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.   

Mechanics of a Servo Control System

A servomotor is an essential component of a servo control system or servomechanism. It is usually paired with an encoding device to accurately provide the speed or position feedback detail. However, not all servomechanisms require a servomotor. A domestic furnace is a good example of a servo control device that does not use a servomotor. The thermostat in a domestic furnace acts as a servomechanism in the sense that it depends on feedback and error-control; however, no motor is directly controlled by it for performing this task.  

Classification of Servos

Servo amplifiers can be further classified based on the type of their performances and their feedback control:

·         Type 0- This type of servos typically generate a constant output value when the error signal remains constant under steady state

·         Type 1- These produce a constant output value when the error signal is null under steady state conditions. However, a constant change of reference would imply a constant error in reference tracking

·         Type 2 – These are capable of providing a steady output value with a null error signal under a steady state. Here a constant change in the reference provides zero error in reference tracking but a steady rate of acceleration of the reference would mean there is a constant error in reference tracking

Here, the bandwidth of the servo control systems, indicate their ability to respond to the rapidly changing input commands.

Servo Control System - What You Should Know

A servomechanism also commonly referred to as servo is a high-end device that works by using feedback and error sensing to automatically correct the performance of any mechanism. Typically, a servo control system is used to help control the speed, or the position but it may also be used in error correction of other parameters. For instance, the cruise control device in your automobile is a good example of a servomechanism. On the other hand, the automatic windows in your vehicle are not. This is because there is no error-correction or negative feedback involved in this process.

Uses of Servo Control Systems

Servomechanism has been commonly used in speed control for a very long time. Some of the early examples include the use of servomotors in steam engines, in the mechanism that governed the speed of the water wheels, in gas turbines for efficient fuel control, and in the aircraft speed propellers used during World War II for steady maneuvering. Servo controlsystems for positioning were first used in military navigation equipment and in fire-control devices.

Today, servo control devices are used in almost every field. Starting from satellite tracking devices, aircraft gun control, automatic machines, to remote controlled boats and airplanes all contain some kind of servo amplifiers. In addition, many cameras using auto-focus also make use of servomotors to simultaneously focus as well as accurately move the lens. It is also found in modern computer hard-disk-drives, and used commonly in industrial devices that require complex motion.

Electronic assembly of printed circuit board

Here you can see the example of the process of drilling a printed circuit board (PCB) by a spindle CNC Drill Machine.

This is a step of PCB electronic assembly process.

Products that Servotronix provides include off-the-shelf products, custom servo drives for placement head mechanisms, and fully-custom drive systems for overall machine control.

Brushless Servo Drives-An Overview

Brushless servo drives are a kind of all digital, précised and DSP based servo drives, which are able to supply up to “32 A peak current” continuous. These servo drives are specially designed to control the velocity, torque or the position of the servo motors as well as for motion control. Often a Low voltage drive is used with the brushless servo drives to save energy by controlling the motion of the servo. Energy saving with the variable torque is an easy process, which only needs a little payment.

Brushless servo drives are specially designed for the brushless servo motors and these drives are completely suitable for the speed, torque, position, and applications of electronic line shafting. The brushless servo drives are commonly made to control the brushless servo motors, but they are also able to handle the brushed servo motors as well.

The brushless servo motor drives are a compact and completely housed unit with all front panel connection through the typical pluggable connectors. This feature has made this servo drives easier to service as well as easier to integrate.

Features and benefits of the Brushless servo drives are mentioned below:

• The brushless servo drives are generally available in three models, which cover the major part of the servo application including the motion control and low voltage drive
• Line-operated, 50/60 Hz, 115 - 240 VAC, available in single or three phase
• The “all digital design” simplifies the process of tuning and drive setup and also eliminates the chance of analog drift.
• Fast step power interface

·        Sinusoidal fluctuation vector power algorithm

• Step multiplier
• Typical placing of PID with anti-windup and feedforward technology
• Support for BLAC, Brush DC and BLDC servos

·        PC based modification through serial port

·        Disparity encoder input

How do the brushless servos help in motion control?

Motion control is a kind of automation in which the velocity or the position of a machine is controlled by using some kind of device like an electric motor, hydraulic pump, or a servo. This process is commonly used in the CNC machines or in the robotics.

These are the basics of Brushless servo motors. With the usage of low voltage drive technology, the servo drives are capable of consuming 25% more power at a speed of 63%.

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.