1 Introduction In this paper, a logistics control manipulator control, for example, analyzed the PLC and the stepper drive control method, the system hardware is mainly involved in S7-200 PLC and SH-2H057 stepper drive.
(1) S7-200 PLC series is the Siemens PLC, this series of products to meet a wide range of automation and control requirements, as a compact design, good scalability, low cost and powerful instructions, makes the S7-200 PLC to meet the control requirements of small-scale. In addition, the wealth of CPU type and voltage level to the users of industrial automation in solving problems, is very strong applicability.
1, S7-200 PLC platform includes a separate S7-200 CPU, or with a variety of optional expansion modules. S7-200 CPU module includes a central processing unit (CPU), power supply and digital I / O points, which are integrated in a compact, stand-alone device.
l CPU responsible for the implementation process and store data in order to control industrial automation or process control tasks;
l is the system input and output control point: to import some equipment from the site acquisition signal, the output part of the control of pumps, motors, and also process control and other equipment;
l CPU and the power to any equipment connected to provide power;
l communications port allows the S7-200 CPU with the programmer or other equipment with them;
l status lights shows the CPU s operating mode (running or stopped), the machine I / O s current status, and check out the system error;
l through the expansion module can provide its communication performance;
l through the expansion module can increase the CPU s I / O points (CPU 221 does not extend);
l Some have built-in real-time clock CPU, or add real-time clock cards;
l EEPROM card can store CPU process, it can be a CPU to another CPU in the process of;
l through the optional plug-in battery box to extend the data in RAM storage time;
l the maximum I / O configuration.
(2) SH-2H057 drive input signal a total of three-way, they are: Step pulse signal CP, the direction of level signal DIR, off electrical and mechanical level signals FREE. They were in the drive internal current limiting resistor through 270A9 access light coupling of the negative input, and the form of identical circuits, the positive three-way coupler for the OPTO input side, the three input signals in the drive way of the internal access into the sun were so OPTO-side need to access external systems VCC side, if the VCC 5 volts direct access; or need additional external current limiting resistor, to ensure the internal drive optocoupler to provide 8-15mA drive current.
l step pulse signal CP
Step pulse signal CP is used to control stepper motor position and velocity, ie: drive to accept a CP pulse of each stepper motor to drive a step rotation angle, CP pulse frequency change is also the rate of change in stepper motor to control the number of CP pulse, you can make precise positioning stepper motor. This can easily achieve the stepper motor speed and positioning purposes. The driver of the CP signal for the low effective, required drive current for the CP signal 8-15mA, pulse width of the CP also has certain requirements, usually not less than 5BCs.
l-level direction signal DIR
DIR-level direction signal used to control the stepper motor direction of rotation. This side is high, the motor for a shift; second terminal is low, the motor for another turn. Motor commutation must be carried out after the motor stopped, and for the signal in one direction must be the first pulse after the last CP and the direction of the next pulse is issued before the first CP.
l de electromechanical level signals FREE
When the drive power supply, the stepper motor is locked (CP pulse is not applied) or running (CP applied pulse), but users want to manually adjust the motor but do not want to turn off the drive power, then you can use this signal, this signal active low, the motor torque in the free-free state; When this signal is high or floating is not received, the cancellation offline.
l About SH-2H057 stepper motor drive type used to drive two-phase or four-phase hybrid stepping motor (also known as Induction), this drive is usually drive motor 60, the following base. Motor outlet in different ways, and the drive connection is different. The system uses the motor for the two-phase 4 wire motor, the drive can be connected directly. Figure 1, the mechanical hand motor drive module schematic.
2 system work manipulator of the system works in part by the chassis, pole, arm, hand, of which the chassis driven by a stepper motor can be smoothly counterclockwise rotation; pole by a stepper motor drive can be moved up and down; arm by the A stepper motor drive can be before and after stretching; hand by the pump control to capture and relaxation. In the position detection signal has a corresponding position for positioning. See Figure 1. (1) shipping process starts from the reset position, upon request to the appropriate ship units (1,2,3 dock), then rotate the chassis to the required position, the column down, arms stretched out, grasping after location of goods column increased, while the arm recovery (to avoid collision with other equipment in operation), and then shipped to the appropriate units (left, or right ship channel), column down, arms stretched out, hands open, the goods out on the correspondingCargo platform.
(2) The purchase process starts from the reset position, upon request to the appropriate delivery platform (left or right delivery platform), then rotate the chassis to the required position, the column down, arms stretched out, grasping after location of goods, increased column while the arm recovery (to avoid collision with other equipment in operation), and then shipped to the appropriate units (1,2,3 dock), the column down, arms stretched out, hands open, the cargo ship on the corresponding sets on.
Step 3 system design control circuit design, PLC relay output module type slower, it uses high-frequency square wave pulse generator, gives step pulse, the oscillation frequency of the speed set by stepper motors, stepper volume is controlled by the position detection, position detection signal in accordance with the PLC output points to cut off the feed motor, stepper motor to achieve the parking, the program flow chart shown in Figure 2.
Robot operation control in the whole process, the use of limit switches and switch panels, and system logic switch operation as an input point, the entire system chassis has five limit switches, respectively, 5 position as the positioning input, there are four limit column position switch, a reset switch, respectively, on the 1st-bit limit input, ceiling spaces, floor spaces. Limit switch arm 3: arms reduction and the median income limit point limit before the arm, the arm after the limit. Grasps limit switch, as the starting point reset input. A total of 13 limit switch complete the control input. The distribution of the limit switch shown in Figure 1,
Since all the control process by controlling the stepper motor driver module and then drive the implementation of stepper motor. Here on the pulse output trigger with integrated stepper motor driver theory explained. S7-200 PLC (CPU 226) of Q0.0 and Q0.1 are on the up / down stepping motor, front / rear step motor to send pulses; CPU 226 of Q0.2 to send pulses to the stepper motor turntable. The stepper motor forward / reverse is the CPU 226 respectively of Q0.4 and Q0.5, respectively up / down stepping motor, front / rear step motor controls; CPU 226 of Q0.6 and Q0.7 Rotary stepper motor respectively positive and negative, grasps pump switch controls.
PLC program is designed manipulator prepared using STEP 7-Micro/WIN32 software data sheet (STL) format. Program design changes to facilitate the design can be completed online debugging, there is no problem then stepping motor connected.
SCADA software configuration control by Beijing Asia King software, configuration software through the variable mapping to achieve a variable PLC registers with the dynamic connection, enabling the host computer to the PLC s control.
4 Conclusion The robot control system, compact structure, reliable action, easy to use, has been used in research and teaching in our school.