Scenarios more suitable for PLC control
Automated production lines dominated by sequential control
For example, in automobile assembly production lines, cars go through multiple stations such as frame installation, engine installation, and interior installation in sequence. PLC can well control the start and stop sequence of equipment at each station to ensure that the car is assembled according to the correct process. For example, the robot at the door installation station first grabs the door and then moves to the body position for installation. The sequence of equipment actions in this process can be controlled by PLC.
Systems with complex logical control
In elevator control systems, PLC can control the running direction, stop floor, and door opening and closing actions (output) of the elevator according to the call button signals (input) in the elevator car and on each floor through complex logical judgment. For example, when there are multiple call signals, PLC dispatches the elevator according to the set priority and running direction rules to meet the needs of passengers.
Process control with low control accuracy requirements
For example, a simple temperature control system is used to control the temperature of a small warehouse. When the temperature sensor detects that the warehouse temperature is lower than the set value, the PLC controls the heating equipment to turn on; when the temperature is higher than the set value, the heating equipment is controlled to turn off. In this case, the temperature control accuracy requirement is not extremely high, and PLC can meet the requirements.
Occasions for large-scale switch quantity control
In building automation systems, control the lights, ventilation equipment, water supply and drainage equipment in the building. For example, through the cooperation of time relays and PLCs, the opening and closing of office lights can be controlled according to the schedule, and the start and stop of ventilation equipment can be controlled according to the humidity sensor signal. These are mainly scenes of switch quantity control, and PLC is a more suitable choice.
Scenarios more suitable for servo control
Equipment with high-precision positioning control
For example, in semiconductor manufacturing equipment, chips require precise position control during photolithography, etching and other processing processes. Servo control can ensure that the workbench of the photolithography machine can be accurately moved to the specified position, and the error can be controlled at the micron or even nanometer level to ensure the precise processing of the chip pattern.
High-performance motion control system
In the field of industrial robots, such as six-axis robots for complex welding, painting, sorting and other operations. Servo control can accurately control the angle and movement speed of each joint of the robot, so that the end effector of the robot can accurately move along the predetermined trajectory, thereby completing high-quality tasks.
Occasions requiring high-precision speed control
For example, in the transmission system of a paper machine, in order to ensure the quality and production efficiency of paper, the paper conveying speed needs to be controlled with high precision. Servo control can accurately control the speed of the motor so that the paper passes through each processing link at a constant speed during the production process, avoiding quality problems such as wrinkles and breaks in the paper.
Systems with high requirements for dynamic response
In CNC machining centers, the tool needs to respond to machining instructions quickly and accurately during the machining process. Servo control enables the tool to quickly accelerate and decelerate, and ensure high-precision position and speed control while moving at high speed to meet the machining requirements of complex parts, such as fast trajectory tracking of the tool when machining complex surfaces.
