Ahmed Khamies El-Shenawy

Comparing different holonomic mobile robots

This paper presents a comparison between three different holonomic mobile robots. The first has three caster wheels with wheel angular velocities actuation and carries the name C3P. The second is omni-directional wheeled mobile robot and the third is a special holonomic robot configuration developed by ETH named Ramsis II. Inverse kinematic and forward dynamic models are presented for each robot for the simulation process. The simulation results illustrate the performance of each robot in comparison to the others. The comparison is done with respect to three main aspects; 1) the mobility, 2)the total energy consumed by each robot in a finite interval of time, and 3) the hardware complexity. A cost functional is obtained to demonstrate the comparison, and a criteria is developed to measure the hardware complexity of each robot. The weight sum method enables the cost functional to show the importance of each aspect and to distinguish between the lowest cost platform with respect to each aspect importance.

Dynamic Model of a Holonomic Mobile Robot with Actuated Caster Wheels

A dynamic model for the holonomic mobile robot C3P is proposed. The C3P has three caster wheels with angular velocities actuation. The model consists of two main dynamic equations which have been derived symbolically using a Lagrange approach. The first equation is the forward dynamics which is used to calculate the wheels angular velocities corresponding to the applied torques on the wheels. The second equation is the steering dynamic estimator for recursive calculation of the steering angles and their derivatives with respect to the wheel angular velocities and acceleration. The velocity control of the C3P using the dynamic model is simulated and compared to the kinematics based controller which have been proposed earlier. The simulation and experimental results clearly show the advantages of the dynamic model in relation to the kinematic one

Controlling a Holonomic Mobile Robot With Singularities

In this paper a method is presented to control a holonomic mobile robot with singularities. The robot has 3 castor wheels, each wheel actuated by its angular velocity only. Using the proposed approach, singular wheel configurations are escaped without adding steering actuation to any wheel. The wheel coupling equation (WCE) virtually actuates the steering angular velocity of one wheel through controlling the actuated angular velocities of the other two wheels. Basing on the WCE and a cascaded control structure a standard wheel velocity controller is used to control the velocity of the robot. Simulations and practical experiments are carried out to illustrate the performance of the proposed approach and controller

Practical evaluation for two different holonomic wheeled mobile robots

This work is a practical evaluation between two different holonomic wheeled mobile robot platforms. The evaluation criteria had been theoretically explained and used on the simulation level in previous publication. The main objective of this paper is evaluating each wheeled mobile robot practically using the proposed criteria. The first robot is the C3P, which has three caster wheels with wheel angular velocities actuation. The second robot is omni-directional wheeled platform with three omni-directional wheels. The inverse and forward kinematics required in the control structure is presented for the practical experiments, which illustrate the performance of each robot. The comparison is done with respect to three main aspects; 1) the mobility, 2) the total energy consumed by each robot in a finite interval of time, and 3) the hardware complexity. A cost functional is obtained to demonstrate the comparison, and a criteria is developed to measure the hardware complexity of each robot. The weight sum method enables the cost functional to show the importance of each aspect and to distinguish between the lowest cost platform with respect to each aspect importance.

SOLVING THE SINGULARITY PROBLEM FOR A HOLONOMIC MOBILE ROBOT

Abstract A holonomic mobile robot with three castor wheels is presented. For each wheel, only the angular velocity is actuated. Due to the actuation characteristics, the actuated inverse solution yields singularities for some common wheel configurations. In this paper two approaches are proposed for solving this singularity problem: 1. The coupling approach is a virtual actuation for the steering angle velocity through controlling the actuated angular velocities of the other wheels. 2. The escaping singularity approach is an external function cascaded to the reference input signal in the control loop. Simulations and practical experiments are carried out to illustrate the performance of the proposed approaches.

Trajectory following and stabilization control of fully actuated AUV using inverse kinematics and self-tuning fuzzy PID.

In this work a design for self-tuning non-linear Fuzzy Proportional Integral Derivative (FPID) controller is presented to control position and speed of Multiple Input Multiple Output (MIMO) fully-actuated Autonomous Underwater Vehicles (AUV) to follow desired trajectories. Non-linearity that results from the hydrodynamics and the coupled AUV dynamics makes the design of a stable controller a very difficult task. In this study, the control scheme in a simulation environment is validated using dynamic and kinematic equations for the AUV model and hydrodynamic damping equations. An AUV configuration with eight thrusters and an inverse kinematic model from a previous work is utilized in the simulation. In the proposed controller, Mamdani fuzzy rules are used to tune the parameters of the PID. Nonlinear fuzzy Gaussian membership functions are selected to give better performance and response in the non-linear system. A control architecture with two feedback loops is designed such that the inner loop is for velocity control and outer loop is for position control. Several test scenarios are executed to validate the controller performance including different complex trajectories with and without injection of ocean current disturbances. A comparison between the proposed FPID controller and the conventional PID controller is studied and shows that the FPID controller has a faster response to the reference signal and more stable behavior in a disturbed non-linear environment.

A Handheld Robot for Orthopedic Surgery - ITD

This paper describes the specification and development of the handheld medical robot ITD for orthopedic surgery. The robot compensates unintended movements of the surgeon and the patient and thus stabilizes the relative position of a drilling tool to the bone. To do so a highly dynamic but lightweight robot is held in the surgeon’s hand and a special occlusion-robust tracking system provides fast and accurate position information. Additionally an inertial tracking system is implemented in the robot. To prove the system’s functionality, experiments with polystyrene foam have been carried out with the first prototype based on the hexapod kinematics. A second prototype provides higher dynamics, lower outlines and weight and is based on the Hexaglide kinematics. Both robots are still too large for routine surgical use but prove good potential for future developments.

Neural Network Frequency Selector for Maximum Power Transfer

 Abstract—This paper propose a method for reaching a maximum power transfer using wireless system. The power is transmitted using the method of impedance matching technique. It depends on choosing the parameters of the transmitter receiver circuit and proper distance and gap media , which allow the transfer of maximum power , we propose a neural network configuration to deliverer the required frequencies to achieve maximum power transfer from the given circuit parameters . The choice depends on thirteen parameters which are divided to fixed parameters like inductance, capacitance and variable parameters like distance and misalignment. The system is tested on the hardware set up and showed acceptable performance illustrated by presented experiments. Index Terms—Energy transfer, maximum power transfer, neural network, wireless power transfer, Witricity.

Practical construction and position control of a modular actuated holonomic wheeled mobile robot

The presented work is related to previous development of the holonomic wheeled mobile robot C3P. This paper focuses on the platform implementation and the kinematics/dynamics solutions used for its position control structure. The platform prototype is proposed in detailed description concerning its construction and configuration. A controller based on feed forwarding the inverse dynamics torques with the inverse kinematics to overcome the platform singularities is proposed. The based controllers practical experiments results illustrate the position controller performance and its efficiency.

Position Control and Stabilization of Fully Actuated AUV using PID Controller

This paper presents an inverse kinematic model for an Autonomous Underwater Vehicle (AUV) with 8 thrusters. The vehicle configuration allow the AUV to have a fully-actuated 6 Degrees of freedom (DOF). Rigid body dynamic model and water environment hydrodynamic model are used in this study. The model is implemented and tested using Matlab and Simulink. A 3D model of the AUV is designed for illustration in this work using Autodesk MAYA. Cascaded position and velocity control approach is studied. A conventional linear Proportional Integral Derivative (PID) controller is used for speed control and PD controller for the position control. Ocean current disturbances are introduced to test the system and control stability. Validation of the model is performed with tests for speed stabilization and position control with and without disturbances.