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Publish Date: May 16, 2008

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Quanser Inverted Pendulum Simple Modeling Demonstration

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Overview

This demonstration includes a sample experiment using the Quanser Inverted Pendulum Trainer, and demonstrates the dampening of the control system in a step-by-step manner. This experiment is a part of a larger set of experiments demonstrating the various educational theories that can be observed and taught using the Quanser Inverted Pendulum trainer.

Click Quanser Controls Design to go back to the main page

 

 

Quanser Inverted Pendulum Simple Model

Please note that the VI required to run this experiment is obtained with the purchase of the Quanser Inverted Pendulum.  This experiment is provided as a demonstration of the step by step instructions

Procedure

Before you start, make sure that you are running the correct VI.  The VI for this particular example is called 07-QNET_ROTPENT_Simple_Modeling.vi.

Double click the 07-QNET_ROTPENT_Simple_Modeling.vi and let LabVIEW load all the relevant subVIs into memory.  After the VI is completely finished loading all of the subVIs into memory, you will see the following screen.  Refer to Table 1 for a description of each element.

Figure 1.  DC Rotational Pendulum Simple Modeling Control Front Panel

Dampening

  1. Hold the arm of the rotary pendulum system stationary and manually perturb the pendulum.
  2. While still holding the arm, examine the response of Pendulum Angle (deg) in the Angle (deg) scope. This is the response from the pendulum system.
  3. Repeat Step 1 and release the arm after several swings.
  4. Examine the Pendulum Angle (deg) response when the arm is not fixed. This is the response from the rotary pendulum system. Given the response from these two systems - pendulum and rotary pendulum -  which converges faster towards angle zero? Why does one system dampen faster than the other?

Table 1 below lists and describes the main elements of the QNET-ROTPENT Simple Modeling virtual instrument user interface. Every element is uniquely identified through an ID number as identified in Figure 1.

Table 1. Main Elements of the DCMCT Rotational Pendulum Simple Modeling Front Panel

ID #

Label

Parameter

Description

Unit

1

Theta

theta

Arm angle measured by encoder on motor.

deg

2

Alpha

alpha

Pendulum angle measured by encoder on pendulum pivot.

deg

3

Current

Im

Motor armature current numeric display.

A

4

Voltage

Vm

Motor input voltage numeric display.

V

5

Signal Type

  

Type of signal generated for the input voltage.

  

6

Amplitude

  

Generated signal amplitude input box.

V

7

Frequency

  

Generated signal frequency input box.

Hz

8

Offset

  

Generated signal offset input box.

V

9

Disturbance

Vsd

Apply simulated disturbance voltage.

V

10

h

h

Sampling time interval of virtual instrument input box.

s

11

Mp1

Mp1

Mass of pendulum link.

kg

12

Mp2

Mp2

Mass of pendulum weight.

kg

13

Lp1

Lp1

Length from pendulum axis of rotation to start of pendulum weight.

m

14

Lp2

Lp2

Length of pendulum weight.

m

15

Calculate

  

Triggers the x_cm1, x_cm2, lp, and Jp calculation.

  

16

x_cm1

xcm,1

Pendulum link center of mass calculated from Lp1.

m

17

x_cm2

xcm,2

Pendulum weight center of mass calculated from Lp1 and Lp2.

m

18

lp

lp

Center of mass of pendulum assembly (link+weight) output box calculated from Lp1 and Lp2.

m

19

Jp

Jp

Pendulum moment of inertia calculated from Mp1, Mp2, Lp1, and Lp2.

kg.m2

20

cycle

  

Number of pendulum cycles to take into account when performing auto-model procedure.

  

21

Modeling OFF

  

Click on this button to begin auto-model procedure.

  

22

Status

  

Output box that reports the current result of the auto-modeling procedure.

  

23

delta_t

delta_t

Total time duration of cycles used for auto-modeling.

  

24

Frequency

  

Frequency of pendulum.

  

25

Jp

  

Experimentally derived pendulum moment of inertia.

  

26

Angle

theta

Scope with measured arm angle (in red) and pendulum angle (in blue).

deg

27

Voltage

Vm

Scope with applied motor voltage (red).

V

28

Pause Plots

  

Pauses the Angle and Voltage scopes.

  

29

Start Generator

  

When not pressed, the generator output is ignored and a voltage of zero is applied to the motor.

  

30

EXIT

  

Stops the LabView virtual instrument from running.

  

31

Q-Guide

  

Loads the QNET Interactive Learning Guide experiment procedure for this VI.

  

32

Real-Time?

  

The green light indicates that the sampling rate is being maintained.

  

 

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This tutorial (this "tutorial") was developed by National Instruments ("NI"). Although technical support of this tutorial may be made available by National Instruments, the content in this tutorial may not be completely tested and verified, and NI does not guarantee its quality in any way or that NI will continue to support this content with each new revision of related products and drivers. THIS TUTORIAL IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND AND SUBJECT TO CERTAIN RESTRICTIONS AS MORE SPECIFICALLY SET FORTH IN NI.COM'S TERMS OF USE (http://ni.com/legal/termsofuse/unitedstates/us/).