Technology
The EL70x7 stepper motor terminal integrates a compact Motion Control solution for stepper motors in a very compact design.
The user can control stepper motors in the low to medium performance range. With an output current of up to 5 A, the EL7047 can achieve a considerable torque of e.g. 5 Nm at a standard stepper motor. The supply voltage of up to 48 VDC allows high speeds with good torque and thus high mechanical performance. The stepper motor and an incremental encoder can be connected directly to the EL70x7.
The stepper motor terminal provides three basic modes of operation.
In standard mode all unipolar and bipolar stepper motors that comply with the specifications of the corresponding EL70x7 can be controlled. Two currents with sine/cosine curve are provided. The current is clocked with 64 kHz and resolved with up to 64-fold microstepping to achieve a smooth current.
Extended mode is based on field-oriented control. This mode can only be used for stepper motors from Beckhoff. The current is not only provided, but controlled in a comprehensive manner. Typical stepper motor problems such as pronounced resonance are therefore finally a thing of the past. Furthermore, the current is adjusted depending on the load, thereby enabling considerable energy savings and lower thermal loads at the stepper motor.
In sensorless mode stepper motors from Beckhoff can be controlled load-dependent without a feedback system.
Realization of more demanding positioning tasks
More demanding positioning tasks can be realized via the TwinCAT automation software from Beckhoff. Like other axes, the stepper motor terminals are integrated via the TwinCAT System Manager and can be used like standard servo axes. Special stepper motor features, such as speed reduction in the event of large following errors, are automatically taken into account via the stepper motor axis option. The effort for changing from a servomotor to a stepper motor - and back - is no greater than changing from one fieldbus to another one under TwinCAT.
The output stages of the stepper motor terminals have an overload protection in the form of an overtemperature warning and switch-off. Together with short circuit detection, diagnostic data are accessible in the process image of the controller. In addition, this status is displayed by the Bus Terminal LEDs, along with other information. The output stage is switched on via an Enable-Bit. The motor current can be set and reduced via a parameter value.
Optimum adaptation to the motor and the implementation of energy-saving features require minimum programming effort. Since all data are set in the form of parameters in the CoE register, it is easily possible to replace an EtherCAT Terminal or store certain parameters for transfer to the next project. It is therefore no longer necessary to transfer certain potentiometer settings or to document DIP switch settings.