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控制工程（英文要点·大三大四）
核心内容
Basic concepts:
in this course, i mainly learned open loop system and closed loop system, Laplace transform and transfer function, the time domain response analysis of the system, frequency domain characteristics analysis of the system.
Explanation of concepts:
Open loop system:
The open loop system has no feedback function. The output of the system has no impact on the controlled object. So open loop system is generally only used in ignoring the external influence and some lower precision situation.
Closed loop system:
The closed loop system has feedback function, the output of the controlled object returns to the input of the controller in a certain way and has impacted on the controller and controlled object. The output signal will be compared to the ideal output, and then controller will adjust the state of the system. It is high accuracy, but with higher cost.
The feedback: the output has impacted to the input.
The positive feedback: it is the output quantity added on the input quantity, result in that the output signal will larger and larger. For example, nuclear reaction. One nucleus(原子核) meet a neutron(中子), then the nucleus becomes into two nucleus and releases two or more neutrons which will meet more nucleus, so the reaction will more and more acute.
The negative feedback: it is the input quantity minuses the output quantity, make the error gradually reduce to zero. Negative feedback is a common method of automatic control system. For example, the temperature regulation system of our bodies. It is a typical negative feedback, when the temperature of our bodies is too high, there will be a signal to tell out brain to reduce the temperature of our bodies , the opposite is the same.
Laplace transform:
Laplace transform can converts mathematical calculus operations(运算) into algebraic operation of linear differential equation(线性微分方程).
Condition: when t<0, f(t)=0; when t ≥0, f(t) is sectional continuous.
The growth rate of f(t) is less than one exponential function(指数函数).
For example,
s is the complex variable, s=σ+jw,
σ is the real part, jw is the imagining part(虚部), σ and w is real number(实数).
F(s) is the Laplace transform of f(t), s is the independent variable(自变量).
F(s) is the imagine function(象函数), f(t) is the original function.
The Laplace transform is more convenient for calculating.
Superposition theorem(叠加定理):
There are some theorems of the calculation of the Laplace transform, one of the most useful is the superposition theorem.
Inverse Laplace transform(拉氏逆变换):
If we already know the imagine function F(s) and seek for the original function , then the function can help us find the original function is called inverse Laplace transform.
But we seldom use this function to get the original function , it is too complex.
Usually, we look up the table of the Laplace transform.
Transfer function(中间函数):
Under zero initial conditions, the ratio of Laplace transform of output and Laplace transform of input.
Zero initial condition: when t=0, the input is zero, and the output is zero.
Transfer function is C(s) is the Laplace transform of the output. The R(s) is the Laplace transform of the input.
For example,
The proportional component(比例环节),
c(t)=Kr(t) G(s)=C(s)/R(s)=K K is the amplification coefficient(放大系数).
s=-3 C(s)=0 ,-3 is the null point(零点)
s=-4 C(s)=∞,-4 is the pole point(极点)
The time domain response of the system analysis:
The time domain response of the system analysis is that under the external action or the input action, the functional relationship of the output and time is called time response of the system.
The time response of the first-order system:
The general form of differential equation:
T: time constant; c(t): output signal;
r(t): input signal.
Transfer function:
For example, the RC circuit is one of the first-order system.
The unit step response of the first-order system(一阶单位阶跃响应):
Inverse Laplace transform of output:
The unit impulse response of the first order system(一阶单位脉冲相应):
-4318025400
Inverse Laplace transform:
The unit slope response of the first-order system(一阶斜坡响应):
Inverse Laplace transform:
Second-order system:
Such as the RLC circuit, the differential equation of it is :
Standard form of the differential equation of the second-order system:
The time constant of the second-order system:
The relative damping ratio(相对阻尼比):
So the transfer function of the second-order system is :
Let the
And we can get the standard form of the transfer function:
There are four types of second-order system:
1,(0<ζ<1) under-damped second-order system(欠阻尼系统)；
2,(ζ=0) non-damped second-order system(无阻尼系统);
3,(ζ>0)over-damped second-order system(过阻尼系统);
4,(ζ=1)critical damping second-order system(临界阻尼系统).
The four types are not the key points of this course, we didn’t learn them very detail, only know what they are, that is all.
Frequency domain characteristics analysis of the system:
Frequency domain method is based on the frequency characteristics or frequency response of the system ,it is a graphical method.
Ti consists of amplitude-frequency characteristics and phase frequency characteristics.
Frequency characteristic is the radio of amplitude and the phase difference of the output and input quantity, and the will change with the frequency change. We can draw the curve in the coordinate system, clearly see the amplitude ratio and phase difference change with frequency change.
This part is not the key point, so i just know this little.
参考：来源：大三大四专业课资料（英文.docx｜专业：机械工程｜课程：控制工程
液压与气压传动（英文要点·大三大四）
核心内容
Basic concepts:
In this course, i mainly learned the advantages and disadvantages of hydraulic transmission, hydraulic pump, hydraulic transmission actuator components, hydraulic control valve, hydraulic basic circuit and some understanding knowledge about pneumatic transmission.
Explanation of concepts:
Hydraulic transmission uses liquid as working medium and uses liquid pressure to transfer the energy.
Composition of hydraulic transmission system:
1, power element, such as hydraulic pump. It transforms the input mechanical energy to the oil pressure energy.
2, actuator, such as hydraulic cylinder and hydraulic motor. It transforms the oil pressure energy to mechanical energy.
3, control element, such as hydraulic valve. It can control the direction of flow, the degree of the pressure and the volume of the flow.
4, auxiliary element, such as oil filter, it can filter impurities(去污).
5, working medium, usually we use the hydraulic oil.
The advantage and disadvantage of hydraulic transmission:
Advantage:
1, light weight, compact structure, small inertia(惯性);
2,it has a wide range of continuously variable(无级变速);
3,convenient operation, easy to control;
4,good security, easy to realize overload protection, easy to dissipate heat;
5,many parts are standard parts, easy to change and fix;
6,good rigidity(好的刚性);
7,easy to achieve linear motion.
Disadvantage:
1, power loss is large; 2, pollute the environment;
3,systematic risk of cracking; 4, higher cost;
5, the demand of using and maintenance technology is higher.
Hydraulic shock(液压冲击): when the speed suddenly become fast or towards to the opposite direction, there will be a very high pressure in the system and some impact. It may hurt the system.
Hydraulic cavitations(空穴): when the speed in the system suddenly become fast, and the oil supply can not meet the requirement, there will be a negative pressure in the system, the air in the oil will come out and become into a bubble, when the bubble go into some high pressure elements, it will break quickly, the oil around will fill the place quickly and generate an impact, cause noisy and shock, hurt the elements.
Hydraulic pump:
The working principle of hydraulic pump is by the change of the sealed vessel volume. Volume increasing is the oil absorption process, the hydraulic oil under the pressure of atmosphere move into the oil pump. Volume decreasing is the oil pressuring process, drain the oil out of pump
Left picture is the graphic symbol of pump.
There are some data of a pump:
Volumetric efficiency(容积效率):
q----- the actual flow
qt-----the theoretical flowfalse
Mechanical efficiency(机械效率):
Tt----- theoretical torque(理论转矩)
T----- actual torque
Overall efficiency(总效率):
Po----- output power
Pi----- input power
There are mainly three kinds of pumps, gear pump, vane pump(叶片泵) and ram pump(柱塞泵). The gear pump is the widely used. The ram pump is always high-pressure pump. I mainly learned the gear pump in this part. The gear pump depends on the closed volume of the meshing gears to realize oil absorption and oil pressure. It is widely used in the low pressure system.
Leakage(泄漏):
1, the gear side clearance leakage is the largest account, for about 70%~75% of the total leakage;
2, the top clearance leakage of the gear;
3, the tooth meshing clearance leakage.
Entrap phenomenon(困油现象):
Part of the oil is trapped in a closed vessel between two pairs of tooth. It can cause high temperature, high pressure. We can make a pair of rectangle unloading groove(卸荷槽) on the cave to solve the problem.
Advantage: simple structure, easy to manufacture,low cost, small size, light weight, reliable work.
Disadvantage: large flow and pressure pulse, large noise.
Hydraulic transmission actuator:
I mainly learned hydraulic cylinder and hydraulic motor. They transform the pressure of liquid to mechanical energy and the output.
The main output of the cylinder is linear motion and force.
The main output of the motor are continuous rotary motion and torque.
Hydraulic cylinder includes single-acting cylinder and double-acting cylinder, these two kinds cylinder are all driven by the pressure of liquid.
It has simple structure and reliable work.
Hydraulic motor:
Classification: High speed hydraulic motor and low speed hydraulic motor.
Efficiency of the hydraulic motor:
High speed hydraulic motor: high speed, quick response, quick action but the output of the torque is small. the P is fixed, so when the n is larger ,the T is smaller.
Low speed high torque hydraulic motor: the speed is very low, the torque is very large, commonly used for engineering machinery and mining machinery.
Hydraulic control valve:
The function of the valve is to control the direction of flow, the degree of the pressure and volume of flow.
The valve can be divided by the function into three kinds: direction control valve, pressure control valve, flow control valve.
Direction control valve:
It includes check valve(单向阀), change valve(换向阀) .
The function of the check valve: restrict the direction of the flow, it can only flow in one direction.
The classification of the change valve:according to the channel and the work position. For example,
The working principle of the directional valve: using the transformation of relative location of valve cove and valve body to determine the on or off of the tube.
Pressure control valve:
This kind of valve includes relief valve(溢流阀), pressure reducing valve(减压阀), sequence valve(顺序阀), pressure switch(压力继电器).
Relief valve: stabilize the inlet pressure and make sure the safe of the pressure of the system. It can be divided into two kinds, one is the directly operated type relief valve(直动式溢流阀), it can keep balance with inlet pressure directly; another is the pilot operated compound relief valve(先导式溢流阀), it can realize remote pressure regulation.
Pressure reducing valve: stabilize the outlet pressure.
It can be divided into three kinds: fixed pressure reducing valve(定值减压阀), fixed differential pressure reducing valve(定差减压阀) and fixed proportional pressure reducing valve(定比减压阀). They work as their their names.
03810Sequence valve: control the components action sequence of hydraulic system.
It can be divided into two kinds too, the directly operation type sequence valve, this kind is always used in low pressure system. The pilot operated compound sequence valve, it can be used in high pressure system.
The difference between the relief valve and the sequence valve:
1, the oil-out port of the relief valve is link to the oil tank, but the oil-out port of the sequence valve is link to another circuit;
2,the oil through the oil-out port of the relief valve is going into the oil tank, but the oil through the oil-out port of the sequence valve is oil with pressure, it need another leaking, then connect to the oil tank.
-889072390 Pressure switch: it is the component which can convert the pressure signal into electrical signal. It can make the hydraulic circuit more easy to measure and control.
Flow control valve: by changing the valve port area size of by changing the length of the duct to control the flow.
The working principle of the flow control: it mainly base on the principle of orifice discharge(小孔出流原理). It can be express as
C---- a coefficient , which is decided by the shape of the valve port, the flow state, character of the pressure oil and so on.
---- the area of the valve port.
---- the pressure difference of the two sides of the valve port.
m---- the coefficient of the flow control valve, always between 0.5 to 1, can be decided by experiment.
The flow control valve can be divided into two kinds, one is the throttle valve(节流阀), another is the flow speed control valve(调速阀).
The throttle valve always works with the relief valve. The flow stability is good for flow speed control valve. The flow speed control valve can not be used reverse. But the ordinary throttle valve can be used reverse.
Hydraulic basic circuit:
In this chapter, i mainly learned three types of hydraulic basic circuits, pressure control loop, speed control loop and directional control loop.
Pressure control loop:
There are pressure limited an adjustable pressure loop(限压和调压回路), relief loop(减压回路), booster loop(增压回路), unloading loop(卸荷回路), pressure holding circuit(保压回路) and balance circuit(平衡回路).
I mainly learned the adjustable pressure loop. For example,
The hydraulic cylinder is the actuator, which can transfer the hydraulic pressure into the mechanical motion.
The 2-positon 4-way direction control valve can change the direction of the flow , which can control the motion of the cylinder.
The ordinary throttle valve is for control the flow, which can control the speed of the motion of the cylinder.
The constant delivery hydraulic pump is for giving the oil a pressure to make it transmit power.
The relief valve can stabilize the inlet pressure and by adjust it , we can control the pressure of the circuit.
Speed control loop:
I mainly learned two types speed control loop, the throttling speed control loop adjusted by throttle valve(流量控制阀节流调速回路) and the variable output volume speed-adjust loop(flow control loop变排量容积调速).
There are three types of throttling speed control loop:
1, entrance throttling speed control loop(进口节流阀调速回路);
2, oil return throttling speed control loop (回油节流调速回路);
3,by-pass throttling speed control loop(旁路节流调速回路).
Entrance throttling speed control loop:
Throttle valve is on the inlet oil line, pump oil pressure is adjusted bye the relief valve.
AD: stepless speed regulation is reliable.
DIS: serious heat, low efficiency, the load is very small.
Oil return throttling speed control loop:
The throttle valve is on the outlet oil line, pump oil pressure is adjusted by the relief valve.
AD: it can bear negative load(the same direction of the movement). Cylinder has a back pressure, the air is not easy to go in, the movement is steady.
DIS: the pressure of the return oil chamber(回油腔) is too high,especially when it bear the negative load. Low efficiency.
By-pass throttling speed control loop:
The throttle valve is on the by-pas path. Part of the oil from the pump flow into the hydraulic cylinder pushing the piston(活塞). Another part of the oil through the throttle valve flowing back to the oil tank. The larger of the throttle valve’s port the slower of the cylinder. Now the relief valve is a safety valve.
AD: high efficiency, heavy load.
There are three types of variable output volume speed-adjust loop:
1, variable pump-constant displacement motor loop;
2,constant displacement pump-variable displacement motor loop;
3,variable pump-variable displacement motor loop.
Left is a constant displacement pump-variable displacement motor loop.
It has a electromagnetic change valve, a bidirectional variable displacement motor(双向变量液压马达) and a constant displacement pump.
Variable displacement pump-constant displacement motor loop:
It is a constant torque loop.
23749083820
Constant displacement pump-variable displacement motor loop:
This is a constant power loop.
Variable displacement pump-variable displacement motor loop:
This loop can adjust the speed in a wide range.
In the first stage, it is a variable pump-constant motor loop. In the second stage, it is a constant pump-variable motor loop.
Direction control loop:
I mainly learned direction charging loop with directional control valve.
This is a direction charging loop and it is also a adjustable pressure loop. There is a 2-position 4-way valve.
Pneumatic driving technique(气压传动技术):
Pneumatic transmission is using compressed as the working medium for energy transfer.
The working principle of pneumatic transmission:
It use the air compressor motor transfer the mechanical energy of motor into the air pressure, then under the action of control components, then the actuator transfer the air pressure to linear motion type or rotary motion type mechanical energy, then work for outside.
AD: low cost, high efficiency ,less pollution.
APP: it is widely used in wood-working machinery and light industrial machinery.
Basic structure:
1, energy element , such as air compressor motor, transfer the mechanical energy into air pressure;
2, control element, such as pressure valve, flow valve and direction valve, control the pressure, flow and direction of airflow;
3,processing element, such as air purifying device, remove the oil dust and dry the air;
4,actuator, such as air cylinder and air motor, transfer the air pressure into mechanical energy;
5,auxiliary element, used for elements’ connection, lubrication(润滑),noise limination, such as pipe joint, silencer, sensor and so on.
参考：来源：大三大四专业课资料（英文.docx｜专业：机械工程｜课程：液压与气压传动
专业英语（英文要点·大三大四）
核心内容
Basic concepts:
In this course, i mainly learned some specialized vocabularies. The lathe and its construction, the structure of the cutting tool and some knowledge about engineering materials.
Explanation of concepts:
Fixed action 固定作用 transverse feed横向进给 mainshaft rotating主轴转动
Longitudinal feed纵向进给 feed movement进给运功 tapping攻螺纹
Drill钻头， 钻孔 screw tap丝锥 turning kinetic车削运动 hand shank 手柄
Rotate speed control 转速控制
Lead screw：transform rotary motion into linear motion
参考：来源：大三大四专业课资料（英文.docx｜专业：机械工程｜课程：专业英语
有限元方法（英文要点·大三大四）
核心内容
Basic concepts:
In this course, i mainly learned about what is the finite element analysis, basis step of finite element analysis, some concepts about FEA and application of ANSYS. This course is mainly about knowing the concept and using in graduation design.
Explanation of concepts:
The concept of FEA:
FEA is an effective method to solve the problem of mathematics. The basic solution is to divide the computational domain(计算域) into a finite number of non overlapping units(不重叠的单元). In each unit, choose some suitable nodes as the interpolation points of the function(函数插值点), make the force acting on the unit is equivalent to acting on the node. The variables in the differential equations are rewritten into a linear expression of the values of the nodes and their derivatives, which are composed of the variables and their derivatives, are to use the binary function to approximate instead, by means of the variational principle or the weighted residual method, the differential equation is solved by the discrete method( HYPERLINK "https://www.baidu.com/s?wd=%E5%BE%AE%E5%88%86%E6%96%B9%E7%A8%8B&tn=44039180_cpr&fenlei=mv6quAkxTZn0IZRqIHckPjm4nH00T1d9njcLPHK9PH6dPjRsPWTL0ZwV5Hcvrjm3rH6sPfKWUMw85HfYnjn4nH6sgvPsT6KdThsqpZwYTjCEQLGCpyw9Uz4Bmy-bIi4WUvYETgN-TLwGUv3En1D3n1R1nW04" \t "http://zhidao.baidu.com/_blank" 微分方程中的变量改写成由各变量或其导数的节点值与所选用的插值函数组成的线性表达式，就是用叉值函数来近似代替 ，借助于 HYPERLINK "https://www.baidu.com/s?wd=%E5%8F%98%E5%88%86%E5%8E%9F%E7%90%86&tn=44039180_cpr&fenlei=mv6quAkxTZn0IZRqIHckPjm4nH00T1d9njcLPHK9PH6dPjRsPWTL0ZwV5Hcvrjm3rH6sPfKWUMw85HfYnjn4nH6sgvPsT6KdThsqpZwYTjCEQLGCpyw9Uz4Bmy-bIi4WUvYETgN-TLwGUv3En1D3n1R1nW04" \t "http://zhidao.baidu.com/_blank" 变分原理或加权余量法，将 HYPERLINK "https://www.baidu.com/s?wd=%E5%BE%AE%E5%88%86%E6%96%B9%E7%A8%8B&tn=44039180_cpr&fenlei=mv6quAkxTZn0IZRqIHckPjm4nH00T1d9njcLPHK9PH6dPjRsPWTL0ZwV5Hcvrjm3rH6sPfKWUMw85HfYnjn4nH6sgvPsT6KdThsqpZwYTjCEQLGCpyw9Uz4Bmy-bIi4WUvYETgN-TLwGUv3En1D3n1R1nW04" \t "http://zhidao.baidu.com/_blank" 微分方程离散求解).
Above is a very professional expression of the concept of FEA, as a matter of fact, in my opinion, it is cutting one whole workpiece into similar units, then calculate the force, stress and many other tings among them, through the results among the little units get the result of the whole workpiece. It is a special summation(累加法).
Basic step of FEA:
1, make the structure discretization, include element division, node number , unit number, node coordinate calculation, displacement constraint condition determination(将结构进行离散化，包括单元划分、结点编号、单元编号、结点坐标计算、位移约束条件确定).
2, calculation of equivalent nodal forces(等效节点力).
3,calculation of stiffness matrix(刚度矩阵first,calculate the stiffness unit by unit, then make them together into a stiffness matrix).
4,establish the integral equilibrium equation(建立平衡方程),introduce the constraint conditions(引入约束条件), and find out the nodal displacement(求解节点位移).
5,calculation of stress(应力计算).
Some relative concepts:
Any component with some function is called deformed body.
Movement caused by bearing force in any position on component is called displacement(位移).
The deformation state caused by bearing force in any position on component is called strain(应变).
The stress state cause by bearing force in any position on component is called stress(应力).
ANSYS:
ANSYS is famous in the world, can used for structural dynamics analysis, structural statics analysis, structural nonlinear analysis, thermal analysis, magnetic field analysis.
Basic step of stress and strain analysis of ANSYS:
1, create an analytical model of the 3D model.
2,define the material and various attributes(属性) of the model.
3,meshing.
4, define the reference plane.
5, choose the stress plane and add the load.
6,calculate and get the result.
参考：来源：大三大四专业课资料（英文.docx｜专业：机械工程｜课程：有限元方法
先进制造技术（英文要点·大三大四）
核心内容
Basic concepts:
In this course, i mainly know about the modern design technology, advanced manufacturing technology, manufacturing automation technology, advanced manufacturing mode , their concepts and some related technology.
Explanation of concepts:
Modern design technology:
It is the technology which is using the new design concepts, design method and design tool to design. The most important of it is the CAD technology.
CAD includes:
1, using computer to carry out the product modeling, assembly, engineering drawing and the design of related documents;
2, product rendering, dynamic display, reliability design, kinematics and dynamics simulation and so on.
Characteristic of CAD:
1, emphasis on computer support and participation in design process.
2, emphasize the auxiliary function of the computer.
3, greatly reduce production costs.
4, labor saving.
Modern design method: optimum design, reliability design, value engineering,
green design.
Advanced manufacturing technology:
We mainly learned about the powder forging forming process(粉末锻造成型工艺), rapid prototyping manufacturing technology(快速原型制造技术) and special manufacturing technology(特殊制造技术).
Powder forging forming process:
It is a new technology which is combining the tradition powder metallurgy and forging. Combining the advantages of powder metallurgy and precision forging: low energy consumption, high material utilization, high precision forgings, good mechanical properties, high fatigue life.
Engineering process:
1,powder preparation, the powder must be with good mobility, less impurities.
2,make the powder molding with pressure, easy for fritting(烧结).
3,parision fritting(型坯烧结), high temperature fritting, increase the strength and density of the parision.
4,heat up before forging. 5, forging.
6, subsequent treatment, mostly surface treatment and heat treatment.
Rapid prototyping manufacturing technology:
It is a integrated technology combining CAD technology, numerical control technology, materials science, mechanical engineering, electronic technology , laser technology and other technology. And it is a integrated system technology can realize from parts design to the 3D entity prototype manufacturing. It includes:
1, SLA, stereolithoraphy apparatus(光敏液相固化成型).
2, LOM, laminated object manufacturing(选区片层凝结法).
3, SLS, selective laser sintering(选区激光烧结法).
(the detail is in 《Rapid Prototyping Manufacturing Technology》)
Special manufacturing technology:
1, laser manufacturing, high accuracy, no contact, almost any materials, high speed.
2, ultrasonic processing, can only process brittle materials.
3, water jet cutting process, use high speed water flow to cut materials, cheap, good for environment.
(the detail is in 《Precision and Special Processing Technology》)
Manufacturing automation technology:
Mainly includes CNC machine tool technology, industrial robot and flexible manufacturing system(FMS柔性制造系统).
FMS is a manufacturing automation system, which makes up by the number of CNC machining equipment, material holding equipment and computer control system. And it can be quickly adjusted according to the changes of manufacturing tasks or production varieties. So it can adapt to many varieties, small batch production.
Advanced manufacturing mode:
Concurrent engineering(CE):
CE is a kind of operating mode, which makes the process and production parallel and design integrated. This mode can make the product developers think about all the factors from product concept design to the demise of the product, almost the entire product life cycle, including quality, cost , schedule and user requirements at the beginning.
参考：来源：大三大四专业课资料（英文.docx｜专业：机械工程｜课程：先进制造技术
机器人技术基础（英文要点·大三大四）
核心内容
Basic concepts:
This course is an understanding course, we learned some information about robots in this course, such as history, application and so on.
Explanation of concepts:
We know that the most popular application of robot is the mechanical arms in factory, and we learned about how the mechanical arm know the position of the tool which is fixed at the end of the arm.
All the mechanical arms are made up of bars and joints, and the movements of them are realized by rotating the joints. So if we mount sensors at the joints to measure the rotation of them, we can know which direction and how much the joints rotation, and if we know the length of the bars, we can calculate die movements of the end of the mechanical arms. Then we can set a coordinate system to get the coordinate of the end of the mechanical arms in the space.
Then, my partners and i built a simple mechanical arm with the fischer, which is used for building robots like placing blocks. The arm can move things from one storage rack to another one. All the movements are controlled by the computer program which is saved in the single chip microcomputer.Then we write a paper about the mechanical arm. And we translate a paper from English into Chinese.
Cartesian coordinate robot(直角坐标机器人)：no rotate pair
Cylindrical coordinate robot(圆柱坐标机器人): one rotate pair
Spherical surface robot(求坐标机器人):two rotate pairs
Articulated robot(多关节机器人): more than 3 rotate pairs
参考：来源：大三大四专业课资料（英文.docx｜专业：机械工程｜课程：机器人技术基础
快速成型制造技术（英文要点·大三大四）
核心内容
Basic concepts:
In this course, we mainly learned the principles,characteristics and applications of several rapid prototyping manufacturing(RPM) .
Explanation of concepts:
RPM is with the help of the computer,laser,precision transmission, digital control ans some other modern technology, combine the CAD and CAM, according the 3D model in computer, can build the product model or sample in a short period of time, without the traditional machining machine tool and die technology.
AD: 1, free forming, without the use of tools or molds;
2, the manufacturing process is fast, form CAD to entities in general as
long as a few hours to teens hours, shorten the product design and
development cycle.
3, add type and digital drive molding method;
4, technology highly integrated, using CAD, CAM,new materials and so on;
5, economic benefits, a large number of cost savings;
6, a wide range of applications, suitable for new product development,
single or small batch production, complex shape parts production ,mold
design and manufacturing and other fields.
Stereolithography apparatus(SLA 光敏液相固化):
034290 The fluid bath is full of light cured resin(光敏树脂), the laser device radiates UV laser scanning the surface of the resin point by point, makes the thin layer of resin in the scanned area solid, and become a thin layer of the workpiece. When one layer is finished, the work platform go down for a distance of a layer. Then the drawing strickle(刮板) moves on the surface and make it smooth. Then repeat the process, until the workpiece is finished. Pick it out, wash it clean, then put it under the UV laser to solid it again. Then the workpiece is already.
AD: 1,high degree of automation of the molding process;
2,high dimensional accuracy, can reach 0.1mm;
3,excellent surface quality, although there may be some arris between
Layers, but the top of the surface can be like the glass;
4,can make the structure very complex and make the size relatively fine;
5,the hollow structure of the die casting can be directly produced;
6, the prototype can replaced the plastic parts in a certain degree.
DIS:1,with the physics and chemical changes in the molding process, the
manufacture is easy to band, need support;
2,the performance of the cured liquid resin is not as good as the commonly
Used industrial plastic, it is more brittle;
3,the cost of operating and maintenance is high;
4,can choose very few materials, mainly are light-sensitivity liquid resin;
5,liquid resin has a certain toxicity and odor, and need to keep avoid the
light;
6,need twice curing.
Laminated object manufacturing(LOM,叠层实体快速成型):
09525There are melt adhesive on one side of the paper, the press roller press the paper and heat it, make the paper stick on the work platform. Then the laser device emits laser to meshing the area which is not the contour of the wokpiece of present layer. Then the work platform went down for a distance of the thickness of the paper. Then the paper roller rolling, take the paper without the cut part away, and bring the new paper on the work platform. Repeat the step until the workpiece is finished. Then pick the workpiece out, wipe off the part with grid, the remain part is the workpiece.
AD: 1, the raw material price is very low, the prototype production cost is low;
2,the size of parts can be very large;
3,no need curing treatment after the manufacturing;
4,no need to design and manufacture the support structure;
5,the waste is easy to peel off(剥落);
6,the workpiece can withstand up to 200℃,and it has high hardness and
Good mechanical properties, can be processed directly;
7,the prototype precision is high.
DIS:when the thickness of the workpiece is very large, the forming process
costs a very long time, the efficiency is low. And the model can’t meet
water.
Selective laser sintering(SLS,选择性激光烧结):
The process is similar to the SLA, but the raw material is power. The powder makes the surface of the powder smooth and heat the surface of the powder to a temperature close melting. Then the laser device emits laser to melt the powder in the area of workpiece counter, then the work platform go down for a distance of a layer. Repeat the process until the workpiece is finished. Finally pick out the workpiece and wipe out the powder.
AD: 1, can choose many materials, metals and non-metallic materials are all
fine;
2, can produce the complex-shape prototype directly;
3,high precision, generally can achieve the 0.05~2.5mm, according the
difference of the powder;
4,no need to support structure, the workpiece is supported by the powder;
5,the material utilization rate is high, the powder which is not used can be
used again;
DIS:1, rough surface, because the raw material is powder, so the surface is like
powder;
2,the sintering process has peculiar smell;
3,sometime need complex auxiliary process, because some materials will
burn when meet high temperature, the work platform need to be
protected with flame retardant gas(阻燃气体);
Fused deposition modeling(FDM,熔融沉积快速成形):
We heat the material wire in the guide sleeve to melt, then squeeze it through the spray nozzle with micro nozzle. The temperature of the melt material is a little higher than the curing temperature. And the temperature of the top layer of the workpiece is a little lower than the curing temperature. So when the melt material comes out of the spray nozzle and meets the cured part, it will cure with the cured part. When one layer is finished, the work platform go down, and repeat.
AD: 1, the manufacturing principle and operation of the whole system is simple,
the maintenance cost is low, and the system is safe;
2, can use non-toxic materials, equipment system can be run in the office
environment;
3, with wax molding parts prototypes, can be directly used for investment
casting(消失模铸造);
4, the part can be shaped to any degree of complexity;
5, there are no chemical changes of the raw material in the molding
process, the distortion of parts is small;
6, the utilization rate of raw material is high, and the material life is long;
7, the support can be removed easily, no need for chemical cleaning, easy
separation;
8, can make colorful prototype directly.
DIS: 1, there are obvious stripes on the surface;
2,the strength of the vertical direction of the extension is weak;
3,have to design and manufacture the support structure;
4,have to scan the entire section of the layer, need long time;
5,the raw materials are expensive.
参考：来源：大三大四专业课资料（英文.docx｜专业：机械工程｜课程：快速成型制造技术
可靠性设计（英文要点·大三大四）
核心内容
Basic concepts:
In this course, I learned about what is reliability and some surface features of reliability, and fault tree analysis and how to use minimum cut set method(最小割集法) to get the rate of the top rate.
Explanation of concepts:
Reliability is an important quality index of the product, which includes the normal service ability of the product. Compared with the traditional safety factor design criterion, the reliability design criterion(可靠性设计规范) is more effective to ensure the safety of the product.
Reliability(R(t)可靠性):
Reliability is the product quality index(system or port) has the time attribute, defined as the product under prescribed conditions within the prescribed time, the ability of completing the function. Degree of reliability is defined as the rate of the product under prescribed conditions within the prescribed time to complete the functions.
Failure rate(λ(t)失效率):
Failure rate means the product work until the moment t and has not failed. And the rate of the product fails in unit time after the moment t.
According to the experiments, we get a curve of failure rate, it has 3 parts.
Initial failure(早期失效): caused by the product defects.
Random failure(偶然失效): caused by the operation mistake or the service mistake.
Loss failure(损耗失效): caused by aging, fatigue, wear and tear.
Maintainability(M(t)维修性):
Degree of maintainability means products after a failure, the rate of completing the repair under specified condition and time.
Mean time to repair: the average time that repair the products.
Repair rate(μ(t)): the rate of completing the repair after a special moment.
Fault tree analysis(故障树分析):
09525X are parts/components of system
G are mid situation event
T is top event
Lowest layer:
G3=x4+x5 G4=x6+x2+x4 G3=x3x4
Low layer:
G1=G3x3G4 G2=x2+G3
Top layer:
T=G1+x1+G2
Then we take the G1, G2, G3, G4 in to the T, we can get:
T=G1+x1+G2
=G3x3G4+x2+G5+x1
=x3x4+x2+x1+x3x5x2
So the minimum cut set is {x1},{x2},{x3,x4},{x3,x5,x2}
So the probability of the T working normal is
P(T)=P(x1)+P(x2)+P(x3x4)+P(x3x5x2)
参考：来源：大三大四专业课资料（英文.docx｜专业：机械工程｜课程：可靠性设计
毕业实习（英文要点·大三大四）
核心内容
Basic concepts:
We paid a visit to some factories, mainly are the Hefei Changyuan hydraulic product company, and the MIMA forklift company.
Explanation of concepts:
As for the Hefei Changyuan hydraulic product company, we mainly visited its workshop, its production line is the flexible production line, many kinds of products are manufactured, most of them are hydraulic motors, hydraulic pumps, hydraulic valves and hydraulic cylinders. It is not a only-assembly factory, but a company can research and develop new products. And there are some advanced equipment in the factory of this company, i find a heat energy burring machine(热能去毛刺机) which is rare in China.
As for the MIMA forklift company, it manufactures forklift. But its forklift is different with the Heli forklift. The Heli forklift uses diesel oil as the fuel, but the MIMA forklift uses electricity, which is more benefit for the environment. And we see some special types of forklift, such as a 30-meter-lift-high forklift, and a large tonnage forklift. The 30-meter-lift-high forklift has a very big bob-weight to keep it balance when it lift things high. As for the large tonnage forklift, it uses solid tyre(实心胎) to afford its weight. And this company is working on developing the AGV(automated guided vehicle). The little car can work along the line on the ground, and it can avoid run into blocks which are putting in its way.
参考：来源：大三大四专业课资料（英文.docx｜专业：机械工程｜课程：毕业实习
测试技术基础（英文要点·复习资料）
核心内容
Sensors
1. Foil Strain Gauge
It is a device used to measure strain on an object.As the object is deformed, the foil is deformed,
causing its electrical resistance to change.
The sensibility can be given as
E
L
dL
R
dR
k
e
+
+
=
=
)
2
1(
/
/
the sensitive coefficient consist 2 parts, the 1st part is caused by Poisson Effect, while the 2nd part
is relative to the change of resistivity caused by strain.
The change of resistance is very small, usually measured using a Wheatstone bridge.
A Wheatstone bridge is an electrical circuit used to measure an unknown electrical resistance by
balancing two legs of a bridge circuit. For example, the quarter wheatstone bridge have one leg
which is the unknown conponent.
and the balacnce conditions for the bridge is ...
so when the object is deformed, the resistance is changed, the galwanometer will not be zero,
with the number showed on it, we can know the unkown part.
Application: strain/ vibration/ torque measurement
2. angle/line displacement sensor
capacitance
d
S
C
=
dielectric constant/section area/the displacement of capavitive boards
circle turn
application: micro-displacement, such as the adjustment of electron microscope
also the capacitance sensor can be used to measure the air quality/ the water level
3. Piezoelectric sensor
some material will generate piezoelectricity/electricity when the material is compressed, that is
piezoelectric effect
measure changes in pressure, acceleration, temperature, strain by converting them to an
electrical charge
application: in many large shopping malls, the escalators will have a piezoelectric or pressure
sensor. when there are people on the elevator, it will run in normal speed; but when there are no
one on it, the speed will be relative low to save energy.
4. cross corelation function
the maximum value of this funtion is at the time difference, which show the lag time between
the two signal.
detect fracture site of a pipeline, we can install two sensors, there have different displacement
from the fracture site, so the signal from the break site to the two sensor will need different time,
and the time defference can be given by the cross corelation function, and by using the time we
can calculate the certain position of the break position. repair
signal processing and its application
1. two kinds of signal: analog signal is countinuous and most in the natural, digital signal is
discrete and for the machine. process information
so when we want to using the analog signal, we should convert it into digital, by
sampling/dicretization(function to sequence), finalization(infinite sequenc to finite)
in sampling, we should avoid frequency aliasing, that means when the digital signal change back
to analog, the useful information contained in the signal should be complete. so the smapling
frequency should more than double maximum frequency for the useful frequency band.
2. Fourier Series and Fourier Transform
the fourier Series normally represent the periodic signal as the sum of simple sine waves and
then we can make frequency-domain analysis.
There are two forms of fourier Series, one is the Trigonimetric function, the other one is the
complex exponential form. the converting between this two forms is using the Euler’s formula.
3. Fast Fourier transform
when we use sofeware programm to process the discrete signal, to reduce the amount of
calculation, we will use FFT to convert analog to digital.
1st the point N should be a power of 2;
2nd by using fft, we can convert the signal from time-domain to frequency-domain.
3rd the fft break up the N point transform into two transform of n/2(n/secends)
when the N is big enough, fft will reduce the number of computations needed for N points from
to 2Nlog2N.
with fft, we can achieve the real-time signal processing, which is really importent for industrial system.
in the experiment cource, we use the fft function in matlab to process signal.
4. filter
4: high pass/ low pass/ band pass/band stop
the design of Butterworth filter
normally, we use the function to determine the order of filter, the wc is cutoff frequency, which is -3db
frequency; the wp .and then we use a fomular to check the coeffient of the filter.
also we use maltab test the filter we design in the experiment course.
(convolution)
参考：来源：aps复习资料.rar / up自己一点点整理的复习资料.pdf｜专业：机械工程｜课程：测试技术基础
机电一体化系统设计（英文要点·复习资料）
核心内容
1. sensor: sensor to position, according the displacement
Ultrasonic sensor measure the displacement by using ultrasonic waves, the sensor send the
waves and recive the wave reflected back from target. it can use the time and the sound speed to
calculate the displacement.
2. actuator: stepper motor, ball screw guide rail, manipulator/ robot arm(steering gear),
3. controller
python for the GUI(Graphical user interface): area, software programs, send the information
of coordinate value to matlab, analyse the changing trend of the value to know which number
that user has writed. send the to the microcontroller named STM32, the microcontroller will
control the actuaor move, to go into more detail, manipulator will catch the corresponding
number of objects as the user write on the screen to the certain area.
integrated design technology for mechatronics system
Rapid Application Development framework, it looks like a letter “V”.
the design of mechatronics system involves the knowledge of machinery, information, electricity
in this course, we are devided into 2 groups, each one have 15 people. and we design a
Electrohydraulic pump and a EHA, from the parameter calculation, structure design, modeling to
analysis and simulation, and we finished thesis and give a presentation to show our design.
the electrohydraulic pump is the conbination of motor and hydraulich pump, in a single shell, so
that it can spare space, but we should consider the friction and heat dissipation with the
hydraulic oil in the schell. and I was resonsible to the simulation of vibration of structure by using
soildworks to measure the natural frequency to avoid resonance. how change the structure
the EHA is an Electro-Hydrostatic Actuator, which is rapidly applied in the field of aviation, in
many modern plane, more than 50% actuator is the EHA.
I was responsible for the simulation of hydraulic system by using the software amesim, I set the
section area of the hydraulic cylinder, the rotational speed, displacement and other paremeters
of the pump, then I give the system a position feedback to improve the stability.
参考：来源：aps复习资料.rar / up自己一点点整理的复习资料.pdf｜专业：机械工程｜课程：机电一体化系统设计
机电传动控制（英文要点·复习资料）
核心内容
motor
1. difference between Synchronous moter and Induction motor:
Synchronous motors and induction motors are the most widely used types of AC motor. In a
synchronous electric motor, the rotation of the shaft is synchronized with the frequency of the
supply current. An Induction Motor is an AC electric motor in which the electric current in the
rotor is produced by electromagnetic induction from the magnetic field of the stator winding.
·Synchronous moter: runs at a constant speed; It is not self-starting; External DC source is
necessary to provide excitation.
·induction motor: cheaper; construction is simple; It does not require any complex circuit for
starting; Speed control is difficult; Efficiency drops at low loads; Poor starting torque
2. difference between AC and Dc moter:
AC. motors are powered from alternating current (A.C.) while D.C. motors are powered from
direct current (D.C.), such as batteries, D.C. power supplies or an AC-to-DC power converter, DC
motor have high torque and easy to control of speed and torque.
3. the Basic structure of DC motor
·Stator(still): Main pole, Steel Core(increse the effect of magnetic fields) and Excitation Winding.
some have Brush
·Rotor(rotation): Armature core, amature Winding
the Stator generate magnetic field, and the rotor have torque to rotation.
4. Start-up mode
Mechanical characteristics of DC motor
we learned start-up mode, which have 3 types. the easiest one is direct start-up, but the current
is too large, so it’s normally not allowed.
the second mode is to add a series resistor in the aemature circuit, normally for small motor.
the ideal no-load speed is n0, the line slop is β.
third mode is to reduce the armature voltage when motor starts up, the energy loss is small and
it is suitable for large motor. n0, β, Is
the process is smooth, because the voltage can be continuously regulated.
speed regulation method and stop mode
参考：来源：aps复习资料.rar / up自己一点点整理的复习资料.pdf｜专业：机械工程｜课程：机电传动控制
控制工程（英文要点·复习资料）
核心内容
this cource is about principle of automatic control
1. open loop and closed loop control
feedback:
positive--fish pool, rotten, the living environment/ a small disturbance to the system will lead to
an incredibal consequence.
negative-- in human’s body, when we are hungry, the blood sugar will decline, the brain tell us to
eat, and after eating, the blood sugar will increase, our body will secrete hormones to balance
the blood sugar. so the system will keep at a stable value.
block diagram: input, output, disturbance, the equivalent transformation for the diagram
2. time domain anslysis
the system is stable or not is an important character for the system in time domain. normally we
will use Routh Criterion : characteristic equation coefficient and the number in the first line of
the Routh formular are positive, the system will be stable.
the unit step response of first-order system
closed-loop transfer function of second order system
3. Laplace transform and tansfer function
the laplace transfer function is like this, but we almost not use the function to transform. we
didn’t learn the related methematic courses before, so we just remeber some commonly used
formula, like impulse function/ step / ramp/ exponential
transfer function is a representaion in terms of the relation between the input and output of a
linear time-invariant system with zero initial conditions.
4. nyquist diagram and bode diagram (frequency domain)
nyquist diagram: use jw to replace s in transfer function. Nyquist stability criterion: when w
change from 0 to ∞, the number of encirclements of point at (-1,j0) is N, Counterclockwise is
positive, the number of poles in the right half plane is p, when z=p-2n equal to 0, system is stable.
z is the number of positive real root of characteristic equation.
bode diagram:
5. PID control/ controller
PID stands for Proportional, Integral, Derivative.
PID control provides a continuous variation of output within a control loop feedback mechanism
to accurately control the process, removing oscillation and increasing efficiency.
proportional control is used to minimize the oscillation characteristic of on/off control
PID control is used for a variety of process variables such as; Temperature, Flow and Pressure.
the relation between input and output of PID controller is
u(t)=kp[e(t)+1/TI∫e(t)dt+TD*de(t)/dt] from 0 to t
参考：来源：aps复习资料.rar / up自己一点点整理的复习资料.pdf｜专业：机械工程｜课程：控制工程
机电传动控制（英文要点·复习资料·motor driving and robots）
核心内容
1. stepper motors and servo motors, AC/DC
the motor can be used in robot, its wheels, legs, tracks, arms, fingers
·In a continuous DC motor, application of power causes the shaft to rotate continually. The shaft
stops only when the power is removed.
·In a stepping motor, applying power causes the shaft to rotate a few degrees, then stop.
Continuous rotation of the shaft requires that the power be pulsed to the motor. they are also
the easiest to use. open loop control, cheap
·the servo motor in typical cases combines a continuous DC motor with a “feedback loop” to
ensure accurate positioning. There are many, many types of servo motors; a common form is the
kind used in radio-controlled cars and planes.
2. motor driving in robot
3. thesis
design of a robot, focus on the application and motor choosing. my thesis is about the Unmanned
Aerial Vehicle(UAV), normally it’s endurance time is short, about half hour, to make it can work
for a long time, I design a system with a car carring battery for the UAV. I design the structure and
the control flow chart, also I chose DC motor for the plane and car, because they are easy to
control and cheap.
参考：来源：aps复习资料.rar / up自己一点点整理的复习资料.pdf｜专业：机械工程｜课程：机电传动控制
机器人技术基础（英文要点·复习资料）
核心内容
1. definition of robot
A robot is a machine—especially one programmable by a computer— capable of carrying out a
complex series of actions automatically. Robots can be guided by an external control device or
the control may be embedded within. Robots may be constructed in a human form, but most
robots are machines designed to perform a task with other forms like a car or just an arm.
2. types of robots, such as and the techniques in robots
·industrial robots: are widely used in automobile manufacturing, machinery processing, such as
welding robot and many kinds of robotic arm for assembly.
·service robot: home service robot can do some housework. Many of them have human forms,
which make them looked more humanized.
·medical robot: Da Vinci surgical robot can help doctor have a remote, precise operation. Some
can provide health-care service.
3. the attitude control of manipulator by using Matrix transformation. it consists of joints and
links, joints provide relative motion, the types of joints include linear and rotary, each joint
provides a degree of freedom.
Rotate α around the x axis， Ф y; ϴ z
Kinematic analysis, normally a rotaion consists of several basic rotation, so we have basic
rotation matrixs.
1st we have translation transformation so we got the position, then rotation transformation to
get the attitude.
4. how to achieve the function
·sensor: testing technology
·actuator: machine design and drive system
·controller: control system, the principle of micro-controller
·software programme: based on C language
参考：来源：aps复习资料.rar / up自己一点点整理的复习资料.pdf｜专业：机械工程｜课程：机器人技术基础