Abstract: An ultrasonic welding system includes an ultrasonic welding stack mounted for linear movement and for applying a controlled force, speed, or a combination of force and speed to a first workpiece to press the first workpiece against a second workpiece to which the first workpiece is to be joined, and an electrically powered linear actuator coupled to the ultrasonic welding stack for moving the stack while applying a controlled force, speed, or a combination of force and speed to said stack, the actuator including an electrical servo motor producing rotational mechanical motion and an integrated converter for converting the rotational motion into linear motion. In one specific implementation, a controller is coupled to the linear actuator for controlling the force applied by said actuator to the ultrasonic welding stack, and a sensor is coupled to the servo motor for producing a signal related to the torque produced by the servo motor and supplying that signal to the controller.