احمدرضا خوگر

In order to evaluate and improve the accuracy of the distance traveled by the laser beam with a fixed distance, first the relation of the pulsed laser reflection signal reflected from the surface of the objects should be calculated and analyzed. Then, the broadening angle of the reflection signal and the relative broadening factor should be determined. In this research, an analytical relationship for distance measurement and detection for pulsed laser and statistical distance measurement has been designed, in which the minimum measurable distance and the necessary calculations for its quantitative estimation are presented. In this regard, the relationship between the broadening coefficient and relevant parameters such as detection distance, radiation angle to the target surface, and radiation reflection signal have been determined and evaluated. Simulation results and experimental results show that the maximum laser range for reliable distance measurement is 36.5 m, which is associated with a statistical error of 0.24 to 0.48 m. As the measurement threshold increases, the distance measurement error and the reliable range decrease. As the laser radiation angle increases, the divergence angle and the broadening coefficient increase, and as the laser pulse width decreases, the broadening coefficient decreases. Since increasing the angle of the target surface increases the divergence of the reflection signal, the mean values ​​and variance of the reflection signal will also increase.

The most common types of mechanical arms are robots that are used as palletizing robots to transport light and heavy loads. In robots that are used to move heavy loads, increasing the carrying capacity of the robot while maintaining dexterously, accuracy, repeatability and lightness has always been one of the issues studied by researchers. With this approach, in the present paper, the kinematic design and dimensional optimization of the geometry of a four-degree robotic robotic arm have been performed. The primary geometry is designed using parallel parallelograms to allow horizontal load carrying. After the initial design of the geometry dimensions of the robot, using the finite element method, the geometric optimization of the structure has been done in such a way that changes in the geometric dimensions of the arms as design parameters result in receiving the best results for the objective function. Deformation of the arms and proper distribution of load force among all arms. Using the optimization results of this paper and achieving a set of parametric relationships for the geometry of the robot structure, a shorter path can be taken to design these robots and With optimal geometry, parameters such as not increasing the dimensions of the arm sections to overcome stress and deformation, not increasing the overall weight of the structure, followed by increasing accuracy, repeatability, more load carrying capacity, robot dexterously and not enlarging the overall dimensions of the robot Improve.

In this article, controlling the end-effector forces is accomplished using a command system with six degrees of freedom. The command system can use a joystick implemented on a parallel mechanism. The follower robot’s end-effector is controlled by the command system and is capable of traversing the reference path with the specified force. To demonstrate this, several paths on different planes are considered and the robot’s end-effector is seen to traverse each assigned path by applying a constant force. It is also possible to identify obstacles and avoid them with this system. The control system is designed so that while approaching an obstacle, the robot’s end-effector does not collide with it. Hence, a general-purpose robot can be navigated with better performance and it can be used as a surgical robot, a robot for carrying sensitive materials or other applications. In such operations, to adjust the contact forces after a collision of the end-effector with the surface, this control system produces the appropriate control feedback. This feedback gives the operator a sense of the forces at the end-effector position and increases the operator manipulation and maneuvering skill.

A Spherical Parallel Mechanism (SPM) is used to rotate a body around a fixed point. Using type synthesis, different kinematic arrangements can be obtained for the robot with three degrees of rotational freedom. The most commonly used structure for this robot is the 3-RRR kinematic architecture which is an overconstrained parallel mechanism and causes several problems of mounting the mechanism, but has the advantage of having high rigidity thus a good accuracy. In this paper two non-overconstrained architectures 3-RRS and 3-RSR that are extracted from the type synthesis are compared with overconstrained one from accuracy point of view based on joint clearance. First, a method to obtain a model of moving platform pose (position and orientation) error based on joint clearance is introduced which leads to a standard convex optimization problem. Then maximum values of six components of the pose error are computed in more than 1000 different configurations within their workspace. It is shown that this displacement is configuration dependent. The obtained results revealed that the 3-RRR SPM has better position accuracy while in the case of orientation, the 3-RRS SPM has lowest maximum error between SPMs under study in the prescribed workspace. It can be concluded that non-overconstrained structures can be used instead of the overconstrained structure. Finally, a comparison was made between the performance indices and the method presented in this paper and results showed that the kinematic sensitivity index is most consistent with the accuracy of the robot.