1 System configuration:
The shelf cold bending unit system is composed of basic structures such as uncoiler, leveling machine, cutting head welding unit, servo feeding unit, online punching press, cold bending unit, fixed-length flying shear, discharging rack, etc. (as shown in Figure 1). Show). It also forms the unique cold-formed forming process characteristics of shelf cold-formed components. According to the data analysis collected from the production site, the actual hole position control accuracy σ is basically stable within ±0.15mm, and the hole position error conforms to the normal distribution law. It is guaranteed that the cumulative error on the total length is small and basically stable within 6σ. Therefore, higher requirements are put forward for the cold-formed manufacturing process of shelf components, and the key technologies and equipment for cold-formed production of shelf components are formed.
2 development direction:
Servo systems generally have two development directions. One is to meet the requirements of general industrial applications. In applications that do not require high performance indicators, the pursuit of low-cost, low-maintenance, and easy-to-use drive products, such as frequency conversion motors, frequency converters, etc. The other is the leading product representing the development level of the servo system—servo motor and servo controller, pursuing high-performance, high-speed, digital, intelligent, and networked drive control to meet the higher application requirements of users.
The application of servo technology in cold forming equipment involves these two development directions. The selection of the host computer involves CNC system or programmable logic controller (PLC), and the standard serial communication interface (such as RS-232C) configured by the servo system , RS-422 interface, special multi-core cable interface, etc.) and special local area network interface for system control and data transmission and processing, the system realizes the following functions: using the online servo device composed of servo motor and servo controller to achieve accurate online punching The positioning control block, the main drive system of the system composed of frequency conversion motors and frequency converters realizes the hydraulic cutting and positioning control of the product online length. Commissioning settings, self-tuning functions, system fault self-diagnosis and analysis functions, etc. need to be set and debugged in combination with the production process of the unit, the data collected on site and its processing results, and the selected upper control computer system and software configuration. .
3 Control Algorithms:
The cold-formed forming equipment adopts the position and speed signals collected from the position rotary encoder at the shaft end of the main drive motor, and contacts the rotary encoder on a certain plane of the cold-formed profile to sample the signal to form the internal and external closed-loop speed of the system's main drive AC variable frequency motor motion control. Position adjustment system, internal speed control closed loop adopts speed real-time detection control algorithm. This not only further improves the low-speed performance of the motor, and reduces the speed fluctuation and torque fluctuation to a very low level, but also ensures the stable operation and speed control of the cold forming process. The external position control closed loop adopts the PID motion control algorithm to ensure the cold forming process. Process position positioning control accuracy and position positioning efficiency.
At present, the servo controllers used in the cold bending forming equipment of shelves have adopted a variety of new algorithms. At present, the commonly used algorithms mainly include PID/IPD (proportional derivative and integral) control switching, feedforward control, real-time speed monitoring, resonance suppression control, variable gain control, vibration suppression control, model specification adaptive control, repeated control, predictive control, Model tracking control, online automatic correction control, fuzzy control, neural network control, etc. By using these functional algorithms, the response speed, stability, accuracy and operability of the servo controller can reach a high level, and the realization of A true full digital control.
System of rack cold forming unit
1 Basic composition:
The system consists of five parts, namely the upper control system composed of computer (PC) or PLC, servo drive control card, AC servo speed regulation system (AC servo controller, servo motor, corresponding control cable, etc.), sensor detection feedback system and the corresponding auxiliary execution system.
2 How it works:
The upper main control system is connected with the servo drive control card, and can send position or speed adjustment commands through the data line, set the PID adjustment parameters (it is designed as an open design during the program design process, which is convenient for online adaptive adjustment), and the data is carried out. Mode (D/A) conversion, the analog signal of ±10V is output through the corresponding control board and converted by the AC servo controller to drive the servo motor. A measuring roller and an incremental rotary encoder conversion device are set on the control object, and feedback signals (A, B, IN pulses) are provided by the rotary encoder to complete the position semi-closed loop or closed loop position feedback control system of the servo system. The sensing element in the position feedback loop-incremental photoelectric encoder transmits the real-time displacement (or rotation angle) change of the moving component to the on-site control station (PC or PLC) in the form of A and B differential pulses for encoding. Count the pulses of the controller to obtain the digital position, speed and other information. The main control host computer calculates the deviation between the given position and the actual position (that is, the feedback position) and adopts the corresponding PID control strategy according to the deviation range. The digital-to-analog conversion is converted into an analog control voltage, which is output to the servo amplifier, and finally adjusts the motion of the motor (forward, reverse, positioning stop, etc.) Position positioning; assist the execution system to complete the corresponding working cycle of the press to realize the stamping process, etc.
Several Main Problems in Control System Design
1 The control accuracy of the input signal
The number of pulses per revolution of the incremental encoder and the circumference of the measuring roller, such as: the difference between a φ90 measuring roller with a photoelectric encoder that outputs 1000 pulses per revolution and a photoelectric encoder that outputs 2000 pulses per revolution, φ50 The difference in control accuracy between the measuring roller and the φ90 measuring roller; the final reflection is the length value corresponding to each output pulse, that is, the ratio of the circumference of the circumference to the number of output pulses per revolution, try to choose a product with a smaller ratio.
2 The control accuracy of the output signal:
Due to the lag of measurement signal and control transmission, the difference in position loop PID control algorithm, Kp, Ki, Kd and sampling period T determined by parameter tuning, etc., in the digital PID adjustment control system, at the beginning, end or large scale of the process When the set value is increased, the integral accumulation will occur, causing the system to overshoot and even oscillate, which is unfavorable for the operation of the servo motor.
The mechanical accuracy of the system is controlled within a certain error range, the electrical control accuracy (encoder pulse) can be improved, and the robustness is strong, which can meet the requirements of high-precision position control in many occasions. The permanent magnet synchronous motor AC servo system is in The technology has tended to be fully mature, with very good low-speed performance, and can realize high-speed control of weak magnetic field, which broadens the speed regulation range of the system and meets the requirements of high-performance servo drives. And with the substantial improvement of the performance of the permanent magnet material and the reduction of the price, its application in the field of industrial production automation will become more and more extensive, and it has become the mainstream of the AC servo system.