56,363 research outputs found
Geometrico-Static Analysis of Under-Constrained Cable-Driven Parallel Robots
No full textThis paper studies the kinematics and statics of cable-driven parallel robots with less than six cables, in crane configuration. A geometrico-static model is provided, together with a general procedure aimed at effectively solving, in analytical form, the inverse and direct position problems. The stability of equilibrium is assessed within the framework of a constrained optimization problem, for which a purely algebraic formulation is provided. A spatial robot with three cables is studied as an application example
Stability Analysis of Underconstrained Cable-Driven Parallel Robots
No full textThis paper studies cable-driven parallel robots with less than six cables, in crane configuration. A geometrico-static model is provided, and the stability of static equilibrium is assessed within the framework of a constrained optimization problem. The method relies on ordinary linear-algebra routines, and it may be very simply applied to the most general architectures. Several examples are provided, concerning robots with a number of cables that range from 2 to 4
Direct Geometrico-Static Problem of Under-Constrained Cable-Driven Parallel Robots with Three Cables
No full textThis paper studies under-constrained cable-driven parallel robots with three cables. A major challenge in the study of these manipulators is the intrinsic coupling between kinematics and statics, which must be tackled simultaneously.
In this contribution, a general elimination procedure is provided that solves the direct geometrico-static problem, which consists in determining the platform posture and the cable tensions when the cable lengths are assigned. The problem is proven to have up to 156 complex solutions
Inverse geometrico-static problem of under-constrained cable-driven parallel robots with three cables
No full textThis paper studies under-constrained cable-driven parallel robots with three cables. A major challenge in the study of these manipulators is the intrinsic coupling between kinematics and statics, which must be tackled simultaneously. In this contribution, general elimination procedures are provided that solve the inverse geometrico-static problem with assigned orientation or position. In the former case, the platform orientation is given, whereas the platform position and the cable lengths and tensions must be computed. In the latter case, the platform position is known, whereas the platform orientation and the cable lengths and tensions must be calculated. These problems are proven to admit up to 1 and 24 real solutions, respectively
Measurement of the ratio of prompt χ c to J / ψ production in pp collisions at √s = 7 TeV
No full textThe prompt production of charmonium χ c and J / ψ states is studied in proton-proton collisions at a centre-of-mass energy of √s = 7 TeV at the Large Hadron Collider. The χ c and J / ψ mesons are identified through their decays χ c → J / ψ γ and J / ψ → μ + μ - using 36 pb - 1 of data collected by the LHCb detector in 2010. The ratio of the prompt production cross-sections for χ c and J / ψ, σ (χ c → J / ψ γ) / σ (J / ψ), is determined as a function of the J / ψ transverse momentum in the range 2 < p T J / ψ < 15 GeV / c. The results are in excellent agreement with next-to-leading order non-relativistic expectations and show a significant discrepancy compared with the colour singlet model prediction at leading order, especially in the low p T J / ψ region
Automatic self-calibration of suspended under-actuated cable-driven parallel robot using incremental measurements
No full textThis paper focuses on the problem of the initial-pose estimation by means of proprioceptive sensors (self-calibration) of suspended under-actuated Cable-Driven Parallel Robots (CDPRs). For this class of manipulators, the initial pose estimation cannot be carried out by means of forward kinematics only, but mechanical equilibrium conditions must be considered as well. In addition, forward kinematics solution is based on cable-length measurements, but if the robot is equipped with incremental sensors cables’ initial values are unknown. In this paper, the self-calibration problem is formulated as a non-linear least square optimization problem (NLLS), based on the direct geometricostatic problem, where only incremental measurements on cable lengths and on swivel pulley angles are required. In addition, a data acquisition algorithm and an initial value selection procedure for the NLLS are proposed, aiming at automatizing the self-calibration procedure. Simulations and experimental results on a 3-cable 6-degree-of-freedom robot are provided so as to prove the effectiveness of the proposed methodology
Solving the Direct Geometrico-Static Problem of 3-3 Cable-Driven Parallel Robots by Interval Analysis: Preliminary Results
No full textThis paper studies the direct geometrico-static analysis of under-constrained cable-driven parallel robots with 3 cables. The task consists in finding all equilibrium configurations of the end-effector when the cable lengths are assigned. An interval-analysis-based procedure is proposed to numerically find the real solutions of the problem for a robot of generic geometry. Three equation sets obtained by different approaches are implemented in the problem-solving algorithm and a comparison between the main merits and drawbacks of each one of them is reported
Further analysis of the 2-2 wire-driven parallel crane
No full textThe 2-2 wire-driven parallel crane is the most simple planar parallel crane
actuated by wires with two wires connected at two different points on
the platform. We present original contributions on the kinematics of
such robot, namely full inverse kinematics,
trajectory, static and singularity analysis in the joint
space
Letter from Carl Hayden to P. J Moran
No full textLetter from Carl T. Hayden to P. J. Moran concerning the alignment of the road to Bright Angel Trail
- …
