scholarly journals Impedance Model-Based Optimal Regulation on Force and Position of Bimanual Robots to Hold an Object

Complexity ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Darong Huang ◽  
Hong Zhan ◽  
Chenguang Yang
Keyword(s):  
Degrees Of Freedom ◽  
Target Position ◽  
Internal Force ◽  
Robot System ◽  
Joint Torques ◽  
Impedance Model ◽  
Generalized Momentum ◽  
Optimal Target ◽  
End Effectors ◽  
Bimanual Robot

Bimanual robots have been studied for decades and regulation on internal force of the being held object by two manipulators becomes a research interest in recent years. In this paper, based on impedance model, a method to obtain the optimal target position for bimanual robots to hold an object is proposed. We introduce a cost function combining the errors of the force and the position and manage to minimize its value to gain the optimal coordinates for the robot end effectors (EE). To implement this method, two necessary algorithms are presented, which are the closed-loop inverse kinematics (CLIK) method to work out joint positions from desired EE pose and the generalized-momentum-based external force observer to measure the subjected force acting on the EE so as to properly compensate for the joint torques. To verify the effectiveness, practicality, and adaptivity of the proposed scheme, in the simulation, a bimanual robot system with three degrees of freedom (DOF) in every manipulator was constructed and employed to hold an object, where the results are satisfactory.

scholarly journals Optimization of Joint Torques of Robot Using Dynamic Redundant Degrees of Freedom.

1992 ◽  
Vol 10 (5) ◽  
pp. 682-688
Author(s):  
Tamio ARAI ◽  
Shih-Hsuan CHIU ◽  
Akira SAIKI ◽  
Hisashi OSUMI
Keyword(s):  
Degrees Of Freedom ◽  
Joint Torques

Physics-Based Seated Posture Prediction for Pregnant Women and Validation Considering Ground and Seat Pan Contacts

2012 ◽  
Vol 134 (7) ◽  
Author(s):  
Bradley Howard ◽  
Aimee Cloutier ◽  
Jingzhou (James) Yang
Keyword(s):  
Pregnant Women ◽  
Objective Function ◽  
Linear Regression Analysis ◽  
Joint Torque ◽  
Joint Torques ◽  
Design Variables ◽  
Optimization Formulation ◽  
Posture Prediction ◽  
Seated Posture ◽  
End Effectors

An understanding of human seated posture is important across many fields of scientific research. Certain demographics, such as pregnant women, have special postural limitations that need to be considered. Physics-based posture prediction is a tool in which seated postures can be quickly and thoroughly analyzed, as long the predicted postures are realistic. This paper proposes and validates an optimization formulation to predict seated posture for pregnant women considering ground and seat pan contacts. For the optimization formulation, the design variables are joint angles (posture); the cost function is dependent on joint torques. Constraints include joint limits, joint torque limits, the distances from the end-effectors to target points, and self-collision avoidance constraints. Three different joint torque cost functions have been investigated to account for the special postural characteristics of pregnant women and consider the support reaction forces (SRFs) associated with seated posture. Postures are predicted for three different reaching tasks in common reaching directions using each of the objective function formulations. The predicted postures are validated against experimental postures obtained using motion capture. A linear regression analysis was used to evaluate the validity of the predicted postures and was the criteria for comparison between the different objective functions. A 56 degree of freedom model was used for the posture prediction. Use of the objective function minimizing the maximum normalized joint torque provided an R2 value of 0.828, proving superior to either of two alternative functions.

scholarly journals Lower Extremity Motor Impairments in Ambulatory Chronic Hemiparetic Stroke: Evidence for Lower Extremity Weakness and Abnormal Muscle and Joint Torque Coupling Patterns

2017 ◽  
Vol 31 (9) ◽  
pp. 814-826 ◽  
Author(s):  
Natalia Sánchez ◽  
Ana Maria Acosta ◽  
Roberto Lopez-Rosado ◽  
Arno H. A. Stienen ◽  
Julius P. A. Dewald
Keyword(s):  
Lower Extremity ◽  
Degrees Of Freedom ◽  
Joint Torque ◽  
Motor Impairments ◽  
Lower Extremity Weakness ◽  
Joint Torques ◽  
Hemiparetic Stroke ◽  
Chronic Hemiparetic Stroke ◽  
Hip Extension ◽  
Flexion And Extension

Although global movement abnormalities in the lower extremity poststroke have been studied, the expression of specific motor impairments such as weakness and abnormal muscle and joint torque coupling patterns have received less attention. We characterized changes in strength, muscle coactivation and associated joint torque couples in the paretic and nonparetic extremity of 15 participants with chronic poststroke hemiparesis (age 59.6 ± 15.2 years) compared with 8 age-matched controls. Participants performed isometric maximum torques in hip abduction, adduction, flexion and extension, knee flexion and extension, ankle dorsi- and plantarflexion and submaximal torques in hip extension and ankle plantarflexion. Surface electromyograms (EMGs) of 10 lower extremity muscles were measured. Relative weakness (paretic extremity compared with the nonparetic extremity) was measured in poststroke participants. Differences in EMGs and joint torques associated with maximum voluntary torques were tested using linear mixed effects models. Results indicate significant poststroke torque weakness in all degrees of freedom except hip extension and adduction, adductor coactivation during extensor tasks, in addition to synergistic muscle coactivation patterns. This was more pronounced in the paretic extremity compared with the nonparetic extremity and with controls. Results also indicated significant interjoint torque couples during maximum and submaximal hip extension in both extremities of poststroke participants and in controls only during maximal hip extension. Additionally, significant interjoint torque couples were identified only in the paretic extremity during ankle plantarflexion. A better understanding of these motor impairments is expected to lead to more effective interventions for poststroke gait and posture.

Do Arm Postures Vary With the Speed of Reaching?

1999 ◽  
Vol 81 (5) ◽  
pp. 2582-2586 ◽  
Author(s):  
Kiisa C. Nishikawa ◽  
Sara T. Murray ◽  
Martha Flanders
Keyword(s):  
Degrees Of Freedom ◽  
Three Dimensional ◽  
Optimal Solution ◽  
Reaching Movements ◽  
Total Force ◽  
Joint Torques ◽  
Dynamic Factors ◽  
Human Arm ◽  
Wide Range ◽  
Dynamic Forces

Do arm postures vary with the speed of reaching? For reaching movements in one plane, the hand has been observed to follow a similar path regardless of speed. Recent work on the control of more complex reaching movements raises the question of whether a similar “speed invariance” also holds for the additional degrees of freedom. Therefore we examined human arm movements involving initial and final hand locations distributed throughout the three-dimensional (3D) workspace of the arm. Despite this added complexity, arm kinematics (summarized by the spatial orientation of the “plane of the arm” and the 3D curvature of the hand path) changed very little for movements performed over a wide range of speeds. If the total force (dynamic + quasistatic) had been optimized by the control system (e.g., as in a minimization of the change in joint torques or the change in muscular forces), the optimal solution would change with speed; slow movements would reflect the minimal antigravity torques, whereas fast movements would be more strongly influenced by dynamic factors. The speed-invariant postures observed in this study are instead consistent with a hypothesized optimization of only the dynamic forces.

Offline decoupled path planning approach for effective coordination of multiple robots

Robotica ◽  
2009 ◽  
Vol 28 (4) ◽  
pp. 477-491 ◽  
Author(s):  
Shital S. Chiddarwar ◽  
N. Ramesh Babu
Keyword(s):  
Path Planning ◽  
Free Path ◽  
Minimum Distance ◽  
Degrees Of Freedom ◽  
Multiple Robots ◽  
A Algorithm ◽  
Two Phase ◽  
Six Degrees Of Freedom ◽  
Planning Approach ◽  
End Effectors

SUMMARYIn this paper, a decoupled offline path planning approach for determining the collision-free path of end effectors of multiple robots involved in coordinated manipulation is proposed. The proposed approach for decoupled path planning is a two-phase approach in which the path for coordinated manipulation is generated with a coupled interaction between collision checking and path planning techniques. Collision checking is done by modelling the links and environment of robot using swept sphere volume technique and utilizing minimum distance heuristic for interference check. While determining the path of the end effector of robots involved in coordinated manipulation, the obstacles present in the workspace are considered as static obstacles and the links of the robots are viewed as dynamic obstacles by the other robot. Coordination is done in offline mode by implementing replanning strategy which adopts incremental A* algorithm for searching the collision-free path. The effectiveness of proposed decoupled approach is demonstrated by considering two examples having multiple six degrees of freedom robots operating in 3D work cell environment with certain static obstacles.

Design and analysis of a tendon-based MRI-compatible surgery robot for transperineal prostate needle placement

2014 ◽  
Vol 229 (2) ◽  
pp. 335-348 ◽  
Author(s):  
Shan Jiang ◽  
Fude Sun ◽  
Jiansheng Dai ◽  
Jun Liu ◽  
Zhiyong Yang
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Degrees Of Freedom ◽  
Virtual Work ◽  
Inverse Kinematic ◽  
Surgical Robot ◽  
Resonance Imaging ◽  
Joint Torques ◽  
Reachable Workspace ◽  
6 Degrees Of Freedom

Tendon-based transmission has significant advantages in the development of a surgical robot, which is fully magnetic resonance imaging compatible and can work dexterously in the very limited space inside magnetic resonance imaging core. According to the requirements of magnetic resonance imaging compatibility, a novel 6 degrees of freedom tendon-based surgical robot composed of three independent modules is developed in this paper. After a brief introduction to the robot, the direct and inverse kinematic equations are deduced by applying the concept of screw displacements, and the reachable workspace of the robot is calculated. As to the static force analysis, we apply the principle of virtual work to derive a transmission between the equivalent joint torques and the tendon forces. By the use of the pseudoinverse technique, a systematic method is developed for the resolution of redundant tendon forces.

Comparison of Sprinting With and Without Running-Specific Prostheses Using Optimal Control Techniques

Robotica ◽  
2019 ◽  
Vol 37 (12) ◽  
pp. 2176-2194 ◽  
Author(s):  
Anna Lena Emonds ◽  
Johannes Funken ◽  
Wolfgang Potthast ◽  
Katja Mombaur
Keyword(s):  
Optimal Control ◽  
Degrees Of Freedom ◽  
Sagittal Plane ◽  
Reference Group ◽  
Optimality Criteria ◽  
Mechanical Work ◽  
Step Frequency ◽  
Joint Torques ◽  
Linear Spring ◽  
Multi Body

SummaryThe purpose of our study was to get deeper insights into sprinting with and without running-specific prostheses and to perform a comparison of the two by combining analysis of known motion capture data with mathematical modeling and optimal control problem (OCP) findings. We established rigid multi-body system models with 14 bodies and 16 degrees of freedom in the sagittal plane for one unilateral transtibial amputee and three non-amputee sprinters. The internal joints are powered by torque actuators except for the passive prosthetic ankle joint which is equipped with a linear spring–damper system. For each model, the dynamics of one sprinting trial was reconstructed by solving a multiphase least squares OCP with discontinuities and constraints. We compared the motions of the amputee athlete and the non-amputee reference group by computing characteristic criteria such as the contribution of joint torques, the absolute mechanical work, step frequency and length, among others. By comparing the amputee athlete with the non-amputee athletes, we found reduced activity in the joints of the prosthetic limb, but increased torques and absolute mechanical work in the arms. We also compared the recorded motions to synthesized motions using different optimality criteria and found that the recorded motions are still far from the optimal solutions for both amputee and non-amputee sprinting.

Study on low vibration isolator arrangement of marine gearboxes based on an impedance model

2020 ◽  
Vol 44 (4) ◽  
pp. 580-591
Author(s):  
Yafeng Ren ◽  
Shan Chang ◽  
Geng Liu
Keyword(s):  
Degrees Of Freedom ◽  
Vibration Isolator ◽  
Underwater Noise ◽  
Impedance Model ◽  
Multiple Degrees Of Freedom ◽  
Stiffness Characteristics ◽  
Local Stiffness ◽  
Isolation Performance ◽  
Synthesis Approach ◽  
Flexible Model

To reduce the underwater noise of ships, gearboxes are usually flexibly installed on the ship’s foundation. A reasonable isolator arrangement can effectively reduce the vibration transmitted from the gears to the foundation. In this paper, a dynamic model of a single-stage vibration-isolated gear system is established based on an impedance synthesis approach. This model is a multiple degrees of freedom, multi-mount, and flexible model that can take into account the local stiffness of the housing and foundation. By studying the influence of installation span, installation offset, and number of isolators on the vibrations of the ship’s foundation, it was determined that reducing isolator span is beneficial to isolation, increasing isolator offset can slightly reduce vibration, increasing the number of isolators does not always increase vibration, and the local stiffness characteristics of the housing and foundation have a greater influence than other factors on the isolation performance.

Design of an Underactuated Robotic End-Effector With a Focus on Power Tool Manipulation

2014 ◽  
Author(s):  
Michael Rouleau ◽  
Dennis Hong
Keyword(s):  
Disaster Response ◽  
Degrees Of Freedom ◽  
Humanoid Robot ◽  
Servo Motor ◽  
End Effector ◽  
Design Considerations ◽  
Wide Range ◽  
End Effectors ◽  
Four Bar Linkage ◽  
Careful Design

End-effectors require careful design considerations to be able to successfully hold and use power tools while maintaining the ability to also grasp a wide range of other objects. This paper describes the design of an end effector for a humanoid robot built for disaster response scenarios. The end effector is comprised of two independently actuated fingers with two opposing stationary rigid hollow pylons built to allow the pinching of objects and to provide protection for the opposing fingers when retracted and not in use. Each finger has two degrees of freedom (DOF) and is actuated with one servo motor through the use of an underactuated four bar linkage. Using only two fingers and two actuators the end-effector has the ability to hold a power tool while also being able to simultaneously actuate the trigger of the tool independently. The combination of compliant fingers and rigid pylons along with the careful design of the palm structure creates a strong robust dexterous end-effort that is simple to control.

scholarly journals ONLINE LEARNING OF THE BODY SCHEMA

2008 ◽  
Vol 05 (02) ◽  
pp. 161-181 ◽  
Author(s):  
MICHA HERSCH ◽  
ERIC SAUSER ◽  
AUDE BILLARD
Keyword(s):  
Online Learning ◽  
Degrees Of Freedom ◽  
Humanoid Robot ◽  
Body Schema ◽  
The Body ◽  
Space Representation ◽  
Real Robot ◽  
Sensorimotor Contingencies ◽  
End Effectors ◽  
Subjective Space

We present an algorithm enabling a humanoid robot to visually learn its body schema, knowing only the number of degrees of freedom in each limb. By "body schema" we mean the joint positions and orientations and thus the kinematic function. The learning is performed by visually observing its end-effectors when moving them. With simulations involving a body schema of more than 20 degrees of freedom, results show that the system is scalable to a high number of degrees of freedom. Real robot experiments confirm the practicality of our approach. Our results illustrate how subjective space representation can develop as a result of sensorimotor contingencies.

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