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Software Tools for Accurate Motor Sizing Publish Date: Aug 03, 2012 | 0 Ratings | out of 5 0.00 Overview In the face of economic uncertainties and increasing environmental concerns, many businesses today are evaluating ways to make their operations more lean, efficient, and environmentally friendly. Examining the electricity bill is a good place to start. With more than 50 percent of the worldwide total energy usage coming from motors, it is obvious that motion control applications have a huge impact. Motors are everywhere – blowers, pumps, compressors, conveyors, machine tools, mixers, shredders, and more. To improve the efficiency and lower the operating costs of the electric motors in your enterprise, you need to consider two factors: using high-efficiency motors and accurately sizing the motors for each task. Table of Contents High-Efficiency Motors 1. Motor Sizing 2. Motor-Sizing Tools 3. Conclusion 4. Additional Resources 5. 1. High-Efficiency Motors The fundamental purpose of any electric motor is to convert electrical power into mechanical energy. A motor running at 50 percent efficiency is converting half of the electrical power into useful mechanical work at the motor shaft, while the rest is wasted. Electricity costs make up 96 percent of the total life-cycle cost of a motor, while the original purchase price and maintenance costs combined contribute only 4 percent. When older motors need service, consider purchasing a new high-efficiency model rather than refurbishing the old motor. According to the U.S. Department of Energy (DOE), switching to a motor with a 4 to 6 percent higher efficiency rating can pay for itself in just two years if the motor is in operation for more than 4,000 hours a year. 2. Motor Sizing The DOE estimates that 80 percent of all motors in the United States are oversized, causing businesses to pay a high price in wasted energy. Although modest oversizing compensates for rising friction over the life of the machine, going too far decreases performance because of higher inertia, lower motor operating efficiency, and higher energy costs. This is even more important when the motor is part of the payload, as in many multiaxis motion control systems. As shown in Figure 1, efficiency drops dramatically when the load is below about 40 percent of the full-rated load listed on the motor nameplate. The key to proper motor sizing is to use accurate payload inertia, friction, and load torque information when selecting the motor. Figure 1. Efficiency drops dramatically when motors operate below 40 percent of the full-rated load. (Source: U.S. Energy Information Administration) When sizing, a good rule of thumb is to choose a motor with a peak and RMS torque rating that is about 25 percent higher than the application requires. Unfortunately, accurately calculating these parameters is the real challenge. Because of the complexity of motor drive systems, the equations to calculate those dynamic parameters are not trivial. 3. Motor-Sizing Tools You can choose from several online sizing tools to assist you in the process. With Kollmorgen Motioneering software, you can use NI tools to size motors. The software includes a database of all the NI stepper and servo motor products as well as AKD servo drives and P7000 stepper drives. The program takes an advanced systems approach to guide you through the process of selecting the right motor for a mechanical component. With Motioneering, you can select from a wide variety of standard mechanism types including leadscrew, rack and pinion, conveyor, nip rolls, and direct coupled rotary devices and enter all the important mechanical parameters such as dimensions, weight, gear ratio, and so on. 1/2 www.ni.com

Additionally, you can directly enter speed and torque load data via the direct data entry screen or you can apply some standard motion profiles to identify the best motor for your application. Figure 3 shows a list of motors that work for the specified mechanical system and the dynamic requirements of this application. Figure 2. Enter the required parameters for mechanical subsystems. Figure 3. List of Motors That Work for the Specified Motion Application While Motioneering is an excellent tool to size the motors of simpler systems that consist of standard components, it doesn’t offer the option to combine multiple components for a more complete system and it doesn’t account for the influence of moving components as payload of a mechanical system. If you are designing more complex mechanical systems, virtual prototyping tools might be helpful to calculate the required parameters. With NI LabVIEW and DS SolidWorks, you can create realistic simulations of motion control systems by connecting SolidWorks motion analysis capabilities to LabVIEW NI SoftMotion programming functions. Using this integration, you can develop the control logic and motion profiles and apply them to the 3D CAD model of your mechanical system to test the operation of the machines and simulate mechanical dynamics, including mass and friction effects, cycle times, and force and torque requirements that are important for sizing motors. A few mouse clicks in a typical 3D CAD environment, for example, provide the rotational inertia of your payload with respect to the motor shaft. Using realistic multiaxis motion profiles to drive your simulation can offer more accurate torque and velocity requirements, which depend on the acceleration characteristics of your motion profiles and the mass, friction, and gear ratio properties of the transmission. When evaluating simulation results, compare RMS values for torque and velocity with the rated performance curve for the motor, and compare peak values with the maximum velocity and intermittent torque limits. 4. Conclusion Because of the complexity of motor drive systems, choosing a motor with the optimal size, cost, weight, and performance for an application can be challenging. If a motor is too small, it can result in overheating, poor control performance, and difficult tuning. If a motor is too large, it can add unnecessary weight and cost to the machine. Today, software tools such as Motioneering and virtual prototyping technology help improve the motor-sizing process. 5. Additional Resources Use Motioneering Software to Select the Best Motor for Standard Mechanical Components Download the software now Learn More about Virtual Prototyping Technology Read a white paper Try the Virtual Prototyping Tools from National Instruments and DS SolidWorks Download the 7–day evaluation version of LabVIEW NI SoftMotion for SolidWorks 2/2 www.ni.com

Understanding Servo Tune out of 5 Publish Date: Jul 09, 2012 | 102 Ratings | 4.22 Overview Servo systems contain error-driven control loops. Servo tuning is an integral part of any motion system and directly impacts the accuracy and performance. A properly tuned system can provide higher precision and more stability. This Developer Zone Tutorial will walk through the process to architect an effective set of parameters to best optimize your system for use with our SoftMotion Software or PCI/PXI boards. Table of Contents 1. 2. 3. Part I: Servo Tune Fundamentals Part II: Tuning Servo Motors Part III: Advanced Tuning Techniques 1. Part I: Servo Tune Fundamentals Introduction Part I of the control concepts. This section is dedicated to the basics of servo tuning refer to part II and part III for specific systems. Understanding Servo Tune document provides information necessary for getting started with tuning servo tune motors. It requires basic knowledge of servo motors, controls, and motion Part I is divided into the following sections: Getting Started: Accessing Servo Gain Tuning Panel PID Control Loop Parameters Step Response Stability in the Time Domain Analyzing the Step Response Plot GETTING STARTED: ACCESSING SERVO GAIN TUNING Both the PCI/PXI motion control boards and NI SoftMotion include a gain tuning panel. Depending on your system you will access this through Measurement & Automation Explorer (MAX) or the LabVIEW project. Use the Gain Tuning Panel to determine the relative stability of a servo system and fine-tune the control loop gains. A system is considered stable if the actual position is finite when the commanded position is finite. In other words, a system is stable if a commanded position results in the motor coming to rest at a single position. A system is considered unstable when any commanded position typically results in an exponential increase in position error. In other words, a system is unstable when the attempts to achieve a position result in oscillations that never dampen. If your system is a 7340 or 7350 PCI/PXI Board follow these steps to access Servo Tune: 1. 2. 3. 4. The following figure shows the Servo Tune Step Response interface. Launch MAX. Expand the Expand Expand branch on the configuration tree. PCI/PXI-73xx Calibration Devices and Interfaces Step Response tab. Motion Controller. , and click Servo Tune . Select the 1/9 www.ni.com

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