Samy F. M. Assal

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.

A novel planar parallel manipulator with high orientation capability for a hybrid machine tool: kinematics, dimensional synthesis and performance evaluation

In order to potentially realize the advantages of planar parallel manipulators to be used for hybrid machine tools, the inherently abundant singularities which diminish the usable workspace must be eliminated. Proper structure synthesis and dimensional synthesis can provide a good solution. So, a non-conventional architecture of a three-PPR planar parallel manipulator is proposed in this paper for a hybrid machine tool. The proposed architecture permits a large dexterous workspace with unlimited orientation capability and no singularities. It also provides partially decoupled motion which permits independent actuators control. The kinematic, singularity, orientation capability and workspace analyses of the proposed manipulator are studied to verify those advantages. Based on a non-dimensional design parameter space, the highly important indices for this application namely the workspace index (WI), the motion/force transmission index, the kinematic and dynamic dexterity indices and the stiffness index are selected to be maximized yielding proper dimensions of the design parameters. Those performance indices are proven to be uniform over all the workspace achieving highly important characteristics of uniform accuracy, acceleration characteristics, rigidity and force transmissibility. Performance evaluation is finally presented to verify the high performance of the proposed non-singular planar parallel manipulator with high orientation capability.

Dynamic Analysis of a Parallel Manipulator-Based Multi-function Mobility Assistive Device for Elderly

Dynamic simulation of manipulators interacting directly with human is crucial for predicating their performance before the actual use. This paper describes the dynamic analysis and simulation of a novel multi-function mobility assistive device for elderly. The device is designed to help patients who suffer from degradation of the lower limbs muscular strength. Rather than one function device, the proposed device is intended to assist in different lower limb activities, namely, sit to stand and walking activities as well as transfer paralyzed patients from bed to wheelchair and help them stand in upright position to improve blood circulation. The device is based on a non-conventional structure of a 3-RPR planer parallel manipulator which has high rigidity due to the parallel structure. It has some interesting kinematic advantages that facilitate structure and control design. Dynamic model for the assistive manipulator is derived using the first type of Lagranges equations. A PD-computed torque controller is tuned using genetic algorithm. Simulation results prove high performance of the proposed device in terms of the low tracking error and the proper actuator force.

Non-singular 3-DOF planar parallel manipulator with high orientational capability for a hybrid machine tool

Since almost all symmetric 3-DOF planar parallel manipulators have inherent singularities which limits the usable workspace, a 3-PPR planar parallel one in a non conventional architecture is developed in this paper for a hybrid machine tool. This architecture permits a large workspace with unlimited orientation capability and no singularities. It also has the advantage of being partially decoupled to independently control the actuators. The kinematics, singularities, orientation capability and workspace analyses of the developed manipulator are studied to verify those advantages. The kinematic and dynamic performances are investigated based on non-dimensional design parameters space. The local kinematic and dynamic dexterity indices are proven to be uniform within the constant orientation workspace. Simulation results are finally presented to verify a high dexterity non-singular planar parallel manipulator.

Fuzzy-based gain scheduling of Exact FeedForward Linearization control and sliding mode control for magnetic ball levitation system: A comparative study

This paper presents a comparative study between two control approaches; an Exact FeedForward Linearization controller developed by fuzzy-gain scheduling and sliding mode controller based on Ackermann and Utkin method. For the later one the sliding surface dynamics are determined explicitly without transforming to the sliding mode canonical form. The benefits of this study are demonstrated practically on a well known benchmark control problem, Magnetic ball levitation system (Maglev), and the performances of both controllers are compared. Important control issues such as tracking ability, control effort, steady state error and noise rejection are experimentally investigated.

A Neuro Fuzzy-Based Gait Trajectory Generator for a Biped Robot Using Kinect Data

Generating gait trajectories is an important step in biped motion control. So, in this paper, a neuro fuzzy (ANFIS)-based gait trajectory generator for a normal walking of a biped robot during the single support phase is developed. Since human sensorimotor controls are done in an optimal way following the principle of optimality, gait trajectories data of human subjects of different hip heights, and accordingly different steps, are captured by Kinect sensor and then used for training the developed ANFIS-based gait generator. In this context, for each subject, the hip and swing limb ankle trajectories are captured, filtered and averaged over steps. The averaged trajectories are approximated using least square fitting with polynomial functions whose coefficients are used as ANFIS outputs and hip heights as inputs. Additionally, constraint equations are obtained for those trajectories and compared with hypothetical constraints in literature to prove that the latter constraints are not consistent with the naturally obtained ones. Furthermore, the averaged trajectories are generalized in terms of the step length and maximum step elevation. The results prove the effectiveness of the approach to generate gait trajectories, which are optimal, for a biped robot.

A novel intention prediction strategy for a shared control tele-manipulation system in unknown environments

This paper addresses the problem of controlling a slave robot with a shared control scheme of a tele-manipulation system in unknown environments. Shared control schemes may be useful for reducing the communication delay in time-critical tele-manipulation systems. Shared control scheme consists of two key components: intention prediction and command arbitration. An intuitive and novel strategy under which the human operator intention could be extracted seamlessly from the hand point to point path during the tele-manipulation process is developed in this paper. The new strategy is based on the environment scene awareness conducted at the remote side at the beginning of the tele-manipulation task. The developed strategy is tested experimentally with a simulation of a robot model in several remote environments to verify its accuracy and effectiveness. The results confirmed significant performance improvement in terms of reduced time using the proposed shared control scheme compared to the direct tele-manipulation scheme.

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.

Robotic Exploration: New Heuristic Backtracking Algorithm, Performance Evaluation and Complexity Metric

Mobile robots have been used to explore novel environments and build useful maps for navigation. Although sensor-based random tree techniques have been used extensively for exploration, they are not efficient for time-critical applications since the robot may visit the same place more than once during backtracking. In this paper, a novel, simple yet effective heuristic backtracking algorithm is proposed to reduce the exploration time and distance travelled. The new algorithm is based on the selection of the most informative node to approach during backtracking. A new environmental complexity metric is developed to evaluate the exploration complexity of different structured environments and thus enable a fair comparison between exploration techniques. An evaluation index is also developed to encapsulate the total performance of an exploration technique in a single number for the comparison of techniques. The developed backtracking algorithm is tested through computer simulations for several structured environments to verify its effectiveness using the developed complexity metric and the evaluation index. The results confirmed significant performance improvement using the proposed algorithm. The new evaluation index is also shown to be representative of the performance and to facilitate comparisons.

Workspace mapping and control of a teleoperated endoscopic surgical robot

This paper presents the experimental implementation of a teleoperated endoscopic surgical manipulator system that uses PHANTOM Omni haptic device as the master. The 4-DOF, 2-PUU 2-PUS, endoscopic surgical parallel manipulator design is carried out using screw theory and Parallel virtual chain methodology to have larger bending angles and workspace volume. The master and slave devices of the teleoperation system are dissimilar in their kinematics and workspace volumes. A workspace mapping technique is implemented based on Position with Modied Rate Control to navigate through the slave workspace without annoying the user. To control the motion of the slave robot, a PID controller is used. The experimental results show the feasibility of the teleoperation surgical system using the 4-DOF parallel manipulator. Also, they indicate the efficiency of the implemented mapping technique and the designed controller to span the slave workspace with high dexterity and good tracking which allows the surgeon to perform the operation with high accuracy.