The NACA and NASA

In the USA, aircraft development as well as aeronautical research languished after 1910. On March 3, 1915, an act of the National Advisory Committee for Aeronautics (NACA) was created by Congress.

The committee immediately noted that a single advisory group of 12 members was not sufficient to breathe life into U.S. Aeronautics. Their insight is apparent in the letter of submittal for the 1^st annual report of the NACA in 1915.

On July 29, 1958, by another act of Congress (Public Law 85-568), the National Aeronautics and Space Administration (NASA) was born. At this same moment, the NACA came to an end. Its programs, people and facilities were instantly transferred to NASA, lock, stock, and barrel. However, NASA was a larger organization than just the old NACA.

Reference: Introduction to flight by John D. Andreson, Jr.

AN APPLICATION OF MOSFET AND PWM TO CONTROL A FAN SPEED

The metal–oxide–semiconductor field-effect transistor (MOSFET) is a transistor used for amplifying or switching electronic signals. In MOSFETs, a voltage on the oxide-insulated gate electrode can induce a conducting channel between the two other contacts called source and drain. The channel can be of N-type or P-type, and is accordingly called an N-MOSFET or a P-MOSFET. It is by far the most common transistor in both digital and analog circuits, though the bipolar junction transistor was at one time much more common.

A MOSFET can be implemented for controlling an fan speed. As known, a trend in automation controlling is to regulate motor, fan, blower speed, etc.

The PWM is preffered method to control motor because has advantage that is no additional heat generated and efficient when it compared to the linear regulating (voltage control) the motor. For this purpose, we use an Arduino boar to prododuce PWM.

Now, lets we do..

Create the circuit: Fan, MOSFET, Arduino board, and Power Supply as bellow.

In the Figure above, it is used Pin10. Input voltage is connected to the power supply; GND  and +V. An fan is connected to drain of MOSFET, then Gate is connected to pin 10 (PWM), and Source is connected to Ground (GND) of arduino. Ground of Arduino is connected to ground of power supply and one of cable of fan is connected to +V of power supply.

The function code that can be used is analogWrite.

Robotics Glossary

Knowledge of robot cannot be seperated base on some of glosarry of robot. Think some meaning, and try to understand how robot work.

acceleration-level - Mathematical formulations working with the change in joint speeds with respect to time. Integrating accelerations twice provides displacements. See position-level and velocity-level.

analytical methods - Purely mathematical methods that do not require iteration.

autonomous - Operating without pre-programmed behaviors and  without supervision from humans.

biomimetic - Mimicking natural biology

closed-form - A problem formulation that does not require iteration for its solution.

conservative motion - A path where both the end-effector and the joints repeatedly follow their same respective trajectories.

degrees of freedom - The number of independent variables in the system. Each joint in a serial robot represents a degree of freedom.

dexterity - A measure of the robot's ability to follow complex paths.

direct search - A method of solving problems numerically using sets of trial solutions to guide a search. The search is direct because it does not explicitly evaluate derivatives.

dynamics - The study of forces that cause motion

dynamic model - A mathematical model describing the motions of the robot and the forces that cause them.

end-effector - The robot's last link. The robot uses the end-effector to accomplish a task. The end-effector may be holding a tool, or the end-effector itself may be a tool. The end-effector is loosely comparable to a human's hand.

end-effector space - A fixed coordinate system referenced to the base of the robot.

equality constraint - A restriction that requires the displacement or motion of the robot to equal a specified value. Equality constraints specify the position and orientation of the robot's end-effector.

error function - The error function assigns a single value that represents the difference between the desired and actual values of one or several dependent variables.

fully constrained robot - A robot with as many independent joints as there are equality constraints on the placement of the end-effector.

inequality constraint - A restriction that limits the value of a dependent or independent variable. Inequality constraints limit the robot's joint travels Ooint limits), joint speeds (speed limits), and torques, (torque limits).

inverse kinematics - The inverse kinematics problem is to find the robot's joint displacements given position and orientation constraints on the robot's end-effector.

iteration - Repeatedly applying a series of operations to progressively advance towards a solution.

Jacobian - The matrix of first-order partial derivatives. For robots, the Jacobian relates the end- effector velocity the joint speeds.

joint space - A coordinate system used to describe the state of the robot in terms of it's joint states. Inverse kinematics may also be thought of as a mapping from end-effector space to joint space.

kinematics - The study of motion without regards to the forces that cause those motions

kinematic influence coefficients - These coefficients describe the total influence the N input joints have on the motion of the robot and allow a direct statement of the complex and coupled nonlinear differential equations controlling the response of the system.

LaGrange multipliers - A mathematical technique for transforming equality constraints into performance criteria, thus expressing a constrained problem as an unconstrained problem.

linearly dependent - A correspondence between quantities or functions that can be described by simply adding, subtracting, or multiplying a scalar.

normalize - Scaling a number of factors so that they will be of similar magnitudes.

numerical methods - Iterative methods of solving problems on a computer. Numerical methods may have an analytical basis or they may involve heuristics. optimization - Calculating the independent variables in a function so as to generate the best function value for a given set of conditions. Optimization usually involves maximizing or minimizing a function.

performance criteria - Measures based on kinematic and dynamic models of the robot useful for evaluating the state of the robot.

plant description - A kinematic and dynamic model of the robot.

position-level - Mathematical formulations working with the joint displacements. See acceleration-level and velocity-level.

pseudoinverse - A simple method of inverting a matrix that is not square. As commonly applied to redundant robots, the pseudoinverse minimizes the two-norm of the joint speeds.

redundancy - More independent variables than constraints.

repeatability - The variability of the end-effector's position and orientation as the robot makes the same moves under the same conditions (load, temp, etc.)

resolved-rate - An extremely simple inverse kinematics method at the velocity-level.

scale - Changing magnitude by linear operation, i.e. multiplying by a scalar.

self-motion - The robot's ability to move it's intermediate links while holding the placement of the end-effector constant.

serial robot - A serial robot is a single chain of joints connected by links.

singularity - A position in the robot's workspace where one or more joints no longer represent independent controlling variables. Commonly used to indicate a position where a particular mathematical formulation fails.

statics - The study of forces that do not cause motion

two-norm - The square root of the sum of the squares. The magnitude of a vector.

velocity-level - Mathematical formulations working with the joint speeds. Integrating the joint speeds once provides the displacements. See acceleration-level and position-level.

workspace - The maximum reach space refers to all of the points the robot can possibly reach. The dexterous workspace is all of the possible points the robot can reach with an arbitrary orientation. The dexterous workspace is usually a subspace of the maximum reach space.

Programmable Logic Controller

Programmable Logic Controller was developed by a group of engineers at General Motors in 1968, when the company were looking for an alternative to replace complex relay control system.

Every system or machine has a controller. Depending on the technology used, controllers can be divided into pneumatic, hydraulic, electrical and electronic controllers.

A digitally operating electronic system, designed for use in an industrial environment, with uses a programmable memory fot the internal storage of user oriented intructions for implementing specific functions such as logic, sequencing, timing, counting and arithmatic, to control, through digital or analog inputs and outputs, various types of machines or processes. Both the PC and its associated peripherals are designed so that they can be easily integrated into an industrial control system and easily used in all their intended functions.

Gas Laws

Air can be considered to be a reasonable approximation to an ideal gas for the range of pressures and temperatures occuring with pneumatics systems and thus obey the ideal gas laws. These are:

1. Boyle's Law

    In an ideal gas in which the mass and temperature remain constant, the volume V veries inversely as the absolute pressure p, i.e.:

                  pV = a constant

2.  Charles's Law

      In an ideal gas in which the mass and the pressure remain constant, the volume V veries directly as  the absolute temperature T, i.e.:

                  V / T = a constant

       Absolute temperatures are measured on the kelvin's scale. To convert from temperatures on the Celcius scale, a reasonable approximation is to add 273. Thus 0^o = 273 ^oK.

 

3.  The Pressure Law

       In an ideal gas in which the mass and volume remain constant, the pressure p veries directly as  the absolute temperature T, i.e.:

                   p / T = a constant

 

        The combination of the three gas laws results in the general gas equation:

                   pV / T = a constant

      
         The constant is for a particular mass of a particular gas and thus the equation can be written for a mass m of gas as:

                  pV = mRT 

           with R, termed the characteristic gas constant, being the value of the constant for 1 kg of the particular ideal gas.  

 

* Reference: Pneumatic and Hydraulic Systems, by W. Bolton

Internal Combustion Engine

Internal Combustion (IC) engine convert chemical energy in a mixture of air and liquid or gaseous fuel into thermal energy in the engine cylinder. This is done in four stroke cycle engines, two stroke cycle engines, or diesel engines.

A complete cycle consisting of four strokes of the piston:
1. intake,
2. compression and combustion,
3. expansion,
4. exhaust

Starting with the piston at the top of the stroke, the fuel-air mixture, previously proportioned and atomized in the a carburetor, is drawn in to the cylinder during the first downward stroke. When the piston nears the top of this stroke, a spark plug fires igniting the gas. The pressure developed during combustion drives the piston downward. At the bottom of the stroke, the exhaust valve opens, and the combustion gasses are rejected during the next upward stroke.

Source: Engineering Problem Solving by Milton C. Shaw

Parameter Performa Engine (Pesawat Terbang)

Ada beberapa parameter performa air-breathing engine yang dapat digunakan dalam desain propulsi. Parameter pertama adalah thrust untuk mendukung proses penerbangan. Thrust adalah gaya dorong yang dihasilkan oleh engine berkaitan dengan meningkatnya momentum dan tekanan, sehingga thrust yang tersedia untuk mendukung penerbangan dapat berupa thrust = drag, thrust > drag (percepatan), atau thrust < drag (perlambatan) pada saat pesawat melakukan penerbangan. Meningkatnya thrust juga dapat dihasilkan dari peningkatan kecepatan gas buang melalui nosel atau dengan penggunaan afterburner.

Specific thrust (ST) merupakan besarnya thrust yang dihasilkan per satuan massa aliran udara atau dengan kata lain besarnya jumlah udara yang dibutuhkan untuk menghasilkan thrust.

Thrust specific fuel consumption (TSFC) didefinisikan sebagai laju jumlah aliran fuel yang dibutuhkan untuk menghasilkan tiap satu satuan thrust. Besar kecilnya TSFC ditunjukkan oleh besar kecilnya fuel yang digunakan untuk menghasilkan thrust pada level yang sama.

Parameter lainnya adalah efisiensi thermal (η_th) yang didefinisikan sebagai perbandingan antara energi panas yang digunakan untuk menghasilkan kerja dengan energi panas yang ditambahkan saat proses pembakaran berlangsung.