Keywords: servo drive technology, linear motor, programmable computer controller, motion control
1 Introduction
The high and new technology of the information age flows to the traditional industries, causing the latter's profound changes. As one of the traditional industries of the machinery industry, under the impact of this new technological revolution, the product structure and the structure of the production system has undergone a qualitative leap, microelectronics technology, microcomputer technology, high-speed development of information, intelligence and mechanical devices and power equipment, prompting the machinery industry has begun a large-scale mechatronics technology revolution.
With the development of computer technology, electronic power technology and sensor technology, the advanced countries of the mechatronics products are endless. Machine tools, automobiles, instrumentation, household appliances, light industrial machinery, textile machinery, packaging machinery, printing machinery, metallurgical machinery, chemical machinery, and industrial robots, intelligent robots, and many other categories of products every year there is new progress. Mechatronics technology has been more and more attention in all aspects, it is in improving people's lives, improve efficiency, energy saving, reduce material consumption, enhance the competitiveness of enterprises play a great role.
In the rapid development of mechatronics technology at the same time, motion control technology as its key components, has also been unprecedented development, domestic and foreign manufacturers have launched new technologies and new products of motion control. This paper mainly introduces the full closed-loop AC servo drive technology (Full Closed AC Servo), linear motor drive technology (Linear Motor Driving), programmable computer controller (Programmable Computer Controller, PCC) and motion control card (Motion Controlling Board) and several other important products. Controlling Board) and several representative new technologies.
2 full closed-loop AC servo drive technology
In some of the positioning accuracy or dynamic response requirements of the mechatronics products, AC servo systems are more and more widely used, of which the digital AC servo system is more in line with the trend of the digital control mode, and debugging, use is very simple, and therefore favored. The drive of this servo system uses an advanced digital signal processor (Digital Signal Processor, DSP), can be sampled on the back end of the motor shaft photoelectric encoder position, between the drive and the motor constitutes a closed-loop position and speed control system, and give full play to the high-speed computing power of the DSP, automatically complete the entire servo system gain adjustment, even tracking load changes, real-time adjustment, and can be adjusted in real time. Can even track the load changes, real-time adjustment of the system gain; some drivers also have a fast Fourier transform (FFT) function, measured the mechanical *** vibration point of the equipment, and through the trap filtering way to eliminate mechanical *** vibration.
In general, most of these digital AC servo systems work in a semi-closed-loop control mode, i.e., the encoder feedback on the servo motor is used as both a speed loop and a position loop. This type of control cannot overcome or compensate for the gap and error in the transmission chain. In order to obtain higher control accuracy, should be installed in the final part of the movement of high-precision detection elements (such as: scale, photoelectric encoder, etc.), that is, to realize the full closed-loop control. Comparison of the traditional full closed-loop control method is: servo system only accepts the speed command, complete the speed loop control, position loop control is completed by the upper controller (most of the full closed-loop machine tool CNC system is this way). This greatly increases the difficulty of the upper controller, but also limits the promotion of servo systems. At present, there has been a more complete, can achieve higher accuracy of the full closed-loop digital servo system, so that the realization of high-precision automation equipment is easier. Its control principle is shown in Figure 1.
The system overcomes the shortcomings of the above semi-closed-loop control system, the servo drive can be directly sampled mounted on the last level of mechanical moving parts of the position feedback components (such as scale, magnetic scale, rotary encoder, etc.), as the position loop, and the motor on the encoder feedback at this time only as the speed loop. This servo system can eliminate the mechanical transmission gap (such as gear gap, screw gap, etc.), to compensate for the mechanical transmission parts of the manufacturing error (such as screw pitch error, etc.), to realize the true closed-loop position control function, to obtain high positioning accuracy. And this full closed-loop control are completed by the servo drive, without the need to increase the burden of the upper controller, and therefore more and more industries in their automation equipment, the transformation and development, began to use this servo system.
3 linear motor drive technology
Linear motors in the machine tool feed servo system applications, in recent years has been emphasized in the world's machine tool industry, and in the industrially developed regions of Western Europe set off a "linear motor heat".
In the machine tool feeding system, the use of linear motors directly driven with the original rotary motor drive the biggest difference is the elimination of the motor to the table (drag plate) between the mechanical transmission links to shorten the length of the machine tool feeding transmission chain to zero, so this transmission is also known as the "zero transmission". It is because of this "zero transmission" mode, brought the original rotary motor drive mode can not achieve the performance indicators and advantages.
1. High-speed response As the system directly canceled some of the response time constant of the mechanical transmission parts (such as screws, etc.), so that the entire closed-loop control system dynamic response performance greatly improved, the response is exceptionally sensitive and fast.
2. Accuracy The linear drive system eliminates the transmission gap and errors generated by mechanical mechanisms such as screws, and reduces the tracking error due to transmission system lag when interpolating the movement. Through the linear position detection feedback control, you can greatly improve the positioning accuracy of the machine tool.
3. High dynamic stiffness Due to the "direct drive", to avoid the start, speed and direction change due to the elastic deformation of the intermediate transmission link, friction and wear and backlash caused by the phenomenon of motion lag, but also to improve the rigidity of its transmission.
4. fast speed, acceleration and deceleration process is short Because the linear motor was first mainly used for magnetic levitation train (speed up to 500Km / h), so used in the machine tool feed drive to meet the maximum speed of ultra-high-speed cutting into the speed (required to reach 60 ~ 100M / min or higher) of course, is not a problem. Also due to the high speed responsiveness of the above "zero transmission", the acceleration and deceleration process is greatly shortened. It is possible to achieve high speed instantaneously at startup and instantaneous quasi-stopping during high-speed operation. Higher acceleration can be obtained, generally up to 2 ~ 10g (g = 9.8m / s2), while the maximum acceleration of the ball screw drive is generally only 0.1 ~ 0.5g.
5. Unlimited length of travel on the guideway through the tandem connection of linear motors, it is possible to extend the length of its travel indefinitely.
6. quiet movement, low noise Due to the elimination of mechanical friction of the drive screw and other components, and the guide can be used as a rolling guide or magnetic cushion levitation guide (no mechanical contact), the movement of the noise will be greatly reduced.
7. High efficiency Because there is no intermediate transmission links, eliminating the energy loss of mechanical friction, transmission efficiency is greatly improved.
The development of linear drive motors is also increasingly fast, in the motion control industry has been emphasized. Relatively developed countries in foreign industrial motion control has begun to promote the use of the corresponding products, including the United States Kollmorgen (Kollmorgen) PLATINNM DDL series of linear motors and SERVOSTAR CD series of digital servo amplifiers constitute a typical linear permanent magnet servo system, which can provide a very high dynamic response speed and acceleration, very high stiffness, Higher positioning accuracy and smooth non-differential movement; Germany Siemens, Japan Mitsui Precision Machinery Company, Taiwan Shangyin Technology Company, etc. also began to apply linear motors in their products.
4 programmable computer controller technology
Since the end of the 1960s, the United States, the first programmable controller (Programming Logical Controller, PLC) since the advent of PLC control technology has gone through 30 years of development, especially with the development of modern computer technology and microelectronics technology, it has been far from the hardware and software technology. Hardware and software technology has been far out of the original "sequential control" of the prototype stage. Programmable computer controller (PCC) is a new generation of programmable controllers on behalf of this development trend.
Compared with the traditional PLC, PCC's most important feature is that it is similar to the mainframe computer time-sharing multi-tasking operating system and the design of diverse application software. Most traditional PLCs use a single-task clock scanning or monitoring program to handle the program's own logic instructions and external I/O channel status acquisition and refresh. Such processing directly leads to the PLC's "control speed" depends on the size of the application program, this result is undoubtedly with the I / O channel in the high real-time control requirements contrary to the PCC's system software perfectly solves this problem, which uses time-sharing multi-tasking mechanism to build its application software running platform, so that the application program running cycle has nothing to do with the length of the program, but the operating system cycle decided by the cycle. It uses a time-sharing multitasking mechanism to build its application platform so that the running cycle of the application is not related to the length of the program, but is determined by the cycle of the operating system. Thus, it distinguishes the scanning cycle of the application program from the external control cycle and meets the requirement of real-time control. Of course, this control cycle can be modified according to the user's actual requirements as long as the CPU computing power allows.
Based on such an operating system, the PCC application program consists of multitasking modules, which brings great convenience to the development of application software for engineering projects. Because this can be easily in accordance with the control project in the various parts of the different functional requirements, such as motion control, data acquisition, alarms, PID regulation operation, communication control, etc., were compiled out of the control program module (task), these modules are running independently, the data and maintain a certain degree of correlation between the modules after step-by-step independent preparation and debugging, together with the PCC can be downloaded to the CPU. These modules can be downloaded to the CPU of PCC after step-by-step independent preparation and debugging, and run in parallel under the scheduling management of multi-task operating system to realize the control requirements of the project.
PCC in the industrial control of powerful functional advantages, reflecting the programmable controller and industrial control computers and DCS (Distributed Industrial Control System) technology integration of the development of the trend, although it is still a relatively young technology, but in its growing number of applications, it is increasingly showing the potential for development can not be underestimated.
5 Motion control card
Motion control card is a kind of industrial PC-based, for a variety of motion control occasions (including displacement, speed, acceleration, etc.) on the control unit. Its emergence is mainly because: (1) in order to meet the new CNC system standardization, flexibility, openness and other requirements; (2) in a variety of industrial equipment (such as packaging machinery, printing machinery, etc.), national defense equipment (such as tracking and positioning systems, etc.), intelligent medical devices, such as the development of automation control systems and transformation of the equipment, the urgent need for a motion control module of the hardware platform; (3) the PC machine in a variety of industrial sites, but also prompted by the appropriate equipment and hardware platform. (3) PC in a variety of industrial sites, also prompted the corresponding control card to give full play to the powerful functions of the PC.
Motion control cards usually use professional motion control chips or high-speed DSP as the core of motion control, mostly used to control stepper motors or servo motors. Generally speaking, motion control cards and PCs form a master-slave control structure: PCs are responsible for the management of the human-machine interface and the real-time monitoring of the control system (e.g., management of the keyboard and mouse, display of the system status, planning of the motion trajectory, sending of control commands, and monitoring of external signals, etc.); the control card completes all the details of the motion control (including the output of pulses and directional signals, the processing of automatic lift and speed, the home position, and the control of the motor). (including the output of pulse and direction signals, the processing of automatic lifting and lowering speeds, the detection of signals such as origin and limit, etc.). Motion control cards are equipped with open function libraries for users to develop and construct their own control systems under DOS or Windows. Therefore, this open structure of the motion control card can be widely used in manufacturing equipment automation in various fields.
This mode of motion control in the control system of foreign automation equipment is more popular, motion control cards have formed an independent specialized industry, with representative products such as the United States PMAC, PARKER motion control cards. Corresponding products have also appeared in the country, such as the DMC300 series card of Chengdu Step Electromechanical Co., Ltd. has been successfully applied to a variety of automation equipment, such as CNC punching machines, automotive parts performance test bench.
6 Conclusion
The rapid development of computer technology and microelectronics technology to promote the industrial motion control technology continues to progress, such as the emergence of a full closed-loop AC servo drive system, linear motor drive technology, programmable computer controllers, motion control cards, and many other advanced and practical technology for the development and manufacture of industrial automation equipment to provide a highly efficient means. This will also certainly contribute to the continuous improvement of China's mechatronics technology level.