Human Arm Impedance and EMG in 3D

Bulletin of Electrical Engineering and Informatics, 2022

In this paper, impedance characteristics are determined for discrete movement. It explores the changes in impedance characteristics of human arm during a complete task. This study considered 3D spatial movement for horizontal adduction and abduction. The human arm is considered as mass-spring-damper system and the modelling is done accordingly. The model is solved for 3 degree of freedom (3DoF) spatial movement usually used for daily work. Inertia, stiffness and damping factor are the impedance characteristics considered in the model. Using position measuring device, the position data of elbow and wrist were obtained with respect to pre-defined references. The data were used to calculate velocity, acceleration and force. Then, the impedance characteristics were determined by solving the equation of motion of the mass-spring-damper system corresponding to different position of the wrist on the trajectory. These impedance factors were then plotted to map the characteristics. The mappi...

Biological Cybernetics, 2004

This paper describes a simple computational model of joint torque and impedance in human arm movements that can be used to simulate three-dimensional movements of the (redundant) arm or leg and to design the control of robots and human-machine interfaces. This model, based on recent physiological findings, assumes that (1) the central nervous system learns the force and impedance to perform a task successfully in a given stable or unstable dynamic environment and (2) stiffness is linearly related to the magnitude of the joint torque and increased to compensate for environment instability. Comparison with existing data shows that this simple model is able to predict impedance geometry well.

Research Square (Research Square), 2024

The broad spread of cooperative robots into many application domains has resulted in a demand for intuitive and effective solutions for teleoperated control. A relevant role in teleoperation has been assumed by impedance controllers, that allow the increase of stability and accuracy during interaction. This paper aims to test a teleoperation method based on an impedance controller, namely tele-impedance control, that is usable in unstructured environments since it relies only on wearable sensors. The proposed solution maps the joint stiffness and position of the human user, computed through six EMG and two M-IMU sensors, into the remote system to be teleoperated. We developed a 2-DoFs virtual task involving virtual physical interactions to compare the performance of our solution with the one of a traditional position-based controller. The study has been conducted on five healthy participants, who experienced both controllers in two different sessions. The tele-impedance approach has proved to be less physically demanding and more intuitive than the position-based one. Experimental data also allow us to investigate the strategy employed by the volunteers in the case of remote interactions, while using the two controllers. Of note, even though with the position controller the variation of subject impedance has no effect on the virtual arm, participants still tend to regulate both impedance and position of their own arm.

2012 4th IEEE RAS & EMBS International Conference on Biomedical Robotics and Biomechatronics (BioRob), 2012

Necessary physical contact between an operator and a force feedback haptic device creates a coupled system consisting of human and machine. This contact, combined with the natural human tendency to increase arm stiffness to attempt to stabilize its motion, can reduce the stability of the system. This paper proposes a method to increase stability on demand while maintaining speed and performance. Operator arm stiffness is not directly measurable, so controllers cannot typically account for this issue. The causes of arm end-point stiffness are examined as related to system stability, and a method for estimating changes in arm stiffness based on arm muscle activity was designed to provide a robotic controller with additional information about the operator. This was accomplished using EMGs to measure muscle activities and estimating the level of arm stiffness, which was used to adjust the dynamic characteristics of an impedance controller. To support this design, the correlation between EMGs and arm stiffness was validated experimentally. Further experiments characterized the effects of the designed system on operator performance. This showed increased stability and faster, more accurate movements using the compensating system. Such a system could be used in many applications, including force assisting devices in industrial facilities.

2014 UKSim-AMSS 16th International Conference on Computer Modelling and Simulation, 2014

This paper presents the impedance characteristics of human arm in daily spatial activity. Human arm is considered as a mass-spring-damper system. The input data in the form of Cartesian position is measured to get dynamic impedance relationship by the motion equation for the mass-springdamper system. Mappings are done by various combinations to observe the nature of the different impedance components during dynamic movement. The significant amount of variation in damping and inertia components are observed in every turning of the arm movement while the stiffness shows the changing behavior throughout the movement. From this study it is known that for this particular movement the arm follows a pattern and same behavior is followed for the repetitions of the movement. The obtained result could be beneficial for the study of upper extremity exoskeleton for human rehabilitation.

2018 7th IEEE International Conference on Biomedical Robotics and Biomechatronics (Biorob), 2018

Human Robot Interaction has become a key point in the development of new robotic interfaces and controllers. In traditional control schemes for teleoperation, master devices are unaware of the user's arm dynamic characteristics, as well as of the complex motor control strategies adopted to perform the task. In this work, we propose a novel impedance controller to regulate the master device's dynamic properties based on the estimation of user's arm stiffness, with the aim of improving shared task performance. We developed a virtual planar reaching task, and we evaluated arm end-point stiffness's main axis changes in magnitude and direction using a non disruptive offline musculoskeletal model-based algorithm. Based on the stiffness modulation, the biomimetic variable impedance controller to adapt the master device's damping matrix. The direction of maximal damping was aligned with the estimated direction of maximal stiffness (Enhancing field), or to the perpendicular to the stiffness main axis (Isotropic field). The task performances under the biomimetic impedance controllers were tested and compared with the null damping condition. The results showed an increase in task performance, in terms of positional error and overshoots, with both biomimetic controllers. The analysis proved the potentiality of the biomimetic impedance modulation controller in terms of execution accuracy.

2011 11th IEEE-RAS International Conference on Humanoid Robots, 2011

The human arm's capability to alter its impedance has motivated multiple developments of robotic manipulators and control methods. It provides advantages during manipulation such as robustness against external disturbances and task adaptability. However, how the impedance of the arm is set depends on the manipulation situation; a general procedure is lacking. This paper aims to fill this gap by providing a method to estimate the impedance parameters of the human arm, while taking the numerical stability of the approach into account. A dynamic arm model and an identification method is presented. Confidential criteria to determine the accuracy of the estimated parameters are given. Finally, the procedure is validated in an experiment with a human subject and the results are discussed.

IEEE SMC'99 Conference Proceedings. 1999 IEEE International Conference on Systems, Man, and Cybernetics (Cat. No.99CH37028), 1999

In the near future many aspect of life will be encompassed by tasks performed in co-operation with robots. As a result, robots need to be made human-friendly and to execute tasks in co-operation with humans. Control systems for such robots should be designed to work by imitating human characteristics. We aim to achieve these goals by controlling a simple one degree-of-freedom robot. First, the impedance characteristics of the human arm in a co-operative task are investigated. Then, these characteristics are implemented in a robot which performs a co-operative task with a human. The proposed control method produced good characteristics for robots co-operating with humans.

제어로봇시스템학회 국제학술대회 논문집, 2002

Control systems for cooperative robots should be designed to work imitating human characteristics. In this study, we tried to investigate the impedance characteristic of human arm in a cooperative task. Human arm was moved in a desired trajectory. The motion was actuated by a 1 degree-of-freedom robot system. Trajectories used in the experiment were minimum jerk (the rate of change of acceleration) trajectories, which was found during human and human cooperative task and optimum for muscle movement. As the muscle is mechanically analogous to a spring-damper system, a second-order equation was considered as the model for arm dynamics. In the model, inertia, stiffness and damping factor were considered. The impedance parameter was estimated from the position and torque data obtained from the experiment and based on the "Estimation of Parametric Model". It was found that the inertia is almost constant over the operational time. The damping factor and stiffness were high at the starting position and became near to zero after 0.4 second. The EMG (electromyography) response of elbow muscles during the movements was also examined.

1999

This paper discusses task-oriented control strategies and their dynamic formation in movements of human arm, with the impedance adjustment as the fundamental control method in its redundant degree-of-freedom (DOF) muscular-skeletal structure. Impedance adjustment mechanisms and dynamic characteristics for the muscularskeletal and spinal reflection systems are described. It is also shown that the impedance adjustment at the joint and muscular levels plays an important role in the manipulation of objects. Dynamic impedance properties (stiffness and viscosity) of the actuating structure, together with the equilibrium trajectory profile of the structure, is defined to be the expression of the motion skill. Then, a task-oriented iterative impedance adjusting algorithm based on Variant Calculus is proposed, and simulation examples on a three-DOF planar arm are presented to show that the task-oriented motion skills can be formed under naturally specified simple objective functions.