What is the definition of "process variable"?
The actual value detected by a sensor as a process is taking place. Also known as the feedback signal.

Learn more about process variable in the class Robotic Control Systems 240 below.


Robotics Training


Class Information
Tooling U-SME classes are offered at the beginner, intermediate, and advanced levels. The typical class consists of 12 to 25 lessons and will take approximately one hour to complete.
Class Name:Robotic Control Systems 240
Description:In this class, you will learn about the basic types control systems. You will also learn about the effects of PID control in closed-loop control systems and how to tune your system in order to achieve the desired performance.
Prerequisites: none
Difficulty:Intermediate
Number of Lessons:13
Language:English, Spanish
 
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Class Outline
  • Objectives
  • Control Systems
  • Line Diagrams
  • Ladder Logic
  • Programming Devices
  • PID
  • PID Motion Control
  • Open-Loop Control Systems
  • Closed-Loop Control Systems
  • Servo Drives
  • Controller Tuning
  • Tuning Applications
  • Summary
  
Class Objectives
  • Describe position control systems.
  • Define line diagrams.
  • Define ladder logic.
  • Describe PLC programming devices.
  • Describe PID control systems.
  • Describe PID motion control.
  • Describe open-loop control systems.
  • Describe closed-loop control systems.
  • Describe servo drives and servomotors.
  • Describe controller tuning.
  • Describe tuning maintenance.

Class Vocabulary

Vocabulary TermDefinition
amplifier A device that increases the size or strength of a signal. Servomotors use amplifiers as part of the motor control system.
auto mode A system that is set for closed-loop control.
automatic feedback Feedback that is controlled by an electronic or electromechanical mechanism rather than a person.
autotune A feature in some motor control devices that automatically adjusts the PID control system at start-up.
closed-loop control A type of control system that automatically changes the output based on the difference between the feedback signal to the input signal. Servomotors can be used on closed-loop control systems.
closed-loop system A type of control system that automatically changes the output based on the difference between the feedback signal to the input signal.
compliance The degree to which a robot can tolerate misalignment. PID control helps ensure robots are within the acceptable range.
continuous process One in which incremental changes take place continuously. PLCs operate using discrete events.
control mechanism A system or device that operates or manipulates another system or device.
control system A manual or automatic mechanism used to manage dynamic processes by adjusting or maintaining physical variables such as temperature, speed, or flow rate.
controller The main device that processes information and carries out instructions in a robot. Also known as the CPU or processor.
controller tuning A system of adjusting the controller's response to error by adjusting values in the PID algorithm.
error The difference between the SP and the PV. When errors are detected, the controller sends instructions to the control system to adjust the output to compensate.
feedback signal The actual value detected by a sensor as a process is taking place. The feedback signal is part of a closed-loop control system.
gain The ability of the control system to increase the power or amplitude of its signal.
hand-held programmer A PLC programming device that combines a display screen and keypad all in one unit. Specially assigned keys allow you to enter program instructions and changes, and navigate and troubleshoot the PLC system.
holding torque The amount of torque required for a motor to remain in a fixed position.
ladder logic The most common programming language for PLCs. Ladder logic is based on line diagrams.
line diagram A diagram that shows the logic of an electrical circuit or system using standard symbols. A line diagram is also known as a ladder diagram because the diagram appears as individual lines or "rungs" connected between two vertical lines.
motion profile The interconnected acceleration, velocity, and position characteristics of a robot control system.
open-loop system A type of control system that uses only an input signal to actuate an output. There is no automatic feedback to adjust the process, so adjustments must be made manually by the operator.
overshoot To exceed a set value.
personal computer PC. A computer designed for an individual user and commercial software. Desktops, laptops, and notebook computers are PCs.
PID One of the most common types of process control. Proportional, integral, derivative control adjusts system outputs when there is a difference between the setpoint and process variable.
PID algorithm A mathematical formula used to control and stablize the outputs of closed-loop control systems. The equation for PID is: Output = Gain (Error + l/Integral Time ∫ Error x deadtime + Derivative Time Constant x ΔError/ ΔTime).
position control A type of control system designed for moving objects or machines to a known position. Servomotors are used for position control.
process variable The actual value detected by a sensor as a process is taking place. Also known as the feedback signal.
programming device A device, usually a personal computer, used to enter instructions into the PLC.
proportional, integral, derivative control One of the most common types of process control. PID adjusts system outputs when there is a difference between the setpoint and process variable.
rung The horizontal programming lines in ladder logic. Each rung controls one output.
servo drive A motor control device that outputs electrical signals to a servomotor to induce motion. The servo drive can be built in as part of the motor or it can be a separate device.
servo system A closed-loop control system that utilizes a servomotor.
servomotor A type of motor used in applications that require precise positioning. Servomotors provide a high amount of holding torque to maintain their position accurately.
setpoint A preset value such as a specific speed or position that the control system is supposed to reach. Also known as the target value.
single-phase AC voltage that has only one sine wave.
soft start A motor starting method that reduces stress on a motor by allowing it to accelerate gradually for a programmed period of time.
target value A preset value such as a specific speed or position that the control system is supposed to reach. Also known as the setpoint.
three-phase AC voltage that has three sine waves.
troubleshooting The systematic examination of the various parts of a system, circuit, or process to identify a malfunctioning part using process of elimination reasoning.
undershoot To fall short of a set value.