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International Scientific Conference “UNITECH 2014” – Gabrovo

TECHNICAL UNIVERSITY OF GABROVO

INTERNATIONAL

SCIENTIFIC CONFERENCE

P R O G R A M

21 - 22 NOVEMBER 2014 GABROVO

„14


International Scientific Conference UNITECH‟14 is organized by the Technical University

of Gabrovo with the assistance of regional business establishments and companies. The

conference is a forum at which traditionally every year at the end of November lecturers

and research workers from home and abroad meet to promote the Development of Science and

Education.

ORGANIZING COMMITTEE

Chairman: Assoc. Prof. Iliya Zhelezarov, Ph.D. Vice Rector in charge of Research and Development

Members: Prof. Jordan Maximov, D.Sc. Assoc. Prof. Mincho Simeonov, Ph.D. Assoc. Prof. Tsvetelina Gankova, Ph.D. Assoc. Prof. Daniela Dimova, Ph.D. Assoc. Prof. Dragomir Chantov, Ph.D.

Technical Assistant: Petya Peneva, MA

PROGRAM COMMITTEE

Chairman: Prof. Raycho Ilarionov, D.Sc. Technical University of Gabrovo, Bulgaria

Members: Acad. Chavdar Rumenin, Bulgaria Acad. Dragoljub Mirjanić, Rep. Srpska, B & H Prof. Lothar Otto, Ph.D., Germany Prof. Walter Maier, Ph.D., Germany Prof. D.H.C. Helmut Hopp, Ph.D., Germany Prof. Jan Brinks, Ph.D., Netherlands Prof. D.H.C. Branimir Djordjević, Ph.D., Serbia Prof. Dr. Petar Maric, Serbia Prof. D.H.C. Yuriyi Kuznetsov, D.Sc., Ukraine Prof. Elena Kovalenko, Ph.D., Ukraine Prof. Igor Sazonov, D.Sc., Belarus Prof. D.H.C. Nikolay Ganev, Ph.D., Czech Republic Prof. Toshko Nenov, Ph.D., Bulgaria Prof. Ventsislav Zimparov, D.Sc., Bulgaria Prof. Stoyan Kapralov, D.Sc., Bulgaria Prof. Rumen Daskalov, D.Sc., Bulgaria Assoc. Prof. Petar Petrov, Ph.D., Bulgaria

UNITECH’14 will be held on 21 and 22 November 2014

at the Technical University of Gabrovо


WORKING PROGRAM

OF THE SCIENTIFIC CONFERENCE

20th

November 2014, Thursday

14.00 – 17.00 h Registration, Rectorat building

21st November 2014, Friday

08.00 – 10.30 h Registration, Rectorat building

10.30 – 11.00 h Opening ceremony – Library building, Conference hall

11.00 – 12.00 h The Role of Informatics in a Modern Health Care System - a

plenary report by Karl P. Pfeiffer - FH JOANNEUM – University of

Applied Sciences Inductive power transfer charging station for static and dynamic

charge of electrical vehicles – a plenary report by Prof.Raycho

Ilarionov, Assoc. Prof. Nikolay Madzharov and Mag. Eng.

Anton Tonchev, Technical University of Gabrovo 12.00 – 13.00 h Lunch

13.00 – 18.00 h Thematic sessions

Electrical Engineering

Electronics and Sensors

Automation

Chemistry and Ecology

Communication Engineering and Technologies

Computer Systems

Computer Technologies

Mathematics and Informatics

Design of Machines and Instruments

Technologies in Mechanical Engineering

Technologies in Textile Production

Mechatronics, Metrology and Quality Management

Hydraulics, Pneumatics and Heat Engineering

Economics and Finance

Organization and Management

Social Sciences and Humanities

Educational Technologies

Physics

15.00 – 15.30 h Coffee break

14.00 h Round table: Closing conference in the agenda of the Project

"Technical University of Gabrovo curricula updating in

conformity with business demands”, Library building, Conference

hall

15.30 h Round table: Education and Active Ageing, Irena Rashkova and

Tsvetelina Petrova, Department for Language and Specialized

TrainingTechnical University of Gabrovo, Integral Building, 3rd

floor, Hall 1324

19.00 h Formal dinnerRestaurant Balkan Hotel

22th

November 2014, Saturday

09.00 – 12.00 h Thematic sessions

International Scientific Conference UNITECH’14 – Gabrovo

EDUCATIONAL TECHNOLOGIES

Chairmеn: Assoc. Prof. Emil Indzov, Ph.D., Sen. Assist. Prof. Tsanka Zlateva, Ph.D.

Building: № 6, Hall 6203

Beginning: 13.00 h.

About the classification of heuristic methods M. Leparov

Technical University of Sofia, Bulgaria

About some ways to heuristic methods design

M. Leparov

Technical University of Sofia, Bulgaria

Development of a standardized scheme for the transfer of knowledge from

third and secondary level education facilities to industry Hagen Helge Hochrinner¹, Jasmina Mihelak-Zupanĉiĉ²

¹University of Applied Sciences FH Joanneum Graz, Austria

²Šolski center Slovenske Konjice-Zreče

Creating a methodfor ergonomicanddesign evaluation of the workplace A. Tsanova, K. Borisova

Technical Collage – Lovech, Bulgaria

Platform for teaching feed forward and jerk control Miloš Božić

1, Marko Rosić

1, Miroslav Bjekić

1, Goran ĐorĊević

2

1Faculty of Technical Sciences Čačak, University of Kragujevac, Serbia

2Faculty of Electronic engineering, University of Nis, Serbia

Mathematical modeling and geogebra as educational technologies of the

new era Tanja Sekulić¹, Valentina Kostić²

¹Technical College of Applied Sciences Zrenjanin, Serbia

²Grammar School Pirot, Pirot, Serbia

Interdisciplinary teaching of informatics L. Skopalik, P. Danailov, M. Koleva

Technical University of Gabrovo, Bulgaria

Developing e-learning module R. Ivanova


Results of using E-learning R. Ivanova


International Scientific Conference “UNITECH 2014” – Gabrovo IV-286

20 41

PLATFORM FOR TEACHING FEED FORWARD AND JERK CONTROL

Miloš Božić1, Marko Rosić1, Miroslav Bjekić1, Goran Đorđević2 1Faculty of Technical Sciences Čačak, University of Kragujevac, Serbia

2Faculty of Electronic engineering, University of Nis, Serbia

Abstract

This paper presents an educational platform for demonstration of the feed forward and jerk control. The main parts of the platform are: linear axis, induction motor, variable frequency drive, and acquisition card with computer. Speed reference is set via the computer and LabVIEW applications. The application allows the selection of different types of ramp shape such as linear, “S”,”U”, “COS” or a polynomial function. The application allows user quick and easy settings of the parameters and monitoring of the system response. In addition to monitoring parameters such as position, velocity and acceleration, the same can be stored in a form suitable for further processing and analysis. Depending on the way of placing the platform it is possible to perform different types of experiments. In the vertical position it is possible to show the work of lifts or elevators, while in a horizontal position can be shown working principle of the crane or a linear axis of some machine. Acceleration sensor is placed on the movable trolley of the platform and measures acceleration which occurs and thus offers the possibility of comparing the estimated acceleration and the one that actually measured. One encoder before and one encoder after gear box was placed to enable the measurement of backlash which exists in the gear box.

Keywords: feed forward, jerk, motion, LabVIEW. INTRODUCTION

Laboratory classes are very important for future engineers. In laboratory, students receive the necessary knowledge and skills to successfully connect theoretical with practical skills. We realized a platform for research and experiments in motion systems for students, to approach problems with feed forward control and the occurrence of jerk.

Most students are familiar with the physical sizes such as distance, velocity and acceleration. Most of them also know that the speed is the first derivative of the position and the acceleration is the first derivative of velocity. But most of them don’t know that the jerk is the first derivate of acceleration. It is clear that in the case of discontinuity in functions of acceleration large values of jerk will occur. With right choice of velocity and acceleration profile occurrence of jerk can be reduced. Polynomials are the most appropriate functions for the velocity profiles, because they are continuous functions. There are also other functions that can be used for this problem, for example function cosine. Function that will be used depends on the abilities of the used controller [1-3].

The picture (Fig. 1) shows the different ramp of speeds. They are created by using a polynomial 2nd, 4th, and 6th order, cosine and the linear function.

0 50 100 150 200 250 300 350 400 450 5000

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

polinom 6. stepenapolinom 4. stepenapolinom 2. stepenacosinusna funkcijausponska funkcija

Fig. 1. Speed profile ramps

Blue characteristic is the "U" type of speed

ramp. Red, green and yellow characteristics are the "S" types of ramps. Which type of the “S” ramps will be used depends on the needs of the application, and deployment options on used controller which generates the reference of speed. To demonstrate the work of the platform cosine function was chosen. If this “COS” ramp has the same maximum speed as

INTERNATIONAL SCIENTIFIC CONFERENCE 21 – 22 November 2014, GABROVO


the linear ramp, then the area above and below the intersection with the linear ramp is the same. This allows easy calculation of the parameters for feed forward control. It also provides easy slope adjustment by changing the time of reaching the maximum speed - T and changing amplitude - A. In picture (Fig. 2) are shown functions of jerk, acceleration, velocity and position.

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1-1.5

-1

-0.5

0

0.5

1

1.5

s [m]v [m/s]a [m/s2]j [m/s3]

Fig. 2. Position, speed, acceleration and jerk for

“COS” function during acceleration ramp

jerk:

2 2sin2Aj t

T Tπ π =

acceleration: 21 cos

2Aa t

Tπ = −

speed: 2sin

2 2A Tv t t

Tπ

π = −

position: 2 21 2 21 cos

2 2 2A Ts t t

T Tπ π

π = − −

MAIN PARTS OF THE PLATFORM

The platform is a robust metal frame that

can be placed in two ways: horizontally or vertically, the length/height of 2m with standard industrial components.

The platform can be used to demonstrate the different motion problems from real industrial plants. The following figure (Fig. 3) shows the main parts of the platform.

Fig. 3. The testing platform

1 – Linear guide rail with carriage - is a

commercial linear guide [4] which has on itself a carriage with recirculating balls. The effective length of the guide is L = 1.3m. At the ends of the guides are mounted mechanical limits and rubber bumpers.

2 – Induction motor [5] with gear box has

next characteristics:

Table 1. Parameters of the induction motor P [кW]

n [rpm] cosφ Ts/

Tn Is/ In

J [Kgm2]

MB [Nm]

0.25 1400 0.65 2.5 3.7 7.20∙104 14 3 – The drive pulley and belt – On the axle

gear is mounted pulley designed for trapezoidal belt width of 12 mm. The radius of the pulley is r = 0.068m.

4 – Incremental encoders - there are two

encoders [6], one before and one after the gearbox. Encoder with resolution of 2500 pulses/revolution. As the radius of the pulley r is 0.068m, that gives scope of O = 0.427 m. The resolution of a one pulse of encoder is:

-60.427 6.1 102500 28 2500O mrez

i imp= = = ⋅

⋅ ⋅


For purposes of this platform this resolution is sufficient. The resolution could be increased 4 times by counting the rising and falling edges of the signal encoder.

Fig. 4. Encoders on the platform

5 – Limit switches - are placed as boundary

limit switches to protect against collision of carriage and metal construction. Inductive sensor is intended for referencing of the system.

6 – Acceleration sensor - is mounted on carriage to measure accelerations on the moving carriage that occur during acceleration and deceleration. Thus acceleration measurement can be performed directly without estimation. Acceleration sensor is one load cell [7]. It is linked with weight of the 1 kg. Because, the acceleration due to gravity g [m/s2] is a constant, then there will be apparent change in the mass of the weight, which will provide information about the current acceleration.

7 – The variable frequency drive (VFD) [8] - which was used within platform has the following characteristics:

Table 2. – The characteristics of variable frequency drive

Power (kW)

Rated voltage (V)

Rated current (A)

Frequency (Hz)

1.5 380 4.1 -500 ÷ 500 Commercial VFD drives, have different

forms of ramps. The VFD drive, which is used within the platform, has the following types of ramps: linear, which can be adjusted with two parameters (the duration time of the ramp and the speed which will be achieved), then "U" ramp "S" ramp, and "CUS" ramp which

represents the adjustable ramps which can be modified on segments.

For the purpose of the platform the internal ramps are not used. The main reason is that, it will be difficult to set specific acceleration and demonstrate feed - forward control and jerk control.

The reference ramps were generated using the acquisition card and PC in the form of voltage signals ± 10V, which is applied to the analog input of the VFD. Negative values of the voltage ramp reference give the movement in one direction and the positive values give the movement in other direction.

As the ramp is given by the external source, the internal ramp in VFD must be set to a minimum time, which in this case is t = 0.05s. In that way, the error by the influence of the VFD internal ramp is reduced to a minimum.

The VFD drive has an internal loop to regulate the output frequency. This loop is set by the parameters: frequency loop gain (FLG) and frequency loop stability (STA). Parameters FLG and STA must be set to the optimum value, so the VFD can satisfactory response to references. The picture (Fig. 5) shows the influence of bad adjusted parameters.

Fig. 5. 1) Influence of backlash of gearbox, 2) Influence of FLG and STA parameters

In addition to the parameters of FLG and STA there is another important parameter, the suppression speed loop filter - SrF.

2

2

1


Fig. 6. Influence of SrF parameter

a) on, b) off The maximum frequency that will be

applied to the motor is f = 100 Hz. Thus, the motor speed is in the range of 0 to 2800 rpm. This produces the speed of carriage in range from 0 to 0.7 m/s. Higher speed leads to weakening of torque. For this reason, the higher values of the speed are not used.

Fig. 7. Problem with speed with frequency

over the 100Hz

8 – A computer with a data acquisition card was used to create speed profiles. Acquisition card [9] has 16 analog channels, 200 kS/s, 16-

bit resolution, 2 AO, 8 DIO, two 24-bit counters. It is also possible to use the PLC controller to generate the velocity profile [10].

MOTION PLANING AND GENERATION OF SPEED PROFILE

The simplest profile for motion planning is trapezoidal velocity profile. The surface which is limited with curve and x - axis is equal to a desired position. To make possible to position the system it is necessary to define parameters, such as desired speed of the carriage V [m/s], the acceleration and deceleration of the system acc/dec [m/s2] and the desired position S [m].

Fig. 8. Analog voltage output as speed

reference

Calculation is performed based on defined parameters: V, Vmax, aacc, adec of acceleration, deceleration and time of constant speed.

accacc

Vta

=,

decdec

Vta

=, 2

acc decconst

t tPtV

+= −

When tacc , tdec and tconst are calculated,

then, program which is implemented, generates a desired velocity profile and makes positioning. Linear ramps are the simplest way for setting speed profiles. But, with higher values of acceleration problem with jerk is magnified.

Instead of using a linear ramp, “COS” ramp can be used. In this way, the ease way of finding the parameters remains, as with the trapezoidal profile. Two surfaces, concave and convex, which form cosine function with a linear ramp are the same size. So, the above equations are also valid in this case.


0 100 200 300 400 500 600 700 800 900 10000

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

v=atv=a/2*(1-cos(2*pi*t/T))v=a*T/2pi*(2*p*t/T-sin(2*pi*t/T))

Fig. 9. Speed profile for cosine and sine

functions Let trapezoidal and "COS" velocity profile

reaches the speed V for the same time interval. Then the maximum acceleration in the "COS" velocity profile is 2 times greater than in the trapezoidal velocity profile. It is possible to calculate surface which form a "COS" curve with the x-axis, as a trapezoid surface with 2 times smaller constant acceleration.

APPLICATION FOR CONTROL OF PLATFORM For the purpose of this platform LabVIEW application was created, shown in figure (Fig. 10.). On the application the following sections can be observed: 1. The choice between manual and automatic set of reference speed: Manual is used to move the carriage to the desired position by manually entering the reference over the slider, and the automatic is used to move carts at a selected speed profile. 2. Selection of speed profiles: trapezoidal or S curve, selecting from the drop-down menu. 3. The maximum speed. 4. The parameters that describe the velocity profile. 5. Calculated parameters (acceleration time, time of constant speed and deceleration time) 6. Diagrams: Position: reference and response Speed: reference and response, acceleration: estimated and measured and jerk: estimated.

Fig. 10. Front panel of application


By simple adjustment of the parameters, the required ramps are obtained. They are forwarded to the analog input of the VFD converter in form of voltage signal ± 10V.

Fig. 11. Reference and response of speed and

position S=1 m; V=0.3 m/s, a=0,6 m/s2 CONCLUSION

In this paper was presented an educational platform for demonstrating the feed forward control for positioning. It was also shown the possibility of using different types of velocity profiles in order to reduce the effects of jerk.

Platform is a suitable system in educating of future engineers who will meet with difficulties in positioning applications, point-to-point applications as well as control of swinging loads. It is particularly useful to measure the acceleration and jerk.

Future steps on this platform will be realization of remote laboratory exercises as well as mathematical modelling of the system.

ACKNOWLEDGMENT

This paper is a result within the project TR33016 which is supported by Ministry of Education, Science and Technological Development of the Republic of Serbia.

REFERENCE [1] P. Lambrechts, M. Boerlage, M. Steinbuch,

"Trajectory planning and feedforward design for electromechanical motion systems", Control Engineering Practice, vol. 13, pp. 145-157, 2005

[2] H. Z. Li, Z. M. Gong, W. Lin, and T. Lippa, "Motion profile planning for reduced jerk and vibration residuals", SIMTech technical reports, Volume 8, Number 1, pp. 32-37, Jan-Mar 2007

[3] B. Knežević, B. Blanuša, "Elevator movement control in the function of jerk value", INFOTEH-JAHORINA Vol. 10, Ref. A-9, p. 40-44, March 2011

[4] Star Linear guides, Technical informations, http://www.ahrinternational.com/star_linear.htm

[5] MGM BA series, motor catalogue, http://www.mgmelectricmotors.com/pdf/technical/BASeriesCatalog.pdf

[6]Encoder Kuebler datasheet, https://www.kuebler.com/PDFs/archiv/drehgeber/3600_en.pdf

[7] Load cell, Technical characteristics, http://www.sah.rs/Senzori/CZL602.html#KARAKTERISTIKE

[8] ATV31 Programming manual, http://www.schneider-electric.com/download/ ww/en/details/2559561-ATV31-Programming-manual/

[9] NI 6034E/6035E/6036E FamilySpecifications, http://www.ni.com/pdf/manuals/ [10] L. Markovic, “Pozicioniranje upotrebom asinhronog motora i frekventnog regulatora bez povratne sprege”, Bachelor thesis, Faculty of Technical Sciences, Čačak, 2011 370721c.pdf

http://www.ahrinternational.com/star_linear.htm

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