Abbas A. Dehghani-Sanij

Adaptive Undulatory Locomotion of a C. elegans Inspired Robot

Although significant progress has been made in the development of robots with serpentine properties, the issues of motion control and adaptation to environmental constraints still require substantial research. This is particularly true for search and rescue applications, where reliable operation in extremely difficult terrain is essential. This paper presents a novel robot design based on the mechanics and neural control of locomotion in Caenorhabditis elegans, a tiny nematode worm. Equipped with an extremely simple yet powerful neurally-inspired decentralized control system, the robot presented here is capable of effective serpentine locomotion. More importantly, it exhibits sensorless path finding, in which obstacles in the environment are overcome, based purely on proprioceptive feedback encoding body shape. Indeed, the robot lacks any form of external sensory capability. The design and implementation of the prototype robot and its control strategy are discussed. In order to validate the control strategy for path finding, experiments and analyses have been performed. The results show that the robot can find its path successfully in the majority of cases. The current limitations have also been discussed.

Effect of bandage thickness on interface pressure applied by compression bandages

Medical compression bandages are widely used in the treatment of chronic venous disorder. In order to design effective compression bandages, researchers have attempted to describe the interface pressure applied by these bandages using mathematical models. This paper reports on the work carried out to derive the mathematical model used to describe the interface pressure applied by single-layer bandage using two different approaches. The first assumes that the bandage thickness is negligible, whereas the second model includes the bandage thickness. The estimated pressures using the two formulae are then compared, simulated over a 3D representation of a real leg and validated experimentally. Both theoretical and experimental results have shown that taking bandage thickness into consideration while estimating the pressures applied by a medical compression bandage will result in more accurate estimation. However, the additional accuracy is clinically insignificant.

Impact of multilayered compression bandages on sub-bandage interface pressure: a model

Background Multi-component medical compression bandages are widely used to treat venous leg ulcers. The sub-bandage interface pressures induced by individual components of the multi-component compression bandage systems are not always simply additive. Current models to explain compression bandage performance do not take account of the increase in leg circumference when each bandage is applied, and this may account for the difference between predicted and actual pressures. Objective To calculate the interface pressure when a multi-component compression bandage system is applied to a leg. Method Use thick wall cylinder theory to estimate the sub-bandage pressure over the leg when a multi-component compression bandage is applied to a leg. Results A mathematical model was developed based on thick cylinder theory to include bandage thickness in the calculation of the interface pressure in multi-component compression systems. In multi-component compression systems, the interface pressure corresponds to the sum of the pressures applied by individual bandage layers. However, the change in the limb diameter caused by additional bandage layers should be considered in the calculation. Adding the interface pressure produced by single components without considering the bandage thickness will result in an overestimate of the overall interface pressure produced by the multi-component compression systems. At the ankle (circumference 25 cm) this error can be 19.2% or even more in the case of four components bandaging systems. Conclusion Bandage thickness should be considered when calculating the pressure applied using multi-component compression systems.

On the Measurement of Situation Awareness for Effective Human-Robot Interaction in Teleoperated Systems

Several methods of measuring the situation awareness (SA) of a human who is teleoperating a robot are compared for the domain of urban search and rescue (USAR), to identify those that have the greatest potential for developing more reliable and accurate ways of measuring SA for effectively operating robot systems. Such comparative studies are essential because SA has been identified as a key human factors issue since post-September 11, 2001, operations for effective task performance in (tele)robotics. This paper discusses the pros and cons of the main aspects that need to be included in developing reliable SA measurement methods from the related domain of air traffic control, in which SA has a long research history. These methods have been adopted and modified accordingly to address needs of teleoperating robot systems and have been tested in a realistic USAR simulated scenario developed especially for performing these assessments. The results were compared against each other as well as with existing measures. A new method of measuring task performance that is more appropriate for USAR is also presented and tested within the comparative studies.

Impact of variation in limb shape on sub-bandage interface pressure

Background Sub-bandage interface pressure generated by medical compression bandages (MCB) and hosiery changes in mobile patients as they move due to the change in the limb size. However, the amount of variation in the interface pressure is dependent on the stiffness of the compression material. Researchers have proposed several indices to describe this change in interface pressure, including the static stiffness index (SSI) and the dynamic stiffness index (DSI). These indices can also be used to classify compression products. Objectives To explore the different proposed indices to describe the stiffness of a compression material and compare it to the engineering stress-strain modulus which is used for the same purpose; To estimate theoretically the change in the interface pressure which is caused by the change in the limb shape as a consequence of calf muscle activity and the associated transient variation in limb dimensions. Method Use Chord modulus to classify compression material; Use thin and thick cylinder wall theory to estimate the variation in the interface pressure due to changes in the limb shape secondary to muscle contraction; Use tensile test devices to obtain the Chord modulus for two different MCB at two different dynamic ranges. Results Chord modulus (E) describes the change in tension in a dynamic situation, and this is labelled as stiffness in the bandaging literature; Chord modulus, with the help of a mathematical model that was developed based on thick wall cylinder theory, can be used to predict the change in sub-bandage interface pressure caused by the change in limb shape secondary to calf muscle activity; Chord modulus can be used to classify bandages and describe how they will behave when they are applied to a leg. Conclusion The dynamic pressure can be predicted using a simple mathematical model using Chord modulus, which can be calculated in vitro using standard tensile testing equipment. In addition, Chord modulus can be used to classify compression bandages and hosiery.

Carbon Black Reinforced Epoxy Resin Nanocomposites as Bending Sensors

By blending electrically conducting carbon black particles and silica into poly(bisphenol A-co-epichlorohydrin) epoxy resin polymer, conductive nanocomposites were prepared by printing onto transparency films and curing. Application of a milling procedure prior to application is beneficial for the reduction of cracks in the subsequent nanocomposites. Electrical conduction of nanocomposite is CB content dependent. A percolation region (19—24% CB on mass of resin) exists where the nanocomposite exhibits a transition from an electrical insulator to conductor. Nanocomposites with 14% and 19% CB on mass of resin demonstrated greatest sensitivity to changes in bending angle, attributed to greater localized changes in the conductive paths within a semi-conducting sensor. Good reproducibility was observed as a result of molecular interactions between CB particles and the epoxy resin.

A Real-Time Gait Event Detection for Lower Limb Prosthesis Control and Evaluation

Lower extremity amputees suffer from mobility limitations which will result in a degradation of their quality of life. Wearable sensors are frequently used to assess spatio-temporal, kinematic and kinetic parameters providing the means to establish an interactive control of the amputee-prosthesis-environment system. Gait events and the gait phase detection of an amputee’s locomotion are vital for controlling lower limb prosthetic devices. The paper presents an approach to real-time gait event detection for lower limb amputees using a wireless gyroscope attached to the shank when performing level ground and ramp activities. The results were validated using both healthy and amputee subjects and showed that the time differences in identifying Initial Contact (IC) and Toe Off (TO) events were larger in a transfemoral amputee when compared to the control subjects and a transtibial amputee (TTA). Overall, the time difference latency lies within a range of ±50 ms while the detection rate was 100% for all activities. Based on the validated results, the IC and TO events can be accurately detected using the proposed system in both control subjects and amputees when performing activities of daily living and can also be utilized in the clinical setup for rehabilitation and assessing the performance of lower limb prosthesis users.

Real-time gait event detection for transfemoral amputees during ramp ascending and descending.

Events and phases detection of the human gait are vital for controlling prosthesis, orthosis and functional electrical stimulation (FES) systems. Wearable sensors are inexpensive, portable and have fast processing capability. They are frequently used to assess spatio-temporal, kinematic and kinetic parameters of the human gait which in turn provide more details about the human voluntary control and ampute-eprosthesis interaction. This paper presents a reliable real-time gait event detection algorithm based on simple heuristics approach, applicable to signals from tri-axial gyroscope for lower limb amputees during ramp ascending and descending. Experimental validation is done by comparing the results of gyroscope signal with footswitches. For healthy subjects, the mean difference between events detected by gyroscope and footswitches is 14 ms and 10.5 ms for initial contact (IC) whereas for toe off (TO) it is -5 ms and -25 ms for ramp up and down respectively. For transfemoral amputee, the error is slightly higher either due to the placement of footswitches underneath the foot or the lack of proper knee flexion and ankle plantarflexion/dorsiflexion during ramp up and down. Finally, repeatability tests showed promising results.

Gait dynamic stability analysis and motor control prediction for varying terrain conditions

This work presents the gait dynamic stability modelling for different walking terrains adopted by the motor. The sensory-motor transitional gait assessment is difficult in clinical environment in case of disorders. The aim of present study was to model and analyse dynamic stability thresholds for gait transitional phases. Experimental data were collected from four healthy subjects while walking on a force platform placed at ramp and level ground walking tracks. The rate-dependent variations in the center of pressure (COP) and ground reaction forces (GRF) were modelled as motor output and input responses. Finite difference and non-linear regression algorithms were implemented to model gait transitions. Dynamic stability estimation for ramp and level ground walking were performed by analysis in time and frequency domains. Our investigation provided interesting results; 1) the overdamped motor output response acts as a compensator for instabilities and oscillations in unloading phase and initial contact, and 2) prediction of ramp ascend walking as the least stable gait than ramp descend for healthy subjects.

Virtual prototyping of a semi-active transfemoral prosthetic leg.

This article presents a virtual prototyping study of a semi-active lower limb prosthesis to improve the functionality of an amputee during prosthesis–environment interaction for level ground walking. Articulated ankle–foot prosthesis and a single-axis semi-active prosthetic knee with active and passive operating modes were considered. Data for level ground walking were collected using a photogrammetric method in order to develop a base-line simulation model and with the hip kinematics input to verify the proposed design. The simulated results show that the semi-active lower limb prosthesis is able to move efficiently in passive mode, and the activation time of the knee actuator can be reduced by approximately 50%. Therefore, this semi-active system has the potential to reduce the energy consumption of the actuators required during level ground walking and requires less compensation from the amputee due to lower deviation of the vertical excursion of body centre of mass.