Real-Time Error Prediction for High-Precision Operation of Parallel Kinematic Machines

2012 ◽  
Author(s):  
Z. M. Bi ◽  
Guoping Wang
Keyword(s):  
Real Time ◽  
Machine Tools ◽  
Real Time Control ◽  
Motion Error ◽  
Parallel Kinematic Machines ◽  
Time Control ◽  
Operation Speed ◽  
Conventional Machine ◽  
Internal Forces ◽  
Parallel Kinematic

Closed-loop parallel kinematic machines (PKMs) have been proposed to improve precision and operation speed over conventional machine tools and robots. However, an embarrassing dilemma is that most of the existing PKMs achieve very lower precision in contrast to equivalent serial machine tools or robots, which are competitive to same tasks. Limited works have been conducted to evaluate errors thus improve precision of machine in real-time control. It becomes necessary to explore the relation of the motion error with the dynamics of a PKM. In this paper, the new model of the error evaluation has been proposed; three major sources of error under consideration are the deformations of the components under dynamic loads, the deformations at joint contacts, and the clearances of passive joints. To illustrate the modeling procedure, the dynamic model of machine is developed to determine internal forces among components and locations of joint contacts. Errors caused by machine dynamics are evaluated analytically in real time; in particular, the errors happened at the contacts of passive joints are estimated based on Hertz theory. The developed error models can be applied to compensate the motion errors of tool tip in real-time. The Exechon parallel kinematic machine is used as a case study, the results from simulation has been compared with the test data.

Direct Pose Measurement: A Suitable Way to Increase the Accuracy of Parallel Robots?

2007 ◽  
Author(s):  
Christian Munzinger ◽  
Martin Kipfmu¨ller
Keyword(s):  
Machine Tool ◽  
Machine Tools ◽  
Parallel Robots ◽  
Dynamic Parameters ◽  
Parallel Mechanisms ◽  
End Effector ◽  
Parallel Kinematic Machines ◽  
Machine Tool Structures ◽  
Conventional Machine ◽  
Parallel Kinematic

Parallel robots are showing a high potential for the application in machine tools requesting high stiffness and dynamics. Nevertheless, a broad use of parallel mechanisms in machine tools is nowadays avoided by the minor accuracy of parallel kinematic machines compared to conventional machine tool structures, which entails the need for complex calibration algorithms. In this paper, a strategy to avoid the calibration of parallel kinematic machines by rearranging the measurement system to the end effector is presented. Because this rearrangement entails a massive modification of the machine tools control circuit that causes stability problems, first tests of the concept have been carried out via simulation. The focus of these tests was to determine the necessary dynamic parameters of a suitable machine tool’s structure. The results of these tests are used to derive guidelines for the design of a machine tool with direct pose measurement. Finally, a design approach for a suitable machine tool is presented.

A Real Time Control Architecture for Continuously Managing Patients in a Care Unit

1995 ◽  
Vol 34 (05) ◽  
pp. 475-488
Author(s):  
B. Seroussi ◽  
J. F. Boisvieux ◽  
V. Morice
Keyword(s):  
Real Time ◽  
Linear Time ◽  
Treatment Plan ◽  
Control Architecture ◽  
Real Time Control ◽  
Time Representation ◽  
Time Control ◽  
Continuous Support ◽  
Definition Of ◽  
Computerized System

Abstract:The monitoring and treatment of patients in a care unit is a complex task in which even the most experienced clinicians can make errors. A hemato-oncology department in which patients undergo chemotherapy asked for a computerized system able to provide intelligent and continuous support in this task. One issue in building such a system is the definition of a control architecture able to manage, in real time, a treatment plan containing prescriptions and protocols in which temporal constraints are expressed in various ways, that is, which supervises the treatment, including controlling the timely execution of prescriptions and suggesting modifications to the plan according to the patient’s evolving condition. The system to solve these issues, called SEPIA, has to manage the dynamic, processes involved in patient care. Its role is to generate, in real time, commands for the patient’s care (execution of tests, administration of drugs) from a plan, and to monitor the patient’s state so that it may propose actions updating the plan. The necessity of an explicit time representation is shown. We propose using a linear time structure towards the past, with precise and absolute dates, open towards the future, and with imprecise and relative dates. Temporal relative scales are introduced to facilitate knowledge representation and access.

Real-time Control for Mobile Robot Considering Environmental Changes

2007 ◽  
Vol 73 (12) ◽  
pp. 1369-1374
Author(s):  
Hiromi SATO ◽  
Yuichiro MORIKUNI ◽  
Kiyotaka KATO
Keyword(s):  
Mobile Robot ◽  
Real Time ◽  
Environmental Changes ◽  
Real Time Control ◽  
Time Control

Using graphs to construct a math model of a microcontroller-based system for preset rate control of a flywheel motor to be used in high-dynamics spacecraft

2020 ◽  
pp. 126-134
Author(s):  
Vladimir V. NEKRASOV
Keyword(s):  
Real Time ◽  
Rotation Rate ◽  
Control Function ◽  
Real Time Control ◽  
Math Model ◽  
The Real ◽  
Time Control ◽  
Power Matrix ◽  
High Dynamics ◽  
Stated Problem

Developing a microcontroller-based system for controlling the flywheel motor of high-dynamics spacecraft using Russian-made parts and components made it possible to make statement of the problem of searching control function for a preset rotation rate of the flywheel rotor. This paper discusses one of the possible options for mathematical study of the stated problem, namely, application of structural analysis based on graph theory. Within the framework of the stated problem a graph was constructed for generating the new required rate, while in order to consider the stochastic case option the incidence and adjacency matrices were constructed. The stated problem was solved using a power matrix which transforms a set of contiguous matrices of the graph of admissible solution edge sequences, the real-time control function was found. Based on the results of this work, operational trials were run for the developed control function of the flywheel motor rotor rotation rate, a math model was constructed for the real-time control function, and conclusions were drawn about the feasibility of implementing the results of this study. Key words: Control function, graph, incidence matrix, adjacency matrix, power matrix, microcontroller control of the flywheel motor, highly dynamic spacecraft.

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