Ingenia developed a new sensorless control algorithm, using position and velocity estimators to eliminate the need for position sensors. This algorithm is ideal for applications in harsh environments such as high (hydrostatic) pressure environments, which are typically faced in sub-sea applications. In many of these type of applications finding suitable sensors is costly and time consuming, assuming the sensors even exists.
Our field oriented control (FOC) algorithm uses a model of the actuator based on the winding resistance and the winding inductance to estimate the current and voltage in the motor. These estimations are compared with actual measured voltage and current. By doing so, we are able to accurately estimate the back-emf and estimate the rotor position of the actuator. Based on this position estimation, we are able to estimate the velocity. We implemented vector control to accurately control the velocity of the rotor, using an easy to tune PID-controller.
The developed algorithm is set up flexible, to be used in a wide range of applications. Once we correctly estimated the parameters of the actuator, setting up the algorithm and controller is easy. Furthermore we can improve and adjust the performance of the system by tuning the vector based PID controller. We successfully implemented our sensorless algorithm for two subsea actuators.