201_3

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Range of signed integer n-bit

-2^(n-1) to 2^(n-1) - 1

Range of unsigned n-bit integer

0 to 2^n - 1

Structure/body of a robot

A frame or chassis to hold components together

Structure/body

A frame or chassis to the other components together

Analog vs. Digital signal

Analog is continuous in time and values, while digital is discrete

Conversion of Analog inputs

Analog signal must be converted to digital for input and input must be converted to analog for output

Which number systems are suitable for computers

Binary and hexadecimal (computers with large memory addresses)

Benefit of twos complement

Can use existing binary adders without any modifications

Arithmetic and logic unit (ALU) of CPU purpose

Data processing (e.g. adding numbers)

Computer controllers

Decides sequence of actions to take based on sensor movements to achieve objective

Computer controller(s)

Decides the sequence of actions to take (i.e. command the actuators) based on sensor measurements to achieve its objective. Can be a cheap microcontroller or expensive processing system. Depends on processing power required.

Control unit of CPU purpose

Determines timing and sequence of operations

Actuators

Devices that affect the environment

Actuators

Devices that manipulate/affect their environment. Examples: motors, hydraulic or pneumatic cylinders, etc. devices that are able to manipulate the plant's inputs to influence the plant's outputs

Sensors

Devices that measure or detect certain attributes of the environment or the robot itself. Examples: buttons, limit switches, shaft encoders, temperature, light, vision, magnetic, lasers, sonar, etc. measure outputs/signals from the plant

Sensors

Devices that measure/detect things about environment or robot

Find twos complement of -5 in 4 bits

Doko

CPU of microprocessor purpose

Executes program instructions

Using a transistor to control the motor's rotational speed

Feed a high-frequency square wave to the base. Increase the duty cycle for faster speed, decrease for slower. If the frequency is too low, motor keeps starting and stopping or at least changing its speed.

What happens if R is too large in a zener regulator?

For the zener diode t keep voltage constant, it must have current flowing through itself and operate in the breakdown region. If R is too large, when the load draws too much current, V(R) will become too large and V(zener) will drop below the required voltage and I(zener) will be zero.

How is a micro controller programmed

High level language (C) is converted to machine code by compiler or low level language (assembly language) is converted to machine code by assembler program

Advantages of Field Effect Transistors

Higher input impedance: generally we can take the gate current for a FET as zero. Lower power requirement Simple manufacturing process Higher miniaturisation possible

Draw the elements of a Mechatronics system

ILILILILILI

Offset Voltage

If both inputs of an op amp are joined together and grounded, the output voltage should certainly be zero. However, for a real op amp, the output voltage is likely to be very different from zero. It may even be at the positive of negative saturation level.

Clipping

If the input signal is so large that the output voltage tries to exceed these limitations, then the output voltage will be clipped. It will also occur whenever the output tries to exceed the maximum possible output current.

The ideal op amp

Infinite open-loop game. Infinite input resistance zero output resistance infinite bandwidth

Pseudocode

Informal (syntax-wise) way of describing the procedure/algorithm that is easy to read and understand.

Registers purpose in CPU

Internal memory locations to store temporary results while ALU is processing

armDown(float pctPwr);

Lowers the arm to its lowest position (until it hits the lower limit switch) at the given percentage power level.

What is a robot

Machine that can sense environment, act based on senses to do a job and js autonomous

Micro controller vs microprocessor (memory and integrated circuits)

Microprocessor: memory is on separate IC to I/O components. - high processing power and memory e.g. (PC) Micro controller: all on one IC - lower processing power and memory e.g. appliances

More bits means...

More precise and more overall memory locations

Advantages for transistors as switches

Much faster switching. Less power consumption Less current needed to initiate switching Smaller size than relays

ROM Memory (Read Only Memory)

Non volatile memory. Can be read but not written to during execution.

Important factors in choosing a micro controller

Number of ports required, interfaces (e.g. PWM) required, memory requirements, processing speed, number of interrupts if needed

How can the assumption of infinite bandwidth be sensibly made?

Op amps are used with negative-feedback loops. These loops reduce the gain and increase the bandwidth by the same factor. The product of gain and roll-off frequency remains constant.

Uses of dedicated ports

PWM, aerial communication, interrupts etc.

Buses from CPU

Paths which transfer digits signals, could be tracks on circuit board or wires

SRAM (Static RAM)

RAM that does not need to be refreshed as long as power is applied. Faster but more expensive than DRAM.

DRAM (Dynamic RAM)

RAM using capacitors, data must be refreshed due to charge leakage

EEPROM (Electrically Erasable Programmable Read-Only Memory)

ROM that can be electrically erased by high voltage and rewritten repeatedly.

EPROM (erasable programmable read-only memory)

ROM that can be programmed more than once, contents are erased using UV light

PROM memory (programmable ROM)

ROM that can be programmed once by user

armUp(float pctPwr);

Raises the arm to its highest position (until it hits the upper limit switch) at the given percentage power level.

ClearTimer(timerName);

Resets the named timer (T1 to T4) to zero

Drawback of twos complement

Result is super dependent on number of bits

Overflow

Result of addition returns number outside range

time1[timerName];

Returns the specified timer count (integer) in milliseconds units

Sonar

Sends 40kHz ultrasonic pulses and measures the time it takes for the reflected waves to arrive to calculate the distance. Assumes a constant speed of sound. Some surfaces may absorb these ultrasonic waves. Has an apporx. 30° beam angle.

Draw a microprocessor system

Shanna

Use of Digital input-output ports

Some digital ports can be configured to be input or output, some can be used for communication and pulse width modulation

Power source

Source of energy for active sensors and actuators and computer controller

StartTask(taskName);

Starts running the designated task

StopAllTasks();

Stops all running tasks including main()

StopTask (taskName);

Stops executing the designated task

5 parts of a robot

Structure, sensors, actuators, computer controllers, power source

Imperfections in the linear range of operations

The ideal op amp has infinite input impedance, zero output impedance, infinite open-circuit gain, and infinite bandwidth. Real op amps don't quite achieve this level of perfection.

Non-inverting amplifier

The input current is zero, the input impedance is infinite. The output impedance is zero since the output voltage Vo does not depend on the load resistance. An ideal amplifier. Vo = ((R1 + R2)/R1)Vi

Slew Rate

The maximum rate at which output voltage can change. If the output voltage tries to exceed this value, then the required rate-of-change of voltage will be too high and the resultant waveform will not be sinusoidal. Instead, it will be at least partially triangular as the voltage changes at its maximum possible rate.

Power source

The source of energy to power the active sensors and actuators as well as the computer controller. Usually electrical power stored in a battery for mobility.

Amplification for Common-Emitter Amplifier

The varying signal V(s) makes V(BE) vary too, producing corresponding changes in i(c) and, therefore, V(c). The changes in V(C) and V(o) are bigger than those in V(s), hence amplification.

Flow Charts

Used to visually describe the program flow. Do NOT write code in flowchart symbols

Cutoff Region

V(BE) < 0.7 V and i(B) = i(E) = 0

Saturated Region

V(BE) = 0.7 V and V(CE) = 0.2 V

Active Region

V(BE) = 0.7 V and V(CE) > 0.2 V

Difference Amplifier Output Voltage

Vo = (Rb/Ra)(V2-V1)

Integrator circuit

Vo = -(1/RC)int(0 -> t) Vi dt

differentiator circuit

Vo = -RC dVi/dt

RAM (Random Access Memory)

Volatile memory that requires power to hold data.

Flyback/Freewheeling Diode

When the switch is closed, current flows through the motor. When the switch is opened, the current is required to reduce to zero, ideally instantaneously. Provides a way for the current to flow after the voltage is dropped instantaneously. However, the motor contains some inductance, so any very rapid change in current produces a very large voltage which could damage the switch. The diode in the circuit enables the motor current to keep flowing after the switch is opened, so the current can reduce more slowly, and no large voltage spike is produced.

Forward Bias ideal Diode

a voltage is applied across the diode so as to drive conventional current from anode to cathode. Under these conditions the diode is a conductor, and has zero resistance

Monostable Mode for 555 timer IC

an external trigger causes the 555 timer to output a single pulse of adjustable duration. Uses include creating time delays, producing bounce-free switches, touch switches, etc.

Diode

are electronic devices which allow current to flow in one direction only.

Zener Diode

are specifically designed to regulate voltage; unlike most diodes, they are intended to operate in the breakdown region.

Transistor

are three-terminal semiconductor devices: a voltage across one pair of the terminals can be used to control the flow of current through another pair. Their main uses are to amplify of switch electronic signals.

Light Sensors

are used to detect ground colour changes. Can be utilised to follow lines or detect borders. The returned reading for the same colour can be: different for each sensor, affected by external light sources, or varying across a range of values (i.e. not constant).

Timers

are used to measure elapsed time of certain events. They run in the background (wait commands pause the program). Timers use signed 32-bit integers. Tick every 1 millisecond. Start counting when the program starts. Should be reset before overflowing. Will reach 2,147,483,647 ms before overflowing

Transistors as switches

by making use of the cutoff and saturation states

Arm Encoder

can be used to determine the absolute position of the arm. First you must move the arm to one of the known limits (upper or lower) which we know/can measure the real arm angle. Once the arm is there, reset the encoders once. Each robot will have it's unique values for the minimum and maximum arm positions.

Wheel Encoders

can be used to work out the linear distance travelled or the angle turned by the robot assuming no slip.

Summer circuits

circuit which produces a weighted sum of the input voltages. Vo = -(Rf/Ra)Va - (Rf/Rb)Vb

Controller

commands the actuators to manipulate the plant output based on sensor measurements to achieve a desired output.

Operational Amplifier

considered by many to be the most useful single device in analogue electronics. Their characteristics are very often close to ideal. Originally, however, they were used in analogue computers to carry out operations such as addition and differentiation, hence the name.

Optical Shaft Encoders

contains a slotted wheel and a light sensor. As the shaft rotates, the light sensor inside generates a digital signal that correspond to counts per revolution

What happens if R is too small in a zener regulator?

current will be large and flow into the zener diode, thus damaging the diode. More current will lead to waste of energy and heat produced could be dangerous.

Tasks

have to be defined before they are started. Like functions, they have prototypes and their own scope. Unlike functions, they do not have inputs or return arguments

Coupling Capacitors in the Common-Emitter Amplifier

ideally allow AC signals to pass, while blocking DC

Summing point constraint

input currents are zero and the input voltages are equal. Other terms are virtual short circuit and virtual earth principle.

Filter

is a circuit designed to pass inputs in a certain frequency range while blocking other inputs.

Robot

is a system that: Physically exists in the real world; can sense its environment or part of it; can act based sensor measurements to achieve and objective; and is autonomous (not remotely controlled by an operator)

Pulse-width Modulation (PWM)

provides a mich more efficient way to control power delivery than more-traditional approaches, such as a variable resistor in series.

Function

section of code that: is named; is independent; performs a specific task; and can return a value to the calling program. It doesn't execute unless it is called by the main program.

Instrumentation Amplifier

superior version of the difference amplifier where the Vo = (Rb/Ra)(1 + (R2/R1))(V2 - V1)

Astable Mode for 555 timer IC

the 555 timer outputs a periodic waveform of adjustable pulse width and frequency. Uses include keeping time in a circuit, making an analogue synthesiser, or simply making lights flash.

Bistable Mode for 555 timer IC

the 555 timer's output toggles between high and low states in response to the state of its two inputs.

Offset-voltage nulling

the effect of voltage on output voltage can be reduced by balancing the op amp using a potentiometer, and this potentiometer is adjusted until zero input gives zero output.

The inverting amplifier

the output voltage is out of phase with the input voltage. Vo = -(R2/R1)Vi

Plant

the system we are trying to control

Reverse Bias ideal Diode

the voltage is connected in the opposite sense, as if to drive conventional current from cathode to anode. The diode now behaves as an open-circuit, so no current flows.

V = 0.7 V

usual assumption for conducting silicon diodes


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