Provided are embodiments for a system including an adaptive controller, wherein the system includes a hydraulic actuator including a fluid medium, and a sensor that is disposed on the hydraulic actuator, wherein the sensor is configured to obtain sensor data of the actuator. The system also includes a processor configured to calculate an ultrasonic velocity in the fluid medium using the sensor data, wherein the processor is further configured to determine a temperature of the fluid medium based at least in part on the calculated velocity, and a controller coupled to the actuator, wherein the controller is configured to control the actuator based at least in part on the calculated velocity and determined temperature. Also provided are embodiments for a method for operating the adaptive controller.