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Control Theory in Industry, Robotics and Infrastructure

Control Theory in Industry, Robotics and Infrastructure. Lachlan Blackhall and Tyler Summers. Motivating Example. You walk into your classroom and turn your air conditioning on to a temperature of 24 degrees.

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Control Theory in Industry, Robotics and Infrastructure

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  1. Control Theory in Industry, Robotics and Infrastructure Lachlan Blackhall and Tyler Summers

  2. Motivating Example • You walk into your classroom and turn your air conditioning on to a temperature of 24 degrees. • The air conditioner turns on until the internal thermostat registers that the air temperature is 24 degrees then shuts off the air conditioner until the temperature rises again. • A simple controller is responsible for keeping you cool!

  3. Systems Modelling

  4. Control Components • A system • Possibly a mathematical model of that system. • A control goal • A sensor to observe the system • An actuator to influence the system • A control algorithm that tells the actuator how to behave based on the observations of the sensor. • A computer or analog circuit to link it together.

  5. Differential Equations • Control is primarily concerned with systems that can be written as differential equations. • Almost everything can be written in this form so control really applies to any physical systems. • It all started with trying to apply external control to simple differential equations.

  6. Industrial Applications • Control emerged as a way to automate: • Manufacturing • Assembly • Processing and Refinement • Has since been used successfully in additional areas: • Robotics • Infrastructure

  7. Revisiting our Example • The thermostat is one of the simplest controllers you can create. • This type of controller is known as a bang-bang controller. • A bang–bang controller (on–off controller) is a feedback controller that switches abruptly between two states.

  8. Bang-Bang Control • They are routinely used to control a plant that accepts a binary input, for example a heater or air conditioner. • Bang–bang controls are actually optimal controls in some cases, although they are also often implemented because of simplicity or convenience.

  9. PID Control • PID stands for proportional–integral–derivative. • PID is a generic control loop feedback mechanism used in industrial control systems. • The control signal has three components based on the error between the observed operation and the nominal set point: • A proportional component • An integral component • A derivative component

  10. PID Control (cont.) • Some history • Developed in the late 1800s • Initially trialled as a way to control US Navy ship steering. • Can be implemented mechanically, using analog electronics and now using digital electronics like FPGAs • Most commonly implemented in industry these days using programmable logic controllers.

  11. PID Control (cont.) used with permission from http://commons.wikimedia.org/wiki/File:PID.svg

  12. PID Control (cont.) • Heuristically: • P depends on the present error • I on the accumulation of past errors • D is a prediction of future errors, based on the current rate of change. • The weighted sum of these three actions is used to adjust the process via a control element or actuator.

  13. PID Control (cont.) • In the absence of knowledge of the underlying process, a PID controller is the best controller. • The response of the controller can be described in terms of the responsiveness of the controller to an error, the degree to which the controller overshoots the set-point and the degree of system oscillation. • Note that the use of the PID algorithm for control does not guarantee optimal control of the system or system stability.

  14. PID Control (cont.) • Some applications may require using only one or two actions to provide the appropriate system control. • This is achieved by setting the other parameters to zero. • A PID controller will be called a PI, PD, P or I controller in the absence of the respective control actions. • http://www.youtube.com/watch?v=ALVo4aJpcF0 – P vs PID Control

  15. Demonstration • LEGO Mindstorms Line Following Robot – Bang-Bang vs P Controller • LEGO Mindstorms Segway Robot – PID Control

  16. Applications of PID • Assembly • Robotics • SCADA • Building Control

  17. Assembly • PID Controllers are vitally important to robots used for automated assembly. • Precision control was the technological breakthrough that allowed robotic assembly to become so commonplace. • Demonstrations: • http://www.youtube.com/watch?v=HPpTK2ezxL0 - 1936 Car Assembly Footage • http://www.youtube.com/watch?v=-_SxW_7v9is – BMW Assembly Plant Footage

  18. Robotics • Beyond assembly industrial robots can perform a great many tasks including: • Welding • painting, • pick and place (such as packaging, palletizing and SMT) • product inspection, and testing • There are lots of other robots out there using PID control.

  19. Robotics (cont.) • Demonstrations: • http://www.youtube.com/watch?v=Fxzh3pFr3Gs - Catching balls and darts (Lund) • http://www.youtube.com/watch?v=SOESSCXGhFo – ABB Challenge • http://www.youtube.com/watch?v=R8UeT9r4cmg - ASIMO • http://www.youtube.com/watch?v=cNZPRsrwumQ – BIG DOG

  20. SCADA • How do you control a number of systems, and a number of controllers that are possibly spread out on a factory floor or over a large geographic footprint?

  21. SCADA • SCADA (supervisory control and data acquisition) are industrial control systems (ICS) that monitor and control industrial, infrastructure, or facility-based processes. • Industrial processes include: • Manufacturing / production / assembly • Power generation, transmission and distribution • Wastewater collection and treatment • Oil and gas pipelines and refineries

  22. SCADA (cont.)

  23. SCADA (cont.) • A SCADA system usually consists of the following subsystems: • A human–machine interface or HMI • A supervisory (computer) system, gathering (acquiring) data on the process and sending commands (control) to the process. • Remote terminal units (RTUs) connecting to sensors in the process, converting sensor signals to digital data and sending digital data to the supervisory system. • Programmable logic controller (PLCs) for implementing PID control through actuators. • Communication infrastructure connecting the supervisory system to the remote terminal units.

  24. SCADA (cont.) • Demonstration Videos • http://www.youtube.com/watch?v=ZSFdOjxB-1I • http://www.youtube.com/watch?v=rj44AkHmVCo&feature=watch_response_rev

  25. Building Control • Modern buildings have a variety of control systems: • HVAC • Energy • Security • Structural stability • http://www.youtube.com/watch?v=gCuPx9shWT0 - Siemens Future Buildings

  26. Group Task • Forms groups of 8-10. • Briefly discuss: • Areas where you think control could or should be used in your society. • Are there systems in your society that could be controlled that are currently not? • Present to the group.

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