Techno Linear Motion Catalog35Technical Information7) Control and ElectronicsControl and electronics are the brains to any linear motion system. In general, a motor controller performsthree main functions. First, it routes current to the motor windings according to rotor position. It alsotransforms input supply voltage into a controllable voltage and current supply for the motor speed andtorque control. Finally, in the case of servo control, it handles all speed and torque feedback loops to meetprescribed static and dynamic requirements. There are many types of control, and each type has manydifferent components. This section will discuss some of the more common types and introduce the majorcomponents associated with each.Input and Output Devicesare the interface between the controller andthe controlled system and, in effect, tie the controller to the outside world.Input devices convert physical quantities to electric signals, while outputdevices allow the controller to act on the system. The electronic brain ofa 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.Inputsinclude transducers, sensors and switches. Sensors andtransducers convert physical data such as speed, position, temperature,acceleration and pressure into electrical signals that are recognized bythe controller. Switches allow the operator to supply information thatsupplements or overrides input data. Outputs include powersemiconductors and ICs, relays, and circuit breakers. By providing controlover electric power subsystems that drive motors and solenoids, they allowthe controller to initiate, halt, or modify action in the controlled system,including turning pneumatic, hydraulic, and electric devices on and off.Sensorsare used in combination with I/O for a variety of tasks. The most common task is to provide thecontroller with a defined work envelope, defining the physical capabilities of the hardware. Typical linearmotion machinery will incorporate switches at both ends of the physical motion limit of each axis to providethe controller with out of bounds information. The switch towards the motor is generally referred to as thehome switchwhile the switch at the far end is called the limit switch. Upon activating one of theseswitches, program execution is usually terminated. The most common types of switches are the mechanicalswitchwhich is activated by physical contact, and the hall effect switchwhich is activated by magneticproperties. Inductive proximity switches and optical sensors are also found on systems. Proximity switcheshave no moving parts and can be extremely repeatable and reliable if used correctly. Optical switches alsohave no moving parts, but they can suffer performance degradation due to dust.Feedback Sensorsare used to perform checks on the static and dynamic state of a system, and aregenerally used with servo systems. Encoders and resolvers are used to sense position information, andare further discussed in the servo motor section of this introduction. Tachometers are used to sense velocityinformation, and accelerometers are used to detect acceleration. Each type of sensor performs differenttasks, and requires different types of interfacing to the control.Proximity switchesare commonly seen in process automation applications. A proximity switch is anelectronic switch that acts when it is in the proximity of an object. Inductive proximity switches can detectany metal object based on local change of inductance, and are highly insensitive to harsh, dirty environments.Capacitiveproximity switches are capable of sensing fluids and nonmetallic objects based on local changesin capacitance. Both should be applied with care as they can be sensitive when detecting objects thatpresent small targets such as corners and edges.MachineControllerMotorDriveCurrentOutputsInputsMachine