scholarly journals Mechanical Impedance Control in the Human Arm While Manually Transporting an Open-Top Fluid Filled Dish

2011 ◽  
Vol 8 (3-4) ◽  
pp. 429-440 ◽  
Author(s):  
Navit Roth ◽  
Rami Seliktar ◽  
Joseph Mizrahi
Keyword(s):  
Angular Velocity ◽  
Impedance Control ◽  
Wrist Joint ◽  
Mechanical Impedance ◽  
Shoulder Girdle ◽  
Compensatory Mechanisms ◽  
First Order ◽  
Order Dependence ◽  
Future Design ◽  
Shoulder Joints

The present study deals with stabilizing aspects of a hand-held dish filled with liquid while walking steadily. This is an attempt to decipher the neuro-muscular strategies employed and the mechanical responses of the arm during certain tasks of manual materials handling. The experimental configuration included a cup and the test-subject’s hand as an ‘end-effector’ of a serial three-link system representing the upper limb. These links are connected together by the wrist, elbow and shoulder joints. The tested subjects walked at constant speed on a treadmill while aiming to minimize liquid spillage from the cup. The motion of the limb and shoulder girdle served as inputs to a model to reveal the impedance adjustments during the simultaneous control of grasping and walking under ordinary conditions, and when one of the joints is affected. A regressive function used to express stiffness, included first-order dependence on angle and on angular velocity. The function used for damping included first-order dependence on angular velocity. Redundancies in the numerical solution were eliminated using multicollinearity diagnostic algorithms. The results revealed that the wrist joint was found to have constant stiffness and damping and no regulation of these coefficients was necessary during gait. Both in the elbow and shoulder joints stiffness included a constant coefficient as well as an angular velocity-dependent coefficient. Although all tested subjects demonstrated ability to prevent spillage of liquid, there was a considerable variability among the results obtained, indicating that the compensatory mechanisms employed by each subject to regulate the mechanical impedance were subjective. These results can help in the optimization of manual materials handeling tasks in industrial settings as well as future design of prosthetic arms, robotic appliances and man machine interfacing devices.

scholarly journals An Obstacle Avoidance Method for Action Support 7-DOF Manipulators Using Impedance Control

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Masafumi Hamaguchi ◽  
Takao Taniguchi
Keyword(s):  
Angular Velocity ◽  
Obstacle Avoidance ◽  
Impedance Control ◽  
Kinematic Redundancy ◽  
End Effector ◽  
Rate Vector

An obstacle avoidance method of action support 7-DOF manipulators is proposed in this paper. The manipulators are controlled with impedance control to follow user's motions. 7-DOF manipulators are able to avoid obstacles without changing the orbit of the end-effector because they have kinematic redundancy. A joint rate vector is used to change angular velocity of an arbitrary joint with kinematic redundancy. The priority of avoidance is introduced into the proposed method, so that avoidance motions precede follow motions when obstacles are close to the manipulators. The usefulness of the proposed method is demonstrated through obstacle avoidance simulations and experiments.

scholarly journals Kinematics of a screw linkage

2021 ◽  
Vol 3 (12) ◽  
Author(s):  
Jing-Shan Zhao ◽  
Song-Tao Wei ◽  
Junjie Ji
Keyword(s):  
Angular Velocity ◽  
Linear Velocity ◽  
Kinematics Analysis ◽  
First Order ◽  
Definition Of

AbstractThis paper proposes a kinematics methodology in twist coordinates for screw linkages. Based on the definition of a twist, both the angular velocity of a link and the linear velocity of a point on it may be explicitly represented in twist coordinates. Through integration on the twist solution numerically or analytically, we may obtain the displacements. By differential or numerical differential interpolation of the twist, we can find the accelerations of the link. The most outstanding advantage of this kinematic algorithm is that only the numerical differential interpolation of the first order is required to calculate the acceleration while only the first order integration of the twist is enough to compute the displacement. This merit makes it particularly fit for developing programmes to accomplish the kinematics analysis of a spatial linkage.

scholarly journals Tidal Variations of the Earth Rotation

2000 ◽  
Vol 178 ◽  
pp. 565-569
Author(s):  
J.M. Ferrándiz ◽  
Yu. V. Barkin ◽  
J. Getino
Keyword(s):  
Angular Velocity ◽  
Earth Rotation ◽  
Polar Motion ◽  
Deformable Body ◽  
The Moon ◽  
First Order ◽  
Andoyer Variables ◽  
The Earth ◽  
Tidal Deformations ◽  
Tidal Variations

AbstractThe equations for the rotation of a weakly deformable celestial body in non canonical Andoyer variables have been used to study the perturbation of Earth rotation due to tidal deformation raised by the Moon and Sun. A theory of the perturbed rotational motion of an isolated weakly deformable body in Andoyer variables and in components of the angular velocity has been developed. Mantle tidal deformations due to lunar and solar influences were analytically described and taken into account. Perturbations of the first order in the Earth’s polar motion were determined.

scholarly journals Trapping of null geodesics in slowly rotating spacetimes

2020 ◽  
Vol 80 (11) ◽  
Author(s):  
Jaroslav Vrba ◽  
Martin Urbanec ◽  
Zdeněk Stuchlík ◽  
John C. Miller
Keyword(s):  
Angular Velocity ◽  
Gravitational Waves ◽  
Compact Objects ◽  
Trapping Efficiency ◽  
Uniform Density ◽  
Slow Rotation ◽  
Null Geodesics ◽  
Effective Potentials ◽  
First Order ◽  
Simple Generalization

AbstractExtremely compact objects containing a region of trapped null geodesics could be of astrophysical relevance due to trapping of neutrinos with consequent impact on cooling processes or trapping of gravitational waves. These objects have previously been studied under the assumption of spherical symmetry. In the present paper, we consider a simple generalization by studying trapping of null geodesics in the framework of the Hartle–Thorne slow-rotation approximation taken to first order in the angular velocity, and considering a uniform-density object with uniform emissivity for the null geodesics. We calculate effective potentials and escape cones for the null geodesics and how they depend on the parameters of the spacetimes, and also calculate the “local” and “global” coefficients of efficiency for the trapping. We demonstrate that due to the rotation the trapping efficiency is different for co-rotating and retrograde null geodesics, and that trapping can occur even for $$R>3GM/c^2$$ R > 3 G M / c 2 , contrary to what happens in the absence of rotation.

An inertial piezoelectric hybrid actuator with large angular velocity and high resolution

2019 ◽  
Vol 30 (14) ◽  
pp. 2099-2111 ◽  
Author(s):  
Huilu Bao ◽  
Jianming Wen ◽  
Kang Chen ◽  
Jijie Ma ◽  
Dan Lei ◽  
...  
Keyword(s):  
High Resolution ◽  
Angular Velocity ◽  
Natural Frequencies ◽  
Angular Displacement ◽  
High Accuracy ◽  
Laser Vibrometer ◽  
Type B ◽  
First Order ◽  
Offset Distance ◽  
Hybrid Actuator

This article proposes an inertial piezoelectric actuator with hybrid design of asymmetrically clamping structures and a bias unit for the achievement of large angular velocity and high resolution. To investigate the influence of asymmetrical clamp and bias unit on the driving performance, two types of actuators were fabricated and tested. Combined effects from asymmetrical clamp and bias unit contribute to type A, while their subtractive effect is applied to type B. Using a scanning laser vibrometer, experiments were conducted to analyze the characteristics of the angular displacement and corresponding velocity. It is indicated that the measured first-order natural frequencies for above two types are 13.828 and 14.141 Hz, which agrees well with the simulation results of 16.666 and 17.379 Hz, respectively. Besides, compared with the actuators with simple asymmetrical clamping structure or bias unit, this hybrid actuator can obtain an angular velocity 6.87 rad/s at 80 V and 16 Hz and a resolution of 2.80 μrad under a square signal of 20 V and 1 Hz and an offset distance of −22 mm. As a result, the proposed actuators can achieve large angular velocity and high resolution, which is potentially applicable to quick positioning with high accuracy.

Functional Recovery of the Upper Limb With an Active Personal Device

2014 ◽  
Author(s):  
Federico Casolo ◽  
Gianluca Savalli
Keyword(s):  
Upper Limb ◽  
Functional Recovery ◽  
Impedance Control ◽  
Mechanical Impedance ◽  
Patient Characteristics ◽  
Memory Space ◽  
Working Volume ◽  
Intention To Move ◽  
The Subject ◽  
Arm Motion

A new personal device to assist the upper limb capable to be mounted on a wheelchair is being tested. The robot is equipped with three brushless motors powered by four electronic boards appositely designed and communicating via I2C protocol; one board works as master for the other three, which have simpler tasks. Most of the driving software has been developed with Matlab and mainly translated into C++ for memory space and boards’ efficiency matters. The system’s end-effector is connected to the subject’s forearm and can cooperate to the arm motion in several different ways. In order to avoid the overstress of the natural joints no further connections are made to the upper limb. The working volume of the limb connected to the device allows the execution of the trajectories required for most of daily living activities. It is addressed to post stroke rehabilitation and to the self-treatment of other patients with serious deficiency of arm forces, like individuals affected by muscular dystrophy. Some working modes exploit the mechanical impedance control to gently interfere with the residual natural motion capability of the subjects. The very preliminary tests of the prototype fitted on a power wheelchair are encouraging: it is light, not too noisy and easy to move for the subject. The first working mode, with full arm gravity compensation, and the second working mode, with partial compensation, have been implemented and are currently being tested with patients, as well as the mode in which the subject is helped to repeat a stereotyped exercise for self-physiotherapy. Beside the fact the control system must be calibrated on patient characteristics, for these initial tasks the system reveals to be user-friendly. Other working modes require to interpret the patient intention to move the upper limb. For a natural approach it is sufficient to decode the movement intention of the patient and the final position he wants the hand to reach, whilst the rest of the limb can be automatically positioned by the system. Different approaches to solve the problem have been experimentally tested, including the use of a headgear with a brain interface. To present knowledge the best results have been obtained by monitoring the movement of another body segment such as the head. The device designed for the functional recovery of upper limb can furthermore be used to monitor and easily certify the evolution of the patient conditions.

Sign in / Sign up

Export Citation Format

Share Document