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1、Service however the settings for the minimum and maximum output frequencies P1080 and P1082 remain active MM440 A PID controller is integrated in the MM440 the same parameters and principles of operation are used as for the MM20 this is the reason that the parameterization and operation of the MM420
2、 and the MM440 are essentially compatible with one another MM440 has a series of additional features and expanded functionality that can be useful for numerous applications The attached document provides users with basic information about the PI controller implemented in the MM420 as well as the PID
3、 controller implemented in the MM440 PDF Using PI Control App en V1 1b en pdf 438 KB Written by A P2285 0 03 s PI closed loop control for MM420 and MM440 Beitrags ID 6440806 Figure 2 2 Quick response with overshoot but instability P2280 0 55 P2285 0 03 s Version 1 1 issue Januar 2007 8 15 Copyright
4、Siemens AG 2007 All rights reserved PDF Using PI Control App en V1 1b doc Figure 2 3 Damped response P2280 0 20 P2285 0 15 s The values of P2280 and P2285 will be determined by the relationship between motor frequency and the PI control quantity e g pressure When optimising a control process we woul
5、d recommend using an oscilloscope to monitor the feedback signal to see the system response The analogue output can be used for this by setting P0771 2266 Most commonly small PI setpoint step changes 1 10 without the PI ramp times P2257 P2258 0 0s are used to evaluate the system response Once the de
6、sired response profile has been achieved the operational ramp times are then set If you are optimising without an oscilloscope we suggest starting with a small P term e g P2280 0 20 and adjusting the I term until stable operation constant achieved A small PI setpoint change should then be given and
7、depending on the system response the parameters adjusted PI closed loop control for MM420 and MM440 Beitrags ID 6440806 Version 1 1 issue Januar 2007 9 15 Copyright Siemens AG 2007 All rights reserved PDF Using PI Control App en V1 1b doc according to the tendencies shown in the figures above In gen
8、eral the most stable control is achieved by using both proportional and integral terms and if the system is liable to experience sudden disturbances we would not recommend setting the P term P2280 greater than 0 50 Ziegler Nichols method of Optimisation The Ziegler Nichols method is a means of calcu
9、lating the Proportional gain and Integral time by measuring the system response to a step change in open loop This is done by putting the inverter in frequency control and monitoring the feedback signal From the feedback response the time before the system starts to respond L and the dominant time c
10、onstant T which is measured by estimating when the system response would have reached its stationary value if the maximum slope was maintained typically measure to where the system response has reached 85 of its final value From L T and the ratio between the frequency step f as of Fmax to the feedba
11、ck value change x it is possible to calculate the P and I terms for a PI control process as follows P gain 0 9 T f L x I time 3L Example With the inverter in frequency control a frequency step of 5 Hz is given and the feedback signal monitored To allow this the following parameters are set P2200 0 P
12、1120 0 0 s P1121 0 0 s P1080 50 0 Hz PI closed loop control for MM420 and MM440 Beitrags ID 6440806 Figure 2 4 Response to 5 Hz step L 100 ms Version 1 1 issue Januar 2007 10 15 Copyright Siemens AG 2007 All rights reserved PDF Using PI Control App en V1 1b doc Figure 2 5 Response to 5 Hz step T 700
13、 ms The frequency step f 5 Hz 50 Hz 10 The feedback step x 0 64 V 10 V 6 4 P gain 0 9 T f L x 9 84 P2280 I time 3L 0 30 s P2285 The PI controller should now be enabled P2200 1 PI closed loop control for MM420 and MM440 Beitrags ID 6440806 Figure 2 6 Step Response in PI control with P2280 9 84 and P2
14、285 0 30 Version 1 1 issue Januar 2007 11 15 Copyright Siemens AG 2007 All rights reserved PDF Using PI Control App en V1 1b doc PI output limits The PI controller generates the frequency at which the inverter runs This is generated as a which is normalized into Hz via P2000 The user can limit the o
15、utput range of the controller using parameters P2291 and P2292 While the inverter will only operate within the frequency range defined by Fmin P1080 and Fmax P1082 the PI output limits can be used to further limit the output frequency Once one of the limits has been reached a bit is set 53 A or 53 B
16、 which can be connected to the digital output via P0731 or used for internal control purposes using BiCo It should be noted that if Fmax P1082 is greater than the value in P2000 then either P2000 or P2291 should be adjusted to allow Fmax to be reached Setting P2292 to a negative value allows bipolar operation of the Pi controller Further features Further features such as a PI setpoint trim can be accessed in user access level 3 P0003 3 These features are described in the Parameter List PI closed
