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Techno Linear Motion Catalog 35 Technical Information 7)    Control and Electronics Control and electronics are the brains to any linear motion system.  In general, a motor controller performs three main functions.   First, it routes current to the motor windings according to rotor position.  It also transforms  input  supply  voltage  into  a  controllable  voltage  and  current  supply  for  the  motor  speed  and torque control.  Finally, in the case of servo control, it handles all speed and torque feedback loops to meet prescribed static and dynamic requirements.  There are many types of control, and each type has many different components.  This section will discuss some of the more common types and introduce the major components associated with each. Input and Output Devices are the interface between the controller and the controlled system and, in effect, tie the controller to the outside world. Input devices convert physical quantities to electric signals, while output devices allow the controller to act on the system.   The electronic brain of a control system depends upon the network of input/output devices (I/O). In the case of closed loop servo control, the inputs are critical to operation. Inputs  include  transducers,  sensors  and  switches.    Sensors  and transducers convert physical data such as speed, position, temperature, acceleration and pressure into electrical signals that are recognized by the  controller.    Switches  allow  the  operator  to  supply  information  that supplements  or  overrides  input  data.    Outputs  include  power semiconductors and IC’s, relays, and circuit breakers.  By providing control over electric power subsystems that drive motors and solenoids, they allow the controller to initiate, halt, or modify action in the controlled system, including turning pneumatic, hydraulic, and electric devices on and off. Sensors are used in combination with I/O for a variety of tasks.  The most common task is to provide the controller with a defined work envelope, defining the physical capabilities of the hardware.  Typical linear motion machinery will incorporate switches at both ends of the physical motion limit of each axis to provide the controller with “out of bounds”  information.  The switch towards the motor is generally referred to as the home  switch  while  the  switch  at  the  far  end  is  called  the  limit  switch.    Upon  activating  one  of  these switches, program execution is usually terminated.  The most common types of switches are the mechanical switch  which  is  activated  by  physical  contact,  and  the  hall effect switch  which  is  activated  by  magnetic properties.  Inductive proximity switches and optical sensors are also found on systems.  Proximity switches have no moving parts and can be extremely repeatable and reliable if  used correctly.  Optical switches also have no moving parts, but they can suffer performance degradation due to dust. Feedback  Sensors  are  used  to  perform  checks  on  the  static  and  dynamic  state  of  a  system,  and  are generally used with servo systems.  Encoders and resolvers are used to sense position information, and are further discussed in the servo motor section of this introduction.  Tachometers are used to sense velocity information, and accelerometers are used to detect acceleration.  Each type of sensor performs different tasks, and requires different types of interfacing to the control. Proximity  switches  are  commonly  seen  in  process  automation  applications.   A  proximity  switch  is  an electronic switch that acts when it is in the proximity of an object.  Inductive proximity switches can detect any metal object based on local change of inductance, and are highly insensitive to harsh, dirty environments. Capacitive proximity switches are capable of sensing fluids and nonmetallic objects based on local changes in capacitance.  Both should be applied with care as they can be sensitive when detecting objects that present small targets such as corners and edges. Machine Controller Motor Drive Current Outputs Inputs Machine