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Power Electronic Controls
Published in William S. Levine, Control System Applications, 2018
George C. Verghese, David G. Taylor, Thomas M. Jahns, Rik W. De Doncker
A more difficult problem in the same direction is high- accuracy position estimation suitable for eliminating the high- resolution position sensor required by most of the nonlinear controls discussed earlier. In some applications, despite the need for high dynamic performance, the use of a traditional position sensor is considered undesirable due to cost, the volume and/or weight of the sensor, or the potential unreliability of the sensor in harsh environments. In this situation, the only alternative is to extract position (and/or speed) information from the available electrical terminal measurements. Of course, this is not an easy thing to do, precisely because of the nonlinearities involved. Some promising results have been reported in the literature on this topic, for permanent-magnet synchronous motors, switched reluctance motors, and for induction motors.
Laser Shutters
Published in Barat Ken, Laser Safety Tools and Training, 2017
Position sensor systems include mechanical microswitches, opto-interrupters, and magnetic reed switches. The independent audit function serves to validate that the command to open actually occurred, and the shutter is not at some point between open and closed. Potential obstructions in the aperture are more likely to occur as the aperture size increases. Many systems use dual switches in both open and closed states for the added security of redundancy.
Real-World Control Device Interfacing
Published in A. Arockia Bazil Raj, FPGA-Based Embedded System Developer's Guide, 2018
A servo motor uses a servo mechanism, which is a closed-loop mechanism that uses position feedback to control the precise angular position of the shaft. The working principle on which a servo motor mainly depends is the Fleming left-hand rule. Basically, servo motors are adapted versions of DC motors, with a position sensor, gear reduction mechanism, and electronic circuit. In general, a normal DC motor powered by a DC source runs at high speed with low torque. Once we assemble a shaft and gear mechanism to that DC motor, then we can increase or decrease the motor speed gradually by increasing the torque. The position sensor senses the location of the shaft from its fixed position and sends the information to the control circuit. A picture of a servo motor with its parts labeled is shown in Figure 9.9. The control circuit decodes the signals accordingly from the position sensor and compares the actual location of the shaft with the reference position and accordingly controls the direction of rotation of the DC motor to reach the decided position. Therefore, servo motors are self-contained mechanical devices that are used to control the shaft position with great precision. There are various kinds of motors, but servo motors are specially designed for specific angular position-related applications. They are found in many applications, like toys, robots, aeroplanes, elevators, rudders, radio-controlled cars, puppets, heavy industrial automation, and so on. Servo motor working principles depend on the PWM control pulse that we feed to the servo motor through a control wire. The advantage of using a servo motor is that the angular position of the motor can be controlled without any feedback mechanism, that is, in an open-loop control configuration. The reference position, that is, where we wish to move the shaft, has to be given from the external driver unit to the motor through its control wire. The servo motor's internal circuit takes care of comparing the actual and reference positions and then drives the motor shaft to the reference position.
Design of intelligent manufacturing system based on digital twin for smart shop floors
Published in International Journal of Computer Integrated Manufacturing, 2023
Mengke Sun, Zongyan Cai, Ningning Zhao
Generally, the RFID reader can communicate with the main PLC system of interior assembly line through profinet protocol, and then OPC UA protocol is adopted between main PLC system and SCACD system in DT-IMS. Of course some RFIDs can communicate directly with systems through OPC UA protocol, such as TBEN-LRFID integrated OPC UA server of TURCK company. Various sensors (e.g. position sensors, pressure sensors, visual sensors) are arranged in the assembly line to realize accurate positioning and precise control of intelligent equipment, for example, the position sensor obtains the position information of the manipulator to guide it to accurately grasp the material. Sensors are generally controlled by the main PLC system. OPC UA server can be embedded into various underlying devices. The data gathered by RFIDs, sensors or other PLC systems is converted to data supporting OPC UA protocol through the server. DT-IMS uses real-time data to drive digital twin model for synchronous simulation and then realizes the real-time monitoring of assembly process. Visual production line assembly process simulation model is built in Unity3D platform. Then, after simulating the operation state of assembly line equipment, material and personnel, the problems such as material blockage, beat imbalance and machine breakdown are found. DT-IMS re-evaluates and optimizes the process scheme and scheduling scheme and then sends control commands to realize the automatic execution and control of the assembly process.