Ivanka Veneva

Adjustable Compliance Joint with Torsion Spring for Human Centred Robots

Human-centred robots should be human-friendly, safe and impact-free. The present work is devoted to the problem of adjustable compliance implementation during the human friendly robots design. A new solution of a compliant joint with passive compliance adjustment based on a leaf torsion spring with variable length is presented. It allows independent positioning and stiffness regulation in a wide range. Some basic characteristics of the leaf torsion spring such as: stiffness, compliance, allowable torque, angle of elastic deformation and generated potential energy are analyzed. Thereafter numerical simulations are performed and the influence of the structural parameters on the basic compliant joint characteristics is estimated. Tests with a specially realized prototype of adjustable compliant joint are carried out and the basic characteristics of the prototype are evaluated. The results from the experimental assessment show a very good correlation with the numerical ones.

Identification of Bone Structure During Automatic Drilling in Orthopedic Surgery

In orthopedic surgery the manipulation “bone drilling” is used very often and it is performed by hand drilling, which causes a lot of problems—getting the big outlets, breaking the tendons or blood vessels, protecting the rear bone wall (which brings one more cutting of the tissue), overheating, and so on. Automatic bone drilling could successfully solve these problems. The drilling orthopedic robot (DORO) is presented as a device for automatic bone drilling execution as well as its technical features and functional applications. The experimental results are shown for identification of the parameters of the drilling process, including the bone structure in part.

PROPULSION SYSTEM WITH PNEUMATIC ARTIFICIAL MUSCLES FOR POWERING ANKLE-FOOT ORTHOSIS

Abstract The aim of this paper is to present the design of device for control of new propulsion system with pneumatic artificial muscles. The propulsion system can be used for ankle joint articulation, for assisting and rehabilitation in cases of injured ankle-foot complex, stroke patients or elderly with functional weakness. Proposed device for control is composed by microcontroller, generator for muscles contractions and sensor system. The microcontroller receives the control signals from sensors and modulates ankle joint flex- ion and extension during human motion. The local joint control with a PID (Proportional-Integral Derivative) position feedback directly calculates desired pressure levels and dictates the necessary contractions. The main goal is to achieve an adaptation of the system and provide the necessary joint torque using position control with feedback.

Control System for Data Acquisition and Processing of Ankle-Foot Orthosis

Abstract The aim of this paper is to present an autonomous control system for active ankle-foot orthoses (AFO). An ankle-foot orthosis is commonly used to help persons with weakness of ankle dorsiflexor muscles due to peripheral or central nervous system disorders. The proposed orthosis has one degree of freedom which foot segment is connected to the shank segment by a rotational joint. In order to assure automatic adaptation of the joint torque the joint is fitted with direct drive actuator attached laterally and controlled by a microcontroller ATmega128. Realizing flexion/extension the actuator applies a torque adequate to the joint position of the human ankle during level ground walking. The control signals are received from two tactile sensor arrays incorporated in the foot part of AFO and in the insole of the healthy leg. During each gait cycle a microcontroller estimates the forward speed and modulates the swing phase flexion and extension in order to achieve quite normal walking dynamics. A feedback with Proportional-Integral-Derivative control (PID control) was used to estimate the trajectory of the foot and positioning the actuated foot segment of the AFO when the foot rotates about the ankle. A graphical presentation of the mathematical model and simulation of the dynamic system is done building a Matlab Simulink block diagram model. The proposed intelligent system is oriented to control different models of personalized ankle-foot orthoses designed using reverse engineering and rapid prototyping by the joint team Bulgarian Academy of Sciences/Cardiff University.

New Exoskeleton Arm Concept Design And Actuation For Haptic Interaction With Virtual Objects

Abstract In the work presented in this paper the conceptual design and actuation of one new exoskeleton of the upper limb is presented. The device is designed for application where both motion tracking and force feedback are required, such as human interaction with virtual environment or rehabilitation tasks. The choice is presented of mechanical structure kinematical equivalent to the structure of the human arm. An actuation system is selected based on braided pneumatic muscle actuators. Antagonistic drive system for each joint is shown, using pulley and cable transmissions. Force/displacement diagrams are presented of two antagonistic acting muscles. Kinematics and dynamic estimations are performed of the system exoskeleton and upper limb. Selected parameters ensure in the antagonistic scheme joint torque regulation and human arm range of motion.

Power frequency spectrum analysis of surface EMG signals of upper limb muscles during elbow flexion – A comparison between healthy subjects and stroke survivors

After a stroke, motor units stop working properly and large, fast-twitch units are more frequently affected. Their impaired functions can be investigated during dynamic tasks using electromyographic (EMG) signal analysis. The aim of this paper is to investigate changes in the parameters of the power/frequency function during elbow flexion between affected, non-affected, and healthy muscles. Fifteen healthy subjects and ten stroke survivors participated in the experiments. Electromyographic data from 6 muscles of the upper limbs during elbow flexion were filtered and normalized to the amplitudes of EMG signals during maximal isometric tasks. The moments when motion started and when the flexion angle reached its maximal value were found. Equal intervals of 0.3407 s were defined between these two moments and one additional interval before the start of the flexion (first one) was supplemented. For each of these intervals the power/frequency function of EMG signals was calculated. The mean (MNF) and median frequencies (MDF), the maximal power (MPw) and the area under the power function (APw) were calculated. MNF was always higher than MDF. A significant decrease in these frequencies was found in only three post-stroke survivors. The frequencies in the first time interval were nearly always the highest among all intervals. The maximal power was nearly zero during first time interval and increased during the next ones. The largest values of MPw and APw were found for the flexor muscles and they increased for the muscles of the affected arm compared to the non-affected one of stroke survivors.

Design and Control of a Force Reflecting Arm Exoskeleton for Virtual Reality Applications.

In this paper, the design of an exoskeleton for the upper limb is presented, aimed primarily at training and rehabilitation in virtual environments. A mechanical model of the exoskeleton arm as haptic device is built up and impedance control scheme is selected as the most suitable for force reflection at the arm. The design of a grounded exoskeleton prototype is revealed in the paper. A driving system based on braided pneumatic muscle is selected to ensure natural security in the interaction. Antagonistic drive system for each joint is shown, using pulley and Bowden cable transmissions. An approach is presented for the joint moments control by antagonistic interaction of bundles with different numbers of pneumatic muscles. Control scheme of joint torque by antagonistic interaction is given, too. Computer simulations are performed to provide power reflection by virtual reality (VR), according to scenario of virtual gymnastics.

Adaptive System for Control of Active Ankle-Foot Orthosis and Gait Analysis

The main aim of this research is the development of an autonomous adaptive system for actuation, data acquisition and control of active ankle-foot orthosis. In this paper the design of a control unit composed by microcontroller, driver and sensor system, and its application to the actuation and position of the foot orthotic segment is presented. The research work combines hardware and software design of the intelligent control device with graphical interface for representation and analysis of the data acquired during human motion. The dynamic system simulation is done in Matlab Simulink and SimMechanics.

Intelligent control design in robotics and rehabilitation

For control purposes in robotics or rehabilitation, we may use properly simplified dynamic models with a reduced number of degrees of freedom. First, we define a set of variables that best characterize its dynamic performance in the required motion task. Second, driving forces/torques are properly assigned in order to achieve the required dynamic performance in an efficient way. The usual performance requirements are for positioning accuracy, movement execution time, and energy expenditure. We consider complex biomechatronic systems (BMS) like human with active orthosis or robotic arm that have to perform two main types of motion tasks: goal-directed movements and motion/posture stabilization. We propose new design concepts and criteria for BMS based on necessary and sufficient conditions for their robust controllability. Using simplified, yet realistic, models, we give several important examples in robotics and rehabilitation to illustrate the main features and advantages of our approach.

Powered Upper Limb Orthosis Actuation System Based on Pneumatic Artificial Muscles

Abstract The actuation system of a powered upper limb orthosis is studied in the work. To create natural safety in the mutual “man-robot” interaction, an actuation system based on pneumatic artificial muscles (PAM) is selected. Experimentally obtained force/contraction diagrams for bundles, consisting of different number of muscles are shown in the paper. The pooling force and the stiffness of the pneumatic actuators is assessed as a function of the number of muscles in the bundle and the supply pressure. Joint motion and torque is achieved by antagonistic actions through pulleys, driven by bundles of pneumatic muscles. Joint stiffness and joint torques are determined on condition of a power balance, as a function of the joint position, pressure, number of muscles and muscles