Effective Tool-Point Acceleration of Serial Chain Mechanisms Based on Basic Geometric Transformations

2009 ◽  
Vol 1 (4) ◽  
Author(s):  
Oziel Rios ◽  
Delbert Tesar

In this paper, a method to manage the actuator parameters of a serial chain mechanism composed of revolute joints to achieve improved responsiveness characteristics (acceleration capability) based on the basic geometric parameters of the mechanism is presented. Here, an analytic framework presented by the authors in an earlier work, which exploits the geometric structure of this type of mechanism is extended to address the tool-point mass and acceleration. The manipulator’s geometry is reduced to a set of lengths, which are representative of the mechanical gains associated with the manipulator and they, along with the transmission ratio of the actuators, are used to map the actuator parameters to their effective values at the tool-point where a direct comparison to the task requirements can be made. With this method, minimal computations are required to evaluate the system’s performance since only the forward kinematic computations are required. The effects of the actuator transmission ratio parameter on the effective tool-point force, mass, and acceleration are investigated for a six-DOF serial chain manipulator. Through this case study, it is demonstrated how the transmission ratio is managed to balance the system’s effective tool-point force and mass to obtain an optimal tool-point acceleration. In addition to the investigation of the effects of the actuator parameters, the method is shown to be useful in the solution of the configuration management or modular design problem since the exponential design space can be searched for a globally optimal solution with minimal computations. The goal of the configuration management problem is to quickly configure and/or reconfigure a robotic manipulator from a finite set of actuator modules.

Author(s):  
Jie Zhang ◽  
Qidong Wang ◽  
Han Zhang ◽  
Min Zhang ◽  
Jianwei Lin

Abstract In this study, a systematic optimization method for the thermal management problem of passenger vehicle was proposed. This article addressed the problem of the drive shaft sheath surface temperature exceeded allowable value. Initially, the causes and initial measures of the thermal problem were studied through computational fluid dynamics (CFD) simulation. Furthermore, the key measures and the relevant parameters were determined through Taguchi method and significance analysis. A prediction model between the parameters and optimization objective was built by radial basis function neural network (RBFNN). Finally, the prediction model and particle swarm optimization (PSO) algorithm were combined to calculate the optimal solution, and the optimal solution was selected for simulation and experiment verification. Experiment results indicated that this method reduced the drive shaft sheath surface temperature promptly, the decreasing amplitude was 22%, which was met the experimental requirements.


2014 ◽  
Vol 599-601 ◽  
pp. 358-361
Author(s):  
Huan Qiang ◽  
Hu Zhang ◽  
Yan Zhou

A design method of modular joint is proposed according to the complicated structure, line exposed and heavier characteristics of multi-DOF (degree of freedom) mechanical arm. In this paper, the design of modular joint was carried on and a model of six-DOF mechanical arm was built through the research on the structure of mechanical arm. On this basis, dynamics simulation will be carried. The results show that the modular design method simplified the structure of the mechanical arm, the dynamics simulation proved it was feasible for the structure design and drive selection.


Author(s):  
Oziel Rios ◽  
Delbert Tesar

A serial robotic manipulator arm is a complex electro-mechanical system whose performance is highly characterized by its actuators. The actuator itself is a complex nonlinear system whose performance can be represented by the speed and torque capabilities of its motor and its accuracy depends on the resolution of the encoder as well as its ability to resist deformations under load. The mechanical gain associated with the transmission is critical to the overall performance of the actuator since it amplifies the motor torque thus improving the force capability of the manipulator housing it, reduces the motor speed to a suitable output speed operating range, enables an improvement in responsiveness (acceleration) and amplifies the stiffness improving the precision under load of the overall system. In this work, a basic analytic process that can be used to manage the actuator gain parameters to obtain an improved arm design based on a set of desired/required performance specifications will be laid out. Key to this analytic process is the mapping of the actuator parameters (speed, torque, stiffness and encoder resolution) to their effective values at the system output via the mechanical gains of the actuators as well as the effective mechanical gains of the manipulator. This forward mapping of the actuator parameters allows the designer to determine how each of the parameters influences the functional capacity of the serial manipulator arm. The actuator gains are then distributed along the effective length of the manipulator to determine the distribution effects on the performance capabilities of the system. The analytic formulation is used to address the issue of configuration management of serial robotic manipulators where the goal is to assemble a system from a finite set of components that meets some required performance specifications. To this end, two examples demonstrating a solution of the configuration management problem are presented. In the first, a manipulator is configured that is intended for light-duty applications while in the second, several manipulators intended for medium and heavy-duty applications are configured. The analytic process developed in this work can reduce the effort in the initial phases of the design process and the total number of design iterations can be reduced.


2009 ◽  
Vol 131 (2) ◽  
Author(s):  
Oziel Rios ◽  
Delbert Tesar

A serial robotic manipulator arm is a complex electromechanical system whose performance is characterized by its actuators. The actuator itself is a complex nonlinear system whose performance can be characterized by the speed and torque capabilities of its motor, and its accuracy depends on the resolution of the encoder as well as its ability to resist deformations under load. The mechanical gain associated with the transmission is critical to the overall performance of the actuator since it amplifies the motor torque, thus improving the force capability of the manipulator housing it, reduces the motor speed to a suitable output speed operating range, and amplifies the stiffness improving the precision under load of the overall system. In this work, a basic analytic process that can be used to manage the actuator gain parameter to obtain an improved arm design based on a set of desired/required performance specifications will be laid out. Key to this analytic process is the mapping of the actuator parameters (speed, torque, stiffness, and encoder resolution) to their effective values at the system output via the mechanical gains of the actuators as well as the effective mechanical gains of the manipulator. This forward mapping of the actuator parameters allows the designer to determine how each of the parameters influences the functional capacity of the serial manipulator arm. The actuator gains are then distributed along the effective length of the manipulator to determine their effects on the performance capabilities of the system. The analytic formulation is also demonstrated to be effective in addressing the issue of configuration management of serial robotic manipulators where the goal is to assemble a system that meets some required performance specifications. To this end, two examples demonstrating a solution of the configuration management problem are presented. The analytic process developed based on the mapping of the mechanical parameters of the actuator to their effective values at the system output is shown to dramatically reduce the effort in the initial phases of the design process, meaning that the number of design iterations can be dramatically reduced.


2014 ◽  
Vol 602-605 ◽  
pp. 743-746
Author(s):  
Dong Dong Xu ◽  
Tong Wang

With the rapid development of science and technology, modern design has become increasingly complex, with the factors needed to be considered more various, find the optimal solution to solve problems, which is the real meaning of product design. In this paper, by analyzing the domestic and foreign research present situation of the modern theory of the modular design, according to the characteristics of complex product system, it will be introduced to the concept design of complex product system modular design, proposed in view of the function of the turbine division method, based on CATIA software research and development of the system design of a turbine, that can effectively shorten the development time, reduce development costs, to lay a good foundation for its innovation, having great theoretical and practical significance for turbine technology development.


1994 ◽  
Vol 116 (3) ◽  
pp. 908-914 ◽  
Author(s):  
R. P. Podhorodeski ◽  
K. H. Pittens

Parallel manipulators consisting of serial branches acting in parallel on a common end effector are examined. All nonredundant, six DOF manipulators corresponding to this in-parallel class of structures are enumerated. A specific in-parallel structure, three branches with two actuated joints per branch (3–2,2,2), is chosen as most promising based upon performance considerations. A class of kimematically simple (KS) serial-chain branch joint layouts suitable for the chosen in-parallel structure is defined. Arguments based upon kinematic equivalency of the branches and mobility of the assembled in-parallel manipulator chain are used to show that there exist only five unique branch joint-layouts belonging to the KS class. It is demonstrated that the solution to the inverse displacement problem for in-parallel manipulators based on the KS branches can be expressed in a closed form. Furthermore, the 3–2,2,2 in-parallel manipulators are shown to belong to a family of manipulators whose forward displacement solutions can be resolved through roots of a 16th order polynomial.


Author(s):  
Farshid Maghami Asl ◽  
A. Galip Ulsoy

An optimal solution, based on Markov Decision Theory, is presented for the capacity management problem in Reconfigurable Manufacturing Systems with stochastic market demand with a time delay between the time capacity change is ordered and the time it is delivered. The optimal policy in this paper is presented as optimal boundaries representing the optimal capacity expansion and reduction levels. The effects of change in the cost function parameters and the delay time on the optimal boundaries are presented for a capacity management scenario. The major differences between this research and the ones in inventory control lie in two folds. One is the fact that unlike inventory, capacity levels can be reduced according to the market demand. The other one is the novel approach presented in this paper to solve the delay problem which unlike the inventory control does not account for the cumulative unmet demand as a decision factor.


Author(s):  
Simona Onori ◽  
Lorenzo Serrao ◽  
Giorgio Rizzoni

This paper proposes a new method for solving the energy management problem for hybrid electric vehicles (HEVs) based on the equivalent consumption minimization strategy (ECMS). After discussing the main features of ECMS, an adaptation law of the equivalence factor used by ECMS is presented, which, using feedback of state of charge, ensures optimality of the strategy proposed. The performance of the A-ECMS is shown in simulation and compared to the optimal solution obtained with dynamic programming.


Author(s):  
K. R. Hareendra Varma ◽  
Ming Z. Huang

Abstract The redundancy resolution problem for kinematically redundant serial chain manipulators is addressed. In this paper, we present a generalization of the geometry based rate allocation algorithm, developed initially in [12] for only minimum norm solution, to obtain the optimal joint rate solution for any specified objective function, with or without weightage. This generalization is made possible through a geometrical interpretation of the common pseudoinverse-based gradient solution scheme, and by developing a modified formulation for the objective function as a minimum criterion not with respect to the origin of the joint rate space, but with respect to another point in the joint rate space represented by the gradient of the specified objective. Application examples of the algorithm including procedures of solution are demonstrated using 7R manipulators with two generic types of geometry. A closed form optimal solution for the 7R anthropomorphic arm considered is also presented.


Author(s):  
Lu Chen ◽  
◽  
Bin Xin ◽  
Jie Chen ◽  
◽  
...  

Multi-objective optimization problems involve two or more conflicting objectives, and they have a set of Pareto optimal solutions instead of a single optimal solution. In order to support the decision maker (DM) to find his/her most preferred solution, we propose an interactive multi-objective optimization method based on the DM’s preferences in the form of indifference tradeoffs. The method combines evolutionary algorithms with the gradient-based interactive step tradeoff (GRIST) method. An evolutionary algorithm is used to generate an approximate Pareto optimal solution at each iteration. The DM is asked to provide indifference tradeoffs whose projection onto the tangent hyperplane of the Pareto front provides a tradeoff direction. An approach for approximating the normal vector of the tangent hyperplane is proposed which is used to calculate the projection. A water quality management problem is used to demonstrate the interaction process of the interactive method. In addition, three benchmark problems are used to test the accuracy of the normal vector approximation approach and compare the proposed method with GRIST.


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