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Speed control is a very important factor to machining quality. In order to get high dynamic performance at the time of the machining speed changing, many kinds of algorithm for the acceleration/deceleration control have been proposed. The techniques which employ polynomial functions or digital convolution to generate velocity profile have been widely used and achieved good performance in motion control system. However, the control cycle of all these methods is one interpolation interval at least, and the velocity jump between two adjacent interpolation intervals during the acceleration/deceleration stage cannot be avoided. In this paper, a hardware fine acceleration/deceleration algorithm inside a single interpolation cycle is proposed to make the velocity change smoothly all the time even inside the interpolation interval. Based on this approach, an acceleration/deceleration fine interpolation circuit is designed with Verilog hardware description language and implemented in field programmable gate array. At last, the algorithm is applied in a three-axes motion controller and achieves a better machining performance than the one without this algorithm. [ABSTRACT FROM AUTHOR]

In this paper, a new CNC core design method, the function-separated design (FSD) method, is proposed to increase the modularity and reconfigurability of CNC systems, simplify the CNC development process, as well as gain a secondary development ability to allow customers or third parties to add or modify NC functions at the shop floor level. With the FSD method, a new CNC core structure is built. In this structure, the CNC core is composed of three main components: engine machine interface, event processor (EP), and system description data (SDD). The engine machine interface provides an interface to machine tools through the parameter settings via a human machine interface (HMI). The EP and SDD are the most important parts. The SDD stores the control rules and modularized NC functions. It is designed as the relatively separated part inside the CNC core. It can also be modified according to the specification changes to access the functions of the CNC core at the shop floor level. To ease the modification of the SDD on the shop floor, the Statechart modeling tool is used to generate a CNC function model; meanwhile, an SDD generator is developed to convert this model into the SDD. The EP is driven by events from the event generator and processes these events by referring to the SDD. The EP always remains the same. With such a structure, the control rules and NC functions of a CNC core can be redesigned or upgraded easily. A case study for implementing a non-circular piston-turning system verifies the feasibility of the proposed design method at the shop floor level. [ABSTRACT FROM AUTHOR]

The round-off error, which is caused by cycle sampling of the interpolation period, affects the interpolation accuracy and motion smoothness of computer numerical control (CNC) machining. To consider the round-off error while restricting the motion parameters within their specified ranges, a time-rounding-up-based feedrate scheduling method is proposed. Firstly, the characteristics of S-shaped acceleration/deceleration (ACC/DEC) algorithm are analyzed by setting the jerk of each section as a variable. The expressions of jerk are derived and some important properties are discovered. According to these properties, it is possible to limit all the motion parameters in their given ranges through increasing the interpolation time and adjusting other motion parameters. Secondly, a new time-rounding-up scheme is designed to guarantee that the total interpolation time of each curve segment is an integer multiple of interpolation period. Then, based on the rounded time, the adjustment principles of the displacement and maximum feedrate are proposed to satisfy the various constraints. Its feasibility is also analyzed. Finally, based on the time-rounding-up scheme and the parameter adjustment principles, a series of feedrate scheduling methods are designed for different situations. For most situations, a non-standard S-shaped ACC/DEC profile can be generated with no round-off error and all the motion parameters can be restricted within their given ranges. A series of simulations and practical experiments are conducted to verify the good performance and applicability of the proposed method. [ABSTRACT FROM AUTHOR]