Ahmed M. R. Fath El-Bab

Investigation of a New High Sensitive Micro-Electromechanical Strain Gauge Sensor Based on Graphene Piezoresistivity

A new strain gauge based on graphene piezoresistivity was fabricated by a novel low cost technique which suits mass production of micro piezoresistor sensors. The strain gauge consists of a monolayer graphene film made by chemical vapor deposition on a copper foil surface, and transferred to Si/SiO2 surface by using a polymethyl-methacrylate (PMMA) assisted transfer method. The film is shaped by laser machine to work as a conductive-piezoresistive material between two deposited electrical silver electrodes. This method of fabrication provides a high productivity due to the homogeneous distribution of the graphene monolayer all over the Si/SiO2 surface. The experimentally measured gauge factor of graphene based device is 255, which promises a new strain gauge sensor of high sensitivity.

Development of parallel manipulator sit to stand assistive device for elderly people

This paper describes a novel mobility assistive device under development in the Egypt-Japan University of Science and Technology (E-JUST). The proposed system can help patients who do not have enough physical strength on the lower limbs during sit to stand due to aging, diseases such as polymyositis and myopathy, and joint replacement surgery complications. It can follow the natural pattern of human motion during sit to stand providing assistance force under the shoulder. The overall device is compact and employees a parallel mechanism which provide more stiffness. Several experiments were carried out in a VICON room to calculate the human motion posture while sit to stand motion in addition estimate the trajectory of the end effector during assisting. Computer simulation was built to verify the performance of the proposed system with the reference trajectory.

Graphene film development on flexible substrate using a new technique: temperature dependency of gauge factor for graphene-based strain sensors

Purpose – The purpose of this paper is to develop a new simple technique to synthesize graphene film on a flexible polyethylene terephthalate (PET) substrate and applied as a strain sensor. Design/methodology/approach – Graphene film was synthesized using laser treatment of graphene oxide (GO) film deposited on PET substrate. A universal laser system was used to simultaneously reduce and pattern the GO film into laser reduced graphene oxide (LRGO) film. Findings – The laser treatment synthesizes a multilayer graphene film with overlapped flakes, which shows structure integrity, mechanical flexibility and electrical conductivity of 1,330 S/m. The developed LRGO/PET film was used to fabricate a high sensitivity strain sensor. The sensitivity and temperature dependency of its gauge factor (GF) was examined at applied strains up to 0.25 per cent and operating temperatures up to 80°C. The fabricated sensor shows stable GF of approximately 78 up to 60°C with standard error of the mean not exceeding approximatel...

Dynamic modeling of a parallel manipulator-based mobility assistive device for elderly people

Recently, more attention has been paid for assisting elderly and people with various disabilities, hence assistive robots have gained much popularity. These robots are usually in a direct contact with the user, therefore dynamic modeling is important for precise control. In this paper, dynamic model for a parallel manipulator-based mobility assistive device is first developed using the first type of Lagranges equations and simulated using MATLAB software. Also, a CAD model of the device is simulated using ADAMS dynamic simulation software for comparison. Both simulations are performed using the same system parameters and end-effector trajectory. In these simulations, the natural trajectory of human motion during sit to stand activity is used. This trajectory is determined using VICON human motion capturing system. Simulations show a good agreement between the results obtained using the dynamic model and the ones obtained using ADAMS software with a root mean square error less than 0.2% for all calculated results.

Sit to stand sensing using wearable IMUs based on adaptive Neuro Fuzzy and Kalman Filter

This paper present a method for measuring the posture of a human body during different phases of sit to stand motion using inertial sensors. The proposed method fuses data from inertial sensors placed in trunk and thigh using Adaptive Neuro-Fuzzy Inference System (ANFIS) followed by a Kalman Filter (KF). The ANFIS attempts to estimate the position of shoulder of the human, at each sampling instant when measurement update step is carried out. The Kalman filter supervises the performance of the ANFIS with the aim of reducing the mismatch between the estimated and actual. The performance of the method is verified by measurements from VICON (motion analysis system). The obtained results show the effectiveness of the proposed algorithm in prediction the human shoulder position with root mean square error 0.018 m and 0.016 m in the x and y direction, respectively.

Shape characterization of a multi-modal tactile display device for biomedical applications

Tactile display has recently been attracting much attention in medical applications such as Minimally Invasive Surgery-MIS. It is needed for surgeons to feel the tissue hardness during MIS. In this paper, a multi modal tactile display device is presented for displaying both shape and stiffness of soft tissues. The concept of design is built upon simple use of several springs which are made from Shape Memory Alloy, SMA, to control shape and stiffness. The mechanical design of the device is described, and sensors (displacement, current and force) are integrated with the device to control the SMA springs. The elongation spring, responsible for displaying the shape is characterized and controlled experimentally. The device shows it can display a displacement of 5 mm in 5 seconds with PI controller using LabVIEW software.

A novel SMA-based micro tactile display device for elasticity range of human soft tissues: Design and simulation

A novel micro tactile display device to display the elasticity of human soft tissues is presented in this paper. The device consists of 16 units in the form of a 4 × 4 units array. Each unit consists of two substrates separated by a 1.75 mm spacer. The first substrate holds a stiffness display pin (1 mm × 1 mm) which is supported by two Shape Memory Alloy (SMA) springs in parallel to provide tunable stiffness. A strain gauge on top of this substrate is used to measure the force applied on that pin. The other substrate includes a planar coil forming a non-contact eddy current sensor that is used to measure the deflection of the pin when subjected to an external force. Both the strain gauge and the eddy current sensors provide feedback signals that are used for characterization and control of the stiffness. Finite element simulation shows that the stiffness range of the designed device matches the range of elasticity of human soft tissues and the eddy current sensor detects up to 1.75 mm deflection which is suitable for characterization purposes. The simulation also studies the cross talk that possibly happen among the eddy current sensors due to the magnetic field.

Time-varying fuzzy logic controller of skid-steering mobile robot based on Lyapunov stability

A kinematic model of a skid-steering mobile robot (SSMR) is analyzed. The influence of relative position between the instantaneous center of rotation and SSMR center of mass is considered in the analysis. Then, a time-varying fuzzy logic controller based on Lyapunov stability criterion is designed. The closed loop system is simulated using Matlab-Simulink on point stabilization from different initial conditions. Results show that the proposed controller reaches almost zero steady state error with smooth trajectory.

LASER Reduced Graphene on Flexible Substrate for Strain Sensing Applications: Temperature Effect on Gauge Factor

New technique is developed to synthesize graphene film on flexible substrate for strain sensing applications. A flexible graphene/Poly-ethylene Terephthalate (PET) strain sensor based on graphene piezoresistivity is produced by a new simple low cost technique. Graphene oxide film on PET substrate is reduced and patterned simultaneously using 2 Watt CO2 LASER beam. The synthesized graphene film is characterized by XRD, FT-IR, SEM, and Raman techniques. Commercial strain gauges are used to predict experimentally the gauge factor (GF) of the graphene film at different values of applied strain. The stability of the graphene film and its GF are studied at different operating temperatures. The fabricated sensor showed high GF of 78 with great linearity and stability up to 60 °C.

Elimination of Clogging in PMMA Microchannels Using Water Assisted CO2 Laser Micromachining

The accuracy and clogging of microchannels are important for assessing the quality of lab on chip (L-O-C) devices. The clogging affects the fluid mixing efficiency and influences the bonding of substrate. In this paper, inexpensive and quick method for microchannel fabrication in polymethyl methacrylate (PMMA) while reducing the thermal damage is introduced. Accordingly, the substrate was covered with a thin layer of water during CO2 laser ablation. The effect of water cooling on the clogging formation, heat affected zone and the microchannel geometry in terms of depth and width is investigated. Clogging formation mechanism in the intersection of Y-channel is studied to improve its quality for microfluidics applications. During the experimental work, the CO2 laser power was varied from 2.4 to 6 W at scanning speed from 5 to 12.5 mm/s. The results showed that covering the PMMA substrate with a thin layer of water prevented clogging formation and reduced the heat affected zone.