Visual Judgments in Motion

1954 ◽  
Vol 7 (3) ◽  
pp. 233-251 ◽  
Author(s):  
E. S. Calvert
Keyword(s):  
Degrees Of Freedom ◽  
Vertical Axis ◽  
Moving Surface ◽  
Practical Result ◽  
Six Degrees Of Freedom ◽  
Three Degrees Of Freedom

Introduction. The judgments discussed in this paper are mainly those which the pilot of an aircraft has to make in order to land. Some of these, as, for instance, the judgment of alignment, are similar to those made by the driver of a moving surface vehicle, but some, as, for instance, the judgment of approach slope, are peculiar to the pilot, and are very much more difficult. The main difficulties of the pilot arise, however, from the fact that an aircraft has six degrees of freedom and is controllable about all three axes, whereas the surface vehicle has only three degrees of freedom and is controllable only about the vertical axis. In bad visibility these extra freedoms confuse the visual indications in ways of which the person who has only driven a surface vehicle has no conception. The result of this has been that until recently most of the engineers concerned in the layout of airports have not realized that pilots have special difficulties; while the pilots, not having studied visual psychology and perspective, have been unable to analyse these difficulties, or even explain them in terms intelligible to the engineers. In this country, we have been able to find methods of bridging the gap, and enabling both parties to talk the same language. The practical result of this can be seen at London Airport.

The Qualitative Synthesis of Parallel Manipulators

2004 ◽  
Vol 126 (4) ◽  
pp. 617-624 ◽  
Author(s):  
Jorge Angeles
Keyword(s):  
Degrees Of Freedom ◽  
Three Dimensional ◽  
Parallel Manipulators ◽  
Qualitative Reasoning ◽  
Rigid Bodies ◽  
Three Dimensions ◽  
Qualitative Synthesis ◽  
Motion Representation ◽  
Six Degrees Of Freedom ◽  
Three Degrees Of Freedom

As shown in this paper, when designing parallel manipulators for tasks involving less than six degrees of freedom, the topology can be laid out by resorting to qualitative reasoning. More specifically, the paper focuses on cases whereby the manipulation tasks pertain to displacements with the algebraic structure of a group. Besides the well-known planar and spherical displacements, this is the case of displacements involving: rotation about a given axis and translation in the direction of the same axis (cylindrical subgroup); translation in two and three dimensions (two- and three-dimensional translation subgroups); three independent translations and rotation about an axis of fixed direction, what is known as the Scho¨nflies subgroup; and similar to the Scho¨nflies subgroup, but with the rotation and the translation in the direction of the axis of rotation replaced by a screw displacement. For completeness, the fundamental concepts of motion representation and groups of displacements, as pertaining to rigid bodies, are first recalled. Finally, the concept of Π-joint, introduced elsewhere, is generalized to two and three degrees of freedom, thereby ending up with the Π2-and the Π3-joints, respectively.

Accuracy estimation of a stretch-retractable single section continuum manipulator based on inverse kinematics

2019 ◽  
Vol 46 (5) ◽  
pp. 573-580
Author(s):  
Hao Wang ◽  
GuoHua Gao ◽  
Qixiao Xia ◽  
Han Ren ◽  
LianShi Li ◽  
...  
Keyword(s):  
Inverse Kinematics ◽  
Degrees Of Freedom ◽  
Kinematic Model ◽  
Content Type ◽  
Kinematics Model ◽  
Six Degrees Of Freedom ◽  
Single Section ◽  
Motion Range ◽  
Continuum Manipulator ◽  
Three Degrees Of Freedom

Purpose The purpose of this paper is to present a novel stretch-retractable single section (SRSS) continuum manipulator which owns three degrees of freedom and higher motion range in three-dimension workspace than regular single continuum manipulator. Moreover, the motion accuracy was analyzed based on the kinematic model. In addition, the experiments were carried out for validation of the theory. Design/methodology/approach A kinematics model of the SRSS continuum manipulator is presented for analysis on bending, rotating and retracting in its workspace. To discuss the motion accuracy of the SRSS continuum manipulator, the dexterity theory was introduced based on the decomposing of the Jacobian matrix. In addition, the accuracy of motion is estimated based on the inverse kinematics and dexterity theory. To verify the presented theory, the motion of free end was tracked by an electromagnetic positioning system. According to the comparison of experimental value and theoretical analysis, the free end error of SRSS continuum manipulator is less than 6.24 per cent in the region with favorable dexterity. Findings This paper presents a new stretch-retractable continuum manipulator that the structure was composed of several springs as the backbone. Thus, the SRSS continuum manipulator could own wide motion range depending on its retractable structure. Then, the motion accuracy character of the SRSS continuum manipulator in the different regions of its workspace was obtained both theoretically and experimentally. The results show that the high accuracy region distributes in the vicinity of the outer boundary of the workspace. The motion accuracy gradually decreases with the motion position approaching to the center of its workspace. Research limitations/implications The presented SRSS continuum manipulator owns three degrees of freedom. The future work would be focused on the two-section structure which will own six degrees of freedom. Practical implications In this study, the SRSS continuum manipulator could be extended to six degrees of freedom continuum robot with two sections that is less one section than regular six degrees of freedom with three single section continuum manipulator. Originality/value The value of this study is to propose a SRSS continuum manipulator which owns three degrees of freedom and could stretch and retract to expend workspace, for which the accuracy in different regions of the workspace was analyzed and validated based on the kinematics model and experiments. The results could be feasible to plan the motion space of the SRSS continuum manipulator for keeping in suitable accuracy region.

The movement coordination of two manipulators, functioning together

2020 ◽  
pp. 115-117
Keyword(s):  
Relative Motion ◽  
Degrees Of Freedom ◽  
Mutual Orientation ◽  
Coordinate Systems ◽  
Movement Coordination ◽  
Six Degrees Of Freedom ◽  
Generalized Coordinates ◽  
Relative Coordinates ◽  
Production Automation ◽  
Three Degrees Of Freedom

The problem of realizing the relative movements of the two manipulators output links having a single control system is considered. This problem arises at controlling two-armed robots and production automation. The relative motion of the output links is provided by a fourth-order matrix, which reflects the mutual orientation of the coordinate systems connected by the output links, and the relative coordinates of these coordinate systems origin. Manipulators have three degrees of freedom, but at the relative movement the working links can realize up to six degrees of freedom. The inverse problems solutions of relative motion are obtained and expressions for the manipulators generalized coordinates taken as control variables are found.

Kinematic Analysis and Design of a Six-Degrees of Freedom 3-RRPS Mechanism for Bone Reduction Surgery

2020 ◽  
Vol 15 (1) ◽  
Author(s):  
Terence Essomba ◽  
Sinh Nguyen Phu
Keyword(s):  
Degrees Of Freedom ◽  
Vertical Axis ◽  
Velocity Model ◽  
Analysis And Design ◽  
Six Degrees Of Freedom ◽  
Bone Fragments ◽  
Kinematic Models ◽  
Surgery First ◽  
Forward Kinematic ◽  
Classical Mechanism

Abstract Robot-assisted bone reduction surgery consists in using robots to reposition the bone fragments into their original place prior to fracture healing. This study presents the application of a 3-RRPS augmented tripod mechanism with six degrees-of-freedom for longitudinal bone reduction surgery. First, the inverse and forward kinematic models of the mechanism are investigated. Particularly, the forward kinematic is solved by applying Sylvester's dialytic method. Second, the velocity model is studied and its singular configurations are identified. The workspace of the 3-RRPS mechanism is then outlined and compared with the Stewart platform, which is a classical mechanism for the targeted application. The results show that this mechanism provides a larger workspace, especially its rotation angle about the vertical axis, which is an important aspect in the bone reduction. A series of simulations on the numerical and graphic software is performed to verify the entire analysis of the parallel mechanism. A physiguide and mscadams software are used to carry out a simulation of a real case of femur fracture reduction using the proposed mechanism to validate its suitability. Finally, a robotic prototype based on the mechanism is manufactured and experimented using an artificial bone model to evaluate the feasibility of the mechanism.

Vibration of a Spring-Supported Body

1965 ◽  
Vol 7 (2) ◽  
pp. 185-192 ◽  
Author(s):  
P. Grootenhuis ◽  
D. J. Ewins
Keyword(s):  
Rigid Body ◽  
Degrees Of Freedom ◽  
Equations Of Motion ◽  
Vertical Axis ◽  
The Body ◽  
Stiffness Ratio ◽  
Six Degrees Of Freedom ◽  
Centre Of Gravity ◽  
Longitudinal Stiffness ◽  
The Matrix

The equations of motion for a rigid body supported on four springs are derived for the general case of the centre-of-gravity being anywhere within the body and allowing for the sideways as well as the longitudinal stiffnesses of the springs. This constitutes a six-degrees-of-freedom case with three degrees of asymmetry. Coupling between motions in all directions occurs even when the centre-of-gravity is at the geometric centre with the exception then of vertical oscillations and rotation about the vertical axis. Any number of additional springs can be allowed for by adding terms to the expression for the potential energy stored in the springs. Allowance is made in the expression for kinetic energy for the products of inertia which arise with an offset centre-of-gravity. The real case is simulated for purposes of analysis by replacing the rigid body by a rectangular box with a light framework and all the mass concentrated at the eight corners. The matrix solution is changed into dimensionless parameters and the effect of an offset centre-of-gravity upon the eigenvalues and eigenvectors studied. Only the proportions of the box and the stiffness ratio between sideways to longitudinal stiffness of the springs remain as factors. The numerical example given is for proportions of height to width to length of 3/4/5 and for a stiffness ratio of 5. Small amounts of offset of the centre-of-gravity from the geometric centre do not alter the dynamic behaviour of the system much but displacing the total mass towards either a lower or an upper corner has marked effects. Some of the natural frequencies associated with motion in rotation when the system is symmetric become less than the frequencies connected with motion in translation for the centre-of-gravity being close to a corner connected to a spring. A large region free from any natural frequency arises when the centre-of-gravity is moved towards a corner furthest removed from the plane containing the springs. The asymptotic conditions for the position of the centre-of-gravity are also considered.

scholarly journals Research on modular implementation method of six-degree-of-freedom robotic arm

2021 ◽  
Vol 2125 (1) ◽  
pp. 012015
Author(s):  
JiaLei Su
Keyword(s):  
Degrees Of Freedom ◽  
Modular Design ◽  
Degree Of Freedom ◽  
Robotic Arm ◽  
Work Intensity ◽  
Six Degrees Of Freedom ◽  
Standard Interface ◽  
Implementation Method ◽  
Six Degree Of Freedom ◽  
Three Degrees Of Freedom

Abstract Single-joint modular design can reduce the work intensity of designers, and also can broaden the combination form of multi-degree-of-freedom robotic arm. In order to adapt to the changes of multiple degrees of freedom and multiple loads, this paper designs a series of standard modules with similar components and the same standard interface, but with different sizes only, and chooses different drive components according to the load when designing the size, and then designs the size of other parts according to the size of the drive components. The final combination of this series of modules into different degrees of freedom robotic arm, such as three degrees of freedom robotic arm, four degrees of freedom robotic arm or even six degrees of freedom robotic arm. In this paper, the most widely used six-degree-of-freedom robotic arm is used as an example, and a detailed design form is proposed.

Control of processing at multi-tool two-support setup

2020 ◽  
pp. 67-73
Author(s):  
N.D. YUsubov ◽  
G.M. Abbasova
Keyword(s):  
Degrees Of Freedom ◽  
Factor Model ◽  
Angular Displacement ◽  
Factor Models ◽  
Technological System ◽  
Displacement Control ◽  
Model Accuracy ◽  
Six Degrees Of Freedom ◽  
Angular Displacements ◽  
And Control

The accuracy of two-tool machining on automatic lathes is analyzed. Full-factor models of distortions and scattering fields of the performed dimensions, taking into account the flexibility of the technological system on six degrees of freedom, i. e. angular displacements in the technological system, were used in the research. Possibilities of design and control of two-tool adjustment are considered. Keywords turning processing, cutting mode, two-tool setup, full-factor model, accuracy, angular displacement, control, calculation [email protected]

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