Characteristics and speed control of the hottest A

Characteristics and speed control of AC variable frequency volume speed regulating circuit introduction of AC variable frequency volume speed regulating circuit variable frequency speed regulating transmission is one of the main development directions of modern electrical transmission. AC asynchronous motor variable frequency speed regulating system has the advantages of simple structure, durability, good dynamic response and high work efficiency [1]. The traditional hydraulic volume speed regulation is to adjust the output flow of the system by changing the displacement of the oil pump or oil motor, so as to control the running speed of the actuator. This speed regulation method is sensitive to various interferences, especially in occasions that require high operating speed of actuator, servo variable mechanism is often used, and servo variable mechanism has high requirements for oil filtration accuracy and high price [2]

if the AC variable frequency volume speed regulation circuit composed of AC variable frequency and hydraulic volume speed regulation is adopted, the advantages of the two can be combined. The characteristics of this speed regulation circuit are: wide speed regulation range, high resolution, good energy saving, strong anti pollution ability, easy to realize computer control, etc. 2. Characteristic analysis (1) frequency converter characteristics take the commonly used Sanken universal digital sam-m voltage type frequency converter as an example. After testing, when the fundamental frequency is below (below 50Hz), the output frequency and voltage of the frequency converter are linear with the frequency control signal (here is 4 ~ 20mA current signal). When the fundamental frequency is above (above 50Hz), the output frequency of the frequency converter is linear with the frequency control signal, but the voltage remains unchanged, That is, the constant torque regulation is below the fundamental frequency, and the constant power regulation is above the fundamental frequency. Considering the minimum speed requirements of the oil pump, set the low speed of this latest and new energy number as the starting frequency corresponding to the 4mA current signal. (2) Speed and loop stiffness characteristics this paper discusses the quantitative pump quantitative motor system controlled by frequency conversion. The schematic diagram of the loop is shown in the dotted box in Figure 1. When the loop leaks and the external load changes, the motor output speed and loop stiffness are respectively: among them, λ=λ p+ λ m+ λ L is the total leakage coefficient of the circuit

vp is the pump displacement

Xp、 Δ XP is the dead zone of the regulation coefficient and regulation parameter of the pump respectively

η pv、 η mv、 η lv、 η Mm is the volumetric efficiency of pumps, motors and pipelines and the mechanical efficiency of motors respectively. LANXESS plans to use pure ethylene derived from renewable resources sugarcane; M is the external load

it can be seen that the circuit leakage and external load have a great impact on the motor speed and stiffness, especially when the pump runs at low speed. The root cause of nm and t changing with M is the change of circuit leakage caused by the change of load, which is also the defect of AC variable frequency volume speed regulation circuit. Therefore, in order to improve the speed stability and stiffness of the circuit, remedial measures must be taken. 3 then how to maintain the closed-loop AC variable-frequency volume speed regulation control system when the spring testing machine encounters a fault is shown in Figure 1: Figure 1 AC variable-frequency volume speed regulation control structure diagram description: the resolution of the photoelectric encoder is 2500 pulses/revolution, and the quadruple frequency circuit can be formed by using the two-phase phase difference of 90 degrees and the zero position reference signal output by itself. The function of "signal processing" is pulse counting and timing, "Controller" is the core of this system. Considering the difficulty of modeling this system, fuzzy controller is adopted. 4. Fuzzy controller summarizes the actual control experience into fuzzy rules, calculates the fuzzy control rule table (see Table 1) offline, and stores it in the computer for control

a two-dimensional controller is used, that is, the frequency control signal U: current value of the frequency converter is obtained according to the speed change and change rate

here, the value of error E (-20, 20), the value of error change EC (-50, 50), and the variation range of U Δ u（-5，5 ）。 Table 1 fuzzy control rule table eec-u- e The fuzzy subsets of EC and u are as follows: e={nl, nm, NS, Ze, PS, PM, pl}

ec={nl, nm, NS, Ze, PS, PM, pl}

u={nl, nm, NS, Ze, PS, PM, pl} the universe of fuzzy quantities is taken as:

{-6, -5, -4, -3, -2, -1, 0, 1, 2, 3, 4, 5, 6} The fuzzy membership table of each variable is shown in Table 2: Table 2 fuzzy membership table of each variable - plpmpszensnm in the state of deteriorating urban air quality in China, the NL quantification factor is selected by the self-adjusting scale factor method, which is mainly adjusted in real time according to the change rate of speed deviation

fuzzy rule: ri:if eisaiandecisbi, then uiisci

membership function is: μ Ri= μ (AI and Bi → CI) (E, EC, Δ u)=［ μ AI (E) and μ Bi (ec)］ → μ Ci( Δ u)

reasoning with max min: α I= μ Ai(e)∧ μ Bi (EC)

area center method for deblurring: