Optimal Synthesis of Cam-Linkage Mechanisms for Precise Path Generation

2006 ◽  
Vol 128 (6) ◽  
pp. 1253-1260 ◽  
Author(s):  
D. Mundo ◽  
J. Y. Liu ◽  
H. S. Yan
Keyword(s):  
Degrees Of Freedom ◽  
Tangential Velocity ◽  
Goal Function ◽  
Optimal Synthesis ◽  
Performance Criteria ◽  
Synthesis Process ◽  
Path Generation ◽  
Linkage Mechanism ◽  
Generation Task ◽  
Synthesis Methodology

The paper proposes a method for the optimal synthesis of planar mechanisms, where a combination of cams and linkages is used in order to obtain a precise path generation. As a first step, based on Gruebler’s mobility criterion, a linkage mechanism is considered, with as many degrees of freedom as required by the generation task. One or more disk cams are then synthesized in order to reduce the system’s mobility and to obtain a single-input combined mechanical system. The final combined mechanism is able to guide a coupler point through any number of precision positions. A strategy for the global optimization of the synthesis process, based on evolutionary theory, is also proposed. A goal function is defined on the basis of dimensional and kinematic constraints and performance criteria, while a genetic algorithm is employed as an optimum searching procedure. An industrial application of the proposed methodology is described, where a path generation problem with time prescription is dealt with. The objective of the generation task is to guide a coupler point along a figure-eight trajectory, with a constant tangential velocity. Such a task is required by polishing machines for fiber optic connectors and similar components. A kinematic simulation of the optimal mechanism is used to validate the proposed synthesis methodology.

KINEMATIC OPTIMIZATION OF MECHANICAL PRESSES BY OPTIMAL SYNTHESIS OF CAM-INTEGRATED LINKAGES

2006 ◽  
Vol 30 (4) ◽  
pp. 519-532 ◽  
Author(s):  
D. Mundo ◽  
G.A. Danieli ◽  
H.S. Yan
Keyword(s):  
Goal Function ◽  
Performance Criteria ◽  
Synthesis Process ◽  
Constant Input ◽  
Generation Task ◽  
Kinematic Behaviour ◽  
Two Phases ◽  
Cutting Processes ◽  
Synthesis Methodology ◽  
Kinematic Optimization

The paper proposes a method for the synthesis of planar mechanisms, where a combination of cams and linkages is used in order to improve the kinematic behaviour of mechanical presses. The purpose is to synthesize a function generating mechanism, with a constant input-velocity, able to move the press ram according to an optimal law of motion. The proposed synthesis methodology consists of two phases. As a first step, a linkage type-synthesis is performed, based on the mobility the generation task requires. An initial multi degree-of-freedom (d.o.f.) mechanism is thus selected. One or more disc cams are then synthesized in order to reduce the system’s mobility and to obtain a single-input combined mechanism. The final system is able to generate a specific input/output relationship, as defined by any number of precision configurations. In order to optimize the synthesis process, according to dimensional and kinematical criteria, a genetic algorithm is employed. A goal function is defined on the basis of both performance criteria and design rules, and minimized by means of evolutionary theory. The proposed methodology is applied to the kinematic optimization of mechanical presses for deep drawing and precision cutting processes.

A Parallely Actuated Work Support Module for Reconfigurable Machining Systems

1998 ◽  
Author(s):  
Venkat Gopalakrishnan ◽  
Sridhar Kota
Keyword(s):  
Machine Tool ◽  
Machine Tools ◽  
Degrees Of Freedom ◽  
Mechanical Design ◽  
Performance Criteria ◽  
Machining Accuracy ◽  
Parallel Mechanisms ◽  
Element Analysis ◽  
Work Support ◽  
Reconfigurable Machining

Abstract In order to respond quickly to changes in market demands and the resulting product design changes, machine tool manufacturers must reduce the machine tool design lead time and machine set-up time. Reconfigurable Machine Tools (RMTs), assembled from machine modules such as spindles, slides and worktables are designed to be easily reconfigured to accommodate new machining requirements. The essential characteristics of RMTs are modularity, flexibility, convertibility and cost effectiveness. The goal of Reconfigurable Machining Systems (RMSs), composed of RMTs and other types of machines, is to provide exactly the capacity and functionality, exactly when needed. The scope of RMSs design includes mechanical hardware, control systems, process planning and tooling. One of the key challenges in the mechanical design of reconfigurable machine tools is to achieve the desired machining accuracy in all intended machine configurations. To meet this challenge we propose (a) to distribute the total number of degrees of freedom between the work-support and the tool and (b) employ parallely-actuated mechanisms for stiffness and ease of reconfigurability. In this paper we present a novel parallely-actuated work-support module as a part of an RMT. Following a brief summary of a few parallel mechanisms used in machine tool applications, this paper presents a three-degree-of-freedom work-support module designed to meet the machining requirements of specific features on a family of automotive cylinder heads. Inverse kinematics, dynamic and finite element analysis are performed to verify the performance criteria such as workspace envelope and rigidity. A prototype of the proposed module is also presented.

scholarly journals Conceptual Design and Computational Modeling Analysis of a Single-Leg System of a Quadruped Bionic Horse Robot Driven by a Cam-Linkage Mechanism

2019 ◽  
Vol 2019 ◽  
pp. 1-13 ◽  
Author(s):  
Liangwen Wang ◽  
Weiwei Zhang ◽  
Caidong Wang ◽  
Fannian Meng ◽  
Wenliao Du ◽  
...  
Keyword(s):  
Motion Analysis ◽  
Kinematic Analysis ◽  
Degrees Of Freedom ◽  
Structural Parameters ◽  
Three Dimensional ◽  
Kinematic Modeling ◽  
Linkage Mechanism ◽  
Vector Method ◽  
Pressure Angle ◽  
End Point

In this study, the configuration of a bionic horse robot for equine-assisted therapy is presented. A single-leg system with two degrees of freedom (DOFs) is driven by a cam-linkage mechanism, and it can adjust the span and height of the leg end-point trajectory. After a brief introduction on the quadruped bionic horse robot, the structure and working principle of a single-leg system are discussed in detail. Kinematic analysis of a single-leg system is conducted, and the relationships between the structural parameters and leg trajectory are obtained. On this basis, the pressure angle characteristics of the cam-linkage mechanism are studied, and the leg end-point trajectories of the robot are obtained for several inclination angles controlled by the rotation of the motor for the stride length adjusting. The closed-loop vector method is used for the kinematic analysis, and the motion analysis system is developed in MATLAB software. The motion analysis results are verified by a three-dimensional simulation model developed in Solidworks software. The presented research on the configuration, kinematic modeling, and pressure angle characteristics of the bionic horse robot lays the foundation for subsequent research on the practical application of the proposed bionic horse robot.

Prescribed performance trajectory tracking control of dynamic positioning ship under input saturation

2020 ◽  
pp. 014233122092888
Author(s):  
Yuanhui Wang ◽  
Haibin Wang ◽  
Mingyu Fu
Keyword(s):  
Trajectory Tracking ◽  
Tracking Control ◽  
Degrees Of Freedom ◽  
Input Saturation ◽  
Small Neighborhood ◽  
Performance Criteria ◽  
Dynamic Positioning ◽  
Trajectory Tracking Control ◽  
Prescribed Performance ◽  
Control Scheme

This paper investigates concentrates on the trajectory tracking control problem of dynamic positioning (DP) ship, in the presence of the time-varying disturbance and input saturation. Firstly, a simplified mathematical model of three degrees of freedom is established. According to the characteristics of the DP ship, an adaptive backstepping controller which combine the prescribed performance function with disturbance observer is proposed. The control scheme can guarantee the transient and steady state performance of the trajectory tracking and meet the prescribed performance criteria. In addition, an auxiliary dynamic system is introduced into the controller to deal with the input saturation problem of the actuator, so that the DP ship can accomplish the task of trajectory tracking under the condition of actuator constraint. Subsequently, in combination of barrier Lyapunov function (BLF), it is proved that the DP system can stabilize and converge rapidly to the small neighborhood of the equilibrium point, which can achieve the prescribed performance. Finally, the effectiveness of the DP control law is demonstrated by a series of simulation experiments.

An Elitist Ants-Search Based Method for Optimum Synthesis of Rigid-Linkage Mechanisms

2015 ◽  
Author(s):  
Nadim Diab ◽  
Ahmad Smaili
Keyword(s):  
Objective Function ◽  
Linear Constraints ◽  
Optimization Techniques ◽  
Path Generation ◽  
Generation Task ◽  
Optimum Synthesis ◽  
Structural Error ◽  
Constant Quantity ◽  
Future Work ◽  
Exploration Exploitation

Mechanical linkages are widely used in the industry and the synthesis of such mechanisms may require optimization depending on the number of precision positions required. Many intelligent optimization techniques (Genetic, Tabu, Simulated Annealing, etc) have been proposed in the literature, one of them being the Ant-Search which was first proposed by the authors in 2007. In this paper, a Modified Ant-Search (MAS) technique is proposed to optimize the synthesis of a four-bar mechanism with a path generation task. Two major improvements are applied over the previous algorithm: ants pheromone update and exploration/exploitation techniques are both modified. Unlike the previous work where a constant quantity of pheromones was added during each iteration, in this paper, the pheromone deposit rate is proportional to the error of the objective function. Such a modification in the pheromone update rule is expected to differentiate between the behaviors of different ants and better govern their motion in the subsequent iterations. Moreover, the second major improvement targets the exploration/exploitation techniques followed by the ants. Unlike the previous work where exploration dominates during the early iteration stages and exploitation during the late ones, this work implements a more dynamic strategy where ants enter and leave the exploration/exploitation processes as governed by parameters related to the objective function error and pheromone deposit levels. Such modifications applied to the Ant-Search (AS) technique are expected to ensure a better chance of converging to a global minimum. The MAS technique is applied for a few path generation tasks with prescribed timing along with a set of linear constraints. Results are compared with previous work in the literature where the newly proposed technique showed appreciable improvement as evaluated by the structural error objective function. Future work possibilities are also introduced.

Manipulator Task-Based Performance Optimization

2004 ◽  
Author(s):  
Chalongrath Pholsiri ◽  
Chetan Kapoor ◽  
Delbert Tesar
Keyword(s):  
Performance Optimization ◽  
Degrees Of Freedom ◽  
Performance Criteria ◽  
Redundancy Resolution ◽  
Task Constraints ◽  
Output Constraints ◽  
Definition Of ◽  
Joint Limits ◽  
Relationship Of ◽  
The Relationship

This research uses new developments in redundancy resolution and real-time capability analysis to improve the ability of an articulated arm to satisfy task constraints. Task constraints are specified using numerical values of position, velocity, force, and accuracy. Inherent in the definition of task constraints is the number of output constraints that the system needs to satisfy. The relationship of this with the input space (degrees of freedom) defines the ability to optimize manipulator performance. This is done through a Task-Based Redundancy Resolution (TBRR) scheme that uses the extra resources to find a solution that avoids system constraints (joint limits, singularities, etc.) and satisfies task constraints. To avoid system constraints, we use well-understood criteria associated with the constraints. For task requirements, the robot capabilities are estimated based on kinematic and dynamic manipulability analyses. We then compare the robot capabilities with the user-specified requirement values. This eliminates a confusing chore of selecting a proper set of performance criteria for a task at hand. The breakthrough of this approach lies in the fact that it continuously evaluates the relationship between task constraints and system resources, and when possible, improves system performance. This makes it equally applicable to redundant and non-redundant systems. The scheme is implemented using an object-oriented operational software framework and its effectiveness is demonstrated in computer simulations of a 10-DOF manipulator.

scholarly journals Design of a Two-DOFs Driving Mechanism for a Motion-Assisted Finger Exoskeleton

2020 ◽  
Vol 10 (7) ◽  
pp. 2619 ◽  
Author(s):  
Giuseppe Carbone ◽  
Eike Christian Gerding ◽  
Burkard Corves ◽  
Daniele Cafolla ◽  
Matteo Russo ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Experimental Tests ◽  
Design Solution ◽  
Driving Mechanism ◽  
Dimensional Synthesis ◽  
Linkage Mechanism ◽  
Healthy Human ◽  
Wide Range ◽  
Finger Motion ◽  
Human Finger

This paper presents a novel exoskeleton mechanism for finger motion assistance. The exoskeleton is designed as a serial 2-degrees-of-freedom wearable mechanism that is able to guide human finger motion. The design process starts by analyzing the motion of healthy human fingers by video motion tracking. The experimental data are used to obtain the kinematics of a human finger. Then, a graphic/geometric synthesis procedure is implemented for achieving the dimensional synthesis of the proposed novel 2 degrees of freedom linkage mechanism for the finger exoskeleton. The proposed linkage mechanism can drive the three finger phalanxes by using two independent actuators that are both installed on the back of the hand palm. A prototype is designed based on the proposed design by using additive manufacturing. Results of numerical simulations and experimental tests are reported and discussed to prove the feasibility and the operational effectiveness of the proposed design solution that can assist a wide range of finger motions with proper adaptability to a variety of human fingers.

A Maximal Loop Approach to Automatic Sketching of Mechanisms

2007 ◽  
Author(s):  
Songhui Nie ◽  
Hongzhao Liu ◽  
Aihong Qiu
Keyword(s):  
Degrees Of Freedom ◽  
Regular Polygon ◽  
Kinematic Chain ◽  
Synthesis Process ◽  
Systematic Design ◽  
Dimensional Synthesis ◽  
Type Synthesis ◽  
Outer Loop ◽  
Comprehensive Method ◽  
Independent Loops

Sketching of mechanisms identified during the type synthesis process constitutes an important link with the subsequent dimensional synthesis process in the systematic design of mechanisms. Based on the independent loops, a simple and comprehensive method for automatically sketching every type of kinematic chain regardless of the number of links and degrees of freedom is proposed. In the method, a maximal feasible outer-loop is derived by the independent loops addition or subtraction such that all the independent loops become its non-crossing inner loops. During automatic sketching of mechanisms process, the joints of kinematic chain are located on vertices of concentric inscribed regular polygon by outer lane to inner lane in terms of the outer loop and the inner loops. The development and application of this algorithm based on the outer loop and the inner loops relationships are demonstrated with the aid of several mechanism examples.

Optimal synthesis of a spherical parallel mechanism for medical application

Robotica ◽  
2014 ◽  
Vol 34 (3) ◽  
pp. 671-686 ◽  
Author(s):  
T. Essomba ◽  
M. A. Laribi ◽  
S. Zeghloul ◽  
G. Poisson
Keyword(s):  
Motion Capture ◽  
Parallel Mechanism ◽  
Degrees Of Freedom ◽  
Medical Application ◽  
Optimal Synthesis ◽  
Objective Functions ◽  
Ultrasound Probe ◽  
Spherical Parallel Mechanism ◽  
Real Coded Genetic Algorithms ◽  
Probe Holder

SUMMARYThis paper introduces the design and the optimization of a probe holder robot for tele-echography applications. To define its kinematic architecture, an approach based on motion capture of an expert's gestures during ultrasound examinations was proposed. The medical gestures analyzed consisted of ultrasound probe movements and were used to characterize the kinematic specifications of the proposed manipulator. The selected architecture was a Spherical Parallel Mechanism (SPM) with 3 degrees of freedom (DoF) and its optimal synthesis was performed using real-coded Genetic Algorithms (GA). The optimization criteria and constraints were established thanks to the collaboration of medical experts and were successively formulated and solved using mono-objective and multi-objective functions.

Pareto optimal synthesis of four-bar mechanisms for path generation

2009 ◽  
Vol 44 (1) ◽  
pp. 180-191 ◽  
Author(s):  
N. Nariman-Zadeh ◽  
M. Felezi ◽  
A. Jamali ◽  
M. Ganji
Keyword(s):  
Optimal Synthesis ◽  
Pareto Optimal ◽  
Path Generation
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