How to Determine the Motor Size for Your Project?

in this lesson we will continue the discussion on the topic of motion control all of us at real Parrs hope you have been following our previous lessons on motion control and have begun to benefit from these lessons now you will apply your base knowledge of servo and stepper motors in this lesson towards how to determine the correct servo motor for your application in this lesson you'll learn the information required to help you size the motor based on payload speed acceleration and other requirements necessary for a desired application [Music] before we get started on today's video if you love our videos be sure to click the like button below then make sure to click Subscribe and the little bell to receive notifications of new real Parrs videos this way you never miss another one this section will help you with the procedures and the understanding of the units of measurement to select the optimum motor for a particular servo or stepper application the servo motor selection process requires a certain number of calculations for you to understand as well as the units of measurement used throughout the equations for you to become familiar with some learners will enjoy performing the calculations manually we will briefly illustrate and describe some of the calculations later on in this lesson while others prefer utilizing one of the many online programs available to help you with all the necessary specifications of the servo motor required for your project and expedite you through the servo motor selection process the targeted end result of this lesson is to provide you with the knowledge on how to obtain the maximum speed load torque and moment of inertia specifications to provide the manufacturer of servo and stepper motors with the help of using a software motor sizing tool this lesson will also help to increase your knowledge in understanding some of the key terms used throughout this lesson let's begin with a review of a few key terms and the units of measurement used to determine your servo motor size the manufacturer of servo motors will need to know the force required to move the load the force to overcome the loads resistance is called moments of inertia moments of inertia quantifies the resistance of a physical object to angular acceleration moments of inertia is two rotational motion as masses to linear motion for example when traveling in a train or any other vehicle have you noticed how you continue to move forward when it stops well you just experienced inertia in general an object's moment of inertia depends on its shape and the distribution of mass within that shape as in the greater the concentration of material away from the objects geometric center the larger the moment of inertia this object will have moment of inertia varies depending upon the axis of rotation specified another example of inertia imagine an ice puck resting on a frozen pond it takes a certain amount of force to set the puck in motion the greater the mass the more force will be needed to move the puck the same is true if the puck were sliding along the ice it would continue to slide until a force is applied to stop the puck the more mass of the puck is the more force will be needed to stop the motion of the puck both moment of inertia and inertia are measures they measure resistance to a change in state inertial mass is defined as force required for acceleration moment of inertia is defined as the torque required for angular acceleration the larger inertia of the object the greater force you need to change the velocity in a given time the SI unit of measurement for moment of inertia is one kilogram meter squared in equations it is usually represented by the variable I next let us review a few examples on how to calculate the moments of inertia of various geometric shapes one of the variables of determining inertia is mass mass is defined as the amount of matter an object has one of the qualities of mass is that it has inertia to determine mass one way you'll need to know the density and volume of the load you are moving density measures how tightly the matter in an object is packed together each material has its own density which you can look up online or in a textbook the scientific unit of density is kilograms per cubic meter volume is the amount of space the object occupies the volume of solids is measured in cubic meters mass is equal to density times volume mass is a measure of how much inertia an object shows great now you're aware of some of the definitions of data required to move forward on how to determine the motor size of your project the sizing software used in this lesson also provides a utility to help you with the calculations such as moments of inertia or determining the mass as I mentioned we will be using a manufacturer software tool to help with the calculations to simplify sizing the correct servo or stepper motor now let's begin with the steps towards sizing your servo motor many software tools offer many solutions for screw belt rack and pinion roll feed index table and arm movement control with our sample application we select the requirement for controlling the rotation of an arm mechanism the first and easiest factor to consider is the available power for the equipment servos are available in 100 volts AC 200 volts ac and 400 volts ac models and are compatible with single-phase or three-phase power next you'll need to determine how much torque the motion application needs remember the torque is how much muscle it takes to rotate a mechanism and comes from three different sources accelerating the mechanisms inertia friction and external forces such as pressing against an object or gravity this is the most difficult part to calculate accurately calculate the inertia of each component of the system and add the values the formulas for calculating rotational inertia of various shapes are readily available on the Internet sample program we will determine the moment of inertia by completing the questions for rotating the arm in the vertical plane and defining the arms dimensions a as 200 millimeters long and B and C as 50 millimeters in width and height we will not use a gearbox for speed reduction in torque control the density of the material will be based on aluminum in which is determined by the software you may also with this sizing software change the calculation mode to mass and enter the mass and kilograms we have selected the entry of 1.4 kilograms for this example there are many online programs to assist in calculating the mass of an object internally and behind-the-scenes the software will multiply the acceleration by the load inertia to calculate the loads acceleration torque the software will also calculate friction forces for sliding loads gravitational forces for vertical loads and any external forces then each force is multiplied by the radius it is acting on known as the moment to calculate the torque the software then calculates the peak torque by adding up all the torque values in the worst-case scenario this is typically when the fastest acceleration is occurring or when there is the most mass on the machine adding up the torque values from external forces gravity and friction to calculate the continuous torque requirements is tedious without the help of a software tool moving along we will now define what the applications motion profile looks like we will use a servo type motor and use the travel amount calculation method we are using what is called a trapezoidal profile and will only be required to provide the acceleration speed of 1.5 seconds and travel time of 3 seconds and the amount of movement in degrees we will rotate the arm three times 360 degrees times three is equal to 1080 degrees after which the moment of inertia of 139 point 1 8 3 times 10 to the negative power of 4 kilogram meters squared is calculated automatically for equipment that performs a repetitive operation plot out the required motor speeds throughout the cycle be sure to allow for acceleration and deceleration time the next screen displays the calculated motor operation conditions that suggests the maximum speed of 120 revolutions per minute load torque of one point zero nine eight not meet er and finally the moment of inertia of one hundred and thirty nine point one eight three times ten to the negative power four kilogram meters squared often the manufacturer provides additional support in selecting a motor with different classification questions you adding an electromagnetic break for example will help hold the load in place when power is removed or at rest and it's always a good idea to add a safety factor to cover any additional changes for the future and load variations not determined the program will allow you to print out the results of the move profile and all the calculations performed by the software at this point the key criteria for choosing a servomotor have been defined and it's time to browse the manufacturers product selection guide to find the motor that matches these requirements find a motor and drive that matches the supply voltage has a rated speed continuous torque and peak torque rating that exceeds the values calculated if there's a motor that's a close match you're finished if not using the supplied software gearing can be applied to match the motor and load more closely servo motors can produce their full rated torque from zero rpm up to many thousands of rpm few machines can take advantage of these speeds without gear reduction gear reduction matches the servo to the load in three ways reducing the speed increasing the torque and lowering the inertia ratio speed is reduced proportional to the gear ratio torque is increased proportional to the gear ratio and most importantly the inertia ratio is lowered by the square of the gear ratio gearbox manufacturers list the inertia of the servo great gearboxes making it easy to include the gearbox inertia into the torque and inertia calculations most of the motors available likely are capable of much higher speeds than required divided the motor speed by the required speed and round down to get a starting gear ratio then divide the required torque by the gear ratio to find the new required torque this will help you narrow the choices down to a few select motors once you have the servomotor selected choose a servo drive rated for the correct input voltage and with sufficient output current to drive the servo motor servo drives can be controlled via several different interface types interface types you can choose from include pulse and Direction digital control analog control and other servo networks a servo drive will provide your solution with high speed control and feedback a reduction in wiring and overall superior Diagnostics capabilities compared to other types of interfaces finally choose any options such as keyed motor shafts shaft seals holding brakes for vertical loads or external braking resistors selecting the best servo system for an application is a skill that improves with practice when in doubt it's a good idea to verify your results with the manufacturer or distributor this concludes the video how to determine the motor size for your application I hope you've learned what's required to move forward in creating your own motion control project this video is one of a series of videos on motor and motion control so please check back with us soon for more motion control topics make sure that you head over to real parse comm to find even more training material for all of your plc programming needs [Music]

Channel: RealPars

Views: 227,182

Rating: 4.9461327 out of 5

Keywords: Motor Size, Motor Sizing, Motor Sizing Software, Motor Sizing Calculations, Servo Motor, Servomotor, Stepper Motor, Steppermotor, Servo Motor Sizing, Servomotor Sizing, Stepper Motor Sizing, Steppermotor Sizing, Motion Control, Moment of Inertia, Inertia, Moment of Inertia Calculation, Motor Size determination

Id: 9MG8-3QuSyQ

Length: 15min 7sec (907 seconds)

Published: Mon Nov 05 2018