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发表于 2016-12-10 18:21:12 | 显示全部楼层 |阅读模式
本帖最后由 3K留德 于 2016-12-20 03:00 编辑



1.      ABS System
An anti-lock braking system is an automobile safety system that allowsthe wheels on a motor vehicle to maintain tractive contact with the roadsurface according to driver inputs while braking, preventing the wheels fromlocking up (ceasing rotation) and avoiding uncontrolled skidding. It is anautomated system that uses the principles of threshold braking and cadencebraking which were practiced by skillful drivers with previous generationbraking systems. It does this at a much faster rate and with better controlthan many drivers could manage.

There are four main components of ABS: wheel speed sensors, valves, apump, and a controller.
Speed sensors
A speed sensor is used to determine the acceleration or deceleration ofthe wheel. These sensors use a magnet and a Hall effect sensor, or a toothedwheel and an electromagnetic coil to generate a signal. The rotation of thewheel or differential induces a magnetic field around the sensor. Thefluctuations of this magnetic field generate a voltage in the sensor. Since thevoltage induced in the sensor is a result of the rotating wheel, this sensorcan become inaccurate at slow speeds. The slower rotation of the wheel cancause inaccurate fluctuations in the magnetic field and thus cause inaccuratereadings to the controller.
There is a valve in the brake line of each brake controlled by the ABS.On some systems, the valve has three positions:
In position one, the valve is open; pressure from the master cylinder ispassed right through to the brake.
In position two, the valve blocks the line, isolating that brake fromthe master cylinder. This prevents the pressure from rising further should thedriver push the brake pedal harder.
In position three, the valve releases some of the pressure from thebrake.
The majority of problems with the valve system occur due to cloggedvalves. When a valve is clogged it is unable to open, close, or changeposition. An inoperable valve will prevent the system from modulating thevalves and controlling pressure supplied to the brakes.
The pump in the ABS is used to restore the pressure to the hydraulicbrakes after the valves have released it. A signal from the controller willrelease the valve at the detection of wheel slip. After a valve release the pressuresupplied from the user, the pump is used to restore a desired amount ofpressure to the braking system. The controller will modulate the pumps statusin order to provide the desired amount of pressure and reduce slipping.
The controller is an ECU type unit in the car which receives informationfrom each individual wheel speed sensor, in turn if a wheel loses traction thesignal is sent to the controller, the controller will then limit the brakeforce (EBD) and activate the ABS modulator which actuates the braking valves onand off.

Wheel slip: In vehicle dynamics, slip is therelative motion between a tire and the road surface it is moving on. This slipcan be generated either by the tire's rotational speed being greater or lessthan the free-rolling speed (usually described as percent slip), or by thetire's plane of rotation being at an angle to its direction of motion.
The longitudinal slip is generally given as a percentage of thedifference between the surface speed of the wheel compared to the speed betweenaxis and road surface, as:

where ω is thelateral component of the rotational speed of the wheel, r is wheel radius at the point of contact and v is vehicle speed. A positive slip indicates that the wheels arespinning; negative slip indicates that they are skidding.

2.       Ignition System
An ignition system generates a spark or heats an electrode to a hightemperature to ignite a fuel-air mixture in spark ignition internal combustionengines oil-fired and gas-fired boilers, rocket engines, etc.

Modern Electronic Ignition Modules: For the most part, there are 2 typesof ignition systems in use today (or variations of them): TCI (Inductionignition) or CDI (Capacitive Discharge Ignition). Both systems use a sensor totrigger a transistor switch (which has replaced the points).

Induction ignition: This is called an induction systembecause the coil is used as a power storage (an "inductor") devicefor the spark. Remember, the coil is powered up, stores near 30,000 volts, andunleashes it when the coil collapses (power supply cutoff). A feature ofinduction ignition is the slightly longer spark duration while the coilcollapses. This is an advantage when starting and for igniting lean/highcompression mixtures at high RPM. These type of systems require coils
meant for "induction" ignitions (they have a higher resistancetypically than CDI coils). Induction ignitions are simpler in design (cheaper)and used often on less sophisticated motors (lawn, motorcycle, etc...)

Capacitive Discharge Ignition: CDI ignition is most widely used today on automotiveand marine engines. A CDI module has "capacitor" storage of its ownand sends a short high voltage (about 250+ volts) pulse through the coil. Thecoil now acts more like a transformer (instead of a storage inductor) andmultiplies this voltage even higher. Modern CDI coils step up the voltage about100:1. So, a typical 250v
CDI module output is stepped up to over 25,000v output from the coil.The CDI output voltage of course can be higher. So you'll see CDI systemsclaiming coil output capability over 40,000- 60,000 volts!!? As you will seethis is not exactly what happens at the plug but for math purposes it worksout. The huge advantage of CDI is the higher coil output and "hotter"spark. The spark duration is much shorter (about 10-12 microseconds) andaccurate. This is better at high RPM but can be a problem for both startingand/or lean mixture/high compression situations. CDI systems can and do use"low" resistance coils.

Advantages of CDI:
i. Improved cooling and heat sinks;
ii. Epoxy-rubber encasing componentsso they can't get wet;
iii. Heavier duty components that canwithstand the heat, vibration, and "duty cycles".

3.       Airbag
An airbag is a type of vehicle safety device and is an occupantrestraint system. The airbag module is designed to inflate extremely rapidlythen quickly deflate during a collision or impact with a surface or a rapidsudden deceleration. It consists of the airbag cushion, a flexible fabric bag,inflation module and impact sensor. The purpose of the airbag is to provide theoccupants a soft cushioning and restraint during a crash event to prevent anyimpact or impact-caused injuries between the flailing occupant and the interiorof the vehicle.

During a crash event, the vehicle's crash sensor(s) provide crucialinformation to the airbag electronic controller unit (ECU), including collisiontype, angle and severity of impact. Using this information, the airbagelectronic controller unit's crash algorithm determines if the crash eventmeets the criteria for deployment and triggers various firing circuits todeploy one or more airbag modules within the vehicle. Working as a supplementalrestraint system to the vehicle's seat-belt systems, airbag module deploymentsare triggered through a pyrotechnic process that is designed to be used once.Newer side-impact airbag modules consist of compressed air cylinders that aretriggered in the event of a side impact vehicle impact.
 楼主| 发表于 2016-12-11 21:27:52 | 显示全部楼层
本帖最后由 3K留德 于 2016-12-11 21:29 编辑


1.Open loop and closed loop control
Open loop: systems in which the output quantity has no effect upon theinput to the control process are called open-loop control systems, and thatopen-loop systems are just that, open ended non-feedback systems.

Closed loop:A Closed-loop Control System, also knownas a feedback control system is a control system which usesthe concept of an open loop system as its forward path but has one or morefeedback loops (hence its name) or paths between  its output and its input. The reference to“feedback”, simply means that some portion of the output is returned “back” tothe input to form part of the systems excitation.

Application of closed loop control:Closed-loop systems aredesigned to automatically achieve and maintain the desired output condition bycomparing it with the actual condition. It does this by generating an errorsignal which is the difference between the output and the reference input. Inother words, a “closed-loop system” is a fully automatic control system inwhich its control action being dependent on the output in some way.

So for example, consider our electric clothes. Suppose we used a sensoror transducer (input device) to continually monitor the temperature or drynessof the clothes and feed a signal relating to the dryness back to the controlleras shown below.

This sensor would monitor the actual dryness of the clothes and compare it with (orsubtract it from) the input reference. The error signal (error = requireddryness – actual dryness) is amplified by the controller, and the controlleroutput makes the necessary correction to the heating system to reduce anyerror. For example if the clothes are too wet the controller may increase thetemperature or drying time. Likewise, if the clothes are nearly dry it mayreduce the temperature or stop the process so as not to overheat or burn theclothes, etc.
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发表于 2016-12-12 16:48:35 | 显示全部楼层
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 楼主| 发表于 2016-12-14 04:16:15 | 显示全部楼层
2.System dynamics – step response
The step response of a system in a given initial state consists of thetime evolution of its outputs when its control inputs are step functions.
Step response is the time behavior of the outputs of a general systemwhen its inputs change from zero to one in a very short time.
From a practical standpoint, knowing how the system responds to a suddeninput is important because large and possibly fast deviations from the longterm steady state may have extreme effects on the component itself and on otherportions of the overall system dependent on this component. In addition, theoverall system cannot act until the component's output settles down to somevicinity of its final state, delaying the overall system response. Formally,knowing the step response of a dynamical system gives information on thestability of such a system, and on its ability to reach one stationary statewhen starting from another.

Overshoot: In control theory, overshoot refers to an output exceeding itsfinal, steady-state value. For a step input, the percentage overshoot is themaximum value minus the step value divided by the step value. In the case ofthe unit step, the overshoot is just the maximum value of the step responseminus one.
Rising time: rise time is the time taken by a signal to change from aspecified low value (10% of final value) to a specified high value (90% offinal value).
Setting time: the time required for the response curve to reach and staywithin a range of certain percentage (usually 5% or 2%) of the final value.
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发表于 2016-12-16 18:06:23 | 显示全部楼层
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 楼主| 发表于 2016-12-17 04:54:47 | 显示全部楼层
Nitro155 发表于 2016-12-16 18:06

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 楼主| 发表于 2016-12-17 05:03:22 | 显示全部楼层
3.PID Controller
A proportional–integral–derivative controller (PID controller) is a controlloop feedback mechanism (controller) commonly used in industrial controlsystems. A PID controller continuously calculates an error value e(t) as thedifference between a desired setpoint and a measured process variable andapplies a correction based on proportional, integral, and derivative terms,(sometimes denoted P, I, and D respectively) which give their name to thecontroller type.

A PID controller continuously calculates an error value e(t) as the differencebetween a desired setpoint and a measured process variable and applies acorrection based on proportional, integral, and derivative terms. Thecontroller attempts to minimize the error over time by adjustment of a controlvariable u(t), such as the position of a control valve, a damper, or the powersupplied to a heating element, to a new value determined by a weighted sum:

Where Kp, Ki and Kd are all non-negative, denote the coefficients forthe proportional, integral, and derivative terms, respectively (sometimesdenoted P, I, and D).

In this model:
P accounts for present values of the error. For example, if the error islarge and positive, the control output will also be large and positive.
I accounts for past values of the error. For example, if the currentoutput is not sufficiently strong, the integral of the error will accumulateover time, and the controller will respond by applying a stronger action.
D accounts for possible future trends of the error, based on its currentrate of change.
For example, Kp increase and the corresponding response.

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发表于 2016-12-19 14:05:07 | 显示全部楼层
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 楼主| 发表于 2016-12-20 02:56:47 | 显示全部楼层
本帖最后由 3K留德 于 2016-12-20 02:58 编辑


1.Degrees of freedom

the degree of freedom (DOF) of a mechanical system is the number of independent parameters that define its configuration.

(2)The number of DOF in space and plane
Degrees of Freedom of a Rigid Body in Space:An unrestrained rigid body in space has six degrees of freedom: three translating motions along the x,y and z axes and three rotary motions around the x,y and z axes respectively.

In a two dimensional plane, there are 3 DOF.
The bar can be translated along the x axis, translated along the y axis,and rotated about its centroid.

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 楼主| 发表于 2016-12-24 03:52:22 | 显示全部楼层
2. Four-Link Mechanism:

Planar four-bar linkages are constructed from four links connected in a loop by four one degree of freedom joints. A joint may be either a revolute, that is a hinged joint, denoted by R, or a prismatic, as sliding joint, denoted by P.

lthe length-condition: the sum of the shortest and the longest rod is smaller or equal to the sum of another two rods.
lthe condition of full rotation pair: when one of the components, which constitute the rotation pair, is the shortest.
lthree types of four-link mechanism
a).double crank mechanism: when the shortest rod is used as rack
b).crank and rocker mechanism: when one of rod, which is besides the shortest one, is used as rack
c).double rocker mechanism: when the rod opposite to the shortest one is used as rack or the mechanism doesn’t satisfy the length-condition
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 楼主| 发表于 2016-12-26 05:03:36 | 显示全部楼层

(1) material of gear
steel: suitable for high speed and heavy load;
cast iron: suitable for low speed and light load.

(2) Arts of Gear:

(3) principle parameter:

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 楼主| 发表于 2016-12-30 00:49:11 | 显示全部楼层
本帖最后由 3K留德 于 2016-12-30 01:33 编辑

【Mechanical Manufacturing Technology】机械制造基础

Turning is a machining process in which a cutting tool describes a helical toolpath by moving more or less linearly while the workpiece rotates.
lAlmost all solid metals, plastics and composites can be machined by conventional machining.
lMachining can produce dimensions to tolerances of less than 0.025mm.
lSurface finishes of better than 0.4μm can be produced by machining processes.

2.Turning parameters:

h: Depth of cut  
Feed f: distance traveled by the tool per one revolution of the work. (mm/rev)
Depth of cut ap: the penetration of the cutting tool below the original surface of the work
The cutting Speed v: the tangential speed

3.meterials of turning tools
Carbon tool steels: Plain carbon steel tools, containing about 0.9% carbon and about 1% manganese, hardened to about 62 Rc, are widely used for woodworking and they can be used in a router to machine aluminium sheet up to about 3mm thick.

High speed steel(HSS):The tungsten (T series) were developed first and typically contain 12 - 18% tungsten, plus about 4% chromium and 1 - 5% vanadium. Most grades contain about 0.5% molybdenum and most grades contain 4 - 12% cobalt.Hardness up to about HRC 67.

Cemented carbide:It is offered in several "grades" containing different proportions of tungsten carbide and binder (usually cobalt). High resistance to abrasion. High solubility in iron requires the additions of tantalum carbide and niobium carbide for steel usage. Hardness up to about HRA 93.

Ceramics: The most common ceramic materials are based on alumina (aluminium oxide), silicon nitride and silicon carbide. Used almost exclusively on turning tool bits. Hardness up to about HRC 93.

Diamond: The hardest substance known to date.
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 楼主| 发表于 2017-1-3 03:26:11 | 显示全部楼层
本帖最后由 3K留德 于 2017-1-16 01:49 编辑


(1)There are six steps in this process:

Place a pattern in sand to create a mold.
Incorporate the pattern and sand in a gating system.
Remove the pattern.
Fill the mold cavity with molten metal.
Allow the metal to cool.
Break away the sand mold and remove the casting.

Gas holes: clean, smooth walled rounded holes of varying size from pin heads to full section thickness.Pinhole is very tiny hole.
Low pouring temperature
Gases blowing from the mould
Excessive turbulence during pouring
Moisture condensed on densors and chills
Use correct pouring temperature and check with pyrometer.

Shrinkage Cavity: Depression in surface or internal void caused by solidification shrinkage that restricts amount of molten metal available in last region to freeze
Pouring temperature is too high causing liquid shrinkage
Failure to supply liquid feed metal
Pre mature solidification
Reduce the pouring temperature
Provide adequate risers, feeders
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 楼主| 发表于 2017-1-6 17:57:18 | 显示全部楼层
本帖最后由 3K留德 于 2017-1-16 01:51 编辑


A DC motor isany of a class of electrical machines that converts direct current electricalpower into mechanical power. The most common types rely on the forces producedby magnetic fields.

A simple DC motor has a stationary set of magnets in the stator andan armature with one or more windings ofinsulated wire wrapped around a soft iron core that concentrates the magneticfield. The windings usually have multiple turns around the core, and in largemotors there can be several parallel current paths. The ends of the wirewinding are connected to a commutator. The commutator allows eacharmature coil to be energized in turn and connects the rotating coils with theexternal power supply through brushes.

B: magneticfields weber
I:current              amperes
L: thelength of the coil     m
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发表于 2017-1-6 22:03:41 | 显示全部楼层
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 楼主| 发表于 2017-1-11 05:42:37 | 显示全部楼层
本帖最后由 3K留德 于 2017-1-16 01:52 编辑

2.       Alternating current motors

An AC motor is an electric motor driven by an alternatingcurrent (AC).

The AC motor commonly consists of two basic parts, an outside stationarystator having coils supplied with alternating current to produce a rotatingmagnetic field, and an inside rotor attached to the output shaft producing asecond rotating magnetic field.

Synchronous motor as an example:

A synchronous electric motor is an AC motor in which, at steady state, the rotation of the shaft issynchronized with the frequency of the supply current; the rotation period is exactlyequal to an integral number of AC cycles. Synchronous motorscontain multiphase AC electromagnets on the stator of the motor that create a magnetic field which rotates in time with theoscillations of the line current. The rotor with permanent magnets or electromagnets turns in step with the stator field atthe same rate and as a result, provides the second synchronized rotating magnetfield of any AC motor.


f:the frequence of the current
p:the pairs of the pole
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发表于 2017-1-11 21:27:35 | 显示全部楼层
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 楼主| 发表于 2017-1-15 03:08:24 | 显示全部楼层
jessebetheSun 发表于 2017-1-11 21:27
楼主楼主 有的图片看不到

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 楼主| 发表于 7 天前 | 显示全部楼层
3.       Control Electric Circuit
Forward - reversal rotation as an example:

Main Circuit
1. MCB : Mini Circuit Breaker
2. FC : Forward Contactor
3. RC : Reverse Contactor
4. SC : Star/Wye Contactor
5. DC : Delta Contactor

Control Circuit
1. FSB : Forward Start Button
2. MC : Main Contactor
3. S0 : Stop Button
4. FSB : Forward Start Button
5. RSB : Reverse Stop Button
6. A1, A2 : Contactor Coil

Engine production units that use induction motors are sometimes needed tobe using an AC motor canrotate forward and backward so that ittakes a tool that can set the direction of rotation ofinduction motors, the picture above is a picture ofa circuit that works to set the directionof rotation of the motor induction 3 phase, beit in the position of star / wye ordelta position.

On the left side of the picture is the main circuit diagram and theright is the control circuit diagram. If we want to change the direction of theAC motor when it rotates, we only need to exchange the two of the three phasewiring. Switches FC and RC fulfill this function. And when RC is got through,we must ensure the switch FC be off. Then we can achieve this by interlockcontacts (FSB and RSB)in the control circuit diagram.
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 楼主| 发表于 前天 18:37 | 显示全部楼层
【Theoretical Mecahnics 理论力学】

1. Parallelogram law of force
The parallelogram of forces is a method for solving (or visualizing) theresults of applying two forces to an object.

When more than two forces are involved, the geometry is no longer parallelogrammatic, but the same principles apply. Forces, being vectors areobserved to obey the laws of vector addition, and so the overall (resultant) force due to the application of a number of forces can be found geometrically by drawing vector arrows for each force. For example, see Figure above. Thisconstruction has the same result as moving F2 so its tail coincides with thehead of F1, and taking the net force as the vector joining the tail of F1 to the head of F2. This procedure can be repeated to add F3 to the resultant F1 +F2, and so forth.
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发表于 昨天 16:57 | 显示全部楼层
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