Kinematic Clearance Sensitivity Analysis of Spatial Structures With Revolute Joints

1999 ◽  
Author(s):  
Carlo Innocenti
Keyword(s):  
Sensitivity Analysis ◽  
Rigid Body ◽  
External Load ◽  
Body Position ◽  
New Method ◽  
Spatial Structures ◽  
Revolute Joints ◽  
Joint Clearances

Abstract The paper presents a new method to assess the influence of joint clearances in spatial structures that are composed of links connected by revolute joints. The method allows assessment of the amount by which joint clearances affect the rigid-body position of a generic link of the structure when an external load is exerted on the link. Unlike other procedures, the proposed method relies on the clearance-free idealization of the structure under investigation. An example shows application of the proposed method to the analysis of the structure derived from a multi-loop manipulator by freezing its actuators.

Kinematic Clearance Sensitivity Analysis of Spatial Structures With Revolute Joints (*)

1999 ◽  
Vol 124 (1) ◽  
pp. 52-57 ◽  
Author(s):  
Carlo Innocenti
Keyword(s):  
Sensitivity Analysis ◽  
Rigid Body ◽  
External Load ◽  
Body Position ◽  
New Method ◽  
Spatial Structures ◽  
Revolute Joints ◽  
Joint Clearances

The paper presents a new method to assess the influence of joint clearances in spatial structures that are composed of links connected by revolute joints. The method allows assessment of the amount by which joint clearances affect the rigid-body position of a generic link of the structure when an external load is exerted on the link. Unlike other procedures, the proposed method relies on the clearance-free idealization of the structure under investigation. An example shows application of the proposed method to the analysis of the structure derived from a multi-loop manipulator by freezing its actuators.

A planar reconfigurable linear rigid-body motion linkage with two operation modes

2014 ◽  
Vol 228 (16) ◽  
pp. 2985-2991 ◽  
Author(s):  
Guangbo Hao ◽  
Xianwen Kong ◽  
Xiuyun He
Keyword(s):  
Rigid Body ◽  
Single Mode ◽  
Rigid Body Motion ◽  
Body Motion ◽  
Reference Guide ◽  
Revolute Joints ◽  
Operation Modes ◽  
Straight Line ◽  
Motion Stage ◽  
Motion Mode

A planar reconfigurable linear (also rectilinear) rigid-body motion linkage (RLRBML) with two operation modes, that is, linear rigid-body motion mode and lockup mode, is presented using only R (revolute) joints. The RLRBML does not require disassembly and external intervention to implement multi-task requirements. It is created via combining a Robert’s linkage and a double parallelogram linkage (with equal lengths of rocker links) arranged in parallel, which can convert a limited circular motion to a linear rigid-body motion without any reference guide way. This linear rigid-body motion is achieved since the double parallelogram linkage can guarantee the translation of the motion stage, and Robert’s linkage ensures the approximate straight line motion of its pivot joint connecting to the double parallelogram linkage. This novel RLRBML is under the linear rigid-body motion mode if the four rocker links in the double parallelogram linkage are not parallel. The motion stage is in the lockup mode if all of the four rocker links in the double parallelogram linkage are kept parallel in a tilted position (but the inner/outer two rocker links are still parallel). In the lockup mode, the motion stage of the RLRBML is prohibited from moving even under power off, but the double parallelogram linkage is still moveable for its own rotation application. It is noted that further RLRBMLs can be obtained from the above RLRBML by replacing Robert’s linkage with any other straight line motion linkage (such as Watt’s linkage). Additionally, a compact RLRBML and two single-mode linear rigid-body motion linkages are presented.

THE CALIBRATION OF AN ARRAY OF ACCELEROMETERS

2011 ◽  
Vol 35 (2) ◽  
pp. 251-267 ◽  
Author(s):  
Dany Dubé ◽  
Philippe Cardou
Keyword(s):  
Angular Velocity ◽  
Rigid Body ◽  
Least Squares ◽  
Calibration Method ◽  
Calibration Procedure ◽  
Rigid Bodies ◽  
New Method ◽  
Scale Factors ◽  
Array Calibration ◽  
The One

An accelerometer-array calibration method is proposed in this paper by which we estimate not only the accelerometer offsets and scale factors, but also their sensitive directions and positions on a rigid body. These latter parameters are computed from the classical equations that describe the kinematics of rigid bodies, and by measuring the accelerometer-array displacements using a magnetic sensor. Unlike calibration schemes that were reported before, the one proposed here guarantees that the estimated accelerometer-array parameters are globally optimum in the least-squares sense. The calibration procedure is tested on OCTA, a rigid body equipped with six biaxial accelerometers. It is demonstrated that the new method significantly reduces the errors when computing the angular velocity of a rigid body from the accelerometer measurements.

Impedance Control of Manipulators With Heavy Payload for Spacecraft Rendezvous and Docking Simulators

2009 ◽  
Author(s):  
Farhad Aghili
Keyword(s):  
Sensitivity Analysis ◽  
Rigid Body ◽  
Impedance Control ◽  
Sensor Noise ◽  
Combined System ◽  
Laboratory Environment ◽  
Force Moment ◽  
Applied Forces ◽  
The Stability ◽  
Rendezvous And Docking

This paper presents a method to control a manipulator system grasping a rigid-body payload so that the motion of the combined system in consequence of external applied forces to be the same as another free-floating rigid-body (with different inertial properties). This allows zero-g emulation of a scaled spacecraft prototype under the test in a 1-g laboratory environment. The controller consisting of motion feedback and force/moment feedback adjusts the motion of the test spacecraft so as to match that of the flight spacecraft. The stability of the overall system is analytically investigated, and the results show that the system remains stable provided that the inertial properties of two spacecraft are different and that an upperbound on the norm of the inertia ratio of the payload to manipulator is respected. Important practical issues such as calibration and sensitivity analysis to sensor noise and quantization are also presented. Finally, experimental results are presented.

A Load Independent Pseudo-Rigid-Body 3R Model for Determining Large Deflection of Beams in Compliant Mechanisms

2008 ◽  
Author(s):  
Hai-Jun Su
Keyword(s):  
Rigid Body ◽  
Numerical Integration ◽  
Large Deflection ◽  
Compliant Mechanisms ◽  
Three Dimensional ◽  
Flexible Beams ◽  
Fea Model ◽  
Revolute Joints ◽  
Characteristic Radius ◽  
Key Steps

Modeling flexible beams that undergo large deflection is one of the key steps in analyzing and synthesizing compliant mechanisms. Geometric nonlinearities introduced by large deflections often complicate the analysis of mechanism systems comprising such members. Several pseudo-rigid-body (PRB) or multi segment models in the literature have been proposed to approximate the tip deflection and slope. However these models are either dependent on external loads or too complicated to analyze. They are neither appropriate for analyzing mechanisms in which loads change significantly as they move, nor for synthesizing mechanisms where a parametric model is preferred. In this paper, a load independent PRB 3R model which comprises of four rigid links joined by three revolute joints and three torsion springs is proposed. The traditional PRB 1R models are first studied for both small deflection beams and large deflection beams. These studies provide fundamental insights to the geometric nonlinearity of large deflection beams. Numerical integration is applied to compute tip deflections for various loads. A three-dimensional search routine has been developed to find the optimal set of characteristic radius factors for the proposed PRB 3R model. Detailed error analysis and comparison against the result by the numerical integration and the PRB 1R model are accomplished for different load modes. The benefits of the PRB 3R model include (a) high accuracy for large deflection beams, (b) load independence which is critical for applications where loads vary significantly and (c) explicit kinematic and static constraint equations derived from the model. To demonstrate the use of the PRB 3R model, a compliant 4-bar linkage is studied and verified by a numerical example. The result shows a maximum tip deflection error of 1.2% compared with the FEA model.

Optimal estimation of rigid body position and attitude from noisy markers coordinates

1994 ◽  
Vol 27 (6) ◽  
pp. 764 ◽  
Author(s):  
Giuseppe Magnani ◽  
Cesare Angeloni ◽  
Alberto Leardini ◽  
Angelo Cappello
Keyword(s):  
Rigid Body ◽  
Body Position ◽  
Optimal Estimation
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