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.

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.   

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%.

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.

Importance of Motion Control in Industrial Applications

In industrial applications, machines are the most important part. The efficiency of the machines lies on its control and the administration of the motion control system. The man function of the motion control system is to control the machines movement. WE can otherwise represent the importance of the control system by saying that they are responsible for controlling the heart beat of the motors. This is the reason why the motion controls for various machines vary as per their applications. For example the motion control system of a ball screw machine system will not produce accurate and precise results when applied to a motor driven tool.

In the normal working of the conventional servo drive system, the motion controller sends electrical pulse signals to the motor. The Servo motor uses a glass scale or rotary encoder to verify the motion and catch error signals. In case no error signals are identified, the encoder placed in the servo system sends back confirmation pulse signals to the motion controller to confirm the utilization of the motion command. In case the tool has glass scales incorporated in to the axis then positioning of the axis in the scale also needs to be verified. For this a signal is again sent from the motion control to the glass scale for the proper positioning of the axis. This is how a motion control system offers extensive accuracy without the backlash of the components of the servo system.

When a machine tool gets calibrated, the motion control checks the value that is entered to check the pitch errors as depicted by the encoders and the amplifiers. These errors occur when the input signals sent do not match the existing processing or motion of the unit. The motion controller has to play a major role in rectifying the error and check the value of the parameters to ensure the production of accurate movement. This is the reason why overshoot or undershoot of the tool is prevented from happening when the machine is moved to a high speed rate. 

A motion control system remains incorporated in almost all servo systems. They not only play an important role in controlling the motion of the machine tools but also prevent damage due to excessive load. By working on the action signals sent to it by the encoder, the controller works on it to ascertain if any error has taken place and accordingly commands the movement of the servo motor. In short it helps in decreasing the power consumption of the machine while increasing its efficiency.

Understanding Motion Control Drives

Motion control is a term that describes a range of applications that involve movement in specific routes designed to precision performance. Earlier motion control applications require only an object to be moved from one place to another without paying too much heed to speed or change of motion. On the other hand, there are machine tool applications which require the exact coordination of all aspects of motion, including a high degree of synchronization for multiple simultaneous movements.

Motion control drives finds heavy usage in the robotics industry. Motion control drives are known to monitor the motion performance of the mechanism. The feedback and the subsequent rectification, if needed, makes it ideally placed to be used in the robotics field. These drives are connected to motors that can be AC or DC. Further categorization can be made of DC brushed, DC brushless, AC Induction, AC synchronization and Stepper.

The motor amplifier or servo drive is designed to takes commands from the motion controller. These signals are incorporated in the analogue version where the voltage with low current is converted to high current signals in order to drive the motor. Motor drives come in many various types and makes and are fitted when matched to a specific motor they need to run. Along with matching the motor technology, the drive needs to ensure a balance of voltage, a continuous current and the balanced correct peak current.

The feedback of the mechanism’s performance can be taken of different parameters like back EMF, current, velocity, acceleration, position and many more. It’s because the control of these parameters will ensure the overall control of the motion of the object. Some of the sources for these feedbacks are:

• Hall effect sensors
• Encoder
• Potentiometer
• Tachometer
• Acceleration specific sensor

A motion control drive’s range of applications is far more specialized than any other manufacturing applications. Motion control drives must be capable of:

• Zero-speed holding torque
• Quick start/stop cycles
• Repeatable velocity and torque profiles
• High accelerating torque
• Synchronization
• Precise speed control
• Positioning capabilities

Motion control can operate two levels – the linear or the rotational axis. A linear axis application like a vehicle in motion has a pre-defined traversing range with predefined end stops. The rotational axis has a vast and almost never-ending traversing range when applied. A rotary table on the other hand travels a pre-defined yet short distance. They have a selected path or direction for moving point to point.

Servo Drives – Facts and Features

Servo drives have revolutionized the way key industrial applications run today. Digital servo has taken the mechanism of motion control to a new height where it amplifies the signals and makes mechanical output faster and more effective.

Benefits of servo drives -

• Higher and more dynamic response
• Reliable
• Cost effective
• Higher productivity and performance
• Accurate output
• Flexibility that can share technologies across diverse types of machines
• Higher safety and hygiene protocols
• User friendly interface that is easily PC adapted for fluid control
• Comprehensive programmed software for easier manipulation
• Higher feedback and report system makes for stronger output functions
• Super speed internal and external communication system enabled across multiple platforms
• Regular and quick updates of speed, position and current status leading to machine precision
• Reduced errors in tracking
• High precision supply of current while saving energy
• Interface for analog reading to use older machines

Digital servo drives function across servomotors like torque, asynchronous and linear motors and the brushless PM AC motors due to high end modular design. Based on 32- bit 400MHz microprocessor, it can used as effectively as a singular product as in a comprehensive system. It can ease the way your machine performs this providing higher output or aid in the machine design. Effective servo drive functions offer complete digital control and manipulation of brushless servo motors, delivers increased current and velocity leading to high precision performance that is the need of the hour across industries. Multi level interfaces, effective feedback system and superior controllers.

Leading vendors design and offer different kinds of servo drives –

• Servo drives that can control low power application for smaller machines requiring less than 1.5 kw. This effectively reduces design time and commission time, as well as provide layouts and CAD drawings.
• Digital servo drives that can handle multiple applications through single-axis motion control. They have inherent dynamic brakes, velocity observer, tuner and suppression algorithms to provide more cost effective motion control output.
• A multi-axis servo drive can helps in decreasing engineering time by helping effectively in networking, programming and operations. Adds greater flexibility and handles global voltage volume needs.
• Some come with high end safety options and flexible designs that can function on multiple levels and interfaces.
• EtherNet Servo Drives standardize the entire communication network leading to faster commissioning and startups, precise and easier configuration. Allows effective control integration with high speed connectivity.
• Some have troubleshooting options built in them, with automatic capacity of motor recognition.