The application of DSP in ultra-precision CNC system

the greatest characteristic of ultra precision machining is new achievements in the development of integrated application of machinery, and at the end of the modern electronics, measurement, computer and other new technology is the result of mechanical and electrical integration, now has become one of the important development direction of mechanical manufacturing.Ultra-precision machining depends on the development of precision machine tools, thus a key part of the ultra precision machine tool shearing precision servo control and super precision measuring system as well as the integration of processing and measuring is widely attention and development.In recent years, the development of microelectronics technology and computer technology has become a technology base to promote the development of servo control technology to high performance.

with the development of large scale integrated circuit technology, DSP chips got rapid development, in signal processing, communications, radar, remote sensing, voice and image processing, electronic measurement, automatic control and many other fields has been widely used.

in terms of ultra precision machine tool servo control, to make the machine table to achieve sub-micron precision linear motion, the introduction of modern control technology is very necessary.

fine control unit, to achieve continuous feed small procedures section, has become the significant characteristics of ultra-precision CNC machining, ultra precision nc interpolation cycle has reached millisecond.Large amount of data, high precision of interpolation operation and control, the computer system can react to processing instruction at high speed, high speed processing and calculate the amount of the movement of the servo motor, then sends out control instructions.DSP data capacity is as high as dozens of MIPS, at the same time, the instruction cycle short as a few nanoseconds, is very suitable for large amount of data of high-speed data acquisition system and real-time control system.Applying DSP to the development of high-performance ultra-precision CNC system is a good strategy.In fact, DSP microprocessor in the ultra precision servo control system, compensation and fast servo tool detection device, machine protection has a successful application.

design and development, and a success.Its core is the ADSP2181 chip, interpolation cycle 5 ms control cycle is 0.5 ms, programming resolution of 2 nm, are the basic conditions of the actual working condition of application.

2 the typical performance of digital signal processor is the main application of the digital signal processor device to quickly achieve a variety of digital signal processing algorithm in real time.As a typical DSP device, the function of ADSP2181 structure as shown.The typical has the following properties: piezoelectric ceramic diamond tool servo device error compensation table in an instruction cycle can finish one multiplication and addition;Program and data space apart, can access instructions and data at the same time;On chip is fast RAM, usually through a separate data bus in two pieces of access at the same time;Fast interrupt processing and hardware I\/O support, more than can be executed in parallel operation;Support pipelining, so take the operation can be overlapped, decoding and execution, etc.

adsp2181 chip of MAC (once – times of multiplication and addition time has reached 33 ns chip has reached more than 200, the number of pin pin number increases, the increase of the mean structure flexibility, such as external memory expansion and communication between the processors.At the same time, the development of DSP chip, the cost of the DSP system, volume, weight and power consumption are reduced greatly.

– a has a good and efficient development tools and assembly language support.ADSP2100 each series provides tools to compile and connection, to generate an executable file, executable files can be written to the DSP program storage area.DSP with simulation software, can run the program, the interrupt simulation, timing, etc, which has a great convenience, very suitable for numerical control development needs.

3 application of DSP in ultra-precision CNC system CNC system can be divided into two types of single processor and multiprocessor.Single processor system with a single CPU as the control core, all functions are carried out by a CPU time, and the software programming is complex, the machine tool feed rate have also been affected.Multiprocessor system is a typical master-slave CPU structure, the main CPU to complete the front control, namely the man-machine interface management, information display and pretreatment, etc;From the CPU to complete the background control the interpolation arithmetic, servo control and feedback processing, such as work, responsible for frequent data computation and I\/O operations.

very short interpolation cycle of ultra-precision CNC system, interpolation interval is small, its control and interpolation arithmetic fairly frequently, and numerical control system in a very short period of time of each axis position of feedback signal processing, the current has reached millisecond interpolation cycle.Single processor CNC system is difficult to achieve such a fast data processing speed, thus make multiprocessor systems using become inevitable.DSP devices because of its powerful data capacity and high speed, for the development of ultra-precision CNC system, is a good choice, and advanced control algorithm used in ultra-precision CNC system.

as a matter of fact, DSP device in the servo control of ultra precision CNC processing, compensation and fast servo tool monitoring, advanced control algorithm USES in such aspects as machine tool protection systems and has a broad and effective application.

3.1 the servo control system based on DSP high speed DSP microprocessor, can realize high precision position servo control superfinishing machine and contour machining control, at the same time provide the heating effect of the machine tools and cutting tools and geometric error compensation and control.Such as Faunc15 – BCNC system USES has 33 MHZ double-precision 64 words long MC68EC030 double CPU microprocessor implements has 1 nm high-speed CNC control system, the high precision contour machining control, automatic feed rate control to ensure the machining path within the allowed error range of the specified path.

, completed the basic workflow ADSP2181 are: read the instruction location, and form a new trajectory calculation, query and deal with external events, to control actuator movement.

using master-slave multiprocessor structure of ultra precision CNC ADSP2181 are 16-bit word length, can be in 33 ns to finish any instruction.Due to the high operation speed, the system of the interpolation period sampling and control cycle to 2 ms and 0.5 ms respectively, the real time and greatly improve the agility of the system.Correspondingly, the control accuracy reached 0. In the process of m, and regular host control, compared to the machining precision of interpolation control cycle integration, comprehensive index greatly improve precision.

3.2 DSP high speed high performance microprocessor control algorithm, especially the application of digital signal processor (DSP), many advanced control strategies and methods, such as adaptive control, learning control, friction control, etc., are used in high precision servo control system, greatly improving the control accuracy and rapidity.

  A.Abler提出了\u201C直接阻尼控制(DDC)算法,并以TMS320C30实现。该算法在使机床定位与跟踪控制精度达到亚微米级的同时,有效地减小了超精密机床的动态振动噪声对机床定位精度的影响。H.Yonezawaetal采用TMS320C30实现了PID+摩擦补偿控制算法,使超精密工作台高速定位精度达到0. YH-I型超精密数控系统基于ADSP2181强大的数据处理能力,实现了FuzzrPid复合控制。伺服控制系统的采样率达到2KHz.在实际运行中,该系统将每个插补周期分为10个控制周期进行伺服控制,从而对插补过程构成更为有效的控制,使曲线插补更加准确。结果表明:该方法大大提高了系统对曲线跟踪的准确性和快速性。与常规主处理器直接做PID伺服控制方法相比,伺服系统的正弦扰动减小了约60%,控制精度则有70%的提高。

  3.3DSP在刀具监控和伺服方面的应用为了对刀具进给运动中的系统误差进行补偿,YH~I超精密数控系统采用自研的压电陶瓷,以ADSP2181微处理器构成伺服结构,实现了开环的伺服控制,其原理结构为:原理结构图由于ADSP2181的快速运算能力,可以对每个插补控制周期的补偿数据进行迅速而准确的运算。该刀具伺服机构使刀具的定位精度达到了微米级,并具有良好、快速的动态新型数控机床主轴交流电机变频调速数控系统贺平、贺刚2夏秀红3(1.湘潭大学计算机科学系,湖南湘潭411105 2.益阳橡胶机械厂技术处,湖南益阳4130003.湘潭大学实习工厂,湖南湘潭41105)器输出交流电正弦波失真所造成的转矩脉动和电机损耗。