INTRODUCTION TO MOTION
COMPONENTS OF MOTION
MOTION CONTROL VARIABLES:
POSITION, ANGLE, SPEED
APPLICATION OF MOTION
3. INTRODUCTION TO MOTION
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
Widely used in the packaging, printing,
textile, semiconductor production and
4. INTRODUCTION TO MOTION
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
5. Common control functions:
Position (point-to-point) control:
Several methods for computing a motion
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
◦ 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.
refers to the control of several
operations so that they all occur in a
◦ 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.
Sequencing generally becomes too
complicated to be handled mechanically in
industrial equipment such as conveyor
◦ 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
11. SPEED CONTROL
Speed can be controlled either
mechanically or, in the case of electric
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
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
14. POINT TO POINT CONTROL
◦ in x-y tables and in machining, where a tool
moves in a straight line while it touches a
work piece along one axis.
16. MOTION CONTROL SYSTEM
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
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
Motor – Motors turn electrical energy
into mechanical energy and produce the
torque required to move to the desired
Mechanical elements – Motors are
designed to provide torque to some
mechanics. These include linear slides,
robotic arms, and special actuators.
18. MOTION CONTROL SYSTEM
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
19. APPLICATION SOFTWARE
Divided into three categories:
◦ Application development environment (ADE)
One of the first things to do is configure
your system for all your motion control
and other hardware.
Prototyping and developing your
In this phase, you create your motion
control profiles and test them on your
system to make sure they are what you
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
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
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
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
The typical motion controller calculates
the motion profile trajectory segments
based on the parameter values you
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,
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
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
The most common position feedback
device is the quadrature encoder, which
gives positions relative to the starting
34. FEEDBACK DEVICES
Other feedback devices:
◦ potentiometers that give analogue position
◦ tachometers that provide velocity feedback
◦ absolute encoders for absolute position
◦ resolvers that also give absolute position
35. MOTION IO
Protection from damaging the system.
Includes limit switches, home switches,
position triggers, and position capture
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
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
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
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
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
◦ 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
When the individual axis of a machine is
not coordinated this is known as slew
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.
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.