Used PLC control stepper motor drives

Used PLC control of stepping motor drives the chongqing university institute of John deasy nc zhu wen chuan-de zhou welcome to e hall exhibition hall 3 PLC controller PLC programmable controller, PLC programming cable. 。 。 In this paper, a new type of stepper motor drive control. The drive to make full use of the single chip microcomputer Δ C door of flexible software control and PLC control the main characteristics of convenience, the traditional PLC, stepper motor control module and driving power close 2 for one, is a new type of motion control products. Traditionally, in the use of PLC control of stepping motor, usually in the PLC plus a special piece of stepper motor control intelligent module, then connected to drive the power to control function. In the market, the price of a PLC controlled in 2000 yuan, and a control intelligent module also value 2000 yuan, plus the drive power from 1500 to 2500 yuan, in some small control is too expensive. This paper introduces a kind of control drive products, using the single chip embedded control software, receive PLC OC gate information, combined stepper motor control module and driving power supply, eliminating the stepper motor control intelligent module, thus greatly reduced the cost. The drive is suitable for all kinds of two phase, less than 3 a stepper motor. A, the system hardware, the system adopts software loop drive, a lot of work done by the software. The hardware circuit is simple. As shown in figure 1. Figure 1 control drive circuit diagram shown in figure 2, cooperate with closed loop control with PLC stepper motor, is a typical application of the drive. Figure 2 system hardware, system working principle is well known, ordinary PLC programmable controller, the input for the OC door or relay, few high-speed pulse output, but generally have pulse counting input interface. We take advantage of this feature points, through the following configuration is easy to complete the process of mechanical motion and position control. Install process control used in the mechanical mechanism of long grating, and set in motion mechanism end limit switch of mechanical origin ( Available photoelectric, hall element) , away from the limit switch is a positive direction for the operation of stepper motor. When step motor power, first run to the mechanical origin, when touching the limit switch, the PLC internal counter is reset automatically. If we want to control the mechanical movement process, through the grating and step motor driving mechanical parts are linked together, determine the stepper motor with grating pulse equivalent, programming on the PLC controller programmable controller to realize the process of high speed and efficient control. Stepper motor, for example, the pulse equivalent to 01001 mm, cooperate with the grating feedback pulse is also equipped with each pulse output is 01001 mm, the stepper motor with each step, a grating feedback signal to the PLC, counter ( Or minus) one Because there are 7 kinds of the stepper motor control drive speed can be selected, select the different speed in different movement situation, when run to determine the position of the stop stepping motor. Frequency control drive at the same time, also bring elevator control, whole step/switch segment, and other functions, so the use of PLC control is very convenient. 3, system software, the system's core is MCU software part. The software consists of the following main modules. As shown in figure 3. Figure 3 control software module initialization module: cleaning procedures required flags, determine whether need to start the motor and reset. Input module: CPU receives from INT1 INT4 level signal. The INT1 to INT3 various combinations to select 7 kinds of commonly used frequency to drive the motor, see table 1. INT4 determines the direction of motion, 1 is turn, 0 means inversion) 。 Table 1 encoding information with the frequency fluctuation frequency module: this module includes lifting frequency according to the table and query data table and counter T0 assignment two sub modules. It guarantees the smooth when switching between two frequencies smooth transition and do not break step. Program in the process of lifting frequency, involves lifting frequency curve 'optimization' as shown in figure 4, the curve equation is determined by the motor parameters. Details refer to other documents. In handling this curve, by increasing time t each delta t f constitute a table, the corresponding frequency and the corresponding generated a MCS - 51 assembly language data sheet ( The initial value) of the timer T0 To query the data table to this curve fitting, do lift frequency optimization process. Figure 4 lifting step frequency curve of the whole switch/segmentation module: seven common frequency in the form of segmentation procedure will drive motor, in order to meet the need of motor with different working condition. And the highest frequency set to step to the drive motor, the motor can empty walk at a high speed. This module is responsible for the complete steps from the whole to the subdivision and expand to the whole of the switch. Output module: this module includes pulse ring and ring pulse output ( T0 break complete) Two sub modules. This system according to the two-phase twenty write programs. To change this module can be widely used in two phase of each stepper motor. Four, conclusion compared with traditional drives, with software instead of hardware for the control drive stepper motor controller and hardware pulse ring circuit, simple structure, cost savings. Using closed loop control, according to the different kinds of position sensor and precision, which can be widely applied to coordinate measuring instrument, such as length comparator different accuracy of precision instrument and machine tool equipment. References [ 1] Landy, zhen-an liu 1 MCS microcomputer application, the group training centre. ( 2] Sun Yucai MCS - 1 51 series single chip microcomputer principle and application of 1, nanjing institute of technology press.
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