An apparatus having a first treatment module and a second treatment module positionable in proximity to the first treatment module, wherein at least one of the first treatment module and the second treatment module includes a welding device for treating one or more workpieces. The apparatus has a controller arranged to: receive a real-time amplitude signal of ultrasonic vibration of at least one of the first treatment module and the second treatment module during a treatment cycle; segment the amplitude signal into a plurality of amplitude segments for the treatment cycle; monitor an amplitude value of each of the plurality of amplitude segments during the treatment cycle; operate a plurality of closed-loop control algorithms to determine a plurality of amplitude adjustment values, each of the plurality of amplitude adjustment values corresponding to a respective one of the plurality of amplitude segments; and apply each amplitude adjustment value to the corresponding respective one of the plurality of amplitude segments during the subsequent treatment cycle in real-time. The treatment cycle comprises treating a single workpiece in a plurality of workpieces, and the treating including a bonding operation, a welding operation, a soldering operation, a fusing operation, or a cutting operation.