Easeus Solutions.

• Velocity control e.g. fans, conveyors, mixers, flow rate control.
• Pressure/force control e.g. pumps and presses,
• Position (point-to-point) control e.g. robots, linear actuators, ejectors, servos.
• Rotation control and swivel control.

• Impedance control: suitable for environment interaction and object manipulation, such as in robots amplifying/reproducing human movement.
• Electronic gearing (or cam profiling): e.g. two rotating drums turning at a given ratio to each other, or with electronic camming where a slave axis follows a profile that is a function of the master position.

VFD/VSD: VARIABLE FREQUENCY/SPEED DRIVES

A variable-frequency drive (VFD) also known as adjustable-frequency drive (AFD), variable-voltage/variable-frequency (VVVF) drive, variable speed drive (VSD), AC drive, micro drive or inverter drive is a type of motor drive used in electro-mechanical drive systems to control AC motor speed and torque by varying motor input frequency and voltage.

VFDs are used in applications ranging from small appliances to large compressors. Voltage can range from low voltage (110V-415V) upto medium and high voltage (1kV-20kV). About 25% of the world's electrical energy is consumed by electric motors in industrial applications. Systems using VFDs are significantly more efficient than those using throttling control of fluid flow, such as in systems with pumps and damper control for fans. Advancements in power electronics has significantly brought down the cost and improved the performance of VFDs hence bringing in more applications for industrial use. There are now a myriad of VFD brands that are reliable and cost effective.

VFDs are highly customizable and can be programmed to run in any of the 4 speed-torque quadrants.

• Quadrant I - Driving or motoring, forward accelerating quadrant with positive speed and torque e.g. fans, conveyors and bottle cappers
• Quadrant II - Generating or braking, forward braking-decelerating quadrant with positive speed and negative torque e.g. when the motor is being overhauled by the load.
• Quadrant III - Driving or motoring, reverse accelerating quadrant with negative speed and torque
• Quadrant IV - Generating or braking, reverse braking-decelerating quadrant with negative speed and positive torque e.g. unwinding applications.

Most applications involve single-quadrant loads operating in quadrant I, such as in variable-torque (e.g. centrifugal pumps or fans) and certain constant-torque (e.g. conveyors and extruders) loads.

VFD offer tremendous energy savings whenever speed is reduced. This is even higher for variable torque applications e.g. fans and centrifugal pumps (due to torque-speed square-law: torque = K.speed²).

AC Drives are used to bring about process and quality improvements in industrial and commercial applications' acceleration, flow, monitoring, pressure, speed, temperature, tension, and torque among other applications.

Apart from quality control and energy savings, VFDs offer other benefits. With a VFD, you can entirely eliminate contactors which are prone to welding. Cost on motor overload protection and MPCB can also be eliminated. Drives accept a wide range above and below the rated input voltage to produce a constant/steady output voltage to the motor. This eliminates overheating and winding degradation hence protecting the motor from surges and sags. Ramping up speed eliminates high starting torque and current surges that are up to eight times the full-load current. All these lessens mechanical and electrical stress, reducing maintenance and repair costs, and extending the life of the motor and the driven equipment. An S-curve ramp can be applied to a conveyor application for smoother deceleration and acceleration control, which reduces the backlash that can occur when a conveyor is accelerating or decelerating.

They are a lot of engineering parameters to consider before you can pick the best drive for your application. These include voltage, power rating, harmonic mitigation, electro-magnetic noise mitigation & EMC filters, vector/field-oriented control, open-loop vs close-loop control, torque requirement, communication, ramp time and ramp curves, voltage and frequency control methods, long leads effect, dynamic and regenerative braking, other motor parameters, among other things. You can contact us for consultation on such matters.

In high-end applications, getting data on the status of, and sending commands to the VFD is important e.g. in pumping stations. Most VFDs offer analog, discrete, serial RS-485 communication, or ethernet communication for such purposes. By leveraging the protocol behind the serial or ethernet communication, you can get all the important information about the drive and motor it is connected to by using only a 2-wire RS-485 or an ethernet cable. This information includes, power, current, output line voltage, DC bus health, rpm/speed, running status, torque percentage, frequency, fault codes, among others. You can also send control commands and parameters to the drive e.g. start stop, jog, reset, ramp behaviour etc. At Easus Solutions, we build such systems to control and get back data from the drive as shown on the image on the side.

SERVOMOTORS AND SERVO DRIVES

A servomotor is a rotary actuator or linear actuator that allows for precise control of angular or linear position, velocity and acceleration. It consists of a suitable motor coupled to a sensor for position feedback. It also requires a relatively sophisticated controller, often a dedicated module designed specifically for use with servomotors.

Servomotors are not any special motors (usually brushed/brushless DC, or PM and induction AC motors), but when they are combined with a position and velocity feedback mechanism, they form a closed-loop servomechanism. For large industrial servomotors, AC induction motors are typically used, often with variable frequency drives to allow control of their speed. For ultimate performance in a compact package, brushless AC motors with permanent magnet fields are used.

The very simplest servomotors use position-only sensing via a potentiometer and bang-bang control of their motor; the motor always rotates at full speed or is stopped. This type of servomotor is not widely used in industrial motion control, but it forms the basis of the simple and cheap servos used for radio-controlled models.

More sophisticated servomotors use optical rotary encoders (incremental or absolute encoders), or the more aged electromagnetic resolvers and sychros, to measure the speed and position of the output shaft and a variable-speed drive to control the motor speed. Both of these enhancements, usually in combination with a PID control algorithm, allow the servomotor to be brought to its commanded position more quickly and more precisely, with less overshooting.

Servomotors are generally used as a high-performance alternative to the stepper motor. Stepper motors have some inherent ability to control position, as they have built-in output steps. This often allows them to be used as an open-loop position control, without the need for a feedback encoder. However, a homing limit switche is needed to revert to a known position on power-up.

Most modern servomotors are designed and supplied around a dedicated servo motor drive that accepts commands and encoder feedback to drive the motor to the desired position. The two are usually supplied by the same manufacturer as a pair. This helps to simplify the contol system.

ROBOTICS

Robotics is an interdisciplinary field that integrates computer science and engineering. Robotics involves design, construction, operation, and use of robots. The goal of robotics is to design machines that can help and assist humans. Robotics develops machines that can substitute for humans and replicate human actions. Robots can be used in many situations for many purposes, but today many are used in dangerous environments (including inspection of radioactive materials, bomb detection and deactivation), manufacturing processes, or where humans cannot survive (e.g. in space, underwater, in high heat, and clean up and containment of hazardous materials and radiation), and for common repetitive tasks.

Robots can take on any form. Some are made to resemble humans in appearance. For our case, we will stick to industrial/manufacturing robots only. In industrial automation, control of robotic manipulators is included in the field of motion control because most of robotic manipulators are driven by electrical servo motors and the key objective is the control of motion.

Industrial robots are classified into different categories depending on their articulation, movement, and work area envelope.

• Articulated Robots - This is what you would typically think of when you imagine an industrial robot. The design features rotary joints and can range from two joint structures to 10 or more joints.
• SCARA Robots - Selective Compliance Articulated Robot Arm (SCARA). They features two parallel joints that provide compliance in one selected plane. They are small, lighweiht, fast and perfect for assembly. The design features rotary joints and can range from two joint structures to 10 or more joints.
• Delta Robots - Also known as 'Spider Robots' or 'Parallel Robots'. The design involves a mounted travelling platform actuated by arms that resemble spider legs hence the name.
• Cartesian Robots - Also called rectilinear or gantry robots. Their design revolves around the linear cartesian plane (XYZ). They also usually feature a rotary arm.
• Cylindrical Robots - The cylindrical robot has a rotary joint along the joint axis for rotation movement and a prismatic joint for linear motion. Their movements occur within a cylindrical-shaped work envelope.
• Polar Robots - Also known as spherical robots. With its combined rotational joint, two rotary joints, and a linear joint, the spherical robot operates in the polar coordinate system to achieve a spherical-shaped work envelope.

Some of the major applications for robots include:

• Welding: including MIG welding, arc welding, spot welding
• Assembly: especially electronics PCB, clean room assemblies, fastening, engine assembly among others.
• Material handling: including part selection and transferring, palletizing, packing, and machine loading, among others.
• Material removal: such as grinding, cutting, deburring, sanding, polishing, routing.
• Inspection: e.g. 3D Laser Vision Robots.
• Machine Tending: Robots can oversee a machine while it performs a job, as well as the process of feeding parts in and out..
• Collaborative Robots: The collaborative application of robotics - 'Cobots' - enables humans and robots to safely and effectively work together in an uncaged environment, with no risk of injuries/damages.

With Industry 4.0, robots have become very versatile with swappable EOATs (End of Arm Tooling). The interconnection of devices allows them to seamlessly swap between different unrelated tasks hence minimizing ownership cost, and maximizing space, and production time.

LINEAR ACTUATORS

An electric linear actuator is a device that converts the rotational motion of an AC or DC motor into linear motion. It can provide both push and pull movements.

This movement makes it possible to lift, drop, slide, adjust, tilt, push or pull, open and close valves, and to position objects.

An electric linear actuator consists of a DC or AC motor, a series of gears and a lead screw with driving nut that pushes the main rod shaft in and out. Some other electronics help to determine the amount of stroke limit switching and positional feedback options.

When coupled with linear encoders or rotary encoders, linear actuators can be used in a servo system for precision linear positioning.

When picking a linear actuator, there are several engineering parameters to consider including: travel length, static load capacity, dynamic load capacity, speed control, and duty cycle. Despite that, electrical linear actuators are popular since they are easy to install, control, and are safe for use including in food & beverage industries.

Inherently, hydaraulic and pneumatic cyclinders can be classified as linear actuators with hydraulic fluid and air transmittig the force respectively instead of a screw.

HYDRAULICS AND ELECTROHYDRAULICS

Hydraulics is understood as the generation of force and motion with the help of hydraulic fluid. The hydraulic fluid is the energy transmission medium. To withstand the forces of compression, the liquid has to be incompressible, can handle high temperatures to avoid boiling, and be a good lubricant for the moving parts. Hydraulic fluids are specifically made with these properties.

An hydraulic system consists of a reservoir that holds the hydraulic fluid. A pump pulls the fluid from the reservoir via a filter. The hydraulic fluid is then pushed through a control valve. If the valve is open, the fluid is pushed into one end or the other of an hydraulic cylinder in order to extend or retract the piston. The final component could be an hydraulic motor or an hydraulic cylinder.

Hydraulic valves can be operated manually by pulling on a lever. They can also be opened pneumatically (air-controlled-valves). Electronically pilotted valves are also very common. The valve also drains fluid from one side of the cylinder into the the reservoir hence completing the cycling the fluid back through the pressure lines.

Hydraulics are great for high power density applications: transmission of great forces through the use of small components. They easily achieve accurate positioning with uniform, load-independent motion, because fluids are hardly compressible. Hydraulics can start up from standstill with maximum power at full load with good contralability and adjustability.

Some applications of hydraulics include:

• Presses
• Hoists and conveyors
• Injection moulding machines
• Mill trains
• Lifts
• Manufacturing and assembly machines
• Transfer lines

When designing an hydraulic system, the main condiserations are dictated by the payload. These include weight of the payload, length of extension, anticipated pressure in the lines. This will determine the sizing of the cylinders, pressure lines, valves, radiators/cooling, reservoirs and pumps. With the help of hydraulic diagrams and simulations, hydraulic systems can be easily tested, installed, diagnosed and mantained.

PNEUMATICS AND ELECTROPNEUMATICS

Hydraulics are very powerful tools with good reliability. However, they are applications in which they are not viable. Hydraulics are generally shunned in food and beverage industries for their likelihood to contaminate the products. In hot and hazardous areas that are likely to catch fire, hydraulics are avoided. These are the areas where pneumatics come in.

Pneumatics originates from from Greek - pneuma ‘wind, breath’. It is a branch of engineering that makes use of gas or pressurized air. Pneumatic systems used in industry are commonly powered by compressed air or compressed inert gases. A pneumatic system constitutes of centrally located and electrically-powered compressor powers cylinders, air motors, pneumatic actuators, and other pneumatic devices.

Compressed air is stored in a cylinder. In order to increase the efficiency of the cylinder and compressor, the air is first filtered to remove dust and other air aerosols. It is then dried to remove moisture content. Some water is okay for most applications but too much water can be a problem. That’s where compressed air drying comes in. Drying can be done before the cylinder, in the cylinder, or after the cylinder. There are six common ways of removing or reducing the amount of water in a compressed air stream. These compressed air drying methods include:

• Aftercoolers:
  -Aircooled
  - Watercooled
• Storage Tank Cooling
• Membrane Type Dryer
• Refrigerant
• Deliquescent / Absorption Drying
• Regenerative / Adsorption Drying
  -Dual Tower Regenerative Desiccant Air Dryers

Just like hydraulics, pneumatic is transmitted via pressure lines. The opening and closing of valves is used to direct the compressed air. Pneumatic valves can be operated pneumatically (use of compressed air), manually with buttons, or via electrical signals (electro-pneumatics). There are several types of valves depending on mode of operation and air paths. Logic AND, OR(shuttle valve), gates are also part of the lineup. Complex logic can be achieved with these valves and gates.

After leaving the compressor cylinder, the air is then lubricated via a venturi mechanism before reaching the valves and pneumatic devices. Some applications do not require lubrication and this can be ignored. The air then extends or retracts pistons in pneumatic actuators for linear motion. Pneumatic devices can also achieve rotary (air motors) and swivel motion. Exhaust air is vented to the atmosphere via a brass silencer.

Some applications of pneumatics include:

• Opening and closing control valves
• Material handling
• Drilling
• Sawing
• Filling
• Packing
• Clamping
• Fastening
• Shifting
• Stamping
• Pressing
etc.

When desgning a pneumatic system, there are several considerations. The rate of cnsumption of air will determine the size of the compressor and cylinder and their components. Most pneumatic devices and valves work with pressure of 4.0 bars and above. This minimum pressure should be mantained at all times. Other considertions include the type of pneumatic cylinder (double-acting or single-acting), valves and logic gates, method of valve actuation, and payload. You will also need to determine if you system will need dried air and/or lubrication.