Smooth Continuous Path Research Articles

Optimal Trajectory Generation for a 6-DOF Parallel Manipulator Using Grey Wolf Optimization Algorithm

SUMMARYIn this paper we designed an optimal trajectory generation (OTG) method to generate easy and errorless continuous path motion with quick converging using Grey Wolf Optimization (GWO) method. The proposed OTG method finds the trajectory path with minimum tracking error, combined speed, joint increasing speed wrinkle, as well as joint lurching move to follow an error-free smooth continuous path.

Analysis of a Progressive Failure of a Work Roll in Hot Strip Mill

In hot rolling mills, premature failure of rolls is a major concern as it adversely affects the mill operation as well as production. Analysis of failed roll materials and actual rolling conditions in service are therefore necessary to understand the roll failure mechanism and thereby improve the service life of rolls. The hot strip mill referred here consists of two stands in a roughing mill and seven stands in a finishing mill. Indefinite chilled double poured cast iron rolls are used in the finishing mill for rolling of the sheet in the last two stands. HSM produces coils in the thickness range of 2–25 mm. This present case describes one of the finishing stand work roll failures and analysis which was carried out using destructive as well as nondestructive testing techniques. The spalled roll showed fatigue arrest marks in a smooth continuous path along the circumferential direction. Characteristic features of the fracture surface were similar to those of surface-initiated spalling which is known as ribbon fatigue spalling. The fracture or spalled region was analyzed with Ultrasonic test to identify the origin of the crack. Past data and roll schedule were also studied for root cause.

Ribbon Fatigue Spalling of a Forged Work Roll Used at a Cold Rolling Mill

Catastrophic failure of a forged work roll used in a cold rolling mill was investigated. The spalled roll showed fatigue arrest marks in a smooth continuous path along the circumferential direction. Characteristic features of the fracture surface were similar to that of surface initiated spalling which is known as ribbon fatigue spalling. The investigation consisted of visual observation, profiling of crack using ultrasonic testing, microstructural characterization by optical and scanning electron microscopy, XRD analysis, and hardness measurements. Ultrasonic evaluation confirmed the initiation of root crack on the roll surface followed by an extensive sub-surface propagation (~815 mm length) of fatigue crack. Microstructural analysis revealed the presence of dendritic columnar structure and coarse irregular carbides indicating improper manufacturing process. Retained austenite content (~12%) as measured using XRD was higher than the usual desirable limit for such application. These microstructural abnormalities deteriorated the fatigue resistance of the roll. Since the roll failed within few hours of the running campaign and there was no operational abnormality reported in the campaign, it can be inferred that the initiation of the fatigue crack was conceived prior to the running campaign. It was an inspection deficiency that the crack was not detected prior to the start of the campaign. Initiation of fatigue crack which could not be detected during inspection led to the premature failure of roll in the early stage of campaign.

Implementation of Smooth Continuous Camera Trajectories for Viewing PDB and VRML Objects

A parametrically defined camera trajectory enabling the accurate and systematic scanning of the entire surface of virtual (Protein Data Bank (PDB)) proteins is developed and implemented. The smooth continuous path guarantees that each local region of the protein is inspected from a variety of directions in a controlled and uniform manner. Manipulation of several parameters governs the density, character and duration of the scan. Applications to the analysis of other real and virtual objects are also considered.

Development of a “walking drive” ultraprecision positioner

The present paper presents a new mechanism to feed a precision table continuously over a long stroke with high rigidity by utilizing deformations of piezoelectric actuators. A driving method names “walking drive” is employed for the mechanism with which the table is driven in a similar way to the walking motions in animals. A precision feed device is developed, and ultraprecision positioning experiments are carried out by using the device combined with a laser-feedback system developed. It is confirmed that the positioner driven by the walking drive has the following advantages: (1) positioning resolution of 5 nm is realized with a simple control method and a simple mechanism, because of no friction against the feed motion; (2) smooth continuous path control with the following error of less than 10 nm is realized over a long stroke despite short strokes of the piezoelectric actuators; and (3) high stiffness of greater than 350 N/μm is realized in the feed direction.

Smooth Continuous Path Motion Generation for Stepping Motors

Many modern machine tool applications require precise, smooth continuous path motion. Often, low cost stepping motor solutions are regarded as inappropriate for this type of application due to their jerky motion. In order to reduce the jerky motion and to investigate various approaches for motion profiling, a dedicated real-time variable pulse control architecture for stepping motors is presented. The effectiveness of the pulse generation architecture is evaluated. The performance of the ’variable pulse algorithm’ regarding smooth motion, is discussed and compared to a more traditional motion generation approach.

Walking Driveによる精密送り機構の開発 (第2報)

This paper presents a method to control feed velocity of precision feed devices driven by means of walking drive, and ultraprecision positioning is realized by a laser feedback controller developed. It is confirmed that the feed velocity can be controlled easily and simply by the method presented. Major results obtained are as follows ; (1) Positioning accuracy of 5 nm is realized, because of no friction against the feed motion. (2) Smooth continuous path control is realized despite short strokes of the piezoelectric actuators. (3) High stiffness of about 40 N/μm is realized in the feed direction.

Path planning simulator for a mobile robot

INTRODUCTION Path planning is a critical problem encountered in the operation of a mobile robot. When driving a car one simultaneously plans a path and executes a locomotion controlling function. Thus, describing a smooth continuous path for the car is straight forward. However, if the planning and execution functions are performed by two different persons some form of path description must be explicitly passed from the planner to the executor. This problem arises in autonomous vehicle control because in many cases, these two functions are executed in separated components. The motion planning problem, in its simplest form, is to find a path from a specified starting position to a specified goal position that avoids collisions with a known set of obstacles. The purpose of this paper is to present a software package that implements the motion planning and collision avoidance systems for an automaton operating amongst static and moving obstacles in a 2-D environment.