Homework Mechatronic Chapter 7,8,9 (Fatahul Arifin)

7/30/2019 Homework Mechatronic Chapter 7,8,9 (Fatahul Arifin)

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Homework Chapter 7,8,9 Page 1

Fatahul Arifin

Student Bridging Course National Kaohsiung University Of Applied Science

Year 2012/2013

7.6 Design a pneumatic valve circuit to give sequence A+, followed by B+ and then

simultaneously followed by A- and B-.

Answer :

To solve this problem we can use the diagram movement of cylinder is like table below:

Cylinder A

Cylinder B

After this table of movement we can draw the figure below.

The equipments are needed:

1. 1 unit compressor

2. 1 unit air-service

3. 2 unit double-acting-cylinder( A and B)

+

-

+

-


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4. 2 unit 5/2-way-control-valvewith pneumatic actuated

5. 4 unit 3/2-way-control-valvewith roller actuated

8.9 Design a mechanical system which can be used to:

a. Operate a sequence of micro switches in a timed sequence.b. Move a tool at a steady rate in one direction and then quickly move it back to the

beginning of the path.

c. Transform a rotation into a linear back-and-forth movement with simple

harmonic motion.

d. Transform a rotation through some angle into a linear displacement.

e. Transform a rotation of a shaft into rotation of another, parallel shaft some distance

away.

f. Transform a rotation of one shaft into rotation of another close shaft which is at right

angles to it.

Anwer

a. Operate a sequence of micro switches in a timed sequence.

The mechanical design for to do this work is camshaft. Camshaft is a shaft that a cam

is fixed firmly, or a cam forms an integral part.

b. Move a tool at a steady rate in one direction and then quickly move it back to the

beginning of the path.

A quick return mechanism such as the one seen below is used where there is a need

to convert rotary motion into reciprocating motion. As the disc rotates the black slide

moves forwards and backwards. Many machines have this type of mechanism and in

the school workshop the best example is the shaping machine.


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c. Transform a rotation into a linear back-and-forth movement with simple

harmonic motion.

The equipment is an eccentric cam to do this work. It is perfectly circular, but the

rotating shaft is off-centre, which affects how it turns. This type of cam produces a

smooth, symmetrical rise and fall motion in the follower, which never pauses to dwell.

d. Transform a rotation through some angle into a linear displacement.

Rack and pinion is a kind of linear actuator that comprises a pair of gears, which

convert rotational motion into linear motion. A circular gear called "the pinion"

engages teeth on a linear "gear" bar called "the rack"; rotational motion applied to the

pinion causes the rack to move, thereby translating the rotational motion of the pinion

into the linear motion of the rack.

e. Transform a rotation of a shaft into rotation of another, parallel shaft some distance

away.

Belt is a loop of flexible material used to link two or more rotating shaft mechanically.

Belts may be used as a source of motion, to spread power efficiently, or to trackrelative movement. Belts are looped over pulleys. In a two pulley system, the belt can

either drive the pulleys in the same direction, or the belt can be crossed, so the

movement of the shafts is reverse.


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f. Transform a rotation of one shaft into rotation of another close shaft which is at right

angles to it.

Bevel gears are used to do this work. Bevel gears are most often mounted on shafts

that are 90 degrees apart, but can be designed to work at other angles as well. The

pitch surface of bevel gears is a cone.

9.4 Suggest possible motors, d.c. or a.c., which can be considered for applications where

(a) cheap, constant torque operation is required,(b) high controlled speeds are required,

(c) low speed are required,

(d) maintenance requirements have to be minimised.

Answer:

a. D.C. shunt wound

A shunt wound motor has a high-resistance field winding connected in parallel with the

armature. It responds to increased load by trying to maintain its speed and this leads to an

increase in armature current. This makes it unsuitable for widely-varying loads, which may

lead to overheating.b. Induction motor with inverter

An induction motor is an asynchronous AC motor where power is transferred to the rotor by

electromagnetic induction, much like transformer action. An induction motor resembles a

rotating transformer, because the stator (stationary part) is essentially the primary side of the

transformer and the rotor (rotating part) is the secondary side.

c. d.c. motor
http://en.wikipedia.org/wiki/Field_winding


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A DC motor is a mechanically commutated electric motor powered from direct current (DC).

The stator is stationary in space by definition and therefore so is its current. The current in the

rotor is switched by the commutator to also be stationary in space. This is how the relative

angle between the stator and rotor magnetic flux is maintained near 90 degrees, which

generates the maximum torque.

d. a.c. motorAn AC motor is an electric motor driven by an alternating current (AC). It commonly consists of

two basic parts, an outside stationary stator having coils supplied with alternating current to

produce a rotating magnetic field, and an inside rotor attached to the output shaft that is

given a torque by the rotating field.

9.5 Explain the principle of the brushless d.c. permanentmagnet motor

Answer :

The brushless DC motor is the combination of a permanent excited synchronous motor and a

frequency inverter. The inverter has to replace the commutator of a conventional DC motor.

Its armature winding corresponds to a three phase winding in delta connection. The

commutator acts like a three phase frequency converter. Stator (excitation) and rotor

(armature) change places.

The commutation of a brushless DC motor depends on the position of the rotor. The angle

between the magneto-motive forces of stator and rotor is fixed to 90o

(el.), so the motor

produces maximum torque and needs low reactive current - it might be useful to advance

commutation by few degrees to compensate the effects of the stray inductance and minimize

reactive current. Speed can only be controlled by the the motor voltage. The motor behaves

like a DC motor. Unlike the synchronous motor there are no problems with instability at any

speed. Because of the PWM frequency inverter, variation of the motor voltage can be

achieved easily by changing the duty cycle of the pulse width modulation. Suitable PWM

techniques allow regenerative breaking, which increases dynamic and efficiency of the drive.

9.6 Explain the principles of operation of the variable reluctance stepper motor.

Answer:

Variable reluctance stepper is kind of the stepper motor. With this form the rotor is made

of soft steel and is cylindrical with four poles, i.e. fewer poles than on the stator. Whenan opposite pair of windings has current switched to them, a magnetic field is produced

with lines of force which pass from the stator poles through the nearest set of poles on

the rotor. Since lines of force can be considered to be rather like elastic thread and always

trying to shorten themselves, the rotor will move until the rotor and stator poles line up.

This is termed the position of minimum reluctance.

This form of stepper generally gives step angles of 7.5o

or 15o.
http://en.wikipedia.org/wiki/Electric_motorhttp://en.wikipedia.org/wiki/Alternating_currenthttp://en.wikipedia.org/wiki/Rotor_%28electric%29http://en.wikipedia.org/wiki/Statorhttp://en.wikipedia.org/wiki/Alternating_currenthttp://en.wikipedia.org/wiki/Electric_motorhttp://en.wikipedia.org/wiki/Commutator_%28electric%29http://en.wikipedia.org/wiki/Direct_currenthttp://en.wikipedia.org/wiki/Electric_motor

Homework Mechatronic Chapter 7,8,9 (Fatahul Arifin)

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