cinvestav. The geometric model of the AH1N2 humanoid robot is deﬁned by kinematic open chains, head, arms, waist and legs, attached to the robot body. We center our work in the inverse geometric model, since from all the models used in robotics, is the most diﬃcult to automate. Its knowledge is needed to control the robot position and attitude in the workspace. We present derivations of the inverse geometric models for the arm and the legs. We also study, in this work, the singularities of the arms and legs because they aﬀect its control in the workspace. We also present the use of kinematic model to built movement constraints that allow us the control of the motion control and specify complex movements. Finally, we use the dynamic models to calculate a Neuro proportional-derivative control and to simulate the robot movement in presence of a destabilising perturbations. The neural network is trained to compensate the eﬀect of gravity.
Keywords:Robotics | Humanoid robot