STAFF AUTOMATION TRAINING Motion Control Basics

1. STAFF AUTOMATION TRAININGMotion Control Basics

2. Chain of Command FlowchartHitchcock’s Law of Diminishing Intelligence Operator Desk (GUI) Position controller Drives Winches

3. The Automation Interface – The Control DeskControl choices:Single or multiple users?Single or multiple desks?Single or multiple desk locations?Fixed or moveable desks?Workload of desks?

4. Feedback Position Controller Brain Brawn/Muscle Winches/Drive train Eyes/Ears Sensors/encoders

5. Motion Control System (position controller) Large Advances in the last 15 years Standard Components now Available The Automation ‘Brain’

6. The Automation ‘Brain’ Drive Technology: Bespoke 1st generation: Modular elements 2nd generation: Fully Modular Next generation:

7. The Automation ‘Muscle’ • Winches – general purpose, large speed range, large torque range • Hydraulics – suitable for large/heavy items • Pneumatics – low torque, fast action • Actuators – usually fixed speed • Solenoids • Chain Drive (Serapid) • Spiralift

8. P P T T The Automation ‘Muscle’ - Hydraulics • Hydraulics – suitable for large/heavy items • High torque for a small footprint • Can be simple to control • Can be tricky to commission/tune.

9. The Body

10. The Automation ‘Eye’ – Sensors • Position Sensors • Incremental Encoder • Absolute (NDAT, SSI, SinCos) Encoder • Resolver • Load Cell

11. Encoders There are two types or rotary encoder- incremental and absolute. The main differences are that incremental encoders give accurate motion of the shaft that has no relative value. Absolute encoders give the accurate current position of the shaft to a relative set value. i.e.- a scenic element using an incremental encoder will move a certain distance from zero. If power is lost and the scenery moved, when the power returns the position value will be incorrect. Absolute encoders will give accurate position data even if the scenery is moved when power is off.

12. Encoders Incremental encoders provide either a single or an A and B pulse, and a reference track, to give position. Absolute encoders have multiple code rings with various binary values, giving the shaft a unique digital output in either binary or grey code. An LED transmitter shines a light source through the disc which is received by a photo sensor, converting the light and dark areas, and the position of the shaft, into computer code. For incremental encoders, this is a relative position and is good for speed as well as position data. Absolute encoders have absolute position. At the school we have EnDat encoders where one revolution of the shaft gives 8192 pulses for absolute and 2048 pulses for incremental. EnDat encoders are bidirectional, allowing configuration data to be sent to the PLC, making then easier to commission.

13. Encoders

14. The Nervous System • Ethernet- moving large amounts of data, not time critical • Profibus- moving small amounts of time-critical data. • Profinet- combination of both for fieldbus applications. • Drive-Cliq- Siemens proprietary encoder interface

15. Profinet

16. PROFINET Taken from the Siemens Profinet Manual (IEC 61158/61784) – “The international standard uses Industrial Ethernet and allows real-time communication all the way to the field level, but also integrates the enterprise level. With the full utilization of existing IT standards, PROFINET allows isochronous motion control applications, efficient cross-manufacturer engineering and high availability of machines and systems on the Industrial Ethernet. PROFINET supports distributed automation and allows fail-safe applications.” Basically Profinet sends larger amounts of data than Profibus, faster than Ethernet, but can be configured with off-the-shelf routers and network switches. Profinet is Profibus protocols over Ethernet.

17. Mechanics 40 years + Ongoing Maintenance40:20:10 Rule: • Drives/Electrical Systems • 20-30 years • Control Desks/control Computers • 10 years (or less)

18. Big Tow Winch

19. 3 Phase motor Gearbox Secondary Brakes Hard Limits Lead Screw Wire rope drum Base Frame

20. The Motor Typically these days in automation we use AC motors because they have better torque and speed control and are cost effective. Our winches are servo motors, having and encoder built in.

21. Asynchronous 3 Phase Squirrel-cage Induction Motor

22. Synchronous 3 Phase AC Motor The speed of the rotor of this motor is same as the rotating magnetic field

23. Asynchronous and synchronous AC motors in Milton Court The slow moving winches in the Concert Hall, and all of the lifts, run on AC asynchronous induction motors (in particular they are 3-phase squirrel-cage motors). In general we run these AC induction motors on a variable frequency drive in order to control the speed, based on the feedback from the encoder. The (fast moving) power flying winches in the Drama Theatre run on Brushless AC Servo motors which are entirely reliant on the drive controlling them to determine (from the encoder feedback) the AC electric current waveforms to drive the motor. In this sort of motor, the rotor is a permanent magnet, and the field being varied is in the stator. A highly accurate encoder is essential for motors such as these as the drive needs to know the position of the rotor in order to compute the current waveform required.

24. Synchronous versus Asynchronous • All induction motors are asynchronous motors. The asynchronous nature of induction motor operation comes from the slip between the rotational speed of the stator field and the slower speed of the rotor. A north pole in the stator induces a south pole in the rotor. The stator pole rotates as the ac voltage varies in amplitude and polarity. The induced pole attempts to follow the rotating stator pole. The rotor field always lags behind the stator field by some amount so it rotates at a speed that is slower than that of the stator. The difference between the two is called the slip created by the necessary change in magnetic field strength- Faradays Law. • Variable frequency drives allow for speed adjustment. • Synchronous motors exist where the rotor is able to move at the same speed as the magnetic field in the stator. This is done via a rare earth magnet on the rotor, which, if set at the correct alignment to the stator, allows flux to rotate rotor at the same frequency as the magnetic field. Our servo motors use encoders to give accurate speed and position control for heavy loads at fast speeds.

25. Stepper Torque Winding Brushless Rotor A Synchronous Synchronous Induction DC Servo Stepper AC Stator Poly Phase Motor choice

26. Winch Specs

27. Gearboxes Speed vs. Load Worm-drive Direct Drive Planetary

28. Holding Brakes Compressed air driven Solenoid and Spring driven GSMD winches Brakes lift in 800ms Brakes on in 100ms

29. Load testing Both sets of brakes, input and output, are tested with a static load: 1.25 x SWL, or 1.5 x SWL for performer flying. One set of brakes is lifted and the load is left on the other set for up to 10 mins. Position is monitored in eChameleon. This is then repeated for the other set. Dynamic lift of 1.1 x SWL at full speed, or 1.25 x SWL for performer flying, with E-stop test. Brake drop testing. One set of brakes is lifted, then the second set is lifted, allowing the load to fall to full speed before the brake is closed, checking that it can arrest the load.

30. Limits Grid High Ultimate Rotary Cam High Initial High Software Show travel Direct Struck plunger or swing arm Low Software Low Initial Low Ultimate Deck

31. Stops and stopping times Stops • Class 0 power off/brakes on. Not applicable in the school. • Class 1 depends on max speed. If load is travelling out, must arrest travel without allowing load to continue under its own momentum before falling back on brakes, creating a shock load. Covers initial limits, slack rope and cross-groove. 0.3s from full speed. • Torque stop includes full reverse torque. e.g. with safe edge protection. • E-stops- controlled stop for 0.5s before dropping E-stop and main contactor. E-stop has dual monitoring. E-stop cable has four wires: 24v signal; two wires carry individually pulsed signals; two wires for monitoring. 250ms checkback. Stopping times • Desk stop button/dead mans handle- decel 1s • Soft limit- user decel set in desk • Initial limit- set in Simotion, drive off allowed. • Ultimate- Safe torque off, drops input in drive and CU. Needs to be linked out to reset with 24v

32. Over-travel If an axis is travelling at 1400mm per second and stops in 0.3 seconds, the over-travel distance will be 420mm. 1400 multiplied by 0.3 equals 420. However, in our controlled stops, the deceleration over that time period suggests a distance travelled of about 300mm. Our Limits are set at this distance apart.

33. Additional Axis Sensors Load Cell Cross Groove Slack Rope Optical Sensors Pressure Pads Ferrous Sensors or Proximities

34. Basics of Control Theory Logic Control A PLC constantly monitors the state of input devices and makes decisions based on a custom program to control the state of output devices. The output devices produce results in response to input conditions within a limited time. PLC’s read limit switches, sensors, and encoders via input/output devices, to control actuators using a user defined logic programme. In closed loop control a process variable is measured, compared to a setpoint and action is taken to correct any deviation.

35. PID CONTROLLER • PROPORTIONAL/INTEGRAL/DERIVATIVE CONTROLLER • CONTROL LOOP FEEDBACK MECHANISM • CONTINUOUSLY CALCULATES AN ERROR VALUE AS THE DIFFERENCE BETWEEN A MEASURED PROCESS VARIABLE AND A SET POINT. • P- PRESENT ERRORS • I- PAST ERRORS • D-FUTURE ERRORS

36. PLC Scan: Limits I/O TM 15 Encoder Comms Desk CU Position controller 3ms Speed controller 125μs

37. Automation System basic architecture Control Desks Desk Network Control Network Central Server Motion Controllers Interconnections Variable speed drives External encoder Field looms

38. Feedback A servomechanism, or servo is an automatic device that uses error-sensing feedback to correct the performance of a mechanism. The term correctly applies only to systems where the feedback or error-correction signals help control mechanical position or other parameters. Encoder Resolver

39. The Control Loop Demand Feedback

40. Control loop monitoring

41. Control Gear MCR/MCC (motor control rack/motor control centre AIM/ALM Drives RF Filter PLC Relays Mains in

42. Milton Court MCC

43. MCR / MCC Desk (Nomad, Solo etc) D4X5 CU320 Drive Server Field Item – Winch etc Control Components

44. MCR / MCC Desk (Nomad, Solo etc) D4X5 CU320 Drive Server Field Item – Winch etc Control Components CU320 The drive control unit, controlled from the D4X5 via Profibus. This is known as the “Drive” level and controls speed and therefore current. Drive Amplifier for the control voltage. Controlled by the CU – no onboard processing and direct connection to the winch DX445 The control unit, known as the Simotion level. The brains of the operation. Also known as the PLC, concerned with position and speed

45. Position Control The position control loop uses encoder data feedback. ‘Following error’ in positon loop is the difference between demand position and actual position. A position window is set during the commissioning process, in Scout. The PLC sends speed setpoint to the CU every 3ms, referencing encoder actual position from demand position. The PLC scans for faults every 12ms. i.e. limits, cross-groove, slack line, overcurrent etc.

46. Speed Control CU 320 - control unit, controls speed and therefore Current, that is, it could be thought of as current controller. Closed loop for speed control. CU applies voltage change to adjust speed. Demand speed → Torque setpoint → Current → Voltage Closed speed loop uses ‘following error’ to calculate the difference between demand and actual speed. Encoder incremental track gives speed feedback, but CU is taking speed setpoint from the PLC.

47. Commissioning in ScoutThe current loop gains proportional (Kp) and integral (Ki) gains control the response of the current loop to a change in current (torque) demand.

48. Commissioning Simotion Level Parameters

50. TracingZero speed enable- current