1. CHAPTER 1
FUNDAMENTAL OF MOTION CONTROL
SYSTEMS AND THEIR APPLICATIONS

2. OUTLINE
 INTRODUCTION TO MOTION
CONTROL
 COMPONENTS OF MOTION
CONTROL SYSTEM
 MOTION CONTROL VARIABLES:
POSITION, ANGLE, SPEED
 APPLICATION OF MOTION
CONTROL

3. INTRODUCTION TO MOTION
CONTROL
 Subfield of automation in which the
position and/or velocity of machines are
controlled using some type of device such
as hydraulic pump, linear actuator or
servo.
 Widely used in the packaging, printing,
textile, semiconductor production and
assembly industries.

4. INTRODUCTION TO MOTION
CONTROL
 The interface between the motion
controller and the drives it controls is very
critical when coordinated motion is required
as it must provide tight synchronization.
 Previously only used analog signal but later
more interfaces were developed for
coordinated motion control.
◦ SERCOS in 1991
◦ Profinet
◦ EtherCAT

5. Common control functions:
 Velocity control.
 Position (point-to-point) control:
 Several methods for computing a motion
trajectory.
 often based on the velocity profiles of a move
such as a triangular profile, trapezoidal profile,
or an S-curve profile.
 Pressure or Force control.

6. Common control functions:
Electronic gearing (or cam profiling):
◦ The position of a slave axis is mathematically
linked to the position of a master axis. A good
example of this would be in a system where two
rotating drums turn at a given ratio to each
other.
◦ A more advanced case of electronic gearing is
electronic camming. With electronic camming, a
slave axis follows a profile that is a function of
the master position.

7. INDUSTRIAL MOTION
CONTROL CATEGORIES:
 Sequencing
 Speed control
 Point-to-point control

8. SEQUENCING
 refers to the control of several
operations so that they all occur in a
particular order.
 simplest example:
◦ progression of events that take place through
the mechanical linkages of a player piano.
◦ opening and closing valves can be sequenced
mechanically with cam shafts.

9. SEQUENCING
 Sequencing generally becomes too
complicated to be handled mechanically in
industrial equipment such as conveyor
lines.
◦ Option: using time delay relays
◦ Better alternative: using PLC

10. SPEED CONTROL
 Refers to applications involving machines
run at varying speeds or torques.
 Source of power for such applications is
generally either an internal combustion
engine, or an electric, hydraulic, or
pneumatic motor.

11. SPEED CONTROL
 Speed can be controlled either
mechanically or, in the case of electric
motors, electronically.
 Mechanical speed-control components
include clutches and brakes, adjustable
speed drives, traction drives,
transmissions, and fluid coupled drives.
 Electronic speed control manipulates
applied electrical power to control
velocity and torque.

12. SPEED CONTROL
 Electronic speed control in ac motors
employs special amplifiers or drives.
These generally vary ac motor speed with
adjustable-frequency inverters.
 More expensive than mechanical speed
controls, they provide the advantage of
reduced energy costs.

13. POINT TO POINT CONTROL
 Refers to applications where something
must move from one point to another at
a constant speed.
 There are two factors that must be
controlled:
◦ Speed
◦ Distance.

14. POINT TO POINT CONTROL
 Examples:
◦ in x-y tables and in machining, where a tool
moves in a straight line while it touches a
work piece along one axis.

15. MOTION CONTROL SYSTEM
COMPONENTS

16. MOTION CONTROL SYSTEM
COMPONENTS
 Application software – You can use
application software to command target positions
and motion control profiles.
 Motion controller – The motion controller
acts as brain of the of the system by taking the
desired target positions and motion profiles and
creating the trajectories for the motors to follow,
but outputting a ±10 V signal for servo motors,
or a step and direction pulses for stepper
motors.
 Amplifier or drive – Amplifiers (also called
drives) take the commands from the controller
and generate the current required to drive or
turn the motor.

17. MOTION CONTROL SYSTEM
COMPONENTS
 Motor – Motors turn electrical energy
into mechanical energy and produce the
torque required to move to the desired
target position.
 Mechanical elements – Motors are
designed to provide torque to some
mechanics. These include linear slides,
robotic arms, and special actuators.

18. MOTION CONTROL SYSTEM
COMPONENTS
 Feedback device or position sensor –
A position feedback device is not
required for some motion control
applications (such as controlling stepper
motors), but is vital for servo motors.
The feedback device, usually a quadrature
encoder, senses the motor position and
reports the result to the controller,
thereby closing the loop to the motion
controller.

19. APPLICATION SOFTWARE
 Divided into three categories:
◦ Configuration
◦ Prototype
◦ Application development environment (ADE)

20. CONFIGURATION
 One of the first things to do is configure
your system for all your motion control
and other hardware.

21. PROTOTYPE
 Prototyping and developing your
application.
 In this phase, you create your motion
control profiles and test them on your
system to make sure they are what you
intended.

22. APPLICATION DEVELOPMENT
ENVIRONMENT
 For this, you use driver-level software in
an ADE such as LabVIEW, C, or Visual
Basic.

23. MOTION CONTROLLER
 A motion controller acts as the brain of
the motion control system and calculates
each commanded move trajectory.
 Because this task is vital, it often takes
place on a digital signal processor (DSP)
on the board itself to prevent

24. MOTION CONTROLLER
 The motion controller uses the
trajectories it calculates to determine the
proper torque command to send to the
motor amplifier and actually cause
motion.
 The motion controller must also close
the PID control loop. Because this
requires a high level of determinism and
is vital to consistent operation, the
control loop typically closes on the board
itself.

25. MOTION CONTROLLER
 Along with closing the control loop, the
motion controller also manages
supervisory control by monitoring the
limits and emergency stops to ensure safe
operation.

26. CALCULATING TRAJECTORY
 The motion trajectory describes the
motion controller board control or
command signal output to the
driver/amplifier, resulting in
motor/motion action that follows the
profile.
 The typical motion controller calculates
the motion profile trajectory segments
based on the parameter values you
program.

27. CALCULATING TRAJECTORY
 The motion controller uses the desired
target position, maximum target velocity,
and acceleration values you give it to
determine how much time it spends in
the three primary move segments (which
include acceleration, constant velocity,
and deceleration).

28. Typical trapezoidal velocity profile

29. MOTOR AMPLIFIERS & DRIVES
 Part of the system that takes commands
from the motion controller in the form of
analogue voltage signals with low current
 Converts them into signals with high
current to drive the motor.

30. MOTOR AMPLIFIERS & DRIVES
 Motor drives come in many different
varieties and are matched to the specific
type of motor they drive.
◦ For example, a stepper motor drive connects
to stepper motors, and not servo motors.
 Along with matching the motor
technology, the drive must also provide
the correct peak current, continuous
current, and voltage to drive the motor.

31. MOTORS & MECHANICAL ELEMENTS
 Motor selection and mechanical design is
a critical part of designing your motion
control system.
 Many motor companies offer assistance in
choosing the right motor.

32. MOTORS & MECHANICAL ELEMENTS
 After determining which technology you
want to use, you need to determine the
torque and inertia at the motor shaft.

33. FEEDBACK DEVICES
 Help the motion controller know the
motor location.
 The most common position feedback
device is the quadrature encoder, which
gives positions relative to the starting
point.

34. FEEDBACK DEVICES
 Other feedback devices:
◦ potentiometers that give analogue position
feedback
◦ tachometers that provide velocity feedback
◦ absolute encoders for absolute position
measurements, and
◦ resolvers that also give absolute position
measurements.

35. MOTION IO
 Protection from damaging the system.
 Includes limit switches, home switches,
position triggers, and position capture
inputs.
 Limit switches provide information about
the end of travel to help you avoid
damaging your system.

36. MOTION CONTROLLER VARIABLES:
POSITION,ANGLE & SPEED
 A system with a feedback controller will
attempt to drive the system to a state
described by the desired input, such as a
velocity.
 In practical applications this setpoint
needs to be generated automatically. A
simple motion control system is used to
generate setpoints over time.

37.  The motion profile is then used to
generate a set of setpoints, and times
they should be output. The setpoint
scheduler will then use a real-time clock
to output these setpoints to the motor
drive.

38. MOTION PROFILES
 Consist of:
◦ Velocity profile
◦ Position profile

39. Trapezoidal velocity profile
 A trapezoidal velocity profile is shown.
 The area under the curve is the total
distance moved. The slope of the initial
and final ramp is the maximum
acceleration and deceleration.
 The top level of the trapezoid is the
maximum velocity.

40. Trapezoidal velocity profile
 Some controllers allow the user to use
the acceleration and deceleration times
instead of the maximum acceleration and
deceleration. This profile gives a
continuous acceleration, but there will be
a jerk (third order derivative) at the four
sharp corners.

41. /s

43. Example 1

44. Example 2
 The motion in Example 2 is so short the axis never reaches the
maximum velocity.
 This is made obvious by the negative time at maximum velocity.

46. Example 3

47. Example 4
 In some cases the jerk should be minimized.
◦ can be achieved by replacing the acceleration ramps
with a smooth polynomial.
 Two quadratic polynomials will be used for the
acceleration, and another two for the deceleration.

50. MULTI AXIS MOTION
 In a machine with multiple axes the
motions of individual axes must often be
coordinated.
◦ A simple example >robot that needs to move
two joints to reach a new position. We could
extend the motion of the slower joints so
that the motion of each joint would begin and
end together.
 When the individual axis of a machine is
not coordinated this is known as slew
motion

51. SLEW MOTION
 Each of the axes will start moving at the
same time, but finish at separate times.
 Consider the example :A three axis
motion is required from the starting
angles of (40, 80, -40) deg, and must end
at (120, 0, 0) deg. The maximum absolute
accelerations and decelerations are (50,
100, 150)degrees/sec2, and the maximum
velocities are (20, 40, 50) degrees/sec.

53. Example 5
 These are done in vector format for
simplicity. All of the joints reach the
maximum acceleration. The fastest
motion is complete in 1.13s, while the
longest motion takes 4.4s.

54. Example 5

55. Interpolated motion
 In interpolated motion the faster joints
are slowed so that they finish in
coordination with the slowest.
 Essential in devices such as CNC milling
machines. If this did not occur a straight
line cut in the x-y plane would actually be
two straight lines.

56. Interpolated motion
 The slew motion example 5 can be
extended where all joints finish their
motion at 4.4s. This can be done by
accelerating at the maximum acceleration,
but setting a new maximum velocity.
 This is shown in the Example 6 using the
results from the Example 5.

57. Example 6