Landstown High School Governors STEM & Technology Academy

Advanced RoboticsChapter 5- Electromechanical Systems

Dr. Barger

• Originally, all manufacturing operations were manually controlled using:

• Gas-filled tubes, • magnetic contacts,• and electrical switchgears,

• With the development of electronics, advances to control devices have occurred,

• Electromechancial,• Optoelectronic, • hydraulic,• Pneumatic,

History and Background

Automated Systems and Subsystems Almost all manufactured products are produced

using some type of electromechanical system. Definitions:

A “System” is a combination of components that work together to form a “unit”.

A “Subsystem” is a component that comprises, or make up, the complete robot.

When “Subsystems” are combined the result is defined as a “synthesized system”.

Examples of subsystems: Electrical power, hydraulic or pneumatic systems,

optoelectronic systems, mechanical systems.

Automated Systems and Subsystems Even though each “System” is unique there

are some basic subsystems common to all automated systems: Energy source, Transmission path, Control, Load, Indicators.

Mechanical Systems A mechancial system produces some form of

mechanical motion, Three basic types of motion are usally used:

Rotary motion (motors), Linear motion (relays, actuators, and cylinders), Reciprocation ( motors and cylinders that usally move

vertically), The energy source for these systems is usally

electrical or fluid power (hydraulic or pneumatic) Control of these systems is accomplished by

changing, Pressure, Direction, Force, or Speed.

Electrical Systems There are four basic types of electrical

systems used in robots, Sensing, Timing, Control, or Rotary motion (motors).

Sensing Systems A sensing system signals a response to a

particular form of energy, Incandescent lamps, Flames, Glow lamps, Electric arcs, Laser light, Other types could include:

Sound, Pressure, Flow and Magnetic,

Conveyor Sensing System

LS 5-1

Timing Systems Timing Systems turn a device on or off, at a

specific time or in step with an operating sequence. Types include:

Delay timing, Provide a lapse in time before the load device

becomes energized. Interval timing,

Is used after a load has been energized and operate using specfied time intervals.

Cycle timing, Is typically more complex and may include both

interval and delay timing systems.

Control Systems Control of an automated manufacturing

system (robot) is carried out by human input, or automatically due to some type of physical change. How complex these changes are is determined by

how complex the operation is that the robot is trying to perform.

Open-loop control systems are the most basic and are using found in two varations: Full control,

Simply turns a system on or off, Partial control,

Partial control alters the system operation, rather than turning it on or off,

Closed-loop System

LS 5-2

In automatic control, interaction between the control unit and the controlled load must occur.

Closed-loop System withAutomatic Adjustment

LS 5-3

• In a “closed loop system” with automatic control this interaction is called ‘feedback”,

• Feedback from the controlled load is sent to a “comparator”,• A comparator compares the feedback to a reference signal or

standard to determine what action should occur next.

Control Systems Digital Control Systems

Digital (numeric) instructions are supplied by variations in pressure, temperature, or electric current.

These instructions change into a series of on/off electrical signals.

These electrical signals are processed by a computer and directed to the appropriate subsystem.

Control Systems Rotary Motion Systems

Electric motors convert electrial energy to mechanical motion in the form of rotary motion.

The rotary motion produces “torque”, The amount of torque produced is determined by the

size of rotary motion (motor),

DC Motor Parts

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DC powered motors are used when speed control is a critical factor. Listed below are the basic parts of a dc motor:

Servomotor

LS 5-9(Adept)

• is used to achieve a precise degree of rotary motion,• Contains no brushes, commutators, or slip rings,• Is comprised of a rotor and stator assembly,

Servo System

LS 5-8

• Servo Systems are machines that change the position of speed of a mechanical object.

• Positioning applications include,• Numerical control machinery,• Process control machinery,• Robotic systems,

DC Stepping Motor

LS 5-11(Superior Electric Co.)

Nearly all high-power servomechanisms use dc stepping motors,Dc stepping motors are used to change electrical pulses into rotary motion,They are more efficient than the servomotor,They develop more torque than the servomotor,

Overload Protection End effector control on industrial robots must

have some protection against overload. Breakaway devices

“Mechanical fuses” are pins or tubes that break or buckle under extreme stress (torque),

“Detents” are two or more elements held in position by spring-loaded mechanisms that move from their original position when placed under stress, and remove or disconnect the power source,

“Pre-loaded springs” may also be used to prevent overload by releasing the spring and the end effector breaks away from the work area.