Understanding Servo Drives

For those who do not know, servo drives are electronic amplifiers used to power-drive servomechanisms. In other words, servo drives work by accepting signals from a control system. After which, it then amplifies the signal and conveys the electric current to a servo monitor so that it would produce a motion that is relative to the given command signal. Usually, command signals represent a preferred velocity, although it can also be a desired position or torque. The servo motor’s definite status is reported back to servo drives through a sensor that is attached to it. Servo drives will then evaluate the actual status of the motor with the commanded motor status.

Contribution of servo drives to businesses

Servo drives and servo systems, as a whole, can be used in computer numerical control (CNC) machining, automation of factories, robotics, and many more. Because of this, when companies are equipped with this state of the art system, there will be significant benefits to the operations of the company. To start with, efficiency will greatly increase since operations are done in an automated manner. Second, servo drives are also cost-efficient. Thus, this kind of system can also help in lessening an industry’s cost of operations. Third, compared to the usual alternating current (AC) motors and direct current (DC) motors, servos are more accurate when it comes to commanded motions. This is because servo drives are built with motor feedback which also detects any unwanted motions. Furthermore, unlike the usual alternating current motors and direct current motors, servo drives have better life cycle.

Versatility and Flexibility through Servo Systems

Since servo systems function better than the typical AC and DC motors, companies that use servos are able to enjoy advantages like being versatile and flexible when it comes to their operations. This is because servos are considered to be the next-generation high performance drives. Servo systems are characterized by its highly innovated software and hardware designs that are capable of delivering better performance.

AC and DC Servo Drives

As mentioned earlier, typical alternating current drives and direct current drives are now things of the past. Through servo systems, industries can now enjoy the benefits of the new and improved ACservo drives and DC servo drives which are more accurate in translating commands, perform better, have better life cycles, and a lot more. Examples of the latest alternating current servo drives include CD Series 5 and PPB direct PWM products.

Servo Drives: Final Verdict

Indeed, through the innovation of servo drives, motor operations of industries are now brought to a new level. Through this system, industries can now enjoy benefits like better performance, cost-efficiency, operational efficiency, precise and accurate work and a lot more.

What Is Motion Control?

Motion control is sub field of automation. This controls the position or the velocity of the machinery. To do this it uses device like a linear actuator, electric motor, hydraulic pump or generally a servo motor.  This is a very important part of robotics and CNC machine tools. This is a very complex system as the kinematics in these machines is usually very simple. Motion control is used greatly in packaging, textile, semi conductor, printing and assembly lines.

The basic design of the motion control is as follows. The control is set to generate set points for the desired outcome and to close positions or velocity (the feedback loop). The signal is then changed into an electrical current by a drive or an amplifier. This is then delivered to the actuator. (An actuator is for motion output and can be a hydraulic pump, electric motor or a linear actuator.)  Some newer models are more accurate because they can close the position internally. 

Feedback sensors such as Hall Effect devices or optical encoders are used to close the position of the actuator bring it back to the motion control. The mechanical components then change the motion into a required movement. This can include shifting, belts, ball screw, gears, and linkages linear or rotational bearings. When co-ordinated motion is required the interface between the motion controllers are critical. They have to provide tight synchronisation.

There are some common control features and these include position control (this is often based on the velocity profiles for example S-curve or triangular profile.), velocity, electronic gearing (also known as cam profiling) this is where the master axis and the position of the slave axis are mathematically linked. For example, when two rotating drums turn at a set ratio to one another, there is also electronic camming and this is where the slave axis abides by a profile that is the job of the master as this does not need to be salted but it has to be animated. There is also pressure and force control.

Motion controllers are used in an array of different industries to help produce and make most of the things we use every day. They help do the jobs that are hard labour for humans and assist in increasing productivity.  There are several companies that globally sell these controls. They develop, manufacture and market servo drives and systems. Their products are predominantly brushless controls; however they do provide drives for alternate motor types. They also provide standard products and can customize to suit your needs.

Helping Increase Safety with Computerized Motors

Car manufacturers and assembly lines have long relied on servo motors in order to increase productivity and consistency on the line. Now, these same AC servo motors are helping to increase safety levels both for the employees of the plants and for those who are driving the vehicles. Technicians have realized the increased parameter options allows for more control over the finished product. This means less variation so that the pieces fit together in a way making them more stable than ever before and increasing the overall safety of the vehicle.

The AC servo motors that control the line help prevent overheating. This type of condition can cause fires, meltdowns and other dangerous situations for those who are monitoring the line. By using a mechanism that makes adjustments immediately, like a servo, the problem never has a chance to develop. It takes much less time to make a correction from the beginning than undoing a problem scenario has blown out of control. Think of it along the lines of laying a drop cloth down when you are painting or trying to clean up the paint off the ground after you are done. One is a simple clean up job and the other is a protracted process.

For the output of the product, because a servo motor can monitor things so closely there are fewer problems with the end product. When bolts and pieces do not meet up exactly, vibrations and other processes can cause things to wiggle loose. This factor often results in tires falling off, seat belts failing, pieces of the engine getting knocked out or other disastrous scenarios. By ensuring everything is exactly uniform, there is less chance of this type of problem. Basically it was the next logical step in the development of motorized vehicle development and the assembly line. The companies had maxed out what could be done with just humans and found a way to utilize the computerized systems in order to increase safety and productivity at the same time. Helping to make life safer is a great side benefit of computerized advances.

How BLDC Motors Work

Before using BLDC motors, understand its mechanism.

You will be able to find BLDC motors or brushless DC motors in industrial equipment, appliances and medical instruments as they provide various advantages as compared to others like it.

However, before usingthese motors particularly for blade pitch control, you must first have a complete understanding of its mechanism which consequently results to a fast review of the construction of a DC motor.

A BLDC motor is particular type of servo motors which basically relies on wire coils on rotors and frames of rigid motors which on the other hand places permanent magnets all over the rotor.

Electric current passing through the windings make some magnetic field which either repels it from the magnet or attracts a winding to the magnet. Brushes placed on stators and contacts placed on rotors choose various windings as power while the rotors turn.

In BLDC motors, the coils make up the motors’ outsides and the rotors provide permanent magnets. Once again, the repulsions and attractions of the coils and the permanent magnets make the rotors spin. However, in BLDC motors, commutations do no occur on spinning shafts.

Even though these motors are more expensive than other brush-DC motors, they provide benefits. Their exterior coils dissipate heat better than those on rotors. BLDC motors do not have commutators or brushes to tire out or need maintenance regularly, thus they can function unattended for a very long period of time. Lastly, these motors don’t produce electromagnetic interference or EMI from machine-driven commutators.

Rather than utilizing mechanical commutators, servo motors like BLDC use automated commutation in switching the coils to on or to off. This kind of commutation is classified into two – the sensorless or the sensor-based.

The sensor-based motors, Hall-effect sensors are placed inside the coils of the motor to sense the position of the permanent magnets of the rotors. Microcontrollers or MCU read the states of the sensors and utilize a particular algorithm to know which of the coils to power as well as when.

On the other hand, sensorless motors require MCUs to measure the back electromotive force orr EMF produced across coils by spinning rotors’ magnets. The back EMF or BEMF defines the magnets’ positions.

However, the sensorless method is faced with a challenge because controller as well should power coils consequently to make the motors turn. Thus, how can one separate pulse-width signals of modulation which drive coils BEMF signals?

The answer is quite simple. Program MCUs to filter high-frequency PWM signals out as well as measure BEMF near the time when PWM signals pass through zero Voltage. The BEMF depends on various factors like coil resistance, number of coil windings, rotor magnets strengths and many others.

Servo Drivers: The Prime Mover of Automated Devices

A servo driver is developed to regulate the position and velocity of various automated devices such as industrial machines, medical equipment and robots. Electromechanical elements such as servo motors help these devices to achieve their desired motion and servo drivers work as electronic amplifiers to these motors.

Servo control systems are pitch control solutions that monitor feedback signals of servo motors and constantly regulate motions to prevent any deviation from the anticipated behavior of machines. They address a lot of mechanical requirements for reducing voltage fluctuations, diminishing loading parameters sensitivity, decreasing steady state errors as well as enhancing the transitory response timing.

Servo systems upturn the bandwidth of the system. Faster response times enable higher machine productivity. Decreasing steady state errors result in high accuracy of servo systems. Lastly, reducing loading parameters sensitivity guarantees that servo systems withstand fluctuations in the output as well as the input parameters.

Servo amplifier

Servo is the name of the motor used to control and manage the mechanical performance of particular machines. In engineering terms it refers to an automatic device and applies this control theory to provide the actual power for the whole mechanism to work. These electric motors have inbuilt motion sensors to control applications for highly controlled motion.

Servo motor control is focused at sensing errors in the mechanism which will then send instant negative feedback or signals to correct this error and enable smooth uninterrupted functioning. These signals can correct multiple parameters from speed to mechanical position.

Controlling a mechanical position with servo amplifier –

Servo mainly uses electric motor to create mechanical force. The concept of servo motor control lies on two factors – there is an actual position and there is a desired position within the mechanism. The difference is sensed and an error signal is then amplified and then converted to reduce or completely erase the error. Other than electric force some servos also use magnetic, pneumatics or hydraulic force to correct position. They are widely used in military and marine navigation systems, satellite tracking.

Controlling a mechanical speed with servo amplifier –

The use of servo in controlling speed has seen many earlier applications like the steam engine. Today the application of servo motor control is found in trains, airplanes as well as ships. But that’s not all. These are also integral part of machine which run huge industrial functions and run the complex industrial motions. The applications of speed control can be seen from complex airplane navigation, to the cruise control function of a car, to a hard disk drive in the laptop, in both cases focusing in error free and precise performance.

Servo motor control is one of the key components of robotic functioning. Constant error sensing feedback keeps all parts of a robotic function in check. They also need very little power to run on and are ideal of machine like robots which run on batteries. They are also essential parts of any remote controlled device. These range from remotes for a child’s toy to a complex one to manage a submarine or an aircraft. Basically they are keys to any application which needs precise mechanical functioning and where error would mean malfunction with serious ramifications. This is why it is so important for the defense industry. Servo mechanism can make smooth functioning through unfriendly terrains as well as hard weather conditions.

The use of servo mechanism is the basis for mechanical accuracy.

Servo Motor Control & Its Uses. Part 1

The Servo motor is in use for quite some time now. Because of its diverse functionality, the servo motor has gained popularity. The easy to use applications mostly in RC electronics and other devices make it a popular and widely used thing.   The Servo motor control refers to the error sensing the feedback control that is used for correcting the performance of a particular system. The RC servo motors are actually DC motors that are fitted with a servo mechanism in order to have accurate control of angular position. The RC servo motor control generally has a 90° to 180° rotation limit. But there other servo motors that come with 360° rotation limit. However, the servo motors do not need to rotate on a continuous basis. It will only rotate between its defined angles. 

The servo motors are majorly used for their precision positioning. These motors are widely used in robotic legs and arms, RC toys, sensor scanners, RC helicopters, cars and airplanes too.  The servo motors that are manufactured nowadays offer cost effective solutions for the users. These servo controls have efficient power saving technology and they can take up high inertial loads too. The servo motion control is exceptionally useful for robotics and thus they are made in small sizes but are very powerful and efficient.   

Benefits of Pick and Place Servo Drives

 In an age of rapid industrialization and intense competition, manufacturers simply cannot afford to compromise on the speed and accuracy of the machines and assembly lines in their production units. Prudence thus lies in investing in servo systems that speed up the functions on the assembly line front and also add to the precision of the operations. Herein stems the importance of pick and place robots in an assembly process. These systems are commonly found in industrial automation processes and are used to sort components and place them in their appropriate slots in the line.

Pick and place servo drives systems are some of the most expensive components in an industrial assembly line but manufacturers usually do not hesitate to invest in these because of the advantages that installing one such system affords. The following are some of the benefits of pick and place systems:

• Speed: Pick and place robotic systems, by automating processes, speed up cycle times. This in turn, leads to faster production, a key requirement for businesses to prosper in a 24X7 world. A servo controlled pick and place system is especially considered matchless on this front.

• Precision: Pick and place systems are almost 100% accurate in their operations, much more than a human being can ever be. When quality is the key to retaining customers, this feature ensures that manufacturing units engaging pick and place systems are consistently able to outsmart competition.

• Reliability: Powered by servo control, pick and place systems, when in top-notch shape, can work round the clock on all days of the week. This enables a manufacturing unit to churn out products in almost no time at all. This in turn, leads to considerable revenues.

• Flexibility: A slight tweak in the programming controls or a few twists and turns of the tools are all that is needed to equip a pick and place system with the capability to deal with multiple applications. This flexibility makes installing such a system extremely cost-effective.

• Cost-Effectiveness: The afore-mentioned features combine to lend a high degree of cost-effectiveness to such systems. Cost effectiveness also accrues from the fact that pick and place systems empower businesses to take up orders in bulk and thus aid business expansion and also reap the benefits of large-scale production.

Advances in technology in recent times complemented by a drop in prices, have made pick and place systems more affordable. It is thus possible for even small-scale production unit owners to own such a servo control system and reap its benefits.

What Are Brushless servo drives?

Brushless servo drives are DSP based all-digital, precision servo drive amplifiers, which are able of supplying “16 A peak” current constant, as well as “32 A peak” up to 230 VAC. The brushless servo drives are designed to perfectly control the position or velocity and torque of a number of brushless torque and servo motors. The design of this servo drive simplifies the commissioning and set up of the brushless servo motors, as the system software of brushless servo drives needs little more than the ordinary ones.

Features of brushless servo drives:

• Several models which cover the major parts of the requirements of the servo application
• Line operated, 50/60 Hz, 115-240 VAC, single or three phase
• The complete digital design of brushless servo drives simplifies the drive tuning and drive set up and removes the analog drift
• Complete fault protection and “optically isolated I/O”
• PWM, ±10VDC, encoder-follower and step-direction control inputs accommodated
• Internal regenerative power control circuit, which requires an external resistor
• Graphical client interface based on PC for motion control, monitoring and commissioning. This interface is attached with the drive through an “optically isolated USB port”.

Benefits of brushless servo drives:

• High efficiency or power saving- The original drive technology of brushless servo drives use low power and offer a high efficiency. It represents a great money saving technique on the 24/7 application than the ordinary servo drives
• High inertial loads- The brushless servo drives use “sophisticated motion control algorithms” to take the advantage of high-torque capacity, offering direct-drive of high inertia loads such as the belt drives and flywheels. It is much more than the traditional servos. This servo drive also provides a smooth responsive pointing control.
• More torque in a lesser price- Brushless servo drives provides 2-4 times more constant torque in lesser price ($300-400 less) than the conventional servo motors.

AC Servo Drives – The Present Industrial Requirement

Servo drives are specially made electronic amplifier that is used to boost or run electric servo mechanisms. All the feedback signals that come from the servo mechanisms are actually monitored by the servo drives. A servo drive continuously adjusts even the smallest deviation from the normal behavior.

It should be known that the main function of a servo drive is to receive the command signals from the control system and then amplify it so as to transmit the electric current to the servo motor. This is done to produce motion that is proportional to command signal. In general, the command signal signifies a preferred velocity but it can also signify a desired torque if and when required. 

The servo drive gets the feedback of the actual status of servo motor control from the servo motor’s attached sensor. The actual status of the motor is then compared with the commanded motor status by the servo drive. The servo drive alters the voltage frequency of the motor in order to correct any small deviation from the desired commanded status. 

The servo motor control rotates at a speed which closely matches the velocity signal that is being received from the control system by the servo drive. There are several parameters like derivative gain, proportional gain and feedback requires proper adjustment so as to achieve the desired performance. This process of adjusting of the parameters is known as performance tuning.   
     

With the advancement in the technology of the microprocessor units there has been a constant growth of cost effective solution and development of a permanent magnet manufacturing technology for the servo motors. There has been a great improvement in the technological development of the high performance and high power semi conductor power devices. Thus, AC servo drives, AC servo motor has now become the basic technology for achieving automation control system in the present industrial scenario. 

AC servo drivers bring in the newest high speed DSP in order to meet the varied requirements of your high speed and high precision control system. The latest AC servo drives have a lot better dynamic feature and stability that the convention PI controls systems of yester years.  

Today’s AC Servo drives includes analogue apparatus within the control loop of a servo motor that helps to minimize the energy consumption and ensures maximum output. They assist in changing frequency of the AC voltage which is received by the motor with the use of electronic devices.

Functions of motion control

Motion control can be said as one of the sub categories in the field of automation. When we work with machines in the field of automation we need to control a lot of parameters of the pump in order to get the desired results so the motion control can be done with the connection of some kind of pump in the motor which can also be a servo. Motion control is a simple thing when we work with simple machines. These are also used in the robotics and the CNC systems were the operation of the same thing is very complex. This is because of the kind of machines involved in both the processes. When we talk about the packaging industries and the textile industries and the assembly industries we understand how wide the scope of the same thing is. The motion control systems are gaining importance today.

The function of the motion control is vast and is not limited. Hence most of the people want to go with the motion control of the machines in order to be satisfied with the result it gives. The first and the most important and the well known function are the control of velocity by the motion control. There after it also can control the velocity and the pressure in other words. So if the motion control is attached to the machines getting the desired results is very important. These are particularly effective when the experiments are carried on. The reason is that one cannot have several different types of machines at the very initial stage. The motion control mechanism proves to be very effective and non expensive way to control motion of the machines in order to get the results as desired. The motion control is also used to control the position also. The position control of the motion control is mainly used in the control of the profiles like the trajectory ones.

The overview of the motion control is very complex. But it’s not very difficult to operate. People find these options very convenient and hence opt for the motion control when they have to control the output. If the input signal is good then the output is the best one can accept and this is the reason that people go for the motion control. The functions are vast and in many kinds of industry too. So the people can get one as per the desire of the people as such.

Working of the servo system

When we talk about the servo system and there functions we know that it is to convert the mechanical motion into a higher and an amplified version of the same kind of motion or the energy. When there is a need to enhance the frequency or the velocity which is again a type of the mechanical motion the work of the servo systems come into being and it is to amplify it. The servo systems are used a lot these days because these have a list of advantages linked to it. The servo systems are known to give high performance rates and also work with a high precision which is great. These are some of the reasons that man today prefers to use the servo systems. Today there are much different kind of models available in the market. The best of the servo systems look the best. These are very small and compact in size but when we talk about the performance of these there is nothing which can beat these. These prove themselves to be very efficient in the work of amplification.

Most of the servo systems these days are the choice of the customers. These are made just the way the customers want it. The basic and the common work of the servo system are kept the same and there are changes which are incorporated in the system as per the needs of the customers. The best feature of the servo system is that these are very friendly to the user and the desired performance can be achieved just by tuning the system well as per the need of the people. These have high efficiency also. There are synchronizations and the gearing option which is also inbuilt makes the efficiency of the output even more. There are temperature control sensors which are mounted on the servo systems. It regulates the temperature. If there is a rise in temperature above the standard point, then it should be controlled because it affects the optimum efficiency of the servo systems.

The servo system is insulated and hence people are happy because the chances of accidents are also less. Some of the features are so great that the servo systems are must wanted by the customers. A servo system is the one people prefer over the other kinds of amplification unit. The standard features are very good and some of the additional features are built by the makers as and when the user demands.

Servo Amplifier

A servo amplifier is a part of the closed loop servo control drive system is designed to primarily control the performance of a mechanism. Basically they are four-quadrant, power amplifiers with regenerative features and equipped to supply power according to the control voltage to the overall motor. These servo amplifiers can supply energy to the load, as well as absorb energy from the load. They are also designed to convert the kinetic energy of the combined motor load into electrical energy while the load is decelerating.

The output of a servo amplifier is an analogue circuit. The circuit enables the current and voltage of the motor to be adjusted to control position, torque and velocity. The feedback and comparator stages though can have a mixture of analog and digital devices.

Few ideal characteristics that are desired in a servo amplifier are as follows:

• Constant Velocity – ability to maintain the commanded velocity. Tachometers are used to record the aberrations between the commanded and actual motor speed.

·         Infinite Acceleration – an ideal amplifier must be able to provide infinite acceleration which can be observed by abruptly starting and stopping the motor.

·         Linear response – the amplifier need to respond proportionally to the changes in the velocity input command.

·         Hold Position – the amplifier should drive the motor in such a way that the latter holds its position irrespective of any external force or disturbance.

·         Overload protection – a low resistance circuit should be there to protect the amplifier from excessive current.

There are a host of servo amplifiers in the market but one should be careful while choosing an amplifier. The compatibility of the servo amplifier with its servo is to be ensured. Some notable types of servo amplifiers are as follows:

• Push Pull amplifiers – one of the earliest designs of amplifiers designed primarily for two transistors to get switched on/off to share the current load for the motor.
• Chopper amplifier – another primitive DC-motor based amplifier that finds limited usage today.
• L Type (Linear Motion) Servo Amplifier – it is fitted with linear positioning function you can basically construct a linear positioning system using such amplifiers as a ball screw or rack & pinion.
• Digital Amplifier – it is usually used for higher machine performance as it promises improved reliability and repeatability through digital technology.
• R Type (Rotation) Servo Amplifier – it provides an additional rotation angle indexing function. Rotation angle index system can be constructed using this amplifier.
• DC servo amplifier – both brush and brushless amplifiers can be found in simple DC motors