Job Sheet 2 Servo Control

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Amberly Black
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1 Job Sheet 2 Servo Control Electrical actuators are replacing hydraulic actuators in many industrial applications. Electric servomotors and linear actuators can perform many of the same physical displacement required for a hydraulic system. As shown in Figure 2-1, a servo control system is made up of three primary components: a programmable logic controller (PLC), a servomotor drive (motion controller), and a servomotor (actuator). The electrical pitch hub training system uses a servomotor and drive to translate the blade pitch to the requested angle. Figure 2-1. Servo Control System Block Diagram. Servomotor Closed loop control systems often employ special motors called servomotors. Unlike a standard motor, servomotors have a position sensor that is either integrated into the motor assembly or remotely mounted outside the motor case that provides positioning information back to the servomotor drive. Integral position feedback devices known as hall-effect sensors, transmitter resolvers, optical encoders, and tachometers can provide a tracking signal to the servomotor drive. These devices aid in tracking the servomotor shaft position and rotating velocity (speed). The position sensor output signals are fed back to the servomotor drive and compared to a programmable set-point value. Festo Didactic Inc

Shaft Housing Rotor Windings Conduit Box Computator Protective Cover Bearing Plate Stator Magnet Brush Cover Brush Computator Figure 2-2. Servomotor Cutaway.

2 Shaft Housing Rotor Windings Conduit Box Computator Protective Cover Bearing Plate Stator Magnet Brush Cover Brush Computator Figure 2-2. Servomotor Cutaway. Different types of servomotors are used in modern servo systems including: DC motors, AC induction motors, DC brushless motors, permanent magnet synchronous (AC brushless) motors, and stepper motors. The electrical pitch hub training system uses a permanent magnet synchronous servomotor (Figure 2-3) for operating with an indirect AC converter or servomotor drive. The servomotor operates with three-phase AC power applied to it. Figure 2-3. Servomotor with Internal Position Sensor. 20 Festo Didactic Inc

3 Servomotor Drive The servomotor drive is also called a motion controller (Figure 2-4). The servomotor drive provides electronic control of the servomotor shaft position, rotating velocity (speed), and The servomotor drive circuitry must convert direct current (DC) or low-frequency alternating current (AC) to higher frequency AC current. Precision positioning and power control is possible by providing a pulse-width modulated (PWM) output signal to the servomotor. Figure 2-4. Servomotor Drive. A servomotor drive can also provide additional functions when controlling a servomotor. A holding brake feature that electrically opposes the motor direction of rotation to slow the shaft speed down more rapidly is often included. Some other common motion controller features include overload current protection, over-voltage protection, and thermal (overheating) protection. Festo Didactic Inc

4 Figure 2-5. Motor Drive Electronics. Figure 2-5 shows a basic block diagram of the electronic stages that are required in a servomotor drive. A digital microprocessor that has other functions built in is called a microcontroller. The microcontroller uses analog-to-digital (A/D) converters (or ADCs) to monitor analog signals from various sensor outputs, such as position, AC current, and/or temperature of the motor. This feedback is continually analyzed by the processor to alter the wave shape, amplitude, and frequency of the PWM output signal that drives the servomotor. A controller interface connects the servomotor drive with a PLC to permit automated control and servo system status information to be communicated throughout the wind turbine data network. The controller interface and high-current motor drive output is electrically isolated from the sensitive microcontroller circuitry in order to minimize conducted electromagnetic interference that may be generated by the spinning motor. 22 Festo Didactic Inc

5 OBJECTIVES In this job, you will operate the pitch servomotor to verify proper operation of your training system. EQUIPMENT REQUIRED Refer to the Equipment Utilization Chart in Appendix A to obtain the list of equipment required for this job. SAFETY PROCEDURES Before proceeding with this job, complete the following checklist. You are wearing safety glasses. You are wearing safety shoes. You are not wearing anything that might get caught such as a tie, jewelry, or loose clothes. If your hair is long, tie it out of the way. The working area is clean and free of oil. Your sleeves are rolled up. Instructor initials: PROCEDURE Setup Perform the Basic Setup procedure described in Appendix D. Use a key to open the electrical box to view the panel inside. Begin Perform the Energizing procedure described in Appendix D. Apply power to the training system by turning on the Main power switch. Enable the motor drive by turning on the Emergency Stop switch (in green position) and pressing the green Start button. NOTE: Ensure the Emergency Stop switch is on (pulled outward). Festo Didactic Inc

6 On the HMI, press the Start Trainer button on the Main screen. Pitch Servomotor Manually jog the pitch servomotor by pressing and holding the Jog button on the Manual screen. Record the actual blade position (in degrees). Record the actual blade position (in degrees). Record the actual blade position (in degrees). Exit the HMI operating system by pressing the Exit (X) button. Wait for the system to close. NOTE: You may have to reset alarms before exiting the software. Use the Main power switch to turn off all system power. Perform the Lockout/Tagout procedure described in Appendix D. Close and lock the electrical box. 24 Festo Didactic Inc

7 Review Questions 1. Were you able to vary the blade pitch successfully? Yes No 2. At what rate did the blade pitch change? Fast Slow 3. Within what precision (in tenths of degrees) could you manually stop the biade pitch? 4. List two parameters that the resolver or encoder can transmit from the servomotor to the motor drive? 5. In addition to the two previously entered parameters, what does the servomotor drive control at its output? Name: Date: Instructor approval: Festo Didactic Inc

ServoStep technology

ServoStep technology What means "ServoStep" "ServoStep" in Ever Elettronica's strategy resumes seven keypoints for quality and performances in motion control applications: Stepping motors Fast Forward Feed Full Digital Drive