Samer Yahya

Geometrical approach of planar hyper-redundant manipulators: Inverse kinematics, path planning and workspace

A new method for inverse kinematics for hyper-redundant manipulators is proposed in this paper to plan the path of the end-effector. The basic idea is that for a given smooth path consisting of points close enough to each other; computing the inverse kinematics for these points is carried out geometrically using the proposed method. In this method, the angles between the adjacent links are set to be the same, which makes lining up of two or more joint axes impossible; therefore, avoiding singularities. The manipulability index has been used to show how far the manipulator from the singularity configuration is. The determination of the workspace of the manipulator using the proposed method has been presented in this paper. The simulation results have been carried out on a planar and a three dimensional manipulators. The effectiveness of the proposed method is clearly demonstrated by comparing its result with results calculated by the well-known method of measuring manipulability which is used for singularity avoidance for the last two decades.

Singularity avoidance of a six degree of freedom three dimensional redundant planar manipulator

This paper focuses on the improvement of singularity avoidance of three dimensional planar redundant manipulators by increasing its degrees of freedom without increasing the number of motors controlling the manipulator. Consequently, the method to build a three dimensional planar manipulator with six-degrees of freedom using three motors instead of six is discussed in detail. A comparison of the manipulability index values for the proposed manipulator is made with the manipulability index values of PUMA arm to demonstrate the effectiveness of using the proposed manipulator for singularity avoidance.

A geometrical inverse kinematics method for hyper-redundant manipulators

Hyper-redundant manipulators have large number of kinematic degrees of freedom, thus processing some unconventional features such as the ability to enter a narrow space while avoiding obstacles. To solve the problem of multi-solution caused by redundancy, a geometrical method is presented in this paper. This proposed method finds one optimal solution to the inverse kinematics of redundant or hyper redundant manipulators from these infinite solutions with fewer computations. This method can be used for any planar n-serial manipulators. Experiments are conducted 3-links redundant manipulator and 10-links hyper-redundant manipulator to demonstrate the effectiveness of this proposed method.

Motion planning of hyper redundant manipulators based on a new geometrical method

Motion planning capability is an essential part of an industrial robot system. Therefore research in robot motion planning remains as one of the important fields of study in the task of building industrial robot systems. A new method for the motion planning is presented in this paper. The basic idea is to find a smooth path consisting of points close enough to each other. Then the computation of the inverse kinematics for these points is accomplished with the help of a new proposed geometrical method to solve the problem of multi-solution caused by redundancy. The advantage of this method is that the angles between the adjacent links are the same, it makes controlling these links easier and the movement of the manipulator itself more stable. This method can be used for the equal length links planar manipulators. To demonstrate the effectiveness of this proposed method, experiments were conducted on a 10-links hyper redundant manipulator in this paper.

Artificial neural networks aided solution to the problem of geometrically bounded singularities and joint limits prevention of a three dimensional planar redundant manipulator

Abstract This paper presents a neural network based on a nonlinear dynamical control of a three-dimensional six degrees of freedom planar redundant manipulator. An artificial controller is used for the computation of fast inverse kinematics, and is effective on geometrically bounded singularities and joint limits prevention of redundant manipulators. A comparison between the results of a multilayer back propagation and the radial basis function neural network has been carried out, and the results show that the radial basis function of neural networks is more attractive due to their fast training, simplicity, and convergence rate. The radial basis function neural network has been used to estimate the centrifugal and gravitational effects of the joints, while the end-effector follows a desired path.

Redundant manipulators kinematics inversion

A robotic system is kinematically redundant when it possesses more degrees of freedom than those required to execute a given task. This paper reviews the well-known methods used to find the inverse kinematics of redundant manipulators. Because redundant manipulators have infinite solutions for their inverse kinematics, therefore the conventional method that was used to calculate the inverse kinematics of non-redundant manipulators cannot be used. The methods used to calculate the inverse kinematics of redundant manipulators are divided into three main categories in this paper: pseudoinverse, artificial intelligence and geometrical methods. These types have been explained, their advantages and disadvantages are also discussed in this paper.

Joint Torque Reduction of a Three Dimensional Redundant Planar Manipulator

Research on joint torque reduction in robot manipulators has received considerable attention in recent years. Minimizing the computational complexity of torque optimization and the ability to calculate the magnitude of the joint torque accurately will result in a safe operation without overloading the joint actuators. This paper presents a mechanical design for a three dimensional planar redundant manipulator with the advantage of the reduction in the number of motors needed to control the joint angle, leading to a decrease in the weight of the manipulator. Many efforts have been focused on decreasing the weight of manipulators, such as using lightweight joints design or setting the actuators at the base of the manipulator and using tendons for the transmission of power to these joints. By using the design of this paper, only three motors are needed to control any n degrees of freedom in a three dimensional planar redundant manipulator instead of n motors. Therefore this design is very effective to decrease the weight of the manipulator as well as the number of motors needed to control the manipulator. In this paper, the torque of all the joints are calculated for the proposed manipulator (with three motors) and the conventional three dimensional planar manipulator (with one motor for each degree of freedom) to show the effectiveness of the proposed manipulator for decreasing the weight of the manipulator and minimizing driving joint torques.

A new geometrical inverse kinematics method for planar hyper redundant manipulators

Obtaining the joint variables that result in a desired position of the robot end-effector called as inverse kinematics is one of the most important problems in robot kinematics and control. As the complexity of robot increases, obtaining the inverse kinematics solution requires the solution of non linear equations having transcendental functions are difficult and computationally expensive. This paper proposed a new geometrical method to find the inverse kinematics of the planar redundant manipulators. Using the proposed method, singularity avoidance is achieved by setting the angles between the adjacent links to be equal, which makes it impossible for any two or more joint axes to line up. Two study cases are simulated in this paper to show the performance of the proposed method.

Fuzzy-logic control of an inverted pendulum on a cart☆

Abstract The inverted pendulum on a cart is an under actuated, unstable non-linear system that is used as a benchmarking problems in control theory. The non-linear nature of the system makes linear controllers, such as the proportional integral derivative (PID) controllers, possibly unfeasible as they only guarantee stability of a linear system. A fuzzy-logic controller provides many different stable controllers applicable to inverted pendulum on a cart. In this paper, the fuzzy parallel distributed compensation (PDC) controller is introduced and implemented on an unstable system, and the performance is demonstrated in MATLAB Simulink. The fuzzy PDC controller is dependent on the Takagi–Sugeno (TS) fuzzy model to obtain the state feedback gains required by solving the linear matrix inequalities (LMI). The LMI produced satisfactory results for all initial pendulum positions simulated even under uniformed disturbance. Our results have been compared against two other works to reveal the effectiveness of the proposed model.

Design and analysis of a proposed light weight three DOF planar industrial manipulator

Minimizing the computational complexity of torque optimization and the ability to calculate the magnitude of the joint torque accurately will result in a safe operation without overloading the joint actuators. Reduced torque will lead to lighter robotic arm and easier control. The main objective of this work is to design a robotic arm with all the motors located at the base so that the arm becomes lighter than the conventional arms. The main advantage from this development is to decrease the torque required to control the arm. The motion of motors is transferred to links via aluminum pulleys, bearings, and timing belts which yields to the need of lighter motors and hence a lighter manipulator. The maximum torque of each joint has been calculated then compared with the torque needed using conventional design to show the effectiveness of the proposed design for decreasing the weight of the manipulator and minimizing driving joint torques.