Internet of Things (IoT)
- network of physical objects (things)
- embedded with sensors, software
- is used for connecting and exchanging data
- with other devices and systems over the Internet
Control system
- an interconnection of physical components
- connected
- direct or regulate itself or another system.
Control theory
- The control of dynamical systems in engineered processes and machines.
- develop a model or algorithm governing the application of system
- minimizing any
- ensuring a level of
- achieve a degree of
A linear system
- Additivity property
x1(t) x2(t) → y1(t) y2(t) - Homogeneity or Scaling property
ax(t) → ay(t) ax1(t) bx2(t) → ay1(t) by2(t)
Closed-Loop Systems
Disadvantages:
- Costly
- Complex
- 又贵又复杂
Advantages:
- Decreased sensitivity of the system 提升系统对抗变化的能力
- Improved rejection of the 提升系统对抗扰动的能力
- Improved measurement noise 提升了测量噪声的衰减，抗噪声
- Improved reduction of the of the system提升了对于稳态误差的减少
- Easy control and adjustment of the transient response of the system
Lead Compensator
Method to find suitable zero and pole location
找到合适的零点和极点步骤：
-
Evaluate the sum of angles
- 首先，振动不变，因此阻尼比不变，根仍在直线上（阻尼比表示根与原点连接cos）
- 然后，由settle time求出横坐标
- 计算出让这一点成为根轨迹上所需的角度补偿
Evaluate the sum of angles from the open-loop to a designed point，which yields the desired transient response.
-
The difference between 180° are the compensator
180° 补偿器所需的角度贡献必须是计算角度角度
-
Arbitrarily select either a lead compensator pole or zero, then find another one by 180° principle
通过和为180°另一个零点或极点的位置
Transducer
-
measure the of the system back to be compared with the input, or , so that the output can be controlled
闭环系统使用传感器（有时称为传感器）来测量系统的输出，并将测量结果反馈给输入或参考信号进行比较，以控制输出
-
The difference between the two values, the is then applied to the system via a .
两个值之间的差值，即误差，然后通过控制器应用于系统。
-
is required to condition the signal if the signal is too small or too noisy
传感器输出信号可能太小而无用，或噪音太大，因此需要使用仪器来调整信号
transducer的分类
classifying transducers
-
By that is， the type of quantity
根据变量，即测量的类型
- Temperature
- Pressure
- Displacement
- Flow
- Humidity
- Velocity
- Acceleration
-
By that is, the operating principle of the transducer being used
根据类型，即传感器的工作原理
- Resistive
- Inductive
- Capacitive
accordingly电阻率、介电常数和磁导率三个属性。
Resistive Transducers
影响因素：
- strain (拉伸材料是否改变应力)
- temperature
For strin：
R=ρL/A L:导体长度 A:横截面面积
For temperature：
𝑅t=𝑅(1+𝛼𝑇)
Inductive Transducers
L=(μN^2 A)/L
Capacitive Transducers
c=eA/d
Temperature Sensors/Transducers
Thermocouple热电偶
Resistance thermometer/resistance temperature detectors (RTDs)
电压 = 电流 ×电阻
Thermistor热敏电阻
-
Negative Temperature Coefficient (NTC) thermistors
负温度系数 (NTC) 热敏电阻
-
Positive Temperature Coefficient (PTC)thermistors
正温度系数 (PTC) 热敏电阻
instrumentation
is required for two reasons:
-
Signal Processing信号处理
(the output is a different variable from the input)
-
Signal Conditioning信号调制
(the output represents the same variable as the input)
本处使用的是
instrumentation包含几下几个方面：
instrumentation使用时需要考虑的事项：
-
- Range (范围max and min)
- Overload protection
- Frequency response频率响应
- Transient response瞬态响应
- Resonant frequency共振频率
-
- Accuracy即输出是否准确
- Precision ：是准确度的度量
- Repeatability： 的能力
- Linearity
- Sensitivity输入端的改变在输出端的反应
- Resolution：
- Stability：
- Slew rate：
- Hysteresis：
-
- Output characteristics：
- Size and weight：
- Power requirements：
- Accessories needed：
- Mounting requirements：
- Environment of transducer location：
- Crosstalk
-
- Ease of speed of calibration and testing
- Time available for calibration and testing
- Stability against drift
- Vulnerability to sudden failure
- Fail safety
- Failure recognition故障识别
-
- Availability and delivery
- Price
- Previous experience以往的经验
zero-order hold数字信号恢复为模拟信号时的近似
- yields a staircase approximation to the analog signal. 产生模拟信号的阶梯近似值。
- 它在 𝑡∈[𝑘𝑇, (𝑘+1)𝑇] 期间保持一个常数 𝑓(𝑘𝑇) 的输出