By using servo motors with integrated electronic control, designing engineers enhance considerably their choice of solutions to render their machines more compact, more productive and more durable.

In many cases, the design of the complete system is facilitated considerably. Maximum benefit of drives with integrated control can be reached if calibration of parameters is effected by a simple bus connection.

Different customers require different solutions. However, drive engineering companies lately encounter a common trend among their clients: decentralised drive solutions and compact drives are clearly gaining in market share.

This was the reason Heidolph Elektro engaged in the development of a high-performance decentralised drive series with an integrated 4-Q positioning control. This series was also meant to be compatible with the company’s gear motor programme HeiDrive. Supported by the Bavarian Ministry of Economy, Heidolph strengthened its knowledge in the field of decentralised drives and started serial production at the beginning of 2006.

Typical characteristics of the new servo motor series called EC-I (EC-Integrated) are its enormous power density and its excellent degree of efficiency.

To achieve these outstanding properties, Heidolph decided to use NeFeB as magnet material and to optimise the motor cross sections of the coil winding. By integrating the complete drive unit into an aluminium profile, excellent thermal properties and a high protection class can be guaranteed.

For this drive concept, both hardware and firmware have been developed by Heidolph.

To optimise the geometric dimensions, a two-board solution was chosen. The control board contains the complete logic, consisting of a 16 Bit-Micro-Controller, program memory, main memory and periphery. A RS232 interface for parameterisation and a CANopen interface allow communication with PC or SPS. The power board features the power supply and the power section.

The output stage consists of six transistors and is able to carry a continuous voltage of up to 15A. Plug connections for the connection of power supply, for exits/entrances and for the interfaces are located on the power board as well. The number of cable connections inside the motor has been reduced to a minimum. To assure optimal heat dissipation, the cooling element of the power board has been integrated into the rear bearing bracket. To increase the surface, a multitude of pins and fins has been attached to the bearing bracket. A forced convection inside the electronic control unit resulted in an additional improvement of thermal properties. Additionally, an immediate cooling of the intermediate circuit capacitors contributes to the heat reduction.

Functions and modes

The control disposes of four different operating modes: if being operated in manual mode, specification of the reference value for speed, rotating direction and brake function is done by means of an analogue signal/by different plugs. The speed regulator can also be controlled via a digital interface (PC or fieldbus). The motor is working performance-dependent on a chosen speed in this mode. If operated in the mode torque control, the motor is working load-dependent with variable speed. The requested torque is alleged via digital interface. To increase the accuracy of the control unit, a characteristic waste curve of the drive is stored in the parameter settings. Finally, the drive can be operated in a positioning mode: the drive stops and starts at defined positions. Users can choose between relative and absolute target positions. Calibration is done via digital interface. If the drive has reached its target position, the position is kept actively, ie: should forces act on the drive, it is regulated thus far that the position can be maintained. Therefore the drive does not need an additional mechanical brake in most cases.

To ensure a customer-friendly commissioning of the drive, the so-called Heidolph Application Tool, a software especially developed for the EC-I series, is at the user’s disposal. This application tool features all input and reporting possibilities and a service program that guarantees a simple handling of the drive.

For the drive’s optimal integration into a customer's application, in most cases it is necessary to change the drive parameters. Through the Application Tool, each parameter can be read out and changed via the interface RS232. To support the analysis, errors and warnings are recorded and shown in the Heidolph Application Tool. This way, a history of eventual errors can be retraced.

To realise this compact and precise drive unit, Heidolph developed a high-resolution encoder. This encoder is able to recognise rotor position and rotating speed. It can exactly determine rotating speed and drive position. The rotor position is determined by means of three hall sensors positioned in an angle of 120°.

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Dipl-Ing (FH) Helmut Pirthauer, Dipl-Ing (FH) Michael Kunz and Dipl-Betriebswirtin (FH) Kathrin Schwägerl are with Heidolph Elektro GmbH & Co KG, Kelheim, Germany. www.heidolph.com