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4.1.1.3
Hybrid Stepper Motor
The term hybrid is derived from the fact that motor is operated with the combined
principles of the permanent magnet and variable reluctance motors in order to
achieve small step length and high torque in spite of motor size. Standard HSM
have 50 rotor teeth and rotate at 1.8 degree per step. Figures 4.4 & 4.5 show a
cross section and cut view of two phase HSM. The windings are placed on the
stator poles and a PM is mounted on the rotor. The important feature of the HSM
is its rotor structure. A cylindrical or disk-shaped magnet lies in the rotor core.
Stator and rotor end-caps are toothed. The coil in pole 1 and pole 3 is connected
in series consisting of phase A and poles 2 and 4 are for phase B. If
stator phase
A is excited pole 1 acquires north polarity while pole 2 acquires south pole while
pole 3 aligns with the rotor's north pole.
Figure 4.4 Cross-section of HSMMicrocontroller:
Microcontroller:
A microcontroller often serves as the “brain” of a mechatronic system.
Like a mini, self-contained computer, it can be programmed to interact with both
the hardware of the system and the user. Even the most basic microcontroller can
perform simple math operations, control digital outputs,
and monitor digital
inputs. As the computer industry has evolved, so has the technology associated
with microcontrollers? Newer microcontrollers are much faster, have more
memory, and have a host of input and output features that dwarf the ability of
40
earlier models. Most modern controllers have analog-to-digital converters, high-
speed timers and counters; interrupt capabilities, outputs that can be pulse-width
modulated, serial communication ports, etc. [14].
A microcontroller is a self-contained
system with peripherals, memory
and a processor that can be used as an embedded system. Most programmable
microcontrollers that are used today are embedded in other consumer products
or machinery including phones,
peripherals, automobiles and household
appliances for computer systems. Due to that, another name for a microcontroller
is "embedded controller." Some embedded systems are more sophisticated, while
others have minimal requirements for memory and programming length and a
low software complexity. Input and output devices include solenoids, LCD
displays, relays, switches and sensors for data like humidity, temperature or light
level, amongst others.
A microcontroller
is a highly integrated chip, which includes on single
chip, all or most of the parts needed for a controller. The microcontroller
typically includes CPU (Central Processing Unit), RAM (Random
Access
Memory), EPROM/PROM/ROM (Erasable Programmable Read Only
Memory), I/O (input/output) – serial and parallel, timers, interrupt controller. For
example, Intel 8051 is 8-bit microcontroller and Intel 8096 is 16-bit
microcontroller.
By only including the features specific to the task (control), cost is
relatively low. A typical microcontroller has bit manipulation instructions, easy
and direct access to I/O (input/output), and quick
and efficient interrupt
processing. Figure 4.3 shows the block diagram of a typical microcontroller.
Microcontroller includes RAM, ROM, serial and parallel interface, timer,
interrupt schedule circuitry (in addition to CPU) in a single chip