XII International Scientific – Professional Symposium INFOTEH®-JAHORINA 2013 Modelling and Control of Electromagnetic Vibratory Actuator Applied in Vibratory Conveying Drives Željko V. Despotović (presenter), Aleksandar I.Ribić Department of Robotics Mihajlo Pupin Institute, University of Belgrade Belgrade, Serbia Volgina 15, Belgrade, zeljko.despotovic@pupin.rs Vladimir Šinik Technical Faculty “Mihajlo Pupin” University of Novi Sad Zrenjanin, Serbia

Introduction The vibratory conveyors and feeders having electromagnetic vibratory drives provide easy flow of particulate materials. Their application is widely used in various manufacturing industries (food, pharmaceutical, cement, etc). These vibrating machines are very popular because of their high efficiency and easy maintenance. This applies in particular to resonant vibratory conveying drives. However, their performance is highly sensitive to different kinds of disturbances. For example, as the conveyor (feeder) vibrations occur at its resonance frequency, vibration amplitude is highly dependent on damping factor. These disturbances can reduce drastically (up to 10 times) the vibration amplitude, thus reducing the performance of the whole vibratory conveying drive. A key element that compensates these influences is the electromagnetic vibratory actuator (EVA).

Typical construction of a vibratory conveying system having electromagnetic vibratory actuator 1-Load Carry Element (LCE) 2-Flexible elements (leaf springs) are made of a fiberglass composite material. 3-Base 4-Rubber mounts 5-Magnetic core 6-Coil 7-Armature 8-Vibratory trough 9-Non contact inductive sensor Electromagnetic Vibratory Actuator EVA

Model of EVA If the short excitation current pulse for EVA is synchronized with the instant when the armature is passing through the equilibrium position ( ) (a) electromechanical part, (b) electromagnet of actuator, (c) equivalent electrical scheme. predominantly inductive nature of EVA

Owing to the predominantly inductive nature of EVA coil, it is very simple, by applying a suitable control, to generate current pulses in this coil which are of the form of triangular half-waves As pulse width in practical applications is very small against the cycling period, its contribution can be approximated by Dirac pulse of the same strength. STRENGTH of the current pulse

Modelling of Mechanical Load z=D+d+p we have to analyze simplified model in the presence of the material in the trough. Two cases important for analysis: Case 1. When the amplitude is relatively small, material is moving together with trough (there is no transport). In this case material is acting as additional mass. 1-complete model 2-simplified model Case 2. At higher amplitudes, transported material is in fluidized state, reacting with a trough as additional damping force.

CONTROL SYSTEM Luenberger observer

PI control Anti-windup structure of the PI controller

SIMULATION RESULTS = 4ms SAMPLING PERIOD CURRENT PULSE DURATION ( SIMULATION RESULTS PARAMETERS . CONVERSION RESOLUTION SAMPLING PERIOD CURRENT PULSE DURATION = 4ms Simulated amplitude response on reference change

At reference and moment there is step change in damping ratio from to Simulated amplitude response on damping ratio change Disturbance response has small maximum error and recovery time defined by integral time constant

The Experimental Results To demonstrate the performance of the proposed feedback controller, the experimental setup : IGBT power converter and control system are used. The control algorithm is implemented on industrial PC platform with 12bit A/D interface for displacement measurement and Linux + RTAI operating system software. Displacement is measured by inductive distance sensor Ni-10, 0-6mm range, analog output 0-10V, Turck production.

To illustrate dynamic characteristics of the EVA load in both cases (empty and full trough), the trough of our experimental conveyor is filled with sugar and the feeder is excited by short current pulse as before. Time responses for the empty and full trough are compared Experimental time responses of the EVA armature displacement: CH1-empty trough, ς=0.01, CH2- fill of sugar, ς=0.1.

Experimental reference change responses: Reference change tests are made for empty and for full trough. Reference is changed in steps from 0.1mm to 1mm and back to 0.1mm. Both responses are well damped and with small overshoots. Experimental reference change responses: CH1- empty trough, CH2- full trough.

After about 1 - 1.5s, the bag is removed from the trough. DISTURBANCE RESPONSE A 250g particulate material bag dropped onto LCE trough is used to demonstrate disturbance response of the electromagnetic vibratory drive. After about 1 - 1.5s, the bag is removed from the trough. The results are presented for amplitude reference and for empty trough, when the effect of disturbance is the highest. Experimental disturbance change responses for empty trough

Prototype of realized Vibratory Conveying Drive EVA current-triangle displacement-sinusoidal Resonance effect

Realized Industrial PC104 platform with 12bit A/D interface Linux + RTAI operating system software Implemented prototype-experimental setup Industrial PC104 platform

CONCLUSION A simple EVA and its load carrying element are analyzed. Despite low price and low maintenance costs, this kind of EVA is often poorly controlled (frequently without feedback), reducing its applicability in precise weighting. A new control structure, based on the state observer and PI controller, proposed in this paper, significantly improves vibratory conveying, thus enabling high performances. The absence of wearing mechanical part, such as gears, cams belts, bearings, eccentrics or motors, makes EVA one of the most promising devices for application in processing of granular and particulate materials (conveying, dosage weighing, etc.) in various manufacturing industries. They are compact, robust and reliable in operation. Efficient control of the device at its resonant frequency, obtained by small values of EVA coil current, results into small power consumption.

Thank You in Attention!!!! Dr Zeljko V. Despotovic, dipl.el.ing zeljko.despotovic@pupin.rs INFOTEH 2013 Jahorina 20-22.03.2013