Motion Controls 

Motion Control refers to various techniques implemented to control the motion of machines and objects. Various technical Platforms such as Robotics, CNC (Computer Numerical Control) and automation operate using motion controls since very precise machine movements are required in most manufacturing processes ranging from micro to macro. Motion control involves both Hardware and software and is used in many products from servo mechanisms to robotic assembly units across wired and wireless Networks. Motion control applications are virtually unlimited; some examples include Robots that transport delicate SiliconWafers during processing of Semiconductors, an automatic sewing arm sewing Quilts very accurately , a large telescope tracking down the position of the star automatically, and navigation control of an autonomous vehicle routinely tracking down the position Targets from a GPS . Though the nature of applications varies, they all require definite and automatic motion Controls, which are provided by the motion control system.

There are three interrelated Controls in motion control technique - servo feedback control , velocity control and position control - to enable the motion control system manage a wide variety of machines in the assembly , textile , printing and Packaging industries , etc .

Servo feedback control – Servo is a mechanism that responds by performing an action conforming to an input . The servo mechanism can be explained by the example of a toaster oven . The temperature of a toaster oven can be set to a specific value and the internal mechanism of the toaster oven works to adjust the temperature to this set value . However the accelerator of a car does not exemplify the servo mechanism since in this case the car operator should provide the speed control to operate the car since it doesn’t have any feedback to control the speed .

Velocity Control – Another common control mechanism is velocity control , which functions to regulate the rate of velocity of the motor so as to obtain the required position .

Position Control – Position control is controlling the servo motor to for any desired position by using simple pulse controlling technique . The series of positions that the object is to be placed is profiled , and this profile is inputted to the servo on a periodic basis . With position profiling the object’s forward velocity can be at any arbitrary movement .

The fundamental configuration of motion control system is as follows:

Application Software - It is used to program intended target positions and profiling the motion control of the system . Generally motion control Software is comprised of configuration , prototype , and application development environment (ADE)

Motion Controller - It is a critical element of the motion control system acting as its brain by taking the pre-defined target positions , precision motion control Profiles, and building trajectories for the Motors to follow . These functions are executed by outputting either an analog signal for servo Motors or a step-and-direction pulse for stepper Motors. The key converting logic and all the motion-related calculations are executed by the motion controller . The motion controller offers supervisory control as well by observing limits and emergency stops and it is also responsible for the high reliability and stability in order to create a safe and successful motion control system .

Amplifier or Drive – Amplifiers, otherwise known as Drives, receive the Instructions from the motion controller and produce the required current essential to drive the motor . Various motor Drives are available in the market but they should be matched with the type of motor they drive , for example stepper motor drive should be connected to the stepper Motors only and not to servo Motors.

Motor - Motors act as the muscle of the motion Control Systems and convert electrical energy into mechanical energy and generate sufficient torque to shift the motor to the desired target position .

Mechanical Elements - Mechanical elements perform the function of providing torque , and are designed based on the nature of their application . Linear Slides, robotic Arms, and special Actuators are some examples of mechanical elements .

Feedback device or Position Sensor – Feedback device plays a crucial role in servo motor and is not required for some of the motion Controls applications namely controlling stepper Motors. Generally the feedback devices sense the motor position and send back the result to the controller and this closes the loop to the motion controller . Feedback devices are designed accordingly to facilitate the motion controller sense where the motor is at . The usual position feedback device is the quadrature encoder , which gives digital position feedback relative to where it starts and is usually connected to the motor . Quadrature Encoders are familiar type of incremental Encoders that utilize two output Channels to sense the position . Some of the feedback devices are Tachometers, which give velocity feedback; Absolute Encoders, which provide absolute position measurements; Potentiometers, which offer analog position feedback; and Resolvers, which also provide absolute analog position measurements in closed loop systems and connected directly with the motor .