ESCON: Speed controller (open loop) with Adaptive IxR Compensation

Principle

Designed for permanent-magnet brushed DC motors and brushless EC motors, the ESCON servo controller family provides the operation mode "Speed controller (open loop)" with "Adaptive IxR Compensation" for dynamic load compensation, despite a low resolution speed signal.

The open loop speed controller feeds the motor with a voltage which corresponds to the applied speed set value. The conversion from speed to voltage is done by means of the motor speed constant k_n. With increasing motor load, its speed would drop. The compensation circuit (IxR) increases the motor voltage with increasing motor current (increasing load).

The compensation must be adjusted to the terminal resistance R of the motor, which is temperature dependent. As the motor current increases at higher loads, the motor temperature rises which in turn causes the motor winding resistance to increase linearly according to the temperature coefficient for copper (0.039 K^-1).

Thanks to the adaptive IxR compensation method, the temperature dependent resistance change is evaluated using a speed sensor and an algorithm and finally corrected.