scholarly journals Testing of a MEMS Dynamic Inclinometer Using the Stewart Platform

Sensors ◽  
2019 ◽  
Vol 19 (19) ◽  
pp. 4233 ◽  
Author(s):  
Zhihua Liu ◽  
Chenguang Cai ◽  
Ming Yang ◽  
Ying Zhang
Keyword(s):  
Mechanical System ◽  
Real Time ◽  
Degrees Of Freedom ◽  
Cross Coupling ◽  
Micro Electro Mechanical System ◽  
Stewart Platform ◽  
Forward Kinematics ◽  
Six Degrees Of Freedom ◽  
Position And Orientation ◽  
The Cross

The micro-electro-mechanical system (MEMS) dynamic inclinometer integrates a tri-axis gyroscope and a tri-axis accelerometer for real-time tilt measurement. The Stewart platform has the ability to generate six degrees of freedom of spatial orbits. The method of applying spatial orbits to the testing of MEMS inclinometers is investigated. Inverse and forward kinematics are analyzed for controlling and measuring the position and orientation of the Stewart platform. The Stewart platform is controlled to generate a conical motion, based on which the sensitivities of the gyroscope, accelerometer, and tilt sensing are determined. Spatial positional orbits are also generated in order to obtain the tilt angles caused by the cross-coupling influence. The experiment is conducted to show that the tested amplitude frequency deviations of the gyroscope and tilt sensing sensitivities between the Stewart platform and the traditional rotator are less than 0.2 dB and 0.1 dB, respectively.

scholarly journals Wrench Capability of a Stewart Platform With Series Elastic Actuators

2018 ◽  
Vol 10 (2) ◽  
Author(s):  
Chawin Ophaswongse ◽  
Rosemarie C. Murray ◽  
Sunil K. Agrawal
Keyword(s):  
Degrees Of Freedom ◽  
Stewart Platform ◽  
Six Degrees Of Freedom ◽  
In Series ◽  
Novel Method ◽  
Machine Interface ◽  
Position And Orientation ◽  
Human Usage ◽  
Series Elastic Actuators ◽  
Series Elastic

This paper proposes a novel method for analyzing linear series elastic actuators (SEAs) in a parallel-actuated Stewart platform, which has full six degrees-of-freedom (DOF) in position and orientation. SEAs can potentially provide a better human–machine interface for the user. However, in the study of parallel-actuated systems with full 6DOF, the effect of compliance in series with actuators has not been adequately studied from the perspective of wrench capabilities. We found that some parameters of the springs and the stroke lengths of the linear actuators play a major role in the actuation limits of the system. This is an important consideration when adding SEAs into a Stewart platform or other parallel-actuated robots to improve their human usage.

Alternative Inverse Kinematic Equations for General RRP and RRR Regional Structures of Manipulators

1996 ◽  
Author(s):  
Peregrine E. J. Riley
Keyword(s):  
Degrees Of Freedom ◽  
Joint Angle ◽  
Inverse Kinematic ◽  
Intersection Point ◽  
Degree Polynomial ◽  
Six Degrees Of Freedom ◽  
Common Intersection ◽  
Position And Orientation ◽  
Spatial Positioning ◽  
Orientational Structure

Abstract Many manipulators with six degrees of freedom are constructed with two distinct sections, a regional structure for spatial positioning, and an orientational structure having a common intersection point for the joint axes. With this arrangement, inverse kinematic solutions for position and orientation may be found separately. While solutions for general three link manipulators have been available since the work of Pieper in 1969, this paper presents new forms of the inverse kinematic equations for general RRP and RRR regional structures. Cartesian coordinates of the F-surface (generated by movement of the outer two joints) together with the outer joint angle are used as the equation variables. In addition, a second degree polynomial approxiamation of the equation may be used for quick iteration to a solution. It is hoped that these new equations will be useful by themselves and in workspace regions where solutions using equations in terms of the joint variables are numerically inaccurate or impossible.

scholarly journals Ultraprecision Real-Time Displacements Calculation Algorithm for the Grating Interferometer System

Sensors ◽  
2019 ◽  
Vol 19 (10) ◽  
pp. 2409 ◽  
Author(s):  
Weinan Ye ◽  
Ming Zhang ◽  
Yu Zhu ◽  
Leijie Wang ◽  
Jinchun Hu ◽  
...  
Keyword(s):  
Real Time ◽  
Affine Transformation ◽  
Degrees Of Freedom ◽  
Diffraction Spot ◽  
Calculation Algorithm ◽  
Six Degrees Of Freedom ◽  
Time Calculation ◽  
Interference Signals ◽  
Grating Interferometer ◽  
Optical Paths

Grating interferometry is an environmentally stable displacement measurement technique that has significant potential for identifying the position of the wafer stage. A fast and precise algorithm is required for real-time calculation of six degrees-of-freedom (DOF) displacement using phase shifts of interference signals. Based on affine transformation, we analyze diffraction spot displacement and changes in the internal and external effective optical paths of the grating interferometer caused by the displacement of the wafer stage (DOWS); then, we establish a phase shift-DOWS model. To solve the DOWS in real time, we present a polynomial approximation algorithm that uses the frequency domain characteristics of nonlinearities to achieve model reduction. The presented algorithm is verified by experiment and ZEMAX simulation.

Real-Time Forward Kinematics of the General 6-6 Stewart Platform Using One Extra Sensor

2000 ◽  
Author(s):  
Tae-Young Lee ◽  
Jae-Kyung Shim
Keyword(s):  
Real Time ◽  
Stewart Platform ◽  
Forward Kinematics ◽  
Double Precision ◽  
Leg Length ◽  
Precision Data ◽  
Constrained System ◽  
C Language ◽  
Estimates Of Solutions ◽  
Actual Configuration

Abstract The forward kinematics of the Stewart platform is to find the postures of the moving platform for a given set of leg lengths. In case of the general Stewart platform, the number of solutions of the problem is up to forty in the complex domain. Theoretically, it is not possible to uniquely determine the actual configuration with six leg length measurements only. An approach to get a single actual configuration is to make over-constrained system by adding extra sensors. This paper presents an algebraic elimination-based method for the real-time forward kinematics of the general Stewart platform with one extra sensor. The proposed algorithm does not require initial estimates of solutions unlike the numerical iterative methods, and can be implemented in C language using conventional double precision data with 15 significant digits. A numerical example is given to confirm the effectiveness and correctness of the developed algorithm for real-time computation.

Comparisons of Turning Abilities of Submarine With Different Rudder Configurations

2018 ◽  
Author(s):  
Dakui Feng ◽  
Xuanshu Chen ◽  
Hao Liu ◽  
Zhiguo Zhang ◽  
Xianzhou Wang
Keyword(s):  
Real Time ◽  
Degrees Of Freedom ◽  
Control Device ◽  
Body Motion ◽  
The Real ◽  
Six Degrees Of Freedom ◽  
Overlapping Grids ◽  
Free Running ◽  
Turning Radius ◽  
Time Changes

Submarine is usually equipped with two different control device arrangements, namely a cruciform and a X rudder configuration. In this paper, numerical simulations of the DARPA Suboff submarine and its retrofitted submarine with a X rudder configuration are presented. Turning simulations in model scale were studied to compare the turning abilities of the two different control device arrangements. The computations were performed with a house viscous CFD solver based on the conservative finite difference method. In the solver, RANS equation are solved coupled with six degrees of freedom (6DOF) solid body motion equations of the submarine in real time. The structured dynamic overlapping grids were used to simulate the real-time changes of the attitude of the submarine and the rotation of the rudder. The volume force method was used to replace the real propeller to realize the self-propelled movement of submarine. In the free running maneuvering simulations, the submarines move at the same initial velocity and rudder angle, restricted to the horizontal plane with four degrees of freedom (4DOF). Comparisons of the trajectory and kinematic parameters including relative turning radius and turning period between the two cases were presented in this paper. The results show that, compared with the cruciform rudder configuration, the X rudder configuration has obvious advantages for submarine in the turning abilities.

Validation of a Novel 3D-Printed Instrumented Spatial Linkage That Measures Changes in the Rotational Axes of the Tibiofemoral Joint

2013 ◽  
Author(s):  
Daniel P. Bonny ◽  
S. M. Howell ◽  
M. L. Hull
Keyword(s):  
Degrees Of Freedom ◽  
Rigid Bodies ◽  
Anatomic Landmarks ◽  
Tibiofemoral Joint ◽  
Six Degrees Of Freedom ◽  
Revolute Joints ◽  
Flexion Extension ◽  
3D Printed ◽  
Total Knee ◽  
Position And Orientation

The two kinematic axes of the tibiofemoral joint, the flexion-extension (F-E) and longitudinal rotation (LR) axes [1], are unrelated to the anatomic landmarks often used to align prostheses during total knee arthroplasty (TKA) [1, 2]. As a result, conventional TKA changes the position and orientation of the joint line, thus changing the position and orientation of the F-E and LR axes and consequently the kinematics of the knee. However, the extent to which TKA changes these axes is unknown. An instrument that can measure the locations of and any changes to these axes is an instrumented spatial linkage (ISL), a series of six instrumented revolute joints that can measure the six degrees of freedom of motion (DOF) between two rigid bodies without constraining motion. Previously, we computationally determined how best to design and use an ISL such that rotational and translational errors in locating the F-E and LR axes were minimized [3]. However, this ISL was not constructed and therefore its ability to measure changes in the axes has not been validated. Therefore the objective was to construct the ISL and quantify the errors in measuring changes in position and orientation of the F-E axis.

Analysis and Design of A New Micro Jerk Sensor with Viscous Coupling

2003 ◽  
Vol 15 (6) ◽  
pp. 582-587 ◽  
Author(s):  
Motohiro Fujiyoshi ◽  
◽  
Yutaka Nonomura ◽  
Fumihito Arai ◽  
Toshio Fukuda ◽  
...  
Keyword(s):  
Mechanical System ◽  
Degrees Of Freedom ◽  
Micro Electro Mechanical System ◽  
New Method ◽  
Mass Ratio ◽  
Viscous Coupling ◽  
Position Change ◽  
Analysis And Design ◽  
Simulation Results ◽  
Spring Coefficient

A new method for jerk detection (derivative of acceleration) is proposed. By using a 2 degrees of freedom (DOF) model with viscous coupling, we measure jerk directly as a position change in mass without differential circuit. Analysis by numerical formulas show the principle of the proposed jerk detection and simulation results show suitable parameters such as viscosity, mass ratio, and spring coefficient ratio for jerk detection. We also propose a micro jerk sensor based on the micro electro mechanical system (MEMS). Results of analysis show that the microstructure is suitable for the proposed viscous coupling.

Sensitivity analysis of a six degrees of freedom displacement measuring device

2013 ◽  
Vol 228 (1) ◽  
pp. 158-168 ◽  
Author(s):  
Andrea Mura
Keyword(s):  
Sensitivity Analysis ◽  
Performance Analysis ◽  
Degrees Of Freedom ◽  
Stewart Platform ◽  
Inverse Kinematic ◽  
Measuring Device ◽  
Six Degrees Of Freedom ◽  
Geometrical Characteristics

Object of this paper is the performance analysis of a six degrees of freedom measuring device based on a modified Stewart platform structure. Because of the device studied in this work represents a novel application of a Stewart like platform, an investigation about its performance has been done, in order to evaluate both behaviour and characteristics of this device in different geometrical configurations. In particular, sensitivity analysis has been carried on about geometrical characteristics and displacements amplitude. To calculate the sensitivity, the inverse kinematic equations of the device have been obtained.

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